draft-ietf-httpbis-p1-messaging-20.txt   draft-ietf-httpbis-p1-messaging-21.txt 
HTTPbis Working Group R. Fielding, Ed. HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Adobe Internet-Draft Adobe
Obsoletes: 2145,2616 (if approved) Y. Lafon, Ed. Obsoletes: 2145,2616 (if approved) J. Reschke, Ed.
Updates: 2817 (if approved) W3C Updates: 2817 (if approved) greenbytes
Intended status: Standards Track J. Reschke, Ed. Intended status: Standards Track October 4, 2012
Expires: January 17, 2013 greenbytes Expires: April 7, 2013
July 16, 2012
HTTP/1.1, part 1: Message Routing and Syntax" Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
draft-ietf-httpbis-p1-messaging-20 draft-ietf-httpbis-p1-messaging-21
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypertext information protocol for distributed, collaborative, hypertext information
systems. HTTP has been in use by the World Wide Web global systems. HTTP has been in use by the World Wide Web global
information initiative since 1990. This document provides an information initiative since 1990. This document provides an
overview of HTTP architecture and its associated terminology, defines overview of HTTP architecture and its associated terminology, defines
the "http" and "https" Uniform Resource Identifier (URI) schemes, the "http" and "https" Uniform Resource Identifier (URI) schemes,
defines the HTTP/1.1 message syntax and parsing requirements, and defines the HTTP/1.1 message syntax and parsing requirements, and
skipping to change at page 1, line 36 skipping to change at page 1, line 35
Discussion of this draft takes place on the HTTPBIS working group Discussion of this draft takes place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
<http://lists.w3.org/Archives/Public/ietf-http-wg/>. <http://lists.w3.org/Archives/Public/ietf-http-wg/>.
The current issues list is at The current issues list is at
<http://tools.ietf.org/wg/httpbis/trac/report/3> and related <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
documents (including fancy diffs) can be found at documents (including fancy diffs) can be found at
<http://tools.ietf.org/wg/httpbis/>. <http://tools.ietf.org/wg/httpbis/>.
The changes in this draft are summarized in Appendix D.21. The changes in this draft are summarized in Appendix D.22.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 17, 2013. This Internet-Draft will expire on April 7, 2013.
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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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Requirement Notation . . . . . . . . . . . . . . . . . . . 7 1.1. Requirement Notation . . . . . . . . . . . . . . . . . . . 6
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 7 2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 7
2.2. Implementation Diversity . . . . . . . . . . . . . . . . . 9 2.2. Implementation Diversity . . . . . . . . . . . . . . . . . 8
2.3. Connections and Transport Independence . . . . . . . . . . 10 2.3. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 9
2.4. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 10 2.4. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.5. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.5. Conformance and Error Handling . . . . . . . . . . . . . . 12
2.6. Conformance and Error Handling . . . . . . . . . . . . . . 13 2.6. Protocol Versioning . . . . . . . . . . . . . . . . . . . 13
2.7. Protocol Versioning . . . . . . . . . . . . . . . . . . . 14 2.7. Uniform Resource Identifiers . . . . . . . . . . . . . . . 15
2.8. Uniform Resource Identifiers . . . . . . . . . . . . . . . 16 2.7.1. http URI scheme . . . . . . . . . . . . . . . . . . . 16
2.8.1. http URI scheme . . . . . . . . . . . . . . . . . . . 17 2.7.2. https URI scheme . . . . . . . . . . . . . . . . . . . 17
2.8.2. https URI scheme . . . . . . . . . . . . . . . . . . . 18 2.7.3. http and https URI Normalization and Comparison . . . 18
2.8.3. http and https URI Normalization and Comparison . . . 19 3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 18
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 20 3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1. Start Line . . . . . . . . . . . . . . . . . . . . . . . . 20 3.1.1. Request Line . . . . . . . . . . . . . . . . . . . . . 20
3.1.1. Request Line . . . . . . . . . . . . . . . . . . . . . 21 3.1.2. Status Line . . . . . . . . . . . . . . . . . . . . . 21
3.1.2. Status Line . . . . . . . . . . . . . . . . . . . . . 22 3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 21
3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 23 3.2.1. Whitespace . . . . . . . . . . . . . . . . . . . . . . 23
3.2.1. Whitespace . . . . . . . . . . . . . . . . . . . . . . 24 3.2.2. Field Parsing . . . . . . . . . . . . . . . . . . . . 23
3.2.2. Field Parsing . . . . . . . . . . . . . . . . . . . . 25 3.2.3. Field Length . . . . . . . . . . . . . . . . . . . . . 24
3.2.3. Field Length . . . . . . . . . . . . . . . . . . . . . 25 3.2.4. Field value components . . . . . . . . . . . . . . . . 24
3.2.4. Field value components . . . . . . . . . . . . . . . . 26 3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 26
3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 27 3.3.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . 26
3.3.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . 27 3.3.2. Content-Length . . . . . . . . . . . . . . . . . . . . 28
3.3.2. Content-Length . . . . . . . . . . . . . . . . . . . . 29 3.3.3. Message Body Length . . . . . . . . . . . . . . . . . 29
3.3.3. Message Body Length . . . . . . . . . . . . . . . . . 30 3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 31
3.4. Handling Incomplete Messages . . . . . . . . . . . . . . . 32 3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 32
3.5. Message Parsing Robustness . . . . . . . . . . . . . . . . 33 4. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . . 32
4. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . . 33 4.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 33
4.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 34 4.1.1. Trailer . . . . . . . . . . . . . . . . . . . . . . . 34
4.2. Compression Codings . . . . . . . . . . . . . . . . . . . 36 4.1.2. Decoding chunked . . . . . . . . . . . . . . . . . . . 35
4.2.1. Compress Coding . . . . . . . . . . . . . . . . . . . 36 4.2. Compression Codings . . . . . . . . . . . . . . . . . . . 35
4.2.2. Deflate Coding . . . . . . . . . . . . . . . . . . . . 36 4.2.1. Compress Coding . . . . . . . . . . . . . . . . . . . 35
4.2.2. Deflate Coding . . . . . . . . . . . . . . . . . . . . 35
4.2.3. Gzip Coding . . . . . . . . . . . . . . . . . . . . . 36 4.2.3. Gzip Coding . . . . . . . . . . . . . . . . . . . . . 36
4.3. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 4.3. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.3.1. Quality Values . . . . . . . . . . . . . . . . . . . . 38 5. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 37
4.4. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 38 5.1. Identifying a Target Resource . . . . . . . . . . . . . . 37
5. Message Routing . . . . . . . . . . . . . . . . . . . . . . . 39 5.2. Connecting Inbound . . . . . . . . . . . . . . . . . . . . 37
5.1. Identifying a Target Resource . . . . . . . . . . . . . . 39 5.3. Request Target . . . . . . . . . . . . . . . . . . . . . . 38
5.2. Connecting Inbound . . . . . . . . . . . . . . . . . . . . 39 5.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.3. Request Target . . . . . . . . . . . . . . . . . . . . . . 40 5.5. Effective Request URI . . . . . . . . . . . . . . . . . . 41
5.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 5.6. Message Forwarding . . . . . . . . . . . . . . . . . . . . 42
5.5. Effective Request URI . . . . . . . . . . . . . . . . . . 43 5.7. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.6. Intermediary Forwarding . . . . . . . . . . . . . . . . . 44 5.8. Message Transforming . . . . . . . . . . . . . . . . . . . 44
5.6.1. End-to-end and Hop-by-hop Header Fields . . . . . . . 45 5.9. Associating a Response to a Request . . . . . . . . . . . 46
5.6.2. Non-modifiable Header Fields . . . . . . . . . . . . . 46 6. Connection Management . . . . . . . . . . . . . . . . . . . . 46
5.7. Associating a Response to a Request . . . . . . . . . . . 47 6.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 46
6. Connection Management . . . . . . . . . . . . . . . . . . . . 47 6.2. Persistent Connections . . . . . . . . . . . . . . . . . . 48
6.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 47 6.2.1. Establishment . . . . . . . . . . . . . . . . . . . . 49
6.2. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 6.2.2. Reuse . . . . . . . . . . . . . . . . . . . . . . . . 50
6.3. Persistent Connections . . . . . . . . . . . . . . . . . . 50 6.2.3. Concurrency . . . . . . . . . . . . . . . . . . . . . 51
6.3.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 50 6.2.4. Failures and Time-outs . . . . . . . . . . . . . . . . 51
6.3.2. Overall Operation . . . . . . . . . . . . . . . . . . 51 6.2.5. Tear-down . . . . . . . . . . . . . . . . . . . . . . 52
6.3.3. Practical Considerations . . . . . . . . . . . . . . . 53 6.3. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 53
6.3.4. Retrying Requests . . . . . . . . . . . . . . . . . . 53 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 54
6.4. Message Transmission Requirements . . . . . . . . . . . . 54 7.1. Header Field Registration . . . . . . . . . . . . . . . . 54
6.4.1. Persistent Connections and Flow Control . . . . . . . 54 7.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 55
6.4.2. Monitoring Connections for Error Status Messages . . . 54 7.3. Internet Media Type Registrations . . . . . . . . . . . . 56
6.4.3. Use of the 100 (Continue) Status . . . . . . . . . . . 54 7.3.1. Internet Media Type message/http . . . . . . . . . . . 56
6.4.4. Closing Connections on Error . . . . . . . . . . . . . 56 7.3.2. Internet Media Type application/http . . . . . . . . . 57
6.5. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 56 7.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 58
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 58 7.5. Transfer Coding Registrations . . . . . . . . . . . . . . 58
7.1. Header Field Registration . . . . . . . . . . . . . . . . 58 7.6. Upgrade Token Registry . . . . . . . . . . . . . . . . . . 59
7.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 59 7.7. Upgrade Token Registration . . . . . . . . . . . . . . . . 60
7.3. Internet Media Type Registrations . . . . . . . . . . . . 59 8. Security Considerations . . . . . . . . . . . . . . . . . . . 60
7.3.1. Internet Media Type message/http . . . . . . . . . . . 59 8.1. Personal Information . . . . . . . . . . . . . . . . . . . 60
7.3.2. Internet Media Type application/http . . . . . . . . . 60 8.2. Abuse of Server Log Information . . . . . . . . . . . . . 60
7.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 61 8.3. Attacks Based On File and Path Names . . . . . . . . . . . 61
7.5. Transfer Coding Registrations . . . . . . . . . . . . . . 62 8.4. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 61
7.6. Upgrade Token Registry . . . . . . . . . . . . . . . . . . 62 8.5. Intermediaries and Caching . . . . . . . . . . . . . . . . 61
7.7. Upgrade Token Registration . . . . . . . . . . . . . . . . 63 8.6. Protocol Element Size Overflows . . . . . . . . . . . . . 62
8. Security Considerations . . . . . . . . . . . . . . . . . . . 63 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 62
8.1. Personal Information . . . . . . . . . . . . . . . . . . . 63 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 64
8.2. Abuse of Server Log Information . . . . . . . . . . . . . 64 10.1. Normative References . . . . . . . . . . . . . . . . . . . 64
8.3. Attacks Based On File and Path Names . . . . . . . . . . . 64 10.2. Informative References . . . . . . . . . . . . . . . . . . 65
8.4. DNS-related Attacks . . . . . . . . . . . . . . . . . . . 65 Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 67
8.5. Intermediaries and Caching . . . . . . . . . . . . . . . . 65 A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 67
8.6. Protocol Element Size Overflows . . . . . . . . . . . . . 65 A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 68
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 66 A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 68
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 67 A.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 69
10.1. Normative References . . . . . . . . . . . . . . . . . . . 67 A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 69
10.2. Informative References . . . . . . . . . . . . . . . . . . 68 Appendix B. ABNF list extension: #rule . . . . . . . . . . . . . 70
Appendix A. HTTP Version History . . . . . . . . . . . . . . . . 71 Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 71
A.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 71
A.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 72
A.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 72
A.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 73
A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 73
Appendix B. ABNF list extension: #rule . . . . . . . . . . . . . 74
Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 75
Appendix D. Change Log (to be removed by RFC Editor before Appendix D. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 78 publication) . . . . . . . . . . . . . . . . . . . . 74
D.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 78 D.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 74
D.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 78 D.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 74
D.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 79 D.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 75
D.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 80 D.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 76
D.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 81 D.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 77
D.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 81 D.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 77
D.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 82 D.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 78
D.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 83 D.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 79
D.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 83 D.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 79
D.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 84 D.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 80
D.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 84 D.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 80
D.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 85 D.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 81
D.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 85 D.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 81
D.14. Since draft-ietf-httpbis-p1-messaging-12 . . . . . . . . . 86 D.14. Since draft-ietf-httpbis-p1-messaging-12 . . . . . . . . . 82
D.15. Since draft-ietf-httpbis-p1-messaging-13 . . . . . . . . . 86 D.15. Since draft-ietf-httpbis-p1-messaging-13 . . . . . . . . . 82
D.16. Since draft-ietf-httpbis-p1-messaging-14 . . . . . . . . . 87 D.16. Since draft-ietf-httpbis-p1-messaging-14 . . . . . . . . . 83
D.17. Since draft-ietf-httpbis-p1-messaging-15 . . . . . . . . . 87 D.17. Since draft-ietf-httpbis-p1-messaging-15 . . . . . . . . . 83
D.18. Since draft-ietf-httpbis-p1-messaging-16 . . . . . . . . . 87 D.18. Since draft-ietf-httpbis-p1-messaging-16 . . . . . . . . . 83
D.19. Since draft-ietf-httpbis-p1-messaging-17 . . . . . . . . . 88 D.19. Since draft-ietf-httpbis-p1-messaging-17 . . . . . . . . . 84
D.20. Since draft-ietf-httpbis-p1-messaging-18 . . . . . . . . . 88 D.20. Since draft-ietf-httpbis-p1-messaging-18 . . . . . . . . . 84
D.21. Since draft-ietf-httpbis-p1-messaging-19 . . . . . . . . . 89 D.21. Since draft-ietf-httpbis-p1-messaging-19 . . . . . . . . . 84
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 D.22. Since draft-ietf-httpbis-p1-messaging-20 . . . . . . . . . 85
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
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. This document is the first in a hypertext information systems. This document is the first in a
series of documents that collectively form the HTTP/1.1 series of documents that collectively form the HTTP/1.1
specification: specification:
RFC xxx1: Message Routing and Syntax RFC xxx1: Message Syntax and Routing
RFC xxx2: Semantics and Payloads RFC xxx2: Semantics and Content
RFC xxx3: Conditional Requests RFC xxx3: Conditional Requests
RFC xxx4: Range Requests RFC xxx4: Range Requests
RFC xxx5: Caching RFC xxx5: Caching
RFC xxx6: Authentication RFC xxx6: Authentication
This HTTP/1.1 specification obsoletes and moves to historic status This HTTP/1.1 specification obsoletes and moves to historic status
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handling that are independent of message semantics, thereby defining handling that are independent of message semantics, thereby defining
the complete set of requirements for message parsers and message- the complete set of requirements for message parsers and message-
forwarding intermediaries. forwarding intermediaries.
1.1. Requirement Notation 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].
Conformance criteria and considerations regarding error handling are
defined in Section 2.5.
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the Augmented Backus-Naur Form (ABNF) This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234] with the list rule extension defined in notation of [RFC5234] with the list rule extension defined in
Appendix B. Appendix C shows the collected ABNF with the list rule Appendix B. Appendix C shows the collected ABNF with the list rule
expanded. expanded.
The following core rules are included by reference, as defined in The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
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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
HTTP is a stateless request/response protocol that operates by HTTP is a stateless request/response protocol that operates by
exchanging messages (Section 3) across a reliable transport or exchanging messages (Section 3) across a reliable transport or
session-layer "connection". An HTTP "client" is a program that session-layer "connection" (Section 6). An HTTP "client" is a
establishes a connection to a server for the purpose of sending one program that establishes a connection to a server for the purpose of
or more HTTP requests. An HTTP "server" is a program that accepts sending one or more HTTP requests. An HTTP "server" is a program
connections in order to service HTTP requests by sending HTTP that accepts connections in order to service HTTP requests by sending
responses. HTTP responses.
The terms client and server refer only to the roles that these The terms client and server refer only to the roles that these
programs perform for a particular connection. The same program might programs perform for a particular connection. The same program might
act as a client on some connections and a server on others. We use act as a client on some connections and a server on others. We use
the term "user agent" to refer to the program that initiates a the term "user agent" to refer to the program that initiates a
request, such as a WWW browser, editor, or spider (web-traversing request, such as a WWW browser, editor, or spider (web-traversing
robot), and the term "origin server" to refer to the program that can robot), and the term "origin server" to refer to the program that can
originate authoritative responses to a request. For general originate authoritative responses to a request. For general
requirements, we use the term "sender" to refer to whichever requirements, we use the term "sender" to refer to whichever
component sent a given message and the term "recipient" to refer to component sent a given message and the term "recipient" to refer to
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A server responds to a client's request by sending one or more HTTP A server responds to a client's request by sending one or more HTTP
response messages, each beginning with a status line that includes response messages, each beginning with a status line that includes
the protocol version, a success or error code, and textual reason the protocol version, a success or error code, and textual reason
phrase (Section 3.1.2), possibly followed by header fields containing phrase (Section 3.1.2), possibly followed by header fields containing
server information, resource metadata, and representation metadata server information, resource metadata, and representation metadata
(Section 3.2), an empty line to indicate the end of the header (Section 3.2), an empty line to indicate the end of the header
section, and finally a message body containing the payload body (if section, and finally a message body containing the payload body (if
any, Section 3.3). any, Section 3.3).
A connection might be used for multiple request/response exchanges,
as defined in Section 6.2.
