draft-ietf-quic-transport-02.txt   draft-ietf-quic-transport-latest.txt 
QUIC Working Group J. Iyengar, Ed. QUIC Working Group J. Iyengar, Ed.
Internet-Draft Google Internet-Draft Google
Intended status: Standards Track M. Thomson, Ed. Intended status: Standards Track M. Thomson, Ed.
Expires: September 14, 2017 Mozilla Expires: October 29, 2017 Mozilla
March 13, 2017 April 27, 2017
QUIC: A UDP-Based Multiplexed and Secure Transport QUIC: A UDP-Based Multiplexed and Secure Transport
draft-ietf-quic-transport-02 draft-ietf-quic-transport-latest
Abstract Abstract
This document defines the core of the QUIC transport protocol. This This document defines the core of the QUIC transport protocol. This
document describes connection establishment, packet format, document describes connection establishment, packet format,
multiplexing and reliability. Accompanying documents describe the multiplexing and reliability. Accompanying documents describe the
cryptographic handshake and loss detection. cryptographic handshake and loss detection.
Note to Readers Note to Readers
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This Internet-Draft will expire on September 14, 2017. This Internet-Draft will expire on October 29, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
2.1. Notational Conventions . . . . . . . . . . . . . . . . . 5 2.1. Notational Conventions . . . . . . . . . . . . . . . . . 5
3. A QUIC Overview . . . . . . . . . . . . . . . . . . . . . . . 5 3. A QUIC Overview . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Low-Latency Connection Establishment . . . . . . . . . . 6 3.1. Low-Latency Connection Establishment . . . . . . . . . . 6
3.2. Stream Multiplexing . . . . . . . . . . . . . . . . . . . 6 3.2. Stream Multiplexing . . . . . . . . . . . . . . . . . . . 6
3.3. Rich Signaling for Congestion Control and Loss Recovery . 6 3.3. Rich Signaling for Congestion Control and Loss Recovery . 6
3.4. Stream and Connection Flow Control . . . . . . . . . . . 6 3.4. Stream and Connection Flow Control . . . . . . . . . . . 7
3.5. Authenticated and Encrypted Header and Payload . . . . . 7 3.5. Authenticated and Encrypted Header and Payload . . . . . 7
3.6. Connection Migration and Resilience to NAT Rebinding . . 7 3.6. Connection Migration and Resilience to NAT Rebinding . . 7
3.7. Version Negotiation . . . . . . . . . . . . . . . . . . . 8 3.7. Version Negotiation . . . . . . . . . . . . . . . . . . . 8
4. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Packet Types and Formats . . . . . . . . . . . . . . . . . . 8 5. Packet Types and Formats . . . . . . . . . . . . . . . . . . 9
5.1. Long Header . . . . . . . . . . . . . . . . . . . . . . . 9 5.1. Long Header . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. Short Header . . . . . . . . . . . . . . . . . . . . . . 11 5.2. Short Header . . . . . . . . . . . . . . . . . . . . . . 11
5.3. Version Negotiation Packet . . . . . . . . . . . . . . . 12 5.3. Version Negotiation Packet . . . . . . . . . . . . . . . 12
5.4. Cleartext Packets . . . . . . . . . . . . . . . . . . . . 13 5.4. Cleartext Packets . . . . . . . . . . . . . . . . . . . . 13
5.5. Encrypted Packets . . . . . . . . . . . . . . . . . . . . 14 5.5. Encrypted Packets . . . . . . . . . . . . . . . . . . . . 14
5.6. Public Reset Packet . . . . . . . . . . . . . . . . . . . 15 5.6. Public Reset Packet . . . . . . . . . . . . . . . . . . . 15
5.6.1. Public Reset Proof . . . . . . . . . . . . . . . . . 15 5.6.1. Public Reset Proof . . . . . . . . . . . . . . . . . 15
5.7. Connection ID . . . . . . . . . . . . . . . . . . . . . . 16 5.7. Connection ID . . . . . . . . . . . . . . . . . . . . . . 16
5.8. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 16 5.8. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 16
5.8.1. Initial Packet Number . . . . . . . . . . . . . . . . 17 5.8.1. Initial Packet Number . . . . . . . . . . . . . . . . 17
5.9. Handling Packets from Different Versions . . . . . . . . 17 5.9. Handling Packets from Different Versions . . . . . . . . 17
6. Frames and Frame Types . . . . . . . . . . . . . . . . . . . 18 6. Frames and Frame Types . . . . . . . . . . . . . . . . . . . 18
7. Life of a Connection . . . . . . . . . . . . . . . . . . . . 19 7. Life of a Connection . . . . . . . . . . . . . . . . . . . . 19
7.1. Version Negotiation . . . . . . . . . . . . . . . . . . . 19 7.1. Version Negotiation . . . . . . . . . . . . . . . . . . . 19
7.1.1. Using Reserved Versions . . . . . . . . . . . . . . . 20 7.1.1. Using Reserved Versions . . . . . . . . . . . . . . . 20
7.2. Cryptographic and Transport Handshake . . . . . . . . . . 21 7.2. Cryptographic and Transport Handshake . . . . . . . . . . 21
7.3. Transport Parameters . . . . . . . . . . . . . . . . . . 22 7.3. Transport Parameters . . . . . . . . . . . . . . . . . . 22
7.3.1. Transport Parameter Definitions . . . . . . . . . . . 24 7.3.1. Transport Parameter Definitions . . . . . . . . . . . 24
7.3.2. Values of Transport Parameters for 0-RTT . . . . . . 24 7.3.2. Values of Transport Parameters for 0-RTT . . . . . . 24
7.3.3. New Transport Parameters . . . . . . . . . . . . . . 25 7.3.3. New Transport Parameters . . . . . . . . . . . . . . 25
7.3.4. Version Negotiation Validation . . . . . . . . . . . 25 7.3.4. Version Negotiation Validation . . . . . . . . . . . 26
7.4. Proof of Source Address Ownership . . . . . . . . . . . . 27 7.4. Proof of Source Address Ownership . . . . . . . . . . . . 27
7.4.1. Client Address Validation Procedure . . . . . . . . . 27 7.4.1. Client Address Validation Procedure . . . . . . . . . 28
7.4.2. Address Validation on Session Resumption . . . . . . 28 7.4.2. Address Validation on Session Resumption . . . . . . 28
7.4.3. Address Validation Token Integrity . . . . . . . . . 29 7.4.3. Address Validation Token Integrity . . . . . . . . . 29
7.5. Connection Migration . . . . . . . . . . . . . . . . . . 29 7.5. Connection Migration . . . . . . . . . . . . . . . . . . 29
7.6. Connection Termination . . . . . . . . . . . . . . . . . 30 7.6. Connection Termination . . . . . . . . . . . . . . . . . 30
8. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 31 8. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 31
8.1. STREAM Frame . . . . . . . . . . . . . . . . . . . . . . 31 8.1. STREAM Frame . . . . . . . . . . . . . . . . . . . . . . 31
8.2. ACK Frame . . . . . . . . . . . . . . . . . . . . . . . . 32 8.2. ACK Frame . . . . . . . . . . . . . . . . . . . . . . . . 33
8.2.1. ACK Block Section . . . . . . . . . . . . . . . . . . 34 8.2.1. ACK Block Section . . . . . . . . . . . . . . . . . . 35
8.2.2. Timestamp Section . . . . . . . . . . . . . . . . . . 35 8.2.2. Timestamp Section . . . . . . . . . . . . . . . . . . 36
8.2.3. ACK Frames and Packet Protection . . . . . . . . . . 37 8.2.3. ACK Frames and Packet Protection . . . . . . . . . . 37
8.3. WINDOW_UPDATE Frame . . . . . . . . . . . . . . . . . . . 38 8.3. MAX_DATA Frame . . . . . . . . . . . . . . . . . . . . . 38
8.4. BLOCKED Frame . . . . . . . . . . . . . . . . . . . . . . 39 8.4. MAX_STREAM_DATA Frame . . . . . . . . . . . . . . . . . . 39
8.5. RST_STREAM Frame . . . . . . . . . . . . . . . . . . . . 39 8.5. MAX_STREAM_ID Frame . . . . . . . . . . . . . . . . . . . 39
8.6. PADDING Frame . . . . . . . . . . . . . . . . . . . . . . 40 8.6. BLOCKED Frame . . . . . . . . . . . . . . . . . . . . . . 40
8.7. PING frame . . . . . . . . . . . . . . . . . . . . . . . 40 8.7. STREAM_BLOCKED Frame . . . . . . . . . . . . . . . . . . 40
8.8. CONNECTION_CLOSE frame . . . . . . . . . . . . . . . . . 40 8.8. RST_STREAM Frame . . . . . . . . . . . . . . . . . . . . 41
8.9. GOAWAY Frame . . . . . . . . . . . . . . . . . . . . . . 41 8.9. PADDING Frame . . . . . . . . . . . . . . . . . . . . . . 41
9. Packetization and Reliability . . . . . . . . . . . . . . . . 42 8.10. PING frame . . . . . . . . . . . . . . . . . . . . . . . 41
9.1. Special Considerations for PMTU Discovery . . . . . . . . 44 8.11. CONNECTION_CLOSE frame . . . . . . . . . . . . . . . . . 42
10. Streams: QUIC's Data Structuring Abstraction . . . . . . . . 45 8.12. GOAWAY Frame . . . . . . . . . . . . . . . . . . . . . . 42
10.1. Life of a Stream . . . . . . . . . . . . . . . . . . . . 45 9. Packetization and Reliability . . . . . . . . . . . . . . . . 43
10.1.1. idle . . . . . . . . . . . . . . . . . . . . . . . . 47 9.1. Special Considerations for PMTU Discovery . . . . . . . . 46
10.1.2. open . . . . . . . . . . . . . . . . . . . . . . . . 47 10. Streams: QUIC's Data Structuring Abstraction . . . . . . . . 46
10.1.3. half-closed (local) . . . . . . . . . . . . . . . . 48 10.1. Life of a Stream . . . . . . . . . . . . . . . . . . . . 47
10.1.4. half-closed (remote) . . . . . . . . . . . . . . . . 48 10.1.1. idle . . . . . . . . . . . . . . . . . . . . . . . . 49
10.1.5. closed . . . . . . . . . . . . . . . . . . . . . . . 48 10.1.2. open . . . . . . . . . . . . . . . . . . . . . . . . 49
10.2. Stream Identifiers . . . . . . . . . . . . . . . . . . . 50 10.1.3. half-closed (local) . . . . . . . . . . . . . . . . 50
10.3. Stream Concurrency . . . . . . . . . . . . . . . . . . . 50 10.1.4. half-closed (remote) . . . . . . . . . . . . . . . . 50
10.4. Sending and Receiving Data . . . . . . . . . . . . . . . 51 10.1.5. closed . . . . . . . . . . . . . . . . . . . . . . . 50
10.5. Stream Prioritization . . . . . . . . . . . . . . . . . 51 10.2. Stream Identifiers . . . . . . . . . . . . . . . . . . . 52
11. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 52 10.3. Stream Concurrency . . . . . . . . . . . . . . . . . . . 52
11.1. Edge Cases and Other Considerations . . . . . . . . . . 54 10.4. Sending and Receiving Data . . . . . . . . . . . . . . . 53
11.1.1. Mid-stream RST_STREAM . . . . . . . . . . . . . . . 54 10.5. Stream Prioritization . . . . . . . . . . . . . . . . . 53
11.1.2. Response to a RST_STREAM . . . . . . . . . . . . . . 54 11. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 54
11.1.3. Offset Increment . . . . . . . . . . . . . . . . . . 54 11.1. Edge Cases and Other Considerations . . . . . . . . . . 55
11.1.4. BLOCKED frames . . . . . . . . . . . . . . . . . . . 55 11.1.1. Mid-stream RST_STREAM . . . . . . . . . . . . . . . 56
12. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 55 11.1.2. Response to a RST_STREAM . . . . . . . . . . . . . . 56
12.1. Connection Errors . . . . . . . . . . . . . . . . . . . 55 11.1.3. Data Limit Increments . . . . . . . . . . . . . . . 56
12.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 56 11.1.4. Stream Limit Increment . . . . . . . . . . . . . . . 57
12.3. Error Codes . . . . . . . . . . . . . . . . . . . . . . 56 11.1.5. Blocking on Flow Control . . . . . . . . . . . . . . 57
13. Security and Privacy Considerations . . . . . . . . . . . . . 60 12. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 57
13.1. Spoofed ACK Attack . . . . . . . . . . . . . . . . . . . 60 12.1. Connection Errors . . . . . . . . . . . . . . . . . . . 58
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 61 12.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 58
14.1. QUIC Transport Parameter Registry . . . . . . . . . . . 61 12.3. Error Codes . . . . . . . . . . . . . . . . . . . . . . 58
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 62 13. Security and Privacy Considerations . . . . . . . . . . . . . 62
15.1. Normative References . . . . . . . . . . . . . . . . . . 62 13.1. Spoofed ACK Attack . . . . . . . . . . . . . . . . . . . 62
15.2. Informative References . . . . . . . . . . . . . . . . . 63 13.2. Slowloris Attacks . . . . . . . . . . . . . . . . . . . 63
15.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 64 13.3. Stream Fragmentation and Reassembly Attacks . . . . . . 63
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 64 13.4. Stream Commitment Attack . . . . . . . . . . . . . . . . 64
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 64 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 64
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 64 14.1. QUIC Transport Parameter Registry . . . . . . . . . . . 64
C.1. Since draft-ietf-quic-transport-01: . . . . . . . . . . . 64 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 65
C.2. Since draft-ietf-quic-transport-00: . . . . . . . . . . . 66 15.1. Normative References . . . . . . . . . . . . . . . . . . 65
C.3. Since draft-hamilton-quic-transport-protocol-01: . . . . 67 15.2. Informative References . . . . . . . . . . . . . . . . . 66
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 67 15.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 67
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 67
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 67
C.1. Since draft-ietf-quic-transport-01: . . . . . . . . . . . 68
C.2. Since draft-ietf-quic-transport-00: . . . . . . . . . . . 70
C.3. Since draft-hamilton-quic-transport-protocol-01: . . . . 70
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 70
1. Introduction 1. Introduction
QUIC is a multiplexed and secure transport protocol that runs on top QUIC is a multiplexed and secure transport protocol that runs on top
of UDP. QUIC aims to provide a flexible set of features that allow of UDP. QUIC aims to provide a flexible set of features that allow
it to be a general-purpose transport for multiple applications. it to be a general-purpose transport for multiple applications.
QUIC implements techniques learned from experience with TCP, SCTP and QUIC implements techniques learned from experience with TCP, SCTP and
other transport protocols. Using UDP as the substrate, QUIC seeks to other transport protocols. Using UDP as the substrate, QUIC seeks to
be compatible with legacy clients and middleboxes. QUIC be compatible with legacy clients and middleboxes. QUIC
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ambiguity problem. QUIC acknowledgments also explicitly encode the ambiguity problem. QUIC acknowledgments also explicitly encode the
delay between the receipt of a packet and its acknowledgment being delay between the receipt of a packet and its acknowledgment being
sent, and together with the monotonically-increasing packet numbers, sent, and together with the monotonically-increasing packet numbers,
this allows for precise network roundtrip-time (RTT) calculation. this allows for precise network roundtrip-time (RTT) calculation.
QUIC's ACK frames support up to 256 ACK blocks, so QUIC is more QUIC's ACK frames support up to 256 ACK blocks, so QUIC is more
resilient to reordering than TCP with SACK support, as well as able resilient to reordering than TCP with SACK support, as well as able
to keep more bytes on the wire when there is reordering or loss. to keep more bytes on the wire when there is reordering or loss.
3.4. Stream and Connection Flow Control 3.4. Stream and Connection Flow Control
QUIC implements stream- and connection-level flow control, closely QUIC implements stream- and connection-level flow control. At a high
following HTTP/2's flow control mechanisms. At a high level, a QUIC level, a QUIC receiver advertises the maximum amount of data that it
receiver advertises the absolute byte offset within each stream up to is willing to receive on each stream. As data is sent, received, and
which the receiver is willing to receive data. As data is sent, delivered on a particular stream, the receiver sends MAX_STREAM_DATA
received, and delivered on a particular stream, the receiver sends frames that increase the advertised limit for that stream, allowing
WINDOW_UPDATE frames that increase the advertised offset limit for the peer to send more data on that stream.
that stream, allowing the peer to send more data on that stream. In
addition to this stream-level flow control, QUIC implements In addition to this stream-level flow control, QUIC implements
connection-level flow control to limit the aggregate buffer that a connection-level flow control to limit the aggregate buffer that a
QUIC receiver is willing to allocate to all streams on a connection. QUIC receiver is willing to allocate to all streams on a connection.
Connection-level flow control works in the same way as stream-level Connection-level flow control works in the same way as stream-level
flow control, but the bytes delivered and highest received offset are flow control, but the bytes delivered and the limits are aggregated
all aggregates across all streams. across all streams.
3.5. Authenticated and Encrypted Header and Payload 3.5. Authenticated and Encrypted Header and Payload
TCP headers appear in plaintext on the wire and are not TCP headers appear in plaintext on the wire and are not
authenticated, causing a plethora of injection and header authenticated, causing a plethora of injection and header
manipulation issues for TCP, such as receive-window manipulation and manipulation issues for TCP, such as receive-window manipulation and
sequence-number overwriting. While some of these are mechanisms used sequence-number overwriting. While some of these are mechanisms used
by middleboxes to improve TCP performance, others are active attacks. by middleboxes to improve TCP performance, others are active attacks.
Even "performance-enhancing" middleboxes that routinely interpose on Even "performance-enhancing" middleboxes that routinely interpose on
the transport state machine end up limiting the evolvability of the the transport state machine end up limiting the evolvability of the
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Generic Frame Layout Figure 5: Generic Frame Layout
Frame types are listed in Table 3. Note that the Frame Type byte in Frame types are listed in Table 3. Note that the Frame Type byte in
STREAM and ACK frames is used to carry other frame-specific flags. STREAM and ACK frames is used to carry other frame-specific flags.
For all other frames, the Frame Type byte simply identifies the For all other frames, the Frame Type byte simply identifies the
frame. These frames are explained in more detail as they are frame. These frames are explained in more detail as they are
referenced later in the document. referenced later in the document.
+------------------+------------------+-------------+ +-------------+------------------+--------------+
| Type-field value | Frame type | Definition | | Type Value | Frame Type Name | Definition |
+------------------+------------------+-------------+ +-------------+------------------+--------------+
| 0x00 | PADDING | Section 8.6 | | 0x00 | PADDING | Section 8.9 |
| | | | | | | |
| 0x01 | RST_STREAM | Section 8.5 | | 0x01 | RST_STREAM | Section 8.8 |
| | | | | | | |
| 0x02 | CONNECTION_CLOSE | Section 8.8 | | 0x02 | CONNECTION_CLOSE | Section 8.11 |
| | | | | | | |
| 0x03 | GOAWAY | Section 8.9 | | 0x03 | GOAWAY | Section 8.12 |
| | | | | | | |
| 0x04 | WINDOW_UPDATE | Section 8.3 | | 0x04 | MAX_DATA | Section 8.3 |
| | | | | | | |
| 0x05 | BLOCKED | Section 8.4 | | 0x05 | MAX_STREAM_DATA | Section 8.4 |
| | | | | | | |
| 0x07 | PING | Section 8.7 | | 0x06 | MAX_STREAM_ID | Section 8.5 |
| | | | | | | |
| 0x40 - 0x7f | ACK | Section 8.2 | | 0x07 | PING | Section 8.10 |
| | | | | | | |
| 0x80 - 0xff | STREAM | Section 8.1 | | 0x08 | BLOCKED | Section 8.6 |
+------------------+------------------+-------------+ | | | |
| 0x09 | STREAM_BLOCKED | Section 8.7 |
| | | |
| 0xa0 - 0x7f | ACK | Section 8.2 |
| | | |
| 0xc0 - 0xff | STREAM | Section 8.1 |
+-------------+------------------+--------------+
Table 3: Frame Types Table 3: Frame Types
7. Life of a Connection 7. Life of a Connection
A QUIC connection is a single conversation between two QUIC A QUIC connection is a single conversation between two QUIC
endpoints. QUIC's connection establishment intertwines version endpoints. QUIC's connection establishment intertwines version
negotiation with the cryptographic and transport handshakes to reduce negotiation with the cryptographic and transport handshakes to reduce
connection establishment latency, as described in Section 7.2. Once connection establishment latency, as described in Section 7.2. Once
established, a connection may migrate to a different IP or port at established, a connection may migrate to a different IP or port at
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with the restrictions implied by these parameters; the description of with the restrictions implied by these parameters; the description of
each parameter includes rules for its handling. each parameter includes rules for its handling.
