draft-ietf-httpbis-p1-messaging-18.txt   draft-ietf-httpbis-p1-messaging-19.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. Gettys Obsoletes: 2145,2616 (if approved) Y. Lafon, Ed.
Updates: 2817 (if approved) Alcatel-Lucent Updates: 2817 (if approved) W3C
Intended status: Standards Track J. Mogul Intended status: Standards Track J. Reschke, Ed.
Expires: July 7, 2012 HP Expires: September 13, 2012 greenbytes
H. Frystyk March 12, 2012
Microsoft
L. Masinter
Adobe
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
Y. Lafon, Ed.
W3C
J. Reschke, Ed.
greenbytes
January 4, 2012
HTTP/1.1, part 1: URIs, Connections, and Message Parsing HTTP/1.1, part 1: URIs, Connections, and Message Parsing
draft-ietf-httpbis-p1-messaging-18 draft-ietf-httpbis-p1-messaging-19
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 is Part 1 of the information initiative since 1990. This document is Part 1 of the
seven-part specification that defines the protocol referred to as seven-part specification that defines the protocol referred to as
"HTTP/1.1" and, taken together, obsoletes RFC 2616 and moves it to "HTTP/1.1" and, taken together, obsoletes RFC 2616 and moves it to
historic status, along with its predecessor RFC 2068. historic status, along with its predecessor RFC 2068.
skipping to change at page 2, line 11 skipping to change at page 1, line 45
Discussion of this draft should take place on the HTTPBIS working Discussion of this draft should take place on the HTTPBIS working
group mailing list (ietf-http-wg@w3.org), which is archived at group 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 C.19. The changes in this draft are summarized in Appendix C.20.
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.
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This Internet-Draft will expire on July 7, 2012. This Internet-Draft will expire on September 13, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Conformance and Error Handling . . . . . . . . . . . . . . 7 1.1. Requirement Notation . . . . . . . . . . . . . . . . . . . 7
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7
1.2.1. ABNF Extension: #rule . . . . . . . . . . . . . . . . 8 2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . 9 2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 7
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2. Connections and Transport Independence . . . . . . . . . . 9
2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 10 2.3. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 9
2.2. Message Orientation and Buffering . . . . . . . . . . . . 11 2.4. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3. Connections and Transport Independence . . . . . . . . . . 12 2.5. Conformance and Error Handling . . . . . . . . . . . . . . 12
2.4. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 12 2.6. Protocol Versioning . . . . . . . . . . . . . . . . . . . 13
2.5. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.7. Uniform Resource Identifiers . . . . . . . . . . . . . . . 15
2.6. Protocol Versioning . . . . . . . . . . . . . . . . . . . 15 2.7.1. http URI scheme . . . . . . . . . . . . . . . . . . . 16
2.7. Uniform Resource Identifiers . . . . . . . . . . . . . . . 17 2.7.2. https URI scheme . . . . . . . . . . . . . . . . . . . 17
2.7.1. http URI scheme . . . . . . . . . . . . . . . . . . . 18 2.7.3. http and https URI Normalization and Comparison . . . 18
2.7.2. https URI scheme . . . . . . . . . . . . . . . . . . . 19 3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 19
2.7.3. http and https URI Normalization and Comparison . . . 20 3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 21 3.1.1. Request Line . . . . . . . . . . . . . . . . . . . . . 20
3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 21 3.1.2. Status Line . . . . . . . . . . . . . . . . . . . . . 21
3.1.1. Request-Line . . . . . . . . . . . . . . . . . . . . . 22 3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 21
3.1.2. Response Status-Line . . . . . . . . . . . . . . . . . 23 3.2.1. Whitespace . . . . . . . . . . . . . . . . . . . . . . 23
3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 23 3.2.2. Field Parsing . . . . . . . . . . . . . . . . . . . . 23
3.2.1. Field Parsing . . . . . . . . . . . . . . . . . . . . 25 3.2.3. Field Length . . . . . . . . . . . . . . . . . . . . . 24
3.2.2. Field Length . . . . . . . . . . . . . . . . . . . . . 25 3.2.4. Field value components . . . . . . . . . . . . . . . . 25
3.2.3. Common Field ABNF Rules . . . . . . . . . . . . . . . 26 3.2.5. ABNF list extension: #rule . . . . . . . . . . . . . . 26
3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 27 3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 27
3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 30 3.3.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . 27
3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 31 3.3.2. Content-Length . . . . . . . . . . . . . . . . . . . . 29
4. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 31 3.3.3. Message Body Length . . . . . . . . . . . . . . . . . 30
4.1. Types of Request Target . . . . . . . . . . . . . . . . . 31 3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 32
4.2. The Resource Identified by a Request . . . . . . . . . . . 33 3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 33
4.3. Effective Request URI . . . . . . . . . . . . . . . . . . 34 4. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . . 33
5. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 35 4.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 34
5.1. Transfer Codings . . . . . . . . . . . . . . . . . . . . . 35 4.2. Compression Codings . . . . . . . . . . . . . . . . . . . 36
5.1.1. Chunked Transfer Coding . . . . . . . . . . . . . . . 36 4.2.1. Compress Coding . . . . . . . . . . . . . . . . . . . 36
5.1.2. Compression Codings . . . . . . . . . . . . . . . . . 38 4.2.2. Deflate Coding . . . . . . . . . . . . . . . . . . . . 36
5.1.3. Transfer Coding Registry . . . . . . . . . . . . . . . 39 4.2.3. Gzip Coding . . . . . . . . . . . . . . . . . . . . . 36
5.2. Product Tokens . . . . . . . . . . . . . . . . . . . . . . 39 4.3. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.3. Quality Values . . . . . . . . . . . . . . . . . . . . . . 40 4.3.1. Quality Values . . . . . . . . . . . . . . . . . . . . 38
6. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 38
6.1. Persistent Connections . . . . . . . . . . . . . . . . . . 40 5. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 39
6.1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 40 5.1. Identifying a Target Resource . . . . . . . . . . . . . . 39
6.1.2. Overall Operation . . . . . . . . . . . . . . . . . . 41 5.2. Connecting Inbound . . . . . . . . . . . . . . . . . . . . 39
6.1.3. Proxy Servers . . . . . . . . . . . . . . . . . . . . 42 5.3. Request Target . . . . . . . . . . . . . . . . . . . . . . 40
6.1.4. Practical Considerations . . . . . . . . . . . . . . . 45 5.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.1.5. Retrying Requests . . . . . . . . . . . . . . . . . . 46 5.5. Effective Request URI . . . . . . . . . . . . . . . . . . 43
6.2. Message Transmission Requirements . . . . . . . . . . . . 46 5.6. Intermediary Forwarding . . . . . . . . . . . . . . . . . 44
6.2.1. Persistent Connections and Flow Control . . . . . . . 46 5.6.1. End-to-end and Hop-by-hop Header Fields . . . . . . . 45
6.2.2. Monitoring Connections for Error Status Messages . . . 46 5.6.2. Non-modifiable Header Fields . . . . . . . . . . . . . 46
6.2.3. Use of the 100 (Continue) Status . . . . . . . . . . . 46 5.7. Associating a Response to a Request . . . . . . . . . . . 47
7. Miscellaneous notes that might disappear . . . . . . . . . . . 48 6. Connection Management . . . . . . . . . . . . . . . . . . . . 47
7.1. Scheme aliases considered harmful . . . . . . . . . . . . 48 6.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 47
7.2. Use of HTTP for proxy communication . . . . . . . . . . . 49 6.2. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.3. Interception of HTTP for access control . . . . . . . . . 49 6.3. Persistent Connections . . . . . . . . . . . . . . . . . . 50
7.4. Use of HTTP by other protocols . . . . . . . . . . . . . . 49 6.3.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 50
7.5. Use of HTTP by media type specification . . . . . . . . . 49 6.3.2. Overall Operation . . . . . . . . . . . . . . . . . . 51
8. Header Field Definitions . . . . . . . . . . . . . . . . . . . 49 6.3.3. Practical Considerations . . . . . . . . . . . . . . . 52
8.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 49 6.3.4. Retrying Requests . . . . . . . . . . . . . . . . . . 53
8.2. Content-Length . . . . . . . . . . . . . . . . . . . . . . 51 6.4. Message Transmission Requirements . . . . . . . . . . . . 54
8.3. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 6.4.1. Persistent Connections and Flow Control . . . . . . . 54
8.4. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.4.2. Monitoring Connections for Error Status Messages . . . 54
8.5. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.4.3. Use of the 100 (Continue) Status . . . . . . . . . . . 54
8.6. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 54 6.4.4. Closing Connections on Error . . . . . . . . . . . . . 56
8.7. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.5. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 56
8.7.1. Upgrade Token Registry . . . . . . . . . . . . . . . . 56 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 58
8.8. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 7.1. Header Field Registration . . . . . . . . . . . . . . . . 58
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 58 7.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 58
9.1. Header Field Registration . . . . . . . . . . . . . . . . 58 7.3. Internet Media Type Registrations . . . . . . . . . . . . 59
9.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 59 7.3.1. Internet Media Type message/http . . . . . . . . . . . 59
9.3. Internet Media Type Registrations . . . . . . . . . . . . 59 7.3.2. Internet Media Type application/http . . . . . . . . . 60
9.3.1. Internet Media Type message/http . . . . . . . . . . . 59 7.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 61
9.3.2. Internet Media Type application/http . . . . . . . . . 61 7.5. Transfer Coding Registrations . . . . . . . . . . . . . . 62
9.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 62 7.6. Upgrade Token Registry . . . . . . . . . . . . . . . . . . 62
9.5. Upgrade Token Registration . . . . . . . . . . . . . . . . 62 7.7. Upgrade Token Registration . . . . . . . . . . . . . . . . 63
10. Security Considerations . . . . . . . . . . . . . . . . . . . 62 8. Security Considerations . . . . . . . . . . . . . . . . . . . 63
10.1. Personal Information . . . . . . . . . . . . . . . . . . . 63 8.1. Personal Information . . . . . . . . . . . . . . . . . . . 63
10.2. Abuse of Server Log Information . . . . . . . . . . . . . 63 8.2. Abuse of Server Log Information . . . . . . . . . . . . . 63
10.3. Attacks Based On File and Path Names . . . . . . . . . . . 63 8.3. Attacks Based On File and Path Names . . . . . . . . . . . 64
10.4. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 63 8.4. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 64
10.5. Proxies and Caching . . . . . . . . . . . . . . . . . . . 64 8.5. Intermediaries and Caching . . . . . . . . . . . . . . . . 64
10.6. Protocol Element Size Overflows . . . . . . . . . . . . . 64 8.6. Protocol Element Size Overflows . . . . . . . . . . . . . 65
10.7. Denial of Service Attacks on Proxies . . . . . . . . . . . 65 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 66
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 65 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 67
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 66 10.1. Normative References . . . . . . . . . . . . . . . . . . . 67
12.1. Normative References . . . . . . . . . . . . . . . . . . . 66 10.2. Informative References . . . . . . . . . . . . . . . . . . 68
12.2. Informative References . . . . . . . . . . . . . . . . . . 67 Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 70
Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 69 A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 71
A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 70 A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 71
A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 70
A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 71 A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 71
A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 72
A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 71 A.3. Changes from RFC 2817 . . . . . . . . . . . . . . . . . . 73
Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 72 Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 73
Appendix C. Change Log (to be removed by RFC Editor before Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 75 publication) . . . . . . . . . . . . . . . . . . . . 76
C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 75 C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 76
C.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 75 C.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 76
C.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 77 C.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 78
C.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 78 C.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 79
C.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 78 C.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 79
C.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 79 C.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 80
C.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 79 C.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 80
C.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 80 C.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 81
C.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 81 C.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 82
C.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 82 C.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 82
C.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 82 C.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 83
C.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 82 C.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 83
C.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 83 C.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 84
C.14. Since draft-ietf-httpbis-p1-messaging-12 . . . . . . . . . 83 C.14. Since draft-ietf-httpbis-p1-messaging-12 . . . . . . . . . 84
C.15. Since draft-ietf-httpbis-p1-messaging-13 . . . . . . . . . 84 C.15. Since draft-ietf-httpbis-p1-messaging-13 . . . . . . . . . 85
C.16. Since draft-ietf-httpbis-p1-messaging-14 . . . . . . . . . 84 C.16. Since draft-ietf-httpbis-p1-messaging-14 . . . . . . . . . 85
C.17. Since draft-ietf-httpbis-p1-messaging-15 . . . . . . . . . 85 C.17. Since draft-ietf-httpbis-p1-messaging-15 . . . . . . . . . 85
C.18. Since draft-ietf-httpbis-p1-messaging-16 . . . . . . . . . 85 C.18. Since draft-ietf-httpbis-p1-messaging-16 . . . . . . . . . 86
C.19. Since draft-ietf-httpbis-p1-messaging-17 . . . . . . . . . 85 C.19. Since draft-ietf-httpbis-p1-messaging-17 . . . . . . . . . 86
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 C.20. Since draft-ietf-httpbis-p1-messaging-18 . . . . . . . . . 87
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
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 MIME- request/response protocol that uses extensible semantics and MIME-
like message payloads for flexible interaction with network-based like message payloads for flexible interaction with network-based
hypertext information systems. HTTP relies upon the Uniform Resource hypertext information systems. HTTP relies upon the Uniform Resource
Identifier (URI) standard [RFC3986] to indicate the target resource Identifier (URI) standard [RFC3986] to indicate the target resource
and relationships between resources. Messages are passed in a format (Section 5.1) and relationships between resources. Messages are
similar to that used by Internet mail [RFC5322] and the Multipurpose passed in a format similar to that used by Internet mail [RFC5322]
Internet Mail Extensions (MIME) [RFC2045] (see Appendix A of [Part3] and the Multipurpose Internet Mail Extensions (MIME) [RFC2045] (see
for the differences between HTTP and MIME messages). Appendix A of [Part3] for the differences between HTTP and MIME
messages).
HTTP is a generic interface protocol for information systems. It is HTTP is a generic interface protocol for information systems. It is
designed to hide the details of how a service is implemented by designed to hide the details of how a service is implemented by
presenting a uniform interface to clients that is independent of the presenting a uniform interface to clients that is independent of the
types of resources provided. Likewise, servers do not need to be types of resources provided. Likewise, servers do not need to be
aware of each client's purpose: an HTTP request can be considered in aware of each client's purpose: an HTTP request can be considered in
isolation rather than being associated with a specific type of client isolation rather than being associated with a specific type of client
or a predetermined sequence of application steps. The result is a or a predetermined sequence of application steps. The result is a
protocol that can be used effectively in many different contexts and protocol that can be used effectively in many different contexts and
for which implementations can evolve independently over time. for which implementations can evolve independently over time.
skipping to change at page 7, line 6 skipping to change at page 7, line 7
defining the protocol referred to as "HTTP/1.1", obsoleting [RFC2616] defining the protocol referred to as "HTTP/1.1", obsoleting [RFC2616]
and [RFC2145]. Part 1 describes the architectural elements that are and [RFC2145]. Part 1 describes the architectural elements that are
used or referred to in HTTP, defines the "http" and "https" URI used or referred to in HTTP, defines the "http" and "https" URI
schemes, describes overall network operation and connection schemes, describes overall network operation and connection
management, and defines HTTP message framing and forwarding management, and defines HTTP message framing and forwarding
requirements. Our goal is to define all of the mechanisms necessary requirements. Our goal is to define all of the mechanisms necessary
for HTTP message handling that are independent of message semantics, for HTTP message handling that are independent of message semantics,
thereby defining the complete set of requirements for message parsers thereby defining the complete set of requirements for message parsers
and message-forwarding intermediaries. and message-forwarding intermediaries.
1.1. Conformance and Error Handling 1.1. Requirement Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"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].
This document defines conformance criteria for several roles in HTTP
communication, including Senders, Recipients, Clients, Servers, User-
Agents, Origin Servers, Intermediaries, Proxies and Gateways. See
Section 2 for definitions of these terms.
An implementation is considered conformant if it complies with all of
the requirements associated with its role(s). Note that SHOULD-level
requirements are relevant here, unless one of the documented
exceptions is applicable.
This document also uses ABNF to define valid protocol elements
(Section 1.2). In addition to the prose requirements placed upon
them, Senders MUST NOT generate protocol elements that are invalid.
Unless noted otherwise, Recipients MAY take steps to recover a usable
protocol element from an invalid construct. However, HTTP does not
define specific error handling mechanisms, except in cases where it
has direct impact on security. This is because different uses of the
protocol require different error handling strategies; for example, a
Web browser may wish to transparently recover from a response where
the Location header field doesn't parse according to the ABNF,
whereby in a systems control protocol using HTTP, this type of error
recovery could lead to dangerous consequences.
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]. notation of [RFC5234] with the list rule extension defined in
Section 3.2.5. Appendix B shows the collected ABNF with the list
rule 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 syntactic convention, ABNF rule names prefixed with "obs-" As a convention, ABNF rule names prefixed with "obs-" denote
denote "obsolete" grammar rules that appear for historical reasons. "obsolete" grammar rules that appear for historical reasons.
1.2.1. ABNF Extension: #rule
The #rule extension to the ABNF rules of [RFC5234] is used to improve
readability.
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, Section 1.2.2).
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 3.2.3
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 B shows the collected ABNF, with the list rules expanded as
explained above.
1.2.2. Basic Rules
This specification uses three rules to denote the use of linear
whitespace: OWS (optional whitespace), RWS (required whitespace), and
BWS ("bad" whitespace).
The OWS rule is used where zero or more linear whitespace octets
might appear. OWS SHOULD either not be produced or be produced as a
single SP. Multiple OWS octets that occur within field-content
SHOULD either be replaced with a single SP or transformed to all SP
octets (each octet other than SP replaced with SP) before
interpreting the field value or forwarding the message downstream.
RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be produced as a single SP.
Multiple RWS octets that occur within field-content SHOULD either be
replaced with a single SP or transformed to all SP octets before
interpreting the field value or forwarding the message downstream.
BWS is used where the grammar allows optional whitespace for
historical reasons but senders SHOULD NOT produce it in messages.
HTTP/1.1 recipients MUST accept such bad optional whitespace and
remove it before interpreting the field value or forwarding the
message downstream.
OWS = *( SP / HTAB / obs-fold )
; "optional" whitespace
RWS = 1*( SP / HTAB / obs-fold )
; "required" whitespace
BWS = OWS
; "bad" whitespace
obs-fold = CRLF ( SP / HTAB )
; obsolete line folding
; see Section 3.2.1
2. Architecture 2. Architecture
HTTP was created for the World Wide Web architecture and has evolved HTTP was created for the World Wide Web architecture and has evolved
over time to support the scalability needs of a worldwide hypertext over time to support the scalability needs of a worldwide hypertext
system. Much of that architecture is reflected in the terminology system. Much of that architecture is reflected in the terminology
and syntax productions used to define HTTP. and syntax productions used to define HTTP.
2.1. Client/Server Messaging 2.1. Client/Server Messaging
skipping to change at page 10, line 47 skipping to change at page 8, line 30
connection (===) between the user agent (UA) and the origin server connection (===) between the user agent (UA) and the origin server
(O). (O).
request > request >
UA ======================================= O UA ======================================= O
< response < response
A client sends an HTTP request to the server in the form of a request A client sends an HTTP request to the server in the form of a request
message, beginning with a request-line that includes a method, URI, message, beginning with a request-line that includes a method, URI,
and protocol version (Section 3.1.1), followed by MIME-like header and protocol version (Section 3.1.1), followed by MIME-like header
fields containing request modifiers, client information, and payload fields containing request modifiers, client information, and
representation metadata (Section 3.2), an empty line to indicate the
end of the header section, and finally a message body containing the
payload body (if any, Section 3.3).
A server responds to the client's request by sending one or more HTTP
response messages, each beginning with a status line that includes
the protocol version, a success or error code, and textual reason
phrase (Section 3.1.2), possibly followed by MIME-like header fields
containing server information, resource metadata, and representation
metadata (Section 3.2), an empty line to indicate the end of the metadata (Section 3.2), an empty line to indicate the end of the
header section, and finally a message body containing the payload header section, and finally a message body containing the payload
body (if any, Section 3.3). body (if any, Section 3.3).
A server responds to the client's request by sending an HTTP response
message, beginning with a status line that includes the protocol
version, a success or error code, and textual reason phrase
(Section 3.1.2), followed by MIME-like header fields containing
server information, resource metadata, and payload metadata
(Section 3.2), an empty line to indicate the end of the header
section, and finally a message body containing the payload body (if
any, Section 3.3).
Note that 1xx responses (Section 7.1 of [Part2]) are not final;
therefore, a server can send zero or more 1xx responses, followed by
exactly one final response (with any other status code).
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: */* Accept: */*
skipping to change at page 11, line 42 skipping to change at page 9, line 26
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: 14 Content-Length: 14
Vary: Accept-Encoding Vary: Accept-Encoding
Content-Type: text/plain Content-Type: text/plain
Hello World! Hello World!
2.2. Message Orientation and Buffering 2.2. Connections and Transport Independence
Fundamentally, HTTP is a message-based protocol. Although message
bodies can be chunked (Section 5.1.1) and implementations often make
parts of a message available progressively, this is not required, and
some widely-used implementations only make a message available when
it is complete. Furthermore, while most proxies will progressively
stream messages, some amount of buffering will take place, and some
proxies might buffer messages to perform transformations, check
content or provide other services.
Therefore, extensions to and uses of HTTP cannot rely on the
availability of a partial message, or assume that messages will not
be buffered. There are strategies that can be used to test for
buffering in a given connection, but it should be understood that
behaviors can differ across connections, and between requests and
responses.
Recipients MUST consider every message in a connection in isolation;
because HTTP is a stateless protocol, it cannot be assumed that two
requests on the same connection are from the same client or share any
other common attributes. In particular, intermediaries might mix
requests from different clients into a single server connection.
Note that some existing HTTP extensions (e.g., [RFC4559]) violate
this requirement, thereby potentially causing interoperability and
security problems.
2.3. Connections and Transport Independence
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
in-order delivery of responses. The mapping of HTTP request and in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of the underlying transport response structures onto the data units of the underlying transport
protocol is outside the scope of this specification. protocol is outside the scope of this specification.
The specific connection protocols to be used for an interaction are The specific connection protocols to be used for an interaction are
determined by client configuration and the target resource's URI. determined by client configuration and the target URI (Section 5.1).
For example, the "http" URI scheme (Section 2.7.1) indicates a For example, the "http" URI scheme (Section 2.7.1) indicates a
default connection of TCP over IP, with a default TCP port of 80, but default connection of TCP over IP, with a default TCP port of 80, but
the client might be configured to use a proxy via some other the client might be configured to use a proxy via some other
connection port or protocol instead of using the defaults. connection port or protocol instead of using the defaults.
A connection might be used for multiple HTTP request/response A connection might be used for multiple HTTP request/response
exchanges, as defined in Section 6.1. exchanges, as defined in Section 6.3.
2.4. Intermediaries 2.3. Intermediaries
HTTP enables the use of intermediaries to satisfy requests through a HTTP enables the use of intermediaries to satisfy requests through a
chain of connections. There are three common forms of HTTP chain of connections. There are three common forms of HTTP
intermediary: proxy, gateway, and tunnel. In some cases, a single intermediary: proxy, gateway, and tunnel. In some cases, a single
intermediary might act as an origin server, proxy, gateway, or intermediary might act as an origin server, proxy, gateway, or
tunnel, switching behavior based on the nature of each request. tunnel, switching behavior based on the nature of each request.
> > > > > > > >
UA =========== A =========== B =========== C =========== O UA =========== A =========== B =========== C =========== O
< < < < < < < <
skipping to change at page 14, line 16 skipping to change at page 11, line 21
enable partitioning or load-balancing of HTTP services across enable partitioning or load-balancing of HTTP services across
multiple machines. multiple machines.
