source: draft-ietf-httpbis/latest/p2-semantics.xml @ 439

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "January">
16  <!ENTITY ID-YEAR "2009">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64]>
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
77     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x='http://purl.org/net/xml2rfc/ext'
79     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
80<front>
81
82  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
83
84  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
85    <organization abbrev="Day Software">Day Software</organization>
86    <address>
87      <postal>
88        <street>23 Corporate Plaza DR, Suite 280</street>
89        <city>Newport Beach</city>
90        <region>CA</region>
91        <code>92660</code>
92        <country>USA</country>
93      </postal>
94      <phone>+1-949-706-5300</phone>
95      <facsimile>+1-949-706-5305</facsimile>
96      <email>fielding@gbiv.com</email>
97      <uri>http://roy.gbiv.com/</uri>
98    </address>
99  </author>
100
101  <author initials="J." surname="Gettys" fullname="Jim Gettys">
102    <organization>One Laptop per Child</organization>
103    <address>
104      <postal>
105        <street>21 Oak Knoll Road</street>
106        <city>Carlisle</city>
107        <region>MA</region>
108        <code>01741</code>
109        <country>USA</country>
110      </postal>
111      <email>jg@laptop.org</email>
112      <uri>http://www.laptop.org/</uri>
113    </address>
114  </author>
115 
116  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
117    <organization abbrev="HP">Hewlett-Packard Company</organization>
118    <address>
119      <postal>
120        <street>HP Labs, Large Scale Systems Group</street>
121        <street>1501 Page Mill Road, MS 1177</street>
122        <city>Palo Alto</city>
123        <region>CA</region>
124        <code>94304</code>
125        <country>USA</country>
126      </postal>
127      <email>JeffMogul@acm.org</email>
128    </address>
129  </author>
130
131  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
132    <organization abbrev="Microsoft">Microsoft Corporation</organization>
133    <address>
134      <postal>
135        <street>1 Microsoft Way</street>
136        <city>Redmond</city>
137        <region>WA</region>
138        <code>98052</code>
139        <country>USA</country>
140      </postal>
141      <email>henrikn@microsoft.com</email>
142    </address>
143  </author>
144
145  <author initials="L." surname="Masinter" fullname="Larry Masinter">
146    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
147    <address>
148      <postal>
149        <street>345 Park Ave</street>
150        <city>San Jose</city>
151        <region>CA</region>
152        <code>95110</code>
153        <country>USA</country>
154      </postal>
155      <email>LMM@acm.org</email>
156      <uri>http://larry.masinter.net/</uri>
157    </address>
158  </author>
159 
160  <author initials="P." surname="Leach" fullname="Paul J. Leach">
161    <organization abbrev="Microsoft">Microsoft Corporation</organization>
162    <address>
163      <postal>
164        <street>1 Microsoft Way</street>
165        <city>Redmond</city>
166        <region>WA</region>
167        <code>98052</code>
168      </postal>
169      <email>paulle@microsoft.com</email>
170    </address>
171  </author>
172   
173  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
174    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
175    <address>
176      <postal>
177        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
178        <street>The Stata Center, Building 32</street>
179        <street>32 Vassar Street</street>
180        <city>Cambridge</city>
181        <region>MA</region>
182        <code>02139</code>
183        <country>USA</country>
184      </postal>
185      <email>timbl@w3.org</email>
186      <uri>http://www.w3.org/People/Berners-Lee/</uri>
187    </address>
188  </author>
189
190  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
191    <organization abbrev="W3C">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>W3C / ERCIM</street>
195        <street>2004, rte des Lucioles</street>
196        <city>Sophia-Antipolis</city>
197        <region>AM</region>
198        <code>06902</code>
199        <country>France</country>
200      </postal>
201      <email>ylafon@w3.org</email>
202      <uri>http://www.raubacapeu.net/people/yves/</uri>
203    </address>
204  </author>
205
206  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
207    <organization abbrev="greenbytes">greenbytes GmbH</organization>
208    <address>
209      <postal>
210        <street>Hafenweg 16</street>
211        <city>Muenster</city><region>NW</region><code>48155</code>
212        <country>Germany</country>
213      </postal>
214      <phone>+49 251 2807760</phone>   
215      <facsimile>+49 251 2807761</facsimile>   
216      <email>julian.reschke@greenbytes.de</email>       
217      <uri>http://greenbytes.de/tech/webdav/</uri>     
218    </address>
219  </author>
220
221  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
222
223<abstract>
224<t>
225   The Hypertext Transfer Protocol (HTTP) is an application-level
226   protocol for distributed, collaborative, hypermedia information
227   systems. HTTP has been in use by the World Wide Web global information
228   initiative since 1990. This document is Part 2 of the seven-part specification
229   that defines the protocol referred to as "HTTP/1.1" and, taken together,
230   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
231   as expressed by request methods, request-header fields, response status codes,
232   and response-header fields.
233</t>
234</abstract>
235
236<note title="Editorial Note (To be removed by RFC Editor)">
237  <t>
238    Discussion of this draft should take place on the HTTPBIS working group
239    mailing list (ietf-http-wg@w3.org). The current issues list is
240    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
241    and related documents (including fancy diffs) can be found at
242    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
243  </t>
244  <t>
245    The changes in this draft are summarized in <xref target="changes.since.05"/>.
246  </t>
247</note>
248</front>
249<middle>
250<section title="Introduction" anchor="introduction">
251<t>
252   This document defines HTTP/1.1 request and response semantics.  Each HTTP
253   message, as defined in &messaging;, is in the form of either a request or
254   a response.  An HTTP server listens on a connection for HTTP requests and
255   responds to each request, in the order received on that connection, with
256   one or more HTTP response messages.  This document defines the commonly
257   agreed upon semantics of the HTTP uniform interface, the intentions defined
258   by each request method, and the various response messages that might be
259   expected as a result of applying that method for the requested resource.
260</t>
261<t>
262   This document is currently disorganized in order to minimize the changes
263   between drafts and enable reviewers to see the smaller errata changes.
264   The next draft will reorganize the sections to better reflect the content.
265   In particular, the sections will be ordered according to the typical
266   processing of an HTTP request message (after message parsing): resource
267   mapping, general header fields, methods, request modifiers, response
268   status, and resource metadata.  The current mess reflects how widely
269   dispersed these topics and associated requirements had become in
270   <xref target="RFC2616"/>.
271</t>
272
273<section title="Requirements" anchor="intro.requirements">
274<t>
275   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
276   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
277   document are to be interpreted as described in <xref target="RFC2119"/>.
278</t>
279<t>
280   An implementation is not compliant if it fails to satisfy one or more
281   of the &MUST; or &REQUIRED; level requirements for the protocols it
282   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
283   level and all the &SHOULD; level requirements for its protocols is said
284   to be "unconditionally compliant"; one that satisfies all the &MUST;
285   level requirements but not all the &SHOULD; level requirements for its
286   protocols is said to be "conditionally compliant."
287</t>
288</section>
289
290<section title="Syntax Notation" anchor="notation">
291  <x:anchor-alias value="CR"/>
292  <x:anchor-alias value="DIGIT"/>
293  <x:anchor-alias value="LF"/>
294  <x:anchor-alias value="VCHAR"/>
295  <x:anchor-alias value="WSP"/>
296<t>
297  This specification uses the ABNF syntax defined in &notation;.
298  The following core rules are included by
299  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
300  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
301  DIGIT (decimal 0-9), DQUOTE (double quote),
302  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
303  OCTET (any 8-bit sequence of data), SP (space),
304  VCHAR (any visible USASCII character),
305  and WSP (whitespace).
306</t>
307
308<section title="Core Rules" anchor="core.rules">
309  <x:anchor-alias value="comment"/>
310  <x:anchor-alias value="obs-text"/>
311  <x:anchor-alias value="quoted-string"/>
312  <x:anchor-alias value="token"/>
313  <x:anchor-alias value="OWS"/>
314  <x:anchor-alias value="RWS"/>
315<t>
316  The core rules below are defined in &basic-rules;:
317</t>
318<figure><artwork type="abnf2616">
319  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
320  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
321  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
322  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
323  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
324  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
325</artwork></figure>
326</section>
327
328<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
329  <x:anchor-alias value="absolute-URI"/>
330  <x:anchor-alias value="Accept"/>
331  <x:anchor-alias value="Accept-Charset"/>
332  <x:anchor-alias value="Accept-Encoding"/>
333  <x:anchor-alias value="Accept-Language"/>
334  <x:anchor-alias value="Accept-Ranges"/>
335  <x:anchor-alias value="Age"/>
336  <x:anchor-alias value="Authorization"/>
337  <x:anchor-alias value="ETag"/>
338  <x:anchor-alias value="fragment"/>
339  <x:anchor-alias value="Host"/>
340  <x:anchor-alias value="HTTP-date"/>
341  <x:anchor-alias value="If-Match"/>
342  <x:anchor-alias value="If-Modified-Since"/>
343  <x:anchor-alias value="If-None-Match"/>
344  <x:anchor-alias value="If-Range"/>
345  <x:anchor-alias value="If-Unmodified-Since"/>
346  <x:anchor-alias value="partial-URI"/>
347  <x:anchor-alias value="product"/>
348  <x:anchor-alias value="Proxy-Authenticate"/>
349  <x:anchor-alias value="Proxy-Authorization"/>
350  <x:anchor-alias value="Range"/>
351  <x:anchor-alias value="TE"/>
352  <x:anchor-alias value="Vary"/>
353  <x:anchor-alias value="WWW-Authenticate"/>
354<t>
355  The ABNF rules below are defined in other parts:
356</t>
357<figure><!--Part1--><artwork type="abnf2616">
358  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
359  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
360  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
361  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
362  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
363  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
364  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
365</artwork></figure>
366<figure><!--Part3--><artwork type="abnf2616">
367  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
368  <x:ref>Accept-Charset</x:ref> =
369             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
370  <x:ref>Accept-Encoding</x:ref> =
371             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
372  <x:ref>Accept-Language</x:ref> =
373             &lt;Accept-Language, defined in &header-accept-language;&gt;
374</artwork></figure>
375<figure><!--Part4--><artwork type="abnf2616">
376  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
377  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
378  <x:ref>If-Modified-Since</x:ref> =
379             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
380  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
381  <x:ref>If-Unmodified-Since</x:ref> =
382             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
383</artwork></figure>
384<figure><!--Part5--><artwork type="abnf2616">
385  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
386  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
387  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
388</artwork></figure>
389<figure><!--Part6--><artwork type="abnf2616">
390  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
391  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
392</artwork><!--Part7--></figure>
393<figure><artwork type="abnf2616">
394  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
395  <x:ref>Proxy-Authenticate</x:ref> =
396             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
397  <x:ref>Proxy-Authorization</x:ref> =
398             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
399  <x:ref>WWW-Authenticate</x:ref> =
400             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
401</artwork></figure>
402</section>
403</section>
404</section>
405
406<section title="Method" anchor="method">
407  <x:anchor-alias value="Method"/>
408  <x:anchor-alias value="extension-method"/>
409<t>
410   The Method  token indicates the method to be performed on the
411   resource identified by the request-target. The method is case-sensitive.