The format of the transport parameters is the TransportParameters The format of the transport parameters is the TransportParameters
struct from Figure 6. This is described using the presentation struct from Figure 6. This is described using the presentation
language from Section 3 of [I-D.ietf-tls-tls13]. language from Section 3 of [I-D.ietf-tls-tls13].
uint32 QuicVersion; uint32 QuicVersion;
enum { enum {
stream_fc_offset(0), initial_max_stream_data(0),
connection_fc_offset(1), initial_max_data(1),
concurrent_streams(2), initial_max_stream_id(2),
idle_timeout(3), idle_timeout(3),
truncate_connection_id(4), truncate_connection_id(4),
(65535) (65535)
} TransportParameterId; } TransportParameterId;
struct { struct {
TransportParameterId parameter; TransportParameterId parameter;
opaque value<0..2^16-1>; opaque value<0..2^16-1>;
} TransportParameter; } TransportParameter;
skipping to change at page 24, line 10 skipping to change at page 24, line 10
properly complete. properly complete.
Definitions for each of the defined transport parameters are included Definitions for each of the defined transport parameters are included
in Section 7.3.1. in Section 7.3.1.
7.3.1. Transport Parameter Definitions 7.3.1. Transport Parameter Definitions
An endpoint MUST include the following parameters in its encoded An endpoint MUST include the following parameters in its encoded
TransportParameters: TransportParameters:
stream_fc_offset (0x0000): The initial stream level flow control initial_max_stream_data (0x0000): The initial stream maximum data
offset parameter is encoded as an unsigned 32-bit integer in units parameter contains the initial value for the maximum data that can
of octets. The sender of this parameter indicates that the flow be sent on any newly created stream. This parameter is encoded as
control offset for all stream data sent toward it is this value. an unsigned 32-bit integer in units of octets. This is equivalent
to an implicit MAX_STREAM_DATA frame (Section 8.4) being sent on
all streams immediately after opening.
connection_fc_offset (0x0001): The connection level flow control initial_max_data (0x0001): The initial maximum data parameter
offset parameter contains the initial connection flow control contains the initial value for the maximum amount of data that can
window encoded as an unsigned 32-bit integer in units of 1024 be sent on the connection. This parameter is encoded as an
octets. That is, the value here is multiplied by 1024 to unsigned 32-bit integer in units of 1024 octets. That is, the
determine the actual flow control offset. The sender of this value here is multiplied by 1024 to determine the actual maximum
parameter sets the byte offset for connection level flow control value. This is equivalent to sending a MAX_DATA (Section 8.3) for
to this value. This is equivalent to sending a WINDOW_UPDATE the connection immediately after completing the handshake.
(Section 8.3) for the connection immediately after completing the
handshake.
concurrent_streams (0x0002): The maximum number of concurrent initial_max_stream_id (0x0002): The initial maximum stream ID
streams parameter is encoded as an unsigned 32-bit integer. parameter contains the initial maximum stream number the peer may
initiate, encoded as an unsigned 32-bit integer. This is
equivalent to sending a MAX_STREAM_ID (Section 8.5) immediately
after completing the handshake. This value MUST NOT be set to 0,
an endpoint MUST generate a QUIC_INVALID_NEGOTIATED_VALUE error if
it receives a value of zero for this parameter.
idle_timeout (0x0003): The idle timeout is a value in seconds that idle_timeout (0x0003): The idle timeout is a value in seconds that
is encoded as an unsigned 16-bit integer. The maximum value is is encoded as an unsigned 16-bit integer. The maximum value is
600 seconds (10 minutes). 600 seconds (10 minutes).
An endpoint MAY use the following transport parameters: An endpoint MAY use the following transport parameters:
truncate_connection_id (0x0004): The truncated connection identifier truncate_connection_id (0x0004): The truncated connection identifier
parameter indicates that packets sent to the peer can omit the parameter indicates that packets sent to the peer can omit the
connection ID. This can be used by an endpoint where the 5-tuple connection ID. This can be used by an endpoint where the 5-tuple
is sufficient to identify a connection. This parameter is zero is sufficient to identify a connection. This parameter is zero
length. Omitting the parameter indicates that the endpoint relies length. Omitting the parameter indicates that the endpoint relies
on the connection ID being present in every packet. on the connection ID being present in every packet.
7.3.2. Values of Transport Parameters for 0-RTT 7.3.2. Values of Transport Parameters for 0-RTT
Transport parameters from the server SHOULD be remembered by the Transport parameters from the server SHOULD be remembered by the
client for use with 0-RTT data. A client that doesn't remember client for use with 0-RTT data. A client that doesn't remember
values from a previous connection can instead assume the following values from a previous connection can instead assume the following
values: stream_fc_offset (65535), connection_fc_offset (65535), values: initial_max_stream_data (65535), initial_max_data (65535),
concurrent_streams (10), idle_timeout (600), truncate_connection_id initial_max_stream_id (20), idle_timeout (600),
(absent). truncate_connection_id (absent).
If assumed values change as a result of completing the handshake, the If assumed values change as a result of completing the handshake, the
client is expected to respect the new values. This introduces some client is expected to respect the new values. This introduces some
potential problems, particularly with respect to transport parameters potential problems, particularly with respect to transport parameters
that establish limits: that establish limits:
o A client might exceed a newly declared connection or stream flow o A client might exceed a newly declared initial value for the
control limit with 0-RTT data. If this occurs, the client ceases connection or stream maximum data limit with 0-RTT data. If this
transmission as though the flow control limit was reached. Once occurs, the client ceases transmission as though these limits were
WINDOW_UPDATE frames indicating an increase to the affected flow reached. The server SHOULD NOT terminate a connection if the
control offsets is received, the client can recommence sending. client has exceeded these limits. Once MAX_DATA or
MAX_STREAM_DATA frames indicating an increase to the affected
maximum data limit is received, the client can recommence sending.
o Similarly, a client might exceed the concurrent stream limit o Similarly, a client might exceed the initial stream limit declared
declared by the server. A client MUST reset any streams that by the server. A client MUST reset any streams that exceed this
exceed this limit. A server SHOULD reset any streams it cannot limit. A server SHOULD reset any streams it cannot handle with a
handle with a code that allows the client to retry any application code that allows the client to retry any application action bound
action bound to those streams. to those streams.
A server MAY close a connection if remembered or assumed 0-RTT A server MAY close a connection if remembered or assumed 0-RTT
transport parameters cannot be supported, using an error code that is transport parameters cannot be supported, using an error code that is
appropriate to the specific condition. For example, a appropriate to the specific condition. For example, a
QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA might be used to indicate QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA might be used to indicate
that exceeding flow control limits caused the error. A client that that exceeding flow control limits caused the error. A client that
has a connection closed due to an error condition SHOULD NOT attempt has a connection closed due to an error condition SHOULD NOT attempt
0-RTT when attempting to create a new connection. 0-RTT when attempting to create a new connection.
7.3.3. New Transport Parameters 7.3.3. New Transport Parameters
skipping to change at page 31, line 16 skipping to change at page 31, line 20
As described in Section 6, Regular packets contain one or more As described in Section 6, Regular packets contain one or more
frames. We now describe the various QUIC frame types that can be frames. We now describe the various QUIC frame types that can be
present in a Regular packet. The use of these frames and various present in a Regular packet. The use of these frames and various
frame header bits are described in subsequent sections. frame header bits are described in subsequent sections.
8.1. STREAM Frame 8.1. STREAM Frame
STREAM frames implicitly create a stream and carry stream data. The STREAM frames implicitly create a stream and carry stream data. The
type byte for a STREAM frame contains embedded flags, and is type byte for a STREAM frame contains embedded flags, and is
formatted as "1FDOOOSS". These bits are parsed as follows: formatted as "11FDOOSS". These bits are parsed as follows:
o The leftmost bit must be set to 1, indicating that this is a o The first two bits must be set to 11, indicating that this is a
STREAM frame. STREAM frame.
o "F" is the FIN bit, which is used for stream termination. o "F" is the FIN bit, which is used for stream termination.
o The "D" bit indicates whether a Data Length field is present in o The "D" bit indicates whether a Data Length field is present in
the STREAM header. When set to 0, this field indicates that the the STREAM header. When set to 0, this field indicates that the
Stream Data field extends to the end of the packet. When set to Stream Data field extends to the end of the packet. When set to
1, this field indicates that Data Length field contains the length 1, this field indicates that Data Length field contains the length
(in bytes) of the Stream Data field. The option to omit the (in bytes) of the Stream Data field. The option to omit the
length should only be used when the packet is a "full-sized" length should only be used when the packet is a "full-sized"
packet, to avoid the risk of corruption via padding. packet, to avoid the risk of corruption via padding.
o The "OOO" bits encode the length of the Offset header field as 0, o The "OO" bits encode the length of the Offset header field as 0,
16, 24, 32, 40, 48, 56, or 64 bits long. 16, 32, or 64 bits long.
o The "SS" bits encode the length of the Stream ID header field as o The "SS" bits encode the length of the Stream ID header field as
8, 16, 24, or 32 bits. (DISCUSS: Consider making this 8, 16, 32, 8, 16, 24, or 32 bits.
64.)
A STREAM frame is shown below. A STREAM frame is shown below.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [Data Length (16)] | | [Data Length (16)] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (8/16/24/32) ... | Stream ID (8/16/24/32) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset (0/16/24/32/40/48/56/64) ... | Offset (0/16/32/64) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Data (*) ... | Stream Data (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: STREAM Frame Format Figure 7: STREAM Frame Format
The STREAM frame contains the following fields: The STREAM frame contains the following fields:
Data Length: An optional 16-bit unsigned number specifying the Data Length: An optional 16-bit unsigned number specifying the
length of the Stream Data field in this STREAM frame. This field length of the Stream Data field in this STREAM frame. This field
is present when the "D" bit is set to 1. is present when the "D" bit is set to 1.
Stream ID: A variable-sized unsigned ID unique to this stream. Stream ID: A variable-sized unsigned ID unique to this stream.
Offset: A variable-sized unsigned number specifying the byte offset Offset: A variable-sized unsigned number specifying the byte offset
in the stream for the data in this STREAM frame. The first byte in the stream for the data in this STREAM frame. When the offset
in the stream has an offset of 0. The largest offset delivered on length is 0, the offset is 0. The first byte in the stream has an
a stream - the sum of the re-constructed offset and data length - offset of 0. The largest offset delivered on a stream - the sum
MUST be less than 2^64. of the re-constructed offset and data length - MUST be less than
2^64.
Stream Data: The bytes from the designated stream to be delivered. Stream Data: The bytes from the designated stream to be delivered.
A STREAM frame MUST have either non-zero data length or the FIN bit A STREAM frame MUST have either non-zero data length or the FIN bit
set. set.
