< draft-ietf-httpbis-p1-messaging-23.txt   draft-ietf-httpbis-p1-messaging-24.txt >
HTTPbis Working Group R. Fielding, Ed. HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Adobe Internet-Draft Adobe
Obsoletes: 2145,2616 (if approved) J. Reschke, Ed. Obsoletes: 2145,2616 (if approved) J. Reschke, Ed.
Updates: 2817,2818 (if approved) greenbytes Updates: 2817,2818 (if approved) greenbytes
Intended status: Standards Track July 15, 2013 Intended status: Standards Track September 25, 2013
Expires: January 16, 2014 Expires: March 29, 2014
Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
draft-ietf-httpbis-p1-messaging-23 draft-ietf-httpbis-p1-messaging-24
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypertext information protocol for distributed, collaborative, hypertext information
systems. HTTP has been in use by the World Wide Web global systems. HTTP has been in use by the World Wide Web global
information initiative since 1990. This document provides an information initiative since 1990. This document provides an
overview of HTTP architecture and its associated terminology, defines overview of HTTP architecture and its associated terminology, defines
the "http" and "https" Uniform Resource Identifier (URI) schemes, the "http" and "https" Uniform Resource Identifier (URI) schemes,
defines the HTTP/1.1 message syntax and parsing requirements, and defines the HTTP/1.1 message syntax and parsing requirements, and
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Discussion of this draft takes place on the HTTPBIS working group Discussion of this draft takes place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
<http://lists.w3.org/Archives/Public/ietf-http-wg/>. <http://lists.w3.org/Archives/Public/ietf-http-wg/>.
The current issues list is at The current issues list is at
<http://tools.ietf.org/wg/httpbis/trac/report/3> and related <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
documents (including fancy diffs) can be found at documents (including fancy diffs) can be found at
<http://tools.ietf.org/wg/httpbis/>. <http://tools.ietf.org/wg/httpbis/>.
The changes in this draft are summarized in Appendix D.3. The changes in this draft are summarized in Appendix C.4.
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 January 16, 2014. This Internet-Draft will expire on March 29, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Requirement Notation . . . . . . . . . . . . . . . . . . . 6 1.1. Requirement Notation . . . . . . . . . . . . . . . . . . . 6
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 7 2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 7
2.2. Implementation Diversity . . . . . . . . . . . . . . . . . 8 2.2. Implementation Diversity . . . . . . . . . . . . . . . . . 8
2.3. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 9 2.3. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 9
2.4. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.5. Conformance and Error Handling . . . . . . . . . . . . . . 12 2.5. Conformance and Error Handling . . . . . . . . . . . . . . 12
2.6. Protocol Versioning . . . . . . . . . . . . . . . . . . . 13 2.6. Protocol Versioning . . . . . . . . . . . . . . . . . . . 14
2.7. Uniform Resource Identifiers . . . . . . . . . . . . . . . 15 2.7. Uniform Resource Identifiers . . . . . . . . . . . . . . . 16
2.7.1. http URI scheme . . . . . . . . . . . . . . . . . . . 16 2.7.1. http URI scheme . . . . . . . . . . . . . . . . . . . 17
2.7.2. https URI scheme . . . . . . . . . . . . . . . . . . . 17 2.7.2. https URI scheme . . . . . . . . . . . . . . . . . . . 18
2.7.3. http and https URI Normalization and Comparison . . . 18 2.7.3. http and https URI Normalization and Comparison . . . 19
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 19 3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 20 3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.1. Request Line . . . . . . . . . . . . . . . . . . . . . 20 3.1.1. Request Line . . . . . . . . . . . . . . . . . . . . . 21
3.1.2. Status Line . . . . . . . . . . . . . . . . . . . . . 21 3.1.2. Status Line . . . . . . . . . . . . . . . . . . . . . 22
3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 22 3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 22
3.2.1. Field Extensibility . . . . . . . . . . . . . . . . . 22 3.2.1. Field Extensibility . . . . . . . . . . . . . . . . . 23
3.2.2. Field Order . . . . . . . . . . . . . . . . . . . . . 22 3.2.2. Field Order . . . . . . . . . . . . . . . . . . . . . 23
3.2.3. Whitespace . . . . . . . . . . . . . . . . . . . . . . 23 3.2.3. Whitespace . . . . . . . . . . . . . . . . . . . . . . 24
3.2.4. Field Parsing . . . . . . . . . . . . . . . . . . . . 24 3.2.4. Field Parsing . . . . . . . . . . . . . . . . . . . . 24
3.2.5. Field Limits . . . . . . . . . . . . . . . . . . . . . 25 3.2.5. Field Limits . . . . . . . . . . . . . . . . . . . . . 26
3.2.6. Field value components . . . . . . . . . . . . . . . . 25 3.2.6. Field value components . . . . . . . . . . . . . . . . 26
3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 27 3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 27
3.3.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . 27 3.3.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . 28
3.3.2. Content-Length . . . . . . . . . . . . . . . . . . . . 29 3.3.2. Content-Length . . . . . . . . . . . . . . . . . . . . 30
3.3.3. Message Body Length . . . . . . . . . . . . . . . . . 30 3.3.3. Message Body Length . . . . . . . . . . . . . . . . . 31
3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 32 3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 33
3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 33 3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 34
4. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . . 34 4. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . . 35
4.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 34 4.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 35
4.1.1. Trailer . . . . . . . . . . . . . . . . . . . . . . . 35 4.1.1. Chunk Extensions . . . . . . . . . . . . . . . . . . . 36
4.1.2. Decoding chunked . . . . . . . . . . . . . . . . . . . 36 4.1.2. Chunked Trailer Part . . . . . . . . . . . . . . . . . 36
4.2. Compression Codings . . . . . . . . . . . . . . . . . . . 37 4.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . . 37
4.2.1. Compress Coding . . . . . . . . . . . . . . . . . . . 37 4.2. Compression Codings . . . . . . . . . . . . . . . . . . . 38
4.2.2. Deflate Coding . . . . . . . . . . . . . . . . . . . . 37 4.2.1. Compress Coding . . . . . . . . . . . . . . . . . . . 38
4.2.3. Gzip Coding . . . . . . . . . . . . . . . . . . . . . 37 4.2.2. Deflate Coding . . . . . . . . . . . . . . . . . . . . 38
4.3. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2.3. Gzip Coding . . . . . . . . . . . . . . . . . . . . . 38
5. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 38 4.3. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.1. Identifying a Target Resource . . . . . . . . . . . . . . 38 4.4. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.2. Connecting Inbound . . . . . . . . . . . . . . . . . . . . 39 5. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 40
5.3. Request Target . . . . . . . . . . . . . . . . . . . . . . 39 5.1. Identifying a Target Resource . . . . . . . . . . . . . . 40
5.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5.2. Connecting Inbound . . . . . . . . . . . . . . . . . . . . 40
5.5. Effective Request URI . . . . . . . . . . . . . . . . . . 43 5.3. Request Target . . . . . . . . . . . . . . . . . . . . . . 41
5.6. Associating a Response to a Request . . . . . . . . . . . 44 5.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.7. Message Forwarding . . . . . . . . . . . . . . . . . . . . 44 5.5. Effective Request URI . . . . . . . . . . . . . . . . . . 44
5.7.1. Via . . . . . . . . . . . . . . . . . . . . . . . . . 45 5.6. Associating a Response to a Request . . . . . . . . . . . 46
5.7.2. Transformations . . . . . . . . . . . . . . . . . . . 46 5.7. Message Forwarding . . . . . . . . . . . . . . . . . . . . 46
6. Connection Management . . . . . . . . . . . . . . . . . . . . 47 5.7.1. Via . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 48 5.7.2. Transformations . . . . . . . . . . . . . . . . . . . 48
6.2. Establishment . . . . . . . . . . . . . . . . . . . . . . 49 6. Connection Management . . . . . . . . . . . . . . . . . . . . 49
6.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 49 6.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 49
6.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 51 6.2. Establishment . . . . . . . . . . . . . . . . . . . . . . 51
6.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . . 51 6.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 51
6.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 52 6.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 52
6.5. Failures and Time-outs . . . . . . . . . . . . . . . . . . 52 6.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . . 53
6.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 53 6.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 54
6.7. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.5. Failures and Time-outs . . . . . . . . . . . . . . . . . . 54
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56 6.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 55
7.1. Header Field Registration . . . . . . . . . . . . . . . . 56 6.7. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 56
7.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 57 7. ABNF list extension: #rule . . . . . . . . . . . . . . . . . . 58
7.3. Internet Media Type Registration . . . . . . . . . . . . . 57 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59
7.3.1. Internet Media Type message/http . . . . . . . . . . . 57 8.1. Header Field Registration . . . . . . . . . . . . . . . . 59
7.3.2. Internet Media Type application/http . . . . . . . . . 58 8.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 60
7.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 60 8.3. Internet Media Type Registration . . . . . . . . . . . . . 60
7.4.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 60 8.3.1. Internet Media Type message/http . . . . . . . . . . . 61
7.4.2. Registration . . . . . . . . . . . . . . . . . . . . . 60 8.3.2. Internet Media Type application/http . . . . . . . . . 62
7.5. Upgrade Token Registry . . . . . . . . . . . . . . . . . . 61 8.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 63
7.5.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 61 8.4.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 63
7.5.2. Upgrade Token Registration . . . . . . . . . . . . . . 61 8.4.2. Registration . . . . . . . . . . . . . . . . . . . . . 63
8. Security Considerations . . . . . . . . . . . . . . . . . . . 62 8.5. Upgrade Token Registry . . . . . . . . . . . . . . . . . . 64
8.1. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 62 8.5.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 64
8.2. Intermediaries and Caching . . . . . . . . . . . . . . . . 62 8.5.2. Upgrade Token Registration . . . . . . . . . . . . . . 65
8.3. Buffer Overflows . . . . . . . . . . . . . . . . . . . . . 63 9. Security Considerations . . . . . . . . . . . . . . . . . . . 65
8.4. Message Integrity . . . . . . . . . . . . . . . . . . . . 63 9.1. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 65
8.5. Server Log Information . . . . . . . . . . . . . . . . . . 64 9.2. Intermediaries and Caching . . . . . . . . . . . . . . . . 65
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 64 9.3. Buffer Overflows . . . . . . . . . . . . . . . . . . . . . 66
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 66 9.4. Message Integrity . . . . . . . . . . . . . . . . . . . . 66
10.1. Normative References . . . . . . . . . . . . . . . . . . . 66 9.5. Server Log Information . . . . . . . . . . . . . . . . . . 67
10.2. Informative References . . . . . . . . . . . . . . . . . . 67 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 67
Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 69 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 69
A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 70 11.1. Normative References . . . . . . . . . . . . . . . . . . . 69
A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 70 11.2. Informative References . . . . . . . . . . . . . . . . . . 70
A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 70 Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 72
A.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 71 A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 73
A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 71 A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 73
Appendix B. ABNF list extension: #rule . . . . . . . . . . . . . 74 A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 73
Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 75 A.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 74
Appendix D. Change Log (to be removed by RFC Editor before A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 74
publication) . . . . . . . . . . . . . . . . . . . . 77 Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 76
D.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 77 Appendix C. Change Log (to be removed by RFC Editor before
D.2. Since draft-ietf-httpbis-p1-messaging-21 . . . . . . . . . 77 publication) . . . . . . . . . . . . . . . . . . . . 79
D.3. Since draft-ietf-httpbis-p1-messaging-22 . . . . . . . . . 79 C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 79
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 C.2. Since draft-ietf-httpbis-p1-messaging-21 . . . . . . . . . 79
C.3. Since draft-ietf-httpbis-p1-messaging-22 . . . . . . . . . 80
C.4. Since draft-ietf-httpbis-p1-messaging-23 . . . . . . . . . 82
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
request/response protocol that uses extensible semantics and self- request/response protocol that uses extensible semantics and self-
descriptive message payloads for flexible interaction with network- descriptive message payloads for flexible interaction with network-
based hypertext information systems. This document is the first in a based hypertext information systems. This document is the first in a
series of documents that collectively form the HTTP/1.1 series of documents that collectively form the HTTP/1.1
specification: specification:
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Conformance criteria and considerations regarding error handling are Conformance criteria and considerations regarding error handling are
defined in Section 2.5. defined in Section 2.5.
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] with the list rule extension defined in notation of [RFC5234] with the list rule extension defined in
Appendix B. Appendix C shows the collected ABNF with the list rule Section 7. Appendix B shows the collected ABNF with the list rule
expanded. expanded.
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).
As a convention, ABNF rule names prefixed with "obs-" denote As a convention, ABNF rule names prefixed with "obs-" denote
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(Section 3.2), an empty line to indicate the end of the header (Section 3.2), an empty line to indicate the end of the header
section, and finally a message body containing the payload body (if section, and finally a message body containing the payload body (if
any, Section 3.3). any, Section 3.3).
A connection might be used for multiple request/response exchanges, A connection might be used for multiple request/response exchanges,
as defined in Section 6.3. as defined in Section 6.3.
The following example illustrates a typical message exchange for a The following example illustrates a typical message exchange for a
GET request on the URI "http://www.example.com/hello.txt": GET request on the URI "http://www.example.com/hello.txt":
client request: Client request:
GET /hello.txt HTTP/1.1 GET /hello.txt HTTP/1.1
User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3 User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3
Host: www.example.com Host: www.example.com
Accept-Language: en, mi Accept-Language: en, mi
server response: Server response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Date: Mon, 27 Jul 2009 12:28:53 GMT Date: Mon, 27 Jul 2009 12:28:53 GMT
Server: Apache Server: Apache
Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT
ETag: "34aa387-d-1568eb00" ETag: "34aa387-d-1568eb00"
Accept-Ranges: bytes Accept-Ranges: bytes
Content-Length: 51 Content-Length: 51
Vary: Accept-Encoding Vary: Accept-Encoding
Content-Type: text/plain Content-Type: text/plain
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that would be significant to the original sender or potentially that would be significant to the original sender or potentially
significant to downstream recipients). For example, a transforming significant to downstream recipients). For example, a transforming
proxy might be acting as a shared annotation server (modifying proxy might be acting as a shared annotation server (modifying
responses to include references to a local annotation database), a responses to include references to a local annotation database), a
malware filter, a format transcoder, or an intranet-to-Internet malware filter, a format transcoder, or an intranet-to-Internet
privacy filter. Such transformations are presumed to be desired by privacy filter. Such transformations are presumed to be desired by
the client (or client organization) that selected the proxy and are the client (or client organization) that selected the proxy and are
beyond the scope of this specification. However, when a proxy is not beyond the scope of this specification. However, when a proxy is not
intended to transform a given message, we use the term "non- intended to transform a given message, we use the term "non-
transforming proxy" to target requirements that preserve HTTP message transforming proxy" to target requirements that preserve HTTP message
semantics. See Section 6.3.4 of [Part2] and Section 7.5 of [Part6] semantics. See Section 6.3.4 of [Part2] and Section 5.5 of [Part6]
for status and warning codes related to transformations. for status and warning codes related to transformations.
A "gateway" (a.k.a., "reverse proxy") is an intermediary that acts as A "gateway" (a.k.a., "reverse proxy") is an intermediary that acts as
an origin server for the outbound connection, but translates received an origin server for the outbound connection, but translates received
requests and forwards them inbound to another server or servers. requests and forwards them inbound to another server or servers.
Gateways are often used to encapsulate legacy or untrusted Gateways are often used to encapsulate legacy or untrusted
information services, to improve server performance through information services, to improve server performance through
"accelerator" caching, and to enable partitioning or load balancing "accelerator" caching, and to enable partitioning or load balancing
of HTTP services across multiple machines. of HTTP services across multiple machines.
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TCP port 80 packets (and occasionally other common port traffic). TCP port 80 packets (and occasionally other common port traffic).
Interception proxies are commonly found on public network access Interception proxies are commonly found on public network access
points, as a means of enforcing account subscription prior to points, as a means of enforcing account subscription prior to
allowing use of non-local Internet services, and within corporate allowing use of non-local Internet services, and within corporate
firewalls to enforce network usage policies. They are firewalls to enforce network usage policies. They are
indistinguishable from a man-in-the-middle attack. indistinguishable from a man-in-the-middle attack.
HTTP is defined as a stateless protocol, meaning that each request HTTP is defined as a stateless protocol, meaning that each request
message can be understood in isolation. Many implementations depend message can be understood in isolation. Many implementations depend
on HTTP's stateless design in order to reuse proxied connections or on HTTP's stateless design in order to reuse proxied connections or
dynamically load-balance requests across multiple servers. Hence, dynamically load-balance requests across multiple servers. Hence, a
servers MUST NOT assume that two requests on the same connection are server MUST NOT assume that two requests on the same connection are
from the same user agent unless the connection is secured and from the same user agent unless the connection is secured and
specific to that agent. Some non-standard HTTP extensions (e.g., specific to that agent. Some non-standard HTTP extensions (e.g.,
[RFC4559]) have been known to violate this requirement, resulting in [RFC4559]) have been known to violate this requirement, resulting in
security and interoperability problems. security and interoperability problems.
2.4. Caches 2.4. Caches
A "cache" is a local store of previous response messages and the A "cache" is a local store of previous response messages and the
subsystem that controls its message storage, retrieval, and deletion. subsystem that controls its message storage, retrieval, and deletion.
A cache stores cacheable responses in order to reduce the response A cache stores cacheable responses in order to reduce the response
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resource owners, and protocol element registrations when they apply resource owners, and protocol element registrations when they apply
beyond the scope of a single communication. beyond the scope of a single communication.
The verb "generate" is used instead of "send" where a requirement The verb "generate" is used instead of "send" where a requirement
differentiates between creating a protocol element and merely differentiates between creating a protocol element and merely
forwarding a received element downstream. forwarding a received element downstream.
An implementation is considered conformant if it complies with all of An implementation is considered conformant if it complies with all of
the requirements associated with the roles it partakes in HTTP. the requirements associated with the roles it partakes in HTTP.
Conformance applies to both the syntax and semantics of HTTP protocol Conformance includes both the syntax and semantics of HTTP protocol
elements. A sender MUST NOT generate protocol elements that convey a elements. A sender MUST NOT generate protocol elements that convey a
meaning that is known by that sender to be false. A sender MUST NOT meaning that is known by that sender to be false. A sender MUST NOT
generate protocol elements that do not match the grammar defined by generate protocol elements that do not match the grammar defined by
the ABNF rules for those protocol elements that are applicable to the the corresponding ABNF rules. Within a given message, a sender MUST
sender's role. If a received protocol element is processed, the NOT generate protocol elements or syntax alternatives that are only
recipient MUST be able to parse any value that would match the ABNF allowed to be generated by participants in other roles (i.e., a role
rules for that protocol element, excluding only those rules not that the sender does not have for that message).
applicable to the recipient's role.
