source: draft-ietf-httpbis/latest/p2-semantics.xml @ 886

Last change on this file since 886 was 886, checked in by julian.reschke@…, 9 years ago

Note change in [884] relating to issue 199 (see #199)

  • Property svn:eol-style set to native
File size: 162.8 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">
[832]15  <!ENTITY ID-MONTH "July">
[741]16  <!ENTITY ID-YEAR "2010">
[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=''/>">
[823]29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[580]30  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
[31]31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
[688]47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x=''/>">
[31]48  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
[835]58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x=''/>">
[31]60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
[190]65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
[263]66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
[700]67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x=''/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x=''/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x=''/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x=''/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x=''/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x=''/>">
[838]73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x=''/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x=''/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x=''/>">
[884]76  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness'
79<?rfc toc="yes" ?>
[29]80<?rfc symrefs="yes" ?>
81<?rfc sortrefs="yes" ?>
[8]82<?rfc compact="yes"?>
83<?rfc subcompact="no" ?>
84<?rfc linkmailto="no" ?>
85<?rfc editing="no" ?>
[203]86<?rfc comments="yes"?>
87<?rfc inline="yes"?>
[799]88<?rfc rfcedstyle="yes"?>
[8]89<?rfc-ext allow-markup-in-artwork="yes" ?>
90<?rfc-ext include-references-in-index="yes" ?>
[308]91<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
[446]92     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
[286]93     xmlns:x=''
94     xmlns:rdf=''>
[120]97  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
[29]99  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
100    <organization abbrev="Day Software">Day Software</organization>
[8]101    <address>
102      <postal>
[29]103        <street>23 Corporate Plaza DR, Suite 280</street>
104        <city>Newport Beach</city>
[8]105        <region>CA</region>
[29]106        <code>92660</code>
107        <country>USA</country>
[8]108      </postal>
[29]109      <phone>+1-949-706-5300</phone>
110      <facsimile>+1-949-706-5305</facsimile>
111      <email></email>
112      <uri></uri>
[8]113    </address>
114  </author>
[29]116  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]117    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]118    <address>
119      <postal>
[29]120        <street>21 Oak Knoll Road</street>
121        <city>Carlisle</city>
[8]122        <region>MA</region>
[29]123        <code>01741</code>
124        <country>USA</country>
[8]125      </postal>
[844]126      <email></email>
127      <uri></uri>
[8]128    </address>
129  </author>
131  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]132    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]133    <address>
134      <postal>
[29]135        <street>HP Labs, Large Scale Systems Group</street>
136        <street>1501 Page Mill Road, MS 1177</street>
[8]137        <city>Palo Alto</city>
138        <region>CA</region>
[29]139        <code>94304</code>
140        <country>USA</country>
[8]141      </postal>
[29]142      <email></email>
[8]143    </address>
144  </author>
146  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]147    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]148    <address>
149      <postal>
[29]150        <street>1 Microsoft Way</street>
151        <city>Redmond</city>
152        <region>WA</region>
153        <code>98052</code>
154        <country>USA</country>
[8]155      </postal>
[29]156      <email></email>
[8]157    </address>
158  </author>
160  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[29]161    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
[8]162    <address>
163      <postal>
[29]164        <street>345 Park Ave</street>
165        <city>San Jose</city>
[8]166        <region>CA</region>
[29]167        <code>95110</code>
168        <country>USA</country>
[8]169      </postal>
[29]170      <email></email>
171      <uri></uri>
[8]172    </address>
173  </author>
175  <author initials="P." surname="Leach" fullname="Paul J. Leach">
176    <organization abbrev="Microsoft">Microsoft Corporation</organization>
177    <address>
178      <postal>
179        <street>1 Microsoft Way</street>
180        <city>Redmond</city>
181        <region>WA</region>
182        <code>98052</code>
183      </postal>
184      <email></email>
185    </address>
186  </author>
188  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
189    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
190    <address>
191      <postal>
[34]192        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
193        <street>The Stata Center, Building 32</street>
194        <street>32 Vassar Street</street>
[8]195        <city>Cambridge</city>
196        <region>MA</region>
197        <code>02139</code>
[29]198        <country>USA</country>
[8]199      </postal>
200      <email></email>
[34]201      <uri></uri>
[8]202    </address>
203  </author>
[95]205  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]206    <organization abbrev="W3C">World Wide Web Consortium</organization>
207    <address>
208      <postal>
209        <street>W3C / ERCIM</street>
210        <street>2004, rte des Lucioles</street>
211        <city>Sophia-Antipolis</city>
212        <region>AM</region>
213        <code>06902</code>
214        <country>France</country>
215      </postal>
216      <email></email>
217      <uri></uri>
218    </address>
219  </author>
[95]221  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
222    <organization abbrev="greenbytes">greenbytes GmbH</organization>
223    <address>
224      <postal>
225        <street>Hafenweg 16</street>
226        <city>Muenster</city><region>NW</region><code>48155</code>
227        <country>Germany</country>
228      </postal>
[609]229      <phone>+49 251 2807760</phone>
230      <facsimile>+49 251 2807761</facsimile>
231      <email></email>
232      <uri></uri>
[95]233    </address>
234  </author>
[31]236  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]237  <workgroup>HTTPbis Working Group</workgroup>
241   The Hypertext Transfer Protocol (HTTP) is an application-level
242   protocol for distributed, collaborative, hypermedia information
[29]243   systems. HTTP has been in use by the World Wide Web global information
[35]244   initiative since 1990. This document is Part 2 of the seven-part specification
[29]245   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]246   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
[29]247   as expressed by request methods, request-header fields, response status codes,
248   and response-header fields.
252<note title="Editorial Note (To be removed by RFC Editor)">
253  <t>
254    Discussion of this draft should take place on the HTTPBIS working group
255    mailing list ( The current issues list is
[848]256    at <eref target=""/>
[36]257    and related documents (including fancy diffs) can be found at
[324]258    <eref target=""/>.
[36]259  </t>
[153]260  <t>
[841]261    The changes in this draft are summarized in <xref target="changes.since.10"/>.
[153]262  </t>
266<section title="Introduction" anchor="introduction">
[162]268   This document defines HTTP/1.1 request and response semantics.  Each HTTP
269   message, as defined in &messaging;, is in the form of either a request or
270   a response.  An HTTP server listens on a connection for HTTP requests and
271   responds to each request, in the order received on that connection, with
272   one or more HTTP response messages.  This document defines the commonly
273   agreed upon semantics of the HTTP uniform interface, the intentions defined
274   by each request method, and the various response messages that might be
275   expected as a result of applying that method for the requested resource.
[162]278   This document is currently disorganized in order to minimize the changes
279   between drafts and enable reviewers to see the smaller errata changes.
280   The next draft will reorganize the sections to better reflect the content.
281   In particular, the sections will be ordered according to the typical
282   processing of an HTTP request message (after message parsing): resource
283   mapping, general header fields, methods, request modifiers, response
284   status, and resource metadata.  The current mess reflects how widely
285   dispersed these topics and associated requirements had become in
286   <xref target="RFC2616"/>.
289<section title="Requirements" anchor="intro.requirements">
291   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
292   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
293   document are to be interpreted as described in <xref target="RFC2119"/>.
296   An implementation is not compliant if it fails to satisfy one or more
[847]297   of the "MUST" or "REQUIRED" level requirements for the protocols it
298   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
299   level and all the "SHOULD" level requirements for its protocols is said
300   to be "unconditionally compliant"; one that satisfies all the "MUST"
301   level requirements but not all the "SHOULD" level requirements for its
302   protocols is said to be "conditionally compliant".
[424]306<section title="Syntax Notation" anchor="notation">
[425]307  <x:anchor-alias value="CR"/>
308  <x:anchor-alias value="DIGIT"/>
309  <x:anchor-alias value="LF"/>
310  <x:anchor-alias value="VCHAR"/>
311  <x:anchor-alias value="WSP"/>
[543]313  This specification uses the ABNF syntax defined in &notation; (which
314  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
315  <xref target="collected.abnf"/> shows the collected ABNF, with the list
316  rule expanded.
[425]319  The following core rules are included by
320  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
321  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
322  DIGIT (decimal 0-9), DQUOTE (double quote),
323  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
324  OCTET (any 8-bit sequence of data), SP (space),
325  VCHAR (any visible USASCII character),
326  and WSP (whitespace).
329<section title="Core Rules" anchor="core.rules">
[398]330  <x:anchor-alias value="obs-text"/>
[229]331  <x:anchor-alias value="quoted-string"/>
332  <x:anchor-alias value="token"/>
[356]333  <x:anchor-alias value="OWS"/>
334  <x:anchor-alias value="RWS"/>
[424]336  The core rules below are defined in &basic-rules;:
338<figure><artwork type="abnf2616">
[229]339  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
340  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
[356]341  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
342  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
[398]343  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
347<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]348  <x:anchor-alias value="absolute-URI"/>
[229]349  <x:anchor-alias value="Accept"/>
350  <x:anchor-alias value="Accept-Charset"/>
351  <x:anchor-alias value="Accept-Encoding"/>
352  <x:anchor-alias value="Accept-Language"/>
353  <x:anchor-alias value="Accept-Ranges"/>
354  <x:anchor-alias value="Age"/>
355  <x:anchor-alias value="Authorization"/>
[688]356  <x:anchor-alias value="comment"/>
[229]357  <x:anchor-alias value="ETag"/>
358  <x:anchor-alias value="Host"/>
359  <x:anchor-alias value="HTTP-date"/>
360  <x:anchor-alias value="If-Match"/>
361  <x:anchor-alias value="If-Modified-Since"/>
362  <x:anchor-alias value="If-None-Match"/>
363  <x:anchor-alias value="If-Range"/>
364  <x:anchor-alias value="If-Unmodified-Since"/>
[391]365  <x:anchor-alias value="partial-URI"/>
[229]366  <x:anchor-alias value="product"/>
367  <x:anchor-alias value="Proxy-Authenticate"/>
368  <x:anchor-alias value="Proxy-Authorization"/>
369  <x:anchor-alias value="Range"/>
370  <x:anchor-alias value="TE"/>
[785]371  <x:anchor-alias value="URI-reference"/>
[229]372  <x:anchor-alias value="Vary"/>
373  <x:anchor-alias value="WWW-Authenticate"/>
[206]375  The ABNF rules below are defined in other parts:
[207]377<figure><!--Part1--><artwork type="abnf2616">
[374]378  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
[688]379  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
[374]380  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
[229]381  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
[391]382  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
[229]383  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
384  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
[785]385  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
387<figure><!--Part3--><artwork type="abnf2616">
[229]388  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
389  <x:ref>Accept-Charset</x:ref> =
[206]390             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
[229]391  <x:ref>Accept-Encoding</x:ref> =
[206]392             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
[229]393  <x:ref>Accept-Language</x:ref> =
[206]394             &lt;Accept-Language, defined in &header-accept-language;&gt;
396<figure><!--Part4--><artwork type="abnf2616">
[229]397  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
398  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
399  <x:ref>If-Modified-Since</x:ref> =
[206]400             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
[229]401  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
402  <x:ref>If-Unmodified-Since</x:ref> =
[206]403             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
405<figure><!--Part5--><artwork type="abnf2616">
[229]406  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
407  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
408  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
410<figure><!--Part6--><artwork type="abnf2616">
[229]411  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
412  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
414<figure><artwork type="abnf2616">
[229]415  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
416  <x:ref>Proxy-Authenticate</x:ref> =
[206]417             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
[229]418  <x:ref>Proxy-Authorization</x:ref> =
[206]419             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
[229]420  <x:ref>WWW-Authenticate</x:ref> =
[206]421             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
[8]427<section title="Method" anchor="method">
[229]428  <x:anchor-alias value="Method"/>
429  <x:anchor-alias value="extension-method"/>
[823]431   The Method token indicates the method to be performed on the resource
432   identified by the Effective Request URI (&effective-request-uri;). The
433   method is case-sensitive.
435<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
[272]436  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
[334]437                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
438                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
439                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
440                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
441                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
442                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
443                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
444                 / <x:ref>extension-method</x:ref>
[229]445  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
448   The list of methods allowed by a resource can be specified in an
449   Allow header field (<xref target="header.allow"/>). The return code of the response
450   always notifies the client whether a method is currently allowed on a
451   resource, since the set of allowed methods can change dynamically. An
452   origin server &SHOULD; return the status code 405 (Method Not Allowed)
453   if the method is known by the origin server but not allowed for the
454   requested resource, and 501 (Not Implemented) if the method is
455   unrecognized or not implemented by the origin server. The methods GET
456   and HEAD &MUST; be supported by all general-purpose servers. All other
457   methods are &OPTIONAL;; however, if the above methods are implemented,
458   they &MUST; be implemented with the same semantics as those specified
459   in <xref target="method.definitions"/>.
