draft-ietf-quic-transport-34.txt   draft-ietf-quic-transport-latest.txt 
QUIC Working Group J. Iyengar, Ed. Internet Engineering Task Force (IETF) J. Iyengar, Ed.
Internet-Draft Fastly Request for Comments: 9000 Fastly
Intended status: Standards Track M. Thomson, Ed. Category: Standards Track M. Thomson, Ed.
Expires: July 19, 2021 Mozilla ISSN: 2070-1721 Mozilla
January 15, 2021 May 2021
QUIC: A UDP-Based Multiplexed and Secure Transport QUIC: A UDP-Based Multiplexed and Secure Transport
draft-ietf-quic-transport-34
Abstract Abstract
This document defines the core of the QUIC transport protocol. QUIC This document defines the core of the QUIC transport protocol. QUIC
provides applications with flow-controlled streams for structured provides applications with flow-controlled streams for structured
communication, low-latency connection establishment, and network path communication, low-latency connection establishment, and network path
migration. QUIC includes security measures that ensure migration. QUIC includes security measures that ensure
confidentiality, integrity, and availability in a range of deployment confidentiality, integrity, and availability in a range of deployment
circumstances. Accompanying documents describe the integration of circumstances. Accompanying documents describe the integration of
TLS for key negotiation, loss detection, and an exemplary congestion TLS for key negotiation, loss detection, and an exemplary congestion
control algorithm. control algorithm.
DO NOT DEPLOY THIS VERSION OF QUIC
DO NOT DEPLOY THIS VERSION OF QUIC UNTIL IT IS IN AN RFC. This
version is still a work in progress. For trial deployments, please
use earlier versions.
Note to Readers
Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org [1]), which is archived at
<https://mailarchive.ietf.org/arch/search/?email_list=quic>
Working Group information can be found at <https://github.com/
quicwg>; source code and issues list for this draft can be found at
<https://github.com/quicwg/base-drafts/labels/-transport>.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79.
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Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on July 19, 2021. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9000.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Document Structure . . . . . . . . . . . . . . . . . . . 8 1.1. Document Structure . . . . . . . . . . . . . . . . . . . 7
1.2. Terms and Definitions . . . . . . . . . . . . . . . . . . 10 1.2. Terms and Definitions . . . . . . . . . . . . . . . . . . 8
1.3. Notational Conventions . . . . . . . . . . . . . . . . . 11 1.3. Notational Conventions . . . . . . . . . . . . . . . . . 9
2. Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1. Stream Types and Identifiers . . . . . . . . . . . . . . 12 2.1. Stream Types and Identifiers . . . . . . . . . . . . . . 11
2.2. Sending and Receiving Data . . . . . . . . . . . . . . . 13 2.2. Sending and Receiving Data . . . . . . . . . . . . . . . 12
2.3. Stream Prioritization . . . . . . . . . . . . . . . . . . 14 2.3. Stream Prioritization . . . . . . . . . . . . . . . . . . 13
2.4. Operations on Streams . . . . . . . . . . . . . . . . . . 14 2.4. Operations on Streams . . . . . . . . . . . . . . . . . . 13
3. Stream States . . . . . . . . . . . . . . . . . . . . . . . . 15 3. Stream States . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1. Sending Stream States . . . . . . . . . . . . . . . . . . 16 3.1. Sending Stream States . . . . . . . . . . . . . . . . . . 15
3.2. Receiving Stream States . . . . . . . . . . . . . . . . . 18 3.2. Receiving Stream States . . . . . . . . . . . . . . . . . 17
3.3. Permitted Frame Types . . . . . . . . . . . . . . . . . . 21 3.3. Permitted Frame Types . . . . . . . . . . . . . . . . . . 20
3.4. Bidirectional Stream States . . . . . . . . . . . . . . . 21 3.4. Bidirectional Stream States . . . . . . . . . . . . . . . 20
3.5. Solicited State Transitions . . . . . . . . . . . . . . . 22 3.5. Solicited State Transitions . . . . . . . . . . . . . . . 22
4. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 23 4. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1. Data Flow Control . . . . . . . . . . . . . . . . . . . . 24 4.1. Data Flow Control . . . . . . . . . . . . . . . . . . . . 23
4.2. Increasing Flow Control Limits . . . . . . . . . . . . . 25 4.2. Increasing Flow Control Limits . . . . . . . . . . . . . 24
4.3. Flow Control Performance . . . . . . . . . . . . . . . . 26 4.3. Flow Control Performance . . . . . . . . . . . . . . . . 25
4.4. Handling Stream Cancellation . . . . . . . . . . . . . . 26 4.4. Handling Stream Cancellation . . . . . . . . . . . . . . 25
4.5. Stream Final Size . . . . . . . . . . . . . . . . . . . . 27 4.5. Stream Final Size . . . . . . . . . . . . . . . . . . . . 26
4.6. Controlling Concurrency . . . . . . . . . . . . . . . . . 27 4.6. Controlling Concurrency . . . . . . . . . . . . . . . . . 27
5. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 28 5. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.1. Connection ID . . . . . . . . . . . . . . . . . . . . . . 29 5.1. Connection ID . . . . . . . . . . . . . . . . . . . . . . 28
5.1.1. Issuing Connection IDs . . . . . . . . . . . . . . . 30 5.1.1. Issuing Connection IDs . . . . . . . . . . . . . . . 29
5.1.2. Consuming and Retiring Connection IDs . . . . . . . . 31 5.1.2. Consuming and Retiring Connection IDs . . . . . . . . 31
5.2. Matching Packets to Connections . . . . . . . . . . . . . 33 5.2. Matching Packets to Connections . . . . . . . . . . . . . 32
5.2.1. Client Packet Handling . . . . . . . . . . . . . . . 33 5.2.1. Client Packet Handling . . . . . . . . . . . . . . . 33
5.2.2. Server Packet Handling . . . . . . . . . . . . . . . 34 5.2.2. Server Packet Handling . . . . . . . . . . . . . . . 33
5.2.3. Considerations for Simple Load Balancers . . . . . . 35 5.2.3. Considerations for Simple Load Balancers . . . . . . 34
5.3. Operations on Connections . . . . . . . . . . . . . . . . 35 5.3. Operations on Connections . . . . . . . . . . . . . . . . 34
6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 36 6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 36
6.1. Sending Version Negotiation Packets . . . . . . . . . . . 37 6.1. Sending Version Negotiation Packets . . . . . . . . . . . 36
6.2. Handling Version Negotiation Packets . . . . . . . . . . 37 6.2. Handling Version Negotiation Packets . . . . . . . . . . 36
6.2.1. Version Negotiation Between Draft Versions . . . . . 37 6.3. Using Reserved Versions . . . . . . . . . . . . . . . . . 37
6.3. Using Reserved Versions . . . . . . . . . . . . . . . . . 38 7. Cryptographic and Transport Handshake . . . . . . . . . . . . 37
7. Cryptographic and Transport Handshake . . . . . . . . . . . . 38 7.1. Example Handshake Flows . . . . . . . . . . . . . . . . . 39
7.1. Example Handshake Flows . . . . . . . . . . . . . . . . . 40 7.2. Negotiating Connection IDs . . . . . . . . . . . . . . . 40
7.2. Negotiating Connection IDs . . . . . . . . . . . . . . . 41 7.3. Authenticating Connection IDs . . . . . . . . . . . . . . 41
7.3. Authenticating Connection IDs . . . . . . . . . . . . . . 42 7.4. Transport Parameters . . . . . . . . . . . . . . . . . . 43
7.4. Transport Parameters . . . . . . . . . . . . . . . . . . 44 7.4.1. Values of Transport Parameters for 0-RTT . . . . . . 44
7.4.1. Values of Transport Parameters for 0-RTT . . . . . . 45 7.4.2. New Transport Parameters . . . . . . . . . . . . . . 46
7.4.2. New Transport Parameters . . . . . . . . . . . . . . 47 7.5. Cryptographic Message Buffering . . . . . . . . . . . . . 47
7.5. Cryptographic Message Buffering . . . . . . . . . . . . . 48 8. Address Validation . . . . . . . . . . . . . . . . . . . . . 47
8. Address Validation . . . . . . . . . . . . . . . . . . . . . 48 8.1. Address Validation during Connection Establishment . . . 48
8.1. Address Validation During Connection Establishment . . . 49 8.1.1. Token Construction . . . . . . . . . . . . . . . . . 49
8.1.1. Token Construction . . . . . . . . . . . . . . . . . 50 8.1.2. Address Validation Using Retry Packets . . . . . . . 49
8.1.2. Address Validation using Retry Packets . . . . . . . 50 8.1.3. Address Validation for Future Connections . . . . . . 50
8.1.3. Address Validation for Future Connections . . . . . . 51 8.1.4. Address Validation Token Integrity . . . . . . . . . 52
8.1.4. Address Validation Token Integrity . . . . . . . . . 53 8.2. Path Validation . . . . . . . . . . . . . . . . . . . . . 53
8.2. Path Validation . . . . . . . . . . . . . . . . . . . . . 54 8.2.1. Initiating Path Validation . . . . . . . . . . . . . 54
8.2.1. Initiating Path Validation . . . . . . . . . . . . . 55 8.2.2. Path Validation Responses . . . . . . . . . . . . . . 55
8.2.2. Path Validation Responses . . . . . . . . . . . . . . 56 8.2.3. Successful Path Validation . . . . . . . . . . . . . 56
8.2.3. Successful Path Validation . . . . . . . . . . . . . 57 8.2.4. Failed Path Validation . . . . . . . . . . . . . . . 56
8.2.4. Failed Path Validation . . . . . . . . . . . . . . . 57 9. Connection Migration . . . . . . . . . . . . . . . . . . . . 57
9. Connection Migration . . . . . . . . . . . . . . . . . . . . 58 9.1. Probing a New Path . . . . . . . . . . . . . . . . . . . 58
9.1. Probing a New Path . . . . . . . . . . . . . . . . . . . 59 9.2. Initiating Connection Migration . . . . . . . . . . . . . 58
9.2. Initiating Connection Migration . . . . . . . . . . . . . 59 9.3. Responding to Connection Migration . . . . . . . . . . . 59
9.3. Responding to Connection Migration . . . . . . . . . . . 60 9.3.1. Peer Address Spoofing . . . . . . . . . . . . . . . . 59
9.3.1. Peer Address Spoofing . . . . . . . . . . . . . . . . 60 9.3.2. On-Path Address Spoofing . . . . . . . . . . . . . . 60
9.3.2. On-Path Address Spoofing . . . . . . . . . . . . . . 61 9.3.3. Off-Path Packet Forwarding . . . . . . . . . . . . . 60
9.3.3. Off-Path Packet Forwarding . . . . . . . . . . . . . 61 9.4. Loss Detection and Congestion Control . . . . . . . . . . 61
9.4. Loss Detection and Congestion Control . . . . . . . . . . 62 9.5. Privacy Implications of Connection Migration . . . . . . 62
9.5. Privacy Implications of Connection Migration . . . . . . 63 9.6. Server's Preferred Address . . . . . . . . . . . . . . . 64
9.6. Server's Preferred Address . . . . . . . . . . . . . . . 65 9.6.1. Communicating a Preferred Address . . . . . . . . . . 64
9.6.1. Communicating a Preferred Address . . . . . . . . . . 65 9.6.2. Migration to a Preferred Address . . . . . . . . . . 64
9.6.2. Migration to a Preferred Address . . . . . . . . . . 65 9.6.3. Interaction of Client Migration and Preferred Address 65
9.6.3. Interaction of Client Migration and Preferred Address 66 9.7. Use of IPv6 Flow Label and Migration . . . . . . . . . . 66
9.7. Use of IPv6 Flow-Label and Migration . . . . . . . . . . 67 10. Connection Termination . . . . . . . . . . . . . . . . . . . 66
10. Connection Termination . . . . . . . . . . . . . . . . . . . 67 10.1. Idle Timeout . . . . . . . . . . . . . . . . . . . . . . 66
10.1. Idle Timeout . . . . . . . . . . . . . . . . . . . . . . 67 10.1.1. Liveness Testing . . . . . . . . . . . . . . . . . . 67
10.1.1. Liveness Testing . . . . . . . . . . . . . . . . . . 68 10.1.2. Deferring Idle Timeout . . . . . . . . . . . . . . . 67
10.1.2. Deferring Idle Timeout . . . . . . . . . . . . . . . 68 10.2. Immediate Close . . . . . . . . . . . . . . . . . . . . 68
10.2. Immediate Close . . . . . . . . . . . . . . . . . . . . 69 10.2.1. Closing Connection State . . . . . . . . . . . . . . 69
10.2.1. Closing Connection State . . . . . . . . . . . . . . 70 10.2.2. Draining Connection State . . . . . . . . . . . . . 70
10.2.2. Draining Connection State . . . . . . . . . . . . . 71 10.2.3. Immediate Close during the Handshake . . . . . . . . 70
10.2.3. Immediate Close During the Handshake . . . . . . . . 71 10.3. Stateless Reset . . . . . . . . . . . . . . . . . . . . 72
10.3. Stateless Reset . . . . . . . . . . . . . . . . . . . . 73 10.3.1. Detecting a Stateless Reset . . . . . . . . . . . . 74
10.3.1. Detecting a Stateless Reset . . . . . . . . . . . . 75 10.3.2. Calculating a Stateless Reset Token . . . . . . . . 75
10.3.2. Calculating a Stateless Reset Token . . . . . . . . 76 10.3.3. Looping . . . . . . . . . . . . . . . . . . . . . . 76
10.3.3. Looping . . . . . . . . . . . . . . . . . . . . . . 77 11. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 77
11. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 78 11.1. Connection Errors . . . . . . . . . . . . . . . . . . . 77
11.1. Connection Errors . . . . . . . . . . . . . . . . . . . 78 11.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 78
11.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 79 12. Packets and Frames . . . . . . . . . . . . . . . . . . . . . 79
12. Packets and Frames . . . . . . . . . . . . . . . . . . . . . 80 12.1. Protected Packets . . . . . . . . . . . . . . . . . . . 79
12.1. Protected Packets . . . . . . . . . . . . . . . . . . . 80 12.2. Coalescing Packets . . . . . . . . . . . . . . . . . . . 80
12.2. Coalescing Packets . . . . . . . . . . . . . . . . . . . 81 12.3. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 81
12.3. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 82 12.4. Frames and Frame Types . . . . . . . . . . . . . . . . . 82
12.4. Frames and Frame Types . . . . . . . . . . . . . . . . . 83 12.5. Frames and Number Spaces . . . . . . . . . . . . . . . . 86
12.5. Frames and Number Spaces . . . . . . . . . . . . . . . . 87 13. Packetization and Reliability . . . . . . . . . . . . . . . . 87
13. Packetization and Reliability . . . . . . . . . . . . . . . . 88 13.1. Packet Processing . . . . . . . . . . . . . . . . . . . 87
13.1. Packet Processing . . . . . . . . . . . . . . . . . . . 88 13.2. Generating Acknowledgments . . . . . . . . . . . . . . . 88
13.2. Generating Acknowledgments . . . . . . . . . . . . . . . 89 13.2.1. Sending ACK Frames . . . . . . . . . . . . . . . . . 88
13.2.1. Sending ACK Frames . . . . . . . . . . . . . . . . . 89 13.2.2. Acknowledgment Frequency . . . . . . . . . . . . . . 89
13.2.2. Acknowledgment Frequency . . . . . . . . . . . . . . 90 13.2.3. Managing ACK Ranges . . . . . . . . . . . . . . . . 90
13.2.3. Managing ACK Ranges . . . . . . . . . . . . . . . . 91 13.2.4. Limiting Ranges by Tracking ACK Frames . . . . . . . 91
13.2.4. Limiting Ranges by Tracking ACK Frames . . . . . . . 92 13.2.5. Measuring and Reporting Host Delay . . . . . . . . . 92
13.2.5. Measuring and Reporting Host Delay . . . . . . . . . 93 13.2.6. ACK Frames and Packet Protection . . . . . . . . . . 92
13.2.6. ACK Frames and Packet Protection . . . . . . . . . . 93 13.2.7. PADDING Frames Consume Congestion Window . . . . . . 92
13.2.7. PADDING Frames Consume Congestion Window . . . . . . 93 13.3. Retransmission of Information . . . . . . . . . . . . . 93
13.3. Retransmission of Information . . . . . . . . . . . . . 94 13.4. Explicit Congestion Notification . . . . . . . . . . . . 95
13.4. Explicit Congestion Notification . . . . . . . . . . . . 96 13.4.1. Reporting ECN Counts . . . . . . . . . . . . . . . . 96
13.4.1. Reporting ECN Counts . . . . . . . . . . . . . . . . 97 13.4.2. ECN Validation . . . . . . . . . . . . . . . . . . . 96
13.4.2. ECN Validation . . . . . . . . . . . . . . . . . . . 97 14. Datagram Size . . . . . . . . . . . . . . . . . . . . . . . . 98
14. Datagram Size . . . . . . . . . . . . . . . . . . . . . . . . 99 14.1. Initial Datagram Size . . . . . . . . . . . . . . . . . 99
14.1. Initial Datagram Size . . . . . . . . . . . . . . . . . 100 14.2. Path Maximum Transmission Unit . . . . . . . . . . . . . 100
14.2. Path Maximum Transmission Unit . . . . . . . . . . . . . 101 14.2.1. Handling of ICMP Messages by PMTUD . . . . . . . . . 101
14.2.1. Handling of ICMP Messages by PMTUD . . . . . . . . . 102 14.3. Datagram Packetization Layer PMTU Discovery . . . . . . 102
14.3. Datagram Packetization Layer PMTU Discovery . . . . . . 103 14.3.1. DPLPMTUD and Initial Connectivity . . . . . . . . . 102
14.3.1. DPLPMTUD and Initial Connectivity . . . . . . . . . 103 14.3.2. Validating the Network Path with DPLPMTUD . . . . . 102
14.3.2. Validating the Network Path with DPLPMTUD . . . . . 103 14.3.3. Handling of ICMP Messages by DPLPMTUD . . . . . . . 102
14.3.3. Handling of ICMP Messages by DPLPMTUD . . . . . . . 103 14.4. Sending QUIC PMTU Probes . . . . . . . . . . . . . . . . 102
14.4. Sending QUIC PMTU Probes . . . . . . . . . . . . . . . . 103 14.4.1. PMTU Probes Containing Source Connection ID . . . . 103
14.4.1. PMTU Probes Containing Source Connection ID . . . . 104 15. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 103
15. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 104 16. Variable-Length Integer Encoding . . . . . . . . . . . . . . 104
16. Variable-Length Integer Encoding . . . . . . . . . . . . . . 105 17. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 105
17. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 106 17.1. Packet Number Encoding and Decoding . . . . . . . . . . 105
17.1. Packet Number Encoding and Decoding . . . . . . . . . . 106 17.2. Long Header Packets . . . . . . . . . . . . . . . . . . 106
17.2. Long Header Packets . . . . . . . . . . . . . . . . . . 107 17.2.1. Version Negotiation Packet . . . . . . . . . . . . . 109
17.2.1. Version Negotiation Packet . . . . . . . . . . . . . 110 17.2.2. Initial Packet . . . . . . . . . . . . . . . . . . . 110
17.2.2. Initial Packet . . . . . . . . . . . . . . . . . . . 111 17.2.3. 0-RTT . . . . . . . . . . . . . . . . . . . . . . . 112
17.2.3. 0-RTT . . . . . . . . . . . . . . . . . . . . . . . 113
17.2.4. Handshake Packet . . . . . . . . . . . . . . . . . . 114 17.2.4. Handshake Packet . . . . . . . . . . . . . . . . . . 114
17.2.5. Retry Packet . . . . . . . . . . . . . . . . . . . . 116 17.2.5. Retry Packet . . . . . . . . . . . . . . . . . . . . 115
17.3. Short Header Packets . . . . . . . . . . . . . . . . . . 118 17.3. Short Header Packets . . . . . . . . . . . . . . . . . . 117
17.3.1. 1-RTT Packet . . . . . . . . . . . . . . . . . . . . 118 17.3.1. 1-RTT Packet . . . . . . . . . . . . . . . . . . . . 117
17.4. Latency Spin Bit . . . . . . . . . . . . . . . . . . . . 120 17.4. Latency Spin Bit . . . . . . . . . . . . . . . . . . . . 119
18. Transport Parameter Encoding . . . . . . . . . . . . . . . . 121 18. Transport Parameter Encoding . . . . . . . . . . . . . . . . 120
18.1. Reserved Transport Parameters . . . . . . . . . . . . . 122 18.1. Reserved Transport Parameters . . . . . . . . . . . . . 121
18.2. Transport Parameter Definitions . . . . . . . . . . . . 122 18.2. Transport Parameter Definitions . . . . . . . . . . . . 121
19. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 126 19. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 125
19.1. PADDING Frames . . . . . . . . . . . . . . . . . . . . . 126 19.1. PADDING Frames . . . . . . . . . . . . . . . . . . . . . 125
19.2. PING Frames . . . . . . . . . . . . . . . . . . . . . . 127 19.2. PING Frames . . . . . . . . . . . . . . . . . . . . . . 126
19.3. ACK Frames . . . . . . . . . . . . . . . . . . . . . . . 127 19.3. ACK Frames . . . . . . . . . . . . . . . . . . . . . . . 126
19.3.1. ACK Ranges . . . . . . . . . . . . . . . . . . . . . 129 19.3.1. ACK Ranges . . . . . . . . . . . . . . . . . . . . . 128
19.3.2. ECN Counts . . . . . . . . . . . . . . . . . . . . . 130 19.3.2. ECN Counts . . . . . . . . . . . . . . . . . . . . . 129
19.4. RESET_STREAM Frames . . . . . . . . . . . . . . . . . . 131 19.4. RESET_STREAM Frames . . . . . . . . . . . . . . . . . . 130
19.5. STOP_SENDING Frames . . . . . . . . . . . . . . . . . . 132 19.5. STOP_SENDING Frames . . . . . . . . . . . . . . . . . . 131
19.6. CRYPTO Frames . . . . . . . . . . . . . . . . . . . . . 132 19.6. CRYPTO Frames . . . . . . . . . . . . . . . . . . . . . 131
19.7. NEW_TOKEN Frames . . . . . . . . . . . . . . . . . . . . 133 19.7. NEW_TOKEN Frames . . . . . . . . . . . . . . . . . . . . 132
19.8. STREAM Frames . . . . . . . . . . . . . . . . . . . . . 134 19.8. STREAM Frames . . . . . . . . . . . . . . . . . . . . . 133
19.9. MAX_DATA Frames . . . . . . . . . . . . . . . . . . . . 136 19.9. MAX_DATA Frames . . . . . . . . . . . . . . . . . . . . 135
19.10. MAX_STREAM_DATA Frames . . . . . . . . . . . . . . . . . 136 19.10. MAX_STREAM_DATA Frames . . . . . . . . . . . . . . . . . 135
19.11. MAX_STREAMS Frames . . . . . . . . . . . . . . . . . . . 137 19.11. MAX_STREAMS Frames . . . . . . . . . . . . . . . . . . . 136
19.12. DATA_BLOCKED Frames . . . . . . . . . . . . . . . . . . 138 19.12. DATA_BLOCKED Frames . . . . . . . . . . . . . . . . . . 137
19.13. STREAM_DATA_BLOCKED Frames . . . . . . . . . . . . . . . 139 19.13. STREAM_DATA_BLOCKED Frames . . . . . . . . . . . . . . . 138
19.14. STREAMS_BLOCKED Frames . . . . . . . . . . . . . . . . . 139 19.14. STREAMS_BLOCKED Frames . . . . . . . . . . . . . . . . . 138
19.15. NEW_CONNECTION_ID Frames . . . . . . . . . . . . . . . . 140 19.15. NEW_CONNECTION_ID Frames . . . . . . . . . . . . . . . . 139
19.16. RETIRE_CONNECTION_ID Frames . . . . . . . . . . . . . . 141 19.16. RETIRE_CONNECTION_ID Frames . . . . . . . . . . . . . . 140
19.17. PATH_CHALLENGE Frames . . . . . . . . . . . . . . . . . 142 19.17. PATH_CHALLENGE Frames . . . . . . . . . . . . . . . . . 141
19.18. PATH_RESPONSE Frames . . . . . . . . . . . . . . . . . . 143 19.18. PATH_RESPONSE Frames . . . . . . . . . . . . . . . . . . 142
19.19. CONNECTION_CLOSE Frames . . . . . . . . . . . . . . . . 143 19.19. CONNECTION_CLOSE Frames . . . . . . . . . . . . . . . . 142
19.20. HANDSHAKE_DONE Frames . . . . . . . . . . . . . . . . . 144 19.20. HANDSHAKE_DONE Frames . . . . . . . . . . . . . . . . . 143
19.21. Extension Frames . . . . . . . . . . . . . . . . . . . . 145 19.21. Extension Frames . . . . . . . . . . . . . . . . . . . . 144
20. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 145 20. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 144
20.1. Transport Error Codes . . . . . . . . . . . . . . . . . 146 20.1. Transport Error Codes . . . . . . . . . . . . . . . . . 145
20.2. Application Protocol Error Codes . . . . . . . . . . . . 147 20.2. Application Protocol Error Codes . . . . . . . . . . . . 146
21. Security Considerations . . . . . . . . . . . . . . . . . . . 148 21. Security Considerations . . . . . . . . . . . . . . . . . . . 147
21.1. Overview of Security Properties . . . . . . . . . . . . 148 21.1. Overview of Security Properties . . . . . . . . . . . . 147
21.1.1. Handshake . . . . . . . . . . . . . . . . . . . . . 148 21.1.1. Handshake . . . . . . . . . . . . . . . . . . . . . 147
21.1.2. Protected Packets . . . . . . . . . . . . . . . . . 150 21.1.2. Protected Packets . . . . . . . . . . . . . . . . . 149
21.1.3. Connection Migration . . . . . . . . . . . . . . . . 151 21.1.3. Connection Migration . . . . . . . . . . . . . . . . 150
21.2. Handshake Denial of Service . . . . . . . . . . . . . . 155 21.2. Handshake Denial of Service . . . . . . . . . . . . . . 154
21.3. Amplification Attack . . . . . . . . . . . . . . . . . . 156 21.3. Amplification Attack . . . . . . . . . . . . . . . . . . 155
21.4. Optimistic ACK Attack . . . . . . . . . . . . . . . . . 156 21.4. Optimistic ACK Attack . . . . . . . . . . . . . . . . . 155
21.5. Request Forgery Attacks . . . . . . . . . . . . . . . . 157 21.5. Request Forgery Attacks . . . . . . . . . . . . . . . . 156
21.5.1. Control Options for Endpoints . . . . . . . . . . . 158 21.5.1. Control Options for Endpoints . . . . . . . . . . . 157
21.5.2. Request Forgery with Client Initial Packets . . . . 159 21.5.2. Request Forgery with Client Initial Packets . . . . 158
21.5.3. Request Forgery with Preferred Addresses . . . . . . 160 21.5.3. Request Forgery with Preferred Addresses . . . . . . 159
21.5.4. Request Forgery with Spoofed Migration . . . . . . . 160 21.5.4. Request Forgery with Spoofed Migration . . . . . . . 159
21.5.5. Request Forgery with Version Negotiation . . . . . . 161 21.5.5. Request Forgery with Version Negotiation . . . . . . 160
21.5.6. Generic Request Forgery Countermeasures . . . . . . 161 21.5.6. Generic Request Forgery Countermeasures . . . . . . 160
21.6. Slowloris Attacks . . . . . . . . . . . . . . . . . . . 162 21.6. Slowloris Attacks . . . . . . . . . . . . . . . . . . . 161
21.7. Stream Fragmentation and Reassembly Attacks . . . . . . 162 21.7. Stream Fragmentation and Reassembly Attacks . . . . . . 161
21.8. Stream Commitment Attack . . . . . . . . . . . . . . . . 163 21.8. Stream Commitment Attack . . . . . . . . . . . . . . . . 162
21.9. Peer Denial of Service . . . . . . . . . . . . . . . . . 163 21.9. Peer Denial of Service . . . . . . . . . . . . . . . . . 162
21.10. Explicit Congestion Notification Attacks . . . . . . . . 164 21.10. Explicit Congestion Notification Attacks . . . . . . . . 163
21.11. Stateless Reset Oracle . . . . . . . . . . . . . . . . . 164 21.11. Stateless Reset Oracle . . . . . . . . . . . . . . . . . 163
21.12. Version Downgrade . . . . . . . . . . . . . . . . . . . 165 21.12. Version Downgrade . . . . . . . . . . . . . . . . . . . 164
21.13. Targeted Attacks by Routing . . . . . . . . . . . . . . 165 21.13. Targeted Attacks by Routing . . . . . . . . . . . . . . 164
21.14. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 165 21.14. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 164
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 165 22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 164
22.1. Registration Policies for QUIC Registries . . . . . . . 166 22.1. Registration Policies for QUIC Registries . . . . . . . 165
22.1.1. Provisional Registrations . . . . . . . . . . . . . 166 22.1.1. Provisional Registrations . . . . . . . . . . . . . 165
22.1.2. Selecting Codepoints . . . . . . . . . . . . . . . . 167 22.1.2. Selecting Codepoints . . . . . . . . . . . . . . . . 166
22.1.3. Reclaiming Provisional Codepoints . . . . . . . . . 167 22.1.3. Reclaiming Provisional Codepoints . . . . . . . . . 166
22.1.4. Permanent Registrations . . . . . . . . . . . . . . 168 22.1.4. Permanent Registrations . . . . . . . . . . . . . . 167
22.2. QUIC Versions Registry . . . . . . . . . . . . . . . . . 168 22.2. QUIC Versions Registry . . . . . . . . . . . . . . . . . 167
22.3. QUIC Transport Parameter Registry . . . . . . . . . . . 169 22.3. QUIC Transport Parameters Registry . . . . . . . . . . . 168
22.4. QUIC Frame Types Registry . . . . . . . . . . . . . . . 171 22.4. QUIC Frame Types Registry . . . . . . . . . . . . . . . 170
22.5. QUIC Transport Error Codes Registry . . . . . . . . . . 171 22.5. QUIC Transport Error Codes Registry . . . . . . . . . . 170
23. References . . . . . . . . . . . . . . . . . . . . . . . . . 173
23.1. Normative References . . . . . . . . . . . . . . . . . . 173 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 172
23.2. Informative References . . . . . . . . . . . . . . . . . 175 23.1. Normative References . . . . . . . . . . . . . . . . . . 172
23.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 178 23.2. Informative References . . . . . . . . . . . . . . . . . 174
Appendix A. Pseudocode . . . . . . . . . . . . . . . . . . . . . 178 Appendix A. Pseudocode . . . . . . . . . . . . . . . . . . . . . 177
A.1. Sample Variable-Length Integer Decoding . . . . . . . . . 178 A.1. Sample Variable-Length Integer Decoding . . . . . . . . . 177
A.2. Sample Packet Number Encoding Algorithm . . . . . . . . . 179 A.2. Sample Packet Number Encoding Algorithm . . . . . . . . . 178
A.3. Sample Packet Number Decoding Algorithm . . . . . . . . . 180 A.3. Sample Packet Number Decoding Algorithm . . . . . . . . . 179
A.4. Sample ECN Validation Algorithm . . . . . . . . . . . . . 181 A.4. Sample ECN Validation Algorithm . . . . . . . . . . . . . 180
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 181 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 181
B.1. Since draft-ietf-quic-transport-32 . . . . . . . . . . . 182 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 184
B.2. Since draft-ietf-quic-transport-31 . . . . . . . . . . . 182
B.3. Since draft-ietf-quic-transport-30 . . . . . . . . . . . 183
B.4. Since draft-ietf-quic-transport-29 . . . . . . . . . . . 183
B.5. Since draft-ietf-quic-transport-28 . . . . . . . . . . . 184
B.6. Since draft-ietf-quic-transport-27 . . . . . . . . . . . 184
B.7. Since draft-ietf-quic-transport-26 . . . . . . . . . . . 185
B.8. Since draft-ietf-quic-transport-25 . . . . . . . . . . . 185
B.9. Since draft-ietf-quic-transport-24 . . . . . . . . . . . 185
B.10. Since draft-ietf-quic-transport-23 . . . . . . . . . . . 186
B.11. Since draft-ietf-quic-transport-22 . . . . . . . . . . . 187
B.12. Since draft-ietf-quic-transport-21 . . . . . . . . . . . 188
B.13. Since draft-ietf-quic-transport-20 . . . . . . . . . . . 188
B.14. Since draft-ietf-quic-transport-19 . . . . . . . . . . . 189
B.15. Since draft-ietf-quic-transport-18 . . . . . . . . . . . 190
B.16. Since draft-ietf-quic-transport-17 . . . . . . . . . . . 190
B.17. Since draft-ietf-quic-transport-16 . . . . . . . . . . . 191
B.18. Since draft-ietf-quic-transport-15 . . . . . . . . . . . 192
B.19. Since draft-ietf-quic-transport-14 . . . . . . . . . . . 192
B.20. Since draft-ietf-quic-transport-13 . . . . . . . . . . . 193
B.21. Since draft-ietf-quic-transport-12 . . . . . . . . . . . 193
B.22. Since draft-ietf-quic-transport-11 . . . . . . . . . . . 194
B.23. Since draft-ietf-quic-transport-10 . . . . . . . . . . . 195
B.24. Since draft-ietf-quic-transport-09 . . . . . . . . . . . 195
B.25. Since draft-ietf-quic-transport-08 . . . . . . . . . . . 196
B.26. Since draft-ietf-quic-transport-07 . . . . . . . . . . . 196
B.27. Since draft-ietf-quic-transport-06 . . . . . . . . . . . 197
B.28. Since draft-ietf-quic-transport-05 . . . . . . . . . . . 198
B.29. Since draft-ietf-quic-transport-04 . . . . . . . . . . . 198
B.30. Since draft-ietf-quic-transport-03 . . . . . . . . . . . 199
B.31. Since draft-ietf-quic-transport-02 . . . . . . . . . . . 199
B.32. Since draft-ietf-quic-transport-01 . . . . . . . . . . . 200
B.33. Since draft-ietf-quic-transport-00 . . . . . . . . . . . 202
B.34. Since draft-hamilton-quic-transport-protocol-01 . . . . . 202
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 202
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 204
1. Overview 1. Overview
QUIC is a secure general-purpose transport protocol. This document QUIC is a secure general-purpose transport protocol. This document
defines version 1 of QUIC, which conforms to the version-independent defines version 1 of QUIC, which conforms to the version-independent
properties of QUIC defined in [QUIC-INVARIANTS]. properties of QUIC defined in [QUIC-INVARIANTS].
QUIC is a connection-oriented protocol that creates a stateful QUIC is a connection-oriented protocol that creates a stateful
interaction between a client and server. interaction between a client and server.
The QUIC handshake combines negotiation of cryptographic and The QUIC handshake combines negotiation of cryptographic and
transport parameters. QUIC integrates the TLS ([TLS13]) handshake, transport parameters. QUIC integrates the TLS handshake [TLS13],
although using a customized framing for protecting packets. The although using a customized framing for protecting packets. The
integration of TLS and QUIC is described in more detail in integration of TLS and QUIC is described in more detail in
[QUIC-TLS]. The handshake is structured to permit the exchange of [QUIC-TLS]. The handshake is structured to permit the exchange of
application data as soon as possible. This includes an option for application data as soon as possible. This includes an option for
clients to send data immediately (0-RTT), which requires some form of clients to send data immediately (0-RTT), which requires some form of
prior communication or configuration to enable. prior communication or configuration to enable.
Endpoints communicate in QUIC by exchanging QUIC packets. Most Endpoints communicate in QUIC by exchanging QUIC packets. Most
packets contain frames, which carry control information and packets contain frames, which carry control information and
application data between endpoints. QUIC authenticates the entirety application data between endpoints. QUIC authenticates the entirety
of each packet and encrypts as much of each packet as is practical. of each packet and encrypts as much of each packet as is practical.
QUIC packets are carried in UDP datagrams ([UDP]) to better QUIC packets are carried in UDP datagrams [UDP] to better facilitate
facilitate deployment in existing systems and networks. deployment in existing systems and networks.
Application protocols exchange information over a QUIC connection via Application protocols exchange information over a QUIC connection via
streams, which are ordered sequences of bytes. Two types of stream streams, which are ordered sequences of bytes. Two types of streams
can be created: bidirectional streams, which allow both endpoints to can be created: bidirectional streams, which allow both endpoints to
send data; and unidirectional streams, which allow a single endpoint send data; and unidirectional streams, which allow a single endpoint
to send data. A credit-based scheme is used to limit stream creation to send data. A credit-based scheme is used to limit stream creation
and to bound the amount of data that can be sent. and to bound the amount of data that can be sent.
QUIC provides the necessary feedback to implement reliable delivery QUIC provides the necessary feedback to implement reliable delivery
and congestion control. An algorithm for detecting and recovering and congestion control. An algorithm for detecting and recovering
from loss of data is described in [QUIC-RECOVERY]. QUIC depends on from loss of data is described in Section 6 of [QUIC-RECOVERY]. QUIC
congestion control to avoid network congestion. An exemplary depends on congestion control to avoid network congestion. An
congestion control algorithm is also described in [QUIC-RECOVERY]. exemplary congestion control algorithm is described in Section 7 of
[QUIC-RECOVERY].
QUIC connections are not strictly bound to a single network path. QUIC connections are not strictly bound to a single network path.
Connection migration uses connection identifiers to allow connections Connection migration uses connection identifiers to allow connections
to transfer to a new network path. Only clients are able to migrate to transfer to a new network path. Only clients are able to migrate
in this version of QUIC. This design also allows connections to in this version of QUIC. This design also allows connections to
continue after changes in network topology or address mappings, such continue after changes in network topology or address mappings, such
as might be caused by NAT rebinding. as might be caused by NAT rebinding.
Once established, multiple options are provided for connection Once established, multiple options are provided for connection
termination. Applications can manage a graceful shutdown, endpoints termination. Applications can manage a graceful shutdown, endpoints
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* Section 4 outlines the operation of flow control. * Section 4 outlines the operation of flow control.
o Connections are the context in which QUIC endpoints communicate. o Connections are the context in which QUIC endpoints communicate.
* Section 5 describes core concepts related to connections, * Section 5 describes core concepts related to connections,
* Section 6 describes version negotiation, * Section 6 describes version negotiation,
* Section 7 details the process for establishing connections, * Section 7 details the process for establishing connections,
* Section 8 describes address validation and critical denial of
* Section 8 describes address validation and critical denial-of-
service mitigations, service mitigations,
* Section 9 describes how endpoints migrate a connection to a new * Section 9 describes how endpoints migrate a connection to a new
network path, network path,
* Section 10 lists the options for terminating an open * Section 10 lists the options for terminating an open
connection, and connection, and
* Section 11 provides guidance for stream and connection error * Section 11 provides guidance for stream and connection error
handling. handling.
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* Section 13 defines models for the transmission, retransmission, * Section 13 defines models for the transmission, retransmission,
and acknowledgment of data, and and acknowledgment of data, and
* Section 14 specifies rules for managing the size of datagrams * Section 14 specifies rules for managing the size of datagrams
carrying QUIC packets. carrying QUIC packets.
o Finally, encoding details of QUIC protocol elements are described o Finally, encoding details of QUIC protocol elements are described
in: in:
* Section 15 (Versions), * Section 15 (versions),
* Section 16 (Integer Encoding), * Section 16 (integer encoding),
* Section 17 (Packet Headers), * Section 17 (packet headers),
* Section 18 (Transport Parameters), * Section 18 (transport parameters),
* Section 19 (Frames), and * Section 19 (frames), and
* Section 20 (Errors). * Section 20 (errors).
Accompanying documents describe QUIC's loss detection and congestion Accompanying documents describe QUIC's loss detection and congestion
control [QUIC-RECOVERY], and the use of TLS and other cryptographic control [QUIC-RECOVERY], and the use of TLS and other cryptographic
mechanisms [QUIC-TLS]. mechanisms [QUIC-TLS].
This document defines QUIC version 1, which conforms to the protocol This document defines QUIC version 1, which conforms to the protocol
invariants in [QUIC-INVARIANTS]. invariants in [QUIC-INVARIANTS].
To refer to QUIC version 1, cite this document. References to the To refer to QUIC version 1, cite this document. References to the
limited set of version-independent properties of QUIC can cite limited set of version-independent properties of QUIC can cite
[QUIC-INVARIANTS]. [QUIC-INVARIANTS].
1.2. Terms and Definitions 1.2. Terms and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in BCP
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Commonly used terms in the document are described below. Commonly used terms in this document are described below.
QUIC: The transport protocol described by this document. QUIC is a QUIC: The transport protocol described by this document. QUIC is a
name, not an acronym. name, not an acronym.
Endpoint: An entity that can participate in a QUIC connection by Endpoint: An entity that can participate in a QUIC connection by
generating, receiving, and processing QUIC packets. There are generating, receiving, and processing QUIC packets. There are
only two types of endpoint in QUIC: client and server. only two types of endpoints in QUIC: client and server.
Client: The endpoint that initiates a QUIC connection. Client: The endpoint that initiates a QUIC connection.
Server: The endpoint that accepts a QUIC connection. Server: The endpoint that accepts a QUIC connection.
QUIC packet: A complete processable unit of QUIC that can be QUIC packet: A complete processable unit of QUIC that can be
encapsulated in a UDP datagram. One or more QUIC packets can be encapsulated in a UDP datagram. One or more QUIC packets can be
encapsulated in a single UDP datagram. encapsulated in a single UDP datagram.
Ack-eliciting Packet: A QUIC packet that contains frames other than Ack-eliciting packet: A QUIC packet that contains frames other than
ACK, PADDING, and CONNECTION_CLOSE. These cause a recipient to ACK, PADDING, and CONNECTION_CLOSE. These cause a recipient to
send an acknowledgment; see Section 13.2.1. send an acknowledgment; see Section 13.2.1.
Frame: A unit of structured protocol information. There are Frame: A unit of structured protocol information. There are
multiple frame types, each of which carries different information. multiple frame types, each of which carries different information.
Frames are contained in QUIC packets. Frames are contained in QUIC packets.
Address: When used without qualification, the tuple of IP version, Address: When used without qualification, the tuple of IP version,
IP address, and UDP port number that represents one end of a IP address, and UDP port number that represents one end of a
network path. network path.
Connection ID: An identifier that is used to identify a QUIC Connection ID: An identifier that is used to identify a QUIC
connection at an endpoint. Each endpoint selects one or more connection at an endpoint. Each endpoint selects one or more
Connection IDs for its peer to include in packets sent towards the connection IDs for its peer to include in packets sent towards the
endpoint. This value is opaque to the peer. endpoint. This value is opaque to the peer.
Stream: A unidirectional or bidirectional channel of ordered bytes Stream: A unidirectional or bidirectional channel of ordered bytes
within a QUIC connection. A QUIC connection can carry multiple within a QUIC connection. A QUIC connection can carry multiple
simultaneous streams. simultaneous streams.
Application: An entity that uses QUIC to send and receive data. Application: An entity that uses QUIC to send and receive data.
This document uses the terms "QUIC packets", "UDP datagrams", and "IP This document uses the terms "QUIC packets", "UDP datagrams", and "IP
packets" to refer to the units of the respective protocols. That is, packets" to refer to the units of the respective protocols. That is,
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surrounded by a pair of matching braces. Each field in this list is surrounded by a pair of matching braces. Each field in this list is
separated by commas. separated by commas.
Individual fields include length information, plus indications about Individual fields include length information, plus indications about
fixed value, optionality, or repetitions. Individual fields use the fixed value, optionality, or repetitions. Individual fields use the
following notational conventions, with all lengths in bits: following notational conventions, with all lengths in bits:
x (A): Indicates that x is A bits long x (A): Indicates that x is A bits long
x (i): Indicates that x holds an integer value using the variable- x (i): Indicates that x holds an integer value using the variable-
length encoding in Section 16 length encoding described in Section 16
x (A..B): Indicates that x can be any length from A to B; A can be x (A..B): Indicates that x can be any length from A to B; A can be
omitted to indicate a minimum of zero bits and B can be omitted to omitted to indicate a minimum of zero bits, and B can be omitted
indicate no set upper limit; values in this format always end on to indicate no set upper limit; values in this format always end
an byte boundary on a byte boundary
x (L) = C: Indicates that x has a fixed value of C with the length x (L) = C: Indicates that x has a fixed value of C; the length of x
described by L, which can use any of the three length forms above is described by L, which can use any of the length forms above
x (L) = C..D: Indicates that x has a value in the range from C to D, x (L) = C..D: Indicates that x has a value in the range from C to D,
inclusive, with the length described by L, as above inclusive, with the length described by L, as above
[x (L)]: Indicates that x is optional (and has length of L) [x (L)]: Indicates that x is optional and has a length of L
x (L) ...: Indicates that zero or more instances of x are present x (L) ...: Indicates that x is repeated zero or more times and that
(and that each instance is length L) each instance has a length of L
This document uses network byte order (that is, big endian) values. This document uses network byte order (that is, big endian) values.
Fields are placed starting from the high-order bits of each byte. Fields are placed starting from the high-order bits of each byte.
By convention, individual fields reference a complex field by using By convention, individual fields reference a complex field by using
the name of the complex field. the name of the complex field.
For example: Figure 1 provides an example:
Example Structure { Example Structure {
One-bit Field (1), One-bit Field (1),
7-bit Field with Fixed Value (7) = 61, 7-bit Field with Fixed Value (7) = 61,
Field with Variable-Length Integer (i), Field with Variable-Length Integer (i),
Arbitrary-Length Field (..), Arbitrary-Length Field (..),
Variable-Length Field (8..24), Variable-Length Field (8..24),
Field With Minimum Length (16..), Field With Minimum Length (16..),
Field With Maximum Length (..128), Field With Maximum Length (..128),
[Optional Field (64)], [Optional Field (64)],
skipping to change at page 12, line 32 skipping to change at page 11, line 32
could be used to refer to the single-bit field in the most could be used to refer to the single-bit field in the most
significant bit of the byte, such as One-bit Field in Figure 1. significant bit of the byte, such as One-bit Field in Figure 1.
2. Streams 2. Streams
Streams in QUIC provide a lightweight, ordered byte-stream Streams in QUIC provide a lightweight, ordered byte-stream
abstraction to an application. Streams can be unidirectional or abstraction to an application. Streams can be unidirectional or
bidirectional. bidirectional.
Streams can be created by sending data. Other processes associated Streams can be created by sending data. Other processes associated
with stream management - ending, cancelling, and managing flow with stream management -- ending, canceling, and managing flow
control - are all designed to impose minimal overheads. For control -- are all designed to impose minimal overheads. For
instance, a single STREAM frame (Section 19.8) can open, carry data instance, a single STREAM frame (Section 19.8) can open, carry data
for, and close a stream. Streams can also be long-lived and can last for, and close a stream. Streams can also be long-lived and can last
the entire duration of a connection. the entire duration of a connection.
Streams can be created by either endpoint, can concurrently send data Streams can be created by either endpoint, can concurrently send data
interleaved with other streams, and can be cancelled. QUIC does not interleaved with other streams, and can be canceled. QUIC does not
provide any means of ensuring ordering between bytes on different provide any means of ensuring ordering between bytes on different
streams. streams.
QUIC allows for an arbitrary number of streams to operate QUIC allows for an arbitrary number of streams to operate
concurrently and for an arbitrary amount of data to be sent on any concurrently and for an arbitrary amount of data to be sent on any
stream, subject to flow control constraints and stream limits; see stream, subject to flow control constraints and stream limits; see
Section 4. Section 4.
2.1. Stream Types and Identifiers 2.1. Stream Types and Identifiers
skipping to change at page 13, line 13 skipping to change at page 12, line 13
streams carry data in one direction: from the initiator of the stream streams carry data in one direction: from the initiator of the stream
to its peer. Bidirectional streams allow for data to be sent in both to its peer. Bidirectional streams allow for data to be sent in both
directions. directions.
Streams are identified within a connection by a numeric value, Streams are identified within a connection by a numeric value,
referred to as the stream ID. A stream ID is a 62-bit integer (0 to referred to as the stream ID. A stream ID is a 62-bit integer (0 to
2^62-1) that is unique for all streams on a connection. Stream IDs 2^62-1) that is unique for all streams on a connection. Stream IDs
are encoded as variable-length integers; see Section 16. A QUIC are encoded as variable-length integers; see Section 16. A QUIC
endpoint MUST NOT reuse a stream ID within a connection. endpoint MUST NOT reuse a stream ID within a connection.
The least significant bit (0x1) of the stream ID identifies the The least significant bit (0x01) of the stream ID identifies the
initiator of the stream. Client-initiated streams have even-numbered initiator of the stream. Client-initiated streams have even-numbered
stream IDs (with the bit set to 0), and server-initiated streams have stream IDs (with the bit set to 0), and server-initiated streams have
odd-numbered stream IDs (with the bit set to 1). odd-numbered stream IDs (with the bit set to 1).
The second least significant bit (0x2) of the stream ID distinguishes The second least significant bit (0x02) of the stream ID
between bidirectional streams (with the bit set to 0) and distinguishes between bidirectional streams (with the bit set to 0)
unidirectional streams (with the bit set to 1). and unidirectional streams (with the bit set to 1).
The two least significant bits from a stream ID therefore identify a The two least significant bits from a stream ID therefore identify a
stream as one of four types, as summarized in Table 1. stream as one of four types, as summarized in Table 1.
+------+----------------------------------+ +------+----------------------------------+
| Bits | Stream Type | | Bits | Stream Type |
+------+----------------------------------+ +------+----------------------------------+
| 0x0 | Client-Initiated, Bidirectional | | 0x00 | Client-Initiated, Bidirectional |
| | | | | |
| 0x1 | Server-Initiated, Bidirectional | | 0x01 | Server-Initiated, Bidirectional |
| | | | | |
| 0x2 | Client-Initiated, Unidirectional | | 0x02 | Client-Initiated, Unidirectional |
| | | | | |
| 0x3 | Server-Initiated, Unidirectional | | 0x03 | Server-Initiated, Unidirectional |
+------+----------------------------------+ +------+----------------------------------+
Table 1: Stream ID Types Table 1: Stream ID Types
The stream space for each type begins at the minimum value (0x0 The stream space for each type begins at the minimum value (0x00
through 0x3 respectively); successive streams of each type are through 0x03, respectively); successive streams of each type are
created with numerically increasing stream IDs. A stream ID that is created with numerically increasing stream IDs. A stream ID that is
used out of order results in all streams of that type with lower- used out of order results in all streams of that type with lower-
numbered stream IDs also being opened. numbered stream IDs also being opened.
2.2. Sending and Receiving Data 2.2. Sending and Receiving Data
STREAM frames (Section 19.8) encapsulate data sent by an application. STREAM frames (Section 19.8) encapsulate data sent by an application.
An endpoint uses the Stream ID and Offset fields in STREAM frames to An endpoint uses the Stream ID and Offset fields in STREAM frames to
place data in order. place data in order.
Endpoints MUST be able to deliver stream data to an application as an Endpoints MUST be able to deliver stream data to an application as an
ordered byte-stream. Delivering an ordered byte-stream requires that ordered byte stream. Delivering an ordered byte stream requires that
an endpoint buffer any data that is received out of order, up to the an endpoint buffer any data that is received out of order, up to the
advertised flow control limit. advertised flow control limit.
QUIC makes no specific allowances for delivery of stream data out of QUIC makes no specific allowances for delivery of stream data out of
order. However, implementations MAY choose to offer the ability to order. However, implementations MAY choose to offer the ability to
deliver data out of order to a receiving application. deliver data out of order to a receiving application.
An endpoint could receive data for a stream at the same stream offset An endpoint could receive data for a stream at the same stream offset
multiple times. Data that has already been received can be multiple times. Data that has already been received can be
discarded. The data at a given offset MUST NOT change if it is sent discarded. The data at a given offset MUST NOT change if it is sent
skipping to change at page 14, line 47 skipping to change at page 13, line 47
information. Instead, it relies on receiving priority information information. Instead, it relies on receiving priority information
from the application. from the application.
A QUIC implementation SHOULD provide ways in which an application can A QUIC implementation SHOULD provide ways in which an application can
indicate the relative priority of streams. An implementation uses indicate the relative priority of streams. An implementation uses
information provided by the application to determine how to allocate information provided by the application to determine how to allocate
resources to active streams. resources to active streams.
2.4. Operations on Streams 2.4. Operations on Streams
This document does not define an API for QUIC, but instead defines a This document does not define an API for QUIC; it instead defines a
set of functions on streams that application protocols can rely upon. set of functions on streams that application protocols can rely upon.
An application protocol can assume that a QUIC implementation An application protocol can assume that a QUIC implementation
provides an interface that includes the operations described in this provides an interface that includes the operations described in this
section. An implementation designed for use with a specific section. An implementation designed for use with a specific
application protocol might provide only those operations that are application protocol might provide only those operations that are
used by that protocol. used by that protocol.
On the sending part of a stream, an application protocol can: On the sending part of a stream, an application protocol can:
o write data, understanding when stream flow control credit o write data, understanding when stream flow control credit
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An application protocol can also request to be informed of state An application protocol can also request to be informed of state
changes on streams, including when the peer has opened or reset a changes on streams, including when the peer has opened or reset a
stream, when a peer aborts reading on a stream, when new data is stream, when a peer aborts reading on a stream, when new data is
available, and when data can or cannot be written to the stream due available, and when data can or cannot be written to the stream due
to flow control. to flow control.
3. Stream States 3. Stream States
This section describes streams in terms of their send or receive This section describes streams in terms of their send or receive
components. Two state machines are described: one for the streams on components. Two state machines are described: one for the streams on
which an endpoint transmits data (Section 3.1), and another for which an endpoint transmits data (Section 3.1) and another for
streams on which an endpoint receives data (Section 3.2). streams on which an endpoint receives data (Section 3.2).
Unidirectional streams use either the sending or receiving state Unidirectional streams use either the sending or receiving state
machine depending on the stream type and endpoint role. machine, depending on the stream type and endpoint role.
Bidirectional streams use both state machines at both endpoints. For Bidirectional streams use both state machines at both endpoints. For
the most part, the use of these state machines is the same whether the most part, the use of these state machines is the same whether
the stream is unidirectional or bidirectional. The conditions for the stream is unidirectional or bidirectional. The conditions for
opening a stream are slightly more complex for a bidirectional stream opening a stream are slightly more complex for a bidirectional stream
because the opening of either the send or receive side causes the because the opening of either the send or receive side causes the
stream to open in both directions. stream to open in both directions.
The state machines shown in this section are largely informative. The state machines shown in this section are largely informative.
This document uses stream states to describe rules for when and how This document uses stream states to describe rules for when and how
different types of frames can be sent and the reactions that are different types of frames can be sent and the reactions that are
expected when different types of frames are received. Though these expected when different types of frames are received. Though these
state machines are intended to be useful in implementing QUIC, these state machines are intended to be useful in implementing QUIC, these
states are not intended to constrain implementations. An states are not intended to constrain implementations. An
implementation can define a different state machine as long as its implementation can define a different state machine as long as its
behavior is consistent with an implementation that implements these behavior is consistent with an implementation that implements these
states. states.
Note: In some cases, a single event or action can cause a transition Note: In some cases, a single event or action can cause a
through multiple states. For instance, sending STREAM with a FIN transition through multiple states. For instance, sending STREAM
bit set can cause two state transitions for a sending stream: from with a FIN bit set can cause two state transitions for a sending
the Ready state to the Send state, and from the Send state to the stream: from the "Ready" state to the "Send" state, and from the
Data Sent state. "Send" state to the "Data Sent" state.
3.1. Sending Stream States 3.1. Sending Stream States
Figure 2 shows the states for the part of a stream that sends data to Figure 2 shows the states for the part of a stream that sends data to
a peer. a peer.
o o
| Create Stream (Sending) | Create Stream (Sending)
| Peer Creates Bidirectional Stream | Peer Creates Bidirectional Stream
v v
skipping to change at page 18, line 5 skipping to change at page 17, line 5
Sending the first STREAM or STREAM_DATA_BLOCKED frame causes a Sending the first STREAM or STREAM_DATA_BLOCKED frame causes a
sending part of a stream to enter the "Send" state. An sending part of a stream to enter the "Send" state. An
implementation might choose to defer allocating a stream ID to a implementation might choose to defer allocating a stream ID to a
stream until it sends the first STREAM frame and enters this state, stream until it sends the first STREAM frame and enters this state,
which can allow for better stream prioritization. which can allow for better stream prioritization.
The sending part of a bidirectional stream initiated by a peer (type The sending part of a bidirectional stream initiated by a peer (type
0 for a server, type 1 for a client) starts in the "Ready" state when 0 for a server, type 1 for a client) starts in the "Ready" state when
the receiving part is created. the receiving part is created.
In the "Send" state, an endpoint transmits - and retransmits as In the "Send" state, an endpoint transmits -- and retransmits as
necessary - stream data in STREAM frames. The endpoint respects the necessary -- stream data in STREAM frames. The endpoint respects the
flow control limits set by its peer, and continues to accept and flow control limits set by its peer and continues to accept and
process MAX_STREAM_DATA frames. An endpoint in the "Send" state process MAX_STREAM_DATA frames. An endpoint in the "Send" state
generates STREAM_DATA_BLOCKED frames if it is blocked from sending by generates STREAM_DATA_BLOCKED frames if it is blocked from sending by
stream flow control limits (Section 4.1). stream flow control limits (Section 4.1).
After the application indicates that all stream data has been sent After the application indicates that all stream data has been sent
and a STREAM frame containing the FIN bit is sent, the sending part and a STREAM frame containing the FIN bit is sent, the sending part
of the stream enters the "Data Sent" state. From this state, the of the stream enters the "Data Sent" state. From this state, the
endpoint only retransmits stream data as necessary. The endpoint endpoint only retransmits stream data as necessary. The endpoint
does not need to check flow control limits or send does not need to check flow control limits or send
STREAM_DATA_BLOCKED frames for a stream in this state. STREAM_DATA_BLOCKED frames for a stream in this state.
MAX_STREAM_DATA frames might be received until the peer receives the MAX_STREAM_DATA frames might be received until the peer receives the
final stream offset. The endpoint can safely ignore any final stream offset. The endpoint can safely ignore any
MAX_STREAM_DATA frames it receives from its peer for a stream in this MAX_STREAM_DATA frames it receives from its peer for a stream in this
state. state.
Once all stream data has been successfully acknowledged, the sending Once all stream data has been successfully acknowledged, the sending
part of the stream enters the "Data Recvd" state, which is a terminal part of the stream enters the "Data Recvd" state, which is a terminal
state. state.
From any of the "Ready", "Send", or "Data Sent" states, an From any state that is one of "Ready", "Send", or "Data Sent", an
application can signal that it wishes to abandon transmission of application can signal that it wishes to abandon transmission of
stream data. Alternatively, an endpoint might receive a STOP_SENDING stream data. Alternatively, an endpoint might receive a STOP_SENDING
frame from its peer. In either case, the endpoint sends a frame from its peer. In either case, the endpoint sends a
RESET_STREAM frame, which causes the stream to enter the "Reset Sent" RESET_STREAM frame, which causes the stream to enter the "Reset Sent"
state. state.
An endpoint MAY send a RESET_STREAM as the first frame that mentions An endpoint MAY send a RESET_STREAM as the first frame that mentions
a stream; this causes the sending part of that stream to open and a stream; this causes the sending part of that stream to open and
then immediately transition to the "Reset Sent" state. then immediately transition to the "Reset Sent" state.
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In the "Recv" state, the endpoint receives STREAM and In the "Recv" state, the endpoint receives STREAM and
STREAM_DATA_BLOCKED frames. Incoming data is buffered and can be STREAM_DATA_BLOCKED frames. Incoming data is buffered and can be
reassembled into the correct order for delivery to the application. reassembled into the correct order for delivery to the application.
As data is consumed by the application and buffer space becomes As data is consumed by the application and buffer space becomes
available, the endpoint sends MAX_STREAM_DATA frames to allow the available, the endpoint sends MAX_STREAM_DATA frames to allow the
peer to send more data. peer to send more data.
When a STREAM frame with a FIN bit is received, the final size of the When a STREAM frame with a FIN bit is received, the final size of the
stream is known; see Section 4.5. The receiving part of the stream stream is known; see Section 4.5. The receiving part of the stream
then enters the "Size Known" state. In this state, the endpoint no then enters the "Size Known" state. In this state, the endpoint no
longer needs to send MAX_STREAM_DATA frames, it only receives any longer needs to send MAX_STREAM_DATA frames; it only receives any
retransmissions of stream data. retransmissions of stream data.
Once all data for the stream has been received, the receiving part Once all data for the stream has been received, the receiving part
enters the "Data Recvd" state. This might happen as a result of enters the "Data Recvd" state. This might happen as a result of
receiving the same STREAM frame that causes the transition to "Size receiving the same STREAM frame that causes the transition to "Size
Known". After all data has been received, any STREAM or Known". After all data has been received, any STREAM or
STREAM_DATA_BLOCKED frames for the stream can be discarded. STREAM_DATA_BLOCKED frames for the stream can be discarded.
The "Data Recvd" state persists until stream data has been delivered The "Data Recvd" state persists until stream data has been delivered
to the application. Once stream data has been delivered, the stream to the application. Once stream data has been delivered, the stream
enters the "Data Read" state, which is a terminal state. enters the "Data Read" state, which is a terminal state.
Receiving a RESET_STREAM frame in the "Recv" or "Size Known" states Receiving a RESET_STREAM frame in the "Recv" or "Size Known" state
causes the stream to enter the "Reset Recvd" state. This might cause causes the stream to enter the "Reset Recvd" state. This might cause
the delivery of stream data to the application to be interrupted. the delivery of stream data to the application to be interrupted.
It is possible that all stream data has already been received when a It is possible that all stream data has already been received when a
RESET_STREAM is received (that is, in the "Data Recvd" state). RESET_STREAM is received (that is, in the "Data Recvd" state).
Similarly, it is possible for remaining stream data to arrive after Similarly, it is possible for remaining stream data to arrive after
receiving a RESET_STREAM frame (the "Reset Recvd" state). An receiving a RESET_STREAM frame (the "Reset Recvd" state). An
implementation is free to manage this situation as it chooses. implementation is free to manage this situation as it chooses.