A gateway behaves as an origin server on its outbound connection and A gateway behaves as an origin server on its outbound connection and
as a user agent on its inbound connection. All HTTP requirements as a user agent on its inbound connection. All HTTP requirements
applicable to an origin server also apply to the outbound applicable to an origin server also apply to the outbound
communication of a gateway. A gateway communicates with inbound communication of a gateway. A gateway communicates with inbound
servers using any protocol that it desires, including private servers using any protocol that it desires, including private
extensions to HTTP that are outside the scope of this specification. extensions to HTTP that are outside the scope of this specification.
However, an HTTP-to-HTTP gateway that wishes to interoperate with However, an HTTP-to-HTTP gateway that wishes to interoperate with
third-party HTTP servers MUST comply with HTTP user agent third-party HTTP servers MUST conform to HTTP user agent requirements
requirements on the gateway's inbound connection and MUST implement on the gateway's inbound connection and MUST implement the Connection
the Connection (Section 8.1) and Via (Section 8.8) header fields for (Section 6.1) and Via (Section 6.2) header fields for both
both connections. connections.
A "tunnel" acts as a blind relay between two connections without A "tunnel" acts as a blind relay between two connections without
changing the messages. Once active, a tunnel is not considered a changing the messages. Once active, a tunnel is not considered a
party to the HTTP communication, though the tunnel might have been party to the HTTP communication, though the tunnel might have been
initiated by an HTTP request. A tunnel ceases to exist when both initiated by an HTTP request. A tunnel ceases to exist when both
ends of the relayed connection are closed. Tunnels are used to ends of the relayed connection are closed. Tunnels are used to
extend a virtual connection through an intermediary, such as when extend a virtual connection through an intermediary, such as when
transport-layer security is used to establish private communication transport-layer security is used to establish private communication
through a shared firewall proxy. through a shared firewall proxy.
skipping to change at page 14, line 45 skipping to change at page 11, line 50
proxy" [RFC3040], "transparent proxy" [RFC1919], or "captive portal", proxy" [RFC3040], "transparent proxy" [RFC1919], or "captive portal",
differs from an HTTP proxy because it has not been selected by the differs from an HTTP proxy because it has not been selected by the
client. Instead, the network intermediary redirects outgoing TCP client. Instead, the network intermediary redirects outgoing TCP
port 80 packets (and occasionally other common port traffic) to an port 80 packets (and occasionally other common port traffic) to an
internal HTTP server. Interception proxies are commonly found on internal HTTP server. Interception proxies are commonly found on
public network access points, as a means of enforcing account public network access points, as a means of enforcing account
subscription prior to allowing use of non-local Internet services, subscription prior to allowing use of non-local Internet services,
and within corporate firewalls to enforce network usage policies. and within corporate firewalls to enforce network usage policies.
They are indistinguishable from a man-in-the-middle attack. They are indistinguishable from a man-in-the-middle attack.
2.5. Caches HTTP is defined as a stateless protocol, meaning that each request
message can be understood in isolation. Many implementations depend
on HTTP's stateless design in order to reuse proxied connections or
dynamically load balance requests across multiple servers. Hence,
servers MUST NOT assume that two requests on the same connection are
from the same user agent unless the connection is secured and
specific to that agent. Some non-standard HTTP extensions (e.g.,
[RFC4559]) have been known to violate this requirement, resulting in
security and interoperability problems.
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
time and network bandwidth consumption on future, equivalent time and network bandwidth consumption on future, equivalent
requests. Any client or server MAY employ a cache, though a cache requests. Any client or server MAY employ a cache, though a cache
cannot be used by a server while it is acting as a tunnel. cannot be used by a server while it is acting as a tunnel.
The effect of a cache is that the request/response chain is shortened The effect of a cache is that the request/response chain is shortened
if one of the participants along the chain has a cached response if one of the participants along the chain has a cached response
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cache behavior and cacheable responses are defined in Section 2 of cache behavior and cacheable responses are defined in Section 2 of
[Part6]. [Part6].
There are a wide variety of architectures and configurations of There are a wide variety of architectures and configurations of
caches and proxies deployed across the World Wide Web and inside caches and proxies deployed across the World Wide Web and inside
large organizations. These systems include national hierarchies of large organizations. These systems include national hierarchies of
proxy caches to save transoceanic bandwidth, systems that broadcast proxy caches to save transoceanic bandwidth, systems that broadcast
or multicast cache entries, organizations that distribute subsets of or multicast cache entries, organizations that distribute subsets of
cached data via optical media, and so on. cached data via optical media, and so on.
2.5. Conformance and Error Handling
This specification targets conformance criteria according to the role
of a participant in HTTP communication. Hence, HTTP requirements are
placed on senders, recipients, clients, servers, user agents,
intermediaries, origin servers, proxies, gateways, or caches,
depending on what behavior is being constrained by the requirement.
An implementation is considered conformant if it complies with all of
the requirements associated with the roles it partakes in HTTP.
Senders MUST NOT generate protocol elements that do not match the
grammar defined by the ABNF rules for those protocol elements.
Unless otherwise noted, recipients MAY attempt to recover a usable
protocol element from an invalid construct. HTTP does not define
specific error handling mechanisms except when they have a direct
impact on security, since different applications of the protocol
require different error handling strategies. For example, a Web
browser might wish to transparently recover from a response where the
Location header field doesn't parse according to the ABNF, whereas a
systems control client might consider any form of error recovery to
be dangerous.
2.6. Protocol Versioning 2.6. Protocol Versioning
HTTP uses a "<major>.<minor>" numbering scheme to indicate versions HTTP uses a "<major>.<minor>" numbering scheme to indicate versions
of the protocol. This specification defines version "1.1". The of the protocol. This specification defines version "1.1". The
protocol version as a whole indicates the sender's compliance with protocol version as a whole indicates the sender's conformance with
the set of requirements laid out in that version's corresponding the set of requirements laid out in that version's corresponding
specification of HTTP. specification of HTTP.
The version of an HTTP message is indicated by an HTTP-Version field The version of an HTTP message is indicated by an HTTP-version field
in the first line of the message. HTTP-Version is case-sensitive. in the first line of the message. HTTP-version is case-sensitive.
HTTP-Version = HTTP-Prot-Name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
HTTP-Prot-Name = %x48.54.54.50 ; "HTTP", case-sensitive HTTP-name = %x48.54.54.50 ; "HTTP", case-sensitive
The HTTP version number consists of two decimal digits separated by a The HTTP version number consists of two decimal digits separated by a
"." (period or decimal point). The first digit ("major version") "." (period or decimal point). The first digit ("major version")
indicates the HTTP messaging syntax, whereas the second digit ("minor indicates the HTTP messaging syntax, whereas the second digit ("minor
version") indicates the highest minor version to which the sender is version") indicates the highest minor version to which the sender is
at least conditionally compliant and able to understand for future conformant and able to understand for future communication. The
communication. The minor version advertises the sender's minor version advertises the sender's communication capabilities even
communication capabilities even when the sender is only using a when the sender is only using a backwards-compatible subset of the
backwards-compatible subset of the protocol, thereby letting the protocol, thereby letting the recipient know that more advanced
recipient know that more advanced features can be used in response features can be used in response (by servers) or in future requests
(by servers) or in future requests (by clients). (by clients).
When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945] When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945]
or a recipient whose version is unknown, the HTTP/1.1 message is or a recipient whose version is unknown, the HTTP/1.1 message is
constructed such that it can be interpreted as a valid HTTP/1.0 constructed such that it can be interpreted as a valid HTTP/1.0
message if all of the newer features are ignored. This specification message if all of the newer features are ignored. This specification
places recipient-version requirements on some new features so that a places recipient-version requirements on some new features so that a
compliant sender will only use compatible features until it has conformant sender will only use compatible features until it has
determined, through configuration or the receipt of a message, that determined, through configuration or the receipt of a message, that
the recipient supports HTTP/1.1. the recipient supports HTTP/1.1.
The interpretation of an HTTP header field does not change between The interpretation of a header field does not change between minor
minor versions of the same major 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 compliance 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 defined such that, when they are understood
by a recipient, they might override or enhance the interpretation of by a recipient, they might override or enhance the interpretation of
previously defined header fields. When an implementation receives an previously defined header fields. When an implementation receives an
unrecognized header field, the recipient MUST ignore that header unrecognized header field, the recipient MUST ignore that header
field for local processing regardless of the message's HTTP version. field for local processing regardless of the message's HTTP version.
An unrecognized header field received by a proxy MUST be forwarded An unrecognized header field received by a proxy MUST be forwarded
downstream unless the header field's field-name is listed in the downstream unless the header field's field-name is listed in the
message's Connection header-field (see Section 8.1). These message's Connection header-field (see Section 6.1). These
requirements allow HTTP's functionality to be enhanced without requirements allow HTTP's functionality to be enhanced without
requiring prior update of all compliant intermediaries. 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 a tunnel) 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 matches what the intermediary understands, and is at least version in that message matches a version to which that intermediary
conditionally compliant to, for both the receiving and sending of is conformant for both the receiving and sending of messages.
messages. Forwarding an HTTP message without rewriting the HTTP- Forwarding an HTTP message without rewriting the HTTP-version might
Version might result in communication errors when downstream result in communication errors when downstream recipients use the
recipients use the message sender's version to determine what message sender's version to determine what features are safe to use
features are safe to use for later communication with that sender. for later communication with that sender.
An HTTP client SHOULD send a request version equal to the highest An HTTP client SHOULD send a request version equal to the highest
version for which the client is at least conditionally compliant and version to which the client is conformant and whose major version is
whose major version is no higher than the highest version supported no higher than the highest version supported by the server, if this
by the server, if this is known. An HTTP client MUST NOT send a is known. An HTTP client MUST NOT send a version to which it is not
version for which it is not at least conditionally compliant. conformant.
An HTTP client MAY send a lower request version if it is known that An HTTP client MAY send a lower request version if it is known that
the server incorrectly implements the HTTP specification, but only the server incorrectly implements the HTTP specification, but only
after the client has attempted at least one normal request and after the client has attempted at least one normal request and
determined from the response status or header fields (e.g., Server) determined from the response status or header fields (e.g., Server)
that the server improperly handles higher request versions. that the server improperly handles higher request versions.
An HTTP server SHOULD send a response version equal to the highest An HTTP server SHOULD send a response version equal to the highest
version for which the server is at least conditionally compliant and version to which the server is conformant and whose major version is
whose major version is less than or equal to the one received in the less than or equal to the one received in the request. An HTTP
request. An HTTP server MUST NOT send a version for which it is not server MUST NOT send a version to which it is not conformant. A
at least conditionally compliant. A server MAY send a 505 (HTTP server MAY send a 505 (HTTP Version Not Supported) response if it
Version Not Supported) response if it cannot send a response using cannot send a response using the major version used in the client's
the major version used in the client's request. request.
An HTTP server MAY send an HTTP/1.0 response to an HTTP/1.0 request An HTTP server MAY send an HTTP/1.0 response to an HTTP/1.0 request
if it is known or suspected that the client incorrectly implements if it is known or suspected that the client incorrectly implements
the HTTP specification and is incapable of correctly processing later the HTTP specification and is incapable of correctly processing later
version responses, such as when a client fails to parse the version version responses, such as when a client fails to parse the version
number correctly or when an intermediary is known to blindly forward number correctly or when an intermediary is known to blindly forward
the HTTP-Version even when it doesn't comply with the given minor the HTTP-version even when it doesn't conform to the given minor
version of the protocol. Such protocol downgrades SHOULD NOT be version of the protocol. Such protocol downgrades SHOULD NOT be
performed unless triggered by specific client attributes, such as performed unless triggered by specific client attributes, such as
when one or more of the request header fields (e.g., User-Agent) when one or more of the request header fields (e.g., User-Agent)
uniquely match the values sent by a client known to be in error. uniquely match the values sent by a client known to be in error.
The intention of HTTP's versioning design is that the major number The intention of HTTP's versioning design is that the major number
will only be incremented if an incompatible message syntax is will only be incremented if an incompatible message syntax is
introduced, and that the minor number will only be incremented when introduced, and that the minor number will only be incremented when
changes made to the protocol have the effect of adding to the message changes made to the protocol have the effect of adding to the message
semantics or implying additional capabilities of the sender. semantics or implying additional capabilities of the sender.
skipping to change at page 18, line 23 skipping to change at page 16, line 22
query = <query, defined in [RFC3986], Section 3.4> query = <query, defined in [RFC3986], Section 3.4>
uri-host = <host, defined in [RFC3986], Section 3.2.2> uri-host = <host, defined in [RFC3986], Section 3.2.2>
partial-URI = relative-part [ "?" query ] partial-URI = relative-part [ "?" query ]
Each protocol element in HTTP that allows a URI reference will Each protocol element in HTTP that allows a URI reference will
indicate in its ABNF production whether the element allows any form indicate in its ABNF production whether the element allows any form
of reference (URI-reference), only a URI in absolute form (absolute- of reference (URI-reference), only a URI in absolute form (absolute-
URI), only the path and optional query components, or some URI), only the path and optional query components, or some
combination of the above. Unless otherwise indicated, URI references combination of the above. Unless otherwise indicated, URI references
are parsed relative to the effective request URI, which defines the are parsed relative to the effective request URI (Section 5.5).
default base URI for references in both the request and its
corresponding response.
2.7.1. http URI scheme 2.7.1. http URI scheme
The "http" URI scheme is hereby defined for the purpose of minting The "http" 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 for namespace governed by a potential HTTP origin server listening for
TCP connections on a given port. TCP connections on a given port.
http-URI = "http:" "//" authority path-abempty [ "?" query ] http-URI = "http:" "//" authority path-abempty [ "?" query ]
skipping to change at page 19, line 19 skipping to change at page 17, line 15
"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.
When an "http" URI is used within a context that calls for access to When an "http" URI is used within a context that calls for access to
the indicated resource, a client MAY attempt access by resolving the the indicated resource, a client MAY attempt access by resolving the
host to an IP address, establishing a TCP connection to that address host to an IP address, establishing a TCP connection to that address
on the indicated port, and sending an HTTP request message on the indicated port, and sending an HTTP request message
(Section 3) containing the URI's identifying data (Section 4) to the (Section 3) containing the URI's identifying data (Section 5) to the
server. If the server responds to that request with a non-interim server. If the server responds to that request with a non-interim
HTTP response message, as described in Section 4 of [Part2], then HTTP response message, as described in Section 4 of [Part2], then
that response is considered an authoritative answer to the client's that response is considered an authoritative answer to the client's
request. request.
Although HTTP is independent of the transport protocol, the "http" Although HTTP is independent of the transport protocol, the "http"
scheme is specific to TCP-based services because the name delegation scheme is specific to TCP-based services because the name delegation
process depends on TCP for establishing authority. An HTTP service process depends on TCP for establishing authority. An HTTP service
based on some other underlying connection protocol would presumably based on some other underlying connection protocol would presumably
be identified using a different URI scheme, just as the "https" be identified using a different URI scheme, just as the "https"
skipping to change at page 21, line 15 skipping to change at page 19, line 12
http://example.com:80/~smith/home.html http://example.com:80/~smith/home.html
http://EXAMPLE.com/%7Esmith/home.html http://EXAMPLE.com/%7Esmith/home.html
http://EXAMPLE.com:/%7esmith/home.html http://EXAMPLE.com:/%7esmith/home.html
3. Message Format 3. Message Format
All HTTP/1.1 messages consist of a start-line followed by a sequence All HTTP/1.1 messages consist of a start-line followed by a sequence
of octets in a format similar to the Internet Message Format of octets in a format similar to the Internet Message Format
[RFC5322]: zero or more header fields (collectively referred to as [RFC5322]: zero or more header fields (collectively referred to as
the "headers" or the "header section"), an empty line indicating the the "headers" or the "header section"), an empty line indicating the
end of the header section, and an optional message-body. end of the header section, and an optional message body.
HTTP-message = start-line HTTP-message = start-line
*( header-field CRLF ) *( header-field CRLF )
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 Recipients 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.
An HTTP message can be parsed as a stream for incremental processing
or forwarding downstream. However, recipients cannot rely on
incremental delivery of partial messages, since some implementations
will buffer or delay message forwarding for the sake of network
efficiency, security checks, or payload transformations.
3.1. Start Line 3.1. Start Line
An HTTP message can either be a request from client to server or a An HTTP message can either be a request from client to server or a
response from server to client. Syntactically, the two types of response from server to client. Syntactically, the two types of
message differ only in the start-line, which is either a Request-Line message differ only in the start-line, which is either a request-line
(for requests) or a Status-Line (for responses), and in the algorithm (for requests) or a status-line (for responses), and in the algorithm
for determining the length of the message-body (Section 3.3). In for determining the length of the message body (Section 3.3). In
theory, a client could receive requests and a server could receive theory, a client could receive requests and a server could receive
responses, distinguishing them by their different start-line formats, responses, distinguishing them by their different start-line formats,
but in practice servers are implemented to only expect a request (a but in practice servers are implemented to only expect a request (a
response is interpreted as an unknown or invalid request method) and response is interpreted as an unknown or invalid request method) and
clients are implemented to only expect a response. clients are implemented to only expect a response.
start-line = Request-Line / Status-Line start-line = request-line / status-line
Implementations MUST NOT send whitespace between the start-line and Implementations MUST NOT send whitespace between the start-line and
the first header field. The presence of such whitespace in a request the first header field. The presence of such whitespace in a request
might be an attempt to trick a server into ignoring that field or might be an attempt to trick a server into ignoring that field or
processing the line after it as a new request, either of which might processing the line after it as a new request, either of which might
result in a security vulnerability if other implementations within result in a security vulnerability if other implementations within
the request chain interpret the same message differently. Likewise, the request chain interpret the same message differently. Likewise,
the presence of such whitespace in a response might be ignored by the presence of such whitespace in a response might be ignored by
some clients or cause others to cease parsing. some clients or cause others to cease parsing.
3.1.1. Request-Line 3.1.1. Request Line
The Request-Line begins with a method token, followed by a single
space (SP), the request-target, another single space (SP), the
protocol version, and ending with CRLF.
Request-Line = Method SP request-target SP HTTP-Version CRLF A request-line begins with a method token, followed by a single space
(SP), the request-target, another single space (SP), the protocol
version, and ending with CRLF.
3.1.1.1. Method 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
See Section 2 of [Part2] for further information, such as the list of
methods defined by this specification, the IANA registry, and
considerations for new methods.
3.1.1.2. request-target The methods defined by this specification can be found in Section 2
of [Part2], along with information regarding the HTTP 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. The four options for request-target are described in the request, as defined in Section 5.3.
Section 4.1.
request-target = "*" No whitespace is allowed inside the method, request-target, and
/ absolute-URI protocol version. Hence, recipients typically parse the request-line
/ ( path-absolute [ "?" query ] ) into its component parts by splitting on the SP characters.
/ authority
Unfortunately, some user agents fail to properly encode hypertext
references that have embedded whitespace, sending the characters
directly instead of properly percent-encoding the disallowed
characters. Recipients of an invalid request-line SHOULD respond
with either a 400 (Bad Request) error or a 301 (Moved Permanently)
redirect with the request-target properly encoded. Recipients SHOULD
NOT attempt to autocorrect and then process the request without a
redirect, since the invalid request-line might be deliberately
crafted to bypass 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-
target. A server MUST be prepared to receive URIs of unbounded line. A server that receives a method longer than any that it
length and respond with the 414 (URI Too Long) status code if the implements SHOULD respond with either a 404 (Not Allowed), if it is
received request-target would be longer than the server wishes to an origin server, or a 501 (Not Implemented) status code. A server
handle (see Section 7.4.15 of [Part2]). MUST be prepared to receive URIs of unbounded length and respond with
the 414 (URI Too Long) status code if the received request-target
would be longer than the server wishes to handle (see Section 7.4.12
of [Part2]).
Various ad-hoc limitations on request-target 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 request-target lengths of 8000 or more octets. support, at a minimum, request-line lengths of up to 8000 octets.
Note: Fragments ([RFC3986], Section 3.5) are not part of the
request-target and thus will not be transmitted in an HTTP
request.
3.1.2. Response 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,
and ending with CRLF. and ending with CRLF.
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF status-line = HTTP-version SP status-code SP reason-phrase CRLF
3.1.2.1. Status Code
The Status-Code element is a 3-digit integer result code of the The status-code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. See Section 4 of attempt to understand and satisfy the request. See Section 4 of
[Part2] for further information, such as the list of status codes [Part2] for further information, such as the list of status codes
defined by this specification, the IANA registry, and considerations defined by this specification, the IANA registry, and considerations
for new status codes. for new status codes.
Status-Code = 3DIGIT status-code = 3DIGIT
3.1.2.2. Reason Phrase
The Reason Phrase exists for the sole purpose of providing a textual The reason-phrase element exists for the sole purpose of providing a
description associated with the numeric status code, out of deference textual description associated with the numeric status code, mostly
to earlier Internet application protocols that were more frequently out of deference to earlier Internet application protocols that were
used with interactive text clients. A client SHOULD ignore the more frequently used with interactive text clients. A client SHOULD
content of the Reason Phrase. ignore the reason-phrase content.
Reason-Phrase = *( HTAB / SP / VCHAR / obs-text ) reason-phrase = *( HTAB / SP / VCHAR / obs-text )
3.2. Header Fields 3.2. Header Fields
Each HTTP header field consists of a case-insensitive field name Each HTTP header field consists of a case-insensitive field name
followed by a colon (":"), optional whitespace, and the field value. followed by a colon (":"), optional whitespace, and the field value.
header-field = field-name ":" OWS field-value BWS header-field = field-name ":" OWS field-value BWS
field-name = token field-name = token
field-value = *( field-content / obs-fold ) field-value = *( field-content / obs-fold )
field-content = *( HTAB / SP / VCHAR / obs-text ) field-content = *( HTAB / SP / VCHAR / obs-text )
obs-fold = CRLF ( SP / HTAB )
; obsolete line folding
; see Section 3.2.2
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 9.2 of [Part2] as containing the header field is defined in Section 10.2 of [Part2] as containing the
origination timestamp for the message in which it appears. origination timestamp for the message in which it appears.
HTTP header fields are fully extensible: there is no limit on the HTTP 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, or on the number of header fields used in a given message. semantics, or on the number of header fields used in a given message.
Existing fields are defined in each part of this specification and in Existing fields are defined in each part of this specification and in
many other specifications outside the standards process. New header many other specifications outside the standards process. New header
fields can be introduced without changing the protocol version if fields can be introduced without changing the protocol version if
their defined semantics allow them to be safely ignored by recipients their defined semantics allow them to be safely ignored by recipients
that do not recognize them. that do not recognize them.
New HTTP header fields SHOULD be registered with IANA according to New HTTP header fields SHOULD be registered with IANA according to
the procedures in Section 3.1 of [Part2]. Unrecognized header fields the procedures in Section 3.1 of [Part2]. Unrecognized header fields
MUST be forwarded by a proxy unless the field-name is listed in the MUST be forwarded by a proxy unless the field-name is listed in the
Connection header field (Section 8.1) or the proxy is specifically Connection header field (Section 6.1) or the proxy is specifically
configured to block or otherwise transform such fields. Unrecognized configured to block or otherwise transform such fields. Unrecognized
header fields SHOULD be ignored by other recipients. header fields SHOULD be ignored by other recipients.
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
skipping to change at page 25, line 5 skipping to change at page 23, line 12
the same field name are received is therefore significant to the the same field name are received is therefore significant to the
interpretation of the combined field value; a proxy MUST NOT change interpretation of the combined field value; a proxy MUST NOT change
the order of these field values when forwarding a message. the order of these field values when forwarding a message.
