source: draft-ietf-httpbis/latest/p2-semantics.xml @ 704

Last change on this file since 704 was 704, checked in by julian.reschke@…, 13 years ago

Bump up document dates, update to latest versions of rfc2629.xslt and xml2rfc.tcl

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File size: 157.4 KB
[29]1<?xml version="1.0" encoding="utf-8"?>
[101]2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
[8]3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
[29]14  <!ENTITY ID-VERSION "latest">
[704]15  <!ENTITY ID-MONTH "October">
[439]16  <!ENTITY ID-YEAR "2009">
[424]17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[31]18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
[695]24  <!ENTITY caching-combining-headers  "<xref target='Part6' x:rel='#combining.headers' xmlns:x=''/>">
[31]25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
[205]26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
[31]28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[580]29  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
[31]30  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
31  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
32  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
33  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
34  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
35  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
36  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
37  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
38  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
39  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
40  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
41  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
42  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
43  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
44  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
45  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
[688]46  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x=''/>">
[31]47  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
48  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
49  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
50  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
51  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
52  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
53  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
54  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
55  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
56  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
57  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
58  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
59  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
60  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
61  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
62  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
63  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
[190]64  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
[263]65  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
[700]66  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x=''/>">
67  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x=''/>">
68  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x=''/>">
69  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x=''/>">
70  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x=''/>">
71  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x=''/>">
73<?rfc toc="yes" ?>
[29]74<?rfc symrefs="yes" ?>
75<?rfc sortrefs="yes" ?>
[8]76<?rfc compact="yes"?>
77<?rfc subcompact="no" ?>
78<?rfc linkmailto="no" ?>
79<?rfc editing="no" ?>
[203]80<?rfc comments="yes"?>
81<?rfc inline="yes"?>
[8]82<?rfc-ext allow-markup-in-artwork="yes" ?>
83<?rfc-ext include-references-in-index="yes" ?>
[308]84<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
[446]85     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
[286]86     xmlns:x=''
87     xmlns:rdf=''>
[120]90  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
[29]92  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
93    <organization abbrev="Day Software">Day Software</organization>
[8]94    <address>
95      <postal>
[29]96        <street>23 Corporate Plaza DR, Suite 280</street>
97        <city>Newport Beach</city>
[8]98        <region>CA</region>
[29]99        <code>92660</code>
100        <country>USA</country>
[8]101      </postal>
[29]102      <phone>+1-949-706-5300</phone>
103      <facsimile>+1-949-706-5305</facsimile>
104      <email></email>
105      <uri></uri>
[8]106    </address>
107  </author>
[29]109  <author initials="J." surname="Gettys" fullname="Jim Gettys">
110    <organization>One Laptop per Child</organization>
[8]111    <address>
112      <postal>
[29]113        <street>21 Oak Knoll Road</street>
114        <city>Carlisle</city>
[8]115        <region>MA</region>
[29]116        <code>01741</code>
117        <country>USA</country>
[8]118      </postal>
[29]119      <email></email>
120      <uri></uri>
[8]121    </address>
122  </author>
124  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]125    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]126    <address>
127      <postal>
[29]128        <street>HP Labs, Large Scale Systems Group</street>
129        <street>1501 Page Mill Road, MS 1177</street>
[8]130        <city>Palo Alto</city>
131        <region>CA</region>
[29]132        <code>94304</code>
133        <country>USA</country>
[8]134      </postal>
[29]135      <email></email>
[8]136    </address>
137  </author>
139  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]140    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]141    <address>
142      <postal>
[29]143        <street>1 Microsoft Way</street>
144        <city>Redmond</city>
145        <region>WA</region>
146        <code>98052</code>
147        <country>USA</country>
[8]148      </postal>
[29]149      <email></email>
[8]150    </address>
151  </author>
153  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[29]154    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
[8]155    <address>
156      <postal>
[29]157        <street>345 Park Ave</street>
158        <city>San Jose</city>
[8]159        <region>CA</region>
[29]160        <code>95110</code>
161        <country>USA</country>
[8]162      </postal>
[29]163      <email></email>
164      <uri></uri>
[8]165    </address>
166  </author>
168  <author initials="P." surname="Leach" fullname="Paul J. Leach">
169    <organization abbrev="Microsoft">Microsoft Corporation</organization>
170    <address>
171      <postal>
172        <street>1 Microsoft Way</street>
173        <city>Redmond</city>
174        <region>WA</region>
175        <code>98052</code>
176      </postal>
177      <email></email>
178    </address>
179  </author>
181  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
182    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
183    <address>
184      <postal>
[34]185        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
186        <street>The Stata Center, Building 32</street>
187        <street>32 Vassar Street</street>
[8]188        <city>Cambridge</city>
189        <region>MA</region>
190        <code>02139</code>
[29]191        <country>USA</country>
[8]192      </postal>
193      <email></email>
[34]194      <uri></uri>
[8]195    </address>
196  </author>
[95]198  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]199    <organization abbrev="W3C">World Wide Web Consortium</organization>
200    <address>
201      <postal>
202        <street>W3C / ERCIM</street>
203        <street>2004, rte des Lucioles</street>
204        <city>Sophia-Antipolis</city>
205        <region>AM</region>
206        <code>06902</code>
207        <country>France</country>
208      </postal>
209      <email></email>
210      <uri></uri>
211    </address>
212  </author>
[95]214  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
215    <organization abbrev="greenbytes">greenbytes GmbH</organization>
216    <address>
217      <postal>
218        <street>Hafenweg 16</street>
219        <city>Muenster</city><region>NW</region><code>48155</code>
220        <country>Germany</country>
221      </postal>
[609]222      <phone>+49 251 2807760</phone>
223      <facsimile>+49 251 2807761</facsimile>
224      <email></email>
225      <uri></uri>
[95]226    </address>
227  </author>
[31]229  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]230  <workgroup>HTTPbis Working Group</workgroup>
234   The Hypertext Transfer Protocol (HTTP) is an application-level
235   protocol for distributed, collaborative, hypermedia information
[29]236   systems. HTTP has been in use by the World Wide Web global information
[35]237   initiative since 1990. This document is Part 2 of the seven-part specification
[29]238   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]239   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
[29]240   as expressed by request methods, request-header fields, response status codes,
241   and response-header fields.
245<note title="Editorial Note (To be removed by RFC Editor)">
246  <t>
247    Discussion of this draft should take place on the HTTPBIS working group
248    mailing list ( The current issues list is
[324]249    at <eref target=""/>
[36]250    and related documents (including fancy diffs) can be found at
[324]251    <eref target=""/>.
[36]252  </t>
[153]253  <t>
[604]254    The changes in this draft are summarized in <xref target="changes.since.07"/>.
[153]255  </t>
259<section title="Introduction" anchor="introduction">
[162]261   This document defines HTTP/1.1 request and response semantics.  Each HTTP
262   message, as defined in &messaging;, is in the form of either a request or
263   a response.  An HTTP server listens on a connection for HTTP requests and
264   responds to each request, in the order received on that connection, with
265   one or more HTTP response messages.  This document defines the commonly
266   agreed upon semantics of the HTTP uniform interface, the intentions defined
267   by each request method, and the various response messages that might be
268   expected as a result of applying that method for the requested resource.
[162]271   This document is currently disorganized in order to minimize the changes
272   between drafts and enable reviewers to see the smaller errata changes.
273   The next draft will reorganize the sections to better reflect the content.
274   In particular, the sections will be ordered according to the typical
275   processing of an HTTP request message (after message parsing): resource
276   mapping, general header fields, methods, request modifiers, response
277   status, and resource metadata.  The current mess reflects how widely
278   dispersed these topics and associated requirements had become in
279   <xref target="RFC2616"/>.
282<section title="Requirements" anchor="intro.requirements">
284   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
285   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
286   document are to be interpreted as described in <xref target="RFC2119"/>.
289   An implementation is not compliant if it fails to satisfy one or more
290   of the &MUST; or &REQUIRED; level requirements for the protocols it
291   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
292   level and all the &SHOULD; level requirements for its protocols is said
293   to be "unconditionally compliant"; one that satisfies all the &MUST;
294   level requirements but not all the &SHOULD; level requirements for its
295   protocols is said to be "conditionally compliant."
[424]299<section title="Syntax Notation" anchor="notation">
[425]300  <x:anchor-alias value="CR"/>
301  <x:anchor-alias value="DIGIT"/>
302  <x:anchor-alias value="LF"/>
303  <x:anchor-alias value="VCHAR"/>
304  <x:anchor-alias value="WSP"/>
[543]306  This specification uses the ABNF syntax defined in &notation; (which
307  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
308  <xref target="collected.abnf"/> shows the collected ABNF, with the list
309  rule expanded.
[425]312  The following core rules are included by
313  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
314  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
315  DIGIT (decimal 0-9), DQUOTE (double quote),
316  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
317  OCTET (any 8-bit sequence of data), SP (space),
318  VCHAR (any visible USASCII character),
319  and WSP (whitespace).
322<section title="Core Rules" anchor="core.rules">
[398]323  <x:anchor-alias value="obs-text"/>
[229]324  <x:anchor-alias value="quoted-string"/>
325  <x:anchor-alias value="token"/>
[356]326  <x:anchor-alias value="OWS"/>
327  <x:anchor-alias value="RWS"/>
[424]329  The core rules below are defined in &basic-rules;:
331<figure><artwork type="abnf2616">
[229]332  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
333  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
[356]334  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
335  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
[398]336  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
340<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]341  <x:anchor-alias value="absolute-URI"/>
[229]342  <x:anchor-alias value="Accept"/>
343  <x:anchor-alias value="Accept-Charset"/>
344  <x:anchor-alias value="Accept-Encoding"/>
345  <x:anchor-alias value="Accept-Language"/>
346  <x:anchor-alias value="Accept-Ranges"/>
347  <x:anchor-alias value="Age"/>
348  <x:anchor-alias value="Authorization"/>
[688]349  <x:anchor-alias value="comment"/>
[229]350  <x:anchor-alias value="ETag"/>
351  <x:anchor-alias value="Host"/>
352  <x:anchor-alias value="HTTP-date"/>
353  <x:anchor-alias value="If-Match"/>
354  <x:anchor-alias value="If-Modified-Since"/>
355  <x:anchor-alias value="If-None-Match"/>
356  <x:anchor-alias value="If-Range"/>
357  <x:anchor-alias value="If-Unmodified-Since"/>
[391]358  <x:anchor-alias value="partial-URI"/>
[229]359  <x:anchor-alias value="product"/>
360  <x:anchor-alias value="Proxy-Authenticate"/>
361  <x:anchor-alias value="Proxy-Authorization"/>
362  <x:anchor-alias value="Range"/>
363  <x:anchor-alias value="TE"/>
[632]364  <x:anchor-alias value="URI"/>
[229]365  <x:anchor-alias value="Vary"/>
366  <x:anchor-alias value="WWW-Authenticate"/>
[206]368  The ABNF rules below are defined in other parts:
[207]370<figure><!--Part1--><artwork type="abnf2616">
[374]371  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
[688]372  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
[374]373  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
[229]374  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
[391]375  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
[229]376  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
377  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
[632]378  <x:ref>URI</x:ref>           = &lt;URI, defined in &uri;&gt;
380<figure><!--Part3--><artwork type="abnf2616">
[229]381  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
382  <x:ref>Accept-Charset</x:ref> =
[206]383             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
[229]384  <x:ref>Accept-Encoding</x:ref> =
[206]385             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
[229]386  <x:ref>Accept-Language</x:ref> =
[206]387             &lt;Accept-Language, defined in &header-accept-language;&gt;
389<figure><!--Part4--><artwork type="abnf2616">
[229]390  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
391  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
392  <x:ref>If-Modified-Since</x:ref> =
[206]393             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
[229]394  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
395  <x:ref>If-Unmodified-Since</x:ref> =
[206]396             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
398<figure><!--Part5--><artwork type="abnf2616">
[229]399  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
400  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
401  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
403<figure><!--Part6--><artwork type="abnf2616">
[229]404  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
405  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
407<figure><artwork type="abnf2616">
[229]408  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
409  <x:ref>Proxy-Authenticate</x:ref> =
[206]410             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
[229]411  <x:ref>Proxy-Authorization</x:ref> =
[206]412             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
[229]413  <x:ref>WWW-Authenticate</x:ref> =
[206]414             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
[8]420<section title="Method" anchor="method">
[229]421  <x:anchor-alias value="Method"/>
422  <x:anchor-alias value="extension-method"/>
424   The Method  token indicates the method to be performed on the
[391]425   resource identified by the request-target. The method is case-sensitive.
427<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
[272]428  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
[334]429                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
430                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
431                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
432                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
433                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
434                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
435                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
436                 / <x:ref>extension-method</x:ref>
[229]437  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
440   The list of methods allowed by a resource can be specified in an
441   Allow header field (<xref target="header.allow"/>). The return code of the response
442   always notifies the client whether a method is currently allowed on a
443   resource, since the set of allowed methods can change dynamically. An
444   origin server &SHOULD; return the status code 405 (Method Not Allowed)
445   if the method is known by the origin server but not allowed for the
446   requested resource, and 501 (Not Implemented) if the method is
447   unrecognized or not implemented by the origin server. The methods GET
448   and HEAD &MUST; be supported by all general-purpose servers. All other
449   methods are &OPTIONAL;; however, if the above methods are implemented,
450   they &MUST; be implemented with the same semantics as those specified
451   in <xref target="method.definitions"/>.