Stream multiplexing is achieved by interleaving STREAM frames from Stream multiplexing is achieved by interleaving STREAM frames from
multiple streams into one or more QUIC packets. A single QUIC packet multiple streams into one or more QUIC packets. A single QUIC packet
MAY bundle STREAM frames from multiple streams. MAY bundle STREAM frames from multiple streams.
skipping to change at page 33, line 9 skipping to change at page 33, line 24
acknowledged by its peer. Once an ACK frame has been acknowledged, acknowledged by its peer. Once an ACK frame has been acknowledged,
the packets it acknowledges SHOULD not be acknowledged again. To the packets it acknowledges SHOULD not be acknowledged again. To
handle cases where the receiver is only sending ACK frames, and hence handle cases where the receiver is only sending ACK frames, and hence
will not receive acknowledgments for its packets, it MAY send a PING will not receive acknowledgments for its packets, it MAY send a PING
frame at most once per RTT to explicitly request acknowledgment. frame at most once per RTT to explicitly request acknowledgment.
To limit receiver state or the size of ACK frames, a receiver MAY To limit receiver state or the size of ACK frames, a receiver MAY
limit the number of ACK blocks it sends. A receiver can do this even limit the number of ACK blocks it sends. A receiver can do this even
without receiving acknowledgment of its ACK frames, with the without receiving acknowledgment of its ACK frames, with the
knowledge this could cause the sender to unnecessarily retransmit knowledge this could cause the sender to unnecessarily retransmit
some data. some data. When this is necessary, the receiver SHOULD acknowledge
newly received packets and stop acknowledging packets received in the
past.
Unlike TCP SACKs, QUIC ACK blocks are cumulative and therefore Unlike TCP SACKs, QUIC ACK blocks are cumulative and therefore
irrevocable. Once a packet has been acknowledged, even if it does irrevocable. Once a packet has been acknowledged, even if it does
not appear in a future ACK frame, it is assumed to be acknowledged. not appear in a future ACK frame, it is assumed to be acknowledged.
QUIC ACK frames contain a timestamp section with up to 255 QUIC ACK frames contain a timestamp section with up to 255
timestamps. Timestamps enable better congestion control, but are not timestamps. Timestamps enable better congestion control, but are not
required for correct loss recovery, and old timestamps are less required for correct loss recovery, and old timestamps are less
valuable, so it is not guaranteed every timestamp will be received by valuable, so it is not guaranteed every timestamp will be received by
the sender. A receiver SHOULD send a timestamp exactly once for each the sender. A receiver SHOULD send a timestamp exactly once for each
received packet containing retransmittable frames. A receiver MAY received packet containing retransmittable frames. A receiver MAY
send timestamps for non-retransmittable packets. send timestamps for non-retransmittable packets. A receiver MUST not
send timestamps in unprotected packets.
A sender MAY intentionally skip packet numbers to introduce entropy A sender MAY intentionally skip packet numbers to introduce entropy
into the connection, to avoid opportunistic acknowledgement attacks. into the connection, to avoid opportunistic acknowledgement attacks.
The sender MUST close the connection if an unsent packet number is The sender MUST close the connection if an unsent packet number is
acknowledged. The format of the ACK frame is efficient at expressing acknowledged. The format of the ACK frame is efficient at expressing
blocks of missing packets; skipping packet numbers between 1 and 255 blocks of missing packets; skipping packet numbers between 1 and 255
effectively provides up to 8 bits of efficient entropy on demand, effectively provides up to 8 bits of efficient entropy on demand,
which should be adequate protection against most opportunistic which should be adequate protection against most opportunistic
acknowledgement attacks. acknowledgement attacks.
The type byte for a ACK frame contains embedded flags, and is The type byte for a ACK frame contains embedded flags, and is
formatted as "01NULLMM". These bits are parsed as follows: formatted as "101NLLMM". These bits are parsed as follows:
o The first two bits must be set to 01 indicating that this is an o The first three bits must be set to 101 indicating that this is an
ACK frame. ACK frame.
o The "N" bit indicates whether the frame has more than 1 range of o The "N" bit indicates whether the frame has more than 1 range of
acknowledged packets (i.e., whether the ACK Block Section contains acknowledged packets (i.e., whether the ACK Block Section contains
a Num Blocks field). a Num Blocks field).
o The "U" bit is unused and MUST be set to zero.
o The two "LL" bits encode the length of the Largest Acknowledged o The two "LL" bits encode the length of the Largest Acknowledged
field as 1, 2, 4, or 6 bytes long. field as 1, 2, 4, or 6 bytes long.
o The two "MM" bits encode the length of the ACK Block Length fields o The two "MM" bits encode the length of the ACK Block Length fields
as 1, 2, 4, or 6 bytes long. as 1, 2, 4, or 6 bytes long.
An ACK frame is shown below. An ACK frame is shown below.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 38, line 16 skipping to change at page 38, line 20
protection keys. protection keys.
For instance, a server acknowledges a TLS ClientHello in the packet For instance, a server acknowledges a TLS ClientHello in the packet
that carries the TLS ServerHello; similarly, a client can acknowledge that carries the TLS ServerHello; similarly, a client can acknowledge
a TLS HelloRetryRequest in the packet containing a second TLS a TLS HelloRetryRequest in the packet containing a second TLS
ClientHello. The complete set of server handshake messages (TLS ClientHello. The complete set of server handshake messages (TLS
ServerHello through to Finished) might be acknowledged by a client in ServerHello through to Finished) might be acknowledged by a client in
protected packets, because it is certain that the server is able to protected packets, because it is certain that the server is able to
decipher the packet. decipher the packet.
8.3. WINDOW_UPDATE Frame 8.3. MAX_DATA Frame
The WINDOW_UPDATE frame (type=0x04) informs the peer of an increase The MAX_DATA frame (type=0x04) is used in flow control to informs the
in an endpoint's flow control receive window for either a single peer of the maximum amount of data that can be sent on the connection
stream, or the entire connection as a whole. as a whole.
The frame is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Maximum Data (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the MAX_DATA frame are as follows:
Maximum Data: A 64-bit unsigned integer indicating the maximum
amount of data that can be sent on the entire connection, in units
of 1024 octets. That is, the updated connection-level data limit
is determined by multiplying the encoded value by 1024.
The sum of the largest received offsets on all streams - including
closed streams - MUST NOT exceed the value advertised by a receiver.
An endpoint MUST terminate a connection with a
QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA error if it receives more
data than the maximum data value that it has sent, unless this is a
result of a change in the initial limits (see Section 7.3.2).
8.4. MAX_STREAM_DATA Frame
The MAX_STREAM_DATA frame (type=0x05) is used in flow control to
inform a peer of the maximum amount of data that can be sent on a
stream.
The frame is as follows: The frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (32) | | Stream ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Flow Control Offset (64) + + Maximum Stream Data (64) +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the WINDOW_UPDATE frame are as follows: The fields in the MAX_STREAM_DATA frame are as follows:
Stream ID: ID of the stream whose flow control windows is being Stream ID: The stream ID of the stream that is affected.
updated, or 0 to specify the connection-level flow control window.
Flow Control Offset: A 64-bit unsigned integer indicating the flow Maximum Stream Data: A 64-bit unsigned integer indicating the
control offset for the given stream (for a stream ID other than 0) maximum amount of data that can be sent on the identified stream,
or the entire connection. in units of octets.
The flow control offset is expressed in units of octets for When counting data toward this limit, an endpoint accounts for the
individual streams (for stream identifiers other than 0). largest received offset of data that is sent or received on the
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
that stream. Receiving STREAM frames might not increase the largest
received offset.
The connection-level flow control offset is expressed in units of The data sent on a stream MUST NOT exceed the largest maximum stream
1024 octets (for a stream identifier of 0). That is, the connection- data value advertised by the receiver. An endpoint MUST terminate a
level flow control offset is determined by multiplying the encoded connection with a QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA error if
value by 1024. it receives more data than the largest maximum stream data that it
has sent for the affected stream, unless this is a result of a change
in the initial limits (see Section 7.3.2).
An endpoint accounts for the maximum offset of data that is sent or 8.5. MAX_STREAM_ID Frame
received on a stream. Loss or reordering can mean that the maximum
offset is greater than the total size of data received on a stream.
Similarly, receiving STREAM frames might not increase the maximum
offset on a stream. A STREAM frame with a FIN bit set or RST_STREAM
causes the final offset for a stream to be fixed.
The maximum data offset on a stream MUST NOT exceed the stream flow The MAX_STREAM_ID frame (type=0x06) informs the peer of the maximum
control offset advertised by the receiver. The sum of the maximum stream ID that they are permitted to open.
data offsets of all streams (including closed streams) MUST NOT
exceed the connection flow control offset advertised by the receiver. The frame is as follows:
An endpoint MUST terminate a connection with a
QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA error if it receives more 0 1 2 3
data than the largest flow control offset that it has sent, unless 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
this is a result of a change in the initial offsets (see +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Stream ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the MAX_STREAM_ID frame are as follows:
Maximum Stream ID: ID of the maximum peer-initiated stream ID for
the connection.
Loss or reordering can mean that a MAX_STREAM_ID frame can be
received which states a lower stream limit than the client has
previously received. MAX_STREAM_ID frames which do not increase the
maximum stream ID MUST be ignored.
A peer MUST NOT initiate a stream with a higher stream ID than the
greatest maximum stream ID it has received. An endpoint MUST
terminate a connection with a QUIC_TOO_MANY_OPEN_STREAMS error if a
peer initiates a stream with a higher stream ID than it has sent,
unless this is a result of a change in the initial limits (see
Section 7.3.2). Section 7.3.2).
8.4. BLOCKED Frame 8.6. BLOCKED Frame
A sender sends a BLOCKED frame (type=0x05) when it is ready to send A sender sends a BLOCKED frame (type=0x08) when it wishes to send
data (and has data to send), but is currently flow control blocked. data, but is unable to due to connection-level flow control (see
BLOCKED frames are purely informational frames, but extremely useful Section 11.1.5). BLOCKED frames can be used as input to tuning of
for debugging purposes. A receiver of a BLOCKED frame should simply flow control algorithms (see Section 11.1.3).
discard it (after possibly printing a helpful log message). The
frame is as follows: The BLOCKED frame does not contain a payload.
8.7. STREAM_BLOCKED Frame
A sender sends a STREAM_BLOCKED frame (type=0x09) when it wishes to
send data, but is unable to due to stream-level flow control. This
frame is analogous to BLOCKED (Section 8.6).
The STREAM_BLOCKED frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (32) | | Stream ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BLOCKED frame contains a single field: The STREAM_BLOCKED frame contains a single field:
Stream ID: A 32-bit unsigned number indicating the stream which is Stream ID: A 32-bit unsigned number indicating the stream which is
flow control blocked. A non-zero Stream ID field specifies the flow control blocked.
stream that is flow control blocked. When zero, the Stream ID
field indicates that the connection is flow control blocked.