412</t>
413<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
414  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
415                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
416                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
417                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
418                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
419                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
420                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
421                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
422                 / <x:ref>extension-method</x:ref>
423  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
424</artwork></figure>
425<t>
426   The list of methods allowed by a resource can be specified in an
427   Allow header field (<xref target="header.allow"/>). The return code of the response
428   always notifies the client whether a method is currently allowed on a
429   resource, since the set of allowed methods can change dynamically. An
430   origin server &SHOULD; return the status code 405 (Method Not Allowed)
431   if the method is known by the origin server but not allowed for the
432   requested resource, and 501 (Not Implemented) if the method is
433   unrecognized or not implemented by the origin server. The methods GET
434   and HEAD &MUST; be supported by all general-purpose servers. All other
435   methods are &OPTIONAL;; however, if the above methods are implemented,
436   they &MUST; be implemented with the same semantics as those specified
437   in <xref target="method.definitions"/>.
438</t>
439
440<section title="Method Registry" anchor="method.registry">
441<t>
442  The HTTP Method Registry defines the name space for the Method token in the
443  Request line of an HTTP request.
444</t>
445<t>
446  Registrations &MUST; include the following fields:
447  <list style="symbols">
448    <t>Method Name (see <xref target="method"/>)</t>
449    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
450    <t>Pointer to specification text</t>
451  </list>
452</t>
453<t>
454  Values to be added to this name space are subject to IETF review
455  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
456  new method names should be traceable through statuses of either 'Obsoletes'
457  or 'Updates' to this document.
458</t>
459<t>
460  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
461</t>
462</section>
463</section>
464
465<section title="Request Header Fields" anchor="request.header.fields">
466  <x:anchor-alias value="request-header"/>
467<t>
468   The request-header fields allow the client to pass additional
469   information about the request, and about the client itself, to the
470   server. These fields act as request modifiers, with semantics
471   equivalent to the parameters on a programming language method
472   invocation.
473</t>
474<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
475  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
476                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
477                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
478                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
479                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
480                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
481                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
482                 / <x:ref>Host</x:ref>                     ; &header-host;
483                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
484                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
485                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
486                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
487                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
488                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
489                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
490                 / <x:ref>Range</x:ref>                    ; &header-range;
491                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
492                 / <x:ref>TE</x:ref>                       ; &header-te;
493                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
494</artwork></figure>
495<t>
496   Request-header field names can be extended reliably only in
497   combination with a change in the protocol version. However, new or
498   experimental header fields &MAY; be given the semantics of request-header
499   fields if all parties in the communication recognize them to
500   be request-header fields. Unrecognized header fields are treated as
501   entity-header fields.
502</t>
503</section>
504
505<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
506  <x:anchor-alias value="Reason-Phrase"/>
507  <x:anchor-alias value="Status-Code"/>
508  <x:anchor-alias value="extension-code"/>
509<t>
510   The Status-Code element is a 3-digit integer result code of the
511   attempt to understand and satisfy the request. The status codes listed
512   below are defined in <xref target="status.codes"/>.
513   The Reason-Phrase is intended to give a short
514   textual description of the Status-Code. The Status-Code is intended
515   for use by automata and the Reason-Phrase is intended for the human
516   user. The client is not required to examine or display the Reason-Phrase.
517</t>
518<t> 
519   The individual values of the numeric status codes defined for
520   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
521   presented below. The reason phrases listed here are only
522   recommendations -- they &MAY; be replaced by local equivalents without
523   affecting the protocol.
524</t>
525<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"/>
526  <x:ref>Status-Code</x:ref>    =
527         "100"  ; <xref target="status.100"/>: Continue
528       / "101"  ; <xref target="status.101"/>: Switching Protocols
529       / "200"  ; <xref target="status.200"/>: OK
530       / "201"  ; <xref target="status.201"/>: Created
531       / "202"  ; <xref target="status.202"/>: Accepted
532       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
533       / "204"  ; <xref target="status.204"/>: No Content
534       / "205"  ; <xref target="status.205"/>: Reset Content
535       / "206"  ; <xref target="status.206"/>: Partial Content
536       / "300"  ; <xref target="status.300"/>: Multiple Choices
537       / "301"  ; <xref target="status.301"/>: Moved Permanently
538       / "302"  ; <xref target="status.302"/>: Found
539       / "303"  ; <xref target="status.303"/>: See Other
540       / "304"  ; <xref target="status.304"/>: Not Modified
541       / "305"  ; <xref target="status.305"/>: Use Proxy
542       / "307"  ; <xref target="status.307"/>: Temporary Redirect
543       / "400"  ; <xref target="status.400"/>: Bad Request
544       / "401"  ; <xref target="status.401"/>: Unauthorized
545       / "402"  ; <xref target="status.402"/>: Payment Required
546       / "403"  ; <xref target="status.403"/>: Forbidden
547       / "404"  ; <xref target="status.404"/>: Not Found
548       / "405"  ; <xref target="status.405"/>: Method Not Allowed
549       / "406"  ; <xref target="status.406"/>: Not Acceptable
550       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
551       / "408"  ; <xref target="status.408"/>: Request Time-out
552       / "409"  ; <xref target="status.409"/>: Conflict
553       / "410"  ; <xref target="status.410"/>: Gone
554       / "411"  ; <xref target="status.411"/>: Length Required
555       / "412"  ; <xref target="status.412"/>: Precondition Failed
556       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
557       / "414"  ; <xref target="status.414"/>: Request-target Too Long
558       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
559       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
560       / "417"  ; <xref target="status.417"/>: Expectation Failed
561       / "500"  ; <xref target="status.500"/>: Internal Server Error
562       / "501"  ; <xref target="status.501"/>: Not Implemented
563       / "502"  ; <xref target="status.502"/>: Bad Gateway
564       / "503"  ; <xref target="status.503"/>: Service Unavailable
565       / "504"  ; <xref target="status.504"/>: Gateway Time-out
566       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
567       / <x:ref>extension-code</x:ref>
568
569  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
570  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
571</artwork></figure>
572<t>
573   HTTP status codes are extensible. HTTP applications are not required
574   to understand the meaning of all registered status codes, though such
575   understanding is obviously desirable. However, applications &MUST;
576   understand the class of any status code, as indicated by the first
577   digit, and treat any unrecognized response as being equivalent to the
578   x00 status code of that class, with the exception that an
579   unrecognized response &MUST-NOT; be cached. For example, if an
580   unrecognized status code of 431 is received by the client, it can
581   safely assume that there was something wrong with its request and
582   treat the response as if it had received a 400 status code. In such
583   cases, user agents &SHOULD; present to the user the entity returned
584   with the response, since that entity is likely to include human-readable
585   information which will explain the unusual status.
586</t>
587
588<section title="Status Code Registry" anchor="status.code.registry">
589<t>
590  The HTTP Status Code Registry defines the name space for the Status-Code
591  token in the Status line of an HTTP response.
592</t>
593<t>
594  Values to be added to this name space are subject to IETF review
595  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
596  new status codes should be traceable through statuses of either 'Obsoletes'
597  or 'Updates' to this document.
598</t>
599<t>
600  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
601</t>
602</section>
603
604</section>
605
606<section title="Response Header Fields" anchor="response.header.fields">
607  <x:anchor-alias value="response-header"/>
608<t>
609   The response-header fields allow the server to pass additional
610   information about the response which cannot be placed in the Status-Line.
611   These header fields give information about the server and about
612   further access to the resource identified by the request-target.