454<section title="Method Registry" anchor="method.registry">
456  The HTTP Method Registry defines the name space for the Method token in the
457  Request line of an HTTP request.
[286]460  Registrations &MUST; include the following fields:
461  <list style="symbols">
462    <t>Method Name (see <xref target="method"/>)</t>
463    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
464    <t>Pointer to specification text</t>
465  </list>
[270]468  Values to be added to this name space are subject to IETF review
[591]469  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
[672]472  The registry itself is maintained at <eref target=""/>.
477<section title="Request Header Fields" anchor="request.header.fields">
[229]478  <x:anchor-alias value="request-header"/>
480   The request-header fields allow the client to pass additional
481   information about the request, and about the client itself, to the
482   server. These fields act as request modifiers, with semantics
483   equivalent to the parameters on a programming language method
484   invocation.
486<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
[229]487  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
[334]488                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
489                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
490                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
491                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
492                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
493                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
494                 / <x:ref>Host</x:ref>                     ; &header-host;
495                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
496                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
497                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
498                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
499                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
500                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
501                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
502                 / <x:ref>Range</x:ref>                    ; &header-range;
503                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
504                 / <x:ref>TE</x:ref>                       ; &header-te;
505                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
508   Request-header field names can be extended reliably only in
509   combination with a change in the protocol version. However, new or
510   experimental header fields &MAY; be given the semantics of request-header
511   fields if all parties in the communication recognize them to
512   be request-header fields. Unrecognized header fields are treated as
513   entity-header fields.
517<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
[229]518  <x:anchor-alias value="Reason-Phrase"/>
519  <x:anchor-alias value="Status-Code"/>
[426]520  <x:anchor-alias value="extension-code"/>
522   The Status-Code element is a 3-digit integer result code of the
[149]523   attempt to understand and satisfy the request. The status codes listed
524   below are defined in <xref target=""/>.
525   The Reason-Phrase is intended to give a short
[8]526   textual description of the Status-Code. The Status-Code is intended
527   for use by automata and the Reason-Phrase is intended for the human
528   user. The client is not required to examine or display the Reason-Phrase.
531   The individual values of the numeric status codes defined for
532   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
533   presented below. The reason phrases listed here are only
534   recommendations -- they &MAY; be replaced by local equivalents without
535   affecting the protocol.
537<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
[229]538  <x:ref>Status-Code</x:ref>    =
[8]539         "100"  ; <xref target="status.100"/>: Continue
[334]540       / "101"  ; <xref target="status.101"/>: Switching Protocols
541       / "200"  ; <xref target="status.200"/>: OK
542       / "201"  ; <xref target="status.201"/>: Created
543       / "202"  ; <xref target="status.202"/>: Accepted
544       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
545       / "204"  ; <xref target="status.204"/>: No Content
546       / "205"  ; <xref target="status.205"/>: Reset Content
[700]547       / "206"  ; &status-206;: Partial Content
[334]548       / "300"  ; <xref target="status.300"/>: Multiple Choices
549       / "301"  ; <xref target="status.301"/>: Moved Permanently
550       / "302"  ; <xref target="status.302"/>: Found
551       / "303"  ; <xref target="status.303"/>: See Other
[700]552       / "304"  ; &status-304;: Not Modified
[334]553       / "305"  ; <xref target="status.305"/>: Use Proxy
554       / "307"  ; <xref target="status.307"/>: Temporary Redirect
555       / "400"  ; <xref target="status.400"/>: Bad Request
[700]556       / "401"  ; &status-401;: Unauthorized
[334]557       / "402"  ; <xref target="status.402"/>: Payment Required
558       / "403"  ; <xref target="status.403"/>: Forbidden
559       / "404"  ; <xref target="status.404"/>: Not Found
560       / "405"  ; <xref target="status.405"/>: Method Not Allowed
561       / "406"  ; <xref target="status.406"/>: Not Acceptable
[700]562       / "407"  ; &status-407;: Proxy Authentication Required
[334]563       / "408"  ; <xref target="status.408"/>: Request Time-out
564       / "409"  ; <xref target="status.409"/>: Conflict
565       / "410"  ; <xref target="status.410"/>: Gone
566       / "411"  ; <xref target="status.411"/>: Length Required
[700]567       / "412"  ; &status-412;: Precondition Failed
[334]568       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
[465]569       / "414"  ; <xref target="status.414"/>: URI Too Long
[334]570       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
[700]571       / "416"  ; status-416;: Requested range not satisfiable
[334]572       / "417"  ; <xref target="status.417"/>: Expectation Failed
573       / "500"  ; <xref target="status.500"/>: Internal Server Error
574       / "501"  ; <xref target="status.501"/>: Not Implemented
575       / "502"  ; <xref target="status.502"/>: Bad Gateway
576       / "503"  ; <xref target="status.503"/>: Service Unavailable
577       / "504"  ; <xref target="status.504"/>: Gateway Time-out
578       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
579       / <x:ref>extension-code</x:ref>
[229]581  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
[398]582  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
585   HTTP status codes are extensible. HTTP applications are not required
586   to understand the meaning of all registered status codes, though such
587   understanding is obviously desirable. However, applications &MUST;
588   understand the class of any status code, as indicated by the first
589   digit, and treat any unrecognized response as being equivalent to the
590   x00 status code of that class, with the exception that an
591   unrecognized response &MUST-NOT; be cached. For example, if an
592   unrecognized status code of 431 is received by the client, it can
593   safely assume that there was something wrong with its request and
594   treat the response as if it had received a 400 status code. In such
595   cases, user agents &SHOULD; present to the user the entity returned
596   with the response, since that entity is likely to include human-readable
597   information which will explain the unusual status.
600<section title="Status Code Registry" anchor="status.code.registry">
602  The HTTP Status Code Registry defines the name space for the Status-Code
603  token in the Status line of an HTTP response.
606  Values to be added to this name space are subject to IETF review
[591]607  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
610  The registry itself is maintained at <eref target=""/>.
[8]616<section title="Response Header Fields" anchor="response.header.fields">
[229]617  <x:anchor-alias value="response-header"/>
619   The response-header fields allow the server to pass additional
620   information about the response which cannot be placed in the Status-Line.
621   These header fields give information about the server and about
[391]622   further access to the resource identified by the request-target.
624<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
[229]625  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
[334]626                  / <x:ref>Age</x:ref>                     ; &header-age;
627                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
628                  / <x:ref>ETag</x:ref>                    ; &header-etag;
629                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
630                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
631                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
632                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
633                  / <x:ref>Vary</x:ref>                    ; &header-vary;
634                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
637   Response-header field names can be extended reliably only in
638   combination with a change in the protocol version. However, new or
639   experimental header fields &MAY; be given the semantics of response-header
640   fields if all parties in the communication recognize them to
641   be response-header fields. Unrecognized header fields are treated as
642   entity-header fields.
646<section title="Entity" anchor="entity">
648   Request and Response messages &MAY; transfer an entity if not otherwise
649   restricted by the request method or response status code. An entity
650   consists of entity-header fields and an entity-body, although some
[29]651   responses will only include the entity-headers. HTTP entity-body and
652   entity-header fields are defined in &payload;.
655   An entity-body is only present in a message when a message-body is
[29]656   present, as described in &message-body;. The entity-body is obtained
[8]657   from the message-body by decoding any Transfer-Encoding that might
658   have been applied to ensure safe and proper transfer of the message.
661<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
663   It is sometimes necessary to determine the identity of the resource
664   associated with a representation.
667   An HTTP request representation, when present, is always associated with an
668   anonymous (i.e., unidentified) resource.
671   In the common case, an HTTP response is a representation of the resource
672   located at the request-URI. However, this is not always the case. To
673   determine the URI of the resource a response is associated with, the
674   following rules are used (first match winning):
676<t><list style="numbers">
677   <t>If the response status code is 200 or 203 and the request method was GET,
678   the response is a representation of the resource at the request-URI.</t>
679   <t>If the response status is 204, 206, or 304 and the request method was GET
680   or HEAD, the response is a partial representation of the resource at the
681   request-URI (see &caching-combining-headers;).</t>
682   <t>If the response has a Content-Location header, and that URI is the same
683   as the request-URI <cref>(see [ref])</cref>, the response is a representation of the
684   resource at the request-URI.</t>
685   <t>If the response has a Content-Location header, and that URI is not the
686   same as the request-URI, the response asserts that it is a representation of
687   the resource at the Content-Location URI (but it may not be).</t>
688   <t>Otherwise, the response is a representation of an anonymous (i.e.,
689   unidentified) resource.</t>
692  <cref anchor="TODO-req-uri">
693   Note that 'request-URI' is used here; however, we need to come up with a
694   term to denote "the URI that can be inferred from examining the
695   request-target and the Host header." (see <eref target="" />).
696   Also, the comparison function is going to have to be defined somewhere,
697   because we already need to compare URIs for things like cache invalidation.</cref>
[8]704<section title="Method Definitions" anchor="method.definitions">
706   The set of common methods for HTTP/1.1 is defined below. Although
707   this set can be expanded, additional methods cannot be assumed to
708   share the same semantics for separately extended clients and servers.
711<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
713<section title="Safe Methods" anchor="safe.methods">
[286]714<iref item="Safe Methods" primary="true"/>
716   Implementors should be aware that the software represents the user in
717   their interactions over the Internet, and should be careful to allow
718   the user to be aware of any actions they might take which may have an
719   unexpected significance to themselves or others.
722   In particular, the convention has been established that the GET and
723   HEAD methods &SHOULD-NOT;  have the significance of taking an action
[286]724   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
[8]725   This allows user agents to represent other methods, such as POST, PUT
726   and DELETE, in a special way, so that the user is made aware of the
727   fact that a possibly unsafe action is being requested.
730   Naturally, it is not possible to ensure that the server does not
731   generate side-effects as a result of performing a GET request; in
732   fact, some dynamic resources consider that a feature. The important
733   distinction here is that the user did not request the side-effects,
734   so therefore cannot be held accountable for them.
738<section title="Idempotent Methods" anchor="idempotent.methods">
[286]739<iref item="Idempotent Methods" primary="true"/>
[657]741   Methods can also have the property of "idempotence" in that, aside
742   from error or expiration issues, the intended effect of multiple
743   identical requests is the same as for a single request.
744   The methods PUT, DELETE, and all safe methods are idempotent.
745   It is important to note that idempotence refers only to changes
746   requested by the client: a server is free to change its state due
747   to multiple requests for the purpose of tracking those requests,
748   versioning of results, etc.
753<section title="OPTIONS" anchor="OPTIONS">
[286]754  <rdf:Description>
755    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
756  </rdf:Description>
[8]757  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
758  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
760   The OPTIONS method represents a request for information about the
761   communication options available on the request/response chain
[391]762   identified by the request-target. This method allows the client to
[8]763   determine the options and/or requirements associated with a resource,
764   or the capabilities of a server, without implying a resource action
765   or initiating a resource retrieval.
768   Responses to this method are not cacheable.
771   If the OPTIONS request includes an entity-body (as indicated by the
772   presence of Content-Length or Transfer-Encoding), then the media type
773   &MUST; be indicated by a Content-Type field. Although this
774   specification does not define any use for such a body, future
775   extensions to HTTP might use the OPTIONS body to make more detailed
[280]776   queries on the server.
[391]779   If the request-target is an asterisk ("*"), the OPTIONS request is
[8]780   intended to apply to the server in general rather than to a specific
781   resource. Since a server's communication options typically depend on
782   the resource, the "*" request is only useful as a "ping" or "no-op"
783   type of method; it does nothing beyond allowing the client to test
784   the capabilities of the server. For example, this can be used to test
785   a proxy for HTTP/1.1 compliance (or lack thereof).
[391]788   If the request-target is not an asterisk, the OPTIONS request applies
[8]789   only to the options that are available when communicating with that
790   resource.
793   A 200 response &SHOULD; include any header fields that indicate
794   optional features implemented by the server and applicable to that
795   resource (e.g., Allow), possibly including extensions not defined by
796   this specification. The response body, if any, &SHOULD; also include
797   information about the communication options. The format for such a
798   body is not defined by this specification, but might be defined by
799   future extensions to HTTP. Content negotiation &MAY; be used to select
800   the appropriate response format. If no response body is included, the
801   response &MUST; include a Content-Length field with a field-value of
802   "0".
805   The Max-Forwards request-header field &MAY; be used to target a
806   specific proxy in the request chain. When a proxy receives an OPTIONS
[374]807   request on an absolute-URI for which request forwarding is permitted,
[8]808   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
809   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
810   instead, the proxy &SHOULD; respond with its own communication options.
811   If the Max-Forwards field-value is an integer greater than zero, the
812   proxy &MUST; decrement the field-value when it forwards the request. If
813   no Max-Forwards field is present in the request, then the forwarded
814   request &MUST-NOT; include a Max-Forwards field.
818<section title="GET" anchor="GET">
[286]819  <rdf:Description>
820    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
821  </rdf:Description>
[8]822  <iref primary="true" item="GET method" x:for-anchor=""/>
823  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
825   The GET method means retrieve whatever information (in the form of an
[391]826   entity) is identified by the request-target. If the request-target refers
[8]827   to a data-producing process, it is the produced data which shall be
828   returned as the entity in the response and not the source text of the
829   process, unless that text happens to be the output of the process.
832   The semantics of the GET method change to a "conditional GET" if the
833   request message includes an If-Modified-Since, If-Unmodified-Since,
834   If-Match, If-None-Match, or If-Range header field. A conditional GET
835   method requests that the entity be transferred only under the
836   circumstances described by the conditional header field(s). The
837   conditional GET method is intended to reduce unnecessary network
838   usage by allowing cached entities to be refreshed without requiring
839   multiple requests or transferring data already held by the client.