Sending RESET_STREAM means that an endpoint cannot guarantee delivery Sending a RESET_STREAM means that an endpoint cannot guarantee
of stream data; however there is no requirement that stream data not delivery of stream data; however, there is no requirement that stream
be delivered if a RESET_STREAM is received. An implementation MAY data not be delivered if a RESET_STREAM is received. An
interrupt delivery of stream data, discard any data that was not implementation MAY interrupt delivery of stream data, discard any
consumed, and signal the receipt of the RESET_STREAM. A RESET_STREAM data that was not consumed, and signal the receipt of the
signal might be suppressed or withheld if stream data is completely RESET_STREAM. A RESET_STREAM signal might be suppressed or withheld
received and is buffered to be read by the application. If the if stream data is completely received and is buffered to be read by
RESET_STREAM is suppressed, the receiving part of the stream remains the application. If the RESET_STREAM is suppressed, the receiving
in "Data Recvd". part of the stream remains in "Data Recvd".
Once the application receives the signal indicating that the stream Once the application receives the signal indicating that the stream
was reset, the receiving part of the stream transitions to the "Reset was reset, the receiving part of the stream transitions to the "Reset
Read" state, which is a terminal state. Read" state, which is a terminal state.
3.3. Permitted Frame Types 3.3. Permitted Frame Types
The sender of a stream sends just three frame types that affect the The sender of a stream sends just three frame types that affect the
state of a stream at either sender or receiver: STREAM state of a stream at either the sender or the receiver: STREAM
(Section 19.8), STREAM_DATA_BLOCKED (Section 19.13), and RESET_STREAM (Section 19.8), STREAM_DATA_BLOCKED (Section 19.13), and RESET_STREAM
(Section 19.4). (Section 19.4).
A sender MUST NOT send any of these frames from a terminal state A sender MUST NOT send any of these frames from a terminal state
("Data Recvd" or "Reset Recvd"). A sender MUST NOT send a STREAM or ("Data Recvd" or "Reset Recvd"). A sender MUST NOT send a STREAM or
STREAM_DATA_BLOCKED frame for a stream in the "Reset Sent" state or STREAM_DATA_BLOCKED frame for a stream in the "Reset Sent" state or
any terminal state, that is, after sending a RESET_STREAM frame. A any terminal state -- that is, after sending a RESET_STREAM frame. A
receiver could receive any of these three frames in any state, due to receiver could receive any of these three frames in any state, due to
the possibility of delayed delivery of packets carrying them. the possibility of delayed delivery of packets carrying them.
The receiver of a stream sends MAX_STREAM_DATA (Section 19.10) and The receiver of a stream sends MAX_STREAM_DATA frames (Section 19.10)
STOP_SENDING frames (Section 19.5). and STOP_SENDING frames (Section 19.5).
The receiver only sends MAX_STREAM_DATA in the "Recv" state. A The receiver only sends MAX_STREAM_DATA frames in the "Recv" state.
receiver MAY send STOP_SENDING in any state where it has not received A receiver MAY send a STOP_SENDING frame in any state where it has
a RESET_STREAM frame; that is states other than "Reset Recvd" or not received a RESET_STREAM frame -- that is, states other than
"Reset Read". However there is little value in sending a "Reset Recvd" or "Reset Read". However, there is little value in
STOP_SENDING frame in the "Data Recvd" state, since all stream data sending a STOP_SENDING frame in the "Data Recvd" state, as all stream
has been received. A sender could receive either of these two frames data has been received. A sender could receive either of these two
in any state as a result of delayed delivery of packets. types of frames in any state as a result of delayed delivery of
packets.
3.4. Bidirectional Stream States 3.4. Bidirectional Stream States
A bidirectional stream is composed of sending and receiving parts. A bidirectional stream is composed of sending and receiving parts.
Implementations can represent states of the bidirectional stream as Implementations can represent states of the bidirectional stream as
composites of sending and receiving stream states. The simplest composites of sending and receiving stream states. The simplest
model presents the stream as "open" when either sending or receiving model presents the stream as "open" when either sending or receiving
parts are in a non-terminal state and "closed" when both sending and parts are in a non-terminal state and "closed" when both sending and
receiving streams are in terminal states. receiving streams are in terminal states.
Table 2 shows a more complex mapping of bidirectional stream states Table 2 shows a more complex mapping of bidirectional stream states
that loosely correspond to the stream states in HTTP/2 [HTTP2]. This that loosely correspond to the stream states defined in HTTP/2
shows that multiple states on sending or receiving parts of streams [HTTP2]. This shows that multiple states on sending or receiving
are mapped to the same composite state. Note that this is just one parts of streams are mapped to the same composite state. Note that
possibility for such a mapping; this mapping requires that data is this is just one possibility for such a mapping; this mapping
acknowledged before the transition to a "closed" or "half-closed" requires that data be acknowledged before the transition to a
state. "closed" or "half-closed" state.
+-----------------------+---------------------+---------------------+ +----------------------+-----------------------+--------------------+
| Sending Part | Receiving Part | Composite State | | Sending Part | Receiving Part | Composite State |
+-----------------------+---------------------+---------------------+ +----------------------+-----------------------+--------------------+
| No Stream/Ready | No Stream/Recv *1 | idle | | No Stream / Ready | No Stream / Recv (*1) | idle |
| | | | | | | |
| Ready/Send/Data Sent | Recv/Size Known | open | | Ready / Send / Data | Recv / Size Known | open |
| | | | | Sent | | |
| Ready/Send/Data Sent | Data Recvd/Data | half-closed | | | | |
| | Read | (remote) | | Ready / Send / Data | Data Recvd / Data | half-closed |
| | | | | Sent | Read | (remote) |
| Ready/Send/Data Sent | Reset Recvd/Reset | half-closed | | | | |
| | Read | (remote) | | Ready / Send / Data | Reset Recvd / Reset | half-closed |
| | | | | Sent | Read | (remote) |
| Data Recvd | Recv/Size Known | half-closed (local) | | | | |
| | | | | Data Recvd | Recv / Size Known | half-closed |
| Reset Sent/Reset | Recv/Size Known | half-closed (local) | | | | (local) |
| Recvd | | | | | | |
| | | | | Reset Sent / Reset | Recv / Size Known | half-closed |
| Reset Sent/Reset | Data Recvd/Data | closed | | Recvd | | (local) |
| Recvd | Read | | | | | |
| | | | | Reset Sent / Reset | Data Recvd / Data | closed |
| Reset Sent/Reset | Reset Recvd/Reset | closed | | Recvd | Read | |
| Recvd | Read | | | | | |
| | | | | Reset Sent / Reset | Reset Recvd / Reset | closed |
| Data Recvd | Data Recvd/Data | closed | | Recvd | Read | |
| | Read | | | | | |
| | | | | Data Recvd | Data Recvd / Data | closed |
| Data Recvd | Reset Recvd/Reset | closed | | | Read | |
| | Read | | | | | |
+-----------------------+---------------------+---------------------+ | Data Recvd | Reset Recvd / Reset | closed |
| | Read | |
+----------------------+-----------------------+--------------------+
Table 2: Possible Mapping of Stream States to HTTP/2 Table 2: Possible Mapping of Stream States to HTTP/2
Note (*1): A stream is considered "idle" if it has not yet been Note (*1): A stream is considered "idle" if it has not yet been
created, or if the receiving part of the stream is in the "Recv" created or if the receiving part of the stream is in the "Recv"
state without yet having received any frames. state without yet having received any frames.
3.5. Solicited State Transitions 3.5. Solicited State Transitions
If an application is no longer interested in the data it is receiving If an application is no longer interested in the data it is receiving
on a stream, it can abort reading the stream and specify an on a stream, it can abort reading the stream and specify an
application error code. application error code.
If the stream is in the "Recv" or "Size Known" states, the transport If the stream is in the "Recv" or "Size Known" state, the transport
SHOULD signal this by sending a STOP_SENDING frame to prompt closure SHOULD signal this by sending a STOP_SENDING frame to prompt closure
of the stream in the opposite direction. This typically indicates of the stream in the opposite direction. This typically indicates
that the receiving application is no longer reading data it receives that the receiving application is no longer reading data it receives
from the stream, but it is not a guarantee that incoming data will be from the stream, but it is not a guarantee that incoming data will be
ignored. ignored.
STREAM frames received after sending a STOP_SENDING frame are still STREAM frames received after sending a STOP_SENDING frame are still
counted toward connection and stream flow control, even though these counted toward connection and stream flow control, even though these
frames can be discarded upon receipt. frames can be discarded upon receipt.
A STOP_SENDING frame requests that the receiving endpoint send a A STOP_SENDING frame requests that the receiving endpoint send a
RESET_STREAM frame. An endpoint that receives a STOP_SENDING frame RESET_STREAM frame. An endpoint that receives a STOP_SENDING frame
MUST send a RESET_STREAM frame if the stream is in the Ready or Send MUST send a RESET_STREAM frame if the stream is in the "Ready" or
state. If the stream is in the "Data Sent" state, the endpoint MAY "Send" state. If the stream is in the "Data Sent" state, the
defer sending the RESET_STREAM frame until the packets containing endpoint MAY defer sending the RESET_STREAM frame until the packets
outstanding data are acknowledged or declared lost. If any containing outstanding data are acknowledged or declared lost. If
outstanding data is declared lost, the endpoint SHOULD send a any outstanding data is declared lost, the endpoint SHOULD send a
RESET_STREAM frame instead of retransmitting the data. RESET_STREAM frame instead of retransmitting the data.
An endpoint SHOULD copy the error code from the STOP_SENDING frame to An endpoint SHOULD copy the error code from the STOP_SENDING frame to
the RESET_STREAM frame it sends, but can use any application error the RESET_STREAM frame it sends, but it can use any application error
code. An endpoint that sends a STOP_SENDING frame MAY ignore the code. An endpoint that sends a STOP_SENDING frame MAY ignore the
error code in any RESET_STREAM frames subsequently received for that error code in any RESET_STREAM frames subsequently received for that
stream. stream.
STOP_SENDING SHOULD only be sent for a stream that has not been reset STOP_SENDING SHOULD only be sent for a stream that has not been reset
by the peer. STOP_SENDING is most useful for streams in the "Recv" by the peer. STOP_SENDING is most useful for streams in the "Recv"
or "Size Known" states. or "Size Known" state.
An endpoint is expected to send another STOP_SENDING frame if a An endpoint is expected to send another STOP_SENDING frame if a
packet containing a previous STOP_SENDING is lost. However, once packet containing a previous STOP_SENDING is lost. However, once
either all stream data or a RESET_STREAM frame has been received for either all stream data or a RESET_STREAM frame has been received for
the stream - that is, the stream is in any state other than "Recv" or the stream -- that is, the stream is in any state other than "Recv"
"Size Known" - sending a STOP_SENDING frame is unnecessary. or "Size Known" -- sending a STOP_SENDING frame is unnecessary.
An endpoint that wishes to terminate both directions of a An endpoint that wishes to terminate both directions of a
bidirectional stream can terminate one direction by sending a bidirectional stream can terminate one direction by sending a
RESET_STREAM frame, and it can encourage prompt termination in the RESET_STREAM frame, and it can encourage prompt termination in the
opposite direction by sending a STOP_SENDING frame. opposite direction by sending a STOP_SENDING frame.
4. Flow Control 4. Flow Control
Receivers need to limit the amount of data that they are required to Receivers need to limit the amount of data that they are required to
buffer, in order to prevent a fast sender from overwhelming them or a buffer, in order to prevent a fast sender from overwhelming them or a
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RESET_STREAM frame, and it can encourage prompt termination in the RESET_STREAM frame, and it can encourage prompt termination in the
opposite direction by sending a STOP_SENDING frame. opposite direction by sending a STOP_SENDING frame.
4. Flow Control 4. Flow Control
Receivers need to limit the amount of data that they are required to Receivers need to limit the amount of data that they are required to
buffer, in order to prevent a fast sender from overwhelming them or a buffer, in order to prevent a fast sender from overwhelming them or a
malicious sender from consuming a large amount of memory. To enable malicious sender from consuming a large amount of memory. To enable
a receiver to limit memory commitments for a connection, streams are a receiver to limit memory commitments for a connection, streams are
flow controlled both individually and across a connection as a whole. flow controlled both individually and across a connection as a whole.
A QUIC receiver controls the maximum amount of data the sender can A QUIC receiver controls the maximum amount of data the sender can
send on a stream as well as across all streams at any time, as send on a stream as well as across all streams at any time, as
described in Section 4.1 and Section 4.2. described in Sections 4.1 and 4.2.
Similarly, to limit concurrency within a connection, a QUIC endpoint Similarly, to limit concurrency within a connection, a QUIC endpoint
controls the maximum cumulative number of streams that its peer can controls the maximum cumulative number of streams that its peer can
initiate, as described in Section 4.6. initiate, as described in Section 4.6.
Data sent in CRYPTO frames is not flow controlled in the same way as Data sent in CRYPTO frames is not flow controlled in the same way as
stream data. QUIC relies on the cryptographic protocol stream data. QUIC relies on the cryptographic protocol
implementation to avoid excessive buffering of data; see [QUIC-TLS]. implementation to avoid excessive buffering of data; see [QUIC-TLS].
To avoid excessive buffering at multiple layers, QUIC implementations To avoid excessive buffering at multiple layers, QUIC implementations
SHOULD provide an interface for the cryptographic protocol SHOULD provide an interface for the cryptographic protocol
implementation to communicate its buffering limits. implementation to communicate its buffering limits.
4.1. Data Flow Control 4.1. Data Flow Control
QUIC employs a limit-based flow-control scheme where a receiver QUIC employs a limit-based flow control scheme where a receiver
advertises the limit of total bytes it is prepared to receive on a advertises the limit of total bytes it is prepared to receive on a
given stream or for the entire connection. This leads to two levels given stream or for the entire connection. This leads to two levels
of data flow control in QUIC: of data flow control in QUIC:
o Stream flow control, which prevents a single stream from consuming o Stream flow control, which prevents a single stream from consuming
the entire receive buffer for a connection by limiting the amount the entire receive buffer for a connection by limiting the amount
of data that can be sent on each stream. of data that can be sent on each stream.
o Connection flow control, which prevents senders from exceeding a o Connection flow control, which prevents senders from exceeding a
receiver's buffer capacity for the connection, by limiting the receiver's buffer capacity for the connection by limiting the
total bytes of stream data sent in STREAM frames on all streams. total bytes of stream data sent in STREAM frames on all streams.
Senders MUST NOT send data in excess of either limit. Senders MUST NOT send data in excess of either limit.
A receiver sets initial limits for all streams through transport A receiver sets initial limits for all streams through transport
parameters during the handshake (Section 7.4). Subsequently, a parameters during the handshake (Section 7.4). Subsequently, a
receiver sends MAX_STREAM_DATA (Section 19.10) or MAX_DATA receiver sends MAX_STREAM_DATA frames (Section 19.10) or MAX_DATA
(Section 19.9) frames to the sender to advertise larger limits. frames (Section 19.9) to the sender to advertise larger limits.
A receiver can advertise a larger limit for a stream by sending a A receiver can advertise a larger limit for a stream by sending a
MAX_STREAM_DATA frame with the corresponding stream ID. A MAX_STREAM_DATA frame with the corresponding stream ID. A
MAX_STREAM_DATA frame indicates the maximum absolute byte offset of a MAX_STREAM_DATA frame indicates the maximum absolute byte offset of a
stream. A receiver could determine the flow control offset to be stream. A receiver could determine the flow control offset to be
advertised based on the current offset of data consumed on that advertised based on the current offset of data consumed on that
stream. stream.
A receiver can advertise a larger limit for a connection by sending a A receiver can advertise a larger limit for a connection by sending a
MAX_DATA frame, which indicates the maximum of the sum of the MAX_DATA frame, which indicates the maximum of the sum of the
absolute byte offsets of all streams. A receiver maintains a absolute byte offsets of all streams. A receiver maintains a
cumulative sum of bytes received on all streams, which is used to cumulative sum of bytes received on all streams, which is used to
check for violations of the advertised connection or stream data check for violations of the advertised connection or stream data
limits. A receiver could determine the maximum data limit to be limits. A receiver could determine the maximum data limit to be
advertised based on the sum of bytes consumed on all streams. advertised based on the sum of bytes consumed on all streams.
Once a receiver advertises a limit for the connection or a stream, it Once a receiver advertises a limit for the connection or a stream, it
is not an error to advertise a smaller limit, but the smaller limit is not an error to advertise a smaller limit, but the smaller limit
has no effect. has no effect.
A receiver MUST close the connection with a FLOW_CONTROL_ERROR error A receiver MUST close the connection with an error of type
(Section 11) if the sender violates the advertised connection or FLOW_CONTROL_ERROR if the sender violates the advertised connection
stream data limits. or stream data limits; see Section 11 for details on error handling.
A sender MUST ignore any MAX_STREAM_DATA or MAX_DATA frames that do A sender MUST ignore any MAX_STREAM_DATA or MAX_DATA frames that do
not increase flow control limits. not increase flow control limits.
If a sender has sent data up to the limit, it will be unable to send If a sender has sent data up to the limit, it will be unable to send
new data and is considered blocked. A sender SHOULD send a new data and is considered blocked. A sender SHOULD send a
STREAM_DATA_BLOCKED or DATA_BLOCKED frame to indicate to the receiver STREAM_DATA_BLOCKED or DATA_BLOCKED frame to indicate to the receiver
that it has data to write but is blocked by flow control limits. If that it has data to write but is blocked by flow control limits. If
a sender is blocked for a period longer than the idle timeout a sender is blocked for a period longer than the idle timeout
(Section 10.1), the receiver might close the connection even when the (Section 10.1), the receiver might close the connection even when the
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A blocked sender is not required to send STREAM_DATA_BLOCKED or A blocked sender is not required to send STREAM_DATA_BLOCKED or
DATA_BLOCKED frames. Therefore, a receiver MUST NOT wait for a DATA_BLOCKED frames. Therefore, a receiver MUST NOT wait for a
STREAM_DATA_BLOCKED or DATA_BLOCKED frame before sending a STREAM_DATA_BLOCKED or DATA_BLOCKED frame before sending a
MAX_STREAM_DATA or MAX_DATA frame; doing so could result in the MAX_STREAM_DATA or MAX_DATA frame; doing so could result in the
sender being blocked for the rest of the connection. Even if the sender being blocked for the rest of the connection. Even if the
sender sends these frames, waiting for them will result in the sender sender sends these frames, waiting for them will result in the sender
being blocked for at least an entire round trip. being blocked for at least an entire round trip.
When a sender receives credit after being blocked, it might be able When a sender receives credit after being blocked, it might be able
to send a large amount of data in response, resulting in short-term to send a large amount of data in response, resulting in short-term
congestion; see Section 7.7 in [QUIC-RECOVERY] for a discussion of congestion; see Section 7.7 of [QUIC-RECOVERY] for a discussion of
how a sender can avoid this congestion. how a sender can avoid this congestion.
4.3. Flow Control Performance 4.3. Flow Control Performance
If an endpoint cannot ensure that its peer always has available flow If an endpoint cannot ensure that its peer always has available flow
control credit that is greater than the peer's bandwidth-delay control credit that is greater than the peer's bandwidth-delay
product on this connection, its receive throughput will be limited by product on this connection, its receive throughput will be limited by
flow control. flow control.
Packet loss can cause gaps in the receive buffer, preventing the Packet loss can cause gaps in the receive buffer, preventing the
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receiver reliably, no matter how the stream is terminated. The final receiver reliably, no matter how the stream is terminated. The final
size is the sum of the Offset and Length fields of a STREAM frame size is the sum of the Offset and Length fields of a STREAM frame
with a FIN flag, noting that these fields might be implicit. with a FIN flag, noting that these fields might be implicit.
Alternatively, the Final Size field of a RESET_STREAM frame carries Alternatively, the Final Size field of a RESET_STREAM frame carries
this value. This guarantees that both endpoints agree on how much this value. This guarantees that both endpoints agree on how much
flow control credit was consumed by the sender on that stream. flow control credit was consumed by the sender on that stream.
An endpoint will know the final size for a stream when the receiving An endpoint will know the final size for a stream when the receiving
part of the stream enters the "Size Known" or "Reset Recvd" state part of the stream enters the "Size Known" or "Reset Recvd" state
(Section 3). The receiver MUST use the final size of the stream to (Section 3). The receiver MUST use the final size of the stream to
account for all bytes sent on the stream in its connection level flow account for all bytes sent on the stream in its connection-level flow
controller. controller.
An endpoint MUST NOT send data on a stream at or beyond the final An endpoint MUST NOT send data on a stream at or beyond the final
size. size.
Once a final size for a stream is known, it cannot change. If a Once a final size for a stream is known, it cannot change. If a
RESET_STREAM or STREAM frame is received indicating a change in the RESET_STREAM or STREAM frame is received indicating a change in the
final size for the stream, an endpoint SHOULD respond with a final size for the stream, an endpoint SHOULD respond with an error
FINAL_SIZE_ERROR error; see Section 11. A receiver SHOULD treat of type FINAL_SIZE_ERROR; see Section 11 for details on error
receipt of data at or beyond the final size as a FINAL_SIZE_ERROR handling. A receiver SHOULD treat receipt of data at or beyond the
error, even after a stream is closed. Generating these errors is not final size as an error of type FINAL_SIZE_ERROR, even after a stream
mandatory, because requiring that an endpoint generate these errors is closed. Generating these errors is not mandatory, because
also means that the endpoint needs to maintain the final size state requiring that an endpoint generate these errors also means that the
for closed streams, which could mean a significant state commitment. endpoint needs to maintain the final size state for closed streams,
which could mean a significant state commitment.
4.6. Controlling Concurrency 4.6. Controlling Concurrency
An endpoint limits the cumulative number of incoming streams a peer An endpoint limits the cumulative number of incoming streams a peer
can open. Only streams with a stream ID less than (max_stream * 4 + can open. Only streams with a stream ID less than "(max_streams * 4
initial_stream_id_for_type) can be opened; see Table 1. Initial + first_stream_id_of_type)" can be opened; see Table 1. Initial
limits are set in the transport parameters; see Section 18.2. limits are set in the transport parameters; see Section 18.2.
Subsequent limits are advertised using MAX_STREAMS frames; see Subsequent limits are advertised using MAX_STREAMS frames; see
Section 19.11. Separate limits apply to unidirectional and Section 19.11. Separate limits apply to unidirectional and
bidirectional streams. bidirectional streams.
If a max_streams transport parameter or a MAX_STREAMS frame is If a max_streams transport parameter or a MAX_STREAMS frame is
received with a value greater than 2^60, this would allow a maximum received with a value greater than 2^60, this would allow a maximum
stream ID that cannot be expressed as a variable-length integer; see stream ID that cannot be expressed as a variable-length integer; see
Section 16. If either is received, the connection MUST be closed Section 16. If either is received, the connection MUST be closed
immediately with a connection error of type TRANSPORT_PARAMETER_ERROR immediately with a connection error of type TRANSPORT_PARAMETER_ERROR
if the offending value was received in a transport parameter or of if the offending value was received in a transport parameter or of
type FRAME_ENCODING_ERROR if it was received in a frame; see type FRAME_ENCODING_ERROR if it was received in a frame; see
Section 10.2. Section 10.2.
Endpoints MUST NOT exceed the limit set by their peer. An endpoint Endpoints MUST NOT exceed the limit set by their peer. An endpoint
that receives a frame with a stream ID exceeding the limit it has that receives a frame with a stream ID exceeding the limit it has
sent MUST treat this as a connection error of type STREAM_LIMIT_ERROR sent MUST treat this as a connection error of type
(Section 11). STREAM_LIMIT_ERROR; see Section 11 for details on error handling.
Once a receiver advertises a stream limit using the MAX_STREAMS Once a receiver advertises a stream limit using the MAX_STREAMS
frame, advertising a smaller limit has no effect. A receiver MUST frame, advertising a smaller limit has no effect. MAX_STREAMS frames
ignore any MAX_STREAMS frame that does not increase the stream limit. that do not increase the stream limit MUST be ignored.
As with stream and connection flow control, this document leaves As with stream and connection flow control, this document leaves
implementations to decide when and how many streams should be implementations to decide when and how many streams should be
advertised to a peer via MAX_STREAMS. Implementations might choose advertised to a peer via MAX_STREAMS. Implementations might choose
to increase limits as streams are closed, to keep the number of to increase limits as streams are closed, to keep the number of
streams available to peers roughly consistent. streams available to peers roughly consistent.
An endpoint that is unable to open a new stream due to the peer's An endpoint that is unable to open a new stream due to the peer's
limits SHOULD send a STREAMS_BLOCKED frame (Section 19.14). This limits SHOULD send a STREAMS_BLOCKED frame (Section 19.14). This
signal is considered useful for debugging. An endpoint MUST NOT wait signal is considered useful for debugging. An endpoint MUST NOT wait
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Packets with long headers include Source Connection ID and Packets with long headers include Source Connection ID and
Destination Connection ID fields. These fields are used to set the Destination Connection ID fields. These fields are used to set the
connection IDs for new connections; see Section 7.2 for details. connection IDs for new connections; see Section 7.2 for details.
Packets with short headers (Section 17.3) only include the Packets with short headers (Section 17.3) only include the
Destination Connection ID and omit the explicit length. The length Destination Connection ID and omit the explicit length. The length
of the Destination Connection ID field is expected to be known to of the Destination Connection ID field is expected to be known to
endpoints. Endpoints using a load balancer that routes based on endpoints. Endpoints using a load balancer that routes based on
connection ID could agree with the load balancer on a fixed length connection ID could agree with the load balancer on a fixed length
for connection IDs, or agree on an encoding scheme. A fixed portion for connection IDs or agree on an encoding scheme. A fixed portion
could encode an explicit length, which allows the entire connection could encode an explicit length, which allows the entire connection
ID to vary in length and still be used by the load balancer. ID to vary in length and still be used by the load balancer.
A Version Negotiation (Section 17.2.1) packet echoes the connection A Version Negotiation (Section 17.2.1) packet echoes the connection
IDs selected by the client, both to ensure correct routing toward the IDs selected by the client, both to ensure correct routing toward the
client and to demonstrate that the packet is in response to a packet client and to demonstrate that the packet is in response to a packet
sent by the client. sent by the client.
A zero-length connection ID can be used when a connection ID is not A zero-length connection ID can be used when a connection ID is not
needed to route to the correct endpoint. However, multiplexing needed to route to the correct endpoint. However, multiplexing
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certain that those protocol features are not in use. certain that those protocol features are not in use.
When an endpoint uses a non-zero-length connection ID, it needs to When an endpoint uses a non-zero-length connection ID, it needs to
ensure that the peer has a supply of connection IDs from which to ensure that the peer has a supply of connection IDs from which to
choose for packets sent to the endpoint. These connection IDs are choose for packets sent to the endpoint. These connection IDs are
supplied by the endpoint using the NEW_CONNECTION_ID frame supplied by the endpoint using the NEW_CONNECTION_ID frame
(Section 19.15). (Section 19.15).
5.1.1. Issuing Connection IDs 5.1.1. Issuing Connection IDs
Each Connection ID has an associated sequence number to assist in Each connection ID has an associated sequence number to assist in
detecting when NEW_CONNECTION_ID or RETIRE_CONNECTION_ID frames refer detecting when NEW_CONNECTION_ID or RETIRE_CONNECTION_ID frames refer
to the same value. The initial connection ID issued by an endpoint to the same value. The initial connection ID issued by an endpoint
is sent in the Source Connection ID field of the long packet header is sent in the Source Connection ID field of the long packet header
(Section 17.2) during the handshake. The sequence number of the (Section 17.2) during the handshake. The sequence number of the
initial connection ID is 0. If the preferred_address transport initial connection ID is 0. If the preferred_address transport
parameter is sent, the sequence number of the supplied connection ID parameter is sent, the sequence number of the supplied connection ID
is 1. is 1.
Additional connection IDs are communicated to the peer using Additional connection IDs are communicated to the peer using
NEW_CONNECTION_ID frames (Section 19.15). The sequence number on NEW_CONNECTION_ID frames (Section 19.15). The sequence number on
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An endpoint that selects a zero-length connection ID during the An endpoint that selects a zero-length connection ID during the
handshake cannot issue a new connection ID. A zero-length handshake cannot issue a new connection ID. A zero-length
Destination Connection ID field is used in all packets sent toward Destination Connection ID field is used in all packets sent toward
such an endpoint over any network path. such an endpoint over any network path.
5.1.2. Consuming and Retiring Connection IDs 5.1.2. Consuming and Retiring Connection IDs
An endpoint can change the connection ID it uses for a peer to An endpoint can change the connection ID it uses for a peer to
another available one at any time during the connection. An endpoint another available one at any time during the connection. An endpoint
consumes connection IDs in response to a migrating peer; see consumes connection IDs in response to a migrating peer; see
Section 9.5 for more. Section 9.5 for more details.
An endpoint maintains a set of connection IDs received from its peer, An endpoint maintains a set of connection IDs received from its peer,
any of which it can use when sending packets. When the endpoint any of which it can use when sending packets. When the endpoint
wishes to remove a connection ID from use, it sends a wishes to remove a connection ID from use, it sends a
RETIRE_CONNECTION_ID frame to its peer. Sending a RETIRE_CONNECTION_ID frame to its peer. Sending a
RETIRE_CONNECTION_ID frame indicates that the connection ID will not RETIRE_CONNECTION_ID frame indicates that the connection ID will not
be used again and requests that the peer replace it with a new be used again and requests that the peer replace it with a new
connection ID using a NEW_CONNECTION_ID frame. connection ID using a NEW_CONNECTION_ID frame.
As discussed in Section 9.5, endpoints limit the use of a connection As discussed in Section 9.5, endpoints limit the use of a connection
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connection ID to the set of active connection IDs. This ordering connection ID to the set of active connection IDs. This ordering
allows an endpoint to replace all active connection IDs without the allows an endpoint to replace all active connection IDs without the
possibility of a peer having no available connection IDs and without possibility of a peer having no available connection IDs and without
exceeding the limit the peer sets in the active_connection_id_limit exceeding the limit the peer sets in the active_connection_id_limit
transport parameter; see Section 18.2. Failure to cease using the transport parameter; see Section 18.2. Failure to cease using the
connection IDs when requested can result in connection failures, as connection IDs when requested can result in connection failures, as
the issuing endpoint might be unable to continue using the connection the issuing endpoint might be unable to continue using the connection
IDs with the active connection. IDs with the active connection.
An endpoint SHOULD limit the number of connection IDs it has retired An endpoint SHOULD limit the number of connection IDs it has retired
locally and have not yet been acknowledged. An endpoint SHOULD allow locally for which RETIRE_CONNECTION_ID frames have not yet been
for sending and tracking a number of RETIRE_CONNECTION_ID frames of acknowledged. An endpoint SHOULD allow for sending and tracking a
at least twice the active_connection_id limit. An endpoint MUST NOT number of RETIRE_CONNECTION_ID frames of at least twice the value of
forget a connection ID without retiring it, though it MAY choose to the active_connection_id_limit transport parameter. An endpoint MUST
treat having connection IDs in need of retirement that exceed this NOT forget a connection ID without retiring it, though it MAY choose
to treat having connection IDs in need of retirement that exceed this
limit as a connection error of type CONNECTION_ID_LIMIT_ERROR. limit as a connection error of type CONNECTION_ID_LIMIT_ERROR.
Endpoints SHOULD NOT issue updates of the Retire Prior To field Endpoints SHOULD NOT issue updates of the Retire Prior To field
before receiving RETIRE_CONNECTION_ID frames that retire all before receiving RETIRE_CONNECTION_ID frames that retire all
connection IDs indicated by the previous Retire Prior To value. connection IDs indicated by the previous Retire Prior To value.
5.2. Matching Packets to Connections 5.2. Matching Packets to Connections
Incoming packets are classified on receipt. Packets can either be Incoming packets are classified on receipt. Packets can either be
associated with an existing connection, or - for servers - associated with an existing connection or -- for servers --
potentially create a new connection. potentially create a new connection.
Endpoints try to associate a packet with an existing connection. If Endpoints try to associate a packet with an existing connection. If
the packet has a non-zero-length Destination Connection ID the packet has a non-zero-length Destination Connection ID
corresponding to an existing connection, QUIC processes that packet corresponding to an existing connection, QUIC processes that packet
accordingly. Note that more than one connection ID can be associated accordingly. Note that more than one connection ID can be associated
with a connection; see Section 5.1. with a connection; see Section 5.1.
If the Destination Connection ID is zero length and the addressing If the Destination Connection ID is zero length and the addressing
information in the packet matches the addressing information the information in the packet matches the addressing information the
endpoint uses to identify a connection with a zero-length connection endpoint uses to identify a connection with a zero-length connection
ID, QUIC processes the packet as part of that connection. An ID, QUIC processes the packet as part of that connection. An
endpoint can use just destination IP and port or both source and endpoint can use just destination IP and port or both source and
destination addresses for identification, though this makes destination addresses for identification, though this makes
connections fragile as described in Section 5.1. connections fragile as described in Section 5.1.
Endpoints can send a Stateless Reset (Section 10.3) for any packets Endpoints can send a Stateless Reset (Section 10.3) for any packets
that cannot be attributed to an existing connection. A stateless that cannot be attributed to an existing connection. A Stateless
reset allows a peer to more quickly identify when a connection Reset allows a peer to more quickly identify when a connection
becomes unusable. becomes unusable.
Packets that are matched to an existing connection are discarded if Packets that are matched to an existing connection are discarded if
the packets are inconsistent with the state of that connection. For the packets are inconsistent with the state of that connection. For
example, packets are discarded if they indicate a different protocol example, packets are discarded if they indicate a different protocol
version than that of the connection, or if the removal of packet version than that of the connection or if the removal of packet
protection is unsuccessful once the expected keys are available. protection is unsuccessful once the expected keys are available.
Invalid packets that lack strong integrity protection, such as Invalid packets that lack strong integrity protection, such as
Initial, Retry, or Version Negotiation, MAY be discarded. An Initial, Retry, or Version Negotiation, MAY be discarded. An
endpoint MUST generate a connection error if processing the contents endpoint MUST generate a connection error if processing the contents
of these packets prior to discovering an error, or fully revert any of these packets prior to discovering an error, or fully revert any
changes made during that processing. changes made during that processing.
5.2.1. Client Packet Handling 5.2.1. Client Packet Handling
Valid packets sent to clients always include a Destination Connection Valid packets sent to clients always include a Destination Connection
ID that matches a value the client selects. Clients that choose to ID that matches a value the client selects. Clients that choose to
receive zero-length connection IDs can use the local address and port receive zero-length connection IDs can use the local address and port
to identify a connection. Packets that do not match an existing to identify a connection. Packets that do not match an existing
connection, based on Destination Connection ID or, if this value is connection -- based on Destination Connection ID or, if this value is
zero-length, local IP address and port, are discarded. zero length, local IP address and port -- are discarded.
Due to packet reordering or loss, a client might receive packets for Due to packet reordering or loss, a client might receive packets for
a connection that are encrypted with a key it has not yet computed. a connection that are encrypted with a key it has not yet computed.
The client MAY drop these packets, or it MAY buffer them in
The client MAY drop these packets, or MAY buffer them in anticipation anticipation of later packets that allow it to compute the key.
of later packets that allow it to compute the key.
If a client receives a packet that uses a different version than it If a client receives a packet that uses a different version than it
initially selected, it MUST discard that packet. initially selected, it MUST discard that packet.
5.2.2. Server Packet Handling 5.2.2. Server Packet Handling
If a server receives a packet that indicates an unsupported version If a server receives a packet that indicates an unsupported version
and if the packet is large enough to initiate a new connection for and if the packet is large enough to initiate a new connection for
any supported version, the server SHOULD send a Version Negotiation any supported version, the server SHOULD send a Version Negotiation
packet as described in Section 6.1. A server MAY limit the number of packet as described in Section 6.1. A server MAY limit the number of
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Servers MUST drop smaller packets that specify unsupported versions. Servers MUST drop smaller packets that specify unsupported versions.
The first packet for an unsupported version can use different The first packet for an unsupported version can use different
semantics and encodings for any version-specific field. In semantics and encodings for any version-specific field. In
particular, different packet protection keys might be used for particular, different packet protection keys might be used for
different versions. Servers that do not support a particular version different versions. Servers that do not support a particular version
are unlikely to be able to decrypt the payload of the packet or are unlikely to be able to decrypt the payload of the packet or
properly interpret the result. Servers SHOULD respond with a Version properly interpret the result. Servers SHOULD respond with a Version
Negotiation packet, provided that the datagram is sufficiently long. Negotiation packet, provided that the datagram is sufficiently long.
Packets with a supported version, or no version field, are matched to Packets with a supported version, or no Version field, are matched to
a connection using the connection ID or - for packets with zero- a connection using the connection ID or -- for packets with zero-
length connection IDs - the local address and port. These packets length connection IDs -- the local address and port. These packets
are processed using the selected connection; otherwise, the server are processed using the selected connection; otherwise, the server
continues below. continues as described below.
If the packet is an Initial packet fully conforming with the If the packet is an Initial packet fully conforming with the
specification, the server proceeds with the handshake (Section 7). specification, the server proceeds with the handshake (Section 7).
This commits the server to the version that the client selected. This commits the server to the version that the client selected.
If a server refuses to accept a new connection, it SHOULD send an If a server refuses to accept a new connection, it SHOULD send an
Initial packet containing a CONNECTION_CLOSE frame with error code Initial packet containing a CONNECTION_CLOSE frame with error code
CONNECTION_REFUSED. CONNECTION_REFUSED.
If the packet is a 0-RTT packet, the server MAY buffer a limited If the packet is a 0-RTT packet, the server MAY buffer a limited
number of these packets in anticipation of a late-arriving Initial number of these packets in anticipation of a late-arriving Initial
packet. Clients are not able to send Handshake packets prior to packet. Clients are not able to send Handshake packets prior to
receiving a server response, so servers SHOULD ignore any such receiving a server response, so servers SHOULD ignore any such
packets. packets.
Servers MUST drop incoming packets under all other circumstances. Servers MUST drop incoming packets under all other circumstances.
5.2.3. Considerations for Simple Load Balancers 5.2.3. Considerations for Simple Load Balancers
A server deployment could load balance among servers using only A server deployment could load-balance among servers using only
source and destination IP addresses and ports. Changes to the source and destination IP addresses and ports. Changes to the
client's IP address or port could result in packets being forwarded client's IP address or port could result in packets being forwarded
to the wrong server. Such a server deployment could use one of the to the wrong server. Such a server deployment could use one of the
following methods for connection continuity when a client's address following methods for connection continuity when a client's address
changes. changes.
o Servers could use an out-of-band mechanism to forward packets to o Servers could use an out-of-band mechanism to forward packets to
the correct server based on Connection ID. the correct server based on connection ID.
o If servers can use a dedicated server IP address or port, other o If servers can use a dedicated server IP address or port, other
than the one that the client initially connects to, they could use than the one that the client initially connects to, they could use
the preferred_address transport parameter to request that clients the preferred_address transport parameter to request that clients
move connections to that dedicated address. Note that clients move connections to that dedicated address. Note that clients
could choose not to use the preferred address. could choose not to use the preferred address.
A server in a deployment that does not implement a solution to A server in a deployment that does not implement a solution to
maintain connection continuity when the client address changes SHOULD maintain connection continuity when the client address changes SHOULD
indicate migration is not supported using the indicate that migration is not supported by using the
disable_active_migration transport parameter. The disable_active_migration transport parameter. The
disable_active_migration transport parameter does not prohibit disable_active_migration transport parameter does not prohibit
connection migration after a client has acted on a preferred_address connection migration after a client has acted on a preferred_address
transport parameter. transport parameter.
Server deployments that use this simple form of load balancing MUST Server deployments that use this simple form of load balancing MUST
avoid the creation of a stateless reset oracle; see Section 21.11. avoid the creation of a stateless reset oracle; see Section 21.11.
5.3. Operations on Connections 5.3. Operations on Connections
This document does not define an API for QUIC, but instead defines a This document does not define an API for QUIC; it instead defines a
set of functions for QUIC connections that application protocols can set of functions for QUIC connections that application protocols can
rely upon. An application protocol can assume that an implementation rely upon. An application protocol can assume that an implementation
of QUIC provides an interface that includes the operations described of QUIC provides an interface that includes the operations described
in this section. An implementation designed for use with a specific in this section. An implementation designed for use with a specific
application protocol might provide only those operations that are application protocol might provide only those operations that are
used by that protocol. used by that protocol.
When implementing the client role, an application protocol can: When implementing the client role, an application protocol can:
o open a connection, which begins the exchange described in o open a connection, which begins the exchange described in
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from the client's resumption ticket and accept or reject Early from the client's resumption ticket and accept or reject Early
Data based on that information. Data based on that information.
In either role, an application protocol can: In either role, an application protocol can:
o configure minimum values for the initial number of permitted o configure minimum values for the initial number of permitted
streams of each type, as communicated in the transport parameters streams of each type, as communicated in the transport parameters
(Section 7.4); (Section 7.4);
o control resource allocation for receive buffers by setting flow o control resource allocation for receive buffers by setting flow
control limits both for streams and for the connection control limits both for streams and for the connection;
o identify whether the handshake has completed successfully or is o identify whether the handshake has completed successfully or is
still ongoing; still ongoing;
o keep a connection from silently closing, either by generating PING o keep a connection from silently closing, by either generating PING
frames (Section 19.2) or by requesting that the transport send frames (Section 19.2) or requesting that the transport send
additional frames before the idle timeout expires (Section 10.1); additional frames before the idle timeout expires (Section 10.1);
and and
o immediately close (Section 10.2) the connection. o immediately close (Section 10.2) the connection.
6. Version Negotiation 6. Version Negotiation
Version negotiation allows a server to indicate that it does not Version negotiation allows a server to indicate that it does not
support the version the client used. A server sends a Version support the version the client used. A server sends a Version
Negotiation packet in response to each packet that might initiate a Negotiation packet in response to each packet that might initiate a
skipping to change at page 37, line 29 skipping to change at page 36, line 46
A server MAY limit the number of Version Negotiation packets it A server MAY limit the number of Version Negotiation packets it
sends. For instance, a server that is able to recognize packets as sends. For instance, a server that is able to recognize packets as
0-RTT might choose not to send Version Negotiation packets in 0-RTT might choose not to send Version Negotiation packets in
response to 0-RTT packets with the expectation that it will response to 0-RTT packets with the expectation that it will
eventually receive an Initial packet. eventually receive an Initial packet.
6.2. Handling Version Negotiation Packets 6.2. Handling Version Negotiation Packets
Version Negotiation packets are designed to allow for functionality Version Negotiation packets are designed to allow for functionality
to be defined in the future that allows QUIC to negotiate the version to be defined in the future that allows QUIC to negotiate the version
of QUIC to use for a connection. Future standards-track of QUIC to use for a connection. Future Standards Track
specifications might change how implementations that support multiple specifications might change how implementations that support multiple
versions of QUIC react to Version Negotiation packets received in versions of QUIC react to Version Negotiation packets received in
response to an attempt to establish a connection using this version. response to an attempt to establish a connection using this version.
A client that supports only this version of QUIC MUST abandon the A client that supports only this version of QUIC MUST abandon the
current connection attempt if it receives a Version Negotiation current connection attempt if it receives a Version Negotiation
packet, with the following two exceptions. A client MUST discard any packet, with the following two exceptions. A client MUST discard any
Version Negotiation packet if it has received and successfully Version Negotiation packet if it has received and successfully
processed any other packet, including an earlier Version Negotiation processed any other packet, including an earlier Version Negotiation
packet. A client MUST discard a Version Negotiation packet that packet. A client MUST discard a Version Negotiation packet that
lists the QUIC version selected by the client. lists the QUIC version selected by the client.
How to perform version negotiation is left as future work defined by How to perform version negotiation is left as future work defined by
future standards-track specifications. In particular, that future future Standards Track specifications. In particular, that future
work will ensure robustness against version downgrade attacks; see work will ensure robustness against version downgrade attacks; see
Section 21.12. Section 21.12.
6.2.1. Version Negotiation Between Draft Versions
[[RFC editor: please remove this section before publication.]]
When a draft implementation receives a Version Negotiation packet, it
MAY use it to attempt a new connection with one of the versions
listed in the packet, instead of abandoning the current connection
attempt; see Section 6.2.
The client MUST check that the Destination and Source Connection ID
fields match the Source and Destination Connection ID fields in a
packet that the client sent. If this check fails, the packet MUST be
discarded.
Once the Version Negotiation packet is determined to be valid, the
client then selects an acceptable protocol version from the list
provided by the server. The client then attempts to create a new
connection using that version. The new connection MUST use a new
random Destination Connection ID different from the one it had
previously sent.
Note that this mechanism does not protect against downgrade attacks
and MUST NOT be used outside of draft implementations.
6.3. Using Reserved Versions 6.3. Using Reserved Versions
For a server to use a new version in the future, clients need to For a server to use a new version in the future, clients need to
correctly handle unsupported versions. Some version numbers correctly handle unsupported versions. Some version numbers
(0x?a?a?a?a as defined in Section 15) are reserved for inclusion in (0x?a?a?a?a, as defined in Section 15) are reserved for inclusion in
fields that contain version numbers. fields that contain version numbers.
Endpoints MAY add reserved versions to any field where unknown or Endpoints MAY add reserved versions to any field where unknown or
unsupported versions are ignored to test that a peer correctly unsupported versions are ignored to test that a peer correctly
ignores the value. For instance, an endpoint could include a ignores the value. For instance, an endpoint could include a
reserved version in a Version Negotiation packet; see Section 17.2.1. reserved version in a Version Negotiation packet; see Section 17.2.1.
Endpoints MAY send packets with a reserved version to test that a Endpoints MAY send packets with a reserved version to test that a
peer correctly discards the packet. peer correctly discards the packet.
7. Cryptographic and Transport Handshake 7. Cryptographic and Transport Handshake
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and uses TLS as described in [QUIC-TLS]; a different QUIC version and uses TLS as described in [QUIC-TLS]; a different QUIC version
could indicate that a different cryptographic handshake protocol is could indicate that a different cryptographic handshake protocol is
in use. in use.
QUIC provides reliable, ordered delivery of the cryptographic QUIC provides reliable, ordered delivery of the cryptographic
handshake data. QUIC packet protection is used to encrypt as much of handshake data. QUIC packet protection is used to encrypt as much of
the handshake protocol as possible. The cryptographic handshake MUST the handshake protocol as possible. The cryptographic handshake MUST
provide the following properties: provide the following properties:
o authenticated key exchange, where o authenticated key exchange, where
* a server is always authenticated, * a server is always authenticated,
* a client is optionally authenticated, * a client is optionally authenticated,
* every connection produces distinct and unrelated keys, and * every connection produces distinct and unrelated keys, and
* keying material is usable for packet protection for both 0-RTT * keying material is usable for packet protection for both 0-RTT
and 1-RTT packets and 1-RTT packets.
o authenticated exchange of values for transport parameters of both o authenticated exchange of values for transport parameters of both
endpoints, and confidentiality protection for server transport endpoints, and confidentiality protection for server transport
parameters (see Section 7.4) parameters (see Section 7.4).
o authenticated negotiation of an application protocol (TLS uses o authenticated negotiation of an application protocol (TLS uses
ALPN [ALPN] for this purpose) Application-Layer Protocol Negotiation (ALPN) [ALPN] for this
purpose).
The CRYPTO frame can be sent in different packet number spaces The CRYPTO frame can be sent in different packet number spaces
(Section 12.3). The offsets used by CRYPTO frames to ensure ordered (Section 12.3). The offsets used by CRYPTO frames to ensure ordered
delivery of cryptographic handshake data start from zero in each delivery of cryptographic handshake data start from zero in each
packet number space. packet number space.
Figure 4 shows a simplified handshake and the exchange of packets and Figure 4 shows a simplified handshake and the exchange of packets and
frames that are used to advance the handshake. Exchange of frames that are used to advance the handshake. Exchange of
application data during the handshake is enabled where possible, application data during the handshake is enabled where possible,
shown with a '*'. Once the handshake is complete, endpoints are able shown with an asterisk ("*"). Once the handshake is complete,
to exchange application data freely. endpoints are able to exchange application data freely.
Client Server Client Server
Initial (CRYPTO) Initial (CRYPTO)
0-RTT (*) ----------> 0-RTT (*) ---------->
Initial (CRYPTO) Initial (CRYPTO)
Handshake (CRYPTO) Handshake (CRYPTO)
<---------- 1-RTT (*) <---------- 1-RTT (*)
Handshake (CRYPTO) Handshake (CRYPTO)
1-RTT (*) ----------> 1-RTT (*) ---------->
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Section 8.1.2. Section 8.1.2.
Once any address validation exchanges are complete, the cryptographic Once any address validation exchanges are complete, the cryptographic
handshake is used to agree on cryptographic keys. The cryptographic handshake is used to agree on cryptographic keys. The cryptographic
handshake is carried in Initial (Section 17.2.2) and Handshake handshake is carried in Initial (Section 17.2.2) and Handshake
(Section 17.2.4) packets. (Section 17.2.4) packets.
Figure 5 provides an overview of the 1-RTT handshake. Each line Figure 5 provides an overview of the 1-RTT handshake. Each line
shows a QUIC packet with the packet type and packet number shown shows a QUIC packet with the packet type and packet number shown
first, followed by the frames that are typically contained in those first, followed by the frames that are typically contained in those
packets. So, for instance the first packet is of type Initial, with packets. For instance, the first packet is of type Initial, with
packet number 0, and contains a CRYPTO frame carrying the packet number 0, and contains a CRYPTO frame carrying the
ClientHello. ClientHello.
Multiple QUIC packets - even of different packet types - can be Multiple QUIC packets -- even of different packet types -- can be
coalesced into a single UDP datagram; see Section 12.2. As a result, coalesced into a single UDP datagram; see Section 12.2. As a result,
this handshake could consist of as few as 4 UDP datagrams, or any this handshake could consist of as few as four UDP datagrams, or any
number more (subject to limits inherent to the protocol, such as number more (subject to limits inherent to the protocol, such as
congestion control and anti-amplification). For instance, the congestion control and anti-amplification). For instance, the
server's first flight contains Initial packets, Handshake packets, server's first flight contains Initial packets, Handshake packets,
and "0.5-RTT data" in 1-RTT packets. and "0.5-RTT data" in 1-RTT packets.
Client Server Client Server
Initial[0]: CRYPTO[CH] -> Initial[0]: CRYPTO[CH] ->
Initial[0]: CRYPTO[SH] ACK[0] Initial[0]: CRYPTO[SH] ACK[0]
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The Destination Connection ID field from the first Initial packet The Destination Connection ID field from the first Initial packet
sent by a client is used to determine packet protection keys for sent by a client is used to determine packet protection keys for
Initial packets. These keys change after receiving a Retry packet; Initial packets. These keys change after receiving a Retry packet;
see Section 5.2 of [QUIC-TLS]. see Section 5.2 of [QUIC-TLS].
The client populates the Source Connection ID field with a value of The client populates the Source Connection ID field with a value of
its choosing and sets the Source Connection ID Length field to its choosing and sets the Source Connection ID Length field to
indicate the length. indicate the length.
The first flight of 0-RTT packets use the same Destination Connection 0-RTT packets in the first flight use the same Destination Connection
ID and Source Connection ID values as the client's first Initial ID and Source Connection ID values as the client's first Initial
packet. packet.
Upon first receiving an Initial or Retry packet from the server, the Upon first receiving an Initial or Retry packet from the server, the
client uses the Source Connection ID supplied by the server as the client uses the Source Connection ID supplied by the server as the
Destination Connection ID for subsequent packets, including any 0-RTT Destination Connection ID for subsequent packets, including any 0-RTT
packets. This means that a client might have to change the packets. This means that a client might have to change the
connection ID it sets in the Destination Connection ID field twice connection ID it sets in the Destination Connection ID field twice
during connection establishment: once in response to a Retry, and during connection establishment: once in response to a Retry packet
once in response to an Initial packet from the server. Once a client and once in response to an Initial packet from the server. Once a
has received a valid Initial packet from the server, it MUST discard client has received a valid Initial packet from the server, it MUST
any subsequent packet it receives on that connection with a different discard any subsequent packet it receives on that connection with a
Source Connection ID. different Source Connection ID.
A client MUST change the Destination Connection ID it uses for A client MUST change the Destination Connection ID it uses for
sending packets in response to only the first received Initial or sending packets in response to only the first received Initial or
Retry packet. A server MUST set the Destination Connection ID it Retry packet. A server MUST set the Destination Connection ID it
uses for sending packets based on the first received Initial packet. uses for sending packets based on the first received Initial packet.
Any further changes to the Destination Connection ID are only Any further changes to the Destination Connection ID are only
permitted if the values are taken from NEW_CONNECTION_ID frames; if permitted if the values are taken from NEW_CONNECTION_ID frames; if
subsequent Initial packets include a different Source Connection ID, subsequent Initial packets include a different Source Connection ID,
they MUST be discarded. This avoids unpredictable outcomes that they MUST be discarded. This avoids unpredictable outcomes that
might otherwise result from stateless processing of multiple Initial might otherwise result from stateless processing of multiple Initial
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original_destination_connection_id transport parameter; if the server original_destination_connection_id transport parameter; if the server
sent a Retry packet, this refers to the first Initial packet received sent a Retry packet, this refers to the first Initial packet received
before sending the Retry packet. If it sends a Retry packet, a before sending the Retry packet. If it sends a Retry packet, a
server also includes the Source Connection ID field from the Retry server also includes the Source Connection ID field from the Retry
packet in the retry_source_connection_id transport parameter. packet in the retry_source_connection_id transport parameter.
The values provided by a peer for these transport parameters MUST The values provided by a peer for these transport parameters MUST
match the values that an endpoint used in the Destination and Source match the values that an endpoint used in the Destination and Source
Connection ID fields of Initial packets that it sent (and received, Connection ID fields of Initial packets that it sent (and received,
for servers). Endpoints MUST validate that received transport for servers). Endpoints MUST validate that received transport
parameters match received Connection ID values. Including connection parameters match received connection ID values. Including connection
ID values in transport parameters and verifying them ensures that ID values in transport parameters and verifying them ensures that an
that an attacker cannot influence the choice of connection ID for a attacker cannot influence the choice of connection ID for a
successful connection by injecting packets carrying attacker-chosen successful connection by injecting packets carrying attacker-chosen
connection IDs during the handshake. connection IDs during the handshake.
An endpoint MUST treat absence of the initial_source_connection_id An endpoint MUST treat the absence of the
transport parameter from either endpoint or absence of the initial_source_connection_id transport parameter from either endpoint
original_destination_connection_id transport parameter from the or the absence of the original_destination_connection_id transport
server as a connection error of type TRANSPORT_PARAMETER_ERROR. parameter from the server as a connection error of type
TRANSPORT_PARAMETER_ERROR.
An endpoint MUST treat the following as a connection error of type An endpoint MUST treat the following as a connection error of type
TRANSPORT_PARAMETER_ERROR or PROTOCOL_VIOLATION: TRANSPORT_PARAMETER_ERROR or PROTOCOL_VIOLATION:
o absence of the retry_source_connection_id transport parameter from o absence of the retry_source_connection_id transport parameter from
the server after receiving a Retry packet, the server after receiving a Retry packet,
o presence of the retry_source_connection_id transport parameter o presence of the retry_source_connection_id transport parameter
when no Retry packet was received, or when no Retry packet was received, or
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Initial: DCID=S1, SCID=C1 -> Initial: DCID=S1, SCID=C1 ->
<- Retry: DCID=C1, SCID=S2 <- Retry: DCID=C1, SCID=S2
Initial: DCID=S2, SCID=C1 -> Initial: DCID=S2, SCID=C1 ->
<- Initial: DCID=C1, SCID=S3 <- Initial: DCID=C1, SCID=S3
... ...
1-RTT: DCID=S3 -> 1-RTT: DCID=S3 ->
<- 1-RTT: DCID=C1 <- 1-RTT: DCID=C1
Figure 8: Use of Connection IDs in a Handshake with Retry Figure 8: Use of Connection IDs in a Handshake with Retry
In both cases (Figure 7 and Figure 8), the client sets the value of In both cases (Figures 7 and 8), the client sets the value of the
the initial_source_connection_id transport parameter to "C1". initial_source_connection_id transport parameter to "C1".
When the handshake does not include a Retry (Figure 7), the server When the handshake does not include a Retry (Figure 7), the server
sets original_destination_connection_id to "S1" and sets original_destination_connection_id to "S1" (note that this value
initial_source_connection_id to "S3". In this case, the server does is chosen by the client) and initial_source_connection_id to "S3".
not include a retry_source_connection_id transport parameter. In this case, the server does not include a
retry_source_connection_id transport parameter.
When the handshake includes a Retry (Figure 8), the server sets When the handshake includes a Retry (Figure 8), the server sets
original_destination_connection_id to "S1", original_destination_connection_id to "S1",
retry_source_connection_id to "S2", and initial_source_connection_id retry_source_connection_id to "S2", and initial_source_connection_id
to "S3". to "S3".
7.4. Transport Parameters 7.4. Transport Parameters
During connection establishment, both endpoints make authenticated During connection establishment, both endpoints make authenticated
declarations of their transport parameters. Endpoints are required declarations of their transport parameters. Endpoints are required
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TRANSPORT_PARAMETER_ERROR. TRANSPORT_PARAMETER_ERROR.
An endpoint MUST NOT send a parameter more than once in a given An endpoint MUST NOT send a parameter more than once in a given
transport parameters extension. An endpoint SHOULD treat receipt of transport parameters extension. An endpoint SHOULD treat receipt of
duplicate transport parameters as a connection error of type duplicate transport parameters as a connection error of type
TRANSPORT_PARAMETER_ERROR. TRANSPORT_PARAMETER_ERROR.
Endpoints use transport parameters to authenticate the negotiation of Endpoints use transport parameters to authenticate the negotiation of
connection IDs during the handshake; see Section 7.3. connection IDs during the handshake; see Section 7.3.
Application Layer Protocol Negotiation (ALPN; see [ALPN]) allows ALPN (see [ALPN]) allows clients to offer multiple application
clients to offer multiple application protocols during connection protocols during connection establishment. The transport parameters
establishment. The transport parameters that a client includes that a client includes during the handshake apply to all application
during the handshake apply to all application protocols that the protocols that the client offers. Application protocols can
client offers. Application protocols can recommend values for recommend values for transport parameters, such as the initial flow
transport parameters, such as the initial flow control limits. control limits. However, application protocols that set constraints
However, application protocols that set constraints on values for on values for transport parameters could make it impossible for a
transport parameters could make it impossible for a client to offer client to offer multiple application protocols if these constraints
multiple application protocols if these constraints conflict. conflict.
7.4.1. Values of Transport Parameters for 0-RTT 7.4.1. Values of Transport Parameters for 0-RTT
Using 0-RTT depends on both client and server using protocol Using 0-RTT depends on both client and server using protocol
parameters that were negotiated from a previous connection. To parameters that were negotiated from a previous connection. To
enable 0-RTT, endpoints store the value of the server transport enable 0-RTT, endpoints store the values of the server transport
parameters from a connection and apply them to any 0-RTT packets that parameters with any session tickets it receives on the connection.
are sent in subsequent connections to that peer that use a session Endpoints also store any information required by the application
ticket issued on that connection. This information is stored with protocol or cryptographic handshake; see Section 4.6 of [QUIC-TLS].
any information required by the application protocol or cryptographic The values of stored transport parameters are used when attempting
handshake; see Section 4.6 of [QUIC-TLS]. 0-RTT using the session tickets.
Remembered transport parameters apply to the new connection until the Remembered transport parameters apply to the new connection until the
handshake completes and the client starts sending 1-RTT packets. handshake completes and the client starts sending 1-RTT packets.
Once the handshake completes, the client uses the transport Once the handshake completes, the client uses the transport
parameters established in the handshake. Not all transport parameters established in the handshake. Not all transport
parameters are remembered, as some do not apply to future connections parameters are remembered, as some do not apply to future connections
or they have no effect on use of 0-RTT. or they have no effect on the use of 0-RTT.
The definition of a new transport parameter (Section 7.4.2) MUST The definition of a new transport parameter (Section 7.4.2) MUST
specify whether storing the transport parameter for 0-RTT is specify whether storing the transport parameter for 0-RTT is
mandatory, optional, or prohibited. A client need not store a mandatory, optional, or prohibited. A client need not store a
transport parameter it cannot process. transport parameter it cannot process.
A client MUST NOT use remembered values for the following parameters: A client MUST NOT use remembered values for the following parameters:
ack_delay_exponent, max_ack_delay, initial_source_connection_id, ack_delay_exponent, max_ack_delay, initial_source_connection_id,
original_destination_connection_id, preferred_address, original_destination_connection_id, preferred_address,
retry_source_connection_id, and stateless_reset_token. The client retry_source_connection_id, and stateless_reset_token. The client
MUST use the server's new values in the handshake instead; if the MUST use the server's new values in the handshake instead; if the
server does not provide new values, the default value is used. server does not provide new values, the default values are used.
A client that attempts to send 0-RTT data MUST remember all other A client that attempts to send 0-RTT data MUST remember all other
transport parameters used by the server that it is able to process. transport parameters used by the server that it is able to process.
The server can remember these transport parameters, or store an The server can remember these transport parameters or can store an
integrity-protected copy of the values in the ticket and recover the integrity-protected copy of the values in the ticket and recover the
information when accepting 0-RTT data. A server uses the transport information when accepting 0-RTT data. A server uses the transport
parameters in determining whether to accept 0-RTT data. parameters in determining whether to accept 0-RTT data.
If 0-RTT data is accepted by the server, the server MUST NOT reduce If 0-RTT data is accepted by the server, the server MUST NOT reduce
any limits or alter any values that might be violated by the client any limits or alter any values that might be violated by the client
with its 0-RTT data. In particular, a server that accepts 0-RTT data with its 0-RTT data. In particular, a server that accepts 0-RTT data
MUST NOT set values for the following parameters (Section 18.2) that MUST NOT set values for the following parameters (Section 18.2) that
are smaller than the remembered value of the parameters. are smaller than the remembered values of the parameters.
o active_connection_id_limit o active_connection_id_limit
o initial_max_data o initial_max_data
o initial_max_stream_data_bidi_local o initial_max_stream_data_bidi_local
o initial_max_stream_data_bidi_remote o initial_max_stream_data_bidi_remote
o initial_max_stream_data_uni o initial_max_stream_data_uni
o initial_max_streams_bidi o initial_max_streams_bidi
o initial_max_streams_uni o initial_max_streams_uni
Omitting or setting a zero value for certain transport parameters can Omitting or setting a zero value for certain transport parameters can
result in 0-RTT data being enabled, but not usable. The applicable result in 0-RTT data being enabled but not usable. The applicable
subset of transport parameters that permit sending of application subset of transport parameters that permit the sending of application
data SHOULD be set to non-zero values for 0-RTT. This includes data SHOULD be set to non-zero values for 0-RTT. This includes
initial_max_data and either initial_max_streams_bidi and initial_max_data and either (1) initial_max_streams_bidi and
initial_max_stream_data_bidi_remote, or initial_max_streams_uni and initial_max_stream_data_bidi_remote or (2) initial_max_streams_uni
initial_max_stream_data_uni. and initial_max_stream_data_uni.
