draft-ietf-httpbis-messaging-19.txt   draft-ietf-httpbis-messaging-latest.txt 
HTTP Working Group R. Fielding, Ed. HTTP Working Group R. Fielding, Ed.
Internet-Draft Adobe Internet-Draft Adobe
Obsoletes: 7230 (if approved) M. Nottingham, Ed. Obsoletes: 7230 (if approved) M. Nottingham, Ed.
Intended status: Standards Track Fastly Intended status: Standards Track Fastly
Expires: March 14, 2022 J. Reschke, Ed. Expires: June 5, 2023 J. Reschke, Ed.
greenbytes greenbytes
September 10, 2021 December 2, 2022
HTTP/1.1 HTTP/1.1
draft-ietf-httpbis-messaging-19 draft-ietf-httpbis-messaging-latest
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level protocol for distributed, collaborative, hypertext information level protocol for distributed, collaborative, hypertext information
systems. This document specifies the HTTP/1.1 message syntax, systems. This document specifies the HTTP/1.1 message syntax,
message parsing, connection management, and related security message parsing, connection management, and related security
concerns. concerns.
This document obsoletes portions of RFC 7230. This document obsoletes portions of RFC 7230.
skipping to change at page 1, line 36 skipping to change at page 1, line 36
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
<https://lists.w3.org/Archives/Public/ietf-http-wg/>. <https://lists.w3.org/Archives/Public/ietf-http-wg/>.
Working Group information can be found at <https://httpwg.org/>; Working Group information can be found at <https://httpwg.org/>;
source code and issues list for this draft can be found at source code and issues list for this draft can be found at
<https://github.com/httpwg/http-core>. <https://github.com/httpwg/http-core>.
The changes in this draft are summarized in Appendix D.20. The changes in this draft are summarized in Appendix D.1.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 14, 2022. This Internet-Draft will expire on June 5, 2023.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2022 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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License. provided without warranty as described in the Revised BSD License.
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11.4. Message Confidentiality . . . . . . . . . . . . . . . . 40 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 40
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
12.1. Field Name Registration . . . . . . . . . . . . . . . . 41 12.1. Field Name Registration . . . . . . . . . . . . . . . . 41
12.2. Media Type Registration . . . . . . . . . . . . . . . . 41 12.2. Media Type Registration . . . . . . . . . . . . . . . . 41
12.3. Transfer Coding Registration . . . . . . . . . . . . . . 41 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 41
12.4. ALPN Protocol ID Registration . . . . . . . . . . . . . 42 12.4. ALPN Protocol ID Registration . . . . . . . . . . . . . 42
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 42
13.1. Normative References . . . . . . . . . . . . . . . . . . 42 13.1. Normative References . . . . . . . . . . . . . . . . . . 42
13.2. Informative References . . . . . . . . . . . . . . . . . 44 13.2. Informative References . . . . . . . . . . . . . . . . . 44
Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 45 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 45
Appendix B. Differences between HTTP and MIME . . . . . . . . . 47 Appendix B. Differences between HTTP and MIME . . . . . . . . . 46
B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 47 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 47
B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 47 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 47
B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 48 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 47
B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 48 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 48
B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 48 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 48
B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 48 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 48
Appendix C. Changes from previous RFCs . . . . . . . . . . . . . 49 Appendix C. Changes from Previous RFCs . . . . . . . . . . . . . 48
C.1. Changes from HTTP/0.9 . . . . . . . . . . . . . . . . . . 49 C.1. Changes from HTTP/0.9 . . . . . . . . . . . . . . . . . . 49
C.2. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 49 C.2. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 49
C.2.1. Multihomed Web Servers . . . . . . . . . . . . . . . 49 C.2.1. Multihomed Web Servers . . . . . . . . . . . . . . . 49
C.2.2. Keep-Alive Connections . . . . . . . . . . . . . . . 49 C.2.2. Keep-Alive Connections . . . . . . . . . . . . . . . 49
C.2.3. Introduction of Transfer-Encoding . . . . . . . . . . 50 C.2.3. Introduction of Transfer-Encoding . . . . . . . . . . 50
C.3. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 50 C.3. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 50
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51
D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 51 D.1. Since draft-ietf-httpbis-messaging-19 . . . . . . . . . . 51
D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 51 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 51
D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 52 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 52 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 53
D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 53
D.7. Since draft-ietf-httpbis-messaging-05 . . . . . . . . . . 53
D.8. Since draft-ietf-httpbis-messaging-06 . . . . . . . . . . 54
D.9. Since draft-ietf-httpbis-messaging-07 . . . . . . . . . . 54
D.10. Since draft-ietf-httpbis-messaging-08 . . . . . . . . . . 54
D.11. Since draft-ietf-httpbis-messaging-09 . . . . . . . . . . 55
D.12. Since draft-ietf-httpbis-messaging-10 . . . . . . . . . . 55
D.13. Since draft-ietf-httpbis-messaging-11 . . . . . . . . . . 55
D.14. Since draft-ietf-httpbis-messaging-12 . . . . . . . . . . 55
D.15. Since draft-ietf-httpbis-messaging-13 . . . . . . . . . . 56
D.16. Since draft-ietf-httpbis-messaging-14 . . . . . . . . . . 56
D.17. Since draft-ietf-httpbis-messaging-15 . . . . . . . . . . 57
D.18. Since draft-ietf-httpbis-messaging-16 . . . . . . . . . . 57
D.19. Since draft-ietf-httpbis-messaging-17 . . . . . . . . . . 57
D.20. Since draft-ietf-httpbis-messaging-18 . . . . . . . . . . 57
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 58
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 60
1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level request/response protocol that uses extensible semantics and level request/response protocol that uses extensible semantics and
self-descriptive messages for flexible interaction with network-based self-descriptive messages for flexible interaction with network-based
hypertext information systems. HTTP/1.1 is defined by: hypertext information systems. HTTP/1.1 is defined by:
o This document o This document
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1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level request/response protocol that uses extensible semantics and level request/response protocol that uses extensible semantics and
self-descriptive messages for flexible interaction with network-based self-descriptive messages for flexible interaction with network-based
hypertext information systems. HTTP/1.1 is defined by: hypertext information systems. HTTP/1.1 is defined by:
o This document o This document
o "HTTP Semantics" [HTTP] o "HTTP Semantics" [HTTP]
o "HTTP Caching" [CACHING] o "HTTP Caching" [CACHING]
This document specifies how HTTP semantics are conveyed using the This document specifies how HTTP semantics are conveyed using the
HTTP/1.1 message syntax, framing and connection management HTTP/1.1 message syntax, framing, and connection management
mechanisms. Its goal is to define the complete set of requirements mechanisms. Its goal is to define the complete set of requirements
for HTTP/1.1 message parsers and message-forwarding intermediaries. for HTTP/1.1 message parsers and message-forwarding intermediaries.
This document obsoletes the portions of RFC 7230 related to HTTP/1.1 This document obsoletes the portions of RFC 7230 related to HTTP/1.1
messaging and connection management, with the changes being messaging and connection management, with the changes being
summarized in Appendix C.3. The other parts of RFC 7230 are summarized in Appendix C.3. The other parts of RFC 7230 are
obsoleted by "HTTP Semantics" [HTTP]. obsoleted by "HTTP Semantics" [HTTP].
1.1. Requirements Notation 1.1. Requirements Notation
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defined in Section 2 of [HTTP]. defined in Section 2 of [HTTP].
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the Augmented Backus-Naur Form (ABNF) This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234], extended with the notation for case- notation of [RFC5234], extended with the notation for case-
sensitivity in strings defined in [RFC7405]. sensitivity in strings defined in [RFC7405].
It also uses a list extension, defined in Section 5.6.1 of [HTTP], It also uses a list extension, defined in Section 5.6.1 of [HTTP],
that allows for compact definition of comma-separated lists using a that allows for compact definition of comma-separated lists using a
'#' operator (similar to how the '*' operator indicates repetition). "#" operator (similar to how the "*" operator indicates repetition).
Appendix A shows the collected grammar with all list operators Appendix A shows the collected grammar with all list operators
expanded to standard ABNF notation. expanded to standard ABNF notation.
As a convention, ABNF rule names prefixed with "obs-" denote As a convention, ABNF rule names prefixed with "obs-" denote obsolete
"obsolete" grammar rules that appear for historical reasons. grammar rules that appear for historical reasons.
The following core rules are included by reference, as defined in The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
visible [USASCII] character). visible [USASCII] character).
The rules below are defined in [HTTP]: The rules below are defined in [HTTP]:
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[RFC5322]: zero or more header field lines (collectively referred to [RFC5322]: zero or more header field lines (collectively referred to
as the "headers" or the "header section"), an empty line indicating as the "headers" or the "header section"), an empty line indicating
the end of the header section, and an optional message body. the end of the header section, and an optional message body.
HTTP-message = start-line CRLF HTTP-message = start-line CRLF
*( field-line CRLF ) *( field-line CRLF )
CRLF CRLF
[ message-body ] [ message-body ]
A message can be either a request from client to server or a response A message can be either a request from client to server or a response
from server to client. Syntactically, the two types of message from server to client. Syntactically, the two types of messages
differ only in the start-line, which is either a request-line (for differ only in the start-line, which is either a request-line (for
requests) or a status-line (for responses), and in the algorithm for requests) or a status-line (for responses), and in the algorithm for
determining the length of the message body (Section 6). determining the length of the message body (Section 6).
start-line = request-line / status-line start-line = request-line / status-line
In theory, a client could receive requests and a server could receive In theory, a client could receive requests and a server could receive
responses, distinguishing them by their different start-line formats. responses, distinguishing them by their different start-line formats.
In practice, servers are implemented to only expect a request (a In practice, servers are implemented to only expect a request (a
response is interpreted as an unknown or invalid request method) and response is interpreted as an unknown or invalid request method), and
clients are implemented to only expect a response. clients are implemented to only expect a response.
HTTP makes use of some protocol elements similar to the Multipurpose HTTP makes use of some protocol elements similar to the Multipurpose
Internet Mail Extensions (MIME) [RFC2045]. See Appendix B for the Internet Mail Extensions (MIME) [RFC2045]. See Appendix B for the
differences between HTTP and MIME messages. differences between HTTP and MIME messages.
2.2. Message Parsing 2.2. Message Parsing
The normal procedure for parsing an HTTP message is to read the The normal procedure for parsing an HTTP message is to read the
start-line into a structure, read each header field line into a hash start-line into a structure, read each header field line into a hash
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correctly or when an intermediary is known to blindly forward the correctly or when an intermediary is known to blindly forward the
HTTP-version even when it doesn't conform to the given minor version HTTP-version even when it doesn't conform to the given minor version
of the protocol. Such protocol downgrades SHOULD NOT be performed of the protocol. Such protocol downgrades SHOULD NOT be performed
unless triggered by specific client attributes, such as when one or unless triggered by specific client attributes, such as when one or
more of the request header fields (e.g., User-Agent) uniquely match more of the request header fields (e.g., User-Agent) uniquely match
the values sent by a client known to be in error. the values sent by a client known to be in error.
3. Request Line 3. Request Line
A request-line begins with a method token, followed by a single space A request-line begins with a method token, followed by a single space
(SP), the request-target, another single space (SP), and ends with (SP), the request-target, and another single space (SP), and ends
the protocol version. with the protocol version.
request-line = method SP request-target SP HTTP-version request-line = method SP request-target SP HTTP-version
Although the request-line grammar rule requires that each of the Although the request-line grammar rule requires that each of the
component elements be separated by a single SP octet, recipients MAY component elements be separated by a single SP octet, recipients MAY
instead parse on whitespace-delimited word boundaries and, aside from instead parse on whitespace-delimited word boundaries and, aside from
the CRLF terminator, treat any form of whitespace as the SP separator the CRLF terminator, treat any form of whitespace as the SP separator
while ignoring preceding or trailing whitespace; such whitespace while ignoring preceding or trailing whitespace; such whitespace
includes one or more of the following octets: SP, HTAB, VT (%x0B), FF includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
(%x0C), or bare CR. However, lenient parsing can result in request (%x0C), or bare CR. However, lenient parsing can result in request
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400 (Bad Request) error or a 301 (Moved Permanently) redirect with 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
the request-target properly encoded. A recipient SHOULD NOT attempt the request-target properly encoded. A recipient SHOULD NOT attempt
to autocorrect and then process the request without a redirect, since to autocorrect and then process the request without a redirect, since
the invalid request-line might be deliberately crafted to bypass the invalid request-line might be deliberately crafted to bypass
security filters along the request chain. security filters along the request chain.
A client MUST send a Host header field (Section 7.2 of [HTTP]) in all A client MUST send a Host header field (Section 7.2 of [HTTP]) in all
HTTP/1.1 request messages. If the target URI includes an authority HTTP/1.1 request messages. If the target URI includes an authority
component, then a client MUST send a field value for Host that is component, then a client MUST send a field value for Host that is
identical to that authority component, excluding any userinfo identical to that authority component, excluding any userinfo
subcomponent and its "@" delimiter (Section 4.2.1 of [HTTP]). If the subcomponent and its "@" delimiter (Section 4.2 of [HTTP]). If the
authority component is missing or undefined for the target URI, then authority component is missing or undefined for the target URI, then
a client MUST send a Host header field with an empty field value. a client MUST send a Host header field with an empty field value.
A server MUST respond with a 400 (Bad Request) status code to any A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field line or request message that contains more than one Host header field line or
a Host header field with an invalid field value. a Host header field with an invalid field value.
