draft-ietf-httpbis-p1-messaging-12.txt   draft-ietf-httpbis-p1-messaging-13.txt 
HTTPbis Working Group R. Fielding, Ed. HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Day Software Internet-Draft Adobe
Obsoletes: 2616 (if approved) J. Gettys Obsoletes: 2145,2616 J. Gettys
Updates: 2817 (if approved) Alcatel-Lucent (if approved) Alcatel-Lucent
Intended status: Standards Track J. Mogul Updates: 2817 (if approved) J. Mogul
Expires: April 28, 2011 HP Intended status: Standards Track HP
H. Frystyk Expires: September 15, 2011 H. Frystyk
Microsoft Microsoft
L. Masinter L. Masinter
Adobe Systems Adobe
P. Leach P. Leach
Microsoft Microsoft
T. Berners-Lee T. Berners-Lee
W3C/MIT W3C/MIT
Y. Lafon, Ed. Y. Lafon, Ed.
W3C W3C
J. Reschke, Ed. J. Reschke, Ed.
greenbytes greenbytes
October 25, 2010 March 14, 2011
HTTP/1.1, part 1: URIs, Connections, and Message Parsing HTTP/1.1, part 1: URIs, Connections, and Message Parsing
draft-ietf-httpbis-p1-messaging-12 draft-ietf-httpbis-p1-messaging-13
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypertext information protocol for distributed, collaborative, hypertext information
systems. HTTP has been in use by the World Wide Web global systems. HTTP has been in use by the World Wide Web global
information initiative since 1990. This document is Part 1 of the information initiative since 1990. This document is Part 1 of the
seven-part specification that defines the protocol referred to as seven-part specification that defines the protocol referred to as
"HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 1 provides "HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 1 provides
an overview of HTTP and its associated terminology, defines the an overview of HTTP and its associated terminology, defines the
skipping to change at page 1, line 47 skipping to change at page 1, line 47
frames, and describes general security concerns for implementations. frames, and describes general security concerns for implementations.
Editorial Note (To be removed by RFC Editor) Editorial Note (To be removed by RFC Editor)
Discussion of this draft should take place on the HTTPBIS working Discussion of this draft should take place on the HTTPBIS working
group mailing list (ietf-http-wg@w3.org). The current issues list is group mailing list (ietf-http-wg@w3.org). The current issues list is
at <http://tools.ietf.org/wg/httpbis/trac/report/3> and related at <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.13. The changes in this draft are summarized in Appendix D.14.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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 April 28, 2011. This Internet-Draft will expire on September 15, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7
1.2.1. ABNF Extension: #rule . . . . . . . . . . . . . . . . 7 1.2.1. ABNF Extension: #rule . . . . . . . . . . . . . . . . 7
1.2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . 8 1.2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . 8
1.2.3. ABNF Rules defined in other Parts of the
Specification . . . . . . . . . . . . . . . . . . . . 10
2. HTTP-related architecture . . . . . . . . . . . . . . . . . . 10 2. HTTP-related architecture . . . . . . . . . . . . . . . . . . 10
2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 10 2.1. Client/Server Messaging . . . . . . . . . . . . . . . . . 10
2.2. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 12 2.2. Connections and Transport Independence . . . . . . . . . . 12
2.3. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3. Intermediaries . . . . . . . . . . . . . . . . . . . . . . 12
2.4. Transport Independence . . . . . . . . . . . . . . . . . . 14 2.4. Caches . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5. HTTP Version . . . . . . . . . . . . . . . . . . . . . . . 14 2.5. Protocol Versioning . . . . . . . . . . . . . . . . . . . 15
2.6. Uniform Resource Identifiers . . . . . . . . . . . . . . . 16 2.6. Uniform Resource Identifiers . . . . . . . . . . . . . . . 17
2.6.1. http URI scheme . . . . . . . . . . . . . . . . . . . 16 2.6.1. http URI scheme . . . . . . . . . . . . . . . . . . . 18
2.6.2. https URI scheme . . . . . . . . . . . . . . . . . . . 18 2.6.2. https URI scheme . . . . . . . . . . . . . . . . . . . 19
2.6.3. http and https URI Normalization and Comparison . . . 18 2.6.3. http and https URI Normalization and Comparison . . . 20
3. HTTP Message . . . . . . . . . . . . . . . . . . . . . . . . . 19 3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1. Message Parsing Robustness . . . . . . . . . . . . . . . . 20 3.1. Message Parsing Robustness . . . . . . . . . . . . . . . . 21
3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 20 3.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 22
3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 22 3.3. Message Body . . . . . . . . . . . . . . . . . . . . . . . 24
3.4. General Header Fields . . . . . . . . . . . . . . . . . . 25 3.4. General Header Fields . . . . . . . . . . . . . . . . . . 27
4. Request . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4. Request . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1. Request-Line . . . . . . . . . . . . . . . . . . . . . . . 26 4.1. Request-Line . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.1. Method . . . . . . . . . . . . . . . . . . . . . . . . 26 4.1.1. Method . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.2. request-target . . . . . . . . . . . . . . . . . . . . 27 4.1.2. request-target . . . . . . . . . . . . . . . . . . . . 28
4.2. The Resource Identified by a Request . . . . . . . . . . . 29 4.2. The Resource Identified by a Request . . . . . . . . . . . 30
4.3. Effective Request URI . . . . . . . . . . . . . . . . . . 29 4.3. Effective Request URI . . . . . . . . . . . . . . . . . . 31
5. Response . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 5. Response . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.1. Status-Line . . . . . . . . . . . . . . . . . . . . . . . 31 5.1. Status-Line . . . . . . . . . . . . . . . . . . . . . . . 33
5.1.1. Status Code and Reason Phrase . . . . . . . . . . . . 31 5.1.1. Status Code and Reason Phrase . . . . . . . . . . . . 33
6. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 32 6. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 33
6.1. Date/Time Formats: Full Date . . . . . . . . . . . . . . . 32 6.1. Date/Time Formats: Full Date . . . . . . . . . . . . . . . 33
6.2. Transfer Codings . . . . . . . . . . . . . . . . . . . . . 34 6.2. Transfer Codings . . . . . . . . . . . . . . . . . . . . . 36
6.2.1. Chunked Transfer Coding . . . . . . . . . . . . . . . 35 6.2.1. Chunked Transfer Coding . . . . . . . . . . . . . . . 37
6.2.2. Compression Codings . . . . . . . . . . . . . . . . . 37 6.2.2. Compression Codings . . . . . . . . . . . . . . . . . 39
6.2.3. Transfer Coding Registry . . . . . . . . . . . . . . . 38 6.2.3. Transfer Coding Registry . . . . . . . . . . . . . . . 40
6.3. Product Tokens . . . . . . . . . . . . . . . . . . . . . . 39 6.3. Product Tokens . . . . . . . . . . . . . . . . . . . . . . 41
6.4. Quality Values . . . . . . . . . . . . . . . . . . . . . . 39 6.4. Quality Values . . . . . . . . . . . . . . . . . . . . . . 41
7. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 39 7. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 41
7.1. Persistent Connections . . . . . . . . . . . . . . . . . . 40 7.1. Persistent Connections . . . . . . . . . . . . . . . . . . 42
7.1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 40 7.1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 42
7.1.2. Overall Operation . . . . . . . . . . . . . . . . . . 40 7.1.2. Overall Operation . . . . . . . . . . . . . . . . . . 42
7.1.3. Proxy Servers . . . . . . . . . . . . . . . . . . . . 42 7.1.3. Proxy Servers . . . . . . . . . . . . . . . . . . . . 44
7.1.4. Practical Considerations . . . . . . . . . . . . . . . 44 7.1.4. Practical Considerations . . . . . . . . . . . . . . . 46
7.2. Message Transmission Requirements . . . . . . . . . . . . 45 7.2. Message Transmission Requirements . . . . . . . . . . . . 47
7.2.1. Persistent Connections and Flow Control . . . . . . . 45 7.2.1. Persistent Connections and Flow Control . . . . . . . 47
7.2.2. Monitoring Connections for Error Status Messages . . . 45 7.2.2. Monitoring Connections for Error Status Messages . . . 47
7.2.3. Use of the 100 (Continue) Status . . . . . . . . . . . 46 7.2.3. Use of the 100 (Continue) Status . . . . . . . . . . . 48
7.2.4. Client Behavior if Server Prematurely Closes 7.2.4. Client Behavior if Server Prematurely Closes
Connection . . . . . . . . . . . . . . . . . . . . . . 48 Connection . . . . . . . . . . . . . . . . . . . . . . 50
8. Miscellaneous notes that might disappear . . . . . . . . . . . 49 8. Miscellaneous notes that might disappear . . . . . . . . . . . 51
8.1. Scheme aliases considered harmful . . . . . . . . . . . . 49 8.1. Scheme aliases considered harmful . . . . . . . . . . . . 51
8.2. Use of HTTP for proxy communication . . . . . . . . . . . 49 8.2. Use of HTTP for proxy communication . . . . . . . . . . . 51
8.3. Interception of HTTP for access control . . . . . . . . . 49 8.3. Interception of HTTP for access control . . . . . . . . . 51
8.4. Use of HTTP by other protocols . . . . . . . . . . . . . . 49 8.4. Use of HTTP by other protocols . . . . . . . . . . . . . . 51
8.5. Use of HTTP by media type specification . . . . . . . . . 49 8.5. Use of HTTP by media type specification . . . . . . . . . 51
9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 49 9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 51
9.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 49 9.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 51
9.2. Content-Length . . . . . . . . . . . . . . . . . . . . . . 50 9.2. Content-Length . . . . . . . . . . . . . . . . . . . . . . 53
9.3. Date . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 9.3. Date . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.3.1. Clockless Origin Server Operation . . . . . . . . . . 52 9.3.1. Clockless Origin Server Operation . . . . . . . . . . 54
9.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 9.4. Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.5. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 9.5. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
9.6. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 54 9.6. Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.7. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 55 9.7. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 58
9.8. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 55 9.8. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 58
9.8.1. Upgrade Token Registry . . . . . . . . . . . . . . . . 56 9.8.1. Upgrade Token Registry . . . . . . . . . . . . . . . . 59
9.9. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 9.9. Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 62
10.1. Header Field Registration . . . . . . . . . . . . . . . . 59 10.1. Header Field Registration . . . . . . . . . . . . . . . . 62
10.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 59 10.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 62
10.3. Internet Media Type Registrations . . . . . . . . . . . . 59 10.3. Internet Media Type Registrations . . . . . . . . . . . . 62
10.3.1. Internet Media Type message/http . . . . . . . . . . . 59 10.3.1. Internet Media Type message/http . . . . . . . . . . . 62
10.3.2. Internet Media Type application/http . . . . . . . . . 61 10.3.2. Internet Media Type application/http . . . . . . . . . 64
10.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 62 10.4. Transfer Coding Registry . . . . . . . . . . . . . . . . . 65
10.5. Upgrade Token Registration . . . . . . . . . . . . . . . . 62 10.5. Upgrade Token Registration . . . . . . . . . . . . . . . . 65
11. Security Considerations . . . . . . . . . . . . . . . . . . . 62 11. Security Considerations . . . . . . . . . . . . . . . . . . . 65
11.1. Personal Information . . . . . . . . . . . . . . . . . . . 63 11.1. Personal Information . . . . . . . . . . . . . . . . . . . 66
11.2. Abuse of Server Log Information . . . . . . . . . . . . . 63 11.2. Abuse of Server Log Information . . . . . . . . . . . . . 66
11.3. Attacks Based On File and Path Names . . . . . . . . . . . 63 11.3. Attacks Based On File and Path Names . . . . . . . . . . . 66
11.4. DNS Spoofing . . . . . . . . . . . . . . . . . . . . . . . 63 11.4. DNS Spoofing . . . . . . . . . . . . . . . . . . . . . . . 66
11.5. Proxies and Caching . . . . . . . . . . . . . . . . . . . 64 11.5. Proxies and Caching . . . . . . . . . . . . . . . . . . . 67
11.6. Denial of Service Attacks on Proxies . . . . . . . . . . . 65 11.6. Denial of Service Attacks on Proxies . . . . . . . . . . . 68
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 65 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 68
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 66 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 69
13.1. Normative References . . . . . . . . . . . . . . . . . . . 66 13.1. Normative References . . . . . . . . . . . . . . . . . . . 69
13.2. Informative References . . . . . . . . . . . . . . . . . . 68 13.2. Informative References . . . . . . . . . . . . . . . . . . 71
Appendix A. Tolerant Applications . . . . . . . . . . . . . . . . 70 Appendix A. Tolerant Applications . . . . . . . . . . . . . . . . 74
Appendix B. Compatibility with Previous Versions . . . . . . . . 71 Appendix B. HTTP Version History . . . . . . . . . . . . . . . . 75
B.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 71 B.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 75
B.1.1. Changes to Simplify Multi-homed Web Servers and B.1.1. Multi-homed Web Servers . . . . . . . . . . . . . . . 76
Conserve IP Addresses . . . . . . . . . . . . . . . . 72 B.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . . 76
B.2. Compatibility with HTTP/1.0 Persistent Connections . . . . 72 B.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 77
B.3. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 73 Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 77
Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 74
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) . . . . . . . . . . . . . . . . . . . . 82
D.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 78 D.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 82
D.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 78 D.2. Since draft-ietf-httpbis-p1-messaging-00 . . . . . . . . . 82
D.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 80 D.3. Since draft-ietf-httpbis-p1-messaging-01 . . . . . . . . . 83
D.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 81 D.4. Since draft-ietf-httpbis-p1-messaging-02 . . . . . . . . . 84
D.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 81 D.5. Since draft-ietf-httpbis-p1-messaging-03 . . . . . . . . . 85
D.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 82 D.6. Since draft-ietf-httpbis-p1-messaging-04 . . . . . . . . . 85
D.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 82 D.7. Since draft-ietf-httpbis-p1-messaging-05 . . . . . . . . . 86
D.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 83 D.8. Since draft-ietf-httpbis-p1-messaging-06 . . . . . . . . . 87
D.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 84 D.9. Since draft-ietf-httpbis-p1-messaging-07 . . . . . . . . . 87
D.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 84 D.10. Since draft-ietf-httpbis-p1-messaging-08 . . . . . . . . . 88
D.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 85 D.11. Since draft-ietf-httpbis-p1-messaging-09 . . . . . . . . . 88
D.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 85 D.12. Since draft-ietf-httpbis-p1-messaging-10 . . . . . . . . . 89
D.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 86 D.13. Since draft-ietf-httpbis-p1-messaging-11 . . . . . . . . . 89
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 D.14. Since draft-ietf-httpbis-p1-messaging-12 . . . . . . . . . 90
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
request/response protocol that uses extensible semantics and MIME- request/response protocol that uses extensible semantics and MIME-
like message payloads for flexible interaction with network-based like message payloads for flexible interaction with network-based
hypertext information systems. HTTP relies upon the Uniform Resource hypertext information systems. HTTP relies upon the Uniform Resource
Identifier (URI) standard [RFC3986] to indicate request targets and Identifier (URI) standard [RFC3986] to indicate the target resource
relationships between resources. Messages are passed in a format and relationships between resources. Messages are passed in a format
similar to that used by Internet mail [RFC5322] and the Multipurpose similar to that used by Internet mail [RFC5322] and the Multipurpose
Internet Mail Extensions (MIME) [RFC2045] (see Appendix A of [Part3] Internet Mail Extensions (MIME) [RFC2045] (see Appendix A of [Part3]
for the differences between HTTP and MIME messages). for the differences between HTTP and MIME messages).
HTTP is a generic interface protocol for information systems. It is HTTP is a generic interface protocol for information systems. It is
designed to hide the details of how a service is implemented by designed to hide the details of how a service is implemented by
presenting a uniform interface to clients that is independent of the presenting a uniform interface to clients that is independent of the
types of resources provided. Likewise, servers do not need to be types of resources provided. Likewise, servers do not need to be
aware of each client's purpose: an HTTP request can be considered in aware of each client's purpose: an HTTP request can be considered in
isolation rather than being associated with a specific type of client isolation rather than being associated with a specific type of client
skipping to change at page 6, line 45 skipping to change at page 6, line 45
defined in terms of what occurs behind the interface. Instead, we defined in terms of what occurs behind the interface. Instead, we
are limited to defining the syntax of communication, the intent of are limited to defining the syntax of communication, the intent of
received communication, and the expected behavior of recipients. If received communication, and the expected behavior of recipients. If
the communication is considered in isolation, then successful actions the communication is considered in isolation, then successful actions
ought to be reflected in corresponding changes to the observable ought to be reflected in corresponding changes to the observable
interface provided by servers. However, since multiple clients might interface provided by servers. However, since multiple clients might
act in parallel and perhaps at cross-purposes, we cannot require that act in parallel and perhaps at cross-purposes, we cannot require that
such changes be observable beyond the scope of a single response. such changes be observable beyond the scope of a single response.
This document is Part 1 of the seven-part specification of HTTP, This document is Part 1 of the seven-part specification of HTTP,
defining the protocol referred to as "HTTP/1.1" and obsoleting defining the protocol referred to as "HTTP/1.1", obsoleting [RFC2616]
[RFC2616]. Part 1 describes the architectural elements that are used and [RFC2145]. Part 1 describes the architectural elements that are
or referred to in HTTP, defines the "http" and "https" URI schemes, used or referred to in HTTP, defines the "http" and "https" URI
describes overall network operation and connection management, and schemes, describes overall network operation and connection
defines HTTP message framing and forwarding requirements. Our goal management, and defines HTTP message framing and forwarding
is to define all of the mechanisms necessary for HTTP message requirements. Our goal is to define all of the mechanisms necessary
handling that are independent of message semantics, thereby defining for HTTP message handling that are independent of message semantics,
the complete set of requirements for message parsers and message- thereby defining the complete set of requirements for message parsers
forwarding intermediaries. and message-forwarding intermediaries.
1.1. Requirements 1.1. Requirements
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].
An implementation is not compliant if it fails to satisfy one or more An implementation is not compliant if it fails to satisfy one or more
of the "MUST" or "REQUIRED" level requirements for the protocols it of the "MUST" or "REQUIRED" level requirements for the protocols it
implements. An implementation that satisfies all the "MUST" or implements. An implementation that satisfies all the "MUST" or
skipping to change at page 9, line 9 skipping to change at page 9, line 9
1.2.2. Basic Rules 1.2.2. Basic Rules
HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all
protocol elements other than the message-body (see Appendix A for protocol elements other than the message-body (see Appendix A for
tolerant applications). tolerant applications).
This specification uses three rules to denote the use of linear This specification uses three rules to denote the use of linear
whitespace: OWS (optional whitespace), RWS (required whitespace), and whitespace: OWS (optional whitespace), RWS (required whitespace), and
BWS ("bad" whitespace). BWS ("bad" whitespace).
The OWS rule is used where zero or more linear whitespace characters The OWS rule is used where zero or more linear whitespace octets
might appear. OWS SHOULD either not be produced or be produced as a might appear. OWS SHOULD either not be produced or be produced as a
single SP character. Multiple OWS characters that occur within single SP. Multiple OWS octets that occur within field-content
field-content SHOULD be replaced with a single SP before interpreting
the field value or forwarding the message downstream.
RWS is used when at least one linear whitespace character is required
to separate field tokens. RWS SHOULD be produced as a single SP
character. Multiple RWS characters that occur within field-content
SHOULD be replaced with a single SP before interpreting the field SHOULD be replaced with a single SP before interpreting the field
value or forwarding the message downstream. value or forwarding the message downstream.
RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be produced as a single SP.
Multiple RWS octets that occur within field-content SHOULD be
replaced with a single SP before 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 HTTP/1.1 recipients MUST accept such bad optional whitespace and
remove it before interpreting the field value or forwarding the remove it before interpreting the field value or forwarding the
message downstream. message downstream.
OWS = *( [ obs-fold ] WSP ) OWS = *( [ obs-fold ] WSP )
; "optional" whitespace ; "optional" whitespace
RWS = 1*( [ obs-fold ] WSP ) RWS = 1*( [ obs-fold ] WSP )
; "required" whitespace ; "required" whitespace
skipping to change at page 10, line 14 skipping to change at page 10, line 14
/ "]" / "?" / "=" / "{" / "}" / "]" / "?" / "=" / "{" / "}"
A string of text is parsed as a single word if it is quoted using A string of text is parsed as a single word if it is quoted using
double-quote marks. double-quote marks.