Note: The "Set-Cookie" header field as implemented in practice can Note: The "Set-Cookie" header field as implemented in practice can
occur multiple times, but does not use the list syntax, and thus occur multiple times, but does not use the list syntax, and thus
cannot be combined into a single line ([RFC6265]). (See Appendix cannot be combined into a single line ([RFC6265]). (See Appendix
A.2.3 of [Kri2001] for details.) Also note that the Set-Cookie2 A.2.3 of [Kri2001] for details.) Also note that the Set-Cookie2
header field specified in [RFC2965] does not share this problem. header field specified in [RFC2965] does not share this problem.
3.2.1. Field Parsing 3.2.1. Whitespace
This specification uses three rules to denote the use of linear
whitespace: OWS (optional whitespace), RWS (required whitespace), and
BWS ("bad" whitespace).
The OWS rule is used where zero or more linear whitespace octets
might appear. OWS SHOULD either not be produced or be produced as a
single SP. Multiple OWS octets that occur within field-content
SHOULD either be replaced with a single SP or transformed to all SP
octets (each octet other than SP replaced with SP) before
interpreting the field value or forwarding the message downstream.
RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be produced as a single SP.
Multiple RWS octets that occur within field-content SHOULD either be
replaced with a single SP or transformed to all SP octets before
interpreting the field value or forwarding the message downstream.
BWS is used where the grammar allows optional whitespace for
historical reasons but senders SHOULD NOT produce it in messages.
HTTP/1.1 recipients MUST accept such bad optional whitespace and
remove it before interpreting the field value or forwarding the
message downstream.
OWS = *( SP / HTAB )
; "optional" whitespace
RWS = 1*( SP / HTAB )
; "required" whitespace
BWS = OWS
; "bad" whitespace
3.2.2. Field Parsing
No whitespace is allowed between the header field-name and colon. In No whitespace is allowed between the header field-name and colon. In
the past, differences in the handling of such whitespace have led to the past, differences in the handling of such whitespace have led to
security vulnerabilities in request routing and response handling. security vulnerabilities in request routing and response handling.
Any received request message that contains whitespace between a Any received request message that contains whitespace between a
header field-name and colon MUST be rejected with a response code of header field-name and colon MUST be rejected with a response code of
400 (Bad Request). A proxy MUST remove any such whitespace from a 400 (Bad Request). A proxy MUST remove any such whitespace from a
response message before forwarding the message downstream. response message before forwarding the message downstream.
A field value MAY be preceded by optional whitespace (OWS); a single A field value MAY be preceded by optional whitespace (OWS); a single
SP is preferred. The field value does not include any leading or SP is preferred. The field value does not include any leading or
trailing white space: OWS occurring before the first non-whitespace trailing white space: OWS occurring before the first non-whitespace
octet of the field value or after the last non-whitespace octet of octet of the field value or after the last non-whitespace octet of
the field value is ignored and SHOULD be removed before further the field value is ignored and SHOULD be removed before further
processing (as this does not change the meaning of the header field). processing (as this does not change the meaning of the header field).
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 9.3.1). HTTP senders MUST NOT produce messages that include (Section 7.3.1). HTTP senders MUST NOT produce messages that include
line folding (i.e., that contain any field-content that matches the line folding (i.e., that contain any field-value that matches the
obs-fold rule) unless the message is intended for packaging within obs-fold rule) unless the message is intended for packaging within
the message/http media type. HTTP recipients SHOULD accept line the message/http media type. HTTP recipients SHOULD accept line
folding and replace any embedded obs-fold whitespace with either a folding and replace any embedded obs-fold whitespace with either a
single SP or a matching number of SP octets (to avoid buffer copying) single SP or a matching number of SP octets (to avoid buffer copying)
prior to interpreting the field value or forwarding the message prior to interpreting the field value or forwarding the message
downstream. downstream.
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] character encoding and supported other character 8859-1 [ISO-8859-1] character encoding and supported other character
sets only through use of [RFC2047] encoding. In practice, most HTTP sets only through use of [RFC2047] encoding. In practice, most HTTP
header field values use only a subset of the US-ASCII character header field values use only a subset of the US-ASCII character
encoding [USASCII]. Newly defined header fields SHOULD limit their encoding [USASCII]. Newly defined header fields SHOULD limit their
field values to US-ASCII octets. Recipients SHOULD treat other (obs- field values to US-ASCII octets. Recipients SHOULD treat other (obs-
text) octets in field content as opaque data. text) octets in field content as opaque data.
3.2.2. Field Length 3.2.3. Field Length
HTTP does not place a pre-defined limit on the length of header HTTP does not place a pre-defined limit on the length of header
fields, either in isolation or as a set. A server MUST be prepared fields, either in isolation or as a set. A server MUST be prepared
to receive request header fields of unbounded length and respond with to receive request header fields of unbounded length and respond with
a 4xx status code if the received header field(s) would be longer a 4xx status code if the received header field(s) would be longer
than the server wishes to handle. than the server wishes to handle.
A client that receives response headers that are longer than it A client that receives response headers that are longer than it
wishes to handle can only treat it as a server error. wishes to handle can only treat it as a server error.
Various ad-hoc limitations on header length are found in practice. Various ad-hoc limitations on header length are found in practice.
It is RECOMMENDED that all HTTP senders and recipients support It is RECOMMENDED that all HTTP senders and recipients support
messages whose combined header fields have 4000 or more octets. messages whose combined header fields have 4000 or more octets.
3.2.3. Common Field ABNF Rules 3.2.4. Field value components
Many HTTP/1.1 header field values consist of words (token or quoted- Many HTTP/1.1 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. These special
characters MUST be in a quoted string to be used within a parameter characters MUST be in a quoted string to be used within a parameter
value (as defined in Section 5.1). 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
skipping to change at page 27, line 9 skipping to change at page 26, line 5
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 = OWS / %x21-27 / %x2A-5B / %x5D-7E / obs-text ctext = OWS / %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 Senders 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 ")").
3.2.5. 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 3.2.4
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 B shows the collected ABNF, with the list rules expanded as
explained above.
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 associated with the request or response. payload body of that request or response. The message body is
identical to the payload body unless a transfer coding has been
applied, as described in Section 3.3.1.
message-body = *OCTET message-body = *OCTET
The message-body differs from the payload body only when a transfer- The rules for when a message body is allowed in a message differ for
coding has been applied, as indicated by the Transfer-Encoding header requests and responses.
field (Section 8.6). If more than one Transfer-Encoding header field
is present in a message, the multiple field-values MUST be combined
into one field-value, according to the algorithm defined in
Section 3.2, before determining the message-body length.
When one or more transfer-codings are applied to a payload in order The presence of a message body in a request is signaled by a a
to form the message-body, the Transfer-Encoding header field MUST Content-Length or Transfer-Encoding header field. Request message
contain the list of transfer-codings applied. Transfer-Encoding is a framing is independent of method semantics, even if the method does
property of the message, not of the payload, and thus MAY be added or not define any use for a message body.
removed by any implementation along the request/response chain under
the constraints found in Section 5.1.
If a message is received that has multiple Content-Length header The presence of a message body in a response depends on both the
fields (Section 8.2) with field-values consisting of the same decimal request method to which it is responding and the response status code
value, or a single Content-Length header field with a field value (Paragraph 2). Responses to the HEAD request method never include a
containing a list of identical decimal values (e.g., "Content-Length: message body because the associated response header fields (e.g.,
42, 42"), indicating that duplicate Content-Length header fields have Transfer-Encoding, Content-Length, etc.) only indicate what their
been generated or combined by an upstream message processor, then the values would have been if the request method had been GET.
recipient MUST either reject the message as invalid or replace the Successful (2xx) responses to CONNECT switch to tunnel mode instead
duplicated field-values with a single valid Content-Length field of having a message body. All 1xx (Informational), 204 (No Content),
containing that decimal value prior to determining the message-body and 304 (Not Modified) responses MUST NOT include a message body.
length. All other responses do include a message body, although the body MAY
be of zero length.
The rules for when a message-body is allowed in a message differ for 3.3.1. Transfer-Encoding
requests and responses.
The presence of a message-body in a request is signaled by the When one or more transfer codings are applied to a payload body in
inclusion of a Content-Length or Transfer-Encoding header field in order to form the message body, a Transfer-Encoding header field MUST
the request's header fields, even if the request method does not be sent in the message and MUST contain the list of corresponding
define any use for a message-body. This allows the request message transfer-coding names in the same order that they were applied.
framing algorithm to be independent of method semantics. Transfer codings are defined in Section 4.
For response messages, whether or not a message-body is included with Transfer-Encoding = 1#transfer-coding
a message is dependent on both the request method and the response
status code (Section 3.1.2.1). Responses to the HEAD request method
never include a message-body because the associated response header
fields (e.g., Transfer-Encoding, Content-Length, etc.) only indicate
what their values would have been if the request method had been GET.
All 1xx (Informational), 204 (No Content), and 304 (Not Modified)
responses MUST NOT include a message-body. All other responses do
include a message-body, although the body MAY be of zero length.
The length of the message-body is determined by one of the following Transfer-Encoding is analogous to the Content-Transfer-Encoding field
of MIME, which was designed to enable safe transport of binary data
over a 7-bit transport service ([RFC2045], Section 6). However, safe
transport has a different focus for an 8bit-clean transfer protocol.
In HTTP's case, Transfer-Encoding is primarily intended to accurately
delimit a dynamically generated payload and to distinguish payload
encodings that are only applied for transport efficiency or security
from those that are characteristics of the target resource.
The "chunked" transfer-coding (Section 4.1) MUST be implemented by
all HTTP/1.1 recipients because it plays a crucial role in delimiting
messages when the payload body size is not known in advance. When
the "chunked" transfer-coding is used, it MUST be the last transfer-
coding applied to form the message body and MUST NOT be applied more
than once in a message body. If any transfer-coding is applied to a
request payload body, the final transfer-coding applied MUST be
"chunked". If any transfer-coding is applied to a response payload
body, then either the final transfer-coding applied MUST be "chunked"
or the message MUST be terminated by closing the connection.
For example,
Transfer-Encoding: gzip, chunked
indicates that the payload body has been compressed using the gzip
coding and then chunked using the chunked coding while forming the
message body.
If more than one Transfer-Encoding header field is present in a
message, the multiple field-values MUST be combined into one field-
value, according to the algorithm defined in Section 3.2, before
determining the message body length.
Unlike Content-Encoding (Section 2.2 of [Part3]), Transfer-Encoding
is a property of the message, not of the payload, and thus MAY be
added or removed by any implementation along the request/response
chain. Additional information about the encoding parameters MAY be
provided by other header fields not defined by this specification.
Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 response to a GET request, neither of which includes a message
body, to indicate that the origin server would have applied a
transfer coding to the message body if the request had been an
unconditional GET. This indication is not required, however, because
any recipient on the response chain (including the origin server) can
remove transfer codings when they are not needed.
Transfer-Encoding was added in HTTP/1.1. It is generally assumed
that implementations advertising only HTTP/1.0 support will not
understand how to process a transfer-encoded payload. A client MUST
NOT send a request containing Transfer-Encoding unless it knows the
server will handle HTTP/1.1 (or later) requests; such knowledge might
be in the form of specific user configuration or by remembering the
version of a prior received response. A server MUST NOT send a
response containing Transfer-Encoding unless the corresponding
request indicates HTTP/1.1 (or later).
A server that receives a request message with a transfer-coding it
does not understand SHOULD respond with 501 (Not Implemented) and
then close the connection.
3.3.2. Content-Length
When a message does not have a Transfer-Encoding header field and the
payload body length can be determined prior to being transferred, a
Content-Length header field SHOULD be sent to indicate the length of
the payload body that is either present as the message body, for
requests and non-HEAD responses other than 304, or would have been
present had the request been an unconditional GET. The length is
expressed as a decimal number of octets.
Content-Length = 1*DIGIT
An example is
Content-Length: 3495
In the case of a response to a HEAD request, Content-Length indicates
the size of the payload body (without any potential transfer-coding)
that would have been sent had the request been a GET. In the case of
a 304 (Not Modified) response to a GET request, Content-Length
indicates the size of the payload body (without any potential
transfer-coding) that would have been sent in a 200 (OK) response.
HTTP's use of Content-Length is significantly different from how it
is used in MIME, where it is an optional field used only within the
"message/external-body" media-type.
Any Content-Length field value greater than or equal to zero is
valid. Since there is no predefined limit to the length of an HTTP
payload, recipients SHOULD anticipate potentially large decimal
numerals and prevent parsing errors due to integer conversion
overflows (Section 8.6).
If a message is received that has multiple Content-Length header
fields (Section 3.3.2) with field-values consisting of the same
decimal value, or a single Content-Length header field with a field
value containing a list of identical decimal values (e.g., "Content-
Length: 42, 42"), indicating that duplicate Content-Length header
fields have been generated or combined by an upstream message
processor, then the recipient MUST either reject the message as
invalid or replace the duplicated field-values with a single valid
Content-Length field containing that decimal value prior to
determining the message body length.
3.3.3. Message Body Length
The length of a message body is determined by one of the following
(in order of precedence): (in order of precedence):
1. Any response to a HEAD request and any response with a status 1. Any response to a HEAD request and any response with a status
code of 100-199, 204, or 304 is always terminated by the first code of 100-199, 204, or 304 is always terminated by the first
empty line after the header fields, regardless of the header empty line after the header fields, regardless of the header
fields present in the message, and thus cannot contain a message- fields present in the message, and thus cannot contain a message
body. body.
2. If a Transfer-Encoding header field is present and the "chunked" 2. Any successful (2xx) response to a CONNECT request implies that
transfer-coding (Section 5.1) is the final encoding, the message- the connection will become a tunnel immediately after the empty
line that concludes the header fields. A client MUST ignore any
Content-Length or Transfer-Encoding header fields received in
such a message.
3. If a Transfer-Encoding header field is present and the "chunked"
transfer-coding (Section 4.1) is the final encoding, the message
body length is determined by reading and decoding the chunked body length is determined by reading and decoding the chunked
data until the transfer-coding indicates the data is complete. data until the transfer-coding indicates the data is complete.
If a Transfer-Encoding header field is present in a response and If a Transfer-Encoding header field is present in a response and
the "chunked" transfer-coding is not the final encoding, the the "chunked" transfer-coding is not the final encoding, the
message-body length is determined by reading the connection until message body length is determined by reading the connection until
it is closed by the server. If a Transfer-Encoding header field it is closed by the server. If a Transfer-Encoding header field
is present in a request and the "chunked" transfer-coding is not is present in a request and the "chunked" transfer-coding is not
the final encoding, the message-body length cannot be determined the final encoding, the message body length cannot be determined
reliably; the server MUST respond with the 400 (Bad Request) reliably; the server MUST respond with the 400 (Bad Request)
status code and then close the connection. status code and then close the connection.
If a message is received with both a Transfer-Encoding header If a message is received with both a Transfer-Encoding header
field and a Content-Length header field, the Transfer-Encoding field and a Content-Length header field, the Transfer-Encoding
overrides the Content-Length. Such a message might indicate an overrides the Content-Length. Such a message might indicate an
attempt to perform request or response smuggling (bypass of attempt to perform request or response smuggling (bypass of
security-related checks on message routing or content) and thus security-related checks on message routing or content) and thus
ought to be handled as an error. The provided Content-Length ought to be handled as an error. The provided Content-Length
MUST be removed, prior to forwarding the message downstream, or MUST be removed, prior to forwarding the message downstream, or
replaced with the real message-body length after the transfer- replaced with the real message body length after the transfer-
coding is decoded. coding is decoded.
3. 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 MUST be
treated as an error to prevent request or response smuggling. If treated as an error to prevent request or response smuggling. If
this is a request message, the server MUST respond with a 400 this is a request message, the server MUST respond with a 400
(Bad Request) status code and then close the connection. If this (Bad Request) status code and then close the connection. If this
is a response message received by a proxy, the proxy MUST discard is a response message received by a proxy, the proxy MUST discard
the received response, send a 502 (Bad Gateway) status code as the received response, send a 502 (Bad Gateway) status code as
its downstream response, and then close the connection. If this its downstream response, and then close the connection. If this
is a response message received by a user-agent, it MUST be is a response message received by a user-agent, it MUST be
treated as an error by discarding the message and closing the treated as an error by discarding the message and closing the
connection. connection.
4. 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 message-body Transfer-Encoding, its decimal value defines the message body
length in octets. If the actual number of octets sent in the length in octets. If the actual number of octets sent in the
message is less than the indicated Content-Length, the recipient message is less than the indicated Content-Length, the recipient
MUST consider the message to be incomplete and treat the MUST consider the message to be incomplete and treat the
connection as no longer usable. If the actual number of octets connection as no longer usable. If the actual number of octets
sent in the message is more than the indicated Content-Length, sent in the message is more than the indicated Content-Length,
the recipient MUST only process the message-body up to the field the recipient MUST only process the message body up to the field
value's number of octets; the remainder of the message MUST value's number of octets; the remainder of the message MUST
either be discarded or treated as the next message in a pipeline. either be discarded or treated as the next message in a pipeline.
For the sake of robustness, a user-agent MAY attempt to detect For the sake of robustness, a user-agent MAY attempt to detect
and correct such an error in message framing if it is parsing the and correct such an error in message framing if it is parsing the
response to the last request on a connection and the connection response to the last request on a connection and the connection
has been closed by the server. has been closed by the server.
5. 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).
6. 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, implementations SHOULD use encoding or length- network failure, implementations SHOULD use encoding or length-
delimited messages whenever possible. The close-delimiting feature delimited messages whenever possible. The close-delimiting feature
exists 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" encoding, since some existing in advance, rather than the "chunked" encoding, since some existing
services respond to "chunked" with a 411 (Length Required) status services respond to "chunked" with a 411 (Length Required) status
code even though they understand the chunked encoding. This is code even though they understand the chunked encoding. This is
typically because such services are implemented via a gateway that typically because such services are implemented via a gateway that
requires a content-length in advance of being called and the server requires a content-length in advance of being called and the server
is unable or unwilling to buffer the entire request before is unable or unwilling to buffer the entire request before
processing. processing.
A client that sends a request containing a message-body MUST include A client that sends a request containing a message body MUST include
a valid Content-Length header field if it does not know the server a valid Content-Length header field if it does not know the server
will handle HTTP/1.1 (or later) requests; such knowledge can be in will handle HTTP/1.1 (or later) requests; such knowledge can be in
the form of specific user configuration or by remembering the version the form of specific user configuration or by remembering the version
of a prior received response. of a prior received response.
3.4. Handling Incomplete Messages 3.4. Handling Incomplete Messages
Request messages that are prematurely terminated, possibly due to a Request messages that are prematurely terminated, possibly due to a
cancelled connection or a server-imposed time-out exception, MUST cancelled connection or a server-imposed time-out exception, MUST
result in closure of the connection; sending an HTTP/1.1 error result in closure of the connection; sending an HTTP/1.1 error
response prior to closing the connection is OPTIONAL. response prior to closing the connection is OPTIONAL.
Response messages that are prematurely terminated, usually by closure Response messages that are prematurely terminated, usually by closure
of the connection prior to receiving the expected number of octets or of the connection prior to receiving the expected number of octets or
by failure to decode a transfer-encoded message-body, MUST be by failure to decode a transfer-encoded message body, MUST be
recorded as incomplete. A response that terminates in the middle of recorded as incomplete. A response that terminates in the middle of
the header block (before the empty line is received) cannot be the header block (before the empty line is received) cannot be
assumed to convey the full semantics of the response and MUST be assumed to convey the full semantics of the response and MUST be
treated as an error. treated as an error.
A message-body that uses the chunked transfer encoding is incomplete A message body that uses the chunked transfer encoding is incomplete
if the zero-sized chunk that terminates the encoding has not been if 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 encoding nor Content-Length is terminated by closure of the transfer encoding 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 block was
received intact. received intact.
A user agent MUST NOT render an incomplete response message-body as A user agent MUST NOT render an incomplete response message body as
if it were complete (i.e., some indication must be given to the user if it were complete (i.e., some indication must be given to the user
that an error occurred). Cache requirements for incomplete responses that an error occurred). Cache requirements for incomplete responses
are defined in Section 2.1 of [Part6]. are defined in Section 2.1 of [Part6].
A server MUST read the entire request message-body or close the A server MUST read the entire request message body or close the
connection after sending its response, since otherwise the remaining connection after sending its response, since otherwise the remaining
data on a persistent connection would be misinterpreted as the next data on a persistent connection would be misinterpreted as the next
request. Likewise, a client MUST read the entire response message- request. Likewise, a client MUST read the entire response message
body if it intends to reuse the same connection for a subsequent body if it intends to reuse the same connection for a subsequent
request. Pipelining multiple requests on a connection is described request. Pipelining multiple requests on a connection is described
in Section 6.1.2.2. in Section 6.3.2.2.
3.5. Message Parsing Robustness 3.5. Message Parsing Robustness
Older HTTP/1.0 client implementations might send an extra CRLF after Older HTTP/1.0 client implementations might send an extra CRLF after
a POST request as a lame workaround for some early server a POST request as a lame 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 client MUST NOT preface or terminated by a line-ending. An HTTP/1.1 client MUST NOT preface or
follow a request with an extra CRLF. If terminating the request follow a request with an extra CRLF. If terminating the request
message-body with a line-ending is desired, then the client MUST message body with a line-ending is desired, then the client MUST
include the terminating CRLF octets as part of the message-body include the terminating CRLF octets as part of the message body
length. length.
In the interest of robustness, servers SHOULD ignore at least one In the interest of robustness, servers SHOULD ignore at least one
empty line received where a Request-Line is expected. In other empty line received where a request-line is expected. In other
words, if the server is reading the protocol stream at the beginning words, if the server is reading the protocol stream at the beginning
of a message and receives a CRLF first, it SHOULD ignore the CRLF. of a message and receives a CRLF first, it SHOULD ignore the CRLF.
Likewise, although the line terminator for the start-line and header Likewise, although the line terminator for the start-line and header
fields is the sequence CRLF, we recommend that recipients recognize a fields is the sequence CRLF, we recommend that recipients recognize a
single LF as a line terminator and ignore any CR. single LF as a line terminator and ignore any CR.
When a server listening only for HTTP request messages, or processing When a server listening only for HTTP request messages, or processing
what appears from the start-line to be an HTTP request message, what appears from the start-line to be an HTTP request message,
receives a sequence of octets that does not match the HTTP-message receives a sequence of octets that does not match the HTTP-message
grammar aside from the robustness exceptions listed above, the server grammar aside from the robustness exceptions listed above, the server
MUST respond with an HTTP/1.1 400 (Bad Request) response. MUST respond with an HTTP/1.1 400 (Bad Request) response.
4. Message Routing 4. Transfer Codings
In most cases, the user agent is provided a URI reference from which
it determines an absolute URI for identifying the target resource.
When a request to the resource is initiated, all or part of that URI
is used to construct the HTTP request-target.
4.1. Types of Request Target
The four options for request-target are dependent on the nature of
the request.
The asterisk "*" form of request-target, which MUST NOT be used with
any request method other than OPTIONS, means that the request applies
to the server as a whole (the listening process) rather than to a
specific named resource at that server. For example,
OPTIONS * HTTP/1.1
The "absolute-URI" form is REQUIRED when the request is being made to
a proxy. The proxy is requested to either forward the request or
service it from a valid cache, and then return the response. Note
that the proxy MAY forward the request on to another proxy or
directly to the server specified by the absolute-URI. In order to
avoid request loops, a proxy that forwards requests to other proxies
MUST be able to recognize and exclude all of its own server names,
including any aliases, local variations, and the numeric IP address.
An example Request-Line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
To allow for transition to absolute-URIs in all requests in future
versions of HTTP, all HTTP/1.1 servers MUST accept the absolute-URI
form in requests, even though HTTP/1.1 clients will only generate
them in requests to proxies.
If a proxy receives a host name that is not a fully qualified domain
name, it MAY add its domain to the host name it received. If a proxy
receives a fully qualified domain name, the proxy MUST NOT change the
host name.