When a received protocol element is parsed, the recipient MUST be
able to parse any value of reasonable length that is applicable to
the recipient's role and matches the grammar defined by the
corresponding ABNF rules. Note, however, that some received protocol
elements might not be parsed. For example, an intermediary
forwarding a message might parse a header-field into generic field-
name and field-value components, but then forward the header field
without further parsing inside the field-value.
HTTP does not have specific length limitations for many of its
protocol elements because the lengths that might be appropriate will
vary widely, depending on the deployment context and purpose of the
implementation. Hence, interoperability between senders and
recipients depends on shared expectations regarding what is a
reasonable length for each protocol element. Furthermore, what is
commonly understood to be a reasonable length for some protocol
elements has changed over the course of the past two decades of HTTP
use, and is expected to continue changing in the future.
At a minimum, a recipient MUST be able to parse and process protocol
element lengths that are at least as long as the values that it
generates for those same protocol elements in other messages. For
example, an origin server that publishes very long URI references to
its own resources needs to be able to parse and process those same
references when received as a request target.
A recipient MUST interpret a received protocol element according to
the semantics defined for it by this specification, including
extensions to this specification, unless the recipient has determined
(through experience or configuration) that the sender incorrectly
implements what is implied by those semantics. For example, an
origin server might disregard the contents of a received Accept-
Encoding header field if inspection of the User-Agent header field
indicates a specific implementation version that is known to fail on
receipt of certain content codings.
Unless noted otherwise, a recipient MAY attempt to recover a usable Unless noted otherwise, a recipient MAY attempt to recover a usable
protocol element from an invalid construct. HTTP does not define protocol element from an invalid construct. HTTP does not define
specific error handling mechanisms except when they have a direct specific error handling mechanisms except when they have a direct
impact on security, since different applications of the protocol impact on security, since different applications of the protocol
require different error handling strategies. For example, a Web require different error handling strategies. For example, a Web
browser might wish to transparently recover from a response where the browser might wish to transparently recover from a response where the
Location header field doesn't parse according to the ABNF, whereas a Location header field doesn't parse according to the ABNF, whereas a
systems control client might consider any form of error recovery to systems control client might consider any form of error recovery to
be dangerous. be dangerous.
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the recipient supports HTTP/1.1. the recipient supports HTTP/1.1.
The interpretation of a header field does not change between minor The interpretation of a header field does not change between minor
versions of the same major HTTP version, though the default behavior versions of the same major HTTP version, though the default behavior
of a recipient in the absence of such a field can change. Unless of a recipient in the absence of such a field can change. Unless
specified otherwise, header fields defined in HTTP/1.1 are defined specified otherwise, header fields defined in HTTP/1.1 are defined
for all versions of HTTP/1.x. In particular, the Host and Connection for all versions of HTTP/1.x. In particular, the Host and Connection
header fields ought to be implemented by all HTTP/1.x implementations header fields ought to be implemented by all HTTP/1.x implementations
whether or not they advertise conformance with HTTP/1.1. whether or not they advertise conformance with HTTP/1.1.
New header fields can be defined such that, when they are understood New header fields can be introduced without changing the protocol
by a recipient, they might override or enhance the interpretation of version if their defined semantics allow them to be safely ignored by
previously defined header fields. When an implementation receives an recipients that do not recognize them. Header field extensibility is
unrecognized header field, the recipient MUST ignore that header discussed in Section 3.2.1.
field for local processing regardless of the message's HTTP version.
An unrecognized header field received by a proxy MUST be forwarded
downstream unless the header field's field-name is listed in the
message's Connection header field (see Section 6.1). These
requirements allow HTTP's functionality to be enhanced without
requiring prior update of deployed intermediaries.
Intermediaries that process HTTP messages (i.e., all intermediaries Intermediaries that process HTTP messages (i.e., all intermediaries
other than those acting as tunnels) MUST send their own HTTP-version other than those acting as tunnels) MUST send their own HTTP-version
in forwarded messages. In other words, they MUST NOT blindly forward in forwarded messages. In other words, they MUST NOT blindly forward
the first line of an HTTP message without ensuring that the protocol the first line of an HTTP message without ensuring that the protocol
version in that message matches a version to which that intermediary version in that message matches a version to which that intermediary
is conformant for both the receiving and sending of messages. is conformant for both the receiving and sending of messages.
Forwarding an HTTP message without rewriting the HTTP-version might Forwarding an HTTP message without rewriting the HTTP-version might
result in communication errors when downstream recipients use the result in communication errors when downstream recipients use the
message sender's version to determine what features are safe to use message sender's version to determine what features are safe to use
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A client SHOULD send a request version equal to the highest version A client SHOULD send a request version equal to the highest version
to which the client is conformant and whose major version is no to which the client is conformant and whose major version is no
higher than the highest version supported by the server, if this is higher than the highest version supported by the server, if this is
known. A client MUST NOT send a version to which it is not known. A client MUST NOT send a version to which it is not
conformant. conformant.
A client MAY send a lower request version if it is known that the A client MAY send a lower request version if it is known that the
server incorrectly implements the HTTP specification, but only after server incorrectly implements the HTTP specification, but only after
the client has attempted at least one normal request and determined the client has attempted at least one normal request and determined
from the response status or header fields (e.g., Server) that the from the response status code or header fields (e.g., Server) that
server improperly handles higher request versions. the server improperly handles higher request versions.
A server SHOULD send a response version equal to the highest version A server SHOULD send a response version equal to the highest version
to which the server is conformant and whose major version is less to which the server is conformant and whose major version is less
than or equal to the one received in the request. A server MUST NOT than or equal to the one received in the request. A server MUST NOT
send a version to which it is not conformant. A server MAY send a send a version to which it is not conformant. A server MAY send a
505 (HTTP Version Not Supported) response if it cannot send a 505 (HTTP Version Not Supported) response if it cannot send a
response using the major version used in the client's request. response using the major version used in the client's request.
A server MAY send an HTTP/1.0 response to a request if it is known or A server MAY send an HTTP/1.0 response to a request if it is known or
suspected that the client incorrectly implements the HTTP suspected that the client incorrectly implements the HTTP
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http-URI = "http:" "//" authority path-abempty [ "?" query ] http-URI = "http:" "//" authority path-abempty [ "?" query ]
[ "#" fragment ] [ "#" fragment ]
The HTTP origin server is identified by the generic syntax's The HTTP origin server is identified by the generic syntax's
authority component, which includes a host identifier and optional authority component, which includes a host identifier and optional
TCP port ([RFC3986], Section 3.2.2). The remainder of the URI, TCP port ([RFC3986], Section 3.2.2). The remainder of the URI,
consisting of both the hierarchical path component and optional query consisting of both the hierarchical path component and optional query
component, serves as an identifier for a potential resource within component, serves as an identifier for a potential resource within
that origin server's name space. that origin server's name space.
A sender MUST NOT generate an "http" URI with an empty host
identifier. A recipient that processes such a URI reference MUST
reject it as invalid.
If the host identifier is provided as an IP address, then the origin If the host identifier is provided as an IP address, then the origin
server is any listener on the indicated TCP port at that IP address. server is any listener on the indicated TCP port at that IP address.
If host is a registered name, then that name is considered an If host is a registered name, then that name is considered an
indirect identifier and the recipient might use a name resolution indirect identifier and the recipient might use a name resolution
service, such as DNS, to find the address of a listener for that service, such as DNS, to find the address of a listener for that
host. The host MUST NOT be empty; if an "http" URI is received with host. If the port subcomponent is empty or not given, then TCP port
an empty host, then it MUST be rejected as invalid. If the port 80 is assumed (the default reserved port for WWW services).
subcomponent is empty or not given, then TCP port 80 is assumed (the
default reserved port for WWW services).
Regardless of the form of host identifier, access to that host is not Regardless of the form of host identifier, access to that host is not
implied by the mere presence of its name or address. The host might implied by the mere presence of its name or address. The host might
or might not exist and, even when it does exist, might or might not or might not exist and, even when it does exist, might or might not
be running an HTTP server or listening to the indicated port. The be running an HTTP server or listening to the indicated port. The
"http" URI scheme makes use of the delegated nature of Internet names "http" URI scheme makes use of the delegated nature of Internet names
and addresses to establish a naming authority (whatever entity has and addresses to establish a naming authority (whatever entity has
the ability to place an HTTP server at that Internet name or address) the ability to place an HTTP server at that Internet name or address)
and allows that authority to determine which names are valid and how and allows that authority to determine which names are valid and how
they might be used. they might be used.
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secured connection. Other protocols might also be used to provide secured connection. Other protocols might also be used to provide
access to "http" identified resources -- it is only the authoritative access to "http" identified resources -- it is only the authoritative
interface that is specific to TCP. interface that is specific to TCP.
The URI generic syntax for authority also includes a deprecated The URI generic syntax for authority also includes a deprecated
userinfo subcomponent ([RFC3986], Section 3.2.1) for including user userinfo subcomponent ([RFC3986], Section 3.2.1) for including user
authentication information in the URI. Some implementations make use authentication information in the URI. Some implementations make use
of the userinfo component for internal configuration of of the userinfo component for internal configuration of
authentication information, such as within command invocation authentication information, such as within command invocation
options, configuration files, or bookmark lists, even though such options, configuration files, or bookmark lists, even though such
usage might expose a user identifier or password. Senders MUST usage might expose a user identifier or password. A sender MUST NOT
exclude the userinfo subcomponent (and its "@" delimiter) when an generate the userinfo subcomponent (and its "@" delimiter) when an
"http" URI is transmitted within a message as a request target or "http" URI reference is generated within a message as a request
header field value. Recipients of an "http" URI reference SHOULD target or header field value. Before making use of an "http" URI
parse for userinfo and treat its presence as an error, since it is reference received from an untrusted source, a recipient ought to
likely being used to obscure the authority for the sake of phishing parse for userinfo and treat its presence as an error; it is likely
attacks. being used to obscure the authority for the sake of phishing attacks.
2.7.2. https URI scheme 2.7.2. https URI scheme
The "https" URI scheme is hereby defined for the purpose of minting The "https" URI scheme is hereby defined for the purpose of minting
identifiers according to their association with the hierarchical identifiers according to their association with the hierarchical
namespace governed by a potential HTTP origin server listening to a namespace governed by a potential HTTP origin server listening to a
given TCP port for TLS-secured connections ([RFC0793], [RFC5246]). given TCP port for TLS-secured connections ([RFC0793], [RFC5246]).
All of the requirements listed above for the "http" scheme are also All of the requirements listed above for the "http" scheme are also
requirements for the "https" scheme, except that a default TCP port requirements for the "https" scheme, except that a default TCP port
of 443 is assumed if the port subcomponent is empty or not given, and of 443 is assumed if the port subcomponent is empty or not given, and
the TCP connection MUST be secured, end-to-end, through the use of the user agent MUST ensure that its connection to the origin server
strong encryption prior to sending the first HTTP request. is secured through the use of strong encryption, end-to-end, prior to
sending the first HTTP request.
https-URI = "https:" "//" authority path-abempty [ "?" query ] https-URI = "https:" "//" authority path-abempty [ "?" query ]
[ "#" fragment ] [ "#" fragment ]
Note that the "https" URI scheme depends on both TLS and TCP for Note that the "https" URI scheme depends on both TLS and TCP for
establishing authority. Resources made available via the "https" establishing authority. Resources made available via the "https"
scheme have no shared identity with the "http" scheme even if their scheme have no shared identity with the "http" scheme even if their
resource identifiers indicate the same authority (the same host resource identifiers indicate the same authority (the same host
listening to the same TCP port). They are distinct name spaces and listening to the same TCP port). They are distinct name spaces and
are considered to be distinct origin servers. However, an extension are considered to be distinct origin servers. However, an extension
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CRLF CRLF
[ message-body ] [ message-body ]
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 into a hash table start-line into a structure, read each header field into a hash table
by field name until the empty line, and then use the parsed data to by field name until the empty line, and then use the parsed data to
determine if a message body is expected. If a message body has been determine if a message body is expected. If a message body has been
indicated, then it is read as a stream until an amount of octets indicated, then it is read as a stream until an amount of octets
equal to the message body length is read or the connection is closed. equal to the message body length is read or the connection is closed.
Recipients MUST parse an HTTP message as a sequence of octets in an A recipient MUST parse an HTTP message as a sequence of octets in an
encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
message as a stream of Unicode characters, without regard for the message as a stream of Unicode characters, without regard for the
specific encoding, creates security vulnerabilities due to the specific encoding, creates security vulnerabilities due to the
varying ways that string processing libraries handle invalid varying ways that string processing libraries handle invalid
multibyte character sequences that contain the octet LF (%x0A). multibyte character sequences that contain the octet LF (%x0A).
String-based parsers can only be safely used within protocol elements String-based parsers can only be safely used within protocol elements
after the element has been extracted from the message, such as within after the element has been extracted from the message, such as within
a header field-value after message parsing has delineated the a header field-value after message parsing has delineated the
individual fields. individual fields.
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incremental delivery of partial messages, since some implementations incremental delivery of partial messages, since some implementations
will buffer or delay message forwarding for the sake of network will buffer or delay message forwarding for the sake of network
efficiency, security checks, or payload transformations. efficiency, security checks, or payload transformations.
A sender MUST NOT send whitespace between the start-line and the A sender MUST NOT send whitespace between the start-line and the
first header field. A recipient that receives whitespace between the first header field. A recipient that receives whitespace between the
start-line and the first header field MUST either reject the message start-line and the first header field MUST either reject the message
as invalid or consume each whitespace-preceded line without further as invalid or consume each whitespace-preceded line without further
processing of it (i.e., ignore the entire line, along with any processing of it (i.e., ignore the entire line, along with any
subsequent lines preceded by whitespace, until a properly formed subsequent lines preceded by whitespace, until a properly formed
header field is received or the header block is terminated). header field is received or the header section is terminated).
The presence of such whitespace in a request might be an attempt to The presence of such whitespace in a request might be an attempt to
trick a server into ignoring that field or processing the line after trick a server into ignoring that field or processing the line after
it as a new request, either of which might result in a security it as a new request, either of which might result in a security
vulnerability if other implementations within the request chain vulnerability if other implementations within the request chain
interpret the same message differently. Likewise, the presence of interpret the same message differently. Likewise, the presence of
such whitespace in a response might be ignored by some clients or such whitespace in a response might be ignored by some clients or
cause others to cease parsing. cause others to cease parsing.
3.1. Start Line 3.1. Start Line
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(SP), the request-target, another single space (SP), the protocol (SP), the request-target, another single space (SP), the protocol
version, and ending with CRLF. version, and ending with CRLF.
request-line = method SP request-target SP HTTP-version CRLF request-line = method SP request-target SP HTTP-version CRLF
The method token indicates the request method to be performed on the The method token indicates the request method to be performed on the
target resource. The request method is case-sensitive. target resource. The request method is case-sensitive.
method = token method = token
The methods defined by this specification can be found in Section 4 The request methods defined by this specification can be found in
of [Part2], along with information regarding the HTTP method registry Section 4 of [Part2], along with information regarding the HTTP
and considerations for defining new methods. method registry and considerations for defining new methods.
The request-target identifies the target resource upon which to apply The request-target identifies the target resource upon which to apply
the request, as defined in Section 5.3. the request, as defined in Section 5.3.
Recipients typically parse the request-line into its component parts Recipients typically parse the request-line into its component parts
by splitting on whitespace (see Section 3.5), since no whitespace is by splitting on whitespace (see Section 3.5), since no whitespace is
allowed in the three components. Unfortunately, some user agents allowed in the three components. Unfortunately, some user agents
fail to properly encode or exclude whitespace found in hypertext fail to properly encode or exclude whitespace found in hypertext
references, resulting in those disallowed characters being sent in a references, resulting in those disallowed characters being sent in a
request-target. request-target.
Recipients of an invalid request-line SHOULD respond with either a Recipients of an invalid request-line SHOULD respond with either a
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. Recipients 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.
HTTP does not place a pre-defined limit on the length of a request- HTTP does not place a pre-defined limit on the length of a request-
line. A server that receives a method longer than any that it line. A server that receives a method longer than any that it
implements SHOULD respond with a 501 (Not Implemented) status code. implements SHOULD respond with a 501 (Not Implemented) status code.
A server MUST be prepared to receive URIs of unbounded length and A server ought to be prepared to receive URIs of unbounded length, as
respond with the 414 (URI Too Long) status code if the received described in Section 2.5, and MUST respond with a 414 (URI Too Long)
request-target would be longer than the server wishes to handle (see status code if the received request-target is longer than the server
Section 6.5.12 of [Part2]). wishes to parse (see Section 6.5.12 of [Part2]).
Various ad-hoc limitations on request-line length are found in Various ad-hoc limitations on request-line length are found in
practice. It is RECOMMENDED that all HTTP senders and recipients practice. It is RECOMMENDED that all HTTP senders and recipients
support, at a minimum, request-line lengths of 8000 octets. support, at a minimum, request-line lengths of 8000 octets.
3.1.2. Status Line 3.1.2. 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, another
space, a possibly-empty textual phrase describing the status code, space, a possibly-empty textual phrase describing the status code,
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; obsolete line folding ; obsolete line folding
; see Section 3.2.4 ; see Section 3.2.4
The field-name token labels the corresponding field-value as having The field-name token labels the corresponding field-value as having
the semantics defined by that header field. For example, the Date the semantics defined by that header field. For example, the Date
header field is defined in Section 7.1.1.2 of [Part2] as containing header field is defined in Section 7.1.1.2 of [Part2] as containing
the origination timestamp for the message in which it appears. the origination timestamp for the message in which it appears.
3.2.1. Field Extensibility 3.2.1. Field Extensibility
HTTP header fields are fully extensible: there is no limit on the Header fields are fully extensible: there is no limit on the
introduction of new field names, each presumably defining new introduction of new field names, each presumably defining new
semantics, nor on the number of header fields used in a given semantics, nor on the number of header fields used in a given
message. Existing fields are defined in each part of this message. Existing fields are defined in each part of this
specification and in many other specifications outside the core specification and in many other specifications outside the core
standard. New header fields can be introduced without changing the standard.
protocol version if their defined semantics allow them to be safely
ignored by recipients that do not recognize them.
New HTTP header fields ought to be registered with IANA in the New header fields can be defined such that, when they are understood
by a recipient, they might override or enhance the interpretation of
previously defined header fields, define preconditions on request
evaluation, or refine the meaning of responses.
A proxy MUST forward unrecognized header fields unless the field-name
is listed in the Connection header field (Section 6.1) or the proxy
is specifically configured to block, or otherwise transform, such
fields. Other recipients SHOULD ignore unrecognized header fields.