613</t>
614<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
615  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
616                  / <x:ref>Age</x:ref>                     ; &header-age;
617                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
618                  / <x:ref>ETag</x:ref>                    ; &header-etag;
619                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
620                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
621                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
622                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
623                  / <x:ref>Vary</x:ref>                    ; &header-vary;
624                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
625</artwork></figure>
626<t>
627   Response-header field names can be extended reliably only in
628   combination with a change in the protocol version. However, new or
629   experimental header fields &MAY; be given the semantics of response-header
630   fields if all parties in the communication recognize them to
631   be response-header fields. Unrecognized header fields are treated as
632   entity-header fields.
633</t>
634</section>
635
636<section title="Entity" anchor="entity">
637<t>
638   Request and Response messages &MAY; transfer an entity if not otherwise
639   restricted by the request method or response status code. An entity
640   consists of entity-header fields and an entity-body, although some
641   responses will only include the entity-headers. HTTP entity-body and
642   entity-header fields are defined in &payload;.
643</t>
644<t>
645   An entity-body is only present in a message when a message-body is
646   present, as described in &message-body;. The entity-body is obtained
647   from the message-body by decoding any Transfer-Encoding that might
648   have been applied to ensure safe and proper transfer of the message.
649</t>
650</section>
651
652
653<section title="Method Definitions" anchor="method.definitions">
654<t>
655   The set of common methods for HTTP/1.1 is defined below. Although
656   this set can be expanded, additional methods cannot be assumed to
657   share the same semantics for separately extended clients and servers.
658</t>
659
660<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
661
662<section title="Safe Methods" anchor="safe.methods">
663<iref item="Safe Methods" primary="true"/>
664<t>
665   Implementors should be aware that the software represents the user in
666   their interactions over the Internet, and should be careful to allow
667   the user to be aware of any actions they might take which may have an
668   unexpected significance to themselves or others.
669</t>
670<t>
671   In particular, the convention has been established that the GET and
672   HEAD methods &SHOULD-NOT;  have the significance of taking an action
673   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
674   This allows user agents to represent other methods, such as POST, PUT
675   and DELETE, in a special way, so that the user is made aware of the
676   fact that a possibly unsafe action is being requested.
677</t>
678<t>
679   Naturally, it is not possible to ensure that the server does not
680   generate side-effects as a result of performing a GET request; in
681   fact, some dynamic resources consider that a feature. The important
682   distinction here is that the user did not request the side-effects,
683   so therefore cannot be held accountable for them.
684</t>
685</section>
686
687<section title="Idempotent Methods" anchor="idempotent.methods">
688<iref item="Idempotent Methods" primary="true"/>
689<t>
690   Methods can also have the property of "idempotence" in that (aside
691   from error or expiration issues) the side-effects of N &gt; 0 identical
692   requests is the same as for a single request. The methods GET, HEAD,
693   PUT and DELETE share this property. Also, the methods OPTIONS and
694   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
695</t>
696<t>
697   However, it is possible that a sequence of several requests is non-idempotent,
698   even if all of the methods executed in that sequence are
699   idempotent. (A sequence is idempotent if a single execution of the
700   entire sequence always yields a result that is not changed by a
701   reexecution of all, or part, of that sequence.) For example, a
702   sequence is non-idempotent if its result depends on a value that is
703   later modified in the same sequence.
704</t>
705<t>
706   A sequence that never has side effects is idempotent, by definition
707   (provided that no concurrent operations are being executed on the
708   same set of resources).
709</t>
710</section>
711</section>
712
713<section title="OPTIONS" anchor="OPTIONS">
714  <rdf:Description>
715    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
716  </rdf:Description>
717  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
718  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
719<t>
720   The OPTIONS method represents a request for information about the
721   communication options available on the request/response chain
722   identified by the request-target. This method allows the client to
723   determine the options and/or requirements associated with a resource,
724   or the capabilities of a server, without implying a resource action
725   or initiating a resource retrieval.
726</t>
727<t>
728   Responses to this method are not cacheable.
729</t>
730<t>
731   If the OPTIONS request includes an entity-body (as indicated by the
732   presence of Content-Length or Transfer-Encoding), then the media type
733   &MUST; be indicated by a Content-Type field. Although this
734   specification does not define any use for such a body, future
735   extensions to HTTP might use the OPTIONS body to make more detailed
736   queries on the server.
737</t>
738<t>
739   If the request-target is an asterisk ("*"), the OPTIONS request is
740   intended to apply to the server in general rather than to a specific
741   resource. Since a server's communication options typically depend on
742   the resource, the "*" request is only useful as a "ping" or "no-op"
743   type of method; it does nothing beyond allowing the client to test
744   the capabilities of the server. For example, this can be used to test
745   a proxy for HTTP/1.1 compliance (or lack thereof).
746</t>
747<t>
748   If the request-target is not an asterisk, the OPTIONS request applies
749   only to the options that are available when communicating with that
750   resource.
751</t>
752<t>
753   A 200 response &SHOULD; include any header fields that indicate
754   optional features implemented by the server and applicable to that
755   resource (e.g., Allow), possibly including extensions not defined by
756   this specification. The response body, if any, &SHOULD; also include
757   information about the communication options. The format for such a
758   body is not defined by this specification, but might be defined by
759   future extensions to HTTP. Content negotiation &MAY; be used to select
760   the appropriate response format. If no response body is included, the
761   response &MUST; include a Content-Length field with a field-value of
762   "0".
763</t>
764<t>
765   The Max-Forwards request-header field &MAY; be used to target a
766   specific proxy in the request chain. When a proxy receives an OPTIONS
767   request on an absolute-URI for which request forwarding is permitted,
768   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
769   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
770   instead, the proxy &SHOULD; respond with its own communication options.
771   If the Max-Forwards field-value is an integer greater than zero, the
772   proxy &MUST; decrement the field-value when it forwards the request. If
773   no Max-Forwards field is present in the request, then the forwarded
774   request &MUST-NOT; include a Max-Forwards field.
775</t>
776</section>
777
778<section title="GET" anchor="GET">
779  <rdf:Description>
780    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
781  </rdf:Description>
782  <iref primary="true" item="GET method" x:for-anchor=""/>
783  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
784<t>
785   The GET method means retrieve whatever information (in the form of an
786   entity) is identified by the request-target. If the request-target refers
787   to a data-producing process, it is the produced data which shall be
788   returned as the entity in the response and not the source text of the
789   process, unless that text happens to be the output of the process.
790</t>
791<t>
792   The semantics of the GET method change to a "conditional GET" if the
793   request message includes an If-Modified-Since, If-Unmodified-Since,
794   If-Match, If-None-Match, or If-Range header field. A conditional GET
795   method requests that the entity be transferred only under the
796   circumstances described by the conditional header field(s). The
797   conditional GET method is intended to reduce unnecessary network
798   usage by allowing cached entities to be refreshed without requiring
799   multiple requests or transferring data already held by the client.
800</t>
801<t>
802   The semantics of the GET method change to a "partial GET" if the
803   request message includes a Range header field. A partial GET requests
804   that only part of the entity be transferred, as described in &header-range;.
805   The partial GET method is intended to reduce unnecessary
806   network usage by allowing partially-retrieved entities to be
807   completed without transferring data already held by the client.
808</t>
809<t>
810   The response to a GET request is cacheable if and only if it meets
811   the requirements for HTTP caching described in &caching;.
812</t>
813<t>
814   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
815</t>
816</section>
817
818<section title="HEAD" anchor="HEAD">
819  <rdf:Description>
820    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
821  </rdf:Description>
822  <iref primary="true" item="HEAD method" x:for-anchor=""/>
823  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
824<t>
825   The HEAD method is identical to GET except that the server &MUST-NOT;
826   return a message-body in the response. The metainformation contained
827   in the HTTP headers in response to a HEAD request &SHOULD; be identical
828   to the information sent in response to a GET request. This method can
829   be used for obtaining metainformation about the entity implied by the
830   request without transferring the entity-body itself. This method is
831   often used for testing hypertext links for validity, accessibility,
832   and recent modification.
833</t>
834<t>
835   The response to a HEAD request &MAY; be cacheable in the sense that the
836   information contained in the response &MAY; be used to update a
837   previously cached entity from that resource. If the new field values
838   indicate that the cached entity differs from the current entity (as
839   would be indicated by a change in Content-Length, Content-MD5, ETag
840   or Last-Modified), then the cache &MUST; treat the cache entry as
841   stale.
842</t>
843</section>
844
845<section title="POST" anchor="POST">
846  <iref primary="true" item="POST method" x:for-anchor=""/>
847  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
848<t>
849   The POST method is used to request that the origin server accept the
850   entity enclosed in the request as data to be processed by the resource
851   identified by the request-target in the Request-Line. POST is designed
852   to allow a uniform method to cover the following functions:
853  <list style="symbols">
854    <t>
855      Annotation of existing resources;
856    </t>
857    <t>
858        Posting a message to a bulletin board, newsgroup, mailing list,
859        or similar group of articles;
860    </t>
861    <t>
862        Providing a block of data, such as the result of submitting a
863        form, to a data-handling process;
864    </t>
865    <t>
866        Extending a database through an append operation.
867    </t>
868  </list>
869</t>
870<t>
871   The actual function performed by the POST method is determined by the
872   server and is usually dependent on the request-target.
873</t>
874<t>
875   The action performed by the POST method might not result in a
876   resource that can be identified by a URI. In this case, either 200
877   (OK) or 204 (No Content) is the appropriate response status,
878   depending on whether or not the response includes an entity that
879   describes the result.
880</t>
881<t>
882   If a resource has been created on the origin server, the response
883   &SHOULD; be 201 (Created) and contain an entity which describes the
884   status of the request and refers to the new resource, and a Location
885   header (see <xref target="header.location"/>).