462<section title="Method Registry" anchor="method.registry">
464  The HTTP Method Registry defines the name space for the Method token in the
465  Request line of an HTTP request.
[286]468  Registrations &MUST; include the following fields:
469  <list style="symbols">
470    <t>Method Name (see <xref target="method"/>)</t>
471    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
472    <t>Pointer to specification text</t>
473  </list>
[270]476  Values to be added to this name space are subject to IETF review
[591]477  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
[672]480  The registry itself is maintained at <eref target=""/>.
485<section title="Request Header Fields" anchor="request.header.fields">
[229]486  <x:anchor-alias value="request-header"/>
488   The request-header fields allow the client to pass additional
489   information about the request, and about the client itself, to the
490   server. These fields act as request modifiers, with semantics
491   equivalent to the parameters on a programming language method
492   invocation.
494<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
[229]495  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
[334]496                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
497                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
498                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
499                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
500                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
501                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
502                 / <x:ref>Host</x:ref>                     ; &header-host;
503                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
504                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
505                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
506                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
507                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
508                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
509                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
510                 / <x:ref>Range</x:ref>                    ; &header-range;
511                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
512                 / <x:ref>TE</x:ref>                       ; &header-te;
513                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
516   Request-header field names can be extended reliably only in
517   combination with a change in the protocol version. However, new or
518   experimental header fields &MAY; be given the semantics of request-header
519   fields if all parties in the communication recognize them to
520   be request-header fields. Unrecognized header fields are treated as
521   entity-header fields.
525<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
[229]526  <x:anchor-alias value="Reason-Phrase"/>
527  <x:anchor-alias value="Status-Code"/>
[426]528  <x:anchor-alias value="extension-code"/>
530   The Status-Code element is a 3-digit integer result code of the
[149]531   attempt to understand and satisfy the request. The status codes listed
[838]532   below are defined in <xref target=""/>, &p4-status-codes;,
533   &p5-status-codes;, and &p7-status-codes;.
[149]536   The Reason-Phrase is intended to give a short
[8]537   textual description of the Status-Code. The Status-Code is intended
538   for use by automata and the Reason-Phrase is intended for the human
539   user. The client is not required to examine or display the Reason-Phrase.
542   The individual values of the numeric status codes defined for
[757]543   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
[8]544   presented below. The reason phrases listed here are only
545   recommendations -- they &MAY; be replaced by local equivalents without
546   affecting the protocol.
548<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"/>
[837]549  <x:ref>Status-Code</x:ref> =
550       "100"  ; <xref target="status.100"/>: Continue
551     / "101"  ; <xref target="status.101"/>: Switching Protocols
552     / "200"  ; <xref target="status.200"/>: OK
553     / "201"  ; <xref target="status.201"/>: Created
554     / "202"  ; <xref target="status.202"/>: Accepted
555     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
556     / "204"  ; <xref target="status.204"/>: No Content
557     / "205"  ; <xref target="status.205"/>: Reset Content
558     / "206"  ; &status-206;: Partial Content
559     / "300"  ; <xref target="status.300"/>: Multiple Choices
560     / "301"  ; <xref target="status.301"/>: Moved Permanently
561     / "302"  ; <xref target="status.302"/>: Found
562     / "303"  ; <xref target="status.303"/>: See Other
563     / "304"  ; &status-304;: Not Modified
564     / "305"  ; <xref target="status.305"/>: Use Proxy
565     / "307"  ; <xref target="status.307"/>: Temporary Redirect
566     / "400"  ; <xref target="status.400"/>: Bad Request
567     / "401"  ; &status-401;: Unauthorized
568     / "402"  ; <xref target="status.402"/>: Payment Required
569     / "403"  ; <xref target="status.403"/>: Forbidden
570     / "404"  ; <xref target="status.404"/>: Not Found
571     / "405"  ; <xref target="status.405"/>: Method Not Allowed
572     / "406"  ; <xref target="status.406"/>: Not Acceptable
573     / "407"  ; &status-407;: Proxy Authentication Required
574     / "408"  ; <xref target="status.408"/>: Request Time-out
575     / "409"  ; <xref target="status.409"/>: Conflict
576     / "410"  ; <xref target="status.410"/>: Gone
577     / "411"  ; <xref target="status.411"/>: Length Required
578     / "412"  ; &status-412;: Precondition Failed
579     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
580     / "414"  ; <xref target="status.414"/>: URI Too Long
581     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
582     / "416"  ; &status-416;: Requested range not satisfiable
583     / "417"  ; <xref target="status.417"/>: Expectation Failed
584     / "500"  ; <xref target="status.500"/>: Internal Server Error
585     / "501"  ; <xref target="status.501"/>: Not Implemented
586     / "502"  ; <xref target="status.502"/>: Bad Gateway
587     / "503"  ; <xref target="status.503"/>: Service Unavailable
588     / "504"  ; <xref target="status.504"/>: Gateway Time-out
589     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
590     / <x:ref>extension-code</x:ref>
[229]592  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
[398]593  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
596   HTTP status codes are extensible. HTTP applications are not required
597   to understand the meaning of all registered status codes, though such
598   understanding is obviously desirable. However, applications &MUST;
599   understand the class of any status code, as indicated by the first
600   digit, and treat any unrecognized response as being equivalent to the
601   x00 status code of that class, with the exception that an
602   unrecognized response &MUST-NOT; be cached. For example, if an
603   unrecognized status code of 431 is received by the client, it can
604   safely assume that there was something wrong with its request and
605   treat the response as if it had received a 400 status code. In such
[866]606   cases, user agents &SHOULD; present to the user the representation enclosed
607   with the response, since that representation is likely to include human-readable
[8]608   information which will explain the unusual status.
611<section title="Status Code Registry" anchor="status.code.registry">
613  The HTTP Status Code Registry defines the name space for the Status-Code
614  token in the Status line of an HTTP response.
617  Values to be added to this name space are subject to IETF review
[591]618  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
621  The registry itself is maintained at <eref target=""/>.
[8]627<section title="Response Header Fields" anchor="response.header.fields">
[229]628  <x:anchor-alias value="response-header"/>
630   The response-header fields allow the server to pass additional
631   information about the response which cannot be placed in the Status-Line.
632   These header fields give information about the server and about
[823]633   further access to the resource identified by the Effective Request URI
634   (&effective-request-uri;).
636<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
[229]637  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
[334]638                  / <x:ref>Age</x:ref>                     ; &header-age;
639                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
640                  / <x:ref>ETag</x:ref>                    ; &header-etag;
641                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
642                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
643                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
644                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
645                  / <x:ref>Vary</x:ref>                    ; &header-vary;
646                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
649   Response-header field names can be extended reliably only in
650   combination with a change in the protocol version. However, new or
651   experimental header fields &MAY; be given the semantics of response-header
652   fields if all parties in the communication recognize them to
653   be response-header fields. Unrecognized header fields are treated as
654   entity-header fields.
[874]658<section title="Representation" anchor="representation">
[866]660   Request and Response messages &MAY; transfer a representation if not otherwise
661   restricted by the request method or response status code. A representation
662   consists of metadata (representation header fields) and data (representation
663   body).  When a complete or partial representation is enclosed in an HTTP message,
664   it is referred to as the payload of the message. HTTP representations
665   are defined in &payload;.
[866]668   A representation body is only present in a message when a message-body is
669   present, as described in &message-body;. The representation body is obtained
[8]670   from the message-body by decoding any Transfer-Encoding that might
671   have been applied to ensure safe and proper transfer of the message.
674<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
676   It is sometimes necessary to determine the identity of the resource
677   associated with a representation.
680   An HTTP request representation, when present, is always associated with an
681   anonymous (i.e., unidentified) resource.
684   In the common case, an HTTP response is a representation of the resource
[823]685   located at the Effective Request URI (see &effective-request-uri;). However,
686   this is not always the case. To determine the URI of the resource a
687   response is associated with, the following rules are used (with the first
688   applicable one being selected):
690<t><list style="numbers">
691   <t>If the response status code is 200 or 203 and the request method was GET,
[823]692   the response is a representation of the resource at the Effective Request URI.</t>
[695]693   <t>If the response status is 204, 206, or 304 and the request method was GET
694   or HEAD, the response is a partial representation of the resource at the
[823]695   Effective Request URI (see &caching-combining-headers;).</t>
[695]696   <t>If the response has a Content-Location header, and that URI is the same
[823]697   as the Effective Request URI, the response is a representation of the
698   resource at the Effective Request URI.</t>
[695]699   <t>If the response has a Content-Location header, and that URI is not the
[823]700   same as the Effective Request URI, the response asserts that it is a
701   representation of the resource at the Content-Location URI (but it may not
702   be).</t>
[695]703   <t>Otherwise, the response is a representation of an anonymous (i.e.,
704   unidentified) resource.</t>
707  <cref anchor="TODO-req-uri">
[823]708   The comparison function is going to have to be defined somewhere,
[695]709   because we already need to compare URIs for things like cache invalidation.</cref>
[8]716<section title="Method Definitions" anchor="method.definitions">
718   The set of common methods for HTTP/1.1 is defined below. Although
719   this set can be expanded, additional methods cannot be assumed to
720   share the same semantics for separately extended clients and servers.
723<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
725<section title="Safe Methods" anchor="safe.methods">
[286]726<iref item="Safe Methods" primary="true"/>
728   Implementors should be aware that the software represents the user in
729   their interactions over the Internet, and should be careful to allow
730   the user to be aware of any actions they might take which may have an
731   unexpected significance to themselves or others.
[708]734   In particular, the convention has been established that the GET, HEAD,
735   OPTIONS, and TRACE methods &SHOULD-NOT;  have the significance of taking an action
[286]736   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
[8]737   This allows user agents to represent other methods, such as POST, PUT
738   and DELETE, in a special way, so that the user is made aware of the
739   fact that a possibly unsafe action is being requested.
742   Naturally, it is not possible to ensure that the server does not
743   generate side-effects as a result of performing a GET request; in
744   fact, some dynamic resources consider that a feature. The important
745   distinction here is that the user did not request the side-effects,
746   so therefore cannot be held accountable for them.
750<section title="Idempotent Methods" anchor="idempotent.methods">
[286]751<iref item="Idempotent Methods" primary="true"/>
[657]753   Methods can also have the property of "idempotence" in that, aside
754   from error or expiration issues, the intended effect of multiple
755   identical requests is the same as for a single request.
756   The methods PUT, DELETE, and all safe methods are idempotent.
757   It is important to note that idempotence refers only to changes
758   requested by the client: a server is free to change its state due
759   to multiple requests for the purpose of tracking those requests,
760   versioning of results, etc.
765<section title="OPTIONS" anchor="OPTIONS">
[286]766  <rdf:Description>
767    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
768  </rdf:Description>
[8]769  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
770  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
772   The OPTIONS method represents a request for information about the
773   communication options available on the request/response chain
[823]774   identified by the Effective Request URI. This method allows the client to
[8]775   determine the options and/or requirements associated with a resource,
776   or the capabilities of a server, without implying a resource action
777   or initiating a resource retrieval.
780   Responses to this method are not cacheable.
[874]783   If the OPTIONS request includes a message-body (as indicated by the
[8]784   presence of Content-Length or Transfer-Encoding), then the media type
785   &MUST; be indicated by a Content-Type field. Although this
786   specification does not define any use for such a body, future
787   extensions to HTTP might use the OPTIONS body to make more detailed
[280]788   queries on the server.
[391]791   If the request-target is an asterisk ("*"), the OPTIONS request is
[8]792   intended to apply to the server in general rather than to a specific
793   resource. Since a server's communication options typically depend on
794   the resource, the "*" request is only useful as a "ping" or "no-op"
795   type of method; it does nothing beyond allowing the client to test
796   the capabilities of the server. For example, this can be used to test
797   a proxy for HTTP/1.1 compliance (or lack thereof).
[391]800   If the request-target is not an asterisk, the OPTIONS request applies
[8]801   only to the options that are available when communicating with that
802   resource.
805   A 200 response &SHOULD; include any header fields that indicate
806   optional features implemented by the server and applicable to that
807   resource (e.g., Allow), possibly including extensions not defined by
808   this specification. The response body, if any, &SHOULD; also include
809   information about the communication options. The format for such a
810   body is not defined by this specification, but might be defined by
811   future extensions to HTTP. Content negotiation &MAY; be used to select
812   the appropriate response format. If no response body is included, the
813   response &MUST; include a Content-Length field with a field-value of
814   "0".
817   The Max-Forwards request-header field &MAY; be used to target a
818   specific proxy in the request chain. When a proxy receives an OPTIONS
[374]819   request on an absolute-URI for which request forwarding is permitted,
[8]820   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
821   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
822   instead, the proxy &SHOULD; respond with its own communication options.
823   If the Max-Forwards field-value is an integer greater than zero, the
824   proxy &MUST; decrement the field-value when it forwards the request. If
825   no Max-Forwards field is present in the request, then the forwarded
826   request &MUST-NOT; include a Max-Forwards field.