These requirements allow HTTP's functionality to be enhanced without
requiring prior update of deployed intermediaries.
All defined header fields ought to be registered with IANA in the
Message Header Field Registry, as described in Section 8.3 of Message Header Field Registry, as described in Section 8.3 of
[Part2]. A proxy MUST forward unrecognized header fields unless the [Part2].
field-name is listed in the Connection header field (Section 6.1) or
the proxy is specifically configured to block, or otherwise
transform, such fields. Other recipients SHOULD ignore unrecognized
header fields.
3.2.2. Field Order 3.2.2. Field Order
The order in which header fields with differing field names are The order in which header fields with differing field names are
received is not significant. However, it is "good practice" to send received is not significant. However, it is "good practice" to send
header fields that contain control data first, such as Host on header fields that contain control data first, such as Host on
requests and Date on responses, so that implementations can decide requests and Date on responses, so that implementations can decide
when not to handle a message as early as possible. A server MUST when not to handle a message as early as possible. A server MUST
wait until the entire header section is received before interpreting wait until the entire header section is received before interpreting
a request message, since later header fields might include a request message, since later header fields might include
conditionals, authentication credentials, or deliberately misleading conditionals, authentication credentials, or deliberately misleading
duplicate header fields that would impact request processing. duplicate header fields that would impact request processing.
A sender MUST NOT generate multiple header fields with the same field A sender MUST NOT generate multiple header fields with the same field
name in a message unless either the entire field value for that name in a message unless either the entire field value for that
header field is defined as a comma-separated list [i.e., #(values)] header field is defined as a comma-separated list [i.e., #(values)]
or the header field is a well-known exception (as noted below). or the header field is a well-known exception (as noted below).
Multiple header fields with the same field name can be combined into A recipient MAY combine multiple header fields with the same field
one "field-name: field-value" pair, without changing the semantics of name into one "field-name: field-value" pair, without changing the
the message, by appending each subsequent field value to the combined semantics of the message, by appending each subsequent field value to
field value in order, separated by a comma. The order in which the combined field value in order, separated by a comma. The order
header fields with the same field name are received is therefore in which header fields with the same field name are received is
significant to the interpretation of the combined field value; a therefore significant to the interpretation of the combined field
proxy MUST NOT change the order of these field values when forwarding value; a proxy MUST NOT change the order of these field values when
a message. forwarding a message.
Note: In practice, the "Set-Cookie" header field ([RFC6265]) often Note: In practice, the "Set-Cookie" header field ([RFC6265]) often
appears multiple times in a response message and does not use the appears multiple times in a response message and does not use the
list syntax, violating the above requirements on multiple header list syntax, violating the above requirements on multiple header
fields with the same name. Since it cannot be combined into a fields with the same name. Since it cannot be combined into a
single field-value, recipients ought to handle "Set-Cookie" as a single field-value, recipients ought to handle "Set-Cookie" as a
special case while processing header fields. (See Appendix A.2.3 special case while processing header fields. (See Appendix A.2.3
of [Kri2001] for details.) of [Kri2001] for details.)
3.2.3. Whitespace 3.2.3. Whitespace
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A recipient of field-content containing multiple sequential octets of A recipient of field-content containing multiple sequential octets of
optional (OWS) or required (RWS) whitespace SHOULD either replace the optional (OWS) or required (RWS) whitespace SHOULD either replace the
sequence with a single SP or transform any non-SP octets in the sequence with a single SP or transform any non-SP octets in the
sequence to SP octets before interpreting the field value or sequence to SP octets before interpreting the field value or
forwarding the message downstream. forwarding the message downstream.
Historically, HTTP header field values could be extended over Historically, HTTP header field values could be extended over
multiple lines by preceding each extra line with at least one space multiple lines by preceding each extra line with at least one space
or horizontal tab (obs-fold). This specification deprecates such or horizontal tab (obs-fold). This specification deprecates such
line folding except within the message/http media type line folding except within the message/http media type
(Section 7.3.1). Senders MUST NOT generate messages that include (Section 8.3.1). A sender MUST NOT generate a message that includes
line folding (i.e., that contain any field-value that contains a line folding (i.e., that has any field-value that contains a match to
match to the obs-fold rule) unless the message is intended for the obs-fold rule) unless the message is intended for packaging
packaging within the message/http media type. within 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
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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 obs- not within a message/http container MUST replace each received obs-
fold with one or more SP octets prior to interpreting the field fold with one or more SP octets prior to interpreting the field
value. value.
Historically, HTTP has allowed field content with text in the ISO- Historically, HTTP has allowed field content with text in the ISO-
8859-1 [ISO-8859-1] charset, supporting other charsets only through 8859-1 [ISO-8859-1] charset, supporting other charsets only through
use of [RFC2047] encoding. In practice, most HTTP header field use of [RFC2047] encoding. In practice, most HTTP header field
values use only a subset of the US-ASCII charset [USASCII]. Newly values use only a subset of the US-ASCII charset [USASCII]. Newly
defined header fields SHOULD limit their field values to US-ASCII defined header fields SHOULD limit their field values to US-ASCII
octets. Recipients SHOULD treat other octets in field content (obs- octets. A recipient SHOULD treat other octets in field content (obs-
text) as opaque data. text) as opaque data.
3.2.5. Field Limits 3.2.5. Field Limits
HTTP does not place a pre-defined limit on the length of each header HTTP does not place a pre-defined limit on the length of each header
field or on the length of the header block as a whole. Various ad- field or on the length of the header section as a whole, as described
hoc limitations on individual header field length are found in in Section 2.5. Various ad-hoc limitations on individual header
practice, often depending on the specific field semantics. field length are found in practice, often depending on the specific
field semantics.
A server MUST be prepared to receive request header fields of A server ought to be prepared to receive request header fields of
unbounded length and respond with an appropriate 4xx (Client Error) unbounded length and MUST respond with an appropriate 4xx (Client
status code if the received header field(s) are larger than the Error) status code if the received header field(s) are larger than
server wishes to process. the server wishes to process.
A client MUST be prepared to receive response header fields of A client ought to be prepared to receive response header fields of
unbounded length. A client MAY discard or truncate received header unbounded length. A client MAY discard or truncate received header
fields that are larger than the client wishes to process if the field fields that are larger than the client wishes to process if the field
semantics are such that the dropped value(s) can be safely ignored semantics are such that the dropped value(s) can be safely ignored
without changing the response semantics. without changing the message framing or response semantics.
3.2.6. Field value components 3.2.6. Field value components
Many HTTP header field values consist of words (token or quoted- Many HTTP header field values consist of words (token or quoted-
string) separated by whitespace or special characters. These special string) separated by whitespace or special characters.
characters MUST be in a quoted string to be used within a parameter
value (as defined in Section 4).
word = token / quoted-string word = token / quoted-string
token = 1*tchar token = 1*tchar
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/ "+" / "-" / "." / "^" / "_" / "`" / "|" / "~" / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/ DIGIT / ALPHA / DIGIT / ALPHA
; any VCHAR, except special ; any VCHAR, except special
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The backslash octet ("\") can be used as a single-octet quoting The backslash octet ("\") can be used as a single-octet quoting
mechanism within quoted-string constructs: mechanism within quoted-string constructs:
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text ) quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
Recipients that process the value of a quoted-string MUST handle a Recipients that process the value of a quoted-string MUST handle a
quoted-pair as if it were replaced by the octet following the quoted-pair as if it were replaced by the octet following the
backslash. backslash.
Senders SHOULD NOT generate a quoted-pair in a quoted-string except A sender SHOULD NOT generate a quoted-pair in a quoted-string except
where necessary to quote DQUOTE and backslash octets occurring within where necessary to quote DQUOTE and backslash octets occurring within
that string. that string.
Comments can be included in some HTTP header fields by surrounding Comments can be included in some HTTP header fields by surrounding
the comment text with parentheses. Comments are only allowed in the comment text with parentheses. Comments are only allowed in
fields containing "comment" as part of their field value definition. fields containing "comment" as part of their field value definition.
comment = "(" *( ctext / quoted-cpair / comment ) ")" comment = "(" *( ctext / quoted-cpair / comment ) ")"
ctext = HTAB / SP / %x21-27 / %x2A-5B / %x5D-7E / obs-text ctext = HTAB / SP / %x21-27 / %x2A-5B / %x5D-7E / obs-text
The backslash octet ("\") can be used as a single-octet quoting The backslash octet ("\") can be used as a single-octet quoting
mechanism within comment constructs: mechanism within comment constructs:
quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text ) quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text )
Senders SHOULD NOT escape octets in comments that do not require A sender SHOULD NOT escape octets in comments that do not require
escaping (i.e., other than the backslash octet "\" and the escaping (i.e., other than the backslash octet "\" and the
parentheses "(" and ")"). parentheses "(" and ")").
3.3. Message Body 3.3. Message Body
The message body (if any) of an HTTP message is used to carry the The message body (if any) of an HTTP message is used to carry the
payload body of that request or response. The message body is payload body of that request or response. The message body is
identical to the payload body unless a transfer coding has been identical to the payload body unless a transfer coding has been
applied, as described in Section 3.3.1. applied, as described in Section 3.3.1.
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Transfer-Encoding is analogous to the Content-Transfer-Encoding field Transfer-Encoding is analogous to the Content-Transfer-Encoding field
of MIME, which was designed to enable safe transport of binary data of MIME, which was designed to enable safe transport of binary data
over a 7-bit transport service ([RFC2045], Section 6). However, safe over a 7-bit transport service ([RFC2045], Section 6). However, safe
transport has a different focus for an 8bit-clean transfer protocol. transport has a different focus for an 8bit-clean transfer protocol.
In HTTP's case, Transfer-Encoding is primarily intended to accurately In HTTP's case, Transfer-Encoding is primarily intended to accurately
delimit a dynamically generated payload and to distinguish payload delimit a dynamically generated payload and to distinguish payload
encodings that are only applied for transport efficiency or security encodings that are only applied for transport efficiency or security
from those that are characteristics of the selected resource. from those that are characteristics of the selected resource.
All HTTP/1.1 recipients MUST implement the chunked transfer coding A recipient MUST be able to parse the chunked transfer coding
(Section 4.1) because it plays a crucial role in framing messages (Section 4.1) because it plays a crucial role in framing messages
when the payload body size is not known in advance. If chunked is when the payload body size is not known in advance. A sender MUST
applied to a payload body, the sender MUST NOT apply chunked more NOT apply chunked more than once to a message body (i.e., chunking an
than once (i.e., chunking an already chunked message is not allowed). already chunked message is not allowed). If any transfer coding
If any transfer coding is applied to a request payload body, the other than chunked is applied to a request payload body, the sender
sender MUST apply chunked as the final transfer coding to ensure that MUST apply chunked as the final transfer coding to ensure that the
the message is properly framed. If any transfer coding is applied to message is properly framed. If any transfer coding other than
a response payload body, the sender MUST either apply chunked as the chunked is applied to a response payload body, the sender MUST either
final transfer coding or terminate the message by closing the apply chunked as the final transfer coding or terminate the message
connection. by closing the connection.
For example, For example,
Transfer-Encoding: gzip, chunked Transfer-Encoding: gzip, chunked
indicates that the payload body has been compressed using the gzip indicates that the payload body has been compressed using the gzip
coding and then chunked using the chunked coding while forming the coding and then chunked using the chunked coding while forming the
message body. message body.
Unlike Content-Encoding (Section 3.1.2.1 of [Part2]), Transfer- Unlike Content-Encoding (Section 3.1.2.1 of [Part2]), Transfer-
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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 4.1 of [Part4]) to a GET 304 (Not Modified) response (Section 4.1 of [Part4]) 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
the origin server would have applied a transfer coding to the message the origin server would have applied a transfer coding to the message
body if the request had been an unconditional GET. This indication body if the request had been an unconditional GET. This indication
is not required, however, because any recipient on the response chain is not required, however, because any recipient on the response chain
(including the origin server) can remove transfer codings when they (including the origin server) can remove transfer codings when they
are not needed. are not needed.
A server MUST NOT send a Transfer-Encoding header field in any
response with a status code of 1xx (Informational) or 204 (No
Content). A server MUST NOT send a Transfer-Encoding header field in
any 2xx (Successful) response to a CONNECT request (Section 4.3.6 of
[Part2]).
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 a transfer-encoded payload. A client MUST understand how to process a transfer-encoded payload. A client MUST
NOT send a request containing Transfer-Encoding unless it knows the NOT send a request containing Transfer-Encoding unless it knows the
server will handle HTTP/1.1 (or later) requests; such knowledge might server will handle HTTP/1.1 (or later) requests; such knowledge might
be in the form of specific user configuration or by remembering the be in the form of specific user configuration or by remembering the
version of a prior received response. A server MUST NOT send a version of a prior received response. A server MUST NOT send a
response containing Transfer-Encoding unless the corresponding response containing Transfer-Encoding unless the corresponding
request indicates HTTP/1.1 (or later). request indicates HTTP/1.1 (or later).
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A server MAY send a Content-Length header field in a 304 (Not A server MAY send a Content-Length header field in a 304 (Not
Modified) response to a conditional GET request (Section 4.1 of Modified) response to a conditional GET request (Section 4.1 of
[Part4]); a server MUST NOT send Content-Length in such a response [Part4]); a server MUST NOT send Content-Length in such a response
unless its field-value equals the decimal number of octets that would unless its field-value equals the decimal number of octets that would
have been sent in the payload body of a 200 (OK) response to the same have been sent in the payload body of a 200 (OK) response to the same
request. request.
A server MUST NOT send a Content-Length header field in any response A server MUST NOT send a Content-Length header field in any response
with a status code of 1xx (Informational) or 204 (No Content). A with a status code of 1xx (Informational) or 204 (No Content). A
server SHOULD NOT send a Content-Length header field in any 2xx server MUST NOT send a Content-Length header field in any 2xx
(Successful) response to a CONNECT request (Section 4.3.6 of (Successful) response to a CONNECT request (Section 4.3.6 of
[Part2]). [Part2]).
Aside from the cases defined above, in the absence of Transfer- Aside from the cases defined above, in the absence of Transfer-
Encoding, an origin server SHOULD send a Content-Length header field Encoding, an origin server SHOULD send a Content-Length header field
when the payload body size is known prior to sending the complete when the payload body size is known prior to sending the complete
header block. This will allow downstream recipients to measure header section. This will allow downstream recipients to measure
transfer progress, know when a received message is complete, and transfer progress, know when a received message is complete, and
potentially reuse the connection for additional requests. potentially reuse the connection for additional requests.
Any Content-Length field value greater than or equal to zero is Any Content-Length field value greater than or equal to zero is
valid. Since there is no predefined limit to the length of a valid. Since there is no predefined limit to the length of a
payload, recipients SHOULD anticipate potentially large decimal payload, a recipient SHOULD anticipate potentially large decimal
numerals and prevent parsing errors due to integer conversion numerals and prevent parsing errors due to integer conversion
overflows (Section 8.3). overflows (Section 9.3).
If a message is received that has multiple Content-Length header If a message is received that has multiple Content-Length header
fields with field-values consisting of the same decimal value, or a fields with field-values consisting of the same decimal value, or a
single Content-Length header field with a field value containing a single Content-Length header field with a field value containing a
list of identical decimal values (e.g., "Content-Length: 42, 42"), list of identical decimal values (e.g., "Content-Length: 42, 42"),
indicating that duplicate Content-Length header fields have been indicating that duplicate Content-Length header fields have been
generated or combined by an upstream message processor, then the generated or combined by an upstream message processor, then the
recipient MUST either reject the message as invalid or replace the recipient MUST either reject the message as invalid or replace the
duplicated field-values with a single valid Content-Length field duplicated field-values with a single valid Content-Length field
containing that decimal value prior to determining the message body containing that decimal value prior to determining the message body
length. length or forwarding the message.
Note: HTTP's use of Content-Length for message framing differs Note: HTTP's use of Content-Length for message framing differs
significantly from the same field's use in MIME, where it is an significantly from the same field's use in MIME, where it is an
optional field used only within the "message/external-body" media- optional field used only within the "message/external-body" media-
type. type.
3.3.3. Message Body Length 3.3.3. Message Body Length
The length of a message body is determined by one of the following The length of a message body is determined by one of the following
(in order of precedence): (in order of precedence):
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Content-Length header field, the Transfer-Encoding overrides the Content-Length header field, the Transfer-Encoding overrides the
Content-Length. Such a message might indicate an attempt to Content-Length. Such a message might indicate an attempt to
perform request or response smuggling (bypass of security-related perform request or response smuggling (bypass of security-related
checks on message routing or content) and thus ought to be checks on message routing or content) and thus ought to be
handled as an error. A sender MUST remove the received Content- handled as an error. A sender MUST remove the received Content-
Length field prior to forwarding such a message downstream. Length field prior to forwarding such a message downstream.
4. If a message is received without Transfer-Encoding and with 4. If a message is received without Transfer-Encoding and with
either multiple Content-Length header fields having differing either multiple Content-Length header fields having differing
field-values or a single Content-Length header field having an field-values or a single Content-Length header field having an
invalid value, then the message framing is invalid and MUST be invalid value, then the message framing is invalid and the
treated as an error to prevent request or response smuggling. If recipient MUST treat it as an unrecoverable error to prevent
this is a request message, the server MUST respond with a 400 request or response smuggling. If this is a request message, the
(Bad Request) status code and then close the connection. If this server MUST respond with a 400 (Bad Request) status code and then
is a response message received by a proxy, the proxy MUST close close the connection. If this is a response message received by
the connection to the server, discard the received response, and a proxy, the proxy MUST close the connection to the server,
send a 502 (Bad Gateway) response to the client. If this is a discard the received response, and send a 502 (Bad Gateway)
response message received by a user agent, it MUST be treated as response to the client. If this is a response message received
an error by discarding the message and closing the connection. by a user agent, the user agent MUST close the connection to the
server and discard the received response.
5. If a valid Content-Length header field is present without 5. If a valid Content-Length header field is present without
Transfer-Encoding, its decimal value defines the expected message Transfer-Encoding, its decimal value defines the expected message
body length in octets. If the sender closes the connection or body length in octets. If the sender closes the connection or
the recipient times out before the indicated number of octets are the recipient times out before the indicated number of octets are
received, the recipient MUST consider the message to be received, the recipient MUST consider the message to be
incomplete and close the connection. incomplete and close the connection.
6. If this is a request message and none of the above are true, then 6. If this is a request message and none of the above are true, then
the message body length is zero (no message body is present). the message body length is zero (no message body is present).