The "authority form" is only used by the CONNECT request method
(Section 6.9 of [Part2]).
The most common form of request-target is that used when making a
request to an origin server ("origin form"). In this case, the
absolute path and query components of the URI MUST be transmitted as
the request-target, and the authority component MUST be transmitted
in a Host header field. For example, a client wishing to retrieve a
representation of the resource, as identified above, directly from
the origin server would open (or reuse) a TCP connection to port 80
of the host "www.example.org" and send the lines:
GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org
followed by the remainder of the Request. Note that the origin form
of request-target always starts with an absolute path; if the target
resource's URI path is empty, then an absolute path of "/" MUST be
provided in the request-target.
If a proxy receives an OPTIONS request with an absolute-URI form of
request-target in which the URI has an empty path and no query
component, then the last proxy on the request chain MUST use a
request-target of "*" when it forwards the request to the indicated
origin server.
For example, the request
OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the final proxy as
OPTIONS * HTTP/1.1
Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org".
The request-target is transmitted in the format specified in
Section 2.7.1. If the request-target is percent-encoded ([RFC3986],
Section 2.1), the origin server MUST decode the request-target in
order to properly interpret the request. Servers SHOULD respond to
invalid request-targets with an appropriate status code.
A non-transforming proxy MUST NOT rewrite the "path-absolute" and
"query" parts of the received request-target when forwarding it to
the next inbound server, except as noted above to replace a null
path-absolute with "/" or "*".
Note: The "no rewrite" rule prevents the proxy from changing the
meaning of the request when the origin server is improperly using
a non-reserved URI character for a reserved purpose. Implementors
need to be aware that some pre-HTTP/1.1 proxies have been known to
rewrite the request-target.
4.2. The Resource Identified by a Request
The exact resource identified by an Internet request is determined by
examining both the request-target and the Host header field.
An origin server that does not allow resources to differ by the
requested host MAY ignore the Host header field value when
determining the resource identified by an HTTP/1.1 request. (But see
Appendix A.1.1 for other requirements on Host support in HTTP/1.1.)
An origin server that does differentiate resources based on the host
requested (sometimes referred to as virtual hosts or vanity host
names) MUST use the following rules for determining the requested
resource on an HTTP/1.1 request:
1. If request-target is an absolute-URI, the host is part of the
request-target. Any Host header field value in the request MUST
be ignored.
2. If the request-target is not an absolute-URI, and the request
includes a Host header field, the host is determined by the Host
header field value.
3. If the host as determined by rule 1 or 2 is not a valid host on
the server, the response MUST be a 400 (Bad Request) error
message.
Recipients of an HTTP/1.0 request that lacks a Host header field MAY
attempt to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to determine what
exact resource is being requested.
4.3. Effective Request URI
HTTP requests often do not carry the absolute URI ([RFC3986], Section
4.3) for the target resource; instead, the URI needs to be inferred
from the request-target, Host header field, and connection context.
The result of this process is called the "effective request URI".
The "target resource" is the resource identified by the effective
request URI.
If the request-target is an absolute-URI, then the effective request
URI is the request-target.
If the request-target uses the origin form or the asterisk form, and
the Host header field is present, then the effective request URI is
constructed by concatenating
o the scheme name: "http" if the request was received over an
insecure TCP connection, or "https" when received over a SSL/
TLS-secured TCP connection,
o the octet sequence "://",
o the authority component, as specified in the Host header field
(Section 8.3), and
o the request-target obtained from the Request-Line, unless the
request-target is just the asterisk "*".
If the request-target uses the origin form or the asterisk form, and
the Host header field is not present, then the effective request URI
is undefined.
Otherwise, when request-target uses the authority form, the effective
request URI is undefined.
Example 1: the effective request URI for the message
GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080
(received over an insecure TCP connection) is "http", plus "://",
plus the authority component "www.example.org:8080", plus the
request-target "/pub/WWW/TheProject.html", thus
"http://www.example.org:8080/pub/WWW/TheProject.html".
Example 2: the effective request URI for the message
OPTIONS * HTTP/1.1
Host: www.example.org
(received over an SSL/TLS secured TCP connection) is "https", plus
"://", plus the authority component "www.example.org", thus
"https://www.example.org".
Effective request URIs are compared using the rules described in
Section 2.7.3, except that empty path components MUST NOT be treated
as equivalent to an absolute path of "/".
5. Protocol Parameters
5.1. Transfer Codings
Transfer-coding values are used to indicate an encoding Transfer-coding values are used to indicate an encoding
transformation that has been, can be, or might need to be applied to transformation that has been, can be, or might need to be applied to
a payload body in order to ensure "safe transport" through the a payload body in order to ensure "safe transport" through the
network. This differs from a content coding in that the transfer- network. This differs from a content coding in that the transfer-
coding is a property of the message rather than a property of the coding is a property of the message rather than a property of the
representation that is being transferred. representation that is being transferred.
transfer-coding = "chunked" ; Section 5.1.1 transfer-coding = "chunked" ; Section 4.1
/ "compress" ; Section 5.1.2.1 / "compress" ; Section 4.2.1
/ "deflate" ; Section 5.1.2.2 / "deflate" ; Section 4.2.2
/ "gzip" ; Section 5.1.2.3 / "gzip" ; Section 4.2.3
/ transfer-extension / transfer-extension
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 values are case-insensitive. HTTP/1.1 uses
transfer-coding values in the TE header field (Section 8.4) and in
the Transfer-Encoding header field (Section 8.6).
Transfer-codings are analogous to the Content-Transfer-Encoding
values of MIME, which were designed to enable safe transport of
binary data over a 7-bit transport service ([RFC2045], Section 6).
However, safe transport has a different focus for an 8bit-clean
transfer protocol. In HTTP, the only unsafe characteristic of
message-bodies is the difficulty in determining the exact message
body length (Section 3.3), or the desire to encrypt data over a
shared transport.
A server that receives a request message with a transfer-coding it All transfer-coding values are case-insensitive. The HTTP Transfer
does not understand SHOULD respond with 501 (Not Implemented) and Coding registry is defined in Section 7.4. HTTP/1.1 uses transfer-
then close the connection. A server MUST NOT send transfer-codings coding values in the TE header field (Section 4.3) and in the
to an HTTP/1.0 client. Transfer-Encoding header field (Section 3.3.1).
5.1.1. Chunked Transfer Coding 4.1. Chunked Transfer Coding
The chunked encoding modifies the body of a message in order to The chunked encoding modifies the body of a message in order to
transfer it as a series of chunks, each with its own size indicator, transfer it as a series of chunks, each with its own size indicator,
followed by an OPTIONAL trailer containing header fields. This followed by an OPTIONAL trailer containing header fields. This
allows dynamically produced content to be transferred along with the allows dynamically produced content to be transferred along with the
information necessary for the recipient to verify that it has information necessary for the recipient to verify that it has
received the full message. received the full 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-ext = *( ";" chunk-ext-name chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
[ "=" 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 chunk-data = 1*OCTET ; a sequence of chunk-size octets
trailer-part = *( header-field CRLF ) 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
The chunk-size field is a string of hex digits indicating the size of The chunk-size field is a string of hex digits indicating the size of
the chunk-data in octets. The chunked encoding is ended by any chunk the chunk-data in octets. The chunked encoding is ended by any chunk
whose size is zero, followed by the trailer, which is terminated by whose size is zero, followed by the trailer, which is terminated by
an empty line. an empty line.
The trailer allows the sender to include additional HTTP header The trailer allows the sender to include additional HTTP header
fields at the end of the message. The Trailer header field can be fields at the end of the message. The Trailer header field can be
used to indicate which header fields are included in a trailer (see used to indicate which header fields are included in a trailer (see
Section 8.5). Section 4.4).
A server using chunked transfer-coding in a response MUST NOT use the A server using chunked transfer-coding in a response MUST NOT use the
trailer for any header fields unless at least one of the following is trailer for any header fields unless at least one of the following is
true: 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 8.4; 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 it. In server where the field originated) without receiving it. In
other words, the server that generated the header (often but not other words, the server that generated the header (often but not
always the origin server) is willing to accept the possibility always the origin server) is willing to accept the possibility
that the trailer fields might be silently discarded along the that the trailer fields might be silently discarded along the
path to the client. path to the client.
This requirement prevents an interoperability failure when the This requirement prevents an interoperability failure when the
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. It avoids a situation where forwarded to an HTTP/1.0 recipient. It avoids a situation where
compliance with the protocol would have necessitated a possibly conformance with the protocol would have necessitated a possibly
infinite buffer on the proxy. infinite buffer on the proxy.
A process for decoding the "chunked" transfer-coding can be A process for decoding the "chunked" transfer-coding can be
represented in pseudo-code as: represented 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
skipping to change at page 38, line 10 skipping to change at page 36, line 10
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
All HTTP/1.1 applications MUST be able to receive and decode the All HTTP/1.1 applications MUST be able to receive and decode the
"chunked" transfer-coding and MUST ignore chunk-ext extensions they "chunked" transfer-coding and MUST ignore chunk-ext extensions they
do not understand. do not understand.
Since "chunked" is the only transfer-coding required to be understood Use of chunk-ext extensions by senders is deprecated; they SHOULD NOT
by HTTP/1.1 recipients, it plays a crucial role in delimiting be sent and definition of new chunk-extensions is discouraged.
messages on a persistent connection. Whenever a transfer-coding is
applied to a payload body in a request, the final transfer-coding
applied MUST be "chunked". If a transfer-coding is applied to a
response payload body, then either the final transfer-coding applied
MUST be "chunked" or the message MUST be terminated by closing the
connection. When the "chunked" transfer-coding is used, it MUST be
the last transfer-coding applied to form the message-body. The
"chunked" transfer-coding MUST NOT be applied more than once in a
message-body.
5.1.2. 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.
Note: Use of program names for the identification of encoding Note: Use of program names for the identification of encoding
formats is not desirable and is discouraged for future encodings. formats is not desirable and is discouraged for future encodings.
Their use here is representative of historical practice, not good Their use here is representative of historical practice, not good
design. design.
Note: For compatibility with previous implementations of HTTP, Note: For compatibility with previous implementations of HTTP,
applications SHOULD consider "x-gzip" and "x-compress" to be applications SHOULD consider "x-gzip" and "x-compress" to be
equivalent to "gzip" and "compress" respectively. equivalent to "gzip" and "compress" respectively.
5.1.2.1. Compress Coding 4.2.1. Compress Coding
The "compress" format is produced by the common UNIX file compression The "compress" format is produced by the common UNIX file compression
program "compress". This format is an adaptive Lempel-Ziv-Welch program "compress". This format is an adaptive Lempel-Ziv-Welch
coding (LZW). coding (LZW).
5.1.2.2. Deflate Coding 4.2.2. Deflate Coding
The "deflate" format is defined as the "deflate" compression The "deflate" format is defined as the "deflate" compression
mechanism (described in [RFC1951]) used inside the "zlib" data format mechanism (described in [RFC1951]) used inside the "zlib" data format
([RFC1950]). ([RFC1950]).
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.
5.1.2.3. Gzip Coding 4.2.3. Gzip Coding
The "gzip" format is produced by the file compression program "gzip" The "gzip" format is produced by the file compression program "gzip"
(GNU zip), as described in [RFC1952]. This format is a Lempel-Ziv (GNU zip), as described in [RFC1952]. This format is a Lempel-Ziv
coding (LZ77) with a 32 bit CRC. coding (LZ77) with a 32 bit CRC.
5.1.3. Transfer Coding Registry 4.3. TE
The HTTP Transfer Coding Registry defines the name space for the
transfer coding names.
Registrations MUST include the following fields: The "TE" header field indicates what extension transfer-codings the
client is willing to accept in the response, and whether or not it is
willing to accept trailer fields in a chunked transfer-coding.
o Name Its value consists of the keyword "trailers" and/or a comma-separated
list of extension transfer-coding names with optional accept
parameters (as described in Section 4).
o Description TE = #t-codings
t-codings = "trailers" / ( transfer-extension [ te-params ] )
te-params = OWS ";" OWS "q=" qvalue *( te-ext )
te-ext = OWS ";" OWS token [ "=" word ]
o Pointer to specification text The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer-coding, as
defined in Section 4.1. This keyword is reserved for use with
transfer-coding values even though it does not itself represent a
transfer-coding.
Names of transfer codings MUST NOT overlap with names of content Examples of its use are:
codings (Section 2.2 of [Part3]), unless the encoding transformation
is identical (as it is the case for the compression codings defined
in Section 5.1.2).
Values to be added to this name space require a specification (see TE: deflate
"Specification Required" in Section 4.1 of [RFC5226]), and MUST TE:
conform to the purpose of transfer coding defined in this section. TE: trailers, deflate;q=0.5
The registry itself is maintained at The TE header field only applies to the immediate connection.
<http://www.iana.org/assignments/http-parameters>. Therefore, the keyword MUST be supplied within a Connection header
field (Section 6.1) whenever TE is present in an HTTP/1.1 message.
5.2. Product Tokens A server tests whether a transfer-coding is acceptable, according to
a TE field, using these rules:
Product tokens are used to allow communicating applications to 1. The "chunked" transfer-coding is always acceptable. If the
identify themselves by software name and version. Most fields using keyword "trailers" is listed, the client indicates that it is
product tokens also allow sub-products which form a significant part willing to accept trailer fields in the chunked response on
of the application to be listed, separated by whitespace. By behalf of itself and any downstream clients. The implication is
convention, the products are listed in order of their significance that, if given, the client is stating that either all downstream
for identifying the application. clients are willing to accept trailer fields in the forwarded
response, or that it will attempt to buffer the response on
behalf of downstream recipients.
product = token ["/" product-version] Note: HTTP/1.1 does not define any means to limit the size of a
product-version = token chunked response such that a client can be assured of buffering
the entire response.
Examples: 2. If the transfer-coding being tested is one of the transfer-
codings listed in the TE field, then it is acceptable unless it
is accompanied by a qvalue of 0. (As defined in Section 4.3.1, a
qvalue of 0 means "not acceptable".)
User-Agent: CERN-LineMode/2.15 libwww/2.17b3 3. If multiple transfer-codings are acceptable, then the acceptable
Server: Apache/0.8.4 transfer-coding with the highest non-zero qvalue is preferred.
The "chunked" transfer-coding always has a qvalue of 1.
Product tokens SHOULD be short and to the point. They MUST NOT be If the TE field-value is empty or if no TE field is present, the only
used for advertising or other non-essential information. Although acceptable transfer-coding is "chunked". A message with no transfer-
any token octet MAY appear in a product-version, this token SHOULD coding is always acceptable.
only be used for a version identifier (i.e., successive versions of
the same product SHOULD only differ in the product-version portion of
the product value).
5.3. Quality Values 4.3.1. Quality Values
Both transfer codings (TE request header field, Section 8.4) and Both transfer codings (TE request header field, Section 4.3) and
content negotiation (Section 5 of [Part3]) use short "floating point" content negotiation (Section 5 of [Part3]) use short "floating point"
numbers to indicate the relative importance ("weight") of various numbers to indicate the relative importance ("weight") of various
negotiable parameters. A weight is normalized to a real number in negotiable parameters. A weight is normalized to a real number in
the range 0 through 1, where 0 is the minimum and 1 the maximum the range 0 through 1, where 0 is the minimum and 1 the maximum
value. If a parameter has a quality value of 0, then content with value. If a parameter has a quality value of 0, then content with
this parameter is "not acceptable" for the client. HTTP/1.1 this parameter is "not acceptable" for the client. HTTP/1.1
applications MUST NOT generate more than three digits after the applications MUST NOT generate more than three digits after the
decimal point. User configuration of these values SHOULD also be decimal point. User configuration of these values SHOULD also be
limited in this fashion. limited in this fashion.
qvalue = ( "0" [ "." 0*3DIGIT ] ) qvalue = ( "0" [ "." 0*3DIGIT ] )
/ ( "1" [ "." 0*3("0") ] ) / ( "1" [ "." 0*3("0") ] )
Note: "Quality values" is a misnomer, since these values merely Note: "Quality values" is a misnomer, since these values merely
represent relative degradation in desired quality. represent relative degradation in desired quality.
6. Connections 4.4. Trailer
6.1. Persistent Connections The "Trailer" header field indicates that the given set of header
fields is present in the trailer of a message encoded with chunked
transfer-coding.
6.1.1. Purpose Trailer = 1#field-name
Prior to persistent connections, a separate TCP connection was An HTTP/1.1 message SHOULD include a Trailer header field in a
established for each request, increasing the load on HTTP servers and message using chunked transfer-coding with a non-empty trailer.
causing congestion on the Internet. The use of inline images and Doing so allows the recipient to know which header fields to expect
other associated data often requires a client to make multiple in the trailer.
requests of the same server in a short amount of time. Analysis of
these performance problems and results from a prototype
implementation are available [Pad1995] [Spe]. Implementation
experience and measurements of actual HTTP/1.1 implementations show
good results [Nie1997]. Alternatives have also been explored, for
example, T/TCP [Tou1998].
Persistent HTTP connections have a number of advantages: If no Trailer header field is present, the trailer SHOULD NOT include
any header fields. See Section 4.1 for restrictions on the use of
trailer fields in a "chunked" transfer-coding.
o By opening and closing fewer TCP connections, CPU time is saved in Message header fields listed in the Trailer header field MUST NOT
routers and hosts (clients, servers, proxies, gateways, tunnels, include the following header fields:
or caches), and memory used for TCP protocol control blocks can be
saved in hosts.
o HTTP requests and responses can be pipelined on a connection. o Transfer-Encoding
Pipelining allows a client to make multiple requests without
waiting for each response, allowing a single TCP connection to be
used much more efficiently, with much lower elapsed time.
o Network congestion is reduced by reducing the number of packets o Content-Length
caused by TCP opens, and by allowing TCP sufficient time to
determine the congestion state of the network.
o Latency on subsequent requests is reduced since there is no time o Trailer
spent in TCP's connection opening handshake.
o HTTP can evolve more gracefully, since errors can be reported 5. Message Routing
without the penalty of closing the TCP connection. Clients using
future versions of HTTP might optimistically try a new feature,
but if communicating with an older server, retry with old
semantics after an error is reported.
HTTP implementations SHOULD implement persistent connections. HTTP request message routing is determined by each client based on
the target resource, the client's proxy configuration, and
establishment or reuse of an inbound connection. The corresponding
response routing follows the same connection chain back to the
client.
6.1.2. Overall Operation 5.1. Identifying a Target Resource
A significant difference between HTTP/1.1 and earlier versions of HTTP is used in a wide variety of applications, ranging from general-
HTTP is that persistent connections are the default behavior of any purpose computers to home appliances. In some cases, communication
HTTP connection. That is, unless otherwise indicated, the client options are hard-coded in a client's configuration. However, most
SHOULD assume that the server will maintain a persistent connection, HTTP clients rely on the same resource identification mechanism and
even after error responses from the server. configuration techniques as general-purpose Web browsers.
Persistent connections provide a mechanism by which a client and a HTTP communication is initiated by a user agent for some purpose.
server can signal the close of a TCP connection. This signaling The purpose is a combination of request semantics, which are defined
takes place using the Connection header field (Section 8.1). Once a in [Part2], and a target resource upon which to apply those
close has been signaled, the client MUST NOT send any more requests semantics. A URI reference (Section 2.7) is typically used as an
on that connection. identifier for the "target resource", which a user agent would
resolve to its absolute form in order to obtain the "target URI".
The target URI excludes the reference's fragment identifier
component, if any, since fragment identifiers are reserved for
client-side processing ([RFC3986], Section 3.5).
6.1.2.1. Negotiation HTTP intermediaries obtain the request semantics and target URI from
the request-line of an incoming request message.
An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to 5.2. Connecting Inbound
maintain a persistent connection unless a Connection header field
including the connection-token "close" was sent in the request. If
the server chooses to close the connection immediately after sending
the response, it SHOULD send a Connection header field including the
connection-token "close".
An HTTP/1.1 client MAY expect a connection to remain open, but would Once the target URI is determined, a client needs to decide whether a
decide to keep it open based on whether the response from a server network request is necessary to accomplish the desired semantics and,
contains a Connection header field with the connection-token close. if so, where that request is to be directed.
In case the client does not want to maintain a connection for more If the client has a response cache and the request semantics can be
than that request, it SHOULD send a Connection header field including satisfied by a cache ([Part6]), then the request is usually directed
the connection-token close. to the cache first.
If either the client or the server sends the close token in the If the request is not satisfied by a cache, then a typical client
Connection header field, that request becomes the last one for the will check its configuration to determine whether a proxy is to be
connection. used to satisfy the request. Proxy configuration is implementation-
dependent, but is often based on URI prefix matching, selective
authority matching, or both, and the proxy itself is usually
identified by an "http" or "https" URI. If a proxy is applicable,
the client connects inbound by establishing (or reusing) a connection
to that proxy.
Clients and servers SHOULD NOT assume that a persistent connection is If no proxy is applicable, a typical client will invoke a handler
maintained for HTTP versions less than 1.1 unless it is explicitly routine, usually specific to the target URI's scheme, to connect
signaled. See Appendix A.1.2 for more information on backward directly to an authority for the target resource. How that is
compatibility with HTTP/1.0 clients. accomplished is dependent on the target URI scheme and defined by its
associated specification, similar to how this specification defines
origin server access for resolution of the "http" (Section 2.7.1) and
"https" (Section 2.7.2) schemes.
In order to remain persistent, all messages on the connection MUST 5.3. Request Target
have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 3.3.
6.1.2.2. Pipelining Once an inbound connection is obtained (Section 6), the client sends
an HTTP request message (Section 3) with a request-target derived
from the target URI. There are four distinct formats for the
request-target, depending on both the method being requested and
whether the request is to a proxy.
A client that supports persistent connections MAY "pipeline" its request-target = origin-form
requests (i.e., send multiple requests without waiting for each / absolute-form
response). A server MUST send its responses to those requests in the / authority-form
same order that the requests were received. / asterisk-form
Clients which assume persistent connections and pipeline immediately origin-form = path-absolute [ "?" query ]
after connection establishment SHOULD be prepared to retry their absolute-form = absolute-URI
connection if the first pipelined attempt fails. If a client does authority-form = authority
such a retry, it MUST NOT pipeline before it knows the connection is asterisk-form = "*"
persistent. Clients MUST also be prepared to resend their requests
if the server closes the connection before sending all of the
corresponding responses.
Clients SHOULD NOT pipeline requests using non-idempotent request The most common form of request-target is the origin-form. When
methods or non-idempotent sequences of request methods (see Section making a request directly to an origin server, other than a CONNECT
6.1.2 of [Part2]). Otherwise, a premature termination of the or server-wide OPTIONS request (as detailed below), a client MUST
transport connection could lead to indeterminate results. A client send only the absolute path and query components of the target URI as
wishing to send a non-idempotent request SHOULD wait to send that the request-target. If the target URI's path component is empty,
request until it has received the response status line for the then the client MUST send "/" as the path within the origin-form of
previous request. request-target. A Host header field is also sent, as defined in
Section 5.4, containing the target URI's authority component
(excluding any userinfo).
6.1.3. Proxy Servers For example, a client wishing to retrieve a representation of the
resource identified as
It is especially important that proxies correctly implement the http://www.example.org/where?q=now
properties of the Connection header field as specified in
Section 8.1.
The proxy server MUST signal persistent connections separately with directly from the origin server would open (or reuse) a TCP
its clients and the origin servers (or other proxy servers) that it connection to port 80 of the host "www.example.org" and send the
connects to. Each persistent connection applies to only one lines:
transport link.
A proxy server MUST NOT establish a HTTP/1.1 persistent connection GET /where?q=now HTTP/1.1
with an HTTP/1.0 client (but see Section 19.7.1 of [RFC2068] for Host: www.example.org
information and discussion of the problems with the Keep-Alive header
field implemented by many HTTP/1.0 clients).