8.5. RST_STREAM Frame 8.8. RST_STREAM Frame
An endpoint may use a RST_STREAM frame (type=0x01) to abruptly An endpoint may use a RST_STREAM frame (type=0x01) to abruptly
terminate a stream. The frame is as follows: terminate a stream. The frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Code (32) | | Error Code (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (32) | | Stream ID (32) |
skipping to change at page 40, line 28 skipping to change at page 41, line 36
Error code: A 32-bit error code which indicates why the stream is Error code: A 32-bit error code which indicates why the stream is
being closed. being closed.
Stream ID: The 32-bit Stream ID of the stream being terminated. Stream ID: The 32-bit Stream ID of the stream being terminated.
Final offset: A 64-bit unsigned integer indicating the absolute byte Final offset: A 64-bit unsigned integer indicating the absolute byte
offset of the end of data written on this stream by the RST_STREAM offset of the end of data written on this stream by the RST_STREAM
sender. sender.
8.6. PADDING Frame 8.9. PADDING Frame
The PADDING frame (type=0x00) has no semantic value. PADDING frames The 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 client packet to the minimum required size, or to
provide protection against traffic analysis for protected packets. provide protection against traffic analysis for protected packets.
A PADDING frame has no content. That is, a PADDING frame consists of A PADDING frame has no content. That is, a PADDING frame consists of
the single octet that identifies the frame as a PADDING frame. the single octet that identifies the frame as a PADDING frame.
8.7. PING frame 8.10. PING frame
Endpoints can use PING frames (type=0x07) to verify that their peers Endpoints can use PING frames (type=0x07) to verify that their peers
are still alive or to check reachability to the peer. The PING frame are still alive or to check reachability to the peer. The PING frame
contains no additional fields. The receiver of a PING frame simply contains no additional fields. The receiver of a PING frame simply
needs to acknowledge the packet containing this frame. The PING needs to acknowledge the packet containing this frame. The PING
frame SHOULD be used to keep a connection alive when a stream is frame SHOULD be used to keep a connection alive when a stream is
open. The default is to send a PING frame after 15 seconds of open. The default is to send a PING frame after 15 seconds of
quiescence. A PING frame has no additional fields. quiescence. A PING frame has no additional fields.
8.8. CONNECTION_CLOSE frame 8.11. CONNECTION_CLOSE frame
An endpoint sends a CONNECTION_CLOSE frame (type=0x02) to notify its An endpoint sends a CONNECTION_CLOSE frame (type=0x02) to notify its
peer that the connection is being closed. If there are open streams peer that the connection is being closed. If there are open streams
that haven't been explicitly closed, they are implicitly closed when that haven't been explicitly closed, they are implicitly closed when
the connection is closed. (Ideally, a GOAWAY frame would be sent the connection is closed. (Ideally, a GOAWAY frame would be sent
with enough time that all streams are torn down.) The frame is as with enough time that all streams are torn down.) The frame is as
follows: follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 41, line 22 skipping to change at page 42, line 30
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason Phrase Length (16) | [Reason Phrase (*)] ... | Reason Phrase Length (16) | [Reason Phrase (*)] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields of a CONNECTION_CLOSE frame are as follows: The fields of a CONNECTION_CLOSE frame are as follows:
Error Code: A 32-bit error code which indicates the reason for Error Code: A 32-bit error code which indicates the reason for
closing this connection. closing this connection.
Reason Phrase Length: A 16-bit unsigned number specifying the length Reason Phrase Length: A 16-bit unsigned number specifying the length
of the reason phrase. This may be zero if the sender chooses to of the reason phrase. Note that a CONNECTION_CLOSE frame cannot
not give details beyond the Error Code. be split between packets, so in practice any limits on packet size
will also limit the space available for a reason phrase.
Reason Phrase: An optional human-readable explanation for why the Reason Phrase: A human-readable explanation for why the connection
connection was closed. was closed. This can be zero length if the sender chooses to not
give details beyond the Error Code. This SHOULD be a UTF-8
encoded string [RFC3629].
8.9. GOAWAY Frame 8.12. GOAWAY Frame
An endpoint uses a GOAWAY frame (type=0x03) to initiate a graceful An endpoint uses a GOAWAY frame (type=0x03) to initiate a graceful
shutdown of a connection. The endpoints will continue to use any shutdown of a connection. The endpoints will continue to use any
active streams, but the sender of the GOAWAY will not initiate or active streams, but the sender of the GOAWAY will not initiate or
accept any additional streams beyond those indicated. The GOAWAY accept any additional streams beyond those indicated. The GOAWAY
frame is as follows: frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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To avoid creating an indefinite feedback loop, an endpoint MUST NOT To avoid creating an indefinite feedback loop, an endpoint MUST NOT
generate an ACK frame in response to a packet containing only ACK or generate an ACK frame in response to a packet containing only ACK or
PADDING frames. PADDING frames.
Strategies and implications of the frequency of generating Strategies and implications of the frequency of generating
acknowledgments are discussed in more detail in [QUIC-RECOVERY]. acknowledgments are discussed in more detail in [QUIC-RECOVERY].
9.1. Special Considerations for PMTU Discovery 9.1. Special Considerations for PMTU Discovery
Traditional ICMP-based path MTU discovery in IPv4 ([RFC1191] is Traditional ICMP-based path MTU discovery in IPv4 [RFC1191] is
potentially vulnerable to off-path attacks that successfully guess potentially vulnerable to off-path attacks that successfully guess
the IP/port 4-tuple and reduce the MTU to a bandwidth-inefficient the IP/port 4-tuple and reduce the MTU to a bandwidth-inefficient
value. TCP connections mitigate this risk by using the (at minimum) value. TCP connections mitigate this risk by using the (at minimum)
8 bytes of transport header echoed in the ICMP message to validate 8 bytes of transport header echoed in the ICMP message to validate
the TCP sequence number as valid for the current connection. the TCP sequence number as valid for the current connection.
However, as QUIC operates over UDP, in IPv4 the echoed information However, as QUIC operates over UDP, in IPv4 the echoed information
could consist only of the IP and UDP headers, which usually has could consist only of the IP and UDP headers, which usually has
insufficient entropy to mitigate off-path attacks. insufficient entropy to mitigate off-path attacks.
As a result, endpoints that implement PMTUD in IPv4 SHOULD take steps As a result, endpoints that implement PMTUD in IPv4 SHOULD take steps
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Data that is received on a stream is delivered in order within that Data that is received on a stream is delivered in order within that
stream, but there is no particular delivery order across streams. stream, but there is no particular delivery order across streams.
Transmit ordering among streams is left to the implementation. Transmit ordering among streams is left to the implementation.
The creation and destruction of streams are expected to have minimal The creation and destruction of streams are expected to have minimal
bandwidth and computational cost. A single STREAM frame may create, bandwidth and computational cost. A single STREAM frame may create,
carry data for, and terminate a stream, or a stream may last the carry data for, and terminate a stream, or a stream may last the
entire duration of a connection. entire duration of a connection.
Streams are individually flow controlled, allowing an endpoint to Streams are individually flow controlled, allowing an endpoint to
limit memory commitment and to apply back pressure. limit memory commitment and to apply back pressure. The creation of
streams is also flow controlled, with each peer declaring the maximum
stream ID it is willing to accept at a given time.
An alternative view of QUIC streams is as an elastic "message" An alternative view of QUIC streams is as an elastic "message"
abstraction, similar to the way ephemeral streams are used in SST abstraction, similar to the way ephemeral streams are used in SST
[SST], which may be a more appealing description for some [SST], which may be a more appealing description for some
applications. applications.
10.1. Life of a Stream 10.1. Life of a Stream
The semantics of QUIC streams is based on HTTP/2 streams, and the The semantics of QUIC streams is based on HTTP/2 streams, and the
lifecycle of a QUIC stream therefore closely follows that of an lifecycle of a QUIC stream therefore closely follows that of an
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flag causes the stream state to become "half-closed (remote)" once flag causes the stream state to become "half-closed (remote)" once
all preceding data has arrived. The receiving endpoint MUST NOT all preceding data has arrived. The receiving endpoint MUST NOT
consider the stream state to have changed until all data has arrived. consider the stream state to have changed until all data has arrived.
Either endpoint can send a RST_STREAM frame from this state, causing Either endpoint can send a RST_STREAM frame from this state, causing
it to transition immediately to "closed". it to transition immediately to "closed".
10.1.3. half-closed (local) 10.1.3. half-closed (local)
A stream that is in the "half-closed (local)" state MUST NOT be used A stream that is in the "half-closed (local)" state MUST NOT be used
for sending STREAM frames; WINDOW_UPDATE and RST_STREAM MAY be sent for sending STREAM frames; MAX_STREAM_DATA and RST_STREAM MAY be sent
in this state. in this state.
A stream transitions from this state to "closed" when a STREAM frame A stream transitions from this state to "closed" when a STREAM frame
that contains a FIN flag is received and all prior data has arrived, that contains a FIN flag is received and all prior data has arrived,
or when either peer sends a RST_STREAM frame. or when either peer sends a RST_STREAM frame.
An endpoint that closes a stream MUST NOT send data beyond the final An endpoint that closes a stream MUST NOT send data beyond the final
offset that it has chosen, see Section 10.1.5 for details. offset that it has chosen, see Section 10.1.5 for details.
An endpoint can receive any type of frame in this state. Providing An endpoint can receive any type of frame in this state. Providing
flow-control credit using WINDOW_UPDATE frames is necessary to flow-control credit using MAX_STREAM_DATA frames is necessary to
continue receiving flow-controlled frames. In this state, a receiver continue receiving flow-controlled frames. In this state, a receiver
MAY ignore WINDOW_UPDATE frames for this stream, which might arrive MAY ignore MAX_STREAM_DATA frames for this stream, which might arrive
for a short period after a frame bearing the FIN flag is sent. for a short period after a frame bearing the FIN flag is sent.
10.1.4. half-closed (remote) 10.1.4. half-closed (remote)
A stream that is "half-closed (remote)" is no longer being used by A stream that is "half-closed (remote)" is no longer being used by
the peer to send any data. In this state, a sender is no longer the peer to send any data. In this state, a sender is no longer
obligated to maintain a receiver stream-level flow-control window. obligated to maintain a receiver stream-level flow-control window.
A stream that is in the "half-closed (remote)" state will have a A stream that is in the "half-closed (remote)" state will have a
final offset for received data, see Section 10.1.5 for details. final offset for received data, see Section 10.1.5 for details.