A server might provide larger initial stream flow control limits for
streams than the remembered values that a client applies when sending
0-RTT. Once the handshake completes, the client updates the flow
control limits on all sending streams using the updated values of
initial_max_stream_data_bidi_remote and initial_max_stream_data_uni.
A server MAY store and recover the previously sent values of the A server MAY store and recover the previously sent values of the
max_idle_timeout, max_udp_payload_size, and disable_active_migration max_idle_timeout, max_udp_payload_size, and disable_active_migration
parameters and reject 0-RTT if it selects smaller values. Lowering parameters and reject 0-RTT if it selects smaller values. Lowering
the values of these parameters while also accepting 0-RTT data could the values of these parameters while also accepting 0-RTT data could
degrade the performance of the connection. Specifically, lowering degrade the performance of the connection. Specifically, lowering
the max_udp_payload_size could result in dropped packets leading to the max_udp_payload_size could result in dropped packets, leading to
worse performance compared to rejecting 0-RTT data outright. worse performance compared to rejecting 0-RTT data outright.
A server MUST reject 0-RTT data if the restored values for transport A server MUST reject 0-RTT data if the restored values for transport
parameters cannot be supported. parameters cannot be supported.
When sending frames in 0-RTT packets, a client MUST only use When sending frames in 0-RTT packets, a client MUST only use
remembered transport parameters; importantly, it MUST NOT use updated remembered transport parameters; importantly, it MUST NOT use updated
values that it learns from the server's updated transport parameters values that it learns from the server's updated transport parameters
or from frames received in 1-RTT packets. Updated values of or from frames received in 1-RTT packets. Updated values of
transport parameters from the handshake apply only to 1-RTT packets. transport parameters from the handshake apply only to 1-RTT packets.
For instance, flow control limits from remembered transport For instance, flow control limits from remembered transport
parameters apply to all 0-RTT packets even if those values are parameters apply to all 0-RTT packets even if those values are
increased by the handshake or by frames sent in 1-RTT packets. A increased by the handshake or by frames sent in 1-RTT packets. A
server MAY treat use of updated transport parameters in 0-RTT as a server MAY treat the use of updated transport parameters in 0-RTT as
connection error of type PROTOCOL_VIOLATION. a connection error of type PROTOCOL_VIOLATION.
7.4.2. New Transport Parameters 7.4.2. New Transport Parameters
New transport parameters can be used to negotiate new protocol New transport parameters can be used to negotiate new protocol
behavior. An endpoint MUST ignore transport parameters that it does behavior. An endpoint MUST ignore transport parameters that it does
not support. Absence of a transport parameter therefore disables any not support. The absence of a transport parameter therefore disables
optional protocol feature that is negotiated using the parameter. As any optional protocol feature that is negotiated using the parameter.
described in Section 18.1, some identifiers are reserved in order to As described in Section 18.1, some identifiers are reserved in order
exercise this requirement. to exercise this requirement.
A client that does not understand a transport parameter can discard A client that does not understand a transport parameter can discard
it and attempt 0-RTT on subsequent connections. However, if the it and attempt 0-RTT on subsequent connections. However, if the
client adds support for a discarded transport parameter, it risks client adds support for a discarded transport parameter, it risks
violating the constraints that the transport parameter establishes if violating the constraints that the transport parameter establishes if
it attempts 0-RTT. New transport parameters can avoid this problem it attempts 0-RTT. New transport parameters can avoid this problem
by setting a default of the most conservative value. Clients can by setting a default of the most conservative value. Clients can
avoid this problem by remembering all parameters, even ones not avoid this problem by remembering all parameters, even those not
currently supported. currently supported.
New transport parameters can be registered according to the rules in New transport parameters can be registered according to the rules in
Section 22.3. Section 22.3.
7.5. Cryptographic Message Buffering 7.5. Cryptographic Message Buffering
Implementations need to maintain a buffer of CRYPTO data received out Implementations need to maintain a buffer of CRYPTO data received out
of order. Because there is no flow control of CRYPTO frames, an of order. Because there is no flow control of CRYPTO frames, an
endpoint could potentially force its peer to buffer an unbounded endpoint could potentially force its peer to buffer an unbounded
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peer is able to receive packets at the transport address that it peer is able to receive packets at the transport address that it
claims. Therefore, after receiving packets from an address that is claims. Therefore, after receiving packets from an address that is
not yet validated, an endpoint MUST limit the amount of data it sends not yet validated, an endpoint MUST limit the amount of data it sends
to the unvalidated address to three times the amount of data received to the unvalidated address to three times the amount of data received
from that address. This limit on the size of responses is known as from that address. This limit on the size of responses is known as
the anti-amplification limit. the anti-amplification limit.
Address validation is performed both during connection establishment Address validation is performed both during connection establishment
(see Section 8.1) and during connection migration (see Section 8.2). (see Section 8.1) and during connection migration (see Section 8.2).
8.1. Address Validation During Connection Establishment 8.1. Address Validation during Connection Establishment
Connection establishment implicitly provides address validation for Connection establishment implicitly provides address validation for
both endpoints. In particular, receipt of a packet protected with both endpoints. In particular, receipt of a packet protected with
Handshake keys confirms that the peer successfully processed an Handshake keys confirms that the peer successfully processed an
Initial packet. Once an endpoint has successfully processed a Initial packet. Once an endpoint has successfully processed a
Handshake packet from the peer, it can consider the peer address to Handshake packet from the peer, it can consider the peer address to
have been validated. have been validated.
Additionally, an endpoint MAY consider the peer address validated if Additionally, an endpoint MAY consider the peer address validated if
the peer uses a connection ID chosen by the endpoint and the the peer uses a connection ID chosen by the endpoint and the
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necessary. A client that sends padded datagrams allows the server to necessary. A client that sends padded datagrams allows the server to
send more data prior to completing address validation. send more data prior to completing address validation.
Loss of an Initial or Handshake packet from the server can cause a Loss of an Initial or Handshake packet from the server can cause a
deadlock if the client does not send additional Initial or Handshake deadlock if the client does not send additional Initial or Handshake
packets. A deadlock could occur when the server reaches its anti- packets. A deadlock could occur when the server reaches its anti-
amplification limit and the client has received acknowledgments for amplification limit and the client has received acknowledgments for
all the data it has sent. In this case, when the client has no all the data it has sent. In this case, when the client has no
reason to send additional packets, the server will be unable to send reason to send additional packets, the server will be unable to send
more data because it has not validated the client's address. To more data because it has not validated the client's address. To
prevent this deadlock, clients MUST send a packet on a probe timeout prevent this deadlock, clients MUST send a packet on a Probe Timeout
(PTO, see Section 6.2 of [QUIC-RECOVERY]). Specifically, the client (PTO); see Section 6.2 of [QUIC-RECOVERY]. Specifically, the client
MUST send an Initial packet in a UDP datagram that contains at least MUST send an Initial packet in a UDP datagram that contains at least
1200 bytes if it does not have Handshake keys, and otherwise send a 1200 bytes if it does not have Handshake keys, and otherwise send a
Handshake packet. Handshake packet.
A server might wish to validate the client address before starting A server might wish to validate the client address before starting
the cryptographic handshake. QUIC uses a token in the Initial packet the cryptographic handshake. QUIC uses a token in the Initial packet
to provide address validation prior to completing the handshake. to provide address validation prior to completing the handshake.
This token is delivered to the client during connection establishment This token is delivered to the client during connection establishment
with a Retry packet (see Section 8.1.2) or in a previous connection with a Retry packet (see Section 8.1.2) or in a previous connection
using the NEW_TOKEN frame (see Section 8.1.3). using the NEW_TOKEN frame (see Section 8.1.3).
In addition to sending limits imposed prior to address validation, In addition to sending limits imposed prior to address validation,
servers are also constrained in what they can send by the limits set servers are also constrained in what they can send by the limits set
by the congestion controller. Clients are only constrained by the by the congestion controller. Clients are only constrained by the
congestion controller. congestion controller.
8.1.1. Token Construction 8.1.1. Token Construction
A token sent in a NEW_TOKEN frame or a Retry packet MUST be A token sent in a NEW_TOKEN frame or a Retry packet MUST be
constructed in a way that allows the server to identify how it was constructed in a way that allows the server to identify how it was
provided to a client. These tokens are carried in the same field, provided to a client. These tokens are carried in the same field but
but require different handling from servers. require different handling from servers.
8.1.2. Address Validation using Retry Packets 8.1.2. Address Validation Using Retry Packets
Upon receiving the client's Initial packet, the server can request Upon receiving the client's Initial packet, the server can request
address validation by sending a Retry packet (Section 17.2.5) address validation by sending a Retry packet (Section 17.2.5)
containing a token. This token MUST be repeated by the client in all containing a token. This token MUST be repeated by the client in all
Initial packets it sends for that connection after it receives the Initial packets it sends for that connection after it receives the
Retry packet. Retry packet.
In response to processing an Initial containing a token that was In response to processing an Initial packet containing a token that
provided in a Retry packet, a server cannot send another Retry was provided in a Retry packet, a server cannot send another Retry
packet; it can only refuse the connection or permit it to proceed. packet; it can only refuse the connection or permit it to proceed.
As long as it is not possible for an attacker to generate a valid As long as it is not possible for an attacker to generate a valid
token for its own address (see Section 8.1.4) and the client is able token for its own address (see Section 8.1.4) and the client is able
to return that token, it proves to the server that it received the to return that token, it proves to the server that it received the
token. token.
A server can also use a Retry packet to defer the state and A server can also use a Retry packet to defer the state and
processing costs of connection establishment. Requiring the server processing costs of connection establishment. Requiring the server
to provide a different connection ID, along with the to provide a different connection ID, along with the
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connection to that server. connection to that server.
A token allows a server to correlate activity between the connection A token allows a server to correlate activity between the connection
where the token was issued and any connection where it is used. where the token was issued and any connection where it is used.
Clients that want to break continuity of identity with a server can Clients that want to break continuity of identity with a server can
discard tokens provided using the NEW_TOKEN frame. In comparison, a discard tokens provided using the NEW_TOKEN frame. In comparison, a
token obtained in a Retry packet MUST be used immediately during the token obtained in a Retry packet MUST be used immediately during the
connection attempt and cannot be used in subsequent connection connection attempt and cannot be used in subsequent connection
attempts. attempts.
A client SHOULD NOT reuse a NEW_TOKEN token for different connection A client SHOULD NOT reuse a token from a NEW_TOKEN frame for
attempts. Reusing a token allows connections to be linked by different connection attempts. Reusing a token allows connections to
entities on the network path; see Section 9.5. be linked by entities on the network path; see Section 9.5.
Clients might receive multiple tokens on a single connection. Aside Clients might receive multiple tokens on a single connection. Aside
from preventing linkability, any token can be used in any connection from preventing linkability, any token can be used in any connection
attempt. Servers can send additional tokens to either enable address attempt. Servers can send additional tokens to either enable address
validation for multiple connection attempts or to replace older validation for multiple connection attempts or replace older tokens
tokens that might become invalid. For a client, this ambiguity means that might become invalid. For a client, this ambiguity means that
that sending the most recent unused token is most likely to be sending the most recent unused token is most likely to be effective.
effective. Though saving and using older tokens has no negative Though saving and using older tokens have no negative consequences,
consequences, clients can regard older tokens as being less likely be clients can regard older tokens as being less likely to be useful to
useful to the server for address validation. the server for address validation.
When a server receives an Initial packet with an address validation When a server receives an Initial packet with an address validation
token, it MUST attempt to validate the token, unless it has already token, it MUST attempt to validate the token, unless it has already
completed address validation. If the token is invalid then the completed address validation. If the token is invalid, then the
server SHOULD proceed as if the client did not have a validated server SHOULD proceed as if the client did not have a validated
address, including potentially sending a Retry. Tokens provided with address, including potentially sending a Retry packet. Tokens
NEW_TOKEN frames and Retry packets can be distinguished by servers provided with NEW_TOKEN frames and Retry packets can be distinguished
(see Section 8.1.1), and the latter validated more strictly. If the by servers (see Section 8.1.1), and the latter can be validated more
validation succeeds, the server SHOULD then allow the handshake to strictly. If the validation succeeds, the server SHOULD then allow
proceed. the handshake to proceed.
Note: The rationale for treating the client as unvalidated rather Note: The rationale for treating the client as unvalidated rather
than discarding the packet is that the client might have received than discarding the packet is that the client might have received
the token in a previous connection using the NEW_TOKEN frame, and the token in a previous connection using the NEW_TOKEN frame, and
if the server has lost state, it might be unable to validate the if the server has lost state, it might be unable to validate the
token at all, leading to connection failure if the packet is token at all, leading to connection failure if the packet is
discarded. discarded.
In a stateless design, a server can use encrypted and authenticated In a stateless design, a server can use encrypted and authenticated
tokens to pass information to clients that the server can later tokens to pass information to clients that the server can later
recover and use to validate a client address. Tokens are not recover and use to validate a client address. Tokens are not
integrated into the cryptographic handshake and so they are not integrated into the cryptographic handshake, and so they are not
authenticated. For instance, a client might be able to reuse a authenticated. For instance, a client might be able to reuse a
token. To avoid attacks that exploit this property, a server can token. To avoid attacks that exploit this property, a server can
limit its use of tokens to only the information needed to validate limit its use of tokens to only the information needed to validate
client addresses. client addresses.
Clients MAY use tokens obtained on one connection for any connection Clients MAY use tokens obtained on one connection for any connection
attempt using the same version. When selecting a token to use, attempt using the same version. When selecting a token to use,
clients do not need to consider other properties of the connection clients do not need to consider other properties of the connection
that is being attempted, including the choice of possible application that is being attempted, including the choice of possible application
protocols, session tickets, or other connection properties. protocols, session tickets, or other connection properties.
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requires access to the integrity protection key for tokens. requires access to the integrity protection key for tokens.
There is no need for a single well-defined format for the token There is no need for a single well-defined format for the token
because the server that generates the token also consumes it. Tokens because the server that generates the token also consumes it. Tokens
sent in Retry packets SHOULD include information that allows the sent in Retry packets SHOULD include information that allows the
server to verify that the source IP address and port in client server to verify that the source IP address and port in client
packets remain constant. packets remain constant.
Tokens sent in NEW_TOKEN frames MUST include information that allows Tokens sent in NEW_TOKEN frames MUST include information that allows
the server to verify that the client IP address has not changed from the server to verify that the client IP address has not changed from
when the token was issued. Servers can use tokens from NEW_TOKEN in when the token was issued. Servers can use tokens from NEW_TOKEN
deciding not to send a Retry packet, even if the client address has frames in deciding not to send a Retry packet, even if the client
changed. If the client IP address has changed, the server MUST address has changed. If the client IP address has changed, the
adhere to the anti-amplification limit; see Section 8. Note that in server MUST adhere to the anti-amplification limit; see Section 8.
the presence of NAT, this requirement might be insufficient to Note that in the presence of NAT, this requirement might be
protect other hosts that share the NAT from amplification attack. insufficient to protect other hosts that share the NAT from
amplification attacks.
Attackers could replay tokens to use servers as amplifiers in DDoS Attackers could replay tokens to use servers as amplifiers in DDoS
attacks. To protect against such attacks, servers MUST ensure that attacks. To protect against such attacks, servers MUST ensure that
replay of tokens is prevented or limited. Servers SHOULD ensure that replay of tokens is prevented or limited. Servers SHOULD ensure that
tokens sent in Retry packets are only accepted for a short time, as tokens sent in Retry packets are only accepted for a short time, as
they are returned immediately by clients. Tokens that are provided they are returned immediately by clients. Tokens that are provided
in NEW_TOKEN frames (Section 19.7) need to be valid for longer, but in NEW_TOKEN frames (Section 19.7) need to be valid for longer but
SHOULD NOT be accepted multiple times. Servers are encouraged to SHOULD NOT be accepted multiple times. Servers are encouraged to
allow tokens to be used only once, if possible; tokens MAY include allow tokens to be used only once, if possible; tokens MAY include
additional information about clients to further narrow applicability additional information about clients to further narrow applicability
or reuse. or reuse.
8.2. Path Validation 8.2. Path Validation
Path validation is used by both peers during connection migration Path validation is used by both peers during connection migration
(see Section 9) to verify reachability after a change of address. In (see Section 9) to verify reachability after a change of address. In
path validation, endpoints test reachability between a specific local path validation, endpoints test reachability between a specific local
address and a specific peer address, where an address is the two- address and a specific peer address, where an address is the 2-tuple
tuple of IP address and port. of IP address and port.
Path validation tests that packets sent on a path to a peer are Path validation tests that packets sent on a path to a peer are
received by that peer. Path validation is used to ensure that received by that peer. Path validation is used to ensure that
packets received from a migrating peer do not carry a spoofed source packets received from a migrating peer do not carry a spoofed source
address. address.
Path validation does not validate that a peer can send in the return Path validation does not validate that a peer can send in the return
direction. Acknowledgments cannot be used for return path validation direction. Acknowledgments cannot be used for return path validation
because they contain insufficient entropy and might be spoofed. because they contain insufficient entropy and might be spoofed.
Endpoints independently determine reachability on each direction of a Endpoints independently determine reachability on each direction of a
path, and therefore return reachability can only be established by path, and therefore return reachability can only be established by
the peer. the peer.
Path validation can be used at any time by either endpoint. For Path validation can be used at any time by either endpoint. For
instance, an endpoint might check that a peer is still in possession instance, an endpoint might check that a peer is still in possession
of its address after a period of quiescence. of its address after a period of quiescence.
Path validation is not designed as a NAT traversal mechanism. Though Path validation is not designed as a NAT traversal mechanism. Though
the mechanism described here might be effective for the creation of the mechanism described here might be effective for the creation of
NAT bindings that support NAT traversal, the expectation is that one NAT bindings that support NAT traversal, the expectation is that one
or other peer is able to receive packets without first having sent a endpoint is able to receive packets without first having sent a
packet on that path. Effective NAT traversal needs additional packet on that path. Effective NAT traversal needs additional
synchronization mechanisms that are not provided here. synchronization mechanisms that are not provided here.
An endpoint MAY include other frames with the PATH_CHALLENGE and An endpoint MAY include other frames with the PATH_CHALLENGE and
PATH_RESPONSE frames used for path validation. In particular, an PATH_RESPONSE frames used for path validation. In particular, an
endpoint can include PADDING frames with a PATH_CHALLENGE frame for endpoint can include PADDING frames with a PATH_CHALLENGE frame for
Path Maximum Transmission Unit Discovery (PMTUD; see Section 14.2.1); Path Maximum Transmission Unit Discovery (PMTUD); see Section 14.2.1.
it can also include its own PATH_CHALLENGE frame with a PATH_RESPONSE An endpoint can also include its own PATH_CHALLENGE frame when
frame. sending a PATH_RESPONSE frame.
An endpoint uses a new connection ID for probes sent from a new local An endpoint uses a new connection ID for probes sent from a new local
address; see Section 9.5. When probing a new path, an endpoint can address; see Section 9.5. When probing a new path, an endpoint can
ensure that its peer has an unused connection ID available for ensure that its peer has an unused connection ID available for
responses. Sending NEW_CONNECTION_ID and PATH_CHALLENGE frames in responses. Sending NEW_CONNECTION_ID and PATH_CHALLENGE frames in
the same packet, if the peer's active_connection_id_limit permits, the same packet, if the peer's active_connection_id_limit permits,
ensures that an unused connection ID will be available to the peer ensures that an unused connection ID will be available to the peer
when sending a response. when sending a response.
An endpoint can choose to simultaneously probe multiple paths. The An endpoint can choose to simultaneously probe multiple paths. The
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8.2.2. Path Validation Responses 8.2.2. Path Validation Responses
On receiving a PATH_CHALLENGE frame, an endpoint MUST respond by On receiving a PATH_CHALLENGE frame, an endpoint MUST respond by
echoing the data contained in the PATH_CHALLENGE frame in a echoing the data contained in the PATH_CHALLENGE frame in a
PATH_RESPONSE frame. An endpoint MUST NOT delay transmission of a PATH_RESPONSE frame. An endpoint MUST NOT delay transmission of a
packet containing a PATH_RESPONSE frame unless constrained by packet containing a PATH_RESPONSE frame unless constrained by
congestion control. congestion control.
A PATH_RESPONSE frame MUST be sent on the network path where the A PATH_RESPONSE frame MUST be sent on the network path where the
PATH_CHALLENGE was received. This ensures that path validation by a PATH_CHALLENGE frame was received. This ensures that path validation
peer only succeeds if the path is functional in both directions. by a peer only succeeds if the path is functional in both directions.
This requirement MUST NOT be enforced by the endpoint that initiates This requirement MUST NOT be enforced by the endpoint that initiates
path validation as that would enable an attack on migration; see path validation, as that would enable an attack on migration; see
Section 9.3.3. Section 9.3.3.
An endpoint MUST expand datagrams that contain a PATH_RESPONSE frame An endpoint MUST expand datagrams that contain a PATH_RESPONSE frame
to at least the smallest allowed maximum datagram size of 1200 bytes. to at least the smallest allowed maximum datagram size of 1200 bytes.
This verifies that the path is able to carry datagrams of this size This verifies that the path is able to carry datagrams of this size
in both directions. However, an endpoint MUST NOT expand the in both directions. However, an endpoint MUST NOT expand the
datagram containing the PATH_RESPONSE if the resulting data exceeds datagram containing the PATH_RESPONSE if the resulting data exceeds
the anti-amplification limit. This is expected to only occur if the the anti-amplification limit. This is expected to only occur if the
received PATH_CHALLENGE was not sent in an expanded datagram. received PATH_CHALLENGE was not sent in an expanded datagram.
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additional PATH_RESPONSE frames. additional PATH_RESPONSE frames.
8.2.3. Successful Path Validation 8.2.3. Successful Path Validation
Path validation succeeds when a PATH_RESPONSE frame is received that Path validation succeeds when a PATH_RESPONSE frame is received that
contains the data that was sent in a previous PATH_CHALLENGE frame. contains the data that was sent in a previous PATH_CHALLENGE frame.
A PATH_RESPONSE frame received on any network path validates the path A PATH_RESPONSE frame received on any network path validates the path
on which the PATH_CHALLENGE was sent. on which the PATH_CHALLENGE was sent.
If an endpoint sends a PATH_CHALLENGE frame in a datagram that is not If an endpoint sends a PATH_CHALLENGE frame in a datagram that is not
expanded to at least 1200 bytes, and if the response to it validates expanded to at least 1200 bytes and if the response to it validates
the peer address, the path is validated but not the path MTU. As a the peer address, the path is validated but not the path MTU. As a
result, the endpoint can now send more than three times the amount of result, the endpoint can now send more than three times the amount of
data that has been received. However, the endpoint MUST initiate data that has been received. However, the endpoint MUST initiate
another path validation with an expanded datagram to verify that the another path validation with an expanded datagram to verify that the
path supports the required MTU. path supports the required MTU.
Receipt of an acknowledgment for a packet containing a PATH_CHALLENGE Receipt of an acknowledgment for a packet containing a PATH_CHALLENGE
frame is not adequate validation, since the acknowledgment can be frame is not adequate validation, since the acknowledgment can be
spoofed by a malicious peer. spoofed by a malicious peer.
8.2.4. Failed Path Validation 8.2.4. Failed Path Validation
Path validation only fails when the endpoint attempting to validate Path validation only fails when the endpoint attempting to validate
the path abandons its attempt to validate the path. the path abandons its attempt to validate the path.
Endpoints SHOULD abandon path validation based on a timer. When Endpoints SHOULD abandon path validation based on a timer. When
setting this timer, implementations are cautioned that the new path setting this timer, implementations are cautioned that the new path
could have a longer round-trip time than the original. A value of could have a longer round-trip time than the original. A value of
three times the larger of the current Probe Timeout (PTO) or the PTO three times the larger of the current PTO or the PTO for the new path
for the new path (that is, using kInitialRtt as defined in (using kInitialRtt, as defined in [QUIC-RECOVERY]) is RECOMMENDED.
[QUIC-RECOVERY]) is RECOMMENDED.
This timeout allows for multiple PTOs to expire prior to failing path This timeout allows for multiple PTOs to expire prior to failing path
validation, so that loss of a single PATH_CHALLENGE or PATH_RESPONSE validation, so that loss of a single PATH_CHALLENGE or PATH_RESPONSE
frame does not cause path validation failure. frame does not cause path validation failure.
Note that the endpoint might receive packets containing other frames Note that the endpoint might receive packets containing other frames
on the new path, but a PATH_RESPONSE frame with appropriate data is on the new path, but a PATH_RESPONSE frame with appropriate data is
required for path validation to succeed. required for path validation to succeed.
When an endpoint abandons path validation, it determines that the When an endpoint abandons path validation, it determines that the
path is unusable. This does not necessarily imply a failure of the path is unusable. This does not necessarily imply a failure of the
connection - endpoints can continue sending packets over other paths connection -- endpoints can continue sending packets over other paths
as appropriate. If no paths are available, an endpoint can wait for as appropriate. If no paths are available, an endpoint can wait for
a new path to become available or close the connection. An endpoint a new path to become available or close the connection. An endpoint
that has no valid network path to its peer MAY signal this using the that has no valid network path to its peer MAY signal this using the
NO_VIABLE_PATH connection error, noting that this is only possible if NO_VIABLE_PATH connection error, noting that this is only possible if
the network path exists but does not support the required MTU the network path exists but does not support the required MTU
(Section 14). (Section 14).
A path validation might be abandoned for other reasons besides A path validation might be abandoned for other reasons besides
failure. Primarily, this happens if a connection migration to a new failure. Primarily, this happens if a connection migration to a new
path is initiated while a path validation on the old path is in path is initiated while a path validation on the old path is in
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9. Connection Migration 9. Connection Migration
The use of a connection ID allows connections to survive changes to The use of a connection ID allows connections to survive changes to
endpoint addresses (IP address and port), such as those caused by an endpoint addresses (IP address and port), such as those caused by an
endpoint migrating to a new network. This section describes the endpoint migrating to a new network. This section describes the
process by which an endpoint migrates to a new address. process by which an endpoint migrates to a new address.
The design of QUIC relies on endpoints retaining a stable address for The design of QUIC relies on endpoints retaining a stable address for
the duration of the handshake. An endpoint MUST NOT initiate the duration of the handshake. An endpoint MUST NOT initiate
connection migration before the handshake is confirmed, as defined in connection migration before the handshake is confirmed, as defined in
section 4.1.2 of [QUIC-TLS]. Section 4.1.2 of [QUIC-TLS].
If the peer sent the disable_active_migration transport parameter, an If the peer sent the disable_active_migration transport parameter, an
endpoint also MUST NOT send packets (including probing packets; see endpoint also MUST NOT send packets (including probing packets; see
Section 9.1) from a different local address to the address the peer Section 9.1) from a different local address to the address the peer
used during the handshake, unless the endpoint has acted on a used during the handshake, unless the endpoint has acted on a
preferred_address transport parameter from the peer. If the peer preferred_address transport parameter from the peer. If the peer
violates this requirement, the endpoint MUST either drop the incoming violates this requirement, the endpoint MUST either drop the incoming
packets on that path without generating a stateless reset or proceed packets on that path without generating a Stateless Reset or proceed
with path validation and allow the peer to migrate. Generating a with path validation and allow the peer to migrate. Generating a
stateless reset or closing the connection would allow third parties Stateless Reset or closing the connection would allow third parties
in the network to cause connections to close by spoofing or otherwise in the network to cause connections to close by spoofing or otherwise
manipulating observed traffic. manipulating observed traffic.
Not all changes of peer address are intentional, or active, Not all changes of peer address are intentional, or active,
migrations. The peer could experience NAT rebinding: a change of migrations. The peer could experience NAT rebinding: a change of
address due to a middlebox, usually a NAT, allocating a new outgoing address due to a middlebox, usually a NAT, allocating a new outgoing
port or even a new outgoing IP address for a flow. An endpoint MUST port or even a new outgoing IP address for a flow. An endpoint MUST
perform path validation (Section 8.2) if it detects any change to a perform path validation (Section 8.2) if it detects any change to a
peer's address, unless it has previously validated that address. peer's address, unless it has previously validated that address.
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packet containing any other frame is a "non-probing packet". packet containing any other frame is a "non-probing packet".
9.2. Initiating Connection Migration 9.2. Initiating Connection Migration
An endpoint can migrate a connection to a new local address by An endpoint can migrate a connection to a new local address by
sending packets containing non-probing frames from that address. sending packets containing non-probing frames from that address.
Each endpoint validates its peer's address during connection Each endpoint validates its peer's address during connection
establishment. Therefore, a migrating endpoint can send to its peer establishment. Therefore, a migrating endpoint can send to its peer
knowing that the peer is willing to receive at the peer's current knowing that the peer is willing to receive at the peer's current
address. Thus an endpoint can migrate to a new local address without address. Thus, an endpoint can migrate to a new local address
first validating the peer's address. without first validating the peer's address.
To establish reachability on the new path, an endpoint initiates path To establish reachability on the new path, an endpoint initiates path
validation (Section 8.2) on the new path. An endpoint MAY defer path validation (Section 8.2) on the new path. An endpoint MAY defer path
validation until after a peer sends the next non-probing frame to its validation until after a peer sends the next non-probing frame to its
new address. new address.
When migrating, the new path might not support the endpoint's current When migrating, the new path might not support the endpoint's current
sending rate. Therefore, the endpoint resets its congestion sending rate. Therefore, the endpoint resets its congestion
controller and RTT estimate, as described in Section 9.4. controller and RTT estimate, as described in Section 9.4.
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endpoint validates ECN capability as described in Section 13.4. endpoint validates ECN capability as described in Section 13.4.
9.3. Responding to Connection Migration 9.3. Responding to Connection Migration
Receiving a packet from a new peer address containing a non-probing Receiving a packet from a new peer address containing a non-probing
frame indicates that the peer has migrated to that address. frame indicates that the peer has migrated to that address.
If the recipient permits the migration, it MUST send subsequent If the recipient permits the migration, it MUST send subsequent
packets to the new peer address and MUST initiate path validation packets to the new peer address and MUST initiate path validation
(Section 8.2) to verify the peer's ownership of the address if (Section 8.2) to verify the peer's ownership of the address if
validation is not already underway. validation is not already underway. If the recipient has no unused
connection IDs from the peer, it will not be able to send anything on
the new path until the peer provides one; see Section 9.5.
An endpoint only changes the address to which it sends packets in An endpoint only changes the address to which it sends packets in
response to the highest-numbered non-probing packet. This ensures response to the highest-numbered non-probing packet. This ensures
that an endpoint does not send packets to an old peer address in the that an endpoint does not send packets to an old peer address in the
case that it receives reordered packets. case that it receives reordered packets.
An endpoint MAY send data to an unvalidated peer address, but it MUST An endpoint MAY send data to an unvalidated peer address, but it MUST
protect against potential attacks as described in Section 9.3.1 and protect against potential attacks as described in Sections 9.3.1 and
Section 9.3.2. An endpoint MAY skip validation of a peer address if 9.3.2. An endpoint MAY skip validation of a peer address if that
that address has been seen recently. In particular, if an endpoint address has been seen recently. In particular, if an endpoint
returns to a previously-validated path after detecting some form of returns to a previously validated path after detecting some form of
spurious migration, skipping address validation and restoring loss spurious migration, skipping address validation and restoring loss
detection and congestion state can reduce the performance impact of detection and congestion state can reduce the performance impact of
the attack. the attack.
After changing the address to which it sends non-probing packets, an After changing the address to which it sends non-probing packets, an
endpoint can abandon any path validation for other addresses. endpoint can abandon any path validation for other addresses.
Receiving a packet from a new peer address could be the result of a Receiving a packet from a new peer address could be the result of a
NAT rebinding at the peer. NAT rebinding at the peer.
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It is possible that a peer is spoofing its source address to cause an It is possible that a peer is spoofing its source address to cause an
endpoint to send excessive amounts of data to an unwilling host. If endpoint to send excessive amounts of data to an unwilling host. If
the endpoint sends significantly more data than the spoofing peer, the endpoint sends significantly more data than the spoofing peer,
connection migration might be used to amplify the volume of data that connection migration might be used to amplify the volume of data that
an attacker can generate toward a victim. an attacker can generate toward a victim.
As described in Section 9.3, an endpoint is required to validate a As described in Section 9.3, an endpoint is required to validate a
peer's new address to confirm the peer's possession of the new peer's new address to confirm the peer's possession of the new
address. Until a peer's address is deemed valid, an endpoint limits address. Until a peer's address is deemed valid, an endpoint limits
the amount of data it sends to that address; see Section 8. In the the amount of data it sends to that address; see Section 8. In the
absence of this limit, an endpoint risks being used for a denial of absence of this limit, an endpoint risks being used for a denial-of-
service attack against an unsuspecting victim. service attack against an unsuspecting victim.
If an endpoint skips validation of a peer address as described above, If an endpoint skips validation of a peer address as described above,
it does not need to limit its sending rate. it does not need to limit its sending rate.
9.3.2. On-Path Address Spoofing 9.3.2. On-Path Address Spoofing
An on-path attacker could cause a spurious connection migration by An on-path attacker could cause a spurious connection migration by
copying and forwarding a packet with a spoofed address such that it copying and forwarding a packet with a spoofed address such that it
arrives before the original packet. The packet with the spoofed arrives before the original packet. The packet with the spoofed
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address when validation of a new peer address fails. Additionally, address when validation of a new peer address fails. Additionally,
receipt of packets with higher packet numbers from the legitimate receipt of packets with higher packet numbers from the legitimate
peer address will trigger another connection migration. This will peer address will trigger another connection migration. This will
cause the validation of the address of the spurious migration to be cause the validation of the address of the spurious migration to be
abandoned, thus containing migrations initiated by the attacker abandoned, thus containing migrations initiated by the attacker
injecting a single packet. injecting a single packet.
If an endpoint has no state about the last validated peer address, it If an endpoint has no state about the last validated peer address, it
MUST close the connection silently by discarding all connection MUST close the connection silently by discarding all connection
state. This results in new packets on the connection being handled state. This results in new packets on the connection being handled
generically. For instance, an endpoint MAY send a stateless reset in generically. For instance, an endpoint MAY send a Stateless Reset in
response to any further incoming packets. response to any further incoming packets.
9.3.3. Off-Path Packet Forwarding 9.3.3. Off-Path Packet Forwarding
An off-path attacker that can observe packets might forward copies of An off-path attacker that can observe packets might forward copies of
genuine packets to endpoints. If the copied packet arrives before genuine packets to endpoints. If the copied packet arrives before
the genuine packet, this will appear as a NAT rebinding. Any genuine the genuine packet, this will appear as a NAT rebinding. Any genuine
packet will be discarded as a duplicate. If the attacker is able to packet will be discarded as a duplicate. If the attacker is able to
continue forwarding packets, it might be able to cause migration to a continue forwarding packets, it might be able to cause migration to a
path via the attacker. This places the attacker on path, giving it path via the attacker. This places the attacker on-path, giving it
the ability to observe or drop all subsequent packets. the ability to observe or drop all subsequent packets.
This style of attack relies on the attacker using a path that has This style of attack relies on the attacker using a path that has
approximately the same characteristics as the direct path between approximately the same characteristics as the direct path between
endpoints. The attack is more reliable if relatively few packets are endpoints. The attack is more reliable if relatively few packets are
sent or if packet loss coincides with the attempted attack. sent or if packet loss coincides with the attempted attack.
A non-probing packet received on the original path that increases the A non-probing packet received on the original path that increases the
maximum received packet number will cause the endpoint to move back maximum received packet number will cause the endpoint to move back
to that path. Eliciting packets on this path increases the to that path. Eliciting packets on this path increases the
likelihood that the attack is unsuccessful. Therefore, mitigation of likelihood that the attack is unsuccessful. Therefore, mitigation of
this attack relies on triggering the exchange of packets. this attack relies on triggering the exchange of packets.
In response to an apparent migration, endpoints MUST validate the In response to an apparent migration, endpoints MUST validate the
previously active path using a PATH_CHALLENGE frame. This induces previously active path using a PATH_CHALLENGE frame. This induces
the sending of new packets on that path. If the path is no longer the sending of new packets on that path. If the path is no longer
viable, the validation attempt will time out and fail; if the path is viable, the validation attempt will time out and fail; if the path is
viable, but no longer desired, the validation will succeed, but only viable but no longer desired, the validation will succeed but only
results in probing packets being sent on the path. results in probing packets being sent on the path.
An endpoint that receives a PATH_CHALLENGE on an active path SHOULD An endpoint that receives a PATH_CHALLENGE on an active path SHOULD
send a non-probing packet in response. If the non-probing packet send a non-probing packet in response. If the non-probing packet
arrives before any copy made by an attacker, this results in the arrives before any copy made by an attacker, this results in the
connection being migrated back to the original path. Any subsequent connection being migrated back to the original path. Any subsequent
migration to another path restarts this entire process. migration to another path restarts this entire process.
This defense is imperfect, but this is not considered a serious This defense is imperfect, but this is not considered a serious
problem. If the path via the attack is reliably faster than the problem. If the path via the attack is reliably faster than the
original path despite multiple attempts to use that original path, it original path despite multiple attempts to use that original path, it
is not possible to distinguish between attack and an improvement in is not possible to distinguish between an attack and an improvement
routing. in routing.
An endpoint could also use heuristics to improve detection of this An endpoint could also use heuristics to improve detection of this
style of attack. For instance, NAT rebinding is improbable if style of attack. For instance, NAT rebinding is improbable if
packets were recently received on the old path; similarly, rebinding packets were recently received on the old path; similarly, rebinding
is rare on IPv6 paths. Endpoints can also look for duplicated is rare on IPv6 paths. Endpoints can also look for duplicated
packets. Conversely, a change in connection ID is more likely to packets. Conversely, a change in connection ID is more likely to
indicate an intentional migration rather than an attack. indicate an intentional migration rather than an attack.
9.4. Loss Detection and Congestion Control 9.4. Loss Detection and Congestion Control
The capacity available on the new path might not be the same as the The capacity available on the new path might not be the same as the
old path. Packets sent on the old path MUST NOT contribute to old path. Packets sent on the old path MUST NOT contribute to
congestion control or RTT estimation for the new path. congestion control or RTT estimation for the new path.
On confirming a peer's ownership of its new address, an endpoint MUST On confirming a peer's ownership of its new address, an endpoint MUST
immediately reset the congestion controller and round-trip time immediately reset the congestion controller and round-trip time
estimator for the new path to initial values (see Appendices A.3 and estimator for the new path to initial values (see Appendices A.3 and
B.3 in [QUIC-RECOVERY]) unless the only change in the peer's address B.3 of [QUIC-RECOVERY]) unless the only change in the peer's address
is its port number. Because port-only changes are commonly the is its port number. Because port-only changes are commonly the
result of NAT rebinding or other middlebox activity, the endpoint MAY result of NAT rebinding or other middlebox activity, the endpoint MAY
instead retain its congestion control state and round-trip estimate instead retain its congestion control state and round-trip estimate
in those cases instead of reverting to initial values. In cases in those cases instead of reverting to initial values. In cases
where congestion control state retained from an old path is used on a where congestion control state retained from an old path is used on a
new path with substantially different characteristics, a sender could new path with substantially different characteristics, a sender could
transmit too aggressively until the congestion controller and the RTT transmit too aggressively until the congestion controller and the RTT
estimator have adapted. Generally, implementations are advised to be estimator have adapted. Generally, implementations are advised to be
cautious when using previous values on a new path. cautious when using previous values on a new path.
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sends data and probes from/to multiple addresses during the migration sends data and probes from/to multiple addresses during the migration
period, since the two resulting paths could have different round-trip period, since the two resulting paths could have different round-trip
times. A receiver of packets on multiple paths will still send ACK times. A receiver of packets on multiple paths will still send ACK
frames covering all received packets. frames covering all received packets.
While multiple paths might be used during connection migration, a While multiple paths might be used during connection migration, a
single congestion control context and a single loss recovery context single congestion control context and a single loss recovery context
(as described in [QUIC-RECOVERY]) could be adequate. For instance, (as described in [QUIC-RECOVERY]) could be adequate. For instance,
an endpoint might delay switching to a new congestion control context an endpoint might delay switching to a new congestion control context
until it is confirmed that an old path is no longer needed (such as until it is confirmed that an old path is no longer needed (such as
the case in Section 9.3.3). the case described in Section 9.3.3).
A sender can make exceptions for probe packets so that their loss A sender can make exceptions for probe packets so that their loss
detection is independent and does not unduly cause the congestion detection is independent and does not unduly cause the congestion
controller to reduce its sending rate. An endpoint might set a controller to reduce its sending rate. An endpoint might set a
separate timer when a PATH_CHALLENGE is sent, which is cancelled if separate timer when a PATH_CHALLENGE is sent, which is canceled if
the corresponding PATH_RESPONSE is received. If the timer fires the corresponding PATH_RESPONSE is received. If the timer fires
before the PATH_RESPONSE is received, the endpoint might send a new before the PATH_RESPONSE is received, the endpoint might send a new
PATH_CHALLENGE, and restart the timer for a longer period of time. PATH_CHALLENGE and restart the timer for a longer period of time.
This timer SHOULD be set as described in Section 6.2.1 of This timer SHOULD be set as described in Section 6.2.1 of
[QUIC-RECOVERY] and MUST NOT be more aggressive. [QUIC-RECOVERY] and MUST NOT be more aggressive.
9.5. Privacy Implications of Connection Migration 9.5. Privacy Implications of Connection Migration
Using a stable connection ID on multiple network paths would allow a Using a stable connection ID on multiple network paths would allow a
passive observer to correlate activity between those paths. An passive observer to correlate activity between those paths. An
endpoint that moves between networks might not wish to have their endpoint that moves between networks might not wish to have their
activity correlated by any entity other than their peer, so different activity correlated by any entity other than their peer, so different
connection IDs are used when sending from different local addresses, connection IDs are used when sending from different local addresses,
as discussed in Section 5.1. For this to be effective, endpoints as discussed in Section 5.1. For this to be effective, endpoints
need to ensure that connection IDs they provide cannot be linked by need to ensure that connection IDs they provide cannot be linked by
any other entity. any other entity.
At any time, endpoints MAY change the Destination Connection ID they At any time, endpoints MAY change the Destination Connection ID they
transmit with to a value that has not been used on another path. transmit with to a value that has not been used on another path.
An endpoint MUST NOT reuse a connection ID when sending from more An endpoint MUST NOT reuse a connection ID when sending from more
than one local address, for example when initiating connection than one local address -- for example, when initiating connection
migration as described in Section 9.2 or when probing a new network migration as described in Section 9.2 or when probing a new network
path as described in Section 9.1. path as described in Section 9.1.
Similarly, an endpoint MUST NOT reuse a connection ID when sending to Similarly, an endpoint MUST NOT reuse a connection ID when sending to
more than one destination address. Due to network changes outside more than one destination address. Due to network changes outside
the control of its peer, an endpoint might receive packets from a new the control of its peer, an endpoint might receive packets from a new
source address with the same destination connection ID, in which case source address with the same Destination Connection ID field value,
it MAY continue to use the current connection ID with the new remote in which case it MAY continue to use the current connection ID with
address while still sending from the same local address. the new remote address while still sending from the same local
address.
These requirements regarding connection ID reuse apply only to the These requirements regarding connection ID reuse apply only to the
sending of packets, as unintentional changes in path without a change sending of packets, as unintentional changes in path without a change
in connection ID are possible. For example, after a period of in connection ID are possible. For example, after a period of
network inactivity, NAT rebinding might cause packets to be sent on a network inactivity, NAT rebinding might cause packets to be sent on a
new path when the client resumes sending. An endpoint responds to new path when the client resumes sending. An endpoint responds to
such an event as described in Section 9.3. such an event as described in Section 9.3.
Using different connection IDs for packets sent in both directions on Using different connection IDs for packets sent in both directions on
each new network path eliminates the use of the connection ID for each new network path eliminates the use of the connection ID for
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to correlate activity. This does not prevent other properties of to correlate activity. This does not prevent other properties of
packets, such as timing and size, from being used to correlate packets, such as timing and size, from being used to correlate
activity. activity.
An endpoint SHOULD NOT initiate migration with a peer that has An endpoint SHOULD NOT initiate migration with a peer that has
requested a zero-length connection ID, because traffic over the new requested a zero-length connection ID, because traffic over the new
path might be trivially linkable to traffic over the old one. If the path might be trivially linkable to traffic over the old one. If the
server is able to associate packets with a zero-length connection ID server is able to associate packets with a zero-length connection ID
to the right connection, it means that the server is using other to the right connection, it means that the server is using other
information to demultiplex packets. For example, a server might information to demultiplex packets. For example, a server might
provide a unique address to every client, for instance using HTTP provide a unique address to every client -- for instance, using HTTP
alternative services [ALTSVC]. Information that might allow correct alternative services [ALTSVC]. Information that might allow correct
routing of packets across multiple network paths will also allow routing of packets across multiple network paths will also allow
activity on those paths to be linked by entities other than the peer. activity on those paths to be linked by entities other than the peer.
A client might wish to reduce linkability by switching to a new A client might wish to reduce linkability by switching to a new
connection ID, source UDP port, or IP address (see [RFC4941]) when connection ID, source UDP port, or IP address (see [RFC8981]) when
sending traffic after a period of inactivity. Changing the address sending traffic after a period of inactivity. Changing the address
from which it sends packets at the same time might cause the server from which it sends packets at the same time might cause the server
to detect a connection migration. This ensures that the mechanisms to detect a connection migration. This ensures that the mechanisms
that support migration are exercised even for clients that do not that support migration are exercised even for clients that do not
experience NAT rebindings or genuine migrations. Changing address experience NAT rebindings or genuine migrations. Changing address
can cause a peer to reset its congestion control state (see can cause a peer to reset its congestion control state (see
Section 9.4), so addresses SHOULD only be changed infrequently. Section 9.4), so addresses SHOULD only be changed infrequently.
An endpoint that exhausts available connection IDs cannot probe new An endpoint that exhausts available connection IDs cannot probe new
paths or initiate migration, nor can it respond to probes or attempts paths or initiate migration, nor can it respond to probes or attempts
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If path validation of the server's preferred address succeeds, the If path validation of the server's preferred address succeeds, the
client MUST abandon validation of the original address and migrate to client MUST abandon validation of the original address and migrate to
using the server's preferred address. If path validation of the using the server's preferred address. If path validation of the
server's preferred address fails but validation of the server's server's preferred address fails but validation of the server's
original address succeeds, the client MAY migrate to its new address original address succeeds, the client MAY migrate to its new address
and continue sending to the server's original address. and continue sending to the server's original address.
If packets received at the server's preferred address have a If packets received at the server's preferred address have a
different source address than observed from the client during the different source address than observed from the client during the
handshake, the server MUST protect against potential attacks as handshake, the server MUST protect against potential attacks as
described in Section 9.3.1 and Section 9.3.2. In addition to described in Sections 9.3.1 and 9.3.2. In addition to intentional
intentional simultaneous migration, this might also occur because the simultaneous migration, this might also occur because the client's
client's access network used a different NAT binding for the server's access network used a different NAT binding for the server's
preferred address. preferred address.
Servers SHOULD initiate path validation to the client's new address Servers SHOULD initiate path validation to the client's new address
upon receiving a probe packet from a different address; see upon receiving a probe packet from a different address; see
Section 8. Section 8.
A client that migrates to a new address SHOULD use a preferred A client that migrates to a new address SHOULD use a preferred
address from the same address family for the server. address from the same address family for the server.
The connection ID provided in the preferred_address transport The connection ID provided in the preferred_address transport
parameter is not specific to the addresses that are provided. This parameter is not specific to the addresses that are provided. This
connection ID is provided to ensure that the client has a connection connection ID is provided to ensure that the client has a connection
ID available for migration, but the client MAY use this connection ID ID available for migration, but the client MAY use this connection ID
on any path. on any path.
9.7. Use of IPv6 Flow-Label and Migration 9.7. Use of IPv6 Flow Label and Migration
Endpoints that send data using IPv6 SHOULD apply an IPv6 flow label Endpoints that send data using IPv6 SHOULD apply an IPv6 flow label
in compliance with [RFC6437], unless the local API does not allow in compliance with [RFC6437], unless the local API does not allow
setting IPv6 flow labels. setting IPv6 flow labels.
The flow label generation MUST be designed to minimize the chances of The flow label generation MUST be designed to minimize the chances of
linkability with a previously used flow label, as a stable flow label linkability with a previously used flow label, as a stable flow label
would enable correlating activity on multiple paths; see Section 9.5. would enable correlating activity on multiple paths; see Section 9.5.
[RFC6437] suggests deriving values using a pseudorandom function to [RFC6437] suggests deriving values using a pseudorandom function to
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o immediate close (Section 10.2) o immediate close (Section 10.2)
o stateless reset (Section 10.3) o stateless reset (Section 10.3)
An endpoint MAY discard connection state if it does not have a An endpoint MAY discard connection state if it does not have a
validated path on which it can send packets; see Section 8.2. validated path on which it can send packets; see Section 8.2.
10.1. Idle Timeout 10.1. Idle Timeout
If a max_idle_timeout is specified by either peer in its transport If a max_idle_timeout is specified by either endpoint in its
parameters (Section 18.2), the connection is silently closed and its transport parameters (Section 18.2), the connection is silently
state is discarded when it remains idle for longer than the minimum closed and its state is discarded when it remains idle for longer
of both peers max_idle_timeout values. than the minimum of the max_idle_timeout value advertised by both
endpoints.
Each endpoint advertises a max_idle_timeout, but the effective value Each endpoint advertises a max_idle_timeout, but the effective value
at an endpoint is computed as the minimum of the two advertised at an endpoint is computed as the minimum of the two advertised
values (or the sole advertised value, if only one endpoint advertises values (or the sole advertised value, if only one endpoint advertises
a nonzero value). By announcing a max_idle_timeout, an endpoint a non-zero value). By announcing a max_idle_timeout, an endpoint
commits to initiating an immediate close (Section 10.2) if it commits to initiating an immediate close (Section 10.2) if it
abandons the connection prior to the effective value. abandons the connection prior to the effective value.
An endpoint restarts its idle timer when a packet from its peer is An endpoint restarts its idle timer when a packet from its peer is
received and processed successfully. An endpoint also restarts its received and processed successfully. An endpoint also restarts its
idle timer when sending an ack-eliciting packet if no other ack- idle timer when sending an ack-eliciting packet if no other ack-
eliciting packets have been sent since last receiving and processing eliciting packets have been sent since last receiving and processing
a packet. Restarting this timer when sending a packet ensures that a packet. Restarting this timer when sending a packet ensures that
connections are not closed after new activity is initiated. connections are not closed after new activity is initiated.
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An endpoint can send a PING or another ack-eliciting frame to test An endpoint can send a PING or another ack-eliciting frame to test
the connection for liveness if the peer could time out soon, such as the connection for liveness if the peer could time out soon, such as
within a PTO; see Section 6.2 of [QUIC-RECOVERY]. This is especially within a PTO; see Section 6.2 of [QUIC-RECOVERY]. This is especially
useful if any available application data cannot be safely retried. useful if any available application data cannot be safely retried.
Note that the application determines what data is safe to retry. Note that the application determines what data is safe to retry.
10.1.2. Deferring Idle Timeout 10.1.2. Deferring Idle Timeout
An endpoint might need to send ack-eliciting packets to avoid an idle An endpoint might need to send ack-eliciting packets to avoid an idle
timeout if it is expecting response data, but does not have or is timeout if it is expecting response data but does not have or is
unable to send application data. unable to send application data.
An implementation of QUIC might provide applications with an option An implementation of QUIC might provide applications with an option
to defer an idle timeout. This facility could be used when the to defer an idle timeout. This facility could be used when the
application wishes to avoid losing state that has been associated application wishes to avoid losing state that has been associated
with an open connection, but does not expect to exchange application with an open connection but does not expect to exchange application
data for some time. With this option, an endpoint could send a PING data for some time. With this option, an endpoint could send a PING
frame (Section 19.2) periodically, which will cause the peer to frame (Section 19.2) periodically, which will cause the peer to
restart its idle timeout period. Sending a packet containing a PING restart its idle timeout period. Sending a packet containing a PING
frame restarts the idle timeout for this endpoint also if this is the frame restarts the idle timeout for this endpoint also if this is the
first ack-eliciting packet sent since receiving a packet. Sending a first ack-eliciting packet sent since receiving a packet. Sending a
PING frame causes the peer to respond with an acknowledgment, which PING frame causes the peer to respond with an acknowledgment, which
also restarts the idle timeout for the endpoint. also restarts the idle timeout for the endpoint.
Application protocols that use QUIC SHOULD provide guidance on when Application protocols that use QUIC SHOULD provide guidance on when
deferring an idle timeout is appropriate. Unnecessary sending of deferring an idle timeout is appropriate. Unnecessary sending of
PING frames could have a detrimental effect on performance. PING frames could have a detrimental effect on performance.
A connection will time out if no packets are sent or received for a A connection will time out if no packets are sent or received for a
period longer than the time negotiated using the max_idle_timeout period longer than the time negotiated using the max_idle_timeout
transport parameter; see Section 10. However, state in middleboxes transport parameter; see Section 10. However, state in middleboxes
might time out earlier than that. Though REQ-5 in [RFC4787] might time out earlier than that. Though REQ-5 in [RFC4787]
recommends a 2 minute timeout interval, experience shows that sending recommends a 2-minute timeout interval, experience shows that sending
packets every 30 seconds is necessary to prevent the majority of packets every 30 seconds is necessary to prevent the majority of
middleboxes from losing state for UDP flows [GATEWAY]. middleboxes from losing state for UDP flows [GATEWAY].
10.2. Immediate Close 10.2. Immediate Close
An endpoint sends a CONNECTION_CLOSE frame (Section 19.19) to An endpoint sends a CONNECTION_CLOSE frame (Section 19.19) to
terminate the connection immediately. A CONNECTION_CLOSE frame terminate the connection immediately. A CONNECTION_CLOSE frame
causes all streams to immediately become closed; open streams can be causes all streams to immediately become closed; open streams can be
assumed to be implicitly reset. assumed to be implicitly reset.
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can exchange messages that are needed for both application endpoints can exchange messages that are needed for both application endpoints
to agree that the connection can be closed, after which the to agree that the connection can be closed, after which the
application requests that QUIC close the connection. When QUIC application requests that QUIC close the connection. When QUIC
consequently closes the connection, a CONNECTION_CLOSE frame with an consequently closes the connection, a CONNECTION_CLOSE frame with an
application-supplied error code will be used to signal closure to the application-supplied error code will be used to signal closure to the
peer. peer.
The closing and draining connection states exist to ensure that The closing and draining connection states exist to ensure that
connections close cleanly and that delayed or reordered packets are connections close cleanly and that delayed or reordered packets are
properly discarded. These states SHOULD persist for at least three properly discarded. These states SHOULD persist for at least three
times the current Probe Timeout (PTO) interval as defined in times the current PTO interval as defined in [QUIC-RECOVERY].
[QUIC-RECOVERY].
Disposing of connection state prior to exiting the closing or Disposing of connection state prior to exiting the closing or
draining state could result in an endpoint generating a stateless draining state could result in an endpoint generating a Stateless
reset unnecessarily when it receives a late-arriving packet. Reset unnecessarily when it receives a late-arriving packet.
Endpoints that have some alternative means to ensure that late- Endpoints that have some alternative means to ensure that late-
arriving packets do not induce a response, such as those that are arriving packets do not induce a response, such as those that are
able to close the UDP socket, MAY end these states earlier to allow able to close the UDP socket, MAY end these states earlier to allow
for faster resource recovery. Servers that retain an open socket for for faster resource recovery. Servers that retain an open socket for
accepting new connections SHOULD NOT end the closing or draining accepting new connections SHOULD NOT end the closing or draining
states early. state early.
Once its closing or draining state ends, an endpoint SHOULD discard Once its closing or draining state ends, an endpoint SHOULD discard
all connection state. The endpoint MAY send a stateless reset in all connection state. The endpoint MAY send a Stateless Reset in
response to any further incoming packets belonging to this response to any further incoming packets belonging to this
connection. connection.
10.2.1. Closing Connection State 10.2.1. Closing Connection State
An endpoint enters the closing state after initiating an immediate An endpoint enters the closing state after initiating an immediate
close. close.
In the closing state, an endpoint retains only enough information to In the closing state, an endpoint retains only enough information to
generate a packet containing a CONNECTION_CLOSE frame and to identify generate a packet containing a CONNECTION_CLOSE frame and to identify
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state and send a packet containing a CONNECTION_CLOSE frame in state and send a packet containing a CONNECTION_CLOSE frame in
response to any UDP datagram that is received. However, an endpoint response to any UDP datagram that is received. However, an endpoint
that discards packet protection keys cannot identify and discard that discards packet protection keys cannot identify and discard
invalid packets. To avoid being used for an amplification attack, invalid packets. To avoid being used for an amplification attack,
such endpoints MUST limit the cumulative size of packets it sends to such endpoints MUST limit the cumulative size of packets it sends to
three times the cumulative size of the packets that are received and three times the cumulative size of the packets that are received and
attributed to the connection. To minimize the state that an endpoint attributed to the connection. To minimize the state that an endpoint
maintains for a closing connection, endpoints MAY send the exact same maintains for a closing connection, endpoints MAY send the exact same
packet in response to any received packet. packet in response to any received packet.
Note: Allowing retransmission of a closing packet is an exception to Note: Allowing retransmission of a closing packet is an exception
the requirement that a new packet number be used for each packet to the requirement that a new packet number be used for each
in Section 12.3. Sending new packet numbers is primarily of packet; see Section 12.3. Sending new packet numbers is primarily
advantage to loss recovery and congestion control, which are not of advantage to loss recovery and congestion control, which are
expected to be relevant for a closed connection. Retransmitting not expected to be relevant for a closed connection.
the final packet requires less state. Retransmitting the final packet requires less state.
While in the closing state, an endpoint could receive packets from a While in the closing state, an endpoint could receive packets from a
new source address, possibly indicating a connection migration; see new source address, possibly indicating a connection migration; see
Section 9. An endpoint in the closing state MUST either discard Section 9. An endpoint in the closing state MUST either discard
packets received from an unvalidated address or limit the cumulative packets received from an unvalidated address or limit the cumulative
size of packets it sends to an unvalidated address to three times the size of packets it sends to an unvalidated address to three times the
size of packets it receives from that address. size of packets it receives from that address.
An endpoint is not expected to handle key updates when it is closing An endpoint is not expected to handle key updates when it is closing
(Section 6 of [QUIC-TLS]). A key update might prevent the endpoint (Section 6 of [QUIC-TLS]). A key update might prevent the endpoint
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packet containing a CONNECTION_CLOSE frame before entering the packet containing a CONNECTION_CLOSE frame before entering the
draining state, using a NO_ERROR code if appropriate. An endpoint draining state, using a NO_ERROR code if appropriate. An endpoint
MUST NOT send further packets. Doing so could result in a constant MUST NOT send further packets. Doing so could result in a constant
exchange of CONNECTION_CLOSE frames until one of the endpoints exits exchange of CONNECTION_CLOSE frames until one of the endpoints exits
the closing state. the closing state.
An endpoint MAY enter the draining state from the closing state if it An endpoint MAY enter the draining state from the closing state if it
receives a CONNECTION_CLOSE frame, which indicates that the peer is receives a CONNECTION_CLOSE frame, which indicates that the peer is
also closing or draining. In this case, the draining state ends when also closing or draining. In this case, the draining state ends when
the closing state would have ended. In other words, the endpoint the closing state would have ended. In other words, the endpoint
uses the same end time, but ceases transmission of any packets on uses the same end time but ceases transmission of any packets on this
this connection. connection.
10.2.3. Immediate Close During the Handshake 10.2.3. Immediate Close during the Handshake
When sending CONNECTION_CLOSE, the goal is to ensure that the peer When sending a CONNECTION_CLOSE frame, the goal is to ensure that the
will process the frame. Generally, this means sending the frame in a peer will process the frame. Generally, this means sending the frame
packet with the highest level of packet protection to avoid the in a packet with the highest level of packet protection to avoid the
packet being discarded. After the handshake is confirmed (see packet being discarded. After the handshake is confirmed (see
Section 4.1.2 of [QUIC-TLS]), an endpoint MUST send any Section 4.1.2 of [QUIC-TLS]), an endpoint MUST send any
CONNECTION_CLOSE frames in a 1-RTT packet. However, prior to CONNECTION_CLOSE frames in a 1-RTT packet. However, prior to
confirming the handshake, it is possible that more advanced packet confirming the handshake, it is possible that more advanced packet
protection keys are not available to the peer, so another protection keys are not available to the peer, so another
CONNECTION_CLOSE frame MAY be sent in a packet that uses a lower CONNECTION_CLOSE frame MAY be sent in a packet that uses a lower
packet protection level. More specifically: packet protection level. More specifically:
o A client will always know whether the server has Handshake keys o A client will always know whether the server has Handshake keys
(see Section 17.2.2.1), but it is possible that a server does not (see Section 17.2.2.1), but it is possible that a server does not
know whether the client has Handshake keys. Under these know whether the client has Handshake keys. Under these
circumstances, a server SHOULD send a CONNECTION_CLOSE frame in circumstances, a server SHOULD send a CONNECTION_CLOSE frame in
both Handshake and Initial packets to ensure that at least one of both Handshake and Initial packets to ensure that at least one of
them is processable by the client. them is processable by the client.
o A client that sends CONNECTION_CLOSE in a 0-RTT packet cannot be o A client that sends a CONNECTION_CLOSE frame in a 0-RTT packet
assured that the server has accepted 0-RTT. Sending a cannot be assured that the server has accepted 0-RTT. Sending a
CONNECTION_CLOSE frame in an Initial packet makes it more likely CONNECTION_CLOSE frame in an Initial packet makes it more likely
that the server can receive the close signal, even if the that the server can receive the close signal, even if the
application error code might not be received. application error code might not be received.
o Prior to confirming the handshake, a peer might be unable to o Prior to confirming the handshake, a peer might be unable to
process 1-RTT packets, so an endpoint SHOULD send CONNECTION_CLOSE process 1-RTT packets, so an endpoint SHOULD send a
in both Handshake and 1-RTT packets. A server SHOULD also send CONNECTION_CLOSE frame in both Handshake and 1-RTT packets. A
CONNECTION_CLOSE in an Initial packet. server SHOULD also send a CONNECTION_CLOSE frame in an Initial
packet.