7. Otherwise, this is a response message without a declared message 7. Otherwise, this is a response message without a declared message
body length, so the message body length is determined by the body length, so the message body length is determined by the
number of octets received prior to the server closing the number of octets received prior to the server closing the
connection. connection.
Since there is no way to distinguish a successfully completed, close- Since there is no way to distinguish a successfully completed, close-
delimited message from a partially-received message interrupted by delimited message from a partially-received message interrupted by
network failure, a server SHOULD use encoding or length-delimited network failure, a server SHOULD generate encoding or length-
messages whenever possible. The close-delimiting feature exists delimited messages whenever possible. The close-delimiting feature
primarily for backwards compatibility with HTTP/1.0. exists primarily for backwards compatibility with HTTP/1.0.
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.
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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 time-out exception, MAY send an a canceled request or a triggered time-out 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 [Part6]. in Section 3 of [Part6].
If a response terminates in the middle of the header block (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
if the size of the message body received (in octets) is less than the if the size of the message body received (in octets) is less than the
value given by Content-Length. A response that has neither chunked value given by Content-Length. A response that has neither chunked
transfer coding nor Content-Length is terminated by closure of the transfer coding nor Content-Length is terminated by closure of the
connection, and thus is considered complete regardless of the number connection, and thus is considered complete regardless of the number
of message body octets received, provided that the header block was of message body octets received, provided that the header section was
received intact. received intact.
3.5. Message Parsing Robustness 3.5. Message Parsing Robustness
Older HTTP/1.0 user agent implementations might send an extra CRLF Older HTTP/1.0 user agent implementations might send an extra CRLF
after a POST request as a workaround for some early server after a POST request as a workaround for some early server
applications that failed to read message body content that was not applications that failed to read message body content that was not
terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
or follow a request with an extra CRLF. If terminating the request or follow a request with an extra CRLF. If terminating the request
message body with a line-ending is desired, then the user agent MUST message body with a line-ending is desired, then the user agent MUST
count the terminating CRLF octets as part of the message body length. count the terminating CRLF octets as part of the message body length.
In the interest of robustness, servers SHOULD ignore at least one In the interest of robustness, a server that is expecting to receive
empty line received where a request-line is expected. In other and parse a request-line SHOULD ignore at least one empty line (CRLF)
words, if a server is reading the protocol stream at the beginning of received prior to the request-line.
a message and receives a CRLF first, the server SHOULD ignore the
CRLF.
Although the line terminator for the start-line and header fields is Although the line terminator for the start-line and header fields is
the sequence CRLF, recipients MAY recognize a single LF as a line the sequence CRLF, a recipient MAY recognize a single LF as a line
terminator and ignore any preceding CR. terminator and ignore any preceding CR.
Although the request-line and status-line grammar rules require that Although the request-line and status-line grammar rules require that
each of the component elements be separated by a single SP octet, each of the component elements be separated by a single SP octet,
recipients MAY instead parse on whitespace-delimited word boundaries recipients MAY instead parse on whitespace-delimited word boundaries
and, aside from the CRLF terminator, treat any form of whitespace as and, aside from the CRLF terminator, treat any form of whitespace as
the SP separator while ignoring preceding or trailing whitespace; the SP separator while ignoring preceding or trailing whitespace;
such whitespace includes one or more of the following octets: SP, such whitespace includes one or more of the following octets: SP,
HTAB, VT (%x0B), FF (%x0C), or bare CR. HTAB, VT (%x0B), FF (%x0C), or bare CR.
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transfer-extension = token *( OWS ";" OWS transfer-parameter ) transfer-extension = token *( OWS ";" OWS transfer-parameter )
Parameters are in the form of attribute/value pairs. Parameters are in the form of attribute/value pairs.
transfer-parameter = attribute BWS "=" BWS value transfer-parameter = attribute BWS "=" BWS value
attribute = token attribute = token
value = word value = word
All transfer-coding names are case-insensitive and ought to be All transfer-coding names are case-insensitive and ought to be
registered within the HTTP Transfer Coding registry, as defined in registered within the HTTP Transfer Coding registry, as defined in
Section 7.4. They are used in the TE (Section 4.3) and Transfer- Section 8.4. They are used in the TE (Section 4.3) and Transfer-
Encoding (Section 3.3.1) header fields. Encoding (Section 3.3.1) header fields.
4.1. Chunked Transfer Coding 4.1. Chunked Transfer Coding
The chunked transfer coding modifies the body of a message in order The chunked transfer coding wraps the payload body in order to
to transfer it as a series of chunks, each with its own size transfer it as a series of chunks, each with its own size indicator,
indicator, followed by an OPTIONAL trailer containing header fields. followed by an OPTIONAL trailer containing header fields. Chunked
This allows dynamically generated content to be transferred along enables content streams of unknown size to be transferred as a
with the information necessary for the recipient to verify that it sequence of length-delimited buffers, which enables the sender to
has received the full message. retain connection persistence and the recipient to know when it has
received the entire message.
chunked-body = *chunk chunked-body = *chunk
last-chunk last-chunk
trailer-part trailer-part
CRLF CRLF
chunk = chunk-size [ chunk-ext ] CRLF chunk = chunk-size [ chunk-ext ] CRLF
chunk-data CRLF chunk-data CRLF
chunk-size = 1*HEXDIG chunk-size = 1*HEXDIG
last-chunk = 1*("0") [ chunk-ext ] CRLF last-chunk = 1*("0") [ chunk-ext ] CRLF
chunk-data = 1*OCTET ; a sequence of chunk-size octets
The chunk-size field is a string of hex digits indicating the size of
the chunk-data in octets. The chunked transfer coding is complete
when a chunk with a chunk-size of zero is received, possibly followed
by a trailer, and finally terminated by an empty line.
A recipient MUST be able to parse and decode the chunked transfer
coding.
4.1.1. Chunk Extensions
The chunked encoding allows each chunk to include zero or more chunk
extensions, immediately following the chunk-size, for the sake of
supplying per-chunk metadata (such as a signature or hash), mid-
message control information, or randomization of message body size.
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-str-nf chunk-ext-val = token / quoted-str-nf
chunk-data = 1*OCTET ; a sequence of chunk-size octets
trailer-part = *( header-field CRLF )
quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
; like quoted-string, but disallowing line folding ; like quoted-string, but disallowing line folding
qdtext-nf = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text qdtext-nf = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
Chunk extensions within the chunked transfer coding are deprecated. The chunked encoding is specific to each connection and is likely to
Senders SHOULD NOT send chunk-ext. Definition of new chunk be removed or recoded by each recipient (including intermediaries)
extensions is discouraged. before any higher-level application would have a chance to inspect
the extensions. Hence, use of chunk extensions is generally limited
to specialized HTTP services such as "long polling" (where client and
server can have shared expectations regarding the use of chunk
extensions) or for padding within an end-to-end secured connection.
The chunk-size field is a string of hex digits indicating the size of A recipient MUST ignore unrecognized chunk extensions. A server
the chunk-data in octets. The chunked transfer coding is complete ought to limit the total length of chunk extensions received in a
when a chunk with a chunk-size of zero is received, possibly followed request to an amount reasonable for the services provided, in the
by a trailer, and finally terminated by an empty line. same way that it applies length limitations and timeouts for other
parts of a message, and generate an appropriate 4xx (Client Error)
response if that amount is exceeded.
4.1.1. Trailer 4.1.2. Chunked Trailer Part
A trailer allows the sender to include additional fields at the end A trailer allows the sender to include additional fields at the end
of a chunked message in order to supply metadata that might be of a chunked message in order to supply metadata that might be
dynamically generated while the message body is sent, such as a dynamically generated while the message body is sent, such as a
message integrity check, digital signature, or post-processing message integrity check, digital signature, or post-processing
status. The trailer MUST NOT contain fields that need to be known status. The trailer fields are identical to header fields, except
before a recipient processes the body, such as Transfer-Encoding, they are sent in a chunked trailer instead of the message's header
Content-Length, and Trailer. section.
When a message includes a message body encoded with the chunked
transfer coding and the sender desires to send metadata in the form
of trailer fields at the end of the message, the sender SHOULD send a
Trailer header field before the message body to indicate which fields
will be present in the trailers. This allows the recipient to
prepare for receipt of that metadata before it starts processing the
body, which is useful if the message is being streamed and the
recipient wishes to confirm an integrity check on the fly.
Trailer = 1#field-name trailer-part = *( header-field CRLF )
If no Trailer header field is present, the sender of a chunked A sender MUST NOT generate a trailer that contains a field which
message body SHOULD send an empty trailer. needs to be known by the recipient before it can begin processing the
message body. For example, most recipients need to know the values
of Content-Encoding and Content-Type in order to select a content
handler, so placing those fields in a trailer would force the
recipient to buffer the entire body before it could begin, greatly
increasing user-perceived latency and defeating one of the main
advantages of using chunked to send data streams of unknown length.
A sender MUST NOT generate a trailer containing a Transfer-Encoding,
Content-Length, or Trailer field.
A server MUST send an empty trailer with the chunked transfer coding A server MUST generate an empty trailer with the chunked transfer
unless at least one of the following is true: coding unless at least one of the following is true:
1. the request included a TE header field that indicates "trailers" 1. the request included a TE header field that indicates "trailers"
is acceptable in the transfer coding of the response, as is acceptable in the transfer coding of the response, as
described in Section 4.3; or, described in Section 4.3; or,
2. the trailer fields consist entirely of optional metadata and the 2. the trailer fields consist entirely of optional metadata and the
recipient could use the message (in a manner acceptable to the recipient could use the message (in a manner acceptable to the
server where the field originated) without receiving that generating server) without receiving that metadata. In other
metadata. In other words, the server that generated the header words, the generating server is willing to accept the possibility
field is willing to accept the possibility that the trailer that the trailer fields might be silently discarded along the
fields might be silently discarded along the path to the client. path to the client.
The above requirement prevents the need for an infinite buffer when a The above requirement prevents the need for an infinite buffer when a
message is being received by an HTTP/1.1 (or later) proxy and message is being received by an HTTP/1.1 (or later) proxy and
forwarded to an HTTP/1.0 recipient. forwarded to an HTTP/1.0 recipient.
4.1.2. Decoding chunked 4.1.3. Decoding Chunked
A process for decoding the chunked transfer coding can be represented A process for decoding the chunked transfer coding can be represented
in pseudo-code as: in pseudo-code as:
length := 0 length := 0
read chunk-size, chunk-ext (if any), and CRLF read chunk-size, chunk-ext (if any), and CRLF
while (chunk-size > 0) { while (chunk-size > 0) {
read chunk-data and CRLF read chunk-data and CRLF
append chunk-data to decoded-body append chunk-data to decoded-body
length := length + chunk-size length := length + chunk-size
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} }
read header-field read header-field
while (header-field not empty) { while (header-field not empty) {
append header-field to existing header fields append header-field to existing header fields
read header-field read header-field
} }
Content-Length := length Content-Length := length
Remove "chunked" from Transfer-Encoding Remove "chunked" from Transfer-Encoding
Remove Trailer from existing header fields Remove Trailer from existing header fields
All recipients MUST be able to receive and decode the chunked
transfer coding and MUST ignore chunk-ext extensions they do not
understand.
4.2. Compression Codings 4.2. Compression Codings
The codings defined below can be used to compress the payload of a The codings defined below can be used to compress the payload of a
message. message.
4.2.1. Compress Coding 4.2.1. Compress Coding
The "compress" coding is an adaptive Lempel-Ziv-Welch (LZW) coding The "compress" coding is an adaptive Lempel-Ziv-Welch (LZW) coding
[Welch] that is commonly produced by the UNIX file compression [Welch] that is commonly produced by the UNIX file compression
program "compress". Recipients SHOULD consider "x-compress" to be program "compress". A recipient SHOULD consider "x-compress" to be
equivalent to "compress". equivalent to "compress".
4.2.2. Deflate Coding 4.2.2. Deflate Coding
The "deflate" coding is a "zlib" data format [RFC1950] containing a The "deflate" coding is a "zlib" data format [RFC1950] containing a
"deflate" compressed data stream [RFC1951] that uses a combination of "deflate" compressed data stream [RFC1951] that uses a combination of
the Lempel-Ziv (LZ77) compression algorithm and Huffman coding. the Lempel-Ziv (LZ77) compression algorithm and Huffman coding.
Note: Some incorrect implementations send the "deflate" compressed Note: Some incorrect implementations send the "deflate" compressed
data without the zlib wrapper. data without the zlib wrapper.
4.2.3. Gzip Coding 4.2.3. Gzip Coding
The "gzip" coding is an LZ77 coding with a 32 bit CRC that is The "gzip" coding is an LZ77 coding with a 32 bit CRC that is
commonly produced by the gzip file compression program [RFC1952]. commonly produced by the gzip file compression program [RFC1952]. A
Recipients SHOULD consider "x-gzip" to be equivalent to "gzip". recipient SHOULD consider "x-gzip" to be equivalent to "gzip".
4.3. TE 4.3. TE
The "TE" header field in a request indicates what transfer codings, The "TE" header field in a request indicates what transfer codings,
besides chunked, the client is willing to accept in response, and besides chunked, the client is willing to accept in response, and
whether or not the client is willing to accept trailer fields in a whether or not the client is willing to accept trailer fields in a
chunked transfer coding. chunked transfer coding.
The TE field-value consists of a comma-separated list of transfer The TE field-value consists of a comma-separated list of transfer
coding names, each allowing for optional parameters (as described in coding names, each allowing for optional parameters (as described in
Section 4), and/or the keyword "trailers". Clients MUST NOT send the Section 4), and/or the keyword "trailers". A client MUST NOT send
chunked transfer coding name in TE; chunked is always acceptable for the chunked transfer coding name in TE; chunked is always acceptable
HTTP/1.1 recipients. for HTTP/1.1 recipients.
TE = #t-codings TE = #t-codings
t-codings = "trailers" / ( transfer-coding [ t-ranking ] ) t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
t-ranking = OWS ";" OWS "q=" rank t-ranking = OWS ";" OWS "q=" rank
rank = ( "0" [ "." 0*3DIGIT ] ) rank = ( "0" [ "." 0*3DIGIT ] )
/ ( "1" [ "." 0*3("0") ] ) / ( "1" [ "." 0*3("0") ] )
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
The presence of the keyword "trailers" indicates that the client is The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer coding, as willing to accept trailer fields in a chunked transfer coding, as
defined in Section 4.1, on behalf of itself and any downstream defined in Section 4.1.2, on behalf of itself and any downstream
clients. For requests from an intermediary, this implies that clients. For requests from an intermediary, this implies that
either: (a) all downstream clients are willing to accept trailer either: (a) all downstream clients are willing to accept trailer
fields in the forwarded response; or, (b) the intermediary will fields in the forwarded response; or, (b) the intermediary will
attempt to buffer the response on behalf of downstream recipients. attempt to buffer the response on behalf of downstream recipients.
Note that HTTP/1.1 does not define any means to limit the size of a Note that HTTP/1.1 does not define any means to limit the size of a
chunked response such that an intermediary can be assured of chunked response such that an intermediary can be assured of
buffering the entire response. buffering the entire response.
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
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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.
Since the TE header field only applies to the immediate connection, a Since the TE header field only applies to the immediate connection, a
sender of TE MUST also send a "TE" connection option within the sender of TE MUST also send a "TE" connection option within the
Connection header field (Section 6.1) in order to prevent the TE Connection header field (Section 6.1) in order to prevent the TE
field from being forwarded by intermediaries that do not support its field from being forwarded by intermediaries that do not support its
semantics. semantics.
4.4. Trailer
When a message includes a message body encoded with the chunked
transfer coding and the sender desires to send metadata in the form
of trailer fields at the end of the message, the sender SHOULD
generate a Trailer header field before the message body to indicate
which fields will be present in the trailers. This allows the
recipient to prepare for receipt of that metadata before it starts
processing the body, which is useful if the message is being streamed
and the recipient wishes to confirm an integrity check on the fly.
Trailer = 1#field-name
5. Message Routing 5. Message Routing
HTTP request message routing is determined by each client based on HTTP request message routing is determined by each client based on
the target resource, the client's proxy configuration, and the target resource, the client's proxy configuration, and
establishment or reuse of an inbound connection. The corresponding establishment or reuse of an inbound connection. The corresponding
response routing follows the same connection chain back to the response routing follows the same connection chain back to the
client. client.
5.1. Identifying a Target Resource 5.1. Identifying a Target Resource
skipping to change at page 40, line 24 skipping to change at page 41, line 52
origin-form origin-form
The most common form of request-target is the origin-form. When The most common form of request-target is the origin-form. When
making a request directly to an origin server, other than a CONNECT making a request directly to an origin server, other than a CONNECT
or server-wide OPTIONS request (as detailed below), a client MUST or server-wide OPTIONS request (as detailed below), a client MUST
send only the absolute path and query components of the target URI as send only the absolute path and query components of the target URI as
the request-target. If the target URI's path component is empty, the request-target. If the target URI's path component is empty,
then the client MUST send "/" as the path within the origin-form of then 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 5.4, containing the target URI's authority component Section 5.4.
(excluding any userinfo).
For example, a client wishing to retrieve a representation of the For example, a client wishing to retrieve a representation of the
resource identified as resource identified as
http://www.example.org/where?q=now http://www.example.org/where?q=now
directly from the origin server would open (or reuse) a TCP directly from the origin server would open (or reuse) a TCP
connection to port 80 of the host "www.example.org" and send the connection to port 80 of the host "www.example.org" and send the
lines: lines:
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make the same request on the client's behalf to either the next make the same request on the client's behalf to either the next
inbound proxy server or directly to the origin server indicated by inbound proxy server or directly to the origin server indicated by
the request-target. Requirements on such "forwarding" of messages the request-target. Requirements on such "forwarding" of messages
are defined in Section 5.7. are defined in Section 5.7.
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
To allow for transition to the absolute-form for all requests in some To allow for transition to the absolute-form for all requests in some
future version of HTTP, HTTP/1.1 servers MUST accept the absolute- future version of HTTP, a server MUST accept the absolute-form in
form in requests, even though HTTP/1.1 clients will only send them in requests, even though HTTP/1.1 clients will only send them in
requests to proxies. requests to proxies.
authority-form 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 4.3.6 of [Part2]). When making a CONNECT request requests (Section 4.3.6 of [Part2]). When making a CONNECT request
to establish a tunnel through one or more proxies, a client MUST send to establish a tunnel through one or more proxies, a client MUST send
only the target URI's authority component (excluding any userinfo) as only the target URI's authority component (excluding any userinfo and
the request-target. For example, its "@" delimiter) as the request-target. For example,
CONNECT www.example.com:80 HTTP/1.1 CONNECT www.example.com:80 HTTP/1.1
asterisk-form 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 4.3.7 of [Part2]). When a client wishes to OPTIONS request (Section 4.3.7 of [Part2]). When a client wishes to
request OPTIONS for the server as a whole, as opposed to a specific request OPTIONS for the server as a whole, as opposed to a specific
named resource of that server, the client MUST send only "*" (%x2A) named resource of that server, the client MUST send only "*" (%x2A)
as the request-target. For example, as the request-target. For example,
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OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org:8001 Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org". after connecting to port 8001 of host "www.example.org".