The following example illustrates a typical message exchange for a The following example illustrates a typical message exchange for a
GET request on the URI "http://www.example.com/hello.txt": GET request on the URI "http://www.example.com/hello.txt":
client request: client request:
GET /hello.txt HTTP/1.1 GET /hello.txt HTTP/1.1
User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3 User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3
Host: www.example.com Host: www.example.com
Accept-Language: en, mi Accept-Language: en, mi
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Content-Type: text/plain Content-Type: text/plain
Hello World! Hello World!
2.2. Implementation Diversity 2.2. Implementation Diversity
When considering the design of HTTP, it is easy to fall into a trap When considering the design of HTTP, it is easy to fall into a trap
of thinking that all user agents are general-purpose browsers and all of thinking that all user agents are general-purpose browsers and all
origin servers are large public websites. That is not the case in origin servers are large public websites. That is not the case in
practice. Common HTTP user agents include household appliances, practice. Common HTTP user agents include household appliances,
stereos, scales, software/firmware updaters, command-line programs, stereos, scales, firmware update scripts, command-line programs,
mobile apps, and communication devices in a multitude of shapes and mobile apps, and communication devices in a multitude of shapes and
sizes. Likewise, common HTTP origin servers include home automation sizes. Likewise, common HTTP origin servers include home automation
units, configurable networking components, office machines, units, configurable networking components, office machines,
autonomous robots, news feeds, traffic cameras, ad selectors, and autonomous robots, news feeds, traffic cameras, ad selectors, and
video delivery platforms. video delivery platforms.
The term "user agent" does not imply that there is a human user The term "user agent" does not imply that there is a human user
directly interacting with the software agent at the time of a directly interacting with the software agent at the time of a
request. In many cases, a user agent is installed or configured to request. In many cases, a user agent is installed or configured to
run in the background and save its results for later inspection (or run in the background and save its results for later inspection (or
save only a subset of those results that might be interesting or save only a subset of those results that might be interesting or
erroneous). Spiders, for example, are typically given a start URI erroneous). Spiders, for example, are typically given a start URI
and configured to follow certain behavior while crawling the Web as a and configured to follow certain behavior while crawling the Web as a
hypertext graph. hypertext graph.
The implementation diversity of HTTP means that we cannot assume the The implementation diversity of HTTP means that we cannot assume the
user agent can make interactive suggestions to a user or provide user agent can make interactive suggestions to a user or provide
adequate warning for security or privacy options. In the few cases adequate warning for security or privacy options. In the few cases
where this specification requires reporting of errors to the user, it where this specification requires reporting of errors to the user, it
is acceptable for such reporting to only be visible in an error is acceptable for such reporting to only be observable in an error
console or log file. Likewise, requirements that an automated action console or log file. Likewise, requirements that an automated action
be confirmed by the user before proceeding can me met via advance be confirmed by the user before proceeding can me met via advance
configuration choices, run-time options, or simply not proceeding configuration choices, run-time options, or simply not proceeding
with the unsafe action. with the unsafe action.
2.3. Connections and Transport Independence 2.3. Intermediaries
HTTP messaging is independent of the underlying transport or session-
layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding
in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of the underlying transport
protocol is outside the scope of this specification.
The specific connection protocols to be used for an interaction are
determined by client configuration and the target URI (Section 5.1).
For example, the "http" URI scheme (Section 2.8.1) indicates a
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
connection port or protocol instead of using the defaults.
A connection might be used for multiple HTTP request/response
exchanges, as defined in Section 6.3.
2.4. 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
< < < < < < < <
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terms inbound and outbound to refer to directions in relation to the terms inbound and outbound to refer to directions in relation to the
request path: "inbound" means toward the origin server and "outbound" request path: "inbound" means toward the origin server and "outbound"
means toward the user agent. means toward the user agent.
A "proxy" is a message forwarding agent that is selected by the A "proxy" is a message forwarding agent that is selected by the
client, usually via local configuration rules, to receive requests client, usually via local configuration rules, to receive requests
for some type(s) of absolute URI and attempt to satisfy those for some type(s) of absolute URI and attempt to satisfy those
requests via translation through the HTTP interface. Some requests via translation through the HTTP interface. Some
translations are minimal, such as for proxy requests for "http" URIs, translations are minimal, such as for proxy requests for "http" URIs,
whereas other requests might require translation to and from entirely whereas other requests might require translation to and from entirely
different application-layer protocols. Proxies are often used to different application-level protocols. Proxies are often used to
group an organization's HTTP requests through a common intermediary group an organization's HTTP requests through a common intermediary
for the sake of security, annotation services, or shared caching. for the sake of security, annotation services, or shared caching.
An HTTP-to-HTTP proxy is called a "transforming proxy" if it is An HTTP-to-HTTP proxy is called a "transforming proxy" if it is
designed or configured to modify request or response messages in a designed or configured to modify request or response messages in a
semantically meaningful way (i.e., modifications, beyond those semantically meaningful way (i.e., modifications, beyond those
required by normal HTTP processing, that change the message in a way required by normal HTTP processing, that change the message in a way
that would be significant to the original sender or potentially that would be significant to the original sender or potentially
significant to downstream recipients). For example, a transforming significant to downstream recipients). For example, a transforming
proxy might be acting as a shared annotation server (modifying proxy might be acting as a shared annotation server (modifying
responses to include references to a local annotation database), a responses to include references to a local annotation database), a
malware filter, a format transcoder, or an intranet-to-Internet malware filter, a format transcoder, or an intranet-to-Internet
privacy filter. Such transformations are presumed to be desired by privacy filter. Such transformations are presumed to be desired by
the client (or client organization) that selected the proxy and are the client (or client organization) that selected the proxy and are
beyond the scope of this specification. However, when a proxy is not beyond the scope of this specification. However, when a proxy is not
intended to transform a given message, we use the term "non- intended to transform a given message, we use the term "non-
transforming proxy" to target requirements that preserve HTTP message transforming proxy" to target requirements that preserve HTTP message
semantics. See Section 4.4.4 of [Part2] and Section 7.6 of [Part6] semantics. See Section 7.3.4 of [Part2] and Section 7.5 of [Part6]
for status and warning codes related to transformations. for status and warning codes related to transformations.
A "gateway" (a.k.a., "reverse proxy") is a receiving agent that acts A "gateway" (a.k.a., "reverse proxy") is a receiving agent that acts
as a layer above some other server(s) and translates the received as a layer above some other server(s) and translates the received
requests to the underlying server's protocol. Gateways are often requests to the underlying server's protocol. Gateways are often
used to encapsulate legacy or untrusted information services, to used to encapsulate legacy or untrusted information services, to
improve server performance through "accelerator" caching, and to improve server performance through "accelerator" caching, and to
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 conform to HTTP user agent requirements third-party HTTP servers MUST conform to HTTP user agent requirements
on the gateway's inbound connection and MUST implement the Connection on the gateway's inbound connection and MUST implement the Connection
(Section 6.1) and Via (Section 6.2) header fields for both (Section 6.1) and Via (Section 5.7) header fields for 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 (TLS, [RFC5246]) is used to establish
through a shared firewall proxy. confidential communication through a shared firewall proxy.
The above categories for intermediary only consider those acting as The above categories for intermediary only consider those acting as
participants in the HTTP communication. There are also participants in the HTTP communication. There are also
intermediaries that can act on lower layers of the network protocol intermediaries that can act on lower layers of the network protocol
stack, filtering or redirecting HTTP traffic without the knowledge or stack, filtering or redirecting HTTP traffic without the knowledge or
permission of message senders. Network intermediaries often permission of message senders. Network intermediaries often
introduce security flaws or interoperability problems by violating introduce security flaws or interoperability problems by violating
HTTP semantics. For example, an "interception proxy" [RFC3040] (also HTTP semantics. For example, an "interception proxy" [RFC3040] (also
commonly known as a "transparent proxy" [RFC1919] or "captive commonly known as a "transparent proxy" [RFC1919] or "captive
portal") differs from an HTTP proxy because it is not selected by the portal") differs from an HTTP proxy because it is not selected by the
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HTTP is defined as a stateless protocol, meaning that each request HTTP is defined as a stateless protocol, meaning that each request
message can be understood in isolation. Many implementations depend message can be understood in isolation. Many implementations depend
on HTTP's stateless design in order to reuse proxied connections or on HTTP's stateless design in order to reuse proxied connections or
dynamically load balance requests across multiple servers. Hence, dynamically load balance requests across multiple servers. Hence,
servers MUST NOT assume that two requests on the same connection are servers MUST NOT assume that two requests on the same connection are
from the same user agent unless the connection is secured and from the same user agent unless the connection is secured and
specific to that agent. Some non-standard HTTP extensions (e.g., specific to that agent. Some non-standard HTTP extensions (e.g.,
[RFC4559]) have been known to violate this requirement, resulting in [RFC4559]) have been known to violate this requirement, resulting in
security and interoperability problems. security and interoperability problems.
2.5. Caches 2.4. Caches
A "cache" is a local store of previous response messages and the A "cache" is a local store of previous response messages and the
subsystem that controls its message storage, retrieval, and deletion. subsystem that controls its message storage, retrieval, and deletion.
A cache stores cacheable responses in order to reduce the response A cache stores cacheable responses in order to reduce the response
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.
2.6. Conformance and Error Handling 2.5. Conformance and Error Handling
This specification targets conformance criteria according to the role This specification targets conformance criteria according to the role
of a participant in HTTP communication. Hence, HTTP requirements are of a participant in HTTP communication. Hence, HTTP requirements are
placed on senders, recipients, clients, servers, user agents, placed on senders, recipients, clients, servers, user agents,
intermediaries, origin servers, proxies, gateways, or caches, intermediaries, origin servers, proxies, gateways, or caches,
depending on what behavior is being constrained by the requirement. depending on what behavior is being constrained by the requirement.
Additional (social) requirements are placed on implementations,
resource owners, and protocol element registrations when they apply
beyond the scope of a single communication.
The verb "generate" is used instead of "send" where a requirement The verb "generate" is used instead of "send" where a requirement
differentiates between creating a protocol element and merely differentiates between creating a protocol element and merely
forwarding a received element downstream. forwarding a received element downstream.
An implementation is considered conformant if it complies with all of An implementation is considered conformant if it complies with all of
the requirements associated with the roles it partakes in HTTP. Note the requirements associated with the roles it partakes in HTTP. Note
that SHOULD-level requirements are relevant here, unless one of the that SHOULD-level requirements are relevant here, unless one of the
documented exceptions is applicable. documented exceptions is applicable.
In addition to the prose requirements placed upon them, senders MUST Conformance applies to both the syntax and semantics of HTTP protocol
NOT generate protocol elements that do not match the grammar defined elements. A sender MUST NOT generate protocol elements that convey a
by the ABNF rules for those protocol elements that are applicable to meaning that is known by that sender to be false. A sender MUST NOT
the sender's role. If a received protocol element is processed, the generate protocol elements that do not match the grammar defined by
the ABNF rules for those protocol elements that are applicable to the
sender's role. If a received protocol element is processed, the
recipient MUST be able to parse any value that would match the ABNF recipient MUST be able to parse any value that would match the ABNF
rules for that protocol element, excluding only those rules not rules for that protocol element, excluding only those rules not
applicable to the recipient's role. applicable to the recipient's role.
Unless noted otherwise, a recipient MAY attempt to recover a usable Unless noted otherwise, a recipient MAY attempt to recover a usable
protocol element from an invalid construct. HTTP does not define protocol element from an invalid construct. HTTP does not define
specific error handling mechanisms except when they have a direct specific error handling mechanisms except when they have a direct
impact on security, since different applications of the protocol impact on security, since different applications of the protocol
require different error handling strategies. For example, a Web require different error handling strategies. For example, a Web
browser might wish to transparently recover from a response where the browser might wish to transparently recover from a response where the
Location header field doesn't parse according to the ABNF, whereas a Location header field doesn't parse according to the ABNF, whereas a
systems control client might consider any form of error recovery to systems control client might consider any form of error recovery to
be dangerous. be dangerous.
2.7. 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 conformance 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.
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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.
However, the minor version was not incremented for the changes However, the minor version was not incremented for the changes
introduced between [RFC2068] and [RFC2616], and this revision is introduced between [RFC2068] and [RFC2616], and this revision is
specifically avoiding any such changes to the protocol. specifically avoiding any such changes to the protocol.
2.8. Uniform Resource Identifiers 2.7. Uniform Resource Identifiers
Uniform Resource Identifiers (URIs) [RFC3986] are used throughout Uniform Resource Identifiers (URIs) [RFC3986] are used throughout
HTTP as the means for identifying resources. URI references are used HTTP as the means for identifying resources (Section 2 of [Part2]).
to target requests, indicate redirects, and define relationships. URI references are used to target requests, indicate redirects, and
HTTP does not limit what a resource might be; it merely defines an define relationships.
interface that can be used to interact with a resource via HTTP.
More information on the scope of URIs and resources can be found in
[RFC3986].
This specification adopts the definitions of "URI-reference", This specification adopts the definitions of "URI-reference",
"absolute-URI", "relative-part", "port", "host", "path-abempty", "absolute-URI", "relative-part", "port", "host", "path-abempty",
"path-absolute", "query", and "authority" from the URI generic syntax "path-absolute", "query", and "authority" from the URI generic
[RFC3986]. In addition, we define a partial-URI rule for protocol syntax. In addition, we define a partial-URI rule for protocol
elements that allow a relative URI but not a fragment. elements that allow a relative URI but not a fragment.
URI-reference = <URI-reference, defined in [RFC3986], Section 4.1> URI-reference = <URI-reference, defined in [RFC3986], Section 4.1>
absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3> absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3>
relative-part = <relative-part, defined in [RFC3986], Section 4.2> relative-part = <relative-part, defined in [RFC3986], Section 4.2>
authority = <authority, defined in [RFC3986], Section 3.2> authority = <authority, defined in [RFC3986], Section 3.2>
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>
query = <query, defined in [RFC3986], Section 3.4> query = <query, defined in [RFC3986], Section 3.4>
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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 (Section 5.5). are parsed relative to the effective request URI (Section 5.5).
2.8.1. 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 ]
The HTTP origin server is identified by the generic syntax's The HTTP origin server is identified by the generic syntax's
authority component, which includes a host identifier and optional authority component, which includes a host identifier and optional
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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 5) 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 7 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"
scheme (below) is used for servers that require an SSL/TLS transport scheme (below) is used for resources that require an end-to-end
layer on a connection. Other protocols might also be used to provide secured connection. Other protocols might also be used to provide
access to "http" identified resources -- it is only the authoritative access to "http" identified resources -- it is only the authoritative
interface used for mapping the namespace that is specific to TCP. interface used for mapping the namespace that is specific to TCP.
The URI generic syntax for authority also includes a deprecated The URI generic syntax for authority also includes a deprecated
userinfo subcomponent ([RFC3986], Section 3.2.1) for including user userinfo subcomponent ([RFC3986], Section 3.2.1) for including user
authentication information in the URI. Some implementations make use authentication information in the URI. Some implementations make use
of the userinfo component for internal configuration of of the userinfo component for internal configuration of
authentication information, such as within command invocation authentication information, such as within command invocation
options, configuration files, or bookmark lists, even though such options, configuration files, or bookmark lists, even though such
usage might expose a user identifier or password. Senders MUST NOT usage might expose a user identifier or password. Senders MUST NOT
include a userinfo subcomponent (and its "@" delimiter) when include a userinfo subcomponent (and its "@" delimiter) when
transmitting an "http" URI in a message. Recipients of HTTP messages transmitting an "http" URI in a message. Recipients of HTTP messages
that contain a URI reference SHOULD parse for the existence of that contain a URI reference SHOULD parse for the existence of
userinfo and treat its presence as an error, likely indicating that userinfo and treat its presence as an error, likely indicating that
the deprecated subcomponent is being used to obscure the authority the deprecated subcomponent is being used to obscure the authority
for the sake of phishing attacks. for the sake of phishing attacks.
2.8.2. https URI scheme 2.7.2. https URI scheme
The "https" URI scheme is hereby defined for the purpose of minting The "https" URI scheme is hereby defined for the purpose of minting
identifiers according to their association with the hierarchical identifiers according to their association with the hierarchical
namespace governed by a potential HTTP origin server listening for namespace governed by a potential HTTP origin server listening to a
SSL/TLS-secured connections on a given TCP port. given TCP port for TLS-secured connections [RFC5246].
All of the requirements listed above for the "http" scheme are also All of the requirements listed above for the "http" scheme are also
requirements for the "https" scheme, except that a default TCP port requirements for the "https" scheme, except that a default TCP port
of 443 is assumed if the port subcomponent is empty or not given, and of 443 is assumed if the port subcomponent is empty or not given, and
the TCP connection MUST be secured for privacy through the use of the TCP connection MUST be secured, end-to-end, through the use of
strong encryption prior to sending the first HTTP request. strong encryption prior to sending the first HTTP request.
https-URI = "https:" "//" authority path-abempty [ "?" query ] https-URI = "https:" "//" authority path-abempty [ "?" query ]
Unlike the "http" scheme, responses to "https" identified requests Unlike the "http" scheme, responses to "https" identified requests
are never "public" and thus MUST NOT be reused for shared caching. are never "public" and thus MUST NOT be reused for shared caching.
They can, however, be reused in a private cache if the message is They can, however, be reused in a private cache if the message is
cacheable by default in HTTP or specifically indicated as such by the cacheable by default in HTTP or specifically indicated as such by the
Cache-Control header field (Section 7.2 of [Part6]). Cache-Control header field (Section 7.2 of [Part6]).
skipping to change at page 19, line 32 skipping to change at page 18, line 18
port). They are distinct name spaces and are considered to be port). They are distinct name spaces and are considered to be
distinct origin servers. However, an extension to HTTP that is distinct origin servers. However, an extension to HTTP that is
defined to apply to entire host domains, such as the Cookie protocol defined to apply to entire host domains, such as the Cookie protocol
[RFC6265], can allow information set by one service to impact [RFC6265], can allow information set by one service to impact
communication with other services within a matching group of host communication with other services within a matching group of host
domains. domains.