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
qdtext = OWS / %x21 / %x23-5B / %x5D-7E / obs-text qdtext = OWS / %x21 / %x23-5B / %x5D-7E / obs-text
; OWS / <VCHAR except DQUOTE and "\"> / obs-text ; OWS / <VCHAR except DQUOTE and "\"> / obs-text
obs-text = %x80-FF obs-text = %x80-FF
The backslash character ("\") can be used as a single-character The backslash octet ("\") can be used as a single-octet quoting
quoting mechanism within quoted-string constructs: mechanism within quoted-string constructs:
quoted-pair = "\" ( WSP / VCHAR / obs-text ) quoted-pair = "\" ( WSP / VCHAR / obs-text )
Producers SHOULD NOT escape characters that do not require escaping Senders SHOULD NOT escape octets that do not require escaping (i.e.,
(i.e., other than DQUOTE and the backslash character). other than DQUOTE and the backslash octet).
1.2.3. ABNF Rules defined in other Parts of the Specification
The ABNF rules below are defined in other parts:
request-header = <request-header, defined in [Part2], Section 3>
response-header = <response-header, defined in [Part2], Section 5>
MIME-Version = <MIME-Version, defined in [Part3], Appendix A.1>
Cache-Control = <Cache-Control, defined in [Part6], Section 3.4>
Pragma = <Pragma, defined in [Part6], Section 3.4>
Warning = <Warning, defined in [Part6], Section 3.6>
2. HTTP-related architecture 2. HTTP-related architecture
HTTP was created for the World Wide Web architecture and has evolved HTTP was created for the World Wide Web architecture and has evolved
over time to support the scalability needs of a worldwide hypertext over time to support the scalability needs of a worldwide hypertext
system. Much of that architecture is reflected in the terminology system. Much of that architecture is reflected in the terminology
and syntax productions used to define HTTP. and syntax productions used to define HTTP.
2.1. Client/Server Messaging 2.1. Client/Server Messaging
skipping to change at page 12, line 19 skipping to change at page 12, line 5
Server: Apache Server: Apache
Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT
ETag: "34aa387-d-1568eb00" ETag: "34aa387-d-1568eb00"
Accept-Ranges: bytes Accept-Ranges: bytes
Content-Length: 14 Content-Length: 14
Vary: Accept-Encoding Vary: Accept-Encoding
Content-Type: text/plain Content-Type: text/plain
Hello World! Hello World!
2.2. Intermediaries 2.2. Connections and Transport Independence
A more complicated situation occurs when one or more intermediaries HTTP messaging is independent of the underlying transport or session-
are present in the request/response chain. There are three common layer connection protocol(s). HTTP only presumes a reliable
forms of intermediary: proxy, gateway, and tunnel. In some cases, a transport with in-order delivery of requests and the corresponding
single intermediary might act as an origin server, proxy, gateway, or 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 resource's URI.
For example, the "http" URI scheme (Section 2.6.1) 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 7.1.
2.3. Intermediaries
HTTP enables the use of intermediaries to satisfy requests through a
chain of connections. There are three common forms of HTTP
intermediary: proxy, gateway, and tunnel. In some cases, a single
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
< < < < < < < <
The figure above shows three intermediaries (A, B, and C) between the The figure above shows three intermediaries (A, B, and C) between the
user agent and origin server. A request or response message that user agent and origin server. A request or response message that
travels the whole chain will pass through four separate connections. travels the whole chain will pass through four separate connections.
Some HTTP communication options might apply only to the connection Some HTTP communication options might apply only to the connection
skipping to change at page 13, line 11 skipping to change at page 13, line 16
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-layer 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
designed or configured to modify request or response messages in a
semantically meaningful way (i.e., modifications, beyond those
required by normal HTTP processing, that change the message in a way
that would be significant to the original sender or potentially
significant to downstream recipients). For example, a transforming
proxy might be acting as a shared annotation server (modifying
responses to include references to a local annotation database), a
malware filter, a format transcoder, or an intranet-to-Internet
privacy filter. Such transformations are presumed to be desired by
the client (or client organization) that selected the proxy and are
beyond the scope of this specification. However, when a proxy is not
intended to transform a given message, we use the term "non-
transforming proxy" to target requirements that preserve HTTP message
semantics.
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 for load balancing or partitioning HTTP services across multiple used to encapsulate legacy or untrusted information services, to
machines. Unlike a proxy, a gateway receives requests as if it were improve server performance through "accelerator" caching, and to
the origin server for the target resource; the requesting client will enable partitioning or load-balancing of HTTP services across
not be aware that it is communicating with a gateway. A gateway multiple machines.
communicates with the client as if the gateway is the origin server
and thus is subject to all of the requirements on origin servers for A gateway behaves as an origin server on its outbound connection and
that connection. A gateway communicates with inbound servers using as a user agent on its inbound connection. All HTTP requirements
any protocol it desires, including private extensions to HTTP that applicable to an origin server also apply to the outbound
are outside the scope of this specification. communication of a gateway. A gateway communicates with inbound
servers using any protocol that it desires, including private
extensions to HTTP that are outside the scope of this specification.
However, an HTTP-to-HTTP gateway that wishes to interoperate with
third-party HTTP servers MUST comply with HTTP user agent
requirements on the gateway's inbound connection and MUST implement
the Connection (Section 9.1) and Via (Section 9.9) header fields for
both connections.
A "tunnel" acts as a blind relay between two connections without A "tunnel" acts as a blind relay between two connections without
changing the messages. Once active, a tunnel is not considered a changing the messages. Once active, a tunnel is not considered a
party to the HTTP communication, though the tunnel might have been party to the HTTP communication, though the tunnel might have been
initiated by an HTTP request. A tunnel ceases to exist when both initiated by an HTTP request. A tunnel ceases to exist when both
ends of the relayed connection are closed. Tunnels are used to ends of the relayed connection are closed. Tunnels are used to
extend a virtual connection through an intermediary, such as when extend a virtual connection through an intermediary, such as when
transport-layer security is used to establish private communication transport-layer security is used to establish private communication
through a shared firewall proxy. through a shared firewall proxy.
2.3. Caches In addition, there may exist network intermediaries that are not
considered part of the HTTP communication but nevertheless act as
filters or redirecting agents (usually violating HTTP semantics,
causing security problems, and otherwise making a mess of things).
Such a network intermediary, often referred to as an "interception
proxy" [RFC3040], "transparent proxy" [RFC1919], or "captive portal",
differs from an HTTP proxy because it has not been selected by the
client. Instead, the network intermediary redirects outgoing TCP
port 80 packets (and occasionally other common port traffic) to an
internal HTTP server. Interception proxies are commonly found on
public network access points, as a means of enforcing account
subscription prior to allowing use of non-local Internet services,
and within corporate firewalls to enforce network usage policies.
They are indistinguishable from a man-in-the-middle attack.
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
skipping to change at page 14, line 20 skipping to change at page 15, line 14
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.
2.4. Transport Independence 2.5. Protocol Versioning
HTTP systems are used in a wide variety of environments, from
corporate intranets with high-bandwidth links to long-distance
communication over low-power radio links and intermittent
connectivity.
HTTP communication usually takes place over TCP/IP connections. The
default port is TCP 80
(<http://www.iana.org/assignments/port-numbers>), but other ports can
be used. This does not preclude HTTP from being implemented on top
of any other protocol on the Internet, or on other networks. HTTP
only presumes a reliable transport; any protocol that provides such
guarantees can be used; the mapping of the HTTP/1.1 request and
response structures onto the transport data units of the protocol in
question is outside the scope of this specification.
In HTTP/1.0, most implementations used a new connection for each
request/response exchange. In HTTP/1.1, a connection might be used
for one or more request/response exchanges, although connections
might be closed for a variety of reasons (see Section 7.1).
2.5. HTTP Version
HTTP uses a "<major>.<minor>" numbering scheme to indicate versions HTTP uses a "<major>.<minor>" numbering scheme to indicate versions
of the protocol. The protocol versioning policy is intended to allow of the protocol. This specification defines version "1.1". The
the sender to indicate the format of a message and its capacity for protocol version as a whole indicates the sender's compliance with
understanding further HTTP communication, rather than the features the set of requirements laid out in that version's corresponding
obtained via that communication. No change is made to the version specification of HTTP.
number for the addition of message components which do not affect
communication behavior or which only add to extensible field values.
The <minor> number is incremented when the changes made to the
protocol add features which do not change the general message parsing
algorithm, but which might add to the message semantics and imply
additional capabilities of the sender. The <major> number is
incremented when the format of a message within the protocol is
changed. See [RFC2145] for a fuller explanation.
The version of an HTTP message is indicated by an HTTP-Version field The version of an HTTP message is indicated by an HTTP-Version field
in the first line of the message. HTTP-Version is case-sensitive. in the first line of the message. HTTP-Version is case-sensitive.
HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT
HTTP-Prot-Name = %x48.54.54.50 ; "HTTP", case-sensitive HTTP-Prot-Name = %x48.54.54.50 ; "HTTP", case-sensitive
Note that the major and minor numbers MUST be treated as separate The HTTP version number consists of two non-negative decimal integers
integers and that each MAY be incremented higher than a single digit. separated by a "." (period or decimal point). The first number
Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is ("major version") indicates the HTTP messaging syntax, whereas the
lower than HTTP/12.3. Leading zeros MUST be ignored by recipients second number ("minor version") indicates the highest minor version
and MUST NOT be sent. to which the sender is at least conditionally compliant and able to
understand for future communication. The minor version advertises
the sender's communication capabilities even when the sender is only
using a backwards-compatible subset of the protocol, thereby letting
the recipient know that more advanced features can be used in
response (by servers) or in future requests (by clients).
An application that sends a request or response message that includes When comparing HTTP versions, the numbers MUST be compared
HTTP-Version of "HTTP/1.1" MUST be at least conditionally compliant numerically rather than lexically. For example, HTTP/2.4 is a lower
with this specification. Applications that are at least version than HTTP/2.13, which in turn is lower than HTTP/12.3.
conditionally compliant with this specification SHOULD use an HTTP- Leading zeros MUST be ignored by recipients and MUST NOT be sent.
Version of "HTTP/1.1" in their messages, and MUST do so for any
message that is not compatible with HTTP/1.0. For more details on
when to send specific HTTP-Version values, see [RFC2145].
The HTTP version of an application is the highest HTTP version for When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945]
which the application is at least conditionally compliant. or a recipient whose version is unknown, the HTTP/1.1 message is
constructed such that it can be interpreted as a valid HTTP/1.0
message if all of the newer features are ignored. This specification
places recipient-version requirements on some new features so that a
compliant sender will only use compatible features until it has
determined, through configuration or the receipt of a message, that
the recipient supports HTTP/1.1.
Proxy and gateway applications need to be careful when forwarding The interpretation of an HTTP header field does not change between
messages in protocol versions different from that of the application. minor versions of the same major version, though the default behavior
Since the protocol version indicates the protocol capability of the of a recipient in the absence of such a field can change. Unless
sender, a proxy/gateway MUST NOT send a message with a version specified otherwise, header fields defined in HTTP/1.1 are defined
indicator which is greater than its actual version. If a higher for all versions of HTTP/1.x. In particular, the Host and Connection
version request is received, the proxy/gateway MUST either downgrade header fields ought to be implemented by all HTTP/1.x implementations
the request version, or respond with an error, or switch to tunnel whether or not they advertise compliance with HTTP/1.1.
behavior.
Due to interoperability problems with HTTP/1.0 proxies discovered New header fields can be defined such that, when they are understood
since the publication of [RFC2068], caching proxies MUST, gateways by a recipient, they might override or enhance the interpretation of
MAY, and tunnels MUST NOT upgrade the request to the highest version previously defined header fields. When an implementation receives an
they support. The proxy/gateway's response to that request MUST be unrecognized header field, the recipient MUST ignore that header
in the same major version as the request. field for local processing regardless of the message's HTTP version.
An unrecognized header field received by a proxy MUST be forwarded
downstream unless the header field's field-name is listed in the
message's Connection header-field (see Section 9.1). These
requirements allow HTTP's functionality to be enhanced without
requiring prior update of all compliant intermediaries.
Note: Converting between versions of HTTP might involve Intermediaries that process HTTP messages (i.e., all intermediaries
modification of header fields required or forbidden by the other than those acting as a tunnel) MUST send their own HTTP-Version
versions involved. in forwarded messages. In other words, they MUST NOT blindly forward
the first line of an HTTP message without ensuring that the protocol
version matches what the intermediary understands, and is at least
conditionally compliant to, for both the receiving and sending of
messages. Forwarding an HTTP message without rewriting the HTTP-
Version might result in communication errors when downstream
recipients use the message sender's version to determine what
features are safe to use for later communication with that sender.
An HTTP client SHOULD send a request version equal to the highest
version for which the client is at least conditionally compliant and
whose major version is no higher than the highest version supported
by the server, if this is known. An HTTP client MUST NOT send a
version for which it is not at least conditionally compliant.
An HTTP client MAY send a lower request version if it is known that
the server incorrectly implements the HTTP specification, but only
after the client has attempted at least one normal request and
determined from the response status or header fields (e.g., Server)
that the server improperly handles higher request versions.
An HTTP server SHOULD send a response version equal to the highest
version for which the server is at least conditionally compliant and
whose major version is less than or equal to the one received in the
request. An HTTP server MUST NOT send a version for which it is not
at least conditionally compliant. A server MAY send a 505 (HTTP
Version Not Supported) response if it cannot send a response using
the major version used in the client's request.
An HTTP server MAY send an HTTP/1.0 response to an HTTP/1.0 request
if it is known or suspected that the client incorrectly implements
the HTTP specification and is incapable of correctly processing later
version responses, such as when a client fails to parse the version
number correctly or when an intermediary is known to blindly forward
the HTTP-Version even when it doesn't comply with the given minor
version of the protocol. Such protocol downgrades SHOULD NOT be
performed unless triggered by specific client attributes, such as
when one or more of the request header fields (e.g., User-Agent)
uniquely match the values sent by a client known to be in error.
The intention of HTTP's versioning design is that the major number
will only be incremented if an incompatible message syntax is
introduced, and that the minor number will only be incremented when
changes made to the protocol have the effect of adding to the message
semantics or implying additional capabilities of the sender.
However, the minor version was not incremented for the changes
introduced between [RFC2068] and [RFC2616], and this revision is
specifically avoiding any such changes to the protocol.
2.6. Uniform Resource Identifiers 2.6. 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. URI references are used
to target requests, indicate redirects, and define relationships. to target requests, indicate redirects, and define relationships.
HTTP does not limit what a resource might be; it merely defines an HTTP does not limit what a resource might be; it merely defines an
interface that can be used to interact with a resource via HTTP. 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 More information on the scope of URIs and resources can be found in
[RFC3986]. [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 [RFC3986]. In "path-absolute", "query", and "authority" from the URI generic syntax
addition, we define a partial-URI rule for protocol elements that [RFC3986]. In addition, we define a partial-URI rule for protocol
allow a relative URI without 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>
uri-host = <host, defined in [RFC3986], Section 3.2.2> uri-host = <host, defined in [RFC3986], Section 3.2.2>
skipping to change at page 16, line 30 skipping to change at page 18, line 4
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>
uri-host = <host, defined in [RFC3986], Section 3.2.2> uri-host = <host, defined in [RFC3986], Section 3.2.2>
partial-URI = relative-part [ "?" query ] partial-URI = relative-part [ "?" query ]
Each protocol element in HTTP that allows a URI reference will Each protocol element in HTTP that allows a URI reference will
indicate in its ABNF production whether the element allows only a URI indicate in its ABNF production whether the element allows any form
in absolute form (absolute-URI), any relative reference (relative- of reference (URI-reference), only a URI in absolute form (absolute-
ref), or some other subset of the URI-reference grammar. Unless URI), only the path and optional query components, or some
otherwise indicated, URI references are parsed relative to the combination of the above. Unless otherwise indicated, URI references
request target (the default base URI for both the request and its are parsed relative to the effective request URI, which defines the
corresponding response). default base URI for references in both the request and its
corresponding response.
2.6.1. http URI scheme 2.6.1. 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. The HTTP server is identified via TCP connections on a given port.
the generic syntax's authority component, which includes a host
identifier and optional TCP port, and the remainder of the URI is
considered to be identifying data corresponding to a resource for
which that server might provide an HTTP interface.
http-URI = "http:" "//" authority path-abempty [ "?" query ] http-URI = "http:" "//" authority path-abempty [ "?" query ]
The host identifier within an authority component is defined in The HTTP origin server is identified by the generic syntax's
[RFC3986], Section 3.2.2. If host is provided as an IP literal or authority component, which includes a host identifier and optional
IPv4 address, then the HTTP server is any listener on the indicated TCP port ([RFC3986], Section 3.2.2). The remainder of the URI,
TCP port at that IP address. If host is a registered name, then that consisting of both the hierarchical path component and optional query
name is considered an indirect identifier and the recipient might use component, serves as an identifier for a potential resource within
a name resolution service, such as DNS, to find the address of a that origin server's name space.
listener for that host. The host MUST NOT be empty; if an "http" URI
is received with an empty host, then it MUST be rejected as invalid. If the host identifier is provided as an IP literal or IPv4 address,
If the port subcomponent is empty or not given, then TCP port 80 is then the origin server is any listener on the indicated TCP port at
that IP address. If host is a registered name, then that name is
considered an indirect identifier and the recipient might use a name
resolution service, such as DNS, to find the address of a listener
for that host. The host MUST NOT be empty; if an "http" URI is
received with an empty host, then it MUST be rejected as invalid. If
the port subcomponent is empty or not given, then TCP port 80 is
assumed (the default reserved port for WWW services). assumed (the default reserved port for WWW services).
Regardless of the form of host identifier, access to that host is not Regardless of the form of host identifier, access to that host is not
implied by the mere presence of its name or address. The host might implied by the mere presence of its name or address. The host might
or might not exist and, even when it does exist, might or might not or might not exist and, even when it does exist, might or might not
be running an HTTP server or listening to the indicated port. The be running an HTTP server or listening to the indicated port. The
"http" URI scheme makes use of the delegated nature of Internet names "http" URI scheme makes use of the delegated nature of Internet names
and addresses to establish a naming authority (whatever entity has and addresses to establish a naming authority (whatever entity has
the ability to place an HTTP server at that Internet name or address) the ability to place an HTTP server at that Internet name or address)
and allows that authority to determine which names are valid and how and allows that authority to determine which names are valid and how
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HTTP response message, as described in Section 5, then that response HTTP response message, as described in Section 5, then that response
is considered an authoritative answer to the client's request. is considered an authoritative answer to the client's 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 servers that require an SSL/TLS transport
layer on a connection. Other protocols might also be used to provide layer on a connection. Other protocols might also be used to provide
access to "http" identified resources --- it is only the access to "http" identified resources -- it is only the authoritative
authoritative interface used for mapping the namespace that is interface used for mapping the namespace that is specific to TCP.
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. The userinfo subcomponent authentication information in the URI. Some implementations make use
(and its "@" delimiter) MUST NOT be used in an "http" URI. URI of the userinfo component for internal configuration of
reference recipients SHOULD parse for the existence of userinfo and authentication information, such as within command invocation
treat its presence as an error, likely indicating that the deprecated options, configuration files, or bookmark lists, even though such
subcomponent is being used to obscure the authority for the sake of usage might expose a user identifier or password. Senders MUST NOT
phishing attacks. include a userinfo subcomponent (and its "@" delimiter) when
transmitting an "http" URI in a message. Recipients of HTTP messages
that contain a URI reference SHOULD parse for the existence of
userinfo and treat its presence as an error, likely indicating that
the deprecated subcomponent is being used to obscure the authority
for the sake of phishing attacks.
2.6.2. https URI scheme 2.6.2. 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 for
SSL/TLS-secured connections on a given TCP port. SSL/TLS-secured connections on a given TCP port.
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 for privacy 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 are ineligible for shared caching. Their are never "public" and thus MUST NOT be reused for shared caching.
default is "private" and might be further constrained via use of the They can, however, be reused in a private cache if the message is
Cache-Control header field. cacheable by default in HTTP or specifically indicated as such by the
Cache-Control header field (Section 3.2 of [Part6]).