842   The semantics of the GET method change to a "partial GET" if the
843   request message includes a Range header field. A partial GET requests
[29]844   that only part of the entity be transferred, as described in &header-range;.
[8]845   The partial GET method is intended to reduce unnecessary
846   network usage by allowing partially-retrieved entities to be
847   completed without transferring data already held by the client.
850   The response to a GET request is cacheable if and only if it meets
[29]851   the requirements for HTTP caching described in &caching;.
854   See <xref target=""/> for security considerations when used for forms.
858<section title="HEAD" anchor="HEAD">
[286]859  <rdf:Description>
860    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
861  </rdf:Description>
[8]862  <iref primary="true" item="HEAD method" x:for-anchor=""/>
863  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
865   The HEAD method is identical to GET except that the server &MUST-NOT;
866   return a message-body in the response. The metainformation contained
867   in the HTTP headers in response to a HEAD request &SHOULD; be identical
868   to the information sent in response to a GET request. This method can
869   be used for obtaining metainformation about the entity implied by the
870   request without transferring the entity-body itself. This method is
871   often used for testing hypertext links for validity, accessibility,
872   and recent modification.
875   The response to a HEAD request &MAY; be cacheable in the sense that the
876   information contained in the response &MAY; be used to update a
877   previously cached entity from that resource. If the new field values
878   indicate that the cached entity differs from the current entity (as
879   would be indicated by a change in Content-Length, Content-MD5, ETag
880   or Last-Modified), then the cache &MUST; treat the cache entry as
881   stale.
885<section title="POST" anchor="POST">
886  <iref primary="true" item="POST method" x:for-anchor=""/>
887  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
889   The POST method is used to request that the origin server accept the
[78]890   entity enclosed in the request as data to be processed by the resource
[391]891   identified by the request-target in the Request-Line. POST is designed
[8]892   to allow a uniform method to cover the following functions:
893  <list style="symbols">
894    <t>
895      Annotation of existing resources;
896    </t>
897    <t>
898        Posting a message to a bulletin board, newsgroup, mailing list,
899        or similar group of articles;
900    </t>
901    <t>
902        Providing a block of data, such as the result of submitting a
903        form, to a data-handling process;
904    </t>
905    <t>
906        Extending a database through an append operation.
907    </t>
908  </list>
911   The actual function performed by the POST method is determined by the
[391]912   server and is usually dependent on the request-target.
915   The action performed by the POST method might not result in a
916   resource that can be identified by a URI. In this case, either 200
917   (OK) or 204 (No Content) is the appropriate response status,
918   depending on whether or not the response includes an entity that
919   describes the result.
922   If a resource has been created on the origin server, the response
923   &SHOULD; be 201 (Created) and contain an entity which describes the
924   status of the request and refers to the new resource, and a Location
925   header (see <xref target="header.location"/>).
928   Responses to this method are not cacheable, unless the response
929   includes appropriate Cache-Control or Expires header fields. However,
930   the 303 (See Other) response can be used to direct the user agent to
931   retrieve a cacheable resource.
935<section title="PUT" anchor="PUT">
936  <iref primary="true" item="PUT method" x:for-anchor=""/>
937  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
[241]939   The PUT method requests that the enclosed entity be stored at the
[391]940   supplied request-target. If the request-target refers to an already
[8]941   existing resource, the enclosed entity &SHOULD; be considered as a
942   modified version of the one residing on the origin server. If the
[391]943   request-target does not point to an existing resource, and that URI is
[8]944   capable of being defined as a new resource by the requesting user
945   agent, the origin server can create the resource with that URI. If a
[391]946   new resource is created at the request-target, the origin server &MUST;
[609]947   inform the user agent
[8]948   via the 201 (Created) response. If an existing resource is modified,
949   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
950   to indicate successful completion of the request. If the resource
[391]951   could not be created or modified with the request-target, an appropriate
[8]952   error response &SHOULD; be given that reflects the nature of the
953   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
[333]954   headers (headers starting with the prefix 'Content-') that it does
955   not understand or implement
[8]956   and &MUST; return a 501 (Not Implemented) response in such cases.
[391]959   If the request passes through a cache and the request-target identifies
[8]960   one or more currently cached entities, those entries &SHOULD; be
961   treated as stale. Responses to this method are not cacheable.
964   The fundamental difference between the POST and PUT requests is
[391]965   reflected in the different meaning of the request-target. The URI in a
[8]966   POST request identifies the resource that will handle the enclosed
967   entity. That resource might be a data-accepting process, a gateway to
968   some other protocol, or a separate entity that accepts annotations.
969   In contrast, the URI in a PUT request identifies the entity enclosed
970   with the request -- the user agent knows what URI is intended and the
971   server &MUST-NOT; attempt to apply the request to some other resource.
972   If the server desires that the request be applied to a different URI,
973   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
974   then make its own decision regarding whether or not to redirect the
975   request.
978   A single resource &MAY; be identified by many different URIs. For
979   example, an article might have a URI for identifying "the current
980   version" which is separate from the URI identifying each particular
981   version. In this case, a PUT request on a general URI might result in
982   several other URIs being defined by the origin server.
985   HTTP/1.1 does not define how a PUT method affects the state of an
986   origin server.
989   Unless otherwise specified for a particular entity-header, the
990   entity-headers in the PUT request &SHOULD; be applied to the resource
991   created or modified by the PUT.
995<section title="DELETE" anchor="DELETE">
996  <iref primary="true" item="DELETE method" x:for-anchor=""/>
997  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
999   The DELETE method requests that the origin server delete the resource
[391]1000   identified by the request-target. This method &MAY; be overridden by human
[8]1001   intervention (or other means) on the origin server. The client cannot
1002   be guaranteed that the operation has been carried out, even if the
1003   status code returned from the origin server indicates that the action
1004   has been completed successfully. However, the server &SHOULD-NOT;
1005   indicate success unless, at the time the response is given, it
1006   intends to delete the resource or move it to an inaccessible
1007   location.
1010   A successful response &SHOULD; be 200 (OK) if the response includes an
1011   entity describing the status, 202 (Accepted) if the action has not
1012   yet been enacted, or 204 (No Content) if the action has been enacted
1013   but the response does not include an entity.
[391]1016   If the request passes through a cache and the request-target identifies
[8]1017   one or more currently cached entities, those entries &SHOULD; be
1018   treated as stale. Responses to this method are not cacheable.
1022<section title="TRACE" anchor="TRACE">
[286]1023  <rdf:Description>
1024    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1025  </rdf:Description>
[8]1026  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1027  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1029   The TRACE method is used to invoke a remote, application-layer loop-back
1030   of the request message. The final recipient of the request
1031   &SHOULD; reflect the message received back to the client as the
1032   entity-body of a 200 (OK) response. The final recipient is either the
1033   origin server or the first proxy or gateway to receive a Max-Forwards
1034   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1035   &MUST-NOT; include an entity.
1038   TRACE allows the client to see what is being received at the other
1039   end of the request chain and use that data for testing or diagnostic
[29]1040   information. The value of the Via header field (&header-via;) is of
[8]1041   particular interest, since it acts as a trace of the request chain.
1042   Use of the Max-Forwards header field allows the client to limit the
1043   length of the request chain, which is useful for testing a chain of
1044   proxies forwarding messages in an infinite loop.
1047   If the request is valid, the response &SHOULD; contain the entire
1048   request message in the entity-body, with a Content-Type of
[263]1049   "message/http" (see &media-type-message-http;). Responses to this method
1050   &MUST-NOT; be cached.
1054<section title="CONNECT" anchor="CONNECT">
1055  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1056  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1058   This specification reserves the method name CONNECT for use with a
1059   proxy that can dynamically switch to being a tunnel (e.g. SSL
[274]1060   tunneling <xref target="RFC2817"/>).
1066<section title="Status Code Definitions" anchor="">
[579]1068   Each Status-Code is described below, including any metainformation required
1069   in the response.
1072<section title="Informational 1xx" anchor="status.1xx">
1074   This class of status code indicates a provisional response,
1075   consisting only of the Status-Line and optional headers, and is
1076   terminated by an empty line. There are no required headers for this
1077   class of status code. Since HTTP/1.0 did not define any 1xx status
1078   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1079   except under experimental conditions.
1082   A client &MUST; be prepared to accept one or more 1xx status responses
1083   prior to a regular response, even if the client does not expect a 100
1084   (Continue) status message. Unexpected 1xx status responses &MAY; be
1085   ignored by a user agent.
1088   Proxies &MUST; forward 1xx responses, unless the connection between the
1089   proxy and its client has been closed, or unless the proxy itself
1090   requested the generation of the 1xx response. (For example, if a
1091   proxy adds a "Expect: 100-continue" field when it forwards a request,
1092   then it need not forward the corresponding 100 (Continue)
1093   response(s).)
1096<section title="100 Continue" anchor="status.100">
1097  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1098  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1100   The client &SHOULD; continue with its request. This interim response is
1101   used to inform the client that the initial part of the request has
1102   been received and has not yet been rejected by the server. The client
1103   &SHOULD; continue by sending the remainder of the request or, if the
1104   request has already been completed, ignore this response. The server
1105   &MUST; send a final response after the request has been completed. See
[29]1106   &use100; for detailed discussion of the use and handling of this
[8]1107   status code.
1111<section title="101 Switching Protocols" anchor="status.101">
1112  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1113  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1115   The server understands and is willing to comply with the client's
[29]1116   request, via the Upgrade message header field (&header-upgrade;), for a
[8]1117   change in the application protocol being used on this connection. The
1118   server will switch protocols to those defined by the response's
1119   Upgrade header field immediately after the empty line which
1120   terminates the 101 response.
1123   The protocol &SHOULD; be switched only when it is advantageous to do
1124   so. For example, switching to a newer version of HTTP is advantageous
1125   over older versions, and switching to a real-time, synchronous
1126   protocol might be advantageous when delivering resources that use
1127   such features.
1132<section title="Successful 2xx" anchor="status.2xx">
1134   This class of status code indicates that the client's request was
1135   successfully received, understood, and accepted.
1138<section title="200 OK" anchor="status.200">
1139  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1140  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1142   The request has succeeded. The information returned with the response
1143   is dependent on the method used in the request, for example:
1144  <list style="hanging">
1145    <t hangText="GET">
1146          an entity corresponding to the requested resource is sent in
1147          the response;
1148    </t>
1149    <t hangText="HEAD">
1150          the entity-header fields corresponding to the requested
1151          resource are sent in the response without any message-body;
1152    </t>
1153    <t hangText="POST">
1154      an entity describing or containing the result of the action;
1155    </t>
1156    <t hangText="TRACE">
1157      an entity containing the request message as received by the
1158      end server.
1159    </t>
1160  </list>
1164<section title="201 Created" anchor="status.201">
1165  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1166  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1168   The request has been fulfilled and resulted in a new resource being
1169   created. The newly created resource can be referenced by the URI(s)
1170   returned in the entity of the response, with the most specific URI
1171   for the resource given by a Location header field. The response
1172   &SHOULD; include an entity containing a list of resource
1173   characteristics and location(s) from which the user or user agent can
1174   choose the one most appropriate. The entity format is specified by
1175   the media type given in the Content-Type header field. The origin
1176   server &MUST; create the resource before returning the 201 status code.
1177   If the action cannot be carried out immediately, the server &SHOULD;
1178   respond with 202 (Accepted) response instead.
1181   A 201 response &MAY; contain an ETag response header field indicating
1182   the current value of the entity tag for the requested variant just
[29]1183   created, see &header-etag;.
1187<section title="202 Accepted" anchor="status.202">
1188  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1189  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1191   The request has been accepted for processing, but the processing has
1192   not been completed.  The request might or might not eventually be
1193   acted upon, as it might be disallowed when processing actually takes
1194   place. There is no facility for re-sending a status code from an
1195   asynchronous operation such as this.
1198   The 202 response is intentionally non-committal. Its purpose is to
1199   allow a server to accept a request for some other process (perhaps a
1200   batch-oriented process that is only run once per day) without
1201   requiring that the user agent's connection to the server persist
1202   until the process is completed. The entity returned with this
1203   response &SHOULD; include an indication of the request's current status
1204   and either a pointer to a status monitor or some estimate of when the
1205   user can expect the request to be fulfilled.
1209<section title="203 Non-Authoritative Information" anchor="status.203">
1210  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1211  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1213   The returned metainformation in the entity-header is not the
1214   definitive set as available from the origin server, but is gathered
1215   from a local or a third-party copy. The set presented &MAY; be a subset
1216   or superset of the original version. For example, including local
1217   annotation information about the resource might result in a superset
1218   of the metainformation known by the origin server. Use of this
1219   response code is not required and is only appropriate when the
1220   response would otherwise be 200 (OK).
1224<section title="204 No Content" anchor="status.204">
1225  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1226  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1228   The server has fulfilled the request but does not need to return an
1229   entity-body, and might want to return updated metainformation. The
1230   response &MAY; include new or updated metainformation in the form of
1231   entity-headers, which if present &SHOULD; be associated with the
1232   requested variant.
1235   If the client is a user agent, it &SHOULD-NOT;  change its document view
1236   from that which caused the request to be sent. This response is
1237   primarily intended to allow input for actions to take place without
1238   causing a change to the user agent's active document view, although
1239   any new or updated metainformation &SHOULD; be applied to the document
1240   currently in the user agent's active view.