The process for authoritative access to an "https" identified The process for authoritative access to an "https" identified
resource is defined in [RFC2818]. resource is defined in [RFC2818].
2.8.3. http and https URI Normalization and Comparison 2.7.3. http and https URI Normalization and Comparison
Since the "http" and "https" schemes conform to the URI generic Since the "http" and "https" schemes conform to the URI generic
syntax, such URIs are normalized and compared according to the syntax, such URIs are normalized and compared according to the
algorithm defined in [RFC3986], Section 6, using the defaults algorithm defined in [RFC3986], Section 6, using the defaults
described above for each scheme. described above for each scheme.
If the port is equal to the default port for a scheme, the normal If the port is equal to the default port for a scheme, the normal
form is to elide the port subcomponent. Likewise, an empty path form is to elide the port subcomponent. Likewise, an empty path
component is equivalent to an absolute path of "/", so the normal component is equivalent to an absolute path of "/", so the normal
form is to provide a path of "/" instead. The scheme and host are form is to provide a path of "/" instead. The scheme and host are
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(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 A sender MUST NOT send whitespace between the start-line and the
the first header field. The presence of such whitespace in a request 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
A request-line begins with a method token, followed by a single space A request-line begins with a method token, followed by a single space
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request-line = method SP request-target SP HTTP-version CRLF request-line = method SP request-target SP HTTP-version CRLF
A server MUST be able to parse any received message that begins with A server MUST be able to parse any received message that begins with
a request-line and matches the ABNF rule for HTTP-message. a request-line and matches the ABNF rule for HTTP-message.
The method token indicates the request method to be performed on the The method token indicates the request method to be performed on the
target resource. The request method is case-sensitive. target resource. The request method is case-sensitive.
method = token method = token
The methods defined by this specification can be found in Section 2 The methods defined by this specification can be found in Section 5
of [Part2], along with information regarding the HTTP method registry of [Part2], along with information regarding the HTTP method registry
and considerations for defining new methods. and considerations for defining new methods.
The request-target identifies the target resource upon which to apply The request-target identifies the target resource upon which to apply
the request, as defined in Section 5.3. the request, as defined in Section 5.3.
No whitespace is allowed inside the method, request-target, and No whitespace is allowed inside the method, request-target, and
protocol version. Hence, recipients typically parse the request-line protocol version. Hence, recipients typically parse the request-line
into its component parts by splitting on the SP characters. into its component parts by splitting on the SP characters.
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redirect, since the invalid request-line might be deliberately redirect, since the invalid request-line might be deliberately
crafted to bypass security filters along the request chain. 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-
line. A server that receives a method longer than any that it line. A server that receives a method longer than any that it
implements SHOULD respond with either a 405 (Method Not Allowed), if implements SHOULD respond with either a 405 (Method Not Allowed), if
it is an origin server, or a 501 (Not Implemented) status code. A it is an origin server, or a 501 (Not Implemented) status code. A
server MUST be prepared to receive URIs of unbounded length and server MUST be prepared to receive URIs of unbounded length and
respond with the 414 (URI Too Long) status code if the received respond with the 414 (URI Too Long) status code if the received
request-target would be longer than the server wishes to handle (see request-target would be longer than the server wishes to handle (see
Section 4.6.12 of [Part2]). Section 7.5.12 of [Part2]).
Various ad-hoc limitations on request-line length are found in Various ad-hoc limitations on request-line length are found in
practice. It is RECOMMENDED that all HTTP senders and recipients practice. It is RECOMMENDED that all HTTP senders and recipients
support, at a minimum, request-line lengths of up to 8000 octets. support, at a minimum, request-line lengths of up to 8000 octets.
3.1.2. Status Line 3.1.2. Status Line
The first line of a response message is the status-line, consisting The first line of a response message is the status-line, consisting
of the protocol version, a space (SP), the status code, another of the protocol version, a space (SP), the status code, another
space, a possibly-empty textual phrase describing the status code, space, a possibly-empty textual phrase describing the status code,
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status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP reason-phrase CRLF
A client MUST be able to parse any received message that begins with A client MUST be able to parse any received message that begins with
a status-line and matches the ABNF rule for HTTP-message. a status-line and matches the ABNF rule for HTTP-message.
The status-code element is a 3-digit integer code describing the The status-code element is a 3-digit integer code describing the
result of the server's attempt to understand and satisfy the client's result of the server's attempt to understand and satisfy the client's
corresponding request. The rest of the response message is to be corresponding request. The rest of the response message is to be
interpreted in light of the semantics defined for that status code. interpreted in light of the semantics defined for that status code.
See Section 4 of [Part2] for information about the semantics of See Section 7 of [Part2] for information about the semantics of
status codes, including the classes of status code (indicated by the status codes, including the classes of status code (indicated by the
first digit), the status codes defined by this specification, first digit), the status codes defined by this specification,
considerations for the definition of new status codes, and the IANA considerations for the definition of new status codes, and the IANA
registry. registry.
status-code = 3DIGIT status-code = 3DIGIT
The reason-phrase element exists for the sole purpose of providing a The reason-phrase element exists for the sole purpose of providing a
textual description associated with the numeric status code, mostly textual description associated with the numeric status code, mostly
out of deference to earlier Internet application protocols that were out of deference to earlier Internet application protocols that were
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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 ) obs-fold = CRLF ( SP / HTAB )
; obsolete line folding ; obsolete line folding
; see Section 3.2.2 ; 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 9.10 of [Part2] as containing the header field is defined in Section 8.1.1.2 of [Part2] as containing
origination timestamp for the message in which it appears. the 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 in the Message
the procedures in Section 3.1 of [Part2]. Unrecognized header fields Header Field Registry, as described in Section 9.3 of [Part2].
MUST be forwarded by a proxy unless the field-name is listed in the Unrecognized header fields MUST be forwarded by a proxy unless the
Connection header field (Section 6.1) or the proxy is specifically field-name is listed in the Connection header field (Section 6.1) or
configured to block or otherwise transform such fields. Unrecognized the proxy is specifically configured to block or otherwise transform
header fields SHOULD be ignored by other recipients. such fields. Unrecognized 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
conditionals, authentication credentials, or deliberately misleading conditionals, authentication credentials, or deliberately misleading
duplicate header fields that would impact request processing. duplicate header fields that would impact request processing.
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SHOULD either be replaced with a single SP or transformed to all SP SHOULD either be replaced with a single SP or transformed to all SP
octets (each octet other than SP replaced with SP) before octets (each octet other than SP replaced with SP) before
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
RWS is used when at least one linear whitespace octet is required to RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be produced as a single SP. separate field tokens. RWS SHOULD be produced as a single SP.
Multiple RWS octets that occur within field-content SHOULD either be Multiple RWS octets that occur within field-content SHOULD either be
replaced with a single SP or transformed to all SP octets before replaced with a single SP or transformed to all SP octets before
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
BWS is used where the grammar allows optional whitespace for BWS is used where the grammar allows optional whitespace, for
historical reasons but senders SHOULD NOT produce it in messages. historical reasons, but senders SHOULD NOT produce it in messages;
HTTP/1.1 recipients MUST accept such bad optional whitespace and recipients MUST accept such bad optional whitespace and remove it
remove it before interpreting the field value or forwarding the before interpreting the field value or forwarding the message
message downstream. downstream.
OWS = *( SP / HTAB ) OWS = *( SP / HTAB )
; "optional" whitespace ; "optional" whitespace
RWS = 1*( SP / HTAB ) RWS = 1*( SP / HTAB )
; "required" whitespace ; "required" whitespace
BWS = OWS BWS = OWS
; "bad" whitespace ; "bad" whitespace
3.2.2. Field Parsing 3.2.2. Field Parsing
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A client that receives response header fields that are longer than it A client that receives response header fields 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 field length are found in Various ad-hoc limitations on header field 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 messages whose combined header fields have 4000 or more support messages whose combined header fields have 4000 or more
octets. octets.
3.2.4. Field value components 3.2.4. Field value components
Many HTTP/1.1 header field values consist of words (token or quoted- Many HTTP header field values consist of words (token or quoted-
string) separated by whitespace or special characters. These special string) separated by whitespace or special characters. 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 4). value (as defined in Section 4).
word = token / quoted-string word = token / quoted-string
token = 1*tchar token = 1*tchar
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/ "+" / "-" / "." / "^" / "_" / "`" / "|" / "~" / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
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The presence of a message body in a request is signaled by a a The presence of a message body in a request is signaled by a a
Content-Length or Transfer-Encoding header field. Request message Content-Length or Transfer-Encoding header field. Request message
framing is independent of method semantics, even if the method does framing is independent of method semantics, even if the method does
not define any use for a message body. not define any use for a message body.
The presence of a message body in a response depends on both the The presence of a message body in a response depends on both the
request method to which it is responding and the response status code request method to which it is responding and the response status code
(Section 3.1.2). Responses to the HEAD request method never include (Section 3.1.2). Responses to the HEAD request method never include
a message body because the associated response header fields (e.g., a message body because the associated response header fields (e.g.,
Transfer-Encoding, Content-Length, etc.) only indicate what their Transfer-Encoding, Content-Length, etc.), if present, indicate only
values would have been if the request method had been GET. 2xx what their values would have been if the request method had been GET
(Successful) responses to CONNECT switch to tunnel mode instead of (Section 5.3.2 of [Part2]). 2xx (Successful) responses to CONNECT
having a message body. All 1xx (Informational), 204 (No Content), switch to tunnel mode instead of having a message body (Section 5.3.6
and 304 (Not Modified) responses MUST NOT include a message body. of [Part2]). All 1xx (Informational), 204 (No Content), and 304 (Not
All other responses do include a message body, although the body MAY Modified) responses MUST NOT include a message body. All other
be of zero length. responses do include a message body, although the body MAY be of zero
length.
3.3.1. Transfer-Encoding 3.3.1. Transfer-Encoding
When one or more transfer codings are applied to a payload body in When one or more transfer codings are applied to a payload body in
order to form the message body, a Transfer-Encoding header field MUST order to form the message body, a Transfer-Encoding header field MUST
be sent in the message and MUST contain the list of corresponding be sent in the message and MUST contain the list of corresponding
transfer-coding names in the same order that they were applied. transfer-coding names in the same order that they were applied.
Transfer codings are defined in Section 4. Transfer codings are defined in Section 4.
Transfer-Encoding = 1#transfer-coding Transfer-Encoding = 1#transfer-coding
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indicates that the payload body has been compressed using the gzip indicates that the payload body has been compressed using the gzip
coding and then chunked using the chunked coding while forming the coding and then chunked using the chunked coding while forming the
message body. message body.
If more than one Transfer-Encoding header field is present in a If more than one Transfer-Encoding header field is present in a
message, the multiple field-values MUST be combined into one field- message, the multiple field-values MUST be combined into one field-
value, according to the algorithm defined in Section 3.2, before value, according to the algorithm defined in Section 3.2, before
determining the message body length. determining the message body length.
Unlike Content-Encoding (Section 5.4 of [Part2]), Transfer-Encoding Unlike Content-Encoding (Section 3.1.2.1 of [Part2]), Transfer-
is a property of the message, not of the payload, and thus MAY be Encoding is a property of the message, not of the payload, and thus
added or removed by any implementation along the request/response MAY be added or removed by any implementation along the request/
chain. Additional information about the encoding parameters MAY be response chain. Additional information about the encoding parameters
provided by other header fields not defined by this specification. 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 Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 (Not Modified) response (Section 4.1 of [Part4]) to a GET 304 (Not Modified) response (Section 4.1 of [Part4]) to a GET
request, neither of which includes a message body, to indicate that request, neither of which includes a message body, to indicate that
the origin server would have applied a transfer coding to the message the origin server would have applied a transfer coding to the message
body if the request had been an unconditional GET. This indication body if the request had been an unconditional GET. This indication
is not required, however, because any recipient on the response chain is not required, however, because any recipient on the response chain
(including the origin server) can remove transfer codings when they (including the origin server) can remove transfer codings when they
are not needed. are not needed.
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version of a prior received response. A server MUST NOT send a version of a prior received response. A server MUST NOT send a
response containing Transfer-Encoding unless the corresponding response containing Transfer-Encoding unless the corresponding
request indicates HTTP/1.1 (or later). request indicates HTTP/1.1 (or later).
A server that receives a request message with a transfer-coding it A server that receives a request message with a transfer-coding it
does not understand SHOULD respond with 501 (Not Implemented) and does not understand SHOULD respond with 501 (Not Implemented) and
then close the connection. then close the connection.
3.3.2. Content-Length 3.3.2. Content-Length
When a message does not have a Transfer-Encoding header field and the When a message is allowed to contain a message body, does not have a
payload body length can be determined prior to being transferred, a Transfer-Encoding header field, and has a payload body length that is
Content-Length header field SHOULD be sent to indicate the length of known to the sender before the message header section has been sent,
the payload body that is either present as the message body, for the sender SHOULD send a Content-Length header field to indicate the
requests and non-HEAD responses other than 304 (Not Modified), or length of the payload body as a decimal number of octets.
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 Content-Length = 1*DIGIT
An example is An example is
Content-Length: 3495 Content-Length: 3495
In the case of a response to a HEAD request, Content-Length indicates A sender MUST NOT send a Content-Length header field in any message
the size of the payload body (without any potential transfer-coding) that contains a Transfer-Encoding header field.
that would have been sent had the request been a GET. In the case of
a 304 (Not Modified) response (Section 4.1 of [Part4]) to a GET A server MAY send a Content-Length header field in a response to a
request, Content-Length indicates the size of the payload body HEAD request (Section 5.3.2 of [Part2]); a server MUST NOT send
(without any potential transfer-coding) that would have been sent in Content-Length in such a response unless its field-value equals the
a 200 (OK) response. decimal number of octets that would have been sent in the payload
body of a response if the same request had used the GET method.
A server MAY send a Content-Length header field in a 304 (Not
Modified) response to a conditional GET request (Section 4.1 of
[Part4]); a server MUST NOT send Content-Length in such a response
unless its field-value equals the decimal number of octets that would
have been sent in the payload body of a 200 (OK) response to the same
request.
A server MUST NOT send a Content-Length header field in any response
with a status code of 1xx (Informational) or 204 (No Content). A
server SHOULD NOT send a Content-Length header field in any 2xx
(Successful) response to a CONNECT request (Section 5.3.6 of
[Part2]).
Any Content-Length field value greater than or equal to zero is Any Content-Length field value greater than or equal to zero is
valid. Since there is no predefined limit to the length of an HTTP valid. Since there is no predefined limit to the length of an HTTP
payload, recipients SHOULD anticipate potentially large decimal payload, recipients SHOULD anticipate potentially large decimal
numerals and prevent parsing errors due to integer conversion numerals and prevent parsing errors due to integer conversion
overflows (Section 8.6). overflows (Section 8.6).
If a message is received that has multiple Content-Length header If a message is received that has multiple Content-Length header
fields with field-values consisting of the same decimal value, or a fields with field-values consisting of the same decimal value, or a
single Content-Length header field with a field value containing a single Content-Length header field with a field value containing a
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6. If this is a request message and none of the above are true, then 6. If this is a request message and none of the above are true, then
the message body length is zero (no message body is present). the message body length is zero (no message body is present).
7. Otherwise, this is a response message without a declared message 7. Otherwise, this is a response message without a declared message
body length, so the message body length is determined by the body length, so the message body length is determined by the
number of octets received prior to the server closing the number of octets received prior to the server closing the
connection. connection.
Since there is no way to distinguish a successfully completed, close- Since there is no way to distinguish a successfully completed, close-
delimited message from a partially-received message interrupted by delimited message from a partially-received message interrupted by
network failure, implementations SHOULD use encoding or length- network failure, a server SHOULD use encoding or length-delimited
delimited messages whenever possible. The close-delimiting feature messages whenever possible. The close-delimiting feature exists
exists primarily for backwards compatibility with HTTP/1.0. 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
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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
canceled connection or a server-imposed time-out exception, MUST canceled 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 error response prior
response prior to closing the connection is OPTIONAL. 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
skipping to change at page 33, line 14 skipping to change at page 32, line 16
if it were complete (i.e., some indication needs to be given to the if it were complete (i.e., some indication needs to be given to the
user that an error occurred). Cache requirements for incomplete user that an error occurred). Cache requirements for incomplete
responses are defined in Section 3 of [Part6]. responses are defined in Section 3 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 6.3.2.2. in Section 6.2.2.1.
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
skipping to change at page 34, line 18 skipping to change at page 33, line 18
/ "gzip" ; Section 4.2.3 / "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. The HTTP Transfer All transfer-coding values are case-insensitive and SHOULD be
Coding registry is defined in Section 7.4. HTTP/1.1 uses transfer- registered within the HTTP Transfer Coding registry, as defined in
coding values in the TE header field (Section 4.3) and in the Section 7.4. They are used in the TE (Section 4.3) and Transfer-
Transfer-Encoding header field (Section 3.3.1). Encoding (Section 3.3.1) header fields.
4.1. 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.
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chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-str-nf chunk-ext-val = token / quoted-str-nf
chunk-data = 1*OCTET ; a sequence of chunk-size octets 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
Chunk extensions within the chucked encoding are deprecated. Senders
SHOULD NOT send chunk-ext. Definition of new chunk extensions is
discouraged.
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 4.1.1. Trailer
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
Section 4.4).