830<section title="GET" anchor="GET">
[286]831  <rdf:Description>
832    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
833  </rdf:Description>
[8]834  <iref primary="true" item="GET method" x:for-anchor=""/>
835  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
[874]837   The GET method means retrieve whatever information (in the form of a
838   representation) currently corresponds to the resource identified by the
[823]839   Effective Request URI.
[823]842   If the Effective Request URI identifies a data-producing process, it is the
[866]843   produced data which shall be returned as the representation in the response and not
[730]844   the source text of the process, unless that text happens to be the output of
845   the process.
848   The semantics of the GET method change to a "conditional GET" if the
849   request message includes an If-Modified-Since, If-Unmodified-Since,
850   If-Match, If-None-Match, or If-Range header field. A conditional GET
[866]851   method requests that the representation be transferred only under the
[8]852   circumstances described by the conditional header field(s). The
853   conditional GET method is intended to reduce unnecessary network
[874]854   usage by allowing cached representations to be refreshed without requiring
[8]855   multiple requests or transferring data already held by the client.
858   The semantics of the GET method change to a "partial GET" if the
859   request message includes a Range header field. A partial GET requests
[866]860   that only part of the representation be transferred, as described in &header-range;.
[8]861   The partial GET method is intended to reduce unnecessary
[866]862   network usage by allowing partially-retrieved representations to be
[8]863   completed without transferring data already held by the client.
866   The response to a GET request is cacheable if and only if it meets
[29]867   the requirements for HTTP caching described in &caching;.
870   See <xref target=""/> for security considerations when used for forms.
874<section title="HEAD" anchor="HEAD">
[286]875  <rdf:Description>
876    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
877  </rdf:Description>
[8]878  <iref primary="true" item="HEAD method" x:for-anchor=""/>
879  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
881   The HEAD method is identical to GET except that the server &MUST-NOT;
[867]882   return a message-body in the response. The metadata contained
[8]883   in the HTTP headers in response to a HEAD request &SHOULD; be identical
884   to the information sent in response to a GET request. This method can
[867]885   be used for obtaining metadata about the representation implied by the
[866]886   request without transferring the representation body. This method is
[8]887   often used for testing hypertext links for validity, accessibility,
888   and recent modification.
891   The response to a HEAD request &MAY; be cacheable in the sense that the
892   information contained in the response &MAY; be used to update a
[874]893   previously cached representation from that resource. If the new field values
894   indicate that the cached representation differs from the current representation (as
[8]895   would be indicated by a change in Content-Length, Content-MD5, ETag
896   or Last-Modified), then the cache &MUST; treat the cache entry as
897   stale.
901<section title="POST" anchor="POST">
902  <iref primary="true" item="POST method" x:for-anchor=""/>
903  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
905   The POST method is used to request that the origin server accept the
[874]906   representation enclosed in the request as data to be processed by the resource
[823]907   identified by the Effective Request URI. POST is designed
[8]908   to allow a uniform method to cover the following functions:
909  <list style="symbols">
910    <t>
911      Annotation of existing resources;
912    </t>
913    <t>
914        Posting a message to a bulletin board, newsgroup, mailing list,
915        or similar group of articles;
916    </t>
917    <t>
918        Providing a block of data, such as the result of submitting a
919        form, to a data-handling process;
920    </t>
921    <t>
922        Extending a database through an append operation.
923    </t>
924  </list>
927   The actual function performed by the POST method is determined by the
[823]928   server and is usually dependent on the Effective Request URI.
931   The action performed by the POST method might not result in a
932   resource that can be identified by a URI. In this case, either 200
933   (OK) or 204 (No Content) is the appropriate response status,
[874]934   depending on whether or not the response includes a representation that
[8]935   describes the result.
938   If a resource has been created on the origin server, the response
[874]939   &SHOULD; be 201 (Created) and contain a representation which describes the
[8]940   status of the request and refers to the new resource, and a Location
941   header (see <xref target="header.location"/>).
944   Responses to this method are not cacheable, unless the response
945   includes appropriate Cache-Control or Expires header fields. However,
946   the 303 (See Other) response can be used to direct the user agent to
947   retrieve a cacheable resource.
951<section title="PUT" anchor="PUT">
952  <iref primary="true" item="PUT method" x:for-anchor=""/>
953  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
[866]955   The PUT method requests that the enclosed representation be stored at the
[823]956   Effective Request URI. If the Effective Request URI refers to an already
[866]957   existing resource, the enclosed representation &SHOULD; be considered a
[823]958   modified version of the one residing on the origin server. Otherwise, if the
959   Effective Request URI does not point to an existing resource, and that URI is
[8]960   capable of being defined as a new resource by the requesting user
[823]961   agent, the origin server can create the resource with that URI.
964   If a new resource is created at the Effective Request URI, the origin
965   server &MUST; inform the user agent
[8]966   via the 201 (Created) response. If an existing resource is modified,
967   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
[823]968   to indicate successful completion of the request.
[866]971   If the resource identified by the Effective Request URI could not be
972   created or modified, an appropriate error response &SHOULD; be given
973   that reflects the nature of the problem.
974   The recipient of the representation &MUST-NOT; ignore any Content-*
[746]975   headers (headers starting with the prefix "Content-") that it does
[333]976   not understand or implement
[8]977   and &MUST; return a 501 (Not Implemented) response in such cases.
[866]980   If the request passes through a cache that has one or more stored
981   responses for the Effective Request URI, those stored responses
982   &SHOULD; be marked as stale if the response to the PUT request
983   is a success status. Responses to the PUT method are not cacheable.
986   The fundamental difference between the POST and PUT requests is
[823]987   reflected in the different meaning of the Effective Request URI. The URI in a
[8]988   POST request identifies the resource that will handle the enclosed
[866]989   representation. That resource might be a data-accepting process, a gateway to
990   some other protocol, or a document that accepts annotations.
991   In contrast, the URI in a PUT request identifies the resource for
992   which enclosed representation is a new or replacement value; the
993   user agent knows what URI is intended and the server &MUST-NOT; attempt
994   to apply the request to some other resource.
[8]995   If the server desires that the request be applied to a different URI,
996   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
997   then make its own decision regarding whether or not to redirect the
998   request.
1001   A single resource &MAY; be identified by many different URIs. For
1002   example, an article might have a URI for identifying "the current
1003   version" which is separate from the URI identifying each particular
1004   version. In this case, a PUT request on a general URI might result in
1005   several other URIs being defined by the origin server.
1008   HTTP/1.1 does not define how a PUT method affects the state of an
1009   origin server.
1012   Unless otherwise specified for a particular entity-header, the
1013   entity-headers in the PUT request &SHOULD; be applied to the resource
1014   created or modified by the PUT.
1018<section title="DELETE" anchor="DELETE">
1019  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1020  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1022   The DELETE method requests that the origin server delete the resource
[823]1023   identified by the Effective Request URI. This method &MAY; be overridden by
1024   human intervention (or other means) on the origin server. The client cannot
[8]1025   be guaranteed that the operation has been carried out, even if the
1026   status code returned from the origin server indicates that the action
1027   has been completed successfully. However, the server &SHOULD-NOT; 
1028   indicate success unless, at the time the response is given, it
1029   intends to delete the resource or move it to an inaccessible
1030   location.
1033   A successful response &SHOULD; be 200 (OK) if the response includes an
[874]1034   representation describing the status, 202 (Accepted) if the action has not
[8]1035   yet been enacted, or 204 (No Content) if the action has been enacted
[866]1036   but the response does not include a representation.
[823]1039   If the request passes through a cache and the Effective Request URI
[874]1040   identifies one or more currently cached representations, those entries &SHOULD; be
1041   treated as stale. Responses to the DELETE method &MUST-NOT; be cached.
1045<section title="TRACE" anchor="TRACE">
[286]1046  <rdf:Description>
1047    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1048  </rdf:Description>
[8]1049  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1050  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1052   The TRACE method is used to invoke a remote, application-layer loop-back
1053   of the request message. The final recipient of the request
1054   &SHOULD; reflect the message received back to the client as the
[874]1055   message-body of a 200 (OK) response. The final recipient is either the
[8]1056   origin server or the first proxy or gateway to receive a Max-Forwards
[866]1057   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1058   A TRACE request &MUST-NOT; include a message-body.
1061   TRACE allows the client to see what is being received at the other
1062   end of the request chain and use that data for testing or diagnostic
[29]1063   information. The value of the Via header field (&header-via;) is of
[8]1064   particular interest, since it acts as a trace of the request chain.
1065   Use of the Max-Forwards header field allows the client to limit the
1066   length of the request chain, which is useful for testing a chain of
1067   proxies forwarding messages in an infinite loop.
[874]1070   If the request is valid, the response &SHOULD; have a Content-Type of
1071   "message/http" (see &media-type-message-http;) and contain a message-body
1072   that encloses a copy of the entire request message.
1073   Responses to the TRACE method &MUST-NOT; be cached.
1077<section title="CONNECT" anchor="CONNECT">
1078  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1079  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1081   This specification reserves the method name CONNECT for use with a
[763]1082   proxy that can dynamically switch to being a tunnel (e.g., SSL
[274]1083   tunneling <xref target="RFC2817"/>).
1089<section title="Status Code Definitions" anchor="">
[867]1091   Each Status-Code is described below, including any metadata required
[579]1092   in the response.
1095<section title="Informational 1xx" anchor="status.1xx">
1097   This class of status code indicates a provisional response,
1098   consisting only of the Status-Line and optional headers, and is
1099   terminated by an empty line. There are no required headers for this
1100   class of status code. Since HTTP/1.0 did not define any 1xx status
1101   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1102   except under experimental conditions.
1105   A client &MUST; be prepared to accept one or more 1xx status responses
1106   prior to a regular response, even if the client does not expect a 100
1107   (Continue) status message. Unexpected 1xx status responses &MAY; be
1108   ignored by a user agent.
1111   Proxies &MUST; forward 1xx responses, unless the connection between the
1112   proxy and its client has been closed, or unless the proxy itself
1113   requested the generation of the 1xx response. (For example, if a
1114   proxy adds a "Expect: 100-continue" field when it forwards a request,
1115   then it need not forward the corresponding 100 (Continue)
1116   response(s).)
1119<section title="100 Continue" anchor="status.100">
1120  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1121  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1123   The client &SHOULD; continue with its request. This interim response is
1124   used to inform the client that the initial part of the request has
1125   been received and has not yet been rejected by the server. The client
1126   &SHOULD; continue by sending the remainder of the request or, if the
1127   request has already been completed, ignore this response. The server
1128   &MUST; send a final response after the request has been completed. See
[29]1129   &use100; for detailed discussion of the use and handling of this
[8]1130   status code.
1134<section title="101 Switching Protocols" anchor="status.101">
1135  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1136  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1138   The server understands and is willing to comply with the client's
[29]1139   request, via the Upgrade message header field (&header-upgrade;), for a
[8]1140   change in the application protocol being used on this connection. The
1141   server will switch protocols to those defined by the response's
1142   Upgrade header field immediately after the empty line which
1143   terminates the 101 response.
1146   The protocol &SHOULD; be switched only when it is advantageous to do
1147   so. For example, switching to a newer version of HTTP is advantageous
1148   over older versions, and switching to a real-time, synchronous
1149   protocol might be advantageous when delivering resources that use
1150   such features.
1155<section title="Successful 2xx" anchor="status.2xx">
1157   This class of status code indicates that the client's request was
1158   successfully received, understood, and accepted.
1161<section title="200 OK" anchor="status.200">
1162  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1163  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1165   The request has succeeded. The information returned with the response
1166   is dependent on the method used in the request, for example:
1167  <list style="hanging">
1168    <t hangText="GET">
[874]1169          a representation corresponding to the requested resource is sent in
[8]1170          the response;
1171    </t>
1172    <t hangText="HEAD">
1173          the entity-header fields corresponding to the requested
1174          resource are sent in the response without any message-body;
1175    </t>
1176    <t hangText="POST">
[874]1177      a representation describing or containing the result of the action;
[8]1178    </t>
1179    <t hangText="TRACE">
[874]1180      a representation containing the request message as received by the
[8]1181      end server.
1182    </t>
1183  </list>
[886]1186   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1187   freshness for 200 responses.
1191<section title="201 Created" anchor="status.201">
1192  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1193  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
[758]1195   The request has been fulfilled and has resulted in a new resource being
[8]1196   created. The newly created resource can be referenced by the URI(s)
[856]1197   returned in the payload of the response, with the most specific URI
[8]1198   for the resource given by a Location header field. The response
[856]1199   &SHOULD; include a payload containing a list of resource
[8]1200   characteristics and location(s) from which the user or user agent can
[856]1201   choose the one most appropriate. The payload format is specified by
[8]1202   the media type given in the Content-Type header field. The origin
1203   server &MUST; create the resource before returning the 201 status code.