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In the absence of more specific guidance elsewhere in this document, In the absence of more specific guidance elsewhere in this document,
implementations SHOULD treat the receipt of a frame that is not implementations SHOULD treat the receipt of a frame that is not
expressly permitted in the description of a state as a connection expressly permitted in the description of a state as a connection
error (Section 12). Frames of unknown types are ignored. error (Section 12). Frames of unknown types are ignored.
(TODO: QUIC_STREAM_NO_ERROR is a special case. Write it up.) (TODO: QUIC_STREAM_NO_ERROR is a special case. Write it up.)
10.2. Stream Identifiers 10.2. Stream Identifiers
Streams are identified by an unsigned 32-bit integer, referred to as Streams are identified by an unsigned 32-bit integer, referred to as
the StreamID. To avoid StreamID collision, clients MUST initiate the Stream ID. To avoid Stream ID collision, clients MUST initiate
streams usinge odd-numbered StreamIDs; streams initiated by the streams using odd-numbered Stream IDs; streams initiated by the
server MUST use even-numbered StreamIDs. server MUST use even-numbered Stream IDs.
A StreamID of zero (0x0) is reserved and used for connection-level A Stream ID of zero (0x0) is reserved and used for connection-level
flow control frames (Section 11); the StreamID of zero cannot be used flow control frames (Section 11); the Stream ID of zero cannot be
to establish a new stream. used to establish a new stream.
StreamID 1 (0x1) is reserved for the cryptographic handshake. Stream ID 1 (0x1) is reserved for the cryptographic handshake.
StreamID 1 MUST NOT be used for application data, and MUST be the Stream ID 1 MUST NOT be used for application data, and MUST be the
first client-initiated stream. first client-initiated stream.
A QUIC endpoint cannot reuse a StreamID on a given connection. A QUIC endpoint cannot reuse a Stream ID on a given connection.
Streams MUST be created in sequential order. Open streams can be Streams MUST be created in sequential order. Open streams can be
used in any order. Streams that are used out of order result in used in any order. Streams that are used out of order result in
lower-numbered streams in the same direction being counted as open. lower-numbered streams in the same direction being counted as open.
All streams, including stream 1, count toward this limit. Thus, a
concurrent stream limit of 0 will cause a connection to be unusable.
Application protocols that use QUIC might require a certain minimum
number of streams to function correctly. If a peer advertises an
concurrent stream limit (concurrent_streams) that is too small for
the selected application protocol to function, an endpoint MUST
terminate the connection with an error of type
QUIC_TOO_MANY_OPEN_STREAMS (Section 12).
10.3. Stream Concurrency 10.3. Stream Concurrency
An endpoint limits the number of concurrently active incoming streams An endpoint limits the number of concurrently active incoming streams
by setting the concurrent stream limit (see Section 7.3.1) in the by adjusting the maximum stream ID. An initial value is set in the
transport parameters. The maximum concurrent streams setting is transport parameters (see Section 7.3.1) and is subsequently
specific to each endpoint and applies only to the peer that receives increased by MAX_STREAM_ID frames (see Section 8.5).
the setting. That is, clients specify the maximum number of
concurrent streams the server can initiate, and servers specify the
maximum number of concurrent streams the client can initiate.
Streams that are in the "open" state or in either of the "half-
closed" states count toward the maximum number of streams that an
endpoint is permitted to open. Streams in any of these three states
count toward the limit advertised in the concurrent stream limit.
A recently closed stream MUST also be considered to count toward this The maximum stream ID is specific to each endpoint and applies only
limit until packets containing all frames required to close the to the peer that receives the setting. That is, clients specify the
stream have been acknowledged. For a stream which closed cleanly, maximum stream ID the server can initiate, and servers specify the
this means all STREAM frames have been acknowledged; for a stream maximum stream ID the client can initiate. Each endpoint may respond
which closed abruptly, this means the RST_STREAM frame has been on streams initiated by the other peer, regardless of whether it is
acknowledged. permitted to initiated new streams.
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 STREAM frame that causes its advertised concurrent that receives a STREAM frame with an ID greater than the limit it has
stream limit to be exceeded MUST treat this as a stream error of type sent MUST treat this as a stream error of type
QUIC_TOO_MANY_OPEN_STREAMS (Section 12). QUIC_TOO_MANY_OPEN_STREAMS (Section 12), unless this is a result of a
change in the initial offsets (see Section 7.3.2).
A receiver MUST NOT renege on an advertisement; that is, once a
receiver advertises a stream ID via a LIMIT_UPDATE frame, it MUST NOT
subsequently advertise a smaller maximum ID. A sender may receive
LIMIT_UPDATE frames out of order; a sender MUST therefore ignore any
LIMIT_UPDATE that does not increase the maximum.
10.4. Sending and Receiving Data 10.4. Sending and Receiving Data
Once a stream is created, endpoints may use the stream to send and Once a stream is created, endpoints may use the stream to send and
receive data. Each endpoint may send a series of STREAM frames receive data. Each endpoint may send a series of STREAM frames
encapsulating data on a stream until the stream is terminated in that encapsulating data on a stream until the stream is terminated in that
direction. Streams are an ordered byte-stream abstraction, and they direction. Streams are an ordered byte-stream abstraction, and they
have no other structure within them. STREAM frame boundaries are not have no other structure within them. STREAM frame boundaries are not
expected to be preserved in retransmissions from the sender or during expected to be preserved in retransmissions from the sender or during
delivery to the application at the receiver. delivery to the application at the receiver.
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control is described in the companion document [QUIC-RECOVERY]. control is described in the companion document [QUIC-RECOVERY].
10.5. Stream Prioritization 10.5. Stream Prioritization
Stream multiplexing has a significant effect on application Stream multiplexing has a significant effect on application
performance if resources allocated to streams are correctly performance if resources allocated to streams are correctly
prioritized. Experience with other multiplexed protocols, such as prioritized. Experience with other multiplexed protocols, such as
HTTP/2 [RFC7540], shows that effective prioritization strategies have HTTP/2 [RFC7540], shows that effective prioritization strategies have
a significant positive impact on performance. a significant positive impact on performance.
QUIC does not provide frames for exchanging priotization information. QUIC does not provide frames for exchanging prioritization
Instead it relies on receiving priority information from the information. Instead it relies on receiving priority information
application that uses QUIC. Protocols that use QUIC are able to from the application that uses QUIC. Protocols that use QUIC are
define any prioritization scheme that suits their application able to define any prioritization scheme that suits their application
semantics. A protocol might define explicit messages for signaling semantics. A protocol might define explicit messages for signaling
priority, such as those defined in HTTP/2; it could define rules that priority, such as those defined in HTTP/2; it could define rules that
allow an endpoint to determine priority based on context; or it could allow an endpoint to determine priority based on context; or it could
leave the determination to the application. leave the determination to 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. When deciding which indicate the relative priority of streams. When deciding which
streams to dedicate resources to, QUIC SHOULD use the information streams to dedicate resources to, QUIC SHOULD use the information
provided by the application. Failure to account for priority of provided by the application. Failure to account for priority of
streams can result in suboptimal performance. streams can result in suboptimal performance.
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QUIC employs a credit-based flow-control scheme similar to HTTP/2's QUIC employs a credit-based flow-control scheme similar to HTTP/2's
flow control [RFC7540]. A receiver advertises the number of octets flow control [RFC7540]. A receiver advertises the number of octets
it is prepared to receive on a given stream and for the entire it is prepared to receive on a given stream and for the entire
connection. This leads to two levels of flow control in QUIC: (i) connection. This leads to two levels of flow control in QUIC: (i)
Connection flow control, which prevents senders from exceeding a Connection flow control, which prevents senders from exceeding a
receiver's buffer capacity for the connection, and (ii) Stream flow receiver's buffer capacity for the connection, and (ii) Stream flow
control, which prevents a single stream from consuming the entire control, which prevents a single stream from consuming the entire
receive buffer for a connection. receive buffer for a connection.
A receiver sends WINDOW_UPDATE frames to the sender to advertise A receiver sends MAX_DATA or MAX_STREAM_DATA frames to the sender to
additional credit by sending the absolute byte offset in the stream advertise additional credit by sending the absolute byte offset in
or in the connection which it is willing to receive. the connection or stream which it is willing to receive.
The initial flow control credit is 65536 bytes for both the stream
and connection flow controllers.
A receiver MAY advertise a larger offset at any point in the A receiver MAY advertise a larger offset at any point by sending
connection by sending a WINDOW_UPDATE frame. A receiver MUST NOT MAX_DATA or MAX_STREAM_DATA frames. A receiver MUST NOT renege on an
renege on an advertisement; that is, once a receiver advertises an advertisement; that is, once a receiver advertises an offset, it MUST
offset via a WINDOW_UPDATE frame, it MUST NOT subsequently advertise NOT subsequently advertise a smaller offset. A sender could receive
a smaller offset. A sender may receive WINDOW_UPDATE frames out of MAX_DATA or MAX_STREAM_DATA frames out of order; a sender MUST
order; a sender MUST therefore ignore any WINDOW_UPDATE that does not therefore ignore any flow control offset that does not move the
move the window forward. window forward.
A receiver MUST close the connection with a A receiver MUST close the connection with a
QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA error (Section 12) if the QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA error (Section 12) if the
peer violates the advertised stream or connection flow control peer violates the advertised connection or stream data limits.
windows.
A sender MUST send BLOCKED frames to indicate it has data to write A sender MUST send BLOCKED frames to indicate it has data to write
but is blocked by lack of connection or stream flow control credit. but is blocked by lack of connection or stream flow control credit.
BLOCKED frames are expected to be sent infrequently in common cases, BLOCKED frames are expected to be sent infrequently in common cases,
but they are considered useful for debugging and monitoring purposes. but they are considered useful for debugging and monitoring purposes.
A receiver advertises credit for a stream by sending a WINDOW_UPDATE A receiver advertises credit for a stream by sending a
frame with the StreamID set appropriately. A receiver may use the MAX_STREAM_DATA frame with the Stream ID set appropriately. A
current offset of data consumed to determine the flow control offset receiver could use the current offset of data consumed to determine
to be advertised. A receiver MAY send copies of a WINDOW_UPDATE the flow control offset to be advertised. A receiver MAY send
frame in multiple packets in order to make sure that the sender MAX_STREAM_DATA frames in multiple packets in order to make sure that
receives it before running out of flow control credit, even if one of the sender receives an update before running out of flow control
the packets is lost. credit, even if one of the packets is lost.