A server using chunked transfer-coding in a response MUST NOT use the A trailer allows the sender to include additional fields at the end
trailer for any header fields unless at least one of the following is of a chunked message in order to supply metadata that might be
true: dynamically generated while the message body is sent, such as a
message integrity check, digital signature, or post-processing
status. The trailer MUST NOT contain fields that need to be known
before a recipient processes the body, such as Transfer-Encoding,
Content-Length, and Trailer.
When a message includes a message body encoded with the chunked
transfer-coding and the sender desires to send metadata in the form
of trailer fields at the end of the message, the sender SHOULD send a
Trailer header field before the message body to indicate which fields
will be present in the trailers. This allows the recipient to
prepare for receipt of that metadata before it starts processing the
body, which is useful if the message is being streamed and the
recipient wishes to confirm an integrity check on the fly.
Trailer = 1#field-name
If no Trailer header field is present, the sender of a chunked
message body SHOULD send an empty trailer.
A server MUST send an empty trailer with the chunked transfer-coding
unless at least one of the following is true:
1. the request included a TE header field that indicates "trailers" 1. the request included a TE header field that indicates "trailers"
is acceptable in the transfer-coding of the response, as is acceptable in the transfer-coding of the response, as
described in Section 4.3; or, described in Section 4.3; or,
2. the trailer fields consist entirely of optional metadata, and the 2. the trailer fields consist entirely of optional metadata and the
recipient could use the message (in a manner acceptable to the recipient could use the message (in a manner acceptable to the
server where the field originated) without receiving it. In server where the field originated) without receiving that
other words, the server that generated the header field (often metadata. In other words, the server that generated the header
but not always the origin server) is willing to accept the field is willing to accept the possibility that the trailer
possibility that the trailer fields might be silently discarded fields might be silently discarded along the path to the client.
along the path to the client.
This requirement prevents an interoperability failure when the The above requirement prevents the need for an infinite buffer when a
message is being received by an HTTP/1.1 (or later) proxy and message is being received by an HTTP/1.1 (or later) proxy and
forwarded to an HTTP/1.0 recipient. It avoids a situation where forwarded to an HTTP/1.0 recipient.
conformance with the protocol would have necessitated a possibly
infinite buffer on the proxy. 4.1.2. Decoding chunked
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
length := length + chunk-size length := length + chunk-size
read chunk-size and CRLF read chunk-size and CRLF
} }
read header-field read header-field
while (header-field not empty) { while (header-field not empty) {
append header-field to existing header fields append header-field to existing header fields
read header-field read header-field
} }
Content-Length := length Content-Length := length
Remove "chunked" from Transfer-Encoding Remove "chunked" from Transfer-Encoding
Remove Trailer from existing header fields
All HTTP/1.1 applications MUST be able to receive and decode the All recipients MUST be able to receive and decode the "chunked"
"chunked" transfer-coding and MUST ignore chunk-ext extensions they transfer-coding and MUST ignore chunk-ext extensions they do not
do not understand. understand.
Use of chunk-ext extensions by senders is deprecated; they SHOULD NOT
be sent and definition of new chunk-extensions is discouraged.
4.2. Compression Codings 4.2. Compression Codings
The codings defined below can be used to compress the payload of a The codings defined below can be used to compress the payload of a
message. message.
Note: Use of program names for the identification of encoding
formats is not desirable and is discouraged for future encodings.
Their use here is representative of historical practice, not good
design.
Note: For compatibility with previous implementations of HTTP,
applications SHOULD consider "x-gzip" and "x-compress" to be
equivalent to "gzip" and "compress" respectively.
4.2.1. 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). Recipients SHOULD consider "x-compress" to be
equivalent to "compress".
4.2.2. 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.
4.2.3. 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. Recipients SHOULD consider "x-gzip"
to be equivalent to "gzip".
4.3. TE 4.3. TE
The "TE" header field indicates what extension transfer-codings the The "TE" header field in a request indicates what transfer-codings,
client is willing to accept in the response, and whether or not it is besides "chunked", the client is willing to accept in response, and
willing to accept trailer fields in a chunked transfer-coding. whether or not the client is willing to accept trailer fields in a
chunked transfer-coding.
Its value consists of the keyword "trailers" and/or a comma-separated The TE field-value consists of a comma-separated list of transfer-
list of extension transfer-coding names with optional accept coding names, each allowing for optional parameters (as described in
parameters (as described in Section 4). Section 4), and/or the keyword "trailers". Clients MUST NOT send the
chunked transfer-coding name in TE; chunked is always acceptable for
HTTP/1.1 recipients.
TE = #t-codings TE = #t-codings
t-codings = "trailers" / ( transfer-extension [ te-params ] ) t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
te-params = OWS ";" OWS "q=" qvalue *( te-ext ) t-ranking = OWS ";" OWS "q=" rank
te-ext = OWS ";" OWS token [ "=" word ] rank = ( "0" [ "." 0*3DIGIT ] )
/ ( "1" [ "." 0*3("0") ] )
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.
Examples of its use are: Three examples of TE use are below.
TE: deflate TE: deflate
TE: TE:
TE: trailers, deflate;q=0.5 TE: trailers, deflate;q=0.5
The TE header field only applies to the immediate connection. The presence of the keyword "trailers" indicates that the client is
Therefore, the keyword MUST be supplied within a Connection header willing to accept trailer fields in a chunked transfer-coding, as
field (Section 6.1) whenever TE is present in an HTTP/1.1 message. defined in Section 4.1, on behalf of itself and any downstream
clients. For chained requests, this implies that either: (a) all
A server tests whether a transfer-coding is acceptable, according to downstream clients are willing to accept trailer fields in the
a TE field, using these rules: forwarded response; or, (b) the client will attempt to buffer the
response on behalf of downstream recipients. Note that HTTP/1.1 does
1. The "chunked" transfer-coding is always acceptable. If the not define any means to limit the size of a chunked response such
keyword "trailers" is listed, the client indicates that it is that a client can be assured of buffering the entire response.
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 4.3.1, a
qvalue of 0 means "not acceptable".)
3. If multiple transfer-codings are acceptable, then the acceptable When multiple transfer-codings are acceptable, the client MAY rank
transfer-coding with the highest non-zero qvalue is preferred. the codings by preference using a case-insensitive "q" parameter
The "chunked" transfer-coding always has a qvalue of 1. (similar to the qvalues used in content negotiation fields, Section
6.3.1 of [Part2]). The rank value is a real number in the range 0
through 1, where 0.001 is the least preferred and 1 is the most
preferred; a value of 0 means "not acceptable".
If the TE field-value is empty or if no TE field is present, the only If the TE field-value is empty or if no TE field is present, the only
acceptable transfer-coding is "chunked". A message with no transfer- acceptable transfer-coding is "chunked". A message with no transfer-
coding is always acceptable. coding is always acceptable.
4.3.1. Quality Values Since the TE header field only applies to the immediate connection, a
sender of TE MUST also send a "TE" connection option within the
Both transfer codings (TE request header field, Section 4.3) and Connection header field (Section 6.1) in order to prevent the TE
content negotiation (Section 8 of [Part2]) use short "floating point" field from being forwarded by intermediaries that do not support its
numbers to indicate the relative importance ("weight") of various semantics.
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
value. If a parameter has a quality value of 0, then content with
this parameter is "not acceptable" for the client. HTTP/1.1
applications MUST NOT generate more than three digits after the
decimal point. User configuration of these values SHOULD also be
limited in this fashion.
qvalue = ( "0" [ "." 0*3DIGIT ] )
/ ( "1" [ "." 0*3("0") ] )
Note: "Quality values" is a misnomer, since these values merely
represent relative degradation in desired quality.
4.4. 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 4.1 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
5. Message Routing 5. Message Routing
HTTP request message routing is determined by each client based on HTTP request message routing is determined by each client based on
the target resource, the client's proxy configuration, and the target resource, the client's proxy configuration, and
establishment or reuse of an inbound connection. The corresponding establishment or reuse of an inbound connection. The corresponding
response routing follows the same connection chain back to the response routing follows the same connection chain back to the
client. client.
5.1. Identifying a Target Resource 5.1. Identifying a Target Resource
HTTP is used in a wide variety of applications, ranging from general- HTTP is used in a wide variety of applications, ranging from general-
purpose computers to home appliances. In some cases, communication purpose computers to home appliances. In some cases, communication
options are hard-coded in a client's configuration. However, most options are hard-coded in a client's configuration. However, most
HTTP clients rely on the same resource identification mechanism and HTTP clients rely on the same resource identification mechanism and
configuration techniques as general-purpose Web browsers. configuration techniques as general-purpose Web browsers.
HTTP communication is initiated by a user agent for some purpose. HTTP communication is initiated by a user agent for some purpose.
The purpose is a combination of request semantics, which are defined The purpose is a combination of request semantics, which are defined
in [Part2], and a target resource upon which to apply those in [Part2], and a target resource upon which to apply those
semantics. A URI reference (Section 2.8) is typically used as an semantics. A URI reference (Section 2.7) is typically used as an
identifier for the "target resource", which a user agent would identifier for the "target resource", which a user agent would
resolve to its absolute form in order to obtain the "target URI". resolve to its absolute form in order to obtain the "target URI".
The target URI excludes the reference's fragment identifier The target URI excludes the reference's fragment identifier
component, if any, since fragment identifiers are reserved for component, if any, since fragment identifiers are reserved for
client-side processing ([RFC3986], Section 3.5). client-side processing ([RFC3986], Section 3.5).
HTTP intermediaries obtain the request semantics and target URI from
the request-line of an incoming request message.
5.2. Connecting Inbound 5.2. Connecting Inbound
Once the target URI is determined, a client needs to decide whether a Once the target URI is determined, a client needs to decide whether a
network request is necessary to accomplish the desired semantics and, network request is necessary to accomplish the desired semantics and,
if so, where that request is to be directed. if so, where that request is to be directed.
If the client has a response cache and the request semantics can be If the client has a response cache and the request semantics can be
satisfied by a cache ([Part6]), then the request is usually directed satisfied by a cache ([Part6]), then the request is usually directed
to the cache first. to the cache first.
skipping to change at page 40, line 15 skipping to change at page 38, line 20
authority matching, or both, and the proxy itself is usually authority matching, or both, and the proxy itself is usually
identified by an "http" or "https" URI. If a proxy is applicable, identified by an "http" or "https" URI. If a proxy is applicable,
the client connects inbound by establishing (or reusing) a connection the client connects inbound by establishing (or reusing) a connection
to that proxy. to that proxy.
If no proxy is applicable, a typical client will invoke a handler If no proxy is applicable, a typical client will invoke a handler
routine, usually specific to the target URI's scheme, to connect routine, usually specific to the target URI's scheme, to connect
directly to an authority for the target resource. How that is directly to an authority for the target resource. How that is
accomplished is dependent on the target URI scheme and defined by its accomplished is dependent on the target URI scheme and defined by its
associated specification, similar to how this specification defines associated specification, similar to how this specification defines
origin server access for resolution of the "http" (Section 2.8.1) and origin server access for resolution of the "http" (Section 2.7.1) and
"https" (Section 2.8.2) schemes. "https" (Section 2.7.2) schemes.
HTTP requirements regarding connection management are defined in
Section 6.
5.3. Request Target 5.3. Request Target
Once an inbound connection is obtained (Section 6), the client sends Once an inbound connection is obtained, the client sends an HTTP
an HTTP request message (Section 3) with a request-target derived request message (Section 3) with a request-target derived from the
from the target URI. There are four distinct formats for the target URI. There are four distinct formats for the request-target,
request-target, depending on both the method being requested and depending on both the method being requested and whether the request
whether the request is to a proxy. is to a proxy.
request-target = origin-form request-target = origin-form
/ absolute-form / absolute-form
/ authority-form / authority-form
/ asterisk-form / asterisk-form
origin-form = path-absolute [ "?" query ] origin-form = path-absolute [ "?" query ]
absolute-form = absolute-URI absolute-form = absolute-URI
authority-form = authority authority-form = authority
asterisk-form = "*" asterisk-form = "*"
skipping to change at page 41, line 31 skipping to change at page 39, line 39
An example absolute-form of request-line would be: An example absolute-form of request-line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
To allow for transition to the absolute-form for all requests in some To allow for transition to the absolute-form for all requests in some
future version of HTTP, HTTP/1.1 servers MUST accept the absolute- future version of HTTP, HTTP/1.1 servers MUST accept the absolute-
form in requests, even though HTTP/1.1 clients will only send them in form in requests, even though HTTP/1.1 clients will only send them in
requests to proxies. requests to proxies.
The authority-form of request-target is only used for CONNECT The authority-form of request-target is only used for CONNECT
requests (Section 2.3.8 of [Part2]). When making a CONNECT request requests (Section 5.3.6 of [Part2]). When making a CONNECT request
to establish a tunnel through one or more proxies, a client MUST send to establish a tunnel through one or more proxies, a client MUST send
only the target URI's authority component (excluding any userinfo) as only the target URI's authority component (excluding any userinfo) as
the request-target. For example, the request-target. For example,
CONNECT www.example.com:80 HTTP/1.1 CONNECT www.example.com:80 HTTP/1.1
The asterisk-form of request-target is only used for a server-wide The asterisk-form of request-target is only used for a server-wide
OPTIONS request (Section 2.3.1 of [Part2]). When a client wishes to OPTIONS request (Section 5.3.7 of [Part2]). When a client wishes to
request OPTIONS for the server as a whole, as opposed to a specific request OPTIONS for the server as a whole, as opposed to a specific
named resource of that server, the client MUST send only "*" (%x2A) named resource of that server, the client MUST send only "*" (%x2A)
as the request-target. For example, as the request-target. For example,
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
If a proxy receives an OPTIONS request with an absolute-form of 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 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 component, then the last proxy on the request chain MUST send a
request-target of "*" when it forwards the request to the indicated request-target of "*" when it forwards the request to the indicated
origin server. origin server.
For example, the request For example, the request
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5.4. Host 5.4. Host
The "Host" header field in a request provides the host and port The "Host" header field in a request provides the host and port
information from the target URI, enabling the origin server to information from the target URI, enabling the origin server to
distinguish among resources while servicing requests for multiple distinguish among resources while servicing requests for multiple
host names on a single IP address. Since the Host field-value is host names on a single IP address. Since the Host field-value is
critical information for handling a request, it SHOULD be sent as the critical information for handling a request, it SHOULD be sent as the
first header field following the request-line. first header field following the request-line.
Host = uri-host [ ":" port ] ; Section 2.8.1 Host = uri-host [ ":" port ] ; Section 2.7.1
A client MUST send a Host header field in all HTTP/1.1 request A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target URI includes an authority component, then messages. If the target URI includes an authority component, then
the Host field-value MUST be identical to that authority component the Host field-value MUST be identical to that authority component
after excluding any userinfo (Section 2.8.1). If the authority after excluding any userinfo (Section 2.7.1). If the authority
component is missing or undefined for the target URI, then the Host component is missing or undefined for the target URI, then the Host
header field MUST be sent with an empty field-value. header field MUST be sent with an empty field-value.
For example, a GET request to the origin server for For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with: <http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1 GET /pub/WWW/ HTTP/1.1
Host: www.example.org Host: www.example.org
The Host header field MUST be sent in an HTTP/1.1 request even if the 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 request-target is in the absolute-form, since this allows the Host
information to be forwarded through ancient HTTP/1.0 proxies that information to be forwarded through ancient HTTP/1.0 proxies that
might not have implemented Host. might not have implemented Host.
When an HTTP/1.1 proxy receives a request with an absolute-form of When a proxy receives a request with an absolute-form of request-
request-target, the proxy MUST ignore the received Host header field target, the proxy MUST ignore the received Host header field (if any)
(if any) and instead replace it with the host information of the and instead replace it with the host information of the request-
request-target. If the proxy forwards the request, it MUST generate target. If the proxy forwards the request, it MUST generate a new
a new Host field-value based on the received request-target rather Host field-value based on the received request-target rather than
than forward the received Host field-value. forward the received Host field-value.
Since the Host header field acts as an application-level routing Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the interception proxy is particularly vulnerable if it relies on the
Host field-value for redirecting requests to internal servers, or for Host field-value for redirecting requests to internal servers, or for
use as a cache key in a shared cache, without first verifying that use as a cache key in a shared cache, without first verifying that
the intercepted connection is targeting a valid IP address for that the intercepted connection is targeting a valid IP address for that
host. host.
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context, in order to identify the intended target resource and context, in order to identify the intended target resource and
properly service the request. The URI derived from this properly service the request. The URI derived from this
reconstruction process is referred to as the "effective request URI". reconstruction process is referred to as the "effective request URI".
For a user agent, the effective request URI is the target 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 If the request-target is in absolute-form, then the effective request
URI is the same as the request-target. Otherwise, the effective URI is the same as the request-target. Otherwise, the effective
request URI is constructed as follows. request URI is constructed as follows.
If the request is received over an SSL/TLS-secured TCP connection, If the request is received over a TLS-secured TCP connection, then
then the effective request URI's scheme is "https"; otherwise, the the effective request URI's scheme is "https"; otherwise, the scheme
scheme is "http". is "http".
If the request-target is in authority-form, then the effective If the request-target is in authority-form, then the effective
request URI's authority component is the same as the request-target. 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- 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, then the authority component is the same as the Host field-
value. Otherwise, the authority component is the concatenation of value. Otherwise, the authority component is the concatenation of
the default host name configured for the server, a colon (":"), and the default host name configured for the server, a colon (":"), and
the connection's incoming TCP port number in decimal form. the connection's incoming TCP port number in decimal form.