1204   If the action cannot be carried out immediately, the server &SHOULD;
1205   respond with 202 (Accepted) response instead.
1208   A 201 response &MAY; contain an ETag response header field indicating
[874]1209   the current value of the entity-tag for the representation of the resource
[856]1210   just created (see &header-etag;).
1214<section title="202 Accepted" anchor="status.202">
1215  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1216  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1218   The request has been accepted for processing, but the processing has
1219   not been completed.  The request might or might not eventually be
1220   acted upon, as it might be disallowed when processing actually takes
1221   place. There is no facility for re-sending a status code from an
1222   asynchronous operation such as this.
1225   The 202 response is intentionally non-committal. Its purpose is to
1226   allow a server to accept a request for some other process (perhaps a
1227   batch-oriented process that is only run once per day) without
1228   requiring that the user agent's connection to the server persist
[866]1229   until the process is completed. The representation returned with this
[8]1230   response &SHOULD; include an indication of the request's current status
1231   and either a pointer to a status monitor or some estimate of when the
1232   user can expect the request to be fulfilled.
1236<section title="203 Non-Authoritative Information" anchor="status.203">
1237  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1238  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
[867]1240   The returned metadata in the entity-header is not the
[8]1241   definitive set as available from the origin server, but is gathered
1242   from a local or a third-party copy. The set presented &MAY; be a subset
1243   or superset of the original version. For example, including local
1244   annotation information about the resource might result in a superset
[867]1245   of the metadata known by the origin server. Use of this
[8]1246   response code is not required and is only appropriate when the
1247   response would otherwise be 200 (OK).
[886]1250   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1251   freshness for 203 responses.
1256<section title="204 No Content" anchor="status.204">
1257  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1258  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
[856]1260   The server has successfully fulfilled the request, but there is no
1261   additional content to return in the response payload body.  The
1262   resource metadata and representation metadata in the response message's
1263   header fields refer to the requested resource and its current
1264   representation, respectively, after the requested action.
1265   For example, if a 204 status is received in response to a PUT
[885]1266   and the response contains an ETag header field, then the value of
[856]1267   that field is the current entity-tag for the representation that
1268   was successfully PUT to the requested resource.
[856]1271   If the client is a user agent, it &SHOULD-NOT; change its document view
[8]1272   from that which caused the request to be sent. This response is
1273   primarily intended to allow input for actions to take place without
1274   causing a change to the user agent's active document view, although
[856]1275   any new or updated metadata &SHOULD; be applied to the document
[8]1276   currently in the user agent's active view.
1279   The 204 response &MUST-NOT; include a message-body, and thus is always
1280   terminated by the first empty line after the header fields.
1284<section title="205 Reset Content" anchor="status.205">
1285  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1286  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1288   The server has fulfilled the request and the user agent &SHOULD; reset
1289   the document view which caused the request to be sent. This response
1290   is primarily intended to allow input for actions to take place via
1291   user input, followed by a clearing of the form in which the input is
1292   given so that the user can easily initiate another input action. The
[866]1293   response &MUST-NOT; include a message-body.
1297<section title="206 Partial Content" anchor="status.206">
1298  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1299  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
[700]1300  <rdf:Description>
1301    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1302  </rdf:Description>
[29]1304   The server has fulfilled the partial GET request for the resource
[874]1305   and the enclosed payload is a partial representation as defined in &status-206;.
[886]1308   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1309   freshness for 206 responses.
1314<section title="Redirection 3xx" anchor="status.3xx">
1316   This class of status code indicates that further action needs to be
1317   taken by the user agent in order to fulfill the request.  The action
1318   required &MAY; be carried out by the user agent without interaction
1319   with the user if and only if the method used in the second request is
[760]1320   known to be "safe", as defined in <xref target="safe.methods"/>.
[759]1321   A client &SHOULD; detect infinite redirection loops, since such loops
1322   generate network traffic for each redirection.
1325  <t>
[756]1326    <x:h>Note:</x:h> An earlier version of this specification recommended a
[629]1327    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1328    Content developers should be aware that there might be clients that
1329    implement such a fixed limitation.
[563]1330  </t>
1333<section title="300 Multiple Choices" anchor="status.300">
1334  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1335  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1337   The requested resource corresponds to any one of a set of
1338   representations, each with its own specific location, and agent-driven
[29]1339   negotiation information (&content-negotiation;) is being provided so that
[8]1340   the user (or user agent) can select a preferred representation and
1341   redirect its request to that location.
[866]1344   Unless it was a HEAD request, the response &SHOULD; include a representation
[8]1345   containing a list of resource characteristics and location(s) from
1346   which the user or user agent can choose the one most appropriate. The
[866]1347   data format is specified by the media type given in the Content-Type
[8]1348   header field. Depending upon the format and the capabilities of
1349   the user agent, selection of the most appropriate choice &MAY; be
1350   performed automatically. However, this specification does not define
1351   any standard for such automatic selection.
1354   If the server has a preferred choice of representation, it &SHOULD;
1355   include the specific URI for that representation in the Location
1356   field; user agents &MAY; use the Location field value for automatic
[884]1357   redirection.
[886]1360   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1361   freshness for 300 responses.
1366<section title="301 Moved Permanently" anchor="status.301">
1367  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1368  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1370   The requested resource has been assigned a new permanent URI and any
1371   future references to this resource &SHOULD; use one of the returned
1372   URIs.  Clients with link editing capabilities ought to automatically
[823]1373   re-link references to the Effective Request URI to one or more of the new
[884]1374   references returned by the server, where possible.
[886]1377   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1378   freshness for 301 responses.
[8]1381   The new permanent URI &SHOULD; be given by the Location field in the
[866]1382   response. Unless the request method was HEAD, the representation of the
[8]1383   response &SHOULD; contain a short hypertext note with a hyperlink to
1384   the new URI(s).
[88]1387   If the 301 status code is received in response to a request method
1388   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1389   then the request &MAY; be automatically redirected by the user agent without
[88]1390   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1391   request unless it can be confirmed by the user, since this might
1392   change the conditions under which the request was issued.
1395  <t>
1396    <x:h>Note:</x:h> When automatically redirecting a POST request after
1397    receiving a 301 status code, some existing HTTP/1.0 user agents
1398    will erroneously change it into a GET request.
1399  </t>
1403<section title="302 Found" anchor="status.302">
1404  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1405  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1407   The requested resource resides temporarily under a different URI.
1408   Since the redirection might be altered on occasion, the client &SHOULD;
[885]1409   continue to use the Effective Request URI for future requests.
1412   The temporary URI &SHOULD; be given by the Location field in the
[866]1413   response. Unless the request method was HEAD, the representation of the
[8]1414   response &SHOULD; contain a short hypertext note with a hyperlink to
1415   the new URI(s).
[88]1418   If the 302 status code is received in response to a request method
1419   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1420   then the request &MAY; be automatically redirected by the user agent without
[88]1421   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1422   request unless it can be confirmed by the user, since this might
1423   change the conditions under which the request was issued.
1426  <t>
[614]1427    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1428    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1429    specify that the client is not allowed to change the method on the
1430    redirected request.  However, most existing user agent implementations
1431    treat 302 as if it were a 303 response, performing a GET on the Location
1432    field-value regardless of the original request method. Therefore, a
1433    previous version of this specification
1434    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1435    status codes
1436    <xref target="status.303" format="none">303</xref> and
1437    <xref target="status.307" format="none">307</xref> for servers that wish
1438    to make unambiguously clear which kind of reaction is expected of the
1439    client.
[563]1440  </t>
1444<section title="303 See Other" anchor="status.303">
1445  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1446  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
[242]1448   The server directs the user agent to a different resource, indicated
1449   by a URI in the Location header field, that provides an indirect
1450   response to the original request.  The user agent &MAY; perform a GET
1451   request on the URI in the Location field in order to obtain a
1452   representation corresponding to the response, be redirected again,
1453   or end with an error status.  The Location URI is not a substitute
1454   reference for the originally requested resource.
[242]1457   The 303 status is generally applicable to any HTTP method.  It is
1458   primarily used to allow the output of a POST action to redirect
1459   the user agent to a selected resource, since doing so provides the
1460   information corresponding to the POST response in a form that
1461   can be separately identified, bookmarked, and cached independent
1462   of the original request.
1465   A 303 response to a GET request indicates that the requested
1466   resource does not have a representation of its own that can be
1467   transferred by the server over HTTP.  The Location URI indicates a
1468   resource that is descriptive of the requested resource such that
1469   the follow-on representation may be useful without implying that
[243]1470   it adequately represents the previously requested resource.
[242]1471   Note that answers to the questions of what can be represented, what
1472   representations are adequate, and what might be a useful description
1473   are outside the scope of HTTP and thus entirely determined by the
[602]1474   URI owner(s).
[884]1477   Except for responses to a HEAD request, the representation of a 303
1478   response &SHOULD; contain a short hypertext note with a hyperlink
1479   to the Location URI.
1483<section title="304 Not Modified" anchor="status.304">
1484  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1485  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
[700]1486  <rdf:Description>
1487    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1488  </rdf:Description>
[45]1490   The response to the request has not been modified since the conditions
[700]1491   indicated by the client's conditional GET request, as defined in &status-304;.
1495<section title="305 Use Proxy" anchor="status.305">
1496  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1497  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
[235]1499   The 305 status was defined in a previous version of this specification
1500   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1504<section title="306 (Unused)" anchor="status.306">
1505  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1506  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1508   The 306 status code was used in a previous version of the
1509   specification, is no longer used, and the code is reserved.
1513<section title="307 Temporary Redirect" anchor="status.307">
1514  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1515  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1517   The requested resource resides temporarily under a different URI.
1518   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
[884]1519   continue to use the Effective Request URI for future requests.
1522   The temporary URI &SHOULD; be given by the Location field in the
[866]1523   response. Unless the request method was HEAD, the representation of the
[8]1524   response &SHOULD; contain a short hypertext note with a hyperlink to
1525   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1526   understand the 307 status. Therefore, the note &SHOULD; contain the
1527   information necessary for a user to repeat the original request on
1528   the new URI.
[88]1531   If the 307 status code is received in response to a request method
1532   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1533   then the request &MAY; be automatically redirected by the user agent without
[88]1534   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1535   request unless it can be confirmed by the user, since this might
1536   change the conditions under which the request was issued.
1541<section title="Client Error 4xx" anchor="status.4xx">
1543   The 4xx class of status code is intended for cases in which the
1544   client seems to have erred. Except when responding to a HEAD request,
[874]1545   the server &SHOULD; include a representation containing an explanation of the
[8]1546   error situation, and whether it is a temporary or permanent
1547   condition. These status codes are applicable to any request method.
[874]1548   User agents &SHOULD; display any included representation to the user.
1551   If the client is sending data, a server implementation using TCP
1552   &SHOULD; be careful to ensure that the client acknowledges receipt of
1553   the packet(s) containing the response, before the server closes the
1554   input connection. If the client continues sending data to the server
1555   after the close, the server's TCP stack will send a reset packet to
1556   the client, which may erase the client's unacknowledged input buffers
1557   before they can be read and interpreted by the HTTP application.
1560<section title="400 Bad Request" anchor="status.400">
1561  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1562  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1564   The request could not be understood by the server due to malformed
[885]1565   syntax. The client &SHOULD-NOT; repeat the request without
[8]1566   modifications.
1570<section title="401 Unauthorized" anchor="status.401">
1571  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1572  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
[700]1573  <rdf:Description>
1574    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1575  </rdf:Description>
[700]1577   The request requires user authentication (see &status-401;).
1581<section title="402 Payment Required" anchor="status.402">
1582  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1583  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1585   This code is reserved for future use.
1589<section title="403 Forbidden" anchor="status.403">
1590  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1591  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1593   The server understood the request, but is refusing to fulfill it.
1594   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1595   If the request method was not HEAD and the server wishes to make
1596   public why the request has not been fulfilled, it &SHOULD; describe the
[866]1597   reason for the refusal in the representation.  If the server does not wish to
[8]1598   make this information available to the client, the status code 404
1599   (Not Found) can be used instead.
1603<section title="404 Not Found" anchor="status.404">
1604  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1605  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
[823]1607   The server has not found anything matching the Effective Request URI. No
[8]1608   indication is given of whether the condition is temporary or
1609   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1610   knows, through some internally configurable mechanism, that an old
1611   resource is permanently unavailable and has no forwarding address.
1612   This status code is commonly used when the server does not wish to
1613   reveal exactly why the request has been refused, or when no other
1614   response is applicable.
1618<section title="405 Method Not Allowed" anchor="status.405">
1619  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1620  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1622   The method specified in the Request-Line is not allowed for the
[823]1623   resource identified by the Effective Request URI. The response &MUST; include an
[8]1624   Allow header containing a list of valid methods for the requested
1625   resource.