6.1.3.1. End-to-end and Hop-by-hop Header Fields followed by the remainder of the request message.
When making a request to a proxy, other than a CONNECT or server-wide
OPTIONS request (as detailed below), a client MUST send the target
URI in absolute-form as the request-target. The proxy is requested
to either service that request from a valid cache, if possible, or
make the same request on the client's behalf to either the next
inbound proxy server or directly to the origin server indicated by
the request-target. Requirements on such "forwarding" of messages
are defined in Section 5.6.
An example absolute-form of request-line would be:
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
future version of HTTP, HTTP/1.1 servers MUST accept the absolute-
form in requests, even though HTTP/1.1 clients will only send them in
requests to proxies.
The authority-form of request-target is only used for CONNECT
requests (Section 6.9 of [Part2]). When making a CONNECT request to
establish a tunnel through one or more proxies, a client MUST send
only the target URI's authority component (excluding any userinfo) as
the request-target. For example,
CONNECT www.example.com:80 HTTP/1.1
The asterisk-form of request-target is only used for a server-wide
OPTIONS request (Section 6.2 of [Part2]). When a client wishes to
request OPTIONS for the server as a whole, as opposed to a specific
named resource of that server, the client MUST send only "*" (%x2A)
as the request-target. For example,
OPTIONS * HTTP/1.1
If a proxy receives an OPTIONS request with an absolute-form of
request-target in which the URI has an empty path and no query
component, then the last proxy on the request chain MUST send a
request-target of "*" when it forwards the request to the indicated
origin server.
For example, the request
OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the final proxy as
OPTIONS * HTTP/1.1
Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org".
5.4. Host
The "Host" header field in a request provides the host and port
information from the target URI, enabling the origin server to
distinguish among resources while servicing requests for multiple
host names on a single IP address. Since the Host field-value is
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
A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target URI includes an authority component, then
the Host field-value MUST be identical to that authority component
after excluding any userinfo (Section 2.7.1). If the authority
component is missing or undefined for the target URI, then the Host
header field MUST be sent with an empty field-value.
For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1
Host: www.example.org
The Host header field MUST be sent in an HTTP/1.1 request even if the
request-target is in the absolute-form, since this allows the Host
information to be forwarded through ancient HTTP/1.0 proxies that
might not have implemented Host.
When an HTTP/1.1 proxy receives a request with an absolute-form of
request-target, the proxy MUST ignore the received Host header field
(if any) and instead replace it with the host information of the
request-target. If the proxy forwards the request, it MUST generate
a new Host field-value based on the received request-target rather
than forward the received Host field-value.
Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the
Host field-value for redirecting requests to internal servers, or for
use as a cache key in a shared cache, without first verifying that
the intercepted connection is targeting a valid IP address for that
host.
A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a
Host header field with an invalid field-value.
5.5. Effective Request URI
A server that receives an HTTP request message MUST reconstruct the
user agent's original target URI, based on the pieces of information
learned from the request-target, Host, and connection context, in
order to identify the intended target resource and properly service
the request. The URI derived from this reconstruction process is
referred to as the "effective request URI".
For a user agent, the effective request URI is the target URI.
If the request-target is in absolute-form, then the effective request
URI is the same as the request-target. Otherwise, the effective
request URI is constructed as follows.
If the request is received over an SSL/TLS-secured TCP connection,
then the effective request URI's scheme is "https"; otherwise, the
scheme is "http".
If the request-target is in authority-form, then the effective
request URI's authority component is the same as the request-target.
Otherwise, if a Host header field is supplied with a non-empty field-
value, then the authority component is the same as the Host field-
value. Otherwise, the authority component is the concatenation of
the default hostname configured for the server, a colon (":"), and
the connection's incoming TCP port number in decimal form.
If the request-target is in authority-form or asterisk-form, then the
effective request URI's combined path and query component is empty.
Otherwise, the combined path and query component is the same as the
request-target.
The components of the effective request URI, once determined as
above, can be combined into absolute-URI form by concatenating the
scheme, "://", authority, and combined path and query component.
Example 1: the following message received over an insecure TCP
connection
GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080
has an effective request URI of
http://www.example.org:8080/pub/WWW/TheProject.html
Example 2: the following message received over an SSL/TLS-secured TCP
connection
OPTIONS * HTTP/1.1
Host: www.example.org
has an effective request URI of
https://www.example.org
An origin server that does not allow resources to differ by requested
host MAY ignore the Host field-value and instead replace it with a
configured server name when constructing the effective request URI.
Recipients of an HTTP/1.0 request that lacks a Host header field MAY
attempt to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to guess the
effective request URI's authority component.
5.6. Intermediary Forwarding
As described in Section 2.3, intermediaries can serve a variety of
roles in the processing of HTTP requests and responses. Some
intermediaries are used to improve performance or availability.
Others are used for access control or to filter content. Since an
HTTP stream has characteristics similar to a pipe-and-filter
architecture, there are no inherent limits to the extent an
intermediary can enhance (or interfere) with either direction of the
stream.
In order to avoid request loops, a proxy that forwards requests to
other proxies MUST be able to recognize and exclude all of its own
server names, including any aliases, local variations, or literal IP
addresses.
If a proxy receives a request-target with a host name that is not a
fully qualified domain name, it MAY add its domain to the host name
it received when forwarding the request. A proxy MUST NOT change the
host name if it is a fully qualified domain name.
A non-transforming proxy MUST NOT rewrite the "path-absolute" and
"query" parts of the received request-target when forwarding it to
the next inbound server, except as noted above to replace an empty
path with "/" or "*".
Intermediaries that forward a message MUST implement the Connection
header field as specified in Section 6.1.
5.6.1. End-to-end and Hop-by-hop Header Fields
For the purpose of defining the behavior of caches and non-caching For the purpose of defining the behavior of caches and non-caching
proxies, we divide HTTP header fields into two categories: proxies, we divide HTTP header fields into two categories:
o End-to-end header fields, which are transmitted to the ultimate o End-to-end header fields, which are transmitted to the ultimate
recipient of a request or response. End-to-end header fields in recipient of a request or response. End-to-end header fields in
responses MUST be stored as part of a cache entry and MUST be responses MUST be stored as part of a cache entry and MUST be
transmitted in any response formed from a cache entry. transmitted in any response formed from a cache entry.
o Hop-by-hop header fields, which are meaningful only for a single o Hop-by-hop header fields, which are meaningful only for a single
skipping to change at page 43, line 48 skipping to change at page 45, line 50
o Trailer o Trailer
o Transfer-Encoding o Transfer-Encoding
o Upgrade o Upgrade
All other header fields defined by HTTP/1.1 are end-to-end header All other header fields defined by HTTP/1.1 are end-to-end header
fields. fields.
Other hop-by-hop header fields MUST be listed in a Connection header Other hop-by-hop header fields MUST be listed in a Connection header
field (Section 8.1). field (Section 6.1).
6.1.3.2. Non-modifiable Header Fields 5.6.2. Non-modifiable Header Fields
Some features of HTTP/1.1, such as Digest Authentication, depend on Some features of HTTP/1.1, such as Digest Authentication, depend on
the value of certain end-to-end header fields. A non-transforming the value of certain end-to-end header fields. A non-transforming
proxy SHOULD NOT modify an end-to-end header field unless the proxy SHOULD NOT modify an end-to-end header field unless the
definition of that header field requires or specifically allows that. definition of that header field requires or specifically allows that.
A non-transforming proxy MUST NOT modify any of the following fields A non-transforming proxy MUST NOT modify any of the following fields
in a request or response, and it MUST NOT add any of these fields if in a request or response, and it MUST NOT add any of these fields if
not already present: not already present:
skipping to change at page 45, line 12 skipping to change at page 47, line 12
Warning 214 (Transformation applied) if one does not already appear Warning 214 (Transformation applied) if one does not already appear
in the message (see Section 3.6 of [Part6]). in the message (see Section 3.6 of [Part6]).
Warning: Unnecessary modification of end-to-end header fields Warning: Unnecessary modification of end-to-end header fields
might cause authentication failures if stronger authentication might cause authentication failures if stronger authentication
mechanisms are introduced in later versions of HTTP. Such mechanisms are introduced in later versions of HTTP. Such
authentication mechanisms MAY rely on the values of header fields authentication mechanisms MAY rely on the values of header fields
not listed here. not listed here.
A non-transforming proxy MUST preserve the message payload ([Part3]), A non-transforming proxy MUST preserve the message payload ([Part3]),
though it MAY change the message-body through application or removal though it MAY change the message body through application or removal
of a transfer-coding (Section 5.1). of a transfer-coding (Section 4).
6.1.4. Practical Considerations 5.7. Associating a Response to a Request
HTTP does not include a request identifier for associating a given
request message with its corresponding one or more response messages.
Hence, it relies on the order of response arrival to correspond
exactly to the order in which requests are made on the same
connection. More than one response message per request only occurs
when one or more informational responses (1xx, see Section 7.1 of
[Part2]) precede a final response to the same request.
A client that uses persistent connections and sends more than one
request per connection MUST maintain a list of outstanding requests
in the order sent on that connection and MUST associate each received
response message to the highest ordered request that has not yet
received a final (non-1xx) response.
6. Connection Management
6.1. Connection
The "Connection" header field allows the sender to specify options
that are desired only for that particular connection. Such
connection options MUST be removed or replaced before the message can
be forwarded downstream by a proxy or gateway. This mechanism also
allows the sender to indicate which HTTP header fields used in the
message are only intended for the immediate recipient ("hop-by-hop"),
as opposed to all recipients on the chain ("end-to-end"), enabling
the message to be self-descriptive and allowing future connection-
specific extensions to be deployed in HTTP without fear that they
will be blindly forwarded by previously deployed intermediaries.
The Connection header field's value has the following grammar:
Connection = 1#connection-token
connection-token = token
A proxy or gateway MUST parse a received Connection header field
before a message is forwarded and, for each connection-token in this
field, remove any header field(s) from the message with the same name
as the connection-token, and then remove the Connection header field
itself or replace it with the sender's own connection options for the
forwarded message.
A sender MUST NOT include field-names in the Connection header field-
value for fields that are defined as expressing constraints for all
recipients in the request or response chain, such as the Cache-
Control header field (Section 3.2 of [Part6]).
The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection
behavior based on the presence of connection options MUST do so based
on the presence of the connection-token rather than only the presence
of the optional header field. In other words, if the connection
option is received as a header field but not indicated within the
Connection field-value, then the recipient MUST ignore the
connection-specific header field because it has likely been forwarded
by an intermediary that is only partially conformant.
When defining new connection options, specifications ought to
carefully consider existing deployed header fields and ensure that
the new connection-token does not share the same name as an unrelated
header field that might already be deployed. Defining a new
connection-token essentially reserves that potential field-name for
carrying additional information related to the connection option,
since it would be unwise for senders to use that field-name for
anything else.
HTTP/1.1 defines the "close" connection option for the sender to
signal that the connection will be closed after completion of the
response. For example,
Connection: close
in either the request or the response header fields indicates that
the connection SHOULD NOT be considered "persistent" (Section 6.3)
after the current request/response is complete.
An HTTP/1.1 client that does not support persistent connections MUST
include the "close" connection option in every request message.
An HTTP/1.1 server that does not support persistent connections MUST
include the "close" connection option in every response message that
does not have a 1xx (Informational) status code.
6.2. Via
The "Via" header field MUST be sent by a proxy or gateway to indicate
the intermediate protocols and recipients between the user agent and
the server on requests, and between the origin server and the client
on responses. It is analogous to the "Received" field used by email
systems (Section 3.6.7 of [RFC5322]) and is intended to be used for
tracking message forwards, avoiding request loops, and identifying
the protocol capabilities of all senders along the request/response
chain.
Via = 1#( received-protocol RWS received-by
[ RWS comment ] )
received-protocol = [ protocol-name "/" ] protocol-version
received-by = ( uri-host [ ":" port ] ) / pseudonym
pseudonym = token
The received-protocol indicates the protocol version of the message
received by the server or client along each segment of the request/
response chain. The received-protocol version is appended to the Via
field value when the message is forwarded so that information about
the protocol capabilities of upstream applications remains visible to
all recipients.
The protocol-name is excluded if and only if it would be "HTTP". The
received-by field is normally the host and optional port number of a
recipient server or client that subsequently forwarded the message.
However, if the real host is considered to be sensitive information,
it MAY be replaced by a pseudonym. If the port is not given, it MAY
be assumed to be the default port of the received-protocol.
Multiple Via field values represent each proxy or gateway that has
forwarded the message. Each recipient MUST append its information
such that the end result is ordered according to the sequence of
forwarding applications.
Comments MAY be used in the Via header field to identify the software
of each recipient, analogous to the User-Agent and Server header
fields. However, all comments in the Via field are optional and MAY
be removed by any recipient prior to forwarding the message.
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
forward the request to a public proxy at p.example.net, which
completes the request by forwarding it to the origin server at
www.example.com. The request received by www.example.com would then
have the following Via header field:
Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
A proxy or gateway used as a portal through a network firewall SHOULD
NOT forward the names and ports of hosts within the firewall region
unless it is explicitly enabled to do so. If not enabled, the
received-by host of any host behind the firewall SHOULD be replaced
by an appropriate pseudonym for that host.
For organizations that have strong privacy requirements for hiding
internal structures, a proxy or gateway MAY combine an ordered
subsequence of Via header field entries with identical received-
protocol values into a single such entry. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Senders SHOULD NOT combine multiple entries unless they are all under
the same organizational control and the hosts have already been
replaced by pseudonyms. Senders MUST NOT combine entries which have
different received-protocol values.
6.3. Persistent Connections
6.3.1. Purpose
Prior to persistent connections, a separate TCP connection was
established for each request, increasing the load on HTTP servers and
causing congestion on the Internet. The use of inline images and
other associated data often requires a client to make multiple
requests of the same server in a short amount of time. Analysis of
these performance problems and results from a prototype
implementation are available [Pad1995] [Spe]. Implementation
experience and measurements of actual HTTP/1.1 implementations show
good results [Nie1997]. Alternatives have also been explored, for
example, T/TCP [Tou1998].
Persistent HTTP connections have a number of advantages:
o By opening and closing fewer TCP connections, CPU time is saved in
routers and hosts (clients, servers, proxies, gateways, tunnels,
or caches), and memory used for TCP protocol control blocks can be
saved in hosts.
o HTTP requests and responses can be pipelined on a connection.
Pipelining allows a client to make multiple requests without
waiting for each response, allowing a single TCP connection to be
used much more efficiently, with much lower elapsed time.
o Network congestion is reduced by reducing the number of packets
caused by TCP opens, and by allowing TCP sufficient time to
determine the congestion state of the network.
o Latency on subsequent requests is reduced since there is no time
spent in TCP's connection opening handshake.
o HTTP can evolve more gracefully, since errors can be reported
without the penalty of closing the TCP connection. Clients using
future versions of HTTP might optimistically try a new feature,
but if communicating with an older server, retry with old
semantics after an error is reported.
HTTP implementations SHOULD implement persistent connections.
6.3.2. Overall Operation
A significant difference between HTTP/1.1 and earlier versions of
HTTP is that persistent connections are the default behavior of any
HTTP connection. That is, unless otherwise indicated, the client
SHOULD assume that the server will maintain a persistent connection,
even after error responses from the server.
Persistent connections provide a mechanism by which a client and a
server can signal the close of a TCP connection. This signaling
takes place using the Connection header field (Section 6.1). Once a
close has been signaled, the client MUST NOT send any more requests
on that connection.
6.3.2.1. Negotiation
An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to
maintain a persistent connection unless a Connection header field
including the connection-token "close" was sent in the request. If
the server chooses to close the connection immediately after sending
the response, it SHOULD send a Connection header field including the
connection-token "close".
An HTTP/1.1 client MAY expect a connection to remain open, but would
decide to keep it open based on whether the response from a server
contains a Connection header field with the connection-token close.
In case the client does not want to maintain a connection for more
than that request, it SHOULD send a Connection header field including
the connection-token close.
If either the client or the server sends the close token in the
Connection header field, that request becomes the last one for the
connection.
Clients and servers SHOULD NOT assume that a persistent connection is
maintained for HTTP versions less than 1.1 unless it is explicitly
signaled. See Appendix A.1.2 for more information on backward
compatibility with HTTP/1.0 clients.
Each persistent connection applies to only one transport link.
A proxy server MUST NOT establish a HTTP/1.1 persistent connection
with an HTTP/1.0 client (but see Section 19.7.1 of [RFC2068] for
information and discussion of the problems with the Keep-Alive header
field implemented by many HTTP/1.0 clients).
In order to remain persistent, all messages on the connection MUST
have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 3.3.
6.3.2.2. Pipelining
A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each
response). A server MUST send its responses to those requests in the
same order that the requests were received.
Clients which assume persistent connections and pipeline immediately
after connection establishment SHOULD be prepared to retry their
connection if the first pipelined attempt fails. If a client does
such a retry, it MUST NOT pipeline before it knows the connection is
persistent. Clients MUST also be prepared to resend their requests
if the server closes the connection before sending all of the
corresponding responses.
Clients SHOULD NOT pipeline requests using non-idempotent request
methods or non-idempotent sequences of request methods (see Section
6.1.2 of [Part2]). Otherwise, a premature termination of the
transport connection could lead to indeterminate results. A client
wishing to send a non-idempotent request SHOULD wait to send that
request until it has received the response status line for the
previous request.
6.3.3. Practical Considerations
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 When a client or server wishes to time-out it SHOULD issue a graceful
close on the transport connection. Clients and servers SHOULD both close on the transport connection. Clients and servers SHOULD both
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line blocking" problem (whereby a request that takes significant line blocking" problem (whereby a request that takes significant
server-side processing and/or has a large payload can block server-side processing and/or has a large payload can block
subsequent requests on the same connection), each connection used subsequent requests on the same connection), each connection used
consumes server resources (sometimes significantly), and furthermore consumes server resources (sometimes significantly), and furthermore
using multiple connections can cause undesirable side effects in using multiple connections can cause undesirable side effects in
congested networks. congested networks.
Note that servers might reject traffic that they deem abusive, Note that servers might reject traffic that they deem abusive,
including an excessive number of connections from a client. including an excessive number of connections from a client.
6.1.5. Retrying Requests 6.3.4. Retrying Requests
Senders can close the transport connection at any time. Therefore, Senders can close the transport connection at any time. Therefore,
clients, servers, and proxies MUST be able to recover from clients, servers, and proxies MUST be able to recover from
asynchronous close events. Client software MAY reopen the transport asynchronous close events. Client software MAY reopen the transport
connection and retransmit the aborted sequence of requests without connection and retransmit the aborted sequence of requests without
user interaction so long as the request sequence is idempotent (see user interaction so long as the request sequence is idempotent (see
Section 6.1.2 of [Part2]). Non-idempotent request methods or Section 6.1.2 of [Part2]). Non-idempotent request methods or
sequences MUST NOT be automatically retried, although user agents MAY sequences MUST NOT be automatically retried, although user agents MAY
offer a human operator the choice of retrying the request(s). offer a human operator the choice of retrying the request(s).
Confirmation by user-agent software with semantic understanding of Confirmation by user-agent software with semantic understanding of
the application MAY substitute for user confirmation. The automatic the application MAY substitute for user confirmation. The automatic
retry SHOULD NOT be repeated if the second sequence of requests retry SHOULD NOT be repeated if the second sequence of requests
fails. fails.
6.2. Message Transmission Requirements 6.4. Message Transmission Requirements
6.2.1. Persistent Connections and Flow Control 6.4.1. Persistent Connections and Flow Control
HTTP/1.1 servers SHOULD maintain persistent connections and use TCP's HTTP/1.1 servers SHOULD maintain persistent connections and use TCP's
flow control mechanisms to resolve temporary overloads, rather than flow control mechanisms to resolve temporary overloads, rather than
terminating connections with the expectation that clients will retry. terminating connections with the expectation that clients will retry.
The latter technique can exacerbate network congestion. The latter technique can exacerbate network congestion.
6.2.2. Monitoring Connections for Error Status Messages 6.4.2. Monitoring Connections for Error Status Messages
An HTTP/1.1 (or later) client sending a message-body SHOULD monitor An HTTP/1.1 (or later) client sending a message body SHOULD monitor
the network connection for an error status code while it is the network connection for an error status code while it is
transmitting the request. If the client sees an error status code, transmitting the request. If the client sees an error status code,
it SHOULD immediately cease transmitting the body. If the body is it SHOULD immediately cease transmitting the body. If the body is
being sent using a "chunked" encoding (Section 5.1), a zero length being sent using a "chunked" encoding (Section 4), a zero length
chunk and empty trailer MAY be used to prematurely mark the end of chunk and empty trailer MAY be used to prematurely mark the end of
the message. If the body was preceded by a Content-Length header the message. If the body was preceded by a Content-Length header
field, the client MUST close the connection. field, the client MUST close the connection.
6.2.3. Use of the 100 (Continue) Status 6.4.3. Use of the 100 (Continue) Status
The purpose of the 100 (Continue) status code (see Section 7.1.1 of The purpose of the 100 (Continue) status code (see Section 7.1.1 of
[Part2]) is to allow a client that is sending a request message with [Part2]) is to allow a client that is sending a request message with
a request body to determine if the origin server is willing to accept a request body to determine if the origin server is willing to accept
the request (based on the request header fields) before the client the request (based on the request header fields) before the client
sends the request body. In some cases, it might either be sends the request body. In some cases, it might either be
inappropriate or highly inefficient for the client to send the body inappropriate or highly inefficient for the client to send the body
if the server will reject the message without looking at the body. if the server will reject the message without looking at the body.
Requirements for HTTP/1.1 clients: Requirements for HTTP/1.1 clients:
o If a client will wait for a 100 (Continue) response before sending o If a client will wait for a 100 (Continue) response before sending
the request body, it MUST send an Expect header field (Section 9.3 the request body, it MUST send an Expect header field (Section
of [Part2]) with the "100-continue" expectation. 10.3 of [Part2]) with the "100-continue" expectation.
o A client MUST NOT send an Expect header field (Section 9.3 of o A client MUST NOT send an Expect header field (Section 10.3 of
[Part2]) with the "100-continue" expectation if it does not intend [Part2]) with the "100-continue" expectation if it does not intend
to send a request body. to send a request body.
Because of the presence of older implementations, the protocol allows Because of the presence of older implementations, the protocol allows
ambiguous situations in which a client might send "Expect: 100- ambiguous situations in which a client might send "Expect: 100-
continue" without receiving either a 417 (Expectation Failed) or a continue" without receiving either a 417 (Expectation Failed) or a
100 (Continue) status code. Therefore, when a client sends this 100 (Continue) status code. Therefore, when a client sends this
header field to an origin server (possibly via a proxy) from which it header field to an origin server (possibly via a proxy) from which it
has never seen a 100 (Continue) status code, the client SHOULD NOT has never seen a 100 (Continue) status code, the client SHOULD NOT
wait for an indefinite period before sending the request body. wait for an indefinite period before sending the request body.
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connection prematurely. connection prematurely.
o If an origin server receives a request that does not include an o If an origin server receives a request that does not include an
Expect header field with the "100-continue" expectation, the Expect header field with the "100-continue" expectation, the
request includes a request body, and the server responds with a request includes a request body, and the server responds with a
final status code before reading the entire request body from the final status code before reading the entire request body from the
transport connection, then the server SHOULD NOT close the transport connection, then the server SHOULD NOT close the
transport connection until it has read the entire request, or transport connection until it has read the entire request, or
until the client closes the connection. Otherwise, the client until the client closes the connection. Otherwise, the client
might not reliably receive the response message. However, this might not reliably receive the response message. However, this
requirement is not be construed as preventing a server from requirement ought not be construed as preventing a server from
defending itself against denial-of-service attacks, or from badly defending itself against denial-of-service attacks, or from badly
broken client implementations. broken client implementations.