3.2.1. origin-form 3.2.1. origin-form
The most common form of request-target is the _origin-form_. The most common form of request-target is the "origin-form".
origin-form = absolute-path [ "?" query ] origin-form = absolute-path [ "?" query ]
When making a request directly to an origin server, other than a When making a request directly to an origin server, other than a
CONNECT or server-wide OPTIONS request (as detailed below), a client CONNECT or server-wide OPTIONS request (as detailed below), a client
MUST send only the absolute path and query components of the target MUST send only the absolute path and query components of the target
URI as the request-target. If the target URI's path component is URI as the request-target. If the target URI's path component is
empty, the client MUST send "/" as the path within the origin-form of empty, the client MUST send "/" as the path within the origin-form of
request-target. A Host header field is also sent, as defined in request-target. A Host header field is also sent, as defined in
Section 7.2 of [HTTP]. Section 7.2 of [HTTP].
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GET /where?q=now HTTP/1.1 GET /where?q=now HTTP/1.1
Host: www.example.org Host: www.example.org
followed by the remainder of the request message. followed by the remainder of the request message.
3.2.2. absolute-form 3.2.2. absolute-form
When making a request to a proxy, other than a CONNECT or server-wide When making a request to a proxy, other than a CONNECT or server-wide
OPTIONS request (as detailed below), a client MUST send the target OPTIONS request (as detailed below), a client MUST send the target
URI in _absolute-form_ as the request-target. URI in "absolute-form" as the request-target.
absolute-form = absolute-URI absolute-form = absolute-URI
The proxy is requested to either service that request from a valid The proxy is requested to either service that request from a valid
cache, if possible, or make the same request on the client's behalf cache, if possible, or make the same request on the client's behalf
to either the next inbound proxy server or directly to the origin either to the next inbound proxy server or directly to the origin
server indicated by the request-target. Requirements on such server indicated by the request-target. Requirements on such
"forwarding" of messages are defined in Section 7.6 of [HTTP]. "forwarding" of messages are defined in Section 7.6 of [HTTP].
An example absolute-form of request-line would be: An example absolute-form of request-line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
A client MUST send a Host header field in an HTTP/1.1 request even if A client MUST send a Host header field in an HTTP/1.1 request even if
the request-target is in the absolute-form, since this allows the the request-target is in the absolute-form, since this allows the
Host information to be forwarded through ancient HTTP/1.0 proxies Host information to be forwarded through ancient HTTP/1.0 proxies
that might not have implemented Host. that might not have implemented Host.
When a proxy receives a request with an absolute-form of request- When a proxy receives a request with an absolute-form of request-
target, the proxy MUST ignore the received Host header field (if any) target, the proxy MUST ignore the received Host header field (if any)
and instead replace it with the host information of the request- and instead replace it with the host information of the request-
target. A proxy that forwards such a request MUST generate a new target. A proxy that forwards such a request MUST generate a new
Host field value based on the received request-target rather than Host field value based on the received request-target rather than
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header field (if any) and instead use the host information of the header field (if any) and instead use the host information of the
request-target. Note that if the request-target does not have an request-target. Note that if the request-target does not have an
authority component, an empty Host header field will be sent in this authority component, an empty Host header field will be sent in this
case. case.
A server MUST accept the absolute-form in requests even though most A server MUST accept the absolute-form in requests even though most
HTTP/1.1 clients will only send the absolute-form to a proxy. HTTP/1.1 clients will only send the absolute-form to a proxy.
3.2.3. authority-form 3.2.3. authority-form
The _authority-form_ of request-target is only used for CONNECT The "authority-form" of request-target is only used for CONNECT
requests (Section 9.3.6 of [HTTP]). It consists of only the uri-host requests (Section 9.3.6 of [HTTP]). It consists of only the uri-host
and port number of the tunnel destination, separated by a colon and port number of the tunnel destination, separated by a colon
(":"). (":").
authority-form = uri-host ":" port authority-form = uri-host ":" port
When making a CONNECT request to establish a tunnel through one or When making a CONNECT request to establish a tunnel through one or
more proxies, a client MUST send only the host and port of the tunnel more proxies, a client MUST send only the host and port of the tunnel
destination as the request-target. The client obtains the host and destination as the request-target. The client obtains the host and
port from the target URI's authority component, except that it sends port from the target URI's authority component, except that it sends
the scheme's default port if the target URI elides the port. For the scheme's default port if the target URI elides the port. For
example, a CONNECT request to "http://www.example.com" looks like example, a CONNECT request to "http://www.example.com" looks like the
following:
CONNECT www.example.com:80 HTTP/1.1 CONNECT www.example.com:80 HTTP/1.1
Host: www.example.com Host: www.example.com
3.2.4. asterisk-form 3.2.4. asterisk-form
The _asterisk-form_ of request-target is only used for a server-wide The "asterisk-form" of request-target is only used for a server-wide
OPTIONS request (Section 9.3.7 of [HTTP]). OPTIONS request (Section 9.3.7 of [HTTP]).
asterisk-form = "*" asterisk-form = "*"
When a client wishes to request OPTIONS for the server as a whole, as When a client wishes to request OPTIONS for the server as a whole, as
opposed to a specific named resource of that server, the client MUST opposed to a specific named resource of that server, the client MUST
send only "*" (%x2A) as the request-target. For example, send only "*" (%x2A) as the request-target. For example,
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
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o If the request-target is in authority-form or asterisk-form, the o If the request-target is in authority-form or asterisk-form, the
target URI's combined path and query component is empty. target URI's combined path and query component is empty.
Otherwise, the target URI's combined path and query component is Otherwise, the target URI's combined path and query component is
the request-target. the request-target.
o The components of a reconstructed target URI, once determined as o The components of a reconstructed target URI, once determined as
above, can be recombined into absolute-URI form by concatenating above, can be recombined into absolute-URI form by concatenating
the scheme, "://", authority, and combined path and query the scheme, "://", authority, and combined path and query
component. component.
Example 1: the following message received over a secure connection Example 1: The following message received over a secure connection
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org Host: www.example.org
has a target URI of has a target URI of
https://www.example.org/pub/WWW/TheProject.html https://www.example.org/pub/WWW/TheProject.html
Example 2: the following message received over an insecure connection Example 2: The following message received over an insecure connection
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org:8080 Host: www.example.org:8080
has a target URI of has a target URI of
http://www.example.org:8080 http://www.example.org:8080
If the target URI's authority component is empty and its URI scheme If the target URI's authority component is empty and its URI scheme
requires a non-empty authority (as is the case for "http" and requires a non-empty authority (as is the case for "http" and
"https"), the server can reject the request or determine whether a "https"), the server can reject the request or determine whether a
configured default applies that is consistent with the incoming configured default applies that is consistent with the incoming
connection's context. Context might include connection details like connection's context. Context might include connection details like
address and port, what security has been applied, and locally-defined address and port, what security has been applied, and locally defined
information specific to that server's configuration. An empty information specific to that server's configuration. An empty
authority is replaced with the configured default before further authority is replaced with the configured default before further
processing of the request. processing of the request.
Supplying a default name for authority within the context of a Supplying a default name for authority within the context of a
secured connection is inherently unsafe if there is any chance that secured connection is inherently unsafe if there is any chance that
the user agent's intended authority might differ from the default. A the user agent's intended authority might differ from the default. A
server that can uniquely identify an authority from the request server that can uniquely identify an authority from the request
context MAY use that identity as a default without this risk. context MAY use that identity as a default without this risk.
Alternatively, it might be better to redirect the request to a safe Alternatively, it might be better to redirect the request to a safe
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Note that reconstructing the client's target URI is only half of the Note that reconstructing the client's target URI is only half of the
process for identifying a target resource. The other half is process for identifying a target resource. The other half is
determining whether that target URI identifies a resource for which determining whether that target URI identifies a resource for which
the server is willing and able to send a response, as defined in the server is willing and able to send a response, as defined in
Section 7.4 of [HTTP]. Section 7.4 of [HTTP].
4. Status Line 4. Status Line
The first line of a response message is the status-line, consisting The first line of a response message is the status-line, consisting
of the protocol version, a space (SP), the status code, another of the protocol version, a space (SP), the status code, and another
space, and ending with an OPTIONAL textual phrase describing the space and ending with an OPTIONAL textual phrase describing the
status code. status code.
status-line = HTTP-version SP status-code SP [reason-phrase] status-line = HTTP-version SP status-code SP [ reason-phrase ]
Although the status-line grammar rule requires that each of the Although the status-line grammar rule requires that each of the
component elements be separated by a single SP octet, recipients MAY component elements be separated by a single SP octet, recipients MAY
instead parse on whitespace-delimited word boundaries and, aside from instead parse on whitespace-delimited word boundaries and, aside from
the line terminator, treat any form of whitespace as the SP separator the line terminator, treat any form of whitespace as the SP separator
while ignoring preceding or trailing whitespace; such whitespace while ignoring preceding or trailing whitespace; such whitespace
includes one or more of the following octets: SP, HTAB, VT (%x0B), FF includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
(%x0C), or bare CR. However, lenient parsing can result in response (%x0C), or bare CR. However, lenient parsing can result in response
splitting security vulnerabilities if there are multiple recipients splitting security vulnerabilities if there are multiple recipients
of the message and each has its own unique interpretation of of the message and each has its own unique interpretation of
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textual description associated with the numeric status code, mostly textual description associated with the numeric status code, mostly
out of deference to earlier Internet application protocols that were out of deference to earlier Internet application protocols that were
more frequently used with interactive text clients. more frequently used with interactive text clients.
reason-phrase = 1*( HTAB / SP / VCHAR / obs-text ) reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
A client SHOULD ignore the reason-phrase content because it is not a A client SHOULD ignore the reason-phrase content because it is not a
reliable channel for information (it might be translated for a given reliable channel for information (it might be translated for a given
locale, overwritten by intermediaries, or discarded when the message locale, overwritten by intermediaries, or discarded when the message
is forwarded via other versions of HTTP). A server MUST send the is forwarded via other versions of HTTP). A server MUST send the
space that separates status-code from the reason-phrase even when the space that separates the status-code from the reason-phrase even when
reason-phrase is absent (i.e., the status-line would end with the the reason-phrase is absent (i.e., the status-line would end with the
three octets SP CR LF). space).
5. Field Syntax 5. Field Syntax
Each field line consists of a case-insensitive field name followed by Each field line consists of a case-insensitive field name followed by
a colon (":"), optional leading whitespace, the field line value, and a colon (":"), optional leading whitespace, the field line value, and
optional trailing whitespace. optional trailing whitespace.
field-line = field-name ":" OWS field-value OWS field-line = field-name ":" OWS field-value OWS
Most HTTP field names and the rules for parsing within field values Rules for parsing within field values are defined in Section 5.5 of
are defined in Section 6.3 of [HTTP]. This section covers the [HTTP]. This section covers the generic syntax for header field
generic syntax for header field inclusion within, and extraction inclusion within, and extraction from, HTTP/1.1 messages.
from, HTTP/1.1 messages.
5.1. Field Line Parsing 5.1. Field Line Parsing
Messages are parsed using a generic algorithm, independent of the Messages are parsed using a generic algorithm, independent of the
individual field names. The contents within a given field line value individual field names. The contents within a given field line value
are not parsed until a later stage of message interpretation (usually are not parsed until a later stage of message interpretation (usually
after the message's entire field section has been processed). after the message's entire field section has been processed).
No whitespace is allowed between the field name and colon. In the No whitespace is allowed between the field name and colon. In the
past, differences in the handling of such whitespace have led to past, differences in the handling of such whitespace have led to
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before the first non-whitespace octet of the field line value, or before the first non-whitespace octet of the field line value, or
after the last non-whitespace octet of the field line value, is after the last non-whitespace octet of the field line value, is
excluded by parsers when extracting the field line value from a field excluded by parsers when extracting the field line value from a field
line. line.
5.2. Obsolete Line Folding 5.2. Obsolete Line Folding
Historically, HTTP/1.x field values could be extended over multiple Historically, HTTP/1.x field values could be extended over multiple
lines by preceding each extra line with at least one space or lines by preceding each extra line with at least one space or
horizontal tab (obs-fold). This specification deprecates such line horizontal tab (obs-fold). This specification deprecates such line
folding except within the message/http media type (Section 10.1). folding except within the "message/http" media type (Section 10.1).
obs-fold = OWS CRLF RWS obs-fold = OWS CRLF RWS
; obsolete line folding ; obsolete line folding
A sender MUST NOT generate a message that includes line folding A sender MUST NOT generate a message that includes line folding
(i.e., that has any field line value that contains a match to the (i.e., that has any field line value that contains a match to the
obs-fold rule) unless the message is intended for packaging within obs-fold rule) unless the message is intended for packaging within
the message/http media type. the "message/http" media type.
A server that receives an obs-fold in a request message that is not A server that receives an obs-fold in a request message that is not
within a message/http container MUST either reject the message by within a "message/http" container MUST either reject the message by
sending a 400 (Bad Request), preferably with a representation sending a 400 (Bad Request), preferably with a representation
explaining that obsolete line folding is unacceptable, or replace explaining that obsolete line folding is unacceptable, or replace
each received obs-fold with one or more SP octets prior to each received obs-fold with one or more SP octets prior to
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
A proxy or gateway that receives an obs-fold in a response message A proxy or gateway that receives an obs-fold in a response message
that is not within a message/http container MUST either discard the that is not within a "message/http" container MUST either discard the
message and replace it with a 502 (Bad Gateway) response, preferably message and replace it with a 502 (Bad Gateway) response, preferably
with a representation explaining that unacceptable line folding was with a representation explaining that unacceptable line folding was
received, or replace each received obs-fold with one or more SP received, or replace each received obs-fold with one or more SP
octets prior to interpreting the field value or forwarding the octets prior to interpreting the field value or forwarding the
message downstream. message downstream.