Resources made available via the "https" scheme have no shared Resources made available via the "https" scheme have no shared
identity with the "http" scheme even if their resource identifiers identity with the "http" scheme even if their resource identifiers
only differ by the single "s" in the scheme name. They are different indicate the same authority (the same host listening to the same TCP
services governed by different authorities. However, some extensions port). They are distinct name spaces and are considered to be
to HTTP that apply to entire host domains, such as the Cookie distinct origin servers. However, an extension to HTTP that is
protocol, do allow one service to effect communication with the other defined to apply to entire host domains, such as the Cookie protocol
services based on host domain matching. [draft-ietf-httpstate-cookie], can allow information set by one
service to impact communication with other services within a matching
group of host 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].
2.6.3. http and https URI Normalization and Comparison 2.6.3. 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.
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than those in the "reserved" set are equivalent to their percent- than those in the "reserved" set are equivalent to their percent-
encoded octets (see [RFC3986], Section 2.1): the normal form is to encoded octets (see [RFC3986], Section 2.1): the normal form is to
not encode them. not encode them.
For example, the following three URIs are equivalent: For example, the following three URIs are equivalent:
http://example.com:80/~smith/home.html http://example.com:80/~smith/home.html
http://EXAMPLE.com/%7Esmith/home.html http://EXAMPLE.com/%7Esmith/home.html
http://EXAMPLE.com:/%7esmith/home.html http://EXAMPLE.com:/%7esmith/home.html
[[TODO-not-here: This paragraph does not belong here. --roy]] If 3. Message Format
path-abempty is the empty string (i.e., there is no slash "/" path
separator following the authority), then the "http" URI MUST be given
as "/" when used as a request-target (Section 4.1.2). If a proxy
receives a host name which is not a fully qualified domain name, it
MAY add its domain to the host name it received. If a proxy receives
a fully qualified domain name, the proxy MUST NOT change the host
name.
3. HTTP Message
All HTTP/1.1 messages consist of a start-line followed by a sequence All HTTP/1.1 messages consist of a start-line followed by a sequence
of characters in a format similar to the Internet Message Format of octets in a format similar to the Internet Message Format
[RFC5322]: zero or more header fields (collectively referred to as [RFC5322]: zero or more header fields (collectively referred to as
the "headers" or the "header section"), an empty line indicating the the "headers" or the "header section"), an empty line indicating the
end of the header section, and an optional message-body. end of the header section, and an optional message-body.
An HTTP message can either be a request from client to server or a An HTTP message can either be a request from client to server or a
response from server to client. Syntactically, the two types of response from server to client. Syntactically, the two types of
message differ only in the start-line, which is either a Request-Line message differ only in the start-line, which is either a Request-Line
(for requests) or a Status-Line (for responses), and in the algorithm (for requests) or a Status-Line (for responses), and in the algorithm
for determining the length of the message-body (Section 3.3). In for determining the length of the message-body (Section 3.3). In
theory, a client could receive requests and a server could receive theory, a client could receive requests and a server could receive
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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.
HTTP-message = start-line HTTP-message = start-line
*( header-field CRLF ) *( header-field CRLF )
CRLF CRLF
[ message-body ] [ message-body ]
start-line = Request-Line / Status-Line start-line = Request-Line / Status-Line
Whitespace (WSP) MUST NOT be sent between the start-line and the Implementations MUST NOT send whitespace between the start-line and
first header field. The presence of whitespace might be an attempt the first header field. The presence of such whitespace in a request
to trick a noncompliant implementation of HTTP into ignoring that might be an attempt to trick a server into ignoring that field or
field or processing the next line as a new request, either of which processing the line after it as a new request, either of which might
might result in security issues when implementations within the result in a security vulnerability if other implementations within
request chain interpret the same message differently. HTTP/1.1 the request chain interpret the same message differently. Likewise,
servers MUST reject such a message with a 400 (Bad Request) response. the presence of such whitespace in a response might be ignored by
some clients or cause others to cease parsing.
3.1. Message Parsing Robustness 3.1. Message Parsing Robustness
In the interest of robustness, servers SHOULD ignore at least one In the interest of robustness, servers SHOULD ignore at least one
empty line received where a Request-Line is expected. In other empty line received where a Request-Line is expected. In other
words, if the server is reading the protocol stream at the beginning words, if the server is reading the protocol stream at the beginning
of a message and receives a CRLF first, it SHOULD ignore the CRLF. of a message and receives a CRLF first, it SHOULD ignore the CRLF.
Some old HTTP/1.0 client implementations generate an extra CRLF after Some old HTTP/1.0 client implementations send an extra CRLF after a
a POST request as a lame workaround for some early server POST request as a lame workaround for some early server applications
applications that failed to read message-body content that was not that failed to read message-body content that was not terminated by a
terminated by a line-ending. An HTTP/1.1 client MUST NOT preface or line-ending. An HTTP/1.1 client MUST NOT preface or follow a request
follow a request with an extra CRLF. If terminating the request with an extra CRLF. If terminating the request message-body with a
message-body with a line-ending is desired, then the client MUST line-ending is desired, then the client MUST include the terminating
include the terminating CRLF octets as part of the message-body CRLF octets as part of the message-body length.
length.
When a server listening only for HTTP request messages, or processing
what appears from the start-line to be an HTTP request message,
receives a sequence of octets that does not match the HTTP-message
grammar aside from the robustness exceptions listed above, the server
MUST respond with an HTTP/1.1 400 (Bad Request) response.
The normal procedure for parsing an HTTP message is to read the The normal procedure for parsing an HTTP message is to read the
start-line into a structure, read each header field into a hash table start-line into a structure, read each header field into a hash table
by field name until the empty line, and then use the parsed data to by field name until the empty line, and then use the parsed data to
determine if a message-body is expected. If a message-body has been determine if a message-body is expected. If a message-body has been
indicated, then it is read as a stream until an amount of octets indicated, then it is read as a stream until an amount of octets
equal to the message-body length is read or the connection is closed. equal to the message-body length is read or the connection is closed.
Care must be taken to parse an HTTP message as a sequence of octets Care must be taken to parse an HTTP message as a sequence of octets
in an encoding that is a superset of US-ASCII. Attempting to parse in an encoding that is a superset of US-ASCII. Attempting to parse
HTTP as a stream of Unicode characters in a character encoding like HTTP as a stream of Unicode characters in a character encoding like
UTF-16 might introduce security flaws due to the differing ways that UTF-16 might introduce security flaws due to the differing ways that
such parsers interpret invalid characters. such parsers interpret invalid characters.
HTTP allows the set of defined header fields to be extended without HTTP allows the set of defined header fields to be extended without
changing the protocol version (see Section 10.1). However, such changing the protocol version (see Section 10.1). Unrecognized
fields might not be recognized by a downstream recipient and might be header fields MUST be forwarded by a proxy unless the proxy is
stripped by non-transparent intermediaries. Unrecognized header specifically configured to block or otherwise transform such fields.
fields MUST be forwarded by transparent proxies and SHOULD be ignored Unrecognized header fields SHOULD be ignored by other recipients.
by a recipient.
3.2. Header Fields 3.2. Header Fields
Each HTTP header field consists of a case-insensitive field name Each HTTP header field consists of a case-insensitive field name
followed by a colon (":"), optional whitespace, and the field value. followed by a colon (":"), optional whitespace, and the field value.
header-field = field-name ":" OWS [ field-value ] OWS header-field = field-name ":" OWS [ field-value ] OWS
field-name = token field-name = token
field-value = *( field-content / OWS ) field-value = *( field-content / OWS )
field-content = *( WSP / VCHAR / obs-text ) field-content = *( WSP / VCHAR / obs-text )
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Each HTTP header field consists of a case-insensitive field name Each HTTP header field consists of a case-insensitive field name
followed by a colon (":"), optional whitespace, and the field value. followed by a colon (":"), optional whitespace, and the field value.
header-field = field-name ":" OWS [ field-value ] OWS header-field = field-name ":" OWS [ field-value ] OWS
field-name = token field-name = token
field-value = *( field-content / OWS ) field-value = *( field-content / OWS )
field-content = *( WSP / VCHAR / obs-text ) field-content = *( WSP / VCHAR / obs-text )
No whitespace is allowed between the header field name and colon. No whitespace is allowed between the header field name and colon.
For security reasons, any request message received containing such For security reasons, any request message received containing such
whitespace MUST be rejected with a response code of 400 (Bad whitespace MUST be rejected with a response code of 400 (Bad
Request). A proxy MUST remove any such whitespace from a response Request). A proxy MUST remove any such whitespace from a response
message before forwarding the message downstream. message before forwarding the message downstream.
A field value MAY be preceded by optional whitespace (OWS); a single A field value MAY be preceded by optional whitespace (OWS); a single
SP is preferred. The field value does not include any leading or SP is preferred. The field value does not include any leading or
trailing white space: OWS occurring before the first non-whitespace trailing white space: OWS occurring before the first non-whitespace
character of the field value or after the last non-whitespace octet of the field value or after the last non-whitespace octet of
character of the field value is ignored and SHOULD be removed before the field value is ignored and SHOULD be removed before further
further processing (as this does not change the meaning of the header processing (as this does not change the meaning of the header field).
field).
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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message unless the entire field value for that header field is message unless the entire field value for that header field is
defined as a comma-separated list [i.e., #(values)]. Multiple header defined as a comma-separated list [i.e., #(values)]. Multiple header
fields with the same field name can be combined into one "field-name: fields with the same field name can be combined into one "field-name:
field-value" pair, without changing the semantics of the message, by field-value" pair, without changing the semantics of the message, by
appending each subsequent field value to the combined field value in appending each subsequent field value to the combined field value in
order, separated by a comma. The order in which header fields with order, separated by a comma. The order in which header fields with
the same field name are received is therefore significant to the the same field name are received is therefore significant to the
interpretation of the combined field value; a proxy MUST NOT change interpretation of the combined field value; a proxy MUST NOT change
the order of these field values when forwarding a message. the order of these field values when forwarding a message.
Note: The "Set-Cookie" header field as implemented in practice (as Note: The "Set-Cookie" header field as implemented in practice can
opposed to how it is specified in [RFC2109]) can occur multiple occur multiple times, but does not use the list syntax, and thus
times, but does not use the list syntax, and thus cannot be cannot be combined into a single line
combined into a single line. (See Appendix A.2.3 of [Kri2001] for ([draft-ietf-httpstate-cookie]). (See Appendix A.2.3 of [Kri2001]
details.) Also note that the Set-Cookie2 header field specified for details.) Also note that the Set-Cookie2 header field
in [RFC2965] does not share this problem. specified in [RFC2965] does not share this problem.
Historically, HTTP header field values could be extended over Historically, HTTP header field values could be extended over
multiple lines by preceding each extra line with at least one space multiple lines by preceding each extra line with at least one space
or horizontal tab character (line folding). This specification or horizontal tab octet (line folding). This specification
deprecates such line folding except within the message/http media deprecates such line folding except within the message/http media
type (Section 10.3.1). HTTP/1.1 senders MUST NOT produce messages type (Section 10.3.1). HTTP/1.1 senders MUST NOT produce messages
that include line folding (i.e., that contain any field-content that that include line folding (i.e., that contain any field-content that
matches the obs-fold rule) unless the message is intended for matches the obs-fold rule) unless the message is intended for
packaging within the message/http media type. HTTP/1.1 recipients packaging within the message/http media type. HTTP/1.1 recipients
SHOULD accept line folding and replace any embedded obs-fold SHOULD accept line folding and replace any embedded obs-fold
whitespace with a single SP prior to interpreting the field value or whitespace with a single SP prior to interpreting the field value or
forwarding the message downstream. forwarding the message downstream.
Historically, HTTP has allowed field content with text in the ISO- Historically, HTTP has allowed field content with text in the ISO-
8859-1 [ISO-8859-1] character encoding and supported other character 8859-1 [ISO-8859-1] character encoding and supported other character
sets only through use of [RFC2047] encoding. In practice, most HTTP sets only through use of [RFC2047] encoding. In practice, most HTTP
header field values use only a subset of the US-ASCII character header field values use only a subset of the US-ASCII character
encoding [USASCII]. Newly defined header fields SHOULD limit their encoding [USASCII]. Newly defined header fields SHOULD limit their
field values to US-ASCII characters. Recipients SHOULD treat other field values to US-ASCII octets. Recipients SHOULD treat other (obs-
(obs-text) octets in field content as opaque data. text) octets in field content as opaque data.
Comments can be included in some HTTP header fields by surrounding Comments can be included in some HTTP header fields by surrounding
the comment text with parentheses. Comments are only allowed in the comment text with parentheses. Comments are only allowed in
fields containing "comment" as part of their field value definition. fields containing "comment" as part of their field value definition.
comment = "(" *( ctext / quoted-cpair / comment ) ")" comment = "(" *( ctext / quoted-cpair / comment ) ")"
ctext = OWS / %x21-27 / %x2A-5B / %x5D-7E / obs-text ctext = OWS / %x21-27 / %x2A-5B / %x5D-7E / obs-text
; OWS / <VCHAR except "(", ")", and "\"> / obs-text ; OWS / <VCHAR except "(", ")", and "\"> / obs-text
The backslash character ("\") can be used as a single-character The backslash octet ("\") can be used as a single-octet quoting
quoting mechanism within comment constructs: mechanism within comment constructs:
quoted-cpair = "\" ( WSP / VCHAR / obs-text ) quoted-cpair = "\" ( WSP / VCHAR / obs-text )
Producers SHOULD NOT escape characters that do not require escaping Senders SHOULD NOT escape octets that do not require escaping (i.e.,
(i.e., other than the backslash character "\" and the parentheses "(" other than the backslash octet "\" and the parentheses "(" and ")").
and ")").
3.3. Message Body 3.3. Message Body
The message-body (if any) of an HTTP message is used to carry the The message-body (if any) of an HTTP message is used to carry the
payload body associated with the request or response. payload body associated with the request or response.
message-body = *OCTET message-body = *OCTET
The message-body differs from the payload body only when a transfer- The message-body differs from the payload body only when a transfer-
coding has been applied, as indicated by the Transfer-Encoding header coding has been applied, as indicated by the Transfer-Encoding header
field (Section 9.7). When one or more transfer-codings are applied field (Section 9.7). If more than one Transfer-Encoding header field
to a payload in order to form the message-body, the Transfer-Encoding is present in a message, the multiple field-values MUST be combined
header field MUST contain the list of transfer-codings applied. into one field-value, according to the algorithm defined in
Transfer-Encoding is a property of the message, not of the payload, Section 3.2, before determining the message-body length.
and thus MAY be added or removed by any implementation along the
request/response chain under the constraints found in Section 6.2. When one or more transfer-codings are applied to a payload in order
to form the message-body, the Transfer-Encoding header field MUST
contain the list of transfer-codings applied. Transfer-Encoding is a
property of the message, not of the payload, and thus MAY be added or
removed by any implementation along the request/response chain under
the constraints found in Section 6.2.
If a message is received that has multiple Content-Length header
fields (Section 9.2) with field-values consisting of the same decimal
value, or a single Content-Length header field with a field value
containing a list of identical decimal values (e.g., "Content-Length:
42, 42"), indicating that duplicate Content-Length header fields have
been generated or combined by an upstream message processor, then the
recipient MUST replace the duplicated fields or field-values with a
single valid Content-Length field containing that decimal value prior
to determining the message-body length.
The rules for when a message-body is allowed in a message differ for The rules for when a message-body is allowed in a message differ for
requests and responses. requests and responses.
The presence of a message-body in a request is signaled by the The presence of a message-body in a request is signaled by the
inclusion of a Content-Length or Transfer-Encoding header field in inclusion of a Content-Length or Transfer-Encoding header field in
the request's header fields, even if the request method does not the request's header fields, even if the request method does not
define any use for a message-body. This allows the request message define any use for a message-body. This allows the request message
framing algorithm to be independent of method semantics. framing algorithm to be independent of method semantics.
For response messages, whether or not a message-body is included with For response messages, whether or not a message-body is included with
a message is dependent on both the request method and the response a message is dependent on both the request method and the response
status code (Section 5.1.1). Responses to the HEAD request method status code (Section 5.1.1). Responses to the HEAD request method
never include a message-body because the associated response header never include a message-body because the associated response header
fields (e.g., Transfer-Encoding, Content-Length, etc.) only indicate fields (e.g., Transfer-Encoding, Content-Length, etc.) only indicate
what their values would have been if the method had been GET. All what their values would have been if the request method had been GET.
1xx (Informational), 204 (No Content), and 304 (Not Modified) All 1xx (Informational), 204 (No Content), and 304 (Not Modified)
responses MUST NOT include a message-body. All other responses do responses MUST NOT include a message-body. All other responses do
include a message-body, although the body MAY be of zero length. include a message-body, although the body MAY be of zero length.
The length of the message-body is determined by one of the following The length of the message-body is determined by one of the following
(in order of precedence): (in order of precedence):
1. Any response to a HEAD request and any response with a status 1. Any response to a HEAD request and any response with a status
code of 100-199, 204, or 304 is always terminated by the first code of 100-199, 204, or 304 is always terminated by the first
empty line after the header fields, regardless of the header empty line after the header fields, regardless of the header
fields present in the message, and thus cannot contain a message- fields present in the message, and thus cannot contain a message-
body. body.
2. If a Transfer-Encoding header field (Section 9.7) is present and 2. If a Transfer-Encoding header field is present and the "chunked"
the "chunked" transfer-coding (Section 6.2) is the final transfer-coding (Section 6.2) is the final encoding, the message-
encoding, the message-body length is determined by reading and body length is determined by reading and decoding the chunked
decoding the chunked data until the transfer-coding indicates the data until the transfer-coding indicates the data is complete.
data is complete.
If a Transfer-Encoding header field is present in a response and If a Transfer-Encoding header field is present in a response and
the "chunked" transfer-coding is not the final encoding, the the "chunked" transfer-coding is not the final encoding, the
message-body length is determined by reading the connection until message-body length is determined by reading the connection until
it is closed by the server. If a Transfer-Encoding header field it is closed by the server. If a Transfer-Encoding header field
is present in a request and the "chunked" transfer-coding is not is present in a request and the "chunked" transfer-coding is not
the final encoding, the message-body length cannot be determined the final encoding, the message-body length cannot be determined
reliably; the server MUST respond with the 400 (Bad Request) reliably; the server MUST respond with the 400 (Bad Request)
status code and then close the connection. status code and then close the connection.
skipping to change at page 24, line 7 skipping to change at page 25, line 49
field and a Content-Length header field, the Transfer-Encoding field and a Content-Length header field, the Transfer-Encoding
overrides the Content-Length. Such a message might indicate an overrides the Content-Length. Such a message might indicate an
attempt to perform request or response smuggling (bypass of attempt to perform request or response smuggling (bypass of
security-related checks on message routing or content) and thus security-related checks on message routing or content) and thus
ought to be handled as an error. The provided Content-Length ought to be handled as an error. The provided Content-Length
MUST be removed, prior to forwarding the message downstream, or MUST be removed, prior to forwarding the message downstream, or
replaced with the real message-body length after the transfer- replaced with the real message-body length after the transfer-
coding is decoded. coding is decoded.
3. If a message is received without Transfer-Encoding and with 3. If a message is received without Transfer-Encoding and with
either multiple Content-Length header fields or a single Content- either multiple Content-Length header fields having differing
Length header field with an invalid value, then the message field-values or a single Content-Length header field having an
framing is invalid and MUST be treated as an error to prevent invalid value, then the message framing is invalid and MUST be
request or response smuggling. If this is a request message, the treated as an error to prevent request or response smuggling. If
server MUST respond with a 400 (Bad Request) status code and then this is a request message, the server MUST respond with a 400
close the connection. If this is a response message received by (Bad Request) status code and then close the connection. If this
a proxy or gateway, the proxy or gateway MUST discard the is a response message received by a proxy, the proxy MUST discard
received response, send a 502 (Bad Gateway) status code as its the received response, send a 502 (Bad Gateway) status code as
downstream response, and then close the connection. If this is a its downstream response, and then close the connection. If this
response message received by a user-agent, it SHOULD be treated is a response message received by a user-agent, it MUST be
as an error by discarding the message and closing the connection. treated as an error by discarding the message and closing the
connection.