1243   The 204 response &MUST-NOT; include a message-body, and thus is always
1244   terminated by the first empty line after the header fields.
1248<section title="205 Reset Content" anchor="status.205">
1249  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1250  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1252   The server has fulfilled the request and the user agent &SHOULD; reset
1253   the document view which caused the request to be sent. This response
1254   is primarily intended to allow input for actions to take place via
1255   user input, followed by a clearing of the form in which the input is
1256   given so that the user can easily initiate another input action. The
1257   response &MUST-NOT; include an entity.
1261<section title="206 Partial Content" anchor="status.206">
1262  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1263  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
[700]1264  <rdf:Description>
1265    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1266  </rdf:Description>
[29]1268   The server has fulfilled the partial GET request for the resource
[700]1269   and the enclosed entity is a partial representation as defined in &status-206;.
1274<section title="Redirection 3xx" anchor="status.3xx">
1276   This class of status code indicates that further action needs to be
1277   taken by the user agent in order to fulfill the request.  The action
1278   required &MAY; be carried out by the user agent without interaction
1279   with the user if and only if the method used in the second request is
1280   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1281   such loops generate network traffic for each redirection.
1284  <t>
[629]1285    <x:h>Note:</x:h> an earlier version of this specification recommended a
1286    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1287    Content developers should be aware that there might be clients that
1288    implement such a fixed limitation.
[563]1289  </t>
1292<section title="300 Multiple Choices" anchor="status.300">
1293  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1294  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1296   The requested resource corresponds to any one of a set of
1297   representations, each with its own specific location, and agent-driven
[29]1298   negotiation information (&content-negotiation;) is being provided so that
[8]1299   the user (or user agent) can select a preferred representation and
1300   redirect its request to that location.
1303   Unless it was a HEAD request, the response &SHOULD; include an entity
1304   containing a list of resource characteristics and location(s) from
1305   which the user or user agent can choose the one most appropriate. The
1306   entity format is specified by the media type given in the Content-Type
1307   header field. Depending upon the format and the capabilities of
1308   the user agent, selection of the most appropriate choice &MAY; be
1309   performed automatically. However, this specification does not define
1310   any standard for such automatic selection.
1313   If the server has a preferred choice of representation, it &SHOULD;
1314   include the specific URI for that representation in the Location
1315   field; user agents &MAY; use the Location field value for automatic
1316   redirection. This response is cacheable unless indicated otherwise.
1320<section title="301 Moved Permanently" anchor="status.301">
1321  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1322  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1324   The requested resource has been assigned a new permanent URI and any
1325   future references to this resource &SHOULD; use one of the returned
1326   URIs.  Clients with link editing capabilities ought to automatically
[391]1327   re-link references to the request-target to one or more of the new
[8]1328   references returned by the server, where possible. This response is
1329   cacheable unless indicated otherwise.
1332   The new permanent URI &SHOULD; be given by the Location field in the
1333   response. Unless the request method was HEAD, the entity of the
1334   response &SHOULD; contain a short hypertext note with a hyperlink to
1335   the new URI(s).
[88]1338   If the 301 status code is received in response to a request method
1339   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1340   then the request &MAY; be automatically redirected by the user agent without
[88]1341   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1342   request unless it can be confirmed by the user, since this might
1343   change the conditions under which the request was issued.
1346  <t>
1347    <x:h>Note:</x:h> When automatically redirecting a POST request after
1348    receiving a 301 status code, some existing HTTP/1.0 user agents
1349    will erroneously change it into a GET request.
1350  </t>
1354<section title="302 Found" anchor="status.302">
1355  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1356  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1358   The requested resource resides temporarily under a different URI.
1359   Since the redirection might be altered on occasion, the client &SHOULD;
[391]1360   continue to use the request-target for future requests.  This response
[8]1361   is only cacheable if indicated by a Cache-Control or Expires header
1362   field.
1365   The temporary URI &SHOULD; be given by the Location field in the
1366   response. Unless the request method was HEAD, the entity of the
1367   response &SHOULD; contain a short hypertext note with a hyperlink to
1368   the new URI(s).
[88]1371   If the 302 status code is received in response to a request method
1372   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1373   then the request &MAY; be automatically redirected by the user agent without
[88]1374   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1375   request unless it can be confirmed by the user, since this might
1376   change the conditions under which the request was issued.
1379  <t>
[614]1380    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1381    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1382    specify that the client is not allowed to change the method on the
1383    redirected request.  However, most existing user agent implementations
1384    treat 302 as if it were a 303 response, performing a GET on the Location
1385    field-value regardless of the original request method. Therefore, a
1386    previous version of this specification
1387    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1388    status codes
1389    <xref target="status.303" format="none">303</xref> and
1390    <xref target="status.307" format="none">307</xref> for servers that wish
1391    to make unambiguously clear which kind of reaction is expected of the
1392    client.
[563]1393  </t>
1397<section title="303 See Other" anchor="status.303">
1398  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1399  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
[242]1401   The server directs the user agent to a different resource, indicated
1402   by a URI in the Location header field, that provides an indirect
1403   response to the original request.  The user agent &MAY; perform a GET
1404   request on the URI in the Location field in order to obtain a
1405   representation corresponding to the response, be redirected again,
1406   or end with an error status.  The Location URI is not a substitute
1407   reference for the originally requested resource.
[242]1410   The 303 status is generally applicable to any HTTP method.  It is
1411   primarily used to allow the output of a POST action to redirect
1412   the user agent to a selected resource, since doing so provides the
1413   information corresponding to the POST response in a form that
1414   can be separately identified, bookmarked, and cached independent
1415   of the original request.
1418   A 303 response to a GET request indicates that the requested
1419   resource does not have a representation of its own that can be
1420   transferred by the server over HTTP.  The Location URI indicates a
1421   resource that is descriptive of the requested resource such that
1422   the follow-on representation may be useful without implying that
[243]1423   it adequately represents the previously requested resource.
[242]1424   Note that answers to the questions of what can be represented, what
1425   representations are adequate, and what might be a useful description
1426   are outside the scope of HTTP and thus entirely determined by the
[602]1427   URI owner(s).
1430   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1431   cacheable by Cache-Control or Expires header fields.  Except for
1432   responses to a HEAD request, the entity of a 303 response &SHOULD;
1433   contain a short hypertext note with a hyperlink to the Location URI.
1437<section title="304 Not Modified" anchor="status.304">
1438  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1439  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
[700]1440  <rdf:Description>
1441    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1442  </rdf:Description>
[45]1444   The response to the request has not been modified since the conditions
[700]1445   indicated by the client's conditional GET request, as defined in &status-304;.
1449<section title="305 Use Proxy" anchor="status.305">
1450  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1451  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
[235]1453   The 305 status was defined in a previous version of this specification
1454   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1458<section title="306 (Unused)" anchor="status.306">
1459  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1460  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1462   The 306 status code was used in a previous version of the
1463   specification, is no longer used, and the code is reserved.
1467<section title="307 Temporary Redirect" anchor="status.307">
1468  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1469  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1471   The requested resource resides temporarily under a different URI.
1472   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
[391]1473   continue to use the request-target for future requests.  This response
[8]1474   is only cacheable if indicated by a Cache-Control or Expires header
1475   field.
1478   The temporary URI &SHOULD; be given by the Location field in the
1479   response. Unless the request method was HEAD, the entity of the
1480   response &SHOULD; contain a short hypertext note with a hyperlink to
1481   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1482   understand the 307 status. Therefore, the note &SHOULD; contain the
1483   information necessary for a user to repeat the original request on
1484   the new URI.
[88]1487   If the 307 status code is received in response to a request method
1488   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1489   then the request &MAY; be automatically redirected by the user agent without
[88]1490   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1491   request unless it can be confirmed by the user, since this might
1492   change the conditions under which the request was issued.
1497<section title="Client Error 4xx" anchor="status.4xx">
1499   The 4xx class of status code is intended for cases in which the
1500   client seems to have erred. Except when responding to a HEAD request,
1501   the server &SHOULD; include an entity containing an explanation of the
1502   error situation, and whether it is a temporary or permanent
1503   condition. These status codes are applicable to any request method.
1504   User agents &SHOULD; display any included entity to the user.
1507   If the client is sending data, a server implementation using TCP
1508   &SHOULD; be careful to ensure that the client acknowledges receipt of
1509   the packet(s) containing the response, before the server closes the
1510   input connection. If the client continues sending data to the server
1511   after the close, the server's TCP stack will send a reset packet to
1512   the client, which may erase the client's unacknowledged input buffers
1513   before they can be read and interpreted by the HTTP application.
1516<section title="400 Bad Request" anchor="status.400">
1517  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1518  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1520   The request could not be understood by the server due to malformed
1521   syntax. The client &SHOULD-NOT;  repeat the request without
1522   modifications.
1526<section title="401 Unauthorized" anchor="status.401">
1527  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1528  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
[700]1529  <rdf:Description>
1530    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1531  </rdf:Description>
[700]1533   The request requires user authentication (see &status-401;).
1537<section title="402 Payment Required" anchor="status.402">
1538  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1539  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1541   This code is reserved for future use.
1545<section title="403 Forbidden" anchor="status.403">
1546  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1547  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1549   The server understood the request, but is refusing to fulfill it.
1550   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1551   If the request method was not HEAD and the server wishes to make
1552   public why the request has not been fulfilled, it &SHOULD; describe the
1553   reason for the refusal in the entity.  If the server does not wish to
1554   make this information available to the client, the status code 404
1555   (Not Found) can be used instead.
1559<section title="404 Not Found" anchor="status.404">
1560  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1561  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
[391]1563   The server has not found anything matching the request-target. No
[8]1564   indication is given of whether the condition is temporary or
1565   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1566   knows, through some internally configurable mechanism, that an old
1567   resource is permanently unavailable and has no forwarding address.
1568   This status code is commonly used when the server does not wish to
1569   reveal exactly why the request has been refused, or when no other
1570   response is applicable.
1574<section title="405 Method Not Allowed" anchor="status.405">
1575  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1576  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1578   The method specified in the Request-Line is not allowed for the
[391]1579   resource identified by the request-target. The response &MUST; include an
[8]1580   Allow header containing a list of valid methods for the requested
1581   resource.
1585<section title="406 Not Acceptable" anchor="status.406">
1586  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1587  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1589   The resource identified by the request is only capable of generating
1590   response entities which have content characteristics not acceptable
1591   according to the accept headers sent in the request.
1594   Unless it was a HEAD request, the response &SHOULD; include an entity
1595   containing a list of available entity characteristics and location(s)
1596   from which the user or user agent can choose the one most
1597   appropriate. The entity format is specified by the media type given
1598   in the Content-Type header field. Depending upon the format and the
1599   capabilities of the user agent, selection of the most appropriate
1600   choice &MAY; be performed automatically. However, this specification
1601   does not define any standard for such automatic selection.
1604  <t>
1605    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1606    not acceptable according to the accept headers sent in the
1607    request. In some cases, this may even be preferable to sending a
1608    406 response. User agents are encouraged to inspect the headers of
1609    an incoming response to determine if it is acceptable.
1610  </t>
1613   If the response could be unacceptable, a user agent &SHOULD;
1614   temporarily stop receipt of more data and query the user for a
1615   decision on further actions.
1619<section title="407 Proxy Authentication Required" anchor="status.407">
1620  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1621  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1623   This code is similar to 401 (Unauthorized), but indicates that the
[700]1624   client must first authenticate itself with the proxy (see &status-407;).
1628<section title="408 Request Timeout" anchor="status.408">
1629  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1630  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1632   The client did not produce a request within the time that the server
1633   was prepared to wait. The client &MAY; repeat the request without
1634   modifications at any later time.
1638<section title="409 Conflict" anchor="status.409">
1639  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1640  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1642   The request could not be completed due to a conflict with the current
1643   state of the resource. This code is only allowed in situations where
1644   it is expected that the user might be able to resolve the conflict
1645   and resubmit the request. The response body &SHOULD; include enough
1646   information for the user to recognize the source of the conflict.
1647   Ideally, the response entity would include enough information for the
1648   user or user agent to fix the problem; however, that might not be
1649   possible and is not required.
1652   Conflicts are most likely to occur in response to a PUT request. For
1653   example, if versioning were being used and the entity being PUT
1654   included changes to a resource which conflict with those made by an
1655   earlier (third-party) request, the server might use the 409 response
1656   to indicate that it can't complete the request. In this case, the
1657   response entity would likely contain a list of the differences
1658   between the two versions in a format defined by the response
1659   Content-Type.
1663<section title="410 Gone" anchor="status.410">
1664  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1665  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1667   The requested resource is no longer available at the server and no
1668   forwarding address is known. This condition is expected to be
1669   considered permanent. Clients with link editing capabilities &SHOULD;
[391]1670   delete references to the request-target after user approval. If the
[8]1671   server does not know, or has no facility to determine, whether or not
1672   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1673   used instead. This response is cacheable unless indicated otherwise.
1676   The 410 response is primarily intended to assist the task of web
1677   maintenance by notifying the recipient that the resource is
1678   intentionally unavailable and that the server owners desire that
1679   remote links to that resource be removed. Such an event is common for
1680   limited-time, promotional services and for resources belonging to
1681   individuals no longer working at the server's site. It is not
1682   necessary to mark all permanently unavailable resources as "gone" or
1683   to keep the mark for any length of time -- that is left to the
1684   discretion of the server owner.
1688<section title="411 Length Required" anchor="status.411">
1689  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1690  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1692   The server refuses to accept the request without a defined Content-Length.