A user agent that receives an obs-fold in a response message that is A user agent that receives an obs-fold in a response message that is
not within a message/http container MUST replace each received not within a "message/http" container MUST replace each received
obs-fold with one or more SP octets prior to interpreting the field obs-fold with one or more SP octets prior to interpreting the field
value. value.
6. Message Body 6. Message Body
The message body (if any) of an HTTP/1.1 message is used to carry The message body (if any) of an HTTP/1.1 message is used to carry
content (Section 6.4 of [HTTP]) for the request or response. The content (Section 6.4 of [HTTP]) for the request or response. The
message body is identical to the content unless a transfer coding has message body is identical to the content unless a transfer coding has
been applied, as described in Section 6.1. been applied, as described in Section 6.1.
message-body = *OCTET message-body = *OCTET
The rules for determining when a message body is present in an The rules for determining when a message body is present in an
HTTP/1.1 message differ for requests and responses. HTTP/1.1 message differ for requests and responses.
The presence of a message body in a request is signaled by a The presence of a message body in a request is signaled by a
Content-Length or Transfer-Encoding header field. Request message Content-Length or Transfer-Encoding header field. Request message
framing is independent of method semantics. framing is independent of method semantics.
The presence of a message body in a response depends on both the The presence of a message body in a response, as detailed in
request method to which it is responding and the response status code Section 6.3, depends on both the request method to which it is
(Section 4), and corresponds to when content is allowed; see responding and the response status code. This corresponds to when
Section 6.4 of [HTTP]. response content is allowed by HTTP semantics (Section 6.4.1 of
[HTTP]).
6.1. Transfer-Encoding 6.1. Transfer-Encoding
The Transfer-Encoding header field lists the transfer coding names The Transfer-Encoding header field lists the transfer coding names
corresponding to the sequence of transfer codings that have been (or corresponding to the sequence of transfer codings that have been (or
will be) applied to the content in order to form the message body. will be) applied to the content in order to form the message body.
Transfer codings are defined in Section 7. Transfer codings are defined in Section 7.
Transfer-Encoding = #transfer-coding Transfer-Encoding = #transfer-coding
; defined in [HTTP], Section 10.1.4 ; defined in [HTTP], Section 10.1.4
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transfer coding other than chunked is applied to a request's content, transfer coding other than chunked is applied to a request's content,
the sender MUST apply chunked as the final transfer coding to ensure the sender MUST apply chunked as the final transfer coding to ensure
that the message is properly framed. If any transfer coding other that the message is properly framed. If any transfer coding other
than chunked is applied to a response's content, the sender MUST than chunked is applied to a response's content, the sender MUST
either apply chunked as the final transfer coding or terminate the either apply chunked as the final transfer coding or terminate the
message by closing the connection. message by closing the connection.
For example, For example,
Transfer-Encoding: gzip, chunked Transfer-Encoding: gzip, chunked
indicates that the content has been compressed using the gzip coding indicates that the content has been compressed using the gzip coding
and then chunked using the chunked coding while forming the message and then chunked using the chunked coding while forming the message
body. body.
Unlike Content-Encoding (Section 8.4.1 of [HTTP]), Transfer-Encoding Unlike Content-Encoding (Section 8.4.1 of [HTTP]), Transfer-Encoding
is a property of the message, not of the representation, and any is a property of the message, not of the representation. Any
recipient along the request/response chain MAY decode the received recipient along the request/response chain MAY decode the received
transfer coding(s) or apply additional transfer coding(s) to the transfer coding(s) or apply additional transfer coding(s) to the
message body, assuming that corresponding changes are made to the message body, assuming that corresponding changes are made to the
Transfer-Encoding field value. Additional information about the Transfer-Encoding field value. Additional information about the
encoding parameters can be provided by other header fields not encoding parameters can be provided by other header fields not
defined by this specification. defined by this specification.
Transfer-Encoding MAY be sent in a response to a HEAD request or in a Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 (Not Modified) response (Section 15.4.5 of [HTTP]) to a GET 304 (Not Modified) response (Section 15.4.5 of [HTTP]) to a GET
request, neither of which includes a message body, to indicate that request, neither of which includes a message body, to indicate that
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any 2xx (Successful) response to a CONNECT request (Section 9.3.6 of any 2xx (Successful) response to a CONNECT request (Section 9.3.6 of
[HTTP]). [HTTP]).
A server that receives a request message with a transfer coding it A server that receives a request message with a transfer coding it
does not understand SHOULD respond with 501 (Not Implemented). does not understand SHOULD respond with 501 (Not Implemented).
Transfer-Encoding was added in HTTP/1.1. It is generally assumed Transfer-Encoding was added in HTTP/1.1. It is generally assumed
that implementations advertising only HTTP/1.0 support will not that implementations advertising only HTTP/1.0 support will not
understand how to process transfer-encoded content, and that an understand how to process transfer-encoded content, and that an
HTTP/1.0 message received with a Transfer-Encoding is likely to have HTTP/1.0 message received with a Transfer-Encoding is likely to have
been forwarded without proper handling of the chunked encoding in been forwarded without proper handling of the chunked transfer coding
transit. in transit.
A client MUST NOT send a request containing Transfer-Encoding unless A client MUST NOT send a request containing Transfer-Encoding unless
it knows the server will handle HTTP/1.1 requests (or later minor it knows the server will handle HTTP/1.1 requests (or later minor
revisions); such knowledge might be in the form of specific user revisions); such knowledge might be in the form of specific user
configuration or by remembering the version of a prior received configuration or by remembering the version of a prior received
response. A server MUST NOT send a response containing Transfer- response. A server MUST NOT send a response containing Transfer-
Encoding unless the corresponding request indicates HTTP/1.1 (or Encoding unless the corresponding request indicates HTTP/1.1 (or
later minor revisions). later minor revisions).
Early implementations of Transfer-Encoding would occasionally send Early implementations of Transfer-Encoding would occasionally send
both a chunked encoding for message framing and an estimated Content- both a chunked transfer coding for message framing and an estimated
Length header field for use by progress bars. This is why Transfer- Content-Length header field for use by progress bars. This is why
Encoding is defined as overriding Content-Length, as opposed to them Transfer-Encoding is defined as overriding Content-Length, as opposed
being mutually incompatible. Unfortunately, forwarding such a to them being mutually incompatible. Unfortunately, forwarding such
message can lead to vulnerabilities regarding request smuggling a message can lead to vulnerabilities regarding request smuggling
(Section 11.2) or response splitting (Section 11.1) attacks if any (Section 11.2) or response splitting (Section 11.1) attacks if any
downstream recipient fails to parse the message according to this downstream recipient fails to parse the message according to this
specification, particularly when a downstream recipient only specification, particularly when a downstream recipient only
implements HTTP/1.0. implements HTTP/1.0.
A server MAY reject a request that contains both Content-Length and A server MAY reject a request that contains both Content-Length and
Transfer-Encoding or process such a request in accordance with the Transfer-Encoding or process such a request in accordance with the
Transfer-Encoding alone. Regardless, the server MUST close the Transfer-Encoding alone. Regardless, the server MUST close the
connection after responding to such a request to avoid the potential connection after responding to such a request to avoid the potential
attacks. attacks.
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message body length cannot be determined reliably; the server message body length cannot be determined reliably; the server
MUST respond with the 400 (Bad Request) status code and then MUST respond with the 400 (Bad Request) status code and then
close the connection. close the connection.
5. If a message is received without Transfer-Encoding and with an 5. If a message is received without Transfer-Encoding and with an
invalid Content-Length header field, then the message framing is invalid Content-Length header field, then the message framing is
invalid and the recipient MUST treat it as an unrecoverable invalid and the recipient MUST treat it as an unrecoverable
error, unless the field value can be successfully parsed as a error, unless the field value can be successfully parsed as a
comma-separated list (Section 5.6.1 of [HTTP]), all values in the comma-separated list (Section 5.6.1 of [HTTP]), all values in the
list are valid, and all values in the list are the same (in which list are valid, and all values in the list are the same (in which
case the message is processed with that single value used as the case, the message is processed with that single value used as the
Content-Length field value). If the unrecoverable error is in a Content-Length field value). If the unrecoverable error is in a
request message, the server MUST respond with a 400 (Bad Request) request message, the server MUST respond with a 400 (Bad Request)
status code and then close the connection. If it is in a status code and then close the connection. If it is in a
response message received by a proxy, the proxy MUST close the response message received by a proxy, the proxy MUST close the
connection to the server, discard the received response, and send connection to the server, discard the received response, and send
a 502 (Bad Gateway) response to the client. If it is in a a 502 (Bad Gateway) response to the client. If it is in a
response message received by a user agent, the user agent MUST response message received by a user agent, the user agent MUST
close the connection to the server and discard the received close the connection to the server and discard the received
response. response.
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A server MAY reject a request that contains a message body but not a A server MAY reject a request that contains a message body but not a
Content-Length by responding with 411 (Length Required). Content-Length by responding with 411 (Length Required).
Unless a transfer coding other than chunked has been applied, a Unless a transfer coding other than chunked has been applied, a
client that sends a request containing a message body SHOULD use a client that sends a request containing a message body SHOULD use a
valid Content-Length header field if the message body length is known valid Content-Length header field if the message body length is known
in advance, rather than the chunked transfer coding, since some in advance, rather than the chunked transfer coding, since some
existing services respond to chunked with a 411 (Length Required) existing services respond to chunked with a 411 (Length Required)
status code even though they understand the chunked transfer coding. status code even though they understand the chunked transfer coding.
This is typically because such services are implemented via a gateway This is typically because such services are implemented via a gateway
that requires a content-length in advance of being called and the that requires a content length in advance of being called, and the
server is unable or unwilling to buffer the entire request before server is unable or unwilling to buffer the entire request before
processing. processing.
A user agent that sends a request that contains a message body MUST A user agent that sends a request that contains a message body MUST
send either a valid Content-Length header field or use the chunked send either a valid Content-Length header field or use the chunked
transfer coding. A client MUST NOT use the chunked transfer encoding transfer coding. A client MUST NOT use the chunked transfer coding
unless it knows the server will handle HTTP/1.1 (or later) requests; unless it knows the server will handle HTTP/1.1 (or later) requests;
such knowledge can be in the form of specific user configuration or such knowledge can be in the form of specific user configuration or
by remembering the version of a prior received response. by remembering the version of a prior received response.
If the final response to the last request on a connection has been If the final response to the last request on a connection has been
completely received and there remains additional data to read, a user completely received and there remains additional data to read, a user
agent MAY discard the remaining data or attempt to determine if that agent MAY discard the remaining data or attempt to determine if that
data belongs as part of the prior message body, which might be the data belongs as part of the prior message body, which might be the
case if the prior message's Content-Length value is incorrect. A case if the prior message's Content-Length value is incorrect. A
client MUST NOT process, cache, or forward such extra data as a client MUST NOT process, cache, or forward such extra data as a
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HTTP/1.1 does not define any means to limit the size of a chunked HTTP/1.1 does not define any means to limit the size of a chunked
response such that an intermediary can be assured of buffering the response such that an intermediary can be assured of buffering the
entire response. Additionally, very large chunk sizes may cause entire response. Additionally, very large chunk sizes may cause
overflows or loss of precision if their values are not represented overflows or loss of precision if their values are not represented
accurately in a receiving implementation. Therefore, recipients MUST accurately in a receiving implementation. Therefore, recipients MUST
anticipate potentially large hexadecimal numerals and prevent parsing anticipate potentially large hexadecimal numerals and prevent parsing
errors due to integer conversion overflows or precision loss due to errors due to integer conversion overflows or precision loss due to
integer representation. integer representation.
The chunked encoding does not define any parameters. Their presence The chunked coding does not define any parameters. Their presence
SHOULD be treated as an error. SHOULD be treated as an error.
7.1.1. Chunk Extensions 7.1.1. Chunk Extensions
The chunked encoding allows each chunk to include zero or more chunk The chunked coding allows each chunk to include zero or more chunk
extensions, immediately following the chunk-size, for the sake of extensions, immediately following the chunk-size, for the sake of
supplying per-chunk metadata (such as a signature or hash), mid- supplying per-chunk metadata (such as a signature or hash), mid-
message control information, or randomization of message body size. message control information, or randomization of message body size.
chunk-ext = *( BWS ";" BWS chunk-ext-name chunk-ext = *( BWS ";" BWS chunk-ext-name
[ BWS "=" BWS chunk-ext-val ] ) [ BWS "=" BWS chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-string chunk-ext-val = token / quoted-string
The chunked encoding is specific to each connection and is likely to The chunked coding is specific to each connection and is likely to be
be removed or recoded by each recipient (including intermediaries) removed or recoded by each recipient (including intermediaries)
before any higher-level application would have a chance to inspect before any higher-level application would have a chance to inspect
the extensions. Hence, use of chunk extensions is generally limited the extensions. Hence, the use of chunk extensions is generally
to specialized HTTP services such as "long polling" (where client and limited to specialized HTTP services such as "long polling" (where
server can have shared expectations regarding the use of chunk client and server can have shared expectations regarding the use of
extensions) or for padding within an end-to-end secured connection. chunk extensions) or for padding within an end-to-end secured
connection.