4. If a valid Content-Length header field (Section 9.2) is present 4. If a valid Content-Length header field is present without
without Transfer-Encoding, its decimal value defines the message- Transfer-Encoding, its decimal value defines the message-body
body length in octets. If the actual number of octets sent in length in octets. If the actual number of octets sent in the
the message is less than the indicated Content-Length, the message is less than the indicated Content-Length, the recipient
recipient MUST consider the message to be incomplete and treat MUST consider the message to be incomplete and treat the
the connection as no longer usable. If the actual number of connection as no longer usable. If the actual number of octets
octets sent in the message is more than the indicated Content- sent in the message is more than the indicated Content-Length,
Length, the recipient MUST only process the message-body up to the recipient MUST only process the message-body up to the field
the field value's number of octets; the remainder of the message value's number of octets; the remainder of the message MUST
MUST either be discarded or treated as the next message in a either be discarded or treated as the next message in a pipeline.
pipeline. For the sake of robustness, a user-agent MAY attempt For the sake of robustness, a user-agent MAY attempt to detect
to detect and correct such an error in message framing if it is and correct such an error in message framing if it is parsing the
parsing the response to the last request on on a connection and response to the last request on on a connection and the
the connection has been closed by the server. connection has been closed by the server.
5. If this is a request message and none of the above are true, then 5. If this is a request message and none of the above are true, then
the message-body length is zero (no message-body is present). the message-body length is zero (no message-body is present).
6. Otherwise, this is a response message without a declared message- 6. 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-
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request. Pipelining multiple requests on a connection is described request. Pipelining multiple requests on a connection is described
in Section 7.1.2.2. in Section 7.1.2.2.
3.4. General Header Fields 3.4. General Header Fields
There are a few header fields which have general applicability for There are a few header fields which have general applicability for
both request and response messages, but which do not apply to the both request and response messages, but which do not apply to the
payload being transferred. These header fields apply only to the payload being transferred. These header fields apply only to the
message being transmitted. message being transmitted.
general-header = Cache-Control ; [Part6], Section 3.2 +-------------------+---------------+
/ Connection ; Section 9.1 | Header Field Name | Defined in... |
/ Date ; Section 9.3 +-------------------+---------------+
/ Pragma ; [Part6], Section 3.4 | Connection | Section 9.1 |
/ Trailer ; Section 9.6 | Date | Section 9.3 |
/ Transfer-Encoding ; Section 9.7 | Trailer | Section 9.6 |
/ Upgrade ; Section 9.8 | Transfer-Encoding | Section 9.7 |
/ Via ; Section 9.9 | Upgrade | Section 9.8 |
/ Warning ; [Part6], Section 3.6 | Via | Section 9.9 |
/ MIME-Version ; [Part3], Appendix A.1 +-------------------+---------------+
General-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or
experimental header fields might be given the semantics of general
header fields if all parties in the communication recognize them to
be general-header fields.
4. Request 4. Request
A request message from a client to a server includes, within the A request message from a client to a server begins with a Request-
first line of that message, the method to be applied to the resource, Line, followed by zero or more header fields, an empty line
the identifier of the resource, and the protocol version in use. signifying the end of the header block, and an optional message body.
Request = Request-Line ; Section 4.1 Request = Request-Line ; Section 4.1
*( header-field CRLF ) ; Section 3.2 *( header-field CRLF ) ; Section 3.2
CRLF CRLF
[ message-body ] ; Section 3.3 [ message-body ] ; Section 3.3
4.1. Request-Line 4.1. Request-Line
The Request-Line begins with a method token, followed by the request- The Request-Line begins with a method token, followed by a single
target and the protocol version, and ending with CRLF. The elements space (SP), the request-target, another single space (SP), the
are separated by SP characters. No CR or LF is allowed except in the protocol version, and ending with CRLF.
final CRLF sequence.
Request-Line = Method SP request-target SP HTTP-Version CRLF Request-Line = Method SP request-target SP HTTP-Version CRLF
4.1.1. Method 4.1.1. Method
The Method token indicates the method to be performed on the resource The Method token indicates the request method to be performed on the
identified by the request-target. The method is case-sensitive. target resource. The request method is case-sensitive.
Method = token Method = token
4.1.2. request-target 4.1.2. request-target
The request-target identifies the resource upon which to apply the The request-target identifies the target resource upon which to apply
request. the request. In most cases, the user agent is provided a URI
reference from which it determines an absolute URI for identifying
the target resource. When a request to the resource is initiated,
all or part of that URI is used to construct the HTTP request-target.
request-target = "*" request-target = "*"
/ absolute-URI / absolute-URI
/ ( path-absolute [ "?" query ] ) / ( path-absolute [ "?" query ] )
/ authority / authority
The four options for request-target are dependent on the nature of The four options for request-target are dependent on the nature of
the request. the request.
The asterisk "*" ("asterisk form") means that the request does not The asterisk "*" form of request-target, which MUST NOT be used with
apply to a particular resource, but to the server itself, and is only any request method other than OPTIONS, means that the request applies
allowed when the method used does not necessarily apply to a to the server as a whole (the listening process) rather than to a
resource. One example would be specific named resource at that server. For example,
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
The absolute-URI form is REQUIRED when the request is being made to a The "absolute-URI" form is REQUIRED when the request is being made to
proxy. The proxy is requested to forward the request or service it a proxy. The proxy is requested to either forward the request or
from a valid cache, and return the response. Note that the proxy MAY service it from a valid cache, and then return the response. Note
forward the request on to another proxy or directly to the server that the proxy MAY forward the request on to another proxy or
specified by the absolute-URI. In order to avoid request loops, a directly to the server specified by the absolute-URI. In order to
proxy MUST be able to recognize all of its server names, including avoid request loops, a proxy that forwards requests to other proxies
any aliases, local variations, and the numeric IP address. An MUST be able to recognize and exclude all of its own server names,
example Request-Line would be: including any aliases, local variations, and the numeric IP address.
An example Request-Line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
To allow for transition to absolute-URIs in all requests in future To allow for transition to absolute-URIs in all requests in future
versions of HTTP, all HTTP/1.1 servers MUST accept the absolute-URI versions of HTTP, all HTTP/1.1 servers MUST accept the absolute-URI
form in requests, even though HTTP/1.1 clients will only generate form in requests, even though HTTP/1.1 clients will only generate
them in requests to proxies. them in requests to proxies.
The authority form is only used by the CONNECT method (Section 7.9 of If a proxy receives a host name that is not a fully qualified domain
[Part2]). name, it MAY add its domain to the host name it received. If a proxy
receives a fully qualified domain name, the proxy MUST NOT change the
host name.
The most common form of request-target is that used to identify a The "authority form" is only used by the CONNECT request method
resource on an origin server or gateway ("path-absolute form"). In (Section 7.9 of [Part2]).
this case the absolute path of the URI MUST be transmitted (see
Section 2.6.1, path-absolute) as the request-target, and the network The most common form of request-target is that used when making a
location of the URI (authority) MUST be transmitted in a Host header request to an origin server ("origin form"). In this case, the
field. For example, a client wishing to retrieve the resource above absolute path and query components of the URI MUST be transmitted as
directly from the origin server would create a TCP connection to port the request-target, and the authority component MUST be transmitted
80 of the host "www.example.org" and send the lines: in a Host header field. For example, a client wishing to retrieve a
representation of the resource, as identified above, directly from
the origin server would open (or reuse) a TCP connection to port 80
of the host "www.example.org" and send the lines:
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org Host: www.example.org
followed by the remainder of the Request. Note that the absolute followed by the remainder of the Request. Note that the origin form
path cannot be empty; if none is present in the original URI, it MUST of request-target always starts with an absolute path; if the target
be given as "/" (the server root). resource's URI path is empty, then an absolute path of "/" MUST be
provided in the request-target.
If a proxy receives a request without any path in the request-target If a proxy receives an OPTIONS request with an absolute-URI form of
and the method specified is capable of supporting the asterisk form request-target in which the URI has an empty path and no query
of request-target, then the last proxy on the request chain MUST component, then the last proxy on the request chain MUST use a
forward the request with "*" as the final request-target. request-target of "*" when it forwards the request to the indicated
origin server.
For example, the request For example, the request
OPTIONS http://www.example.org:8001 HTTP/1.1 OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the proxy as would be forwarded by the final proxy as
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org:8001 Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org". after connecting to port 8001 of host "www.example.org".
The request-target is transmitted in the format specified in The request-target is transmitted in the format specified in
Section 2.6.1. If the request-target is percent-encoded ([RFC3986], Section 2.6.1. If the request-target is percent-encoded ([RFC3986],
Section 2.1), the origin server MUST decode the request-target in Section 2.1), the origin server MUST decode the request-target in
order to properly interpret the request. Servers SHOULD respond to order to properly interpret the request. Servers SHOULD respond to
invalid request-targets with an appropriate status code. invalid request-targets with an appropriate status code.
A transparent proxy MUST NOT rewrite the "path-absolute" part of the A non-transforming proxy MUST NOT rewrite the "path-absolute" part of
received request-target when forwarding it to the next inbound the received request-target when forwarding it to the next inbound
server, except as noted above to replace a null path-absolute with server, except as noted above to replace a null path-absolute with
"/" or "*". "/" or "*".
Note: The "no rewrite" rule prevents the proxy from changing the Note: The "no rewrite" rule prevents the proxy from changing the
meaning of the request when the origin server is improperly using meaning of the request when the origin server is improperly using
a non-reserved URI character for a reserved purpose. Implementors a non-reserved URI character for a reserved purpose. Implementors
need to be aware that some pre-HTTP/1.1 proxies have been known to need to be aware that some pre-HTTP/1.1 proxies have been known to
rewrite the request-target. rewrite the request-target.
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-
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URI is the request-target. URI is the request-target.
If the request-target uses the path-absolute form or the asterisk If the request-target uses the path-absolute form or the asterisk
form, and the Host header field is present, then the effective form, and the Host header field is present, then the effective
request URI is constructed by concatenating request URI is constructed by concatenating
o the scheme name: "http" if the request was received over an o the scheme name: "http" if the request was received over an
insecure TCP connection, or "https" when received over a SSL/ insecure TCP connection, or "https" when received over a SSL/
TLS-secured TCP connection, TLS-secured TCP connection,
o the character sequence "://", o the octet sequence "://",
o the authority component, as specified in the Host header field o the authority component, as specified in the Host header field
(Section 9.4), and (Section 9.4), and
o the request-target obtained from the Request-Line, unless the o the request-target obtained from the Request-Line, unless the
request-target is just the asterisk "*". request-target is just the asterisk "*".
If the request-target uses the path-absolute form or the asterisk If the request-target uses the path-absolute form or the asterisk
form, and the Host header field is not present, then the effective form, and the Host header field is not present, then the effective
request URI is undefined. request URI is undefined.
skipping to change at page 31, line 18 skipping to change at page 33, line 8
with an HTTP response message. with an HTTP response message.
Response = Status-Line ; Section 5.1 Response = Status-Line ; Section 5.1
*( header-field CRLF ) ; Section 3.2 *( header-field CRLF ) ; Section 3.2
CRLF CRLF
[ message-body ] ; Section 3.3 [ message-body ] ; Section 3.3
5.1. Status-Line 5.1. 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 followed by a numeric status code and its of the protocol version, a space (SP), the status code, another
associated textual phrase, with each element separated by SP space, a possibly-empty textual phrase describing the status code,
characters. No CR or LF is allowed except in the final CRLF and ending with CRLF.
sequence.
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
5.1.1. Status Code and Reason Phrase 5.1.1. Status Code and Reason Phrase
The Status-Code element is a 3-digit integer result code of the The Status-Code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. These codes are fully attempt to understand and satisfy the request. These codes are fully
defined in Section 8 of [Part2]. The Reason Phrase exists for the defined in Section 8 of [Part2]. The Reason Phrase exists for the
sole purpose of providing a textual description associated with the sole purpose of providing a textual description associated with the
numeric status code, out of deference to earlier Internet application numeric status code, out of deference to earlier Internet application
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product = token ["/" product-version] product = token ["/" product-version]
product-version = token product-version = token
Examples: Examples:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3 User-Agent: CERN-LineMode/2.15 libwww/2.17b3
Server: Apache/0.8.4 Server: Apache/0.8.4
Product tokens SHOULD be short and to the point. They MUST NOT be Product tokens SHOULD be short and to the point. They MUST NOT be
used for advertising or other non-essential information. Although used for advertising or other non-essential information. Although
any token character MAY appear in a product-version, this token any token octet MAY appear in a product-version, this token SHOULD
SHOULD only be used for a version identifier (i.e., successive only be used for a version identifier (i.e., successive versions of
versions of the same product SHOULD only differ in the product- the same product SHOULD only differ in the product-version portion of
version portion of the product value). the product value).
6.4. Quality Values 6.4. Quality Values
Both transfer codings (TE request header field, Section 9.5) and Both transfer codings (TE request header field, Section 9.5) and
content negotiation (Section 5 of [Part3]) use short "floating point" content negotiation (Section 5 of [Part3]) use short "floating point"
numbers to indicate the relative importance ("weight") of various numbers to indicate the relative importance ("weight") of various
negotiable parameters. A weight is normalized to a real number in negotiable parameters. A weight is normalized to a real number in
the range 0 through 1, where 0 is the minimum and 1 the maximum the range 0 through 1, where 0 is the minimum and 1 the maximum
value. If a parameter has a quality value of 0, then content with value. If a parameter has a quality value of 0, then content with
this parameter is "not acceptable" for the client. HTTP/1.1 this parameter is "not acceptable" for the client. HTTP/1.1
skipping to change at page 40, line 9 skipping to change at page 42, line 9
Note: "Quality values" is a misnomer, since these values merely Note: "Quality values" is a misnomer, since these values merely
represent relative degradation in desired quality. represent relative degradation in desired quality.
7. Connections 7. Connections
7.1. Persistent Connections 7.1. Persistent Connections
7.1.1. Purpose 7.1.1. Purpose
Prior to persistent connections, a separate TCP connection was Prior to persistent connections, a separate TCP connection was
established to fetch each URL, increasing the load on HTTP servers established for each request, increasing the load on HTTP servers and
and causing congestion on the Internet. The use of inline images and causing congestion on the Internet. The use of inline images and
other associated data often requires a client to make multiple other associated data often requires a client to make multiple
requests of the same server in a short amount of time. Analysis of requests of the same server in a short amount of time. Analysis of
these performance problems and results from a prototype these performance problems and results from a prototype
implementation are available [Pad1995] [Spe]. Implementation implementation are available [Pad1995] [Spe]. Implementation
experience and measurements of actual HTTP/1.1 implementations show experience and measurements of actual HTTP/1.1 implementations show
good results [Nie1997]. Alternatives have also been explored, for good results [Nie1997]. Alternatives have also been explored, for
example, T/TCP [Tou1998]. example, T/TCP [Tou1998].
Persistent HTTP connections have a number of advantages: Persistent HTTP connections have a number of advantages:
skipping to change at page 41, line 34 skipping to change at page 43, line 34
In case the client does not want to maintain a connection for more In case the client does not want to maintain a connection for more
than that request, it SHOULD send a Connection header field including than that request, it SHOULD send a Connection header field including
the connection-token close. the connection-token close.
If either the client or the server sends the close token in the If either the client or the server sends the close token in the
Connection header field, that request becomes the last one for the Connection header field, that request becomes the last one for the
connection. connection.
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 B.2 for more information on backward signaled. See Appendix B.1.2 for more information on backward
compatibility with HTTP/1.0 clients. compatibility with HTTP/1.0 clients.
In order to remain persistent, all messages on the connection MUST In order to remain persistent, all messages on the connection MUST
have a self-defined message length (i.e., one not defined by closure have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 3.3. of the connection), as described in Section 3.3.
7.1.2.2. Pipelining 7.1.2.2. 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
skipping to change at page 42, line 8 skipping to change at page 44, line 8
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 methods or Clients SHOULD NOT pipeline requests using non-idempotent request
non-idempotent sequences of methods (see Section 7.1.2 of [Part2]). methods or non-idempotent sequences of request methods (see Section
Otherwise, a premature termination of the transport connection could 7.1.2 of [Part2]). Otherwise, a premature termination of the
lead to indeterminate results. A client wishing to send a non- transport connection could lead to indeterminate results. A client
idempotent request SHOULD wait to send that request until it has wishing to send a non-idempotent request SHOULD wait to send that
received the response status line for the previous request. request until it has received the response status line for the
previous request.
7.1.3. Proxy Servers 7.1.3. Proxy Servers
It is especially important that proxies correctly implement the It is especially important that proxies correctly implement the
properties of the Connection header field as specified in properties of the Connection header field as specified in
Section 9.1. Section 9.1.
The proxy server MUST signal persistent connections separately with The proxy server MUST signal persistent connections separately with
its clients and the origin servers (or other proxy servers) that it its clients and the origin servers (or other proxy servers) that it
connects to. Each persistent connection applies to only one connects to. Each persistent connection applies to only one
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All other header fields defined by HTTP/1.1 are end-to-end header All other header fields defined by HTTP/1.1 are end-to-end header
fields. fields.
Other hop-by-hop header fields MUST be listed in a Connection header Other hop-by-hop header fields MUST be listed in a Connection header
field (Section 9.1). field (Section 9.1).
7.1.3.2. Non-modifiable Header Fields 7.1.3.2. Non-modifiable Header Fields
Some features of HTTP/1.1, such as Digest Authentication, depend on Some features of HTTP/1.1, such as Digest Authentication, depend on
the value of certain end-to-end header fields. A transparent proxy the value of certain end-to-end header fields. A non-transforming
SHOULD NOT modify an end-to-end header field unless the definition of proxy SHOULD NOT modify an end-to-end header field unless the
that header field requires or specifically allows that. definition of that header field requires or specifically allows that.
A transparent proxy MUST NOT modify any of the following fields in a A non-transforming proxy MUST NOT modify any of the following fields
request or response, and it MUST NOT add any of these fields if not in a request or response, and it MUST NOT add any of these fields if
already present: not already present:
o Content-Location o Content-Location
o Content-MD5 o Content-MD5
o ETag o ETag
o Last-Modified o Last-Modified
A transparent proxy MUST NOT modify any of the following fields in a A non-transforming proxy MUST NOT modify any of the following fields
response: in a response:
o Expires o Expires
but it MAY add any of these fields if not already present. If an but it MAY add any of these fields if not already present. If an
Expires header field is added, it MUST be given a field-value Expires header field is added, it MUST be given a field-value
identical to that of the Date header field in that response. identical to that of the Date header field in that response.
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, or in
any request: any request:
o Content-Encoding o Content-Encoding
o Content-Range o Content-Range
o Content-Type o Content-Type
A non-transparent proxy MAY modify or add these fields to a message A transforming proxy MAY modify or add these fields to a message that
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 3.6 of [Part6]). in the message (see Section 3.6 of [Part6]).
Warning: Unnecessary modification of end-to-end header fields Warning: Unnecessary modification of end-to-end header fields
might cause authentication failures if stronger authentication might cause authentication failures if stronger authentication
mechanisms are introduced in later versions of HTTP. Such mechanisms are introduced in later versions of HTTP. Such
authentication mechanisms MAY rely on the values of header fields authentication mechanisms MAY rely on the values of header fields
not listed here. not listed here.
A transparent proxy MUST preserve the message payload ([Part3]), A non-transforming proxy MUST preserve the message payload ([Part3]),
though it MAY change the message-body through application or removal though it MAY change the message-body through application or removal
of a transfer-coding (Section 6.2). of a transfer-coding (Section 6.2).
7.1.4. Practical Considerations 7.1.4. Practical Considerations
Servers will usually have some time-out value beyond which they will Servers will usually have some time-out value beyond which they will
no longer maintain an inactive connection. Proxy servers might make no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making this a higher value since it is likely that the client will be making
more connections through the same server. The use of persistent more connections through the same server. The use of persistent
connections places no requirements on the length (or existence) of connections places no requirements on the length (or existence) of
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time. For example, a client might have started to send a new request time. For example, a client might have started to send a new request
at the same time that the server has decided to close the "idle" at the same time that the server has decided to close the "idle"
connection. From the server's point of view, the connection is being connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a closed while it was idle, but from the client's point of view, a
request is in progress. request is in progress.