1693   The client &MAY; repeat the request if it adds a valid
1694   Content-Length header field containing the length of the message-body
1695   in the request message.
1699<section title="412 Precondition Failed" anchor="status.412">
1700  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1701  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
[700]1702  <rdf:Description>
1703    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1704  </rdf:Description>
1706   The precondition given in one or more of the request-header fields
[45]1707   evaluated to false when it was tested on the server, as defined in
[700]1708   &status-412;.
1712<section title="413 Request Entity Too Large" anchor="status.413">
1713  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1716   The server is refusing to process a request because the request
1717   entity is larger than the server is willing or able to process. The
1718   server &MAY; close the connection to prevent the client from continuing
1719   the request.
1722   If the condition is temporary, the server &SHOULD; include a Retry-After
1723   header field to indicate that it is temporary and after what
1724   time the client &MAY; try again.
[465]1728<section title="414 URI Too Long" anchor="status.414">
1729  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1730  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
[391]1732   The server is refusing to service the request because the request-target
[8]1733   is longer than the server is willing to interpret. This rare
1734   condition is only likely to occur when a client has improperly
1735   converted a POST request to a GET request with long query
1736   information, when the client has descended into a URI "black hole" of
1737   redirection (e.g., a redirected URI prefix that points to a suffix of
1738   itself), or when the server is under attack by a client attempting to
1739   exploit security holes present in some servers using fixed-length
[391]1740   buffers for reading or manipulating the request-target.
1744<section title="415 Unsupported Media Type" anchor="status.415">
1745  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1746  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1748   The server is refusing to service the request because the entity of
1749   the request is in a format not supported by the requested resource
1750   for the requested method.
1754<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1755  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1756  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
[700]1757  <rdf:Description>
1758    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1759  </rdf:Description>
[29]1761   The request included a Range request-header field (&header-range;) and none of
[8]1762   the range-specifier values in this field overlap the current extent
[700]1763   of the selected resource. See &status-416;
1767<section title="417 Expectation Failed" anchor="status.417">
1768  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1769  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1771   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1772   could not be met by this server, or, if the server is a proxy,
1773   the server has unambiguous evidence that the request could not be met
1774   by the next-hop server.
1779<section title="Server Error 5xx" anchor="status.5xx">
1781   Response status codes beginning with the digit "5" indicate cases in
1782   which the server is aware that it has erred or is incapable of
1783   performing the request. Except when responding to a HEAD request, the
1784   server &SHOULD; include an entity containing an explanation of the
1785   error situation, and whether it is a temporary or permanent
1786   condition. User agents &SHOULD; display any included entity to the
1787   user. These response codes are applicable to any request method.
1790<section title="500 Internal Server Error" anchor="status.500">
1791  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1792  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1794   The server encountered an unexpected condition which prevented it
1795   from fulfilling the request.
1799<section title="501 Not Implemented" anchor="status.501">
1800  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1801  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1803   The server does not support the functionality required to fulfill the
1804   request. This is the appropriate response when the server does not
1805   recognize the request method and is not capable of supporting it for
1806   any resource.
1810<section title="502 Bad Gateway" anchor="status.502">
1811  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1812  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1814   The server, while acting as a gateway or proxy, received an invalid
1815   response from the upstream server it accessed in attempting to
1816   fulfill the request.
1820<section title="503 Service Unavailable" anchor="status.503">
1821  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1822  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1824   The server is currently unable to handle the request due to a
1825   temporary overloading or maintenance of the server. The implication
1826   is that this is a temporary condition which will be alleviated after
1827   some delay. If known, the length of the delay &MAY; be indicated in a
1828   Retry-After header. If no Retry-After is given, the client &SHOULD;
1829   handle the response as it would for a 500 response.
1832  <t>
1833    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1834    server must use it when becoming overloaded. Some servers may wish
1835    to simply refuse the connection.
1836  </t>
1840<section title="504 Gateway Timeout" anchor="status.504">
1841  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1842  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1844   The server, while acting as a gateway or proxy, did not receive a
1845   timely response from the upstream server specified by the URI (e.g.
1846   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1847   to access in attempting to complete the request.
1850  <t>
1851    <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1852    return 400 or 500 when DNS lookups time out.
1853  </t>
1857<section title="505 HTTP Version Not Supported" anchor="status.505">
1858  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1859  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
[172]1861   The server does not support, or refuses to support, the protocol
[8]1862   version that was used in the request message. The server is
1863   indicating that it is unable or unwilling to complete the request
[29]1864   using the same major version as the client, as described in &http-version;,
[8]1865   other than with this error message. The response &SHOULD; contain
1866   an entity describing why that version is not supported and what other
1867   protocols are supported by that server.
1875<section title="Header Field Definitions" anchor="header.fields">
[117]1877   This section defines the syntax and semantics of HTTP/1.1 header fields
1878   related to request and response semantics.
1881   For entity-header fields, both sender and recipient refer to either the
1882   client or the server, depending on who sends and who receives the entity.
1885<section title="Allow" anchor="header.allow">
1886  <iref primary="true" item="Allow header" x:for-anchor=""/>
1887  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
[229]1888  <x:anchor-alias value="Allow"/>
[356]1889  <x:anchor-alias value="Allow-v"/>
[697]1891   The "Allow" response-header field lists the set of methods advertised as
1892   supported by the resource identified by the request-target. The purpose of
1893   this field is strictly to inform the recipient of valid methods
[698]1894   associated with the resource.
[356]1896<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
[366]1897  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
[356]1898  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1901      Example of use:
1903<figure><artwork type="example">
[356]1904  Allow: GET, HEAD, PUT
[240]1907      The actual set of allowed methods is defined
[8]1908      by the origin server at the time of each request.
1911      A proxy &MUST-NOT; modify the Allow header field even if it does not
1912      understand all the methods specified, since the user agent might
1913      have other means of communicating with the origin server.
1917<section title="Expect" anchor="header.expect">
1918  <iref primary="true" item="Expect header" x:for-anchor=""/>
1919  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
[229]1920  <x:anchor-alias value="Expect"/>
[356]1921  <x:anchor-alias value="Expect-v"/>
[229]1922  <x:anchor-alias value="expectation"/>
1923  <x:anchor-alias value="expectation-extension"/>
1924  <x:anchor-alias value="expect-params"/>
[697]1926   The "Expect" request-header field is used to indicate that particular
[8]1927   server behaviors are required by the client.
[356]1929<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
[366]1930  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
[356]1931  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
[356]1933  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1934  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
[229]1935                           *<x:ref>expect-params</x:ref> ]
[356]1936  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1939   A server that does not understand or is unable to comply with any of
1940   the expectation values in the Expect field of a request &MUST; respond
1941   with appropriate error status. The server &MUST; respond with a 417
1942   (Expectation Failed) status if any of the expectations cannot be met
1943   or, if there are other problems with the request, some other 4xx
1944   status.
1947   This header field is defined with extensible syntax to allow for
1948   future extensions. If a server receives a request containing an
1949   Expect field that includes an expectation-extension that it does not
1950   support, it &MUST; respond with a 417 (Expectation Failed) status.
1953   Comparison of expectation values is case-insensitive for unquoted
1954   tokens (including the 100-continue token), and is case-sensitive for
1955   quoted-string expectation-extensions.
1958   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1959   return a 417 (Expectation Failed) status if it receives a request
1960   with an expectation that it cannot meet. However, the Expect
1961   request-header itself is end-to-end; it &MUST; be forwarded if the
1962   request is forwarded.
1965   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1966   Expect header.
[137]1969   See &use100; for the use of the 100 (Continue) status.
1973<section title="From" anchor="header.from">
1974  <iref primary="true" item="From header" x:for-anchor=""/>
1975  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
[229]1976  <x:anchor-alias value="From"/>
[356]1977  <x:anchor-alias value="From-v"/>
[229]1978  <x:anchor-alias value="mailbox"/>
[697]1980   The "From" request-header field, if given, &SHOULD; contain an Internet
[8]1981   e-mail address for the human user who controls the requesting user
1982   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
[327]1983   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
[356]1985<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
[366]1986  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
[356]1987  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
[327]1989  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1992   An example is:
1994<figure><artwork type="example">
[356]1995  From:
1998   This header field &MAY; be used for logging purposes and as a means for
1999   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
2000   be used as an insecure form of access protection. The interpretation
2001   of this field is that the request is being performed on behalf of the
2002   person given, who accepts responsibility for the method performed. In
2003   particular, robot agents &SHOULD; include this header so that the
2004   person responsible for running the robot can be contacted if problems
2005   occur on the receiving end.
2008   The Internet e-mail address in this field &MAY; be separate from the
2009   Internet host which issued the request. For example, when a request
2010   is passed through a proxy the original issuer's address &SHOULD; be
2011   used.
2014   The client &SHOULD-NOT;  send the From header field without the user's
2015   approval, as it might conflict with the user's privacy interests or
2016   their site's security policy. It is strongly recommended that the
2017   user be able to disable, enable, and modify the value of this field
2018   at any time prior to a request.
2022<section title="Location" anchor="header.location">
2023  <iref primary="true" item="Location header" x:for-anchor=""/>
2024  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
[229]2025  <x:anchor-alias value="Location"/>
[356]2026  <x:anchor-alias value="Location-v"/>
[698]2028   The "Location" response-header field is used to identify a newly created
2029   resource, or to redirect the recipient to a different location for
2030   completion of the request.
2033   For 201 (Created) responses, the Location is the URI of the new resource
2034   which was created by the request. For 3xx responses, the location &SHOULD;
2035   indicate the server's preferred URI for automatic redirection to the
2036   resource.
2039   The field value consists of a single URI.
[356]2041<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
[366]2042  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
[632]2043  <x:ref>Location-v</x:ref>     = <x:ref>URI</x:ref>
2046   An example is:
2048<figure><artwork type="example">
[356]2049  Location:
2052   There are circumstances in which a fragment identifier in a Location URI would not be appropriate:
2053   <list style="symbols">
2054      <t>With a 201 Created response, because in this usage the Location header specifies the URI for the entire created resource.</t>
2055      <t>With 305 Use Proxy.</t>
2056   </list>
2059  <t>
2060    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2061    from Location in that the Content-Location identifies the original
2062    location of the entity enclosed in the response. It is therefore
2063    possible for a response to contain header fields for both Location
2064    and Content-Location.
2065  </t>
2069<section title="Max-Forwards" anchor="header.max-forwards">
2070  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2071  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
[229]2072  <x:anchor-alias value="Max-Forwards"/>
[356]2073  <x:anchor-alias value="Max-Forwards-v"/>
[697]2075   The "Max-Forwards" request-header field provides a mechanism with the
[698]2076   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2077   methods to limit the number of times that the request is forwarded by
2078   proxies or gateways. This can be useful when the client is attempting to
2079   trace a request which appears to be failing or looping in mid-chain.
[356]2081<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
[366]2082  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
[356]2083  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2086   The Max-Forwards value is a decimal integer indicating the remaining
2087   number of times this request message may be forwarded.
2090   Each proxy or gateway recipient of a TRACE or OPTIONS request
2091   containing a Max-Forwards header field &MUST; check and update its
2092   value prior to forwarding the request. If the received value is zero
2093   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2094   respond as the final recipient. If the received Max-Forwards value is
2095   greater than zero, then the forwarded message &MUST; contain an updated
2096   Max-Forwards field with a value decremented by one (1).
2099   The Max-Forwards header field &MAY; be ignored for all other methods
2100   defined by this specification and for any extension methods for which
2101   it is not explicitly referred to as part of that method definition.
2105<section title="Referer" anchor="header.referer">
2106  <iref primary="true" item="Referer header" x:for-anchor=""/>
2107  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
[229]2108  <x:anchor-alias value="Referer"/>
[356]2109  <x:anchor-alias value="Referer-v"/>
[698]2111   The "Referer" [sic] request-header field allows the client to specify the
2112   URI of the resource from which the request-target was obtained (the
2113   "referrer", although the header field is misspelled.).
2116   The Referer header allows servers to generate lists of back-links to
2117   resources for interest, logging, optimized caching, etc. It also allows
2118   obsolete or mistyped links to be traced for maintenance. Some servers use
2119   Referer as a means of controlling where they allow links from (so-called
2120   "deep linking"), but it should be noted that legitimate requests are not
2121   required to contain a Referer header field.
2124   If the request-target was obtained from a source that does not have its own
2125   URI (e.g., input from the user keyboard), the Referer field MUST either be
2126   sent with the value "about:blank", or not be sent at all. Note that this
2127   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
[356]2129<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
[366]2130  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
[391]2131  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2134   Example:
2136<figure><artwork type="example">
[356]2137  Referer:
2140   If the field value is a relative URI, it &SHOULD; be interpreted
[391]2141   relative to the request-target. The URI &MUST-NOT; include a fragment. See
[8]2142   <xref target=""/> for security considerations.
2146<section title="Retry-After" anchor="header.retry-after">
2147  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2148  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
[229]2149  <x:anchor-alias value="Retry-After"/>
[356]2150  <x:anchor-alias value="Retry-After-v"/>
[356]2152   The response-header "Retry-After" field can be used with a 503 (Service
[8]2153   Unavailable) response to indicate how long the service is expected to
2154   be unavailable to the requesting client. This field &MAY; also be used
2155   with any 3xx (Redirection) response to indicate the minimum time the
[698]2156   user-agent is asked wait before issuing the redirected request.
2159   The value of this field can be either an HTTP-date or an integer number
[8]2160   of seconds (in decimal) after the time of the response.