Requirements for HTTP/1.1 proxies: Requirements for HTTP/1.1 proxies:
o If a proxy receives a request that includes an Expect header field o If a proxy receives a request that includes an Expect header field
with the "100-continue" expectation, and the proxy either knows with the "100-continue" expectation, and the proxy either knows
that the next-hop server complies with HTTP/1.1 or higher, or does that the next-hop server complies with HTTP/1.1 or higher, or does
not know the HTTP version of the next-hop server, it MUST forward not know the HTTP version of the next-hop server, it MUST forward
the request, including the Expect header field. the request, including the Expect header field.
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o Proxies SHOULD maintain a record of the HTTP version numbers o Proxies SHOULD maintain a record of the HTTP version numbers
received from recently-referenced next-hop servers. received from recently-referenced next-hop servers.
o A proxy MUST NOT forward a 100 (Continue) response if the request o A proxy MUST NOT forward a 100 (Continue) response if the request
message was received from an HTTP/1.0 (or earlier) client and did message was received from an HTTP/1.0 (or earlier) client and did
not include an Expect header field with the "100-continue" not include an Expect header field with the "100-continue"
expectation. This requirement overrides the general rule for expectation. This requirement overrides the general rule for
forwarding of 1xx responses (see Section 7.1 of [Part2]). forwarding of 1xx responses (see Section 7.1 of [Part2]).
7. Miscellaneous notes that might disappear 6.4.4. Closing Connections on Error
7.1. Scheme aliases considered harmful
[[TBD-aliases-harmful: describe why aliases like webcal are
harmful.]]
7.2. Use of HTTP for proxy communication
[[TBD-proxy-other: Configured to use HTTP to proxy HTTP or other
protocols.]]
7.3. Interception of HTTP for access control
[[TBD-intercept: Interception of HTTP traffic for initiating access
control.]]
7.4. Use of HTTP by other protocols
[[TBD-profiles: Profiles of HTTP defined by other protocol.
Extensions of HTTP like WebDAV.]]
7.5. Use of HTTP by media type specification
[[TBD-hypertext: Instructions on composing HTTP requests via
hypertext formats.]]
8. Header Field Definitions
This section defines the syntax and semantics of HTTP header fields
related to message origination, framing, and routing.
+-------------------+---------------+
| Header Field Name | Defined in... |
+-------------------+---------------+
| Connection | Section 8.1 |
| Content-Length | Section 8.2 |
| Host | Section 8.3 |
| TE | Section 8.4 |
| Trailer | Section 8.5 |
| Transfer-Encoding | Section 8.6 |
| Upgrade | Section 8.7 |
| Via | Section 8.8 |
+-------------------+---------------+
8.1. Connection
The "Connection" header field allows the sender to specify options
that are desired only for that particular connection. Such
connection options MUST be removed or replaced before the message can
be forwarded downstream by a proxy or gateway. This mechanism also
allows the sender to indicate which HTTP header fields used in the
message are only intended for the immediate recipient ("hop-by-hop"),
as opposed to all recipients on the chain ("end-to-end"), enabling
the message to be self-descriptive and allowing future connection-
specific extensions to be deployed in HTTP without fear that they
will be blindly forwarded by previously deployed intermediaries.
The Connection header field's value has the following grammar:
Connection = 1#connection-token
connection-token = token
A proxy or gateway MUST parse a received Connection header field
before a message is forwarded and, for each connection-token in this
field, remove any header field(s) from the message with the same name
as the connection-token, and then remove the Connection header field
itself or replace it with the sender's own connection options for the
forwarded message.
A sender MUST NOT include field-names in the Connection header field-
value for fields that are defined as expressing constraints for all
recipients in the request or response chain, such as the Cache-
Control header field (Section 3.2 of [Part6]).
The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection
behavior based on the presence of connection options MUST do so based
on the presence of the connection-token rather than only the presence
of the optional header field. In other words, if the connection
option is received as a header field but not indicated within the
Connection field-value, then the recipient MUST ignore the
connection-specific header field because it has likely been forwarded
by an intermediary that is only partially compliant.
When defining new connection options, specifications ought to
carefully consider existing deployed header fields and ensure that
the new connection-token does not share the same name as an unrelated
header field that might already be deployed. Defining a new
connection-token essentially reserves that potential field-name for
carrying additional information related to the connection option,
since it would be unwise for senders to use that field-name for
anything else.
HTTP/1.1 defines the "close" connection option for the sender to
signal that the connection will be closed after completion of the
response. For example,
Connection: close
in either the request or the response header fields indicates that
the connection SHOULD NOT be considered "persistent" (Section 6.1)
after the current request/response is complete.
An HTTP/1.1 client that does not support persistent connections MUST
include the "close" connection option in every request message.
An HTTP/1.1 server that does not support persistent connections MUST
include the "close" connection option in every response message that
does not have a 1xx (Informational) status code.
8.2. Content-Length
The "Content-Length" header field indicates the size of the message-
body, in decimal number of octets, for any message other than a
response to a HEAD request or a response with a status code of 304.
In the case of a response to a HEAD request, Content-Length indicates
the size of the payload body (not including any potential transfer-
coding) that would have been sent had the request been a GET. In the
case of a 304 (Not Modified) response to a GET request, Content-
Length indicates the size of the payload body (not including any
potential transfer-coding) that would have been sent in a 200 (OK)
response.
Content-Length = 1*DIGIT
An example is
Content-Length: 3495
Implementations SHOULD use this field to indicate the message-body
length when no transfer-coding is being applied and the payload's
body length can be determined prior to being transferred.
Section 3.3 describes how recipients determine the length of a
message-body.
Any Content-Length greater than or equal to zero is a valid value.
Note that the use of this field in HTTP is significantly different
from the corresponding definition in MIME, where it is an optional
field used within the "message/external-body" content-type.
8.3. Host
The "Host" header field in a request provides the host and port
information from the target resource's URI, enabling the origin
server to distinguish between resources while servicing requests for
multiple host names on a single IP address. Since the Host field-
value is 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
A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target resource's URI includes an authority
component, then the Host field-value MUST be identical to that
authority component after excluding any userinfo (Section 2.7.1). If
the authority component is missing or undefined for the target
resource's URI, then the Host header field MUST be sent with an empty
field-value.
For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1
Host: www.example.org
The Host header field MUST be sent in an HTTP/1.1 request even if the
request-target is in the form of an absolute-URI, since this allows
the Host information to be forwarded through ancient HTTP/1.0 proxies
that might not have implemented Host.
When an HTTP/1.1 proxy receives a request with a request-target in
the form of an absolute-URI, the proxy MUST ignore the received Host
header field (if any) and instead replace it with the host
information of the request-target. When a proxy forwards a request,
it MUST generate the Host header field based on the received
absolute-URI rather than the received Host.
Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the
Host header field value for redirecting requests to internal servers,
or for use as a cache key in a shared cache, without first verifying
that the intercepted connection is targeting a valid IP address for
that host.
A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a
Host header field with an invalid field-value.
See Sections 4.2 and A.1.1 for other requirements relating to Host.
8.4. TE
The "TE" header field indicates what extension transfer-codings it is
willing to accept in the response, and whether or not it is willing
to accept trailer fields in a chunked transfer-coding.
Its value consists of the keyword "trailers" and/or a comma-separated
list of extension transfer-coding names with optional accept
parameters (as described in Section 5.1).
TE = #t-codings
t-codings = "trailers" / ( transfer-extension [ te-params ] )
te-params = OWS ";" OWS "q=" qvalue *( te-ext )
te-ext = OWS ";" OWS token [ "=" word ]
The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer-coding, as
defined in Section 5.1.1. This keyword is reserved for use with
transfer-coding values even though it does not itself represent a
transfer-coding.
Examples of its use are:
TE: deflate
TE:
TE: trailers, deflate;q=0.5
The TE header field only applies to the immediate connection.
Therefore, the keyword MUST be supplied within a Connection header
field (Section 8.1) whenever TE is present in an HTTP/1.1 message.
A server tests whether a transfer-coding is acceptable, according to
a TE field, using these rules:
1. The "chunked" transfer-coding is always acceptable. If the
keyword "trailers" is listed, the client indicates that it is
willing to accept trailer fields in the chunked response on
behalf of itself and any downstream clients. The implication is
that, if given, the client is stating that either all downstream
clients are willing to accept trailer fields in the forwarded
response, or that it will attempt to buffer the response on
behalf of downstream recipients.
Note: HTTP/1.1 does not define any means to limit the size of a
chunked response such that a client can be assured of buffering
the entire response.
2. If the transfer-coding being tested is one of the transfer-
codings listed in the TE field, then it is acceptable unless it
is accompanied by a qvalue of 0. (As defined in Section 5.3, a
qvalue of 0 means "not acceptable".)
3. If multiple transfer-codings are acceptable, then the acceptable
transfer-coding with the highest non-zero qvalue is preferred.
The "chunked" transfer-coding always has a qvalue of 1.
If the TE field-value is empty or if no TE field is present, the only
transfer-coding is "chunked". A message with no transfer-coding is
always acceptable.
8.5. Trailer
The "Trailer" header field indicates that the given set of header
fields is present in the trailer of a message encoded with chunked
transfer-coding.
Trailer = 1#field-name
An HTTP/1.1 message SHOULD include a Trailer header field in a
message using chunked transfer-coding with a non-empty trailer.
Doing so allows the recipient to know which header fields to expect
in the trailer.
If no Trailer header field is present, the trailer SHOULD NOT include
any header fields. See Section 5.1.1 for restrictions on the use of
trailer fields in a "chunked" transfer-coding.
Message header fields listed in the Trailer header field MUST NOT
include the following header fields:
o Transfer-Encoding
o Content-Length
o Trailer
8.6. Transfer-Encoding
The "Transfer-Encoding" header field indicates what transfer-codings
(if any) have been applied to the message body. It differs from
Content-Encoding (Section 2.2 of [Part3]) in that transfer-codings
are a property of the message (and therefore are removed by
intermediaries), whereas content-codings are not.
Transfer-Encoding = 1#transfer-coding
Transfer-codings are defined in Section 5.1. An example is:
Transfer-Encoding: chunked
If multiple encodings have been applied to a representation, the
transfer-codings MUST be listed in the order in which they were
applied. Additional information about the encoding parameters MAY be
provided by other header fields not defined by this specification.
Many older HTTP/1.0 applications do not understand the Transfer- If the client is sending data, a server implementation using TCP
Encoding header field. SHOULD be careful to ensure that the client acknowledges receipt of
the packet(s) containing the response, before the server closes the
input connection. If the client continues sending data to the server
after the close, the server's TCP stack will send a reset packet to
the client, which might erase the client's unacknowledged input
buffers before they can be read and interpreted by the HTTP
application.
8.7. Upgrade 6.5. Upgrade
The "Upgrade" header field allows the client to specify what The "Upgrade" header field allows the client to specify what
additional communication protocols it would like to use, if the additional communication protocols it would like to use, if the
server chooses to switch protocols. Servers can use it to indicate server chooses to switch protocols. Servers can use it to indicate
what protocols they are willing to switch to. what protocols they are willing to switch to.
Upgrade = 1#product Upgrade = 1#protocol
protocol = protocol-name ["/" protocol-version]
protocol-name = token
protocol-version = token
For example, For example,
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
The Upgrade header field is intended to provide a simple mechanism The Upgrade header field is intended to provide a simple mechanism
for transition from HTTP/1.1 to some other, incompatible protocol. for transitioning from HTTP/1.1 to some other, incompatible protocol.
It does so by allowing the client to advertise its desire to use It does so by allowing the client to advertise its desire to use
another protocol, such as a later version of HTTP with a higher major another protocol, such as a later version of HTTP with a higher major
version number, even though the current request has been made using version number, even though the current request has been made using
HTTP/1.1. This eases the difficult transition between incompatible HTTP/1.1. This eases the difficult transition between incompatible
protocols by allowing the client to initiate a request in the more protocols by allowing the client to initiate a request in the more
commonly supported protocol while indicating to the server that it commonly supported protocol while indicating to the server that it
would like to use a "better" protocol if available (where "better" is would like to use a "better" protocol if available (where "better" is
determined by the server, possibly according to the nature of the determined by the server, possibly according to the nature of the
request method or target resource). request method or target resource).
skipping to change at page 56, line 4 skipping to change at page 57, line 32
protocols upon the existing transport-layer connection. Upgrade protocols upon the existing transport-layer connection. Upgrade
cannot be used to insist on a protocol change; its acceptance and use cannot be used to insist on a protocol change; its acceptance and use
by the server is optional. The capabilities and nature of the by the server is optional. The capabilities and nature of the
application-layer communication after the protocol change is entirely application-layer communication after the protocol change is entirely
dependent upon the new protocol chosen, although the first action dependent upon the new protocol chosen, although the first action
after changing the protocol MUST be a response to the initial HTTP after changing the protocol MUST be a response to the initial HTTP
request containing the Upgrade header field. request containing the Upgrade header field.
The Upgrade header field only applies to the immediate connection. The Upgrade header field only applies to the immediate connection.
Therefore, the upgrade keyword MUST be supplied within a Connection Therefore, the upgrade keyword MUST be supplied within a Connection
header field (Section 8.1) whenever Upgrade is present in an HTTP/1.1 header field (Section 6.1) whenever Upgrade is present in an HTTP/1.1
message. message.
The Upgrade header field cannot be used to indicate a switch to a The Upgrade header field cannot be used to indicate a switch to a
protocol on a different connection. For that purpose, it is more protocol on a different connection. For that purpose, it is more
appropriate to use a 3xx redirection response (Section 7.3 of appropriate to use a 3xx redirection response (Section 7.3 of
[Part2]). [Part2]).
Servers MUST include the "Upgrade" header field in 101 (Switching Servers MUST include the "Upgrade" header field in 101 (Switching
Protocols) responses to indicate which protocol(s) are being switched Protocols) responses to indicate which protocol(s) are being switched
to, and MUST include it in 426 (Upgrade Required) responses to to, and MUST include it in 426 (Upgrade Required) responses to
indicate acceptable protocols to upgrade to. Servers MAY include it indicate acceptable protocols to upgrade to. Servers MAY include it
in any other response to indicate that they are willing to upgrade to in any other response to indicate that they are willing to upgrade to
one of the specified protocols. one of the specified protocols.
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 can be registered with IANA using specification. Additional tokens can be registered with IANA using
the registration procedure defined below. the registration procedure defined in Section 7.6.
8.7.1. Upgrade Token Registry
The HTTP Upgrade Token Registry defines the name space for product
tokens used to identify protocols in the Upgrade header field. Each
registered token is associated with contact information and an
optional set of specifications that details how the connection will
be processed after it has been upgraded.
Registrations are allowed on a First Come First Served basis as
described in Section 4.1 of [RFC5226]. The specifications need not
be IETF documents or be subject to IESG review. Registrations are
subject to the following rules:
1. A token, once registered, stays registered forever.
2. The registration MUST name a responsible party for the
registration.
3. The registration MUST name a point of contact.
4. The registration MAY name a set of specifications associated with
that token. Such specifications need not be publicly available.
5. The responsible party MAY change the registration at any time.
The IANA will keep a record of all such changes, and make them
available upon request.
6. The responsible party for the first registration of a "product"
token MUST approve later registrations of a "version" token
together with that "product" token before they can be registered.
7. If absolutely required, the IESG MAY reassign the responsibility
for a token. This will normally only be used in the case when a
responsible party cannot be contacted.
8.8. Via
The "Via" header field MUST be sent by a proxy or gateway to indicate
the intermediate protocols and recipients between the user agent and
the server on requests, and between the origin server and the client
on responses. It is analogous to the "Received" field used by email
systems (Section 3.6.7 of [RFC5322]) and is intended to be used for
tracking message forwards, avoiding request loops, and identifying
the protocol capabilities of all senders along the request/response
chain.
Via = 1#( received-protocol RWS received-by
[ RWS comment ] )
received-protocol = [ protocol-name "/" ] protocol-version
protocol-name = token
protocol-version = token
received-by = ( uri-host [ ":" port ] ) / pseudonym
pseudonym = token
The received-protocol indicates the protocol version of the message
received by the server or client along each segment of the request/
response chain. The received-protocol version is appended to the Via
field value when the message is forwarded so that information about
the protocol capabilities of upstream applications remains visible to
all recipients.
The protocol-name is excluded if and only if it would be "HTTP". The
received-by field is normally the host and optional port number of a
recipient server or client that subsequently forwarded the message.
However, if the real host is considered to be sensitive information,
it MAY be replaced by a pseudonym. If the port is not given, it MAY
be assumed to be the default port of the received-protocol.
Multiple Via field values represent each proxy or gateway that has
forwarded the message. Each recipient MUST append its information
such that the end result is ordered according to the sequence of
forwarding applications.
Comments MAY be used in the Via header field to identify the software
of each recipient, analogous to the User-Agent and Server header
fields. However, all comments in the Via field are optional and MAY
be removed by any recipient prior to forwarding the message.
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
forward the request to a public proxy at p.example.net, which
completes the request by forwarding it to the origin server at
www.example.com. The request received by www.example.com would then
have the following Via header field:
Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
A proxy or gateway used as a portal through a network firewall SHOULD
NOT forward the names and ports of hosts within the firewall region
unless it is explicitly enabled to do so. If not enabled, the
received-by host of any host behind the firewall SHOULD be replaced
by an appropriate pseudonym for that host.
For organizations that have strong privacy requirements for hiding
internal structures, a proxy or gateway MAY combine an ordered
subsequence of Via header field entries with identical received-
protocol values into a single such entry. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Senders SHOULD NOT combine multiple entries unless they are all under 7. IANA Considerations
the same organizational control and the hosts have already been
replaced by pseudonyms. Senders MUST NOT combine entries which have
different received-protocol values.
9. IANA Considerations 7.1. Header Field Registration
9.1. Header Field Registration HTTP header fields are registered within the Message Header Field
Registry [RFC3864] maintained by IANA at <http://www.iana.org/
assignments/message-headers/message-header-index.html>.
The Message Header Field Registry located at <http://www.iana.org/ This document defines the following HTTP header fields, so their
assignments/message-headers/message-header-index.html> shall be associated registry entries shall be updated according to the
updated with the permanent registrations below (see [RFC3864]): permanent registrations below:
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+---------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+---------------+
| Connection | http | standard | Section 8.1 | | Connection | http | standard | Section 6.1 |
| Content-Length | http | standard | Section 8.2 | | Content-Length | http | standard | Section 3.3.2 |
| Host | http | standard | Section 8.3 | | Host | http | standard | Section 5.4 |
| TE | http | standard | Section 8.4 | | TE | http | standard | Section 4.3 |
| Trailer | http | standard | Section 8.5 | | Trailer | http | standard | Section 4.4 |
| Transfer-Encoding | http | standard | Section 8.6 | | Transfer-Encoding | http | standard | Section 3.3.1 |
| Upgrade | http | standard | Section 8.7 | | Upgrade | http | standard | Section 6.5 |
| Via | http | standard | Section 8.8 | | Via | http | standard | Section 6.2 |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+---------------+
Furthermore, the header field name "Close" shall be registered as Furthermore, the header field-name "Close" shall be registered as
"reserved", as its use as HTTP header field would be in conflict with "reserved", since using that name as an HTTP header field might
the use of the "close" connection option for the "Connection" header conflict with the "close" connection option of the "Connection"
field (Section 8.1). header field (Section 6.1).
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
| Close | http | reserved | Section 9.1 | | Close | http | reserved | Section 7.1 |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
9.2. URI Scheme Registration 7.2. URI Scheme Registration
The entries for the "http" and "https" URI Schemes in the registry IANA maintains the registry of URI Schemes [RFC4395] at
located at <http://www.iana.org/assignments/uri-schemes.html> shall <http://www.iana.org/assignments/uri-schemes.html>.
be updated to point to Sections 2.7.1 and 2.7.2 of this document (see
[RFC4395]).
9.3. Internet Media Type Registrations This document defines the following URI schemes, so their associated
registry entries shall be updated according to the permanent
registrations below:
+------------+------------------------------------+---------------+
| URI Scheme | Description | Reference |
+------------+------------------------------------+---------------+
| http | Hypertext Transfer Protocol | Section 2.7.1 |
| https | Hypertext Transfer Protocol Secure | Section 2.7.2 |
+------------+------------------------------------+---------------+
7.3. Internet Media Type Registrations
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 [RFC4288]). registered with IANA (see [RFC4288]).
9.3.1. Internet Media Type message/http 7.3.1. 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
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 9.3.1). Published specification: This specification (see Section 7.3.1).
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
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/Change controller: IESG Author/Change controller: IESG
9.3.2. Internet Media Type application/http 7.3.2. 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.
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: 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 9.3.2).
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
skipping to change at page 62, line 4 skipping to change at page 61, line 20
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/Change controller: IESG Author/Change controller: IESG
9.4. Transfer Coding Registry 7.4. Transfer Coding Registry
The registration procedure for HTTP Transfer Codings is now defined The HTTP Transfer Coding Registry defines the name space for transfer
by Section 5.1.3 of this document. coding names.
The HTTP Transfer Codings Registry located at Registrations MUST include the following fields:
<http://www.iana.org/assignments/http-parameters> shall be updated
with the registrations below:
+----------+--------------------------------------+-----------------+ o Name
| Name | Description | Reference |
+----------+--------------------------------------+-----------------+
| chunked | Transfer in a series of chunks | Section 5.1.1 |
| compress | UNIX "compress" program method | Section 5.1.2.1 |
| deflate | "deflate" compression mechanism | Section 5.1.2.2 |
| | ([RFC1951]) used inside the "zlib" | |
| | data format ([RFC1950]) | |
| gzip | Same as GNU zip [RFC1952] | Section 5.1.2.3 |
+----------+--------------------------------------+-----------------+
9.5. Upgrade Token Registration o Description
The registration procedure for HTTP Upgrade Tokens -- previously o Pointer to specification text
defined in Section 7.2 of [RFC2817] -- is now defined by
Section 8.7.1 of this document.
The HTTP Status Code Registry located at Names of transfer codings MUST NOT overlap with names of content
<http://www.iana.org/assignments/http-upgrade-tokens/> shall be codings (Section 2.2 of [Part3]) unless the encoding transformation
updated with the registration below: is identical, as it is the case for the compression codings defined
in Section 4.2.
+-------+---------------------------+-------------------------------+ Values to be added to this name space require IETF Review (see
| Value | Description | Reference | Section 4.1 of [RFC5226]), and MUST conform to the purpose of
+-------+---------------------------+-------------------------------+ transfer coding defined in this section.
| HTTP | Hypertext Transfer | Section 2.6 of this |
| | Protocol | specification |
+-------+---------------------------+-------------------------------+
10. Security Considerations The registry itself is maintained at
<http://www.iana.org/assignments/http-parameters>.
7.5. Transfer Coding Registrations
The HTTP Transfer Coding Registry shall be updated with the
registrations below:
+----------+----------------------------------------+---------------+
| Name | Description | Reference |
+----------+----------------------------------------+---------------+
| chunked | Transfer in a series of chunks | Section 4.1 |
| compress | UNIX "compress" program method | Section 4.2.1 |
| deflate | "deflate" compression mechanism | Section 4.2.2 |
| | ([RFC1951]) used inside the "zlib" | |
| | data format ([RFC1950]) | |
| gzip | Same as GNU zip [RFC1952] | Section 4.2.3 |
+----------+----------------------------------------+---------------+
7.6. Upgrade Token Registry
The HTTP Upgrade Token Registry defines the name space for protocol-
name tokens used to identify protocols in the Upgrade header field.
Each registered protocol-name is associated with contact information
and an optional set of specifications that details how the connection
will be processed after it has been upgraded.
Registrations require IETF Review (see Section 4.1 of [RFC5226]) and
are subject to the following rules:
1. A protocol-name token, once registered, stays registered forever.
2. The registration MUST name a responsible party for the
registration.