886</t>
887<t>
888   Responses to this method are not cacheable, unless the response
889   includes appropriate Cache-Control or Expires header fields. However,
890   the 303 (See Other) response can be used to direct the user agent to
891   retrieve a cacheable resource.
892</t>
893</section>
894
895<section title="PUT" anchor="PUT">
896  <iref primary="true" item="PUT method" x:for-anchor=""/>
897  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
898<t>
899   The PUT method requests that the enclosed entity be stored at the
900   supplied request-target. If the request-target refers to an already
901   existing resource, the enclosed entity &SHOULD; be considered as a
902   modified version of the one residing on the origin server. If the
903   request-target does not point to an existing resource, and that URI is
904   capable of being defined as a new resource by the requesting user
905   agent, the origin server can create the resource with that URI. If a
906   new resource is created at the request-target, the origin server &MUST;
907         inform the user agent
908   via the 201 (Created) response. If an existing resource is modified,
909   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
910   to indicate successful completion of the request. If the resource
911   could not be created or modified with the request-target, an appropriate
912   error response &SHOULD; be given that reflects the nature of the
913   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
914   headers (headers starting with the prefix 'Content-') that it does
915   not understand or implement
916   and &MUST; return a 501 (Not Implemented) response in such cases.
917</t>
918<t>
919   If the request passes through a cache and the request-target identifies
920   one or more currently cached entities, those entries &SHOULD; be
921   treated as stale. Responses to this method are not cacheable.
922</t>
923<t>
924   The fundamental difference between the POST and PUT requests is
925   reflected in the different meaning of the request-target. The URI in a
926   POST request identifies the resource that will handle the enclosed
927   entity. That resource might be a data-accepting process, a gateway to
928   some other protocol, or a separate entity that accepts annotations.
929   In contrast, the URI in a PUT request identifies the entity enclosed
930   with the request -- the user agent knows what URI is intended and the
931   server &MUST-NOT; attempt to apply the request to some other resource.
932   If the server desires that the request be applied to a different URI,
933   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
934   then make its own decision regarding whether or not to redirect the
935   request.
936</t>
937<t>
938   A single resource &MAY; be identified by many different URIs. For
939   example, an article might have a URI for identifying "the current
940   version" which is separate from the URI identifying each particular
941   version. In this case, a PUT request on a general URI might result in
942   several other URIs being defined by the origin server.
943</t>
944<t>
945   HTTP/1.1 does not define how a PUT method affects the state of an
946   origin server.
947</t>
948<t>
949   Unless otherwise specified for a particular entity-header, the
950   entity-headers in the PUT request &SHOULD; be applied to the resource
951   created or modified by the PUT.
952</t>
953</section>
954
955<section title="DELETE" anchor="DELETE">
956  <iref primary="true" item="DELETE method" x:for-anchor=""/>
957  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
958<t>
959   The DELETE method requests that the origin server delete the resource
960   identified by the request-target. This method &MAY; be overridden by human
961   intervention (or other means) on the origin server. The client cannot
962   be guaranteed that the operation has been carried out, even if the
963   status code returned from the origin server indicates that the action
964   has been completed successfully. However, the server &SHOULD-NOT; 
965   indicate success unless, at the time the response is given, it
966   intends to delete the resource or move it to an inaccessible
967   location.
968</t>
969<t>
970   A successful response &SHOULD; be 200 (OK) if the response includes an
971   entity describing the status, 202 (Accepted) if the action has not
972   yet been enacted, or 204 (No Content) if the action has been enacted
973   but the response does not include an entity.
974</t>
975<t>
976   If the request passes through a cache and the request-target identifies
977   one or more currently cached entities, those entries &SHOULD; be
978   treated as stale. Responses to this method are not cacheable.
979</t>
980</section>
981
982<section title="TRACE" anchor="TRACE">
983  <rdf:Description>
984    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
985  </rdf:Description>
986  <iref primary="true" item="TRACE method" x:for-anchor=""/>
987  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
988<t>
989   The TRACE method is used to invoke a remote, application-layer loop-back
990   of the request message. The final recipient of the request
991   &SHOULD; reflect the message received back to the client as the
992   entity-body of a 200 (OK) response. The final recipient is either the
993   origin server or the first proxy or gateway to receive a Max-Forwards
994   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
995   &MUST-NOT; include an entity.
996</t>
997<t>
998   TRACE allows the client to see what is being received at the other
999   end of the request chain and use that data for testing or diagnostic
1000   information. The value of the Via header field (&header-via;) is of
1001   particular interest, since it acts as a trace of the request chain.
1002   Use of the Max-Forwards header field allows the client to limit the
1003   length of the request chain, which is useful for testing a chain of
1004   proxies forwarding messages in an infinite loop.
1005</t>
1006<t>
1007   If the request is valid, the response &SHOULD; contain the entire
1008   request message in the entity-body, with a Content-Type of
1009   "message/http" (see &media-type-message-http;). Responses to this method
1010   &MUST-NOT; be cached.
1011</t>
1012</section>
1013
1014<section title="CONNECT" anchor="CONNECT">
1015  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1016  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1017<t>
1018   This specification reserves the method name CONNECT for use with a
1019   proxy that can dynamically switch to being a tunnel (e.g. SSL
1020   tunneling <xref target="RFC2817"/>).
1021</t>
1022</section>
1023</section>
1024
1025
1026<section title="Status Code Definitions" anchor="status.codes">
1027<t>
1028   Each Status-Code is described below, including a description of which
1029   method(s) it can follow and any metainformation required in the
1030   response.
1031</t>
1032
1033<section title="Informational 1xx" anchor="status.1xx">
1034<t>
1035   This class of status code indicates a provisional response,
1036   consisting only of the Status-Line and optional headers, and is
1037   terminated by an empty line. There are no required headers for this
1038   class of status code. Since HTTP/1.0 did not define any 1xx status
1039   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1040   except under experimental conditions.
1041</t>
1042<t>
1043   A client &MUST; be prepared to accept one or more 1xx status responses
1044   prior to a regular response, even if the client does not expect a 100
1045   (Continue) status message. Unexpected 1xx status responses &MAY; be
1046   ignored by a user agent.
1047</t>
1048<t>
1049   Proxies &MUST; forward 1xx responses, unless the connection between the
1050   proxy and its client has been closed, or unless the proxy itself
1051   requested the generation of the 1xx response. (For example, if a
1052   proxy adds a "Expect: 100-continue" field when it forwards a request,
1053   then it need not forward the corresponding 100 (Continue)
1054   response(s).)
1055</t>
1056
1057<section title="100 Continue" anchor="status.100">
1058  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1059  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1060<t>
1061   The client &SHOULD; continue with its request. This interim response is
1062   used to inform the client that the initial part of the request has
1063   been received and has not yet been rejected by the server. The client
1064   &SHOULD; continue by sending the remainder of the request or, if the
1065   request has already been completed, ignore this response. The server
1066   &MUST; send a final response after the request has been completed. See
1067   &use100; for detailed discussion of the use and handling of this
1068   status code.
1069</t>
1070</section>
1071
1072<section title="101 Switching Protocols" anchor="status.101">
1073  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1074  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1075<t>
1076   The server understands and is willing to comply with the client's
1077   request, via the Upgrade message header field (&header-upgrade;), for a
1078   change in the application protocol being used on this connection. The
1079   server will switch protocols to those defined by the response's
1080   Upgrade header field immediately after the empty line which
1081   terminates the 101 response.
1082</t>
1083<t>
1084   The protocol &SHOULD; be switched only when it is advantageous to do
1085   so. For example, switching to a newer version of HTTP is advantageous
1086   over older versions, and switching to a real-time, synchronous
1087   protocol might be advantageous when delivering resources that use
1088   such features.
1089</t>
1090</section>
1091</section>
1092
1093<section title="Successful 2xx" anchor="status.2xx">
1094<t>
1095   This class of status code indicates that the client's request was
1096   successfully received, understood, and accepted.
1097</t>
1098
1099<section title="200 OK" anchor="status.200">
1100  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1101  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1102<t>
1103   The request has succeeded. The information returned with the response
1104   is dependent on the method used in the request, for example:
1105  <list style="hanging">
1106    <t hangText="GET">
1107          an entity corresponding to the requested resource is sent in
1108          the response;
1109    </t>
1110    <t hangText="HEAD">
1111          the entity-header fields corresponding to the requested
1112          resource are sent in the response without any message-body;
1113    </t>
1114    <t hangText="POST">
1115      an entity describing or containing the result of the action;
1116    </t>
1117    <t hangText="TRACE">
1118      an entity containing the request message as received by the
1119      end server.
1120    </t>
1121  </list>
1122</t>
1123</section>
1124
1125<section title="201 Created" anchor="status.201">
1126  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1127  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1128<t>
1129   The request has been fulfilled and resulted in a new resource being
1130   created. The newly created resource can be referenced by the URI(s)
1131   returned in the entity of the response, with the most specific URI
1132   for the resource given by a Location header field. The response
1133   &SHOULD; include an entity containing a list of resource
1134   characteristics and location(s) from which the user or user agent can
1135   choose the one most appropriate. The entity format is specified by
1136   the media type given in the Content-Type header field. The origin
1137   server &MUST; create the resource before returning the 201 status code.
1138   If the action cannot be carried out immediately, the server &SHOULD;
1139   respond with 202 (Accepted) response instead.