A recipient MUST ignore unrecognized chunk extensions. A server A recipient MUST ignore unrecognized chunk extensions. A server
ought to limit the total length of chunk extensions received in a ought to limit the total length of chunk extensions received in a
request to an amount reasonable for the services provided, in the request to an amount reasonable for the services provided, in the
same way that it applies length limitations and timeouts for other same way that it applies length limitations and timeouts for other
parts of a message, and generate an appropriate 4xx (Client Error) parts of a message, and generate an appropriate 4xx (Client Error)
response if that amount is exceeded. response if that amount is exceeded.
7.1.2. Chunked Trailer Section 7.1.2. Chunked Trailer Section
A trailer section allows the sender to include additional fields at A trailer section allows the sender to include additional fields at
the end of a chunked message in order to supply metadata that might the end of a chunked message in order to supply metadata that might
be dynamically generated while the content is sent, such as a message be dynamically generated while the content is sent, such as a message
integrity check, digital signature, or post-processing status. The integrity check, digital signature, or post-processing status. The
proper use and limitations of trailer fields are defined in proper use and limitations of trailer fields are defined in
Section 6.5 of [HTTP]. Section 6.5 of [HTTP].
trailer-section = *( field-line CRLF ) trailer-section = *( field-line CRLF )
A recipient that removes the chunked encoding from a message MAY A recipient that removes the chunked coding from a message MAY
selectively retain or discard the received trailer fields. A selectively retain or discard the received trailer fields. A
recipient that retains a received trailer field MUST either store/ recipient that retains a received trailer field MUST either store/
forward the trailer field separately from the received header fields forward the trailer field separately from the received header fields
or merge the received trailer field into the header section. A or merge the received trailer field into the header section. A
recipient MUST NOT merge a received trailer field into the header recipient MUST NOT merge a received trailer field into the header
section unless its corresponding header field definition explicitly section unless its corresponding header field definition explicitly
permits and instructs how the trailer field value can be safely permits and instructs how the trailer field value can be safely
merged. merged.
7.1.3. Decoding Chunked 7.1.3. Decoding Chunked
skipping to change at page 27, line 18 skipping to change at page 27, line 18
o Description o Description
o Pointer to specification text o Pointer to specification text
Names of transfer codings MUST NOT overlap with names of content Names of transfer codings MUST NOT overlap with names of content
codings (Section 8.4.1 of [HTTP]) unless the encoding transformation codings (Section 8.4.1 of [HTTP]) unless the encoding transformation
is identical, as is the case for the compression codings defined in is identical, as is the case for the compression codings defined in
Section 7.2. Section 7.2.
The TE header field (Section 10.1.4 of [HTTP]) uses a pseudo The TE header field (Section 10.1.4 of [HTTP]) uses a pseudo-
parameter named "q" as rank value when multiple transfer codings are parameter named "q" as the rank value when multiple transfer codings
acceptable. Future registrations of transfer codings SHOULD NOT are acceptable. Future registrations of transfer codings SHOULD NOT
define parameters called "q" (case-insensitively) in order to avoid define parameters called "q" (case-insensitively) in order to avoid
ambiguities. ambiguities.
Values to be added to this namespace require IETF Review (see Values to be added to this namespace require IETF Review (see
Section 4.8 of [RFC8126]), and MUST conform to the purpose of Section 4.8 of [RFC8126]) and MUST conform to the purpose of transfer
transfer coding defined in this specification. coding defined in this specification.
Use of program names for the identification of encoding formats is Use of program names for the identification of encoding formats is
not desirable and is discouraged for future encodings. not desirable and is discouraged for future encodings.
7.4. Negotiating Transfer Codings 7.4. Negotiating Transfer Codings
The TE field (Section 10.1.4 of [HTTP]) is used in HTTP/1.1 to The TE field (Section 10.1.4 of [HTTP]) is used in HTTP/1.1 to
indicate what transfer-codings, besides chunked, the client is indicate what transfer codings, besides chunked, the client is
willing to accept in the response, and whether the client is willing willing to accept in the response and whether the client is willing
to preserve trailer fields in a chunked transfer coding. to preserve trailer fields in a chunked transfer coding.
A client MUST NOT send the chunked transfer coding name in TE; A client MUST NOT send the chunked transfer coding name in TE;
chunked is always acceptable for HTTP/1.1 recipients. chunked is always acceptable for HTTP/1.1 recipients.
Three examples of TE use are below. Three examples of TE use are below.
TE: deflate TE: deflate
TE: TE:
TE: trailers, deflate;q=0.5 TE: trailers, deflate;q=0.5
When multiple transfer codings are acceptable, the client MAY rank When multiple transfer codings are acceptable, the client MAY rank
the codings by preference using a case-insensitive "q" parameter the codings by preference using a case-insensitive "q" parameter
(similar to the qvalues used in content negotiation fields, (similar to the qvalues used in content negotiation fields; see
Section 12.4.2 of [HTTP]). The rank value is a real number in the Section 12.4.2 of [HTTP]). The rank value is a real number in the
range 0 through 1, where 0.001 is the least preferred and 1 is the range 0 through 1, where 0.001 is the least preferred and 1 is the
most preferred; a value of 0 means "not acceptable". most preferred; a value of 0 means "not acceptable".
If the TE field value is empty or if no TE field is present, the only If the TE field value is empty or if no TE field is present, the only
acceptable transfer coding is chunked. A message with no transfer acceptable transfer coding is chunked. A message with no transfer
coding is always acceptable. coding is always acceptable.
The keyword "trailers" indicates that the sender will not discard The keyword "trailers" indicates that the sender will not discard
trailer fields, as described in Section 6.5 of [HTTP]. trailer fields, as described in Section 6.5 of [HTTP].
skipping to change at page 28, line 28 skipping to change at page 28, line 28
8. Handling Incomplete Messages 8. Handling Incomplete Messages
A server that receives an incomplete request message, usually due to A server that receives an incomplete request message, usually due to
a canceled request or a triggered timeout exception, MAY send an a canceled request or a triggered timeout exception, MAY send an
error response prior to closing the connection. error response prior to closing the connection.
A client that receives an incomplete response message, which can A client that receives an incomplete response message, which can
occur when a connection is closed prematurely or when decoding a occur when a connection is closed prematurely or when decoding a
supposedly chunked transfer coding fails, MUST record the message as supposedly chunked transfer coding fails, MUST record the message as
incomplete. Cache requirements for incomplete responses are defined incomplete. Cache requirements for incomplete responses are defined
in Section 3 of [CACHING]. in Section 3.3 of [CACHING].
If a response terminates in the middle of the header section (before If a response terminates in the middle of the header section (before
the empty line is received) and the status code might rely on header the empty line is received) and the status code might rely on header
fields to convey the full meaning of the response, then the client fields to convey the full meaning of the response, then the client
cannot assume that meaning has been conveyed; the client might need cannot assume that meaning has been conveyed; the client might need
to repeat the request in order to determine what action to take next. to repeat the request in order to determine what action to take next.
A message body that uses the chunked transfer coding is incomplete if A message body that uses the chunked transfer coding is incomplete if
the zero-sized chunk that terminates the encoding has not been the zero-sized chunk that terminates the encoding has not been
received. A message that uses a valid Content-Length is incomplete received. A message that uses a valid Content-Length is incomplete
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protocols. Each HTTP connection maps to one underlying transport protocols. Each HTTP connection maps to one underlying transport
connection. connection.
9.2. Associating a Response to a Request 9.2. Associating a Response to a Request
HTTP/1.1 does not include a request identifier for associating a HTTP/1.1 does not include a request identifier for associating a
given request message with its corresponding one or more response given request message with its corresponding one or more response
messages. Hence, it relies on the order of response arrival to messages. Hence, it relies on the order of response arrival to
correspond exactly to the order in which requests are made on the correspond exactly to the order in which requests are made on the
same connection. More than one response message per request only same connection. More than one response message per request only
occurs when one or more informational responses (1xx, see occurs when one or more informational responses (1xx; see
Section 15.2 of [HTTP]) precede a final response to the same request. Section 15.2 of [HTTP]) precede a final response to the same request.
A client that has more than one outstanding request on a connection A client that has more than one outstanding request on a connection
MUST maintain a list of outstanding requests in the order sent and MUST maintain a list of outstanding requests in the order sent and
MUST associate each received response message on that connection to MUST associate each received response message on that connection to
the first outstanding request that has not yet received a final (non- the first outstanding request that has not yet received a final (non-
1xx) response. 1xx) response.
If a client receives data on a connection that doesn't have If a client receives data on a connection that doesn't have
outstanding requests, the client MUST NOT consider that data to be a outstanding requests, the client MUST NOT consider that data to be a
valid response; the client SHOULD close the connection, since message valid response; the client SHOULD close the connection, since message
delimitation is now ambiguous, unless the data consists only of one delimitation is now ambiguous, unless the data consists only of one
or more CRLF (which can be discarded, as per Section 2.2). or more CRLF (which can be discarded per Section 2.2).
9.3. Persistence 9.3. Persistence
HTTP/1.1 defaults to the use of _persistent connections_, allowing HTTP/1.1 defaults to the use of "persistent connections", allowing
multiple requests and responses to be carried over a single multiple requests and responses to be carried over a single
connection. HTTP implementations SHOULD support persistent connection. HTTP implementations SHOULD support persistent
connections. connections.
A recipient determines whether a connection is persistent or not A recipient determines whether a connection is persistent or not
based on the protocol version and Connection header field based on the protocol version and Connection header field
(Section 7.6.1 of [HTTP]) in the most recently received message, if (Section 7.6.1 of [HTTP]) in the most recently received message, if
any: any:
o If the close connection option is present (Section 9.6), the o If the "close" connection option is present (Section 9.6), the
connection will not persist after the current response; else, connection will not persist after the current response; else,
o If the received protocol is HTTP/1.1 (or later), the connection o If the received protocol is HTTP/1.1 (or later), the connection
will persist after the current response; else, will persist after the current response; else,
o If the received protocol is HTTP/1.0, the "keep-alive" connection o If the received protocol is HTTP/1.0, the "keep-alive" connection
option is present, either the recipient is not a proxy or the option is present, either the recipient is not a proxy or the
message is a response, and the recipient wishes to honor the message is a response, and the recipient wishes to honor the
HTTP/1.0 "keep-alive" mechanism, the connection will persist after HTTP/1.0 "keep-alive" mechanism, the connection will persist after
the current response; otherwise, the current response; otherwise,
o The connection will close after the current response. o The connection will close after the current response.
A client that does not support persistent connections MUST send the A client that does not support persistent connections MUST send the
close connection option in every request message. "close" connection option in every request message.
A server that does not support persistent connections MUST send the A server that does not support persistent connections MUST send the
close connection option in every response message that does not have "close" connection option in every response message that does not
a 1xx (Informational) status code. have a 1xx (Informational) status code.
A client MAY send additional requests on a persistent connection A client MAY send additional requests on a persistent connection
until it sends or receives a close connection option or receives an until it sends or receives a "close" connection option or receives an
HTTP/1.0 response without a "keep-alive" connection option. HTTP/1.0 response without a "keep-alive" connection option.
In order to remain persistent, all messages on a connection need to In order to remain persistent, all messages on a connection need to
have a self-defined message length (i.e., one not defined by closure have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 6. A server MUST read of the connection), as described in Section 6. A server MUST read
the entire request message body or close the connection after sending the entire request message body or close the connection after sending
its response, since otherwise the remaining data on a persistent its response; otherwise, the remaining data on a persistent
connection would be misinterpreted as the next request. Likewise, a connection would be misinterpreted as the next request. Likewise, a
client MUST read the entire response message body if it intends to client MUST read the entire response message body if it intends to
reuse the same connection for a subsequent request. reuse the same connection for a subsequent request.
A proxy server MUST NOT maintain a persistent connection with an A proxy server MUST NOT maintain a persistent connection with an
HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and HTTP/1.0 client (see Appendix C.2.2 for information and discussion of
discussion of the problems with the Keep-Alive header field the problems with the Keep-Alive header field implemented by many
implemented by many HTTP/1.0 clients). HTTP/1.0 clients).
See Appendix C.2.2 for more information on backwards compatibility See Appendix C.2.2 for more information on backwards compatibility
with HTTP/1.0 clients. with HTTP/1.0 clients.
9.3.1. Retrying Requests 9.3.1. Retrying Requests
Connections can be closed at any time, with or without intention. Connections can be closed at any time, with or without intention.
Implementations ought to anticipate the need to recover from Implementations ought to anticipate the need to recover from
asynchronous close events. The conditions under which a client can asynchronous close events. The conditions under which a client can
automatically retry a sequence of outstanding requests are defined in automatically retry a sequence of outstanding requests are defined in
Section 9.2.2 of [HTTP]. Section 9.2.2 of [HTTP].
9.3.2. Pipelining 9.3.2. Pipelining
A client that supports persistent connections MAY _pipeline_ its A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each requests (i.e., send multiple requests without waiting for each
response). A server MAY process a sequence of pipelined requests in response). A server MAY process a sequence of pipelined requests in
parallel if they all have safe methods (Section 9.2.1 of [HTTP]), but parallel if they all have safe methods (Section 9.2.1 of [HTTP]), but
it MUST send the corresponding responses in the same order that the it MUST send the corresponding responses in the same order that the
requests were received. requests were received.