3. The registration MUST name a point of contact.
4. The registration MAY name a set of specifications associated with
that token. Such specifications need not be publicly available.
5. The registration SHOULD name a set of expected "protocol-version"
tokens associated with that token at the time of registration.
6. The responsible party MAY change the registration at any time.
The IANA will keep a record of all such changes, and make them
available upon request.
7. The IESG MAY reassign responsibility for a protocol token. This
will normally only be used in the case when a responsible party
cannot be contacted.
This registration procedure for HTTP Upgrade Tokens replaces that
previously defined in Section 7.2 of [RFC2817].
7.7. Upgrade Token Registration
The HTTP Upgrade Token Registry shall be updated with the
registration below:
+-------+----------------------+----------------------+-------------+
| Value | Description | Expected Version | Reference |
| | | Tokens | |
+-------+----------------------+----------------------+-------------+
| HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.6 |
| | Protocol | (e.g, "2.0") | |
+-------+----------------------+----------------------+-------------+
The responsible party is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force".
8. Security Considerations
This section is meant to inform application developers, information This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks. some suggestions for reducing security risks.
10.1. Personal Information 8.1. Personal Information
HTTP clients are often privy to large amounts of personal information HTTP clients are often privy to large amounts of personal information
(e.g., the user's name, location, mail address, passwords, encryption (e.g., the user's name, location, mail address, passwords, encryption
keys, etc.), and SHOULD be very careful to prevent unintentional keys, etc.), and SHOULD be very careful to prevent unintentional
leakage of this information. We very strongly recommend that a leakage of this information. We very strongly recommend that a
convenient interface be provided for the user to control convenient interface be provided for the user to control
dissemination of such information, and that designers and dissemination of such information, and that designers and
implementors be particularly careful in this area. History shows implementors be particularly careful in this area. History shows
that errors in this area often create serious security and/or privacy that errors in this area often create serious security and/or privacy
problems and generate highly adverse publicity for the implementor's problems and generate highly adverse publicity for the implementor's
company. company.
10.2. Abuse of Server Log Information 8.2. Abuse of 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 which might identify their reading patterns or subjects of requests which might identify their reading patterns or subjects of
interest. This information is clearly confidential in nature and its interest. In particular, log information gathered at an intermediary
handling can be constrained by law in certain countries. People often contains a history of user agent interaction, across a
using HTTP to provide data are responsible for ensuring that such multitude of sites, that can be traced to individual users.
material is not distributed without the permission of any individuals
that are identifiable by the published results.
10.3. Attacks Based On File and Path Names HTTP log information is confidential in nature; its handling is often
constrained by laws and regulations. Log information needs to be
securely stored and appropriate guidelines followed for its analysis.
Anonymization of personal information within individual entries
helps, but is generally not sufficient to prevent real log traces
from being re-identified based on correlation with other access
characteristics. As such, access traces that are keyed to a specific
client should not be published even if the key is pseudonymous.
To minimize the risk of theft or accidental publication, log
information should be purged of personally identifiable information,
including user identifiers, IP addresses, and user-provided query
parameters, as soon as that information is no longer necessary to
support operational needs for security, auditing, or fraud control.
8.3. Attacks Based On File and Path Names
Implementations of HTTP origin servers SHOULD be careful to restrict Implementations of HTTP origin servers SHOULD be careful to restrict
the documents returned by HTTP requests to be only those that were the documents returned by HTTP requests to be only those that were
intended by the server administrators. If an HTTP server translates intended by the server administrators. If an HTTP server translates
HTTP URIs directly into file system calls, the server MUST take HTTP URIs directly into file system calls, the server MUST take
special care not to serve files that were not intended to be special care not to serve files that were not intended to be
delivered to HTTP clients. For example, UNIX, Microsoft Windows, and delivered to HTTP clients. For example, UNIX, Microsoft Windows, and
other operating systems use ".." as a path component to indicate a other operating systems use ".." as a path component to indicate a
directory level above the current one. On such a system, an HTTP directory level above the current one. On such a system, an HTTP
server MUST disallow any such construct in the request-target if it server MUST disallow any such construct in the request-target if it
would otherwise allow access to a resource outside those intended to would otherwise allow access to a resource outside those intended to
be accessible via the HTTP server. Similarly, files intended for be accessible via the HTTP server. Similarly, files intended for
reference only internally to the server (such as access control reference only internally to the server (such as access control
files, configuration files, and script code) MUST be protected from files, configuration files, and script code) MUST be protected from
inappropriate retrieval, since they might contain sensitive inappropriate retrieval, since they might contain sensitive
information. Experience has shown that minor bugs in such HTTP information. Experience has shown that minor bugs in such HTTP
server implementations have turned into security risks. server implementations have turned into security risks.
10.4. DNS-related Attacks 8.4. 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]).
10.5. Proxies and Caching 8.5. Intermediaries and Caching
By their very nature, HTTP proxies 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 proxies run can result in serious of the systems on which the intermediaries run can result in serious
security and privacy problems. Proxies have access to security- security and privacy problems. Intermediaries have access to
related information, personal information about individual users and security-related information, personal information about individual
organizations, and proprietary information belonging to users and users and organizations, and proprietary information belonging to
content providers. A compromised proxy, or a proxy implemented or users and content providers. A compromised intermediary, or an
configured without regard to security and privacy considerations, intermediary implemented or configured without regard to security and
might be used in the commission of a wide range of potential attacks. privacy considerations, might be used in the commission of a wide
range of potential attacks.
Proxy operators need to protect the systems on which proxies run as Intermediaries that contain a shared cache are especially vulnerable
they would protect any system that contains or transports sensitive to cache poisoning attacks.
information. In particular, log information gathered at proxies
often contains highly sensitive personal information, and/or
information about organizations. Log information needs to be
carefully guarded, and appropriate guidelines for use need to be
developed and followed. (Section 10.2).
Proxy implementors need to consider the privacy and security Implementors need to consider the privacy and security implications
implications of their design and coding decisions, and of the of their design and coding decisions, and of the configuration
configuration options they provide to proxy operators (especially the options they provide to operators (especially the default
default configuration). configuration).
Users of a proxy need to be aware that proxies are no trustworthier 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.
The judicious use of cryptography, when appropriate, might suffice to The judicious use of cryptography, when appropriate, might suffice to
protect against a broad range of security and privacy attacks. Such protect against a broad range of security and privacy attacks. Such
cryptography is beyond the scope of the HTTP/1.1 specification. cryptography is beyond the scope of the HTTP/1.1 specification.
10.6. Protocol Element Size Overflows 8.6. Protocol Element Size 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 size limits on request-targets (Section 3.1.1.2) recommendations for minimum size limits on request-line
and blocks of header fields (Section 3.2). These are minimum (Section 3.1.1) and blocks of header fields (Section 3.2). These are
recommendations, chosen to be supportable even by implementations minimum recommendations, chosen to be supportable even by
with limited resources; it is expected that most implementations will implementations with limited resources; it is expected that most
choose substantially higher limits. implementations will 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 7.4.15 of that have request-targets that are too long (Section 7.4.12 of
[Part2]) or request entities that are too large (Section 7.4 of [Part2]) or request entities that are too large (Section 7.4 of
[Part2]). [Part2]).
Other fields (including but not limited to request methods, response Other fields (including but not limited to request methods, response
status phrases, header field-names, and body chunks) SHOULD be status phrases, header field-names, and body chunks) SHOULD be
limited by implementations carefully, so as to not impede limited by implementations carefully, so as to not impede
interoperability. interoperability.
10.7. Denial of Service Attacks on Proxies 9. Acknowledgments
They exist. They are hard to defend against. Research continues.
Beware.
11. Acknowledgments
This document revision builds on the work that went into RFC 2616 and This edition of HTTP builds on the many contributions that went into
its predecessors. See Section 16 of [RFC2616] for detailed RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including substantial
acknowledgements. contributions made by the previous authors, editors, and working
group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding, Henrik
Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter, Paul
J. Leach, and Mark Nottingham. See Section 16 of [RFC2616] for
additional acknowledgements from prior revisions.
Since 1999, many contributors have helped by reporting bugs, asking Since 1999, the following contributors have helped improve the HTTP
smart questions, drafting and reviewing text, and discussing open specification by reporting bugs, asking smart questions, drafting or
issues: reviewing text, and evaluating open issues:
Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrien de Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrien de
Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alex Rousskov, Alexey Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alex Rousskov, Alexey
Melnikov, Alisha Smith, Amichai Rothman, Amit Klein, Amos Jeffries, Melnikov, Alisha Smith, Amichai Rothman, Amit Klein, Amos Jeffries,
Andreas Maier, Andreas Petersson, Anne van Kesteren, Anthony Bryan, Andreas Maier, Andreas Petersson, Anne van Kesteren, Anthony Bryan,
Asbjorn Ulsberg, Balachander Krishnamurthy, Barry Leiba, Ben Laurie, Asbjorn Ulsberg, Balachander Krishnamurthy, Barry Leiba, Ben Laurie,
Benjamin Niven-Jenkins, Bil Corry, Bill Burke, Bjoern Hoehrmann, Bob Benjamin Niven-Jenkins, Bil Corry, Bill Burke, Bjoern Hoehrmann, Bob
Scheifler, Boris Zbarsky, Brett Slatkin, Brian Kell, Brian McBarron, Scheifler, Boris Zbarsky, Brett Slatkin, Brian Kell, Brian McBarron,
Brian Pane, Brian Smith, Bryce Nesbitt, Cameron Heavon-Jones, Carl Brian Pane, Brian Smith, Bryce Nesbitt, Cameron Heavon-Jones, Carl
Kugler, Charles Fry, Chris Newman, Cyrus Daboo, Dale Robert Anderson, Kugler, Carsten Bormann, Charles Fry, Chris Newman, Cyrus Daboo, Dale
Dan Winship, Daniel Stenberg, Dave Cridland, Dave Crocker, Dave Robert Anderson, Dan Winship, Daniel Stenberg, Dave Cridland, Dave
Kristol, David Booth, David Singer, David W. Morris, Diwakar Shetty, Crocker, Dave Kristol, David Booth, David Singer, David W. Morris,
Dmitry Kurochkin, Drummond Reed, Duane Wessels, Edward Lee, Eliot Diwakar Shetty, Dmitry Kurochkin, Drummond Reed, Duane Wessels,
Lear, Eran Hammer-Lahav, Eric D. Williams, Eric J. Bowman, Eric Edward Lee, Eliot Lear, Eran Hammer-Lahav, Eric D. Williams, Eric J.
Lawrence, Erik Aronesty, Florian Weimer, Frank Ellermann, Fred Bohle, Bowman, Eric Lawrence, Eric Rescorla, Erik Aronesty, Florian Weimer,
Geoffrey Sneddon, Gervase Markham, Greg Wilkins, Harald Tveit Frank Ellermann, Fred Bohle, Geoffrey Sneddon, Gervase Markham, Greg
Alvestrand, Harry Halpin, Helge Hess, Henrik Nordstrom, Henry S. Wilkins, Harald Tveit Alvestrand, Harry Halpin, Helge Hess, Henrik
Thompson, Henry Story, Herbert van de Sompel, Howard Melman, Hugo Nordstrom, Henry S. Thompson, Henry Story, Herbert van de Sompel,
Haas, Ian Hickson, Ingo Struck, J. Ross Nicoll, James H. Manger, Howard Melman, Hugo Haas, Ian Hickson, Ingo Struck, J. Ross Nicoll,
James Lacey, James M. Snell, Jamie Lokier, Jan Algermissen, Jeff James H. Manger, James Lacey, James M. Snell, Jamie Lokier, Jan
Hodges (for coming up with the term 'effective Request-URI'), Jeff Algermissen, Jeff Hodges (for coming up with the term 'effective
Walden, Jim Luther, Joe D. Williams, Joe Gregorio, Joe Orton, John C. Request-URI'), Jeff Walden, Jim Luther, Joe D. Williams, Joe
Klensin, John C. Mallery, John Cowan, John Kemp, John Panzer, John Gregorio, Joe Orton, John C. Klensin, John C. Mallery, John Cowan,
Schneider, John Stracke, Jonas Sicking, Jonathan Moore, Jonathan John Kemp, John Panzer, John Schneider, John Stracke, Jonas Sicking,
Rees, Jordi Ros, Joris Dobbelsteen, Josh Cohen, Julien Pierre, Jonathan Billington, Jonathan Moore, Jonathan Rees, Jordi Ros, Joris
Jungshik Shin, Justin Chapweske, Justin Erenkrantz, Justin James, Dobbelsteen, Josh Cohen, Julien Pierre, Jungshik Shin, Justin
Kalvinder Singh, Karl Dubost, Keith Hoffman, Keith Moore, Koen Chapweske, Justin Erenkrantz, Justin James, Kalvinder Singh, Karl
Holtman, Konstantin Voronkov, Kris Zyp, Lisa Dusseault, Maciej Dubost, Keith Hoffman, Keith Moore, Koen Holtman, Konstantin
Stachowiak, Marc Schneider, Marc Slemko, Mark Baker, Mark Nottingham Voronkov, Kris Zyp, Lisa Dusseault, Maciej Stachowiak, Marc
(Working Group chair), Mark Pauley, Martin J. Duerst, Martin Thomson, Schneider, Marc Slemko, Mark Baker, Mark Pauley, Markus Lanthaler,
Matt Lynch, Matthew Cox, Max Clark, Michael Burrows, Michael Martin J. Duerst, Martin Thomson, Matt Lynch, Matthew Cox, Max Clark,
Hausenblas, Mike Amundsen, Mike Kelly, Mike Schinkel, Miles Sabin, Michael Burrows, Michael Hausenblas, Mike Amundsen, Mike Belshe, Mike
Mykyta Yevstifeyev, Nathan Rixham, Nicholas Shanks, Nico Williams, Kelly, Mike Schinkel, Miles Sabin, Mykyta Yevstifeyev, Nathan Rixham,
Nicolas Alvarez, Noah Slater, Pablo Castro, Pat Hayes, Patrick R. Nicholas Shanks, Nico Williams, Nicolas Alvarez, Nicolas Mailhot,
McManus, Paul E. Jones, Paul Hoffman, Paul Marquess, Peter Saint- Noah Slater, Pablo Castro, Pat Hayes, Patrick R. McManus, Paul E.
Andre, Peter Watkins, Phil Archer, Phillip Hallam-Baker, Poul-Henning
Kamp, Preethi Natarajan, Reto Bachmann-Gmuer, Richard Cyganiak,
Robert Brewer, Robert Collins, Robert O'Callahan, Robert Olofsson,
Robert Sayre, Robert Siemer, Robert de Wilde, Roberto Javier Godoy,
Ronny Widjaja, S. Mike Dierken, Salvatore Loreto, Sam Johnston, Sam
Ruby, Scott Lawrence (for maintaining the original issues list), Sean
B. Palmer, Shane McCarron, Stefan Eissing, Stefan Tilkov, Stefanos
Harhalakis, Stephane Bortzmeyer, Stuart Williams, Subbu Allamaraju,
Sylvain Hellegouarch, Tapan Divekar, Thomas Broyer, Thomas Nordin,
Thomas Roessler, Tim Morgan, Tim Olsen, Travis Snoozy, Tyler Close,
Vincent Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo
Sanchez Vega, William A. Rowe Jr., William Chan, Willy Tarreau,
Xiaoshu Wang, Yaron Goland, Yngve Nysaeter Pettersen, Yogesh Bang,
Yutaka Oiwa, and Zed A. Shaw.
12. References Jones, Paul Hoffman, Paul Marquess, Peter Saint-Andre, Peter Watkins,
Phil Archer, Phillip Hallam-Baker, Poul-Henning Kamp, Preethi
Natarajan, Ray Polk, Reto Bachmann-Gmuer, Richard Cyganiak, Robert
Brewer, Robert Collins, Robert O'Callahan, Robert Olofsson, Robert
Sayre, Robert Siemer, Robert de Wilde, Roberto Javier Godoy, Ronny
Widjaja, S. Mike Dierken, Salvatore Loreto, Sam Johnston, Sam Ruby,
Scott Lawrence (for maintaining the original issues list), Sean B.
Palmer, Shane McCarron, Stefan Eissing, Stefan Tilkov, Stefanos
Harhalakis, Stephane Bortzmeyer, Stephen Farrell, Stuart Williams,
Subbu Allamaraju, Sylvain Hellegouarch, Tapan Divekar, Ted Hardie,
Thomas Broyer, Thomas Nordin, Thomas Roessler, Tim Morgan, Tim Olsen,
Travis Snoozy, Tyler Close, Vincent Murphy, Wenbo Zhu, Werner
Baumann, Wilbur Streett, Wilfredo Sanchez Vega, William A. Rowe Jr.,
William Chan, Willy Tarreau, Xiaoshu Wang, Yaron Goland, Yngve
Nysaeter Pettersen, Yogesh Bang, Yutaka Oiwa, Zed A. Shaw, and Zhong
Yu.
12.1. Normative References 10. References
10.1. Normative References
[ISO-8859-1] International Organization for Standardization, [ISO-8859-1] International Organization for Standardization,
"Information technology -- 8-bit single-byte coded "Information technology -- 8-bit single-byte coded
graphic character sets -- Part 1: Latin alphabet No. graphic character sets -- Part 1: Latin alphabet No.
1", ISO/IEC 8859-1:1998, 1998. 1", ISO/IEC 8859-1:1998, 1998.
[Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part2] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., "HTTP/1.1, part 2: Message Semantics",
Ed., and J. Reschke, Ed., "HTTP/1.1, part 2: Message draft-ietf-httpbis-p2-semantics-19 (work in progress),
Semantics", draft-ietf-httpbis-p2-semantics-18 (work in March 2012.
progress), January 2012.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part3] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., "HTTP/1.1, part 3: Message Payload and Content
Ed., and J. Reschke, Ed., "HTTP/1.1, part 3: Message Negotiation", draft-ietf-httpbis-p3-payload-19 (work in
Payload and Content Negotiation", progress), March 2012.
draft-ietf-httpbis-p3-payload-18 (work in progress),
January 2012.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part6] Fielding, R., Ed., Lafon, Y., Ed., Nottingham, M., Ed.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
Ed., Nottingham, M., Ed., and J. Reschke, Ed., draft-ietf-httpbis-p6-cache-19 (work in progress),
"HTTP/1.1, part 6: Caching", March 2012.
draft-ietf-httpbis-p6-cache-18 (work in progress),
January 2012.
[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.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and
G. Randers-Pehrson, "GZIP file format specification G. Randers-Pehrson, "GZIP file format specification
version 4.3", RFC 1952, May 1996. version 4.3", RFC 1952, May 1996.
skipping to change at page 67, line 37 skipping to change at page 68, line 22
STD 66, RFC 3986, January 2005. STD 66, RFC 3986, January 2005.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
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.
12.2. Informative References 10.2. Informative References
[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and [Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and
Politics", ACM Transactions on Internet Technology Vol. Politics", ACM Transactions on Internet Technology Vol.
1, #2, November 2001, 1, #2, November 2001,
<http://arxiv.org/abs/cs.SE/0105018>. <http://arxiv.org/abs/cs.SE/0105018>.
[Nie1997] Frystyk, H., Gettys, J., Prud'hommeaux, E., Lie, H., [Nie1997] Frystyk, H., Gettys, J., Prud'hommeaux, E., Lie, H.,
and C. Lilley, "Network Performance Effects of and C. Lilley, "Network Performance Effects of
HTTP/1.1, CSS1, and PNG", ACM Proceedings of the ACM HTTP/1.1, CSS1, and PNG", ACM Proceedings of the ACM
SIGCOMM '97 conference on Applications, technologies, SIGCOMM '97 conference on Applications, technologies,
skipping to change at page 70, line 11 skipping to change at page 70, line 45
connections, or name-based virtual hosts. The proliferation of connections, or name-based virtual hosts. The proliferation of
incompletely-implemented applications calling themselves "HTTP/1.0" incompletely-implemented applications calling themselves "HTTP/1.0"
further necessitated a protocol version change in order for two further necessitated a protocol version change in order for two
communicating applications to determine each other's true communicating applications to determine each other's true
capabilities. capabilities.
HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
requirements that enable reliable implementations, adding only those requirements that enable reliable implementations, adding only those
new features that will either be safely ignored by an HTTP/1.0 new features that will either be safely ignored by an HTTP/1.0
recipient or only sent when communicating with a party advertising recipient or only sent when communicating with a party advertising
compliance with HTTP/1.1. conformance with HTTP/1.1.
It is beyond the scope of a protocol specification to mandate It is beyond the scope of a protocol specification to mandate
compliance with previous versions. HTTP/1.1 was deliberately conformance with previous versions. HTTP/1.1 was deliberately
designed, however, to make supporting previous versions easy. We designed, however, to make supporting previous versions easy. We
would expect a general-purpose HTTP/1.1 server to understand any would expect a general-purpose HTTP/1.1 server to understand any
valid request in the format of HTTP/1.0 and respond appropriately valid request in the format of HTTP/1.0 and respond appropriately
with an HTTP/1.1 message that only uses features understood (or with an HTTP/1.1 message that only uses features understood (or
safely ignored) by HTTP/1.0 clients. Likewise, would expect an safely ignored) by HTTP/1.0 clients. Likewise, we would expect an
HTTP/1.1 client to understand any valid HTTP/1.0 response. HTTP/1.1 client to understand any valid HTTP/1.0 response.
Since HTTP/0.9 did not support header fields in a request, there is Since HTTP/0.9 did not support header fields in a request, there is
no mechanism for it to support name-based virtual hosts (selection of no mechanism for it to support name-based virtual hosts (selection of
resource by inspection of the Host header field). Any server that resource by inspection of the Host header field). Any server that
implements name-based virtual hosts ought to disable support for implements name-based virtual hosts ought to disable support for
HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact, HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
badly constructed HTTP/1.x requests wherein a buggy client failed to badly constructed HTTP/1.x requests wherein a buggy client failed to
properly encode linear whitespace found in a URI reference and placed properly encode linear whitespace found in a URI reference and placed
in the request-target. in the request-target.
A.1. Changes from HTTP/1.0 A.1. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0 This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1. and HTTP/1.1.
A.1.1. Multi-homed Web Servers A.1.1. Multi-homed Web Servers
The requirements that clients and servers support the Host header The requirements that clients and servers support the Host header
field (Section 8.3), report an error if it is missing from an field (Section 5.4), report an error if it is missing from an
HTTP/1.1 request, and accept absolute URIs (Section 3.1.1.2) are HTTP/1.1 request, and accept absolute URIs (Section 5.3) are among
among the most important changes defined by HTTP/1.1. the most important changes defined by HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request than the IP address
to which that request was directed. The Host header field was to which that request was directed. The Host header field was
introduced during the development of HTTP/1.1 and, though it was introduced during the development of HTTP/1.1 and, though it was
quickly implemented by most HTTP/1.0 browsers, additional quickly implemented by most HTTP/1.0 browsers, additional
requirements were placed on all HTTP/1.1 requests in order to ensure requirements were placed on all HTTP/1.1 requests in order to ensure
complete adoption. At the time of this writing, most HTTP-based complete adoption. At the time of this writing, most HTTP-based
services are dependent upon the Host header field for targeting services are dependent upon the Host header field for targeting
skipping to change at page 71, line 40 skipping to change at page 72, line 25
Clients are also encouraged to consider the use of Connection: keep- Clients are also encouraged to consider the use of Connection: keep-
alive in requests carefully; while they can enable persistent alive in requests carefully; while they can enable persistent
connections with HTTP/1.0 servers, clients using them need will need connections with HTTP/1.0 servers, clients using them need will need
to monitor the connection for "hung" requests (which indicate that to monitor the connection for "hung" requests (which indicate that
the client ought stop sending the header), and this mechanism ought the client ought stop sending the header), and this mechanism ought
not be used by clients at all when a proxy is being used. not be used by clients at all when a proxy is being used.