Connection flow control is a limit to the total bytes of stream data Connection flow control is a limit to the total bytes of stream data
sent in STREAM frames on all streams contributing to connection flow sent in STREAM frames on all streams. A receiver advertises credit
control. A receiver advertises credit for a connection by sending a for a connection by sending a MAX_DATA frame. A receiver maintains a
WINDOW_UPDATE frame with the StreamID set to zero (0x00). A receiver cumulative sum of bytes received on all streams, which are used to
maintains a cumulative sum of bytes received on all streams check for flow control violations. A receiver might use a sum of
contributing to connection-level flow control, to check for flow bytes consumed on all contributing streams to determine the maximum
control violations. A receiver may maintain a cumulative sum of data limit to be advertised.
bytes consumed on all contributing streams to determine the
connection-level flow control offset to be advertised.
11.1. Edge Cases and Other Considerations 11.1. Edge Cases and Other Considerations
There are some edge cases which must be considered when dealing with There are some edge cases which must be considered when dealing with
stream and connection level flow control. Given enough time, both stream and connection level flow control. Given enough time, both
endpoints must agree on flow control state. If one end believes it endpoints must agree on flow control state. If one end believes it
can send more than the other end is willing to receive, the can send more than the other end is willing to receive, the
connection will be torn down when too much data arrives. Conversely connection will be torn down when too much data arrives.
if a sender believes it is blocked, while endpoint B expects more
data can be received, then the connection can be in a deadlock, with Conversely if a sender believes it is blocked, while endpoint B
the sender waiting for a WINDOW_UPDATE which will never come. expects more data can be received, then the connection can be in a
deadlock, with the sender waiting for a MAX_DATA or MAX_STREAM_DATA
frame which will never come.
11.1.1. Mid-stream RST_STREAM 11.1.1. Mid-stream RST_STREAM
On receipt of a RST_STREAM frame, an endpoint will tear down state On receipt of a RST_STREAM frame, an endpoint will tear down state
for the matching stream and ignore further data arriving on that for the matching stream and ignore further data arriving on that
stream. This could result in the endpoints getting out of sync, stream. This could result in the endpoints getting out of sync,
since the RST_STREAM frame may have arrived out of order and there since the RST_STREAM frame may have arrived out of order and there
may be further bytes in flight. The data sender would have counted may be further bytes in flight. The data sender would have counted
the data against its connection level flow control budget, but a the data against its connection level flow control budget, but a
receiver that has not received these bytes would not know to include receiver that has not received these bytes would not know to include
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the stream in its connection level flow controller. the stream in its connection level flow controller.
11.1.2. Response to a RST_STREAM 11.1.2. Response to a RST_STREAM
Since streams are bidirectional, a sender of a RST_STREAM needs to Since streams are bidirectional, a sender of a RST_STREAM needs to
know how many bytes the peer has sent on the stream. If an endpoint know how many bytes the peer has sent on the stream. If an endpoint
receives a RST_STREAM frame and has sent neither a FIN nor a receives a RST_STREAM frame and has sent neither a FIN nor a
RST_STREAM, it MUST send a RST_STREAM in response, bearing the offset RST_STREAM, it MUST send a RST_STREAM in response, bearing the offset
of the last byte sent on this stream as the final offset. of the last byte sent on this stream as the final offset.
11.1.3. Offset Increment 11.1.3. Data Limit Increments
This document leaves when and how many bytes to advertise in a This document leaves when and how many bytes to advertise in a
WINDOW_UPDATE to the implementation, but offers a few considerations. MAX_DATA or MAX_STREAM_DATA to implementations, but offers a few
WINDOW_UPDATE frames constitute overhead, and therefore, sending a considerations. These frames contribute to connection overhead.
WINDOW_UPDATE with small offset increments is undesirable. At the Therefore frequently sending frames with small changes is
same time, sending WINDOW_UPDATES with large offset increments undesirable. At the same time, infrequent updates require larger
requires the sender to commit to that amount of buffer. increments to limits if blocking is to be avoided. Thus, larger
updates require a receiver to commit to larger resource commitments.
Thus there is a tradeoff between resource commitment and overhead
when determining how large a limit is advertised.
Implementations must find the correct tradeoff between these sides to A receiver MAY use an autotuning mechanism to tune the frequency and
determine how large an offset increment to send in a WINDOW_UPDATE. amount that it increases data limits based on a roundtrip time
estimate and the rate at which the receiving application consumes
data, similar to common TCP implementations.
A receiver MAY use an autotuning mechanism to tune the size of the 11.1.4. Stream Limit Increment
offset increment to advertise based on a roundtrip time estimate and
the rate at which the receiving application consumes data, similar to
common TCP implementations.
11.1.4. BLOCKED frames As with flow control, this document leaves when and how many streams
to make available to a peer via MAX_STREAM_ID to implementations, but
offers a few considerations. MAX_STREAM_ID frames constitute minimal
overhead, while withholding MAX_STREAM_ID frames can prevent the peer
from using the available parallelism.
If a sender does not receive a WINDOW_UPDATE frame when it has run Implementations will likely want to increase the maximum stream ID as
out of flow control credit, the sender will be blocked and MUST send peer-initiated streams close. A receiver MAY also advance the
a BLOCKED frame. A BLOCKED frame is expected to be useful for maximum stream ID based on current activity, system conditions, and
debugging at the receiver. A receiver SHOULD NOT wait for a BLOCKED other environmental factors.
frame before sending a WINDOW_UPDATE, since doing so will cause at
least one roundtrip of quiescence. For smooth operation of the 11.1.5. Blocking on Flow Control
congestion controller, it is generally considered best to not let the
sender go into quiescence if avoidable. To avoid blocking a sender, If a sender does not receive a MAX_DATA or MAX_STREAM_DATA frame when
and to reasonably account for the possibiity of loss, a receiver it has run out of flow control credit, the sender will be blocked and
should send a WINDOW_UPDATE frame at least two roundtrips before it MUST send a BLOCKED or STREAM_BLOCKED frame. These frames are
expects the sender to get blocked. expected to be useful for debugging at the receiver; they do not
require any other action. A receiver SHOULD NOT wait for a BLOCKED
or STREAM_BLOCKED frame before sending MAX_DATA or MAX_STREAM_DATA,
since doing so will mean that a sender is unable to send for an
entire round trip.
For smooth operation of the congestion controller, it is generally
considered best to not let the sender go into quiescence if
avoidable. To avoid blocking a sender, and to reasonably account for
the possibiity of loss, a receiver should send a MAX_DATA or
MAX_STREAM_DATA frame at least two roundtrips before it expects the
sender to get blocked.
12. Error Handling 12. 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. Errors can affect an entire connection (see error to its peer. Errors can affect an entire connection (see
Section 12.1), or a single stream (see Section 12.2). Section 12.1), or a single stream (see Section 12.2).
The most appropriate error code (Section 12.3) SHOULD be included in The most appropriate error code (Section 12.3) SHOULD be included in
the frame that signals the error. Where this specification the frame that signals the error. Where this specification
identifies error conditions, it also identifies the error code that identifies error conditions, it also identifies the error code that
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Public Reset is not suitable for any error that can be signaled with Public Reset is not suitable for any error that can be signaled with
a CONNECTION_CLOSE or RST_STREAM frame. Public Reset MUST NOT be a CONNECTION_CLOSE or RST_STREAM frame. Public Reset MUST NOT be
sent by an endpoint that has the state necessary to send a frame on sent by an endpoint that has the state necessary to send a frame on
the connection. the connection.
12.1. Connection Errors 12.1. Connection Errors
Errors that result in the connection being unusable, such as an Errors that result in the connection being unusable, such as an
obvious violation of protocol semantics or corruption of state that obvious violation of protocol semantics or corruption of state that
affects an entire connection, MUST be signaled using a affects an entire connection, MUST be signaled using a
CONNECTION_CLOSE frame (Section 8.8). An endpoint MAY close the CONNECTION_CLOSE frame (Section 8.11). An endpoint MAY close the
connection in this manner, even if the error only affects a single connection in this manner, even if the error only affects a single
stream. stream.
A CONNECTION_CLOSE frame could be sent in a packet that is lost. An A CONNECTION_CLOSE frame could be sent in a packet that is lost. An
endpoint SHOULD be prepared to retransmit a packet containing a endpoint SHOULD be prepared to retransmit a packet containing a
CONNECTION_CLOSE frame if it receives more packets on a terminated CONNECTION_CLOSE frame if it receives more packets on a terminated
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 An endpoint that chooses not to retransmit packets containing
CONNECTION_CLOSE risks a peer missing the first such packet. The CONNECTION_CLOSE risks a peer missing the first such packet. The
only mechanism available to an endpoint that continues to receive only mechanism available to an endpoint that continues to receive
data for a terminated connection is to send a Public Reset packet. data for a terminated connection is to send a Public Reset packet.
12.2. Stream Errors 12.2. Stream Errors
If the error affects a single stream, but otherwise leaves the If the error affects a single stream, but otherwise leaves the
connection in a recoverable state, the endpoint can sent a RST_STREAM connection in a recoverable state, the endpoint can sent a RST_STREAM
frame (Section 8.5) with an appropriate error code to terminate just frame (Section 8.8) with an appropriate error code to terminate just
the affected stream. the affected stream.
Stream 1 is critical to the functioning of the entire connection. If Stream 1 is critical to the functioning of the entire connection. If
stream 1 is closed with either a RST_STREAM or STREAM frame bearing stream 1 is closed with either a RST_STREAM or STREAM frame bearing
the FIN flag, an endpoint MUST generate a connection error of type the FIN flag, an endpoint MUST generate a connection error of type
QUIC_CLOSED_CRITICAL_STREAM. QUIC_CLOSED_CRITICAL_STREAM.
Some application protocols make other streams critical to that Some application protocols make other streams critical to that
protocol. An application protocol does not need to inform the protocol. An application protocol does not need to inform the
transport that a stream is critical; it can instead generate transport that a stream is critical; it can instead generate
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The second mitigation is that the server can require that The second mitigation is that the server can require that
acknowledgments for sent packets match the encryption level of the acknowledgments for sent packets match the encryption level of the
sent packet. This mitigation is useful if the connection has an sent packet. This mitigation is useful if the connection has an
ephemeral forward-secure key that is generated and used for every new ephemeral forward-secure key that is generated and used for every new
connection. If a packet sent is encrypted with a forward-secure key, connection. If a packet sent is encrypted with a forward-secure key,
then any acknowledgments that are received for them MUST also be then any acknowledgments that are received for them MUST also be
forward-secure encrypted. Since the attacker will not have the forward-secure encrypted. Since the attacker will not have the
forward secure key, the attacker will not be able to generate forward secure key, the attacker will not be able to generate
forward-secure encrypted packets with ACK frames. forward-secure encrypted packets with ACK frames.