This means that clients, servers, and proxies MUST be able to recover This means that clients, servers, and proxies MUST be able to recover
from asynchronous close events. Client software SHOULD reopen the from asynchronous close events. Client software SHOULD reopen the
transport connection and retransmit the aborted sequence of requests transport connection and retransmit the aborted sequence of requests
without user interaction so long as the request sequence is without user interaction so long as the request sequence is
idempotent (see Section 7.1.2 of [Part2]). Non-idempotent methods or idempotent (see Section 7.1.2 of [Part2]). Non-idempotent request
sequences MUST NOT be automatically retried, although user agents MAY methods or sequences MUST NOT be automatically retried, although user
offer a human operator the choice of retrying the request(s). agents MAY offer a human operator the choice of retrying the
Confirmation by user-agent software with semantic understanding of request(s). Confirmation by user-agent software with semantic
the application MAY substitute for user confirmation. The automatic understanding of the application MAY substitute for user
retry SHOULD NOT be repeated if the second sequence of requests confirmation. The automatic retry SHOULD NOT be repeated if the
fails. second sequence of requests fails.
Servers SHOULD always respond to at least one request per connection, Servers SHOULD always respond to at least one request per connection,
if at all possible. Servers SHOULD NOT close a connection in the if at all possible. Servers SHOULD NOT close a connection in the
middle of transmitting a response, unless a network or client failure middle of transmitting a response, unless a network or client failure
is suspected. is suspected.
Clients (including proxies) SHOULD limit the number of simultaneous Clients (including proxies) SHOULD limit the number of simultaneous
connections that they maintain to a given server (including proxies). connections that they maintain to a given server (including proxies).
Previous revisions of HTTP gave a specific number of connections as a Previous revisions of HTTP gave a specific number of connections as a
skipping to change at page 46, line 24 skipping to change at page 48, line 24
[Part2]) is to allow a client that is sending a request message with [Part2]) is to allow a client that is sending a request message with
a request body to determine if the origin server is willing to accept a request body to determine if the origin server is willing to accept
the request (based on the request header fields) before the client the request (based on the request header fields) before the client
sends the request body. In some cases, it might either be sends the request body. In some cases, it might either be
inappropriate or highly inefficient for the client to send the body inappropriate or highly inefficient for the client to send the body
if the server will reject the message without looking at the body. if the server will reject the message without looking at the body.
Requirements for HTTP/1.1 clients: Requirements for HTTP/1.1 clients:
o If a client will wait for a 100 (Continue) response before sending o If a client will wait for a 100 (Continue) response before sending
the request body, it MUST send an Expect request-header field the request body, it MUST send an Expect header field (Section 9.2
(Section 9.2 of [Part2]) with the "100-continue" expectation. of [Part2]) with the "100-continue" expectation.
o A client MUST NOT send an Expect request-header field (Section 9.2 o A client MUST NOT send an Expect header field (Section 9.2 of
of [Part2]) with the "100-continue" expectation if it does not [Part2]) with the "100-continue" expectation if it does not intend
intend to send a request body. to send a request body.
Because of the presence of older implementations, the protocol allows Because of the presence of older implementations, the protocol allows
ambiguous situations in which a client might send "Expect: 100- ambiguous situations in which a client might send "Expect: 100-
continue" without receiving either a 417 (Expectation Failed) or a continue" without receiving either a 417 (Expectation Failed) or a
100 (Continue) status code. Therefore, when a client sends this 100 (Continue) status code. Therefore, when a client sends this
header field to an origin server (possibly via a proxy) from which it header field to an origin server (possibly via a proxy) from which it
has never seen a 100 (Continue) status code, the client SHOULD NOT has never seen a 100 (Continue) status code, the client SHOULD NOT
wait for an indefinite period before sending the request body. wait for an indefinite period before sending the request body.
Requirements for HTTP/1.1 origin servers: Requirements for HTTP/1.1 origin servers:
o Upon receiving a request which includes an Expect request-header o Upon receiving a request which includes an Expect header field
field with the "100-continue" expectation, an origin server MUST with the "100-continue" expectation, an origin server MUST either
either respond with 100 (Continue) status code and continue to respond with 100 (Continue) status code and continue to read from
read from the input stream, or respond with a final status code. the input stream, or respond with a final status code. The origin
The origin server MUST NOT wait for the request body before server MUST NOT wait for the request body before sending the 100
sending the 100 (Continue) response. If it responds with a final (Continue) response. If it responds with a final status code, it
status code, it MAY close the transport connection or it MAY MAY close the transport connection or it MAY continue to read and
continue to read and discard the rest of the request. It MUST NOT discard the rest of the request. It MUST NOT perform the request
perform the requested method if it returns a final status code. method if it returns a final status code.
o An origin server SHOULD NOT send a 100 (Continue) response if the o An origin server SHOULD NOT send a 100 (Continue) response if the
request message does not include an Expect request-header field request message does not include an Expect header field with the
with the "100-continue" expectation, and MUST NOT send a 100 "100-continue" expectation, and MUST NOT send a 100 (Continue)
(Continue) response if such a request comes from an HTTP/1.0 (or response if such a request comes from an HTTP/1.0 (or earlier)
earlier) client. There is an exception to this rule: for client. There is an exception to this rule: for compatibility
compatibility with [RFC2068], a server MAY send a 100 (Continue) with [RFC2068], a server MAY send a 100 (Continue) status code in
status code in response to an HTTP/1.1 PUT or POST request that response to an HTTP/1.1 PUT or POST request that does not include
does not include an Expect request-header field with the "100- an Expect header field with the "100-continue" expectation. This
continue" expectation. This exception, the purpose of which is to exception, the purpose of which is to minimize any client
minimize any client processing delays associated with an processing delays associated with an undeclared wait for 100
undeclared wait for 100 (Continue) status code, applies only to (Continue) status code, applies only to HTTP/1.1 requests, and not
HTTP/1.1 requests, and not to requests with any other HTTP-version to requests with any other HTTP-version value.
value.
o An origin server MAY omit a 100 (Continue) response if it has o An origin server MAY omit a 100 (Continue) response if it has
already received some or all of the request body for the already received some or all of the request body for the
corresponding request. corresponding request.
o An origin server that sends a 100 (Continue) response MUST o An origin server that sends a 100 (Continue) response MUST
ultimately send a final status code, once the request body is ultimately send a final status code, once the request body is
received and processed, unless it terminates the transport received and processed, unless it terminates the transport
connection prematurely. connection prematurely.
o If an origin server receives a request that does not include an o If an origin server receives a request that does not include an
Expect request-header field with the "100-continue" expectation, Expect header field with the "100-continue" expectation, the
the request includes a request body, and the server responds with request includes a request body, and the server responds with a
a final status code before reading the entire request body from final status code before reading the entire request body from the
the transport connection, then the server SHOULD NOT close the transport connection, then the server SHOULD NOT close the
transport connection until it has read the entire request, or transport connection until it has read the entire request, or
until the client closes the connection. Otherwise, the client until the client closes the connection. Otherwise, the client
might not reliably receive the response message. However, this might not reliably receive the response message. However, this
requirement is not be construed as preventing a server from requirement is not be construed as preventing a server from
defending itself against denial-of-service attacks, or from badly defending itself against denial-of-service attacks, or from badly
broken client implementations. broken client implementations.
Requirements for HTTP/1.1 proxies: Requirements for HTTP/1.1 proxies:
o If a proxy receives a request that includes an Expect request- o If a proxy receives a request that includes an Expect header field
header field with the "100-continue" expectation, and the proxy with the "100-continue" expectation, and the proxy either knows
either knows that the next-hop server complies with HTTP/1.1 or that the next-hop server complies with HTTP/1.1 or higher, or does
higher, or does not know the HTTP version of the next-hop server, not know the HTTP version of the next-hop server, it MUST forward
it MUST forward the request, including the Expect header field. the request, including the Expect header field.
o If the proxy knows that the version of the next-hop server is o If the proxy knows that the version of the next-hop server is
HTTP/1.0 or lower, it MUST NOT forward the request, and it MUST HTTP/1.0 or lower, it MUST NOT forward the request, and it MUST
respond with a 417 (Expectation Failed) status code. respond with a 417 (Expectation Failed) status code.
o Proxies SHOULD maintain a cache recording the HTTP version numbers o Proxies SHOULD maintain a cache recording the HTTP version numbers
received from recently-referenced next-hop servers. received from recently-referenced next-hop servers.
o A proxy MUST NOT forward a 100 (Continue) response if the request o A proxy MUST NOT forward a 100 (Continue) response if the request
message was received from an HTTP/1.0 (or earlier) client and did message was received from an HTTP/1.0 (or earlier) client and did
not include an Expect request-header field with the "100-continue" not include an Expect header field with the "100-continue"
expectation. This requirement overrides the general rule for expectation. This requirement overrides the general rule for
forwarding of 1xx responses (see Section 8.1 of [Part2]). forwarding of 1xx responses (see Section 8.1 of [Part2]).
7.2.4. Client Behavior if Server Prematurely Closes Connection 7.2.4. Client Behavior if Server Prematurely Closes Connection
If an HTTP/1.1 client sends a request which includes a request body, If an HTTP/1.1 client sends a request which includes a request body,
but which does not include an Expect request-header field with the but which does not include an Expect header field with the "100-
"100-continue" expectation, and if the client is not directly continue" expectation, and if the client is not directly connected to
connected to an HTTP/1.1 origin server, and if the client sees the an HTTP/1.1 origin server, and if the client sees the connection
connection close before receiving a status line from the server, the close before receiving a status line from the server, the client
client SHOULD retry the request. If the client does retry this SHOULD retry the request. If the client does retry this request, it
request, it MAY use the following "binary exponential backoff" MAY use the following "binary exponential backoff" algorithm to be
algorithm to be assured of obtaining a reliable response: assured of obtaining a reliable response:
1. Initiate a new connection to the server 1. Initiate a new connection to the server
2. Transmit the request-header fields 2. Transmit the request-line, header fields, and the CRLF that
indicates the end of header fields.
3. Initialize a variable R to the estimated round-trip time to the 3. Initialize a variable R to the estimated round-trip time to the
server (e.g., based on the time it took to establish the server (e.g., based on the time it took to establish the
connection), or to a constant value of 5 seconds if the round- connection), or to a constant value of 5 seconds if the round-
trip time is not available. trip time is not available.
4. Compute T = R * (2**N), where N is the number of previous retries 4. Compute T = R * (2**N), where N is the number of previous retries
of this request. of this request.
5. Wait either for an error response from the server, or for T 5. Wait either for an error response from the server, or for T
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[[TBD-profiles: Profiles of HTTP defined by other protocol. [[TBD-profiles: Profiles of HTTP defined by other protocol.
Extensions of HTTP like WebDAV.]] Extensions of HTTP like WebDAV.]]
8.5. Use of HTTP by media type specification 8.5. Use of HTTP by media type specification
[[TBD-hypertext: Instructions on composing HTTP requests via [[TBD-hypertext: Instructions on composing HTTP requests via
hypertext formats.]] hypertext formats.]]
9. Header Field Definitions 9. Header Field Definitions
This section defines the syntax and semantics of HTTP/1.1 header This section defines the syntax and semantics of HTTP header fields
fields related to message framing and transport protocols. related to message framing and transport protocols.
9.1. Connection 9.1. Connection
The "Connection" general-header field allows the sender to specify The "Connection" header field allows the sender to specify options
options that are desired for that particular connection and MUST NOT that are desired only for that particular connection. Such
be communicated by proxies over further connections. connection options MUST be removed or replaced before the message can
be forwarded downstream by a proxy or gateway. This mechanism also
allows the sender to indicate which HTTP header fields used in the
message are only intended for the immediate recipient ("hop-by-hop"),
as opposed to all recipients on the chain ("end-to-end"), enabling
the message to be self-descriptive and allowing future connection-
specific extensions to be deployed in HTTP without fear that they
will be blindly forwarded by previously deployed intermediaries.
The Connection header field's value has the following grammar: The Connection header field's value has the following grammar:
Connection = "Connection" ":" OWS Connection-v Connection = "Connection" ":" OWS Connection-v
Connection-v = 1#connection-token Connection-v = 1#connection-token
connection-token = token connection-token = token
HTTP/1.1 proxies MUST parse the Connection header field before a A proxy or gateway MUST parse a received Connection header field
message is forwarded and, for each connection-token in this field, before a message is forwarded and, for each connection-token in this
remove any header field(s) from the message with the same name as the field, remove any header field(s) from the message with the same name
connection-token. Connection options are signaled by the presence of as the connection-token, and then remove the Connection header field
a connection-token in the Connection header field, not by any itself or replace it with the sender's own connection options for the
corresponding additional header field(s), since the additional header forwarded message.
field might not be sent if there are no parameters associated with
that connection option.
Message header fields listed in the Connection header field MUST NOT A sender MUST NOT include field-names in the Connection header field-
include end-to-end header fields, such as Cache-Control. value for fields that are defined as expressing constraints for all
recipients in the request or response chain, such as the Cache-
Control header field (Section 3.2 of [Part6]).
The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection
behavior based on the presence of connection options MUST do so based
on the presence of the connection-token rather than only the presence
of the optional header field. In other words, if the connection
option is received as a header field but not indicated within the
Connection field-value, then the recipient MUST ignore the
connection-specific header field because it has likely been forwarded
by an intermediary that is only partially compliant.
When defining new connection options, specifications ought to
carefully consider existing deployed header fields and ensure that
the new connection-token does not share the same name as an unrelated
header field that might already be deployed. Defining a new
connection-token essentially reserves that potential field-name for
carrying additional information related to the connection option,
since it would be unwise for senders to use that field-name for
anything else.
HTTP/1.1 defines the "close" connection option for the sender to HTTP/1.1 defines the "close" connection option for the sender to
signal that the connection will be closed after completion of the signal that the connection will be closed after completion of the
response. For example, response. For 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 7.1) the connection SHOULD NOT be considered "persistent" (Section 7.1)
after the current request/response is complete. after the current request/response is complete.
An HTTP/1.1 client that does not support persistent connections MUST An HTTP/1.1 client that does not support persistent connections MUST
include the "close" connection option in every request message. include the "close" connection option in every request message.
An HTTP/1.1 server that does not support persistent connections MUST An HTTP/1.1 server that does not support persistent connections MUST
include the "close" connection option in every response message that include the "close" connection option in every response message that
does not have a 1xx (Informational) status code. does not have a 1xx (Informational) status code.
A system receiving an HTTP/1.0 (or lower-version) message that
includes a Connection header field MUST, for each connection-token in
this field, remove and ignore any header field(s) from the message
with the same name as the connection-token. This protects against
mistaken forwarding of such header fields by pre-HTTP/1.1 proxies.
See Appendix B.2.
9.2. Content-Length 9.2. Content-Length
The "Content-Length" header field indicates the size of the message- The "Content-Length" header field indicates the size of the message-
body, in decimal number of octets, for any message other than a body, in decimal number of octets, for any message other than a
response to the HEAD method or a response with a status code of 304. response to a HEAD request or a response with a status code of 304.
In the case of responses to the HEAD method, it indicates the size of In the case of a response to a HEAD request, Content-Length indicates
the payload body (not including any potential transfer-coding) that the size of the payload body (not including any potential transfer-
would have been sent had the request been a GET. In the case of the coding) that would have been sent had the request been a GET. In the
304 (Not Modified) response, it indicates the size of the payload case of a 304 (Not Modified) response to a GET request, Content-
body (not including any potential transfer-coding) that would have Length indicates the size of the payload body (not including any
been sent in a 200 (OK) response. potential transfer-coding) that would have been sent in a 200 (OK)
response.
Content-Length = "Content-Length" ":" OWS 1*Content-Length-v Content-Length = "Content-Length" ":" OWS 1*Content-Length-v
Content-Length-v = 1*DIGIT Content-Length-v = 1*DIGIT
An example is An example is
Content-Length: 3495 Content-Length: 3495
Implementations SHOULD use this field to indicate the message-body Implementations SHOULD use this field to indicate the message-body
length when no transfer-coding is being applied and the payload's length when no transfer-coding is being applied and the payload's
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message-body. message-body.
Any Content-Length greater than or equal to zero is a valid value. Any Content-Length greater than or equal to zero is a valid value.
Note that the use of this field in HTTP is significantly different Note that the use of this field in HTTP is significantly different
from the corresponding definition in MIME, where it is an optional from the corresponding definition in MIME, where it is an optional
field used within the "message/external-body" content-type. field used within the "message/external-body" content-type.
9.3. Date 9.3. Date
The "Date" general-header field represents the date and time at which The "Date" header field represents the date and time at which the
the message was originated, having the same semantics as the message was originated, having the same semantics as the Origination
Origination Date Field (orig-date) defined in Section 3.6.1 of Date Field (orig-date) defined in Section 3.6.1 of [RFC5322]. The
[RFC5322]. The field value is an HTTP-date, as described in field value is an HTTP-date, as described in Section 6.1; it MUST be
Section 6.1; it MUST be sent in rfc1123-date format. sent in rfc1123-date format.
Date = "Date" ":" OWS Date-v Date = "Date" ":" OWS Date-v
Date-v = HTTP-date Date-v = HTTP-date
An example is An example is
Date: Tue, 15 Nov 1994 08:12:31 GMT Date: Tue, 15 Nov 1994 08:12:31 GMT
Origin servers MUST include a Date header field in all responses, Origin servers MUST include a Date header field in all responses,
except in these cases: except in these cases:
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(Internal Server Error) or 503 (Service Unavailable), and it is (Internal Server Error) or 503 (Service Unavailable), and it is
inconvenient or impossible to generate a valid Date. inconvenient or impossible to generate a valid Date.
3. If the server does not have a clock that can provide a reasonable 3. If the server does not have a clock that can provide a reasonable
approximation of the current time, its responses MUST NOT include approximation of the current time, its responses MUST NOT include
a Date header field. In this case, the rules in Section 9.3.1 a Date header field. In this case, the rules in Section 9.3.1
MUST be followed. MUST be followed.
A received message that does not have a Date header field MUST be A received message that does not have a Date header field MUST be
assigned one by the recipient if the message will be cached by that assigned one by the recipient if the message will be cached by that
recipient or gatewayed via a protocol which requires a Date. recipient.
Clients can use the Date header field as well; in order to keep Clients can use the Date header field as well; in order to keep
request messages small, they are advised not to include it when it request messages small, they are advised not to include it when it
doesn't convey any useful information (as it is usually the case for doesn't convey any useful information (as it is usually the case for
requests that do not contain a payload). requests that do not contain a payload).
The HTTP-date sent in a Date header field SHOULD NOT represent a date The HTTP-date sent in a Date header field SHOULD NOT represent a date
and time subsequent to the generation of the message. It SHOULD and time subsequent to the generation of the message. It SHOULD
represent the best available approximation of the date and time of represent the best available approximation of the date and time of
message generation, unless the implementation has no means of message generation, unless the implementation has no means of
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An origin server without a clock MUST NOT assign Expires or Last- An origin server without a clock MUST NOT assign Expires or Last-
Modified values to a response, unless these values were associated Modified values to a response, unless these values were associated
with the resource by a system or user with a reliable clock. It MAY with the resource by a system or user with a reliable clock. It MAY
assign an Expires value that is known, at or before server assign an Expires value that is known, at or before server
configuration time, to be in the past (this allows "pre-expiration" configuration time, to be in the past (this allows "pre-expiration"
of responses without storing separate Expires values for each of responses without storing separate Expires values for each
resource). resource).
9.4. Host 9.4. Host
The "Host" request-header field specifies the Internet host and port The "Host" header field in a request provides the host and port
number of the resource being requested, allowing the origin server or information from the target resource's URI, enabling the origin
gateway to differentiate between internally-ambiguous URLs, such as server to distinguish between resources while servicing requests for
the root "/" URL of a server for multiple host names on a single IP multiple host names on a single IP address. Since the Host field-
address. value is critical information for handling a request, it SHOULD be
sent as the first header field following the Request-Line.