A.2. Changes from RFC 2616 A.2. Changes from RFC 2616
Empty list elements in list productions have been deprecated. Clarify that the string "HTTP" in the HTTP-version ABFN production is
(Section 1.2.1)
Rules about implicit linear whitespace between certain grammar
productions have been removed; now it's only allowed when
specifically pointed out in the ABNF. (Section 1.2.2)
Clarify that the string "HTTP" in the HTTP-Version ABFN production is
case sensitive. Restrict the version numbers to be single digits due case sensitive. Restrict the version numbers to be single digits due
to the fact that implementations are known to handle multi-digit to the fact that implementations are known to handle multi-digit
version numbers incorrectly. (Section 2.6) version numbers incorrectly. (Section 2.6)
Update use of abs_path production from RFC 1808 to the path-absolute
+ query components of RFC 3986. State that the asterisk form is
allowed for the OPTIONS request method only. (Section 5.3)
Require that invalid whitespace around field-names be rejected. Require that invalid whitespace around field-names be rejected.
(Section 3.2) (Section 3.2)
Rules about implicit linear whitespace between certain grammar
productions have been removed; now whitespace is only allowed where
specifically defined in the ABNF. (Section 3.2.1)
The NUL octet is no longer allowed in comment and quoted-string text. The NUL octet is no longer allowed in comment and quoted-string text.
The quoted-pair rule no longer allows escaping control characters The quoted-pair rule no longer allows escaping control characters
other than HTAB. Non-ASCII content in header fields and reason other than HTAB. Non-ASCII content in header fields and reason
phrase has been obsoleted and made opaque (the TEXT rule was phrase has been obsoleted and made opaque (the TEXT rule was
removed). (Section 3.2.3) removed). (Section 3.2.4)
Empty list elements in list productions have been deprecated.
(Section 3.2.5)
Require recipients to handle bogus Content-Length header fields as Require recipients to handle bogus Content-Length header fields as
errors. (Section 3.3) errors. (Section 3.3)
Remove reference to non-existent identity transfer-coding value Remove reference to non-existent identity transfer-coding value
tokens. (Sections 3.3 and 5.1) tokens. (Sections 3.3 and 4)
Update use of abs_path production from RFC 1808 to the path-absolute
+ query components of RFC 3986. State that the asterisk form is
allowed for the OPTIONS request method only. (Section 3.1.1.2)
Clarification that the chunk length does not include the count of the Clarification that the chunk length does not include the count of the
octets in the chunk header and trailer. Furthermore disallowed line octets in the chunk header and trailer. Furthermore disallowed line
folding in chunk extensions. (Section 5.1.1) folding in chunk extensions, and deprecate their use. (Section 4.1)
Registration of Transfer Codings now requires IETF Review
(Section 7.4)
Remove hard limit of two connections per server. Remove requirement Remove hard limit of two connections per server. Remove requirement
to retry a sequence of requests as long it was idempotent. Remove to retry a sequence of requests as long it was idempotent. Remove
requirements about when servers are allowed to close connections requirements about when servers are allowed to close connections
prematurely. (Section 6.1.4) prematurely. (Section 6.3.3)
Remove requirement to retry requests under certain cirumstances when Remove requirement to retry requests under certain cirumstances when
the server prematurely closes the connection. (Section 6.2) the server prematurely closes the connection. (Section 6.4)
Change ABNF productions for header fields to only define the field Change ABNF productions for header fields to only define the field
value. (Section 8) value.
Clarify exactly when close connection options must be sent. Clarify exactly when close connection options must be sent.
(Section 8.1) (Section 6.1)
Define the semantics of the "Upgrade" header field in responses other Define the semantics of the "Upgrade" header field in responses other
than 101 (this was incorporated from [RFC2817]). (Section 8.7) than 101 (this was incorporated from [RFC2817]). (Section 6.5)
A.3. Changes from RFC 2817
Registration of Upgrade tokens now requires IETF Review (Section 7.6)
Appendix B. Collected ABNF Appendix B. Collected ABNF
BWS = OWS BWS = OWS
Chunked-Body = *chunk last-chunk trailer-part CRLF
Connection = *( "," OWS ) connection-token *( OWS "," [ OWS Connection = *( "," OWS ) connection-token *( OWS "," [ OWS
connection-token ] ) connection-token ] )
Content-Length = 1*DIGIT Content-Length = 1*DIGIT
HTTP-Prot-Name = %x48.54.54.50 ; HTTP
HTTP-Version = HTTP-Prot-Name "/" DIGIT "." 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-version = HTTP-name "/" DIGIT "." DIGIT
Host = uri-host [ ":" port ] Host = uri-host [ ":" port ]
Method = token OWS = *( SP / HTAB )
OWS = *( SP / HTAB / obs-fold )
RWS = 1*( SP / HTAB / obs-fold )
Reason-Phrase = *( HTAB / SP / VCHAR / obs-text )
Request-Line = Method SP request-target SP HTTP-Version CRLF
Status-Code = 3DIGIT
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
RWS = 1*( SP / HTAB )
TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ] TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] ) Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS
transfer-coding ] ) transfer-coding ] )
URI-reference = <URI-reference, defined in [RFC3986], Section 4.1> URI-reference = <URI-reference, defined in [RFC3986], Section 4.1>
Upgrade = *( "," OWS ) product *( OWS "," [ OWS product ] ) Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
Via = *( "," OWS ) received-protocol RWS received-by [ RWS comment ] Via = *( "," OWS ) received-protocol RWS received-by [ RWS comment ]
*( OWS "," [ OWS received-protocol RWS received-by [ RWS comment ] ] *( OWS "," [ OWS received-protocol RWS received-by [ RWS comment ] ]
) )
absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3> absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3>
absolute-form = absolute-URI
asterisk-form = "*"
attribute = token attribute = token
authority = <authority, defined in [RFC3986], Section 3.2> authority = <authority, defined in [RFC3986], Section 3.2>
authority-form = authority
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-data = 1*OCTET chunk-data = 1*OCTET
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-size = 1*HEXDIG chunk-size = 1*HEXDIG
chunked-body = *chunk last-chunk trailer-part CRLF
comment = "(" *( ctext / quoted-cpair / comment ) ")" comment = "(" *( ctext / quoted-cpair / comment ) ")"
connection-token = token connection-token = token
ctext = OWS / %x21-27 ; '!'-''' ctext = OWS / %x21-27 ; '!'-'''
/ %x2A-5B ; '*'-'[' / %x2A-5B ; '*'-'['
/ %x5D-7E ; ']'-'~' / %x5D-7E ; ']'-'~'
/ obs-text / obs-text
field-content = *( HTAB / SP / VCHAR / obs-text ) field-content = *( HTAB / SP / VCHAR / obs-text )
field-name = token field-name = token
field-value = *( field-content / obs-fold ) field-value = *( field-content / obs-fold )
header-field = field-name ":" OWS field-value BWS header-field = field-name ":" OWS field-value BWS
http-URI = "http://" authority path-abempty [ "?" query ] http-URI = "http://" authority path-abempty [ "?" query ]
https-URI = "https://" authority path-abempty [ "?" query ] https-URI = "https://" authority path-abempty [ "?" query ]
last-chunk = 1*"0" [ chunk-ext ] CRLF last-chunk = 1*"0" [ chunk-ext ] CRLF
message-body = *OCTET message-body = *OCTET
method = token
obs-fold = CRLF ( SP / HTAB ) obs-fold = CRLF ( SP / HTAB )
obs-text = %x80-FF obs-text = %x80-FF
origin-form = path-absolute [ "?" query ]
partial-URI = relative-part [ "?" query ] partial-URI = relative-part [ "?" query ]
path-abempty = <path-abempty, defined in [RFC3986], Section 3.3> path-abempty = <path-abempty, defined in [RFC3986], Section 3.3>
path-absolute = <path-absolute, defined in [RFC3986], Section 3.3> path-absolute = <path-absolute, defined in [RFC3986], Section 3.3>
port = <port, defined in [RFC3986], Section 3.2.3> port = <port, defined in [RFC3986], Section 3.2.3>
product = token [ "/" product-version ] protocol = protocol-name [ "/" protocol-version ]
product-version = token
protocol-name = token protocol-name = token
protocol-version = token protocol-version = token
pseudonym = token pseudonym = token
qdtext = OWS / "!" / %x23-5B ; '#'-'[' qdtext = OWS / "!" / %x23-5B ; '#'-'['
/ %x5D-7E ; ']'-'~' / %x5D-7E ; ']'-'~'
/ obs-text / obs-text
qdtext-nf = HTAB / SP / "!" / %x23-5B ; '#'-'[' qdtext-nf = HTAB / SP / "!" / %x23-5B ; '#'-'['
/ %x5D-7E ; ']'-'~' / %x5D-7E ; ']'-'~'
/ obs-text / obs-text
query = <query, defined in [RFC3986], Section 3.4> query = <query, defined in [RFC3986], Section 3.4>
quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text ) quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text )
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text ) quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
qvalue = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] ) qvalue = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
reason-phrase = *( HTAB / SP / VCHAR / obs-text )
received-by = ( uri-host [ ":" port ] ) / pseudonym received-by = ( uri-host [ ":" port ] ) / pseudonym
received-protocol = [ protocol-name "/" ] protocol-version received-protocol = [ protocol-name "/" ] protocol-version
relative-part = <relative-part, defined in [RFC3986], Section 4.2> relative-part = <relative-part, defined in [RFC3986], Section 4.2>
request-target = "*" / absolute-URI / ( path-absolute [ "?" query ] ) request-line = method SP request-target SP HTTP-version CRLF
/ authority request-target = origin-form / absolute-form / authority-form /
asterisk-form
special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" / special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}" DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}"
start-line = Request-Line / Status-Line start-line = request-line / status-line
status-code = 3DIGIT
status-line = HTTP-version SP status-code SP reason-phrase CRLF
t-codings = "trailers" / ( transfer-extension [ te-params ] ) t-codings = "trailers" / ( transfer-extension [ te-params ] )
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
te-ext = OWS ";" OWS token [ "=" word ] te-ext = OWS ";" OWS token [ "=" word ]
te-params = OWS ";" OWS "q=" qvalue *te-ext te-params = OWS ";" OWS "q=" qvalue *te-ext
token = 1*tchar token = 1*tchar
trailer-part = *( header-field CRLF ) trailer-part = *( header-field CRLF )
transfer-coding = "chunked" / "compress" / "deflate" / "gzip" / transfer-coding = "chunked" / "compress" / "deflate" / "gzip" /
transfer-extension transfer-extension
skipping to change at page 75, line 23 skipping to change at page 76, line 14
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
ABNF diagnostics: ABNF diagnostics:
; Chunked-Body defined but not used
; Connection defined but not used ; Connection defined but not used
; Content-Length defined but not used ; Content-Length defined but not used
; HTTP-message defined but not used ; HTTP-message defined but not used
; Host defined but not used ; Host defined but not used
; TE defined but not used ; TE defined but not used
; Trailer defined but not used ; Trailer defined but not used
; Transfer-Encoding defined but not used ; Transfer-Encoding defined but not used
; URI-reference defined but not used ; URI-reference defined but not used
; Upgrade defined but not used ; Upgrade defined but not used
; Via defined but not used ; Via defined but not used
; chunked-body defined but not used
; http-URI defined but not used ; http-URI defined but not used
; https-URI defined but not used ; https-URI defined but not used
; partial-URI defined but not used ; partial-URI defined but not used
; special defined but not used ; special defined but not used
Appendix C. Change Log (to be removed by RFC Editor before publication) Appendix C. Change Log (to be removed by RFC Editor before publication)
C.1. Since RFC 2616 C.1. Since RFC 2616
Extracted relevant partitions from [RFC2616]. Extracted relevant partitions from [RFC2616].
skipping to change at page 78, line 36 skipping to change at page 79, line 28
Ongoing work on IANA Message Header Field Registration Ongoing work on IANA Message Header Field Registration
(<http://tools.ietf.org/wg/httpbis/trac/ticket/40>): (<http://tools.ietf.org/wg/httpbis/trac/ticket/40>):
o Reference RFC 3984, and update header field registrations for o Reference RFC 3984, and update header field registrations for
headers defined in this document. headers defined in this document.
Ongoing work on ABNF conversion Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>): (<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Replace string literals when the string really is case-sensitive o Replace string literals when the string really is case-sensitive
(HTTP-Version). (HTTP-version).
C.5. Since draft-ietf-httpbis-p1-messaging-03 C.5. Since draft-ietf-httpbis-p1-messaging-03
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/28>: "Connection o <http://tools.ietf.org/wg/httpbis/trac/ticket/28>: "Connection
closing" closing"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/97>: "Move o <http://tools.ietf.org/wg/httpbis/trac/ticket/97>: "Move
registrations and registry information to IANA Considerations" registrations and registry information to IANA Considerations"
skipping to change at page 80, line 16 skipping to change at page 81, line 10
encoded words" encoded words"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/74>: "Character o <http://tools.ietf.org/wg/httpbis/trac/ticket/74>: "Character
Encodings in TEXT" Encodings in TEXT"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/77>: "Line Folding" o <http://tools.ietf.org/wg/httpbis/trac/ticket/77>: "Line Folding"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/83>: "OPTIONS * and o <http://tools.ietf.org/wg/httpbis/trac/ticket/83>: "OPTIONS * and
proxies" proxies"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/94>: "Reason-Phrase o <http://tools.ietf.org/wg/httpbis/trac/ticket/94>: "reason-phrase
BNF" BNF"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/111>: "Use of TEXT" o <http://tools.ietf.org/wg/httpbis/trac/ticket/111>: "Use of TEXT"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/118>: "Join o <http://tools.ietf.org/wg/httpbis/trac/ticket/118>: "Join
"Differences Between HTTP Entities and RFC 2045 Entities"?" "Differences Between HTTP Entities and RFC 2045 Entities"?"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/134>: "RFC822 o <http://tools.ietf.org/wg/httpbis/trac/ticket/134>: "RFC822
reference left in discussion of date formats" reference left in discussion of date formats"
skipping to change at page 84, line 43 skipping to change at page 85, line 31
o <http://tools.ietf.org/wg/httpbis/trac/ticket/276>: "untangle o <http://tools.ietf.org/wg/httpbis/trac/ticket/276>: "untangle
ABNFs for header fields" ABNFs for header fields"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/286>: "Content- o <http://tools.ietf.org/wg/httpbis/trac/ticket/286>: "Content-
Length ABNF broken" Length ABNF broken"
C.16. Since draft-ietf-httpbis-p1-messaging-14 C.16. Since draft-ietf-httpbis-p1-messaging-14
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/273>: "HTTP-Version o <http://tools.ietf.org/wg/httpbis/trac/ticket/273>: "HTTP-version
should be redefined as fixed length pair of DIGIT . DIGIT" should be redefined as fixed length pair of DIGIT . DIGIT"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/282>: "Recommend o <http://tools.ietf.org/wg/httpbis/trac/ticket/282>: "Recommend
minimum sizes for protocol elements" minimum sizes for protocol elements"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/283>: "Set o <http://tools.ietf.org/wg/httpbis/trac/ticket/283>: "Set
expectations around buffering" expectations around buffering"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/288>: "Considering o <http://tools.ietf.org/wg/httpbis/trac/ticket/288>: "Considering
messages in isolation" messages in isolation"
skipping to change at page 86, line 14 skipping to change at page 87, line 5
o <http://tools.ietf.org/wg/httpbis/trac/ticket/323>: "intended o <http://tools.ietf.org/wg/httpbis/trac/ticket/323>: "intended
maturity level vs normative references" maturity level vs normative references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/324>: "Intermediary o <http://tools.ietf.org/wg/httpbis/trac/ticket/324>: "Intermediary
rewriting of queries" rewriting of queries"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/158>: "Proxy- o <http://tools.ietf.org/wg/httpbis/trac/ticket/158>: "Proxy-
Connection and Keep-Alive" Connection and Keep-Alive"
C.20. Since draft-ietf-httpbis-p1-messaging-18
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/250>: "message-body
in CONNECT response"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/302>: "Misplaced
text on connection handling in p2"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/335>: "wording of
line folding rule"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/343>: "chunk-
extensions"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/346>: "make IANA
policy definitions consistent"
Index Index
A A
absolute-URI form (of request-target) 32 absolute-form (of request-target) 41
accelerator 13 accelerator 11
application/http Media Type 61 application/http Media Type 60
asterisk form (of request-target) 31 asterisk-form (of request-target) 41
authority form (of request-target) 32 authority-form (of request-target) 41
B B
browser 10 browser 7
C C
cache 14 cache 12
cacheable 15 cacheable 12
captive portal 14 captive portal 11
chunked (Coding Format) 36 chunked (Coding Format) 34
client 10 client 7
Coding Format Coding Format
chunked 36 chunked 34
compress 38 compress 36
deflate 38 deflate 36
gzip 39 gzip 36
compress (Coding Format) 38 compress (Coding Format) 36
connection 10 connection 7
Connection header field 49 Connection header field 47
Content-Length header field 51 Content-Length header field 29
D D
deflate (Coding Format) 38 deflate (Coding Format) 36
downstream 13 downstream 10
E E
effective request URI 34 effective request URI 43
G G
gateway 13 gateway 11
Grammar Grammar
absolute-URI 18 absolute-form 40
absolute-URI 16
ALPHA 7 ALPHA 7
attribute 35 asterisk-form 40
authority 18 attribute 34
BWS 9 authority 16
chunk 36 authority-form 40
chunk-data 36 BWS 23
chunk-ext 36 chunk 34
chunk-ext-name 36 chunk-data 34
chunk-ext-val 36 chunk-ext 34
chunk-size 36 chunk-ext-name 34
Chunked-Body 36 chunk-ext-val 34
comment 26 chunk-size 34
Connection 50 chunked-body 34
connection-token 50 comment 25
Content-Length 51 Connection 47
connection-token 47
Content-Length 29
CR 7 CR 7
CRLF 7 CRLF 7
ctext 26 ctext 25
CTL 7 CTL 7
date2 35 date2 34
date3 35 date3 34
DIGIT 7 DIGIT 7
DQUOTE 7 DQUOTE 7
field-content 23 field-content 22
field-name 23 field-name 22
field-value 23 field-value 22
header-field 23 header-field 22
HEXDIG 7 HEXDIG 7
Host 52 Host 42
HTAB 7 HTAB 7
HTTP-message 21 HTTP-message 19
HTTP-Prot-Name 15 HTTP-name 13
http-URI 18 http-URI 16
HTTP-Version 15 HTTP-version 13
https-URI 20 https-URI 18
last-chunk 36 last-chunk 34
LF 7 LF 7
message-body 27 message-body 27
Method 22 method 20
obs-text 26 obs-fold 22
obs-text 25
OCTET 7 OCTET 7
OWS 9 origin-form 40
path-absolute 18 OWS 23
port 18 path-absolute 16
product 39 port 16
product-version 39 protocol-name 49
protocol-name 57 protocol-version 49
protocol-version 57 pseudonym 49
pseudonym 57 qdtext 25
qdtext 26 qdtext-nf 34
qdtext-nf 36 query 16
query 18 quoted-cpair 26
quoted-cpair 27 quoted-pair 25
quoted-pair 26 quoted-str-nf 34
quoted-str-nf 36 quoted-string 25
quoted-string 26 qvalue 38
qvalue 40 reason-phrase 21
Reason-Phrase 23 received-by 49
received-by 57 received-protocol 49
received-protocol 57 request-line 20
Request-Line 22 request-target 40
request-target 22 RWS 23
RWS 9
SP 7 SP 7
special 26 special 25
start-line 21 start-line 20
Status-Code 23 status-code 21
Status-Line 23 status-line 21
t-codings 53 t-codings 37
tchar 26 tchar 25
TE 53 TE 37
te-ext 53 te-ext 37
te-params 53 te-params 37
token 26 token 25
Trailer 54 Trailer 38
trailer-part 36 trailer-part 34
transfer-coding 35 transfer-coding 34
Transfer-Encoding 54 Transfer-Encoding 28
transfer-extension 35 transfer-extension 34
transfer-parameter 35 transfer-parameter 34
Upgrade 55 Upgrade 56
uri-host 18 uri-host 16
URI-reference 18 URI-reference 16
value 35 value 34
VCHAR 7 VCHAR 7
Via 57 Via 49
word 26 word 25
gzip (Coding Format) 39 gzip (Coding Format) 36
H H
header field 21 header field 19
Header Fields Header Fields
Connection 49 Connection 47
Content-Length 51 Content-Length 29
Host 51 Host 42
TE 53 TE 36
Trailer 54 Trailer 38
Transfer-Encoding 54 Transfer-Encoding 27
Upgrade 55 Upgrade 56
Via 57 Via 49
header section 21 header section 19
headers 21 headers 19
Host header field 51 Host header field 42
http URI scheme 18 http URI scheme 16
https URI scheme 19 https URI scheme 17
I I
inbound 13 inbound 10
interception proxy 14 interception proxy 11
intermediary 12 intermediary 9
M M
Media Type Media Type
application/http 61 application/http 60
message/http 59 message/http 59
message 10 message 8
message/http Media Type 59 message/http Media Type 59
method 20
N N
non-transforming proxy 13 non-transforming proxy 10
O O
origin form (of request-target) 32 origin server 7
origin server 10 origin-form (of request-target) 40
outbound 13 outbound 10
P P
proxy 13 proxy 10
R R
recipient 10 recipient 7
request 10 request 8
resource 17 request-target 20
response 10 resource 15
reverse proxy 13 response 8
reverse proxy 11
S S
sender 10 sender 7
server 10 server 7
spider 10 spider 7
T T
target resource 34 target resource 39
TE header field 53 target URI 39
Trailer header field 54 TE header field 36
Transfer-Encoding header field 54 Trailer header field 38
transforming proxy 13 Transfer-Encoding header field 27
transparent proxy 14 transforming proxy 10
tunnel 14 transparent proxy 11
tunnel 11
U U
Upgrade header field 55 Upgrade header field 56
upstream 13 upstream 10
URI scheme URI scheme
http 18 http 16
https 19 https 17
user agent 10 user agent 7
V V
Via header field 57 Via header field 49
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
URI: http://roy.gbiv.com/ URI: http://roy.gbiv.com/
Jim Gettys
Alcatel-Lucent Bell Labs
21 Oak Knoll Road
Carlisle, MA 01741
USA
EMail: jg@freedesktop.org
URI: http://gettys.wordpress.com/
Jeffrey C. Mogul
Hewlett-Packard Company
HP Labs, Large Scale Systems Group
1501 Page Mill Road, MS 1177
Palo Alto, CA 94304
USA
EMail: JeffMogul@acm.org
Henrik Frystyk Nielsen
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
EMail: henrikn@microsoft.com
Larry Masinter
Adobe Systems Incorporated
345 Park Ave
San Jose, CA 95110
USA
EMail: LMM@acm.org
URI: http://larry.masinter.net/
Paul J. Leach
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
EMail: paulle@microsoft.com
Tim Berners-Lee
World Wide Web Consortium
MIT Computer Science and Artificial Intelligence Laboratory
The Stata Center, Building 32
32 Vassar Street
Cambridge, MA 02139
USA
EMail: timbl@w3.org
URI: http://www.w3.org/People/Berners-Lee/
Yves Lafon (editor) Yves Lafon (editor)
World Wide Web Consortium World Wide Web Consortium
W3C / ERCIM W3C / ERCIM
2004, rte des Lucioles 2004, rte des Lucioles
Sophia-Antipolis, AM 06902 Sophia-Antipolis, AM 06902
France France
EMail: ylafon@w3.org EMail: ylafon@w3.org
URI: http://www.raubacapeu.net/people/yves/ URI: http://www.raubacapeu.net/people/yves/
 End of changes. 312 change blocks. 
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