Sending a CONNECTION_CLOSE of type 0x1d in an Initial or Handshake Sending a CONNECTION_CLOSE of type 0x1d in an Initial or Handshake
packet could expose application state or be used to alter application packet could expose application state or be used to alter application
state. A CONNECTION_CLOSE of type 0x1d MUST be replaced by a state. A CONNECTION_CLOSE of type 0x1d MUST be replaced by a
CONNECTION_CLOSE of type 0x1c when sending the frame in Initial or CONNECTION_CLOSE of type 0x1c when sending the frame in Initial or
Handshake packets. Otherwise, information about the application Handshake packets. Otherwise, information about the application
state might be revealed. Endpoints MUST clear the value of the state might be revealed. Endpoints MUST clear the value of the
Reason Phrase field and SHOULD use the APPLICATION_ERROR code when Reason Phrase field and SHOULD use the APPLICATION_ERROR code when
converting to a CONNECTION_CLOSE of type 0x1c. converting to a CONNECTION_CLOSE of type 0x1c.
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state. An endpoint that has no state for the connection does not state. An endpoint that has no state for the connection does not
enter a closing or draining period on sending a CONNECTION_CLOSE enter a closing or draining period on sending a CONNECTION_CLOSE
frame. frame.
10.3. Stateless Reset 10.3. Stateless Reset
A stateless reset is provided as an option of last resort for an A stateless reset is provided as an option of last resort for an
endpoint that does not have access to the state of a connection. A endpoint that does not have access to the state of a connection. A
crash or outage might result in peers continuing to send data to an crash or outage might result in peers continuing to send data to an
endpoint that is unable to properly continue the connection. An endpoint that is unable to properly continue the connection. An
endpoint MAY send a stateless reset in response to receiving a packet endpoint MAY send a Stateless Reset in response to receiving a packet
that it cannot associate with an active connection. that it cannot associate with an active connection.
A stateless reset is not appropriate for indicating errors in active A stateless reset is not appropriate for indicating errors in active
connections. An endpoint that wishes to communicate a fatal connections. An endpoint that wishes to communicate a fatal
connection error MUST use a CONNECTION_CLOSE frame if it is able. connection error MUST use a CONNECTION_CLOSE frame if it is able.
To support this process, an endpoint issues a stateless reset token, To support this process, an endpoint issues a stateless reset token,
which is a 16-byte value that is hard to guess. If the peer which is a 16-byte value that is hard to guess. If the peer
subsequently receives a stateless reset, which is a UDP datagram that subsequently receives a Stateless Reset, which is a UDP datagram that
ends in that stateless reset token, the peer will immediately end the ends in that stateless reset token, the peer will immediately end the
connection. connection.
A stateless reset token is specific to a connection ID. An endpoint A stateless reset token is specific to a connection ID. An endpoint
issues a stateless reset token by including the value in the issues a stateless reset token by including the value in the
Stateless Reset Token field of a NEW_CONNECTION_ID frame. Servers Stateless Reset Token field of a NEW_CONNECTION_ID frame. Servers
can also issue a stateless_reset_token transport parameter during the can also issue a stateless_reset_token transport parameter during the
handshake that applies to the connection ID that it selected during handshake that applies to the connection ID that it selected during
the handshake. These exchanges are protected by encryption, so only the handshake. These exchanges are protected by encryption, so only
client and server know their value. Note that clients cannot use the client and server know their value. Note that clients cannot use the
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An endpoint that receives packets that it cannot process sends a An endpoint that receives packets that it cannot process sends a
packet in the following layout (see Section 1.3): packet in the following layout (see Section 1.3):
Stateless Reset { Stateless Reset {
Fixed Bits (2) = 1, Fixed Bits (2) = 1,
Unpredictable Bits (38..), Unpredictable Bits (38..),
Stateless Reset Token (128), Stateless Reset Token (128),
} }
Figure 10: Stateless Reset Packet Figure 10: Stateless Reset
This design ensures that a stateless reset packet is - to the extent This design ensures that a Stateless Reset is -- to the extent
possible - indistinguishable from a regular packet with a short possible -- indistinguishable from a regular packet with a short
header. header.
A stateless reset uses an entire UDP datagram, starting with the A Stateless Reset uses an entire UDP datagram, starting with the
first two bits of the packet header. The remainder of the first byte first two bits of the packet header. The remainder of the first byte
and an arbitrary number of bytes following it are set to values that and an arbitrary number of bytes following it are set to values that
SHOULD be indistinguishable from random. The last 16 bytes of the SHOULD be indistinguishable from random. The last 16 bytes of the
datagram contain a Stateless Reset Token. datagram contain a stateless reset token.
To entities other than its intended recipient, a stateless reset will To entities other than its intended recipient, a Stateless Reset will
appear to be a packet with a short header. For the stateless reset appear to be a packet with a short header. For the Stateless Reset
to appear as a valid QUIC packet, the Unpredictable Bits field needs to appear as a valid QUIC packet, the Unpredictable Bits field needs
to include at least 38 bits of data (or 5 bytes, less the two fixed to include at least 38 bits of data (or 5 bytes, less the two fixed
bits). bits).
The resulting minimum size of 21 bytes does not guarantee that a The resulting minimum size of 21 bytes does not guarantee that a
stateless reset is difficult to distinguish from other packets if the Stateless Reset is difficult to distinguish from other packets if the
recipient requires the use of a connection ID. To achieve that end, recipient requires the use of a connection ID. To achieve that end,
the endpoint SHOULD ensure that all packets it sends are at least 22 the endpoint SHOULD ensure that all packets it sends are at least 22
bytes longer than the minimum connection ID length that it requests bytes longer than the minimum connection ID length that it requests
the peer to include in its packets, adding PADDING frames as the peer to include in its packets, adding PADDING frames as
necessary. This ensures that any stateless reset sent by the peer is necessary. This ensures that any Stateless Reset sent by the peer is
indistinguishable from a valid packet sent to the endpoint. An indistinguishable from a valid packet sent to the endpoint. An
endpoint that sends a stateless reset in response to a packet that is endpoint that sends a Stateless Reset in response to a packet that is
43 bytes or shorter SHOULD send a stateless reset that is one byte 43 bytes or shorter SHOULD send a Stateless Reset that is one byte
shorter than the packet it responds to. shorter than the packet it responds to.
These values assume that the Stateless Reset Token is the same length These values assume that the stateless reset token is the same length
as the minimum expansion of the packet protection AEAD. Additional as the minimum expansion of the packet protection AEAD. Additional
unpredictable bytes are necessary if the endpoint could have unpredictable bytes are necessary if the endpoint could have
negotiated a packet protection scheme with a larger minimum negotiated a packet protection scheme with a larger minimum
expansion. expansion.
An endpoint MUST NOT send a stateless reset that is three times or An endpoint MUST NOT send a Stateless Reset that is three times or
more larger than the packet it receives to avoid being used for more larger than the packet it receives to avoid being used for
amplification. Section 10.3.3 describes additional limits on amplification. Section 10.3.3 describes additional limits on
stateless reset size. Stateless Reset size.
Endpoints MUST discard packets that are too small to be valid QUIC Endpoints MUST discard packets that are too small to be valid QUIC
packets. To give an example, with the set of AEAD functions defined packets. To give an example, with the set of AEAD functions defined
in [QUIC-TLS], short header packets that are smaller than 21 bytes in [QUIC-TLS], short header packets that are smaller than 21 bytes
are never valid. are never valid.
Endpoints MUST send stateless reset packets formatted as a packet Endpoints MUST send Stateless Resets formatted as a packet with a
with a short header. However, endpoints MUST treat any packet ending short header. However, endpoints MUST treat any packet ending in a
in a valid stateless reset token as a stateless reset, as other QUIC valid stateless reset token as a Stateless Reset, as other QUIC
versions might allow the use of a long header. versions might allow the use of a long header.
An endpoint MAY send a stateless reset in response to a packet with a An endpoint MAY send a Stateless Reset in response to a packet with a
long header. Sending a stateless reset is not effective prior to the long header. Sending a Stateless Reset is not effective prior to the
stateless reset token being available to a peer. In this QUIC stateless reset token being available to a peer. In this QUIC
version, packets with a long header are only used during connection version, packets with a long header are only used during connection
establishment. Because the stateless reset token is not available establishment. Because the stateless reset token is not available
until connection establishment is complete or near completion, until connection establishment is complete or near completion,
ignoring an unknown packet with a long header might be as effective ignoring an unknown packet with a long header might be as effective
as sending a stateless reset. as sending a Stateless Reset.
An endpoint cannot determine the Source Connection ID from a packet An endpoint cannot determine the Source Connection ID from a packet
with a short header, therefore it cannot set the Destination with a short header; therefore, it cannot set the Destination
Connection ID in the stateless reset packet. The Destination Connection ID in the Stateless Reset. The Destination Connection ID
Connection ID will therefore differ from the value used in previous will therefore differ from the value used in previous packets. A
packets. A random Destination Connection ID makes the connection ID random Destination Connection ID makes the connection ID appear to be
appear to be the result of moving to a new connection ID that was the result of moving to a new connection ID that was provided using a
provided using a NEW_CONNECTION_ID frame (Section 19.15). NEW_CONNECTION_ID frame; see Section 19.15.
Using a randomized connection ID results in two problems: Using a randomized connection ID results in two problems:
o The packet might not reach the peer. If the Destination o The packet might not reach the peer. If the Destination
Connection ID is critical for routing toward the peer, then this Connection ID is critical for routing toward the peer, then this
packet could be incorrectly routed. This might also trigger packet could be incorrectly routed. This might also trigger
another Stateless Reset in response; see Section 10.3.3. A another Stateless Reset in response; see Section 10.3.3. A
Stateless Reset that is not correctly routed is an ineffective Stateless Reset that is not correctly routed is an ineffective
error detection and recovery mechanism. In this case, endpoints error detection and recovery mechanism. In this case, endpoints
will need to rely on other methods - such as timers - to detect will need to rely on other methods -- such as timers -- to detect
that the connection has failed. that the connection has failed.
o The randomly generated connection ID can be used by entities other o The randomly generated connection ID can be used by entities other
than the peer to identify this as a potential stateless reset. An than the peer to identify this as a potential Stateless Reset. An
endpoint that occasionally uses different connection IDs might endpoint that occasionally uses different connection IDs might
introduce some uncertainty about this. introduce some uncertainty about this.
This stateless reset design is specific to QUIC version 1. An This stateless reset design is specific to QUIC version 1. An
endpoint that supports multiple versions of QUIC needs to generate a endpoint that supports multiple versions of QUIC needs to generate a
stateless reset that will be accepted by peers that support any Stateless Reset that will be accepted by peers that support any
version that the endpoint might support (or might have supported version that the endpoint might support (or might have supported
prior to losing state). Designers of new versions of QUIC need to be prior to losing state). Designers of new versions of QUIC need to be
aware of this and either reuse this design, or use a portion of the aware of this and either (1) reuse this design or (2) use a portion
packet other than the last 16 bytes for carrying data. of the packet other than the last 16 bytes for carrying data.
10.3.1. Detecting a Stateless Reset 10.3.1. Detecting a Stateless Reset
An endpoint detects a potential stateless reset using the trailing 16 An endpoint detects a potential Stateless Reset using the trailing 16
bytes of the UDP datagram. An endpoint remembers all Stateless Reset bytes of the UDP datagram. An endpoint remembers all stateless reset
Tokens associated with the connection IDs and remote addresses for tokens associated with the connection IDs and remote addresses for
datagrams it has recently sent. This includes Stateless Reset Tokens datagrams it has recently sent. This includes Stateless Reset Token
from NEW_CONNECTION_ID frames and the server's transport parameters field values from NEW_CONNECTION_ID frames and the server's transport
but excludes Stateless Reset Tokens associated with connection IDs parameters but excludes stateless reset tokens associated with
that are either unused or retired. The endpoint identifies a connection IDs that are either unused or retired. The endpoint
received datagram as a stateless reset by comparing the last 16 bytes identifies a received datagram as a Stateless Reset by comparing the
of the datagram with all Stateless Reset Tokens associated with the last 16 bytes of the datagram with all stateless reset tokens
remote address on which the datagram was received. associated with the remote address on which the datagram was
received.
This comparison can be performed for every inbound datagram. This comparison can be performed for every inbound datagram.
Endpoints MAY skip this check if any packet from a datagram is Endpoints MAY skip this check if any packet from a datagram is
successfully processed. However, the comparison MUST be performed successfully processed. However, the comparison MUST be performed
when the first packet in an incoming datagram either cannot be when the first packet in an incoming datagram either cannot be
associated with a connection, or cannot be decrypted. associated with a connection or cannot be decrypted.
An endpoint MUST NOT check for any Stateless Reset Tokens associated An endpoint MUST NOT check for any stateless reset tokens associated
with connection IDs it has not used or for connection IDs that have with connection IDs it has not used or for connection IDs that have
been retired. been retired.
When comparing a datagram to Stateless Reset Token values, endpoints When comparing a datagram to stateless reset token values, endpoints
MUST perform the comparison without leaking information about the MUST perform the comparison without leaking information about the
value of the token. For example, performing this comparison in value of the token. For example, performing this comparison in
constant time protects the value of individual Stateless Reset Tokens constant time protects the value of individual stateless reset tokens
from information leakage through timing side channels. Another from information leakage through timing side channels. Another
approach would be to store and compare the transformed values of approach would be to store and compare the transformed values of
Stateless Reset Tokens instead of the raw token values, where the stateless reset tokens instead of the raw token values, where the
transformation is defined as a cryptographically-secure pseudo-random transformation is defined as a cryptographically secure pseudorandom
function using a secret key (e.g., block cipher, HMAC [RFC2104]). An function using a secret key (e.g., block cipher, Hashed Message
endpoint is not expected to protect information about whether a Authentication Code (HMAC) [RFC2104]). An endpoint is not expected
packet was successfully decrypted, or the number of valid Stateless to protect information about whether a packet was successfully
Reset Tokens. decrypted or the number of valid stateless reset tokens.
If the last 16 bytes of the datagram are identical in value to a If the last 16 bytes of the datagram are identical in value to a
Stateless Reset Token, the endpoint MUST enter the draining period stateless reset token, the endpoint MUST enter the draining period
and not send any further packets on this connection. and not send any further packets on this connection.
10.3.2. Calculating a Stateless Reset Token 10.3.2. Calculating a Stateless Reset Token
The stateless reset token MUST be difficult to guess. In order to The stateless reset token MUST be difficult to guess. In order to
create a Stateless Reset Token, an endpoint could randomly generate create a stateless reset token, an endpoint could randomly generate
([RANDOM]) a secret for every connection that it creates. However, [RANDOM] a secret for every connection that it creates. However,
this presents a coordination problem when there are multiple this presents a coordination problem when there are multiple
instances in a cluster or a storage problem for an endpoint that instances in a cluster or a storage problem for an endpoint that
might lose state. Stateless reset specifically exists to handle the might lose state. Stateless reset specifically exists to handle the
case where state is lost, so this approach is suboptimal. case where state is lost, so this approach is suboptimal.
A single static key can be used across all connections to the same A single static key can be used across all connections to the same
endpoint by generating the proof using a pseudorandom function that endpoint by generating the proof using a pseudorandom function that
takes a static key and the connection ID chosen by the endpoint (see takes a static key and the connection ID chosen by the endpoint (see
Section 5.1) as input. An endpoint could use HMAC [RFC2104] (for Section 5.1) as input. An endpoint could use HMAC [RFC2104] (for
example, HMAC(static_key, connection_id)) or HKDF [RFC5869] (for example, HMAC(static_key, connection_id)) or the HMAC-based Key
example, using the static key as input keying material, with the Derivation Function (HKDF) [RFC5869] (for example, using the static
connection ID as salt). The output of this function is truncated to key as input keying material, with the connection ID as salt). The
16 bytes to produce the Stateless Reset Token for that connection. output of this function is truncated to 16 bytes to produce the
stateless reset token for that connection.
An endpoint that loses state can use the same method to generate a An endpoint that loses state can use the same method to generate a
valid Stateless Reset Token. The connection ID comes from the packet valid stateless reset token. The connection ID comes from the packet
that the endpoint receives. that the endpoint receives.
This design relies on the peer always sending a connection ID in its This design relies on the peer always sending a connection ID in its
packets so that the endpoint can use the connection ID from a packet packets so that the endpoint can use the connection ID from a packet
to reset the connection. An endpoint that uses this design MUST to reset the connection. An endpoint that uses this design MUST
either use the same connection ID length for all connections or either use the same connection ID length for all connections or
encode the length of the connection ID such that it can be recovered encode the length of the connection ID such that it can be recovered
without state. In addition, it cannot provide a zero-length without state. In addition, it cannot provide a zero-length
connection ID. connection ID.
Revealing the Stateless Reset Token allows any entity to terminate Revealing the stateless reset token allows any entity to terminate
the connection, so a value can only be used once. This method for the connection, so a value can only be used once. This method for
choosing the Stateless Reset Token means that the combination of choosing the stateless reset token means that the combination of
connection ID and static key MUST NOT be used for another connection. connection ID and static key MUST NOT be used for another connection.
A denial of service attack is possible if the same connection ID is A denial-of-service attack is possible if the same connection ID is
used by instances that share a static key, or if an attacker can used by instances that share a static key or if an attacker can cause
cause a packet to be routed to an instance that has no state but the a packet to be routed to an instance that has no state but the same
same static key; see Section 21.11. A connection ID from a static key; see Section 21.11. A connection ID from a connection
connection that is reset by revealing the Stateless Reset Token MUST that is reset by revealing the stateless reset token MUST NOT be
NOT be reused for new connections at nodes that share a static key. reused for new connections at nodes that share a static key.
The same Stateless Reset Token MUST NOT be used for multiple The same stateless reset token MUST NOT be used for multiple
connection IDs. Endpoints are not required to compare new values connection IDs. Endpoints are not required to compare new values
against all previous values, but a duplicate value MAY be treated as against all previous values, but a duplicate value MAY be treated as
a connection error of type PROTOCOL_VIOLATION. a connection error of type PROTOCOL_VIOLATION.
Note that Stateless Reset packets do not have any cryptographic Note that Stateless Resets do not have any cryptographic protection.
protection.
10.3.3. Looping 10.3.3. Looping
The design of a Stateless Reset is such that without knowing the The design of a Stateless Reset is such that without knowing the
stateless reset token it is indistinguishable from a valid packet. stateless reset token it is indistinguishable from a valid packet.
For instance, if a server sends a Stateless Reset to another server For instance, if a server sends a Stateless Reset to another server,
it might receive another Stateless Reset in response, which could it might receive another Stateless Reset in response, which could
lead to an infinite exchange. lead to an infinite exchange.
An endpoint MUST ensure that every Stateless Reset that it sends is An endpoint MUST ensure that every Stateless Reset that it sends is
smaller than the packet that triggered it, unless it maintains state smaller than the packet that triggered it, unless it maintains state
sufficient to prevent looping. In the event of a loop, this results sufficient to prevent looping. In the event of a loop, this results
in packets eventually being too small to trigger a response. in packets eventually being too small to trigger a response.
An endpoint can remember the number of Stateless Reset packets that An endpoint can remember the number of Stateless Resets that it has
it has sent and stop generating new Stateless Reset packets once a sent and stop generating new Stateless Resets once a limit is
limit is reached. Using separate limits for different remote reached. Using separate limits for different remote addresses will
addresses will ensure that Stateless Reset packets can be used to ensure that Stateless Resets can be used to close connections when
close connections when other peers or connections have exhausted other peers or connections have exhausted limits.
limits.
Reducing the size of a Stateless Reset below 41 bytes means that the A Stateless Reset that is smaller than 41 bytes might be identifiable
packet could reveal to an observer that it is a Stateless Reset, as a Stateless Reset by an observer, depending upon the length of the
depending upon the length of the peer's connection IDs. Conversely, peer's connection IDs. Conversely, not sending a Stateless Reset in
refusing to send a Stateless Reset in response to a small packet response to a small packet might result in Stateless Resets not being
might result in Stateless Reset not being useful in detecting cases useful in detecting cases of broken connections where only very small
of broken connections where only very small packets are sent; such packets are sent; such failures might only be detected by other
failures might only be detected by other means, such as timers. means, such as timers.
11. Error Handling 11. Error Handling
An endpoint that detects an error SHOULD signal the existence of that An endpoint that detects an error SHOULD signal the existence of that
error to its peer. Both transport-level and application-level errors error to its peer. Both transport-level and application-level errors
can affect an entire connection; see Section 11.1. Only application- can affect an entire connection; see Section 11.1. Only application-
level errors can be isolated to a single stream; see Section 11.2. level errors can be isolated to a single stream; see Section 11.2.
The most appropriate error code (Section 20) SHOULD be included in The most appropriate error code (Section 20) SHOULD be included in
the frame that signals the error. Where this specification the frame that signals the error. Where this specification
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connection. Limiting the number of retransmissions and the time over connection. Limiting the number of retransmissions and the time over
which this final packet is sent limits the effort expended on which this final packet is sent limits the effort expended on
terminated connections. terminated connections.
An endpoint that chooses not to retransmit packets containing a An endpoint that chooses not to retransmit packets containing a
CONNECTION_CLOSE frame risks a peer missing the first such packet. CONNECTION_CLOSE frame risks a peer missing the first such packet.
The only mechanism available to an endpoint that continues to receive The only mechanism available to an endpoint that continues to receive
data for a terminated connection is to attempt the stateless reset data for a terminated connection is to attempt the stateless reset
process (Section 10.3). process (Section 10.3).
As the AEAD on Initial packets does not provide strong As the AEAD for Initial packets does not provide strong
authentication, an endpoint MAY discard an invalid Initial packet. authentication, an endpoint MAY discard an invalid Initial packet.
Discarding an Initial packet is permitted even where this Discarding an Initial packet is permitted even where this
specification otherwise mandates a connection error. An endpoint can specification otherwise mandates a connection error. An endpoint can
only discard a packet if it does not process the frames in the packet only discard a packet if it does not process the frames in the packet
or reverts the effects of any processing. Discarding invalid Initial or reverts the effects of any processing. Discarding invalid Initial
packets might be used to reduce exposure to denial of service; see packets might be used to reduce exposure to denial of service; see
Section 21.2. Section 21.2.
11.2. Stream Errors 11.2. Stream Errors
If an application-level error affects a single stream, but otherwise If an application-level error affects a single stream but otherwise
leaves the connection in a recoverable state, the endpoint can send a leaves the connection in a recoverable state, the endpoint can send a
RESET_STREAM frame (Section 19.4) with an appropriate error code to RESET_STREAM frame (Section 19.4) with an appropriate error code to
terminate just the affected stream. terminate just the affected stream.
Resetting a stream without the involvement of the application Resetting a stream without the involvement of the application
protocol could cause the application protocol to enter an protocol could cause the application protocol to enter an
unrecoverable state. RESET_STREAM MUST only be instigated by the unrecoverable state. RESET_STREAM MUST only be instigated by the
application protocol that uses QUIC. application protocol that uses QUIC.
The semantics of the application error code carried in RESET_STREAM The semantics of the application error code carried in RESET_STREAM
are defined by the application protocol. Only the application are defined by the application protocol. Only the application
protocol is able to cause a stream to be terminated. A local protocol is able to cause a stream to be terminated. A local
instance of the application protocol uses a direct API call and a instance of the application protocol uses a direct API call, and a
remote instance uses the STOP_SENDING frame, which triggers an remote instance uses the STOP_SENDING frame, which triggers an
automatic RESET_STREAM. automatic RESET_STREAM.
Application protocols SHOULD define rules for handling streams that Application protocols SHOULD define rules for handling streams that
are prematurely cancelled by either endpoint. are prematurely canceled by either endpoint.
12. Packets and Frames 12. Packets and Frames
QUIC endpoints communicate by exchanging packets. Packets have QUIC endpoints communicate by exchanging packets. Packets have
confidentiality and integrity protection; see Section 12.1. Packets confidentiality and integrity protection; see Section 12.1. Packets
are carried in UDP datagrams; see Section 12.2. are carried in UDP datagrams; see Section 12.2.
This version of QUIC uses the long packet header during connection This version of QUIC uses the long packet header during connection
establishment; see Section 17.2. Packets with the long header are establishment; see Section 17.2. Packets with the long header are
Initial (Section 17.2.2), 0-RTT (Section 17.2.3), Handshake Initial (Section 17.2.2), 0-RTT (Section 17.2.3), Handshake
skipping to change at page 80, line 32 skipping to change at page 79, line 32
12.1. Protected Packets 12.1. Protected Packets
QUIC packets have different levels of cryptographic protection based QUIC packets have different levels of cryptographic protection based
on the type of packet. Details of packet protection are found in on the type of packet. Details of packet protection are found in
[QUIC-TLS]; this section includes an overview of the protections that [QUIC-TLS]; this section includes an overview of the protections that
are provided. are provided.
Version Negotiation packets have no cryptographic protection; see Version Negotiation packets have no cryptographic protection; see
[QUIC-INVARIANTS]. [QUIC-INVARIANTS].
Retry packets use an authenticated encryption with associated data Retry packets use an AEAD function [AEAD] to protect against
function (AEAD; [AEAD]) to protect against accidental modification.
Initial packets use an AEAD, the keys for which are derived using a
value that is visible on the wire. Initial packets therefore do not
have effective confidentiality protection. Initial protection exists
to ensure that the sender of the packet is on the network path. Any
entity that receives an Initial packet from a client can recover the
keys that will allow them to both read the contents of the packet and
generate Initial packets that will be successfully authenticated at
either endpoint. The AEAD also protects Initial packets against
accidental modification. accidental modification.
Initial packets use an AEAD function, the keys for which are derived
using a value that is visible on the wire. Initial packets therefore
do not have effective confidentiality protection. Initial protection
exists to ensure that the sender of the packet is on the network
path. Any entity that receives an Initial packet from a client can
recover the keys that will allow them to both read the contents of
the packet and generate Initial packets that will be successfully
authenticated at either endpoint. The AEAD also protects Initial
packets against accidental modification.
All other packets are protected with keys derived from the All other packets are protected with keys derived from the
cryptographic handshake. The cryptographic handshake ensures that cryptographic handshake. The cryptographic handshake ensures that
only the communicating endpoints receive the corresponding keys for only the communicating endpoints receive the corresponding keys for
Handshake, 0-RTT, and 1-RTT packets. Packets protected with 0-RTT Handshake, 0-RTT, and 1-RTT packets. Packets protected with 0-RTT
and 1-RTT keys have strong confidentiality and integrity protection. and 1-RTT keys have strong confidentiality and integrity protection.
The Packet Number field that appears in some packet types has The Packet Number field that appears in some packet types has
alternative confidentiality protection that is applied as part of alternative confidentiality protection that is applied as part of
header protection; see Section 5.4 of [QUIC-TLS] for details. The header protection; see Section 5.4 of [QUIC-TLS] for details. The
underlying packet number increases with each packet sent in a given underlying packet number increases with each packet sent in a given
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Initial (Section 17.2.2), 0-RTT (Section 17.2.3), and Handshake Initial (Section 17.2.2), 0-RTT (Section 17.2.3), and Handshake
(Section 17.2.4) packets contain a Length field that determines the (Section 17.2.4) packets contain a Length field that determines the
end of the packet. The length includes both the Packet Number and end of the packet. The length includes both the Packet Number and
Payload fields, both of which are confidentiality protected and Payload fields, both of which are confidentiality protected and
initially of unknown length. The length of the Payload field is initially of unknown length. The length of the Payload field is
learned once header protection is removed. learned once header protection is removed.
Using the Length field, a sender can coalesce multiple QUIC packets Using the Length field, a sender can coalesce multiple QUIC packets
into one UDP datagram. This can reduce the number of UDP datagrams into one UDP datagram. This can reduce the number of UDP datagrams
needed to complete the cryptographic handshake and start sending needed to complete the cryptographic handshake and start sending
data. This can also be used to construct PMTU probes; see data. This can also be used to construct Path Maximum Transmission
Section 14.4.1. Receivers MUST be able to process coalesced packets. Unit (PMTU) probes; see Section 14.4.1. Receivers MUST be able to
process coalesced packets.
Coalescing packets in order of increasing encryption levels (Initial, Coalescing packets in order of increasing encryption levels (Initial,
0-RTT, Handshake, 1-RTT; see Section 4.1.4 of [QUIC-TLS]) makes it 0-RTT, Handshake, 1-RTT; see Section 4.1.4 of [QUIC-TLS]) makes it
more likely the receiver will be able to process all the packets in a more likely that the receiver will be able to process all the packets
single pass. A packet with a short header does not include a length, in a single pass. A packet with a short header does not include a
so it can only be the last packet included in a UDP datagram. An length, so it can only be the last packet included in a UDP datagram.
endpoint SHOULD include multiple frames in a single packet if they An endpoint SHOULD include multiple frames in a single packet if they
are to be sent at the same encryption level, instead of coalescing are to be sent at the same encryption level, instead of coalescing
multiple packets at the same encryption level. multiple packets at the same encryption level.
Receivers MAY route based on the information in the first packet Receivers MAY route based on the information in the first packet
contained in a UDP datagram. Senders MUST NOT coalesce QUIC packets contained in a UDP datagram. Senders MUST NOT coalesce QUIC packets
with different connection IDs into a single UDP datagram. Receivers with different connection IDs into a single UDP datagram. Receivers
SHOULD ignore any subsequent packets with a different Destination SHOULD ignore any subsequent packets with a different Destination
Connection ID than the first packet in the datagram. Connection ID than the first packet in the datagram.
Every QUIC packet that is coalesced into a single UDP datagram is Every QUIC packet that is coalesced into a single UDP datagram is
separate and complete. The receiver of coalesced QUIC packets MUST separate and complete. The receiver of coalesced QUIC packets MUST
individually process each QUIC packet and separately acknowledge individually process each QUIC packet and separately acknowledge
them, as if they were received as the payload of different UDP them, as if they were received as the payload of different UDP
datagrams. For example, if decryption fails (because the keys are datagrams. For example, if decryption fails (because the keys are
not available or any other reason), the receiver MAY either discard not available or for any other reason), the receiver MAY either
or buffer the packet for later processing and MUST attempt to process discard or buffer the packet for later processing and MUST attempt to
the remaining packets. process the remaining packets.
Retry packets (Section 17.2.5), Version Negotiation packets Retry packets (Section 17.2.5), Version Negotiation packets
(Section 17.2.1), and packets with a short header (Section 17.3) do (Section 17.2.1), and packets with a short header (Section 17.3) do
not contain a Length field and so cannot be followed by other packets not contain a Length field and so cannot be followed by other packets
in the same UDP datagram. Note also that there is no situation where in the same UDP datagram. Note also that there is no situation where
a Retry or Version Negotiation packet is coalesced with another a Retry or Version Negotiation packet is coalesced with another
packet. packet.
12.3. Packet Numbers 12.3. Packet Numbers
The packet number is an integer in the range 0 to 2^62-1. This The packet number is an integer in the range 0 to 2^62-1. This
number is used in determining the cryptographic nonce for packet number is used in determining the cryptographic nonce for packet
protection. Each endpoint maintains a separate packet number for protection. Each endpoint maintains a separate packet number for
sending and receiving. sending and receiving.
Packet numbers are limited to this range because they need to be Packet numbers are limited to this range because they need to be
representable in whole in the Largest Acknowledged field of an ACK representable in whole in the Largest Acknowledged field of an ACK
frame (Section 19.3). When present in a long or short header frame (Section 19.3). When present in a long or short header,
however, packet numbers are reduced and encoded in 1 to 4 bytes; see however, packet numbers are reduced and encoded in 1 to 4 bytes; see
Section 17.1. Section 17.1.
Version Negotiation (Section 17.2.1) and Retry (Section 17.2.5) Version Negotiation (Section 17.2.1) and Retry (Section 17.2.5)
packets do not include a packet number. packets do not include a packet number.
Packet numbers are divided into 3 spaces in QUIC: Packet numbers are divided into three spaces in QUIC:
o Initial space: All Initial packets (Section 17.2.2) are in this Initial space: All Initial packets (Section 17.2.2) are in this
space. space.
o Handshake space: All Handshake packets (Section 17.2.4) are in Handshake space: All Handshake packets (Section 17.2.4) are in this
this space. space.
o Application data space: All 0-RTT (Section 17.2.3) and 1-RTT Application data space: All 0-RTT (Section 17.2.3) and 1-RTT
(Section 17.3.1) packets are in this space. (Section 17.3.1) packets are in this space.
As described in [QUIC-TLS], each packet type uses different As described in [QUIC-TLS], each packet type uses different
protection keys. protection keys.
Conceptually, a packet number space is the context in which a packet Conceptually, a packet number space is the context in which a packet
can be processed and acknowledged. Initial packets can only be sent can be processed and acknowledged. Initial packets can only be sent
with Initial packet protection keys and acknowledged in packets that with Initial packet protection keys and acknowledged in packets that
are also Initial packets. Similarly, Handshake packets are sent at are also Initial packets. Similarly, Handshake packets are sent at
the Handshake encryption level and can only be acknowledged in the Handshake encryption level and can only be acknowledged in
skipping to change at page 83, line 7 skipping to change at page 82, line 7
different packet number spaces. Packet numbers in each space start different packet number spaces. Packet numbers in each space start
at packet number 0. Subsequent packets sent in the same packet at packet number 0. Subsequent packets sent in the same packet
number space MUST increase the packet number by at least one. number space MUST increase the packet number by at least one.
0-RTT and 1-RTT data exist in the same packet number space to make 0-RTT and 1-RTT data exist in the same packet number space to make
loss recovery algorithms easier to implement between the two packet loss recovery algorithms easier to implement between the two packet
types. types.
A QUIC endpoint MUST NOT reuse a packet number within the same packet A QUIC endpoint MUST NOT reuse a packet number within the same packet
number space in one connection. If the packet number for sending number space in one connection. If the packet number for sending
reaches 2^62 - 1, the sender MUST close the connection without reaches 2^62-1, the sender MUST close the connection without sending
sending a CONNECTION_CLOSE frame or any further packets; an endpoint a CONNECTION_CLOSE frame or any further packets; an endpoint MAY send
MAY send a Stateless Reset (Section 10.3) in response to further a Stateless Reset (Section 10.3) in response to further packets that
packets that it receives. it receives.
A receiver MUST discard a newly unprotected packet unless it is A receiver MUST discard a newly unprotected packet unless it is
certain that it has not processed another packet with the same packet certain that it has not processed another packet with the same packet
number from the same packet number space. Duplicate suppression MUST number from the same packet number space. Duplicate suppression MUST
happen after removing packet protection for the reasons described in happen after removing packet protection for the reasons described in
Section 9.5 of [QUIC-TLS]. Section 9.5 of [QUIC-TLS].
Endpoints that track all individual packets for the purposes of Endpoints that track all individual packets for the purposes of
detecting duplicates are at risk of accumulating excessive state. detecting duplicates are at risk of accumulating excessive state.
The data required for detecting duplicates can be limited by The data required for detecting duplicates can be limited by
maintaining a minimum packet number below which all packets are maintaining a minimum packet number below which all packets are
immediately dropped. Any minimum needs to account for large immediately dropped. Any minimum needs to account for large
variations in round trip time, which includes the possibility that a variations in round-trip time, which includes the possibility that a
peer might probe network paths with much larger round trip times; see peer might probe network paths with much larger round-trip times; see
Section 9. Section 9.
Packet number encoding at a sender and decoding at a receiver are Packet number encoding at a sender and decoding at a receiver are
described in Section 17.1. described in Section 17.1.
12.4. Frames and Frame Types 12.4. Frames and Frame Types
The payload of QUIC packets, after removing packet protection, The payload of QUIC packets, after removing packet protection,
consists of a sequence of complete frames, as shown in Figure 11. consists of a sequence of complete frames, as shown in Figure 11.
Version Negotiation, Stateless Reset, and Retry packets do not Version Negotiation, Stateless Reset, and Retry packets do not
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Frame Type (i), Frame Type (i),
Type-Dependent Fields (..), Type-Dependent Fields (..),
} }
Figure 12: Generic Frame Layout Figure 12: Generic Frame Layout
Table 3 lists and summarizes information about each frame type that Table 3 lists and summarizes information about each frame type that
is defined in this specification. A description of this summary is is defined in this specification. A description of this summary is
included after the table. included after the table.
+-------------+----------------------+----------------+------+------+ +------------+----------------------+----------------+------+------+
| Type Value | Frame Type Name | Definition | Pkts | Spec | | Type Value | Frame Type Name | Definition | Pkts | Spec |
+-------------+----------------------+----------------+------+------+ +------------+----------------------+----------------+------+------+
| 0x00 | PADDING | Section 19.1 | IH01 | NP | | 0x00 | PADDING | Section 19.1 | IH01 | NP |
| | | | | | | | | | | |
| 0x01 | PING | Section 19.2 | IH01 | | | 0x01 | PING | Section 19.2 | IH01 | |
| | | | | | | | | | | |
| 0x02 - 0x03 | ACK | Section 19.3 | IH_1 | NC | | 0x02-0x03 | ACK | Section 19.3 | IH_1 | NC |
| | | | | | | | | | | |
| 0x04 | RESET_STREAM | Section 19.4 | __01 | | | 0x04 | RESET_STREAM | Section 19.4 | __01 | |
| | | | | | | | | | | |
| 0x05 | STOP_SENDING | Section 19.5 | __01 | | | 0x05 | STOP_SENDING | Section 19.5 | __01 | |
| | | | | | | | | | | |
| 0x06 | CRYPTO | Section 19.6 | IH_1 | | | 0x06 | CRYPTO | Section 19.6 | IH_1 | |
| | | | | | | | | | | |
| 0x07 | NEW_TOKEN | Section 19.7 | ___1 | | | 0x07 | NEW_TOKEN | Section 19.7 | ___1 | |
| | | | | | | | | | | |
| 0x08 - 0x0f | STREAM | Section 19.8 | __01 | F | | 0x08-0x0f | STREAM | Section 19.8 | __01 | F |
| | | | | | | | | | | |
| 0x10 | MAX_DATA | Section 19.9 | __01 | | | 0x10 | MAX_DATA | Section 19.9 | __01 | |
| | | | | | | | | | | |
| 0x11 | MAX_STREAM_DATA | Section 19.10 | __01 | | | 0x11 | MAX_STREAM_DATA | Section 19.10 | __01 | |
| | | | | | | | | | | |
| 0x12 - 0x13 | MAX_STREAMS | Section 19.11 | __01 | | | 0x12-0x13 | MAX_STREAMS | Section 19.11 | __01 | |
| | | | | | | | | | | |
| 0x14 | DATA_BLOCKED | Section 19.12 | __01 | | | 0x14 | DATA_BLOCKED | Section 19.12 | __01 | |
| | | | | | | | | | | |
| 0x15 | STREAM_DATA_BLOCKED | Section 19.13 | __01 | | | 0x15 | STREAM_DATA_BLOCKED | Section 19.13 | __01 | |
| | | | | | | | | | | |
| 0x16 - 0x17 | STREAMS_BLOCKED | Section 19.14 | __01 | | | 0x16-0x17 | STREAMS_BLOCKED | Section 19.14 | __01 | |
| | | | | | | | | | | |
| 0x18 | NEW_CONNECTION_ID | Section 19.15 | __01 | P | | 0x18 | NEW_CONNECTION_ID | Section 19.15 | __01 | P |
| | | | | | | | | | | |
| 0x19 | RETIRE_CONNECTION_ID | Section 19.16 | __01 | | | 0x19 | RETIRE_CONNECTION_ID | Section 19.16 | __01 | |
| | | | | | | | | | | |
| 0x1a | PATH_CHALLENGE | Section 19.17 | __01 | P | | 0x1a | PATH_CHALLENGE | Section 19.17 | __01 | P |
| | | | | | | | | | | |
| 0x1b | PATH_RESPONSE | Section 19.18 | ___1 | P | | 0x1b | PATH_RESPONSE | Section 19.18 | ___1 | P |
| | | | | | | | | | | |
| 0x1c - 0x1d | CONNECTION_CLOSE | Section 19.19 | ih01 | N | | 0x1c-0x1d | CONNECTION_CLOSE | Section 19.19 | ih01 | N |
| | | | | | | | | | | |
| 0x1e | HANDSHAKE_DONE | Section 19.20 | ___1 | | | 0x1e | HANDSHAKE_DONE | Section 19.20 | ___1 | |
+-------------+----------------------+----------------+------+------+ +------------+----------------------+----------------+------+------+
Table 3: Frame Types Table 3: Frame Types
The format and semantics of each frame type are explained in more The format and semantics of each frame type are explained in more
detail in Section 19. The remainder of this section provides a detail in Section 19. The remainder of this section provides a
summary of important and general information. summary of important and general information.
The Frame Type in ACK, STREAM, MAX_STREAMS, STREAMS_BLOCKED, and The Frame Type in ACK, STREAM, MAX_STREAMS, STREAMS_BLOCKED, and
CONNECTION_CLOSE frames is used to carry other frame-specific flags. CONNECTION_CLOSE frames is used to carry other frame-specific flags.
For all other frames, the Frame Type field simply identifies the For all other frames, the Frame Type field simply identifies the
frame. frame.
The "Pkts" column in Table 3 lists the types of packets that each The "Pkts" column in Table 3 lists the types of packets that each
frame type could appear in, indicated by the following characters: frame type could appear in, indicated by the following characters:
I: Initial (Section 17.2.2) I: Initial (Section 17.2.2)
H: Handshake (Section 17.2.4) H: Handshake (Section 17.2.4)
0: 0-RTT (Section 17.2.3) 0: 0-RTT (Section 17.2.3)
1: 1-RTT (Section 17.3.1) 1: 1-RTT (Section 17.3.1)
ih: Only a CONNECTION_CLOSE frame of type 0x1c can appear in Initial ih: Only a CONNECTION_CLOSE frame of type 0x1c can appear in Initial
or Handshake packets. or Handshake packets.
For more detail about these restrictions, see Section 12.5. Note For more details about these restrictions, see Section 12.5. Note
that all frames can appear in 1-RTT packets. An endpoint MUST treat that all frames can appear in 1-RTT packets. An endpoint MUST treat
receipt of a frame in a packet type that is not permitted as a receipt of a frame in a packet type that is not permitted as a
connection error of type PROTOCOL_VIOLATION. connection error of type PROTOCOL_VIOLATION.
The "Spec" column in Table 3 summarizes any special rules governing The "Spec" column in Table 3 summarizes any special rules governing
the processing or generation of the frame type, as indicated by the the processing or generation of the frame type, as indicated by the
following characters: following characters:
N: Packets containing only frames with this marking are not ack- N: Packets containing only frames with this marking are not ack-
eliciting; see Section 13.2. eliciting; see Section 13.2.
C: Packets containing only frames with this marking do not count C: Packets containing only frames with this marking do not count
toward bytes in flight for congestion control purposes; see toward bytes in flight for congestion control purposes; see
[QUIC-RECOVERY]. [QUIC-RECOVERY].
P: Packets containing only frames with this marking can be used to P: Packets containing only frames with this marking can be used to
probe new network paths during connection migration; see probe new network paths during connection migration; see
Section 9.1. Section 9.1.
F: The content of frames with this marking are flow controlled; see F: The contents of frames with this marking are flow controlled;
Section 4. see Section 4.
The "Pkts" and "Spec" columns in Table 3 do not form part of the IANA The "Pkts" and "Spec" columns in Table 3 do not form part of the IANA
registry; see Section 22.4. registry; see Section 22.4.
An endpoint MUST treat the receipt of a frame of unknown type as a An endpoint MUST treat the receipt of a frame of unknown type as a
connection error of type FRAME_ENCODING_ERROR. connection error of type FRAME_ENCODING_ERROR.
All frames are idempotent in this version of QUIC. That is, a valid All frames are idempotent in this version of QUIC. That is, a valid
frame does not cause undesirable side effects or errors when received frame does not cause undesirable side effects or errors when received
more than once. more than once.
The Frame Type field uses a variable-length integer encoding (see The Frame Type field uses a variable-length integer encoding (see
Section 16) with one exception. To ensure simple and efficient Section 16), with one exception. To ensure simple and efficient
implementations of frame parsing, a frame type MUST use the shortest implementations of frame parsing, a frame type MUST use the shortest
possible encoding. For frame types defined in this document, this possible encoding. For frame types defined in this document, this
means a single-byte encoding, even though it is possible to encode means a single-byte encoding, even though it is possible to encode
these values as a two-, four- or eight-byte variable-length integer. these values as a two-, four-, or eight-byte variable-length integer.
For instance, though 0x4001 is a legitimate two-byte encoding for a For instance, though 0x4001 is a legitimate two-byte encoding for a
variable-length integer with a value of 1, PING frames are always variable-length integer with a value of 1, PING frames are always
encoded as a single byte with the value 0x01. This rule applies to encoded as a single byte with the value 0x01. This rule applies to
all current and future QUIC frame types. An endpoint MAY treat the all current and future QUIC frame types. An endpoint MAY treat the
receipt of a frame type that uses a longer encoding than necessary as receipt of a frame type that uses a longer encoding than necessary as
a connection error of type PROTOCOL_VIOLATION. a connection error of type PROTOCOL_VIOLATION.
12.5. Frames and Number Spaces 12.5. Frames and Number Spaces
Some frames are prohibited in different packet number spaces. The Some frames are prohibited in different packet number spaces. The
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can only appear in the application data packet number space: can only appear in the application data packet number space:
o PADDING, PING, and CRYPTO frames MAY appear in any packet number o PADDING, PING, and CRYPTO frames MAY appear in any packet number
space. space.
o CONNECTION_CLOSE frames signaling errors at the QUIC layer (type o CONNECTION_CLOSE frames signaling errors at the QUIC layer (type
0x1c) MAY appear in any packet number space. CONNECTION_CLOSE 0x1c) MAY appear in any packet number space. CONNECTION_CLOSE
frames signaling application errors (type 0x1d) MUST only appear frames signaling application errors (type 0x1d) MUST only appear
in the application data packet number space. in the application data packet number space.
o ACK frames MAY appear in any packet number space, but can only o ACK frames MAY appear in any packet number space but can only
acknowledge packets that appeared in that packet number space. acknowledge packets that appeared in that packet number space.
However, as noted below, 0-RTT packets cannot contain ACK frames. However, as noted below, 0-RTT packets cannot contain ACK frames.
o All other frame types MUST only be sent in the application data o All other frame types MUST only be sent in the application data
packet number space. packet number space.
Note that it is not possible to send the following frames in 0-RTT Note that it is not possible to send the following frames in 0-RTT
packets for various reasons: ACK, CRYPTO, HANDSHAKE_DONE, NEW_TOKEN, packets for various reasons: ACK, CRYPTO, HANDSHAKE_DONE, NEW_TOKEN,
PATH_RESPONSE, and RETIRE_CONNECTION_ID. A server MAY treat receipt PATH_RESPONSE, and RETIRE_CONNECTION_ID. A server MAY treat receipt
of these frames in 0-RTT packets as a connection error of type of these frames in 0-RTT packets as a connection error of type
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progress. Implementations are advised to include as few streams as progress. Implementations are advised to include as few streams as
necessary in outgoing packets without losing transmission efficiency necessary in outgoing packets without losing transmission efficiency
to underfilled packets. to underfilled packets.
13.1. Packet Processing 13.1. Packet Processing
A packet MUST NOT be acknowledged until packet protection has been A packet MUST NOT be acknowledged until packet protection has been
successfully removed and all frames contained in the packet have been successfully removed and all frames contained in the packet have been
processed. For STREAM frames, this means the data has been enqueued processed. For STREAM frames, this means the data has been enqueued
in preparation to be received by the application protocol, but it in preparation to be received by the application protocol, but it
does not require that data is delivered and consumed. does not require that data be delivered and consumed.
Once the packet has been fully processed, a receiver acknowledges Once the packet has been fully processed, a receiver acknowledges
receipt by sending one or more ACK frames containing the packet receipt by sending one or more ACK frames containing the packet
number of the received packet. number of the received packet.
An endpoint SHOULD treat receipt of an acknowledgment for a packet it An endpoint SHOULD treat receipt of an acknowledgment for a packet it
did not send as a connection error of type PROTOCOL_VIOLATION, if it did not send as a connection error of type PROTOCOL_VIOLATION, if it
is able to detect the condition. Further discussion of how this is able to detect the condition. For further discussion of how this
might be achieved is in Section 21.4. might be achieved, see Section 21.4.
13.2. Generating Acknowledgments 13.2. Generating Acknowledgments
Endpoints acknowledge all packets they receive and process. However, Endpoints acknowledge all packets they receive and process. However,
only ack-eliciting packets cause an ACK frame to be sent within the only ack-eliciting packets cause an ACK frame to be sent within the
maximum ack delay. Packets that are not ack-eliciting are only maximum ack delay. Packets that are not ack-eliciting are only
acknowledged when an ACK frame is sent for other reasons. acknowledged when an ACK frame is sent for other reasons.
When sending a packet for any reason, an endpoint SHOULD attempt to When sending a packet for any reason, an endpoint SHOULD attempt to
include an ACK frame if one has not been sent recently. Doing so include an ACK frame if one has not been sent recently. Doing so
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controlled, an endpoint MUST NOT send more than one such packet in controlled, an endpoint MUST NOT send more than one such packet in
response to receiving an ack-eliciting packet. response to receiving an ack-eliciting packet.
An endpoint MUST NOT send a non-ack-eliciting packet in response to a An endpoint MUST NOT send a non-ack-eliciting packet in response to a
non-ack-eliciting packet, even if there are packet gaps that precede non-ack-eliciting packet, even if there are packet gaps that precede
the received packet. This avoids an infinite feedback loop of the received packet. This avoids an infinite feedback loop of
acknowledgments, which could prevent the connection from ever acknowledgments, which could prevent the connection from ever
becoming idle. Non-ack-eliciting packets are eventually acknowledged becoming idle. Non-ack-eliciting packets are eventually acknowledged
when the endpoint sends an ACK frame in response to other events. when the endpoint sends an ACK frame in response to other events.
An endpoint that is only sending ACK frames will not receive
acknowledgments from its peer unless those acknowledgments are
included in packets with ack-eliciting frames. An endpoint SHOULD
send an ACK frame with other frames when there are new ack-eliciting
packets to acknowledge. When only non-ack-eliciting packets need to
be acknowledged, an endpoint MAY choose not to send an ACK frame with
outgoing frames until an ack-eliciting packet has been received.
An endpoint that is only sending non-ack-eliciting packets might
choose to occasionally add an ack-eliciting frame to those packets to
ensure that it receives an acknowledgment; see Section 13.2.4. In
that case, an endpoint MUST NOT send an ack-eliciting frame in all
packets that would otherwise be non-ack-eliciting, to avoid an
infinite feedback loop of acknowledgments.
In order to assist loss detection at the sender, an endpoint SHOULD In order to assist loss detection at the sender, an endpoint SHOULD
generate and send an ACK frame without delay when it receives an ack- generate and send an ACK frame without delay when it receives an ack-
eliciting packet either: eliciting packet either:
o when the received packet has a packet number less than another o when the received packet has a packet number less than another
ack-eliciting packet that has been received, or ack-eliciting packet that has been received, or
o when the packet has a packet number larger than the highest- o when the packet has a packet number larger than the highest-
numbered ack-eliciting packet that has been received and there are numbered ack-eliciting packet that has been received and there are
missing packets between that packet and this packet. missing packets between that packet and this packet.
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codepoint in the IP header SHOULD be acknowledged immediately, to codepoint in the IP header SHOULD be acknowledged immediately, to
reduce the peer's response time to congestion events. reduce the peer's response time to congestion events.
The algorithms in [QUIC-RECOVERY] are expected to be resilient to The algorithms in [QUIC-RECOVERY] are expected to be resilient to
receivers that do not follow the guidance offered above. However, an receivers that do not follow the guidance offered above. However, an
implementation should only deviate from these requirements after implementation should only deviate from these requirements after
careful consideration of the performance implications of a change, careful consideration of the performance implications of a change,
for connections made by the endpoint and for other users of the for connections made by the endpoint and for other users of the
network. network.
An endpoint that is only sending ACK frames will not receive
acknowledgments from its peer unless those acknowledgments are
included in packets with ack-eliciting frames. An endpoint SHOULD
send an ACK frame with other frames when there are new ack-eliciting
packets to acknowledge. When only non-ack-eliciting packets need to
be acknowledged, an endpoint MAY wait until an ack-eliciting packet
has been received to include an ACK frame with outgoing frames.
A receiver MUST NOT send an ack-eliciting frame in all packets that
would otherwise be non-ack-eliciting, to avoid an infinite feedback
loop of acknowledgments.
13.2.2. Acknowledgment Frequency 13.2.2. Acknowledgment Frequency
A receiver determines how frequently to send acknowledgments in A receiver determines how frequently to send acknowledgments in
response to ack-eliciting packets. This determination involves a response to ack-eliciting packets. This determination involves a
trade-off. trade-off.
Endpoints rely on timely acknowledgment to detect loss; see Section 6 Endpoints rely on timely acknowledgment to detect loss; see Section 6
of [QUIC-RECOVERY]. Window-based congestion controllers, such as the of [QUIC-RECOVERY]. Window-based congestion controllers, such as the
one in Section 7 of [QUIC-RECOVERY], rely on acknowledgments to one described in Section 7 of [QUIC-RECOVERY], rely on
manage their congestion window. In both cases, delaying acknowledgments to manage their congestion window. In both cases,
acknowledgments can adversely affect performance. delaying acknowledgments can adversely affect performance.
On the other hand, reducing the frequency of packets that carry only On the other hand, reducing the frequency of packets that carry only
acknowledgments reduces packet transmission and processing cost at acknowledgments reduces packet transmission and processing cost at
both endpoints. It can improve connection throughput on severely both endpoints. It can improve connection throughput on severely
asymmetric links and reduce the volume of acknowledgment traffic asymmetric links and reduce the volume of acknowledgment traffic
using return path capacity; see Section 3 of [RFC3449]. using return path capacity; see Section 3 of [RFC3449].
A receiver SHOULD send an ACK frame after receiving at least two ack- A receiver SHOULD send an ACK frame after receiving at least two ack-
eliciting packets. This recommendation is general in nature and eliciting packets. This recommendation is general in nature and
consistent with recommendations for TCP endpoint behavior [RFC5681]. consistent with recommendations for TCP endpoint behavior [RFC5681].
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whether to send an ACK frame in response. whether to send an ACK frame in response.
13.2.3. Managing ACK Ranges 13.2.3. Managing ACK Ranges
When an ACK frame is sent, one or more ranges of acknowledged packets When an ACK frame is sent, one or more ranges of acknowledged packets
are included. Including acknowledgments for older packets reduces are included. Including acknowledgments for older packets reduces
the chance of spurious retransmissions caused by losing previously the chance of spurious retransmissions caused by losing previously
sent ACK frames, at the cost of larger ACK frames. sent ACK frames, at the cost of larger ACK frames.
ACK frames SHOULD always acknowledge the most recently received ACK frames SHOULD always acknowledge the most recently received
packets, and the more out-of-order the packets are, the more packets, and the more out of order the packets are, the more
important it is to send an updated ACK frame quickly, to prevent the important it is to send an updated ACK frame quickly, to prevent the
peer from declaring a packet as lost and spuriously retransmitting peer from declaring a packet as lost and spuriously retransmitting
the frames it contains. An ACK frame is expected to fit within a the frames it contains. An ACK frame is expected to fit within a
single QUIC packet. If it does not, then older ranges (those with single QUIC packet. If it does not, then older ranges (those with
the smallest packet numbers) are omitted. the smallest packet numbers) are omitted.
A receiver limits the number of ACK Ranges (Section 19.3.1) it A receiver limits the number of ACK Ranges (Section 19.3.1) it
remembers and sends in ACK frames, both to limit the size of ACK remembers and sends in ACK frames, both to limit the size of ACK
frames and to avoid resource exhaustion. After receiving frames and to avoid resource exhaustion. After receiving
acknowledgments for an ACK frame, the receiver SHOULD stop tracking acknowledgments for an ACK frame, the receiver SHOULD stop tracking
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It is possible that retaining many ACK Ranges could cause an ACK It is possible that retaining many ACK Ranges could cause an ACK
frame to become too large. A receiver can discard unacknowledged ACK frame to become too large. A receiver can discard unacknowledged ACK
Ranges to limit ACK frame size, at the cost of increased Ranges to limit ACK frame size, at the cost of increased
retransmissions from the sender. This is necessary if an ACK frame retransmissions from the sender. This is necessary if an ACK frame
would be too large to fit in a packet. Receivers MAY also limit ACK would be too large to fit in a packet. Receivers MAY also limit ACK
frame size further to preserve space for other frames or to limit the frame size further to preserve space for other frames or to limit the
capacity that acknowledgments consume. capacity that acknowledgments consume.
A receiver MUST retain an ACK Range unless it can ensure that it will A receiver MUST retain an ACK Range unless it can ensure that it will
not subsequently accept packets with numbers in that range. not subsequently accept packets with numbers in that range.
Maintaining a minimum packet number that increases as ranges are Maintaining a minimum packet number that increases as ranges are
discarded is one way to achieve this with minimal state. discarded is one way to achieve this with minimal state.
Receivers can discard all ACK Ranges, but they MUST retain the Receivers can discard all ACK Ranges, but they MUST retain the
largest packet number that has been successfully processed as that is largest packet number that has been successfully processed, as that
used to recover packet numbers from subsequent packets; see is used to recover packet numbers from subsequent packets; see
Section 17.1. Section 17.1.
A receiver SHOULD include an ACK Range containing the largest A receiver SHOULD include an ACK Range containing the largest
received packet number in every ACK frame. The Largest Acknowledged received packet number in every ACK frame. The Largest Acknowledged
field is used in ECN validation at a sender and including a lower field is used in ECN validation at a sender, and including a lower
value than what was included in a previous ACK frame could cause ECN value than what was included in a previous ACK frame could cause ECN
to be unnecessarily disabled; see Section 13.4.2. to be unnecessarily disabled; see Section 13.4.2.
Section 13.2.4 describes an exemplary approach for determining what Section 13.2.4 describes an exemplary approach for determining what
packets to acknowledge in each ACK frame. Though the goal of this packets to acknowledge in each ACK frame. Though the goal of this
algorithm is to generate an acknowledgment for every packet that is algorithm is to generate an acknowledgment for every packet that is
processed, it is still possible for acknowledgments to be lost. processed, it is still possible for acknowledgments to be lost.
13.2.4. Limiting Ranges by Tracking ACK Frames 13.2.4. Limiting Ranges by Tracking ACK Frames
When a packet containing an ACK frame is sent, the largest When a packet containing an ACK frame is sent, the Largest
acknowledged in that frame can be saved. When a packet containing an Acknowledged field in that frame can be saved. When a packet
ACK frame is acknowledged, the receiver can stop acknowledging containing an ACK frame is acknowledged, the receiver can stop
packets less than or equal to the largest acknowledged in the sent acknowledging packets less than or equal to the Largest Acknowledged
ACK frame. field in the sent ACK frame.
A receiver that sends only non-ack-eliciting packets, such as ACK A receiver that sends only non-ack-eliciting packets, such as ACK
frames, might not receive an acknowledgment for a long period of frames, might not receive an acknowledgment for a long period of
time. This could cause the receiver to maintain state for a large time. This could cause the receiver to maintain state for a large
number of ACK frames for a long period of time, and ACK frames it number of ACK frames for a long period of time, and ACK frames it
sends could be unnecessarily large. In such a case, a receiver could sends could be unnecessarily large. In such a case, a receiver could
send a PING or other small ack-eliciting frame occasionally, such as send a PING or other small ack-eliciting frame occasionally, such as
once per round trip, to elicit an ACK from the peer. once per round trip, to elicit an ACK from the peer.
In cases without ACK frame loss, this algorithm allows for a minimum In cases without ACK frame loss, this algorithm allows for a minimum
of 1 RTT of reordering. In cases with ACK frame loss and reordering, of 1 RTT of reordering. In cases with ACK frame loss and reordering,
this approach does not guarantee that every acknowledgment is seen by this approach does not guarantee that every acknowledgment is seen by
the sender before it is no longer included in the ACK frame. Packets the sender before it is no longer included in the ACK frame. Packets
could be received out of order and all subsequent ACK frames could be received out of order, and all subsequent ACK frames
containing them could be lost. In this case, the loss recovery containing them could be lost. In this case, the loss recovery
algorithm could cause spurious retransmissions, but the sender will algorithm could cause spurious retransmissions, but the sender will
continue making forward progress. continue making forward progress.
13.2.5. Measuring and Reporting Host Delay 13.2.5. Measuring and Reporting Host Delay
An endpoint measures the delays intentionally introduced between the An endpoint measures the delays intentionally introduced between the
time the packet with the largest packet number is received and the time the packet with the largest packet number is received and the
time an acknowledgment is sent. The endpoint encodes this time an acknowledgment is sent. The endpoint encodes this
acknowledgment delay in the ACK Delay field of an ACK frame; see acknowledgment delay in the ACK Delay field of an ACK frame; see
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13.3. Retransmission of Information 13.3. Retransmission of Information
QUIC packets that are determined to be lost are not retransmitted QUIC packets that are determined to be lost are not retransmitted
whole. The same applies to the frames that are contained within lost whole. The same applies to the frames that are contained within lost
packets. Instead, the information that might be carried in frames is packets. Instead, the information that might be carried in frames is
sent again in new frames as needed. sent again in new frames as needed.
New frames and packets are used to carry information that is New frames and packets are used to carry information that is
determined to have been lost. In general, information is sent again determined to have been lost. In general, information is sent again
when a packet containing that information is determined to be lost when a packet containing that information is determined to be lost,
and sending ceases when a packet containing that information is and sending ceases when a packet containing that information is
acknowledged. acknowledged.
o Data sent in CRYPTO frames is retransmitted according to the rules o Data sent in CRYPTO frames is retransmitted according to the rules
in [QUIC-RECOVERY], until all data has been acknowledged. Data in in [QUIC-RECOVERY], until all data has been acknowledged. Data in
CRYPTO frames for Initial and Handshake packets is discarded when CRYPTO frames for Initial and Handshake packets is discarded when
keys for the corresponding packet number space are discarded. keys for the corresponding packet number space are discarded.
o Application data sent in STREAM frames is retransmitted in new o Application data sent in STREAM frames is retransmitted in new
STREAM frames unless the endpoint has sent a RESET_STREAM for that STREAM frames unless the endpoint has sent a RESET_STREAM for that
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The content of a RESET_STREAM frame MUST NOT change when it is The content of a RESET_STREAM frame MUST NOT change when it is
sent again. sent again.
o Similarly, a request to cancel stream transmission, as encoded in o Similarly, a request to cancel stream transmission, as encoded in
a STOP_SENDING frame, is sent until the receiving part of the a STOP_SENDING frame, is sent until the receiving part of the
stream enters either a "Data Recvd" or "Reset Recvd" state; see stream enters either a "Data Recvd" or "Reset Recvd" state; see
Section 3.5. Section 3.5.
o Connection close signals, including packets that contain o Connection close signals, including packets that contain
CONNECTION_CLOSE frames, are not sent again when packet loss is CONNECTION_CLOSE frames, are not sent again when packet loss is
detected, but as described in Section 10. detected. Resending these signals is described in Section 10.
o The current connection maximum data is sent in MAX_DATA frames. o The current connection maximum data is sent in MAX_DATA frames.