1140</t>
1141<t>
1142   A 201 response &MAY; contain an ETag response header field indicating
1143   the current value of the entity tag for the requested variant just
1144   created, see &header-etag;.
1145</t>
1146</section>
1147
1148<section title="202 Accepted" anchor="status.202">
1149  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1150  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1151<t>
1152   The request has been accepted for processing, but the processing has
1153   not been completed.  The request might or might not eventually be
1154   acted upon, as it might be disallowed when processing actually takes
1155   place. There is no facility for re-sending a status code from an
1156   asynchronous operation such as this.
1157</t>
1158<t>
1159   The 202 response is intentionally non-committal. Its purpose is to
1160   allow a server to accept a request for some other process (perhaps a
1161   batch-oriented process that is only run once per day) without
1162   requiring that the user agent's connection to the server persist
1163   until the process is completed. The entity returned with this
1164   response &SHOULD; include an indication of the request's current status
1165   and either a pointer to a status monitor or some estimate of when the
1166   user can expect the request to be fulfilled.
1167</t>
1168</section>
1169
1170<section title="203 Non-Authoritative Information" anchor="status.203">
1171  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1172  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1173<t>
1174   The returned metainformation in the entity-header is not the
1175   definitive set as available from the origin server, but is gathered
1176   from a local or a third-party copy. The set presented &MAY; be a subset
1177   or superset of the original version. For example, including local
1178   annotation information about the resource might result in a superset
1179   of the metainformation known by the origin server. Use of this
1180   response code is not required and is only appropriate when the
1181   response would otherwise be 200 (OK).
1182</t>
1183</section>
1184
1185<section title="204 No Content" anchor="status.204">
1186  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1187  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1188<t>
1189   The server has fulfilled the request but does not need to return an
1190   entity-body, and might want to return updated metainformation. The
1191   response &MAY; include new or updated metainformation in the form of
1192   entity-headers, which if present &SHOULD; be associated with the
1193   requested variant.
1194</t>
1195<t>
1196   If the client is a user agent, it &SHOULD-NOT;  change its document view
1197   from that which caused the request to be sent. This response is
1198   primarily intended to allow input for actions to take place without
1199   causing a change to the user agent's active document view, although
1200   any new or updated metainformation &SHOULD; be applied to the document
1201   currently in the user agent's active view.
1202</t>
1203<t>
1204   The 204 response &MUST-NOT; include a message-body, and thus is always
1205   terminated by the first empty line after the header fields.
1206</t>
1207</section>
1208
1209<section title="205 Reset Content" anchor="status.205">
1210  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1211  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1212<t>
1213   The server has fulfilled the request and the user agent &SHOULD; reset
1214   the document view which caused the request to be sent. This response
1215   is primarily intended to allow input for actions to take place via
1216   user input, followed by a clearing of the form in which the input is
1217   given so that the user can easily initiate another input action. The
1218   response &MUST-NOT; include an entity.
1219</t>
1220</section>
1221
1222<section title="206 Partial Content" anchor="status.206">
1223  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1224  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1225<t>
1226   The server has fulfilled the partial GET request for the resource
1227   and the enclosed entity is a partial representation as defined in &range;.
1228</t>
1229</section>
1230</section>
1231
1232<section title="Redirection 3xx" anchor="status.3xx">
1233<t>
1234   This class of status code indicates that further action needs to be
1235   taken by the user agent in order to fulfill the request.  The action
1236   required &MAY; be carried out by the user agent without interaction
1237   with the user if and only if the method used in the second request is
1238   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1239   such loops generate network traffic for each redirection.
1240  <list><t>
1241      <x:h>Note:</x:h> previous versions of this specification recommended a
1242      maximum of five redirections. Content developers should be aware
1243      that there might be clients that implement such a fixed
1244      limitation.
1245  </t></list>
1246</t>
1247
1248<section title="300 Multiple Choices" anchor="status.300">
1249  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1250  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1251<t>
1252   The requested resource corresponds to any one of a set of
1253   representations, each with its own specific location, and agent-driven
1254   negotiation information (&content-negotiation;) is being provided so that
1255   the user (or user agent) can select a preferred representation and
1256   redirect its request to that location.
1257</t>
1258<t>
1259   Unless it was a HEAD request, the response &SHOULD; include an entity
1260   containing a list of resource characteristics and location(s) from
1261   which the user or user agent can choose the one most appropriate. The
1262   entity format is specified by the media type given in the Content-Type
1263   header field. Depending upon the format and the capabilities of
1264   the user agent, selection of the most appropriate choice &MAY; be
1265   performed automatically. However, this specification does not define
1266   any standard for such automatic selection.
1267</t>
1268<t>
1269   If the server has a preferred choice of representation, it &SHOULD;
1270   include the specific URI for that representation in the Location
1271   field; user agents &MAY; use the Location field value for automatic
1272   redirection. This response is cacheable unless indicated otherwise.
1273</t>
1274</section>
1275
1276<section title="301 Moved Permanently" anchor="status.301">
1277  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1278  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1279<t>
1280   The requested resource has been assigned a new permanent URI and any
1281   future references to this resource &SHOULD; use one of the returned
1282   URIs.  Clients with link editing capabilities ought to automatically
1283   re-link references to the request-target to one or more of the new
1284   references returned by the server, where possible. This response is
1285   cacheable unless indicated otherwise.
1286</t>
1287<t>
1288   The new permanent URI &SHOULD; be given by the Location field in the
1289   response. Unless the request method was HEAD, the entity of the
1290   response &SHOULD; contain a short hypertext note with a hyperlink to
1291   the new URI(s).
1292</t>
1293<t>
1294   If the 301 status code is received in response to a request method
1295   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1296   then the request &MAY; be automatically redirected by the user agent without
1297   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1298   request unless it can be confirmed by the user, since this might
1299   change the conditions under which the request was issued.
1300  <list><t>
1301      <x:h>Note:</x:h> When automatically redirecting a POST request after
1302      receiving a 301 status code, some existing HTTP/1.0 user agents
1303      will erroneously change it into a GET request.
1304  </t></list>
1305</t>
1306</section>
1307
1308<section title="302 Found" anchor="status.302">
1309  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1310  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1311<t>
1312   The requested resource resides temporarily under a different URI.
1313   Since the redirection might be altered on occasion, the client &SHOULD;
1314   continue to use the request-target for future requests.  This response
1315   is only cacheable if indicated by a Cache-Control or Expires header
1316   field.
1317</t>
1318<t>
1319   The temporary URI &SHOULD; be given by the Location field in the
1320   response. Unless the request method was HEAD, the entity of the
1321   response &SHOULD; contain a short hypertext note with a hyperlink to
1322   the new URI(s).
1323</t>
1324<t>
1325   If the 302 status code is received in response to a request method
1326   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1327   then the request &MAY; be automatically redirected by the user agent without
1328   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1329   request unless it can be confirmed by the user, since this might
1330   change the conditions under which the request was issued.
1331  <list><t>
1332      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1333      to change the method on the redirected request.  However, most
1334      existing user agent implementations treat 302 as if it were a 303
1335      response, performing a GET on the Location field-value regardless
1336      of the original request method. The status codes 303 and 307 have
1337      been added for servers that wish to make unambiguously clear which
1338      kind of reaction is expected of the client.
1339  </t></list>
1340</t>
1341</section>
1342
1343<section title="303 See Other" anchor="status.303">
1344  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1345  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1346<t>
1347   The server directs the user agent to a different resource, indicated
1348   by a URI in the Location header field, that provides an indirect
1349   response to the original request.  The user agent &MAY; perform a GET
1350   request on the URI in the Location field in order to obtain a
1351   representation corresponding to the response, be redirected again,
1352   or end with an error status.  The Location URI is not a substitute
1353   reference for the originally requested resource.
1354</t>
1355<t>
1356   The 303 status is generally applicable to any HTTP method.  It is
1357   primarily used to allow the output of a POST action to redirect
1358   the user agent to a selected resource, since doing so provides the
1359   information corresponding to the POST response in a form that
1360   can be separately identified, bookmarked, and cached independent
1361   of the original request.
1362</t>
1363<t>
1364   A 303 response to a GET request indicates that the requested
1365   resource does not have a representation of its own that can be
1366   transferred by the server over HTTP.  The Location URI indicates a
1367   resource that is descriptive of the requested resource such that
1368   the follow-on representation may be useful without implying that
1369   it adequately represents the previously requested resource.
1370   Note that answers to the questions of what can be represented, what
1371   representations are adequate, and what might be a useful description
1372   are outside the scope of HTTP and thus entirely determined by the
1373   resource owner(s).
1374</t>
1375<t>
1376   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1377   cacheable by Cache-Control or Expires header fields.  Except for
1378   responses to a HEAD request, the entity of a 303 response &SHOULD;
1379   contain a short hypertext note with a hyperlink to the Location URI.
1380</t>
1381</section>
1382
1383<section title="304 Not Modified" anchor="status.304">
1384  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1385  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1386<t>
1387   The response to the request has not been modified since the conditions
1388   indicated by the client's conditional GET request, as defined in &conditional;.
1389</t>
1390</section>
1391
1392<section title="305 Use Proxy" anchor="status.305">
1393  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1394  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1395<t>
1396   The 305 status was defined in a previous version of this specification
1397   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1398</t>
1399</section>
1400
1401<section title="306 (Unused)" anchor="status.306">
1402  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1403  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1404<t>
1405   The 306 status code was used in a previous version of the
1406   specification, is no longer used, and the code is reserved.
