Use and Interpretation of HTTP Version Numbers
RFC 2145
Document | Type |
RFC - Informational
(May 1997; No errata)
Obsoleted by RFC 7230
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Authors | Henrik Nielsen , Jeffrey Mogul , Roy Fielding , Jim Gettys | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 2145 (Informational) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. C. Mogul Request for Comments: 2145 DEC Category: Informational R. Fielding UC Irvine J. Gettys DEC H. Frystyk MIT/LCS May 1997 Use and Interpretation of HTTP Version Numbers Status of this Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Distribution of this document is unlimited. Please send comments to the HTTP working group at <http-wg@cuckoo.hpl.hp.com>. Discussions of the working group are archived at <URL:http://www.ics.uci.edu/pub/ietf/http/>. General discussions about HTTP and the applications which use HTTP should take place on the <www-talk@w3.org> mailing list. Abstract HTTP request and response messages include an HTTP protocol version number. Some confusion exists concerning the proper use and interpretation of HTTP version numbers, and concerning interoperability of HTTP implementations of different protocol versions. This document is an attempt to clarify the situation. It is not a modification of the intended meaning of the existing HTTP/1.0 and HTTP/1.1 documents, but it does describe the intention of the authors of those documents, and can be considered definitive when there is any ambiguity in those documents concerning HTTP version numbers, for all versions of HTTP. Mogul, et. al. Informational [Page 1] RFC 2145 HTTP Version Numbers May 1997 TABLE OF CONTENTS 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 Robustness Principle . . . . . . . . . . . . . . . . . . 3 2 HTTP version numbers. . . . . . . . . . . . . . . . . . . . . . 3 2.1 Proxy behavior. . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Compatibility between minor versions of the same major version. . . . . . . . . . . . . . . . . . . . . . . . 4 2.3 Which version number to send in a message. . . . . . . . 5 3 Security Considerations . . . . . . . . . . . . . . . . . . . . 6 4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Authors' addresses. . . . . . . . . . . . . . . . . . . . . . . 6 1 Introduction HTTP request and response messages include an HTTP protocol version number. According to section 3.1 of the HTTP/1.1 specification [2], HTTP uses a "<major>.<minor>" numbering scheme to indicate versions of the protocol. The protocol versioning policy is intended to allow the sender to indicate the format of a message and its capacity for understanding further HTTP communication, rather than the features obtained via that communication. No change is made to the version 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 may 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. The same language appears in the description of HTTP/1.0 [1]. Many readers of these documents have expressed some confusion about the intended meaning of this policy. Also, some people who wrote HTTP implementations before RFC1945 [1] was issued were not aware of the intentions behind the introduction of version numbers in HTTP/1.0. This has led to debate and inconsistency regarding the use and interpretation of HTTP version numbers, and has led to interoperability problems in certain cases. Mogul, et. al. Informational [Page 2] RFC 2145 HTTP Version Numbers May 1997 This document is an attempt to clarify the situation. It is not a modification of the intended meaning of the existing HTTP/1.0 and HTTP/1.1 documents, but it does describe the intention of the authors of those documents. In any case where either of those two documents is ambiguous regarding the use and interpretation of HTTP version numbers, this document should be considered the definitive as to theShow full document text