5.4. Host 5.4. Host
The "Host" header field in a request provides the host and port The "Host" header field in a request provides the host and port
information from the target URI, enabling the origin server to information from the target URI, enabling the origin server to
distinguish among resources while servicing requests for multiple distinguish among resources while servicing requests for multiple
host names on a single IP address. Since the Host field-value is host names on a single IP address.
critical information for handling a request, it SHOULD be sent as the
first header field following the request-line.
Host = uri-host [ ":" port ] ; Section 2.7.1 Host = uri-host [ ":" port ] ; Section 2.7.1
A client MUST send a Host header field in all HTTP/1.1 request A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target URI includes an authority component, then messages. If the target URI includes an authority component, then a
the Host field-value MUST be identical to that authority component client MUST send a field-value for Host that is identical to that
after excluding any userinfo (Section 2.7.1). If the authority authority component, excluding any userinfo subcomponent and its "@"
component is missing or undefined for the target URI, then the Host delimiter (Section 2.7.1). If the authority component is missing or
header field MUST be sent with an empty field-value. undefined for the target URI, then a client MUST send a Host header
field with an empty field-value.
Since the Host field-value is critical information for handling a
request, a user agent SHOULD generate Host as the first header field
following the request-line.
For example, a GET request to the origin server for For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with: <http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1 GET /pub/WWW/ HTTP/1.1
Host: www.example.org Host: www.example.org
The Host header field MUST be sent in an HTTP/1.1 request even if the A client MUST send a Host header field in an HTTP/1.1 request even if
request-target is in the absolute-form, since this allows the Host the request-target is in the absolute-form, since this allows the
information to be forwarded through ancient HTTP/1.0 proxies that Host information to be forwarded through ancient HTTP/1.0 proxies
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. If the proxy forwards the request, it 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
forward the received Host field-value. forward the received Host field-value.
Since the Host header field acts as an application-level routing Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the interception proxy is particularly vulnerable if it relies on the
Host field-value for redirecting requests to internal servers, or for Host field-value for redirecting requests to internal servers, or for
use as a cache key in a shared cache, without first verifying that use as a cache key in a shared cache, without first verifying that
the intercepted connection is targeting a valid IP address for that the intercepted connection is targeting a valid IP address for that
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As described in Section 2.3, intermediaries can serve a variety of As described in Section 2.3, intermediaries can serve a variety of
roles in the processing of HTTP requests and responses. Some roles in the processing of HTTP requests and responses. Some
intermediaries are used to improve performance or availability. intermediaries are used to improve performance or availability.
Others are used for access control or to filter content. Since an Others are used for access control or to filter content. Since an
HTTP stream has characteristics similar to a pipe-and-filter HTTP stream has characteristics similar to a pipe-and-filter
architecture, there are no inherent limits to the extent an architecture, there are no inherent limits to the extent an
intermediary can enhance (or interfere) with either direction of the intermediary can enhance (or interfere) with either direction of the
stream. stream.
Intermediaries that forward a message MUST implement the Connection An intermediary not acting as a tunnel MUST implement the Connection
header field, as specified in Section 6.1, to exclude fields that are header field, as specified in Section 6.1, and exclude fields from
only intended for the incoming connection. being forwarded that are only intended for the incoming connection.
In order to avoid request loops, a proxy that forwards requests to An intermediary MUST NOT forward a message to itself unless it is
other proxies MUST be able to recognize and exclude all of its own protected from an infinite request loop. In general, an intermediary
server names, including any aliases, local variations, or literal IP ought to recognize its own server names, including any aliases, local
addresses. variations, or literal IP addresses, and respond to such requests
directly.
5.7.1. Via 5.7.1. Via
The "Via" header field indicates the presence of intermediate The "Via" header field indicates the presence of intermediate
protocols and recipients between the user agent and the server (on protocols and recipients between the user agent and the server (on
requests) or between the origin server and the client (on responses), requests) or between the origin server and the client (on responses),
similar to the "Received" header field in email (Section 3.6.7 of similar to the "Received" header field in email (Section 3.6.7 of
[RFC5322]). Via can be used for tracking message forwards, avoiding [RFC5322]). Via can be used for tracking message forwards, avoiding
request loops, and identifying the protocol capabilities of senders request loops, and identifying the protocol capabilities of senders
along the request/response chain. along the request/response chain.
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capabilities of the request/response chain such that they remain capabilities of the request/response chain such that they remain
visible to downstream recipients; this can be useful for determining visible to downstream recipients; this can be useful for determining
what backwards-incompatible features might be safe to use in what backwards-incompatible features might be safe to use in
response, or within a later request, as described in Section 2.6. response, or within a later request, as described in Section 2.6.
For brevity, the protocol-name is omitted when the received protocol For brevity, the protocol-name is omitted when the received protocol
is HTTP. is HTTP.
The received-by field is normally the host and optional port number The received-by field is normally the host and optional port number
of a recipient server or client that subsequently forwarded the of a recipient server or client that subsequently forwarded the
message. However, if the real host is considered to be sensitive message. However, if the real host is considered to be sensitive
information, it MAY be replaced by a pseudonym. If the port is not information, a sender MAY replace it with a pseudonym. If a port is
given, it MAY be assumed to be the default port of the received- not provided, a recipient MAY interpret that as meaning it was
protocol. received on the default TCP port, if any, for the received-protocol.
Comments MAY be used in the Via header field to identify the software A sender MAY generate comments in the Via header field to identify
of each recipient, analogous to the User-Agent and Server header the software of each recipient, analogous to the User-Agent and
fields. However, all comments in the Via field are optional and MAY Server header fields. However, all comments in the Via field are
be removed by any recipient prior to forwarding the message. optional and a recipient MAY remove them prior to forwarding the
message.
For example, a request message could be sent from an HTTP/1.0 user For example, a request message could be sent from an HTTP/1.0 user
agent to an internal proxy code-named "fred", which uses HTTP/1.1 to agent to an internal proxy code-named "fred", which uses HTTP/1.1 to
forward the request to a public proxy at p.example.net, which forward the request to a public proxy at p.example.net, which
completes the request by forwarding it to the origin server at completes the request by forwarding it to the origin server at
www.example.com. The request received by www.example.com would then www.example.com. The request received by www.example.com would then
have the following Via header field: have the following Via header field:
Via: 1.0 fred, 1.1 p.example.net Via: 1.0 fred, 1.1 p.example.net
A proxy or gateway used as a portal through a network firewall SHOULD An intermediary used as a portal through a network firewall SHOULD
NOT forward the names and ports of hosts within the firewall region NOT forward the names and ports of hosts within the firewall region
unless it is explicitly enabled to do so. If not enabled, the unless it is explicitly enabled to do so. If not enabled, such an
received-by host of any host behind the firewall SHOULD be replaced intermediary SHOULD replace each received-by host of any host behind
by an appropriate pseudonym for that host. the firewall by an appropriate pseudonym for that host.
A proxy or gateway MAY combine an ordered subsequence of Via header An intermediary MAY combine an ordered subsequence of Via header
field entries into a single such entry if the entries have identical field entries into a single such entry if the entries have identical
received-protocol values. For example, received-protocol values. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Senders SHOULD NOT combine multiple entries unless they are all under A sender SHOULD NOT combine multiple entries unless they are all
the same organizational control and the hosts have already been under the same organizational control and the hosts have already been
replaced by pseudonyms. Senders MUST NOT combine entries that have replaced by pseudonyms. A sender MUST NOT combine entries that have
different received-protocol values. different received-protocol values.
5.7.2. Transformations 5.7.2. Transformations
Some intermediaries include features for transforming messages and Some intermediaries include features for transforming messages and
their payloads. A transforming proxy might, for example, convert their payloads. A transforming proxy might, for example, convert
between image formats in order to save cache space or to reduce the between image formats in order to save cache space or to reduce the
amount of traffic on a slow link. However, operational problems amount of traffic on a slow link. However, operational problems
might occur when these transformations are applied to payloads might occur when these transformations are applied to payloads
intended for critical applications, such as medical imaging or intended for critical applications, such as medical imaging or
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application or removal of a transfer coding (Section 4). application or removal of a transfer coding (Section 4).
A non-transforming proxy MUST NOT modify the message payload (Section A non-transforming proxy MUST NOT modify the message payload (Section
3.3 of [Part2]). A transforming proxy MUST NOT modify the payload of 3.3 of [Part2]). A transforming proxy MUST NOT modify the payload of
a message that contains the no-transform cache-control directive. a message that contains the no-transform cache-control directive.
A transforming proxy MAY transform the payload of a message that does A transforming proxy MAY transform the payload of a message that does
not contain the no-transform cache-control directive; if the payload not contain the no-transform cache-control directive; if the payload
is transformed, the transforming proxy MUST add a Warning header is transformed, the transforming proxy MUST add a Warning header
field with the warn-code of 214 ("Transformation Applied") if one field with the warn-code of 214 ("Transformation Applied") if one
does not already appear in the message (see Section 7.5 of [Part6]). does not already appear in the message (see Section 5.5 of [Part6]).
If the payload of a 200 (OK) response is transformed, the If the payload of a 200 (OK) response is transformed, the
transforming proxy can also inform downstream recipients that a transforming proxy can also inform downstream recipients that a
transformation has been applied by changing the response status code transformation has been applied by changing the response status code
to 203 (Non-Authoritative Information) (Section 6.3.4 of [Part2]). to 203 (Non-Authoritative Information) (Section 6.3.4 of [Part2]).
6. Connection Management 6. Connection Management
HTTP messaging is independent of the underlying transport or session- HTTP messaging is independent of the underlying transport or session-
layer connection protocol(s). HTTP only presumes a reliable layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding transport with in-order delivery of requests and the corresponding
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The Connection header field's value has the following grammar: The Connection header field's value has the following grammar:
Connection = 1#connection-option Connection = 1#connection-option
connection-option = token connection-option = token
Connection options are case-insensitive. Connection options are case-insensitive.
A sender MUST NOT send a connection option corresponding to a header A sender MUST NOT send a connection option corresponding to a header
field that is intended for all recipients of the payload. For field that is intended for all recipients of the payload. For
example, Cache-Control is never appropriate as a connection option example, Cache-Control is never appropriate as a connection option
(Section 7.2 of [Part6]). (Section 5.2 of [Part6]).
The connection options do not have to correspond to a header field The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection connection option. Recipients that trigger certain connection
behavior based on the presence of connection options MUST do so based behavior based on the presence of connection options MUST do so based
on the presence of the connection-option rather than only the on the presence of the connection-option rather than only the
presence of the optional header field. In other words, if the presence of the optional header field. In other words, if the
connection option is received as a header field but not indicated connection option is received as a header field but not indicated
within the Connection field-value, then the recipient MUST ignore the within the Connection field-value, then the recipient MUST ignore the
skipping to change at page 49, line 33 skipping to change at page 51, line 16
since it would be unwise for senders to use that field-name for since it would be unwise for senders to use that field-name for
anything else. anything else.
The "close" connection option is defined for a sender to signal that The "close" connection option is defined for a sender to signal that
this connection will be closed after completion of the response. For this connection will be closed after completion of the response. For
example, example,
Connection: close Connection: close
in either the request or the response header fields indicates that in either the request or the response header fields indicates that
the connection MUST be closed after the current request/response is the sender is going to close the connection after the current
complete (Section 6.6). request/response is complete (Section 6.6).
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 "close" connection option in every response message that does not
have a 1xx (Informational) status code. have a 1xx (Informational) status code.
6.2. Establishment 6.2. Establishment
skipping to change at page 50, line 33 skipping to change at page 52, line 17
o The connection will close after the current response. o The connection will close after the current response.
A server MAY assume that an HTTP/1.1 client intends to maintain a A server MAY assume that an HTTP/1.1 client intends to maintain a
persistent connection until a close connection option is received in persistent connection until a close connection option is received in
a request. a request.
A client MAY reuse a persistent connection until it sends or receives A client MAY reuse a persistent connection until it sends or receives
a close connection option or receives an HTTP/1.0 response without a a close connection option or receives an HTTP/1.0 response without a
"keep-alive" connection option. "keep-alive" connection option.
In order to remain persistent, all messages on a connection MUST have In order to remain persistent, all messages on a connection need to
a self-defined message length (i.e., one not defined by closure of have a self-defined message length (i.e., one not defined by closure
the connection), as described in Section 3.3. A server MUST read the of the connection), as described in Section 3.3. A server MUST read
entire request message body or close the connection after sending its the entire request message body or close the connection after sending
response, since otherwise the remaining data on a persistent its response, since 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 Section 19.7.1 of [RFC2068] for information and
discussion of the problems with the Keep-Alive header field discussion of the problems with the Keep-Alive header field
implemented by many HTTP/1.0 clients). implemented by many HTTP/1.0 clients).
Clients and servers SHOULD NOT assume that a persistent connection is Clients and servers SHOULD NOT assume that a persistent connection is
skipping to change at page 51, line 30 skipping to change at page 53, line 13
means to detect that the original request was never applied. For means to detect that the original request was never applied. For
example, a user agent that knows (through design or configuration) example, a user agent that knows (through design or configuration)
that a POST request to a given resource is safe can repeat that that a POST request to a given resource is safe can repeat that
request automatically. Likewise, a user agent designed specifically request automatically. Likewise, a user agent designed specifically
to operate on a version control repository might be able to recover to operate on a version control repository might be able to recover
from partial failure conditions by checking the target resource from partial failure conditions by checking the target resource
revision(s) after a failed connection, reverting or fixing any revision(s) after a failed connection, reverting or fixing any
changes that were partially applied, and then automatically retrying changes that were partially applied, and then automatically retrying
the requests that failed. the requests that failed.
An automatic retry SHOULD NOT be repeated if it fails. A client SHOULD NOT automatically retry a failed automatic retry.
6.3.2. Pipelining 6.3.2. 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 4.2.1 of [Part2]), parallel if they all have safe methods (Section 4.2.1 of [Part2]),
but MUST send the corresponding responses in the same order that the but MUST send the corresponding responses in the same order that the
requests were received. requests were received.
A client that pipelines requests MUST be prepared to retry those A client that pipelines requests SHOULD retry unanswered requests if
requests if the connection closes before it receives all of the the connection closes before it receives all of the corresponding
corresponding responses. A client that assumes a persistent responses. When retrying pipelined requests after a failed
connection and pipelines immediately after connection establishment connection (a connection not explicitly closed by the server in its
MUST NOT pipeline on a retry connection until it knows the connection last complete response), a client MUST NOT pipeline immediately after
is persistent. connection establishment, since the first remaining request in the
prior pipeline might have caused an error response that can be lost
again if multiple requests are sent on a prematurely closed
connection (see the TCP reset problem described in Section 6.6).
Idempotent methods (Section 4.2.2 of [Part2]) are significant to Idempotent methods (Section 4.2.2 of [Part2]) are significant to
pipelining because they can be automatically retried after a pipelining because they can be automatically retried after a
connection failure. A user agent SHOULD NOT pipeline requests after connection failure. A user agent SHOULD NOT pipeline requests after
a non-idempotent method until the final response status code for that a non-idempotent method, until the final response status code for
method has been received, unless the user agent has a means to detect that method has been received, unless the user agent has a means to
and recover from partial failure conditions involving the pipelined detect and recover from partial failure conditions involving the
sequence. pipelined sequence.
An intermediary that receives pipelined requests MAY pipeline those An intermediary that receives pipelined requests MAY pipeline those
requests when forwarding them inbound, since it can rely on the requests when forwarding them inbound, since it can rely on the
outbound user agent(s) to determine what requests can be safely outbound user agent(s) to determine what requests can be safely
pipelined. If the inbound connection fails before receiving a pipelined. If the inbound connection fails before receiving a
response, the pipelining intermediary MAY attempt to retry a sequence response, the pipelining intermediary MAY attempt to retry a sequence
of requests that have yet to receive a response if the requests all of requests that have yet to receive a response if the requests all
have idempotent methods; otherwise, the pipelining intermediary have idempotent methods; otherwise, the pipelining intermediary
SHOULD forward any received responses and then close the SHOULD forward any received responses and then close the
corresponding outbound connection(s) so that the outbound user corresponding outbound connection(s) so that the outbound user
agent(s) can recover accordingly. agent(s) can recover accordingly.
6.4. Concurrency 6.4. Concurrency
Clients SHOULD limit the number of simultaneous connections that they A client SHOULD limit the number of simultaneous open connections
maintain to a given server. that it maintains to a given server.
Previous revisions of HTTP gave a specific number of connections as a Previous revisions of HTTP gave a specific number of connections as a
ceiling, but this was found to be impractical for many applications. ceiling, but this was found to be impractical for many applications.
As a result, this specification does not mandate a particular maximum As a result, this specification does not mandate a particular maximum
number of connections, but instead encourages clients to be number of connections, but instead encourages clients to be
conservative when opening multiple connections. conservative when opening multiple connections.
Multiple connections are typically used to avoid the "head-of-line Multiple connections are typically used to avoid the "head-of-line
blocking" problem, wherein a request that takes significant server- blocking" problem, wherein a request that takes significant server-
side processing and/or has a large payload blocks subsequent requests side processing and/or has a large payload blocks subsequent requests
skipping to change at page 52, line 48 skipping to change at page 54, line 35
6.5. Failures and Time-outs 6.5. Failures and Time-outs
Servers will usually have some time-out value beyond which they will Servers will usually have some time-out value beyond which they will
no longer maintain an inactive connection. Proxy servers might make no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making this a higher value since it is likely that the client will be making
more connections through the same server. The use of persistent more connections through the same server. The use of persistent
connections places no requirements on the length (or existence) of connections places no requirements on the length (or existence) of
this time-out for either the client or the server. this time-out for either the client or the server.
When a client or server wishes to time-out it SHOULD issue a graceful A client or server that wishes to time-out SHOULD issue a graceful
close on the transport connection. Clients and servers SHOULD both close on the connection. Implementations SHOULD constantly monitor
constantly watch for the other side of the transport close, and open connections for a received closure signal and respond to it as
respond to it as appropriate. If a client or server does not detect appropriate, since prompt closure of both sides of a connection
the other side's close promptly it could cause unnecessary resource enables allocated system resources to be reclaimed.
drain on the network.
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.