[356]2162<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
[366]2163  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
[356]2164  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
[229]2166<t anchor="">
2167  <x:anchor-alias value="delta-seconds"/>
[212]2168   Time spans are non-negative decimal integers, representing time in
2169   seconds.
2171<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
[229]2172  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
[8]2175   Two examples of its use are
2177<figure><artwork type="example">
[356]2178  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2179  Retry-After: 120
2182   In the latter example, the delay is 2 minutes.
2186<section title="Server" anchor="header.server">
2187  <iref primary="true" item="Server header" x:for-anchor=""/>
2188  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
[229]2189  <x:anchor-alias value="Server"/>
[356]2190  <x:anchor-alias value="Server-v"/>
[697]2192   The "Server" response-header field contains information about the
[698]2193   software used by the origin server to handle the request.
2196   The field can contain multiple product tokens (&product-tokens;) and
2197   comments (&header-fields;) identifying the server and any significant
2198   subproducts. The product tokens are listed in order of their significance
2199   for identifying the application.
[356]2201<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
[366]2202  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
[370]2203  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2204                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2207   Example:
2209<figure><artwork type="example">
[356]2210  Server: CERN/3.0 libwww/2.17
2213   If the response is being forwarded through a proxy, the proxy
2214   application &MUST-NOT; modify the Server response-header. Instead, it
[72]2215   &MUST; include a Via field (as described in &header-via;).
2218  <t>
2219    <x:h>Note:</x:h> Revealing the specific software version of the server might
2220    allow the server machine to become more vulnerable to attacks
2221    against software that is known to contain security holes. Server
2222    implementors are encouraged to make this field a configurable
2223    option.
2224  </t>
2228<section title="User-Agent" anchor="header.user-agent">
2229  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2230  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
[229]2231  <x:anchor-alias value="User-Agent"/>
[356]2232  <x:anchor-alias value="User-Agent-v"/>
[697]2234   The "User-Agent" request-header field contains information about the
[8]2235   user agent originating the request. This is for statistical purposes,
2236   the tracing of protocol violations, and automated recognition of user
2237   agents for the sake of tailoring responses to avoid particular user
[698]2238   agent limitations.
2241   User agents &SHOULD; include this field with requests. The field can contain
2242   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2243   identifying the agent and any subproducts which form a significant part of
2244   the user agent. By convention, the product tokens are listed in order of
2245   their significance for identifying the application.
[356]2247<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
[366]2248  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
[370]2249  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2250                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2253   Example:
2255<figure><artwork type="example">
[356]2256  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
[29]2262<section title="IANA Considerations" anchor="IANA.considerations">
2264<section title="Method Registry" anchor="method.registration">
2266  The registration procedure for HTTP Methods is defined by
2267  <xref target="method.registry"/> of this document.
2270   The HTTP Method Registry located at <eref target=""/>
2271   should be populated with the registrations below:
[682]2273<?BEGININC p2-semantics.iana-methods ?>
[270]2274<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
[288]2275<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
[270]2276   <ttcol>Method</ttcol>
[286]2277   <ttcol>Safe</ttcol>
[270]2278   <ttcol>Reference</ttcol>
2279   <c>CONNECT</c>
[286]2280   <c>no</c>
[270]2281   <c>
2282      <xref target="CONNECT"/>
2283   </c>
2284   <c>DELETE</c>
[286]2285   <c>no</c>
[270]2286   <c>
2287      <xref target="DELETE"/>
2288   </c>
2289   <c>GET</c>
[286]2290   <c>yes</c>
[270]2291   <c>
2292      <xref target="GET"/>
2293   </c>
2294   <c>HEAD</c>
[286]2295   <c>yes</c>
[270]2296   <c>
2297      <xref target="HEAD"/>
2298   </c>
2299   <c>OPTIONS</c>
[286]2300   <c>yes</c>
[270]2301   <c>
2302      <xref target="OPTIONS"/>
2303   </c>
2304   <c>POST</c>
[286]2305   <c>no</c>
[270]2306   <c>
2307      <xref target="POST"/>
2308   </c>
2309   <c>PUT</c>
[286]2310   <c>no</c>
[270]2311   <c>
2312      <xref target="PUT"/>
2313   </c>
2314   <c>TRACE</c>
[286]2315   <c>yes</c>
[270]2316   <c>
2317      <xref target="TRACE"/>
2318   </c>
[682]2321<?ENDINC p2-semantics.iana-methods ?>
[255]2324<section title="Status Code Registry" anchor="status.code.registration">
[288]2326   The registration procedure for HTTP Status Codes -- previously defined
2327   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2328   by <xref target="status.code.registry"/> of this document.
2331   The HTTP Status Code Registry located at <eref target=""/>
2332   should be updated with the registrations below:
[682]2334<?BEGININC p2-semantics.iana-status-codes ?>
[255]2335<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
[288]2336<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
[255]2337   <ttcol>Value</ttcol>
2338   <ttcol>Description</ttcol>
2339   <ttcol>Reference</ttcol>
2340   <c>100</c>
2341   <c>Continue</c>
2342   <c>
2343      <xref target="status.100"/>
2344   </c>
2345   <c>101</c>
2346   <c>Switching Protocols</c>
2347   <c>
2348      <xref target="status.101"/>
2349   </c>
2350   <c>200</c>
2351   <c>OK</c>
2352   <c>
2353      <xref target="status.200"/>
2354   </c>
2355   <c>201</c>
2356   <c>Created</c>
2357   <c>
2358      <xref target="status.201"/>
2359   </c>
2360   <c>202</c>
2361   <c>Accepted</c>
2362   <c>
2363      <xref target="status.202"/>
2364   </c>
2365   <c>203</c>
2366   <c>Non-Authoritative Information</c>
2367   <c>
2368      <xref target="status.203"/>
2369   </c>
2370   <c>204</c>
2371   <c>No Content</c>
2372   <c>
2373      <xref target="status.204"/>
2374   </c>
2375   <c>205</c>
2376   <c>Reset Content</c>
2377   <c>
2378      <xref target="status.205"/>
2379   </c>
2380   <c>300</c>
2381   <c>Multiple Choices</c>
2382   <c>
2383      <xref target="status.300"/>
2384   </c>
2385   <c>301</c>
2386   <c>Moved Permanently</c>
2387   <c>
2388      <xref target="status.301"/>
2389   </c>
2390   <c>302</c>
2391   <c>Found</c>
2392   <c>
2393      <xref target="status.302"/>
2394   </c>
2395   <c>303</c>
2396   <c>See Other</c>
2397   <c>
2398      <xref target="status.303"/>
2399   </c>
2400   <c>305</c>
2401   <c>Use Proxy</c>
2402   <c>
2403      <xref target="status.305"/>
2404   </c>
2405   <c>306</c>
2406   <c>(Unused)</c>
2407   <c>
2408      <xref target="status.306"/>
2409   </c>
2410   <c>307</c>
2411   <c>Temporary Redirect</c>
2412   <c>
2413      <xref target="status.307"/>
2414   </c>
2415   <c>400</c>
2416   <c>Bad Request</c>
2417   <c>
2418      <xref target="status.400"/>
2419   </c>
2420   <c>402</c>
2421   <c>Payment Required</c>
2422   <c>
2423      <xref target="status.402"/>
2424   </c>
2425   <c>403</c>
2426   <c>Forbidden</c>
2427   <c>
2428      <xref target="status.403"/>
2429   </c>
2430   <c>404</c>
2431   <c>Not Found</c>
2432   <c>
2433      <xref target="status.404"/>
2434   </c>
2435   <c>405</c>
2436   <c>Method Not Allowed</c>
2437   <c>
2438      <xref target="status.405"/>
2439   </c>
2440   <c>406</c>
2441   <c>Not Acceptable</c>
2442   <c>
2443      <xref target="status.406"/>
2444   </c>
2445   <c>407</c>
2446   <c>Proxy Authentication Required</c>
2447   <c>
2448      <xref target="status.407"/>
2449   </c>
2450   <c>408</c>
2451   <c>Request Timeout</c>
2452   <c>
2453      <xref target="status.408"/>
2454   </c>
2455   <c>409</c>
2456   <c>Conflict</c>
2457   <c>
2458      <xref target="status.409"/>
2459   </c>
2460   <c>410</c>
2461   <c>Gone</c>
2462   <c>
2463      <xref target="status.410"/>
2464   </c>
2465   <c>411</c>
2466   <c>Length Required</c>
2467   <c>
2468      <xref target="status.411"/>
2469   </c>
2470   <c>413</c>
2471   <c>Request Entity Too Large</c>
2472   <c>
2473      <xref target="status.413"/>
2474   </c>
2475   <c>414</c>
[465]2476   <c>URI Too Long</c>
[255]2477   <c>
2478      <xref target="status.414"/>
2479   </c>
2480   <c>415</c>
2481   <c>Unsupported Media Type</c>
2482   <c>
2483      <xref target="status.415"/>
2484   </c>
2485   <c>417</c>
2486   <c>Expectation Failed</c>
2487   <c>
2488      <xref target="status.417"/>
2489   </c>
2490   <c>500</c>
2491   <c>Internal Server Error</c>
2492   <c>
2493      <xref target="status.500"/>
2494   </c>
2495   <c>501</c>
2496   <c>Not Implemented</c>
2497   <c>
2498      <xref target="status.501"/>
2499   </c>
2500   <c>502</c>
2501   <c>Bad Gateway</c>
2502   <c>
2503      <xref target="status.502"/>
2504   </c>
2505   <c>503</c>
2506   <c>Service Unavailable</c>
2507   <c>
2508      <xref target="status.503"/>
2509   </c>
2510   <c>504</c>
2511   <c>Gateway Timeout</c>
2512   <c>
2513      <xref target="status.504"/>
2514   </c>
2515   <c>505</c>
2516   <c>HTTP Version Not Supported</c>
2517   <c>
2518      <xref target="status.505"/>
2519   </c>
[682]2522<?ENDINC p2-semantics.iana-status-codes ?>
[253]2524<section title="Message Header Registration" anchor="message.header.registration">
2526   The Message Header Registry located at <eref target=""/> should be updated
2527   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]2529<?BEGININC p2-semantics.iana-headers ?>
[253]2530<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]2531<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]2532   <ttcol>Header Field Name</ttcol>
2533   <ttcol>Protocol</ttcol>
2534   <ttcol>Status</ttcol>
2535   <ttcol>Reference</ttcol>
[253]2537   <c>Allow</c>
2538   <c>http</c>
2539   <c>standard</c>
2540   <c>
2541      <xref target="header.allow"/>
2542   </c>
2543   <c>Expect</c>
2544   <c>http</c>
2545   <c>standard</c>
2546   <c>
2547      <xref target="header.expect"/>
2548   </c>
2549   <c>From</c>
2550   <c>http</c>
2551   <c>standard</c>
2552   <c>
2553      <xref target="header.from"/>
2554   </c>
2555   <c>Location</c>
2556   <c>http</c>
2557   <c>standard</c>
2558   <c>
2559      <xref target="header.location"/>
2560   </c>
2561   <c>Max-Forwards</c>
2562   <c>http</c>
2563   <c>standard</c>
2564   <c>
2565      <xref target="header.max-forwards"/>
2566   </c>
2567   <c>Referer</c>
2568   <c>http</c>
2569   <c>standard</c>
2570   <c>
2571      <xref target="header.referer"/>
2572   </c>
2573   <c>Retry-After</c>
2574   <c>http</c>
2575   <c>standard</c>
2576   <c>
2577      <xref target="header.retry-after"/>
2578   </c>
2579   <c>Server</c>
2580   <c>http</c>
2581   <c>standard</c>
2582   <c>
2583      <xref target="header.server"/>
2584   </c>
2585   <c>User-Agent</c>
2586   <c>http</c>
2587   <c>standard</c>
2588   <c>
2589      <xref target="header.user-agent"/>
2590   </c>
[680]2593<?ENDINC p2-semantics.iana-headers ?>
[290]2595   The change controller is: "IETF ( - Internet Engineering Task Force".
[8]2600<section title="Security Considerations" anchor="security.considerations">
2602   This section is meant to inform application developers, information
2603   providers, and users of the security limitations in HTTP/1.1 as
2604   described by this document. The discussion does not include
2605   definitive solutions to the problems revealed, though it does make
2606   some suggestions for reducing security risks.
2609<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2611   Like any generic data transfer protocol, HTTP cannot regulate the
2612   content of the data that is transferred, nor is there any a priori
2613   method of determining the sensitivity of any particular piece of
2614   information within the context of any given request. Therefore,
2615   applications &SHOULD; supply as much control over this information as
2616   possible to the provider of that information. Four header fields are
2617   worth special mention in this context: Server, Via, Referer and From.
2620   Revealing the specific software version of the server might allow the
2621   server machine to become more vulnerable to attacks against software
2622   that is known to contain security holes. Implementors &SHOULD; make the
2623   Server header field a configurable option.
2626   Proxies which serve as a portal through a network firewall &SHOULD;
2627   take special precautions regarding the transfer of header information
2628   that identifies the hosts behind the firewall. In particular, they
2629   &SHOULD; remove, or replace with sanitized versions, any Via fields
2630   generated behind the firewall.
2633   The Referer header allows reading patterns to be studied and reverse
2634   links drawn. Although it can be very useful, its power can be abused
2635   if user details are not separated from the information contained in
2636   the Referer. Even when the personal information has been removed, the
2637   Referer header might indicate a private document's URI whose
2638   publication would be inappropriate.