1629<section title="406 Not Acceptable" anchor="status.406">
1630  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1631  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1633   The resource identified by the request is only capable of generating
[874]1634   response representations which have content characteristics not acceptable
[8]1635   according to the accept headers sent in the request.
[866]1638   Unless it was a HEAD request, the response &SHOULD; include a representation
1639   containing a list of available representation characteristics and location(s)
[8]1640   from which the user or user agent can choose the one most
[866]1641   appropriate. The data format is specified by the media type given
[8]1642   in the Content-Type header field. Depending upon the format and the
1643   capabilities of the user agent, selection of the most appropriate
1644   choice &MAY; be performed automatically. However, this specification
1645   does not define any standard for such automatic selection.
1648  <t>
1649    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1650    not acceptable according to the accept headers sent in the
1651    request. In some cases, this may even be preferable to sending a
1652    406 response. User agents are encouraged to inspect the headers of
1653    an incoming response to determine if it is acceptable.
1654  </t>
1657   If the response could be unacceptable, a user agent &SHOULD;
1658   temporarily stop receipt of more data and query the user for a
1659   decision on further actions.
1663<section title="407 Proxy Authentication Required" anchor="status.407">
1664  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1665  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1667   This code is similar to 401 (Unauthorized), but indicates that the
[700]1668   client must first authenticate itself with the proxy (see &status-407;).
1672<section title="408 Request Timeout" anchor="status.408">
1673  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1674  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1676   The client did not produce a request within the time that the server
1677   was prepared to wait. The client &MAY; repeat the request without
1678   modifications at any later time.
1682<section title="409 Conflict" anchor="status.409">
1683  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1684  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1686   The request could not be completed due to a conflict with the current
1687   state of the resource. This code is only allowed in situations where
1688   it is expected that the user might be able to resolve the conflict
1689   and resubmit the request. The response body &SHOULD; include enough
1690   information for the user to recognize the source of the conflict.
[874]1691   Ideally, the response representation would include enough information for the
[8]1692   user or user agent to fix the problem; however, that might not be
1693   possible and is not required.
1696   Conflicts are most likely to occur in response to a PUT request. For
[866]1697   example, if versioning were being used and the representation being PUT
[8]1698   included changes to a resource which conflict with those made by an
1699   earlier (third-party) request, the server might use the 409 response
1700   to indicate that it can't complete the request. In this case, the
[866]1701   response representation would likely contain a list of the differences
[8]1702   between the two versions in a format defined by the response
1703   Content-Type.
1707<section title="410 Gone" anchor="status.410">
1708  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1709  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1711   The requested resource is no longer available at the server and no
1712   forwarding address is known. This condition is expected to be
1713   considered permanent. Clients with link editing capabilities &SHOULD;
[823]1714   delete references to the Effective Request URI after user approval. If the
[8]1715   server does not know, or has no facility to determine, whether or not
1716   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
[884]1717   used instead.
1720   The 410 response is primarily intended to assist the task of web
1721   maintenance by notifying the recipient that the resource is
1722   intentionally unavailable and that the server owners desire that
1723   remote links to that resource be removed. Such an event is common for
1724   limited-time, promotional services and for resources belonging to
1725   individuals no longer working at the server's site. It is not
1726   necessary to mark all permanently unavailable resources as "gone" or
1727   to keep the mark for any length of time -- that is left to the
1728   discretion of the server owner.
[886]1731   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1732   for 410 responses.
1737<section title="411 Length Required" anchor="status.411">
1738  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1739  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1741   The server refuses to accept the request without a defined Content-Length.
1742   The client &MAY; repeat the request if it adds a valid
1743   Content-Length header field containing the length of the message-body
1744   in the request message.
1748<section title="412 Precondition Failed" anchor="status.412">
1749  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1750  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
[700]1751  <rdf:Description>
1752    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1753  </rdf:Description>
1755   The precondition given in one or more of the request-header fields
[45]1756   evaluated to false when it was tested on the server, as defined in
[700]1757   &status-412;.
1761<section title="413 Request Entity Too Large" anchor="status.413">
1762  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1763  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1765   The server is refusing to process a request because the request
[874]1766   representation is larger than the server is willing or able to process. The
[8]1767   server &MAY; close the connection to prevent the client from continuing
1768   the request.
1771   If the condition is temporary, the server &SHOULD; include a Retry-After
1772   header field to indicate that it is temporary and after what
1773   time the client &MAY; try again.
[465]1777<section title="414 URI Too Long" anchor="status.414">
1778  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1779  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
[823]1781   The server is refusing to service the request because the Effective Request URI
[8]1782   is longer than the server is willing to interpret. This rare
1783   condition is only likely to occur when a client has improperly
1784   converted a POST request to a GET request with long query
1785   information, when the client has descended into a URI "black hole" of
1786   redirection (e.g., a redirected URI prefix that points to a suffix of
1787   itself), or when the server is under attack by a client attempting to
1788   exploit security holes present in some servers using fixed-length
[823]1789   buffers for reading or manipulating the Effective Request URI.
1793<section title="415 Unsupported Media Type" anchor="status.415">
1794  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1795  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
[866]1797   The server is refusing to service the request because the representation of
[8]1798   the request is in a format not supported by the requested resource
1799   for the requested method.
1803<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1804  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1805  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
[700]1806  <rdf:Description>
1807    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1808  </rdf:Description>
[29]1810   The request included a Range request-header field (&header-range;) and none of
[8]1811   the range-specifier values in this field overlap the current extent
[885]1812   of the selected resource. See &status-416;.
1816<section title="417 Expectation Failed" anchor="status.417">
1817  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1818  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1820   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1821   could not be met by this server, or, if the server is a proxy,
1822   the server has unambiguous evidence that the request could not be met
1823   by the next-hop server.
1828<section title="Server Error 5xx" anchor="status.5xx">
1830   Response status codes beginning with the digit "5" indicate cases in
1831   which the server is aware that it has erred or is incapable of
1832   performing the request. Except when responding to a HEAD request, the
[874]1833   server &SHOULD; include a representation containing an explanation of the
[8]1834   error situation, and whether it is a temporary or permanent
[874]1835   condition. User agents &SHOULD; display any included representation to the
[8]1836   user. These response codes are applicable to any request method.
1839<section title="500 Internal Server Error" anchor="status.500">
1840  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1841  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1843   The server encountered an unexpected condition which prevented it
1844   from fulfilling the request.
1848<section title="501 Not Implemented" anchor="status.501">
1849  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1850  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1852   The server does not support the functionality required to fulfill the
1853   request. This is the appropriate response when the server does not
1854   recognize the request method and is not capable of supporting it for
1855   any resource.
1859<section title="502 Bad Gateway" anchor="status.502">
1860  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1861  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1863   The server, while acting as a gateway or proxy, received an invalid
1864   response from the upstream server it accessed in attempting to
1865   fulfill the request.
1869<section title="503 Service Unavailable" anchor="status.503">
1870  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1871  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1873   The server is currently unable to handle the request due to a
1874   temporary overloading or maintenance of the server. The implication
1875   is that this is a temporary condition which will be alleviated after
1876   some delay. If known, the length of the delay &MAY; be indicated in a
1877   Retry-After header. If no Retry-After is given, the client &SHOULD;
1878   handle the response as it would for a 500 response.
1881  <t>
1882    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1883    server must use it when becoming overloaded. Some servers may wish
1884    to simply refuse the connection.
1885  </t>
1889<section title="504 Gateway Timeout" anchor="status.504">
1890  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1891  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1893   The server, while acting as a gateway or proxy, did not receive a
[763]1894   timely response from the upstream server specified by the URI (e.g.,
1895   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
[8]1896   to access in attempting to complete the request.
1899  <t>
[757]1900    <x:h>Note</x:h> to implementors: some deployed proxies are known to
[563]1901    return 400 or 500 when DNS lookups time out.
1902  </t>
1906<section title="505 HTTP Version Not Supported" anchor="status.505">
1907  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1908  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
[172]1910   The server does not support, or refuses to support, the protocol
[8]1911   version that was used in the request message. The server is
1912   indicating that it is unable or unwilling to complete the request
[29]1913   using the same major version as the client, as described in &http-version;,
[8]1914   other than with this error message. The response &SHOULD; contain
[874]1915   a representation describing why that version is not supported and what other
[8]1916   protocols are supported by that server.
1924<section title="Header Field Definitions" anchor="header.fields">
[117]1926   This section defines the syntax and semantics of HTTP/1.1 header fields
1927   related to request and response semantics.
1930   For entity-header fields, both sender and recipient refer to either the
[866]1931   client or the server, depending on who sends and who receives the message.
1934<section title="Allow" anchor="header.allow">
1935  <iref primary="true" item="Allow header" x:for-anchor=""/>
1936  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
[229]1937  <x:anchor-alias value="Allow"/>
[356]1938  <x:anchor-alias value="Allow-v"/>
[697]1940   The "Allow" response-header field lists the set of methods advertised as
[823]1941   supported by the resource identified by the Effective Request URI. The purpose of
[697]1942   this field is strictly to inform the recipient of valid methods
[698]1943   associated with the resource.
[356]1945<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
[366]1946  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
[356]1947  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1950      Example of use:
1952<figure><artwork type="example">
[356]1953  Allow: GET, HEAD, PUT
[240]1956      The actual set of allowed methods is defined
[8]1957      by the origin server at the time of each request.
1960      A proxy &MUST-NOT; modify the Allow header field even if it does not
1961      understand all the methods specified, since the user agent might
1962      have other means of communicating with the origin server.
1966<section title="Expect" anchor="header.expect">
1967  <iref primary="true" item="Expect header" x:for-anchor=""/>
1968  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
[229]1969  <x:anchor-alias value="Expect"/>
[356]1970  <x:anchor-alias value="Expect-v"/>
[229]1971  <x:anchor-alias value="expectation"/>
1972  <x:anchor-alias value="expectation-extension"/>
1973  <x:anchor-alias value="expect-params"/>
[697]1975   The "Expect" request-header field is used to indicate that particular
[8]1976   server behaviors are required by the client.
[356]1978<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]1979  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
[356]1980  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
[356]1982  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1983  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
[229]1984                           *<x:ref>expect-params</x:ref> ]
[356]1985  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1988   A server that does not understand or is unable to comply with any of
1989   the expectation values in the Expect field of a request &MUST; respond
1990   with appropriate error status. The server &MUST; respond with a 417
1991   (Expectation Failed) status if any of the expectations cannot be met
1992   or, if there are other problems with the request, some other 4xx
1993   status.
1996   This header field is defined with extensible syntax to allow for
1997   future extensions. If a server receives a request containing an
1998   Expect field that includes an expectation-extension that it does not
1999   support, it &MUST; respond with a 417 (Expectation Failed) status.
2002   Comparison of expectation values is case-insensitive for unquoted
2003   tokens (including the 100-continue token), and is case-sensitive for
2004   quoted-string expectation-extensions.
2007   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2008   return a 417 (Expectation Failed) status if it receives a request
2009   with an expectation that it cannot meet. However, the Expect
2010   request-header itself is end-to-end; it &MUST; be forwarded if the
2011   request is forwarded.
2014   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2015   Expect header.
[137]2018   See &use100; for the use of the 100 (Continue) status.
2022<section title="From" anchor="header.from">
2023  <iref primary="true" item="From header" x:for-anchor=""/>
2024  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
[229]2025  <x:anchor-alias value="From"/>
[356]2026  <x:anchor-alias value="From-v"/>
[229]2027  <x:anchor-alias value="mailbox"/>
[697]2029   The "From" request-header field, if given, &SHOULD; contain an Internet
[8]2030   e-mail address for the human user who controls the requesting user
2031   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
[327]2032   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
[356]2034<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
[366]2035  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
[356]2036  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
[327]2038  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2041   An example is:
2043<figure><artwork type="example">
[356]2044  From:
2047   This header field &MAY; be used for logging purposes and as a means for
2048   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2049   be used as an insecure form of access protection. The interpretation
2050   of this field is that the request is being performed on behalf of the
2051   person given, who accepts responsibility for the method performed. In
2052   particular, robot agents &SHOULD; include this header so that the
2053   person responsible for running the robot can be contacted if problems
2054   occur on the receiving end.
2057   The Internet e-mail address in this field &MAY; be separate from the
2058   Internet host which issued the request. For example, when a request
2059   is passed through a proxy the original issuer's address &SHOULD; be
2060   used.
2063   The client &SHOULD-NOT;  send the From header field without the user's
2064   approval, as it might conflict with the user's privacy interests or
2065   their site's security policy. It is strongly recommended that the
2066   user be able to disable, enable, and modify the value of this field
2067   at any time prior to a request.