Servers SHOULD maintain persistent connections and allow the A server SHOULD sustain persistent connections, when possible, and
underlying transport's flow control mechanisms to resolve temporary allow the underlying transport's flow control mechanisms to resolve
overloads, rather than terminate connections with the expectation temporary overloads, rather than terminate connections with the
that clients will retry. The latter technique can exacerbate network expectation that clients will retry. The latter technique can
congestion. exacerbate network congestion.
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 an error response, it SHOULD immediately cease client sees a response that indicates the server does not wish to
transmitting the body and close the connection. receive the message body and is closing the connection, the client
SHOULD immediately cease transmitting the body and close its side of
the connection.
6.6. Tear-down 6.6. Tear-down
The Connection header field (Section 6.1) provides a "close" The Connection header field (Section 6.1) provides a "close"
connection option that a sender SHOULD send when it wishes to close connection option that a sender SHOULD send when it wishes to close
the connection after the current request/response pair. the connection after the current request/response pair.
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 close) and MUST requests on that connection (after the one containing close) and MUST
close the connection after reading the final response message close the connection after reading the final response message
skipping to change at page 54, line 48 skipping to change at page 56, line 34
Upgrade = 1#protocol Upgrade = 1#protocol
protocol = protocol-name ["/" protocol-version] protocol = protocol-name ["/" protocol-version]
protocol-name = token protocol-name = token
protocol-version = token protocol-version = token
A server that sends a 101 (Switching Protocols) response MUST send an A server that sends a 101 (Switching Protocols) response MUST send an
Upgrade header field to indicate the new protocol(s) to which the Upgrade header field to indicate the new protocol(s) to which the
connection is being switched; if multiple protocol layers are being connection is being switched; if multiple protocol layers are being
switched, the new protocols MUST be listed in layer-ascending order. switched, the sender MUST list the protocols in layer-ascending
A server MUST NOT switch to a protocol that was not indicated by the order. A server MUST NOT switch to a protocol that was not indicated
client in the corresponding request's Upgrade header field. A server by the client in the corresponding request's Upgrade header field. A
MAY choose to ignore the order of preference indicated by the client server MAY choose to ignore the order of preference indicated by the
and select the new protocol(s) based on other factors, such as the client and select the new protocol(s) based on other factors, such as
nature of the request or the current load on the server. the nature of the request or the current load on the server.
A server that sends a 426 (Upgrade Required) response MUST send an A server that sends a 426 (Upgrade Required) response MUST send an
Upgrade header field to indicate the acceptable protocols, in order Upgrade header field to indicate the acceptable protocols, in order
of descending preference. of descending preference.
A server MAY send an Upgrade header field in any other response to A server MAY send an Upgrade header field in any other response to
advertise that it implements support for upgrading to the listed advertise that it implements support for upgrading to the listed
protocols, in order of descending preference, when appropriate for a protocols, in order of descending preference, when appropriate for a
future request. future request.
The following is a hypothetical example sent by a client: The following is a hypothetical example sent by a client:
GET /hello.txt HTTP/1.1 GET /hello.txt HTTP/1.1
Host: www.example.com Host: www.example.com
Connection: upgrade Connection: upgrade
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
Upgrade cannot be used to insist on a protocol change; its acceptance Upgrade cannot be used to insist on a protocol change; its acceptance
and use by the server is optional. The capabilities and nature of and use by the server is optional. The capabilities and nature of
the application-level communication after the protocol change is the application-level communication after the protocol change is
entirely dependent upon the new protocol(s) chosen, although the entirely dependent upon the new protocol(s) chosen. However,
first action after changing the protocol MUST be a response to the immediately after sending the 101 response, the server is expected to
initial HTTP request that contained the Upgrade header field. continue responding to the original request as if it had received its
equivalent within the new protocol (i.e., the server still has an
outstanding request to satisfy after the protocol has been changed,
and is expected to do so without requiring the request to be
repeated).
For example, if the Upgrade header field is received in a GET request For example, if the Upgrade header field is received in a GET request
and the server decides to switch protocols, it first responds with a and the server decides to switch protocols, it first responds with a
101 (Switching Protocols) message in HTTP/1.1 and then immediately 101 (Switching Protocols) message in HTTP/1.1 and then immediately
follows that with the new protocol's equivalent of a response to a follows that with the new protocol's equivalent of a response to a
GET on the target resource. This allows a connection to be upgraded GET on the target resource. This allows a connection to be upgraded
to protocols with the same semantics as HTTP without the latency cost to protocols with the same semantics as HTTP without the latency cost
of an additional round-trip. A server MUST NOT switch protocols of an additional round-trip. A server MUST NOT switch protocols
unless the received message semantics can be honored by the new unless the received message semantics can be honored by the new
protocol; an OPTIONS request can be honored by any protocol. protocol; an OPTIONS request can be honored by any protocol.
skipping to change at page 56, line 10 skipping to change at page 57, line 50
[... data stream switches to HTTP/2.0 with an appropriate response [... data stream switches to HTTP/2.0 with an appropriate response
(as defined by new protocol) to the "GET /hello.txt" request ...] (as defined by new protocol) to the "GET /hello.txt" request ...]
When Upgrade is sent, the sender MUST also send a Connection header When Upgrade is sent, the sender MUST also send a Connection header
field (Section 6.1) that contains an "upgrade" connection option, in field (Section 6.1) that contains an "upgrade" connection option, in
order to prevent Upgrade from being accidentally forwarded by order to prevent Upgrade from being accidentally forwarded by
intermediaries that might not implement the listed protocols. A intermediaries that might not implement the listed protocols. A
server MUST ignore an Upgrade header field that is received in an server MUST ignore an Upgrade header field that is received in an
HTTP/1.0 request. HTTP/1.0 request.
A client cannot begin using an upgraded protocol on the connection
until it has completely sent the request message (i.e., the client
can't change the protocol it is sending in the middle of a message).
If a server receives both Upgrade and an Expect header field with the
"100-continue" expectation (Section 5.1.1 of [Part2]), the server
MUST send a 100 (Continue) response before sending a 101 (Switching
Protocols) response.
The Upgrade header field only applies to switching protocols on top The Upgrade header field only applies to switching protocols on top
of the existing connection; it cannot be used to switch the of the existing connection; it cannot be used to switch the
underlying connection (transport) protocol, nor to switch the underlying connection (transport) protocol, nor to switch the
existing communication to a different connection. For those existing communication to a different connection. For those
purposes, it is more appropriate to use a 3xx (Redirection) response purposes, it is more appropriate to use a 3xx (Redirection) response
(Section 6.4 of [Part2]). (Section 6.4 of [Part2]).
This specification only defines the protocol name "HTTP" for use by This specification only defines the protocol name "HTTP" for use by
the family of Hypertext Transfer Protocols, as defined by the HTTP the family of Hypertext Transfer Protocols, as defined by the HTTP
version rules of Section 2.6 and future updates to this version rules of Section 2.6 and future updates to this
specification. Additional tokens ought to be registered with IANA specification. Additional tokens ought to be registered with IANA
using the registration procedure defined in Section 7.5. using the registration procedure defined in Section 8.5.
7. IANA Considerations 7. ABNF list extension: #rule
7.1. Header Field Registration A #rule extension to the ABNF rules of [RFC5234] is used to improve
readability in the definitions of some header field values.
A construct "#" is defined, similar to "*", for defining comma-
delimited lists of elements. The full form is "<n>#<m>element"
indicating at least <n> and at most <m> elements, each separated by a
single comma (",") and optional whitespace (OWS).
Thus, a sender MUST expand the list construct as follows:
1#element => element *( OWS "," OWS element )
and:
#element => [ 1#element ]
and for n >= 1 and m > 1:
<n>#<m>element => element <n-1>*<m-1>( OWS "," OWS element )
For compatibility with legacy list rules, a recipient MUST parse and
ignore a reasonable number of empty list elements: enough to handle
common mistakes by senders that merge values, but not so much that
they could be used as a denial of service mechanism. In other words,
a recipient MUST expand the list construct as follows:
#element => [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
1#element => *( "," OWS ) element *( OWS "," [ OWS element ] )
Empty elements do not contribute to the count of elements present.
For example, given these ABNF productions:
example-list = 1#example-list-elmt
example-list-elmt = token ; see Section 3.2.6
Then the following are valid values for example-list (not including
the double quotes, which are present for delimitation only):
"foo,bar"
"foo ,bar,"
"foo , ,bar,charlie "
In contrast, the following values would be invalid, since at least
one non-empty element is required by the example-list production:
""
","
", ,"
Appendix B shows the collected ABNF after the list constructs have
been expanded, as described above, for recipients.
8. IANA Considerations
8.1. Header Field Registration
HTTP header fields are registered within the Message Header Field HTTP header fields are registered within the Message Header Field
Registry maintained at <http://www.iana.org/assignments/ Registry maintained at <http://www.iana.org/assignments/
message-headers/message-header-index.html>. message-headers/message-header-index.html>.
This document defines the following HTTP header fields, so their This document defines the following HTTP header fields, so their
associated registry entries shall be updated according to the associated registry entries shall be updated according to the
permanent registrations below (see [BCP90]): permanent registrations below (see [BCP90]):
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
| Connection | http | standard | Section 6.1 | | Connection | http | standard | Section 6.1 |
| Content-Length | http | standard | Section 3.3.2 | | Content-Length | http | standard | Section 3.3.2 |
| Host | http | standard | Section 5.4 | | Host | http | standard | Section 5.4 |
| TE | http | standard | Section 4.3 | | TE | http | standard | Section 4.3 |
| Trailer | http | standard | Section 4.1.1 | | Trailer | http | standard | Section 4.4 |
| Transfer-Encoding | http | standard | Section 3.3.1 | | Transfer-Encoding | http | standard | Section 3.3.1 |
| Upgrade | http | standard | Section 6.7 | | Upgrade | http | standard | Section 6.7 |
| Via | http | standard | Section 5.7.1 | | Via | http | standard | Section 5.7.1 |
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
Furthermore, the header field-name "Close" shall be registered as Furthermore, the header field-name "Close" shall be registered as
"reserved", since using that name as an HTTP header field might "reserved", since using that name as an HTTP header field might
conflict with the "close" connection option of the "Connection" conflict with the "close" connection option of the "Connection"
header field (Section 6.1). header field (Section 6.1).
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
| Close | http | reserved | Section 7.1 | | Close | http | reserved | Section 8.1 |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
7.2. URI Scheme Registration 8.2. URI Scheme Registration
IANA maintains the registry of URI Schemes [BCP115] at IANA maintains the registry of URI Schemes [BCP115] at
<http://www.iana.org/assignments/uri-schemes.html>. <http://www.iana.org/assignments/uri-schemes.html>.
This document defines the following URI schemes, so their associated This document defines the following URI schemes, so their associated
registry entries shall be updated according to the permanent registry entries shall be updated according to the permanent
registrations below: registrations below:
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
| URI Scheme | Description | Reference | | URI Scheme | Description | Reference |
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
| http | Hypertext Transfer Protocol | Section 2.7.1 | | http | Hypertext Transfer Protocol | Section 2.7.1 |
| https | Hypertext Transfer Protocol Secure | Section 2.7.2 | | https | Hypertext Transfer Protocol Secure | Section 2.7.2 |
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
7.3. Internet Media Type Registration 8.3. Internet Media Type Registration
This document serves as the specification for the Internet media This document serves as the specification for the Internet media
types "message/http" and "application/http". The following is to be types "message/http" and "application/http". The following is to be
registered with IANA (see [BCP13]). registered with IANA (see [BCP13]).
7.3.1. Internet Media Type message/http 8.3.1. Internet Media Type message/http
The message/http type can be used to enclose a single HTTP request or The message/http type can be used to enclose a single HTTP request or
response message, provided that it obeys the MIME restrictions for response message, provided that it obeys the MIME restrictions for
all "message" types regarding line length and encodings. all "message" types regarding line length and encodings.
Type name: message Type name: message
Subtype name: http Subtype name: http
Required parameters: none Required parameters: none
skipping to change at page 58, line 4 skipping to change at page 61, line 18
response message, provided that it obeys the MIME restrictions for response message, provided that it obeys the MIME restrictions for
all "message" types regarding line length and encodings. all "message" types regarding line length and encodings.
Type name: message Type name: message
Subtype name: http Subtype name: http
Required parameters: none Required parameters: none
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed message (e.g., version: The HTTP-version number of the enclosed message (e.g.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
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: none Security considerations: none
Interoperability considerations: none Interoperability considerations: none
Published specification: This specification (see Section 7.3.1). Published specification: This specification (see Section 8.3.1).
Applications that use this media type: Applications that use this media type:
Additional information: Additional information:
Magic number(s): none Magic number(s): none
File extension(s): none File extension(s): none
Macintosh file type code(s): none Macintosh file type code(s): none
skipping to change at page 58, line 35 skipping to change at page 62, line 4
Magic number(s): none Magic number(s): none
File extension(s): none File extension(s): none
Macintosh file type code(s): none Macintosh file type code(s): none
Person and email address to contact for further information: See Person and email address to contact for further information: See
Authors Section. Authors Section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: none Restrictions on usage: none
Author: See Authors Section. Author: See Authors Section.
Change controller: IESG Change controller: IESG
7.3.2. Internet Media Type application/http 8.3.2. Internet Media Type application/http
The application/http type can be used to enclose a pipeline of one or The application/http type can be used to enclose a pipeline of one or
more HTTP request or response messages (not intermixed). more HTTP request or response messages (not intermixed).
Type name: application Type name: application
Subtype name: http Subtype name: http
Required parameters: none Required parameters: none
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.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
skipping to change at page 59, line 26 skipping to change at page 62, line 39
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 E-mail. is required when transmitted via E-mail.
Security considerations: none Security considerations: none
Interoperability considerations: none Interoperability considerations: none
Published specification: This specification (see Section 7.3.2). Published specification: This specification (see Section 8.3.2).
Applications that use this media type: Applications that use this media type:
Additional information: Additional information:
Magic number(s): none Magic number(s): none
File extension(s): none File extension(s): none
Macintosh file type code(s): none Macintosh file type code(s): none
Person and email address to contact for further information: See Person and email address to contact for further information: See
Authors Section. Authors Section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: none Restrictions on usage: none
Author: See Authors Section. Author: See Authors Section.
Change controller: IESG Change controller: IESG
7.4. Transfer Coding Registry 8.4. Transfer Coding Registry
The HTTP Transfer Coding Registry defines the name space for transfer The HTTP Transfer Coding Registry defines the name space for transfer
coding names. It is maintained at coding names. It is maintained at
<http://www.iana.org/assignments/http-parameters>. <http://www.iana.org/assignments/http-parameters>.
7.4.1. Procedure 8.4.1. Procedure
Registrations MUST include the following fields: Registrations MUST include the following fields:
o Name o Name
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
skipping to change at page 60, line 33 skipping to change at page 63, line 45
transformation is identical, as is the case for the compression transformation is identical, as is the case for the compression
codings defined in Section 4.2. codings defined in Section 4.2.
Values to be added to this name space require IETF Review (see Values to be added to this name space require IETF Review (see
Section 4.1 of [RFC5226]), and MUST conform to the purpose of Section 4.1 of [RFC5226]), and MUST conform to the purpose of
transfer coding defined in this specification. transfer 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.
7.4.2. Registration 8.4.2. Registration
The HTTP Transfer Coding Registry shall be updated with the The HTTP Transfer Coding Registry shall be updated with the
registrations below: registrations below:
+------------+--------------------------------------+---------------+ +------------+--------------------------------------+---------------+
| Name | Description | Reference | | Name | Description | Reference |
+------------+--------------------------------------+---------------+ +------------+--------------------------------------+---------------+
| chunked | Transfer in a series of chunks | Section 4.1 | | chunked | Transfer in a series of chunks | Section 4.1 |
| compress | UNIX "compress" data format [Welch] | Section 4.2.1 | | compress | UNIX "compress" data format [Welch] | Section 4.2.1 |
| deflate | "deflate" compressed data | Section 4.2.2 | | deflate | "deflate" compressed data | Section 4.2.2 |
| | ([RFC1951]) inside the "zlib" data | | | | ([RFC1951]) inside the "zlib" data | |
| | format ([RFC1950]) | | | | format ([RFC1950]) | |
| gzip | GZIP file format [RFC1952] | Section 4.2.3 | | gzip | GZIP file format [RFC1952] | Section 4.2.3 |
| x-compress | Deprecated (alias for compress) | Section 4.2.1 | | x-compress | Deprecated (alias for compress) | Section 4.2.1 |
| x-gzip | Deprecated (alias for gzip) | Section 4.2.3 | | x-gzip | Deprecated (alias for gzip) | Section 4.2.3 |
+------------+--------------------------------------+---------------+ +------------+--------------------------------------+---------------+
7.5. Upgrade Token Registry 8.5. Upgrade Token Registry
The HTTP Upgrade Token Registry defines the name space for protocol- The HTTP Upgrade Token Registry defines the name space for protocol-
name tokens used to identify protocols in the Upgrade header field. name tokens used to identify protocols in the Upgrade header field.
The registry is maintained at The registry is maintained at
<http://www.iana.org/assignments/http-upgrade-tokens>. <http://www.iana.org/assignments/http-upgrade-tokens>.
7.5.1. Procedure 8.5.1. Procedure
Each registered protocol name is associated with contact information Each registered protocol name is associated with contact information
and an optional set of specifications that details how the connection and an optional set of specifications that details how the connection
will be processed after it has been upgraded. will be processed after it has been upgraded.
Registrations happen on a "First Come First Served" basis (see Registrations happen on a "First Come First Served" basis (see
Section 4.1 of [RFC5226]) and are subject to the following rules: Section 4.1 of [RFC5226]) and are subject to the following rules:
1. A protocol-name token, once registered, stays registered forever. 1. A protocol-name token, once registered, stays registered forever.
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The IANA will keep a record of all such changes, and make them The IANA will keep a record of all such changes, and make them
available upon request. available upon request.
7. The IESG MAY reassign responsibility for a protocol token. This 7. The IESG MAY reassign responsibility for a protocol token. This
will normally only be used in the case when a responsible party will normally only be used in the case when a responsible party
cannot be contacted. cannot be contacted.
This registration procedure for HTTP Upgrade Tokens replaces that This registration procedure for HTTP Upgrade Tokens replaces that
previously defined in Section 7.2 of [RFC2817]. previously defined in Section 7.2 of [RFC2817].