If the request-target is in authority-form or asterisk-form, then the If the request-target is in authority-form or asterisk-form, then the
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Example 1: the following message received over an insecure TCP Example 1: the following message received over an insecure TCP
connection connection
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080 Host: www.example.org:8080
has an effective request URI of has an effective request URI of
http://www.example.org:8080/pub/WWW/TheProject.html http://www.example.org:8080/pub/WWW/TheProject.html
Example 2: the following message received over an SSL/TLS-secured TCP Example 2: the following message received over a TLS-secured TCP
connection connection
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org Host: www.example.org
has an effective request URI of has an effective request URI of
https://www.example.org https://www.example.org
An origin server that does not allow resources to differ by requested 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 host MAY ignore the Host field-value and instead replace it with a
configured server name when constructing the effective request URI. configured server name when constructing the effective request URI.
Recipients of an HTTP/1.0 request that lacks a Host header field MAY 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 attempt to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to guess the something unique to a particular host) in order to guess the
effective request URI's authority component. effective request URI's authority component.
5.6. Intermediary Forwarding 5.6. Message Forwarding
As described in Section 2.4, intermediaries can serve a variety of As described in Section 2.3, intermediaries can serve a variety of
roles in the processing of HTTP requests and responses. Some roles in the processing of HTTP requests and responses. Some
intermediaries are used to improve performance or availability. intermediaries are used to improve performance or availability.
Others are used for access control or to filter content. Since an Others are used for access control or to filter content. Since an
HTTP stream has characteristics similar to a pipe-and-filter HTTP stream has characteristics similar to a pipe-and-filter
architecture, there are no inherent limits to the extent an architecture, there are no inherent limits to the extent an
intermediary can enhance (or interfere) with either direction of the intermediary can enhance (or interfere) with either direction of the
stream. stream.
Intermediaries that forward a message MUST implement the Connection
header field, as specified in Section 6.1, to exclude fields that are
only intended for the incoming connection.
In order to avoid request loops, a proxy that forwards requests to 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 other proxies MUST be able to recognize and exclude all of its own
server names, including any aliases, local variations, or literal IP server names, including any aliases, local variations, or literal IP
addresses. addresses.
If a proxy receives a request-target with a host name that is not a 5.7. Via
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 The "Via" header field MUST be sent by a proxy or gateway in
"query" parts of the received request-target when forwarding it to forwarded messages to indicate the intermediate protocols and
the next inbound server, except as noted above to replace an empty recipients between the user agent and the server on requests, and
path with "/" or "*". 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]). Via is used in HTTP for tracking message
forwards, avoiding request loops, and identifying the protocol
capabilities of all senders along the request/response chain.
Intermediaries that forward a message MUST implement the Connection Via = 1#( received-protocol RWS received-by
header field as specified in Section 6.1. [ RWS comment ] )
received-protocol = [ protocol-name "/" ] protocol-version
received-by = ( uri-host [ ":" port ] ) / pseudonym
pseudonym = token
5.6.1. End-to-end and Hop-by-hop Header Fields 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.
For the purpose of defining the behavior of caches and non-caching The protocol-name is excluded if and only if it would be "HTTP". The
proxies, we divide HTTP header fields into two categories: 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.
o End-to-end header fields, which are transmitted to the ultimate Multiple Via field values represent each proxy or gateway that has
recipient of a request or response. End-to-end header fields in forwarded the message. Each recipient MUST append its information
responses MUST be stored as part of a cache entry and MUST be such that the end result is ordered according to the sequence of
transmitted in any response formed from a cache entry. forwarding applications.
o Hop-by-hop header fields, which are meaningful only for a single Comments MAY be used in the Via header field to identify the software
transport-level connection, and are not stored by caches or of each recipient, analogous to the User-Agent and Server header
forwarded by proxies. fields. However, all comments in the Via field are optional and MAY
be removed by any recipient prior to forwarding the message.
The following HTTP/1.1 header fields are hop-by-hop header fields: 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:
o Connection Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
o Keep-Alive (Section 19.7.1.1 of [RFC2068]) 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.
o Proxy-Authenticate (Section 4.2 of [Part7]) A proxy or gateway MAY combine an ordered subsequence of Via header
field entries into a single such entry if the entries have identical
received-protocol values. For example,
o Proxy-Authorization (Section 4.3 of [Part7]) Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
o TE could be collapsed to
o Trailer Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
o Transfer-Encoding 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.
o Upgrade 5.8. Message Transforming
All other header fields defined by HTTP/1.1 are end-to-end header If a proxy receives a request-target with a host name that is not a
fields. fully qualified domain name, it MAY add its own 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.
Other hop-by-hop header fields MUST be listed in a Connection header A non-transforming proxy MUST NOT modify the "path-absolute" and
field (Section 6.1). "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 "*".
5.6.2. Non-modifiable Header Fields A non-transforming proxy MUST preserve the message payload (Section
3.3 of [Part2]), though it MAY change the message body through
application or removal of a transfer-coding (Section 4).
Some features of HTTP/1.1, such as Digest Authentication, depend on A non-transforming proxy SHOULD NOT modify header fields that provide
the value of certain end-to-end header fields. A non-transforming information about the end points of the communication chain, the
proxy SHOULD NOT modify an end-to-end header field unless the resource state, or the selected representation.
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:
o Allow (Section 9.5 of [Part2]) o Allow (Section 8.4.1 of [Part2])
o Content-Location (Section 9.8 of [Part2]) o Content-Location (Section 3.1.4.2 of [Part2])
o Content-MD5 (Section 14.15 of [RFC2616]) o Content-MD5 (Section 14.15 of [RFC2616])
o ETag (Section 2.3 of [Part4]) o ETag (Section 2.3 of [Part4])
o Last-Modified (Section 2.2 of [Part4]) o Last-Modified (Section 2.2 of [Part4])
o Server (Section 9.17 of [Part2]) o Server (Section 8.4.2 of [Part2])
A non-transforming proxy MUST NOT modify any of the following fields
in a response:
o Expires (Section 7.3 of [Part6])
but it MAY add any of these fields if not already present. If an A non-transforming proxy MUST NOT modify an Expires header field
Expires header field is added, it MUST be given a field value (Section 7.3 of [Part6]) if already present in a response, but it MAY
identical to that of the Date header field in that response. add an Expires header field with a field-value identical to that of
the Date header field.
A proxy MUST NOT modify or add any of the following fields in a A proxy MUST NOT modify or add any of the following fields in a
message that contains the no-transform cache-control directive, or in message that contains the no-transform cache-control directive:
any request:
o Content-Encoding (Section 9.6 of [Part2]) o Content-Encoding (Section 3.1.2.2 of [Part2])
o Content-Range (Section 5.2 of [Part5]) o Content-Range (Section 5.2 of [Part5])
o Content-Type (Section 9.9 of [Part2]) o Content-Type (Section 3.1.1.5 of [Part2])
A transforming proxy MAY modify or add these fields to a message that A transforming proxy MAY modify or add these fields to a message that
does not include no-transform, but if it does so, it MUST add a does not include no-transform, but if it does so, it MUST add a
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 7.6 of [Part6]). in the message (see Section 7.5 of [Part6]).
Warning: Unnecessary modification of end-to-end header fields
might cause authentication failures if stronger authentication
mechanisms are introduced in later versions of HTTP. Such
authentication mechanisms MAY rely on the values of header fields
not listed here.
A non-transforming proxy MUST preserve the message payload ([Part2]), Warning: Unnecessary modification of header fields might cause
though it MAY change the message body through application or removal authentication failures if stronger authentication mechanisms are
of a transfer-coding (Section 4). introduced in later versions of HTTP. Such authentication
mechanisms MAY rely on the values of header fields not listed
here.
5.7. Associating a Response to a Request 5.9. Associating a Response to a Request
HTTP does not include a request identifier for associating a given HTTP does not include a request identifier for associating a given
request message with its corresponding one or more response messages. request message with its corresponding one or more response messages.
Hence, it relies on the order of response arrival to correspond Hence, it relies on the order of response arrival to correspond
exactly to the order in which requests are made on the same exactly to the order in which requests are made on the same
connection. More than one response message per request only occurs connection. More than one response message per request only occurs
when one or more informational responses (1xx, see Section 4.3 of when one or more informational responses (1xx, see Section 7.2 of
[Part2]) precede a final response to the same request. [Part2]) precede a final response to the same request.
A client that uses persistent connections and sends more than one A client that uses persistent connections and sends more than one
request per connection MUST maintain a list of outstanding requests request per connection MUST maintain a list of outstanding requests
in the order sent on that connection and MUST associate each received in the order sent on that connection and MUST associate each received
response message to the highest ordered request that has not yet response message to the highest ordered request that has not yet
received a final (non-1xx) response. received a final (non-1xx) response.
6. Connection Management 6. Connection Management
HTTP messaging is independent of the underlying transport or session-
layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding
in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of an underlying transport
protocol is outside the scope of this specification.
As described in Section 5.2, the specific connection protocols to be
used for an HTTP interaction are determined by client configuration
and the target URI. 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 the client might be configured to use a
proxy via some other connection, port, or protocol.
HTTP implementations are expected to engage in connection management,
which includes maintaining the state of current connections,
establishing a new connection or reusing an existing connection,
processing messages received on a connection, detecting connection
failures, and closing each connection. Most clients maintain
multiple connections in parallel, including more than one connection
per server endpoint. Most servers are designed to maintain thousands
of concurrent connections, while controlling request queues to enable
fair use and detect denial of service attacks.
6.1. Connection 6.1. Connection
The "Connection" header field allows the sender to specify options The "Connection" header field allows the sender to indicate desired
that are desired only for that particular connection. Such control options for the current connection. In order to avoid
connection options MUST be removed or replaced before the message can confusing downstream recipients, a proxy or gateway MUST remove or
be forwarded downstream by a proxy or gateway. This mechanism also replace any received connection options before forwarding the
allows the sender to indicate which HTTP header fields used in the message.
message are only intended for the immediate recipient ("hop-by-hop"),
as opposed to all recipients on the chain ("end-to-end"), enabling When a header field is used to supply control information for or
the message to be self-descriptive and allowing future connection- about the current connection, the sender SHOULD list the
specific extensions to be deployed in HTTP without fear that they corresponding field-name within the "Connection" header field. A
will be blindly forwarded by previously deployed intermediaries. proxy or gateway MUST parse a received Connection header field before
a message is forwarded and, for each connection-option in this field,
remove any header field(s) from the message with the same name as the
connection-option, and then remove the Connection header field itself
(or replace it with the intermediary's own connection options for the
forwarded message).
Hence, the Connection header field provides a declarative way of
distinguishing header fields that are only intended for the immediate
recipient ("hop-by-hop") from those fields that are intended for all
recipients on the chain ("end-to-end"), enabling the message to be
self-descriptive and allowing future connection-specific extensions
to be deployed without fear that they will be blindly forwarded by
older intermediaries.
The Connection header field's value has the following grammar: The Connection header field's value has the following grammar:
Connection = 1#connection-option Connection = 1#connection-option
connection-option = token connection-option = token
Connection options are compared case-insensitively. Connection options are case-insensitive.
A proxy or gateway MUST parse a received Connection header field
before a message is forwarded and, for each connection-option in this
field, remove any header field(s) from the message with the same name
as the connection-option, 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- A sender MUST NOT include field-names in the Connection header field-
value for fields that are defined as expressing constraints for all value for fields that are defined as expressing constraints for all
recipients in the request or response chain, such as the Cache- recipients in the request or response chain, such as the Cache-
Control header field (Section 7.2 of [Part6]). Control header field (Section 7.2 of [Part6]).
The connection options do not have to correspond to a header field The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection connection option. Recipients that trigger certain connection
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When defining new connection options, specifications ought to When defining new connection options, specifications ought to
carefully consider existing deployed header fields and ensure that carefully consider existing deployed header fields and ensure that
the new connection option does not share the same name as an the new connection option does not share the same name as an
unrelated header field that might already be deployed. Defining a unrelated header field that might already be deployed. Defining a
new connection option essentially reserves that potential field-name new connection option essentially reserves that potential field-name
for carrying additional information related to the connection option, for carrying additional information related to the connection option,
since it would be unwise for senders to use that field-name for since it would be unwise for senders to use that field-name for
anything else. anything else.
HTTP/1.1 defines the "close" connection option for the sender to The "close" connection option is defined for a sender to signal that
signal that the connection will be closed after completion of the this connection will be closed after completion of the response. For
response. For example, example,
Connection: close Connection: close
in either the request or the response header fields indicates that in either the request or the response header fields indicates that
the connection SHOULD NOT be considered "persistent" (Section 6.3) the connection SHOULD be closed after the current request/response is
after the current request/response is complete. complete (Section 6.2.5).
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 A client that does not support persistent connections MUST send the
the same organizational control and the hosts have already been "close" connection option in every request message.
replaced by pseudonyms. Senders MUST NOT combine entries which have
different received-protocol values.
6.3. Persistent Connections A server that does not support persistent connections MUST send the
"close" connection option in every response message that does not
have a 1xx (Informational) status code.
6.3.1. Purpose 6.2. Persistent Connections
Prior to persistent connections, a separate TCP connection was HTTP was originally designed to use a separate connection for each
established for each request, increasing the load on HTTP servers and request/response pair. As the Web evolved and embedded requests
causing congestion on the Internet. The use of inline images and became common for inline images, the connection establishment
other associated data often requires a client to make multiple overhead was a significant drain on performance and a concern for
requests of the same server in a short amount of time. Analysis of Internet congestion. Message framing (via Content-Length) and
these performance problems and results from a prototype optional long-lived connections (via Keep-Alive) were added to
implementation are available [Pad1995] [Spe]. Implementation HTTP/1.0 in order to improve performance for some requests. However,
experience and measurements of actual HTTP/1.1 implementations show these extensions were insufficient for dynamically generated
good results [Nie1997]. Alternatives have also been explored, for responses and difficult to use with intermediaries.
example, T/TCP [Tou1998].
Persistent HTTP connections have a number of advantages: HTTP/1.1 defaults to the use of "persistent connections", which allow
multiple requests and responses to be carried over a single
connection. The "close" connection-option is used to signal that a
connection will close after the current request/response. Persistent
connections have a number of advantages:
o By opening and closing fewer TCP connections, CPU time is saved in o By opening and closing fewer connections, CPU time is saved in
routers and hosts (clients, servers, proxies, gateways, tunnels, routers and hosts (clients, servers, proxies, gateways, tunnels,
or caches), and memory used for TCP protocol control blocks can be or caches), and memory used for protocol control blocks can be
saved in hosts. saved in hosts.
o HTTP requests and responses can be pipelined on a connection. o Most requests and responses can be pipelined on a connection.
Pipelining allows a client to make multiple requests without Pipelining allows a client to make multiple requests without
waiting for each response, allowing a single TCP connection to be waiting for each response, allowing a single connection to be used
used much more efficiently, with much lower elapsed time. much more efficiently and with less overall latency.
o Network congestion is reduced by reducing the number of packets o For TCP connections, network congestion is reduced by eliminating
caused by TCP opens, and by allowing TCP sufficient time to the packets associated with the three way handshake and graceful
determine the congestion state of the network. close procedures, and by allowing sufficient time to determine the
congestion state of the network.
o Latency on subsequent requests is reduced since there is no time o Latency on subsequent requests is reduced since there is no time
spent in TCP's connection opening handshake. spent in the connection opening handshake.
o HTTP can evolve more gracefully, since errors can be reported o HTTP can evolve more gracefully, since most errors can be reported
without the penalty of closing the TCP connection. Clients using without the penalty of closing the connection. Clients using
future versions of HTTP might optimistically try a new feature, future versions of HTTP might optimistically try a new feature,
but if communicating with an older server, retry with old but if communicating with an older server, retry with old
semantics after an error is reported. semantics after an error is reported.
HTTP implementations SHOULD implement persistent connections. HTTP implementations SHOULD implement persistent connections.
6.3.2. Overall Operation 6.2.1. Establishment
A significant difference between HTTP/1.1 and earlier versions of It is beyond the scope of this specification to describe how
HTTP is that persistent connections are the default behavior of any connections are established via various transport or session-layer
HTTP connection. That is, unless otherwise indicated, the client protocols. Each connection applies to only one transport link.
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 A recipient determines whether a connection is persistent or not
server can signal the close of a TCP connection. This signaling based on the most recently received message's protocol version and
takes place using the Connection header field (Section 6.1). Once a Connection header field (if any):
close has been signaled, the client MUST NOT send any more requests
on that connection.
6.3.2.1. Negotiation o If the close connection option is present, the connection will not
persist after the current response; else,
An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to o If the received protocol is HTTP/1.1 (or later), the connection
maintain a persistent connection unless a Connection header field will persist after the current response; else,
including the connection option "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 option "close".
An HTTP/1.1 client MAY expect a connection to remain open, but would o If the received protocol is HTTP/1.0, the "keep-alive" connection
decide to keep it open based on whether the response from a server option is present, the recipient is not a proxy, and the recipient
contains a Connection header field with the connection option wishes to honor the HTTP/1.0 "keep-alive" mechanism, the
"close". In case the client does not want to maintain a connection connection will persist after the current response; otherwise,
for more than that request, it SHOULD send a Connection header field
including the connection option "close".
If either the client or the server sends the "close" option in the o The connection will close after the current response.
Connection header field, that request becomes the last one for the
connection. A proxy server MUST NOT maintain a persistent connection with an
HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
discussion of the problems with the Keep-Alive header field
implemented by many HTTP/1.0 clients).
6.2.2. Reuse
In order to remain persistent, all messages on a connection MUST have
a self-defined message length (i.e., one not defined by closure of
the connection), as described in Section 3.3.
A server MAY assume that an HTTP/1.1 client intends to maintain a
persistent connection until a close connection option is received in
a request.
A client MAY reuse a persistent connection until it sends or receives
a close connection option or receives an HTTP/1.0 response without a
"keep-alive" connection option.