The Host field value MUST represent the naming authority of the
origin server or gateway given by the original URL obtained from the
user or referring resource (generally an http URI, as described in
Section 2.6.1).
Host = "Host" ":" OWS Host-v Host = "Host" ":" OWS Host-v
Host-v = uri-host [ ":" port ] ; Section 2.6.1 Host-v = uri-host [ ":" port ] ; Section 2.6.1
A "host" without any trailing port information implies the default A client MUST send a Host header field in all HTTP/1.1 request
port for the service requested (e.g., "80" for an HTTP URL). For messages. If the target resource's URI includes an authority
example, a request on the origin server for component, then the Host field-value MUST be identical to that
<http://www.example.org/pub/WWW/> would properly include: authority component after excluding any userinfo (Section 2.6.1). If
the authority component is missing or undefined for the target
resource's URI, then the Host header field MUST be sent with an empty
field-value.
For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1 GET /pub/WWW/ HTTP/1.1
Host: www.example.org Host: www.example.org
A client MUST include a Host header field in all HTTP/1.1 request The Host header field MUST be sent in an HTTP/1.1 request even if the
messages. If the requested URI does not include an Internet host request-target is in the form of an absolute-URI, since this allows
name for the service being requested, then the Host header field MUST the Host information to be forwarded through ancient HTTP/1.0 proxies
be given with an empty value. An HTTP/1.1 proxy MUST ensure that any that might not have implemented Host.
request message it forwards does contain an appropriate Host header
field that identifies the service being requested by the proxy. All When an HTTP/1.1 proxy receives a request with a request-target in
Internet-based HTTP/1.1 servers MUST respond with a 400 (Bad Request) the form of an absolute-URI, the proxy MUST ignore the received Host
status code to any HTTP/1.1 request message which lacks a Host header header field (if any) and instead replace it with the host
field. information of the request-target. When a proxy forwards a request,
it MUST generate the Host header field based on the received
absolute-URI rather than the received Host.
Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the
Host header field value for redirecting requests to internal servers,
or for use as a cache key in a shared cache, without first verifying
that the intercepted connection is targeting a valid IP address for
that host.
A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a
Host header field with an invalid field-value.
See Sections 4.2 and B.1.1 for other requirements relating to Host. See Sections 4.2 and B.1.1 for other requirements relating to Host.
9.5. TE 9.5. TE
The "TE" request-header field indicates what extension transfer- The "TE" header field indicates what extension transfer-codings it is
codings it is willing to accept in the response, and whether or not willing to accept in the response, and whether or not it is willing
it is willing to accept trailer fields in a chunked transfer-coding. to accept trailer fields in a chunked transfer-coding.
Its value consists of the keyword "trailers" and/or a comma-separated Its value consists of the keyword "trailers" and/or a comma-separated
list of extension transfer-coding names with optional accept list of extension transfer-coding names with optional accept
parameters (as described in Section 6.2). parameters (as described in Section 6.2).
TE = "TE" ":" OWS TE-v TE = "TE" ":" OWS TE-v
TE-v = #t-codings TE-v = #t-codings
t-codings = "trailers" / ( transfer-extension [ te-params ] ) t-codings = "trailers" / ( transfer-extension [ te-params ] )
te-params = OWS ";" OWS "q=" qvalue *( te-ext ) te-params = OWS ";" OWS "q=" qvalue *( te-ext )
te-ext = OWS ";" OWS token [ "=" word ] te-ext = OWS ";" OWS token [ "=" word ]
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3. If multiple transfer-codings are acceptable, then the acceptable 3. If multiple transfer-codings are acceptable, then the acceptable
transfer-coding with the highest non-zero qvalue is preferred. transfer-coding with the highest non-zero qvalue is preferred.
The "chunked" transfer-coding always has a qvalue of 1. The "chunked" transfer-coding always has a qvalue of 1.
If the TE field-value is empty or if no TE field is present, the only If the TE field-value is empty or if no TE field is present, the only
transfer-coding is "chunked". A message with no transfer-coding is transfer-coding is "chunked". A message with no transfer-coding is
always acceptable. always acceptable.
9.6. Trailer 9.6. Trailer
The "Trailer" general-header field indicates that the given set of The "Trailer" header field indicates that the given set of header
header fields is present in the trailer of a message encoded with fields is present in the trailer of a message encoded with chunked
chunked transfer-coding. transfer-coding.
Trailer = "Trailer" ":" OWS Trailer-v Trailer = "Trailer" ":" OWS Trailer-v
Trailer-v = 1#field-name Trailer-v = 1#field-name
An HTTP/1.1 message SHOULD include a Trailer header field in a An HTTP/1.1 message SHOULD include a Trailer header field in a
message using chunked transfer-coding with a non-empty trailer. message using chunked transfer-coding with a non-empty trailer.
Doing so allows the recipient to know which header fields to expect Doing so allows the recipient to know which header fields to expect
in the trailer. in the trailer.
If no Trailer header field is present, the trailer SHOULD NOT include If no Trailer header field is present, the trailer SHOULD NOT include
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include the following header fields: include the following header fields:
o Transfer-Encoding o Transfer-Encoding
o Content-Length o Content-Length
o Trailer o Trailer
9.7. Transfer-Encoding 9.7. Transfer-Encoding
The "Transfer-Encoding" general-header field indicates what transfer- The "Transfer-Encoding" header field indicates what transfer-codings
codings (if any) have been applied to the message body. It differs (if any) have been applied to the message body. It differs from
from Content-Encoding (Section 2.2 of [Part3]) in that transfer- Content-Encoding (Section 2.2 of [Part3]) in that transfer-codings
codings are a property of the message (and therefore are removed by are a property of the message (and therefore are removed by
intermediaries), whereas content-codings are not. intermediaries), whereas content-codings are not.
Transfer-Encoding = "Transfer-Encoding" ":" OWS Transfer-Encoding = "Transfer-Encoding" ":" OWS
Transfer-Encoding-v Transfer-Encoding-v
Transfer-Encoding-v = 1#transfer-coding Transfer-Encoding-v = 1#transfer-coding
Transfer-codings are defined in Section 6.2. An example is: Transfer-codings are defined in Section 6.2. An example is:
Transfer-Encoding: chunked Transfer-Encoding: chunked
If multiple encodings have been applied to a representation, the If multiple encodings have been applied to a representation, the
transfer-codings MUST be listed in the order in which they were transfer-codings MUST be listed in the order in which they were
applied. Additional information about the encoding parameters MAY be applied. Additional information about the encoding parameters MAY be
provided by other header fields not defined by this specification. provided by other header fields not defined by this specification.
Many older HTTP/1.0 applications do not understand the Transfer- Many older HTTP/1.0 applications do not understand the Transfer-
Encoding header field. Encoding header field.
9.8. Upgrade 9.8. Upgrade
The "Upgrade" general-header field allows the client to specify what The "Upgrade" header field allows the client to specify what
additional communication protocols it would like to use, if the additional communication protocols it would like to use, if the
server chooses to switch protocols. Additionally, the server MUST server chooses to switch protocols. Servers can use it to indicate
use the Upgrade header field within a 101 (Switching Protocols) what protocols they are willing to switch to.
response to indicate which protocol(s) are being switched to.
Upgrade = "Upgrade" ":" OWS Upgrade-v Upgrade = "Upgrade" ":" OWS Upgrade-v
Upgrade-v = 1#product Upgrade-v = 1#product
For example, For example,
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
The Upgrade header field is intended to provide a simple mechanism The Upgrade header field is intended to provide a simple mechanism
for transition from HTTP/1.1 to some other, incompatible protocol. for transition from HTTP/1.1 to some other, incompatible protocol.
It does so by allowing the client to advertise its desire to use It does so by allowing the client to advertise its desire to use
another protocol, such as a later version of HTTP with a higher major another protocol, such as a later version of HTTP with a higher major
version number, even though the current request has been made using version number, even though the current request has been made using
HTTP/1.1. This eases the difficult transition between incompatible HTTP/1.1. This eases the difficult transition between incompatible
protocols by allowing the client to initiate a request in the more protocols by allowing the client to initiate a request in the more
commonly supported protocol while indicating to the server that it commonly supported protocol while indicating to the server that it
would like to use a "better" protocol if available (where "better" is would like to use a "better" protocol if available (where "better" is
determined by the server, possibly according to the nature of the determined by the server, possibly according to the nature of the
method and/or resource being requested). request method or target resource).
The Upgrade header field only applies to switching application-layer The Upgrade header field only applies to switching application-layer
protocols upon the existing transport-layer connection. Upgrade protocols upon the existing transport-layer connection. Upgrade
cannot be used to insist on a protocol change; its acceptance and use cannot be used to insist on a protocol change; its acceptance and use
by the server is optional. The capabilities and nature of the by the server is optional. The capabilities and nature of the
application-layer communication after the protocol change is entirely application-layer communication after the protocol change is entirely
dependent upon the new protocol chosen, although the first action dependent upon the new protocol chosen, although the first action
after changing the protocol MUST be a response to the initial HTTP after changing the protocol MUST be a response to the initial HTTP
request containing the Upgrade header field. request containing the Upgrade header field.
The Upgrade header field only applies to the immediate connection. The Upgrade header field only applies to the immediate connection.
Therefore, the upgrade keyword MUST be supplied within a Connection Therefore, the upgrade keyword MUST be supplied within a Connection
header field (Section 9.1) whenever Upgrade is present in an HTTP/1.1 header field (Section 9.1) whenever Upgrade is present in an HTTP/1.1
message. message.
The Upgrade header field cannot be used to indicate a switch to a The Upgrade header field cannot be used to indicate a switch to a
protocol on a different connection. For that purpose, it is more protocol on a different connection. For that purpose, it is more
appropriate to use a 301, 302, 303, or 305 redirection response. appropriate to use a 3xx redirection response (Section 8.3 of
[Part2]).
Servers MUST include the "Upgrade" header field in 101 (Switching
Protocols) responses to indicate which protocol(s) are being switched
to, and MUST include it in 426 (Upgrade Required) responses to
indicate acceptable protocols to upgrade to. Servers MAY include it
in any other response to indicate that they are willing to upgrade to
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 2.5 and future updates to this version rules of Section 2.5 and future updates to this
specification. Additional tokens can be registered with IANA using specification. Additional tokens can be registered with IANA using
the registration procedure defined below. the registration procedure defined below.
9.8.1. Upgrade Token Registry 9.8.1. Upgrade Token Registry
The HTTP Upgrade Token Registry defines the name space for product The HTTP Upgrade Token Registry defines the name space for product
skipping to change at page 57, line 29 skipping to change at page 60, line 29
6. The responsible party for the first registration of a "product" 6. The responsible party for the first registration of a "product"
token MUST approve later registrations of a "version" token token MUST approve later registrations of a "version" token
together with that "product" token before they can be registered. together with that "product" token before they can be registered.
7. If absolutely required, the IESG MAY reassign the responsibility 7. If absolutely required, the IESG MAY reassign the responsibility
for a token. This will normally only be used in the case when a for a token. This will normally only be used in the case when a
responsible party cannot be contacted. responsible party cannot be contacted.
9.9. Via 9.9. Via
The "Via" general-header field MUST be used by gateways and proxies The "Via" header field MUST be sent by a proxy or gateway to indicate
to indicate the intermediate protocols and recipients between the the intermediate protocols and recipients between the user agent and
user agent and the server on requests, and between the origin server the server on requests, and between the origin server and the client
and the client on responses. It is analogous to the "Received" field on responses. It is analogous to the "Received" field used by email
defined in Section 3.6.7 of [RFC5322] and is intended to be used for systems (Section 3.6.7 of [RFC5322]) and is intended to be used for
tracking message forwards, avoiding request loops, and identifying tracking message forwards, avoiding request loops, and identifying
the protocol capabilities of all senders along the request/response the protocol capabilities of all senders along the request/response
chain. chain.
Via = "Via" ":" OWS Via-v Via = "Via" ":" OWS Via-v
Via-v = 1#( received-protocol RWS received-by Via-v = 1#( received-protocol RWS received-by
[ RWS comment ] ) [ RWS comment ] )
received-protocol = [ protocol-name "/" ] protocol-version received-protocol = [ protocol-name "/" ] protocol-version
protocol-name = token protocol-name = token
protocol-version = token protocol-version = token
received-by = ( uri-host [ ":" port ] ) / pseudonym received-by = ( uri-host [ ":" port ] ) / pseudonym
pseudonym = token pseudonym = token
The received-protocol indicates the protocol version of the message The received-protocol indicates the protocol version of the message
received by the server or client along each segment of the request/ received by the server or client along each segment of the request/
response chain. The received-protocol version is appended to the Via response chain. The received-protocol version is appended to the Via
field value when the message is forwarded so that information about field value when the message is forwarded so that information about
the protocol capabilities of upstream applications remains visible to the protocol capabilities of upstream applications remains visible to
all recipients. all recipients.
The protocol-name is optional if and only if it would be "HTTP". The 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 received-by field is normally the host and optional port number of a
recipient server or client that subsequently forwarded the message. recipient server or client that subsequently forwarded the message.
However, if the real host is considered to be sensitive information, 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 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. be assumed to be the default port of the received-protocol.
Multiple Via field values represent each proxy or gateway that has Multiple Via field values represent each proxy or gateway that has
forwarded the message. Each recipient MUST append its information forwarded the message. Each recipient MUST append its information
such that the end result is ordered according to the sequence of such that the end result is ordered according to the sequence of
forwarding applications. forwarding applications.
Comments MAY be used in the Via header field to identify the software Comments MAY be used in the Via header field to identify the software
of the recipient proxy or gateway, analogous to the User-Agent and of each recipient, analogous to the User-Agent and Server header
Server header fields. However, all comments in the Via field are fields. However, all comments in the Via field are optional and MAY
optional and MAY be removed by any recipient prior to forwarding the be removed by any recipient prior to forwarding the message.
message.
For example, a request message could be sent from an HTTP/1.0 user For example, a request message could be sent from an HTTP/1.0 user
agent to an internal proxy code-named "fred", which uses HTTP/1.1 to agent to an internal proxy code-named "fred", which uses HTTP/1.1 to
forward the request to a public proxy at p.example.net, which forward the request to a public proxy at p.example.net, which
completes the request by forwarding it to the origin server at completes the request by forwarding it to the origin server at
www.example.com. The request received by www.example.com would then www.example.com. The request received by www.example.com would then
have the following Via header field: have the following Via header field:
Via: 1.0 fred, 1.1 p.example.net (Apache/1.1) Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
Proxies and gateways used as a portal through a network firewall A proxy or gateway used as a portal through a network firewall SHOULD
SHOULD NOT, by default, forward the names and ports of hosts within NOT forward the names and ports of hosts within the firewall region
the firewall region. This information SHOULD only be propagated if unless it is explicitly enabled to do so. If not enabled, the
explicitly enabled. If not enabled, the received-by host of any host received-by host of any host behind the firewall SHOULD be replaced
behind the firewall SHOULD be replaced by an appropriate pseudonym by an appropriate pseudonym for that host.
for that host.
For organizations that have strong privacy requirements for hiding For organizations that have strong privacy requirements for hiding
internal structures, a proxy MAY combine an ordered subsequence of internal structures, a proxy or gateway MAY combine an ordered
Via header field entries with identical received-protocol values into subsequence of Via header field entries with identical received-
a single such entry. For example, protocol values into a single such entry. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Applications SHOULD NOT combine multiple entries unless they are all Senders SHOULD NOT combine multiple entries unless they are all under
under the same organizational control and the hosts have already been the same organizational control and the hosts have already been
replaced by pseudonyms. Applications MUST NOT combine entries which replaced by pseudonyms. Senders MUST NOT combine entries which have
have different received-protocol values. different received-protocol values.
10. IANA Considerations 10. IANA Considerations
10.1. Header Field Registration 10.1. Header Field Registration
The Message Header Field Registry located at <http://www.iana.org/ The Message Header Field Registry located at <http://www.iana.org/
assignments/message-headers/message-header-index.html> shall be assignments/message-headers/message-header-index.html> shall be
updated with the permanent registrations below (see [RFC3864]): updated with the permanent registrations below (see [RFC3864]):
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+-------------+
skipping to change at page 65, line 22 skipping to change at page 68, line 22
cryptography is beyond the scope of the HTTP/1.1 specification. cryptography is beyond the scope of the HTTP/1.1 specification.
11.6. Denial of Service Attacks on Proxies 11.6. Denial of Service Attacks on Proxies
They exist. They are hard to defend against. Research continues. They exist. They are hard to defend against. Research continues.
Beware. Beware.
12. Acknowledgments 12. Acknowledgments
HTTP has evolved considerably over the years. It has benefited from HTTP has evolved considerably over the years. It has benefited from
a large and active developer community--the many people who have a large and active developer community -- the many people who have
participated on the www-talk mailing list--and it is that community participated on the www-talk mailing list -- and it is that community
which has been most responsible for the success of HTTP and of the which has been most responsible for the success of HTTP and of the
World-Wide Web in general. Marc Andreessen, Robert Cailliau, Daniel World-Wide Web in general. Marc Andreessen, Robert Cailliau, Daniel
W. Connolly, Bob Denny, John Franks, Jean-Francois Groff, Phillip M. W. Connolly, Bob Denny, John Franks, Jean-Francois Groff, Phillip M.
Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob McCool, Lou Montulli, Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob McCool, Lou Montulli,
Dave Raggett, Tony Sanders, and Marc VanHeyningen deserve special Dave Raggett, Tony Sanders, and Marc VanHeyningen deserve special
recognition for their efforts in defining early aspects of the recognition for their efforts in defining early aspects of the
protocol. protocol.
This document has benefited greatly from the comments of all those This document has benefited greatly from the comments of all those
participating in the HTTP-WG. In addition to those already participating in the HTTP-WG. In addition to those already
skipping to change at page 66, line 28 skipping to change at page 69, line 28
constructs defined by David H. Crocker for [RFC5234]. Similarly, it constructs defined by David H. Crocker for [RFC5234]. Similarly, it
reuses many of the definitions provided by Nathaniel Borenstein and reuses many of the definitions provided by Nathaniel Borenstein and
Ned Freed for MIME [RFC2045]. We hope that their inclusion in this Ned Freed for MIME [RFC2045]. We hope that their inclusion in this
specification will help reduce past confusion over the relationship specification will help reduce past confusion over the relationship
between HTTP and Internet mail message formats. between HTTP and Internet mail message formats.
13. References 13. References
13.1. Normative References 13.1. Normative References
[ISO-8859-1] International Organization for Standardization, [ISO-8859-1] International Organization for
"Information technology -- 8-bit single-byte coded Standardization, "Information
graphic character sets -- Part 1: Latin alphabet No. technology -- 8-bit single-byte coded
1", ISO/IEC 8859-1:1998, 1998. graphic character sets -- Part 1:
Latin alphabet No. 1", ISO/
IEC 8859-1:1998, 1998.
[Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part2] Fielding, R., Ed., Gettys, J., Mogul,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., J., Frystyk, H., Masinter, L., Leach,
Ed., and J. Reschke, Ed., "HTTP/1.1, part 2: Message P., Berners-Lee, T., Lafon, Y., Ed.,
Semantics", draft-ietf-httpbis-p2-semantics-12 (work in and J. Reschke, Ed., "HTTP/1.1, part
progress), October 2010. 2: Message Semantics",
draft-ietf-httpbis-p2-semantics-13
(work in progress), March 2011.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part3] Fielding, R., Ed., Gettys, J., Mogul,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., J., Frystyk, H., Masinter, L., Leach,
Ed., and J. Reschke, Ed., "HTTP/1.1, part 3: Message P., Berners-Lee, T., Lafon, Y., Ed.,
Payload and Content Negotiation", and J. Reschke, Ed., "HTTP/1.1, part
draft-ietf-httpbis-p3-payload-12 (work in progress), 3: Message Payload and Content
October 2010. Negotiation",
draft-ietf-httpbis-p3-payload-13 (work
in progress), March 2011.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part6] Fielding, R., Ed., Gettys, J., Mogul,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., J., Frystyk, H., Masinter, L., Leach,
Ed., Nottingham, M., Ed., and J. Reschke, Ed., P., Berners-Lee, T., Lafon, Y., Ed.,
"HTTP/1.1, part 6: Caching", Nottingham, M., Ed., and J. Reschke,
draft-ietf-httpbis-p6-cache-12 (work in progress), Ed., "HTTP/1.1, part 6: Caching",
October 2010. draft-ietf-httpbis-p6-cache-13 (work
in progress), March 2011.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB
Format Specification version 3.3", RFC 1950, May 1996. Compressed Data Format Specification
version 3.3", RFC 1950, May 1996.