2071<section title="Location" anchor="header.location">
2072  <iref primary="true" item="Location header" x:for-anchor=""/>
2073  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
[229]2074  <x:anchor-alias value="Location"/>
[356]2075  <x:anchor-alias value="Location-v"/>
[698]2077   The "Location" response-header field is used to identify a newly created
2078   resource, or to redirect the recipient to a different location for
2079   completion of the request.
2082   For 201 (Created) responses, the Location is the URI of the new resource
2083   which was created by the request. For 3xx responses, the location &SHOULD;
2084   indicate the server's preferred URI for automatic redirection to the
2085   resource.
[785]2088   The field value consists of a single URI-reference. When it has the form
2089   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2090   the final value is computed by resolving it against the effective request
2091   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
[356]2093<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
[366]2094  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
[785]2095  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2098<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2099<artwork type="example">
2100  Location:
2101</artwork></figure><figure><artwork type="example">  Location: /index.html
[785]2104   There are circumstances in which a fragment identifier in a Location URI
2105   would not be appropriate:
[659]2106   <list style="symbols">
[785]2107      <t>With a 201 Created response, because in this usage the Location header
2108      specifies the URI for the entire created resource.</t>
[659]2109      <t>With 305 Use Proxy.</t>
2110   </list>
2113  <t>
[785]2114    <x:h>Note:</x:h> This specification does not define precedence rules
[791]2115    for the case where the original URI, as navigated to by the user
[785]2116    agent, and the Location header field value both contain fragment
2117    identifiers.
2118  </t>
2121  <t>
[563]2122    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
[866]2123    from Location in that the Content-Location identifies the most specific
2124    resource corresponding to the enclosed representation.
2125    It is therefore possible for a response to contain header fields for
2126    both Location and Content-Location.
[563]2127  </t>
2131<section title="Max-Forwards" anchor="header.max-forwards">
2132  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2133  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
[229]2134  <x:anchor-alias value="Max-Forwards"/>
[356]2135  <x:anchor-alias value="Max-Forwards-v"/>
[697]2137   The "Max-Forwards" request-header field provides a mechanism with the
[698]2138   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2139   methods to limit the number of times that the request is forwarded by
2140   proxies or gateways. This can be useful when the client is attempting to
2141   trace a request which appears to be failing or looping in mid-chain.
[356]2143<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
[366]2144  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
[356]2145  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2148   The Max-Forwards value is a decimal integer indicating the remaining
2149   number of times this request message may be forwarded.
2152   Each proxy or gateway recipient of a TRACE or OPTIONS request
2153   containing a Max-Forwards header field &MUST; check and update its
2154   value prior to forwarding the request. If the received value is zero
2155   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2156   respond as the final recipient. If the received Max-Forwards value is
2157   greater than zero, then the forwarded message &MUST; contain an updated
2158   Max-Forwards field with a value decremented by one (1).
2161   The Max-Forwards header field &MAY; be ignored for all other methods
2162   defined by this specification and for any extension methods for which
2163   it is not explicitly referred to as part of that method definition.
2167<section title="Referer" anchor="header.referer">
2168  <iref primary="true" item="Referer header" x:for-anchor=""/>
2169  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
[229]2170  <x:anchor-alias value="Referer"/>
[356]2171  <x:anchor-alias value="Referer-v"/>
[698]2173   The "Referer" [sic] request-header field allows the client to specify the
[823]2174   URI of the resource from which the Effective Request URI was obtained (the
[698]2175   "referrer", although the header field is misspelled.).
2178   The Referer header allows servers to generate lists of back-links to
2179   resources for interest, logging, optimized caching, etc. It also allows
2180   obsolete or mistyped links to be traced for maintenance. Some servers use
2181   Referer as a means of controlling where they allow links from (so-called
2182   "deep linking"), but it should be noted that legitimate requests are not
2183   required to contain a Referer header field.
[823]2186   If the Effective Request URI was obtained from a source that does not have its own
[812]2187   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
[593]2188   sent with the value "about:blank", or not be sent at all. Note that this
2189   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
[356]2191<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
[366]2192  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
[391]2193  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2196   Example:
2198<figure><artwork type="example">
[356]2199  Referer:
2202   If the field value is a relative URI, it &SHOULD; be interpreted
[823]2203   relative to the Effective Request URI. The URI &MUST-NOT; include a fragment. See
[8]2204   <xref target=""/> for security considerations.
2208<section title="Retry-After" anchor="header.retry-after">
2209  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2210  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
[229]2211  <x:anchor-alias value="Retry-After"/>
[356]2212  <x:anchor-alias value="Retry-After-v"/>
[356]2214   The response-header "Retry-After" field can be used with a 503 (Service
[8]2215   Unavailable) response to indicate how long the service is expected to
2216   be unavailable to the requesting client. This field &MAY; also be used
2217   with any 3xx (Redirection) response to indicate the minimum time the
[698]2218   user-agent is asked wait before issuing the redirected request.
2221   The value of this field can be either an HTTP-date or an integer number
[8]2222   of seconds (in decimal) after the time of the response.
[356]2224<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
[366]2225  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
[356]2226  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
[229]2228<t anchor="">
2229  <x:anchor-alias value="delta-seconds"/>
[212]2230   Time spans are non-negative decimal integers, representing time in
2231   seconds.
2233<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
[229]2234  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
[8]2237   Two examples of its use are
2239<figure><artwork type="example">
[356]2240  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2241  Retry-After: 120
2244   In the latter example, the delay is 2 minutes.
2248<section title="Server" anchor="header.server">
2249  <iref primary="true" item="Server header" x:for-anchor=""/>
2250  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
[229]2251  <x:anchor-alias value="Server"/>
[356]2252  <x:anchor-alias value="Server-v"/>
[697]2254   The "Server" response-header field contains information about the
[698]2255   software used by the origin server to handle the request.
2258   The field can contain multiple product tokens (&product-tokens;) and
2259   comments (&header-fields;) identifying the server and any significant
2260   subproducts. The product tokens are listed in order of their significance
2261   for identifying the application.
[356]2263<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
[366]2264  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
[370]2265  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2266                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2269   Example:
2271<figure><artwork type="example">
[356]2272  Server: CERN/3.0 libwww/2.17
2275   If the response is being forwarded through a proxy, the proxy
2276   application &MUST-NOT; modify the Server response-header. Instead, it
[72]2277   &MUST; include a Via field (as described in &header-via;).
2280  <t>
2281    <x:h>Note:</x:h> Revealing the specific software version of the server might
2282    allow the server machine to become more vulnerable to attacks
2283    against software that is known to contain security holes. Server
2284    implementors are encouraged to make this field a configurable
2285    option.
2286  </t>
2290<section title="User-Agent" anchor="header.user-agent">
2291  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2292  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
[229]2293  <x:anchor-alias value="User-Agent"/>
[356]2294  <x:anchor-alias value="User-Agent-v"/>
[697]2296   The "User-Agent" request-header field contains information about the
[8]2297   user agent originating the request. This is for statistical purposes,
2298   the tracing of protocol violations, and automated recognition of user
2299   agents for the sake of tailoring responses to avoid particular user
[698]2300   agent limitations.
2303   User agents &SHOULD; include this field with requests. The field can contain
2304   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2305   identifying the agent and any subproducts which form a significant part of
2306   the user agent. By convention, the product tokens are listed in order of
2307   their significance for identifying the application.
[356]2309<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
[366]2310  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
[370]2311  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2312                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2315   Example:
2317<figure><artwork type="example">
[356]2318  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
[29]2324<section title="IANA Considerations" anchor="IANA.considerations">
2326<section title="Method Registry" anchor="method.registration">
2328  The registration procedure for HTTP Methods is defined by
2329  <xref target="method.registry"/> of this document.
[818]2332   The HTTP Method Registry should be created at <eref target=""/>
2333   and be populated with the registrations below:
[682]2335<?BEGININC p2-semantics.iana-methods ?>
[270]2336<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
[288]2337<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
[270]2338   <ttcol>Method</ttcol>
[286]2339   <ttcol>Safe</ttcol>
[270]2340   <ttcol>Reference</ttcol>
2341   <c>CONNECT</c>
[286]2342   <c>no</c>
[270]2343   <c>
2344      <xref target="CONNECT"/>
2345   </c>
2346   <c>DELETE</c>
[286]2347   <c>no</c>
[270]2348   <c>
2349      <xref target="DELETE"/>
2350   </c>
2351   <c>GET</c>
[286]2352   <c>yes</c>
[270]2353   <c>
2354      <xref target="GET"/>
2355   </c>
2356   <c>HEAD</c>
[286]2357   <c>yes</c>
[270]2358   <c>
2359      <xref target="HEAD"/>
2360   </c>
2361   <c>OPTIONS</c>
[286]2362   <c>yes</c>
[270]2363   <c>
2364      <xref target="OPTIONS"/>
2365   </c>
2366   <c>POST</c>
[286]2367   <c>no</c>
[270]2368   <c>
2369      <xref target="POST"/>
2370   </c>
2371   <c>PUT</c>
[286]2372   <c>no</c>
[270]2373   <c>
2374      <xref target="PUT"/>
2375   </c>
2376   <c>TRACE</c>
[286]2377   <c>yes</c>
[270]2378   <c>
2379      <xref target="TRACE"/>
2380   </c>
[682]2383<?ENDINC p2-semantics.iana-methods ?>
[255]2386<section title="Status Code Registry" anchor="status.code.registration">
[288]2388   The registration procedure for HTTP Status Codes -- previously defined
2389   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2390   by <xref target="status.code.registry"/> of this document.