A client that pipelines requests SHOULD retry unanswered requests if A client that pipelines requests SHOULD retry unanswered requests if
the connection closes before it receives all of the corresponding the connection closes before it receives all of the corresponding
responses. When retrying pipelined requests after a failed responses. When retrying pipelined requests after a failed
connection (a connection not explicitly closed by the server in its connection (a connection not explicitly closed by the server in its
skipping to change at page 33, line 20 skipping to change at page 33, line 20
A client, server, or proxy MAY close the transport connection at any A client, server, or proxy MAY close the transport connection at any
time. For example, a client might have started to send a new request time. For example, a client might have started to send a new request
at the same time that the server has decided to close the "idle" at the same time that the server has decided to close the "idle"
connection. From the server's point of view, the connection is being connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a closed while it was idle, but from the client's point of view, a
request is in progress. request is in progress.
A server SHOULD sustain persistent connections, when possible, and A server SHOULD sustain persistent connections, when possible, and
allow the underlying transport's flow-control mechanisms to resolve allow the underlying transport's flow-control mechanisms to resolve
temporary overloads, rather than terminate connections with the temporary overloads rather than terminate connections with the
expectation that clients will retry. The latter technique can expectation that clients will retry. The latter technique can
exacerbate network congestion or server load. exacerbate network congestion or server load.
A client sending a message body SHOULD monitor the network connection A client sending a message body SHOULD monitor the network connection
for an error response while it is transmitting the request. If the for an error response while it is transmitting the request. If the
client sees a response that indicates the server does not wish to client sees a response that indicates the server does not wish to
receive the message body and is closing the connection, the client receive the message body and is closing the connection, the client
SHOULD immediately cease transmitting the body and close its side of SHOULD immediately cease transmitting the body and close its side of
the connection. the connection.
9.6. Tear-down 9.6. Tear-down
The "close" connection option is defined as a signal that the sender The "close" connection option is defined as a signal that the sender
will close this connection after completion of the response. A will close this connection after completion of the response. A
sender SHOULD send a Connection header field (Section 7.6.1 of sender SHOULD send a Connection header field (Section 7.6.1 of
[HTTP]) containing the close connection option when it intends to [HTTP]) containing the "close" connection option when it intends to
close a connection. For example, close a connection. For example,
Connection: close Connection: close
as a request header field indicates that this is the last request as a request header field indicates that this is the last request
that the client will send on this connection, while in a response the that the client will send on this connection, while in a response,
same field indicates that the server is going to close this the same field indicates that the server is going to close this
connection after the response message is complete. connection after the response message is complete.
Note that the field name "Close" is reserved, since using that name Note that the field name "Close" is reserved, since using that name
as a header field might conflict with the close connection option. as a header field might conflict with the "close" connection option.
A client that sends a close connection option MUST NOT send further A client that sends a "close" connection option MUST NOT send further
requests on that connection (after the one containing the close) and requests on that connection (after the one containing the "close")
MUST close the connection after reading the final response message and MUST close the connection after reading the final response
corresponding to this request. message corresponding to this request.
A server that receives a close connection option MUST initiate A server that receives a "close" connection option MUST initiate
closure of the connection (see below) after it sends the final closure of the connection (see below) after it sends the final
response to the request that contained the close connection option. response to the request that contained the "close" connection option.
The server SHOULD send a close connection option in its final The server SHOULD send a "close" connection option in its final
response on that connection. The server MUST NOT process any further response on that connection. The server MUST NOT process any further
requests received on that connection. requests received on that connection.
A server that sends a close connection option MUST initiate closure A server that sends a "close" connection option MUST initiate closure
of the connection (see below) after it sends the response containing of the connection (see below) after it sends the response containing
the close connection option. The server MUST NOT process any further the "close" connection option. The server MUST NOT process any
requests received on that connection. further requests received on that connection.
A client that receives a close connection option MUST cease sending A client that receives a "close" connection option MUST cease sending
requests on that connection and close the connection after reading requests on that connection and close the connection after reading
the response message containing the close connection option; if the response message containing the "close" connection option; if
additional pipelined requests had been sent on the connection, the additional pipelined requests had been sent on the connection, the
client SHOULD NOT assume that they will be processed by the server. client SHOULD NOT assume that they will be processed by the server.
If a server performs an immediate close of a TCP connection, there is If a server performs an immediate close of a TCP connection, there is
a significant risk that the client will not be able to read the last a significant risk that the client will not be able to read the last
HTTP response. If the server receives additional data from the HTTP response. If the server receives additional data from the
client on a fully closed connection, such as another request sent by client on a fully closed connection, such as another request sent by
the client before receiving the server's response, the server's TCP the client before receiving the server's response, the server's TCP
stack will send a reset packet to the client; unfortunately, the stack will send a reset packet to the client; unfortunately, the
reset packet might erase the client's unacknowledged input buffers reset packet might erase the client's unacknowledged input buffers
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9.7. TLS Connection Initiation 9.7. TLS Connection Initiation
Conceptually, HTTP/TLS is simply sending HTTP messages over a Conceptually, HTTP/TLS is simply sending HTTP messages over a
connection secured via TLS [TLS13]. connection secured via TLS [TLS13].
The HTTP client also acts as the TLS client. It initiates a The HTTP client also acts as the TLS client. It initiates a
connection to the server on the appropriate port and sends the TLS connection to the server on the appropriate port and sends the TLS
ClientHello to begin the TLS handshake. When the TLS handshake has ClientHello to begin the TLS handshake. When the TLS handshake has
finished, the client may then initiate the first HTTP request. All finished, the client may then initiate the first HTTP request. All
HTTP data MUST be sent as TLS "application data", but is otherwise HTTP data MUST be sent as TLS "application data" but is otherwise
treated like a normal connection for HTTP (including potential reuse treated like a normal connection for HTTP (including potential reuse
as a persistent connection). as a persistent connection).
9.8. TLS Connection Closure 9.8. TLS Connection Closure
TLS uses an exchange of closure alerts prior to (non-error) TLS uses an exchange of closure alerts prior to (non-error)
connection closure to provide secure connection closure; see connection closure to provide secure connection closure; see
Section 6.1 of [TLS13]. When a valid closure alert is received, an Section 6.1 of [TLS13]. When a valid closure alert is received, an
implementation can be assured that no further data will be received implementation can be assured that no further data will be received
on that connection. on that connection.
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When an implementation knows that it has sent or received all the When an implementation knows that it has sent or received all the
message data that it cares about, typically by detecting HTTP message message data that it cares about, typically by detecting HTTP message
boundaries, it might generate an "incomplete close" by sending a boundaries, it might generate an "incomplete close" by sending a
closure alert and then closing the connection without waiting to closure alert and then closing the connection without waiting to
receive the corresponding closure alert from its peer. receive the corresponding closure alert from its peer.
An incomplete close does not call into question the security of the An incomplete close does not call into question the security of the
data already received, but it could indicate that subsequent data data already received, but it could indicate that subsequent data
might have been truncated. As TLS is not directly aware of HTTP might have been truncated. As TLS is not directly aware of HTTP
message framing, it is necessary to examine the HTTP data itself to message framing, it is necessary to examine the HTTP data itself to
determine whether messages were complete. Handling of incomplete determine whether messages are complete. Handling of incomplete
messages is defined in Section 8. messages is defined in Section 8.
When encountering an incomplete close, a client SHOULD treat as When encountering an incomplete close, a client SHOULD treat as
completed all requests for which it has received as much data as completed all requests for which it has received either
specified in the Content-Length header or, when a Transfer-Encoding
of chunked is used, for which the terminal zero-length chunk has been 1. as much data as specified in the Content-Length header field or
received. A response that has neither chunked transfer coding nor
Content-Length is complete only if a valid closure alert has been 2. the terminal zero-length chunk (when Transfer-Encoding of chunked
received. Treating an incomplete message as complete could expose is used).
A response that has neither chunked transfer coding nor Content-
Length is complete only if a valid closure alert has been received.
Treating an incomplete message as complete could expose
implementations to attack. implementations to attack.
A client detecting an incomplete close SHOULD recover gracefully. A client detecting an incomplete close SHOULD recover gracefully.
Clients MUST send a closure alert before closing the connection. Clients MUST send a closure alert before closing the connection.
Clients that do not expect to receive any more data MAY choose not to Clients that do not expect to receive any more data MAY choose not to
wait for the server's closure alert and simply close the connection, wait for the server's closure alert and simply close the connection,
thus generating an incomplete close on the server side. thus generating an incomplete close on the server side.
Servers SHOULD be prepared to receive an incomplete close from the Servers SHOULD be prepared to receive an incomplete close from the
client, since the client can often determine when the end of server client, since the client can often locate the end of server data.
data is.
Servers MUST attempt to initiate an exchange of closure alerts with Servers MUST attempt to initiate an exchange of closure alerts with
the client before closing the connection. Servers MAY close the the client before closing the connection. Servers MAY close the
connection after sending the closure alert, thus generating an connection after sending the closure alert, thus generating an
incomplete close on the client side. incomplete close on the client side.
10. Enclosing Messages as Data 10. Enclosing Messages as Data
10.1. Media Type message/http 10.1. Media Type message/http
The message/http media type can be used to enclose a single HTTP The "message/http" media type can be used to enclose a single HTTP
request or response message, provided that it obeys the MIME request or response message, provided that it obeys the MIME
restrictions for all "message" types regarding line length and restrictions for all "message" types regarding line length and
encodings. Because of the line length limitations, field values encodings. Because of the line length limitations, field values
within message/http are allowed to use line folding (obs-fold), as within "message/http" are allowed to use line folding (obs-fold), as
described in Section 5.2, to convey the field value over multiple described in Section 5.2, to convey the field value over multiple
lines. A recipient of message/http data MUST replace any obsolete lines. A recipient of "message/http" data MUST replace any obsolete
line folding with one or more SP characters when the message is line folding with one or more SP characters when the message is
consumed. consumed.
Type name: message Type name: message
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
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msgtype: The message type -- "request" or "response". If not msgtype: The message type -- "request" or "response". If not
present, the type can be determined from the first line of the present, the type can be determined from the first line of the
body. body.
Encoding considerations: only "7bit", "8bit", or "binary" are Encoding considerations: only "7bit", "8bit", or "binary" are
permitted permitted
Security considerations: see Section 11 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 10.1). Published specification: RFC 9112 (see Section 10.1).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Magic number(s): N/A Additional information: Magic number(s): N/A
Deprecated alias names for this type: N/A Deprecated alias names for this type: N/A
File extension(s): N/A File extension(s): N/A
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Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: See Authors' Addresses section. Author: See Authors' Addresses section.
Change controller: IESG Change controller: IESG
10.2. Media Type application/http 10.2. Media Type application/http
The application/http media type can be used to enclose a pipeline of The "application/http" media type can be used to enclose a pipeline
one or more HTTP request or response messages (not intermixed). of one or more HTTP request or response messages (not intermixed).
Type name: application Type name: application
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed messages (e.g., version: The HTTP-version number of the enclosed messages (e.g.,
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body. body.
Encoding considerations: HTTP messages enclosed by this type are in Encoding considerations: HTTP messages enclosed by this type are in
"binary" format; use of an appropriate Content-Transfer-Encoding "binary" format; use of an appropriate Content-Transfer-Encoding
is required when transmitted via email. is required when transmitted via email.
Security considerations: see Section 11 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 10.2). Published specification: RFC 9112 (see Section 10.2).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Deprecated alias names for this type: N/A Additional information: Deprecated alias names for this type: N/A
Magic number(s): N/A Magic number(s): N/A
File extension(s): N/A File extension(s): N/A
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11. Security Considerations 11. Security Considerations
This section is meant to inform developers, information providers, This section is meant to inform developers, information providers,
and users about known security considerations relevant to HTTP and users about known security considerations relevant to HTTP
message syntax and parsing. Security considerations about HTTP message syntax and parsing. Security considerations about HTTP
semantics, content, and routing are addressed in [HTTP]. semantics, content, and routing are addressed in [HTTP].
11.1. Response Splitting 11.1. Response Splitting
Response splitting (a.k.a., CRLF injection) is a common technique, Response splitting (a.k.a. CRLF injection) is a common technique,
used in various attacks on Web usage, that exploits the line-based used in various attacks on Web usage, that exploits the line-based
nature of HTTP message framing and the ordered association of nature of HTTP message framing and the ordered association of
requests to responses on persistent connections [Klein]. This requests to responses on persistent connections [Klein]. This
technique can be particularly damaging when the requests pass through technique can be particularly damaging when the requests pass through
a shared cache. a shared cache.
Response splitting exploits a vulnerability in servers (usually Response splitting exploits a vulnerability in servers (usually
within an application server) where an attacker can send encoded data within an application server) where an attacker can send encoded data
within some parameter of the request that is later decoded and echoed within some parameter of the request that is later decoded and echoed
within any of the response header fields of the response. If the within any of the response header fields of the response. If the
decoded data is crafted to look like the response has ended and a decoded data is crafted to look like the response has ended and a
subsequent response has begun, the response has been split and the subsequent response has begun, the response has been split, and the
content within the apparent second response is controlled by the content within the apparent second response is controlled by the
attacker. The attacker can then make any other request on the same attacker. The attacker can then make any other request on the same
persistent connection and trick the recipients (including persistent connection and trick the recipients (including
intermediaries) into believing that the second half of the split is intermediaries) into believing that the second half of the split is
an authoritative answer to the second request. an authoritative answer to the second request.
For example, a parameter within the request-target might be read by For example, a parameter within the request-target might be read by
an application server and reused within a redirect, resulting in the an application server and reused within a redirect, resulting in the
same parameter being echoed in the Location header field of the same parameter being echoed in the Location header field of the
response. If the parameter is decoded by the application and not response. If the parameter is decoded by the application and not
properly encoded when placed in the response field, the attacker can properly encoded when placed in the response field, the attacker can
send encoded CRLF octets and other content that will make the send encoded CRLF octets and other content that will make the
application's single response look like two or more responses. application's single response look like two or more responses.