7.5.2. Upgrade Token Registration 8.5.2. Upgrade Token Registration
The HTTP Upgrade Token Registry shall be updated with the The HTTP Upgrade Token Registry shall be updated with the
registration below: registration below:
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
| Value | Description | Expected Version | Reference | | Value | Description | Expected Version | Reference |
| | | Tokens | | | | | Tokens | |
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
| HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.6 | | HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.6 |
| | Protocol | (e.g, "2.0") | | | | Protocol | (e.g, "2.0") | |
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
The responsible party is: "IETF (iesg@ietf.org) - Internet The responsible party is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
8. Security Considerations 9. Security Considerations
This section is meant to inform developers, information providers, This section is meant to inform developers, information providers,
and users of known security concerns relevant to HTTP/1.1 message and users of known security concerns relevant to HTTP/1.1 message
syntax, parsing, and routing. syntax, parsing, and routing.
8.1. DNS-related Attacks 9.1. DNS-related Attacks
HTTP clients rely heavily on the Domain Name Service (DNS), and are HTTP clients rely heavily on the Domain Name Service (DNS), and are
thus generally prone to security attacks based on the deliberate thus generally prone to security attacks based on the deliberate
misassociation of IP addresses and DNS names not protected by DNSSEC. misassociation of IP addresses and DNS names not protected by DNSSEC.
Clients need to be cautious in assuming the validity of an IP number/ Clients need to be cautious in assuming the validity of an IP number/
DNS name association unless the response is protected by DNSSEC DNS name association unless the response is protected by DNSSEC
([RFC4033]). ([RFC4033]).
8.2. Intermediaries and Caching 9.2. Intermediaries and Caching
By their very nature, HTTP intermediaries are men-in-the-middle, and By their very nature, HTTP intermediaries are men-in-the-middle, and
represent an opportunity for man-in-the-middle attacks. Compromise represent an opportunity for man-in-the-middle attacks. Compromise
of the systems on which the intermediaries run can result in serious of the systems on which the intermediaries run can result in serious
security and privacy problems. Intermediaries have access to security and privacy problems. Intermediaries have access to
security-related information, personal information about individual security-related information, personal information about individual
users and organizations, and proprietary information belonging to users and organizations, and proprietary information belonging to
users and content providers. A compromised intermediary, or an users and content providers. A compromised intermediary, or an
intermediary implemented or configured without regard to security and intermediary implemented or configured without regard to security and
privacy considerations, might be used in the commission of a wide privacy considerations, might be used in the commission of a wide
skipping to change at page 63, line 6 skipping to change at page 66, line 16
to cache poisoning attacks. to cache poisoning attacks.
Implementers need to consider the privacy and security implications Implementers need to consider the privacy and security implications
of their design and coding decisions, and of the configuration of their design and coding decisions, and of the configuration
options they provide to operators (especially the default options they provide to operators (especially the default
configuration). configuration).
Users need to be aware that intermediaries are no more trustworthy Users need to be aware that intermediaries are no more trustworthy
than the people who run them; HTTP itself cannot solve this problem. than the people who run them; HTTP itself cannot solve this problem.
8.3. Buffer Overflows 9.3. Buffer Overflows
Because HTTP uses mostly textual, character-delimited fields, Because HTTP uses mostly textual, character-delimited fields,
attackers can overflow buffers in implementations, and/or perform a attackers can overflow buffers in implementations, and/or perform a
Denial of Service against implementations that accept fields with Denial of Service against implementations that accept fields with
unlimited lengths. unlimited lengths.
To promote interoperability, this specification makes specific To promote interoperability, this specification makes specific
recommendations for minimum size limits on request-line recommendations for minimum size limits on request-line
(Section 3.1.1) and blocks of header fields (Section 3.2). These are (Section 3.1.1) and header fields (Section 3.2). These are minimum
minimum recommendations, chosen to be supportable even by recommendations, chosen to be supportable even by implementations
implementations with limited resources; it is expected that most with limited resources; it is expected that most implementations will
implementations will choose substantially higher limits. choose substantially higher limits.
This specification also provides a way for servers to reject messages This specification also provides a way for servers to reject messages
that have request-targets that are too long (Section 6.5.12 of that have request-targets that are too long (Section 6.5.12 of
[Part2]) or request entities that are too large (Section 6.5 of [Part2]) or request entities that are too large (Section 6.5 of
[Part2]). Additional status codes related to capacity limits have [Part2]). Additional status codes related to capacity limits have
been defined by extensions to HTTP [RFC6585]. been defined by extensions to HTTP [RFC6585].
Recipients SHOULD carefully limit the extent to which they read other Recipients ought to carefully limit the extent to which they read
fields, including (but not limited to) request methods, response other fields, including (but not limited to) request methods,
status phrases, header field-names, and body chunks, so as to avoid response status phrases, header field-names, and body chunks, so as
denial of service attacks without impeding interoperability. to avoid denial of service attacks without impeding interoperability.
8.4. Message Integrity 9.4. Message Integrity
HTTP does not define a specific mechanism for ensuring message HTTP does not define a specific mechanism for ensuring message
integrity, instead relying on the error-detection ability of integrity, instead relying on the error-detection ability of
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. Additional integrity delimited framing to detect completeness. Additional integrity
mechanisms, such as hash functions or digital signatures applied to mechanisms, such as hash functions or digital signatures applied to
the content, can be selectively added to messages via extensible the content, can be selectively added to messages via extensible
metadata header fields. Historically, the lack of a single integrity metadata header fields. Historically, the lack of a single integrity
mechanism has been justified by the informal nature of most HTTP mechanism has been justified by the informal nature of most HTTP
communication. However, the prevalence of HTTP as an information communication. However, the prevalence of HTTP as an information
skipping to change at page 64, line 10 skipping to change at page 67, line 19
necessary. For example, a browser being used to view medical history necessary. For example, a browser being used to view medical history
or drug interaction information needs to indicate to the user when or drug interaction information needs to indicate to the user when
such information is detected by the protocol to be incomplete, such information is detected by the protocol to be incomplete,
expired, or corrupted during transfer. Such mechanisms might be expired, or corrupted during transfer. Such mechanisms might be
selectively enabled via user agent extensions or the presence of selectively enabled via user agent extensions or the presence of
message integrity metadata in a response. At a minimum, user agents message integrity metadata in a response. At a minimum, user agents
ought to provide some indication that allows a user to distinguish ought to provide some indication that allows a user to distinguish
between a complete and incomplete response message (Section 3.4) when between a complete and incomplete response message (Section 3.4) when
such verification is desired. such verification is desired.
8.5. Server Log Information 9.5. Server Log Information
A server is in the position to save personal data about a user's A server is in the position to save personal data about a user's
requests over time, which might identify their reading patterns or requests over time, which might identify their reading patterns or
subjects of interest. In particular, log information gathered at an subjects of interest. In particular, log information gathered at an
intermediary often contains a history of user agent interaction, intermediary often contains a history of user agent interaction,
across a multitude of sites, that can be traced to individual users. across a multitude of sites, that can be traced to individual users.
HTTP log information is confidential in nature; its handling is often HTTP log information is confidential in nature; its handling is often
constrained by laws and regulations. Log information needs to be constrained by laws and regulations. Log information needs to be
securely stored and appropriate guidelines followed for its analysis. securely stored and appropriate guidelines followed for its analysis.
Anonymization of personal information within individual entries Anonymization of personal information within individual entries
helps, but is generally not sufficient to prevent real log traces helps, but is generally not sufficient to prevent real log traces
from being re-identified based on correlation with other access from being re-identified based on correlation with other access
characteristics. As such, access traces that are keyed to a specific characteristics. As such, access traces that are keyed to a specific
client should not be published even if the key is pseudonymous. client are unsafe to publish even if the key is pseudonymous.
To minimize the risk of theft or accidental publication, log To minimize the risk of theft or accidental publication, log
information should be purged of personally identifiable information, information ought to be purged of personally identifiable
including user identifiers, IP addresses, and user-provided query information, including user identifiers, IP addresses, and user-
parameters, as soon as that information is no longer necessary to provided query parameters, as soon as that information is no longer
support operational needs for security, auditing, or fraud control. necessary to support operational needs for security, auditing, or
fraud control.
9. Acknowledgments 10. Acknowledgments
This edition of HTTP/1.1 builds on the many contributions that went This edition of HTTP/1.1 builds on the many contributions that went
into RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including into RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including
substantial contributions made by the previous authors, editors, and substantial contributions made by the previous authors, editors, and
working group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding, working group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding,
Henrik Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter, Henrik Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter,
and Paul J. Leach. Mark Nottingham oversaw this effort as working and Paul J. Leach. Mark Nottingham oversaw this effort as working
group chair. group chair.
Since 1999, the following contributors have helped improve the HTTP Since 1999, the following contributors have helped improve the HTTP
skipping to change at page 65, line 38 skipping to change at page 68, line 48
Stracke, John Sullivan, Jonas Sicking, Jonathan A. Rees, Jonathan Stracke, John Sullivan, Jonas Sicking, Jonathan A. Rees, Jonathan
Billington, Jonathan Moore, Jonathan Silvera, Jordi Ros, Joris Billington, Jonathan Moore, Jonathan Silvera, Jordi Ros, Joris
Dobbelsteen, Josh Cohen, Julien Pierre, Jungshik Shin, Justin Dobbelsteen, Josh Cohen, Julien Pierre, Jungshik Shin, Justin
Chapweske, Justin Erenkrantz, Justin James, Kalvinder Singh, Karl Chapweske, Justin Erenkrantz, Justin James, Kalvinder Singh, Karl
Dubost, Keith Hoffman, Keith Moore, Ken Murchison, Koen Holtman, Dubost, Keith Hoffman, Keith Moore, Ken Murchison, Koen Holtman,
Konstantin Voronkov, Kris Zyp, Lisa Dusseault, Maciej Stachowiak, Konstantin Voronkov, Kris Zyp, Lisa Dusseault, Maciej Stachowiak,
Manu Sporny, Marc Schneider, Marc Slemko, Mark Baker, Mark Pauley, Manu Sporny, Marc Schneider, Marc Slemko, Mark Baker, Mark Pauley,
Mark Watson, Markus Isomaki, Markus Lanthaler, Martin J. Duerst, Mark Watson, Markus Isomaki, Markus Lanthaler, Martin J. Duerst,
Martin Musatov, Martin Nilsson, Martin Thomson, Matt Lynch, Matthew Martin Musatov, Martin Nilsson, Martin Thomson, Matt Lynch, Matthew
Cox, Max Clark, Michael Burrows, Michael Hausenblas, Michael Sweet, Cox, Max Clark, Michael Burrows, Michael Hausenblas, Michael Sweet,
Mike Amundsen, Mike Belshe, Mike Bishop, Mike Kelly, Mike Schinkel, Michael Tuexen, Michael Welzl, Mike Amundsen, Mike Belshe, Mike
Miles Sabin, Murray S. Kucherawy, Mykyta Yevstifeyev, Nathan Rixham, Bishop, Mike Kelly, Mike Schinkel, Miles Sabin, Murray S. Kucherawy,
Nicholas Shanks, Nico Williams, Nicolas Alvarez, Nicolas Mailhot, Mykyta Yevstifeyev, Nathan Rixham, Nicholas Shanks, Nico Williams,
Noah Slater, Osama Mazahir, Pablo Castro, Pat Hayes, Patrick R. Nicolas Alvarez, Nicolas Mailhot, Noah Slater, Osama Mazahir, Pablo
McManus, Paul E. Jones, Paul Hoffman, Paul Marquess, Peter Lepeska, Castro, Pat Hayes, Patrick R. McManus, Paul E. Jones, Paul Hoffman,
Peter Occil, Peter Saint-Andre, Peter Watkins, Phil Archer, Philippe Paul Marquess, Peter Lepeska, Peter Occil, Peter Saint-Andre, Peter
Mougin, Phillip Hallam-Baker, Piotr Dobrogost, Poul-Henning Kamp, Watkins, Phil Archer, Philippe Mougin, Phillip Hallam-Baker, Piotr
Preethi Natarajan, Rajeev Bector, Ray Polk, Reto Bachmann-Gmuer, Dobrogost, Poul-Henning Kamp, Preethi Natarajan, Rajeev Bector, Ray
Richard Cyganiak, Robby Simpson, Robert Brewer, Robert Collins, Polk, Reto Bachmann-Gmuer, Richard Cyganiak, Robby Simpson, Robert
Robert Mattson, Robert O'Callahan, Robert Olofsson, Robert Sayre, Brewer, Robert Collins, Robert Mattson, Robert O'Callahan, Robert
Robert Siemer, Robert de Wilde, Roberto Javier Godoy, Roberto Peon, Olofsson, Robert Sayre, Robert Siemer, Robert de Wilde, Roberto
Roland Zink, Ronny Widjaja, S. Mike Dierken, Salvatore Loreto, Sam Javier Godoy, Roberto Peon, Roland Zink, Ronny Widjaja, Ryan
Johnston, Sam Pullara, Sam Ruby, Scott Lawrence (who maintained the Hamilton, S. Mike Dierken, Salvatore Loreto, Sam Johnston, Sam
original issues list), Sean B. Palmer, Shane McCarron, Shigeki Ohtsu, Pullara, Sam Ruby, Scott Lawrence (who maintained the original issues
Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane list), Sean B. Palmer, Sebastien Barnoud, Shane McCarron, Shigeki
Ohtsu, Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane
Bortzmeyer, Stephen Farrell, Stephen Ludin, Stuart Williams, Subbu Bortzmeyer, Stephen Farrell, Stephen Ludin, Stuart Williams, Subbu
Allamaraju, Sylvain Hellegouarch, Tapan Divekar, Tatsuya Hayashi, Ted Allamaraju, Sylvain Hellegouarch, Tapan Divekar, Tatsuhiro Tsujikawa,
Hardie, Thomas Broyer, Thomas Fossati, Thomas Maslen, Thomas Nordin, Tatsuya Hayashi, Ted Hardie, Thomas Broyer, Thomas Fossati, Thomas
Thomas Roessler, Tim Bray, Tim Morgan, Tim Olsen, Tom Zhou, Travis Maslen, Thomas Nordin, Thomas Roessler, Tim Bray, Tim Morgan, Tim
Snoozy, Tyler Close, Vincent Murphy, Wenbo Zhu, Werner Baumann, Olsen, Tom Zhou, Travis Snoozy, Tyler Close, Vincent Murphy, Wenbo
Wilbur Streett, Wilfredo Sanchez Vega, William A. Rowe Jr., William Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez Vega, William
Chan, Willy Tarreau, Xiaoshu Wang, Yaron Goland, Yngve Nysaeter A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang, Yaron Goland,
Pettersen, Yoav Nir, Yogesh Bang, Yutaka Oiwa, Yves Lafon (long-time Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang, Yuchung Cheng,
member of the editor team), Zed A. Shaw, and Zhong Yu. Yutaka Oiwa, Yves Lafon (long-time member of the editor team), Zed A.
Shaw, and Zhong Yu.
See Section 16 of [RFC2616] for additional acknowledgements from See Section 16 of [RFC2616] for additional acknowledgements from
prior revisions. prior revisions.
10. References 11. References
10.1. Normative References 11.1. Normative References
[Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Semantics and Content", Transfer Protocol (HTTP/1.1): Semantics and Content",
draft-ietf-httpbis-p2-semantics-23 (work in progress), draft-ietf-httpbis-p2-semantics-24 (work in progress),
July 2013. September 2013.
[Part4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [Part4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Conditional Requests", Transfer Protocol (HTTP/1.1): Conditional Requests",
draft-ietf-httpbis-p4-conditional-23 (work in draft-ietf-httpbis-p4-conditional-24 (work in
progress), July 2013. progress), September 2013.
[Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
"Hypertext Transfer Protocol (HTTP/1.1): Range "Hypertext Transfer Protocol (HTTP/1.1): Range
Requests", draft-ietf-httpbis-p5-range-23 (work in Requests", draft-ietf-httpbis-p5-range-24 (work in
progress), July 2013. progress), September 2013.
[Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
draft-ietf-httpbis-p6-cache-23 (work in progress), draft-ietf-httpbis-p6-cache-24 (work in progress),
July 2013. September 2013.
[Part7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [Part7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Authentication", Transfer Protocol (HTTP/1.1): Authentication",
draft-ietf-httpbis-p7-auth-23 (work in progress), draft-ietf-httpbis-p7-auth-24 (work in progress),
July 2013. September 2013.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data
Format Specification version 3.3", RFC 1950, May 1996. Format Specification version 3.3", RFC 1950, May 1996.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format
Specification version 1.3", RFC 1951, May 1996. Specification version 1.3", RFC 1951, May 1996.
skipping to change at page 67, line 30 skipping to change at page 70, line 41
Syntax Specifications: ABNF", STD 68, RFC 5234, Syntax Specifications: ABNF", STD 68, RFC 5234,
January 2008. January 2008.
[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 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), June 1984.
10.2. Informative References 11.2. Informative References
[BCP115] Hansen, T., Hardie, T., and L. Masinter, "Guidelines [BCP115] Hansen, T., Hardie, T., and L. Masinter, "Guidelines
and Registration Procedures for New URI Schemes", and Registration Procedures for New URI Schemes",
BCP 115, RFC 4395, February 2006. BCP 115, RFC 4395, February 2006.
[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type [BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, January 2013. RFC 6838, January 2013.
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
skipping to change at page 71, line 27 skipping to change at page 74, line 39
A.1.3. Introduction of Transfer-Encoding A.1.3. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field HTTP/1.1 introduces the Transfer-Encoding header field
(Section 3.3.1). Transfer codings need to be decoded prior to (Section 3.3.1). Transfer codings need to be decoded prior to
forwarding an HTTP message over a MIME-compliant protocol. forwarding an HTTP message over a MIME-compliant protocol.
A.2. Changes from RFC 2616 A.2. Changes from RFC 2616
HTTP's approach to error handling has been explained. (Section 2.5) HTTP's approach to error handling has been explained. (Section 2.5)
The expectation to support HTTP/0.9 requests has been removed.
The term "Effective Request URI" has been introduced. (Section 5.5)
HTTP messages can be (and often are) buffered by implementations;
despite it sometimes being available as a stream, HTTP is
fundamentally a message-oriented protocol. (Section 3)
Minimum supported sizes for various protocol elements have been
suggested, to improve interoperability.