2393   The HTTP Status Code Registry located at <eref target=""/>
2394   should be updated with the registrations below:
[682]2396<?BEGININC p2-semantics.iana-status-codes ?>
[255]2397<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
[288]2398<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
[255]2399   <ttcol>Value</ttcol>
2400   <ttcol>Description</ttcol>
2401   <ttcol>Reference</ttcol>
2402   <c>100</c>
2403   <c>Continue</c>
2404   <c>
2405      <xref target="status.100"/>
2406   </c>
2407   <c>101</c>
2408   <c>Switching Protocols</c>
2409   <c>
2410      <xref target="status.101"/>
2411   </c>
2412   <c>200</c>
2413   <c>OK</c>
2414   <c>
2415      <xref target="status.200"/>
2416   </c>
2417   <c>201</c>
2418   <c>Created</c>
2419   <c>
2420      <xref target="status.201"/>
2421   </c>
2422   <c>202</c>
2423   <c>Accepted</c>
2424   <c>
2425      <xref target="status.202"/>
2426   </c>
2427   <c>203</c>
2428   <c>Non-Authoritative Information</c>
2429   <c>
2430      <xref target="status.203"/>
2431   </c>
2432   <c>204</c>
2433   <c>No Content</c>
2434   <c>
2435      <xref target="status.204"/>
2436   </c>
2437   <c>205</c>
2438   <c>Reset Content</c>
2439   <c>
2440      <xref target="status.205"/>
2441   </c>
2442   <c>300</c>
2443   <c>Multiple Choices</c>
2444   <c>
2445      <xref target="status.300"/>
2446   </c>
2447   <c>301</c>
2448   <c>Moved Permanently</c>
2449   <c>
2450      <xref target="status.301"/>
2451   </c>
2452   <c>302</c>
2453   <c>Found</c>
2454   <c>
2455      <xref target="status.302"/>
2456   </c>
2457   <c>303</c>
2458   <c>See Other</c>
2459   <c>
2460      <xref target="status.303"/>
2461   </c>
2462   <c>305</c>
2463   <c>Use Proxy</c>
2464   <c>
2465      <xref target="status.305"/>
2466   </c>
2467   <c>306</c>
2468   <c>(Unused)</c>
2469   <c>
2470      <xref target="status.306"/>
2471   </c>
2472   <c>307</c>
2473   <c>Temporary Redirect</c>
2474   <c>
2475      <xref target="status.307"/>
2476   </c>
2477   <c>400</c>
2478   <c>Bad Request</c>
2479   <c>
2480      <xref target="status.400"/>
2481   </c>
2482   <c>402</c>
2483   <c>Payment Required</c>
2484   <c>
2485      <xref target="status.402"/>
2486   </c>
2487   <c>403</c>
2488   <c>Forbidden</c>
2489   <c>
2490      <xref target="status.403"/>
2491   </c>
2492   <c>404</c>
2493   <c>Not Found</c>
2494   <c>
2495      <xref target="status.404"/>
2496   </c>
2497   <c>405</c>
2498   <c>Method Not Allowed</c>
2499   <c>
2500      <xref target="status.405"/>
2501   </c>
2502   <c>406</c>
2503   <c>Not Acceptable</c>
2504   <c>
2505      <xref target="status.406"/>
2506   </c>
2507   <c>407</c>
2508   <c>Proxy Authentication Required</c>
2509   <c>
2510      <xref target="status.407"/>
2511   </c>
2512   <c>408</c>
2513   <c>Request Timeout</c>
2514   <c>
2515      <xref target="status.408"/>
2516   </c>
2517   <c>409</c>
2518   <c>Conflict</c>
2519   <c>
2520      <xref target="status.409"/>
2521   </c>
2522   <c>410</c>
2523   <c>Gone</c>
2524   <c>
2525      <xref target="status.410"/>
2526   </c>
2527   <c>411</c>
2528   <c>Length Required</c>
2529   <c>
2530      <xref target="status.411"/>
2531   </c>
2532   <c>413</c>
2533   <c>Request Entity Too Large</c>
2534   <c>
2535      <xref target="status.413"/>
2536   </c>
2537   <c>414</c>
[465]2538   <c>URI Too Long</c>
[255]2539   <c>
2540      <xref target="status.414"/>
2541   </c>
2542   <c>415</c>
2543   <c>Unsupported Media Type</c>
2544   <c>
2545      <xref target="status.415"/>
2546   </c>
2547   <c>417</c>
2548   <c>Expectation Failed</c>
2549   <c>
2550      <xref target="status.417"/>
2551   </c>
2552   <c>500</c>
2553   <c>Internal Server Error</c>
2554   <c>
2555      <xref target="status.500"/>
2556   </c>
2557   <c>501</c>
2558   <c>Not Implemented</c>
2559   <c>
2560      <xref target="status.501"/>
2561   </c>
2562   <c>502</c>
2563   <c>Bad Gateway</c>
2564   <c>
2565      <xref target="status.502"/>
2566   </c>
2567   <c>503</c>
2568   <c>Service Unavailable</c>
2569   <c>
2570      <xref target="status.503"/>
2571   </c>
2572   <c>504</c>
2573   <c>Gateway Timeout</c>
2574   <c>
2575      <xref target="status.504"/>
2576   </c>
2577   <c>505</c>
2578   <c>HTTP Version Not Supported</c>
2579   <c>
2580      <xref target="status.505"/>
2581   </c>
[682]2584<?ENDINC p2-semantics.iana-status-codes ?>
[253]2586<section title="Message Header Registration" anchor="message.header.registration">
2588   The Message Header Registry located at <eref target=""/> should be updated
2589   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]2591<?BEGININC p2-semantics.iana-headers ?>
[253]2592<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]2593<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]2594   <ttcol>Header Field Name</ttcol>
2595   <ttcol>Protocol</ttcol>
2596   <ttcol>Status</ttcol>
2597   <ttcol>Reference</ttcol>
[253]2599   <c>Allow</c>
2600   <c>http</c>
2601   <c>standard</c>
2602   <c>
2603      <xref target="header.allow"/>
2604   </c>
2605   <c>Expect</c>
2606   <c>http</c>
2607   <c>standard</c>
2608   <c>
2609      <xref target="header.expect"/>
2610   </c>
2611   <c>From</c>
2612   <c>http</c>
2613   <c>standard</c>
2614   <c>
2615      <xref target="header.from"/>
2616   </c>
2617   <c>Location</c>
2618   <c>http</c>
2619   <c>standard</c>
2620   <c>
2621      <xref target="header.location"/>
2622   </c>
2623   <c>Max-Forwards</c>
2624   <c>http</c>
2625   <c>standard</c>
2626   <c>
2627      <xref target="header.max-forwards"/>
2628   </c>
2629   <c>Referer</c>
2630   <c>http</c>
2631   <c>standard</c>
2632   <c>
2633      <xref target="header.referer"/>
2634   </c>
2635   <c>Retry-After</c>
2636   <c>http</c>
2637   <c>standard</c>
2638   <c>
2639      <xref target="header.retry-after"/>
2640   </c>
2641   <c>Server</c>
2642   <c>http</c>
2643   <c>standard</c>
2644   <c>
2645      <xref target="header.server"/>
2646   </c>
2647   <c>User-Agent</c>
2648   <c>http</c>
2649   <c>standard</c>
2650   <c>
2651      <xref target="header.user-agent"/>
2652   </c>
[680]2655<?ENDINC p2-semantics.iana-headers ?>
[290]2657   The change controller is: "IETF ( - Internet Engineering Task Force".
[8]2662<section title="Security Considerations" anchor="security.considerations">
2664   This section is meant to inform application developers, information
2665   providers, and users of the security limitations in HTTP/1.1 as
2666   described by this document. The discussion does not include
2667   definitive solutions to the problems revealed, though it does make
2668   some suggestions for reducing security risks.
2671<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2673   Like any generic data transfer protocol, HTTP cannot regulate the
2674   content of the data that is transferred, nor is there any a priori
2675   method of determining the sensitivity of any particular piece of
2676   information within the context of any given request. Therefore,
2677   applications &SHOULD; supply as much control over this information as
2678   possible to the provider of that information. Four header fields are
2679   worth special mention in this context: Server, Via, Referer and From.
2682   Revealing the specific software version of the server might allow the
2683   server machine to become more vulnerable to attacks against software
2684   that is known to contain security holes. Implementors &SHOULD; make the
2685   Server header field a configurable option.
2688   Proxies which serve as a portal through a network firewall &SHOULD;
2689   take special precautions regarding the transfer of header information
2690   that identifies the hosts behind the firewall. In particular, they
2691   &SHOULD; remove, or replace with sanitized versions, any Via fields
2692   generated behind the firewall.
2695   The Referer header allows reading patterns to be studied and reverse
2696   links drawn. Although it can be very useful, its power can be abused
2697   if user details are not separated from the information contained in
2698   the Referer. Even when the personal information has been removed, the
2699   Referer header might indicate a private document's URI whose
2700   publication would be inappropriate.
2703   The information sent in the From field might conflict with the user's
2704   privacy interests or their site's security policy, and hence it
2705   &SHOULD-NOT;  be transmitted without the user being able to disable,
2706   enable, and modify the contents of the field. The user &MUST; be able
2707   to set the contents of this field within a user preference or
2708   application defaults configuration.
2711   We suggest, though do not require, that a convenient toggle interface
2712   be provided for the user to enable or disable the sending of From and
2713   Referer information.
2716   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2717   fields can sometimes be used to determine that a specific client or
2718   server have a particular security hole which might be exploited.
2719   Unfortunately, this same information is often used for other valuable
2720   purposes for which HTTP currently has no better mechanism.
[666]2723   Some methods, like TRACE (<xref target="TRACE"/>) may expose
[866]2724   information sent in request headers in the response.
[666]2725   Clients &SHOULD; be careful with sensitive information, like Cookies,
2726   Authorization credentials and other headers that might be used to
2727   collect data from the client.
[184]2731<section title="Encoding Sensitive Information in URIs" anchor="">
2733   Because the source of a link might be private information or might
2734   reveal an otherwise private information source, it is strongly
2735   recommended that the user be able to select whether or not the
2736   Referer field is sent. For example, a browser client could have a
2737   toggle switch for browsing openly/anonymously, which would
2738   respectively enable/disable the sending of Referer and From
2739   information.
[172]2742   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
[8]2743   HTTP request if the referring page was transferred with a secure
2744   protocol.
[823]2747   Authors of services should not use GET-based forms for the submission of
2748   sensitive data because that data will be encoded in the request-target. Many
2749   existing servers, proxies, and user agents log or display the request-target
2750   in places where it might be visible to third parties. Such services can
[172]2751   use POST-based form submission instead.
2755<section title="Location Headers and Spoofing" anchor="location.spoofing">
2757   If a single server supports multiple organizations that do not trust
2758   one another, then it &MUST; check the values of Location and Content-Location
2759   headers in responses that are generated under control of
2760   said organizations to make sure that they do not attempt to
2761   invalidate resources over which they have no authority.
2767<section title="Acknowledgments" anchor="ack">
[119]2772<references title="Normative References">
[31]2774<reference anchor="Part1">
[119]2775  <front>
2776    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2777    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2778      <organization abbrev="Day Software">Day Software</organization>
2779      <address><email></email></address>
2780    </author>
2781    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2782      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2783      <address><email></email></address>
[119]2784    </author>
2785    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2786      <organization abbrev="HP">Hewlett-Packard Company</organization>
2787      <address><email></email></address>
2788    </author>
2789    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2790      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2791      <address><email></email></address>
2792    </author>
2793    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2794      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2795      <address><email></email></address>
2796    </author>
2797    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2798      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2799      <address><email></email></address>
2800    </author>
2801    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2802      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2803      <address><email></email></address>
2804    </author>
2805    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2806      <organization abbrev="W3C">World Wide Web Consortium</organization>
2807      <address><email></email></address>
2808    </author>
2809    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2810      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2811      <address><email></email></address>
2812    </author>
2813    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2814  </front>
2815  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2816  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2819<reference anchor="Part3">
[119]2820  <front>
2821    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2822    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2823      <organization abbrev="Day Software">Day Software</organization>
2824      <address><email></email></address>
2825    </author>
2826    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2827      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2828      <address><email></email></address>
[119]2829    </author>
2830    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2831      <organization abbrev="HP">Hewlett-Packard Company</organization>
2832      <address><email></email></address>
2833    </author>
2834    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2835      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2836      <address><email></email></address>
2837    </author>
2838    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2839      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2840      <address><email></email></address>
2841    </author>
2842    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2843      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2844      <address><email></email></address>
2845    </author>
2846    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2847      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2848      <address><email></email></address>
2849    </author>
2850    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2851      <organization abbrev="W3C">World Wide Web Consortium</organization>
2852      <address><email></email></address>
2853    </author>
2854    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2855      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2856      <address><email></email></address>
2857    </author>
2858    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2859  </front>
2860  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2861  <x:source href="p3-payload.xml" basename="p3-payload"/>
2864<reference anchor="Part4">
[119]2865  <front>
2866    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2867    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2868      <organization abbrev="Day Software">Day Software</organization>
2869      <address><email></email></address>
2870    </author>
2871    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2872      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2873      <address><email></email></address>
[119]2874    </author>
2875    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2876      <organization abbrev="HP">Hewlett-Packard Company</organization>
2877      <address><email></email></address>
2878    </author>
2879    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2880      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2881      <address><email></email></address>
2882    </author>
2883    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2884      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2885      <address><email></email></address>
2886    </author>
2887    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2888      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2889      <address><email></email></address>
2890    </author>
2891    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2892      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2893      <address><email></email></address>
2894    </author>
2895    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2896      <organization abbrev="W3C">World Wide Web Consortium</organization>
2897      <address><email></email></address>
2898    </author>
2899    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2900      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2901      <address><email></email></address>
2902    </author>
2903    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2904  </front>
2905  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2906  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2909<reference anchor="Part5">
[119]2910  <front>
2911    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2912    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2913      <organization abbrev="Day Software">Day Software</organization>
2914      <address><email></email></address>
2915    </author>
2916    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2917      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2918      <address><email></email></address>
[119]2919    </author>
2920    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2921      <organization abbrev="HP">Hewlett-Packard Company</organization>
2922      <address><email></email></address>
2923    </author>
2924    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2925      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2926      <address><email></email></address>
2927    </author>
2928    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2929      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2930      <address><email></email></address>
2931    </author>
2932    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2933      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2934      <address><email></email></address>
2935    </author>
2936    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2937      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2938      <address><email></email></address>
2939    </author>
2940    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2941      <organization abbrev="W3C">World Wide Web Consortium</organization>
2942      <address><email></email></address>
2943    </author>
2944    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2945      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2946      <address><email></email></address>
2947    </author>
2948    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2949  </front>
2950  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2951  <x:source href="p5-range.xml" basename="p5-range"/>
2954<reference anchor="Part6">
[119]2955  <front>
2956    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2957    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2958      <organization abbrev="Day Software">Day Software</organization>
2959      <address><email></email></address>
2960    </author>
2961    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2962      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2963      <address><email></email></address>
[119]2964    </author>
2965    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2966      <organization abbrev="HP">Hewlett-Packard Company</organization>
2967      <address><email></email></address>
2968    </author>
2969    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2970      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2971      <address><email></email></address>
2972    </author>
2973    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2974      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2975      <address><email></email></address>
2976    </author>
2977    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2978      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2979      <address><email></email></address>
2980    </author>