A common defense against response splitting is to filter requests for A common defense against response splitting is to filter requests for
data that looks like encoded CR and LF (e.g., "%0D" and "%0A"). data that looks like encoded CR and LF (e.g., "%0D" and "%0A").
However, that assumes the application server is only performing URI However, that assumes the application server is only performing URI
decoding, rather than more obscure data transformations like charset decoding rather than more obscure data transformations like charset
transcoding, XML entity translation, base64 decoding, sprintf transcoding, XML entity translation, base64 decoding, sprintf
reformatting, etc. A more effective mitigation is to prevent reformatting, etc. A more effective mitigation is to prevent
anything other than the server's core protocol libraries from sending anything other than the server's core protocol libraries from sending
a CR or LF within the header section, which means restricting the a CR or LF within the header section, which means restricting the
output of header fields to APIs that filter for bad octets and not output of header fields to APIs that filter for bad octets and not
allowing application servers to write directly to the protocol allowing application servers to write directly to the protocol
stream. stream.
11.2. Request Smuggling 11.2. Request Smuggling
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underlying transport protocols and the use of length or chunk- underlying transport protocols and the use of length or chunk-
delimited framing to detect completeness. Historically, the lack of delimited framing to detect completeness. Historically, the lack of
a single integrity mechanism has been justified by the informal a single integrity mechanism has been justified by the informal
nature of most HTTP communication. However, the prevalence of HTTP nature of most HTTP communication. However, the prevalence of HTTP
as an information access mechanism has resulted in its increasing use as an information access mechanism has resulted in its increasing use
within environments where verification of message integrity is within environments where verification of message integrity is
crucial. crucial.
The mechanisms provided with the "https" scheme, such as The mechanisms provided with the "https" scheme, such as
authenticated encryption, provide protection against modification of authenticated encryption, provide protection against modification of
messages. Care is needed however to ensure that connection closure messages. Care is needed, however, to ensure that connection closure
cannot be used to truncate messages (see Section 9.8). User agents cannot be used to truncate messages (see Section 9.8). User agents
might refuse to accept incomplete messages or treat them specially. might refuse to accept incomplete messages or treat them specially.
For example, a browser being used to view medical history or drug For example, a browser being used to view medical history or drug
interaction information needs to indicate to the user when such interaction information needs to indicate to the user when such
information is detected by the protocol to be incomplete, expired, or information is detected by the protocol to be incomplete, expired, or
corrupted during transfer. Such mechanisms might be selectively corrupted during transfer. Such mechanisms might be selectively
enabled via user agent extensions or the presence of message enabled via user agent extensions or the presence of message
integrity metadata in a response. integrity metadata in a response.
The "http" scheme provides no protection against accidental or The "http" scheme provides no protection against accidental or
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The "https" scheme can be used to identify resources that require a The "https" scheme can be used to identify resources that require a
confidential connection, as described in Section 4.2.2 of [HTTP]. confidential connection, as described in Section 4.2.2 of [HTTP].
12. IANA Considerations 12. IANA Considerations
The change controller for the following registrations is: "IETF The change controller for the following registrations is: "IETF
(iesg@ietf.org) - Internet Engineering Task Force". (iesg@ietf.org) - Internet Engineering Task Force".
12.1. Field Name Registration 12.1. Field Name Registration
First, introduce the new "Hypertext Transfer Protocol (HTTP) Field IANA has added the following field names to the "Hypertext Transfer
Name Registry" at <https://www.iana.org/assignments/http-fields> as Protocol (HTTP) Field Name Registry" at
described in Section 18.4 of [HTTP]. <https://www.iana.org/assignments/http-fields>, as described in
Section 18.4 of [HTTP].
Then, please update the registry with the field names listed in the
table below:
+-------------------+----------+------+------------+ +-------------------+-----------+---------+------------+
| Field Name | Status | Ref. | Comments | | Field Name | Status | Section | Comments |
+-------------------+----------+------+------------+ +-------------------+-----------+---------+------------+
| Close | standard | 9.6 | (reserved) | | Close | permanent | 9.6 | (reserved) |
| MIME-Version | standard | B.1 | | | MIME-Version | permanent | B.1 | |
| Transfer-Encoding | standard | 6.1 | | | Transfer-Encoding | permanent | 6.1 | |
+-------------------+----------+------+------------+ +-------------------+-----------+---------+------------+
Table 1 Table 1
12.2. Media Type Registration 12.2. Media Type Registration
Please update the "Media Types" registry at IANA has updated the "Media Types" registry at
<https://www.iana.org/assignments/media-types> with the registration <https://www.iana.org/assignments/media-types> with the registration
information in Section 10.1 and Section 10.2 for the media types information in Sections 10.1 and 10.2 for the media types "message/
"message/http" and "application/http", respectively. http" and "application/http", respectively.
12.3. Transfer Coding Registration 12.3. Transfer Coding Registration
Please update the "HTTP Transfer Coding Registry" at IANA has updated the "HTTP Transfer Coding Registry" at
<https://www.iana.org/assignments/http-parameters/> with the <https://www.iana.org/assignments/http-parameters/> with the
registration procedure of Section 7.3 and the content coding names registration procedure of Section 7.3 and the content coding names
summarized in the table below. summarized in the table below.
+------------+-------------------------------+-----------+ +------------+-------------------------------------------+---------+
| Name | Description | Reference | | Name | Description | Section |
+------------+-------------------------------+-----------+ +------------+-------------------------------------------+---------+
| chunked | Transfer in a series of | Section | | chunked | Transfer in a series of chunks | 7.1 |
| | chunks | 7.1 | | compress | UNIX "compress" data format [Welch] | 7.2 |
| compress | UNIX "compress" data format | Section | | deflate | "deflate" compressed data ([RFC1951]) | 7.2 |
| | [Welch] | 7.2 | | | inside the "zlib" data format ([RFC1950]) | |
| deflate | "deflate" compressed data | Section | | gzip | GZIP file format [RFC1952] | 7.2 |
| | ([RFC1951]) inside the "zlib" | 7.2 | | trailers | (reserved) | 12.3 |
| | data format ([RFC1950]) | | | x-compress | Deprecated (alias for compress) | 7.2 |
| gzip | GZIP file format [RFC1952] | Section | | x-gzip | Deprecated (alias for gzip) | 7.2 |
| | | 7.2 | +------------+-------------------------------------------+---------+
| trailers | (reserved) | Section |
| | | 12.3 |
| x-compress | Deprecated (alias for | Section |
| | compress) | 7.2 |
| x-gzip | Deprecated (alias for gzip) | Section |
| | | 7.2 |
+------------+-------------------------------+-----------+
Table 2 Table 2
| *Note:* the coding name "trailers" is reserved because its use | *Note:* the coding name "trailers" is reserved because its use
| would conflict with the keyword "trailers" in the TE header | would conflict with the keyword "trailers" in the TE header
| field (Section 10.1.4 of [HTTP]). | field (Section 10.1.4 of [HTTP]).
12.4. ALPN Protocol ID Registration 12.4. ALPN Protocol ID Registration
Please update the "TLS Application-Layer Protocol Negotiation (ALPN) IANA has updated the "TLS Application-Layer Protocol Negotiation
Protocol IDs" registry at <https://www.iana.org/assignments/tls- (ALPN) Protocol IDs" registry at <https://www.iana.org/assignments/
extensiontype-values/tls-extensiontype-values.xhtml> with the tls-extensiontype-values/> with the registration below:
registration below:
+----------+-----------------------------+----------------+ +----------+-----------------------------+-----------+
| Protocol | Identification Sequence | Reference | | Protocol | Identification Sequence | Reference |
+----------+-----------------------------+----------------+ +----------+-----------------------------+-----------+
| HTTP/1.1 | 0x68 0x74 0x74 0x70 0x2f | (this | | HTTP/1.1 | 0x68 0x74 0x74 0x70 0x2f | RFC 9112 |
| | 0x31 0x2e 0x31 ("http/1.1") | specification) | | | 0x31 0x2e 0x31 ("http/1.1") | |
+----------+-----------------------------+----------------+ +----------+-----------------------------+-----------+
Table 3 Table 3
13. References 13. References
13.1. Normative References 13.1. Normative References
[CACHING] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [CACHING] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Caching", Work in Progress, Internet-Draft, Ed., "HTTP Caching", Work in Progress, Internet-Draft,
draft-ietf-httpbis-cache-latest, September 2021, draft-ietf-httpbis-cache-latest, December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis- <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
cache-latest>. cache-latest>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", Work in Progress, Internet-Draft, Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
draft-ietf-httpbis-semantics-latest, September 2021, draft-ietf-httpbis-semantics-latest, December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis- <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-latest>. semantics-latest>.
[RFC1950] Deutsch, L.P. and J-L. Gailly, "ZLIB Compressed Data [RFC1950] Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format
Format Specification version 3.3", RFC 1950, Specification version 3.3", RFC 1950,
DOI 10.17487/RFC1950, May 1996, DOI 10.17487/RFC1950, May 1996,
<https://www.rfc-editor.org/info/rfc1950>. <https://www.rfc-editor.org/info/rfc1950>.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996, version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
<https://www.rfc-editor.org/info/rfc1951>. <https://www.rfc-editor.org/info/rfc1951>.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L.P., and [RFC1952] Deutsch, P., "GZIP file format specification version 4.3",
G. Randers-Pehrson, "GZIP file format specification RFC 1952, DOI 10.17487/RFC1952, May 1996,
version 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
<https://www.rfc-editor.org/info/rfc1952>. <https://www.rfc-editor.org/info/rfc1952>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
skipping to change at page 44, line 14 skipping to change at page 44, line 9
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[USASCII] American National Standards Institute, "Coded Character [USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986. Interchange", ANSI X3.4, 1986.
[Welch] Welch, T. A., "A Technique for High-Performance Data [Welch] Welch, T., "A Technique for High-Performance Data
Compression", IEEE Computer 17(6), June 1984. Compression", IEEE Computer 17(6),
DOI 10.1109/MC.1984.1659158, June 1984,
<https://ieeexplore.ieee.org/document/1659158/>.
13.2. Informative References 13.2. Informative References
[Err4667] RFC Errata, Erratum ID 4667, RFC 7230, [HTTP/1.0] Berners-Lee, T., Fielding, R., and H. Frystyk, "Hypertext
<https://www.rfc-editor.org/errata/eid4667>. Transfer Protocol -- HTTP/1.0", RFC 1945,
[HTTP/1.0] Berners-Lee, T., Fielding, R.T., and H.F. Nielsen,
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
DOI 10.17487/RFC1945, May 1996, DOI 10.17487/RFC1945, May 1996,
<https://www.rfc-editor.org/info/rfc1945>. <https://www.rfc-editor.org/info/rfc1945>.
[Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting, [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
Web Cache Poisoning Attacks, and Related Topics", March Web Cache Poisoning Attacks, and Related Topics", March
2004, <https://packetstormsecurity.com/papers/general/ 2004, <https://packetstormsecurity.com/papers/general/
whitepaper_httpresponse.pdf>. whitepaper_httpresponse.pdf>.
[Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
Request Smuggling", June 2005, Request Smuggling", June 2005,
<https://www.cgisecurity.com/lib/HTTP-Request- <https://www.cgisecurity.com/lib/HTTP-Request-
Smuggling.pdf>. Smuggling.pdf>.
[RFC2045] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996, Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/info/rfc2045>. <https://www.rfc-editor.org/info/rfc2045>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996, DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>. <https://www.rfc-editor.org/info/rfc2046>.
[RFC2049] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Extensions (MIME) Part Five: Conformance Criteria and
Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996, Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
<https://www.rfc-editor.org/info/rfc2049>. <https://www.rfc-editor.org/info/rfc2049>.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T. [RFC2068] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
RFC 2068, DOI 10.17487/RFC2068, January 1997, RFC 2068, DOI 10.17487/RFC2068, January 1997,
<https://www.rfc-editor.org/info/rfc2068>. <https://www.rfc-editor.org/info/rfc2068>.
[RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud, [RFC2557] Palme, J., Hopmann, A., and N. Shelness, "MIME
"MIME Encapsulation of Aggregate Documents, such as HTML Encapsulation of Aggregate Documents, such as HTML
(MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999, (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
<https://www.rfc-editor.org/info/rfc2557>. <https://www.rfc-editor.org/info/rfc2557>.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008, DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>. <https://www.rfc-editor.org/info/rfc5322>.
[RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Transfer Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Collected ABNF Appendix A. Collected ABNF
In the collected ABNF below, list rules are expanded as per In the collected ABNF below, list rules are expanded per
Section 5.6.1 of [HTTP]. Section 5.6.1 of [HTTP].