Clients and servers SHOULD NOT assume that a persistent connection is Clients and servers SHOULD NOT assume that a persistent connection is
maintained for HTTP versions less than 1.1 unless it is explicitly maintained for HTTP versions less than 1.1 unless it is explicitly
signaled. See Appendix A.1.2 for more information on backward signaled. See Appendix A.1.2 for more information on backward
compatibility with HTTP/1.0 clients. compatibility with HTTP/1.0 clients.
Each persistent connection applies to only one transport link. 6.2.2.1. Pipelining
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 A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each requests (i.e., send multiple requests without waiting for each
response). A server MUST send its responses to those requests in the response). A server MUST send its responses to those requests in the
same order that the requests were received. same order that the requests were received.
Clients which assume persistent connections and pipeline immediately Clients which assume persistent connections and pipeline immediately
after connection establishment SHOULD be prepared to retry their after connection establishment SHOULD be prepared to retry their
connection if the first pipelined attempt fails. If a client does connection if the first pipelined attempt fails. If a client does
such a retry, it MUST NOT pipeline before it knows the connection is such a retry, it MUST NOT pipeline before it knows the connection is
persistent. Clients MUST also be prepared to resend their requests persistent. Clients MUST also be prepared to resend their requests
if the server closes the connection before sending all of the if the server closes the connection before sending all of the
corresponding responses. corresponding responses.
Clients SHOULD NOT pipeline requests using non-idempotent request Clients SHOULD NOT pipeline requests using non-idempotent request
methods or non-idempotent sequences of request methods (see Section methods or non-idempotent sequences of request methods (see Section
2.1.2 of [Part2]). Otherwise, a premature termination of the 5.2.2 of [Part2]). Otherwise, a premature termination of the
transport connection could lead to indeterminate results. A client transport connection could lead to indeterminate results. A client
wishing to send a non-idempotent request SHOULD wait to send that wishing to send a non-idempotent request SHOULD wait to send that
request until it has received the response status line for the request until it has received the response status line for the
previous request. previous request.
6.3.3. Practical Considerations 6.2.2.2. Retrying Requests
Servers will usually have some time-out value beyond which they will
no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making
more connections through the same server. The use of persistent
connections places no requirements on the length (or existence) of
this time-out for either the client or the server.
When a client or server wishes to time-out it SHOULD issue a graceful
close on the transport connection. Clients and servers SHOULD both
constantly watch for the other side of the transport close, and
respond to it as appropriate. If a client or server does not detect
the other side's close promptly it could cause unnecessary resource
drain on the network.
A client, server, or proxy MAY close the transport connection at any
time. For example, a client might have started to send a new request
at the same time that the server has decided to close the "idle"
connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a
request is in progress.
Clients (including proxies) SHOULD limit the number of simultaneous
connections that they maintain to a given server (including proxies).
Previous revisions of HTTP gave a specific number of connections as a
ceiling, but this was found to be impractical for many applications.
As a result, this specification does not mandate a particular maximum
number of connections, but instead encourages clients to be
conservative when opening multiple connections.
In particular, while using multiple connections avoids the "head-of-
line blocking" problem (whereby a request that takes significant
server-side processing and/or has a large payload can block
subsequent requests on the same connection), each connection used
consumes server resources (sometimes significantly), and furthermore
using multiple connections can cause undesirable side effects in
congested networks.
Note that servers might reject traffic that they deem abusive,
including an excessive number of connections from a client.
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 2.1.2 of [Part2]). Non-idempotent request methods or Section 5.2.2 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.
6.4. Message Transmission Requirements 6.2.3. Concurrency
6.4.1. Persistent Connections and Flow Control
HTTP/1.1 servers SHOULD maintain persistent connections and use TCP's
flow control mechanisms to resolve temporary overloads, rather than
terminating connections with the expectation that clients will retry.
The latter technique can exacerbate network congestion.
6.4.2. Monitoring Connections for Error Status Messages
An HTTP/1.1 (or later) client sending a message body SHOULD monitor
the network connection for an error status code while it is
transmitting the request. If the client sees an error status code,
it SHOULD immediately cease transmitting the body. If the body is
being sent using a "chunked" encoding (Section 4), a zero length
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
field, the client MUST close the connection.
6.4.3. Use of the 100 (Continue) Status Clients SHOULD limit the number of simultaneous connections that they
maintain to a given server.
The purpose of the 100 (Continue) status code (see Section 4.3.1 of Previous revisions of HTTP gave a specific number of connections as a
[Part2]) is to allow a client that is sending a request message with ceiling, but this was found to be impractical for many applications.
a request body to determine if the origin server is willing to accept As a result, this specification does not mandate a particular maximum
the request (based on the request header fields) before the client number of connections, but instead encourages clients to be
sends the request body. In some cases, it might either be conservative when opening multiple connections.
inappropriate or highly inefficient for the client to send the body
if the server will reject the message without looking at the body.
Requirements for HTTP/1.1 clients: Multiple connections are typically used to avoid the "head-of-line
blocking" problem, wherein a request that takes significant server-
side processing and/or has a large payload blocks subsequent requests
on the same connection. However, each connection consumes server
resources. Furthermore, using multiple connections can cause
undesirable side effects in congested networks.
o If a client will wait for a 100 (Continue) response before sending Note that servers might reject traffic that they deem abusive,
the request body, it MUST send an Expect header field (Section including an excessive number of connections from a client.
9.11 of [Part2]) with the "100-continue" expectation.
o A client MUST NOT send an Expect header field with the "100- 6.2.4. Failures and Time-outs
continue" expectation if it does not intend to send a request
body.
Because of the presence of older implementations, the protocol allows Servers will usually have some time-out value beyond which they will
ambiguous situations in which a client might send "Expect: 100- no longer maintain an inactive connection. Proxy servers might make
continue" without receiving either a 417 (Expectation Failed) or a this a higher value since it is likely that the client will be making
100 (Continue) status code. Therefore, when a client sends this more connections through the same server. The use of persistent
header field to an origin server (possibly via a proxy) from which it connections places no requirements on the length (or existence) of
has never seen a 100 (Continue) status code, the client SHOULD NOT this time-out for either the client or the server.
wait for an indefinite period before sending the request body.
Requirements for HTTP/1.1 origin servers: When a client or server wishes to time-out it SHOULD issue a graceful
close on the transport connection. Clients and servers SHOULD both
constantly watch for the other side of the transport close, and
respond to it as appropriate. If a client or server does not detect
the other side's close promptly it could cause unnecessary resource
drain on the network.
o Upon receiving a request which includes an Expect header field A client, server, or proxy MAY close the transport connection at any
with the "100-continue" expectation, an origin server MUST either time. For example, a client might have started to send a new request
respond with 100 (Continue) status code and continue to read from at the same time that the server has decided to close the "idle"
the input stream, or respond with a final status code. The origin connection. From the server's point of view, the connection is being
server MUST NOT wait for the request body before sending the 100 closed while it was idle, but from the client's point of view, a
(Continue) response. If it responds with a final status code, it request is in progress.
MAY close the transport connection or it MAY continue to read and
discard the rest of the request. It MUST NOT perform the request
method if it returns a final status code.
o An origin server SHOULD NOT send a 100 (Continue) response if the Servers SHOULD maintain persistent connections and allow the
request message does not include an Expect header field with the underlying transport's flow control mechanisms to resolve temporary
"100-continue" expectation, and MUST NOT send a 100 (Continue) overloads, rather than terminate connections with the expectation
response if such a request comes from an HTTP/1.0 (or earlier) that clients will retry. The latter technique can exacerbate network
client. There is an exception to this rule: for compatibility congestion.
with [RFC2068], a server MAY send a 100 (Continue) status code in
response to an HTTP/1.1 PUT or POST request that does not include
an Expect header field with the "100-continue" expectation. This
exception, the purpose of which is to minimize any client
processing delays associated with an undeclared wait for 100
(Continue) status code, applies only to HTTP/1.1 requests, and not
to requests with any other HTTP-version value.
o An origin server MAY omit a 100 (Continue) response if it has A client sending a message body SHOULD monitor the network connection
already received some or all of the request body for the for an error status code while it is transmitting the request. If
corresponding request. the client sees an error status code, it SHOULD immediately cease
transmitting the body and close the connection.
o An origin server that sends a 100 (Continue) response MUST 6.2.5. Tear-down
ultimately send a final status code, once the request body is
received and processed, unless it terminates the transport
connection prematurely.
o If an origin server receives a request that does not include an The Connection header field (Section 6.1) provides a "close"
Expect header field with the "100-continue" expectation, the connection option that a sender SHOULD send when it wishes to close
request includes a request body, and the server responds with a the connection after the current request/response pair.
final status code before reading the entire request body from the
transport connection, then the server SHOULD NOT close the
transport connection until it has read the entire request, or
until the client closes the connection. Otherwise, the client
might not reliably receive the response message. However, this
requirement ought not be construed as preventing a server from
defending itself against denial-of-service attacks, or from badly
broken client implementations.
Requirements for HTTP/1.1 proxies: A client that sends a close connection option MUST NOT send further
requests on that connection (after the one containing close) and MUST
close the connection after reading the final response message
corresponding to this request.
o If a proxy receives a request that includes an Expect header field A server that receives a close connection option MUST initiate a
with the "100-continue" expectation, and the proxy either knows lingering close of the connection after it sends the final response
that the next-hop server complies with HTTP/1.1 or higher, or does to the request that contained close. The server SHOULD include a
not know the HTTP version of the next-hop server, it MUST forward close connection option in its final response on that connection.
the request, including the Expect header field. The server MUST NOT process any further requests received on that
connection.
o If the proxy knows that the version of the next-hop server is A server that sends a close connection option MUST initiate a
HTTP/1.0 or lower, it MUST NOT forward the request, and it MUST lingering close of the connection after it sends the response
respond with a 417 (Expectation Failed) status code. containing close. The server MUST NOT process any further requests
received on that connection.
o Proxies SHOULD maintain a record of the HTTP version numbers A client that receives a close connection option MUST cease sending
received from recently-referenced next-hop servers. requests on that connection and close the connection after reading
the response message containing the close; if additional pipelined
requests had been sent on the connection, the client SHOULD assume
that they will not be processed by the server.
o A proxy MUST NOT forward a 100 (Continue) response if the request If a server performs an immediate close of a TCP connection, there is
message was received from an HTTP/1.0 (or earlier) client and did a significant risk that the client will not be able to read the last
not include an Expect header field with the "100-continue" HTTP response. If the server receives additional data from the
expectation. This requirement overrides the general rule for client on a fully-closed connection, such as another request that was
forwarding of 1xx responses (see Section 4.3 of [Part2]). sent by the client before receiving the server's response, the
server's TCP stack will send a reset packet to the client;
unfortunately, the reset packet might erase the client's
unacknowledged input buffers before they can be read and interpreted
by the client's HTTP parser.
6.4.4. Closing Connections on Error To avoid the TCP reset problem, a server can perform a lingering
close on a connection by closing only the write side of the read/
write connection (a half-close) and continuing to read from the
connection until the connection is closed by the client or the server
is reasonably certain that its own TCP stack has received the
client's acknowledgement of the packet(s) containing the server's
last response. It is then safe for the server to fully close the
connection.
If the client is sending data, a server implementation using TCP It is unknown whether the reset problem is exclusive to TCP or might
SHOULD be careful to ensure that the client acknowledges receipt of also be found in other transport connection protocols.
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.
6.5. Upgrade 6.3. Upgrade
The "Upgrade" header field allows the client to specify what The "Upgrade" header field is intended to provide a simple mechanism
additional communication protocols it would like to use, if the for transitioning from HTTP/1.1 to some other protocol on the same
server chooses to switch protocols. Servers can use it to indicate connection. A client MAY send a list of protocols in the Upgrade
what protocols they are willing to switch to. header field of a request to invite the server to switch to one or
more of those protocols before sending the final response. A server
MUST send an Upgrade header field in 101 (Switching Protocols)
responses to indicate which protocol(s) are being switched to, and
MUST send it in 426 (Upgrade Required) responses to indicate
acceptable protocols. A server MAY send an Upgrade header field in
any other response to indicate that they might be willing to upgrade
to one of the specified protocols for a future request.
Upgrade = 1#protocol Upgrade = 1#protocol
protocol = protocol-name ["/" protocol-version] protocol = protocol-name ["/" protocol-version]
protocol-name = token protocol-name = token
protocol-version = token protocol-version = token
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 Upgrade eases the difficult transition between incompatible protocols
for transitioning from HTTP/1.1 to some other, incompatible protocol. by allowing the client to initiate a request in the more commonly
It does so by allowing the client to advertise its desire to use supported protocol while indicating to the server that it would like
another protocol, such as a later version of HTTP with a higher major to use a "better" protocol if available (where "better" is determined
version number, even though the current request has been made using by the server, possibly according to the nature of the request method
HTTP/1.1. This eases the difficult transition between incompatible or target resource).
protocols by allowing the client to initiate a request in the more
commonly supported protocol while indicating to the server that it
would like to use a "better" protocol if available (where "better" is
determined by the server, possibly according to the nature of the
request method or target resource).
The Upgrade header field only applies to switching application-layer Upgrade cannot be used to insist on a protocol change; its acceptance
protocols upon the existing transport-layer connection. Upgrade and use by the server is optional. The capabilities and nature of
cannot be used to insist on a protocol change; its acceptance and use the application-level communication after the protocol change is
by the server is optional. The capabilities and nature of the entirely dependent upon the new protocol chosen, although the first
application-layer communication after the protocol change is entirely action after changing the protocol MUST be a response to the initial
dependent upon the new protocol chosen, although the first action HTTP request that contained the Upgrade header field.
after changing the protocol MUST be a response to the initial HTTP
request containing the Upgrade header field.
The Upgrade header field only applies to the immediate connection. For example, if the Upgrade header field is received in a GET request
Therefore, the upgrade keyword MUST be supplied within a Connection and the server decides to switch protocols, then it MUST first
header field (Section 6.1) whenever Upgrade is present in an HTTP/1.1 respond with a 101 (Switching Protocols) message in HTTP/1.1 and then
message. immediately follow that with the new protocol's equivalent of a
response to a GET on the target resource. This allows a connection
to be upgraded to protocols with the same semantics as HTTP without
the latency cost of an additional round-trip. A server MUST NOT
switch protocols unless the received message semantics can be honored
by the new protocol; an OPTIONS request can be honored by any
protocol.
The Upgrade header field cannot be used to indicate a switch to a When Upgrade is sent, a sender MUST also send a Connection header
protocol on a different connection. For that purpose, it is more field (Section 6.1) that contains the "upgrade" connection option, in
appropriate to use a 3xx (Redirection) response (Section 4.5 of order to prevent Upgrade from being accidentally forwarded by
[Part2]). intermediaries that might not implement the listed protocols. A
server MUST ignore an Upgrade header field that is received in an
HTTP/1.0 request.
Servers MUST include the "Upgrade" header field in 101 (Switching The Upgrade header field only applies to switching application-level
Protocols) responses to indicate which protocol(s) are being switched protocols on the existing connection; it cannot be used to switch to
to, and MUST include it in 426 (Upgrade Required) responses to a protocol on a different connection. For that purpose, it is more
indicate acceptable protocols to upgrade to. Servers MAY include it appropriate to use a 3xx (Redirection) response (Section 7.4 of
in any other response to indicate that they are willing to upgrade to [Part2]).
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 2.7 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 in Section 7.6. the registration procedure defined in Section 7.6.
7. IANA Considerations 7. IANA Considerations
7.1. Header Field Registration 7.1. Header Field Registration
HTTP header fields are registered within the Message Header Field HTTP header fields are registered within the Message Header Field
Registry [RFC3864] maintained by IANA at <http://www.iana.org/ Registry [RFC3864] maintained by IANA at <http://www.iana.org/
assignments/message-headers/message-header-index.html>. assignments/message-headers/message-header-index.html>.
skipping to change at page 58, line 30 skipping to change at page 55, line 14
associated registry entries shall be updated according to the associated registry entries shall be updated according to the
permanent registrations below: permanent registrations below:
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
| Connection | http | standard | Section 6.1 | | Connection | http | standard | Section 6.1 |
| Content-Length | http | standard | Section 3.3.2 | | Content-Length | http | standard | Section 3.3.2 |
| Host | http | standard | Section 5.4 | | Host | http | standard | Section 5.4 |
| TE | http | standard | Section 4.3 | | TE | http | standard | Section 4.3 |
| Trailer | http | standard | Section 4.4 | | Trailer | http | standard | Section 4.1.1 |
| Transfer-Encoding | http | standard | Section 3.3.1 | | Transfer-Encoding | http | standard | Section 3.3.1 |
| Upgrade | http | standard | Section 6.5 | | Upgrade | http | standard | Section 6.3 |
| Via | http | standard | Section 6.2 | | Via | http | standard | Section 5.7 |
+-------------------+----------+----------+---------------+ +-------------------+----------+----------+---------------+
Furthermore, the header field-name "Close" shall be registered as Furthermore, the header field-name "Close" shall be registered as
"reserved", since using that name as an HTTP header field might "reserved", since using that name as an HTTP header field might
conflict with the "close" connection option of the "Connection" conflict with the "close" connection option of the "Connection"
header field (Section 6.1). header field (Section 6.1).
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
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IANA maintains the registry of URI Schemes [RFC4395] at IANA maintains the registry of URI Schemes [RFC4395] at
<http://www.iana.org/assignments/uri-schemes.html>. <http://www.iana.org/assignments/uri-schemes.html>.