13.2. Slowloris Attacks
The attacks commonly known as Slowloris [SLOWLORIS] try to keep many
connections to the target endpoint open and hold them open as long as
possible. These attacks can be executed against a QUIC endpoint by
generating the minimum amount of activity necessary to avoid being
closed for inactivity. This might involve sending small amounts of
data, gradually opening flow control windows in order to control the
sender rate, or manufacturing ACK frames that simulate a high loss
rate.
QUIC deployments SHOULD provide mitigations for the Slowloris
attacks, such as increasing the maximum number of clients the server
will allow, limiting the number of connections a single IP address is
allowed to make, imposing restrictions on the minimum transfer speed
a connection is allowed to have, and restricting the length of time
an endpoint is allowed to stay connected.
13.3. Stream Fragmentation and Reassembly Attacks
An adversarial endpoint might intentionally fragment the data on
stream buffers in order to cause disproportionate memory commitment.
An adversarial endpoint could open a stream and send some STREAM
frames containing arbitrary fragments of the stream content.
The attack is mitigated if flow control windows correspond to
available memory. However, some receivers will over-commit memory
and advertise flow control offsets in the aggregate that exceed
actual available memory. The over-commitment strategy can lead to
better performance when endpoints are well behaved, but renders
endpoints vulnerable to the stream fragmentation attack.
QUIC deployments SHOULD provide mitigations against the stream
fragmentation attack. Mitigations could consist of avoiding over-
committing memory, delaying reassembly of STREAM frames, implementing
heuristics based on the age and duration of reassembly holes, or some
combination.
13.4. Stream Commitment Attack
An adversarial endpoint can open lots of streams, exhausting state on
an endpoint. The adversarial endpoint could repeat the process on a
large number of connections, in a manner similar to SYN flooding
attacks in TCP.
Normally, clients will open streams sequentially, as explained in
Section 10.2. However, when several streams are initiated at short
intervals, transmission error may cause STREAM DATA frames opening
streams to be received out of sequence. A receiver is obligated to
open intervening streams if a higher-numbered stream ID is received.
Thus, on a new connection, opening stream 2000001 opens 1 million
streams, as required by the specification.
The number of active streams is limited by the concurrent stream
limit transport parameter, as explained in Section 10.3. If chosen
judisciously, this limit mitigates the effect of the stream
commitment attack. However, setting the limit too low could affect
performance when applications expect to open large number of streams.
14. IANA Considerations 14. IANA Considerations
14.1. QUIC Transport Parameter Registry 14.1. QUIC Transport Parameter Registry
IANA [SHALL add/has added] a registry for "QUIC Transport Parameters" IANA [SHALL add/has added] a registry for "QUIC Transport Parameters"
under a "QUIC Protocol" heading. under a "QUIC Protocol" heading.
The "QUIC Transport Parameters" registry governs a 16-bit space. The "QUIC Transport Parameters" registry governs a 16-bit space.
This space is split into two spaces that are governed by different This space is split into two spaces that are governed by different
policies. Values with the first byte in the range 0x00 to 0xfe (in policies. Values with the first byte in the range 0x00 to 0xfe (in
skipping to change at page 62, line 5 skipping to change at page 65, line 13
the value. the value.
The nominated expert(s) verify that a specification exists and is The nominated expert(s) verify that a specification exists and is
readily accessible. The expert(s) are encouraged to be biased readily accessible. The expert(s) are encouraged to be biased
towards approving registrations unless they are abusive, frivolous, towards approving registrations unless they are abusive, frivolous,
or actively harmful (not merely aesthetically displeasing, or or actively harmful (not merely aesthetically displeasing, or
architecturally dubious). architecturally dubious).
The initial contents of this registry are shown in Table 4. The initial contents of this registry are shown in Table 4.
+--------+------------------------+---------------+ +--------+-------------------------+---------------+
| Value | Parameter Name | Specification | | Value | Parameter Name | Specification |
+--------+------------------------+---------------+ +--------+-------------------------+---------------+
| 0x0000 | stream_fc_offset | Section 7.3.1 | | 0x0000 | initial_max_stream_data | Section 7.3.1 |
| | | | | | | |
| 0x0001 | connection_fc_offset | Section 7.3.1 | | 0x0001 | initial_max_data | Section 7.3.1 |
| | | | | | | |
| 0x0002 | concurrent_streams | Section 7.3.1 | | 0x0002 | initial_max_stream_id | Section 7.3.1 |
| | | | | | | |
| 0x0003 | idle_timeout | Section 7.3.1 | | 0x0003 | idle_timeout | Section 7.3.1 |
| | | | | | | |
| 0x0004 | truncate_connection_id | Section 7.3.1 | | 0x0004 | truncate_connection_id | Section 7.3.1 |
+--------+------------------------+---------------+ +--------+-------------------------+---------------+
Table 4: Initial QUIC Transport Parameters Entries Table 4: Initial QUIC Transport Parameters Entries
15. References 15. References
15.1. Normative References 15.1. Normative References
[I-D.ietf-tls-tls13] [I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-19 (work in progress), Version 1.3", draft-ietf-tls-tls13-19 (work in progress),
March 2017. March 2017.
[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". and Congestion Control", draft-ietf-quic-recovery-latest
(work in progress).
[QUIC-TLS] [QUIC-TLS]
Thomson, M., Ed. and S. Turner, Ed., "Using Transport Thomson, M., Ed. and S. Turner, Ed., "Using Transport
Layer Security (TLS) to Secure QUIC". Layer Security (TLS) to Secure QUIC", draft-ietf-quic-tls-
latest (work in progress).
[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,
<http://www.rfc-editor.org/info/rfc1191>. <http://www.rfc-editor.org/info/rfc1191>.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
1996, <http://www.rfc-editor.org/info/rfc1981>. 1996, <http://www.rfc-editor.org/info/rfc1981>.
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>. <http://www.rfc-editor.org/info/rfc4821>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
15.2. Informative References 15.2. Informative References
skipping to change at page 63, line 44 skipping to change at page 67, line 10
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <http://www.rfc-editor.org/info/rfc7301>. July 2014, <http://www.rfc-editor.org/info/rfc7301>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [RFC7540] 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,
<http://www.rfc-editor.org/info/rfc7540>. <http://www.rfc-editor.org/info/rfc7540>.
[SST] Ford, B., "Structured Streams: A New Transport [SLOWLORIS]
Abstraction", DOI 10.1145/1282427.1282421, ACM RSnake Hansen, R., "Welcome to Slowloris...", June 2009,
SIGCOMM Computer Communication Review Volume 37 Issue 4, <https://web.archive.org/web/20150315054838/
October 2007. http://ha.ckers.org/slowloris/>.
[SST] Ford, B., "Structured streams", ACM SIGCOMM Computer
Communication Review Vol. 37, pp. 361,
DOI 10.1145/1282427.1282421, October 2007.
15.3. URIs 15.3. URIs
[1] https://github.com/quicwg/base-drafts/wiki/QUIC-Versions [1] https://github.com/quicwg/base-drafts/wiki/QUIC-Versions
Appendix A. Contributors Appendix A. Contributors
The original authors of this specification were Ryan Hamilton, Jana The original authors of this specification were Ryan Hamilton, Jana
Iyengar, Ian Swett, and Alyssa Wilk. Iyengar, Ian Swett, and Alyssa Wilk.
skipping to change at page 65, line 7 skipping to change at page 68, line 21
o Define reserved version values for "greasing" negotiation (#112, o Define reserved version values for "greasing" negotiation (#112,
#278) #278)
o The initial packet number is randomized (#35, #283) o The initial packet number is randomized (#35, #283)
o Narrow the packet number encoding range requirement (#67, #286, o Narrow the packet number encoding range requirement (#67, #286,
#299, #323, #356) #299, #323, #356)
o Defined client address validation (#52, #118, #120, #275) o Defined client address validation (#52, #118, #120, #275)
o Define transport parameters as a TLS extension (#122) o Define transport parameters as a TLS extension (#49, #122)
o SCUP and COPT parameters are no longer valid (#116, #117) o SCUP and COPT parameters are no longer valid (#116, #117)
o Transport parameters for 0-RTT are either remembered from before, o Transport parameters for 0-RTT are either remembered from before,
or assume default values (#126) or assume default values (#126)
o The server chooses connection IDs in its final flight (#119, #349, o The server chooses connection IDs in its final flight (#119, #349,
#361) #361)
o The server echoes the Connection ID and packet number fields when o The server echoes the Connection ID and packet number fields when
sending a Version Negotiation packet (#133, #295, #244) sending a Version Negotiation packet (#133, #295, #244)
o Definied a minimum packet size for the initial handshake packet o Defined a minimum packet size for the initial handshake packet
from the client (#69, #136, #139, #164) from the client (#69, #136, #139, #164)
o Path MTU Discovery (#64, #106) o Path MTU Discovery (#64, #106)
o The initial handshake packet from the client needs to fit in a o The initial handshake packet from the client needs to fit in a
single packet (#338) single packet (#338)
o Forbid acknowledgment of packets containing only ACK and PADDING o Forbid acknowledgment of packets containing only ACK and PADDING
(#291) (#291)
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in them can be (#157, #298) in them can be (#157, #298)
o Error handling definitions (#335) o Error handling definitions (#335)
o Split error codes into four sections (#74) o Split error codes into four sections (#74)
o Forbid the use of Public Reset where CONNECTION_CLOSE is possible o Forbid the use of Public Reset where CONNECTION_CLOSE is possible
(#289) (#289)
o Define packet protection rules (#336) o Define packet protection rules (#336)
o Require that stream be entirely delivered or reset, including o Require that stream be entirely delivered or reset, including
acknowledgment of all STREAM frames or the RST_STREAM, before it acknowledgment of all STREAM frames or the RST_STREAM, before it
closes (#381) closes (#381)
o Remove stream reservation from state machine (#174, #280) o Remove stream reservation from state machine (#174, #280)
o Only stream 0 does not contributing to connection-level flow o Only stream 1 does not contribute to connection-level flow control
control (#204) (#204)
o Stream 1 counts towards the maximum concurrent stream limit (#201, o Stream 1 counts towards the maximum concurrent stream limit (#201,
#282) #282)
o Remove connection-level flow control exclusion for some streams o Remove connection-level flow control exclusion for some streams
(except 1) (#246) (except 1) (#246)
o RST_STREAM affects connection-level flow control (#162, #163) o RST_STREAM affects connection-level flow control (#162, #163)
o Flow control accounting uses the maximum data offset on each o Flow control accounting uses the maximum data offset on each
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