Header fields that span multiple lines ("line folding") are
deprecated. (Section 3.2.4)
The HTTP-version ABNF production has been clarified to be case- The HTTP-version ABNF production has been clarified to be case-
sensitive. Additionally, version numbers has been restricted to sensitive. Additionally, version numbers has been restricted to
single digits, due to the fact that implementations are known to single digits, due to the fact that implementations are known to
handle multi-digit version numbers incorrectly. (Section 2.6) handle multi-digit version numbers incorrectly. (Section 2.6)
The HTTPS URI scheme is now defined by this specification;
previously, it was done in Section 2.4 of [RFC2818]. (Section 2.7.2)
The HTTPS URI scheme implies end-to-end security. (Section 2.7.2)
Userinfo (i.e., username and password) are now disallowed in HTTP and Userinfo (i.e., username and password) are now disallowed in HTTP and
HTTPS URIs, because of security issues related to their transmission HTTPS URIs, because of security issues related to their transmission
on the wire. (Section 2.7.1) on the wire. (Section 2.7.1)
The HTTPS URI scheme is now defined by this specification;
previously, it was done in Section 2.4 of [RFC2818]. Furthermore, it
implies end-to-end security. (Section 2.7.2)
HTTP messages can be (and often are) buffered by implementations;
despite it sometimes being available as a stream, HTTP is
fundamentally a message-oriented protocol. Minimum supported sizes
for various protocol elements have been suggested, to improve
interoperability. (Section 3)
Invalid whitespace around field-names is now required to be rejected, Invalid whitespace around field-names is now required to be rejected,
because accepting it represents a security vulnerability. because accepting it represents a security vulnerability. The ABNF
productions defining header fields now only list the field value.
(Section 3.2) (Section 3.2)
The ABNF productions defining header fields now only list the field
value. (Section 3.2)
Rules about implicit linear whitespace between certain grammar Rules about implicit linear whitespace between certain grammar
productions have been removed; now whitespace is only allowed where productions have been removed; now whitespace is only allowed where
specifically defined in the ABNF. (Section 3.2.3) specifically defined in the ABNF. (Section 3.2.3)
The NUL octet is no longer allowed in comment and quoted-string text, Header fields that span multiple lines ("line folding") are
and handling of backslash-escaping in them has been clarified. deprecated. (Section 3.2.4)
(Section 3.2.6)
The quoted-pair rule no longer allows escaping control characters
other than HTAB. (Section 3.2.6)
Non-ASCII content in header fields and the reason phrase has been The NUL octet is no longer allowed in comment and quoted-string text,
obsoleted and made opaque (the TEXT rule was removed). and handling of backslash-escaping in them has been clarified. The
quoted-pair rule no longer allows escaping control characters other
than HTAB. Non-ASCII content in header fields and the reason phrase
has been obsoleted and made opaque (the TEXT rule was removed).
(Section 3.2.6) (Section 3.2.6)
Bogus "Content-Length" header fields are now required to be handled Bogus "Content-Length" header fields are now required to be handled
as errors by recipients. (Section 3.3.2) as errors by recipients. (Section 3.3.2)
The "identity" transfer coding token has been removed. (Sections 3.3
and 4)
The algorithm for determining the message body length has been The algorithm for determining the message body length has been
clarified to indicate all of the special cases (e.g., driven by clarified to indicate all of the special cases (e.g., driven by
methods or status codes) that affect it, and that new protocol methods or status codes) that affect it, and that new protocol
elements cannot define such special cases. (Section 3.3.3) elements cannot define such special cases. CONNECT is a new, special
case in determining message body length. "multipart/byteranges" is no
"multipart/byteranges" is no longer a way of determining message body longer a way of determining message body length detection.
length detection. (Section 3.3.3)
CONNECT is a new, special case in determining message body length.
(Section 3.3.3) (Section 3.3.3)
The "identity" transfer coding token has been removed. (Sections 3.3
and 4)
Chunk length does not include the count of the octets in the chunk Chunk length does not include the count of the octets in the chunk
header and trailer. (Section 4.1) header and trailer. Line folding in chunk extensions is disallowed.
(Section 4.1)
Use of chunk extensions is deprecated, and line folding in them is The meaning of the "deflate" content coding has been clarified.
disallowed. (Section 4.1) (Section 4.2.2)
The segment + query components of RFC3986 have been used to define
the request-target, instead of abs_path from RFC 1808. (Section 5.3)
The asterisk form of the request-target is only allowed in the The segment + query components of RFC 3986 have been used to define
OPTIONS method. (Section 5.3) the request-target, instead of abs_path from RFC 1808. The asterisk-
form of the request-target is only allowed with the OPTIONS method.
Exactly when "close" connection options have to be sent has been (Section 5.3)
clarified. (Section 6.1)
"hop-by-hop" header fields are required to appear in the Connection The term "Effective Request URI" has been introduced. (Section 5.5)
header field; just because they're defined as hop-by-hop in this
specification doesn't exempt them. (Section 6.1)
The limit of two connections per server has been removed. Gateways do not need to generate Via header fields anymore.
(Section 6.3) (Section 5.7.1)
An idempotent sequence of requests is no longer required to be Exactly when "close" connection options have to be sent has been
retried. (Section 6.3) clarified. Also, "hop-by-hop" header fields are required to appear
in the Connection header field; just because they're defined as hop-
by-hop in this specification doesn't exempt them. (Section 6.1)
The limit of two connections per server has been removed. An
idempotent sequence of requests is no longer required to be retried.
The requirement to retry requests under certain circumstances when The requirement to retry requests under certain circumstances when
the server prematurely closes the connection has been removed. the server prematurely closes the connection has been removed. Also,
(Section 6.3) some extraneous requirements about when servers are allowed to close
Some extraneous requirements about when servers are allowed to close
connections prematurely have been removed. (Section 6.3) connections prematurely have been removed. (Section 6.3)
The semantics of the Upgrade header field is now defined in responses The semantics of the Upgrade header field is now defined in responses
other than 101 (this was incorporated from [RFC2817]). (Section 6.7) other than 101 (this was incorporated from [RFC2817]). Furthermore,
the ordering in the field value is now significant. (Section 6.7)
Registration of Transfer Codings now requires IETF Review Empty list elements in list productions (e.g., a list header field
(Section 7.4) containing ", ,") have been deprecated. (Section 7)
The meaning of the "deflate" content coding has been clarified. Registration of Transfer Codings now requires IETF Review
(Section 4.2.2) (Section 8.4)
This specification now defines the Upgrade Token Registry, previously This specification now defines the Upgrade Token Registry, previously
defined in Section 7.2 of [RFC2817]. (Section 7.5) defined in Section 7.2 of [RFC2817]. (Section 8.5)
The expectation to support HTTP/0.9 requests has been removed.
(Appendix A)
Issues with the Keep-Alive and Proxy-Connection header fields in Issues with the Keep-Alive and Proxy-Connection header fields in
requests are pointed out, with use of the latter being discouraged requests are pointed out, with use of the latter being discouraged
altogether. (Appendix A.1.2) altogether. (Appendix A.1.2)
Empty list elements in list productions (e.g., a list header field Appendix B. Collected ABNF
containing ", ,") have been deprecated. (Appendix B)
Appendix B. ABNF list extension: #rule
A #rule extension to the ABNF rules of [RFC5234] is used to improve
readability in the definitions of some header field values.
A construct "#" is defined, similar to "*", for defining comma-
delimited lists of elements. The full form is "<n>#<m>element"
indicating at least <n> and at most <m> elements, each separated by a
single comma (",") and optional whitespace (OWS).
Thus,
1#element => element *( OWS "," OWS element )
and:
#element => [ 1#element ]
and for n >= 1 and m > 1:
<n>#<m>element => element <n-1>*<m-1>( OWS "," OWS element )
For compatibility with legacy list rules, recipients SHOULD accept
empty list elements. In other words, consumers would follow the list
productions:
#element => [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
1#element => *( "," OWS ) element *( OWS "," [ OWS element ] )
Note that empty elements do not contribute to the count of elements
present, though.
For example, given these ABNF productions:
example-list = 1#example-list-elmt
example-list-elmt = token ; see Section 3.2.6
Then these are valid values for example-list (not including the
double quotes, which are present for delimitation only):
"foo,bar"
"foo ,bar,"
"foo , ,bar,charlie "
But these values would be invalid, as at least one non-empty element
is required:
""
","
", ,"
Appendix C shows the collected ABNF, with the list rules expanded as
explained above.
Appendix C. Collected ABNF
BWS = OWS BWS = OWS
Connection = *( "," OWS ) connection-option *( OWS "," [ OWS Connection = *( "," OWS ) connection-option *( OWS "," [ OWS
connection-option ] ) connection-option ] )
Content-Length = 1*DIGIT Content-Length = 1*DIGIT
HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body HTTP-message = start-line *( header-field CRLF ) CRLF [ 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
Host = uri-host [ ":" port ] Host = uri-host [ ":" port ]
OWS = *( SP / HTAB ) OWS = *( SP / HTAB )
RWS = 1*( SP / HTAB ) RWS = 1*( SP / HTAB )
skipping to change at page 77, line 40 skipping to change at page 79, line 24
transfer-extension transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter ) transfer-extension = token *( OWS ";" OWS transfer-parameter )
transfer-parameter = attribute BWS "=" BWS value transfer-parameter = attribute BWS "=" BWS value
uri-host = <host, defined in [RFC3986], Section 3.2.2> uri-host = <host, defined in [RFC3986], Section 3.2.2>
value = word value = word
word = token / quoted-string word = token / quoted-string
Appendix D. Change Log (to be removed by RFC Editor before publication) Appendix C. Change Log (to be removed by RFC Editor before publication)
D.1. Since RFC 2616 C.1. Since RFC 2616
Changes up to the first Working Group Last Call draft are summarized Changes up to the first Working Group Last Call draft are summarized
in <http://trac.tools.ietf.org/html/ in <http://trac.tools.ietf.org/html/
draft-ietf-httpbis-p1-messaging-21#appendix-D>. draft-ietf-httpbis-p1-messaging-21#appendix-D>.
D.2. Since draft-ietf-httpbis-p1-messaging-21 C.2. Since draft-ietf-httpbis-p1-messaging-21
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/128>: "Cite HTTPS o <http://tools.ietf.org/wg/httpbis/trac/ticket/128>: "Cite HTTPS
URI scheme definition" (the spec now includes the HTTPs scheme URI scheme definition" (the spec now includes the HTTPs scheme
definition and thus updates RFC 2818) definition and thus updates RFC 2818)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/389>: "mention of o <http://tools.ietf.org/wg/httpbis/trac/ticket/389>: "mention of
'proxies' in section about caches" 'proxies' in section about caches"
skipping to change at page 79, line 14 skipping to change at page 80, line 47
o <http://tools.ietf.org/wg/httpbis/trac/ticket/420>: "Content- o <http://tools.ietf.org/wg/httpbis/trac/ticket/420>: "Content-
Length SHOULD be sent" Length SHOULD be sent"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/431>: "origin-form o <http://tools.ietf.org/wg/httpbis/trac/ticket/431>: "origin-form
does not allow path starting with "//"" does not allow path starting with "//""
o <http://tools.ietf.org/wg/httpbis/trac/ticket/433>: "ambiguity in o <http://tools.ietf.org/wg/httpbis/trac/ticket/433>: "ambiguity in
part 1 example" part 1 example"
D.3. Since draft-ietf-httpbis-p1-messaging-22 C.3. Since draft-ietf-httpbis-p1-messaging-22
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/435>: "Part1 should o <http://tools.ietf.org/wg/httpbis/trac/ticket/435>: "Part1 should
have a reference to TCP (RFC 793)" have a reference to TCP (RFC 793)"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/438>: "media type o <http://tools.ietf.org/wg/httpbis/trac/ticket/438>: "media type
registration template issues" registration template issues"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/441>: P1 editorial
nits
o <http://tools.ietf.org/wg/httpbis/trac/ticket/442>: "BWS" (vs o <http://tools.ietf.org/wg/httpbis/trac/ticket/442>: "BWS" (vs
conformance) conformance)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/444>: "obs-fold o <http://tools.ietf.org/wg/httpbis/trac/ticket/444>: "obs-fold
language" language"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/445>: "Ordering in o <http://tools.ietf.org/wg/httpbis/trac/ticket/445>: "Ordering in
Upgrade" Upgrade"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/446>: "p1 editorial o <http://tools.ietf.org/wg/httpbis/trac/ticket/446>: "p1 editorial
skipping to change at page 80, line 14 skipping to change at page 82, line 5
o <http://tools.ietf.org/wg/httpbis/trac/ticket/476>: "SHOULD and o <http://tools.ietf.org/wg/httpbis/trac/ticket/476>: "SHOULD and
conformance" conformance"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/477>: "Pipelining o <http://tools.ietf.org/wg/httpbis/trac/ticket/477>: "Pipelining
language" language"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/482>: "proxy o <http://tools.ietf.org/wg/httpbis/trac/ticket/482>: "proxy
handling of a really bad Content-Length" handling of a really bad Content-Length"
C.4. Since draft-ietf-httpbis-p1-messaging-23
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/343>: "chunk-
extensions" (un-deprecated and explained)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/483>: "MUST fix
Content-Length?"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/492>: "list notation
defined in appendix"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/497>: "Fine-Tuning
when Upgrade takes effect"
Index Index
A A
absolute-form (of request-target) 40 absolute-form (of request-target) 42
accelerator 10 accelerator 10
application/http Media Type 58 application/http Media Type 62
asterisk-form (of request-target) 41 asterisk-form (of request-target) 42
authority-form (of request-target) 41 authority-form (of request-target) 42
B B
browser 7 browser 7
C C
cache 11 cache 11
cacheable 12 cacheable 12
captive portal 11 captive portal 11
chunked (Coding Format) 27, 30, 34 chunked (Coding Format) 28, 31, 35
client 7 client 7
close 48, 53 close 49, 55
compress (Coding Format) 37 compress (Coding Format) 38
connection 7 connection 7
Connection header field 48, 53 Connection header field 49, 55
Content-Length header field 29 Content-Length header field 30
D D
deflate (Coding Format) 37 deflate (Coding Format) 38
downstream 9 downstream 9
E E
effective request URI 43 effective request URI 44
G G
gateway 10 gateway 10
Grammar Grammar
absolute-form 40 absolute-form 41
absolute-path 16 absolute-path 16
absolute-URI 16 absolute-URI 16
ALPHA 6 ALPHA 6
asterisk-form 40 asterisk-form 41
attribute 34 attribute 35
authority 16 authority 16
authority-form 40 authority-form 41
BWS 24 BWS 24
chunk 35 chunk 35-36
chunk-data 35 chunk-data 35-36
chunk-ext 35 chunk-ext 35-36
chunk-ext-name 35 chunk-ext-name 35-36
chunk-ext-val 35 chunk-ext-val 35-36
chunk-size 35 chunk-size 35-36
chunked-body 35 chunked-body 35-36
comment 26 comment 27
Connection 48 Connection 50
connection-option 48 connection-option 50
Content-Length 29 Content-Length 30
CR 6 CR 6
CRLF 6 CRLF 6
ctext 26 ctext 27
CTL 6 CTL 6
date2 34 date2 35
date3 34 date3 35
DIGIT 6 DIGIT 6
DQUOTE 6 DQUOTE 6
field-content 22 field-content 22
field-name 22 field-name 22
field-value 22 field-value 22
fragment 16 fragment 16
header-field 22 header-field 22
HEXDIG 6 HEXDIG 6
Host 42 Host 43
HTAB 6 HTAB 6
HTTP-message 19 HTTP-message 19
HTTP-name 13 HTTP-name 14
http-URI 16 http-URI 17
HTTP-version 13 HTTP-version 14
https-URI 18 https-URI 18
last-chunk 35 last-chunk 35-36
LF 6 LF 6
message-body 27 message-body 27
method 20 method 21
obs-fold 22 obs-fold 22
obs-text 26 obs-text 27
OCTET 6 OCTET 6
origin-form 40 origin-form 41
OWS 24 OWS 24
partial-URI 16 partial-URI 16
port 16 port 16
protocol-name 45 protocol-name 47
protocol-version 45 protocol-version 47
pseudonym 45 pseudonym 47
qdtext 26 qdtext 27
qdtext-nf 35 qdtext-nf 35-36
query 16 query 16
quoted-cpair 26 quoted-cpair 27
quoted-pair 26 quoted-pair 27
quoted-str-nf 35 quoted-str-nf 35-36
quoted-string 26 quoted-string 27
rank 37 rank 39
reason-phrase 21 reason-phrase 22
received-by 45 received-by 47
received-protocol 45 received-protocol 47
request-line 20 request-line 21
request-target 40 request-target 41
RWS 24 RWS 24
segment 16 segment 16
SP 6 SP 6
special 26 special 26
start-line 20 start-line 21
status-code 21 status-code 22
status-line 21 status-line 22
t-codings 37 t-codings 39
t-ranking 37 t-ranking 39
tchar 26 tchar 26
TE 37 TE 39
token 26 token 26
Trailer 35 Trailer 40
trailer-part 35 trailer-part 35-37
transfer-coding 34 transfer-coding 35
Transfer-Encoding 27 Transfer-Encoding 28
transfer-extension 34 transfer-extension 35
transfer-parameter 34 transfer-parameter 35
Upgrade 54 Upgrade 56
uri-host 16 uri-host 16
URI-reference 16 URI-reference 16
value 34 value 35
VCHAR 6 VCHAR 6
Via 45 Via 47
word 26 word 26
gzip (Coding Format) 37 gzip (Coding Format) 38
H H
header field 19 header field 19
header section 19 header section 19
headers 19 headers 19
Host header field 41 Host header field 43
http URI scheme 16 http URI scheme 17
https URI scheme 17 https URI scheme 18
I I
inbound 9 inbound 9
interception proxy 11 interception proxy 11
intermediary 9 intermediary 9
M M
Media Type Media Type
application/http 58 application/http 62
message/http 57 message/http 61
message 7 message 7
message/http Media Type 57 message/http Media Type 61
method 20 method 21
N N
non-transforming proxy 10 non-transforming proxy 10
O O
origin server 7 origin server 7
origin-form (of request-target) 40 origin-form (of request-target) 41
outbound 9 outbound 9
P P
proxy 10 proxy 10
R R
recipient 7 recipient 7
request 7 request 7
request-target 20 request-target 21
resource 15 resource 16
response 7 response 7
reverse proxy 10 reverse proxy 10
S S
sender 7 sender 7
server 7 server 7
spider 7 spider 7
T T
target resource 38 target resource 40
target URI 38 target URI 40
TE header field 37 TE header field 38
Trailer header field 35 Trailer header field 40
Transfer-Encoding header field 27 Transfer-Encoding header field 28
transforming proxy 10 transforming proxy 10
transparent proxy 11 transparent proxy 11
tunnel 11 tunnel 11
U U
Upgrade header field 54 Upgrade header field 56
upstream 9 upstream 9
URI scheme URI scheme
http 16 http 17
https 17 https 18
user agent 7 user agent 7
V V
Via header field 45 Via header field 46
Authors' Addresses Authors' Addresses
Roy T. Fielding (editor) Roy T. Fielding (editor)
Adobe Systems Incorporated Adobe Systems Incorporated
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
USA USA
EMail: fielding@gbiv.com EMail: fielding@gbiv.com
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