1407</t>
1408</section>
1409
1410<section title="307 Temporary Redirect" anchor="status.307">
1411  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1412  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1413<t>
1414   The requested resource resides temporarily under a different URI.
1415   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1416   continue to use the request-target for future requests.  This response
1417   is only cacheable if indicated by a Cache-Control or Expires header
1418   field.
1419</t>
1420<t>
1421   The temporary URI &SHOULD; be given by the Location field in the
1422   response. Unless the request method was HEAD, the entity of the
1423   response &SHOULD; contain a short hypertext note with a hyperlink to
1424   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1425   understand the 307 status. Therefore, the note &SHOULD; contain the
1426   information necessary for a user to repeat the original request on
1427   the new URI.
1428</t>
1429<t>
1430   If the 307 status code is received in response to a request method
1431   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1432   then the request &MAY; be automatically redirected by the user agent without
1433   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1434   request unless it can be confirmed by the user, since this might
1435   change the conditions under which the request was issued.
1436</t>
1437</section>
1438</section>
1439
1440<section title="Client Error 4xx" anchor="status.4xx">
1441<t>
1442   The 4xx class of status code is intended for cases in which the
1443   client seems to have erred. Except when responding to a HEAD request,
1444   the server &SHOULD; include an entity containing an explanation of the
1445   error situation, and whether it is a temporary or permanent
1446   condition. These status codes are applicable to any request method.
1447   User agents &SHOULD; display any included entity to the user.
1448</t>
1449<t>
1450   If the client is sending data, a server implementation using TCP
1451   &SHOULD; be careful to ensure that the client acknowledges receipt of
1452   the packet(s) containing the response, before the server closes the
1453   input connection. If the client continues sending data to the server
1454   after the close, the server's TCP stack will send a reset packet to
1455   the client, which may erase the client's unacknowledged input buffers
1456   before they can be read and interpreted by the HTTP application.
1457</t>
1458
1459<section title="400 Bad Request" anchor="status.400">
1460  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1461  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1462<t>
1463   The request could not be understood by the server due to malformed
1464   syntax. The client &SHOULD-NOT;  repeat the request without
1465   modifications.
1466</t>
1467</section>
1468
1469<section title="401 Unauthorized" anchor="status.401">
1470  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1471  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1472<t>
1473   The request requires user authentication (see &auth;).
1474</t>
1475</section>
1476
1477<section title="402 Payment Required" anchor="status.402">
1478  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1479  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1480<t>
1481   This code is reserved for future use.
1482</t>
1483</section>
1484
1485<section title="403 Forbidden" anchor="status.403">
1486  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1487  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1488<t>
1489   The server understood the request, but is refusing to fulfill it.
1490   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1491   If the request method was not HEAD and the server wishes to make
1492   public why the request has not been fulfilled, it &SHOULD; describe the
1493   reason for the refusal in the entity.  If the server does not wish to
1494   make this information available to the client, the status code 404
1495   (Not Found) can be used instead.
1496</t>
1497</section>
1498
1499<section title="404 Not Found" anchor="status.404">
1500  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1501  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1502<t>
1503   The server has not found anything matching the request-target. No
1504   indication is given of whether the condition is temporary or
1505   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1506   knows, through some internally configurable mechanism, that an old
1507   resource is permanently unavailable and has no forwarding address.
1508   This status code is commonly used when the server does not wish to
1509   reveal exactly why the request has been refused, or when no other
1510   response is applicable.
1511</t>
1512</section>
1513
1514<section title="405 Method Not Allowed" anchor="status.405">
1515  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1516  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1517<t>
1518   The method specified in the Request-Line is not allowed for the
1519   resource identified by the request-target. The response &MUST; include an
1520   Allow header containing a list of valid methods for the requested
1521   resource.
1522</t>
1523</section>
1524
1525<section title="406 Not Acceptable" anchor="status.406">
1526  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1527  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1528<t>
1529   The resource identified by the request is only capable of generating
1530   response entities which have content characteristics not acceptable
1531   according to the accept headers sent in the request.
1532</t>
1533<t>
1534   Unless it was a HEAD request, the response &SHOULD; include an entity
1535   containing a list of available entity characteristics and location(s)
1536   from which the user or user agent can choose the one most
1537   appropriate. The entity format is specified by the media type given
1538   in the Content-Type header field. Depending upon the format and the
1539   capabilities of the user agent, selection of the most appropriate
1540   choice &MAY; be performed automatically. However, this specification
1541   does not define any standard for such automatic selection.
1542  <list><t>
1543      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1544      not acceptable according to the accept headers sent in the
1545      request. In some cases, this may even be preferable to sending a
1546      406 response. User agents are encouraged to inspect the headers of
1547      an incoming response to determine if it is acceptable.
1548  </t></list>
1549</t>
1550<t>
1551   If the response could be unacceptable, a user agent &SHOULD;
1552   temporarily stop receipt of more data and query the user for a
1553   decision on further actions.
1554</t>
1555</section>
1556
1557<section title="407 Proxy Authentication Required" anchor="status.407">
1558  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1559  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1560<t>
1561   This code is similar to 401 (Unauthorized), but indicates that the
1562   client must first authenticate itself with the proxy (see &auth;).
1563</t>
1564</section>
1565
1566<section title="408 Request Timeout" anchor="status.408">
1567  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1568  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1569<t>
1570   The client did not produce a request within the time that the server
1571   was prepared to wait. The client &MAY; repeat the request without
1572   modifications at any later time.
1573</t>
1574</section>
1575
1576<section title="409 Conflict" anchor="status.409">
1577  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1578  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1579<t>
1580   The request could not be completed due to a conflict with the current
1581   state of the resource. This code is only allowed in situations where
1582   it is expected that the user might be able to resolve the conflict
1583   and resubmit the request. The response body &SHOULD; include enough
1584   information for the user to recognize the source of the conflict.
1585   Ideally, the response entity would include enough information for the
1586   user or user agent to fix the problem; however, that might not be
1587   possible and is not required.
1588</t>
1589<t>
1590   Conflicts are most likely to occur in response to a PUT request. For
1591   example, if versioning were being used and the entity being PUT
1592   included changes to a resource which conflict with those made by an
1593   earlier (third-party) request, the server might use the 409 response
1594   to indicate that it can't complete the request. In this case, the
1595   response entity would likely contain a list of the differences
1596   between the two versions in a format defined by the response
1597   Content-Type.
1598</t>
1599</section>
1600
1601<section title="410 Gone" anchor="status.410">
1602  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1603  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1604<t>
1605   The requested resource is no longer available at the server and no
1606   forwarding address is known. This condition is expected to be
1607   considered permanent. Clients with link editing capabilities &SHOULD;
1608   delete references to the request-target after user approval. If the
1609   server does not know, or has no facility to determine, whether or not
1610   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1611   used instead. This response is cacheable unless indicated otherwise.
1612</t>
1613<t>
1614   The 410 response is primarily intended to assist the task of web
1615   maintenance by notifying the recipient that the resource is
1616   intentionally unavailable and that the server owners desire that
1617   remote links to that resource be removed. Such an event is common for
1618   limited-time, promotional services and for resources belonging to
1619   individuals no longer working at the server's site. It is not
1620   necessary to mark all permanently unavailable resources as "gone" or
1621   to keep the mark for any length of time -- that is left to the
1622   discretion of the server owner.
1623</t>
1624</section>
1625
1626<section title="411 Length Required" anchor="status.411">
1627  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1628  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1629<t>
1630   The server refuses to accept the request without a defined Content-Length.
1631   The client &MAY; repeat the request if it adds a valid
1632   Content-Length header field containing the length of the message-body
1633   in the request message.
1634</t>
1635</section>
1636
1637<section title="412 Precondition Failed" anchor="status.412">
1638  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1639  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1640<t>
1641   The precondition given in one or more of the request-header fields
1642   evaluated to false when it was tested on the server, as defined in
1643   &conditional;.
1644</t>
1645</section>
1646
1647<section title="413 Request Entity Too Large" anchor="status.413">
1648  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1649  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1650<t>
1651   The server is refusing to process a request because the request
1652   entity is larger than the server is willing or able to process. The
1653   server &MAY; close the connection to prevent the client from continuing
1654   the request.
1655</t>
1656<t>
1657   If the condition is temporary, the server &SHOULD; include a Retry-After
1658   header field to indicate that it is temporary and after what
1659   time the client &MAY; try again.
1660</t>
1661</section>
1662
1663<section title="414 Request-target Too Long" anchor="status.414">
1664  <iref primary="true" item="414 Request-target Too Long (status code)" x:for-anchor=""/>
1665  <iref primary="true" item="Status Codes" subitem="414 Request-target Too Long" x:for-anchor=""/>
1666<t>
1667   The server is refusing to service the request because the request-target
1668   is longer than the server is willing to interpret. This rare
1669   condition is only likely to occur when a client has improperly
1670   converted a POST request to a GET request with long query
1671   information, when the client has descended into a URI "black hole" of
1672   redirection (e.g., a redirected URI prefix that points to a suffix of
1673   itself), or when the server is under attack by a client attempting to
1674   exploit security holes present in some servers using fixed-length
1675   buffers for reading or manipulating the request-target.
1676</t>
1677</section>
1678
1679<section title="415 Unsupported Media Type" anchor="status.415">
1680  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1682<t>
1683   The server is refusing to service the request because the entity of
1684   the request is in a format not supported by the requested resource
1685   for the requested method.