2641   The information sent in the From field might conflict with the user's
2642   privacy interests or their site's security policy, and hence it
2643   &SHOULD-NOT;  be transmitted without the user being able to disable,
2644   enable, and modify the contents of the field. The user &MUST; be able
2645   to set the contents of this field within a user preference or
2646   application defaults configuration.
2649   We suggest, though do not require, that a convenient toggle interface
2650   be provided for the user to enable or disable the sending of From and
2651   Referer information.
2654   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2655   fields can sometimes be used to determine that a specific client or
2656   server have a particular security hole which might be exploited.
2657   Unfortunately, this same information is often used for other valuable
2658   purposes for which HTTP currently has no better mechanism.
[666]2661   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2662   information sent in request headers in the response entity.
2663   Clients &SHOULD; be careful with sensitive information, like Cookies,
2664   Authorization credentials and other headers that might be used to
2665   collect data from the client.
[184]2669<section title="Encoding Sensitive Information in URIs" anchor="">
2671   Because the source of a link might be private information or might
2672   reveal an otherwise private information source, it is strongly
2673   recommended that the user be able to select whether or not the
2674   Referer field is sent. For example, a browser client could have a
2675   toggle switch for browsing openly/anonymously, which would
2676   respectively enable/disable the sending of Referer and From
2677   information.
[172]2680   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
[8]2681   HTTP request if the referring page was transferred with a secure
2682   protocol.
[172]2685   Authors of services should not use
2686   GET-based forms for the submission of sensitive data because that
[391]2687   data will be encoded in the Request-target. Many existing
2688   servers, proxies, and user agents log or display the Request-target in
[172]2689   places where it might be visible to third parties. Such services can
2690   use POST-based form submission instead.
2694<section title="Location Headers and Spoofing" anchor="location.spoofing">
2696   If a single server supports multiple organizations that do not trust
2697   one another, then it &MUST; check the values of Location and Content-Location
2698   headers in responses that are generated under control of
2699   said organizations to make sure that they do not attempt to
2700   invalidate resources over which they have no authority.
2706<section title="Acknowledgments" anchor="ack">
[119]2711<references title="Normative References">
[31]2713<reference anchor="Part1">
[119]2714  <front>
2715    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2716    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2717      <organization abbrev="Day Software">Day Software</organization>
2718      <address><email></email></address>
2719    </author>
2720    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2721      <organization>One Laptop per Child</organization>
2722      <address><email></email></address>
2723    </author>
2724    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2725      <organization abbrev="HP">Hewlett-Packard Company</organization>
2726      <address><email></email></address>
2727    </author>
2728    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2729      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2730      <address><email></email></address>
2731    </author>
2732    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2733      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2734      <address><email></email></address>
2735    </author>
2736    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2737      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2738      <address><email></email></address>
2739    </author>
2740    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2741      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2742      <address><email></email></address>
2743    </author>
2744    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2745      <organization abbrev="W3C">World Wide Web Consortium</organization>
2746      <address><email></email></address>
2747    </author>
2748    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2749      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2750      <address><email></email></address>
2751    </author>
2752    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2753  </front>
2754  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2755  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2758<reference anchor="Part3">
[119]2759  <front>
2760    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2761    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2762      <organization abbrev="Day Software">Day Software</organization>
2763      <address><email></email></address>
2764    </author>
2765    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2766      <organization>One Laptop per Child</organization>
2767      <address><email></email></address>
2768    </author>
2769    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2770      <organization abbrev="HP">Hewlett-Packard Company</organization>
2771      <address><email></email></address>
2772    </author>
2773    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2774      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2775      <address><email></email></address>
2776    </author>
2777    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2778      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2779      <address><email></email></address>
2780    </author>
2781    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2782      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2783      <address><email></email></address>
2784    </author>
2785    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2786      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2787      <address><email></email></address>
2788    </author>
2789    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2790      <organization abbrev="W3C">World Wide Web Consortium</organization>
2791      <address><email></email></address>
2792    </author>
2793    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2794      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2795      <address><email></email></address>
2796    </author>
2797    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2798  </front>
2799  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2800  <x:source href="p3-payload.xml" basename="p3-payload"/>
2803<reference anchor="Part4">
[119]2804  <front>
2805    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2806    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2807      <organization abbrev="Day Software">Day Software</organization>
2808      <address><email></email></address>
2809    </author>
2810    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2811      <organization>One Laptop per Child</organization>
2812      <address><email></email></address>
2813    </author>
2814    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2815      <organization abbrev="HP">Hewlett-Packard Company</organization>
2816      <address><email></email></address>
2817    </author>
2818    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2819      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2820      <address><email></email></address>
2821    </author>
2822    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2823      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2824      <address><email></email></address>
2825    </author>
2826    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2827      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2828      <address><email></email></address>
2829    </author>
2830    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2831      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2832      <address><email></email></address>
2833    </author>
2834    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2835      <organization abbrev="W3C">World Wide Web Consortium</organization>
2836      <address><email></email></address>
2837    </author>
2838    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2839      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2840      <address><email></email></address>
2841    </author>
2842    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2843  </front>
2844  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2845  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2848<reference anchor="Part5">
[119]2849  <front>
2850    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2851    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2852      <organization abbrev="Day Software">Day Software</organization>
2853      <address><email></email></address>
2854    </author>
2855    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2856      <organization>One Laptop per Child</organization>
2857      <address><email></email></address>
2858    </author>
2859    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2860      <organization abbrev="HP">Hewlett-Packard Company</organization>
2861      <address><email></email></address>
2862    </author>
2863    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2864      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2865      <address><email></email></address>
2866    </author>
2867    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2868      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2869      <address><email></email></address>
2870    </author>
2871    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2872      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2873      <address><email></email></address>
2874    </author>
2875    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2876      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2877      <address><email></email></address>
2878    </author>
2879    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2880      <organization abbrev="W3C">World Wide Web Consortium</organization>
2881      <address><email></email></address>
2882    </author>
2883    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2884      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2885      <address><email></email></address>
2886    </author>
2887    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2888  </front>
2889  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2890  <x:source href="p5-range.xml" basename="p5-range"/>
2893<reference anchor="Part6">
[119]2894  <front>
2895    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2896    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2897      <organization abbrev="Day Software">Day Software</organization>
2898      <address><email></email></address>
2899    </author>
2900    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2901      <organization>One Laptop per Child</organization>
2902      <address><email></email></address>
2903    </author>
2904    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2905      <organization abbrev="HP">Hewlett-Packard Company</organization>
2906      <address><email></email></address>
2907    </author>
2908    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2909      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2910      <address><email></email></address>
2911    </author>
2912    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2913      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2914      <address><email></email></address>
2915    </author>
2916    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2917      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2918      <address><email></email></address>
2919    </author>
2920    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2921      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2922      <address><email></email></address>
2923    </author>
2924    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2925      <organization abbrev="W3C">World Wide Web Consortium</organization>
2926      <address><email></email></address>
2927    </author>
[601]2928    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2929      <organization />
2930      <address><email></email></address>
2931    </author>
[119]2932    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2933      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2934      <address><email></email></address>
2935    </author>
2936    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2937  </front>
2938  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2939  <x:source href="p6-cache.xml" basename="p6-cache"/>
2942<reference anchor="Part7">
[119]2943  <front>
2944    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2945    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2946      <organization abbrev="Day Software">Day Software</organization>
2947      <address><email></email></address>
2948    </author>
2949    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2950      <organization>One Laptop per Child</organization>
2951      <address><email></email></address>
2952    </author>
2953    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2954      <organization abbrev="HP">Hewlett-Packard Company</organization>
2955      <address><email></email></address>
2956    </author>
2957    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2958      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2959      <address><email></email></address>
2960    </author>
2961    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2962      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2963      <address><email></email></address>
2964    </author>
2965    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2966      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2967      <address><email></email></address>
2968    </author>
2969    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2970      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2971      <address><email></email></address>
2972    </author>
2973    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2974      <organization abbrev="W3C">World Wide Web Consortium</organization>
2975      <address><email></email></address>
2976    </author>
2977    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2978      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2979      <address><email></email></address>
2980    </author>
2981    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2982  </front>
2983  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2984  <x:source href="p7-auth.xml" basename="p7-auth"/>
[119]2987<reference anchor="RFC2119">
2988  <front>
2989    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2990    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2991      <organization>Harvard University</organization>
2992      <address><email></email></address>
2993    </author>
2994    <date month="March" year="1997"/>
2995  </front>
2996  <seriesInfo name="BCP" value="14"/>
2997  <seriesInfo name="RFC" value="2119"/>
[425]3000<reference anchor="RFC5234">
3001  <front>
3002    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3003    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3004      <organization>Brandenburg InternetWorking</organization>
3005      <address>
3006      <postal>
3007      <street>675 Spruce Dr.</street>
3008      <city>Sunnyvale</city>
3009      <region>CA</region>
3010      <code>94086</code>
3011      <country>US</country></postal>
3012      <phone>+1.408.246.8253</phone>
3013      <email></email></address> 
3014    </author>
3015    <author initials="P." surname="Overell" fullname="Paul Overell">
3016      <organization>THUS plc.</organization>
3017      <address>
3018      <postal>
3019      <street>1/2 Berkeley Square</street>
3020      <street>99 Berkely Street</street>
3021      <city>Glasgow</city>
3022      <code>G3 7HR</code>
3023      <country>UK</country></postal>
3024      <email></email></address>
3025    </author>
3026    <date month="January" year="2008"/>
3027  </front>
3028  <seriesInfo name="STD" value="68"/>
3029  <seriesInfo name="RFC" value="5234"/>
3034<references title="Informative References">
[129]3036<reference anchor="RFC1945">
3037  <front>
3038    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3039    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3040      <organization>MIT, Laboratory for Computer Science</organization>
3041      <address><email></email></address>
3042    </author>
3043    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3044      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3045      <address><email></email></address>
3046    </author>
3047    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3048      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3049      <address><email></email></address>
3050    </author>
3051    <date month="May" year="1996"/>
3052  </front>
3053  <seriesInfo name="RFC" value="1945"/>
[119]3056<reference anchor="RFC2068">
3057  <front>
3058    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3059    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3060      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3061      <address><email></email></address>
3062    </author>
3063    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3064      <organization>MIT Laboratory for Computer Science</organization>
3065      <address><email></email></address>
3066    </author>
3067    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3068      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3069      <address><email></email></address>
3070    </author>
3071    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3072      <organization>MIT Laboratory for Computer Science</organization>
3073      <address><email></email></address>
3074    </author>
3075    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3076      <organization>MIT Laboratory for Computer Science</organization>
3077      <address><email></email></address>
3078    </author>
3079    <date month="January" year="1997"/>
3080  </front>
3081  <seriesInfo name="RFC" value="2068"/>
[36]3084<reference anchor="RFC2616">
[119]3085  <front>
3086    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3087    <author initials="R." surname="Fielding" fullname="R. Fielding">
3088      <organization>University of California, Irvine</organization>
3089      <address><email></email></address>
3090    </author>
3091    <author initials="J." surname="Gettys" fullname="J. Gettys">
3092      <organization>W3C</organization>
3093      <address><email></email></address>
3094    </author>
3095    <author initials="J." surname="Mogul" fullname="J. Mogul">
3096      <organization>Compaq Computer Corporation</organization>
3097      <address><email></email></address>
3098    </author>
3099    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3100      <organization>MIT Laboratory for Computer Science</organization>
3101      <address><email></email></address>
3102    </author>
3103    <author initials="L." surname="Masinter" fullname="L. Masinter">
3104      <organization>Xerox Corporation</organization>
3105      <address><email></email></address>
3106    </author>
3107    <author initials="P." surname="Leach" fullname="P. Leach">
3108      <organization>Microsoft Corporation</organization>
3109      <address><email></email></address>
3110    </author>
3111    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3112      <organization>W3C</organization>
3113      <address><email></email></address>
3114    </author>
3115    <date month="June" year="1999"/>
3116  </front>
3117  <seriesInfo name="RFC" value="2616"/>
[255]3120<reference anchor='RFC2817'>
3121  <front>
3122    <title>Upgrading to TLS Within HTTP/1.1</title>
3123    <author initials='R.' surname='Khare' fullname='R. Khare'>
3124      <organization>4K Associates / UC Irvine</organization>
3125      <address><email></email></address>
3126    </author>
3127    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3128      <organization>Agranat Systems, Inc.</organization>
3129      <address><email></email></address>
3130    </author>
3131    <date year='2000' month='May' />
3132  </front>
3133  <seriesInfo name='RFC' value='2817' />
[253]3136<reference anchor='RFC3864'>
3137  <front>
3138    <title>Registration Procedures for Message Header Fields</title>
3139    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3140      <organization>Nine by Nine</organization>
3141      <address><email></email></address>
3142    </author>
3143    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3144      <organization>BEA Systems</organization>
3145      <address><email></email></address>
3146    </author>
3147    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3148      <organization>HP Labs</organization>
3149      <address><email></email></address>
3150    </author>
3151    <date year='2004' month='September' />
3152  </front>
3153  <seriesInfo name='BCP' value='90' />
3154  <seriesInfo name='RFC' value='3864' />
[262]3157<reference anchor='RFC5226'>
3158  <front>
3159    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3160    <author initials='T.' surname='Narten' fullname='T. Narten'>
3161      <organization>IBM</organization>
3162      <address><email></email></address>
3163    </author>
3164    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3165      <organization>Google</organization>
3166      <address><email></email></address>
3167    </author>
3168    <date year='2008' month='May' />
3169  </front>
3170  <seriesInfo name='BCP' value='26' />
3171  <seriesInfo name='RFC' value='5226' />
[327]3174<reference anchor="RFC5322">
3175  <front>
3176    <title>Internet Message Format</title>
3177    <author initials="P." surname="Resnick" fullname="P. Resnick">
3178      <organization>Qualcomm Incorporated</organization>
3179    </author>
3180    <date year="2008" month="October"/>
3181  </front>
3182  <seriesInfo name="RFC" value="5322"/>
[99]3187<section title="Compatibility with Previous Versions" anchor="compatibility">
[8]3188<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3190   Clarified which error code should be used for inbound server failures
3191   (e.g. DNS failures). (<xref target="status.504"/>).