An updated value is sent in a MAX_DATA frame if the packet An updated value is sent in a MAX_DATA frame if the packet
containing the most recently sent MAX_DATA frame is declared lost, containing the most recently sent MAX_DATA frame is declared lost
or when the endpoint decides to update the limit. Care is or when the endpoint decides to update the limit. Care is
necessary to avoid sending this frame too often as the limit can necessary to avoid sending this frame too often, as the limit can
increase frequently and cause an unnecessarily large number of increase frequently and cause an unnecessarily large number of
MAX_DATA frames to be sent; see Section 4.2. MAX_DATA frames to be sent; see Section 4.2.
o The current maximum stream data offset is sent in MAX_STREAM_DATA o The current maximum stream data offset is sent in MAX_STREAM_DATA
frames. Like MAX_DATA, an updated value is sent when the packet frames. Like MAX_DATA, an updated value is sent when the packet
containing the most recent MAX_STREAM_DATA frame for a stream is containing the most recent MAX_STREAM_DATA frame for a stream is
lost or when the limit is updated, with care taken to prevent the lost or when the limit is updated, with care taken to prevent the
frame from being sent too often. An endpoint SHOULD stop sending frame from being sent too often. An endpoint SHOULD stop sending
MAX_STREAM_DATA frames when the receiving part of the stream MAX_STREAM_DATA frames when the receiving part of the stream
enters a "Size Known" or "Reset Recvd" state. enters a "Size Known" or "Reset Recvd" state.
o The limit on streams of a given type is sent in MAX_STREAMS o The limit on streams of a given type is sent in MAX_STREAMS
frames. Like MAX_DATA, an updated value is sent when a packet frames. Like MAX_DATA, an updated value is sent when a packet
containing the most recent MAX_STREAMS for a stream type frame is containing the most recent MAX_STREAMS for a stream type frame is
declared lost or when the limit is updated, with care taken to declared lost or when the limit is updated, with care taken to
prevent the frame from being sent too often. prevent the frame from being sent too often.
o Blocked signals are carried in DATA_BLOCKED, STREAM_DATA_BLOCKED, o Blocked signals are carried in DATA_BLOCKED, STREAM_DATA_BLOCKED,
and STREAMS_BLOCKED frames. DATA_BLOCKED frames have connection and STREAMS_BLOCKED frames. DATA_BLOCKED frames have connection
scope, STREAM_DATA_BLOCKED frames have stream scope, and scope, STREAM_DATA_BLOCKED frames have stream scope, and
STREAMS_BLOCKED frames are scoped to a specific stream type. New STREAMS_BLOCKED frames are scoped to a specific stream type. A
frames are sent if packets containing the most recent frame for a new frame is sent if a packet containing the most recent frame for
scope is lost, but only while the endpoint is blocked on the a scope is lost, but only while the endpoint is blocked on the
corresponding limit. These frames always include the limit that corresponding limit. These frames always include the limit that
is causing blocking at the time that they are transmitted. is causing blocking at the time that they are transmitted.
o A liveness or path validation check using PATH_CHALLENGE frames is o A liveness or path validation check using PATH_CHALLENGE frames is
sent periodically until a matching PATH_RESPONSE frame is received sent periodically until a matching PATH_RESPONSE frame is received
or until there is no remaining need for liveness or path or until there is no remaining need for liveness or path
validation checking. PATH_CHALLENGE frames include a different validation checking. PATH_CHALLENGE frames include a different
payload each time they are sent. payload each time they are sent.
o Responses to path validation using PATH_RESPONSE frames are sent o Responses to path validation using PATH_RESPONSE frames are sent
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acknowledged. acknowledged.
Endpoints SHOULD prioritize retransmission of data over sending new Endpoints SHOULD prioritize retransmission of data over sending new
data, unless priorities specified by the application indicate data, unless priorities specified by the application indicate
otherwise; see Section 2.3. otherwise; see Section 2.3.
Even though a sender is encouraged to assemble frames containing up- Even though a sender is encouraged to assemble frames containing up-
to-date information every time it sends a packet, it is not forbidden to-date information every time it sends a packet, it is not forbidden
to retransmit copies of frames from lost packets. A sender that to retransmit copies of frames from lost packets. A sender that
retransmits copies of frames needs to handle decreases in available retransmits copies of frames needs to handle decreases in available
payload size due to change in packet number length, connection ID payload size due to changes in packet number length, connection ID
length, and path MTU. A receiver MUST accept packets containing an length, and path MTU. A receiver MUST accept packets containing an
outdated frame, such as a MAX_DATA frame carrying a smaller maximum outdated frame, such as a MAX_DATA frame carrying a smaller maximum
data than one found in an older packet. data value than one found in an older packet.
A sender SHOULD avoid retransmitting information from packets once A sender SHOULD avoid retransmitting information from packets once
they are acknowledged. This includes packets that are acknowledged they are acknowledged. This includes packets that are acknowledged
after being declared lost, which can happen in the presence of after being declared lost, which can happen in the presence of
network reordering. Doing so requires senders to retain information network reordering. Doing so requires senders to retain information
about packets after they are declared lost. A sender can discard about packets after they are declared lost. A sender can discard
this information after a period of time elapses that adequately this information after a period of time elapses that adequately
allows for reordering, such as a PTO (Section 6.2 of allows for reordering, such as a PTO (Section 6.2 of
[QUIC-RECOVERY]), or on other events, such as reaching a memory [QUIC-RECOVERY]), or based on other events, such as reaching a memory
limit. limit.
Upon detecting losses, a sender MUST take appropriate congestion Upon detecting losses, a sender MUST take appropriate congestion
control action. The details of loss detection and congestion control control action. The details of loss detection and congestion control
are described in [QUIC-RECOVERY]. are described in [QUIC-RECOVERY].
13.4. Explicit Congestion Notification 13.4. Explicit Congestion Notification
QUIC endpoints can use Explicit Congestion Notification (ECN) QUIC endpoints can use ECN [RFC3168] to detect and respond to network
[RFC3168] to detect and respond to network congestion. ECN allows an congestion. ECN allows an endpoint to set an ECN-Capable Transport
endpoint to set an ECT codepoint in the ECN field of an IP packet. A (ECT) codepoint in the ECN field of an IP packet. A network node can
network node can then indicate congestion by setting the CE codepoint then indicate congestion by setting the ECN-CE codepoint in the ECN
in the ECN field instead of dropping the packet [RFC8087]. Endpoints field instead of dropping the packet [RFC8087]. Endpoints react to
react to reported congestion by reducing their sending rate in reported congestion by reducing their sending rate in response, as
response, as described in [QUIC-RECOVERY]. described in [QUIC-RECOVERY].
To enable ECN, a sending QUIC endpoint first determines whether a To enable ECN, a sending QUIC endpoint first determines whether a
path supports ECN marking and whether the peer reports the ECN values path supports ECN marking and whether the peer reports the ECN values
in received IP headers; see Section 13.4.2. in received IP headers; see Section 13.4.2.
13.4.1. Reporting ECN Counts 13.4.1. Reporting ECN Counts
Use of ECN requires the receiving endpoint to read the ECN field from The use of ECN requires the receiving endpoint to read the ECN field
an IP packet, which is not possible on all platforms. If an endpoint from an IP packet, which is not possible on all platforms. If an
does not implement ECN support or does not have access to received endpoint does not implement ECN support or does not have access to
ECN fields, it does not report ECN counts for packets it receives. received ECN fields, it does not report ECN counts for packets it
receives.
Even if an endpoint does not set an ECT field on packets it sends, Even if an endpoint does not set an ECT field in packets it sends,
the endpoint MUST provide feedback about ECN markings it receives, if the endpoint MUST provide feedback about ECN markings it receives, if
these are accessible. Failing to report the ECN counts will cause these are accessible. Failing to report the ECN counts will cause
the sender to disable use of ECN for this connection. the sender to disable the use of ECN for this connection.
On receiving an IP packet with an ECT(0), ECT(1) or CE codepoint, an On receiving an IP packet with an ECT(0), ECT(1), or ECN-CE
ECN-enabled endpoint accesses the ECN field and increases the codepoint, an ECN-enabled endpoint accesses the ECN field and
corresponding ECT(0), ECT(1), or CE count. These ECN counts are increases the corresponding ECT(0), ECT(1), or ECN-CE count. These
included in subsequent ACK frames; see Section 13.2 and Section 19.3. ECN counts are included in subsequent ACK frames; see Sections 13.2
and 19.3.
Each packet number space maintains separate acknowledgment state and Each packet number space maintains separate acknowledgment state and
separate ECN counts. Coalesced QUIC packets (see Section 12.2) share separate ECN counts. Coalesced QUIC packets (see Section 12.2) share
the same IP header so the ECN counts are incremented once for each the same IP header so the ECN counts are incremented once for each
coalesced QUIC packet. coalesced QUIC packet.
For example, if one each of an Initial, Handshake, and 1-RTT QUIC For example, if one each of an Initial, Handshake, and 1-RTT QUIC
packet are coalesced into a single UDP datagram, the ECN counts for packet are coalesced into a single UDP datagram, the ECN counts for
all three packet number spaces will be incremented by one each, based all three packet number spaces will be incremented by one each, based
on the ECN field of the single IP header. on the ECN field of the single IP header.
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ECN counts are only incremented when QUIC packets from the received ECN counts are only incremented when QUIC packets from the received
IP packet are processed. As such, duplicate QUIC packets are not IP packet are processed. As such, duplicate QUIC packets are not
processed and do not increase ECN counts; see Section 21.10 for processed and do not increase ECN counts; see Section 21.10 for
relevant security concerns. relevant security concerns.
13.4.2. ECN Validation 13.4.2. ECN Validation
It is possible for faulty network devices to corrupt or erroneously It is possible for faulty network devices to corrupt or erroneously
drop packets that carry a non-zero ECN codepoint. To ensure drop packets that carry a non-zero ECN codepoint. To ensure
connectivity in the presence of such devices, an endpoint validates connectivity in the presence of such devices, an endpoint validates
the ECN counts for each network path and disables use of ECN on that the ECN counts for each network path and disables the use of ECN on
path if errors are detected. that path if errors are detected.
To perform ECN validation for a new path: To perform ECN validation for a new path:
o The endpoint sets an ECT(0) codepoint in the IP header of early o The endpoint sets an ECT(0) codepoint in the IP header of early
outgoing packets sent on a new path to the peer ([RFC8311]). outgoing packets sent on a new path to the peer [RFC8311].
o The endpoint monitors whether all packets sent with an ECT o The endpoint monitors whether all packets sent with an ECT
codepoint are eventually deemed lost (Section 6 of codepoint are eventually deemed lost (Section 6 of
[QUIC-RECOVERY]), indicating that ECN validation has failed. [QUIC-RECOVERY]), indicating that ECN validation has failed.
If an endpoint has cause to expect that IP packets with an ECT If an endpoint has cause to expect that IP packets with an ECT
codepoint might be dropped by a faulty network element, the endpoint codepoint might be dropped by a faulty network element, the endpoint
could set an ECT codepoint for only the first ten outgoing packets on could set an ECT codepoint for only the first ten outgoing packets on
a path, or for a period of three PTOs (see Section 6.2 of a path, or for a period of three PTOs (see Section 6.2 of
[QUIC-RECOVERY]). If all packets marked with non-zero ECN codepoints [QUIC-RECOVERY]). If all packets marked with non-zero ECN codepoints
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one possible algorithm. one possible algorithm.
Other methods of probing paths for ECN support are possible, as are Other methods of probing paths for ECN support are possible, as are
different marking strategies. Implementations MAY use other methods different marking strategies. Implementations MAY use other methods
defined in RFCs; see [RFC8311]. Implementations that use the ECT(1) defined in RFCs; see [RFC8311]. Implementations that use the ECT(1)
codepoint need to perform ECN validation using the reported ECT(1) codepoint need to perform ECN validation using the reported ECT(1)
counts. counts.
13.4.2.1. Receiving ACK Frames with ECN Counts 13.4.2.1. Receiving ACK Frames with ECN Counts
Erroneous application of CE markings by the network can result in Erroneous application of ECN-CE markings by the network can result in
degraded connection performance. An endpoint that receives an ACK degraded connection performance. An endpoint that receives an ACK
frame with ECN counts therefore validates the counts before using frame with ECN counts therefore validates the counts before using
them. It performs this validation by comparing newly received counts them. It performs this validation by comparing newly received counts
against those from the last successfully processed ACK frame. Any against those from the last successfully processed ACK frame. Any
increase in the ECN counts is validated based on the ECN markings increase in the ECN counts is validated based on the ECN markings
that were applied to packets that are newly acknowledged in the ACK that were applied to packets that are newly acknowledged in the ACK
frame. frame.
If an ACK frame newly acknowledges a packet that the endpoint sent If an ACK frame newly acknowledges a packet that the endpoint sent
with either the ECT(0) or ECT(1) codepoint set, ECN validation fails with either the ECT(0) or ECT(1) codepoint set, ECN validation fails
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If validation fails, then the endpoint MUST disable ECN. It stops If validation fails, then the endpoint MUST disable ECN. It stops
setting the ECT codepoint in IP packets that it sends, assuming that setting the ECT codepoint in IP packets that it sends, assuming that
either the network path or the peer does not support ECN. either the network path or the peer does not support ECN.
Even if validation fails, an endpoint MAY revalidate ECN for the same Even if validation fails, an endpoint MAY revalidate ECN for the same
path at any later time in the connection. An endpoint could continue path at any later time in the connection. An endpoint could continue
to periodically attempt validation. to periodically attempt validation.
Upon successful validation, an endpoint MAY continue to set an ECT Upon successful validation, an endpoint MAY continue to set an ECT
codepoint in subsequent packets it sends, with the expectation that codepoint in subsequent packets it sends, with the expectation that
the path is ECN-capable. Network routing and path elements can the path is ECN capable. Network routing and path elements can
however change mid-connection; an endpoint MUST disable ECN if change mid-connection; an endpoint MUST disable ECN if validation
validation later fails. later fails.
14. Datagram Size 14. Datagram Size
A UDP datagram can include one or more QUIC packets. The datagram A UDP datagram can include one or more QUIC packets. The datagram
size refers to the total UDP payload size of a single UDP datagram size refers to the total UDP payload size of a single UDP datagram
carrying QUIC packets. The datagram size includes one or more QUIC carrying QUIC packets. The datagram size includes one or more QUIC
packet headers and protected payloads, but not the UDP or IP headers. packet headers and protected payloads, but not the UDP or IP headers.
The maximum datagram size is defined as the largest size of UDP The maximum datagram size is defined as the largest size of UDP
payload that can be sent across a network path using a single UDP payload that can be sent across a network path using a single UDP
datagram. QUIC MUST NOT be used if the network path cannot support a datagram. QUIC MUST NOT be used if the network path cannot support a
maximum datagram size of at least 1200 bytes. maximum datagram size of at least 1200 bytes.
QUIC assumes a minimum IP packet size of at least 1280 bytes. This QUIC assumes a minimum IP packet size of at least 1280 bytes. This
is the IPv6 minimum size ([IPv6]) and is also supported by most is the IPv6 minimum size [IPv6] and is also supported by most modern
modern IPv4 networks. Assuming the minimum IP header size of 40 IPv4 networks. Assuming the minimum IP header size of 40 bytes for
bytes for IPv6 and 20 bytes for IPv4 and a UDP header size of 8 IPv6 and 20 bytes for IPv4 and a UDP header size of 8 bytes, this
bytes, this results in a maximum datagram size of 1232 bytes for IPv6 results in a maximum datagram size of 1232 bytes for IPv6 and 1252
and 1252 bytes for IPv4. Thus, modern IPv4 and all IPv6 network bytes for IPv4. Thus, modern IPv4 and all IPv6 network paths are
paths are expected to be able to support QUIC. expected to be able to support QUIC.
Note: This requirement to support a UDP payload of 1200 bytes limits Note: This requirement to support a UDP payload of 1200 bytes
the space available for IPv6 extension headers to 32 bytes or IPv4 limits the space available for IPv6 extension headers to 32 bytes
options to 52 bytes if the path only supports the IPv6 minimum MTU or IPv4 options to 52 bytes if the path only supports the IPv6
of 1280 bytes. This affects Initial packets and path validation. minimum MTU of 1280 bytes. This affects Initial packets and path
validation.
Any maximum datagram size larger than 1200 bytes can be discovered Any maximum datagram size larger than 1200 bytes can be discovered
using Path Maximum Transmission Unit Discovery (PMTUD; see using Path Maximum Transmission Unit Discovery (PMTUD) (see
Section 14.2.1) or Datagram Packetization Layer PMTU Discovery Section 14.2.1) or Datagram Packetization Layer PMTU Discovery
(DPLPMTUD; see Section 14.3). (DPLPMTUD) (see Section 14.3).
Enforcement of the max_udp_payload_size transport parameter Enforcement of the max_udp_payload_size transport parameter
(Section 18.2) might act as an additional limit on the maximum (Section 18.2) might act as an additional limit on the maximum
datagram size. A sender can avoid exceeding this limit, once the datagram size. A sender can avoid exceeding this limit, once the
value is known. However, prior to learning the value of the value is known. However, prior to learning the value of the
transport parameter, endpoints risk datagrams being lost if they send transport parameter, endpoints risk datagrams being lost if they send
datagrams larger than the smallest allowed maximum datagram size of datagrams larger than the smallest allowed maximum datagram size of
1200 bytes. 1200 bytes.
UDP datagrams MUST NOT be fragmented at the IP layer. In IPv4 UDP datagrams MUST NOT be fragmented at the IP layer. In IPv4
([IPv4]), the DF bit MUST be set if possible, to prevent [IPv4], the Don't Fragment (DF) bit MUST be set if possible, to
fragmentation on the path. prevent fragmentation on the path.
QUIC sometimes requires datagrams to be no smaller than a certain QUIC sometimes requires datagrams to be no smaller than a certain
size; see Section 8.1 as an example. However, the size of a datagram size; see Section 8.1 as an example. However, the size of a datagram
is not authenticated. That is, if an endpoint receives a datagram of is not authenticated. That is, if an endpoint receives a datagram of
a certain size, it cannot know that the sender sent the datagram at a certain size, it cannot know that the sender sent the datagram at
the same size. Therefore, an endpoint MUST NOT close a connection the same size. Therefore, an endpoint MUST NOT close a connection
when it receives a datagram that does not meet size constraints; the when it receives a datagram that does not meet size constraints; the
endpoint MAY however discard such datagrams. endpoint MAY discard such datagrams.
14.1. Initial Datagram Size 14.1. Initial Datagram Size
A client MUST expand the payload of all UDP datagrams carrying A client MUST expand the payload of all UDP datagrams carrying
Initial packets to at least the smallest allowed maximum datagram Initial packets to at least the smallest allowed maximum datagram
size of 1200 bytes by adding PADDING frames to the Initial packet or size of 1200 bytes by adding PADDING frames to the Initial packet or
by coalescing the Initial packet; see Section 12.2. Initial packets by coalescing the Initial packet; see Section 12.2. Initial packets
can even be coalesced with invalid packets, which a receiver will can even be coalesced with invalid packets, which a receiver will
discard. Similarly, a server MUST expand the payload of all UDP discard. Similarly, a server MUST expand the payload of all UDP
datagrams carrying ack-eliciting Initial packets to at least the datagrams carrying ack-eliciting Initial packets to at least the
skipping to change at page 101, line 26 skipping to change at page 100, line 30
datagram with a payload that is smaller than the smallest allowed datagram with a payload that is smaller than the smallest allowed
maximum datagram size of 1200 bytes. A server MAY also immediately maximum datagram size of 1200 bytes. A server MAY also immediately
close the connection by sending a CONNECTION_CLOSE frame with an close the connection by sending a CONNECTION_CLOSE frame with an
error code of PROTOCOL_VIOLATION; see Section 10.2.3. error code of PROTOCOL_VIOLATION; see Section 10.2.3.
The server MUST also limit the number of bytes it sends before The server MUST also limit the number of bytes it sends before
validating the address of the client; see Section 8. validating the address of the client; see Section 8.
14.2. Path Maximum Transmission Unit 14.2. Path Maximum Transmission Unit
The Path Maximum Transmission Unit (PMTU) is the maximum size of the The PMTU is the maximum size of the entire IP packet, including the
entire IP packet including the IP header, UDP header, and UDP IP header, UDP header, and UDP payload. The UDP payload includes one
payload. The UDP payload includes one or more QUIC packet headers or more QUIC packet headers and protected payloads. The PMTU can
and protected payloads. The PMTU can depend on path characteristics, depend on path characteristics and can therefore change over time.
and can therefore change over time. The largest UDP payload an The largest UDP payload an endpoint sends at any given time is
endpoint sends at any given time is referred to as the endpoint's referred to as the endpoint's maximum datagram size.
maximum datagram size.
An endpoint SHOULD use DPLPMTUD (Section 14.3) or PMTUD An endpoint SHOULD use DPLPMTUD (Section 14.3) or PMTUD
(Section 14.2.1) to determine whether the path to a destination will (Section 14.2.1) to determine whether the path to a destination will
support a desired maximum datagram size without fragmentation. In support a desired maximum datagram size without fragmentation. In
the absence of these mechanisms, QUIC endpoints SHOULD NOT send the absence of these mechanisms, QUIC endpoints SHOULD NOT send
datagrams larger than the smallest allowed maximum datagram size. datagrams larger than the smallest allowed maximum datagram size.
Both DPLPMTUD and PMTUD send datagrams that are larger than the Both DPLPMTUD and PMTUD send datagrams that are larger than the
current maximum datagram size, referred to as PMTU probes. All QUIC current maximum datagram size, referred to as PMTU probes. All QUIC
packets that are not sent in a PMTU probe SHOULD be sized to fit packets that are not sent in a PMTU probe SHOULD be sized to fit
within the maximum datagram size to avoid the datagram being within the maximum datagram size to avoid the datagram being
fragmented or dropped ([RFC8085]). fragmented or dropped [RFC8085].
If a QUIC endpoint determines that the PMTU between any pair of local If a QUIC endpoint determines that the PMTU between any pair of local
and remote IP addresses cannot support the smallest allowed maximum and remote IP addresses cannot support the smallest allowed maximum
datagram size of 1200 bytes, it MUST immediately cease sending QUIC datagram size of 1200 bytes, it MUST immediately cease sending QUIC
packets, except for those in PMTU probes or those containing packets, except for those in PMTU probes or those containing
CONNECTION_CLOSE frames, on the affected path. An endpoint MAY CONNECTION_CLOSE frames, on the affected path. An endpoint MAY
terminate the connection if an alternative path cannot be found. terminate the connection if an alternative path cannot be found.
Each pair of local and remote addresses could have a different PMTU. Each pair of local and remote addresses could have a different PMTU.
QUIC implementations that implement any kind of PMTU discovery QUIC implementations that implement any kind of PMTU discovery
therefore SHOULD maintain a maximum datagram size for each therefore SHOULD maintain a maximum datagram size for each
combination of local and remote IP addresses. combination of local and remote IP addresses.
A QUIC implementation MAY be more conservative in computing the A QUIC implementation MAY be more conservative in computing the
maximum datagram size to allow for unknown tunnel overheads or IP maximum datagram size to allow for unknown tunnel overheads or IP
header options/extensions. header options/extensions.
14.2.1. Handling of ICMP Messages by PMTUD 14.2.1. Handling of ICMP Messages by PMTUD
Path Maximum Transmission Unit Discovery (PMTUD; [RFC1191], PMTUD [RFC1191] [RFC8201] relies on reception of ICMP messages (that
[RFC8201]) relies on reception of ICMP messages (e.g., IPv6 Packet is, IPv6 Packet Too Big (PTB) messages) that indicate when an IP
Too Big messages) that indicate when an IP packet is dropped because packet is dropped because it is larger than the local router MTU.
it is larger than the local router MTU. DPLPMTUD can also optionally DPLPMTUD can also optionally use these messages. This use of ICMP
use these messages. This use of ICMP messages is potentially messages is potentially vulnerable to attacks by entities that cannot
vulnerable to attacks by entities that cannot observe packets but observe packets but might successfully guess the addresses used on
might successfully guess the addresses used on the path. These the path. These attacks could reduce the PMTU to a bandwidth-
attacks could reduce the PMTU to a bandwidth-inefficient value. inefficient value.
An endpoint MUST ignore an ICMP message that claims the PMTU has An endpoint MUST ignore an ICMP message that claims the PMTU has
decreased below QUIC's smallest allowed maximum datagram size. decreased below QUIC's smallest allowed maximum datagram size.
The requirements for generating ICMP ([RFC1812], [RFC4443]) state The requirements for generating ICMP [RFC1812] [RFC4443] state that
that the quoted packet should contain as much of the original packet the quoted packet should contain as much of the original packet as
as possible without exceeding the minimum MTU for the IP version. possible without exceeding the minimum MTU for the IP version. The
The size of the quoted packet can actually be smaller, or the size of the quoted packet can actually be smaller, or the information
information unintelligible, as described in Section 1.1 of unintelligible, as described in Section 1.1 of [DPLPMTUD].
[DPLPMTUD].
QUIC endpoints using PMTUD SHOULD validate ICMP messages to protect QUIC endpoints using PMTUD SHOULD validate ICMP messages to protect
from packet injection as specified in [RFC8201] and Section 5.2 of from packet injection as specified in [RFC8201] and Section 5.2 of
[RFC8085]. This validation SHOULD use the quoted packet supplied in [RFC8085]. This validation SHOULD use the quoted packet supplied in
the payload of an ICMP message to associate the message with a the payload of an ICMP message to associate the message with a
corresponding transport connection (see Section 4.6.1 of [DPLPMTUD]). corresponding transport connection (see Section 4.6.1 of [DPLPMTUD]).
ICMP message validation MUST include matching IP addresses and UDP ICMP message validation MUST include matching IP addresses and UDP
ports ([RFC8085]) and, when possible, connection IDs to an active ports [RFC8085] and, when possible, connection IDs to an active QUIC
QUIC session. The endpoint SHOULD ignore all ICMP messages that fail session. The endpoint SHOULD ignore all ICMP messages that fail
validation. validation.
An endpoint MUST NOT increase PMTU based on ICMP messages; see An endpoint MUST NOT increase the PMTU based on ICMP messages; see
Section 3, clause 6 of [DPLPMTUD]. Any reduction in QUIC's maximum Item 6 in Section 3 of [DPLPMTUD]. Any reduction in QUIC's maximum
datagram size in response to ICMP messages MAY be provisional until datagram size in response to ICMP messages MAY be provisional until
QUIC's loss detection algorithm determines that the quoted packet has QUIC's loss detection algorithm determines that the quoted packet has
actually been lost. actually been lost.
14.3. Datagram Packetization Layer PMTU Discovery 14.3. Datagram Packetization Layer PMTU Discovery
Datagram Packetization Layer PMTU Discovery (DPLPMTUD; [DPLPMTUD]) DPLPMTUD [DPLPMTUD] relies on tracking loss or acknowledgment of QUIC
relies on tracking loss or acknowledgment of QUIC packets that are packets that are carried in PMTU probes. PMTU probes for DPLPMTUD
carried in PMTU probes. PMTU probes for DPLPMTUD that use the that use the PADDING frame implement "Probing using padding data", as
PADDING frame implement "Probing using padding data", as defined in defined in Section 4.1 of [DPLPMTUD].
Section 4.1 of [DPLPMTUD].
Endpoints SHOULD set the initial value of BASE_PLPMTU (Section 5.1 of Endpoints SHOULD set the initial value of BASE_PLPMTU (Section 5.1 of
[DPLPMTUD]) to be consistent with QUIC's smallest allowed maximum [DPLPMTUD]) to be consistent with QUIC's smallest allowed maximum
datagram size. The MIN_PLPMTU is the same as the BASE_PLPMTU. datagram size. The MIN_PLPMTU is the same as the BASE_PLPMTU.
QUIC endpoints implementing DPLPMTUD maintain a DPLPMTUD Maximum QUIC endpoints implementing DPLPMTUD maintain a DPLPMTUD Maximum
Packet Size (MPS, Section 4.4 of [DPLPMTUD]) for each combination of Packet Size (MPS) (Section 4.4 of [DPLPMTUD]) for each combination of
local and remote IP addresses. This corresponds to the maximum local and remote IP addresses. This corresponds to the maximum
datagram size. datagram size.
14.3.1. DPLPMTUD and Initial Connectivity 14.3.1. DPLPMTUD and Initial Connectivity
From the perspective of DPLPMTUD, QUIC is an acknowledged From the perspective of DPLPMTUD, QUIC is an acknowledged
Packetization Layer (PL). A QUIC sender can therefore enter the Packetization Layer (PL). A QUIC sender can therefore enter the
DPLPMTUD BASE state (Section 5.2 of [DPLPMTUD]) when the QUIC DPLPMTUD BASE state (Section 5.2 of [DPLPMTUD]) when the QUIC
connection handshake has been completed. connection handshake has been completed.
14.3.2. Validating the Network Path with DPLPMTUD 14.3.2. Validating the Network Path with DPLPMTUD
QUIC is an acknowledged PL, therefore a QUIC sender does not QUIC is an acknowledged PL; therefore, a QUIC sender does not
implement a DPLPMTUD CONFIRMATION_TIMER while in the SEARCH_COMPLETE implement a DPLPMTUD CONFIRMATION_TIMER while in the SEARCH_COMPLETE
state; see Section 5.2 of [DPLPMTUD]. state; see Section 5.2 of [DPLPMTUD].
14.3.3. Handling of ICMP Messages by DPLPMTUD 14.3.3. Handling of ICMP Messages by DPLPMTUD
An endpoint using DPLPMTUD requires the validation of any received An endpoint using DPLPMTUD requires the validation of any received
ICMP Packet Too Big (PTB) message before using the PTB information, ICMP PTB message before using the PTB information, as defined in
as defined in Section 4.6 of [DPLPMTUD]. In addition to UDP port Section 4.6 of [DPLPMTUD]. In addition to UDP port validation, QUIC
validation, QUIC validates an ICMP message by using other PL validates an ICMP message by using other PL information (e.g.,
information (e.g., validation of connection IDs in the quoted packet validation of connection IDs in the quoted packet of any received
of any received ICMP message). ICMP message).
The considerations for processing ICMP messages described in The considerations for processing ICMP messages described in
Section 14.2.1 also apply if these messages are used by DPLPMTUD. Section 14.2.1 also apply if these messages are used by DPLPMTUD.
14.4. Sending QUIC PMTU Probes 14.4. Sending QUIC PMTU Probes
PMTU probes are ack-eliciting packets. PMTU probes are ack-eliciting packets.
Endpoints could limit the content of PMTU probes to PING and PADDING Endpoints could limit the content of PMTU probes to PING and PADDING
frames, since packets that are larger than the current maximum frames, since packets that are larger than the current maximum
datagram size are more likely to be dropped by the network. Loss of datagram size are more likely to be dropped by the network. Loss of
a QUIC packet that is carried in a PMTU probe is therefore not a a QUIC packet that is carried in a PMTU probe is therefore not a
reliable indication of congestion and SHOULD NOT trigger a congestion reliable indication of congestion and SHOULD NOT trigger a congestion
control reaction; see Section 3, Bullet 7 of [DPLPMTUD]. However, control reaction; see Item 7 in Section 3 of [DPLPMTUD]. However,
PMTU probes consume congestion window, which could delay subsequent PMTU probes consume congestion window, which could delay subsequent
transmission by an application. transmission by an application.
14.4.1. PMTU Probes Containing Source Connection ID 14.4.1. PMTU Probes Containing Source Connection ID
Endpoints that rely on the destination connection ID for routing Endpoints that rely on the Destination Connection ID field for
incoming QUIC packets are likely to require that the connection ID be routing incoming QUIC packets are likely to require that the
included in PMTU probes to route any resulting ICMP messages connection ID be included in PMTU probes to route any resulting ICMP
(Section 14.2.1) back to the correct endpoint. However, only long messages (Section 14.2.1) back to the correct endpoint. However,
header packets (Section 17.2) contain the Source Connection ID field, only long header packets (Section 17.2) contain the Source Connection
and long header packets are not decrypted or acknowledged by the peer ID field, and long header packets are not decrypted or acknowledged
once the handshake is complete. by the peer once the handshake is complete.
One way to construct a PMTU probe is to coalesce (see Section 12.2) a One way to construct a PMTU probe is to coalesce (see Section 12.2) a
packet with a long header, such as a Handshake or 0-RTT packet packet with a long header, such as a Handshake or 0-RTT packet
(Section 17.2), with a short header packet in a single UDP datagram. (Section 17.2), with a short header packet in a single UDP datagram.
If the resulting PMTU probe reaches the endpoint, the packet with the If the resulting PMTU probe reaches the endpoint, the packet with the
long header will be ignored, but the short header packet will be long header will be ignored, but the short header packet will be
acknowledged. If the PMTU probe causes an ICMP message to be sent, acknowledged. If the PMTU probe causes an ICMP message to be sent,
the first part of the probe will be quoted in that message. If the the first part of the probe will be quoted in that message. If the
Source Connection ID field is within the quoted portion of the probe, Source Connection ID field is within the quoted portion of the probe,
that could be used for routing or validation of the ICMP message. that could be used for routing or validation of the ICMP message.
Note: The purpose of using a packet with a long header is only to Note: The purpose of using a packet with a long header is only to
ensure that the quoted packet contained in the ICMP message ensure that the quoted packet contained in the ICMP message
contains a Source Connection ID field. This packet does not need contains a Source Connection ID field. This packet does not need
to be a valid packet and it can be sent even if there is no to be a valid packet, and it can be sent even if there is no
current use for packets of that type. current use for packets of that type.
15. Versions 15. Versions
QUIC versions are identified using a 32-bit unsigned number. QUIC versions are identified using a 32-bit unsigned number.
The version 0x00000000 is reserved to represent version negotiation. The version 0x00000000 is reserved to represent version negotiation.
This version of the specification is identified by the number This version of the specification is identified by the number
0x00000001. 0x00000001.
skipping to change at page 105, line 9 skipping to change at page 104, line 9
across all versions of the protocol are described in across all versions of the protocol are described in
[QUIC-INVARIANTS]. [QUIC-INVARIANTS].
Version 0x00000001 of QUIC uses TLS as a cryptographic handshake Version 0x00000001 of QUIC uses TLS as a cryptographic handshake
protocol, as described in [QUIC-TLS]. protocol, as described in [QUIC-TLS].
Versions with the most significant 16 bits of the version number Versions with the most significant 16 bits of the version number
cleared are reserved for use in future IETF consensus documents. cleared are reserved for use in future IETF consensus documents.
Versions that follow the pattern 0x?a?a?a?a are reserved for use in Versions that follow the pattern 0x?a?a?a?a are reserved for use in
forcing version negotiation to be exercised. That is, any version forcing version negotiation to be exercised -- that is, any version
number where the low four bits of all bytes is 1010 (in binary). A number where the low four bits of all bytes is 1010 (in binary). A
client or server MAY advertise support for any of these reserved client or server MAY advertise support for any of these reserved
versions. versions.
Reserved version numbers will never represent a real protocol; a Reserved version numbers will never represent a real protocol; a
client MAY use one of these version numbers with the expectation that client MAY use one of these version numbers with the expectation that
the server will initiate version negotiation; a server MAY advertise the server will initiate version negotiation; a server MAY advertise
support for one of these versions and can expect that clients ignore support for one of these versions and can expect that clients ignore
the value. the value.
16. Variable-Length Integer Encoding 16. Variable-Length Integer Encoding
QUIC packets and frames commonly use a variable-length encoding for QUIC packets and frames commonly use a variable-length encoding for
non-negative integer values. This encoding ensures that smaller non-negative integer values. This encoding ensures that smaller
integer values need fewer bytes to encode. integer values need fewer bytes to encode.
The QUIC variable-length integer encoding reserves the two most The QUIC variable-length integer encoding reserves the two most
significant bits of the first byte to encode the base 2 logarithm of significant bits of the first byte to encode the base-2 logarithm of
the integer encoding length in bytes. The integer value is encoded the integer encoding length in bytes. The integer value is encoded
on the remaining bits, in network byte order. on the remaining bits, in network byte order.
This means that integers are encoded on 1, 2, 4, or 8 bytes and can This means that integers are encoded on 1, 2, 4, or 8 bytes and can
encode 6-, 14-, 30-, or 62-bit values respectively. Table 4 encode 6-, 14-, 30-, or 62-bit values, respectively. Table 4
summarizes the encoding properties. summarizes the encoding properties.
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
| 2Bit | Length | Usable Bits | Range | | 2MSB | Length | Usable Bits | Range |
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
| 00 | 1 | 6 | 0-63 | | 00 | 1 | 6 | 0-63 |
| | | | | | | | | |
| 01 | 2 | 14 | 0-16383 | | 01 | 2 | 14 | 0-16383 |
| | | | | | | | | |
| 10 | 4 | 30 | 0-1073741823 | | 10 | 4 | 30 | 0-1073741823 |
| | | | | | | | | |
| 11 | 8 | 62 | 0-4611686018427387903 | | 11 | 8 | 62 | 0-4611686018427387903 |
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
Table 4: Summary of Integer Encodings Table 4: Summary of Integer Encodings
Examples and a sample decoding algorithm are shown in Appendix A.1. An example of a decoding algorithm and sample encodings are shown in
Appendix A.1.
Values do not need to be encoded on the minimum number of bytes Values do not need to be encoded on the minimum number of bytes
necessary, with the sole exception of the Frame Type field; see necessary, with the sole exception of the Frame Type field; see
Section 12.4. Section 12.4.
Versions (Section 15), packet numbers sent in the header Versions (Section 15), packet numbers sent in the header
(Section 17.1), and the length of connection IDs in long header (Section 17.1), and the length of connection IDs in long header
packets (Section 17.2) are described using integers, but do not use packets (Section 17.2) are described using integers but do not use
this encoding. this encoding.
17. Packet Formats 17. Packet Formats
All numeric values are encoded in network byte order (that is, big- All numeric values are encoded in network byte order (that is, big
endian) and all field sizes are in bits. Hexadecimal notation is endian), and all field sizes are in bits. Hexadecimal notation is
used for describing the value of fields. used for describing the value of fields.
17.1. Packet Number Encoding and Decoding 17.1. Packet Number Encoding and Decoding
Packet numbers are integers in the range 0 to 2^62-1 (Section 12.3). Packet numbers are integers in the range 0 to 2^62-1 (Section 12.3).
When present in long or short packet headers, they are encoded in 1 When present in long or short packet headers, they are encoded in 1
to 4 bytes. The number of bits required to represent the packet to 4 bytes. The number of bits required to represent the packet
number is reduced by including only the least significant bits of the number is reduced by including only the least significant bits of the
packet number. packet number.
The encoded packet number is protected as described in Section 5.4 of The encoded packet number is protected as described in Section 5.4 of
[QUIC-TLS]. [QUIC-TLS].
Prior to receiving an acknowledgment for a packet number space, the Prior to receiving an acknowledgment for a packet number space, the
full packet number MUST be included; it is not to be truncated as full packet number MUST be included; it is not to be truncated, as
described below. described below.
After an acknowledgment is received for a packet number space, the After an acknowledgment is received for a packet number space, the
sender MUST use a packet number size able to represent more than sender MUST use a packet number size able to represent more than
twice as large a range than the difference between the largest twice as large a range as the difference between the largest
acknowledged packet and packet number being sent. A peer receiving acknowledged packet number and the packet number being sent. A peer
the packet will then correctly decode the packet number, unless the receiving the packet will then correctly decode the packet number,
packet is delayed in transit such that it arrives after many higher- unless the packet is delayed in transit such that it arrives after
numbered packets have been received. An endpoint SHOULD use a large many higher-numbered packets have been received. An endpoint SHOULD
enough packet number encoding to allow the packet number to be use a large enough packet number encoding to allow the packet number
recovered even if the packet arrives after packets that are sent to be recovered even if the packet arrives after packets that are
afterwards. sent afterwards.
As a result, the size of the packet number encoding is at least one As a result, the size of the packet number encoding is at least one
bit more than the base-2 logarithm of the number of contiguous bit more than the base-2 logarithm of the number of contiguous
unacknowledged packet numbers, including the new packet. Pseudocode unacknowledged packet numbers, including the new packet. Pseudocode
and examples for packet number encoding can be found in Appendix A.2. and an example for packet number encoding can be found in
Appendix A.2.
At a receiver, protection of the packet number is removed prior to At a receiver, protection of the packet number is removed prior to
recovering the full packet number. The full packet number is then recovering the full packet number. The full packet number is then
reconstructed based on the number of significant bits present, the reconstructed based on the number of significant bits present, the
value of those bits, and the largest packet number received in a value of those bits, and the largest packet number received in a
successfully authenticated packet. Recovering the full packet number successfully authenticated packet. Recovering the full packet number
is necessary to successfully remove packet protection. is necessary to successfully complete the removal of packet
protection.
Once header protection is removed, the packet number is decoded by Once header protection is removed, the packet number is decoded by
finding the packet number value that is closest to the next expected finding the packet number value that is closest to the next expected
packet. The next expected packet is the highest received packet packet. The next expected packet is the highest received packet
number plus one. Pseudocode and an example for packet number number plus one. Pseudocode and an example for packet number
decoding can be found in Appendix A.3. decoding can be found in Appendix A.3.
17.2. Long Header Packets 17.2. Long Header Packets
Long Header Packet { Long Header Packet {
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Source Connection ID Length (8), Source Connection ID Length (8),
Source Connection ID (0..160), Source Connection ID (0..160),
Type-Specific Payload (..), Type-Specific Payload (..),
} }
Figure 13: Long Header Packet Format Figure 13: Long Header Packet Format
Long headers are used for packets that are sent prior to the Long headers are used for packets that are sent prior to the
establishment of 1-RTT keys. Once 1-RTT keys are available, a sender establishment of 1-RTT keys. Once 1-RTT keys are available, a sender
switches to sending packets using the short header (Section 17.3). switches to sending packets using the short header (Section 17.3).
The long form allows for special packets - such as the Version The long form allows for special packets -- such as the Version
Negotiation packet - to be represented in this uniform fixed-length Negotiation packet -- to be represented in this uniform fixed-length
packet format. Packets that use the long header contain the packet format. Packets that use the long header contain the
following fields: following fields:
Header Form: The most significant bit (0x80) of byte 0 (the first Header Form: The most significant bit (0x80) of byte 0 (the first
byte) is set to 1 for long headers. byte) is set to 1 for long headers.
Fixed Bit: The next bit (0x40) of byte 0 is set to 1, unless the Fixed Bit: The next bit (0x40) of byte 0 is set to 1, unless the
packet is a Version Negotiation packet. Packets containing a zero packet is a Version Negotiation packet. Packets containing a zero
value for this bit are not valid packets in this version and MUST value for this bit are not valid packets in this version and MUST
be discarded. A value of 1 for this bit allows QUIC to coexist be discarded. A value of 1 for this bit allows QUIC to coexist
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a mask of 0x0f) of byte 0 are determined by the packet type. a mask of 0x0f) of byte 0 are determined by the packet type.
Version: The QUIC Version is a 32-bit field that follows the first Version: The QUIC Version is a 32-bit field that follows the first
byte. This field indicates the version of QUIC that is in use and byte. This field indicates the version of QUIC that is in use and
determines how the rest of the protocol fields are interpreted. determines how the rest of the protocol fields are interpreted.
Destination Connection ID Length: The byte following the version Destination Connection ID Length: The byte following the version
contains the length in bytes of the Destination Connection ID contains the length in bytes of the Destination Connection ID
field that follows it. This length is encoded as an 8-bit field that follows it. This length is encoded as an 8-bit
unsigned integer. In QUIC version 1, this value MUST NOT exceed unsigned integer. In QUIC version 1, this value MUST NOT exceed
20. Endpoints that receive a version 1 long header with a value 20 bytes. Endpoints that receive a version 1 long header with a
larger than 20 MUST drop the packet. In order to properly form a value larger than 20 MUST drop the packet. In order to properly
Version Negotiation packet, servers SHOULD be able to read longer form a Version Negotiation packet, servers SHOULD be able to read
connection IDs from other QUIC versions. longer connection IDs from other QUIC versions.
Destination Connection ID: The Destination Connection ID field Destination Connection ID: The Destination Connection ID field
follows the Destination Connection ID Length field, which follows the Destination Connection ID Length field, which
indicates the length of this field. Section 7.2 describes the use indicates the length of this field. Section 7.2 describes the use
of this field in more detail. of this field in more detail.
Source Connection ID Length: The byte following the Destination Source Connection ID Length: The byte following the Destination
Connection ID contains the length in bytes of the Source Connection ID contains the length in bytes of the Source
Connection ID field that follows it. This length is encoded as a Connection ID field that follows it. This length is encoded as an
8-bit unsigned integer. In QUIC version 1, this value MUST NOT 8-bit unsigned integer. In QUIC version 1, this value MUST NOT
exceed 20 bytes. Endpoints that receive a version 1 long header exceed 20 bytes. Endpoints that receive a version 1 long header
with a value larger than 20 MUST drop the packet. In order to with a value larger than 20 MUST drop the packet. In order to
properly form a Version Negotiation packet, servers SHOULD be able properly form a Version Negotiation packet, servers SHOULD be able
to read longer connection IDs from other QUIC versions. to read longer connection IDs from other QUIC versions.
Source Connection ID: The Source Connection ID field follows the Source Connection ID: The Source Connection ID field follows the
Source Connection ID Length field, which indicates the length of Source Connection ID Length field, which indicates the length of
this field. Section 7.2 describes the use of this field in more this field. Section 7.2 describes the use of this field in more
detail. detail.
Type-Specific Payload: The remainder of the packet, if any, is type- Type-Specific Payload: The remainder of the packet, if any, is type
specific. specific.
In this version of QUIC, the following packet types with the long In this version of QUIC, the following packet types with the long
header are defined: header are defined:
+------+-----------+-----------------+ +------+-----------+-----------------+
| Type | Name | Section | | Type | Name | Section |
+------+-----------+-----------------+ +------+-----------+-----------------+
| 0x0 | Initial | Section 17.2.2 | | 0x00 | Initial | Section 17.2.2 |
| | | | | | | |
| 0x1 | 0-RTT | Section 17.2.3 | | 0x01 | 0-RTT | Section 17.2.3 |
| | | | | | | |
| 0x2 | Handshake | Section 17.2.4 | | 0x02 | Handshake | Section 17.2.4 |
| | | | | | | |
| 0x3 | Retry | Section 17.2.5 | | 0x03 | Retry | Section 17.2.5 |
+------+-----------+-----------------+ +------+-----------+-----------------+
Table 5: Long Header Packet Types Table 5: Long Header Packet Types
The header form bit, Destination and Source Connection ID lengths, The header form bit, Destination and Source Connection ID lengths,
Destination and Source Connection ID fields, and Version fields of a Destination and Source Connection ID fields, and Version fields of a
long header packet are version-independent. The other fields in the long header packet are version independent. The other fields in the
first byte are version-specific. See [QUIC-INVARIANTS] for details first byte are version specific. See [QUIC-INVARIANTS] for details
on how packets from different versions of QUIC are interpreted. on how packets from different versions of QUIC are interpreted.
The interpretation of the fields and the payload are specific to a The interpretation of the fields and the payload are specific to a
version and packet type. While type-specific semantics for this version and packet type. While type-specific semantics for this
version are described in the following sections, several long-header version are described in the following sections, several long header
packets in this version of QUIC contain these additional fields: packets in this version of QUIC contain these additional fields:
Reserved Bits: Two bits (those with a mask of 0x0c) of byte 0 are Reserved Bits: Two bits (those with a mask of 0x0c) of byte 0 are
reserved across multiple packet types. These bits are protected reserved across multiple packet types. These bits are protected
using header protection; see Section 5.4 of [QUIC-TLS]. The value using header protection; see Section 5.4 of [QUIC-TLS]. The value
included prior to protection MUST be set to 0. An endpoint MUST included prior to protection MUST be set to 0. An endpoint MUST
treat receipt of a packet that has a non-zero value for these bits treat receipt of a packet that has a non-zero value for these bits
after removing both packet and header protection as a connection after removing both packet and header protection as a connection
error of type PROTOCOL_VIOLATION. Discarding such a packet after error of type PROTOCOL_VIOLATION. Discarding such a packet after
only removing header protection can expose the endpoint to only removing header protection can expose the endpoint to
attacks; see Section 9.5 of [QUIC-TLS]. attacks; see Section 9.5 of [QUIC-TLS].
Packet Number Length: In packet types that contain a Packet Number Packet Number Length: In packet types that contain a Packet Number
field, the least significant two bits (those with a mask of 0x03) field, the least significant two bits (those with a mask of 0x03)
of byte 0 contain the length of the packet number, encoded as an of byte 0 contain the length of the Packet Number field, encoded
unsigned, two-bit integer that is one less than the length of the as an unsigned two-bit integer that is one less than the length of
packet number field in bytes. That is, the length of the packet the Packet Number field in bytes. That is, the length of the
number field is the value of this field, plus one. These bits are Packet Number field is the value of this field plus one. These
protected using header protection; see Section 5.4 of [QUIC-TLS]. bits are protected using header protection; see Section 5.4 of
[QUIC-TLS].
Length: The length of the remainder of the packet (that is, the Length: This is the length of the remainder of the packet (that is,
Packet Number and Payload fields) in bytes, encoded as a variable- the Packet Number and Payload fields) in bytes, encoded as a
length integer (Section 16). variable-length integer (Section 16).
Packet Number: The packet number field is 1 to 4 bytes long. The Packet Number: This field is 1 to 4 bytes long. The packet number
packet number is protected using header protection; see is protected using header protection; see Section 5.4 of
Section 5.4 of [QUIC-TLS]. The length of the packet number field [QUIC-TLS]. The length of the Packet Number field is encoded in
is encoded in the Packet Number Length bits of byte 0; see above. the Packet Number Length bits of byte 0; see above.
Packet Payload: This is the payload of the packet -- containing a
sequence of frames -- that is protected using packet protection.
17.2.1. Version Negotiation Packet 17.2.1. Version Negotiation Packet
A Version Negotiation packet is inherently not version-specific. A Version Negotiation packet is inherently not version specific.
Upon receipt by a client, it will be identified as a Version Upon receipt by a client, it will be identified as a Version
Negotiation packet based on the Version field having a value of 0. Negotiation packet based on the Version field having a value of 0.
The Version Negotiation packet is a response to a client packet that The Version Negotiation packet is a response to a client packet that
contains a version that is not supported by the server, and is only contains a version that is not supported by the server. It is only
sent by servers. sent by servers.
The layout of a Version Negotiation packet is: The layout of a Version Negotiation packet is:
Version Negotiation Packet { Version Negotiation Packet {
Header Form (1) = 1, Header Form (1) = 1,
Unused (7), Unused (7),
Version (32) = 0, Version (32) = 0,
Destination Connection ID Length (8), Destination Connection ID Length (8),
Destination Connection ID (0..2040), Destination Connection ID (0..2040),
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Destination Connection ID of the received packet, which is initially Destination Connection ID of the received packet, which is initially
randomly selected by a client. Echoing both connection IDs gives randomly selected by a client. Echoing both connection IDs gives
clients some assurance that the server received the packet and that clients some assurance that the server received the packet and that
the Version Negotiation packet was not generated by an entity that the Version Negotiation packet was not generated by an entity that
did not observe the Initial packet. did not observe the Initial packet.
Future versions of QUIC could have different requirements for the Future versions of QUIC could have different requirements for the
lengths of connection IDs. In particular, connection IDs might have lengths of connection IDs. In particular, connection IDs might have
a smaller minimum length or a greater maximum length. Version- a smaller minimum length or a greater maximum length. Version-
specific rules for the connection ID therefore MUST NOT influence a specific rules for the connection ID therefore MUST NOT influence a
server decision about whether to send a Version Negotiation packet. decision about whether to send a Version Negotiation packet.
The remainder of the Version Negotiation packet is a list of 32-bit The remainder of the Version Negotiation packet is a list of 32-bit
versions that the server supports. versions that the server supports.
A Version Negotiation packet is not acknowledged. It is only sent in A Version Negotiation packet is not acknowledged. It is only sent in
response to a packet that indicates an unsupported version; see response to a packet that indicates an unsupported version; see
Section 5.2.2. Section 5.2.2.
The Version Negotiation packet does not include the Packet Number and The Version Negotiation packet does not include the Packet Number and
Length fields present in other packets that use the long header form. Length fields present in other packets that use the long header form.
Consequently, a Version Negotiation packet consumes an entire UDP Consequently, a Version Negotiation packet consumes an entire UDP
datagram. datagram.
A server MUST NOT send more than one Version Negotiation packet in A server MUST NOT send more than one Version Negotiation packet in
response to a single UDP datagram. response to a single UDP datagram.
See Section 6 for a description of the version negotiation process. See Section 6 for a description of the version negotiation process.
17.2.2. Initial Packet 17.2.2. Initial Packet
An Initial packet uses long headers with a type value of 0x0. It An Initial packet uses long headers with a type value of 0x00. It
carries the first CRYPTO frames sent by the client and server to carries the first CRYPTO frames sent by the client and server to
perform key exchange, and carries ACKs in either direction. perform key exchange, and it carries ACK frames in either direction.
Initial Packet { Initial Packet {
Header Form (1) = 1, Header Form (1) = 1,
Fixed Bit (1) = 1, Fixed Bit (1) = 1,
Long Packet Type (2) = 0, Long Packet Type (2) = 0,
Reserved Bits (2), Reserved Bits (2),
Packet Number Length (2), Packet Number Length (2),
Version (32), Version (32),
Destination Connection ID Length (8), Destination Connection ID Length (8),
Destination Connection ID (0..160), Destination Connection ID (0..160),
skipping to change at page 112, line 12 skipping to change at page 111, line 32
Figure 15: Initial Packet Figure 15: Initial Packet
The Initial packet contains a long header as well as the Length and The Initial packet contains a long header as well as the Length and
Packet Number fields; see Section 17.2. The first byte contains the Packet Number fields; see Section 17.2. The first byte contains the
Reserved and Packet Number Length bits; see also Section 17.2. Reserved and Packet Number Length bits; see also Section 17.2.
Between the Source Connection ID and Length fields, there are two Between the Source Connection ID and Length fields, there are two
additional fields specific to the Initial packet. additional fields specific to the Initial packet.
Token Length: A variable-length integer specifying the length of the Token Length: A variable-length integer specifying the length of the
Token field, in bytes. This value is zero if no token is present. Token field, in bytes. This value is 0 if no token is present.
Initial packets sent by the server MUST set the Token Length field Initial packets sent by the server MUST set the Token Length field
to zero; clients that receive an Initial packet with a non-zero to 0; clients that receive an Initial packet with a non-zero Token
Token Length field MUST either discard the packet or generate a Length field MUST either discard the packet or generate a
connection error of type PROTOCOL_VIOLATION. connection error of type PROTOCOL_VIOLATION.
Token: The value of the token that was previously provided in a Token: The value of the token that was previously provided in a
Retry packet or NEW_TOKEN frame; see Section 8.1. Retry packet or NEW_TOKEN frame; see Section 8.1.
Packet Payload: The payload of the packet.
In order to prevent tampering by version-unaware middleboxes, Initial In order to prevent tampering by version-unaware middleboxes, Initial
packets are protected with connection- and version-specific keys packets are protected with connection- and version-specific keys
(Initial keys) as described in [QUIC-TLS]. This protection does not (Initial keys) as described in [QUIC-TLS]. This protection does not
provide confidentiality or integrity against attackers that can provide confidentiality or integrity against attackers that can
observe packets, but provides some level of protection against observe packets, but it does prevent attackers that cannot observe
attackers that cannot observe packets. packets from spoofing Initial packets.
The client and server use the Initial packet type for any packet that The client and server use the Initial packet type for any packet that
contains an initial cryptographic handshake message. This includes contains an initial cryptographic handshake message. This includes
all cases where a new packet containing the initial cryptographic all cases where a new packet containing the initial cryptographic
message needs to be created, such as the packets sent after receiving message needs to be created, such as the packets sent after receiving
a Retry packet (Section 17.2.5). a Retry packet; see Section 17.2.5.
A server sends its first Initial packet in response to a client A server sends its first Initial packet in response to a client
Initial. A server MAY send multiple Initial packets. The Initial. A server MAY send multiple Initial packets. The
cryptographic key exchange could require multiple round trips or cryptographic key exchange could require multiple round trips or
retransmissions of this data. retransmissions of this data.
The payload of an Initial packet includes a CRYPTO frame (or frames) The payload of an Initial packet includes a CRYPTO frame (or frames)
containing a cryptographic handshake message, ACK frames, or both. containing a cryptographic handshake message, ACK frames, or both.
PING, PADDING, and CONNECTION_CLOSE frames of type 0x1c are also PING, PADDING, and CONNECTION_CLOSE frames of type 0x1c are also
permitted. An endpoint that receives an Initial packet containing permitted. An endpoint that receives an Initial packet containing
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A client stops both sending and processing Initial packets when it A client stops both sending and processing Initial packets when it
sends its first Handshake packet. A server stops sending and sends its first Handshake packet. A server stops sending and
processing Initial packets when it receives its first Handshake processing Initial packets when it receives its first Handshake
packet. Though packets might still be in flight or awaiting packet. Though packets might still be in flight or awaiting
acknowledgment, no further Initial packets need to be exchanged acknowledgment, no further Initial packets need to be exchanged
beyond this point. Initial packet protection keys are discarded (see beyond this point. Initial packet protection keys are discarded (see
Section 4.9.1 of [QUIC-TLS]) along with any loss recovery and Section 4.9.1 of [QUIC-TLS]) along with any loss recovery and
congestion control state; see Section 6.4 of [QUIC-RECOVERY]. congestion control state; see Section 6.4 of [QUIC-RECOVERY].
Any data in CRYPTO frames is discarded - and no longer retransmitted Any data in CRYPTO frames is discarded -- and no longer retransmitted
- when Initial keys are discarded. -- when Initial keys are discarded.
17.2.3. 0-RTT 17.2.3. 0-RTT
A 0-RTT packet uses long headers with a type value of 0x1, followed A 0-RTT packet uses long headers with a type value of 0x01, followed
by the Length and Packet Number fields; see Section 17.2. The first by the Length and Packet Number fields; see Section 17.2. The first
byte contains the Reserved and Packet Number Length bits; see byte contains the Reserved and Packet Number Length bits; see
Section 17.2. A 0-RTT packet is used to carry "early" data from the Section 17.2. A 0-RTT packet is used to carry "early" data from the
client to the server as part of the first flight, prior to handshake client to the server as part of the first flight, prior to handshake
completion. As part of the TLS handshake, the server can accept or completion. As part of the TLS handshake, the server can accept or
reject this early data. reject this early data.
See Section 2.3 of [TLS13] for a discussion of 0-RTT data and its See Section 2.3 of [TLS13] for a discussion of 0-RTT data and its
limitations. limitations.
skipping to change at page 114, line 49 skipping to change at page 114, line 7
client cannot send an ACK frame in a 0-RTT packet, because that can client cannot send an ACK frame in a 0-RTT packet, because that can
only acknowledge a 1-RTT packet. An acknowledgment for a 1-RTT only acknowledge a 1-RTT packet. An acknowledgment for a 1-RTT
packet MUST be carried in a 1-RTT packet. packet MUST be carried in a 1-RTT packet.
A server SHOULD treat a violation of remembered limits A server SHOULD treat a violation of remembered limits
(Section 7.4.1) as a connection error of an appropriate type (for (Section 7.4.1) as a connection error of an appropriate type (for
instance, a FLOW_CONTROL_ERROR for exceeding stream data limits). instance, a FLOW_CONTROL_ERROR for exceeding stream data limits).
17.2.4. Handshake Packet 17.2.4. Handshake Packet
A Handshake packet uses long headers with a type value of 0x2, A Handshake packet uses long headers with a type value of 0x02,
followed by the Length and Packet Number fields; see Section 17.2. followed by the Length and Packet Number fields; see Section 17.2.
The first byte contains the Reserved and Packet Number Length bits; The first byte contains the Reserved and Packet Number Length bits;
see Section 17.2. It is used to carry cryptographic handshake see Section 17.2. It is used to carry cryptographic handshake
messages and acknowledgments from the server and client. messages and acknowledgments from the server and client.
Handshake Packet { Handshake Packet {
Header Form (1) = 1, Header Form (1) = 1,
Fixed Bit (1) = 1, Fixed Bit (1) = 1,
Long Packet Type (2) = 2, Long Packet Type (2) = 2,
Reserved Bits (2), Reserved Bits (2),
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first Handshake packet sent by a server contains a packet number of first Handshake packet sent by a server contains a packet number of
0. 0.
The payload of this packet contains CRYPTO frames and could contain The payload of this packet contains CRYPTO frames and could contain
PING, PADDING, or ACK frames. Handshake packets MAY contain PING, PADDING, or ACK frames. Handshake packets MAY contain
CONNECTION_CLOSE frames of type 0x1c. Endpoints MUST treat receipt CONNECTION_CLOSE frames of type 0x1c. Endpoints MUST treat receipt
of Handshake packets with other frames as a connection error of type of Handshake packets with other frames as a connection error of type
PROTOCOL_VIOLATION. PROTOCOL_VIOLATION.
Like Initial packets (see Section 17.2.2.1), data in CRYPTO frames Like Initial packets (see Section 17.2.2.1), data in CRYPTO frames
for Handshake packets is discarded - and no longer retransmitted - for Handshake packets is discarded -- and no longer retransmitted --
when Handshake protection keys are discarded. when Handshake protection keys are discarded.
17.2.5. Retry Packet 17.2.5. Retry Packet
A Retry packet uses a long packet header with a type value of 0x3. As shown in Figure 17, a Retry packet uses a long packet header with
It carries an address validation token created by the server. It is a type value of 0x03. It carries an address validation token created
used by a server that wishes to perform a retry; see Section 8.1. by the server. It is used by a server that wishes to perform a
retry; see Section 8.1.