BWS = <BWS, see [HTTP], Section 5.6.3> BWS = <BWS, see [HTTP], Section 5.6.3>
HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [ HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [
message-body ] message-body ]
HTTP-name = %x48.54.54.50 ; HTTP HTTP-name = %x48.54.54.50 ; HTTP
HTTP-version = HTTP-name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
OWS = <OWS, see [HTTP], Section 5.6.3> OWS = <OWS, see [HTTP], Section 5.6.3>
skipping to change at page 47, line 8 skipping to change at page 46, line 46
token = <token, see [HTTP], Section 5.6.2> token = <token, see [HTTP], Section 5.6.2>
trailer-section = *( field-line CRLF ) trailer-section = *( field-line CRLF )
transfer-coding = <transfer-coding, see [HTTP], Section 10.1.4> transfer-coding = <transfer-coding, see [HTTP], Section 10.1.4>
uri-host = <host, see [URI], Section 3.2.2> uri-host = <host, see [URI], Section 3.2.2>
Appendix B. Differences between HTTP and MIME Appendix B. Differences between HTTP and MIME
HTTP/1.1 uses many of the constructs defined for the Internet Message HTTP/1.1 uses many of the constructs defined for the Internet Message
Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME) Format [RFC5322] and Multipurpose Internet Mail Extensions (MIME)
[RFC2045] to allow a message body to be transmitted in an open [RFC2045] to allow a message body to be transmitted in an open
variety of representations and with extensible fields. However, RFC variety of representations and with extensible fields. However, some
2045 is focused only on email; applications of HTTP have many of these constructs have been reinterpreted to better fit the needs
characteristics that differ from email; hence, HTTP has features that of interactive communication, leading to some differences in how MIME
differ from MIME. These differences were carefully chosen to constructs are used within HTTP. These differences were carefully
optimize performance over binary connections, to allow greater chosen to optimize performance over binary connections, allow greater
freedom in the use of new media types, to make date comparisons freedom in the use of new media types, ease date comparisons, and
easier, and to acknowledge the practice of some early HTTP servers accommodate common implementations.
and clients.
This appendix describes specific areas where HTTP differs from MIME. This appendix describes specific areas where HTTP differs from MIME.
Proxies and gateways to and from strict MIME environments need to be Proxies and gateways to and from strict MIME environments need to be
aware of these differences and provide the appropriate conversions aware of these differences and provide the appropriate conversions
where necessary. where necessary.
B.1. MIME-Version B.1. MIME-Version
HTTP is not a MIME-compliant protocol. However, messages can include HTTP is not a MIME-compliant protocol. However, messages can include
a single MIME-Version header field to indicate what version of the a single MIME-Version header field to indicate what version of the
MIME protocol was used to construct the message. Use of the MIME- MIME protocol was used to construct the message. Use of the MIME-
Version header field indicates that the message is in full Version header field indicates that the message is in full
conformance with the MIME protocol (as defined in [RFC2045]). conformance with the MIME protocol (as defined in [RFC2045]).
Senders are responsible for ensuring full conformance (where Senders are responsible for ensuring full conformance (where
possible) when exporting HTTP messages to strict MIME environments. possible) when exporting HTTP messages to strict MIME environments.
B.2. Conversion to Canonical Form B.2. Conversion to Canonical Form
MIME requires that an Internet mail body part be converted to MIME requires that an Internet mail body part be converted to
canonical form prior to being transferred, as described in Section 4 canonical form prior to being transferred, as described in Section 4
of [RFC2049], and that content with a type of "text" represent line of [RFC2049], and that content with a type of "text" represents line
breaks as CRLF, forbidding the use of CR or LF outside of line break breaks as CRLF, forbidding the use of CR or LF outside of line break
sequences [RFC2046]. In contrast, HTTP does not care whether CRLF, sequences [RFC2046]. In contrast, HTTP does not care whether CRLF,
bare CR, or bare LF are used to indicate a line break within content. bare CR, or bare LF are used to indicate a line break within content.
A proxy or gateway from HTTP to a strict MIME environment ought to A proxy or gateway from HTTP to a strict MIME environment ought to
translate all line breaks within text media types to the RFC 2049 translate all line breaks within text media types to the RFC 2049
canonical form of CRLF. Note, however, this might be complicated by canonical form of CRLF. Note, however, this might be complicated by
the presence of a Content-Encoding and by the fact that HTTP allows the presence of a Content-Encoding and by the fact that HTTP allows
the use of some charsets that do not use octets 13 and 10 to the use of some charsets that do not use octets 13 and 10 to
represent CR and LF, respectively. represent CR and LF, respectively.
skipping to change at page 48, line 20 skipping to change at page 48, line 7
B.3. Conversion of Date Formats B.3. Conversion of Date Formats
HTTP/1.1 uses a restricted set of date formats (Section 5.6.7 of HTTP/1.1 uses a restricted set of date formats (Section 5.6.7 of
[HTTP]) to simplify the process of date comparison. Proxies and [HTTP]) to simplify the process of date comparison. Proxies and
gateways from other protocols ought to ensure that any Date header gateways from other protocols ought to ensure that any Date header
field present in a message conforms to one of the HTTP/1.1 formats field present in a message conforms to one of the HTTP/1.1 formats
and rewrite the date if necessary. and rewrite the date if necessary.
B.4. Conversion of Content-Encoding B.4. Conversion of Content-Encoding
MIME does not include any concept equivalent to HTTP/1.1's Content- MIME does not include any concept equivalent to HTTP's Content-
Encoding header field. Since this acts as a modifier on the media Encoding header field. Since this acts as a modifier on the media
type, proxies and gateways from HTTP to MIME-compliant protocols type, proxies and gateways from HTTP to MIME-compliant protocols
ought to either change the value of the Content-Type header field or ought to either change the value of the Content-Type header field or
decode the representation before forwarding the message. (Some decode the representation before forwarding the message. (Some
experimental applications of Content-Type for Internet mail have used experimental applications of Content-Type for Internet mail have used
a media-type parameter of ";conversions=<content-coding>" to perform a media-type parameter of ";conversions=<content-coding>" to perform
a function equivalent to Content-Encoding. However, this parameter a function equivalent to Content-Encoding. However, this parameter
is not part of the MIME standards). is not part of the MIME standards.)
B.5. Conversion of Content-Transfer-Encoding B.5. Conversion of Content-Transfer-Encoding
HTTP does not use the Content-Transfer-Encoding field of MIME. HTTP does not use the Content-Transfer-Encoding field of MIME.
Proxies and gateways from MIME-compliant protocols to HTTP need to Proxies and gateways from MIME-compliant protocols to HTTP need to
remove any Content-Transfer-Encoding prior to delivering the response remove any Content-Transfer-Encoding prior to delivering the response
message to an HTTP client. message to an HTTP client.
Proxies and gateways from HTTP to MIME-compliant protocols are Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format responsible for ensuring that the message is in the correct format
skipping to change at page 49, line 8 skipping to change at page 48, line 44
HTTP implementations that share code with MHTML [RFC2557] HTTP implementations that share code with MHTML [RFC2557]
implementations need to be aware of MIME line length limitations. implementations need to be aware of MIME line length limitations.
Since HTTP does not have this limitation, HTTP does not fold long Since HTTP does not have this limitation, HTTP does not fold long
lines. MHTML messages being transported by HTTP follow all lines. MHTML messages being transported by HTTP follow all
conventions of MHTML, including line length limitations and folding, conventions of MHTML, including line length limitations and folding,
canonicalization, etc., since HTTP transfers message-bodies without canonicalization, etc., since HTTP transfers message-bodies without
modification and, aside from the "multipart/byteranges" type modification and, aside from the "multipart/byteranges" type
(Section 14.6 of [HTTP]), does not interpret the content or any MIME (Section 14.6 of [HTTP]), does not interpret the content or any MIME
header lines that might be contained therein. header lines that might be contained therein.
Appendix C. Changes from previous RFCs Appendix C. Changes from Previous RFCs
C.1. Changes from HTTP/0.9 C.1. Changes from HTTP/0.9
Since HTTP/0.9 did not support header fields in a request, there is Since HTTP/0.9 did not support header fields in a request, there is
no mechanism for it to support name-based virtual hosts (selection of no mechanism for it to support name-based virtual hosts (selection of
resource by inspection of the Host header field). Any server that resource by inspection of the Host header field). Any server that
implements name-based virtual hosts ought to disable support for implements name-based virtual hosts ought to disable support for
HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact, HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
badly constructed HTTP/1.x requests caused by a client failing to badly constructed HTTP/1.x requests caused by a client failing to
properly encode the request-target. properly encode the request-target.
C.2. Changes from HTTP/1.0 C.2. Changes from HTTP/1.0
C.2.1. Multihomed Web Servers C.2.1. Multihomed Web Servers
The requirements that clients and servers support the Host header The requirements that clients and servers support the Host header
field (Section 7.2 of [HTTP]), report an error if it is missing from field (Section 7.2 of [HTTP]), report an error if it is missing from
an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are among an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are among
the most important changes defined by HTTP/1.1. the most important changes defined by HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request other than the IP
to which that request was directed. The Host header field was address to which that request was directed. The Host header field
introduced during the development of HTTP/1.1 and, though it was was introduced during the development of HTTP/1.1 and, though it was
quickly implemented by most HTTP/1.0 browsers, additional quickly implemented by most HTTP/1.0 browsers, additional
requirements were placed on all HTTP/1.1 requests in order to ensure requirements were placed on all HTTP/1.1 requests in order to ensure
complete adoption. At the time of this writing, most HTTP-based complete adoption. At the time of this writing, most HTTP-based
services are dependent upon the Host header field for targeting services are dependent upon the Host header field for targeting
requests. requests.
C.2.2. Keep-Alive Connections C.2.2. Keep-Alive Connections
In HTTP/1.0, each connection is established by the client prior to In HTTP/1.0, each connection is established by the client prior to
the request and closed by the server after sending the response. the request and closed by the server after sending the response.
skipping to change at page 50, line 17 skipping to change at page 50, line 13
hung connection. hung connection.
One attempted solution was the introduction of a Proxy-Connection One attempted solution was the introduction of a Proxy-Connection
header field, targeted specifically at proxies. In practice, this header field, targeted specifically at proxies. In practice, this
was also unworkable, because proxies are often deployed in multiple was also unworkable, because proxies are often deployed in multiple
layers, bringing about the same problem discussed above. layers, bringing about the same problem discussed above.
As a result, clients are encouraged not to send the Proxy-Connection As a result, clients are encouraged not to send the Proxy-Connection
header field in any requests. header field in any requests.
Clients are also encouraged to consider the use of Connection: keep- Clients are also encouraged to consider the use of "Connection: keep-
alive in requests carefully; while they can enable persistent alive" in requests carefully; while they can enable persistent
connections with HTTP/1.0 servers, clients using them will need to connections with HTTP/1.0 servers, clients using them will need to
monitor the connection for "hung" requests (which indicate that the monitor the connection for "hung" requests (which indicate that the
client ought to stop sending the header field), and this mechanism client ought to stop sending the header field), and this mechanism
ought not be used by clients at all when a proxy is being used. ought not be used by clients at all when a proxy is being used.
C.2.3. Introduction of Transfer-Encoding C.2.3. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1). HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
Transfer codings need to be decoded prior to forwarding an HTTP Transfer codings need to be decoded prior to forwarding an HTTP
message over a MIME-compliant protocol. message over a MIME-compliant protocol.
skipping to change at page 50, line 45 skipping to change at page 50, line 41
document has been reduced to just the messaging syntax and connection document has been reduced to just the messaging syntax and connection
management requirements specific to HTTP/1.1. management requirements specific to HTTP/1.1.
Bare CRs have been prohibited outside of content. (Section 2.2) Bare CRs have been prohibited outside of content. (Section 2.2)
The ABNF definition of authority-form has changed from the more The ABNF definition of authority-form has changed from the more
general authority component of a URI (in which port is optional) to general authority component of a URI (in which port is optional) to
the specific host:port format that is required by CONNECT. the specific host:port format that is required by CONNECT.
(Section 3.2.3) (Section 3.2.3)
Required recipients to avoid smuggling/splitting attacks when Recipients are required to avoid smuggling/splitting attacks when
processing an ambiguous message framing. (Section 6.1) processing an ambiguous message framing. (Section 6.1)
In the ABNF for chunked extensions, re-introduced (bad) whitespace In the ABNF for chunked extensions, (bad) whitespace around ";" and
around ";" and "=". Whitespace was removed in [RFC7230], but that "=" has been reintroduced. Whitespace was removed in [RFC7230], but
change was found to break existing implementations (see [Err4667]). that change was found to break existing implementations.
(Section 7.1.1) (Section 7.1.1)
Trailer field semantics now transcend the specifics of chunked Trailer field semantics now transcend the specifics of chunked
encoding. The decoding algorithm for chunked (Section 7.1.3) has transfer coding. The decoding algorithm for chunked (Section 7.1.3)
been updated to encourage storage/forwarding of trailer fields has been updated to encourage storage/forwarding of trailer fields
separately from the header section, to only allow merging into the separately from the header section, to only allow merging into the
header section if the recipient knows the corresponding field header section if the recipient knows the corresponding field
definition permits and defines how to merge, and otherwise to discard definition permits and defines how to merge, and otherwise to discard
the trailer fields instead of merging. The trailer part is now the trailer fields instead of merging. The trailer part is now
called the trailer section to be more consistent with the header called the trailer section to be more consistent with the header
section and more distinct from a body part. (Section 7.1.2) section and more distinct from a body part. (Section 7.1.2)
Disallowed transfer coding parameters called "q" in order to avoid Transfer coding parameters called "q" are disallowed in order to
conflicts with the use of ranks in the TE header field. avoid conflicts with the use of ranks in the TE header field.
(Section 7.3) (Section 7.3)
Appendix D. Change Log Appendix D. Change Log
This section is to be removed before publishing as an RFC. This section is to be removed before publishing as an RFC.
D.1. Between RFC7230 and draft 00 See <https://www.ietf.org/archive/id/draft-ietf-httpbis-messaging-
19.html#appendix-D> for changes up to version 19 of this document.