1686</t>
1687</section>
1688
1689<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1690  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1691  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1692<t>
1693   The request included a Range request-header field (&header-range;) and none of
1694   the range-specifier values in this field overlap the current extent
1695   of the selected resource.
1696</t>
1697</section>
1698
1699<section title="417 Expectation Failed" anchor="status.417">
1700  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1701  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1702<t>
1703   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1704   could not be met by this server, or, if the server is a proxy,
1705   the server has unambiguous evidence that the request could not be met
1706   by the next-hop server.
1707</t>
1708</section>
1709</section>
1710
1711<section title="Server Error 5xx" anchor="status.5xx">
1712<t>
1713   Response status codes beginning with the digit "5" indicate cases in
1714   which the server is aware that it has erred or is incapable of
1715   performing the request. Except when responding to a HEAD request, the
1716   server &SHOULD; include an entity containing an explanation of the
1717   error situation, and whether it is a temporary or permanent
1718   condition. User agents &SHOULD; display any included entity to the
1719   user. These response codes are applicable to any request method.
1720</t>
1721
1722<section title="500 Internal Server Error" anchor="status.500">
1723  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1724  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1725<t>
1726   The server encountered an unexpected condition which prevented it
1727   from fulfilling the request.
1728</t>
1729</section>
1730
1731<section title="501 Not Implemented" anchor="status.501">
1732  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1733  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1734<t>
1735   The server does not support the functionality required to fulfill the
1736   request. This is the appropriate response when the server does not
1737   recognize the request method and is not capable of supporting it for
1738   any resource.
1739</t>
1740</section>
1741
1742<section title="502 Bad Gateway" anchor="status.502">
1743  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1744  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1745<t>
1746   The server, while acting as a gateway or proxy, received an invalid
1747   response from the upstream server it accessed in attempting to
1748   fulfill the request.
1749</t>
1750</section>
1751
1752<section title="503 Service Unavailable" anchor="status.503">
1753  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1754  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1755<t>
1756   The server is currently unable to handle the request due to a
1757   temporary overloading or maintenance of the server. The implication
1758   is that this is a temporary condition which will be alleviated after
1759   some delay. If known, the length of the delay &MAY; be indicated in a
1760   Retry-After header. If no Retry-After is given, the client &SHOULD;
1761   handle the response as it would for a 500 response.
1762  <list><t>
1763      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1764      server must use it when becoming overloaded. Some servers may wish
1765      to simply refuse the connection.
1766  </t></list>
1767</t>
1768</section>
1769
1770<section title="504 Gateway Timeout" anchor="status.504">
1771  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1773<t>
1774   The server, while acting as a gateway or proxy, did not receive a
1775   timely response from the upstream server specified by the URI (e.g.
1776   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1777   to access in attempting to complete the request.
1778  <list><t>
1779      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1780      return 400 or 500 when DNS lookups time out.
1781  </t></list>
1782</t>
1783</section>
1784
1785<section title="505 HTTP Version Not Supported" anchor="status.505">
1786  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1787  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1788<t>
1789   The server does not support, or refuses to support, the protocol
1790   version that was used in the request message. The server is
1791   indicating that it is unable or unwilling to complete the request
1792   using the same major version as the client, as described in &http-version;,
1793   other than with this error message. The response &SHOULD; contain
1794   an entity describing why that version is not supported and what other
1795   protocols are supported by that server.
1796</t>
1797
1798</section>
1799</section>
1800</section>
1801
1802
1803<section title="Header Field Definitions" anchor="header.fields">
1804<t>
1805   This section defines the syntax and semantics of HTTP/1.1 header fields
1806   related to request and response semantics.
1807</t>
1808<t>
1809   For entity-header fields, both sender and recipient refer to either the
1810   client or the server, depending on who sends and who receives the entity.
1811</t>
1812
1813<section title="Allow" anchor="header.allow">
1814  <iref primary="true" item="Allow header" x:for-anchor=""/>
1815  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1816  <x:anchor-alias value="Allow"/>
1817  <x:anchor-alias value="Allow-v"/>
1818<t>
1819      The response-header field "Allow" lists the set of methods advertised as
1820      supported by the resource identified by the request-target. The purpose of
1821      this field is strictly to inform the recipient of valid methods
1822      associated with the resource. An Allow header field &MUST; be
1823      present in a 405 (Method Not Allowed) response.
1824</t>
1825<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1826  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1827  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1828</artwork></figure>
1829<t>
1830      Example of use:
1831</t>
1832<figure><artwork type="example">
1833  Allow: GET, HEAD, PUT
1834</artwork></figure>
1835<t>
1836      The actual set of allowed methods is defined
1837      by the origin server at the time of each request.
1838</t>
1839<t>
1840      A proxy &MUST-NOT; modify the Allow header field even if it does not
1841      understand all the methods specified, since the user agent might
1842      have other means of communicating with the origin server.
1843</t>
1844</section>
1845
1846<section title="Expect" anchor="header.expect">
1847  <iref primary="true" item="Expect header" x:for-anchor=""/>
1848  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1849  <x:anchor-alias value="Expect"/>
1850  <x:anchor-alias value="Expect-v"/>
1851  <x:anchor-alias value="expectation"/>
1852  <x:anchor-alias value="expectation-extension"/>
1853  <x:anchor-alias value="expect-params"/>
1854<t>
1855   The request-header field "Expect" is used to indicate that particular
1856   server behaviors are required by the client.
1857</t>
1858<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"/>
1859  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1860  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1861 
1862  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1863  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1864                           *<x:ref>expect-params</x:ref> ]
1865  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1866</artwork></figure>
1867<t>
1868   A server that does not understand or is unable to comply with any of
1869   the expectation values in the Expect field of a request &MUST; respond
1870   with appropriate error status. The server &MUST; respond with a 417
1871   (Expectation Failed) status if any of the expectations cannot be met
1872   or, if there are other problems with the request, some other 4xx
1873   status.
1874</t>
1875<t>
1876   This header field is defined with extensible syntax to allow for
1877   future extensions. If a server receives a request containing an
1878   Expect field that includes an expectation-extension that it does not
1879   support, it &MUST; respond with a 417 (Expectation Failed) status.
1880</t>
1881<t>
1882   Comparison of expectation values is case-insensitive for unquoted
1883   tokens (including the 100-continue token), and is case-sensitive for
1884   quoted-string expectation-extensions.
1885</t>
1886<t>
1887   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1888   return a 417 (Expectation Failed) status if it receives a request
1889   with an expectation that it cannot meet. However, the Expect
1890   request-header itself is end-to-end; it &MUST; be forwarded if the
1891   request is forwarded.
1892</t>
1893<t>
1894   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1895   Expect header.
1896</t>
1897<t>
1898   See &use100; for the use of the 100 (Continue) status.
1899</t>
1900</section>
1901
1902<section title="From" anchor="header.from">
1903  <iref primary="true" item="From header" x:for-anchor=""/>
1904  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1905  <x:anchor-alias value="From"/>
1906  <x:anchor-alias value="From-v"/>
1907  <x:anchor-alias value="mailbox"/>
1908<t>
1909   The request-header field "From", if given, &SHOULD; contain an Internet
1910   e-mail address for the human user who controls the requesting user
1911   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1912   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1913</t>
1914<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1915  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1916  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1917 
1918  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1919</artwork></figure>
1920<t>
1921   An example is:
1922</t>
1923<figure><artwork type="example">
1924  From: webmaster@example.org
1925</artwork></figure>
1926<t>
1927   This header field &MAY; be used for logging purposes and as a means for
1928   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1929   be used as an insecure form of access protection. The interpretation
1930   of this field is that the request is being performed on behalf of the
1931   person given, who accepts responsibility for the method performed. In
1932   particular, robot agents &SHOULD; include this header so that the
1933   person responsible for running the robot can be contacted if problems
1934   occur on the receiving end.
1935</t>
1936<t>
1937   The Internet e-mail address in this field &MAY; be separate from the
1938   Internet host which issued the request. For example, when a request
1939   is passed through a proxy the original issuer's address &SHOULD; be
1940   used.
1941</t>
1942<t>
1943   The client &SHOULD-NOT;  send the From header field without the user's
1944   approval, as it might conflict with the user's privacy interests or
1945   their site's security policy. It is strongly recommended that the
1946   user be able to disable, enable, and modify the value of this field
1947   at any time prior to a request.
1948</t>
1949</section>
1950
1951<section title="Location" anchor="header.location">
1952  <iref primary="true" item="Location header" x:for-anchor=""/>
1953  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1954  <x:anchor-alias value="Location"/>
1955  <x:anchor-alias value="Location-v"/>
1956<t>
1957   The response-header field "Location" is used for the identification of a
1958   new resource or to redirect the recipient to a location other than the
1959   request-target for completion of the request.  For 201 (Created)
1960   responses, the Location is that of the new resource which was created
1961   by the request. For 3xx responses, the location &SHOULD; indicate the
1962   server's preferred URI for automatic redirection to the resource. The
1963   field value consists of a single absolute URI.
1964</t>
1965<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1966  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1967  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1968</artwork></figure>
1969<t>
1970   An example is:
1971</t>
1972<figure><artwork type="example">
1973  Location: http://www.example.org/pub/WWW/People.html
1974</artwork></figure>
1975<t>
1976  <list><t>
1977      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1978      from Location in that the Content-Location identifies the original
1979      location of the entity enclosed in the response. It is therefore
1980      possible for a response to contain header fields for both Location
1981      and Content-Location.