2981    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2982      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2983      <address><email></email></address>
2984    </author>
2985    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2986      <organization abbrev="W3C">World Wide Web Consortium</organization>
2987      <address><email></email></address>
2988    </author>
[601]2989    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2990      <address><email></email></address>
2991    </author>
[119]2992    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2993      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2994      <address><email></email></address>
2995    </author>
2996    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2997  </front>
2998  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2999  <x:source href="p6-cache.xml" basename="p6-cache"/>
3002<reference anchor="Part7">
[119]3003  <front>
3004    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3005    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3006      <organization abbrev="Day Software">Day Software</organization>
3007      <address><email></email></address>
3008    </author>
3009    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3010      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3011      <address><email></email></address>
[119]3012    </author>
3013    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3014      <organization abbrev="HP">Hewlett-Packard Company</organization>
3015      <address><email></email></address>
3016    </author>
3017    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3018      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3019      <address><email></email></address>
3020    </author>
3021    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3022      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3023      <address><email></email></address>
3024    </author>
3025    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3026      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3027      <address><email></email></address>
3028    </author>
3029    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3030      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3031      <address><email></email></address>
3032    </author>
3033    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3034      <organization abbrev="W3C">World Wide Web Consortium</organization>
3035      <address><email></email></address>
3036    </author>
3037    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3038      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3039      <address><email></email></address>
3040    </author>
3041    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3042  </front>
3043  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3044  <x:source href="p7-auth.xml" basename="p7-auth"/>
[119]3047<reference anchor="RFC2119">
3048  <front>
3049    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3050    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3051      <organization>Harvard University</organization>
3052      <address><email></email></address>
3053    </author>
3054    <date month="March" year="1997"/>
3055  </front>
3056  <seriesInfo name="BCP" value="14"/>
3057  <seriesInfo name="RFC" value="2119"/>
[785]3060<reference anchor="RFC3986">
3061 <front>
3062  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3063  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3064    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3065    <address>
3066       <email></email>
3067       <uri></uri>
3068    </address>
3069  </author>
3070  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3071    <organization abbrev="Day Software">Day Software</organization>
3072    <address>
3073      <email></email>
3074      <uri></uri>
3075    </address>
3076  </author>
3077  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3078    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3079    <address>
3080      <email></email>
3081      <uri></uri>
3082    </address>
3083  </author>
3084  <date month='January' year='2005'></date>
3085 </front>
3086 <seriesInfo name="RFC" value="3986"/>
3087 <seriesInfo name="STD" value="66"/>
[425]3090<reference anchor="RFC5234">
3091  <front>
3092    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3093    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3094      <organization>Brandenburg InternetWorking</organization>
3095      <address>
[728]3096        <email></email>
3097      </address> 
[425]3098    </author>
3099    <author initials="P." surname="Overell" fullname="Paul Overell">
3100      <organization>THUS plc.</organization>
3101      <address>
[728]3102        <email></email>
3103      </address>
[425]3104    </author>
3105    <date month="January" year="2008"/>
3106  </front>
3107  <seriesInfo name="STD" value="68"/>
3108  <seriesInfo name="RFC" value="5234"/>
3113<references title="Informative References">
[129]3115<reference anchor="RFC1945">
3116  <front>
3117    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3118    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3119      <organization>MIT, Laboratory for Computer Science</organization>
3120      <address><email></email></address>
3121    </author>
3122    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3123      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3124      <address><email></email></address>
3125    </author>
3126    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3127      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3128      <address><email></email></address>
3129    </author>
3130    <date month="May" year="1996"/>
3131  </front>
3132  <seriesInfo name="RFC" value="1945"/>
[119]3135<reference anchor="RFC2068">
3136  <front>
3137    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3138    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3139      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3140      <address><email></email></address>
3141    </author>
3142    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3143      <organization>MIT Laboratory for Computer Science</organization>
3144      <address><email></email></address>
3145    </author>
3146    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3147      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3148      <address><email></email></address>
3149    </author>
3150    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3151      <organization>MIT Laboratory for Computer Science</organization>
3152      <address><email></email></address>
3153    </author>
3154    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3155      <organization>MIT Laboratory for Computer Science</organization>
3156      <address><email></email></address>
3157    </author>
3158    <date month="January" year="1997"/>
3159  </front>
3160  <seriesInfo name="RFC" value="2068"/>
[36]3163<reference anchor="RFC2616">
[119]3164  <front>
3165    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3166    <author initials="R." surname="Fielding" fullname="R. Fielding">
3167      <organization>University of California, Irvine</organization>
3168      <address><email></email></address>
3169    </author>
3170    <author initials="J." surname="Gettys" fullname="J. Gettys">
3171      <organization>W3C</organization>
3172      <address><email></email></address>
3173    </author>
3174    <author initials="J." surname="Mogul" fullname="J. Mogul">
3175      <organization>Compaq Computer Corporation</organization>
3176      <address><email></email></address>
3177    </author>
3178    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3179      <organization>MIT Laboratory for Computer Science</organization>
3180      <address><email></email></address>
3181    </author>
3182    <author initials="L." surname="Masinter" fullname="L. Masinter">
3183      <organization>Xerox Corporation</organization>
3184      <address><email></email></address>
3185    </author>
3186    <author initials="P." surname="Leach" fullname="P. Leach">
3187      <organization>Microsoft Corporation</organization>
3188      <address><email></email></address>
3189    </author>
3190    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3191      <organization>W3C</organization>
3192      <address><email></email></address>
3193    </author>
3194    <date month="June" year="1999"/>
3195  </front>
3196  <seriesInfo name="RFC" value="2616"/>
[255]3199<reference anchor='RFC2817'>
3200  <front>
3201    <title>Upgrading to TLS Within HTTP/1.1</title>
3202    <author initials='R.' surname='Khare' fullname='R. Khare'>
3203      <organization>4K Associates / UC Irvine</organization>
3204      <address><email></email></address>
3205    </author>
3206    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3207      <organization>Agranat Systems, Inc.</organization>
3208      <address><email></email></address>
3209    </author>
3210    <date year='2000' month='May' />
3211  </front>
3212  <seriesInfo name='RFC' value='2817' />
[253]3215<reference anchor='RFC3864'>
3216  <front>
3217    <title>Registration Procedures for Message Header Fields</title>
3218    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3219      <organization>Nine by Nine</organization>
3220      <address><email></email></address>
3221    </author>
3222    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3223      <organization>BEA Systems</organization>
3224      <address><email></email></address>
3225    </author>
3226    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3227      <organization>HP Labs</organization>
3228      <address><email></email></address>
3229    </author>
3230    <date year='2004' month='September' />
3231  </front>
3232  <seriesInfo name='BCP' value='90' />
3233  <seriesInfo name='RFC' value='3864' />
[262]3236<reference anchor='RFC5226'>
3237  <front>
3238    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3239    <author initials='T.' surname='Narten' fullname='T. Narten'>
3240      <organization>IBM</organization>
3241      <address><email></email></address>
3242    </author>
3243    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3244      <organization>Google</organization>
3245      <address><email></email></address>
3246    </author>
3247    <date year='2008' month='May' />
3248  </front>
3249  <seriesInfo name='BCP' value='26' />
3250  <seriesInfo name='RFC' value='5226' />
[327]3253<reference anchor="RFC5322">
3254  <front>
3255    <title>Internet Message Format</title>
3256    <author initials="P." surname="Resnick" fullname="P. Resnick">
3257      <organization>Qualcomm Incorporated</organization>
3258    </author>
3259    <date year="2008" month="October"/>
3260  </front> 
3261  <seriesInfo name="RFC" value="5322"/>
[99]3266<section title="Compatibility with Previous Versions" anchor="compatibility">
[8]3267<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3269   Clarified which error code should be used for inbound server failures
[763]3270   (e.g., DNS failures). (<xref target="status.504"/>).
[140]3273   201 (Created) had a race that required an Etag be sent when a resource is
[8]3274   first created. (<xref target="status.201"/>).
[614]3277   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3278   failure to implement status code 302 properly.
3279   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
[8]3282   Rewrite of message transmission requirements to make it much harder
3283   for implementors to get it wrong, as the consequences of errors here
3284   can have significant impact on the Internet, and to deal with the
3285   following problems:
3286  <list style="numbers">
3287      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3288         this was incorrectly placing a requirement on the behavior of
3289         an implementation of a future version of HTTP/1.x</t>
3291      <t>Made it clear that user-agents should retry requests, not
3292         "clients" in general.</t>
3294      <t>Converted requirements for clients to ignore unexpected 100
3295         (Continue) responses, and for proxies to forward 100 responses,
3296         into a general requirement for 1xx responses.</t>
3298      <t>Modified some TCP-specific language, to make it clearer that
3299         non-TCP transports are possible for HTTP.</t>
3301      <t>Require that the origin server &MUST-NOT; wait for the request
3302         body before it sends a required 100 (Continue) response.</t>
3304      <t>Allow, rather than require, a server to omit 100 (Continue) if
3305         it has already seen some of the request body.</t>
3307      <t>Allow servers to defend against denial-of-service attacks and
3308         broken clients.</t>
3309  </list>
[29]3312   This change adds the Expect header and 417 status code.
3315   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3316   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3319   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]3320   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3324<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
[262]3326  This document takes over the Status Code Registry, previously defined
3327  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3328  (<xref target="status.code.registry"/>)
[108]3331  Clarify definition of POST.
3332  (<xref target="POST"/>)
3335  Failed to consider that there are
3336  many other request methods that are safe to automatically redirect,
3337  and further that the user agent is able to make that determination
3338  based on the request method semantics.
3339  (Sections <xref format="counter" target="status.301"/>,
3340  <xref format="counter" target="status.302"/> and
[233]3341  <xref format="counter" target="status.307"/>)
[235]3344  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3345  It used to indicate that the requested resource must be accessed through the
3346  proxy given by the Location field. The Location field gave the URI of the
3347  proxy. The recipient was expected to repeat this single request via the proxy.
3348  (<xref target="status.305"/>)
[232]3351  Reclassify Allow header as response header, removing the option to
3352  specify it in a PUT request.
[240]3353  Relax the server requirement on the contents of the Allow header and
3354  remove requirement on clients to always trust the header value.
[232]3355  (<xref target="header.allow"/>)
[785]3358  Correct syntax of Location header to allow URI references (including
3359  relative references and fragments), as referred symbol "absoluteURI" wasn't
3360  what was expected, and add some clarifications as to when use of fragments
3361  would not be appropriate.
[114]3362  (<xref target="header.location"/>)
[593]3365  Allow Referer value of "about:blank" as alternative to not specifying it.
3366  (<xref target="header.referer"/>)
[112]3369  In the description of the Server header, the Via field
3370  was described as a SHOULD. The requirement was and is stated
3371  correctly in the description of the Via header in &header-via;.
3372  (<xref target="header.server"/>)
[680]3378<?BEGININC p2-semantics.abnf-appendix ?>
[427]3379<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
3381<artwork type="abnf" name="p2-semantics.parsed-abnf">
3382<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3383<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3384<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3385<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3386<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
[538]3387<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
[427]3388<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3389<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3390<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3392<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3393<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3394<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3396<x:ref>From</x:ref> = "From:" OWS From-v
3397<x:ref>From-v</x:ref> = mailbox
[678]3399<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
[648]3400<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3402<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
[454]3403If-Modified-Since =
3404 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
[427]3405<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3406<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
[454]3407If-Unmodified-Since =
3408 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
[427]3410<x:ref>Location</x:ref> = "Location:" OWS Location-v
[785]3411<x:ref>Location-v</x:ref> = URI-reference
3413<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3414<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
[581]3415<x:ref>Method</x:ref> = %x4F. ; OPTIONS
3416 / %x47.45.54 ; GET
3417 / %x48.45.41.44 ; HEAD
3418 / %x50.4F.53.54 ; POST
3419 / %x50.55.54 ; PUT
3420 / %x44.45.4C.45.54.45 ; DELETE
3421 / %x54. ; TRACE
3422 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3423 / extension-method
[427]3425<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
[454]3427Proxy-Authenticate =
3428 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3429Proxy-Authorization =
3430 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
[427]3432<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3433<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3434<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3435<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3436<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3437<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3438<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3440<x:ref>Server</x:ref> = "Server:" OWS Server-v
3441<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3442<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
[425]3443 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3444 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3445 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3446 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3447 "505" / extension-code
[837]3449<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
[785]3451<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
[427]3452<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3453<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
[538]3455<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
[454]3457WWW-Authenticate =
3458 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
[648]3460<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
[688]3462<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3464<x:ref>delta-seconds</x:ref> = 1*DIGIT
3466<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3467<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3468<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
[425]3469 *expect-params ]
[427]3470<x:ref>extension-code</x:ref> = 3DIGIT
3471<x:ref>extension-method</x:ref> = token
3473<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3475<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
[648]3477<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
[678]3478<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3480<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3482<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
[425]3483 Accept-Language / Authorization / Expect / From / Host / If-Match /
3484 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3485 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3486 User-Agent
[427]3487<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
[425]3488 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
[427]3490<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
[532]3493<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3494; Reason-Phrase defined but not used
[425]3495; Status-Code defined but not used
3496; request-header defined but not used
3497; response-header defined but not used
[680]3499<?ENDINC p2-semantics.abnf-appendix ?>
[252]3501<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3503<section title="Since RFC2616">
3505  Extracted relevant partitions from <xref target="RFC2616"/>.
3509<section title="Since draft-ietf-httpbis-p2-semantics-00">
[116]3511  Closed issues:
3512  <list style="symbols"> 
3513    <t>
[324]3514      <eref target=""/>:
[116]3515      "Via is a MUST"
3516      (<eref target=""/>)
3517    </t>