[140]3194   201 (Created) had a race that required an Etag be sent when a resource is
[8]3195   first created. (<xref target="status.201"/>).
[614]3198   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3199   failure to implement status code 302 properly.
3200   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
[8]3203   Rewrite of message transmission requirements to make it much harder
3204   for implementors to get it wrong, as the consequences of errors here
3205   can have significant impact on the Internet, and to deal with the
3206   following problems:
3207  <list style="numbers">
3208      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3209         this was incorrectly placing a requirement on the behavior of
3210         an implementation of a future version of HTTP/1.x</t>
3212      <t>Made it clear that user-agents should retry requests, not
3213         "clients" in general.</t>
3215      <t>Converted requirements for clients to ignore unexpected 100
3216         (Continue) responses, and for proxies to forward 100 responses,
3217         into a general requirement for 1xx responses.</t>
3219      <t>Modified some TCP-specific language, to make it clearer that
3220         non-TCP transports are possible for HTTP.</t>
3222      <t>Require that the origin server &MUST-NOT; wait for the request
3223         body before it sends a required 100 (Continue) response.</t>
3225      <t>Allow, rather than require, a server to omit 100 (Continue) if
3226         it has already seen some of the request body.</t>
3228      <t>Allow servers to defend against denial-of-service attacks and
3229         broken clients.</t>
3230  </list>
[29]3233   This change adds the Expect header and 417 status code.
3236   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3237   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3240   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
[266]3241   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3245<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
[262]3247  This document takes over the Status Code Registry, previously defined
3248  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3249  (<xref target="status.code.registry"/>)
[108]3252  Clarify definition of POST.
3253  (<xref target="POST"/>)
3256  Failed to consider that there are
3257  many other request methods that are safe to automatically redirect,
3258  and further that the user agent is able to make that determination
3259  based on the request method semantics.
3260  (Sections <xref format="counter" target="status.301"/>,
3261  <xref format="counter" target="status.302"/> and
[233]3262  <xref format="counter" target="status.307"/>)
[235]3265  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3266  It used to indicate that the requested resource must be accessed through the
3267  proxy given by the Location field. The Location field gave the URI of the
3268  proxy. The recipient was expected to repeat this single request via the proxy.
3269  (<xref target="status.305"/>)
[232]3272  Reclassify Allow header as response header, removing the option to
3273  specify it in a PUT request.
[240]3274  Relax the server requirement on the contents of the Allow header and
3275  remove requirement on clients to always trust the header value.
[232]3276  (<xref target="header.allow"/>)
[114]3279  Correct syntax of Location header to allow fragment,
3280  as referred symbol wasn't what was expected, and add some
3281  clarifications as to when it would not be appropriate.
3282  (<xref target="header.location"/>)
[593]3285  Allow Referer value of "about:blank" as alternative to not specifying it.
3286  (<xref target="header.referer"/>)
[112]3289  In the description of the Server header, the Via field
3290  was described as a SHOULD. The requirement was and is stated
3291  correctly in the description of the Via header in &header-via;.
3292  (<xref target="header.server"/>)
[680]3298<?BEGININC p2-semantics.abnf-appendix ?>
[427]3299<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
3301<artwork type="abnf" name="p2-semantics.parsed-abnf">
3302<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3303<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3304<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3305<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3306<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
[538]3307<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
[427]3308<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3309<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3310<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3312<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3313<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3314<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3316<x:ref>From</x:ref> = "From:" OWS From-v
3317<x:ref>From-v</x:ref> = mailbox
[678]3319<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
[648]3320<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3322<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
[454]3323If-Modified-Since =
3324 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
[427]3325<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3326<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
[454]3327If-Unmodified-Since =
3328 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
[427]3330<x:ref>Location</x:ref> = "Location:" OWS Location-v
[632]3331<x:ref>Location-v</x:ref> = URI
3333<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3334<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
[581]3335<x:ref>Method</x:ref> = %x4F. ; OPTIONS
3336 / %x47.45.54 ; GET
3337 / %x48.45.41.44 ; HEAD
3338 / %x50.4F.53.54 ; POST
3339 / %x50.55.54 ; PUT
3340 / %x44.45.4C.45.54.45 ; DELETE
3341 / %x54. ; TRACE
3342 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3343 / extension-method
[427]3345<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
[454]3347Proxy-Authenticate =
3348 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3349Proxy-Authorization =
3350 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
[427]3352<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3353<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3354<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3355<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3356<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3357<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3358<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3360<x:ref>Server</x:ref> = "Server:" OWS Server-v
3361<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3362<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
[425]3363 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3364 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3365 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3366 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3367 "505" / extension-code
[678]3369<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.8&gt;
[648]3371<x:ref>URI</x:ref> = &lt;URI, defined in [Part1], Section 2.6&gt;
[427]3372<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3373<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
[538]3375<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
[454]3377WWW-Authenticate =
3378 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
[648]3380<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
[688]3382<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3384<x:ref>delta-seconds</x:ref> = 1*DIGIT
3386<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3387<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3388<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
[425]3389 *expect-params ]
[427]3390<x:ref>extension-code</x:ref> = 3DIGIT
3391<x:ref>extension-method</x:ref> = token
3393<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3395<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
[648]3397<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
[678]3398<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3400<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3402<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
[425]3403 Accept-Language / Authorization / Expect / From / Host / If-Match /
3404 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3405 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3406 User-Agent
[427]3407<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
[425]3408 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
[427]3410<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
[532]3413<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3414; Reason-Phrase defined but not used
[425]3415; Status-Code defined but not used
3416; request-header defined but not used
3417; response-header defined but not used
[680]3419<?ENDINC p2-semantics.abnf-appendix ?>
[252]3421<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3423<section title="Since RFC2616">
3425  Extracted relevant partitions from <xref target="RFC2616"/>.
3429<section title="Since draft-ietf-httpbis-p2-semantics-00">
[116]3431  Closed issues:
3432  <list style="symbols">
3433    <t>
[324]3434      <eref target=""/>:
[116]3435      "Via is a MUST"
3436      (<eref target=""/>)
3437    </t>
3438    <t>
[324]3439      <eref target=""/>:
[116]3440      "Fragments allowed in Location"
3441      (<eref target=""/>)
3442    </t>
3443    <t>
[324]3444      <eref target=""/>:
[116]3445      "Safe Methods vs Redirection"
3446      (<eref target=""/>)
3447    </t>
3448    <t>
[324]3449      <eref target=""/>:
[116]3450      "Revise description of the POST method"
3451      (<eref target=""/>)
3452    </t>
3453    <t>
[324]3454      <eref target=""/>:
[152]3455      "Normative and Informative references"
3456    </t>
3457    <t>
[324]3458      <eref target=""/>:
[116]3459      "RFC2606 Compliance"
3460    </t>
[129]3461    <t>
[324]3462      <eref target=""/>:
[129]3463      "Informative references"
3464    </t>
[130]3465    <t>
[324]3466      <eref target=""/>:
[130]3467      "Redundant cross-references"
3468    </t>
[116]3469  </list>
3472  Other changes:
3473  <list style="symbols">
3474    <t>
3475      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3476    </t>
3477  </list>
[170]3481<section title="Since draft-ietf-httpbis-p2-semantics-01">
[180]3483  Closed issues:
3484  <list style="symbols">
3485    <t>
[324]3486      <eref target=""/>:
[180]3487      "PUT side effects"
3488    </t>
[201]3489    <t>
[324]3490      <eref target=""/>:
[201]3491      "Duplicate Host header requirements"
3492    </t>
[180]3493  </list>
[324]3496  Ongoing work on ABNF conversion (<eref target=""/>):
[190]3497  <list style="symbols">
3498    <t>
3499      Move "Product Tokens" section (back) into Part 1, as "token" is used
3500      in the definition of the Upgrade header.
3501    </t>
[205]3502    <t>
3503      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3504    </t>
[210]3505    <t>
[212]3506      Copy definition of delta-seconds from Part6 instead of referencing it.
[210]3507    </t>
[190]3508  </list>
[252]3512<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
[232]3514  Closed issues:
3515  <list style="symbols">
3516    <t>
[324]3517      <eref target=""/>:
[240]3518      "Requiring Allow in 405 responses"
3519    </t>
3520    <t>
[324]3521      <eref target=""/>:
[262]3522      "Status Code Registry"
3523    </t>
3524    <t>
[324]3525      <eref target=""/>:
[237]3526      "Redirection vs. Location"
3527    </t>
3528    <t>
[324]3529      <eref target=""/>:
[242]3530      "Cacheability of 303 response"
3531    </t>
3532    <t>
[324]3533      <eref target=""/>:
[236]3534      "305 Use Proxy"
3535    </t>
3536    <t>
[324]3537      <eref target=""/>:
[232]3538      "Classification for Allow header"
3539    </t>
[241]3540    <t>
[324]3541      <eref target=""/>:
[241]3542      "PUT - 'store under' vs 'store at'"
3543    </t>
[232]3544  </list>
[324]3547  Ongoing work on IANA Message Header Registration (<eref target=""/>):
[253]3548  <list style="symbols">
3549    <t>
3550      Reference RFC 3984, and update header registrations for headers defined
3551      in this document.
3552    </t>
3553  </list>
[324]3556  Ongoing work on ABNF conversion (<eref target=""/>):
[260]3557  <list style="symbols">
3558    <t>
3559      Replace string literals when the string really is case-sensitive (method).
3560    </t>
3561  </list>
[267]3565<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
[274]3567  Closed issues:
3568  <list style="symbols">
3569    <t>
[324]3570      <eref target=""/>:
[280]3571      "OPTIONS request bodies"
3572    </t>
3573    <t>
[324]3574      <eref target=""/>:
[274]3575      "Description of CONNECT should refer to RFC2817"
3576    </t>
[300]3577    <t>
[324]3578      <eref target=""/>:
[300]3579      "Location Content-Location reference request/response mixup"
3580    </t>
[274]3581  </list>
[324]3584  Ongoing work on Method Registry (<eref target=""/>):
[270]3585  <list style="symbols">
3586    <t>
3587      Added initial proposal for registration process, plus initial
3588      content (non-HTTP/1.1 methods to be added by a separate specification).
3589    </t>
3590  </list>
[323]3594<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
[327]3596  Closed issues:
3597  <list style="symbols">
3598    <t>
[333]3599      <eref target=""/>:
3600      "Content-*"
3601    </t>
3602    <t>
[327]3603      <eref target=""/>:
3604      "RFC 2822 is updated by RFC 5322"
3605    </t>
3606  </list>
3609  Ongoing work on ABNF conversion (<eref target=""/>):
3610  <list style="symbols">
3611    <t>
3612      Use "/" instead of "|" for alternatives.
3613    </t>
[356]3614    <t>
3615      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
[357]3616      whitespace ("OWS") and required whitespace ("RWS").
[356]3617    </t>
3618    <t>
[357]3619      Rewrite ABNFs to spell out whitespace rules, factor out
3620      header value format definitions.
[356]3621    </t>
[334]3622  </list>
[382]3626<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
[398]3628  Closed issues:
3629  <list style="symbols">
3630    <t>
3631      <eref target=""/>:
3632      "Reason-Phrase BNF"
3633    </t>
3634  </list>
[543]3637  Final work on ABNF conversion (<eref target=""/>):
[421]3638  <list style="symbols">
3639    <t>
[424]3640      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]3641    </t>
3642  </list>
[547]3646<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
[579]3648  Closed issues:
3649  <list style="symbols">
3650    <t>
[593]3651      <eref target=""/>:
3652      "Clarify when Referer is sent"
3653    </t>
3654    <t>
[579]3655      <eref target=""/>:
3656      "status codes vs methods"
3657    </t>
[591]3658    <t>
3659      <eref target=""/>:
3660      "Do not require "updates" relation for specs that register status codes or method names"
3661    </t>
[579]3662  </list>
[604]3666<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
[614]3668  Closed issues:
3669  <list style="symbols">
3670    <t>
[658]3671      <eref target=""/>:
3672      "Idempotency"
3673    </t>
3674    <t>
3675      <eref target=""/>:
3676      "TRACE security considerations"
3677    </t>
3678    <t>
[695]3679      <eref target=""/>:
3680      "Clarify rules for determining what entities a response carries"
3681    </t>
3682    <t>
[614]3683      <eref target=""/>:
3684      "update note citing RFC 1945 and 2068"
3685    </t>
[629]3686    <t>
3687      <eref target=""/>:
3688      "update note about redirect limit"
3689    </t>
[632]3690    <t>
3691      <eref target=""/>:
3692      "Location header ABNF should use 'URI'"
3693    </t>
[665]3694    <t>
3695      <eref target=""/>:
3696      "fragments in Location vs status 303"
3697    </t>
[700]3698    <t>
3699      <eref target=""/>:
3700      "move IANA registrations for optional status codes"
3701    </t>
[614]3702  </list>
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