RFC 1950 is an Informational RFC, thus it might be less RFC 1950 is an Informational RFC, thus
stable than this specification. On the other hand, it might be less stable than this
this downward reference was present since the specification. On the other hand,
publication of RFC 2068 in 1997 ([RFC2068]), therefore this downward reference was present
it is unlikely to cause problems in practice. See also since the publication of RFC 2068 in
[BCP97]. 1997 ([RFC2068]), therefore it is
unlikely to cause problems in
practice. See also [BCP97].
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format [RFC1951] Deutsch, P., "DEFLATE Compressed Data
Specification version 1.3", RFC 1951, May 1996. Format Specification version 1.3",
RFC 1951, May 1996.
RFC 1951 is an Informational RFC, thus it might be less RFC 1951 is an Informational RFC, thus
stable than this specification. On the other hand, it might be less stable than this
this downward reference was present since the specification. On the other hand,
publication of RFC 2068 in 1997 ([RFC2068]), therefore this downward reference was present
it is unlikely to cause problems in practice. See also since the publication of RFC 2068 in
[BCP97]. 1997 ([RFC2068]), therefore it is
unlikely to cause problems in
practice. See also [BCP97].
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and [RFC1952] Deutsch, P., Gailly, J-L., Adler, M.,
G. Randers-Pehrson, "GZIP file format specification Deutsch, L., and G. Randers-Pehrson,
version 4.3", RFC 1952, May 1996. "GZIP file format specification
version 4.3", RFC 1952, May 1996.
RFC 1952 is an Informational RFC, thus it might be less RFC 1952 is an Informational RFC, thus
stable than this specification. On the other hand, it might be less stable than this
this downward reference was present since the specification. On the other hand,
publication of RFC 2068 in 1997 ([RFC2068]), therefore this downward reference was present
it is unlikely to cause problems in practice. See also since the publication of RFC 2068 in
[BCP97]. 1997 ([RFC2068]), therefore it is
unlikely to cause problems in
practice. See also [BCP97].
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in
Requirement Levels", BCP 14, RFC 2119, March 1997. RFCs to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, [RFC3986] Berners-Lee, T., Fielding, R., and L.
"Uniform Resource Identifier (URI): Generic Syntax", Masinter, "Uniform Resource Identifier
STD 66, RFC 3986, January 2005. (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC5234] Crocker, D., Ed. and P. Overell,
Syntax Specifications: ABNF", STD 68, RFC 5234, "Augmented BNF for Syntax
January 2008. Specifications: ABNF", STD 68,
RFC 5234, January 2008.
[USASCII] American National Standards Institute, "Coded Character [USASCII] American National Standards Institute,
Set -- 7-bit American Standard Code for Information "Coded Character Set -- 7-bit American
Interchange", ANSI X3.4, 1986. Standard Code for Information
Interchange", ANSI X3.4, 1986.
13.2. Informative References 13.2. Informative References
[BCP97] Klensin, J. and S. Hartman, "Handling Normative [BCP97] Klensin, J. and S. Hartman, "Handling
References to Standards-Track Documents", BCP 97, Normative References to Standards-
RFC 4897, June 2007. Track Documents", BCP 97, RFC 4897,
June 2007.
[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and [Kri2001] Kristol, D., "HTTP Cookies: Standards,
Politics", ACM Transactions on Internet Technology Vol. Privacy, and Politics", ACM
1, #2, November 2001, Transactions on Internet
<http://arxiv.org/abs/cs.SE/0105018>. Technology Vol. 1, #2, November 2001,
<http://arxiv.org/abs/cs.SE/0105018>.
[Nie1997] Frystyk, H., Gettys, J., Prud'hommeaux, E., Lie, H., [Nie1997] Frystyk, H., Gettys, J.,
and C. Lilley, "Network Performance Effects of Prud'hommeaux, E., Lie, H., and C.
HTTP/1.1, CSS1, and PNG", ACM Proceedings of the ACM Lilley, "Network Performance Effects
SIGCOMM '97 conference on Applications, technologies, of HTTP/1.1, CSS1, and PNG",
architectures, and protocols for computer communication ACM Proceedings of the ACM SIGCOMM '97
SIGCOMM '97, September 1997, conference on Applications,
<http://doi.acm.org/10.1145/263105.263157>. 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", [Pad1995] Padmanabhan, V. and J. Mogul,
Computer Networks and ISDN Systems v. 28, pp. 25-35, "Improving HTTP Latency", Computer
December 1995, Networks and ISDN Systems v. 28, pp.
<http://portal.acm.org/citation.cfm?id=219094>. 25-35, December 1995, <http://
portal.acm.org/
citation.cfm?id=219094>.
[RFC1123] Braden, R., "Requirements for Internet Hosts - [RFC1123] Braden, R., "Requirements for Internet
Application and Support", STD 3, RFC 1123, Hosts - Application and Support",
October 1989. STD 3, RFC 1123, October 1989.
[RFC1900] Carpenter, B. and Y. Rekhter, "Renumbering Needs Work", [RFC1900] Carpenter, B. and Y. Rekhter,
RFC 1900, February 1996. "Renumbering Needs Work", RFC 1900,
February 1996.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, [RFC1919] Chatel, M., "Classical versus
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, Transparent IP Proxies", RFC 1919,
May 1996. March 1996.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet [RFC1945] Berners-Lee, T., Fielding, R., and H.
Mail Extensions (MIME) Part One: Format of Internet Nielsen, "Hypertext Transfer Protocol
Message Bodies", RFC 2045, November 1996. -- HTTP/1.0", RFC 1945, May 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail [RFC2045] Freed, N. and N. Borenstein,
Extensions) Part Three: Message Header Extensions for "Multipurpose Internet Mail Extensions
Non-ASCII Text", RFC 2047, November 1996. (MIME) Part One: Format of Internet
Message Bodies", RFC 2045,
November 1996.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and [RFC2047] Moore, K., "MIME (Multipurpose
T. Berners-Lee, "Hypertext Transfer Protocol -- Internet Mail Extensions) Part Three:
HTTP/1.1", RFC 2068, January 1997. Message Header Extensions for Non-
ASCII Text", RFC 2047, November 1996.
[RFC2109] Kristol, D. and L. Montulli, "HTTP State Management [RFC2068] Fielding, R., Gettys, J., Mogul, J.,
Mechanism", RFC 2109, February 1997. Nielsen, H., and T. Berners-Lee,
"Hypertext Transfer Protocol --
HTTP/1.1", RFC 2068, January 1997.
[RFC2145] Mogul, J., Fielding, R., Gettys, J., and H. Nielsen, [RFC2145] Mogul, J., Fielding, R., Gettys, J.,
"Use and Interpretation of HTTP Version Numbers", and H. Nielsen, "Use and
RFC 2145, May 1997. Interpretation of HTTP Version
Numbers", RFC 2145, May 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Frystyk, H., Masinter, L., Leach, P.,
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1",
RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within [RFC2817] Khare, R. and S. Lawrence, "Upgrading
HTTP/1.1", RFC 2817, May 2000. to TLS Within HTTP/1.1", RFC 2817,
May 2000.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over TLS",
RFC 2818, May 2000.
[RFC2965] Kristol, D. and L. Montulli, "HTTP State Management [RFC2965] Kristol, D. and L. Montulli, "HTTP
Mechanism", RFC 2965, October 2000. State Management Mechanism", RFC 2965,
October 2000.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration [RFC3040] Cooper, I., Melve, I., and G.
Procedures for Message Header Fields", BCP 90, Tomlinson, "Internet Web Replication
RFC 3864, September 2004. and Caching Taxonomy", RFC 3040,
January 2001.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications [RFC3864] Klyne, G., Nottingham, M., and J.
and Registration Procedures", BCP 13, RFC 4288, Mogul, "Registration Procedures for
December 2005. Message Header Fields", BCP 90,
RFC 3864, September 2004.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines [RFC4288] Freed, N. and J. Klensin, "Media Type
and Registration Procedures for New URI Schemes", Specifications and Registration
BCP 115, RFC 4395, February 2006. Procedures", BCP 13, RFC 4288,
December 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing [RFC4395] Hansen, T., Hardie, T., and L.
an IANA Considerations Section in RFCs", BCP 26, Masinter, "Guidelines and Registration
RFC 5226, May 2008. Procedures for New URI Schemes",
BCP 115, RFC 4395, February 2006.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC5226] Narten, T. and H. Alvestrand,
October 2008. "Guidelines for Writing an IANA
Considerations Section in RFCs",
BCP 26, RFC 5226, May 2008.
[Spe] Spero, S., "Analysis of HTTP Performance Problems", [RFC5322] Resnick, P., "Internet Message
<http://sunsite.unc.edu/mdma-release/http-prob.html>. Format", RFC 5322, October 2008.
[Tou1998] Touch, J., Heidemann, J., and K. Obraczka, "Analysis of [Spe] Spero, S., "Analysis of HTTP
HTTP Performance", ISI Research Report ISI/RR-98-463, Performance Problems", <http://
Aug 1998, <http://www.isi.edu/touch/pubs/http-perf96/>. sunsite.unc.edu/mdma-release/
http-prob.html>.
(original report dated Aug. 1996) [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)
[draft-ietf-httpstate-cookie] Barth, A., "HTTP State Management
Mechanism",
draft-ietf-httpstate-cookie-23 (work
in progress), March 2011.
Appendix A. Tolerant Applications Appendix A. Tolerant Applications
Although this document specifies the requirements for the generation Although this document specifies the requirements for the generation
of HTTP/1.1 messages, not all applications will be correct in their of HTTP/1.1 messages, not all applications will be correct in their
implementation. We therefore recommend that operational applications implementation. We therefore recommend that operational applications
be tolerant of deviations whenever those deviations can be be tolerant of deviations whenever those deviations can be
interpreted unambiguously. interpreted unambiguously.
Clients SHOULD be tolerant in parsing the Status-Line and servers
SHOULD be tolerant when parsing the Request-Line. In particular,
they SHOULD accept any amount of WSP characters between fields, even
though only a single SP is required.
The line terminator for header fields is the sequence CRLF. However, The line terminator for header fields is the sequence CRLF. However,
we recommend that applications, when parsing such headers fields, we recommend that applications, when parsing such headers fields,
recognize a single LF as a line terminator and ignore the leading CR. recognize a single LF as a line terminator and ignore the leading CR.
The character set of a representation SHOULD be labeled as the lowest The character encoding of a representation SHOULD be labeled as the
common denominator of the character codes used within that lowest common denominator of the character codes used within that
representation, with the exception that not labeling the representation, with the exception that not labeling the
representation is preferred over labeling the representation with the representation is preferred over labeling the representation with the
labels US-ASCII or ISO-8859-1. See [Part3]. labels US-ASCII or ISO-8859-1. See [Part3].
Additional rules for requirements on parsing and encoding of dates Additional rules for requirements on parsing and encoding of dates
and other potential problems with date encodings include: and other potential problems with date encodings include:
o HTTP/1.1 clients and caches SHOULD assume that an RFC-850 date o HTTP/1.1 clients and caches SHOULD assume that an RFC-850 date
which appears to be more than 50 years in the future is in fact in which appears to be more than 50 years in the future is in fact in
the past (this helps solve the "year 2000" problem). the past (this helps solve the "year 2000" problem).
skipping to change at page 71, line 5 skipping to change at page 75, line 5
proper value. proper value.
o All expiration-related calculations MUST be done in GMT. The o All expiration-related calculations MUST be done in GMT. The
local time zone MUST NOT influence the calculation or comparison local time zone MUST NOT influence the calculation or comparison
of an age or expiration time. of an age or expiration time.
o If an HTTP header field incorrectly carries a date value with a o If an HTTP header field incorrectly carries a date value with a
time zone other than GMT, it MUST be converted into GMT using the time zone other than GMT, it MUST be converted into GMT using the
most conservative possible conversion. most conservative possible conversion.
Appendix B. Compatibility with Previous Versions Appendix B. 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 method and no metadata. HTTP/1.0, as the Internet with only a single request method (GET) and no metadata.
defined by [RFC1945], added a range of request methods and MIME-like HTTP/1.0, as defined by [RFC1945], added a range of request methods
messaging that could include metadata about the data transferred and and MIME-like messaging that could include metadata about the data
modifiers on the request/response semantics. However, HTTP/1.0 did transferred and modifiers on the request/response semantics.
not sufficiently take into consideration the effects of hierarchical However, HTTP/1.0 did not sufficiently take into consideration the
proxies, caching, the need for persistent connections, or name-based effects of hierarchical proxies, caching, the need for persistent
virtual hosts. The proliferation of incompletely-implemented connections, or name-based virtual hosts. The proliferation of
applications calling themselves "HTTP/1.0" further necessitated a incompletely-implemented applications calling themselves "HTTP/1.0"
protocol version change in order for two communicating applications further necessitated a protocol version change in order for two
to determine each other's true capabilities. communicating applications to determine each other's true
capabilities.
HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
requirements that enable reliable implementations, adding only those requirements that enable reliable implementations, adding only those
new features that will either be safely ignored by an HTTP/1.0 new features that will either be safely ignored by an HTTP/1.0
recipient or only sent when communicating with a party advertising recipient or only sent when communicating with a party advertising
compliance with HTTP/1.1. compliance with HTTP/1.1.
It is beyond the scope of a protocol specification to mandate It is beyond the scope of a protocol specification to mandate
compliance with previous versions. HTTP/1.1 was deliberately compliance with previous versions. HTTP/1.1 was deliberately
designed, however, to make supporting previous versions easy. It is designed, however, to make supporting previous versions easy. We
worth noting that, at the time of composing this specification, we would expect a general-purpose HTTP/1.1 server to understand any
would expect general-purpose HTTP/1.1 servers to: valid request in the format of HTTP/1.0 and respond appropriately
with an HTTP/1.1 message that only uses features understood (or
o understand any valid request in the format of HTTP/1.0 and 1.1; safely ignored) by HTTP/1.0 clients. Likewise, would expect an
HTTP/1.1 client to understand any valid HTTP/1.0 response.
o respond appropriately with a message in the same major version
used by the client.
And we would expect HTTP/1.1 clients to:
o understand any valid response in the format of HTTP/1.0 or 1.1.
For most implementations of HTTP/1.0, each connection is established Since HTTP/0.9 did not support header fields in a request, there is
by the client prior to the request and closed by the server after no mechanism for it to support name-based virtual hosts (selection of
sending the response. Some implementations implement the Keep-Alive resource by inspection of the Host header field). Any server that
version of persistent connections described in Section 19.7.1 of implements name-based virtual hosts ought to disable support for
[RFC2068]. HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
badly constructed HTTP/1.x requests wherein a buggy client failed to
properly encode linear whitespace found in a URI reference and placed
in the request-target.
B.1. Changes from HTTP/1.0 B.1. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0 This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1. and HTTP/1.1.
B.1.1. Changes to Simplify Multi-homed Web Servers and Conserve IP B.1.1. Multi-homed Web Servers
Addresses
The requirements that clients and servers support the Host request- The requirements that clients and servers support the Host header
header field (Section 9.4), report an error if it is missing from an field (Section 9.4), report an error if it is missing from an
HTTP/1.1 request, and accept absolute URIs (Section 4.1.2) are among HTTP/1.1 request, and accept absolute URIs (Section 4.1.2) are among
the most important changes defined by this specification. the most important changes defined by HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request than the IP address
to which that request was directed. The changes outlined above will to which that request was directed. The Host header field was
allow the Internet, once older HTTP clients are no longer common, to introduced during the development of HTTP/1.1 and, though it was
support multiple Web sites from a single IP address, greatly quickly implemented by most HTTP/1.0 browsers, additional
simplifying large operational Web servers, where allocation of many requirements were placed on all HTTP/1.1 requests in order to ensure
IP addresses to a single host has created serious problems. The complete adoption. At the time of this writing, most HTTP-based
Internet will also be able to recover the IP addresses that have been services are dependent upon the Host header field for targeting
allocated for the sole purpose of allowing special-purpose domain requests.
names to be used in root-level HTTP URLs. Given the rate of growth
of the Web, and the number of servers already deployed, it is
extremely important that all implementations of HTTP (including
updates to existing HTTP/1.0 applications) correctly implement these
requirements:
o Both clients and servers MUST support the Host request-header
field.
o A client that sends an HTTP/1.1 request MUST send a Host header
field.
o Servers MUST report a 400 (Bad Request) error if an HTTP/1.1
request does not include a Host request-header field.
o Servers MUST accept absolute URIs. B.1.2. Keep-Alive Connections
B.2. Compatibility with HTTP/1.0 Persistent Connections For most implementations of HTTP/1.0, each connection is established
by the client prior to the request and closed by the server after
sending the response. However, some implementations implement the
Keep-Alive version of persistent connections described in Section
19.7.1 of [RFC2068].
Some clients and servers might wish to be compatible with some Some clients and servers might wish to be compatible with some
previous implementations of persistent connections in HTTP/1.0 previous implementations of persistent connections in HTTP/1.0
clients and servers. Persistent connections in HTTP/1.0 are clients and servers. Persistent connections in HTTP/1.0 are
explicitly negotiated as they are not the default behavior. HTTP/1.0 explicitly negotiated as they are not the default behavior. HTTP/1.0
experimental implementations of persistent connections are faulty, experimental implementations of persistent connections are faulty,
and the new facilities in HTTP/1.1 are designed to rectify these and the new facilities in HTTP/1.1 are designed to rectify these
problems. The problem was that some existing HTTP/1.0 clients might problems. The problem was that some existing HTTP/1.0 clients might
send Keep-Alive to a proxy server that doesn't understand Connection, send Keep-Alive to a proxy server that doesn't understand Connection,
which would then erroneously forward it to the next inbound server, which would then erroneously forward it to the next inbound server,
skipping to change at page 73, line 15 skipping to change at page 77, line 5
talking to proxies. talking to proxies.
However, talking to proxies is the most important use of persistent However, talking to proxies is the most important use of persistent
connections, so that prohibition is clearly unacceptable. Therefore, connections, so that prohibition is clearly unacceptable. Therefore,
we need some other mechanism for indicating a persistent connection we need some other mechanism for indicating a persistent connection
is desired, which is safe to use even when talking to an old proxy is desired, which is safe to use even when talking to an old proxy
that ignores Connection. Persistent connections are the default for that ignores Connection. Persistent connections are the default for
HTTP/1.1 messages; we introduce a new keyword (Connection: close) for HTTP/1.1 messages; we introduce a new keyword (Connection: close) for
declaring non-persistence. See Section 9.1. declaring non-persistence. See Section 9.1.
The original HTTP/1.0 form of persistent connections (the Connection: B.2. Changes from RFC 2616
Keep-Alive and Keep-Alive header field) is documented in Section
19.7.1 of [RFC2068].
B.3. Changes from RFC 2616
Empty list elements in list productions have been deprecated. Empty list elements in list productions have been deprecated.
(Section 1.2.1) (Section 1.2.1)
Rules about implicit linear whitespace between certain grammar Rules about implicit linear whitespace between certain grammar
productions have been removed; now it's only allowed when productions have been removed; now it's only allowed when
specifically pointed out in the ABNF. The NUL character is no longer specifically pointed out in the ABNF. The NUL octet is no longer
allowed in comment and quoted-string text. The quoted-pair rule no allowed in comment and quoted-string text. The quoted-pair rule no
longer allows escaping control characters other than HTAB. Non-ASCII longer allows escaping control characters other than HTAB. Non-ASCII
content in header fields and reason phrase has been obsoleted and content in header fields and reason phrase has been obsoleted and
made opaque (the TEXT rule was removed) (Section 1.2.2) made opaque (the TEXT rule was removed) (Section 1.2.2)
Clarify that HTTP-Version is case sensitive. (Section 2.5) Clarify that HTTP-Version is case sensitive. (Section 2.5)
Require that invalid whitespace around field-names be rejected. Require that invalid whitespace around field-names be rejected.