This document defines the following URI schemes, so their associated This document defines the following URI schemes, so their associated
registry entries shall be updated according to the permanent registry entries shall be updated according to the permanent
registrations below: registrations below:
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
| URI Scheme | Description | Reference | | URI Scheme | Description | Reference |
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
| http | Hypertext Transfer Protocol | Section 2.8.1 | | http | Hypertext Transfer Protocol | Section 2.7.1 |
| https | Hypertext Transfer Protocol Secure | Section 2.8.2 | | https | Hypertext Transfer Protocol Secure | Section 2.7.2 |
+------------+------------------------------------+---------------+ +------------+------------------------------------+---------------+
7.3. Internet Media Type Registrations 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]).
7.3.1. Internet Media Type message/http 7.3.1. Internet Media Type message/http
skipping to change at page 61, line 52 skipping to change at page 58, line 34
Registrations MUST include the following fields: Registrations MUST include the following fields:
o Name o Name
o Description o Description
o Pointer to specification text o Pointer to specification text
Names of transfer codings MUST NOT overlap with names of content Names of transfer codings MUST NOT overlap with names of content
codings (Section 5.4 of [Part2]) unless the encoding transformation codings (Section 3.1.2.1 of [Part2]) unless the encoding
is identical, as it is the case for the compression codings defined transformation is identical, as is the case for the compression
in Section 4.2. codings defined in Section 4.2.
Values to be added to this name space require IETF Review (see Values to be added to this name space require IETF Review (see
Section 4.1 of [RFC5226]), and MUST conform to the purpose of Section 4.1 of [RFC5226]), and MUST conform to the purpose of
transfer coding defined in this section. transfer coding defined in this section. Use of program names for
the identification of encoding formats is not desirable and is
discouraged for future encodings.
The registry itself is maintained at The registry itself is maintained at
<http://www.iana.org/assignments/http-parameters>. <http://www.iana.org/assignments/http-parameters>.
7.5. Transfer Coding Registrations 7.5. Transfer Coding Registrations
The HTTP Transfer Coding Registry shall be updated with the The HTTP Transfer Coding Registry shall be updated with the
registrations below: registrations below:
+----------+----------------------------------------+---------------+ +----------+----------------------------------------+---------------+
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7.7. Upgrade Token Registration 7.7. Upgrade Token Registration
The HTTP Upgrade Token Registry shall be updated with the The HTTP Upgrade Token Registry shall be updated with the
registration below: registration below:
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
| Value | Description | Expected Version | Reference | | Value | Description | Expected Version | Reference |
| | | Tokens | | | | | Tokens | |
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
| HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.7 | | HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.6 |
| | Protocol | (e.g, "2.0") | | | | Protocol | (e.g, "2.0") | |
+-------+----------------------+----------------------+-------------+ +-------+----------------------+----------------------+-------------+
The responsible party is: "IETF (iesg@ietf.org) - Internet The responsible party is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
8. Security Considerations 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.
8.1. 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
(e.g., the user's name, location, mail address, passwords, encryption information, including both information provided by the user to
keys, etc.), and SHOULD be very careful to prevent unintentional interact with resources (e.g., the user's name, location, mail
leakage of this information. We very strongly recommend that a address, passwords, encryption keys, etc.) and information about the
convenient interface be provided for the user to control user's browsing activity over time (e.g., history, bookmarks, etc.).
dissemination of such information, and that designers and HTTP implementations need to prevent unintentional leakage of this
implementers be particularly careful in this area. History shows information.
that errors in this area often create serious security and/or privacy
problems and generate highly adverse publicity for the implementer's
company.
8.2. 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. In particular, log information gathered at an intermediary interest. In particular, log information gathered at an intermediary
often contains a history of user agent interaction, across a often contains a history of user agent interaction, across a
multitude of sites, that can be traced to individual users. multitude of sites, that can be traced to individual users.
HTTP log information is confidential in nature; its handling is often HTTP log information is confidential in nature; its handling is often
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client should not be published even if the key is pseudonymous. client should not be published even if the key is pseudonymous.
To minimize the risk of theft or accidental publication, log To minimize the risk of theft or accidental publication, log
information should be purged of personally identifiable information, information should be purged of personally identifiable information,
including user identifiers, IP addresses, and user-provided query including user identifiers, IP addresses, and user-provided query
parameters, as soon as that information is no longer necessary to parameters, as soon as that information is no longer necessary to
support operational needs for security, auditing, or fraud control. support operational needs for security, auditing, or fraud control.
8.3. Attacks Based On File and Path Names 8.3. Attacks Based On File and Path Names
Implementations of HTTP origin servers SHOULD be careful to restrict Origin servers SHOULD be careful to restrict the documents returned
the documents returned by HTTP requests to be only those that were by HTTP requests to be only those that were intended by the server
intended by the server administrators. If an HTTP server translates administrators. If an HTTP server translates HTTP URIs directly into
HTTP URIs directly into file system calls, the server MUST take file system calls, the server MUST take special care not to serve
special care not to serve files that were not intended to be files that were not intended to be delivered to HTTP clients. For
delivered to HTTP clients. For example, UNIX, Microsoft Windows, and example, UNIX, Microsoft Windows, and other operating systems use
other operating systems use ".." as a path component to indicate a ".." as a path component to indicate a directory level above the
directory level above the current one. On such a system, an HTTP current one. On such a system, an HTTP server MUST disallow any such
server MUST disallow any such construct in the request-target if it construct in the request-target if it would otherwise allow access to
would otherwise allow access to a resource outside those intended to a resource outside those intended to be accessible via the HTTP
be accessible via the HTTP server. Similarly, files intended for server. Similarly, files intended for reference only internally to
reference only internally to the server (such as access control the server (such as access control files, configuration files, and
files, configuration files, and script code) MUST be protected from script code) MUST be protected from inappropriate retrieval, since
inappropriate retrieval, since they might contain sensitive they might contain sensitive information.
information. Experience has shown that minor bugs in such HTTP
server implementations have turned into security risks.
8.4. 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]).
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to cache poisoning attacks. to cache poisoning attacks.
Implementers need to consider the privacy and security implications Implementers need to consider the privacy and security implications
of their design and coding decisions, and of the configuration of their design and coding decisions, and of the configuration
options they provide to operators (especially the default options they provide to operators (especially the default
configuration). configuration).
Users need to be aware that intermediaries are no more trustworthy Users need to be aware that intermediaries are no more trustworthy
than the people who run them; HTTP itself cannot solve this problem. than the people who run them; HTTP itself cannot solve this problem.
The judicious use of cryptography, when appropriate, might suffice to
protect against a broad range of security and privacy attacks. Such
cryptography is beyond the scope of the HTTP/1.1 specification.
8.6. 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 minimum size limits on request-line recommendations for minimum size limits on request-line
(Section 3.1.1) and blocks of header fields (Section 3.2). These are (Section 3.1.1) and blocks of header fields (Section 3.2). These are
minimum recommendations, chosen to be supportable even by minimum recommendations, chosen to be supportable even by
implementations with limited resources; it is expected that most implementations with limited resources; it is expected that most
implementations will 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 4.6.12 of that have request-targets that are too long (Section 7.5.12 of
[Part2]) or request entities that are too large (Section 4.6 of [Part2]) or request entities that are too large (Section 7.5 of
[Part2]). [Part2]).
Other fields (including but not limited to request methods, response Recipients SHOULD carefully limit the extent to which they read other
status phrases, header field-names, and body chunks) SHOULD be fields, including (but not limited to) request methods, response
limited by implementations carefully, so as to not impede status phrases, header field-names, and body chunks, so as to avoid
interoperability. denial of service attacks without impeding interoperability.
9. Acknowledgments 9. Acknowledgments
This edition of HTTP builds on the many contributions that went into This edition of HTTP builds on the many contributions that went into
RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including substantial RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including substantial
contributions made by the previous authors, editors, and working contributions made by the previous authors, editors, and working
group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding, Henrik group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding, Henrik
Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter, Paul Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter, Paul
J. Leach, and Mark Nottingham. See Section 16 of [RFC2616] for J. Leach, and Mark Nottingham. See Section 16 of [RFC2616] for
additional acknowledgements from prior revisions. additional acknowledgements from prior revisions.
Since 1999, the following contributors have helped improve the HTTP Since 1999, the following contributors have helped improve the HTTP
specification by reporting bugs, asking smart questions, drafting or specification by reporting bugs, asking smart questions, drafting or
reviewing text, and evaluating open issues: reviewing text, and evaluating open issues:
Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrien W. de Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrien W. de
Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alek Storm, Alex Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alek Storm, Alex
Rousskov, Alexandre Morgaut, Alexey Melnikov, Alisha Smith, Amichai Rousskov, Alexandre Morgaut, Alexey Melnikov, Alisha Smith, Amichai
Rothman, Amit Klein, Amos Jeffries, Andreas Maier, Andreas Petersson, Rothman, Amit Klein, Amos Jeffries, Andreas Maier, Andreas Petersson,
Anne van Kesteren, Anthony Bryan, Asbjorn Ulsberg, Balachander Anil Sharma, Anne van Kesteren, Anthony Bryan, Asbjorn Ulsberg,
Krishnamurthy, Barry Leiba, Ben Laurie, Benjamin Niven-Jenkins, Bil Balachander Krishnamurthy, Barry Leiba, Ben Laurie, Benjamin Niven-
Corry, Bill Burke, Bjoern Hoehrmann, Bob Scheifler, Boris Zbarsky, Jenkins, Bil Corry, Bill Burke, Bjoern Hoehrmann, Bob Scheifler,
Brett Slatkin, Brian Kell, Brian McBarron, Brian Pane, Brian Smith, Boris Zbarsky, Brett Slatkin, Brian Kell, Brian McBarron, Brian Pane,
Bryce Nesbitt, Cameron Heavon-Jones, Carl Kugler, Carsten Bormann, Brian Smith, Bryce Nesbitt, Cameron Heavon-Jones, Carl Kugler,
Charles Fry, Chris Newman, Cyrus Daboo, Dale Robert Anderson, Dan Carsten Bormann, Charles Fry, Chris Newman, Cyrus Daboo, Dale Robert
Winship, Daniel Stenberg, Dave Cridland, Dave Crocker, Dave Kristol, Anderson, Dan Wing, Dan Winship, Daniel Stenberg, Dave Cridland, Dave
David Booth, David Singer, David W. Morris, Diwakar Shetty, Dmitry Crocker, Dave Kristol, David Booth, David Singer, David W. Morris,
Kurochkin, Drummond Reed, Duane Wessels, Edward Lee, Eliot Lear, Eran Diwakar Shetty, Dmitry Kurochkin, Drummond Reed, Duane Wessels,
Hammer-Lahav, Eric D. Williams, Eric J. Bowman, Eric Lawrence, Eric Edward Lee, Eliot Lear, Eran Hammer-Lahav, Eric D. Williams, Eric J.
Rescorla, Erik Aronesty, Florian Weimer, Frank Ellermann, Fred Bohle, Bowman, Eric Lawrence, Eric Rescorla, Erik Aronesty, Evan Prodromou,
Geoffrey Sneddon, Gervase Markham, Greg Wilkins, Harald Tveit Florian Weimer, Frank Ellermann, Fred Bohle, Gabriel Montenegro,
Alvestrand, Harry Halpin, Helge Hess, Henrik Nordstrom, Henry S. Geoffrey Sneddon, Gervase Markham, Grahame Grieve, Greg Wilkins,
Thompson, Henry Story, Herbert van de Sompel, Howard Melman, Hugo Harald Tveit Alvestrand, Harry Halpin, Helge Hess, Henrik Nordstrom,
Haas, Ian Hickson, Ingo Struck, J. Ross Nicoll, James H. Manger, Henry S. Thompson, Henry Story, Herbert van de Sompel, Howard Melman,
James Lacey, James M. Snell, Jamie Lokier, Jan Algermissen, Jeff Hugo Haas, Ian Fette, Ian Hickson, Ido Safruti, Ingo Struck, J. Ross
Hodges (who came up with the term 'effective Request-URI'), Jeff Nicoll, James H. Manger, James Lacey, James M. Snell, Jamie Lokier,
Walden, Jim Luther, Joe D. Williams, Joe Gregorio, Joe Orton, John C. Jan Algermissen, Jeff Hodges (who came up with the term 'effective
Klensin, John C. Mallery, John Cowan, John Kemp, John Panzer, John Request-URI'), Jeff Walden, Jim Luther, Joe D. Williams, Joe
Schneider, John Stracke, John Sullivan, Jonas Sicking, Jonathan Gregorio, Joe Orton, John C. Klensin, John C. Mallery, John Cowan,
Billington, Jonathan Moore, Jonathan Rees, Jonathan Silvera, Jordi John Kemp, John Panzer, John Schneider, John Stracke, John Sullivan,
Ros, Joris Dobbelsteen, Josh Cohen, Julien Pierre, Jungshik Shin, Jonas Sicking, Jonathan Billington, Jonathan Moore, Jonathan Rees,
Justin Chapweske, Justin Erenkrantz, Justin James, Kalvinder Singh, Jonathan Silvera, Jordi Ros, Joris Dobbelsteen, Josh Cohen, Julien
Karl Dubost, Keith Hoffman, Keith Moore, Koen Holtman, Konstantin Pierre, Jungshik Shin, Justin Chapweske, Justin Erenkrantz, Justin
Voronkov, Kris Zyp, Lisa Dusseault, Maciej Stachowiak, Marc James, Kalvinder Singh, Karl Dubost, Keith Hoffman, Keith Moore, Koen
Schneider, Marc Slemko, Mark Baker, Mark Pauley, Mark Watson, Markus Holtman, Konstantin Voronkov, Kris Zyp, Lisa Dusseault, Maciej
Isomaki, Markus Lanthaler, Martin J. Duerst, Martin Musatov, Martin Stachowiak, Marc Schneider, Marc Slemko, Mark Baker, Mark Pauley,
Nilsson, Martin Thomson, Matt Lynch, Matthew Cox, Max Clark, Michael Mark Watson, Markus Isomaki, Markus Lanthaler, Martin J. Duerst,
Burrows, Michael Hausenblas, Mike Amundsen, Mike Belshe, Mike Kelly, Martin Musatov, Martin Nilsson, Martin Thomson, Matt Lynch, Matthew
Mike Schinkel, Miles Sabin, Murray S. Kucherawy, Mykyta Yevstifeyev, Cox, Max Clark, Michael Burrows, Michael Hausenblas, Mike Amundsen,
Nathan Rixham, Nicholas Shanks, Nico Williams, Nicolas Alvarez, Mike Belshe, Mike Kelly, Mike Schinkel, Miles Sabin, Murray S.
Nicolas Mailhot, Noah Slater, Pablo Castro, Pat Hayes, Patrick R. Kucherawy, Mykyta Yevstifeyev, Nathan Rixham, Nicholas Shanks, Nico
McManus, Paul E. Jones, Paul Hoffman, Paul Marquess, Peter Lepeska, Williams, Nicolas Alvarez, Nicolas Mailhot, Noah Slater, Pablo
Peter Saint-Andre, Peter Watkins, Phil Archer, Phillip Hallam-Baker, Castro, Pat Hayes, Patrick R. McManus, Paul E. Jones, Paul Hoffman,
Poul-Henning Kamp, Preethi Natarajan, Ray Polk, Reto Bachmann-Gmuer, Paul Marquess, Peter Lepeska, Peter Saint-Andre, Peter Watkins, Phil
Archer, Philippe Mougin, Phillip Hallam-Baker, Poul-Henning Kamp,
Preethi Natarajan, Rajeev Bector, Ray Polk, Reto Bachmann-Gmuer,
Richard Cyganiak, Robert Brewer, Robert Collins, Robert O'Callahan, Richard Cyganiak, Robert Brewer, Robert Collins, Robert O'Callahan,
Robert Olofsson, Robert Sayre, Robert Siemer, Robert de Wilde, Robert Olofsson, Robert Sayre, Robert Siemer, Robert de Wilde,
Roberto Javier Godoy, Roberto Peon, Ronny Widjaja, S. Mike Dierken, Roberto Javier Godoy, Roberto Peon, Ronny Widjaja, S. Mike Dierken,
Salvatore Loreto, Sam Johnston, Sam Ruby, Scott Lawrence (who Salvatore Loreto, Sam Johnston, Sam Ruby, Scott Lawrence (who
maintained the original issues list), Sean B. Palmer, Shane McCarron, maintained the original issues list), Sean B. Palmer, Shane McCarron,
Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane
Bortzmeyer, Stephen Farrell, Stephen Ludin, Stuart Williams, Subbu Bortzmeyer, Stephen Farrell, Stephen Ludin, Stuart Williams, Subbu
Allamaraju, Sylvain Hellegouarch, Tapan Divekar, Tatsuya Hayashi, Ted Allamaraju, Sylvain Hellegouarch, Tapan Divekar, Tatsuya Hayashi, Ted
Hardie, Thomas Broyer, Thomas Nordin, Thomas Roessler, Tim Bray, Tim Hardie, Thomas Broyer, Thomas Nordin, Thomas Roessler, Tim Bray, Tim
Morgan, Tim Olsen, Tom Zhou, Travis Snoozy, Tyler Close, Vincent Morgan, Tim Olsen, Tom Zhou, Travis Snoozy, Tyler Close, Vincent
Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez
Vega, William A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang, Vega, William A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang,
Yaron Goland, Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang, Yutaka Yaron Goland, Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang, Yutaka
Oiwa, Zed A. Shaw, and Zhong Yu. Oiwa, Yves Lafon (long-time member of the editor team), Zed A. Shaw,
and Zhong Yu.
10. References 10. References
10.1. Normative References 10.1. Normative References
[Part2] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
"HTTP/1.1, part 2: Semantics and Payloads", Transfer Protocol (HTTP/1.1): Semantics and Content",
draft-ietf-httpbis-p2-semantics-20 (work in progress), draft-ietf-httpbis-p2-semantics-21 (work in progress),
July 2012. October 2012.
[Part4] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
"HTTP/1.1, part 4: Conditional Requests", Transfer Protocol (HTTP/1.1): Conditional Requests",
draft-ietf-httpbis-p4-conditional-20 (work in draft-ietf-httpbis-p4-conditional-21 (work in
progress), July 2012. progress), October 2012.
[Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
"HTTP/1.1, part 5: Range Requests", "Hypertext Transfer Protocol (HTTP/1.1): Range
draft-ietf-httpbis-p5-range-20 (work in progress), Requests", draft-ietf-httpbis-p5-range-21 (work in
July 2012. progress), October 2012.
[Part6] Fielding, R., Ed., Lafon, Y., Ed., Nottingham, M., Ed., [Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
and J. Reschke, Ed., "HTTP/1.1, part 6: Caching", Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
draft-ietf-httpbis-p6-cache-20 (work in progress), draft-ietf-httpbis-p6-cache-21 (work in progress),
July 2012. October 2012.
[Part7] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
"HTTP/1.1, part 7: Authentication", Transfer Protocol (HTTP/1.1): Authentication",
draft-ietf-httpbis-p7-auth-20 (work in progress), draft-ietf-httpbis-p7-auth-21 (work in progress),
July 2012. October 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 69, line 4 skipping to change at page 65, line 29
10.2. Informative References 10.2. Informative 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.
[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.,
and C. Lilley, "Network Performance Effects of
HTTP/1.1, CSS1, and PNG", ACM Proceedings of the ACM
SIGCOMM '97 conference on Applications, technologies,
architectures, and protocols for computer communication
SIGCOMM '97, September 1997,
<http://doi.acm.org/10.1145/263105.263157>.
[Pad1995] Padmanabhan, V. and J. Mogul, "Improving HTTP Latency",
Computer Networks and ISDN Systems v. 28, pp. 25-35,
December 1995,
<http://portal.acm.org/citation.cfm?id=219094>.
[RFC1919] Chatel, M., "Classical versus Transparent IP Proxies", [RFC1919] Chatel, M., "Classical versus Transparent IP Proxies",
RFC 1919, March 1996. RFC 1919, March 1996.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen,
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
May 1996. May 1996.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
Mail Extensions (MIME) Part One: Format of Internet Mail Extensions (MIME) Part One: Format of Internet
Message Bodies", RFC 2045, November 1996. Message Bodies", RFC 2045, November 1996.
skipping to change at page 70, line 36 skipping to change at page 66, line 46
BCP 115, RFC 4395, February 2006. BCP 115, RFC 4395, February 2006.
[RFC4559] Jaganathan, K., Zhu, L., and J. Brezak, "SPNEGO-based [RFC4559] Jaganathan, K., Zhu, L., and J. Brezak, "SPNEGO-based
Kerberos and NTLM HTTP Authentication in Microsoft Kerberos and NTLM HTTP Authentication in Microsoft
Windows", RFC 4559, June 2006. Windows", RFC 4559, June 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26, an IANA Considerations Section in RFCs", BCP 26,
RFC 5226, May 2008. RFC 5226, May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
October 2008. October 2008.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
April 2011. April 2011.
[Spe] Spero, S., "Analysis of HTTP Performance Problems",
<http://sunsite.unc.edu/mdma-release/http-prob.html>.
[Tou1998] Touch, J., Heidemann, J., and K. Obraczka, "Analysis of
HTTP Performance", ISI Research Report ISI/RR-98-463,
Aug 1998, <http://www.isi.edu/touch/pubs/http-perf96/>.
(original report dated Aug. 1996)
Appendix A. HTTP Version History Appendix A. HTTP Version History
HTTP has been in use by the World-Wide Web global information HTTP has been in use by the World-Wide Web global information
initiative since 1990. The first version of HTTP, later referred to initiative since 1990. The first version of HTTP, later referred to
as HTTP/0.9, was a simple protocol for hypertext data transfer across as HTTP/0.9, was a simple protocol for hypertext data transfer across
the Internet with only a single request method (GET) and no metadata. the Internet with only a single request method (GET) and no metadata.
HTTP/1.0, as defined by [RFC1945], added a range of request methods HTTP/1.0, as defined by [RFC1945], added a range of request methods
and MIME-like messaging that could include metadata about the data and MIME-like messaging that could include metadata about the data
transferred and modifiers on the request/response semantics. transferred and modifiers on the request/response semantics.
However, HTTP/1.0 did not sufficiently take into consideration the However, HTTP/1.0 did not sufficiently take into consideration the
skipping to change at page 73, line 17 skipping to change at page 69, line 17
HTTP/1.1 introduces the Transfer-Encoding header field HTTP/1.1 introduces the Transfer-Encoding header field
(Section 3.3.1). Proxies/gateways MUST remove any transfer-coding (Section 3.3.1). Proxies/gateways MUST remove any transfer-coding
prior to forwarding a message via a MIME-compliant protocol. prior to forwarding a message via a MIME-compliant protocol.
A.2. Changes from RFC 2616 A.2. Changes from RFC 2616
Clarify that the string "HTTP" in the HTTP-version ABNF production is Clarify that the string "HTTP" in the HTTP-version ABNF 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 2.7) 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) Change ABNF productions for header fields to only define the field
value. (Section 3.2)
Rules about implicit linear whitespace between certain grammar Rules about implicit linear whitespace between certain grammar
productions have been removed; now whitespace is only allowed where productions have been removed; now whitespace is only allowed where
specifically defined in the ABNF. (Section 3.2.1) 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 3.2.4) removed). (Section 3.2.4)
Empty list elements in list productions have been deprecated. Require recipients to handle bogus "Content-Length" header fields as
(Appendix B)
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 4) tokens. (Sections 3.3 and 4)
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, and deprecate their use. (Section 4.1) folding in chunk extensions, and deprecate their use. (Section 4.1)
Registration of Transfer Codings now requires IETF Review Update use of abs_path production from RFC 1808 to the path-absolute
(Section 7.4) + query components of RFC 3986. State that the asterisk form is
allowed for the OPTIONS request method only. (Section 5.3)
Clarify exactly when "close" connection options have to be sent; drop
notion of header fields being "hop-by-hop" without being listed in
the Connection header field. (Section 6.1)
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 6.3.3) prematurely. (Section 6.2)
Remove requirement to retry requests under certain circumstances when Remove requirement to retry requests under certain circumstances when
the server prematurely closes the connection. (Section 6.4) the server prematurely closes the connection. (Section 6.2.2)
Change ABNF productions for header fields to only define the field
value.
Clarify exactly when "close" connection options have to be sent.
(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 6.5) than 101 (this was incorporated from [RFC2817]). (Section 6.3)
Registration of Transfer Codings now requires IETF Review
(Section 7.4)
Take over the Upgrade Token Registry, previously defined in Section Take over the Upgrade Token Registry, previously defined in Section
7.2 of [RFC2817]. (Section 7.6) 7.2 of [RFC2817]. (Section 7.6)
Empty list elements in list productions have been deprecated.
(Appendix B)
Appendix B. ABNF list extension: #rule Appendix B. ABNF list extension: #rule
A #rule extension to the ABNF rules of [RFC5234] is used to improve A #rule extension to the ABNF rules of [RFC5234] is used to improve
readability in the definitions of some header field values. readability in the definitions of some header field values.
A construct "#" is defined, similar to "*", for defining comma- A construct "#" is defined, similar to "*", for defining comma-
delimited lists of elements. The full form is "<n>#<m>element" delimited lists of elements. The full form is "<n>#<m>element"
indicating at least <n> and at most <m> elements, each separated by a indicating at least <n> and at most <m> elements, each separated by a
single comma (",") and optional whitespace (OWS). single comma (",") and optional whitespace (OWS).
skipping to change at page 77, line 24 skipping to change at page 73, line 21
/ %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" ] )
rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
reason-phrase = *( HTAB / SP / VCHAR / obs-text ) 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-line = method SP request-target SP HTTP-version CRLF request-line = method SP request-target SP HTTP-version CRLF
request-target = origin-form / absolute-form / authority-form / request-target = origin-form / absolute-form / authority-form /
asterisk-form asterisk-form
special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" / special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}" DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}"
start-line = request-line / status-line start-line = request-line / status-line
status-code = 3DIGIT status-code = 3DIGIT
status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP reason-phrase CRLF
t-codings = "trailers" / ( transfer-extension [ te-params ] ) t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
t-ranking = OWS ";" OWS "q=" rank
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
te-ext = OWS ";" OWS token [ "=" word ]
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
transfer-extension = token *( OWS ";" OWS transfer-parameter ) transfer-extension = token *( OWS ";" OWS transfer-parameter )
transfer-parameter = attribute BWS "=" BWS value transfer-parameter = attribute BWS "=" BWS value
uri-host = <host, defined in [RFC3986], Section 3.2.2> uri-host = <host, defined in [RFC3986], Section 3.2.2>
value = word value = word
word = token / quoted-string word = token / quoted-string
Appendix D. Change Log (to be removed by RFC Editor before publication) Appendix D. Change Log (to be removed by RFC Editor before publication)
D.1. Since RFC 2616 D.1. Since RFC 2616
Extracted relevant partitions from [RFC2616]. Extracted relevant partitions from [RFC2616].
D.2. Since draft-ietf-httpbis-p1-messaging-00 D.2. Since draft-ietf-httpbis-p1-messaging-00
skipping to change at page 83, line 30 skipping to change at page 79, line 24
o <http://tools.ietf.org/wg/httpbis/trac/ticket/161>: "base for o <http://tools.ietf.org/wg/httpbis/trac/ticket/161>: "base for
numeric protocol elements" numeric protocol elements"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/162>: "comment ABNF" o <http://tools.ietf.org/wg/httpbis/trac/ticket/162>: "comment ABNF"
Partly resolved issues: Partly resolved issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/88>: "205 Bodies" o <http://tools.ietf.org/wg/httpbis/trac/ticket/88>: "205 Bodies"
(took out language that implied that there might be methods for (took out language that implied that there might be methods for
which a request body MUST NOT be included) which a payload body MUST NOT be included)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/163>: "editorial o <http://tools.ietf.org/wg/httpbis/trac/ticket/163>: "editorial
improvements around HTTP-date" improvements around HTTP-date"
D.9. Since draft-ietf-httpbis-p1-messaging-07 D.9. Since draft-ietf-httpbis-p1-messaging-07
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/93>: "Repeating o <http://tools.ietf.org/wg/httpbis/trac/ticket/93>: "Repeating
single-value header fields" single-value header fields"
skipping to change at page 89, line 24 skipping to change at page 85, line 17
o <http://tools.ietf.org/wg/httpbis/trac/ticket/361>: "ABNF o <http://tools.ietf.org/wg/httpbis/trac/ticket/361>: "ABNF
requirements for recipients" requirements for recipients"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/368>: "note o <http://tools.ietf.org/wg/httpbis/trac/ticket/368>: "note
introduction of new IANA registries as normative changes" introduction of new IANA registries as normative changes"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/374>: "Reference to o <http://tools.ietf.org/wg/httpbis/trac/ticket/374>: "Reference to
ISO-8859-1 is informative" ISO-8859-1 is informative"
D.22. Since draft-ietf-httpbis-p1-messaging-20
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/378>: "is 'q=' case-
sensitive?"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/383>: "Semantics of
HTTPS"
Other changes:
o Drop notion of header fields being "hop-by-hop" without being
listed in the Connection header field.
o Section about connection management rewritten; dropping some
historic information.
o Move description of "100-continue" into Part 2.
o Rewrite the persistent connection and Upgrade requirements to be
actionable by role and consistent with the rest of HTTP.
Index Index
A A
absolute-form (of request-target) 41 absolute-form (of request-target) 39
accelerator 11 accelerator 10
application/http Media Type 60 application/http Media Type 57
asterisk-form (of request-target) 41 asterisk-form (of request-target) 39
authority-form (of request-target) 41 authority-form (of request-target) 39
B B
browser 8 browser 7
C C
cache 13 cache 11
cacheable 13 cacheable 12
captive portal 12 captive portal 11
chunked (Coding Format) 34 chunked (Coding Format) 33
client 7 client 7
Coding Format close 46, 52
chunked 34 compress (Coding Format) 35
compress 36
deflate 36
gzip 36
compress (Coding Format) 36
connection 7 connection 7
Connection header field 47 Connection header field 46, 52
Content-Length header field 29 Content-Length header field 28
D D
deflate (Coding Format) 36 deflate (Coding Format) 35
downstream 11 downstream 9
E E
effective request URI 43 effective request URI 41
G G
gateway 11 gateway 10
Grammar Grammar
absolute-form 40 absolute-form 38
absolute-URI 17 absolute-URI 15
ALPHA 7 ALPHA 6
asterisk-form 40 asterisk-form 38
attribute 34 attribute 33
authority 17 authority 15
authority-form 40 authority-form 38
BWS 24 BWS 23
chunk 34 chunk 33
chunk-data 34 chunk-data 33
chunk-ext 34 chunk-ext 33
chunk-ext-name 34 chunk-ext-name 33
chunk-ext-val 34 chunk-ext-val 33
chunk-size 34 chunk-size 33
chunked-body 34 chunked-body 33
comment 27 comment 25
Connection 47 Connection 47
connection-option 47 connection-option 47
Content-Length 29 Content-Length 28
CR 7 CR 6
CRLF 7 CRLF 6
ctext 27 ctext 25
CTL 7 CTL 6
date2 34 date2 33
date3 34 date3 33
DIGIT 7 DIGIT 6
DQUOTE 7 DQUOTE 6
field-content 23 field-content 21
field-name 23 field-name 21
field-value 23 field-value 21
header-field 23 header-field 21
HEXDIG 7 HEXDIG 6
Host 42 Host 40
HTAB 7 HTAB 6
HTTP-message 20 HTTP-message 18
HTTP-name 14 HTTP-name 13
http-URI 17 http-URI 16
HTTP-version 14 HTTP-version 13
https-URI 19 https-URI 17
last-chunk 34 last-chunk 33
LF 7 LF 6
message-body 27 message-body 26
method 21 method 20
obs-fold 23 obs-fold 21
obs-text 26 obs-text 25
OCTET 7 OCTET 6
origin-form 40 origin-form 38
OWS 24 OWS 23
partial-URI 17 partial-URI 15
path-absolute 17 path-absolute 15
port 17 port 15
protocol-name 49 protocol-name 43
protocol-version 49 protocol-version 43
pseudonym 49 pseudonym 43
qdtext 26 qdtext 25
qdtext-nf 34 qdtext-nf 33
query 17 query 15
quoted-cpair 27 quoted-cpair 25
quoted-pair 26 quoted-pair 25
quoted-str-nf 34 quoted-str-nf 33
quoted-string 26 quoted-string 25
qvalue 38 rank 36
reason-phrase 22 reason-phrase 21
received-by 49 received-by 43
received-protocol 49 received-protocol 43
request-line 21 request-line 20
request-target 40 request-target 38
RWS 24 RWS 23
SP 7 SP 6
special 26 special 25
start-line 21 start-line 19
status-code 22 status-code 21
status-line 22 status-line 21
t-codings 37 t-codings 36
tchar 26 t-ranking 36
TE 37 tchar 25
te-ext 37 TE 36
te-params 37 token 25
token 26 Trailer 34
Trailer 38 trailer-part 33
trailer-part 34 transfer-coding 33
transfer-coding 34 Transfer-Encoding 26
Transfer-Encoding 28 transfer-extension 33
transfer-extension 34 transfer-parameter 33
transfer-parameter 34 Upgrade 53
Upgrade 57 uri-host 15
uri-host 17 URI-reference 15
URI-reference 17 value 33
value 34 VCHAR 6
VCHAR 7 Via 43
Via 49 word 25
word 26
gzip (Coding Format) 36 gzip (Coding Format) 36
H H
header field 20 header field 18
Header Fields header section 18
Connection 47 headers 18
Content-Length 29 Host header field 40
Host 42 http URI scheme 16
TE 36 https URI scheme 17
Trailer 38
Transfer-Encoding 27
Upgrade 56
Via 49
header section 20
headers 20
Host header field 42
http URI scheme 17
https URI scheme 18
I I
inbound 11 inbound 9
interception proxy 12 interception proxy 11
intermediary 10 intermediary 9
M M
Media Type Media Type
application/http 60 application/http 57
message/http 59 message/http 56
message 8 message 7
message/http Media Type 59 message/http Media Type 56
method 21 method 20
N N
non-transforming proxy 11 non-transforming proxy 10
O O
origin server 8 origin server 7
origin-form (of request-target) 40 origin-form (of request-target) 38
outbound 11 outbound 9
P P
proxy 11 proxy 10
R R
recipient 8 recipient 7
request 8 request 7
request-target 21 request-target 20
resource 16 resource 15
response 8 response 7
reverse proxy 11 reverse proxy 10
S S
sender 8 sender 7
server 7 server 7
spider 8 spider 7
T T
target resource 39 target resource 37
target URI 39 target URI 37
TE header field 36 TE header field 36
Trailer header field 38 Trailer header field 34
Transfer-Encoding header field 27 Transfer-Encoding header field 26
transforming proxy 11 transforming proxy 10
transparent proxy 12 transparent proxy 11
tunnel 12 tunnel 11
U U
Upgrade header field 56 Upgrade header field 53
upstream 11 upstream 9
URI scheme URI scheme
http 17 http 16
https 18 https 17
user agent 8 user agent 7
V V
Via header field 49 Via header field 43
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/
Yves Lafon (editor)
World Wide Web Consortium
W3C / ERCIM
2004, rte des Lucioles
Sophia-Antipolis, AM 06902
France
EMail: ylafon@w3.org
URI: http://www.raubacapeu.net/people/yves/
Julian F. Reschke (editor) Julian F. Reschke (editor)
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
Muenster, NW 48155 Muenster, NW 48155
Germany Germany
EMail: julian.reschke@greenbytes.de EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/ URI: http://greenbytes.de/tech/webdav/
 End of changes. 236 change blocks. 
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