Retry Packet { Retry Packet {
Header Form (1) = 1, Header Form (1) = 1,
Fixed Bit (1) = 1, Fixed Bit (1) = 1,
Long Packet Type (2) = 3, Long Packet Type (2) = 3,
Unused (4), Unused (4),
Version (32), Version (32),
Destination Connection ID Length (8), Destination Connection ID Length (8),
Destination Connection ID (0..160), Destination Connection ID (0..160),
Source Connection ID Length (8), Source Connection ID Length (8),
Source Connection ID (0..160), Source Connection ID (0..160),
Retry Token (..), Retry Token (..),
Retry Integrity Tag (128), Retry Integrity Tag (128),
} }
Figure 17: Retry Packet Figure 17: Retry Packet
A Retry packet (shown in Figure 17) does not contain any protected A Retry packet does not contain any protected fields. The value in
fields. The value in the Unused field is set to an arbitrary value the Unused field is set to an arbitrary value by the server; a client
by the server; a client MUST ignore these bits. In addition to the MUST ignore these bits. In addition to the fields from the long
fields from the long header, it contains these additional fields: header, it contains these additional fields:
Retry Token: An opaque token that the server can use to validate the Retry Token: An opaque token that the server can use to validate the
client's address. client's address.
Retry Integrity Tag: See the Retry Packet Integrity section of Retry Integrity Tag: Defined in Section "Retry Packet Integrity"
[QUIC-TLS]. [QUIC-TLS] of [QUIC-TLS].
17.2.5.1. Sending a Retry Packet 17.2.5.1. Sending a Retry Packet
The server populates the Destination Connection ID with the The server populates the Destination Connection ID with the
connection ID that the client included in the Source Connection ID of connection ID that the client included in the Source Connection ID of
the Initial packet. the Initial packet.
The server includes a connection ID of its choice in the Source The server includes a connection ID of its choice in the Source
Connection ID field. This value MUST NOT be equal to the Destination Connection ID field. This value MUST NOT be equal to the Destination
Connection ID field of the packet sent by the client. A client MUST Connection ID field of the packet sent by the client. A client MUST
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packet in response to a single UDP datagram. packet in response to a single UDP datagram.
17.2.5.2. Handling a Retry Packet 17.2.5.2. Handling a Retry Packet
A client MUST accept and process at most one Retry packet for each A client MUST accept and process at most one Retry packet for each
connection attempt. After the client has received and processed an connection attempt. After the client has received and processed an
Initial or Retry packet from the server, it MUST discard any Initial or Retry packet from the server, it MUST discard any
subsequent Retry packets that it receives. subsequent Retry packets that it receives.
Clients MUST discard Retry packets that have a Retry Integrity Tag Clients MUST discard Retry packets that have a Retry Integrity Tag
that cannot be validated; see the Retry Packet Integrity section of that cannot be validated; see Section 5.8 of [QUIC-TLS]. This
[QUIC-TLS]. This diminishes an attacker's ability to inject a Retry diminishes an attacker's ability to inject a Retry packet and
packet and protects against accidental corruption of Retry packets. protects against accidental corruption of Retry packets. A client
A client MUST discard a Retry packet with a zero-length Retry Token MUST discard a Retry packet with a zero-length Retry Token field.
field.
The client responds to a Retry packet with an Initial packet that The client responds to a Retry packet with an Initial packet that
includes the provided Retry Token to continue connection includes the provided Retry token to continue connection
establishment. establishment.
A client sets the Destination Connection ID field of this Initial A client sets the Destination Connection ID field of this Initial
packet to the value from the Source Connection ID in the Retry packet to the value from the Source Connection ID field in the Retry
packet. Changing Destination Connection ID also results in a change packet. Changing the Destination Connection ID field also results in
to the keys used to protect the Initial packet. It also sets the a change to the keys used to protect the Initial packet. It also
Token field to the token provided in the Retry. The client MUST NOT sets the Token field to the token provided in the Retry packet. The
change the Source Connection ID because the server could include the client MUST NOT change the Source Connection ID because the server
connection ID as part of its token validation logic; see could include the connection ID as part of its token validation
Section 8.1.4. logic; see Section 8.1.4.
A Retry packet does not include a packet number and cannot be A Retry packet does not include a packet number and cannot be
explicitly acknowledged by a client. explicitly acknowledged by a client.
17.2.5.3. Continuing a Handshake After Retry 17.2.5.3. Continuing a Handshake after Retry
Subsequent Initial packets from the client include the connection ID Subsequent Initial packets from the client include the connection ID
and token values from the Retry packet. The client copies the Source and token values from the Retry packet. The client copies the Source
Connection ID field from the Retry packet to the Destination Connection ID field from the Retry packet to the Destination
Connection ID field and uses this value until an Initial packet with Connection ID field and uses this value until an Initial packet with
an updated value is received; see Section 7.2. The value of the an updated value is received; see Section 7.2. The value of the
Token field is copied to all subsequent Initial packets; see Token field is copied to all subsequent Initial packets; see
Section 8.1.2. Section 8.1.2.
Other than updating the Destination Connection ID and Token fields, Other than updating the Destination Connection ID and Token fields,
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contain confidential information that will most likely be contain confidential information that will most likely be
retransmitted on receiving a Retry packet. The keys used to protect retransmitted on receiving a Retry packet. The keys used to protect
these new 0-RTT packets will not change as a result of responding to these new 0-RTT packets will not change as a result of responding to
a Retry packet. However, the data sent in these packets could be a Retry packet. However, the data sent in these packets could be
different than what was sent earlier. Sending these new packets with different than what was sent earlier. Sending these new packets with
the same packet number is likely to compromise the packet protection the same packet number is likely to compromise the packet protection
for those packets because the same key and nonce could be used to for those packets because the same key and nonce could be used to
protect different content. A server MAY abort the connection if it protect different content. A server MAY abort the connection if it
detects that the client reset the packet number. detects that the client reset the packet number.
The connection IDs used on Initial and Retry packets exchanged The connection IDs used in Initial and Retry packets exchanged
between client and server are copied to the transport parameters and between client and server are copied to the transport parameters and
validated as described in Section 7.3. validated as described in Section 7.3.
17.3. Short Header Packets 17.3. Short Header Packets
This version of QUIC defines a single packet type that uses the short This version of QUIC defines a single packet type that uses the short
packet header. packet header.
17.3.1. 1-RTT Packet 17.3.1. 1-RTT Packet
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header protection can expose the endpoint to attacks; see header protection can expose the endpoint to attacks; see
Section 9.5 of [QUIC-TLS]. Section 9.5 of [QUIC-TLS].
Key Phase: The next bit (0x04) of byte 0 indicates the key phase, Key Phase: The next bit (0x04) of byte 0 indicates the key phase,
which allows a recipient of a packet to identify the packet which allows a recipient of a packet to identify the packet
protection keys that are used to protect the packet. See protection keys that are used to protect the packet. See
[QUIC-TLS] for details. This bit is protected using header [QUIC-TLS] for details. This bit is protected using header
protection; see Section 5.4 of [QUIC-TLS]. protection; see Section 5.4 of [QUIC-TLS].
Packet Number Length: The least significant two bits (those with a Packet Number Length: The least significant two bits (those with a
mask of 0x03) of byte 0 contain the length of the packet number, mask of 0x03) of byte 0 contain the length of the Packet Number
encoded as an unsigned, two-bit integer that is one less than the field, encoded as an unsigned two-bit integer that is one less
length of the packet number field in bytes. That is, the length than the length of the Packet Number field in bytes. That is, the
of the packet number field is the value of this field, plus one. length of the Packet Number field is the value of this field plus
one. These bits are protected using header protection; see
These bits are protected using header protection; see Section 5.4 Section 5.4 of [QUIC-TLS].
of [QUIC-TLS].
Destination Connection ID: The Destination Connection ID is a Destination Connection ID: The Destination Connection ID is a
connection ID that is chosen by the intended recipient of the connection ID that is chosen by the intended recipient of the
packet. See Section 5.1 for more details. packet. See Section 5.1 for more details.
Packet Number: The packet number field is 1 to 4 bytes long. The Packet Number: The Packet Number field is 1 to 4 bytes long. The
packet number is protected using header protection; see packet number is protected using header protection; see
Section 5.4 of [QUIC-TLS]. The length of the packet number field Section 5.4 of [QUIC-TLS]. The length of the Packet Number field
is encoded in Packet Number Length field. See Section 17.1 for is encoded in Packet Number Length field. See Section 17.1 for
details. details.
Packet Payload: 1-RTT packets always include a 1-RTT protected Packet Payload: 1-RTT packets always include a 1-RTT protected
payload. payload.
The header form bit and the connection ID field of a short header The header form bit and the Destination Connection ID field of a
packet are version-independent. The remaining fields are specific to short header packet are version independent. The remaining fields
the selected QUIC version. See [QUIC-INVARIANTS] for details on how are specific to the selected QUIC version. See [QUIC-INVARIANTS] for
packets from different versions of QUIC are interpreted. details on how packets from different versions of QUIC are
interpreted.
17.4. Latency Spin Bit 17.4. Latency Spin Bit
The latency spin bit, which is defined for 1-RTT packets The latency spin bit, which is defined for 1-RTT packets
(Section 17.3.1), enables passive latency monitoring from observation (Section 17.3.1), enables passive latency monitoring from observation
points on the network path throughout the duration of a connection. points on the network path throughout the duration of a connection.
The server reflects the spin value received, while the client 'spins' The server reflects the spin value received, while the client "spins"
it after one RTT. On-path observers can measure the time between two it after one RTT. On-path observers can measure the time between two
spin bit toggle events to estimate the end-to-end RTT of a spin bit toggle events to estimate the end-to-end RTT of a
connection. connection.
The spin bit is only present in 1-RTT packets, since it is possible The spin bit is only present in 1-RTT packets, since it is possible
to measure the initial RTT of a connection by observing the to measure the initial RTT of a connection by observing the
handshake. Therefore, the spin bit is available after version handshake. Therefore, the spin bit is available after version
negotiation and connection establishment are completed. On-path negotiation and connection establishment are completed. On-path
measurement and use of the latency spin bit is further discussed in measurement and use of the latency spin bit are further discussed in
[QUIC-MANAGEABILITY]. [QUIC-MANAGEABILITY].
The spin bit is an OPTIONAL feature of this version of QUIC. An The spin bit is an OPTIONAL feature of this version of QUIC. An
endpoint that does not support this feature MUST disable it, as endpoint that does not support this feature MUST disable it, as
defined below. defined below.
Each endpoint unilaterally decides if the spin bit is enabled or Each endpoint unilaterally decides if the spin bit is enabled or
disabled for a connection. Implementations MUST allow administrators disabled for a connection. Implementations MUST allow administrators
of clients and servers to disable the spin bit either globally or on of clients and servers to disable the spin bit either globally or on
a per-connection basis. Even when the spin bit is not disabled by a per-connection basis. Even when the spin bit is not disabled by
the administrator, endpoints MUST disable their use of the spin bit the administrator, endpoints MUST disable their use of the spin bit
for a random selection of at least one in every 16 network paths, or for a random selection of at least one in every 16 network paths, or
for one in every 16 connection IDs, in order to ensure that QUIC for one in every 16 connection IDs, in order to ensure that QUIC
connections that disable the spin bit are commonly observed on the connections that disable the spin bit are commonly observed on the
network. As each endpoint disables the spin bit independently, this network. As each endpoint disables the spin bit independently, this
ensures that the spin bit signal is disabled on approximately one in ensures that the spin bit signal is disabled on approximately one in
eight network paths. eight network paths.
When the spin bit is disabled, endpoints MAY set the spin bit to any When the spin bit is disabled, endpoints MAY set the spin bit to any
value, and MUST ignore any incoming value. It is RECOMMENDED that value and MUST ignore any incoming value. It is RECOMMENDED that
endpoints set the spin bit to a random value either chosen endpoints set the spin bit to a random value either chosen
independently for each packet or chosen independently for each independently for each packet or chosen independently for each
connection ID. connection ID.
If the spin bit is enabled for the connection, the endpoint maintains If the spin bit is enabled for the connection, the endpoint maintains
a spin value for each network path and sets the spin bit in the a spin value for each network path and sets the spin bit in the
packet header to the currently stored value when a 1-RTT packet is packet header to the currently stored value when a 1-RTT packet is
sent on that path. The spin value is initialized to 0 in the sent on that path. The spin value is initialized to 0 in the
endpoint for each network path. Each endpoint also remembers the endpoint for each network path. Each endpoint also remembers the
highest packet number seen from its peer on each path. highest packet number seen from its peer on each path.
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When a server receives a 1-RTT packet that increases the highest When a server receives a 1-RTT packet that increases the highest
packet number seen by the server from the client on a given network packet number seen by the server from the client on a given network
path, it sets the spin value for that path to be equal to the spin path, it sets the spin value for that path to be equal to the spin
bit in the received packet. bit in the received packet.
When a client receives a 1-RTT packet that increases the highest When a client receives a 1-RTT packet that increases the highest
packet number seen by the client from the server on a given network packet number seen by the client from the server on a given network
path, it sets the spin value for that path to the inverse of the spin path, it sets the spin value for that path to the inverse of the spin
bit in the received packet. bit in the received packet.
An endpoint resets the spin value for a network path to zero when An endpoint resets the spin value for a network path to 0 when
changing the connection ID being used on that network path. changing the connection ID being used on that network path.
18. Transport Parameter Encoding 18. Transport Parameter Encoding
The extension_data field of the quic_transport_parameters extension The extension_data field of the quic_transport_parameters extension
defined in [QUIC-TLS] contains the QUIC transport parameters. They defined in [QUIC-TLS] contains the QUIC transport parameters. They
are encoded as a sequence of transport parameters, as shown in are encoded as a sequence of transport parameters, as shown in
Figure 18: Figure 18:
Transport Parameters { Transport Parameters {
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Transport Parameter Value field in bytes. Transport Parameter Value field in bytes.
QUIC encodes transport parameters into a sequence of bytes, which is QUIC encodes transport parameters into a sequence of bytes, which is
then included in the cryptographic handshake. then included in the cryptographic handshake.
18.1. Reserved Transport Parameters 18.1. Reserved Transport Parameters
Transport parameters with an identifier of the form "31 * N + 27" for Transport parameters with an identifier of the form "31 * N + 27" for
integer values of N are reserved to exercise the requirement that integer values of N are reserved to exercise the requirement that
unknown transport parameters be ignored. These transport parameters unknown transport parameters be ignored. These transport parameters
have no semantics, and can carry arbitrary values. have no semantics and can carry arbitrary values.
18.2. Transport Parameter Definitions 18.2. Transport Parameter Definitions
This section details the transport parameters defined in this This section details the transport parameters defined in this
document. document.
Many transport parameters listed here have integer values. Those Many transport parameters listed here have integer values. Those
transport parameters that are identified as integers use a variable- transport parameters that are identified as integers use a variable-
length integer encoding; see Section 16. Transport parameters have a length integer encoding; see Section 16. Transport parameters have a
default value of 0 if the transport parameter is absent unless default value of 0 if the transport parameter is absent, unless
otherwise stated. otherwise stated.
The following transport parameters are defined: The following transport parameters are defined:
original_destination_connection_id (0x00): The value of the original_destination_connection_id (0x00): This parameter is the
Destination Connection ID field from the first Initial packet sent value of the Destination Connection ID field from the first
by the client; see Section 7.3. This transport parameter is only Initial packet sent by the client; see Section 7.3. This
sent by a server. transport parameter is only sent by a server.
max_idle_timeout (0x01): The max idle timeout is a value in max_idle_timeout (0x01): The maximum idle timeout is a value in
milliseconds that is encoded as an integer; see (Section 10.1). milliseconds that is encoded as an integer; see (Section 10.1).
Idle timeout is disabled when both endpoints omit this transport Idle timeout is disabled when both endpoints omit this transport
parameter or specify a value of 0. parameter or specify a value of 0.
stateless_reset_token (0x02): A stateless reset token is used in stateless_reset_token (0x02): A stateless reset token is used in
verifying a stateless reset; see Section 10.3. This parameter is verifying a stateless reset; see Section 10.3. This parameter is
a sequence of 16 bytes. This transport parameter MUST NOT be sent a sequence of 16 bytes. This transport parameter MUST NOT be sent
by a client, but MAY be sent by a server. A server that does not by a client but MAY be sent by a server. A server that does not
send this transport parameter cannot use stateless reset send this transport parameter cannot use stateless reset
(Section 10.3) for the connection ID negotiated during the (Section 10.3) for the connection ID negotiated during the
handshake. handshake.
max_udp_payload_size (0x03): The maximum UDP payload size parameter max_udp_payload_size (0x03): The maximum UDP payload size parameter
is an integer value that limits the size of UDP payloads that the is an integer value that limits the size of UDP payloads that the
endpoint is willing to receive. UDP datagrams with payloads endpoint is willing to receive. UDP datagrams with payloads
larger than this limit are not likely to be processed by the larger than this limit are not likely to be processed by the
receiver. receiver.
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packets. packets.
initial_max_data (0x04): The initial maximum data parameter is an initial_max_data (0x04): The initial maximum data parameter is an
integer value that contains the initial value for the maximum integer value that contains the initial value for the maximum
amount of data that can be sent on the connection. This is amount of data that can be sent on the connection. This is
equivalent to sending a MAX_DATA (Section 19.9) for the connection equivalent to sending a MAX_DATA (Section 19.9) for the connection
immediately after completing the handshake. immediately after completing the handshake.
initial_max_stream_data_bidi_local (0x05): This parameter is an initial_max_stream_data_bidi_local (0x05): This parameter is an
integer value specifying the initial flow control limit for integer value specifying the initial flow control limit for
locally-initiated bidirectional streams. This limit applies to locally initiated bidirectional streams. This limit applies to
newly created bidirectional streams opened by the endpoint that newly created bidirectional streams opened by the endpoint that
sends the transport parameter. In client transport parameters, sends the transport parameter. In client transport parameters,
this applies to streams with an identifier with the least this applies to streams with an identifier with the least
significant two bits set to 0x0; in server transport parameters, significant two bits set to 0x00; in server transport parameters,
this applies to streams with the least significant two bits set to this applies to streams with the least significant two bits set to
0x1. 0x01.
initial_max_stream_data_bidi_remote (0x06): This parameter is an initial_max_stream_data_bidi_remote (0x06): This parameter is an
integer value specifying the initial flow control limit for peer- integer value specifying the initial flow control limit for peer-
initiated bidirectional streams. This limit applies to newly initiated bidirectional streams. This limit applies to newly
created bidirectional streams opened by the endpoint that receives created bidirectional streams opened by the endpoint that receives
the transport parameter. In client transport parameters, this the transport parameter. In client transport parameters, this
applies to streams with an identifier with the least significant applies to streams with an identifier with the least significant
two bits set to 0x1; in server transport parameters, this applies two bits set to 0x01; in server transport parameters, this applies
to streams with the least significant two bits set to 0x0. to streams with the least significant two bits set to 0x00.
initial_max_stream_data_uni (0x07): This parameter is an integer initial_max_stream_data_uni (0x07): This parameter is an integer
value specifying the initial flow control limit for unidirectional value specifying the initial flow control limit for unidirectional
streams. This limit applies to newly created unidirectional streams. This limit applies to newly created unidirectional
streams opened by the endpoint that receives the transport streams opened by the endpoint that receives the transport
parameter. In client transport parameters, this applies to parameter. In client transport parameters, this applies to
streams with an identifier with the least significant two bits set streams with an identifier with the least significant two bits set
to 0x3; in server transport parameters, this applies to streams to 0x03; in server transport parameters, this applies to streams
with the least significant two bits set to 0x2. with the least significant two bits set to 0x02.
initial_max_streams_bidi (0x08): The initial maximum bidirectional initial_max_streams_bidi (0x08): The initial maximum bidirectional
streams parameter is an integer value that contains the initial streams parameter is an integer value that contains the initial
maximum number of bidirectional streams the endpoint that receives maximum number of bidirectional streams the endpoint that receives
this transport parameter is permitted to initiate. If this this transport parameter is permitted to initiate. If this
parameter is absent or zero, the peer cannot open bidirectional parameter is absent or zero, the peer cannot open bidirectional
streams until a MAX_STREAMS frame is sent. Setting this parameter streams until a MAX_STREAMS frame is sent. Setting this parameter
is equivalent to sending a MAX_STREAMS (Section 19.11) of the is equivalent to sending a MAX_STREAMS (Section 19.11) of the
corresponding type with the same value. corresponding type with the same value.
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preferred_address (0x0d): The server's preferred address is used to preferred_address (0x0d): The server's preferred address is used to
effect a change in server address at the end of the handshake, as effect a change in server address at the end of the handshake, as
described in Section 9.6. This transport parameter is only sent described in Section 9.6. This transport parameter is only sent
by a server. Servers MAY choose to only send a preferred address by a server. Servers MAY choose to only send a preferred address
of one address family by sending an all-zero address and port of one address family by sending an all-zero address and port
(0.0.0.0:0 or [::]:0) for the other family. IP addresses are (0.0.0.0:0 or [::]:0) for the other family. IP addresses are
encoded in network byte order. encoded in network byte order.
The preferred_address transport parameter contains an address and The preferred_address transport parameter contains an address and
port for both IP version 4 and 6. The four-byte IPv4 Address port for both IPv4 and IPv6. The four-byte IPv4 Address field is
field is followed by the associated two-byte IPv4 Port field. followed by the associated two-byte IPv4 Port field. This is
This is followed by a 16-byte IPv6 Address field and two-byte IPv6 followed by a 16-byte IPv6 Address field and two-byte IPv6 Port
Port field. After address and port pairs, a Connection ID Length field. After address and port pairs, a Connection ID Length field
field describes the length of the following Connection ID field. describes the length of the following Connection ID field.
Finally, a 16-byte Stateless Reset Token field includes the Finally, a 16-byte Stateless Reset Token field includes the
stateless reset token associated with the connection ID. The stateless reset token associated with the connection ID. The
format of this transport parameter is shown in Figure 20. format of this transport parameter is shown in Figure 20 below.
The Connection ID field and the Stateless Reset Token field The Connection ID field and the Stateless Reset Token field
contain an alternative connection ID that has a sequence number of contain an alternative connection ID that has a sequence number of
1; see Section 5.1.1. Having these values sent alongside the 1; see Section 5.1.1. Having these values sent alongside the
preferred address ensures that there will be at least one unused preferred address ensures that there will be at least one unused
active connection ID when the client initiates migration to the active connection ID when the client initiates migration to the
preferred address. preferred address.
The Connection ID and Stateless Reset Token fields of a preferred The Connection ID and Stateless Reset Token fields of a preferred
address are identical in syntax and semantics to the corresponding address are identical in syntax and semantics to the corresponding
fields of a NEW_CONNECTION_ID frame (Section 19.15). A server fields of a NEW_CONNECTION_ID frame (Section 19.15). A server
that chooses a zero-length connection ID MUST NOT provide a that chooses a zero-length connection ID MUST NOT provide a
preferred address. Similarly, a server MUST NOT include a zero- preferred address. Similarly, a server MUST NOT include a zero-
length connection ID in this transport parameter. A client MUST length connection ID in this transport parameter. A client MUST
treat violation of these requirements as a connection error of treat a violation of these requirements as a connection error of
type TRANSPORT_PARAMETER_ERROR. type TRANSPORT_PARAMETER_ERROR.
Preferred Address { Preferred Address {
IPv4 Address (32), IPv4 Address (32),
IPv4 Port (16), IPv4 Port (16),
IPv6 Address (128), IPv6 Address (128),
IPv6 Port (16), IPv6 Port (16),
Connection ID Length (8), Connection ID Length (8),
Connection ID (..), Connection ID (..),
Stateless Reset Token (128), Stateless Reset Token (128),
} }
Figure 20: Preferred Address format Figure 20: Preferred Address Format
active_connection_id_limit (0x0e): The active connection ID limit is active_connection_id_limit (0x0e): This is an integer value
an integer value specifying the maximum number of connection IDs specifying the maximum number of connection IDs from the peer that
from the peer that an endpoint is willing to store. This value an endpoint is willing to store. This value includes the
includes the connection ID received during the handshake, that connection ID received during the handshake, that received in the
received in the preferred_address transport parameter, and those preferred_address transport parameter, and those received in
received in NEW_CONNECTION_ID frames. The value of the NEW_CONNECTION_ID frames. The value of the
active_connection_id_limit parameter MUST be at least 2. An active_connection_id_limit parameter MUST be at least 2. An
endpoint that receives a value less than 2 MUST close the endpoint that receives a value less than 2 MUST close the
connection with an error of type TRANSPORT_PARAMETER_ERROR. If connection with an error of type TRANSPORT_PARAMETER_ERROR. If
this transport parameter is absent, a default of 2 is assumed. If this transport parameter is absent, a default of 2 is assumed. If
an endpoint issues a zero-length connection ID, it will never send an endpoint issues a zero-length connection ID, it will never send
a NEW_CONNECTION_ID frame and therefore ignores the a NEW_CONNECTION_ID frame and therefore ignores the
active_connection_id_limit value received from its peer. active_connection_id_limit value received from its peer.
initial_source_connection_id (0x0f): The value that the endpoint initial_source_connection_id (0x0f): This is the value that the
included in the Source Connection ID field of the first Initial endpoint included in the Source Connection ID field of the first
packet it sends for the connection; see Section 7.3. Initial packet it sends for the connection; see Section 7.3.
retry_source_connection_id (0x10): The value that the server retry_source_connection_id (0x10): This is the value that the server
included in the Source Connection ID field of a Retry packet; see included in the Source Connection ID field of a Retry packet; see
Section 7.3. This transport parameter is only sent by a server. Section 7.3. This transport parameter is only sent by a server.
If present, transport parameters that set initial per-stream flow If present, transport parameters that set initial per-stream flow
control limits (initial_max_stream_data_bidi_local, control limits (initial_max_stream_data_bidi_local,
initial_max_stream_data_bidi_remote, and initial_max_stream_data_uni) initial_max_stream_data_bidi_remote, and initial_max_stream_data_uni)
are equivalent to sending a MAX_STREAM_DATA frame (Section 19.10) on are equivalent to sending a MAX_STREAM_DATA frame (Section 19.10) on
every stream of the corresponding type immediately after opening. If every stream of the corresponding type immediately after opening. If
the transport parameter is absent, streams of that type start with a the transport parameter is absent, streams of that type start with a
flow control limit of 0. flow control limit of 0.
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19. Frame Types and Formats 19. Frame Types and Formats
As described in Section 12.4, packets contain one or more frames. As described in Section 12.4, packets contain one or more frames.
This section describes the format and semantics of the core QUIC This section describes the format and semantics of the core QUIC
frame types. frame types.
19.1. PADDING Frames 19.1. PADDING Frames
A PADDING frame (type=0x00) has no semantic value. PADDING frames A PADDING frame (type=0x00) has no semantic value. PADDING frames
can be used to increase the size of a packet. Padding can be used to can be used to increase the size of a packet. Padding can be used to
increase an initial client packet to the minimum required size, or to increase an Initial packet to the minimum required size or to provide
provide protection against traffic analysis for protected packets. protection against traffic analysis for protected packets.
PADDING frames are formatted as shown in Figure 21, which shows that PADDING frames are formatted as shown in Figure 21, which shows that
PADDING frames have no content. That is, a PADDING frame consists of PADDING frames have no content. That is, a PADDING frame consists of
the single byte that identifies the frame as a PADDING frame. the single byte that identifies the frame as a PADDING frame.
PADDING Frame { PADDING Frame {
Type (i) = 0x00, Type (i) = 0x00,
} }
Figure 21: PADDING Frame Format Figure 21: PADDING Frame Format
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from timing out; see Section 10.1.2. from timing out; see Section 10.1.2.
19.3. ACK Frames 19.3. ACK Frames
Receivers send ACK frames (types 0x02 and 0x03) to inform senders of Receivers send ACK frames (types 0x02 and 0x03) to inform senders of
packets they have received and processed. The ACK frame contains one packets they have received and processed. The ACK frame contains one
or more ACK Ranges. ACK Ranges identify acknowledged packets. If or more ACK Ranges. ACK Ranges identify acknowledged packets. If
the frame type is 0x03, ACK frames also contain the cumulative count the frame type is 0x03, ACK frames also contain the cumulative count
of QUIC packets with associated ECN marks received on the connection of QUIC packets with associated ECN marks received on the connection
up until this point. QUIC implementations MUST properly handle both up until this point. QUIC implementations MUST properly handle both
types and, if they have enabled ECN for packets they send, they types, and, if they have enabled ECN for packets they send, they
SHOULD use the information in the ECN section to manage their SHOULD use the information in the ECN section to manage their
congestion state. congestion state.
QUIC acknowledgments are irrevocable. Once acknowledged, a packet QUIC acknowledgments are irrevocable. Once acknowledged, a packet
remains acknowledged, even if it does not appear in a future ACK remains acknowledged, even if it does not appear in a future ACK
frame. This is unlike reneging for TCP SACKs ([RFC2018]). frame. This is unlike reneging for TCP Selective Acknowledgments
(SACKs) [RFC2018].
Packets from different packet number spaces can be identified using Packets from different packet number spaces can be identified using
the same numeric value. An acknowledgment for a packet needs to the same numeric value. An acknowledgment for a packet needs to
indicate both a packet number and a packet number space. This is indicate both a packet number and a packet number space. This is
accomplished by having each ACK frame only acknowledge packet numbers accomplished by having each ACK frame only acknowledge packet numbers
in the same space as the packet in which the ACK frame is contained. in the same space as the packet in which the ACK frame is contained.
Version Negotiation and Retry packets cannot be acknowledged because Version Negotiation and Retry packets cannot be acknowledged because
they do not contain a packet number. Rather than relying on ACK they do not contain a packet number. Rather than relying on ACK
frames, these packets are implicitly acknowledged by the next Initial frames, these packets are implicitly acknowledged by the next Initial
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values within the same number of bytes, at the cost of lower values within the same number of bytes, at the cost of lower
resolution. resolution.
ACK Range Count: A variable-length integer specifying the number of ACK Range Count: A variable-length integer specifying the number of
ACK Range fields in the frame. ACK Range fields in the frame.
First ACK Range: A variable-length integer indicating the number of First ACK Range: A variable-length integer indicating the number of
contiguous packets preceding the Largest Acknowledged that are contiguous packets preceding the Largest Acknowledged that are
being acknowledged. That is, the smallest packet acknowledged in being acknowledged. That is, the smallest packet acknowledged in
the range is determined by subtracting the First ACK Range value the range is determined by subtracting the First ACK Range value
from the Largest Acknowledged. from the Largest Acknowledged field.
ACK Ranges: Contains additional ranges of packets that are ACK Ranges: Contains additional ranges of packets that are
alternately not acknowledged (Gap) and acknowledged (ACK Range); alternately not acknowledged (Gap) and acknowledged (ACK Range);
see Section 19.3.1. see Section 19.3.1.
ECN Counts: The three ECN Counts; see Section 19.3.2. ECN Counts: The three ECN counts; see Section 19.3.2.
19.3.1. ACK Ranges 19.3.1. ACK Ranges
Each ACK Range consists of alternating Gap and ACK Range Length Each ACK Range consists of alternating Gap and ACK Range Length
values in descending packet number order. ACK Ranges can be values in descending packet number order. ACK Ranges can be
repeated. The number of Gap and ACK Range Length values is repeated. The number of Gap and ACK Range Length values is
determined by the ACK Range Count field; one of each value is present determined by the ACK Range Count field; one of each value is present
for each value in the ACK Range Count field. for each value in the ACK Range Count field.
ACK Ranges are structured as shown in Figure 24. ACK Ranges are structured as shown in Figure 24.
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contiguous acknowledged packets preceding the largest packet contiguous acknowledged packets preceding the largest packet
number, as determined by the preceding Gap. number, as determined by the preceding Gap.
Gap and ACK Range Length values use a relative integer encoding for Gap and ACK Range Length values use a relative integer encoding for
efficiency. Though each encoded value is positive, the values are efficiency. Though each encoded value is positive, the values are
subtracted, so that each ACK Range describes progressively lower- subtracted, so that each ACK Range describes progressively lower-
numbered packets. numbered packets.
Each ACK Range acknowledges a contiguous range of packets by Each ACK Range acknowledges a contiguous range of packets by
indicating the number of acknowledged packets that precede the indicating the number of acknowledged packets that precede the
largest packet number in that range. A value of zero indicates that largest packet number in that range. A value of 0 indicates that
only the largest packet number is acknowledged. Larger ACK Range only the largest packet number is acknowledged. Larger ACK Range
values indicate a larger range, with corresponding lower values for values indicate a larger range, with corresponding lower values for
the smallest packet number in the range. Thus, given a largest the smallest packet number in the range. Thus, given a largest
packet number for the range, the smallest value is determined by the packet number for the range, the smallest value is determined by the
formula: following formula:
smallest = largest - ack_range smallest = largest - ack_range
An ACK Range acknowledges all packets between the smallest packet An ACK Range acknowledges all packets between the smallest packet
number and the largest, inclusive. number and the largest, inclusive.
The largest value for an ACK Range is determined by cumulatively The largest value for an ACK Range is determined by cumulatively
subtracting the size of all preceding ACK Range Lengths and Gaps. subtracting the size of all preceding ACK Range Lengths and Gaps.
Each Gap indicates a range of packets that are not being Each Gap indicates a range of packets that are not being
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largest = previous_smallest - gap - 2 largest = previous_smallest - gap - 2
If any computed packet number is negative, an endpoint MUST generate If any computed packet number is negative, an endpoint MUST generate
a connection error of type FRAME_ENCODING_ERROR. a connection error of type FRAME_ENCODING_ERROR.
19.3.2. ECN Counts 19.3.2. ECN Counts
The ACK frame uses the least significant bit of the type value (that The ACK frame uses the least significant bit of the type value (that
is, type 0x03) to indicate ECN feedback and report receipt of QUIC is, type 0x03) to indicate ECN feedback and report receipt of QUIC
packets with associated ECN codepoints of ECT(0), ECT(1), or CE in packets with associated ECN codepoints of ECT(0), ECT(1), or ECN-CE
the packet's IP header. ECN Counts are only present when the ACK in the packet's IP header. ECN counts are only present when the ACK
frame type is 0x03. frame type is 0x03.
When present, there are 3 ECN counts, as shown in Figure 25. When present, there are three ECN counts, as shown in Figure 25.
ECN Counts { ECN Counts {
ECT0 Count (i), ECT0 Count (i),
ECT1 Count (i), ECT1 Count (i),
ECN-CE Count (i), ECN-CE Count (i),
} }
Figure 25: ECN Count Format Figure 25: ECN Count Format
The three ECN Counts are: The ECN count fields are:
ECT0 Count: A variable-length integer representing the total number ECT0 Count: A variable-length integer representing the total number
of packets received with the ECT(0) codepoint in the packet number of packets received with the ECT(0) codepoint in the packet number
space of the ACK frame. space of the ACK frame.
ECT1 Count: A variable-length integer representing the total number ECT1 Count: A variable-length integer representing the total number
of packets received with the ECT(1) codepoint in the packet number of packets received with the ECT(1) codepoint in the packet number
space of the ACK frame. space of the ACK frame.
CE Count: A variable-length integer representing the total number of ECN-CE Count: A variable-length integer representing the total
packets received with the CE codepoint in the packet number space number of packets received with the ECN-CE codepoint in the packet
of the ACK frame. number space of the ACK frame.
ECN counts are maintained separately for each packet number space. ECN counts are maintained separately for each packet number space.
19.4. RESET_STREAM Frames 19.4. RESET_STREAM Frames
An endpoint uses a RESET_STREAM frame (type=0x04) to abruptly An endpoint uses a RESET_STREAM frame (type=0x04) to abruptly
terminate the sending part of a stream. terminate the sending part of a stream.
After sending a RESET_STREAM, an endpoint ceases transmission and After sending a RESET_STREAM, an endpoint ceases transmission and
retransmission of STREAM frames on the identified stream. A receiver retransmission of STREAM frames on the identified stream. A receiver
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Type (i) = 0x04, Type (i) = 0x04,
Stream ID (i), Stream ID (i),
Application Protocol Error Code (i), Application Protocol Error Code (i),
Final Size (i), Final Size (i),
} }
Figure 26: RESET_STREAM Frame Format Figure 26: RESET_STREAM Frame Format
RESET_STREAM frames contain the following fields: RESET_STREAM frames contain the following fields:
Stream ID: A variable-length integer encoding of the Stream ID of Stream ID: A variable-length integer encoding of the stream ID of
the stream being terminated. the stream being terminated.
Application Protocol Error Code: A variable-length integer Application Protocol Error Code: A variable-length integer
containing the application protocol error code (see Section 20.2) containing the application protocol error code (see Section 20.2)
that indicates why the stream is being closed. that indicates why the stream is being closed.
Final Size: A variable-length integer indicating the final size of Final Size: A variable-length integer indicating the final size of
the stream by the RESET_STREAM sender, in unit of bytes; see the stream by the RESET_STREAM sender, in units of bytes; see
Section 4.5. Section 4.5.
19.5. STOP_SENDING Frames 19.5. STOP_SENDING Frames
An endpoint uses a STOP_SENDING frame (type=0x05) to communicate that An endpoint uses a STOP_SENDING frame (type=0x05) to communicate that
incoming data is being discarded on receipt at application request. incoming data is being discarded on receipt per application request.
STOP_SENDING requests that a peer cease transmission on a stream. STOP_SENDING requests that a peer cease transmission on a stream.
A STOP_SENDING frame can be sent for streams in the Recv or Size A STOP_SENDING frame can be sent for streams in the "Recv" or "Size
Known states; see Section 3.1. Receiving a STOP_SENDING frame for a Known" states; see Section 3.2. Receiving a STOP_SENDING frame for a
locally-initiated stream that has not yet been created MUST be locally initiated stream that has not yet been created MUST be
treated as a connection error of type STREAM_STATE_ERROR. An treated as a connection error of type STREAM_STATE_ERROR. An
endpoint that receives a STOP_SENDING frame for a receive-only stream endpoint that receives a STOP_SENDING frame for a receive-only stream
MUST terminate the connection with error STREAM_STATE_ERROR. MUST terminate the connection with error STREAM_STATE_ERROR.
STOP_SENDING frames are formatted as shown in Figure 27. STOP_SENDING frames are formatted as shown in Figure 27.
STOP_SENDING Frame { STOP_SENDING Frame {
Type (i) = 0x05, Type (i) = 0x05,
Stream ID (i), Stream ID (i),
Application Protocol Error Code (i), Application Protocol Error Code (i),
} }
Figure 27: STOP_SENDING Frame Format Figure 27: STOP_SENDING Frame Format
STOP_SENDING frames contain the following fields: STOP_SENDING frames contain the following fields:
Stream ID: A variable-length integer carrying the Stream ID of the Stream ID: A variable-length integer carrying the stream ID of the
stream being ignored. stream being ignored.
Application Protocol Error Code: A variable-length integer Application Protocol Error Code: A variable-length integer
containing the application-specified reason the sender is ignoring containing the application-specified reason the sender is ignoring
the stream; see Section 20.2. the stream; see Section 20.2.
19.6. CRYPTO Frames 19.6. CRYPTO Frames
A CRYPTO frame (type=0x06) is used to transmit cryptographic A CRYPTO frame (type=0x06) is used to transmit cryptographic
handshake messages. It can be sent in all packet types except 0-RTT. handshake messages. It can be sent in all packet types except 0-RTT.
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Length: A variable-length integer specifying the length of the Length: A variable-length integer specifying the length of the
Crypto Data field in this CRYPTO frame. Crypto Data field in this CRYPTO frame.
Crypto Data: The cryptographic message data. Crypto Data: The cryptographic message data.
There is a separate flow of cryptographic handshake data in each There is a separate flow of cryptographic handshake data in each
encryption level, each of which starts at an offset of 0. This encryption level, each of which starts at an offset of 0. This
implies that each encryption level is treated as a separate CRYPTO implies that each encryption level is treated as a separate CRYPTO
stream of data. stream of data.
The largest offset delivered on a stream - the sum of the offset and The largest offset delivered on a stream -- the sum of the offset and
data length - cannot exceed 2^62-1. Receipt of a frame that exceeds data length -- cannot exceed 2^62-1. Receipt of a frame that exceeds
this limit MUST be treated as a connection error of type this limit MUST be treated as a connection error of type
FRAME_ENCODING_ERROR or CRYPTO_BUFFER_EXCEEDED. FRAME_ENCODING_ERROR or CRYPTO_BUFFER_EXCEEDED.
Unlike STREAM frames, which include a Stream ID indicating to which Unlike STREAM frames, which include a stream ID indicating to which
stream the data belongs, the CRYPTO frame carries data for a single stream the data belongs, the CRYPTO frame carries data for a single
stream per encryption level. The stream does not have an explicit stream per encryption level. The stream does not have an explicit
end, so CRYPTO frames do not have a FIN bit. end, so CRYPTO frames do not have a FIN bit.
19.7. NEW_TOKEN Frames 19.7. NEW_TOKEN Frames
A server sends a NEW_TOKEN frame (type=0x07) to provide the client A server sends a NEW_TOKEN frame (type=0x07) to provide the client
with a token to send in the header of an Initial packet for a future with a token to send in the header of an Initial packet for a future
connection. connection.
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duplicate values, which might be used to link connection attempts; duplicate values, which might be used to link connection attempts;
see Section 8.1.3. see Section 8.1.3.
Clients MUST NOT send NEW_TOKEN frames. A server MUST treat receipt Clients MUST NOT send NEW_TOKEN frames. A server MUST treat receipt
of a NEW_TOKEN frame as a connection error of type of a NEW_TOKEN frame as a connection error of type
PROTOCOL_VIOLATION. PROTOCOL_VIOLATION.
19.8. STREAM Frames 19.8. STREAM Frames
STREAM frames implicitly create a stream and carry stream data. The STREAM frames implicitly create a stream and carry stream data. The
STREAM frame Type field takes the form 0b00001XXX (or the set of Type field in the STREAM frame takes the form 0b00001XXX (or the set
values from 0x08 to 0x0f). The three low-order bits of the frame of values from 0x08 to 0x0f). The three low-order bits of the frame
type determine the fields that are present in the frame: type determine the fields that are present in the frame:
o The OFF bit (0x04) in the frame type is set to indicate that there o The OFF bit (0x04) in the frame type is set to indicate that there
is an Offset field present. When set to 1, the Offset field is is an Offset field present. When set to 1, the Offset field is
present. When set to 0, the Offset field is absent and the Stream present. When set to 0, the Offset field is absent and the Stream
Data starts at an offset of 0 (that is, the frame contains the Data starts at an offset of 0 (that is, the frame contains the
first bytes of the stream, or the end of a stream that includes no first bytes of the stream, or the end of a stream that includes no
data). data).
o The LEN bit (0x02) in the frame type is set to indicate that there o The LEN bit (0x02) in the frame type is set to indicate that there
is a Length field present. If this bit is set to 0, the Length is a Length field present. If this bit is set to 0, the Length
field is absent and the Stream Data field extends to the end of field is absent and the Stream Data field extends to the end of
the packet. If this bit is set to 1, the Length field is present. the packet. If this bit is set to 1, the Length field is present.
o The FIN bit (0x01) indicates that the frame marks the end of the o The FIN bit (0x01) indicates that the frame marks the end of the
stream. The final size of the stream is the sum of the offset and stream. The final size of the stream is the sum of the offset and
the length of this frame. the length of this frame.
An endpoint MUST terminate the connection with error An endpoint MUST terminate the connection with error
STREAM_STATE_ERROR if it receives a STREAM frame for a locally- STREAM_STATE_ERROR if it receives a STREAM frame for a locally
initiated stream that has not yet been created, or for a send-only initiated stream that has not yet been created, or for a send-only
stream. stream.
STREAM frames are formatted as shown in Figure 30. STREAM frames are formatted as shown in Figure 30.
STREAM Frame { STREAM Frame {
Type (i) = 0x08..0x0f, Type (i) = 0x08..0x0f,
Stream ID (i), Stream ID (i),
[Offset (i)], [Offset (i)],
[Length (i)], [Length (i)],
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Stream Data field in this STREAM frame. This field is present Stream Data field in this STREAM frame. This field is present
when the LEN bit is set to 1. When the LEN bit is set to 0, the when the LEN bit is set to 1. When the LEN bit is set to 0, the
Stream Data field consumes all the remaining bytes in the packet. Stream Data field consumes all the remaining bytes in the packet.
Stream Data: The bytes from the designated stream to be delivered. Stream Data: The bytes from the designated stream to be delivered.
When a Stream Data field has a length of 0, the offset in the STREAM When a Stream Data field has a length of 0, the offset in the STREAM
frame is the offset of the next byte that would be sent. frame is the offset of the next byte that would be sent.
The first byte in the stream has an offset of 0. The largest offset The first byte in the stream has an offset of 0. The largest offset
delivered on a stream - the sum of the offset and data length - delivered on a stream -- the sum of the offset and data length --
cannot exceed 2^62-1, as it is not possible to provide flow control cannot exceed 2^62-1, as it is not possible to provide flow control
credit for that data. Receipt of a frame that exceeds this limit credit for that data. Receipt of a frame that exceeds this limit
MUST be treated as a connection error of type FRAME_ENCODING_ERROR or MUST be treated as a connection error of type FRAME_ENCODING_ERROR or
FLOW_CONTROL_ERROR. FLOW_CONTROL_ERROR.
19.9. MAX_DATA Frames 19.9. MAX_DATA Frames
A MAX_DATA frame (type=0x10) is used in flow control to inform the A MAX_DATA frame (type=0x10) is used in flow control to inform the
peer of the maximum amount of data that can be sent on the connection peer of the maximum amount of data that can be sent on the connection
as a whole. as a whole.
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Figure 31: MAX_DATA Frame Format Figure 31: MAX_DATA Frame Format
MAX_DATA frames contain the following field: MAX_DATA frames contain the following field:
Maximum Data: A variable-length integer indicating the maximum Maximum Data: A variable-length integer indicating the maximum
amount of data that can be sent on the entire connection, in units amount of data that can be sent on the entire connection, in units
of bytes. of bytes.
All data sent in STREAM frames counts toward this limit. The sum of All data sent in STREAM frames counts toward this limit. The sum of
the final sizes on all streams - including streams in terminal states the final sizes on all streams -- including streams in terminal
- MUST NOT exceed the value advertised by a receiver. An endpoint states -- MUST NOT exceed the value advertised by a receiver. An
MUST terminate a connection with a FLOW_CONTROL_ERROR error if it endpoint MUST terminate a connection with an error of type
receives more data than the maximum data value that it has sent. FLOW_CONTROL_ERROR if it receives more data than the maximum data
This includes violations of remembered limits in Early Data; see value that it has sent. This includes violations of remembered
Section 7.4.1. limits in Early Data; see Section 7.4.1.
19.10. MAX_STREAM_DATA Frames 19.10. MAX_STREAM_DATA Frames
A MAX_STREAM_DATA frame (type=0x11) is used in flow control to inform A MAX_STREAM_DATA frame (type=0x11) is used in flow control to inform
a peer of the maximum amount of data that can be sent on a stream. a peer of the maximum amount of data that can be sent on a stream.
A MAX_STREAM_DATA frame can be sent for streams in the Recv state; A MAX_STREAM_DATA frame can be sent for streams in the "Recv" state;
see Section 3.1. Receiving a MAX_STREAM_DATA frame for a locally- see Section 3.2. Receiving a MAX_STREAM_DATA frame for a locally
initiated stream that has not yet been created MUST be treated as a initiated stream that has not yet been created MUST be treated as a
connection error of type STREAM_STATE_ERROR. An endpoint that connection error of type STREAM_STATE_ERROR. An endpoint that
receives a MAX_STREAM_DATA frame for a receive-only stream MUST receives a MAX_STREAM_DATA frame for a receive-only stream MUST
terminate the connection with error STREAM_STATE_ERROR. terminate the connection with error STREAM_STATE_ERROR.
MAX_STREAM_DATA frames are formatted as shown in Figure 32. MAX_STREAM_DATA frames are formatted as shown in Figure 32.
MAX_STREAM_DATA Frame { MAX_STREAM_DATA Frame {
Type (i) = 0x11, Type (i) = 0x11,
Stream ID (i), Stream ID (i),
Maximum Stream Data (i), Maximum Stream Data (i),
} }
Figure 32: MAX_STREAM_DATA Frame Format Figure 32: MAX_STREAM_DATA Frame Format
MAX_STREAM_DATA frames contain the following fields: MAX_STREAM_DATA frames contain the following fields:
Stream ID: The stream ID of the stream that is affected encoded as a Stream ID: The stream ID of the affected stream, encoded as a
variable-length integer. variable-length integer.
Maximum Stream Data: A variable-length integer indicating the Maximum Stream Data: A variable-length integer indicating the
maximum amount of data that can be sent on the identified stream, maximum amount of data that can be sent on the identified stream,
in units of bytes. in units of bytes.
When counting data toward this limit, an endpoint accounts for the When counting data toward this limit, an endpoint accounts for the
largest received offset of data that is sent or received on the largest received offset of data that is sent or received on the
stream. Loss or reordering can mean that the largest received offset stream. Loss or reordering can mean that the largest received offset
on a stream can be greater than the total size of data received on on a stream can be greater than the total size of data received on
that stream. Receiving STREAM frames might not increase the largest that stream. Receiving STREAM frames might not increase the largest
received offset. received offset.
The data sent on a stream MUST NOT exceed the largest maximum stream The data sent on a stream MUST NOT exceed the largest maximum stream
data value advertised by the receiver. An endpoint MUST terminate a data value advertised by the receiver. An endpoint MUST terminate a
connection with a FLOW_CONTROL_ERROR error if it receives more data connection with an error of type FLOW_CONTROL_ERROR if it receives
than the largest maximum stream data that it has sent for the more data than the largest maximum stream data that it has sent for
affected stream. This includes violations of remembered limits in the affected stream. This includes violations of remembered limits
Early Data; see Section 7.4.1. in Early Data; see Section 7.4.1.
19.11. MAX_STREAMS Frames 19.11. MAX_STREAMS Frames
A MAX_STREAMS frame (type=0x12 or 0x13) inform the peer of the A MAX_STREAMS frame (type=0x12 or 0x13) informs the peer of the
cumulative number of streams of a given type it is permitted to open. cumulative number of streams of a given type it is permitted to open.
A MAX_STREAMS frame with a type of 0x12 applies to bidirectional A MAX_STREAMS frame with a type of 0x12 applies to bidirectional
streams, and a MAX_STREAMS frame with a type of 0x13 applies to streams, and a MAX_STREAMS frame with a type of 0x13 applies to
unidirectional streams. unidirectional streams.
MAX_STREAMS frames are formatted as shown in Figure 33; MAX_STREAMS frames are formatted as shown in Figure 33.
MAX_STREAMS Frame { MAX_STREAMS Frame {
Type (i) = 0x12..0x13, Type (i) = 0x12..0x13,
Maximum Streams (i), Maximum Streams (i),
} }
Figure 33: MAX_STREAMS Frame Format Figure 33: MAX_STREAMS Frame Format
MAX_STREAMS frames contain the following field: MAX_STREAMS frames contain the following field:
Maximum Streams: A count of the cumulative number of streams of the Maximum Streams: A count of the cumulative number of streams of the
corresponding type that can be opened over the lifetime of the corresponding type that can be opened over the lifetime of the
connection. This value cannot exceed 2^60, as it is not possible connection. This value cannot exceed 2^60, as it is not possible
to encode stream IDs larger than 2^62-1. Receipt of a frame that to encode stream IDs larger than 2^62-1. Receipt of a frame that
permits opening of a stream larger than this limit MUST be treated permits opening of a stream larger than this limit MUST be treated
as a FRAME_ENCODING_ERROR. as a connection error of type FRAME_ENCODING_ERROR.
Loss or reordering can cause a MAX_STREAMS frame to be received that Loss or reordering can cause an endpoint to receive a MAX_STREAMS
state a lower stream limit than an endpoint has previously received. frame with a lower stream limit than was previously received.
MAX_STREAMS frames that do not increase the stream limit MUST be MAX_STREAMS frames that do not increase the stream limit MUST be
ignored. ignored.
An endpoint MUST NOT open more streams than permitted by the current An endpoint MUST NOT open more streams than permitted by the current
stream limit set by its peer. For instance, a server that receives a stream limit set by its peer. For instance, a server that receives a
unidirectional stream limit of 3 is permitted to open stream 3, 7, unidirectional stream limit of 3 is permitted to open streams 3, 7,
and 11, but not stream 15. An endpoint MUST terminate a connection and 11, but not stream 15. An endpoint MUST terminate a connection
with a STREAM_LIMIT_ERROR error if a peer opens more streams than was with an error of type STREAM_LIMIT_ERROR if a peer opens more streams
permitted. This includes violations of remembered limits in Early than was permitted. This includes violations of remembered limits in
Data; see Section 7.4.1. Early Data; see Section 7.4.1.
Note that these frames (and the corresponding transport parameters) Note that these frames (and the corresponding transport parameters)
do not describe the number of streams that can be opened do not describe the number of streams that can be opened
concurrently. The limit includes streams that have been closed as concurrently. The limit includes streams that have been closed as
well as those that are open. well as those that are open.
19.12. DATA_BLOCKED Frames 19.12. DATA_BLOCKED Frames
A sender SHOULD send a DATA_BLOCKED frame (type=0x14) when it wishes A sender SHOULD send a DATA_BLOCKED frame (type=0x14) when it wishes
to send data, but is unable to do so due to connection-level flow to send data but is unable to do so due to connection-level flow
control; see Section 4. DATA_BLOCKED frames can be used as input to control; see Section 4. DATA_BLOCKED frames can be used as input to
tuning of flow control algorithms; see Section 4.2. tuning of flow control algorithms; see Section 4.2.
DATA_BLOCKED frames are formatted as shown in Figure 34. DATA_BLOCKED frames are formatted as shown in Figure 34.
DATA_BLOCKED Frame { DATA_BLOCKED Frame {
Type (i) = 0x14, Type (i) = 0x14,
Maximum Data (i), Maximum Data (i),
} }
Figure 34: DATA_BLOCKED Frame Format Figure 34: DATA_BLOCKED Frame Format
DATA_BLOCKED frames contain the following field: DATA_BLOCKED frames contain the following field:
Maximum Data: A variable-length integer indicating the connection- Maximum Data: A variable-length integer indicating the connection-
level limit at which blocking occurred. level limit at which blocking occurred.
19.13. STREAM_DATA_BLOCKED Frames 19.13. STREAM_DATA_BLOCKED Frames
A sender SHOULD send a STREAM_DATA_BLOCKED frame (type=0x15) when it A sender SHOULD send a STREAM_DATA_BLOCKED frame (type=0x15) when it
wishes to send data, but is unable to do so due to stream-level flow wishes to send data but is unable to do so due to stream-level flow
control. This frame is analogous to DATA_BLOCKED (Section 19.12). control. This frame is analogous to DATA_BLOCKED (Section 19.12).
An endpoint that receives a STREAM_DATA_BLOCKED frame for a send-only An endpoint that receives a STREAM_DATA_BLOCKED frame for a send-only
stream MUST terminate the connection with error STREAM_STATE_ERROR. stream MUST terminate the connection with error STREAM_STATE_ERROR.
STREAM_DATA_BLOCKED frames are formatted as shown in Figure 35. STREAM_DATA_BLOCKED frames are formatted as shown in Figure 35.
STREAM_DATA_BLOCKED Frame { STREAM_DATA_BLOCKED Frame {
Type (i) = 0x15, Type (i) = 0x15,
Stream ID (i), Stream ID (i),
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Stream ID: A variable-length integer indicating the stream that is Stream ID: A variable-length integer indicating the stream that is
blocked due to flow control. blocked due to flow control.
Maximum Stream Data: A variable-length integer indicating the offset Maximum Stream Data: A variable-length integer indicating the offset
of the stream at which the blocking occurred. of the stream at which the blocking occurred.
19.14. STREAMS_BLOCKED Frames 19.14. STREAMS_BLOCKED Frames
A sender SHOULD send a STREAMS_BLOCKED frame (type=0x16 or 0x17) when A sender SHOULD send a STREAMS_BLOCKED frame (type=0x16 or 0x17) when
it wishes to open a stream, but is unable to due to the maximum it wishes to open a stream but is unable to do so due to the maximum
stream limit set by its peer; see Section 19.11. A STREAMS_BLOCKED stream limit set by its peer; see Section 19.11. A STREAMS_BLOCKED
frame of type 0x16 is used to indicate reaching the bidirectional frame of type 0x16 is used to indicate reaching the bidirectional
stream limit, and a STREAMS_BLOCKED frame of type 0x17 is used to stream limit, and a STREAMS_BLOCKED frame of type 0x17 is used to
indicate reaching the unidirectional stream limit. indicate reaching the unidirectional stream limit.
A STREAMS_BLOCKED frame does not open the stream, but informs the A STREAMS_BLOCKED frame does not open the stream, but informs the
peer that a new stream was needed and the stream limit prevented the peer that a new stream was needed and the stream limit prevented the
creation of the stream. creation of the stream.
STREAMS_BLOCKED frames are formatted as shown in Figure 36. STREAMS_BLOCKED frames are formatted as shown in Figure 36.
skipping to change at page 140, line 11 skipping to change at page 139, line 11
} }
Figure 36: STREAMS_BLOCKED Frame Format Figure 36: STREAMS_BLOCKED Frame Format
STREAMS_BLOCKED frames contain the following field: STREAMS_BLOCKED frames contain the following field:
Maximum Streams: A variable-length integer indicating the maximum Maximum Streams: A variable-length integer indicating the maximum
number of streams allowed at the time the frame was sent. This number of streams allowed at the time the frame was sent. This
value cannot exceed 2^60, as it is not possible to encode stream value cannot exceed 2^60, as it is not possible to encode stream
IDs larger than 2^62-1. Receipt of a frame that encodes a larger IDs larger than 2^62-1. Receipt of a frame that encodes a larger
stream ID MUST be treated as a STREAM_LIMIT_ERROR or a stream ID MUST be treated as a connection error of type
FRAME_ENCODING_ERROR. STREAM_LIMIT_ERROR or FRAME_ENCODING_ERROR.
19.15. NEW_CONNECTION_ID Frames 19.15. NEW_CONNECTION_ID Frames
An endpoint sends a NEW_CONNECTION_ID frame (type=0x18) to provide An endpoint sends a NEW_CONNECTION_ID frame (type=0x18) to provide
its peer with alternative connection IDs that can be used to break its peer with alternative connection IDs that can be used to break
linkability when migrating connections; see Section 9.5. linkability when migrating connections; see Section 9.5.
NEW_CONNECTION_ID frames are formatted as shown in Figure 37. NEW_CONNECTION_ID frames are formatted as shown in Figure 37.
NEW_CONNECTION_ID Frame { NEW_CONNECTION_ID Frame {
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FRAME_ENCODING_ERROR. FRAME_ENCODING_ERROR.
Connection ID: A connection ID of the specified length. Connection ID: A connection ID of the specified length.
Stateless Reset Token: A 128-bit value that will be used for a Stateless Reset Token: A 128-bit value that will be used for a
stateless reset when the associated connection ID is used; see stateless reset when the associated connection ID is used; see
Section 10.3. Section 10.3.
An endpoint MUST NOT send this frame if it currently requires that An endpoint MUST NOT send this frame if it currently requires that
its peer send packets with a zero-length Destination Connection ID. its peer send packets with a zero-length Destination Connection ID.
Changing the length of a connection ID to or from zero-length makes Changing the length of a connection ID to or from zero length makes
it difficult to identify when the value of the connection ID changed. it difficult to identify when the value of the connection ID changed.
An endpoint that is sending packets with a zero-length Destination An endpoint that is sending packets with a zero-length Destination
Connection ID MUST treat receipt of a NEW_CONNECTION_ID frame as a Connection ID MUST treat receipt of a NEW_CONNECTION_ID frame as a
connection error of type PROTOCOL_VIOLATION. connection error of type PROTOCOL_VIOLATION.
Transmission errors, timeouts and retransmissions might cause the Transmission errors, timeouts, and retransmissions might cause the
same NEW_CONNECTION_ID frame to be received multiple times. Receipt same NEW_CONNECTION_ID frame to be received multiple times. Receipt
of the same frame multiple times MUST NOT be treated as a connection of the same frame multiple times MUST NOT be treated as a connection
error. A receiver can use the sequence number supplied in the error. A receiver can use the sequence number supplied in the
NEW_CONNECTION_ID frame to handle receiving the same NEW_CONNECTION_ID frame to handle receiving the same
NEW_CONNECTION_ID frame multiple times. NEW_CONNECTION_ID frame multiple times.
If an endpoint receives a NEW_CONNECTION_ID frame that repeats a If an endpoint receives a NEW_CONNECTION_ID frame that repeats a
previously issued connection ID with a different Stateless Reset previously issued connection ID with a different Stateless Reset
Token or a different sequence number, or if a sequence number is used Token field value or a different Sequence Number field value, or if a
for different connection IDs, the endpoint MAY treat that receipt as sequence number is used for different connection IDs, the endpoint
a connection error of type PROTOCOL_VIOLATION. MAY treat that receipt as a connection error of type
PROTOCOL_VIOLATION.
The Retire Prior To field applies to connection IDs established The Retire Prior To field applies to connection IDs established
during connection setup and the preferred_address transport during connection setup and the preferred_address transport
parameter; see Section 5.1.2. The Retire Prior To field MUST be less parameter; see Section 5.1.2. The value in the Retire Prior To field
than or equal to the Sequence Number field. Receiving a value MUST be less than or equal to the value in the Sequence Number field.
greater than the Sequence Number MUST be treated as a connection Receiving a value in the Retire Prior To field that is greater than
that in the Sequence Number field MUST be treated as a connection
error of type FRAME_ENCODING_ERROR. error of type FRAME_ENCODING_ERROR.
Once a sender indicates a Retire Prior To value, smaller values sent Once a sender indicates a Retire Prior To value, smaller values sent
in subsequent NEW_CONNECTION_ID frames have no effect. A receiver in subsequent NEW_CONNECTION_ID frames have no effect. A receiver
MUST ignore any Retire Prior To fields that do not increase the MUST ignore any Retire Prior To fields that do not increase the
largest received Retire Prior To value. largest received Retire Prior To value.