(Section 3.2) (Section 3.2)
Require recipients to handle bogus Content-Length header fields as Require recipients to handle bogus Content-Length header fields as
errors. (Section 3.3) errors. (Section 3.3)
Remove reference to non-existent identity transfer-coding value Remove reference to non-existent identity transfer-coding value
tokens. (Sections 3.3 and 6.2) tokens. (Sections 3.3 and 6.2)
Update use of abs_path production from RFC 1808 to the path-absolute Update use of abs_path production from RFC 1808 to the path-absolute
+ query components of RFC 3986. (Section 4.1.2) + query components of RFC 3986. State that the asterisk form is
allowed for the OPTIONS request method only. (Section 4.1.2)
Clarification that the chunk length does not include the count of the Clarification that the chunk length does not include the count of the
octets in the chunk header and trailer. Furthermore disallowed line octets in the chunk header and trailer. Furthermore disallowed line
folding in chunk extensions. (Section 6.2.1) folding in chunk extensions. (Section 6.2.1)
Remove hard limit of two connections per server. (Section 7.1.4) Remove hard limit of two connections per server. (Section 7.1.4)
Clarify exactly when close connection options must be sent. Clarify exactly when close connection options must be sent.
(Section 9.1) (Section 9.1)
Define the semantics of the "Upgrade" header field in responses other
than 101 (this was incorporated from [RFC2817]). (Section 9.8)
Appendix C. Collected ABNF Appendix C. Collected ABNF
BWS = OWS BWS = OWS
Cache-Control = <Cache-Control, defined in [Part6], Section 3.4>
Chunked-Body = *chunk last-chunk trailer-part CRLF Chunked-Body = *chunk last-chunk trailer-part CRLF
Connection = "Connection:" OWS Connection-v Connection = "Connection:" OWS Connection-v
Connection-v = *( "," OWS ) connection-token *( OWS "," [ OWS Connection-v = *( "," OWS ) connection-token *( OWS "," [ OWS
connection-token ] ) connection-token ] )
Content-Length = "Content-Length:" OWS 1*Content-Length-v Content-Length = "Content-Length:" OWS 1*Content-Length-v
Content-Length-v = 1*DIGIT Content-Length-v = 1*DIGIT
Date = "Date:" OWS Date-v Date = "Date:" OWS Date-v
Date-v = HTTP-date Date-v = HTTP-date
GMT = %x47.4D.54 ; GMT GMT = %x47.4D.54 ; GMT
HTTP-Prot-Name = %x48.54.54.50 ; HTTP HTTP-Prot-Name = %x48.54.54.50 ; HTTP
HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT
skipping to change at page 74, line 32 skipping to change at page 78, line 21
GMT = %x47.4D.54 ; GMT GMT = %x47.4D.54 ; GMT
HTTP-Prot-Name = %x48.54.54.50 ; HTTP HTTP-Prot-Name = %x48.54.54.50 ; HTTP
HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT HTTP-Version = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT
HTTP-date = rfc1123-date / obs-date HTTP-date = rfc1123-date / obs-date
HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body
] ]
Host = "Host:" OWS Host-v Host = "Host:" OWS Host-v
Host-v = uri-host [ ":" port ] Host-v = uri-host [ ":" port ]
MIME-Version = <MIME-Version, defined in [Part3], Appendix A.1>
Method = token Method = token
OWS = *( [ obs-fold ] WSP ) OWS = *( [ obs-fold ] WSP )
Pragma = <Pragma, defined in [Part6], Section 3.4>
RWS = 1*( [ obs-fold ] WSP ) RWS = 1*( [ obs-fold ] WSP )
Reason-Phrase = *( WSP / VCHAR / obs-text ) Reason-Phrase = *( WSP / VCHAR / obs-text )
Request = Request-Line *( header-field CRLF ) CRLF [ message-body ] Request = Request-Line *( header-field CRLF ) CRLF [ message-body ]
Request-Line = Method SP request-target SP HTTP-Version CRLF Request-Line = Method SP request-target SP HTTP-Version CRLF
Response = Status-Line *( header-field CRLF ) CRLF [ message-body ] Response = Status-Line *( header-field CRLF ) CRLF [ message-body ]
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
TE = "TE:" OWS TE-v TE = "TE:" OWS TE-v
skipping to change at page 75, line 17 skipping to change at page 78, line 51
URI-reference = <URI-reference, defined in [RFC3986], Section 4.1> URI-reference = <URI-reference, defined in [RFC3986], Section 4.1>
Upgrade = "Upgrade:" OWS Upgrade-v Upgrade = "Upgrade:" OWS Upgrade-v
Upgrade-v = *( "," OWS ) product *( OWS "," [ OWS product ] ) Upgrade-v = *( "," OWS ) product *( OWS "," [ OWS product ] )
Via = "Via:" OWS Via-v Via = "Via:" OWS Via-v
Via-v = *( "," OWS ) received-protocol RWS received-by [ RWS comment Via-v = *( "," OWS ) received-protocol RWS received-by [ RWS comment
] *( OWS "," [ OWS received-protocol RWS received-by [ RWS comment ] ] *( OWS "," [ OWS received-protocol RWS received-by [ RWS comment ]
] ) ] )
Warning = <Warning, defined in [Part6], Section 3.6>
absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3> absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3>
asctime-date = day-name SP date3 SP time-of-day SP year asctime-date = day-name SP date3 SP time-of-day SP year
attribute = token attribute = token
authority = <authority, defined in [RFC3986], Section 3.2> authority = <authority, defined in [RFC3986], Section 3.2>
chunk = chunk-size *WSP [ chunk-ext ] CRLF chunk-data CRLF chunk = chunk-size *WSP [ chunk-ext ] CRLF chunk-data CRLF
chunk-data = 1*OCTET chunk-data = 1*OCTET
chunk-ext = *( ";" *WSP chunk-ext-name [ "=" chunk-ext-val ] *WSP ) chunk-ext = *( ";" *WSP chunk-ext-name [ "=" chunk-ext-val ] *WSP )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-str-nf chunk-ext-val = token / quoted-str-nf
skipping to change at page 76, line 17 skipping to change at page 79, line 43
/ %x57.65.64.6E.65.73.64.61.79 ; Wednesday / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
/ %x54.68.75.72.73.64.61.79 ; Thursday / %x54.68.75.72.73.64.61.79 ; Thursday
/ %x46.72.69.64.61.79 ; Friday / %x46.72.69.64.61.79 ; Friday
/ %x53.61.74.75.72.64.61.79 ; Saturday / %x53.61.74.75.72.64.61.79 ; Saturday
/ %x53.75.6E.64.61.79 ; Sunday / %x53.75.6E.64.61.79 ; Sunday
field-content = *( WSP / VCHAR / obs-text ) field-content = *( WSP / VCHAR / obs-text )
field-name = token field-name = token
field-value = *( field-content / OWS ) field-value = *( field-content / OWS )
general-header = Cache-Control / Connection / Date / Pragma / Trailer
/ Transfer-Encoding / Upgrade / Via / Warning / MIME-Version
header-field = field-name ":" OWS [ field-value ] OWS header-field = field-name ":" OWS [ field-value ] OWS
hour = 2DIGIT hour = 2DIGIT
http-URI = "http://" authority path-abempty [ "?" query ] http-URI = "http://" authority path-abempty [ "?" query ]
https-URI = "https://" authority path-abempty [ "?" query ] https-URI = "https://" authority path-abempty [ "?" query ]
last-chunk = 1*"0" *WSP [ chunk-ext ] CRLF last-chunk = 1*"0" *WSP [ chunk-ext ] CRLF
message-body = *OCTET message-body = *OCTET
minute = 2DIGIT minute = 2DIGIT
month = %x4A.61.6E ; Jan month = %x4A.61.6E ; Jan
skipping to change at page 77, line 23 skipping to change at page 80, line 47
query = <query, defined in [RFC3986], Section 3.4> query = <query, defined in [RFC3986], Section 3.4>
quoted-cpair = "\" ( WSP / VCHAR / obs-text ) quoted-cpair = "\" ( WSP / VCHAR / obs-text )
quoted-pair = "\" ( WSP / VCHAR / obs-text ) quoted-pair = "\" ( WSP / VCHAR / obs-text )
quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
qvalue = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] ) qvalue = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
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-header = <request-header, defined in [Part2], Section 3>
request-target = "*" / absolute-URI / ( path-absolute [ "?" query ] ) request-target = "*" / absolute-URI / ( path-absolute [ "?" query ] )
/ authority / authority
response-header = <response-header, defined in [Part2], Section 5>
rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
second = 2DIGIT second = 2DIGIT
special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" / special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}" DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}"
start-line = Request-Line / Status-Line start-line = Request-Line / Status-Line
t-codings = "trailers" / ( transfer-extension [ te-params ] ) t-codings = "trailers" / ( transfer-extension [ te-params ] )
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
te-ext = OWS ";" OWS token [ "=" word ] te-ext = OWS ";" OWS token [ "=" word ]
te-params = OWS ";" OWS "q=" qvalue *te-ext te-params = OWS ";" OWS "q=" qvalue *te-ext
skipping to change at page 78, line 4 skipping to change at page 81, line 25
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
year = 4DIGIT year = 4DIGIT
ABNF diagnostics: ABNF diagnostics:
; Chunked-Body defined but not used ; Chunked-Body defined but not used
; Connection defined but not used
; Content-Length defined but not used ; Content-Length defined but not used
; Date defined but not used
; HTTP-message defined but not used ; HTTP-message defined but not used
; Host defined but not used ; Host defined but not used
; Request defined but not used ; Request defined but not used
; Response defined but not used ; Response defined but not used
; TE defined but not used ; TE defined but not used
; Trailer defined but not used
; Transfer-Encoding defined but not used
; URI-reference defined but not used ; URI-reference defined but not used
; general-header defined but not used ; Upgrade defined but not used
; Via defined but not used
; http-URI defined but not used ; http-URI defined but not used
; https-URI defined but not used ; https-URI defined but not used
; partial-URI defined but not used ; partial-URI defined but not used
; request-header defined but not used
; response-header defined but not used
; special defined but not used ; special defined but not used
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 86, line 31 skipping to change at page 90, line 8
request URI: handling of missing host in HTTP/1.0" request URI: handling of missing host in HTTP/1.0"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/248>: "confusing o <http://tools.ietf.org/wg/httpbis/trac/ticket/248>: "confusing
Date requirements for clients" Date requirements for clients"
Partly resolved issues: Partly resolved issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/95>: "Handling o <http://tools.ietf.org/wg/httpbis/trac/ticket/95>: "Handling
multiple Content-Length headers" multiple Content-Length headers"
D.14. Since draft-ietf-httpbis-p1-messaging-12
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/75>: "RFC2145
Normative"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/159>: "HTTP(s) URI
scheme definitions" (tune the requirements on userinfo)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/210>: "define
'transparent' proxy"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/224>: "Header
Classification"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/233>: "Is * usable
as a request-uri for new methods?"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/240>: "Migrate
Upgrade details from RFC2817"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/276>: "untangle
ABNFs for header fields"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/279>: "update RFC
2109 reference"
Index Index
A A
absolute-URI form (of request-target) 27 absolute-URI form (of request-target) 29
application/http Media Type 61 accelerator 13
asterisk form (of request-target) 27 application/http Media Type 64
authority form (of request-target) 27 asterisk form (of request-target) 28
authority form (of request-target) 29
B B
browser 10 browser 10
C C
cache 13 cache 14
cacheable 14 cacheable 14
chunked (Coding Format) 35 captive portal 14
chunked (Coding Format) 37
client 10 client 10
Coding Format Coding Format
chunked 35 chunked 37
compress 38 compress 40
deflate 38 deflate 40
gzip 38 gzip 40
compress (Coding Format) 38 compress (Coding Format) 40
connection 10 connection 10
Connection header 49 Connection header field 51
Content-Length header 50 Content-Length header field 53
D D
Date header 51 Date header field 53
deflate (Coding Format) 38 deflate (Coding Format) 40
downstream 12 downstream 12
E E
effective request URI 29 effective request URI 31
G G
gateway 13 gateway 13
Grammar Grammar
absolute-URI 16 absolute-URI 17
ALPHA 7 ALPHA 7
asctime-date 34 asctime-date 36
attribute 34 attribute 36
authority 16 authority 17
BWS 9 BWS 9
chunk 35 chunk 37
chunk-data 35 chunk-data 37
chunk-ext 35 chunk-ext 37
chunk-ext-name 35 chunk-ext-name 37
chunk-ext-val 35 chunk-ext-val 37
chunk-size 35 chunk-size 37
Chunked-Body 35 Chunked-Body 37
comment 22 comment 23
Connection 49 Connection 52
connection-token 49 connection-token 52
Connection-v 49 Connection-v 52
Content-Length 50 Content-Length 53
Content-Length-v 50 Content-Length-v 53
CR 7 CR 7
CRLF 7 CRLF 7
ctext 22 ctext 23
CTL 7 CTL 7
Date 51 Date 53
Date-v 51 Date-v 53
date1 33 date1 35
date2 34 date2 36
date3 34 date3 36
day 33 day 35
day-name 33 day-name 35
day-name-l 33 day-name-l 35
DIGIT 7 DIGIT 7
DQUOTE 7 DQUOTE 7
extension-code 32 field-content 22
extension-method 26 field-name 22
field-content 20 field-value 22
field-name 20 GMT 35
field-value 20 header-field 22
general-header 26
GMT 33
header-field 20
HEXDIG 7 HEXDIG 7
Host 52 Host 55
Host-v 52 Host-v 55
hour 33 hour 35
HTTP-date 32 HTTP-date 34
HTTP-message 19 HTTP-message 21
HTTP-Prot-Name 15 HTTP-Prot-Name 15
http-URI 16 http-URI 18
HTTP-Version 15 HTTP-Version 15
https-URI 18 https-URI 19
last-chunk 35 last-chunk 37
LF 7 LF 7
message-body 22 message-body 24
Method 26 Method 28
minute 33 minute 35
month 33 month 35
obs-date 33 obs-date 35
obs-text 10 obs-text 10
OCTET 7 OCTET 7
OWS 9 OWS 9
path-absolute 16 path-absolute 17
port 16 port 17
product 39 product 41
product-version 39 product-version 41
protocol-name 57 protocol-name 60
protocol-version 57 protocol-version 60
pseudonym 57 pseudonym 60
qdtext 10 qdtext 10
qdtext-nf 35 qdtext-nf 37
query 16 query 17
quoted-cpair 22 quoted-cpair 24
quoted-pair 10 quoted-pair 10
quoted-str-nf 35 quoted-str-nf 37
quoted-string 10 quoted-string 10
qvalue 39 qvalue 41
Reason-Phrase 32 Reason-Phrase 33
received-by 57 received-by 60
received-protocol 57 received-protocol 60
Request 26 Request 28
Request-Line 26 Request-Line 28
request-target 27 request-target 28
Response 31 Response 32
rfc850-date 34 rfc850-date 36
rfc1123-date 33 rfc1123-date 35
RWS 9 RWS 9
second 33 second 35
SP 7 SP 7
special 9 special 9
Status-Code 32 Status-Code 33
Status-Line 31 Status-Line 33
t-codings 53 t-codings 56
tchar 9 tchar 9
TE 53 TE 56
te-ext 53 te-ext 56
te-params 53 te-params 56
TE-v 53 TE-v 56
time-of-day 33 time-of-day 35
token 9 token 9
Trailer 54 Trailer 57
trailer-part 35 trailer-part 37
Trailer-v 54 Trailer-v 57
transfer-coding 34 transfer-coding 36
Transfer-Encoding 55 Transfer-Encoding 58
Transfer-Encoding-v 55 Transfer-Encoding-v 58
transfer-extension 34 transfer-extension 36
transfer-parameter 34 transfer-parameter 36
Upgrade 55 Upgrade 58
Upgrade-v 55 Upgrade-v 58
uri-host 16 uri-host 17
URI-reference 16 URI-reference 17
value 34 value 36
VCHAR 7 VCHAR 7
Via 57 Via 60
Via-v 57 Via-v 60
word 9 word 9
WSP 7 WSP 7
year 33 year 35
gzip (Coding Format) 38 gzip (Coding Format) 40
H H
header field 19 header field 20
header section 19 Header Fields
Headers Connection 51
Connection 49 Content-Length 53
Content-Length 50 Date 53
Date 51 Host 55
Host 52 TE 56
TE 53 Trailer 57
Trailer 54 Transfer-Encoding 58
Transfer-Encoding 55 Upgrade 58
Upgrade 55 Via 60
Via 57 header section 20
headers 19 headers 20
Host header 52 Host header field 55
http URI scheme 16 http URI scheme 18
https URI scheme 18 https URI scheme 19
I I
inbound 12 inbound 12
interception proxy 14
intermediary 12 intermediary 12
M M
Media Type Media Type
application/http 61 application/http 64
message/http 59 message/http 62
message 11 message 11
message/http Media Type 59 message/http Media Type 62
N
non-transforming proxy 13
O O
origin form (of request-target) 29
origin server 10 origin server 10
outbound 12 outbound 12
P P
path-absolute form (of request-target) 27 proxy 13
proxy 12
R R
request 11 request 11
resource 16 resource 17
response 11 response 11
reverse proxy 13 reverse proxy 13
S S
server 10 server 10
spider 10 spider 10
T T
target resource 29 target resource 31
TE header 53 TE header field 56
Trailer header 54 Trailer header field 57
Transfer-Encoding header 55 Transfer-Encoding header field 58
tunnel 13 transforming proxy 13
transparent proxy 14
tunnel 14
U U
Upgrade header 55 Upgrade header field 58
upstream 12 upstream 12
URI scheme URI scheme
http 16 http 18
https 18 https 19
user agent 10 user agent 10
V V
Via header 57 Via header field 60
Authors' Addresses Authors' Addresses
Roy T. Fielding (editor) Roy T. Fielding (editor)
Day Software Adobe Systems Incorporated
23 Corporate Plaza DR, Suite 280 345 Park Ave
Newport Beach, CA 92660 San Jose, CA 95110
USA USA
Phone: +1-949-706-5300
Fax: +1-949-706-5305
EMail: fielding@gbiv.com EMail: fielding@gbiv.com
URI: http://roy.gbiv.com/ URI: http://roy.gbiv.com/
Jim Gettys Jim Gettys
Alcatel-Lucent Bell Labs Alcatel-Lucent Bell Labs
21 Oak Knoll Road 21 Oak Knoll Road
Carlisle, MA 01741 Carlisle, MA 01741
USA USA
EMail: jg@freedesktop.org EMail: jg@freedesktop.org
skipping to change at page 91, line 33 skipping to change at page 96, line 4
URI: http://roy.gbiv.com/ URI: http://roy.gbiv.com/
Jim Gettys Jim Gettys
Alcatel-Lucent Bell Labs Alcatel-Lucent Bell Labs
21 Oak Knoll Road 21 Oak Knoll Road
Carlisle, MA 01741 Carlisle, MA 01741
USA USA
EMail: jg@freedesktop.org EMail: jg@freedesktop.org
URI: http://gettys.wordpress.com/ URI: http://gettys.wordpress.com/
Jeffrey C. Mogul Jeffrey C. Mogul
Hewlett-Packard Company Hewlett-Packard Company
HP Labs, Large Scale Systems Group HP Labs, Large Scale Systems Group
1501 Page Mill Road, MS 1177 1501 Page Mill Road, MS 1177
Palo Alto, CA 94304 Palo Alto, CA 94304
USA USA
EMail: JeffMogul@acm.org EMail: JeffMogul@acm.org
Henrik Frystyk Nielsen Henrik Frystyk Nielsen
Microsoft Corporation Microsoft Corporation
1 Microsoft Way 1 Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
USA USA
EMail: henrikn@microsoft.com EMail: henrikn@microsoft.com
Larry Masinter Larry Masinter
Adobe Systems, Incorporated Adobe Systems Incorporated
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
USA USA
EMail: LMM@acm.org EMail: LMM@acm.org
URI: http://larry.masinter.net/ URI: http://larry.masinter.net/
Paul J. Leach Paul J. Leach
Microsoft Corporation Microsoft Corporation
1 Microsoft Way 1 Microsoft Way
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