The changes were purely editorial:
o Change boilerplate and abstract to indicate the "draft" status,
and update references to ancestor specifications.
o Adjust historical notes.
o Update links to sibling specifications.
o Replace sections listing changes from RFC 2616 by new empty
sections referring to RFC 723x.
o Remove acknowledgements specific to RFC 723x.
o Move "Acknowledgements" to the very end and make them unnumbered.
D.2. Since draft-ietf-httpbis-messaging-00
The changes in this draft are editorial, with respect to HTTP as a
whole, to move all core HTTP semantics into [HTTP]:
o Moved introduction, architecture, conformance, and ABNF extensions
from RFC 7230 (Messaging) to semantics [HTTP].
o Moved discussion of MIME differences from RFC 7231 (Semantics) to
Appendix B since they mostly cover transforming 1.1 messages.
o Moved all extensibility tips, registration procedures, and
registry tables from the IANA considerations to normative
sections, reducing the IANA considerations to just instructions
that will be removed prior to publication as an RFC.
D.3. Since draft-ietf-httpbis-messaging-01
o Cite RFC 8126 instead of RFC 5226 (<https://github.com/httpwg/
http-core/issues/75>)
o Resolved erratum 4779, no change needed here
(<https://github.com/httpwg/http-core/issues/87>,
<https://www.rfc-editor.org/errata/eid4779>)
o In Section 7, fixed prose claiming transfer parameters allow bare
names (<https://github.com/httpwg/http-core/issues/88>,
<https://www.rfc-editor.org/errata/eid4839>)
o Resolved erratum 4225, no change needed here
(<https://github.com/httpwg/http-core/issues/90>,
<https://www.rfc-editor.org/errata/eid4225>)
o Replace "response code" with "response status code"
(<https://github.com/httpwg/http-core/issues/94>,
<https://www.rfc-editor.org/errata/eid4050>)
o In Section 9.3, clarify statement about HTTP/1.0 keep-alive
(<https://github.com/httpwg/http-core/issues/96>,
<https://www.rfc-editor.org/errata/eid4205>)
o In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
(<https://github.com/httpwg/http-core/issues/101>,
<https://www.rfc-editor.org/errata/eid4667>, <https://www.rfc-
editor.org/errata/eid4825>)
o In Section 7.3, state that transfer codings should not use
parameters named "q" (<https://github.com/httpwg/http-core/
issues/15>, <https://www.rfc-editor.org/errata/eid4683>)
o In Section 7, mark coding name "trailers" as reserved in the IANA
registry (<https://github.com/httpwg/http-core/issues/108>)
D.4. Since draft-ietf-httpbis-messaging-02
o In Section 4, explain why the reason phrase should be ignored by
clients (<https://github.com/httpwg/http-core/issues/60>).
o Add Section 9.2 to explain how request/response correlation is
performed (<https://github.com/httpwg/http-core/issues/145>)
D.5. Since draft-ietf-httpbis-messaging-03
o In Section 9.2, caution against treating data on a connection as
part of a not-yet-issued request (<https://github.com/httpwg/http-
core/issues/26>)
o In Section 7, remove the predefined codings from the ABNF and make
it generic instead (<https://github.com/httpwg/http-core/
issues/66>)
o Use RFC 7405 ABNF notation for case-sensitive string constants
(<https://github.com/httpwg/http-core/issues/133>)
D.6. Since draft-ietf-httpbis-messaging-04
o In Section 7.8 of [HTTP], clarify that protocol-name is to be
matched case-insensitively (<https://github.com/httpwg/http-core/
issues/8>)
o In Section 5.2, add leading optional whitespace to obs-fold ABNF
(<https://github.com/httpwg/http-core/issues/19>,
<https://www.rfc-editor.org/errata/eid4189>)
o In Section 4, add clarifications about empty reason phrases
(<https://github.com/httpwg/http-core/issues/197>)
o Move discussion of retries from Section 9.3.1 into [HTTP]
(<https://github.com/httpwg/http-core/issues/230>)
D.7. Since draft-ietf-httpbis-messaging-05
o In Section 7.1.2, the trailer part has been renamed the trailer
section (for consistency with the header section) and trailers are
no longer merged as header fields by default, but rather can be
discarded, kept separate from header fields, or merged with header
fields only if understood and defined as being mergeable
(<https://github.com/httpwg/http-core/issues/16>)
o In Section 2.1 and related Sections, move the trailing CRLF from
the line grammars into the message format
(<https://github.com/httpwg/http-core/issues/62>)
o Moved Section 2.3 down (<https://github.com/httpwg/http-core/
issues/68>)
o In Section 7.8 of [HTTP], use 'websocket' instead of 'HTTP/2.0' in
examples (<https://github.com/httpwg/http-core/issues/112>)
o Move version non-specific text from Section 6 into semantics as
"payload" (<https://github.com/httpwg/http-core/issues/159>)
o In Section 9.8, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
D.8. Since draft-ietf-httpbis-messaging-06
o In Section 12.4, update the ALPN protocol ID for HTTP/1.1
(<https://github.com/httpwg/http-core/issues/49>)
o In Section 5, align with updates to field terminology in semantics
(<https://github.com/httpwg/http-core/issues/111>)
o In Section 7.6.1 of [HTTP], clarify that new connection options
indeed need to be registered (<https://github.com/httpwg/http-
core/issues/285>)
o In Section 1.1, reference RFC 8174 as well
(<https://github.com/httpwg/http-core/issues/303>)
D.9. Since draft-ietf-httpbis-messaging-07
o Move TE: trailers into [HTTP] (<https://github.com/httpwg/http-
core/issues/18>)
o In Section 6.3, adjust requirements for handling multiple content-
length values (<https://github.com/httpwg/http-core/issues/59>)
o Throughout, replace "effective request URI" with "target URI"
(<https://github.com/httpwg/http-core/issues/259>)
o In Section 6.1, don't claim Transfer-Encoding is supported by
HTTP/2 or later (<https://github.com/httpwg/http-core/issues/297>)
D.10. Since draft-ietf-httpbis-messaging-08
o In Section 2.2, disallow bare CRs (<https://github.com/httpwg/
http-core/issues/31>)
o Appendix A now uses the sender variant of the "#" list expansion
(<https://github.com/httpwg/http-core/issues/192>)
o In Section 5, adjust IANA "Close" entry for new registry format
(<https://github.com/httpwg/http-core/issues/273>)
D.11. Since draft-ietf-httpbis-messaging-09
o Switch to xml2rfc v3 mode for draft generation
(<https://github.com/httpwg/http-core/issues/394>)
D.12. Since draft-ietf-httpbis-messaging-10
o In Section 6.3, note that TCP half-close does not delimit a
request; talk about corresponding server-side behaviour in
Section 9.6 (<https://github.com/httpwg/http-core/issues/22>)
o Moved requirements specific to HTTP/1.1 from [HTTP] into
Section 3.2 (<https://github.com/httpwg/http-core/issues/182>)
o In Section 6.1 (Transfer-Encoding), adjust ABNF to allow empty
lists (<https://github.com/httpwg/http-core/issues/210>)
o In Section 9.7, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
o Moved definitions of "TE" and "Upgrade" into [HTTP]
(<https://github.com/httpwg/http-core/issues/392>)
o Moved definition of "Connection" into [HTTP]
(<https://github.com/httpwg/http-core/issues/407>)
D.13. Since draft-ietf-httpbis-messaging-11
o Move IANA Upgrade Token Registry instructions to [HTTP]
(<https://github.com/httpwg/http-core/issues/450>)
D.14. Since draft-ietf-httpbis-messaging-12
o Moved content of history appendix to Semantics
(<https://github.com/httpwg/http-core/issues/451>)
o Moved note about "close" being reserved as field name to
Section 9.3 (<https://github.com/httpwg/http-core/issues/500>)
o Moved table of transfer codings into Section 12.3
(<https://github.com/httpwg/http-core/issues/506>)
o In Section 13.2, updated the URI for the [Linhart] paper
(<https://github.com/httpwg/http-core/issues/517>)
o Changed document title to just "HTTP/1.1"
(<https://github.com/httpwg/http-core/issues/524>)
o In Section 7, moved transfer-coding ABNF to Section 10.1.4 of
[HTTP] (<https://github.com/httpwg/http-core/issues/531>)
o Changed to using "payload data" when defining requirements about
the data being conveyed within a message, instead of the terms
"payload body" or "response body" or "representation body", since
they often get confused with the HTTP/1.1 message body (which
includes transfer coding) (<https://github.com/httpwg/http-core/
issues/553>)
D.15. Since draft-ietf-httpbis-messaging-13
o In Section 6.3, clarify that a message needs to be checked for
both Content-Length and Transfer-Encoding, before processing
Transfer-Encoding, and that ought to be treated as an error, but
an intermediary can choose to forward the message downstream after
removing the Content-Length and processing the Transfer-Encoding
(<https://github.com/httpwg/http-core/issues/617>)
o Changed to using "content" instead of "payload" or "payload data"
to avoid confusion with the payload of version-specific messaging
frames (<https://github.com/httpwg/http-core/issues/654>)
D.16. Since draft-ietf-httpbis-messaging-14
o In Section 9.6, define the close connection option, since its
definition was removed from the Connection header field for being
specific to 1.1 (<https://github.com/httpwg/http-core/issues/678>)
o In Section 3.3, clarify how the target URI is reconstructed when
the request-target is not in absolute-form and highlight risk in
selecting a default host (<https://github.com/httpwg/http-core/
issues/722>)
o In Section 7.1, clarify large chunk handling issues
(<https://github.com/httpwg/http-core/issues/749>)
o In Section 2.2, explicitly close the connection after sending a
400 (<https://github.com/httpwg/http-core/issues/750>)
o In Section 2.3, refine version requirements for intermediaries
(<https://github.com/httpwg/http-core/issues/751>)
o In Section 7.1.3, don't remove the Trailer header field
(<https://github.com/httpwg/http-core/issues/793>)
o In Section 3.2.3, changed the ABNF definition of authority-form
from the authority component (in which port is optional) to the
host:port format that has always been required by CONNECT
(<https://github.com/httpwg/http-core/issues/806>)
D.17. Since draft-ietf-httpbis-messaging-15
o None.
D.18. Since draft-ietf-httpbis-messaging-16
This draft addresses mostly editorial issues raised during or past D.1. Since draft-ietf-httpbis-messaging-19
IETF Last Call; see <https://github.com/httpwg/http-core/
issues?q=label%3Ah1-messaging+created%3A%3E2021-05-26> for a summary.
This (unpublished) draft contains changes that were made after draft
19 was approved by the IESG. Most changes are editorial only.
Furthermore: Furthermore:
o In Section 6.1, require recipients to avoid smuggling/splitting o In Section 12.1, change status 'standard' to 'permanent'
attacks when processing an ambiguous message framing (<https://github.com/httpwg/http-core/issues/978>)
(<https://github.com/httpwg/http-core/issues/879>)
D.19. Since draft-ietf-httpbis-messaging-17
o In Section 4, rephrase text about status code definitions in
[HTTP] (<https://github.com/httpwg/http-core/issues/915>)
o In Section 9.2, clarify how to match responses to requests
(<https://github.com/httpwg/http-core/issues/915>)
o Made reference to [RFC5322] normative, as it is referenced from
the ABNF (for "From" header field) (<https://github.com/httpwg/
http-core/issues/915>)
o In Section 5.2, include text about message/http that previously
was in [HTTP] (<https://github.com/httpwg/http-core/issues/923>)
o Throughout, disambiguate "selected representation" and "selected
response" (now "chosen response") (<https://github.com/httpwg/
http-core/issues/958>)
D.20. Since draft-ietf-httpbis-messaging-18
o Improve a few crossrefs into [HTTP] (<https://github.com/httpwg/
http-core/issues/966>)
o In Section 7.1.2, improve readability of formerly overlong
sentence (<https://github.com/httpwg/http-core/issues/966>)
o Slightly rephrase Section 9.8 (<https://github.com/httpwg/http- o In Section 4, align the prose about empty reason phrases with the
core/pull/972>) current ABNF (<https://github.com/httpwg/http-core/issues/1005>)
Acknowledgements Acknowledgements
See Appendix "Acknowledgements" of [HTTP]. See Appendix "Acknowledgements" of [HTTP], which applies to this
document as well.
Index Index
A C D F G H M O R T X A C D F G H M O R T X
A A
absolute-form (of request-target) Section 3.2.2 absolute-form (of request-target) Section 3.2.2
application/http Media Type *_Section 10.2_* application/http Media Type *_Section 10.2_*
asterisk-form (of request-target) Section 3.2.4 asterisk-form (of request-target) Section 3.2.4
skipping to change at page 60, line 43 skipping to change at page 54, line 22
Roy T. Fielding (editor) Roy T. Fielding (editor)
Adobe Adobe
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
United States of America United States of America
Email: fielding@gbiv.com Email: fielding@gbiv.com
URI: https://roy.gbiv.com/ URI: https://roy.gbiv.com/
Mark Nottingham (editor) Mark Nottingham (editor)
Fastly Fastly
Prahran VIC Prahran
Australia Australia
Email: mnot@mnot.net Email: mnot@mnot.net
URI: https://www.mnot.net/ URI: https://www.mnot.net/
Julian Reschke (editor) Julian Reschke (editor)
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
48155 Münster 48155 Münster
Germany Germany
Email: julian.reschke@greenbytes.de Email: julian.reschke@greenbytes.de
URI: https://greenbytes.de/tech/webdav/ URI: https://greenbytes.de/tech/webdav/
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