An endpoint that receives a NEW_CONNECTION_ID frame with a sequence An endpoint that receives a NEW_CONNECTION_ID frame with a sequence
number smaller than the Retire Prior To field of a previously number smaller than the Retire Prior To field of a previously
received NEW_CONNECTION_ID frame MUST send a corresponding received NEW_CONNECTION_ID frame MUST send a corresponding
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PATH_CHALLENGE frames contain the following field: PATH_CHALLENGE frames contain the following field:
Data: This 8-byte field contains arbitrary data. Data: This 8-byte field contains arbitrary data.
Including 64 bits of entropy in a PATH_CHALLENGE frame ensures that Including 64 bits of entropy in a PATH_CHALLENGE frame ensures that
it is easier to receive the packet than it is to guess the value it is easier to receive the packet than it is to guess the value
correctly. correctly.
The recipient of this frame MUST generate a PATH_RESPONSE frame The recipient of this frame MUST generate a PATH_RESPONSE frame
(Section 19.18) containing the same Data. (Section 19.18) containing the same Data value.
19.18. PATH_RESPONSE Frames 19.18. PATH_RESPONSE Frames
A PATH_RESPONSE frame (type=0x1b) is sent in response to a A PATH_RESPONSE frame (type=0x1b) is sent in response to a
PATH_CHALLENGE frame. PATH_CHALLENGE frame.
PATH_RESPONSE frames are formatted as shown in Figure 40, which is PATH_RESPONSE frames are formatted as shown in Figure 40. The format
identical to the PATH_CHALLENGE frame (Section 19.17). of a PATH_RESPONSE frame is identical to that of the PATH_CHALLENGE
frame; see Section 19.17.
PATH_RESPONSE Frame { PATH_RESPONSE Frame {
Type (i) = 0x1b, Type (i) = 0x1b,
Data (64), Data (64),
} }
Figure 40: PATH_RESPONSE Frame Format Figure 40: PATH_RESPONSE Frame Format
If the content of a PATH_RESPONSE frame does not match the content of If the content of a PATH_RESPONSE frame does not match the content of
a PATH_CHALLENGE frame previously sent by the endpoint, the endpoint a PATH_CHALLENGE frame previously sent by the endpoint, the endpoint
MAY generate a connection error of type PROTOCOL_VIOLATION. MAY generate a connection error of type PROTOCOL_VIOLATION.
19.19. CONNECTION_CLOSE Frames 19.19. CONNECTION_CLOSE Frames
An endpoint sends a CONNECTION_CLOSE frame (type=0x1c or 0x1d) to An endpoint sends a CONNECTION_CLOSE frame (type=0x1c or 0x1d) to
notify its peer that the connection is being closed. The notify its peer that the connection is being closed. The
CONNECTION_CLOSE with a frame type of 0x1c is used to signal errors CONNECTION_CLOSE frame with a type of 0x1c is used to signal errors
at only the QUIC layer, or the absence of errors (with the NO_ERROR at only the QUIC layer, or the absence of errors (with the NO_ERROR
code). The CONNECTION_CLOSE frame with a type of 0x1d is used to code). The CONNECTION_CLOSE frame with a type of 0x1d is used to
signal an error with the application that uses QUIC. signal an error with the application that uses QUIC.
If there are open streams that have not been explicitly closed, they If there are open streams that have not been explicitly closed, they
are implicitly closed when the connection is closed. are implicitly closed when the connection is closed.
CONNECTION_CLOSE frames are formatted as shown in Figure 41. CONNECTION_CLOSE frames are formatted as shown in Figure 41.
CONNECTION_CLOSE Frame { CONNECTION_CLOSE Frame {
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Error Code (i), Error Code (i),
[Frame Type (i)], [Frame Type (i)],
Reason Phrase Length (i), Reason Phrase Length (i),
Reason Phrase (..), Reason Phrase (..),
} }
Figure 41: CONNECTION_CLOSE Frame Format Figure 41: CONNECTION_CLOSE Frame Format
CONNECTION_CLOSE frames contain the following fields: CONNECTION_CLOSE frames contain the following fields:
Error Code: A variable-length integer error code that indicates the Error Code: A variable-length integer that indicates the reason for
reason for closing this connection. A CONNECTION_CLOSE frame of closing this connection. A CONNECTION_CLOSE frame of type 0x1c
type 0x1c uses codes from the space defined in Section 20.1. A uses codes from the space defined in Section 20.1. A
CONNECTION_CLOSE frame of type 0x1d uses codes from the CONNECTION_CLOSE frame of type 0x1d uses codes defined by the
application protocol error code space; see Section 20.2. application protocol; see Section 20.2.
Frame Type: A variable-length integer encoding the type of frame Frame Type: A variable-length integer encoding the type of frame
that triggered the error. A value of 0 (equivalent to the mention that triggered the error. A value of 0 (equivalent to the mention
of the PADDING frame) is used when the frame type is unknown. The of the PADDING frame) is used when the frame type is unknown. The
application-specific variant of CONNECTION_CLOSE (type 0x1d) does application-specific variant of CONNECTION_CLOSE (type 0x1d) does
not include this field. not include this field.
Reason Phrase Length: A variable-length integer specifying the Reason Phrase Length: A variable-length integer specifying the
length of the reason phrase in bytes. Because a CONNECTION_CLOSE length of the reason phrase in bytes. Because a CONNECTION_CLOSE
frame cannot be split between packets, any limits on packet size frame cannot be split between packets, any limits on packet size
will also limit the space available for a reason phrase. will also limit the space available for a reason phrase.
Reason Phrase: Additional diagnostic information for the closure. Reason Phrase: Additional diagnostic information for the closure.
This can be zero length if the sender chooses not to give details This can be zero length if the sender chooses not to give details
beyond the Error Code. This SHOULD be a UTF-8 encoded string beyond the Error Code value. This SHOULD be a UTF-8 encoded
[RFC3629], though the frame does not carry information, such as string [RFC3629], though the frame does not carry information,
language tags, that would aid comprehension by any entity other such as language tags, that would aid comprehension by any entity
than the one that created the text. other than the one that created the text.
The application-specific variant of CONNECTION_CLOSE (type 0x1d) can The application-specific variant of CONNECTION_CLOSE (type 0x1d) can
only be sent using 0-RTT or 1-RTT packets; see Section 12.5. When an only be sent using 0-RTT or 1-RTT packets; see Section 12.5. When an
application wishes to abandon a connection during the handshake, an application wishes to abandon a connection during the handshake, an
endpoint can send a CONNECTION_CLOSE frame (type 0x1c) with an error endpoint can send a CONNECTION_CLOSE frame (type 0x1c) with an error
code of APPLICATION_ERROR in an Initial or a Handshake packet. code of APPLICATION_ERROR in an Initial or Handshake packet.
19.20. HANDSHAKE_DONE Frames 19.20. HANDSHAKE_DONE Frames
The server uses a HANDSHAKE_DONE frame (type=0x1e) to signal The server uses a HANDSHAKE_DONE frame (type=0x1e) to signal
confirmation of the handshake to the client. confirmation of the handshake to the client.
HANDSHAKE_DONE frames are formatted as shown in Figure 42, which HANDSHAKE_DONE frames are formatted as shown in Figure 42, which
shows that HANDSHAKE_DONE frames have no content. shows that HANDSHAKE_DONE frames have no content.
HANDSHAKE_DONE Frame { HANDSHAKE_DONE Frame {
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An extension to QUIC that wishes to use a new type of frame MUST An extension to QUIC that wishes to use a new type of frame MUST
first ensure that a peer is able to understand the frame. An first ensure that a peer is able to understand the frame. An
endpoint can use a transport parameter to signal its willingness to endpoint can use a transport parameter to signal its willingness to
receive extension frame types. One transport parameter can indicate receive extension frame types. One transport parameter can indicate
support for one or more extension frame types. support for one or more extension frame types.
Extensions that modify or replace core protocol functionality Extensions that modify or replace core protocol functionality
(including frame types) will be difficult to combine with other (including frame types) will be difficult to combine with other
extensions that modify or replace the same functionality unless the extensions that modify or replace the same functionality unless the
behavior of the combination is explicitly defined. Such extensions behavior of the combination is explicitly defined. Such extensions
SHOULD define their interaction with previously-defined extensions SHOULD define their interaction with previously defined extensions
modifying the same protocol components. modifying the same protocol components.
Extension frames MUST be congestion controlled and MUST cause an ACK Extension frames MUST be congestion controlled and MUST cause an ACK
frame to be sent. The exception is extension frames that replace or frame to be sent. The exception is extension frames that replace or
supplement the ACK frame. Extension frames are not included in flow supplement the ACK frame. Extension frames are not included in flow
control unless specified in the extension. control unless specified in the extension.
An IANA registry is used to manage the assignment of frame types; see An IANA registry is used to manage the assignment of frame types; see
Section 22.4. Section 22.4.
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QUIC transport error codes and application error codes are 62-bit QUIC transport error codes and application error codes are 62-bit
unsigned integers. unsigned integers.
20.1. Transport Error Codes 20.1. Transport Error Codes
This section lists the defined QUIC transport error codes that can be This section lists the defined QUIC transport error codes that can be
used in a CONNECTION_CLOSE frame with a type of 0x1c. These errors used in a CONNECTION_CLOSE frame with a type of 0x1c. These errors
apply to the entire connection. apply to the entire connection.
NO_ERROR (0x0): An endpoint uses this with CONNECTION_CLOSE to NO_ERROR (0x00): An endpoint uses this with CONNECTION_CLOSE to
signal that the connection is being closed abruptly in the absence signal that the connection is being closed abruptly in the absence
of any error. of any error.
INTERNAL_ERROR (0x1): The endpoint encountered an internal error and INTERNAL_ERROR (0x01): The endpoint encountered an internal error
cannot continue with the connection. and cannot continue with the connection.
CONNECTION_REFUSED (0x2): The server refused to accept a new CONNECTION_REFUSED (0x02): The server refused to accept a new
connection. connection.
FLOW_CONTROL_ERROR (0x3): An endpoint received more data than it FLOW_CONTROL_ERROR (0x03): An endpoint received more data than it
permitted in its advertised data limits; see Section 4. permitted in its advertised data limits; see Section 4.
STREAM_LIMIT_ERROR (0x4): An endpoint received a frame for a stream STREAM_LIMIT_ERROR (0x04): An endpoint received a frame for a stream
identifier that exceeded its advertised stream limit for the identifier that exceeded its advertised stream limit for the
corresponding stream type. corresponding stream type.
STREAM_STATE_ERROR (0x5): An endpoint received a frame for a stream STREAM_STATE_ERROR (0x05): An endpoint received a frame for a stream
that was not in a state that permitted that frame; see Section 3. that was not in a state that permitted that frame; see Section 3.
FINAL_SIZE_ERROR (0x6): An endpoint received a STREAM frame FINAL_SIZE_ERROR (0x06): (1) An endpoint received a STREAM frame
containing data that exceeded the previously established final containing data that exceeded the previously established final
size. Or an endpoint received a STREAM frame or a RESET_STREAM size, (2) an endpoint received a STREAM frame or a RESET_STREAM
frame containing a final size that was lower than the size of frame containing a final size that was lower than the size of
stream data that was already received. Or an endpoint received a stream data that was already received, or (3) an endpoint received
STREAM frame or a RESET_STREAM frame containing a different final a STREAM frame or a RESET_STREAM frame containing a different
size to the one already established. final size to the one already established.
FRAME_ENCODING_ERROR (0x7): An endpoint received a frame that was FRAME_ENCODING_ERROR (0x07): An endpoint received a frame that was
badly formatted. For instance, a frame of an unknown type, or an badly formatted -- for instance, a frame of an unknown type or an
ACK frame that has more acknowledgment ranges than the remainder ACK frame that has more acknowledgment ranges than the remainder
of the packet could carry. of the packet could carry.
TRANSPORT_PARAMETER_ERROR (0x8): An endpoint received transport TRANSPORT_PARAMETER_ERROR (0x08): An endpoint received transport
parameters that were badly formatted, included an invalid value, parameters that were badly formatted, included an invalid value,
omitted a mandatory transport parameter, included a forbidden omitted a mandatory transport parameter, included a forbidden
transport parameter, or were otherwise in error. transport parameter, or were otherwise in error.
CONNECTION_ID_LIMIT_ERROR (0x9): The number of connection IDs CONNECTION_ID_LIMIT_ERROR (0x09): The number of connection IDs
provided by the peer exceeds the advertised provided by the peer exceeds the advertised
active_connection_id_limit. active_connection_id_limit.
PROTOCOL_VIOLATION (0xa): An endpoint detected an error with PROTOCOL_VIOLATION (0x0a): An endpoint detected an error with
protocol compliance that was not covered by more specific error protocol compliance that was not covered by more specific error
codes. codes.
INVALID_TOKEN (0xb): A server received a client Initial that INVALID_TOKEN (0x0b): A server received a client Initial that
contained an invalid Token field. contained an invalid Token field.
APPLICATION_ERROR (0xc): The application or application protocol APPLICATION_ERROR (0x0c): The application or application protocol
caused the connection to be closed. caused the connection to be closed.
CRYPTO_BUFFER_EXCEEDED (0xd): An endpoint has received more data in CRYPTO_BUFFER_EXCEEDED (0x0d): An endpoint has received more data in
CRYPTO frames than it can buffer. CRYPTO frames than it can buffer.
KEY_UPDATE_ERROR (0xe): An endpoint detected errors in performing KEY_UPDATE_ERROR (0x0e): An endpoint detected errors in performing
key updates; see Section 6 of [QUIC-TLS]. key updates; see Section 6 of [QUIC-TLS].
AEAD_LIMIT_REACHED (0xf): An endpoint has reached the AEAD_LIMIT_REACHED (0x0f): An endpoint has reached the
confidentiality or integrity limit for the AEAD algorithm used by confidentiality or integrity limit for the AEAD algorithm used by
the given connection. the given connection.
NO_VIABLE_PATH (0x10): An endpoint has determined that the network NO_VIABLE_PATH (0x10): An endpoint has determined that the network
path is incapable of supporting QUIC. An endpoint is unlikely to path is incapable of supporting QUIC. An endpoint is unlikely to
receive CONNECTION_CLOSE carrying this code except when the path receive a CONNECTION_CLOSE frame carrying this code except when
does not support a large enough MTU. the path does not support a large enough MTU.
CRYPTO_ERROR (0x1XX): The cryptographic handshake failed. A range CRYPTO_ERROR (0x0100-0x01ff): The cryptographic handshake failed. A
of 256 values is reserved for carrying error codes specific to the range of 256 values is reserved for carrying error codes specific
cryptographic handshake that is used. Codes for errors occurring to the cryptographic handshake that is used. Codes for errors
when TLS is used for the crypto handshake are described in occurring when TLS is used for the cryptographic handshake are
Section 4.8 of [QUIC-TLS]. described in Section 4.8 of [QUIC-TLS].
See Section 22.5 for details of registering new error codes. See Section 22.5 for details on registering new error codes.
In defining these error codes, several principles are applied. Error In defining these error codes, several principles are applied. Error
conditions that might require specific action on the part of a conditions that might require specific action on the part of a
recipient are given unique codes. Errors that represent common recipient are given unique codes. Errors that represent common
conditions are given specific codes. Absent either of these conditions are given specific codes. Absent either of these
conditions, error codes are used to identify a general function of conditions, error codes are used to identify a general function of
the stack, like flow control or transport parameter handling. the stack, like flow control or transport parameter handling.
Finally, generic errors are provided for conditions where Finally, generic errors are provided for conditions where
implementations are unable or unwilling to use more specific codes. implementations are unable or unwilling to use more specific codes.
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The goal of QUIC is to provide a secure transport connection. The goal of QUIC is to provide a secure transport connection.
Section 21.1 provides an overview of those properties; subsequent Section 21.1 provides an overview of those properties; subsequent
sections discuss constraints and caveats regarding these properties, sections discuss constraints and caveats regarding these properties,
including descriptions of known attacks and countermeasures. including descriptions of known attacks and countermeasures.
21.1. Overview of Security Properties 21.1. Overview of Security Properties
A complete security analysis of QUIC is outside the scope of this A complete security analysis of QUIC is outside the scope of this
document. This section provides an informal description of the document. This section provides an informal description of the
desired security properties as an aid to implementors and to help desired security properties as an aid to implementers and to help
guide protocol analysis. guide protocol analysis.
QUIC assumes the threat model described in [SEC-CONS] and provides QUIC assumes the threat model described in [SEC-CONS] and provides
protections against many of the attacks that arise from that model. protections against many of the attacks that arise from that model.
For this purpose, attacks are divided into passive and active For this purpose, attacks are divided into passive and active
attacks. Passive attackers have the capability to read packets from attacks. Passive attackers have the ability to read packets from the
the network, while active attackers also have the capability to write network, while active attackers also have the ability to write
packets into the network. However, a passive attack could involve an packets into the network. However, a passive attack could involve an
attacker with the ability to cause a routing change or other attacker with the ability to cause a routing change or other
modification in the path taken by packets that comprise a connection. modification in the path taken by packets that comprise a connection.
Attackers are additionally categorized as either on-path attackers or Attackers are additionally categorized as either on-path attackers or
off-path attackers. An on-path attacker can read, modify, or remove off-path attackers. An on-path attacker can read, modify, or remove
any packet it observes such that it no longer reaches its any packet it observes such that the packet no longer reaches its
destination, while an off-path attacker observes the packets, but destination, while an off-path attacker observes the packets but
cannot prevent the original packet from reaching its intended cannot prevent the original packet from reaching its intended
destination. Both types of attackers can also transmit arbitrary destination. Both types of attackers can also transmit arbitrary
packets. This definition differs from that of Section 3.5 of packets. This definition differs from that of Section 3.5 of
[SEC-CONS] in that an off-path attacker is able to observe packets. [SEC-CONS] in that an off-path attacker is able to observe packets.
Properties of the handshake, protected packets, and connection Properties of the handshake, protected packets, and connection
migration are considered separately. migration are considered separately.
21.1.1. Handshake 21.1.1. Handshake
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Address validation (Section 8) is used to verify that an entity that Address validation (Section 8) is used to verify that an entity that
claims a given address is able to receive packets at that address. claims a given address is able to receive packets at that address.
Address validation limits amplification attack targets to addresses Address validation limits amplification attack targets to addresses
for which an attacker can observe packets. for which an attacker can observe packets.
Prior to address validation, endpoints are limited in what they are Prior to address validation, endpoints are limited in what they are
able to send. Endpoints cannot send data toward an unvalidated able to send. Endpoints cannot send data toward an unvalidated
address in excess of three times the data received from that address. address in excess of three times the data received from that address.
Note: The anti-amplification limit only applies when an endpoint Note: The anti-amplification limit only applies when an endpoint
responds to packets received from an unvalidated address. The responds to packets received from an unvalidated address. The
anti-amplification limit does not apply to clients when anti-amplification limit does not apply to clients when
establishing a new connection or when initiating connection establishing a new connection or when initiating connection
migration. migration.
21.1.1.2. Server-Side DoS 21.1.1.2. Server-Side DoS
Computing the server's first flight for a full handshake is Computing the server's first flight for a full handshake is
potentially expensive, requiring both a signature and a key exchange potentially expensive, requiring both a signature and a key exchange
computation. In order to prevent computational DoS attacks, the computation. In order to prevent computational DoS attacks, the
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servers to validate a client's IP address prior to doing any servers to validate a client's IP address prior to doing any
expensive computations at the cost of a single round trip. After a expensive computations at the cost of a single round trip. After a
successful handshake, servers can issue new tokens to a client, which successful handshake, servers can issue new tokens to a client, which
will allow new connection establishment without incurring this cost. will allow new connection establishment without incurring this cost.
21.1.1.3. On-Path Handshake Termination 21.1.1.3. On-Path Handshake Termination
An on-path or off-path attacker can force a handshake to fail by An on-path or off-path attacker can force a handshake to fail by
replacing or racing Initial packets. Once valid Initial packets have replacing or racing Initial packets. Once valid Initial packets have
been exchanged, subsequent Handshake packets are protected with the been exchanged, subsequent Handshake packets are protected with the
handshake keys and an on-path attacker cannot force handshake failure Handshake keys, and an on-path attacker cannot force handshake
other than by dropping packets to cause endpoints to abandon the failure other than by dropping packets to cause endpoints to abandon
attempt. the attempt.
An on-path attacker can also replace the addresses of packets on An on-path attacker can also replace the addresses of packets on
either side and therefore cause the client or server to have an either side and therefore cause the client or server to have an
incorrect view of the remote addresses. Such an attack is incorrect view of the remote addresses. Such an attack is
indistinguishable from the functions performed by a NAT. indistinguishable from the functions performed by a NAT.
21.1.1.4. Parameter Negotiation 21.1.1.4. Parameter Negotiation
The entire handshake is cryptographically protected, with the Initial The entire handshake is cryptographically protected, with the Initial
packets being encrypted with per-version keys and the Handshake and packets being encrypted with per-version keys and the Handshake and
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Retry packets have limited protection due to the use of version- Retry packets have limited protection due to the use of version-
specific keying material; see [QUIC-TLS] for more details. This specific keying material; see [QUIC-TLS] for more details. This
section considers passive and active attacks against protected section considers passive and active attacks against protected
packets. packets.
Both on-path and off-path attackers can mount a passive attack in Both on-path and off-path attackers can mount a passive attack in
which they save observed packets for an offline attack against packet which they save observed packets for an offline attack against packet
protection at a future time; this is true for any observer of any protection at a future time; this is true for any observer of any
packet on any network. packet on any network.
A blind attacker, one who injects packets without being able to An attacker that injects packets without being able to observe valid
observe valid packets for a connection, is unlikely to be successful, packets for a connection is unlikely to be successful, since packet
since packet protection ensures that valid packets are only generated protection ensures that valid packets are only generated by endpoints
by endpoints that possess the key material established during the that possess the key material established during the handshake; see
handshake; see Section 7 and Section 21.1.1. Similarly, any active Sections 7 and 21.1.1. Similarly, any active attacker that observes
attacker that observes packets and attempts to insert new data or packets and attempts to insert new data or modify existing data in
modify existing data in those packets should not be able to generate those packets should not be able to generate packets deemed valid by
packets deemed valid by the receiving endpoint, other than Initial the receiving endpoint, other than Initial packets.
packets.
A spoofing attack, in which an active attacker rewrites unprotected A spoofing attack, in which an active attacker rewrites unprotected
parts of a packet that it forwards or injects, such as the source or parts of a packet that it forwards or injects, such as the source or
destination address, is only effective if the attacker can forward destination address, is only effective if the attacker can forward
packets to the original endpoint. Packet protection ensures that the packets to the original endpoint. Packet protection ensures that the
packet payloads can only be processed by the endpoints that completed packet payloads can only be processed by the endpoints that completed
the handshake, and invalid packets are ignored by those endpoints. the handshake, and invalid packets are ignored by those endpoints.
An attacker can also modify the boundaries between packets and UDP An attacker can also modify the boundaries between packets and UDP
datagrams, causing multiple packets to be coalesced into a single datagrams, causing multiple packets to be coalesced into a single
datagram, or splitting coalesced packets into multiple datagrams. datagram or splitting coalesced packets into multiple datagrams.
Aside from datagrams containing Initial packets, which require Aside from datagrams containing Initial packets, which require
padding, modification of how packets are arranged in datagrams has no padding, modification of how packets are arranged in datagrams has no
functional effect on a connection, although it might change some functional effect on a connection, although it might change some
performance characteristics. performance characteristics.
21.1.3. Connection Migration 21.1.3. Connection Migration
Connection Migration (Section 9) provides endpoints with the ability Connection migration (Section 9) provides endpoints with the ability
to transition between IP addresses and ports on multiple paths, using to transition between IP addresses and ports on multiple paths, using
one path at a time for transmission and receipt of non-probing one path at a time for transmission and receipt of non-probing
frames. Path validation (Section 8.2) establishes that a peer is frames. Path validation (Section 8.2) establishes that a peer is
both willing and able to receive packets sent on a particular path. both willing and able to receive packets sent on a particular path.
This helps reduce the effects of address spoofing by limiting the This helps reduce the effects of address spoofing by limiting the
number of packets sent to a spoofed address. number of packets sent to a spoofed address.
This section describes the intended security properties of connection This section describes the intended security properties of connection
migration under various types of DoS attacks. migration under various types of DoS attacks.
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required to send packets through the attacker to establish required to send packets through the attacker to establish
connectivity on a given path. connectivity on a given path.
An on-path attacker can: An on-path attacker can:
o Inspect packets o Inspect packets
o Modify IP and UDP packet headers o Modify IP and UDP packet headers
o Inject new packets o Inject new packets
o Delay packets
o Delay packets
o Reorder packets o Reorder packets
o Drop packets o Drop packets
o Split and merge datagrams along packet boundaries o Split and merge datagrams along packet boundaries
An on-path attacker cannot: An on-path attacker cannot:
o Modify an authenticated portion of a packet and cause the o Modify an authenticated portion of a packet and cause the
recipient to accept that packet recipient to accept that packet
An on-path attacker has the opportunity to modify the packets that it An on-path attacker has the opportunity to modify the packets that it
observes, however any modifications to an authenticated portion of a observes; however, any modifications to an authenticated portion of a
packet will cause it to be dropped by the receiving endpoint as packet will cause it to be dropped by the receiving endpoint as
invalid, as packet payloads are both authenticated and encrypted. invalid, as packet payloads are both authenticated and encrypted.
In the presence of an on-path attacker, QUIC aims to provide the QUIC aims to constrain the capabilities of an on-path attacker as
following properties: follows:
1. An on-path attacker can prevent use of a path for a connection, 1. An on-path attacker can prevent the use of a path for a
causing the connection to fail if it cannot use a different path connection, causing the connection to fail if it cannot use a
that does not contain the attacker. This can be achieved by different path that does not contain the attacker. This can be
dropping all packets, modifying them so that they fail to achieved by dropping all packets, modifying them so that they
decrypt, or other methods. fail to decrypt, or other methods.
2. An on-path attacker can prevent migration to a new path for which 2. An on-path attacker can prevent migration to a new path for which
the attacker is also on-path by causing path validation to fail the attacker is also on-path by causing path validation to fail
on the new path. on the new path.
3. An on-path attacker cannot prevent a client from migrating to a 3. An on-path attacker cannot prevent a client from migrating to a
path for which the attacker is not on-path. path for which the attacker is not on-path.
4. An on-path attacker can reduce the throughput of a connection by 4. An on-path attacker can reduce the throughput of a connection by
delaying packets or dropping them. delaying packets or dropping them.
5. An on-path attacker cannot cause an endpoint to accept a packet 5. An on-path attacker cannot cause an endpoint to accept a packet
for which it has modified an authenticated portion of that for which it has modified an authenticated portion of that
packet. packet.
21.1.3.2. Off-Path Active Attacks 21.1.3.2. Off-Path Active Attacks
An off-path attacker is not directly on the path between a client and An off-path attacker is not directly on the path between a client and
server, but could be able to obtain copies of some or all packets server but could be able to obtain copies of some or all packets sent
sent between the client and the server. It is also able to send between the client and the server. It is also able to send copies of
copies of those packets to either endpoint. those packets to either endpoint.
An off-path attacker can: An off-path attacker can:
o Inspect packets o Inspect packets
o Inject new packets o Inject new packets
o Reorder injected packets o Reorder injected packets
An off-path attacker cannot: An off-path attacker cannot:
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For the purposes of this discussion, it is assumed that an off-path For the purposes of this discussion, it is assumed that an off-path
attacker has the ability to inject a modified copy of a packet into attacker has the ability to inject a modified copy of a packet into
the network that will reach the destination endpoint prior to the the network that will reach the destination endpoint prior to the
arrival of the original packet observed by the attacker. In other arrival of the original packet observed by the attacker. In other
words, an attacker has the ability to consistently "win" a race with words, an attacker has the ability to consistently "win" a race with
the legitimate packets between the endpoints, potentially causing the the legitimate packets between the endpoints, potentially causing the
original packet to be ignored by the recipient. original packet to be ignored by the recipient.
It is also assumed that an attacker has the resources necessary to It is also assumed that an attacker has the resources necessary to
affect NAT state, potentially both causing an endpoint to lose its affect NAT state. In particular, an attacker can cause an endpoint
NAT binding, and an attacker to obtain the same port for use with its to lose its NAT binding and then obtain the same port for use with
traffic. its own traffic.
In the presence of an off-path attacker, QUIC aims to provide the QUIC aims to constrain the capabilities of an off-path attacker as
following properties: follows:
1. An off-path attacker can race packets and attempt to become a 1. An off-path attacker can race packets and attempt to become a
"limited" on-path attacker. "limited" on-path attacker.
2. An off-path attacker can cause path validation to succeed for 2. An off-path attacker can cause path validation to succeed for
forwarded packets with the source address listed as the off-path forwarded packets with the source address listed as the off-path
attacker as long as it can provide improved connectivity between attacker as long as it can provide improved connectivity between
the client and the server. the client and the server.
3. An off-path attacker cannot cause a connection to close once the 3. An off-path attacker cannot cause a connection to close once the
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o Modify the authenticated and encrypted portion of a packet and o Modify the authenticated and encrypted portion of a packet and
cause the recipient to accept that packet cause the recipient to accept that packet
A limited on-path attacker can only delay packets up to the point A limited on-path attacker can only delay packets up to the point
that the original packets arrive before the duplicate packets, that the original packets arrive before the duplicate packets,
meaning that it cannot offer routing with worse latency than the meaning that it cannot offer routing with worse latency than the
original path. If a limited on-path attacker drops packets, the original path. If a limited on-path attacker drops packets, the
original copy will still arrive at the destination endpoint. original copy will still arrive at the destination endpoint.
In the presence of a limited on-path attacker, QUIC aims to provide QUIC aims to constrain the capabilities of a limited off-path
the following properties: attacker as follows:
1. A limited on-path attacker cannot cause a connection to close 1. A limited on-path attacker cannot cause a connection to close
once the handshake has completed. once the handshake has completed.
2. A limited on-path attacker cannot cause an idle connection to 2. A limited on-path attacker cannot cause an idle connection to
close if the client is first to resume activity. close if the client is first to resume activity.
3. A limited on-path attacker can cause an idle connection to be 3. A limited on-path attacker can cause an idle connection to be
deemed lost if the server is the first to resume activity. deemed lost if the server is the first to resume activity.
Note that these guarantees are the same guarantees provided for any Note that these guarantees are the same guarantees provided for any
NAT, for the same reasons. NAT, for the same reasons.
21.2. Handshake Denial of Service 21.2. Handshake Denial of Service
As an encrypted and authenticated transport QUIC provides a range of As an encrypted and authenticated transport, QUIC provides a range of
protections against denial of service. Once the cryptographic protections against denial of service. Once the cryptographic
handshake is complete, QUIC endpoints discard most packets that are handshake is complete, QUIC endpoints discard most packets that are
not authenticated, greatly limiting the ability of an attacker to not authenticated, greatly limiting the ability of an attacker to
interfere with existing connections. interfere with existing connections.
Once a connection is established QUIC endpoints might accept some Once a connection is established, QUIC endpoints might accept some
unauthenticated ICMP packets (see Section 14.2.1), but the use of unauthenticated ICMP packets (see Section 14.2.1), but the use of
these packets is extremely limited. The only other type of packet these packets is extremely limited. The only other type of packet
that an endpoint might accept is a stateless reset (Section 10.3), that an endpoint might accept is a stateless reset (Section 10.3),
which relies on the token being kept secret until it is used. which relies on the token being kept secret until it is used.
During the creation of a connection, QUIC only provides protection During the creation of a connection, QUIC only provides protection
against attack from off the network path. All QUIC packets contain against attacks from off the network path. All QUIC packets contain
proof that the recipient saw a preceding packet from its peer. proof that the recipient saw a preceding packet from its peer.
Addresses cannot change during the handshake, so endpoints can Addresses cannot change during the handshake, so endpoints can
discard packets that are received on a different network path. discard packets that are received on a different network path.
The Source and Destination Connection ID fields are the primary means The Source and Destination Connection ID fields are the primary means
of protection against off-path attack during the handshake; see of protection against an off-path attack during the handshake; see
Section 8.1. These are required to match those set by a peer. Section 8.1. These are required to match those set by a peer.
Except for an Initial and stateless reset packets, an endpoint only Except for Initial packets and Stateless Resets, an endpoint only
accepts packets that include a Destination Connection ID field that accepts packets that include a Destination Connection ID field that
matches a value the endpoint previously chose. This is the only matches a value the endpoint previously chose. This is the only
protection offered for Version Negotiation packets. protection offered for Version Negotiation packets.
The Destination Connection ID field in an Initial packet is selected The Destination Connection ID field in an Initial packet is selected
by a client to be unpredictable, which serves an additional purpose. by a client to be unpredictable, which serves an additional purpose.
The packets that carry the cryptographic handshake are protected with The packets that carry the cryptographic handshake are protected with
a key that is derived from this connection ID and a salt specific to a key that is derived from this connection ID and a salt specific to
the QUIC version. This allows endpoints to use the same process for the QUIC version. This allows endpoints to use the same process for
authenticating packets that they receive as they use after the authenticating packets that they receive as they use after the
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access to capabilities of its peer that might otherwise be access to capabilities of its peer that might otherwise be
unavailable to the attacker. For a networking protocol, a request unavailable to the attacker. For a networking protocol, a request
forgery attack is often used to exploit any implicit authorization forgery attack is often used to exploit any implicit authorization
conferred on the peer by the victim due to the peer's location in the conferred on the peer by the victim due to the peer's location in the
network. network.
For request forgery to be effective, an attacker needs to be able to For request forgery to be effective, an attacker needs to be able to
influence what packets the peer sends and where these packets are influence what packets the peer sends and where these packets are
sent. If an attacker can target a vulnerable service with a sent. If an attacker can target a vulnerable service with a
controlled payload, that service might perform actions that are controlled payload, that service might perform actions that are
attributed to the attacker's peer, but decided by the attacker. attributed to the attacker's peer but are decided by the attacker.
For example, cross-site request forgery [CSRF] exploits on the Web For example, cross-site request forgery [CSRF] exploits on the Web
cause a client to issue requests that include authorization cookies cause a client to issue requests that include authorization cookies
[COOKIE], allowing one site access to information and actions that [COOKIE], allowing one site access to information and actions that
are intended to be restricted to a different site. are intended to be restricted to a different site.
As QUIC runs over UDP, the primary attack modality of concern is one As QUIC runs over UDP, the primary attack modality of concern is one
where an attacker can select the address to which its peer sends UDP where an attacker can select the address to which its peer sends UDP
datagrams and can control some of the unprotected content of those datagrams and can control some of the unprotected content of those
packets. As much of the data sent by QUIC endpoints is protected, packets. As much of the data sent by QUIC endpoints is protected,
this includes control over ciphertext. An attack is successful if an this includes control over ciphertext. An attack is successful if an
attacker can cause a peer to send a UDP datagram to a host that will attacker can cause a peer to send a UDP datagram to a host that will
perform some action based on content in the datagram. perform some action based on content in the datagram.
This section discusses ways in which QUIC might be used for request This section discusses ways in which QUIC might be used for request
forgery attacks. forgery attacks.
This section also describes limited countermeasures that can be This section also describes limited countermeasures that can be
implemented by QUIC endpoints. These mitigations can be employed implemented by QUIC endpoints. These mitigations can be employed
unilaterally by a QUIC implementation or deployment, without unilaterally by a QUIC implementation or deployment, without
potential targets for request forgery attacks taking action. However potential targets for request forgery attacks taking action.
these countermeasures could be insufficient if UDP-based services do However, these countermeasures could be insufficient if UDP-based
not properly authorize requests. services do not properly authorize requests.
Because the migration attack described in Section 21.5.4 is quite Because the migration attack described in Section 21.5.4 is quite
powerful and does not have adequate countermeasures, QUIC server powerful and does not have adequate countermeasures, QUIC server
implementations should assume that attackers can cause them to implementations should assume that attackers can cause them to
generate arbitrary UDP payloads to arbitrary destinations. QUIC generate arbitrary UDP payloads to arbitrary destinations. QUIC
servers SHOULD NOT be deployed in networks that do not deploy ingress servers SHOULD NOT be deployed in networks that do not deploy ingress
filtering [BCP38] and also have inadequately secured UDP endpoints. filtering [BCP38] and also have inadequately secured UDP endpoints.
Although it is not generally possible to ensure that clients are not Although it is not generally possible to ensure that clients are not
co-located with vulnerable endpoints, this version of QUIC does not co-located with vulnerable endpoints, this version of QUIC does not
allow servers to migrate, thus preventing spoofed migration attacks allow servers to migrate, thus preventing spoofed migration attacks
on clients. Any future extension which allows server migration MUST on clients. Any future extension that allows server migration MUST
also define countermeasures for forgery attacks. also define countermeasures for forgery attacks.
21.5.1. Control Options for Endpoints 21.5.1. Control Options for Endpoints
QUIC offers some opportunities for an attacker to influence or QUIC offers some opportunities for an attacker to influence or
control where its peer sends UDP datagrams: control where its peer sends UDP datagrams:
o initial connection establishment (Section 7), where a server is o initial connection establishment (Section 7), where a server is
able to choose where a client sends datagrams, for example by able to choose where a client sends datagrams -- for example, by
populating DNS records; populating DNS records;
o preferred addresses (Section 9.6), where a server is able to o preferred addresses (Section 9.6), where a server is able to
choose where a client sends datagrams; choose where a client sends datagrams;
o spoofed connection migrations (Section 9.3.1), where a client is o spoofed connection migrations (Section 9.3.1), where a client is
able to use source address spoofing to select where a server sends able to use source address spoofing to select where a server sends
subsequent datagrams; and subsequent datagrams; and
o spoofed packets that cause a server to send a Version Negotiation o spoofed packets that cause a server to send a Version Negotiation
packet Section 21.5.5. packet (Section 21.5.5).
In all cases, the attacker can cause its peer to send datagrams to a In all cases, the attacker can cause its peer to send datagrams to a
victim that might not understand QUIC. That is, these packets are victim that might not understand QUIC. That is, these packets are
sent by the peer prior to address validation; see Section 8. sent by the peer prior to address validation; see Section 8.
Outside of the encrypted portion of packets, QUIC offers an endpoint Outside of the encrypted portion of packets, QUIC offers an endpoint
several options for controlling the content of UDP datagrams that its several options for controlling the content of UDP datagrams that its
peer sends. The Destination Connection ID field offers direct peer sends. The Destination Connection ID field offers direct
control over bytes that appear early in packets sent by the peer; see control over bytes that appear early in packets sent by the peer; see
Section 5.1. The Token field in Initial packets offers a server Section 5.1. The Token field in Initial packets offers a server
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This section assumes that limiting control over datagram content is This section assumes that limiting control over datagram content is
not feasible. The focus of the mitigations in subsequent sections is not feasible. The focus of the mitigations in subsequent sections is
on limiting the ways in which datagrams that are sent prior to on limiting the ways in which datagrams that are sent prior to
address validation can be used for request forgery. address validation can be used for request forgery.
21.5.2. Request Forgery with Client Initial Packets 21.5.2. Request Forgery with Client Initial Packets
An attacker acting as a server can choose the IP address and port on An attacker acting as a server can choose the IP address and port on
which it advertises its availability, so Initial packets from clients which it advertises its availability, so Initial packets from clients
are assumed to be available for use in this sort of attack. The are assumed to be available for use in this sort of attack. The
address validation implicit in the handshake ensures that - for a new address validation implicit in the handshake ensures that -- for a
connection - a client will not send other types of packet to a new connection -- a client will not send other types of packets to a
destination that does not understand QUIC or is not willing to accept destination that does not understand QUIC or is not willing to accept
a QUIC connection. a QUIC connection.
Initial packet protection (Section 5.2 of [QUIC-TLS]) makes it Initial packet protection (Section 5.2 of [QUIC-TLS]) makes it
difficult for servers to control the content of Initial packets sent difficult for servers to control the content of Initial packets sent
by clients. A client choosing an unpredictable Destination by clients. A client choosing an unpredictable Destination
Connection ID ensures that servers are unable to control any of the Connection ID ensures that servers are unable to control any of the
encrypted portion of Initial packets from clients. encrypted portion of Initial packets from clients.
However, the Token field is open to server control and does allow a However, the Token field is open to server control and does allow a
server to use clients to mount request forgery attacks. Use of server to use clients to mount request forgery attacks. The use of
tokens provided with the NEW_TOKEN frame (Section 8.1.3) offers the tokens provided with the NEW_TOKEN frame (Section 8.1.3) offers the
only option for request forgery during connection establishment. only option for request forgery during connection establishment.
Clients however are not obligated to use the NEW_TOKEN frame. Clients, however, are not obligated to use the NEW_TOKEN frame.
Request forgery attacks that rely on the Token field can be avoided Request forgery attacks that rely on the Token field can be avoided
if clients send an empty Token field when the server address has if clients send an empty Token field when the server address has
changed from when the NEW_TOKEN frame was received. changed from when the NEW_TOKEN frame was received.
Clients could avoid using NEW_TOKEN if the server address changes. Clients could avoid using NEW_TOKEN if the server address changes.
However, not including a Token field could adversely affect However, not including a Token field could adversely affect
performance. Servers could rely on NEW_TOKEN to enable sending of performance. Servers could rely on NEW_TOKEN to enable the sending
data in excess of the three times limit on sending data; see of data in excess of the three-times limit on sending data; see
Section 8.1. In particular, this affects cases where clients use Section 8.1. In particular, this affects cases where clients use
0-RTT to request data from servers. 0-RTT to request data from servers.
Sending a Retry packet (Section 17.2.5) offers a server the option to Sending a Retry packet (Section 17.2.5) offers a server the option to
change the Token field. After sending a Retry, the server can also change the Token field. After sending a Retry, the server can also
control the Destination Connection ID field of subsequent Initial control the Destination Connection ID field of subsequent Initial
packets from the client. This also might allow indirect control over packets from the client. This also might allow indirect control over
the encrypted content of Initial packets. However, the exchange of a the encrypted content of Initial packets. However, the exchange of a
Retry packet validates the server's address, thereby preventing the Retry packet validates the server's address, thereby preventing the
use of subsequent Initial packets for request forgery. use of subsequent Initial packets for request forgery.
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to after confirming the handshake; see Section 9.6. The Destination to after confirming the handshake; see Section 9.6. The Destination
Connection ID field of packets that the client sends to a preferred Connection ID field of packets that the client sends to a preferred
address can be used for request forgery. address can be used for request forgery.
A client MUST NOT send non-probing frames to a preferred address A client MUST NOT send non-probing frames to a preferred address
prior to validating that address; see Section 8. This greatly prior to validating that address; see Section 8. This greatly
reduces the options that a server has to control the encrypted reduces the options that a server has to control the encrypted
portion of datagrams. portion of datagrams.
This document does not offer any additional countermeasures that are This document does not offer any additional countermeasures that are
specific to use of preferred addresses and can be implemented by specific to the use of preferred addresses and can be implemented by
endpoints. The generic measures described in Section 21.5.6 could be endpoints. The generic measures described in Section 21.5.6 could be
used as further mitigation. used as further mitigation.
21.5.4. Request Forgery with Spoofed Migration 21.5.4. Request Forgery with Spoofed Migration
Clients are able to present a spoofed source address as part of an Clients are able to present a spoofed source address as part of an
apparent connection migration to cause a server to send datagrams to apparent connection migration to cause a server to send datagrams to
that address. that address.
The Destination Connection ID field in any packets that a server The Destination Connection ID field in any packets that a server
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A server that only sends probing packets (Section 9.1) to an address A server that only sends probing packets (Section 9.1) to an address
prior to address validation provides an attacker with only limited prior to address validation provides an attacker with only limited
control over the encrypted portion of datagrams. However, control over the encrypted portion of datagrams. However,
particularly for NAT rebinding, this can adversely affect particularly for NAT rebinding, this can adversely affect
performance. If the server sends frames carrying application data, performance. If the server sends frames carrying application data,
an attacker might be able to control most of the content of an attacker might be able to control most of the content of
datagrams. datagrams.
This document does not offer specific countermeasures that can be This document does not offer specific countermeasures that can be
implemented by endpoints aside from the generic measures described in implemented by endpoints, aside from the generic measures described
Section 21.5.6. However, countermeasures for address spoofing at the in Section 21.5.6. However, countermeasures for address spoofing at
network level, in particular ingress filtering [BCP38], are the network level -- in particular, ingress filtering [BCP38] -- are
especially effective against attacks that use spoofing and originate especially effective against attacks that use spoofing and originate
from an external network. from an external network.
21.5.5. Request Forgery with Version Negotiation 21.5.5. Request Forgery with Version Negotiation
Clients that are able to present a spoofed source address on a packet Clients that are able to present a spoofed source address on a packet
can cause a server to send a Version Negotiation packet can cause a server to send a Version Negotiation packet
Section 17.2.1 to that address. (Section 17.2.1) to that address.
The absence of size restrictions on the connection ID fields for The absence of size restrictions on the connection ID fields for
packets of an unknown version increases the amount of data that the packets of an unknown version increases the amount of data that the
client controls from the resulting datagram. The first byte of this client controls from the resulting datagram. The first byte of this
packet is not under client control and the next four bytes are zero, packet is not under client control and the next four bytes are zero,
but the client is able to control up to 512 bytes starting from the but the client is able to control up to 512 bytes starting from the
fifth byte. fifth byte.
No specific countermeasures are provided for this attack, though No specific countermeasures are provided for this attack, though
generic protections Section 21.5.6 could apply. In this case, generic protections (Section 21.5.6) could apply. In this case,
ingress filtering [BCP38] is also effective. ingress filtering [BCP38] is also effective.
21.5.6. Generic Request Forgery Countermeasures 21.5.6. Generic Request Forgery Countermeasures
The most effective defense against request forgery attacks is to The most effective defense against request forgery attacks is to
modify vulnerable services to use strong authentication. However, modify vulnerable services to use strong authentication. However,
this is not always something that is within the control of a QUIC this is not always something that is within the control of a QUIC
deployment. This section outlines some others steps that QUIC deployment. This section outlines some other steps that QUIC
endpoints could take unilaterally. These additional steps are all endpoints could take unilaterally. These additional steps are all
discretionary as, depending on circumstances, they could interfere discretionary because, depending on circumstances, they could
with or prevent legitimate uses. interfere with or prevent legitimate uses.
Services offered over loopback interfaces often lack proper Services offered over loopback interfaces often lack proper
authentication. Endpoints MAY prevent connection attempts or authentication. Endpoints MAY prevent connection attempts or
migration to a loopback address. Endpoints SHOULD NOT allow migration to a loopback address. Endpoints SHOULD NOT allow
connections or migration to a loopback address if the same service connections or migration to a loopback address if the same service
was previously available at a different interface or if the address was previously available at a different interface or if the address
was provided by a service at a non-loopback address. Endpoints that was provided by a service at a non-loopback address. Endpoints that
depend on these capabilities could offer an option to disable these depend on these capabilities could offer an option to disable these
protections. protections.
Similarly, endpoints could regard a change in address to link-local Similarly, endpoints could regard a change in address to a link-local
address [RFC4291] or an address in a private use range [RFC1918] from address [RFC4291] or an address in a private-use range [RFC1918] from
a global, unique-local [RFC4193], or non-private address as a a global, unique-local [RFC4193], or non-private address as a
potential attempt at request forgery. Endpoints could refuse to use potential attempt at request forgery. Endpoints could refuse to use
these addresses entirely, but that carries a significant risk of these addresses entirely, but that carries a significant risk of
interfering with legitimate uses. Endpoints SHOULD NOT refuse to use interfering with legitimate uses. Endpoints SHOULD NOT refuse to use
an address unless they have specific knowledge about the network an address unless they have specific knowledge about the network
indicating that sending datagrams to unvalidated addresses in a given indicating that sending datagrams to unvalidated addresses in a given
range is not safe. range is not safe.
Endpoints MAY choose to reduce the risk of request forgery by not Endpoints MAY choose to reduce the risk of request forgery by not
including values from NEW_TOKEN frames in Initial packets or by only including values from NEW_TOKEN frames in Initial packets or by only
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Endpoints are not expected to have specific information about the Endpoints are not expected to have specific information about the
location of servers that could be vulnerable targets of a request location of servers that could be vulnerable targets of a request
forgery attack. However, it might be possible over time to identify forgery attack. However, it might be possible over time to identify
specific UDP ports that are common targets of attacks or particular specific UDP ports that are common targets of attacks or particular
patterns in datagrams that are used for attacks. Endpoints MAY patterns in datagrams that are used for attacks. Endpoints MAY
choose to avoid sending datagrams to these ports or not send choose to avoid sending datagrams to these ports or not send
datagrams that match these patterns prior to validating the datagrams that match these patterns prior to validating the
destination address. Endpoints MAY retire connection IDs containing destination address. Endpoints MAY retire connection IDs containing
patterns known to be problematic without using them. patterns known to be problematic without using them.
Note: Modifying endpoints to apply these protections is more Note: Modifying endpoints to apply these protections is more
efficient than deploying network-based protections, as endpoints efficient than deploying network-based protections, as endpoints
do not need to perform any additional processing when sending to do not need to perform any additional processing when sending to
an address that has been validated. an address that has been validated.
21.6. Slowloris Attacks 21.6. Slowloris Attacks
The attacks commonly known as Slowloris ([SLOWLORIS]) try to keep The attacks commonly known as Slowloris [SLOWLORIS] try to keep many
many connections to the target endpoint open and hold them open as connections to the target endpoint open and hold them open as long as
long as possible. These attacks can be executed against a QUIC possible. These attacks can be executed against a QUIC endpoint by
endpoint by generating the minimum amount of activity necessary to generating the minimum amount of activity necessary to avoid being
avoid being closed for inactivity. This might involve sending small closed for inactivity. This might involve sending small amounts of
amounts of data, gradually opening flow control windows in order to data, gradually opening flow control windows in order to control the
control the sender rate, or manufacturing ACK frames that simulate a sender rate, or manufacturing ACK frames that simulate a high loss
high loss rate. rate.
QUIC deployments SHOULD provide mitigations for the Slowloris QUIC deployments SHOULD provide mitigations for the Slowloris
attacks, such as increasing the maximum number of clients the server attacks, such as increasing the maximum number of clients the server
will allow, limiting the number of connections a single IP address is will allow, limiting the number of connections a single IP address is
allowed to make, imposing restrictions on the minimum transfer speed allowed to make, imposing restrictions on the minimum transfer speed
a connection is allowed to have, and restricting the length of time a connection is allowed to have, and restricting the length of time
an endpoint is allowed to stay connected. an endpoint is allowed to stay connected.
21.7. Stream Fragmentation and Reassembly Attacks 21.7. Stream Fragmentation and Reassembly Attacks
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stream data, causing the receiver to commit resources for the unsent stream data, causing the receiver to commit resources for the unsent
data. This could cause a disproportionate receive buffer memory data. This could cause a disproportionate receive buffer memory
commitment and/or the creation of a large and inefficient data commitment and/or the creation of a large and inefficient data
structure at the receiver. structure at the receiver.
An adversarial receiver might intentionally not acknowledge packets An adversarial receiver might intentionally not acknowledge packets
containing stream data in an attempt to force the sender to store the containing stream data in an attempt to force the sender to store the
unacknowledged stream data for retransmission. unacknowledged stream data for retransmission.
The attack on receivers is mitigated if flow control windows The attack on receivers is mitigated if flow control windows
correspond to available memory. However, some receivers will over- correspond to available memory. However, some receivers will
commit memory and advertise flow control offsets in the aggregate overcommit memory and advertise flow control offsets in the aggregate
that exceed actual available memory. The over-commitment strategy that exceed actual available memory. The overcommitment strategy can
can lead to better performance when endpoints are well behaved, but lead to better performance when endpoints are well behaved, but
renders endpoints vulnerable to the stream fragmentation attack. renders endpoints vulnerable to the stream fragmentation attack.
QUIC deployments SHOULD provide mitigations against stream QUIC deployments SHOULD provide mitigations for stream fragmentation
fragmentation attacks. Mitigations could consist of avoiding over- attacks. Mitigations could consist of avoiding overcommitting
committing memory, limiting the size of tracking data structures, memory, limiting the size of tracking data structures, delaying
delaying reassembly of STREAM frames, implementing heuristics based reassembly of STREAM frames, implementing heuristics based on the age
on the age and duration of reassembly holes, or some combination. and duration of reassembly holes, or some combination of these.
21.8. Stream Commitment Attack 21.8. Stream Commitment Attack
An adversarial endpoint can open a large number of streams, An adversarial endpoint can open a large number of streams,
exhausting state on an endpoint. The adversarial endpoint could exhausting state on an endpoint. The adversarial endpoint could
repeat the process on a large number of connections, in a manner repeat the process on a large number of connections, in a manner
similar to SYN flooding attacks in TCP. similar to SYN flooding attacks in TCP.
Normally, clients will open streams sequentially, as explained in Normally, clients will open streams sequentially, as explained in
Section 2.1. However, when several streams are initiated at short Section 2.1. However, when several streams are initiated at short
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streams of the same type; see Section 3.2. Thus, on a new streams of the same type; see Section 3.2. Thus, on a new
connection, opening stream 4000000 opens 1 million and 1 client- connection, opening stream 4000000 opens 1 million and 1 client-
initiated bidirectional streams. initiated bidirectional streams.
The number of active streams is limited by the The number of active streams is limited by the
initial_max_streams_bidi and initial_max_streams_uni transport initial_max_streams_bidi and initial_max_streams_uni transport
parameters as updated by any received MAX_STREAMS frames, as parameters as updated by any received MAX_STREAMS frames, as
explained in Section 4.6. If chosen judiciously, these limits explained in Section 4.6. If chosen judiciously, these limits
mitigate the effect of the stream commitment attack. However, mitigate the effect of the stream commitment attack. However,
setting the limit too low could affect performance when applications setting the limit too low could affect performance when applications
expect to open large number of streams. expect to open a large number of streams.
21.9. Peer Denial of Service 21.9. Peer Denial of Service
QUIC and TLS both contain frames or messages that have legitimate QUIC and TLS both contain frames or messages that have legitimate
uses in some contexts, but that can be abused to cause a peer to uses in some contexts, but these frames or messages can be abused to
expend processing resources without having any observable impact on cause a peer to expend processing resources without having any
the state of the connection. observable impact on the state of the connection.
Messages can also be used to change and revert state in small or Messages can also be used to change and revert state in small or
inconsequential ways, such as by sending small increments to flow inconsequential ways, such as by sending small increments to flow
control limits. control limits.
If processing costs are disproportionately large in comparison to If processing costs are disproportionately large in comparison to
bandwidth consumption or effect on state, then this could allow a bandwidth consumption or effect on state, then this could allow a
malicious peer to exhaust processing capacity. malicious peer to exhaust processing capacity.
While there are legitimate uses for all messages, implementations While there are legitimate uses for all messages, implementations
SHOULD track cost of processing relative to progress and treat SHOULD track cost of processing relative to progress and treat
excessive quantities of any non-productive packets as indicative of excessive quantities of any non-productive packets as indicative of
an attack. Endpoints MAY respond to this condition with a connection an attack. Endpoints MAY respond to this condition with a connection
error, or by dropping packets. error or by dropping packets.
21.10. Explicit Congestion Notification Attacks 21.10. Explicit Congestion Notification Attacks
An on-path attacker could manipulate the value of ECN fields in the An on-path attacker could manipulate the value of ECN fields in the
IP header to influence the sender's rate. [RFC3168] discusses IP header to influence the sender's rate. [RFC3168] discusses
manipulations and their effects in more detail. manipulations and their effects in more detail.
A limited on-path attacker can duplicate and send packets with A limited on-path attacker can duplicate and send packets with
modified ECN fields to affect the sender's rate. If duplicate modified ECN fields to affect the sender's rate. If duplicate
packets are discarded by a receiver, an attacker will need to race packets are discarded by a receiver, an attacker will need to race
the duplicate packet against the original to be successful in this the duplicate packet against the original to be successful in this
attack. Therefore, QUIC endpoints ignore the ECN field on an IP attack. Therefore, QUIC endpoints ignore the ECN field in an IP
packet unless at least one QUIC packet in that IP packet is packet unless at least one QUIC packet in that IP packet is
successfully processed; see Section 13.4. successfully processed; see Section 13.4.
21.11. Stateless Reset Oracle 21.11. Stateless Reset Oracle
Stateless resets create a possible denial of service attack analogous Stateless resets create a possible denial-of-service attack analogous
to a TCP reset injection. This attack is possible if an attacker is to a TCP reset injection. This attack is possible if an attacker is
able to cause a stateless reset token to be generated for a able to cause a stateless reset token to be generated for a
connection with a selected connection ID. An attacker that can cause connection with a selected connection ID. An attacker that can cause
this token to be generated can reset an active connection with the this token to be generated can reset an active connection with the
same connection ID. same connection ID.
If a packet can be routed to different instances that share a static If a packet can be routed to different instances that share a static
key, for example by changing an IP address or port, then an attacker key -- for example, by changing an IP address or port -- then an
can cause the server to send a stateless reset. To defend against attacker can cause the server to send a stateless reset. To defend
this style of denial of service, endpoints that share a static key against this style of denial of service, endpoints that share a
for stateless reset (see Section 10.3.2) MUST be arranged so that static key for stateless resets (see Section 10.3.2) MUST be arranged
packets with a given connection ID always arrive at an instance that so that packets with a given connection ID always arrive at an
has connection state, unless that connection is no longer active. instance that has connection state, unless that connection is no
longer active.
More generally, servers MUST NOT generate a stateless reset if a More generally, servers MUST NOT generate a stateless reset if a
connection with the corresponding connection ID could be active on connection with the corresponding connection ID could be active on
any endpoint using the same static key. any endpoint using the same static key.
In the case of a cluster that uses dynamic load balancing, it is In the case of a cluster that uses dynamic load balancing, it is
possible that a change in load balancer configuration could occur possible that a change in load-balancer configuration could occur
while an active instance retains connection state. Even if an while an active instance retains connection state. Even if an
instance retains connection state, the change in routing and instance retains connection state, the change in routing and
resulting stateless reset will result in the connection being resulting stateless reset will result in the connection being
terminated. If there is no chance of the packet being routed to the terminated. If there is no chance of the packet being routed to the
correct instance, it is better to send a stateless reset than wait correct instance, it is better to send a stateless reset than wait
for the connection to time out. However, this is acceptable only if for the connection to time out. However, this is acceptable only if
the routing cannot be influenced by an attacker. the routing cannot be influenced by an attacker.
21.12. Version Downgrade 21.12. Version Downgrade
This document defines QUIC Version Negotiation packets in Section 6 This document defines QUIC Version Negotiation packets (Section 6),
that can be used to negotiate the QUIC version used between two which can be used to negotiate the QUIC version used between two
endpoints. However, this document does not specify how this endpoints. However, this document does not specify how this
negotiation will be performed between this version and subsequent negotiation will be performed between this version and subsequent
future versions. In particular, Version Negotiation packets do not future versions. In particular, Version Negotiation packets do not
contain any mechanism to prevent version downgrade attacks. Future contain any mechanism to prevent version downgrade attacks. Future
versions of QUIC that use Version Negotiation packets MUST define a versions of QUIC that use Version Negotiation packets MUST define a
mechanism that is robust against version downgrade attacks. mechanism that is robust against version downgrade attacks.
21.13. Targeted Attacks by Routing 21.13. Targeted Attacks by Routing
Deployments should limit the ability of an attacker to target a new Deployments should limit the ability of an attacker to target a new
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addresses. Once an instance is selected, a connection ID can be addresses. Once an instance is selected, a connection ID can be
selected so that later packets are routed to the same instance. selected so that later packets are routed to the same instance.
21.14. Traffic Analysis 21.14. Traffic Analysis
The length of QUIC packets can reveal information about the length of The length of QUIC packets can reveal information about the length of
the content of those packets. The PADDING frame is provided so that the content of those packets. The PADDING frame is provided so that
endpoints have some ability to obscure the length of packet content; endpoints have some ability to obscure the length of packet content;
see Section 19.1. see Section 19.1.
Note however that defeating traffic analysis is challenging and the Defeating traffic analysis is challenging and the subject of active
subject of active research. Length is not the only way that research. Length is not the only way that information might leak.
information might leak. Endpoints might also reveal sensitive Endpoints might also reveal sensitive information through other side
information through other side channels, such as the timing of channels, such as the timing of packets.
packets.
22. IANA Considerations 22. IANA Considerations
This document establishes several registries for the management of This document establishes several registries for the management of
codepoints in QUIC. These registries operate on a common set of codepoints in QUIC. These registries operate on a common set of
policies as defined in Section 22.1. policies as defined in Section 22.1.
22.1. Registration Policies for QUIC Registries 22.1. Registration Policies for QUIC Registries
All QUIC registries allow for both provisional and permanent All QUIC registries allow for both provisional and permanent
registration of codepoints. This section documents policies that are registration of codepoints. This section documents policies that are
common to these registries. common to these registries.
22.1.1. Provisional Registrations 22.1.1. Provisional Registrations
Provisional registration of codepoints are intended to allow for Provisional registrations of codepoints are intended to allow for
private use and experimentation with extensions to QUIC. Provisional private use and experimentation with extensions to QUIC. Provisional
registrations only require the inclusion of the codepoint value and registrations only require the inclusion of the codepoint value and
contact information. However, provisional registrations could be contact information. However, provisional registrations could be
reclaimed and reassigned for another purpose. reclaimed and reassigned for another purpose.
Provisional registrations require Expert Review, as defined in Provisional registrations require Expert Review, as defined in
Section 4.5 of [RFC8126]. Designated expert(s) are advised that only Section 4.5 of [RFC8126]. The designated expert or experts are
registrations for an excessive proportion of remaining codepoint advised that only registrations for an excessive proportion of
space or the very first unassigned value (see Section 22.1.2) can be remaining codepoint space or the very first unassigned value (see
rejected. Section 22.1.2) can be rejected.
Provisional registrations will include a date field that indicates Provisional registrations will include a Date field that indicates
when the registration was last updated. A request to update the date when the registration was last updated. A request to update the date
on any provisional registration can be made without review from the on any provisional registration can be made without review from the
designated expert(s). designated expert(s).
All QUIC registries include the following fields to support All QUIC registries include the following fields to support
provisional registration: provisional registration:
Value: The assigned codepoint. Value: The assigned codepoint.
Status: "permanent" or "provisional".
Status: "Permanent" or "Provisional".
Specification: A reference to a publicly available specification for Specification: A reference to a publicly available specification for
the value. the value.
Date: The date of the last update to the registration.
Date: The date of last update to the registration.
Change Controller: The entity that is responsible for the definition Change Controller: The entity that is responsible for the definition
of the registration. of the registration.
Contact: Contact details for the registrant. Contact: Contact details for the registrant.
Notes: Supplementary notes about the registration. Notes: Supplementary notes about the registration.
Provisional registrations MAY omit the Specification and Notes Provisional registrations MAY omit the Specification and Notes
fields, plus any additional fields that might be required for a fields, plus any additional fields that might be required for a
permanent registration. The Date field is not required as part of permanent registration. The Date field is not required as part of
requesting a registration as it is set to the date the registration requesting a registration, as it is set to the date the registration
is created or updated. is created or updated.
22.1.2. Selecting Codepoints 22.1.2. Selecting Codepoints
New uses of codepoints from QUIC registries SHOULD use a randomly New requests for codepoints from QUIC registries SHOULD use a
selected codepoint that excludes both existing allocations and the randomly selected codepoint that excludes both existing allocations
first unallocated codepoint in the selected space. Requests for and the first unallocated codepoint in the selected space. Requests
multiple codepoints MAY use a contiguous range. This minimizes the for multiple codepoints MAY use a contiguous range. This minimizes
risk that differing semantics are attributed to the same codepoint by the risk that differing semantics are attributed to the same
different implementations. codepoint by different implementations.
Use of the first unassigned codepoint is reserved for allocation The use of the first unassigned codepoint is reserved for allocation
using the Standards Action policy; see Section 4.9 of [RFC8126]. The using the Standards Action policy; see Section 4.9 of [RFC8126]. The
early codepoint assignment process [EARLY-ASSIGN] can be used for early codepoint assignment process [EARLY-ASSIGN] can be used for
these values. these values.
For codepoints that are encoded in variable-length integers For codepoints that are encoded in variable-length integers
(Section 16), such as frame types, codepoints that encode to four or (Section 16), such as frame types, codepoints that encode to four or
eight bytes (that is, values 2^14 and above) SHOULD be used unless eight bytes (that is, values 2^14 and above) SHOULD be used unless
the usage is especially sensitive to having a longer encoding. the usage is especially sensitive to having a longer encoding.
Applications to register codepoints in QUIC registries MAY include a Applications to register codepoints in QUIC registries MAY include a
requested codepoint as part of the registration. IANA MUST allocate requested codepoint as part of the registration. IANA MUST allocate
the selected codepoint if the codepoint is unassigned and the the selected codepoint if the codepoint is unassigned and the
requirements of the registration policy are met. requirements of the registration policy are met.
22.1.3. Reclaiming Provisional Codepoints 22.1.3. Reclaiming Provisional Codepoints
A request might be made to remove an unused provisional registration A request might be made to remove an unused provisional registration
from the registry to reclaim space in a registry, or portion of the from the registry to reclaim space in a registry, or a portion of the
registry (such as the 64-16383 range for codepoints that use registry (such as the 64-16383 range for codepoints that use
variable-length encodings). This SHOULD be done only for the variable-length encodings). This SHOULD be done only for the
codepoints with the earliest recorded date and entries that have been codepoints with the earliest recorded date, and entries that have
updated less than a year prior SHOULD NOT be reclaimed. been updated less than a year prior SHOULD NOT be reclaimed.
A request to remove a codepoint MUST be reviewed by the designated A request to remove a codepoint MUST be reviewed by the designated
expert(s). The expert(s) MUST attempt to determine whether the experts. The experts MUST attempt to determine whether the codepoint
codepoint is still in use. Experts are advised to contact the listed is still in use. Experts are advised to contact the listed contacts
contacts for the registration, plus as wide a set of protocol for the registration, plus as wide a set of protocol implementers as
implementers as possible in order to determine whether any use of the possible in order to determine whether any use of the codepoint is
codepoint is known. The expert(s) are advised to allow at least four known. The experts are also advised to allow at least four weeks for
weeks for responses. responses.
If any use of the codepoints is identified by this search or a If any use of the codepoints is identified by this search or a
request to update the registration is made, the codepoint MUST NOT be request to update the registration is made, the codepoint MUST NOT be
reclaimed. Instead, the date on the registration is updated. A note reclaimed. Instead, the date on the registration is updated. A note
might be added for the registration recording relevant information might be added for the registration recording relevant information
that was learned. that was learned.
If no use of the codepoint was identified and no request was made to If no use of the codepoint was identified and no request was made to
update the registration, the codepoint MAY be removed from the update the registration, the codepoint MAY be removed from the
registry. registry.
This review and consultation process also applies to requests to This review and consultation process also applies to requests to
change a provisional registration into a permanent registration, change a provisional registration into a permanent registration,
except that the goal is not to determine whether there is no use of except that the goal is not to determine whether there is no use of
the codepoint, but to determine that the registration is an accurate the codepoint but to determine that the registration is an accurate
representation of any deployed usage. representation of any deployed usage.
22.1.4. Permanent Registrations 22.1.4. Permanent Registrations
Permanent registrations in QUIC registries use the Specification Permanent registrations in QUIC registries use the Specification
Required policy ([RFC8126]), unless otherwise specified. The Required policy (Section 4.6 of [RFC8126]), unless otherwise
designated expert(s) verify that a specification exists and is specified. The designated expert or experts verify that a
readily accessible. Expert(s) are encouraged to be biased towards specification exists and is readily accessible. Experts are
approving registrations unless they are abusive, frivolous, or encouraged to be biased towards approving registrations unless they
actively harmful (not merely aesthetically displeasing, or are abusive, frivolous, or actively harmful (not merely aesthetically
architecturally dubious). The creation of a registry MAY specify displeasing or architecturally dubious). The creation of a registry
additional constraints on permanent registrations. MAY specify additional constraints on permanent registrations.
The creation of a registry MAY identify a range of codepoints where The creation of a registry MAY identify a range of codepoints where
registrations are governed by a different registration policy. For registrations are governed by a different registration policy. For
instance, the frame type registry in Section 22.4 has a stricter instance, the "QUIC Frame Types" registry (Section 22.4) has a
policy for codepoints in the range from 0 to 63. stricter policy for codepoints in the range from 0 to 63.
Any stricter requirements for permanent registrations do not prevent Any stricter requirements for permanent registrations do not prevent
provisional registrations for affected codepoints. For instance, a provisional registrations for affected codepoints. For instance, a
provisional registration for a frame type of 61 could be requested. provisional registration for a frame type of 61 could be requested.
All registrations made by Standards Track publications MUST be All registrations made by Standards Track publications MUST be
permanent. permanent.
All registrations in this document are assigned a permanent status All registrations in this document are assigned a permanent status
and list a change controller of the IETF and a contact of the QUIC and list a change controller of the IETF and a contact of the QUIC
working group (quic@ietf.org). Working Group (quic@ietf.org).
22.2. QUIC Versions Registry 22.2. QUIC Versions Registry
IANA [SHALL add/has added] a registry for "QUIC Versions" under a IANA has added a registry for "QUIC Versions" under a "QUIC" heading.
"QUIC" heading.
The "QUIC Versions" registry governs a 32-bit space; see Section 15. The "QUIC Versions" registry governs a 32-bit space; see Section 15.
This registry follows the registration policy from Section 22.1. This registry follows the registration policy from Section 22.1.
Permanent registrations in this registry are assigned using the Permanent registrations in this registry are assigned using the
Specification Required policy ([RFC8126]). Specification Required policy (Section 4.6 of [RFC8126]).
The codepoint of 0x00000001 to the protocol is assigned with The codepoint of 0x00000001 for the protocol is assigned with
permanent status to the protocol defined in this document. The permanent status to the protocol defined in this document. The
codepoint of 0x00000000 is permanently reserved; the note for this codepoint of 0x00000000 is permanently reserved; the note for this
codepoint [shall] indicate[s] that this version is reserved for codepoint indicates that this version is reserved for version
Version Negotiation. negotiation.
All codepoints that follow the pattern 0x?a?a?a?a are reserved and All codepoints that follow the pattern 0x?a?a?a?a are reserved, MUST
MUST NOT be assigned by IANA and MUST NOT appear in the listing of NOT be assigned by IANA, and MUST NOT appear in the listing of
assigned values. assigned values.
[[RFC editor: please remove the following note before publication.]] 22.3. QUIC Transport Parameters Registry
IANA note: Several pre-standardization versions will likely be in
use at the time of publication. There is no need to document
these in an RFC, but recording information about these version
will ensure that the information in the registry is accurate. The
document editors or working group chairs can facilitate getting
the necessary information.
22.3. QUIC Transport Parameter Registry
IANA [SHALL add/has added] a registry for "QUIC Transport Parameters" IANA has added a registry for "QUIC Transport Parameters" under a
under a "QUIC" heading. "QUIC" heading.
The "QUIC Transport Parameters" registry governs a 62-bit space. The "QUIC Transport Parameters" registry governs a 62-bit space.
This registry follows the registration policy from Section 22.1. This registry follows the registration policy from Section 22.1.
Permanent registrations in this registry are assigned using the Permanent registrations in this registry are assigned using the
Specification Required policy ([RFC8126]). Specification Required policy (Section 4.6 of [RFC8126]), except for
values between 0x00 and 0x3f (in hexadecimal), inclusive, which are
assigned using Standards Action or IESG Approval as defined in
Sections 4.9 and 4.10 of [RFC8126].
In addition to the fields in Section 22.1.1, permanent registrations In addition to the fields listed in Section 22.1.1, permanent
in this registry MUST include the following field: registrations in this registry MUST include the following field:
Parameter Name: A short mnemonic for the parameter. Parameter Name: A short mnemonic for the parameter.
The initial contents of this registry are shown in Table 6. The initial contents of this registry are shown in Table 6.
+-------+-------------------------------------+---------------+ +-------+-------------------------------------+---------------+
| Value | Parameter Name | Specification | | Value | Parameter Name | Specification |
+-------+-------------------------------------+---------------+ +-------+-------------------------------------+---------------+
| 0x00 | original_destination_connection_id | Section 18.2 | | 0x00 | original_destination_connection_id | Section 18.2 |
| | | | | | | |
skipping to change at page 170, line 43 skipping to change at page 169, line 43
| | | | | | | |
| 0x0d | preferred_address | Section 18.2 | | 0x0d | preferred_address | Section 18.2 |
| | | | | | | |
| 0x0e | active_connection_id_limit | Section 18.2 | | 0x0e | active_connection_id_limit | Section 18.2 |
| | | | | | | |
| 0x0f | initial_source_connection_id | Section 18.2 | | 0x0f | initial_source_connection_id | Section 18.2 |
| | | | | | | |
| 0x10 | retry_source_connection_id | Section 18.2 | | 0x10 | retry_source_connection_id | Section 18.2 |
+-------+-------------------------------------+---------------+ +-------+-------------------------------------+---------------+
Table 6: Initial QUIC Transport Parameters Entries Table 6: Initial QUIC Transport Parameters Registry Entries
Each value of the format "31 * N + 27" for integer values of N (that Each value of the form "31 * N + 27" for integer values of N (that
is, 27, 58, 89, ...) are reserved; these values MUST NOT be assigned is, 27, 58, 89, ...) are reserved; these values MUST NOT be assigned
by IANA and MUST NOT appear in the listing of assigned values. by IANA and MUST NOT appear in the listing of assigned values.
22.4. QUIC Frame Types Registry 22.4. QUIC Frame Types Registry
IANA [SHALL add/has added] a registry for "QUIC Frame Types" under a IANA has added a registry for "QUIC Frame Types" under a "QUIC"
"QUIC" heading. heading.
The "QUIC Frame Types" registry governs a 62-bit space. This The "QUIC Frame Types" registry governs a 62-bit space. This
registry follows the registration policy from Section 22.1. registry follows the registration policy from Section 22.1.
Permanent registrations in this registry are assigned using the Permanent registrations in this registry are assigned using the
Specification Required policy ([RFC8126]), except for values between Specification Required policy (Section 4.6 of [RFC8126]), except for
0x00 and 0x3f (in hexadecimal; inclusive), which are assigned using values between 0x00 and 0x3f (in hexadecimal), inclusive, which are
Standards Action or IESG Approval as defined in Section 4.9 and 4.10 assigned using Standards Action or IESG Approval as defined in
of [RFC8126]. Sections 4.9 and 4.10 of [RFC8126].
In addition to the fields in Section 22.1.1, permanent registrations In addition to the fields listed in Section 22.1.1, permanent
in this registry MUST include the following field: registrations in this registry MUST include the following field:
Frame Name: A short mnemonic for the frame type. Frame Type Name: A short mnemonic for the frame type.
In addition to the advice in Section 22.1, specifications for new In addition to the advice in Section 22.1, specifications for new
permanent registrations SHOULD describe the means by which an permanent registrations SHOULD describe the means by which an
endpoint might determine that it can send the identified type of endpoint might determine that it can send the identified type of
frame. An accompanying transport parameter registration is expected frame. An accompanying transport parameter registration is expected
for most registrations; see Section 22.3. Specifications for for most registrations; see Section 22.3. Specifications for
permanent registrations also need to describe the format and assigned permanent registrations also need to describe the format and assigned
semantics of any fields in the frame. semantics of any fields in the frame.
The initial contents of this registry are tabulated in Table 3. Note The initial contents of this registry are tabulated in Table 3. Note
that the registry does not include the "Pkts" and "Spec" columns from that the registry does not include the "Pkts" and "Spec" columns from
Table 3. Table 3.
22.5. QUIC Transport Error Codes Registry 22.5. QUIC Transport Error Codes Registry
IANA [SHALL add/has added] a registry for "QUIC Transport Error IANA has added a registry for "QUIC Transport Error Codes" under a
Codes" under a "QUIC" heading. "QUIC" heading.
The "QUIC Transport Error Codes" registry governs a 62-bit space. The "QUIC Transport Error Codes" registry governs a 62-bit space.
This space is split into three regions that are governed by different This space is split into three ranges that are governed by different
policies. Permanent registrations in this registry are assigned policies. Permanent registrations in this registry are assigned
using the Specification Required policy ([RFC8126]), except for using the Specification Required policy (Section 4.6 of [RFC8126]),
values between 0x00 and 0x3f (in hexadecimal; inclusive), which are except for values between 0x00 and 0x3f (in hexadecimal), inclusive,
assigned using Standards Action or IESG Approval as defined in which are assigned using Standards Action or IESG Approval as defined
Section 4.9 and 4.10 of [RFC8126]. in Sections 4.9 and 4.10 of [RFC8126].
In addition to the fields in Section 22.1.1, permanent registrations In addition to the fields listed in Section 22.1.1, permanent
in this registry MUST include the following fields: registrations in this registry MUST include the following fields:
Code: A short mnemonic for the parameter. Code: A short mnemonic for the parameter.
Description: A brief description of the error code semantics, which Description: A brief description of the error code semantics, which
MAY be a summary if a specification reference is provided. MAY be a summary if a specification reference is provided.
The initial contents of this registry are shown in Table 7. The initial contents of this registry are shown in Table 7.
+------+---------------------------+----------------+---------------+ +-------------+-----------------------+--------------+--------------+
| Valu | Code | Description | Specification | | Value | Code | Description | Specificatio |
| e | | | | | | | | n |
+------+---------------------------+----------------+---------------+ +-------------+-----------------------+--------------+--------------+
| 0x0 | NO_ERROR | No error | Section 20 | | 0x00 | NO_ERROR | No error | Section 20 |
| | | | | | | | | |
| 0x1 | INTERNAL_ERROR | Implementation | Section 20 | | 0x01 | INTERNAL_ERROR | Implementati | Section 20 |
| | | error | | | | | on error | |
| | | | | | | | | |
| 0x2 | CONNECTION_REFUSED | Server refuses | Section 20 | | 0x02 | CONNECTION_REFUSED | Server | Section 20 |
| | | a connection | | | | | refuses a | |
| | | | | | | | connection | |
| 0x3 | FLOW_CONTROL_ERROR | Flow control | Section 20 | | | | | |
| | | error | | | 0x03 | FLOW_CONTROL_ERROR | Flow control | Section 20 |
| | | | | | | | error | |
| 0x4 | STREAM_LIMIT_ERROR | Too many | Section 20 | | | | | |
| | | streams opened | | | 0x04 | STREAM_LIMIT_ERROR | Too many | Section 20 |
| | | | | | | | streams | |
| 0x5 | STREAM_STATE_ERROR | Frame received | Section 20 | | | | opened | |
| | | in invalid | | | | | | |
| | | stream state | | | 0x05 | STREAM_STATE_ERROR | Frame | Section 20 |
| | | | | | | | received in | |
| 0x6 | FINAL_SIZE_ERROR | Change to | Section 20 | | | | invalid | |
| | | final size | | | | | stream state | |
| | | | | | | | | |
| 0x7 | FRAME_ENCODING_ERROR | Frame encoding | Section 20 | | 0x06 | FINAL_SIZE_ERROR | Change to | Section 20 |
| | | error | | | | | final size | |
| | | | | | | | | |
| 0x8 | TRANSPORT_PARAMETER_ERROR | Error in | Section 20 | | 0x07 | FRAME_ENCODING_ERROR | Frame | Section 20 |
| | | transport | | | | | encoding | |
| | | parameters | | | | | error | |
| | | | | | | | | |
| 0x9 | CONNECTION_ID_LIMIT_ERROR | Too many | Section 20 | | 0x08 | TRANSPORT_PARAMETER_E | Error in | Section 20 |
| | | connection IDs | | | | RROR | transport | |
| | | received | | | | | parameters | |
| | | | | | | | | |
| 0xa | PROTOCOL_VIOLATION | Generic | Section 20 | | 0x09 | CONNECTION_ID_LIMIT_E | Too many | Section 20 |
| | | protocol | | | | RROR | connection | |
| | | violation | | | | | IDs received | |
| | | | | | | | | |
| 0xb | INVALID_TOKEN | Invalid Token | Section 20 | | 0x0a | PROTOCOL_VIOLATION | Generic | Section 20 |
| | | Received | | | | | protocol | |
| | | | | | | | violation | |
| 0xc | APPLICATION_ERROR | Application | Section 20 | | | | | |
| | | error | | | 0x0b | INVALID_TOKEN | Invalid | Section 20 |
| | | | | | | | Token | |
| 0xd | CRYPTO_BUFFER_EXCEEDED | CRYPTO data | Section 20 | | | | received | |
| | | buffer | | | | | | |
| | | overflowed | | | 0x0c | APPLICATION_ERROR | Application | Section 20 |
| | | | | | | | error | |
| 0xe | KEY_UPDATE_ERROR | Invalid packet | Section 20 | | | | | |
| | | protection | | | 0x0d | CRYPTO_BUFFER_EXCEEDE | CRYPTO data | Section 20 |
| | | update | | | | D | buffer | |
| | | | | | | | overflowed | |
| 0xf | AEAD_LIMIT_REACHED | Excessive use | Section 20 | | | | | |
| | | of packet | | | 0x0e | KEY_UPDATE_ERROR | Invalid | Section 20 |
| | | protection | | | | | packet | |
| | | keys | | | | | protection | |
| | | | | | | | update | |
| 0x10 | NO_VIABLE_PATH | No viable | Section 20 | | | | | |
| | | network path | | | 0x0f | AEAD_LIMIT_REACHED | Excessive | Section 20 |
| | | exists | | | | | use of | |
+------+---------------------------+----------------+---------------+ | | | packet | |
| | | protection | |
| | | keys | |
| | | | |
| 0x10 | NO_VIABLE_PATH | No viable | Section 20 |
| | | network path | |
| | | exists | |
| | | | |
| 0x0100-0x0 | CRYPTO_ERROR | TLS alert | Section 20 |
| 1ff | | code | |
+-------------+-----------------------+--------------+--------------+
Table 7: Initial QUIC Transport Error Codes Entries Table 7: Initial QUIC Transport Error Codes Registry Entries
23. References 23. References
23.1. Normative References 23.1. Normative References
[BCP38] Ferguson, P. and D. Senie, "Network Ingress Filtering: [BCP38] Consisting of: [RFC2827],
Defeating Denial of Service Attacks which employ IP Source <https://www.rfc-editor.org/info/bcp38>.
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
May 2000, <https://www.rfc-editor.org/info/bcp38>.
[DPLPMTUD] [DPLPMTUD]
Fairhurst, G., Jones, T., Tuexen, M., Ruengeler, I., and Fairhurst, G., Jones, T., Tuexen, M., Ruengeler, I., and
T. Voelker, "Packetization Layer Path MTU Discovery for T. Voelker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899, Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/info/rfc8899>. September 2020, <https://www.rfc-editor.org/info/rfc8899>.
[EARLY-ASSIGN] [EARLY-ASSIGN]
Cotton, M., "Early IANA Allocation of Standards Track Code Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
2014, <https://www.rfc-editor.org/info/rfc7120>. 2014, <https://www.rfc-editor.org/info/rfc7120>.
[IPv4] Postel, J., "Internet Protocol", STD 5, RFC 791, [IPv4] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981, DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>. <https://www.rfc-editor.org/info/rfc791>.
[QUIC-INVARIANTS] [QUIC-INVARIANTS]
Thomson, M., "Version-Independent Properties of QUIC", Thomson, M., "Version-Independent Properties of QUIC",
draft-ietf-quic-invariants-13 (work in progress), January RFC 8999, DOI 10.17487/RFC8999, May 2021,
2021. <https://www.rfc-editor.org/info/rfc8999>.
[QUIC-RECOVERY] [QUIC-RECOVERY]
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", draft-ietf-quic-recovery-34 (work and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
in progress), January 2021. May 2021, <https://www.rfc-editor.org/info/rfc9002>.
[QUIC-TLS] [QUIC-TLS]
Thomson, M., Ed. and S. Turner, Ed., "Using Transport Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
Layer Security (TLS) to Secure QUIC", draft-ietf-quic- QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
tls-34 (work in progress), January 2021. <https://www.rfc-editor.org/info/rfc9001>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990, DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>. <https://www.rfc-editor.org/info/rfc1191>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
May 2000, <https://www.rfc-editor.org/info/rfc2827>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001, RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>. <https://www.rfc-editor.org/info/rfc3168>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>. 2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
skipping to change at page 175, line 48 skipping to change at page 175, line 15
[ALTSVC] Nottingham, M., McManus, P., and J. Reschke, "HTTP [ALTSVC] Nottingham, M., McManus, P., and J. Reschke, "HTTP
Alternative Services", RFC 7838, DOI 10.17487/RFC7838, Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
April 2016, <https://www.rfc-editor.org/info/rfc7838>. April 2016, <https://www.rfc-editor.org/info/rfc7838>.
[COOKIE] Barth, A., "HTTP State Management Mechanism", RFC 6265, [COOKIE] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>. <https://www.rfc-editor.org/info/rfc6265>.
[CSRF] Barth, A., Jackson, C., and J. Mitchell, "Robust defenses [CSRF] Barth, A., Jackson, C., and J. Mitchell, "Robust defenses
for cross-site request forgery", Proceedings of the 15th for cross-site request forgery", Proceedings of the 15th
ACM conference on Computer and communications security - ACM conference on Computer and communications security,
CCS '08, DOI 10.1145/1455770.1455782, 2008. DOI 10.1145/1455770.1455782, ACM, October 2008.
[EARLY-DESIGN] [EARLY-DESIGN]
Roskind, J., "QUIC: Multiplexed Transport Over UDP", Roskind, J., "QUIC: Multiplexed Stream Transport Over
December 2013, <https://goo.gl/dMVtFi>. UDP", December 2013, <https://docs.google.com/document/
d/1RNHkx_VvKWyWg6Lr8SZ-saqsQx7rFV-ev2jRFUoVD34/
edit?usp=sharing>.
[GATEWAY] Haetoenen, S., Nyrhinen, A., Eggert, L., Strowes, S., [GATEWAY] Haetoenen, S., Nyrhinen, A., Eggert, L., Strowes, S.,
Sarolahti, P., and M. Kojo, "An experimental study of home Sarolahti, P., and M. Kojo, "An experimental study of home
gateway characteristics", Proceedings of the 10th annual gateway characteristics", DOI 10.1145/1879141.1879174,
conference on Internet measurement - IMC '10, Proceedings of the 10th ACM SIGCOMM conference on Internet
DOI 10.1145/1879141.1879174, 2010. measurement - IMC '10, November 2010.
[HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>. <https://www.rfc-editor.org/info/rfc7540>.
[IPv6] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [IPv6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
[QUIC-MANAGEABILITY] [QUIC-MANAGEABILITY]
Kuehlewind, M. and B. Trammell, "Manageability of the QUIC Kuehlewind, M. and B. Trammell, "Manageability of the QUIC
Transport Protocol", draft-ietf-quic-manageability-08 Transport Protocol", draft-ietf-quic-manageability-18
(work in progress), November 2020. (work in progress), July 2022.
[RANDOM] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RANDOM] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>. <https://www.rfc-editor.org/info/rfc4086>.
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995, RFC 1812, DOI 10.17487/RFC1812, June 1995,
<https://www.rfc-editor.org/info/rfc1812>. <https://www.rfc-editor.org/info/rfc1812>.
skipping to change at page 177, line 29 skipping to change at page 176, line 44
Control Message Protocol (ICMPv6) for the Internet Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89, Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006, RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>. <https://www.rfc-editor.org/info/rfc4443>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address [RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>. 2007, <https://www.rfc-editor.org/info/rfc4787>.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<https://www.rfc-editor.org/info/rfc4941>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009, Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>. <https://www.rfc-editor.org/info/rfc5681>.
[RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869, Key Derivation Function (HKDF)", RFC 5869,
DOI 10.17487/RFC5869, May 2010, DOI 10.17487/RFC5869, May 2010,
<https://www.rfc-editor.org/info/rfc5869>. <https://www.rfc-editor.org/info/rfc5869>.
[RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme [RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme
Updates for Secure Real-time Transport Protocol (SRTP) Updates for Secure Real-time Transport Protocol (SRTP)
Extension for Datagram Transport Layer Security (DTLS)", Extension for Datagram Transport Layer Security (DTLS)",
RFC 7983, DOI 10.17487/RFC7983, September 2016, RFC 7983, DOI 10.17487/RFC7983, September 2016,
<https://www.rfc-editor.org/info/rfc7983>. <https://www.rfc-editor.org/info/rfc7983>.
[RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using [RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using
Explicit Congestion Notification (ECN)", RFC 8087, Explicit Congestion Notification (ECN)", RFC 8087,
DOI 10.17487/RFC8087, March 2017, DOI 10.17487/RFC8087, March 2017,
<https://www.rfc-editor.org/info/rfc8087>. <https://www.rfc-editor.org/info/rfc8087>.
[RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves,
"Temporary Address Extensions for Stateless Address
Autoconfiguration in IPv6", RFC 8981,
DOI 10.17487/RFC8981, February 2021,
<https://www.rfc-editor.org/info/rfc8981>.
[SEC-CONS] [SEC-CONS]
Rescorla, E. and B. Korver, "Guidelines for Writing RFC Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003, DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>. <https://www.rfc-editor.org/info/rfc3552>.
[SLOWLORIS] [SLOWLORIS]
RSnake Hansen, R., "Welcome to Slowloris...", June 2009, "RSnake" Hansen, R., "Welcome to Slowloris - the low
<https://web.archive.org/web/20150315054838/ bandwidth, yet greedy and poisonous HTTP client!", June
2009, <https://web.archive.org/web/20150315054838/
http://ha.ckers.org/slowloris/>. http://ha.ckers.org/slowloris/>.
23.3. URIs
[1] mailto:quic@ietf.org
Appendix A. Pseudocode Appendix A. Pseudocode
The pseudocode in this section describes sample algorithms. These The pseudocode in this section describes sample algorithms. These
algorithms are intended to be correct and clear, rather than being algorithms are intended to be correct and clear, rather than being
optimally performant. optimally performant.
The pseudocode segments in this section are licensed as Code The pseudocode segments in this section are licensed as Code
Components; see the copyright notice. Components; see the Copyright Notice.
A.1. Sample Variable-Length Integer Decoding A.1. Sample Variable-Length Integer Decoding
The pseudocode in Figure 43 shows how a variable-length integer can The pseudocode in Figure 43 shows how a variable-length integer can
be read from a stream of bytes. The function ReadVarint takes a be read from a stream of bytes. The function ReadVarint takes a
single argument, a sequence of bytes which can be read in network single argument -- a sequence of bytes, which can be read in network
byte order. byte order.
ReadVarint(data): ReadVarint(data):
// The length of variable-length integers is encoded in the // The length of variable-length integers is encoded in the
// first two bits of the first byte. // first two bits of the first byte.
v = data.next_byte() v = data.next_byte()
prefix = v >> 6 prefix = v >> 6
length = 1 << prefix length = 1 << prefix
// Once the length is known, remove these bits and read any // Once the length is known, remove these bits and read any
skipping to change at page 179, line 20 skipping to change at page 178, line 36
A.2. Sample Packet Number Encoding Algorithm A.2. Sample Packet Number Encoding Algorithm
The pseudocode in Figure 44 shows how an implementation can select an The pseudocode in Figure 44 shows how an implementation can select an
appropriate size for packet number encodings. appropriate size for packet number encodings.
The EncodePacketNumber function takes two arguments: The EncodePacketNumber function takes two arguments:
o full_pn is the full packet number of the packet being sent. o full_pn is the full packet number of the packet being sent.
o largest_acked is the largest packet number which has been o largest_acked is the largest packet number that has been
acknowledged by the peer in the current packet number space, if acknowledged by the peer in the current packet number space, if
any. any.
EncodePacketNumber(full_pn, largest_acked): EncodePacketNumber(full_pn, largest_acked):
// The number of bits must be at least one more // The number of bits must be at least one more
// than the base-2 logarithm of the number of contiguous // than the base-2 logarithm of the number of contiguous
// unacknowledged packet numbers, including the new packet. // unacknowledged packet numbers, including the new packet.
if largest_acked is None: if largest_acked is None:
num_unacked = full_pn + 1 num_unacked = full_pn + 1
else: else:
num_unacked = full_pn - largest_acked num_unacked = full_pn - largest_acked
min_bits = log(num_unacked, 2) + 1 min_bits = log(num_unacked, 2) + 1
num_bytes = ceil(min_bits / 8) num_bytes = ceil(min_bits / 8)
// Encode the integer value and truncate to // Encode the integer value and truncate to
// the num_bytes least-significant bytes. // the num_bytes least significant bytes.
return encode(full_pn, num_bytes) return encode(full_pn, num_bytes)
Figure 44: Sample Packet Number Encoding Algorithm Figure 44: Sample Packet Number Encoding Algorithm
For example, if an endpoint has received an acknowledgment for packet For example, if an endpoint has received an acknowledgment for packet
0xabe8bc and is sending a packet with a number of 0xac5c02, there are 0xabe8b3 and is sending a packet with a number of 0xac5c02, there are
29,519 (0x734f) outstanding packets. In order to represent at least 29,519 (0x734f) outstanding packet numbers. In order to represent at
twice this range (59,038 packets, or 0xe69e), 16 bits are required. least twice this range (59,038 packets, or 0xe69e), 16 bits are
required.
In the same state, sending a packet with a number of 0xace8fe uses In the same state, sending a packet with a number of 0xace8fe uses
the 24-bit encoding, because at least 18 bits are required to the 24-bit encoding, because at least 18 bits are required to
represent twice the range (131,182 packets, or 0x2006e). represent twice the range (131,222 packets, or 0x020096).
A.3. Sample Packet Number Decoding Algorithm A.3. Sample Packet Number Decoding Algorithm
The pseudocode in Figure 45 includes an example algorithm for The pseudocode in Figure 45 includes an example algorithm for
decoding packet numbers after header protection has been removed. decoding packet numbers after header protection has been removed.
The DecodePacketNumber function takes three arguments: The DecodePacketNumber function takes three arguments:
o largest_pn is the largest packet number that has been successfully o largest_pn is the largest packet number that has been successfully
processed in the current packet number space. processed in the current packet number space.
skipping to change at page 181, line 18 skipping to change at page 180, line 49
determines whether the path supports ECN; see Section 13.4. If the determines whether the path supports ECN; see Section 13.4. If the
path supports ECN, the goal is to use ECN. Endpoints might also path supports ECN, the goal is to use ECN. Endpoints might also
periodically reassess a path that was determined to not support ECN. periodically reassess a path that was determined to not support ECN.
This section describes one method for testing new paths. This This section describes one method for testing new paths. This
algorithm is intended to show how a path might be tested for ECN algorithm is intended to show how a path might be tested for ECN
support. Endpoints can implement different methods. support. Endpoints can implement different methods.
The path is assigned an ECN state that is one of "testing", The path is assigned an ECN state that is one of "testing",
"unknown", "failed", or "capable". On paths with a "testing" or "unknown", "failed", or "capable". On paths with a "testing" or
"capable" state the endpoint sends packets with an ECT marking, by "capable" state, the endpoint sends packets with an ECT marking --
default ECT(0); otherwise, the endpoint sends unmarked packets. ECT(0) by default; otherwise, the endpoint sends unmarked packets.
To start testing a path, the ECN state is set to "testing" and To start testing a path, the ECN state is set to "testing", and
existing ECN counts are remembered as a baseline. existing ECN counts are remembered as a baseline.
The testing period runs for a number of packets or a limited time, as The testing period runs for a number of packets or a limited time, as
determined by the endpoint. The goal is not to limit the duration of determined by the endpoint. The goal is not to limit the duration of
the testing period, but to ensure that enough marked packets are sent the testing period but to ensure that enough marked packets are sent
for received ECN counts to provide a clear indication of how the path for received ECN counts to provide a clear indication of how the path
treats marked packets. Section 13.4.2 suggests limiting this to 10 treats marked packets. Section 13.4.2 suggests limiting this to ten
packets or 3 times the probe timeout. packets or three times the PTO.
After the testing period ends, the ECN state for the path becomes After the testing period ends, the ECN state for the path becomes
"unknown". From the "unknown" state, successful validation of the "unknown". From the "unknown" state, successful validation of the
ECN counts an ACK frame (see Section 13.4.2.1) causes the ECN state ECN counts in an ACK frame (see Section 13.4.2.1) causes the ECN
for the path to become "capable", unless no marked packet has been state for the path to become "capable", unless no marked packet has
acknowledged. been acknowledged.
If validation of ECN counts fails at any time, the ECN state for the If validation of ECN counts fails at any time, the ECN state for the
affected path becomes "failed". An endpoint can also mark the ECN affected path becomes "failed". An endpoint can also mark the ECN
state for a path as "failed" if marked packets are all declared lost state for a path as "failed" if marked packets are all declared lost
or if they are all CE marked. or if they are all ECN-CE marked.
Following this algorithm ensures that ECN is rarely disabled for Following this algorithm ensures that ECN is rarely disabled for
paths that properly support ECN. Any path that incorrectly modifies paths that properly support ECN. Any path that incorrectly modifies
markings will cause ECN to be disabled. For those rare cases where markings will cause ECN to be disabled. For those rare cases where
marked packets are discarded by the path, the short duration of the marked packets are discarded by the path, the short duration of the
testing period limits the number of losses incurred. testing period limits the number of losses incurred.
Appendix B. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
Issue and pull request numbers are listed with a leading octothorp.
B.1. Since draft-ietf-quic-transport-32
o Endpoints are required to limit the total data they send in
response to an apparent connection migration to three times what
was received (#4257, #4264)
o Added an error code for path validation failures (#4257, #4331)
o Defined DoS protections for clients during the handshake (#4259,
#4330, #4344)
o Prohibited connection errors when datagrams are not the required
size (#4273, #4342)
o Stop using initial timeout for path validation (#4261, #4262,
#4263).
o A number of improvements to IANA considerations:
* Added a registry for versions (#4345, #4280)
* Clarified rules for first reserved value (#4378, #4389)
* Reserved values are not added to the registry (#4372, #4428)
o Added final version numbers (#4430)
B.2. Since draft-ietf-quic-transport-31
o Require expansion of datagrams to ensure that a path supports at
least 1200 bytes in both directions:
* During the handshake ack-eliciting Initial packets from the
server need to be expanded (#4183, #4188)
* Path validation now requires packets containing PATH_CHALLENGE
and PATH_RESPONSE to be expanded and PATH_RESPONSE is sent on
the same network path (#4216, #4226)
o Though senders need to expand datagrams in some cases, receivers
cannot enforce this requirement (#4253, #4254)
o Split contact into contact and change controller for IANA
registrations (#4230, #4239)
B.3. Since draft-ietf-quic-transport-30
o Use TRANSPORT_PARAMETER_ERROR for an invalid transport parameter
(#4099, #4100)
o Add a new error code for AEAD_LIMIT_REACHED code to avoid conflict
(#4087, #4088)
o Allow use of address validation token when server address changes
(#4076, #4089)
B.4. Since draft-ietf-quic-transport-29
o Require the same connection ID on coalesced packets (#3800, #3930)
o Allow caching of packets that can't be decrypted, by allowing the
reported acknowledgment delay to exceed max_ack_delay prior to
confirming the handshake (#3821, #3980, #4035, #3874)
o Allow connection ID to be used for address validation (#3834,
#3924)
o Required protocol operations are no longer directed at
implementations, but are features provided to application
protocols (#3838, #3935)
o Narrow requirements for reset of congestion state on path change
(#3842, #3945)
o Add a three times amplification limit for sending of
CONNECTION_CLOSE with reduced state (#3845, #3864)
o Change error code for invalid RETIRE_CONNECTION_ID frames (#3860,
#3861)
o Recommend retention of state for lost packets to allow for late
arrival and avoid unnecessary retransmission (#3956, #3957)
o Allow a server to reject connections if a client reuses packet
numbers after Retry (#3989, #3990)
o Limit recommendation for immediate acknowledgment to when ack-
eliciting packets are reordered (#4001, #4000)
B.5. Since draft-ietf-quic-transport-28
o Made SERVER_BUSY error (0x2) more generic, now CONNECTION_REFUSED
(#3709, #3690, #3694)
o Allow TRANSPORT_PARAMETER_ERROR when validating connection IDs
(#3703, #3691)
o Integrate QUIC-specific language from draft-ietf-tsvwg-datagram-
plpmtud (#3695, #3702)
o disable_active_migration does not apply to the addresses offered
in server_preferred_address (#3608, #3670)
B.6. Since draft-ietf-quic-transport-27
o Allowed CONNECTION_CLOSE in any packet number space, with a
requirement to use a new transport-level error for application-
specific errors in Initial and Handshake packets (#3430, #3435,
#3440)
o Clearer requirements for address validation (#2125, #3327)
o Security analysis of handshake and migration (#2143, #2387, #2925)
o The entire payload of a datagram is used when counting bytes for
mitigating amplification attacks (#3333, #3470)
o Connection IDs can be used at any time, including in the handshake
(#3348, #3560, #3438, #3565)
o Only one ACK should be sent for each instance of reordering
(#3357, #3361)
o Remove text allowing a server to proceed with a bad Retry token
(#3396, #3398)
o Ignore active_connection_id_limit with a zero-length connection ID
(#3427, #3426)
o Require active_connection_id_limit be remembered for 0-RTT (#3423,
#3425)
o Require ack_delay not be remembered for 0-RTT (#3433, #3545)
o Redefined max_packet_size to max_udp_datagram_size (#3471, #3473)
o Guidance on limiting outstanding attempts to retire connection IDs
(#3489, #3509, #3557, #3547)
o Restored text on dropping bogus Version Negotiation packets
(#3532, #3533)
o Clarified that largest acknowledged needs to be saved, but not
necessarily signaled in all cases (#3541, #3581)
o Addressed linkability risk with the use of preferred_address
(#3559, #3563)
o Added authentication of handshake connection IDs (#3439, #3499)
o Opening a stream in the wrong direction is an error (#3527)
B.7. Since draft-ietf-quic-transport-26
o Change format of transport parameters to use varints (#3294,
#3169)
B.8. Since draft-ietf-quic-transport-25
o Define the use of CONNECTION_CLOSE prior to establishing
connection state (#3269, #3297, #3292)
o Allow use of address validation tokens after client address
changes (#3307, #3308)
o Define the timer for address validation (#2910, #3339)
B.9. Since draft-ietf-quic-transport-24
o Added HANDSHAKE_DONE to signal handshake confirmation (#2863,
#3142, #3145)
o Add integrity check to Retry packets (#3014, #3274, #3120)
o Specify handling of reordered NEW_CONNECTION_ID frames (#3194,
#3202)
o Require checking of sequence numbers in RETIRE_CONNECTION_ID
(#3037, #3036)
o active_connection_id_limit is enforced (#3193, #3197, #3200,
#3201)
o Correct overflow in packet number decode algorithm (#3187, #3188)
o Allow use of CRYPTO_BUFFER_EXCEEDED for CRYPTO frame errors
(#3258, #3186)
o Define applicability and scope of NEW_TOKEN (#3150, #3152, #3155,
#3156)
o Tokens from Retry and NEW_TOKEN must be differentiated (#3127,
#3128)
o Allow CONNECTION_CLOSE in response to invalid token (#3168, #3107)
o Treat an invalid CONNECTION_CLOSE as an invalid frame (#2475,
#3230, #3231)
o Throttle when sending CONNECTION_CLOSE after discarding state
(#3095, #3157)
o Application-variant of CONNECTION_CLOSE can only be sent in 0-RTT
or 1-RTT packets (#3158, #3164)
o Advise sending while blocked to avoid idle timeout (#2744, #3266)
o Define error codes for invalid frames (#3027, #3042)
o Idle timeout is symmetric (#2602, #3099)
o Prohibit IP fragmentation (#3243, #3280)
o Define the use of provisional registration for all registries
(#3109, #3020, #3102, #3170)
o Packets on one path must not adjust values for a different path
(#2909, #3139)
B.10. Since draft-ietf-quic-transport-23
o Allow ClientHello to span multiple packets (#2928, #3045)
o Client Initial size constraints apply to UDP datagram payload
(#3053, #3051)
o Stateless reset changes (#2152, #2993)
* tokens need to be compared in constant time
* detection uses UDP datagrams, not packets
* tokens cannot be reused (#2785, #2968)
o Clearer rules for sharing of UDP ports and use of connection IDs
when doing so (#2844, #2851)
o A new connection ID is necessary when responding to migration
(#2778, #2969)
o Stronger requirements for connection ID retirement (#3046, #3096)
o NEW_TOKEN cannot be empty (#2978, #2977)
o PING can be sent at any encryption level (#3034, #3035)
o CONNECTION_CLOSE is not ack-eliciting (#3097, #3098)
o Frame encoding error conditions updated (#3027, #3042)
o Non-ack-eliciting packets cannot be sent in response to non-ack-
eliciting packets (#3100, #3104)
o Servers have to change connection IDs in Retry (#2837, #3147)
B.11. Since draft-ietf-quic-transport-22
o Rules for preventing correlation by connection ID tightened
(#2084, #2929)
o Clarified use of CONNECTION_CLOSE in Handshake packets (#2151,
#2541, #2688)
o Discourage regressions of largest acknowledged in ACK (#2205,
#2752)
o Improved robustness of validation process for ECN counts (#2534,
#2752)
o Require endpoints to ignore spurious migration attempts (#2342,
#2893)
o Transport parameter for disabling migration clarified to allow NAT
rebinding (#2389, #2893)
o Document principles for defining new error codes (#2388, #2880)
o Reserve transport parameters for greasing (#2550, #2873)
o A maximum ACK delay of 0 is used for handshake packet number
spaces (#2646, #2638)
o Improved rules for use of congestion control state on new paths
(#2685, #2918)
o Removed recommendation to coordinate spin for multiple connections
that share a path (#2763, #2882)
o Allow smaller stateless resets and recommend a smaller minimum on
packets that might trigger a stateless reset (#2770, #2869, #2927,
#3007).
o Provide guidance around the interface to QUIC as used by
application protocols (#2805, #2857)
o Frames other than STREAM can cause STREAM_LIMIT_ERROR (#2825,
#2826)
o Tighter rules about processing of rejected 0-RTT packets (#2829,
#2840, #2841)
o Explanation of the effect of Retry on 0-RTT packets (#2842, #2852)
o Cryptographic handshake needs to provide server transport
parameter encryption (#2920, #2921)
o Moved ACK generation guidance from recovery draft to transport
draft (#1860, #2916).
B.12. Since draft-ietf-quic-transport-21
o Connection ID lengths are now one octet, but limited in version 1
to 20 octets of length (#2736, #2749)
B.13. Since draft-ietf-quic-transport-20
o Error codes are encoded as variable-length integers (#2672, #2680)
o NEW_CONNECTION_ID includes a request to retire old connection IDs
(#2645, #2769)
o Tighter rules for generating and explicitly eliciting ACK frames
(#2546, #2794)
o Recommend having only one packet per encryption level in a
datagram (#2308, #2747)
o More normative language about use of stateless reset (#2471,
#2574)
o Allow reuse of stateless reset tokens (#2732, #2733)
o Allow, but not require, enforcing non-duplicate transport
parameters (#2689, #2691)
o Added an active_connection_id_limit transport parameter (#1994,
#1998)
o max_ack_delay transport parameter defaults to 0 (#2638, #2646)
o When sending 0-RTT, only remembered transport parameters apply
(#2458, #2360, #2466, #2461)
o Define handshake completion and confirmation; define clearer rules
when it encryption keys should be discarded (#2214, #2267, #2673)
o Prohibit path migration prior to handshake confirmation (#2309,
#2370)
o PATH_RESPONSE no longer needs to be received on the validated path
(#2582, #2580, #2579, #2637)
o PATH_RESPONSE frames are not stored and retransmitted (#2724,
#2729)
o Document hack for enabling routing of ICMP when doing PMTU probing
(#1243, #2402)
B.14. Since draft-ietf-quic-transport-19
o Refine discussion of 0-RTT transport parameters (#2467, #2464)
o Fewer transport parameters need to be remembered for 0-RTT (#2624,
#2467)
o Spin bit text incorporated (#2564)
o Close the connection when maximum stream ID in MAX_STREAMS exceeds
2^62 - 1 (#2499, #2487)
o New connection ID required for intentional migration (#2414,
#2413)
o Connection ID issuance can be rate-limited (#2436, #2428)
o The "QUIC bit" is ignored in Version Negotiation (#2400, #2561)
o Initial packets from clients need to be padded to 1200 unless a
Handshake packet is sent as well (#2522, #2523)
o CRYPTO frames can be discarded if too much data is buffered
(#1834, #2524)
o Stateless reset uses a short header packet (#2599, #2600)
B.15. Since draft-ietf-quic-transport-18
o Removed version negotiation; version negotiation, including
authentication of the result, will be addressed in the next
version of QUIC (#1773, #2313)
o Added discussion of the use of IPv6 flow labels (#2348, #2399)
o A connection ID can't be retired in a packet that uses that
connection ID (#2101, #2420)
o Idle timeout transport parameter is in milliseconds (from seconds)
(#2453, #2454)
o Endpoints are required to use new connection IDs when they use new
network paths (#2413, #2414)
o Increased the set of permissible frames in 0-RTT (#2344, #2355)
B.16. Since draft-ietf-quic-transport-17
o Stream-related errors now use STREAM_STATE_ERROR (#2305)
o Endpoints discard initial keys as soon as handshake keys are
available (#1951, #2045)
o Expanded conditions for ignoring ICMP packet too big messages
(#2108, #2161)
o Remove rate control from PATH_CHALLENGE/PATH_RESPONSE (#2129,
#2241)
o Endpoints are permitted to discard malformed initial packets
(#2141)
o Clarified ECN implementation and usage requirements (#2156, #2201)
o Disable ECN count verification for packets that arrive out of
order (#2198, #2215)
o Use Probe Timeout (PTO) instead of RTO (#2206, #2238)
o Loosen constraints on retransmission of ACK ranges (#2199, #2245)
o Limit Retry and Version Negotiation to once per datagram (#2259,
#2303)
o Set a maximum value for max_ack_delay transport parameter (#2282,
#2301)
o Allow server preferred address for both IPv4 and IPv6 (#2122,
#2296)
o Corrected requirements for migration to a preferred address
(#2146, #2349)
o ACK of non-existent packet is illegal (#2298, #2302)
B.17. Since draft-ietf-quic-transport-16
o Stream limits are defined as counts, not maximums (#1850, #1906)
o Require amplification attack defense after closing (#1905, #1911)
o Remove reservation of application error code 0 for STOPPING
(#1804, #1922)
o Renumbered frames (#1945)
o Renumbered transport parameters (#1946)
o Numeric transport parameters are expressed as varints (#1608,
#1947, #1955)
o Reorder the NEW_CONNECTION_ID frame (#1952, #1963)
o Rework the first byte (#2006)
* Fix the 0x40 bit
* Change type values for long header
* Add spin bit to short header (#631, #1988)
* Encrypt the remainder of the first byte (#1322)
* Move packet number length to first byte
* Move ODCIL to first byte of retry packets
* Simplify packet number protection (#1575)
o Allow STOP_SENDING to open a remote bidirectional stream (#1797,
#2013)
o Added mitigation for off-path migration attacks (#1278, #1749,
#2033)
o Don't let the PMTU to drop below 1280 (#2063, #2069)
o Require peers to replace retired connection IDs (#2085)
o Servers are required to ignore Version Negotiation packets (#2088)
o Tokens are repeated in all Initial packets (#2089)
o Clarified how PING frames are sent after loss (#2094)
o Initial keys are discarded once Handshake are available (#1951,
#2045)
o ICMP PTB validation clarifications (#2161, #2109, #2108)
B.18. Since draft-ietf-quic-transport-15
Substantial editorial reorganization; no technical changes.
B.19. Since draft-ietf-quic-transport-14
o Merge ACK and ACK_ECN (#1778, #1801)
o Explicitly communicate max_ack_delay (#981, #1781)
o Validate original connection ID after Retry packets (#1710, #1486,
#1793)
o Idle timeout is optional and has no specified maximum (#1765)
o Update connection ID handling; add RETIRE_CONNECTION_ID type
(#1464, #1468, #1483, #1484, #1486, #1495, #1729, #1742, #1799,
#1821)
o Include a Token in all Initial packets (#1649, #1794)
o Prevent handshake deadlock (#1764, #1824)
B.20. Since draft-ietf-quic-transport-13
o Streams open when higher-numbered streams of the same type open
(#1342, #1549)
o Split initial stream flow control limit into 3 transport
parameters (#1016, #1542)
o All flow control transport parameters are optional (#1610)
o Removed UNSOLICITED_PATH_RESPONSE error code (#1265, #1539)
o Permit stateless reset in response to any packet (#1348, #1553)
o Recommended defense against stateless reset spoofing (#1386,
#1554)
o Prevent infinite stateless reset exchanges (#1443, #1627)
o Forbid processing of the same packet number twice (#1405, #1624)
o Added a packet number decoding example (#1493)
o More precisely define idle timeout (#1429, #1614, #1652)
o Corrected format of Retry packet and prevented looping (#1492,
#1451, #1448, #1498)
o Permit 0-RTT after receiving Version Negotiation or Retry (#1507,
#1514, #1621)
o Permit Retry in response to 0-RTT (#1547, #1552)
o Looser verification of ECN counters to account for ACK loss
(#1555, #1481, #1565)
o Remove frame type field from APPLICATION_CLOSE (#1508, #1528)
B.21. Since draft-ietf-quic-transport-12
o Changes to integration of the TLS handshake (#829, #1018, #1094,
#1165, #1190, #1233, #1242, #1252, #1450, #1458)
* The cryptographic handshake uses CRYPTO frames, not stream 0
* QUIC packet protection is used in place of TLS record
protection
* Separate QUIC packet number spaces are used for the handshake
* Changed Retry to be independent of the cryptographic handshake
* Added NEW_TOKEN frame and Token fields to Initial packet
* Limit the use of HelloRetryRequest to address TLS needs (like
key shares)
o Enable server to transition connections to a preferred address
(#560, #1251, #1373)
o Added ECN feedback mechanisms and handling; new ACK_ECN frame
(#804, #805, #1372)
o Changed rules and recommendations for use of new connection IDs
(#1258, #1264, #1276, #1280, #1419, #1452, #1453, #1465)
o Added a transport parameter to disable intentional connection
migration (#1271, #1447)
o Packets from different connection ID can't be coalesced (#1287,
#1423)
o Fixed sampling method for packet number encryption; the length
field in long headers includes the packet number field in addition
to the packet payload (#1387, #1389)
o Stateless Reset is now symmetric and subject to size constraints
(#466, #1346)
o Added frame type extension mechanism (#58, #1473)
B.22. Since draft-ietf-quic-transport-11
o Enable server to transition connections to a preferred address
(#560, #1251)
o Packet numbers are encrypted (#1174, #1043, #1048, #1034, #850,
#990, #734, #1317, #1267, #1079)
o Packet numbers use a variable-length encoding (#989, #1334)
o STREAM frames can now be empty (#1350)
B.23. Since draft-ietf-quic-transport-10
o Swap payload length and packed number fields in long header
(#1294)
o Clarified that CONNECTION_CLOSE is allowed in Handshake packet
(#1274)
o Spin bit reserved (#1283)
o Coalescing multiple QUIC packets in a UDP datagram (#1262, #1285)
o A more complete connection migration (#1249)
o Refine opportunistic ACK defense text (#305, #1030, #1185)
o A Stateless Reset Token isn't mandatory (#818, #1191)
o Removed implicit stream opening (#896, #1193)
o An empty STREAM frame can be used to open a stream without sending
data (#901, #1194)
o Define stream counts in transport parameters rather than a maximum
stream ID (#1023, #1065)
o STOP_SENDING is now prohibited before streams are used (#1050)
o Recommend including ACK in Retry packets and allow PADDING (#1067,
#882)
o Endpoints now become closing after an idle timeout (#1178, #1179)
o Remove implication that Version Negotiation is sent when a packet
of the wrong version is received (#1197)
B.24. Since draft-ietf-quic-transport-09
o Added PATH_CHALLENGE and PATH_RESPONSE frames to replace PING with
Data and PONG frame. Changed ACK frame type from 0x0e to 0x0d.
(#1091, #725, #1086)
o A server can now only send 3 packets without validating the client
address (#38, #1090)
o Delivery order of stream data is no longer strongly specified
(#252, #1070)
o Rework of packet handling and version negotiation (#1038)
o Stream 0 is now exempt from flow control until the handshake
completes (#1074, #725, #825, #1082)
o Improved retransmission rules for all frame types: information is
retransmitted, not packets or frames (#463, #765, #1095, #1053)
o Added an error code for server busy signals (#1137)
o Endpoints now set the connection ID that their peer uses.
Connection IDs are variable length. Removed the
omit_connection_id transport parameter and the corresponding short
header flag. (#1089, #1052, #1146, #821, #745, #821, #1166, #1151)
B.25. Since draft-ietf-quic-transport-08
o Clarified requirements for BLOCKED usage (#65, #924)
o BLOCKED frame now includes reason for blocking (#452, #924, #927,
#928)
o GAP limitation in ACK Frame (#613)
o Improved PMTUD description (#614, #1036)
o Clarified stream state machine (#634, #662, #743, #894)
o Reserved versions don't need to be generated deterministically
(#831, #931)
o You don't always need the draining period (#871)
o Stateless reset clarified as version-specific (#930, #986)
o initial_max_stream_id_x transport parameters are optional (#970,
#971)
o ACK delay assumes a default value during the handshake (#1007,
#1009)
o Removed transport parameters from NewSessionTicket (#1015)
B.26. Since draft-ietf-quic-transport-07
o The long header now has version before packet number (#926, #939)
o Rename and consolidate packet types (#846, #822, #847)
o Packet types are assigned new codepoints and the Connection ID
Flag is inverted (#426, #956)
o Removed type for Version Negotiation and use Version 0 (#963,
#968)
o Streams are split into unidirectional and bidirectional (#643,
#656, #720, #872, #175, #885)
* Stream limits now have separate uni- and bi-directional
transport parameters (#909, #958)
* Stream limit transport parameters are now optional and default
to 0 (#970, #971)
o The stream state machine has been split into read and write (#634,
#894)
o Employ variable-length integer encodings throughout (#595)
o Improvements to connection close
* Added distinct closing and draining states (#899, #871)
* Draining period can terminate early (#869, #870)
* Clarifications about stateless reset (#889, #890)
o Address validation for connection migration (#161, #732, #878)
o Clearly defined retransmission rules for BLOCKED (#452, #65, #924)
o negotiated_version is sent in server transport parameters (#710,
#959)
o Increased the range over which packet numbers are randomized
(#864, #850, #964)
B.27. Since draft-ietf-quic-transport-06
o Replaced FNV-1a with AES-GCM for all "Cleartext" packets (#554)
o Split error code space between application and transport (#485)
o Stateless reset token moved to end (#820)
o 1-RTT-protected long header types removed (#848)
o No acknowledgments during draining period (#852)
o Remove "application close" as a separate close type (#854)
o Remove timestamps from the ACK frame (#841)
o Require transport parameters to only appear once (#792)
B.28. Since draft-ietf-quic-transport-05
o Stateless token is server-only (#726)
o Refactor section on connection termination (#733, #748, #328,
#177)
o Limit size of Version Negotiation packet (#585)
o Clarify when and what to ack (#736)
o Renamed STREAM_ID_NEEDED to STREAM_ID_BLOCKED
o Clarify Keep-alive requirements (#729)
B.29. Since draft-ietf-quic-transport-04
o Introduce STOP_SENDING frame, RESET_STREAM only resets in one
direction (#165)
o Removed GOAWAY; application protocols are responsible for graceful
shutdown (#696)
o Reduced the number of error codes (#96, #177, #184, #211)
o Version validation fields can't move or change (#121)
o Removed versions from the transport parameters in a
NewSessionTicket message (#547)
o Clarify the meaning of "bytes in flight" (#550)
o Public reset is now stateless reset and not visible to the path
(#215)
o Reordered bits and fields in STREAM frame (#620)
o Clarifications to the stream state machine (#572, #571)
o Increased the maximum length of the Largest Acknowledged field in
ACK frames to 64 bits (#629)
o truncate_connection_id is renamed to omit_connection_id (#659)
o CONNECTION_CLOSE terminates the connection like TCP RST (#330,
#328)
o Update labels used in HKDF-Expand-Label to match TLS 1.3 (#642)
B.30. Since draft-ietf-quic-transport-03
o Change STREAM and RESET_STREAM layout
o Add MAX_STREAM_ID settings
B.31. Since draft-ietf-quic-transport-02
o The size of the initial packet payload has a fixed minimum (#267,
#472)
o Define when Version Negotiation packets are ignored (#284, #294,
#241, #143, #474)
o The 64-bit FNV-1a algorithm is used for integrity protection of
unprotected packets (#167, #480, #481, #517)
o Rework initial packet types to change how the connection ID is
chosen (#482, #442, #493)
o No timestamps are forbidden in unprotected packets (#542, #429)
o Cryptographic handshake is now on stream 0 (#456)
o Remove congestion control exemption for cryptographic handshake
(#248, #476)
o Version 1 of QUIC uses TLS; a new version is needed to use a
different handshake protocol (#516)
o STREAM frames have a reduced number of offset lengths (#543, #430)
o Split some frames into separate connection- and stream- level
frames (#443)
* WINDOW_UPDATE split into MAX_DATA and MAX_STREAM_DATA (#450)
* BLOCKED split to match WINDOW_UPDATE split (#454)
* Define STREAM_ID_NEEDED frame (#455)
o A NEW_CONNECTION_ID frame supports connection migration without
linkability (#232, #491, #496)
o Transport parameters for 0-RTT are retained from a previous
connection (#405, #513, #512)
* A client in 0-RTT no longer required to reset excess streams
(#425, #479)
o Expanded security considerations (#440, #444, #445, #448)
B.32. Since draft-ietf-quic-transport-01
o Defined short and long packet headers (#40, #148, #361)
o Defined a versioning scheme and stable fields (#51, #361)
o Define reserved version values for "greasing" negotiation (#112,
#278)
o The initial packet number is randomized (#35, #283)
o Narrow the packet number encoding range requirement (#67, #286,
#299, #323, #356)
o Defined client address validation (#52, #118, #120, #275)
o Define transport parameters as a TLS extension (#49, #122)
o SCUP and COPT parameters are no longer valid (#116, #117)
o Transport parameters for 0-RTT are either remembered from before,
or assume default values (#126)
o The server chooses connection IDs in its final flight (#119, #349,
#361)
o The server echoes the Connection ID and packet number fields when
sending a Version Negotiation packet (#133, #295, #244)
o Defined a minimum packet size for the initial handshake packet
from the client (#69, #136, #139, #164)
o Path MTU Discovery (#64, #106)
o The initial handshake packet from the client needs to fit in a
single packet (#338)
o Forbid acknowledgment of packets containing only ACK and PADDING
(#291)
o Require that frames are processed when packets are acknowledged
(#381, #341)
o Removed the STOP_WAITING frame (#66)
o Don't require retransmission of old timestamps for lost ACK frames
(#308)
o Clarified that frames are not retransmitted, but the information
in them can be (#157, #298)
o Error handling definitions (#335)
o Split error codes into four sections (#74)
o Forbid the use of Public Reset where CONNECTION_CLOSE is possible
(#289)
o Define packet protection rules (#336)
o Require that stream be entirely delivered or reset, including
acknowledgment of all STREAM frames or the RESET_STREAM, before it
closes (#381)
o Remove stream reservation from state machine (#174, #280)
o Only stream 1 does not contribute to connection-level flow control
(#204)
o Stream 1 counts towards the maximum concurrent stream limit (#201,
#282)
o Remove connection-level flow control exclusion for some streams
(except 1) (#246)
o RESET_STREAM affects connection-level flow control (#162, #163)
o Flow control accounting uses the maximum data offset on each
stream, rather than bytes received (#378)
o Moved length-determining fields to the start of STREAM and ACK
(#168, #277)
o Added the ability to pad between frames (#158, #276)
o Remove error code and reason phrase from GOAWAY (#352, #355)
o GOAWAY includes a final stream number for both directions (#347)
o Error codes for RESET_STREAM and CONNECTION_CLOSE are now at a
consistent offset (#249)
o Defined priority as the responsibility of the application protocol
(#104, #303)
B.33. Since draft-ietf-quic-transport-00
o Replaced DIVERSIFICATION_NONCE flag with KEY_PHASE flag
o Defined versioning
o Reworked description of packet and frame layout
o Error code space is divided into regions for each component
o Use big endian for all numeric values
B.34. Since draft-hamilton-quic-transport-protocol-01
o Adopted as base for draft-ietf-quic-tls
o Updated authors/editors list
o Added IANA Considerations section
o Moved Contributors and Acknowledgments to appendices
Contributors Contributors
The original design and rationale behind this protocol draw The original design and rationale behind this protocol draw
significantly from work by Jim Roskind [EARLY-DESIGN]. significantly from work by Jim Roskind [EARLY-DESIGN].
The IETF QUIC Working Group received an enormous amount of support The IETF QUIC Working Group received an enormous amount of support
from many people. The following people provided substantive from many people. The following people provided substantive
contributions to this document: contributions to this document:
o Alessandro Ghedini o Alessandro Ghedini
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