1982  </t></list>
1983</t>
1984<t>
1985   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1986   <list style="symbols">
1987      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1988      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1989      <t>With 305 Use Proxy.</t>
1990   </list>
1991</t>
1992</section>
1993
1994<section title="Max-Forwards" anchor="header.max-forwards">
1995  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1996  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1997  <x:anchor-alias value="Max-Forwards"/>
1998  <x:anchor-alias value="Max-Forwards-v"/>
1999<t>
2000   The request-header "Max-Forwards" field provides a mechanism with the
2001   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2002   number of proxies or gateways that can forward the request to the
2003   next inbound server. This can be useful when the client is attempting
2004   to trace a request chain which appears to be failing or looping in
2005   mid-chain.
2006</t>
2007<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2008  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2009  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2010</artwork></figure>
2011<t>
2012   The Max-Forwards value is a decimal integer indicating the remaining
2013   number of times this request message may be forwarded.
2014</t>
2015<t>
2016   Each proxy or gateway recipient of a TRACE or OPTIONS request
2017   containing a Max-Forwards header field &MUST; check and update its
2018   value prior to forwarding the request. If the received value is zero
2019   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2020   respond as the final recipient. If the received Max-Forwards value is
2021   greater than zero, then the forwarded message &MUST; contain an updated
2022   Max-Forwards field with a value decremented by one (1).
2023</t>
2024<t>
2025   The Max-Forwards header field &MAY; be ignored for all other methods
2026   defined by this specification and for any extension methods for which
2027   it is not explicitly referred to as part of that method definition.
2028</t>
2029</section>
2030
2031<section title="Referer" anchor="header.referer">
2032  <iref primary="true" item="Referer header" x:for-anchor=""/>
2033  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2034  <x:anchor-alias value="Referer"/>
2035  <x:anchor-alias value="Referer-v"/>
2036<t>
2037   The request-header field "Referer" [sic] allows the client to specify,
2038   for the server's benefit, the address (URI) of the resource from
2039   which the request-target was obtained (the "referrer", although the
2040   header field is misspelled.) The Referer request-header allows a
2041   server to generate lists of back-links to resources for interest,
2042   logging, optimized caching, etc. It also allows obsolete or mistyped
2043   links to be traced for maintenance. The Referer field &MUST-NOT; be
2044   sent if the request-target was obtained from a source that does not have
2045   its own URI, such as input from the user keyboard.
2046</t>
2047<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2048  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2049  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2050</artwork></figure>
2051<t>
2052   Example:
2053</t>
2054<figure><artwork type="example">
2055  Referer: http://www.example.org/hypertext/Overview.html
2056</artwork></figure>
2057<t>
2058   If the field value is a relative URI, it &SHOULD; be interpreted
2059   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2060   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2061</t>
2062</section>
2063
2064<section title="Retry-After" anchor="header.retry-after">
2065  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2066  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2067  <x:anchor-alias value="Retry-After"/>
2068  <x:anchor-alias value="Retry-After-v"/>
2069<t>
2070   The response-header "Retry-After" field can be used with a 503 (Service
2071   Unavailable) response to indicate how long the service is expected to
2072   be unavailable to the requesting client. This field &MAY; also be used
2073   with any 3xx (Redirection) response to indicate the minimum time the
2074   user-agent is asked wait before issuing the redirected request. The
2075   value of this field can be either an HTTP-date or an integer number
2076   of seconds (in decimal) after the time of the response.
2077</t>
2078<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2079  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2080  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2081</artwork></figure>
2082<t anchor="rule.delta-seconds">
2083  <x:anchor-alias value="delta-seconds"/>
2084   Time spans are non-negative decimal integers, representing time in
2085   seconds.
2086</t>
2087<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2088  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2089</artwork></figure>
2090<t>
2091   Two examples of its use are
2092</t>
2093<figure><artwork type="example">
2094  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2095  Retry-After: 120
2096</artwork></figure>
2097<t>
2098   In the latter example, the delay is 2 minutes.
2099</t>
2100</section>
2101
2102<section title="Server" anchor="header.server">
2103  <iref primary="true" item="Server header" x:for-anchor=""/>
2104  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2105  <x:anchor-alias value="Server"/>
2106  <x:anchor-alias value="Server-v"/>
2107<t>
2108   The response-header field "Server" contains information about the
2109   software used by the origin server to handle the request. The field
2110   can contain multiple product tokens (&product-tokens;) and comments
2111   identifying the server and any significant subproducts. The product
2112   tokens are listed in order of their significance for identifying the
2113   application.
2114</t>
2115<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2116  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2117  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2118                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2119</artwork></figure>
2120<t>
2121   Example:
2122</t>
2123<figure><artwork type="example">
2124  Server: CERN/3.0 libwww/2.17
2125</artwork></figure>
2126<t>
2127   If the response is being forwarded through a proxy, the proxy
2128   application &MUST-NOT; modify the Server response-header. Instead, it
2129   &MUST; include a Via field (as described in &header-via;).
2130  <list><t>
2131      <x:h>Note:</x:h> Revealing the specific software version of the server might
2132      allow the server machine to become more vulnerable to attacks
2133      against software that is known to contain security holes. Server
2134      implementors are encouraged to make this field a configurable
2135      option.
2136  </t></list>
2137</t>
2138</section>
2139
2140<section title="User-Agent" anchor="header.user-agent">
2141  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2142  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2143  <x:anchor-alias value="User-Agent"/>
2144  <x:anchor-alias value="User-Agent-v"/>
2145<t>
2146   The request-header field "User-Agent" contains information about the
2147   user agent originating the request. This is for statistical purposes,
2148   the tracing of protocol violations, and automated recognition of user
2149   agents for the sake of tailoring responses to avoid particular user
2150   agent limitations. User agents &SHOULD; include this field with
2151   requests. The field can contain multiple product tokens (&product-tokens;)
2152   and comments identifying the agent and any subproducts which form a
2153   significant part of the user agent. By convention, the product tokens
2154   are listed in order of their significance for identifying the
2155   application.
2156</t>
2157<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2158  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2159  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2160                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2161</artwork></figure>
2162<t>
2163   Example:
2164</t>
2165<figure><artwork type="example">
2166  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2167</artwork></figure>
2168</section>
2169
2170</section>
2171
2172<section title="IANA Considerations" anchor="IANA.considerations">
2173
2174<section title="Method Registry" anchor="method.registration">
2175<t>
2176  The registration procedure for HTTP Methods is defined by
2177  <xref target="method.registry"/> of this document.
2178</t>
2179<t>
2180   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2181   should be populated with the registrations below:
2182</t>
2183<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2184<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2185   <ttcol>Method</ttcol>
2186   <ttcol>Safe</ttcol>
2187   <ttcol>Reference</ttcol>
2188   <c>CONNECT</c>
2189   <c>no</c>
2190   <c>
2191      <xref target="CONNECT"/>
2192   </c>
2193   <c>DELETE</c>
2194   <c>no</c>
2195   <c>
2196      <xref target="DELETE"/>
2197   </c>
2198   <c>GET</c>
2199   <c>yes</c>
2200   <c>
2201      <xref target="GET"/>
2202   </c>
2203   <c>HEAD</c>
2204   <c>yes</c>
2205   <c>
2206      <xref target="HEAD"/>
2207   </c>
2208   <c>OPTIONS</c>
2209   <c>yes</c>
2210   <c>
2211      <xref target="OPTIONS"/>
2212   </c>
2213   <c>POST</c>
2214   <c>no</c>
2215   <c>
2216      <xref target="POST"/>
2217   </c>
2218   <c>PUT</c>
2219   <c>no</c>
2220   <c>
2221      <xref target="PUT"/>
2222   </c>
2223   <c>TRACE</c>
2224   <c>yes</c>
2225   <c>
2226      <xref target="TRACE"/>
2227   </c>
2228</texttable>
2229<!--(END)-->
2230</section>
2231
2232<section title="Status Code Registry" anchor="status.code.registration">
2233<t>
2234   The registration procedure for HTTP Status Codes -- previously defined
2235   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2236   by <xref target="status.code.registry"/> of this document.
2237</t>
2238<t>
2239   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2240   should be updated with the registrations below:
2241</t>
2242<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2243<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2244   <ttcol>Value</ttcol>
2245   <ttcol>Description</ttcol>
2246   <ttcol>Reference</ttcol>
2247   <c>100</c>
2248   <c>Continue</c>
2249   <c>
2250      <xref target="status.100"/>
2251   </c>
2252   <c>101</c>
2253   <c>Switching Protocols</c>
2254   <c>
2255      <xref target="status.101"/>
2256   </c>
2257   <c>200</c>
2258   <c>OK</c>
2259   <c>
2260      <xref target="status.200"/>
2261   </c>
2262   <c>201</c>
2263   <c>Created</c>
2264   <c>
2265      <xref target="status.201"/>
2266   </c>
2267   <c>202</c>
2268   <c>Accepted</c>
2269   <c>
2270      <xref target="status.202"/>
2271   </c>
2272   <c>203</c>
2273   <c>Non-Authoritative Information</c>
2274   <c>
2275      <xref target="status.203"/>
2276   </c>
2277   <c>204</c>
2278   <c>No Content</c>
2279   <c>
2280      <xref target="status.204"/>
2281   </c>
2282   <c>205</c>
2283   <c>Reset Content</c>
2284   <c>
2285      <xref target="status.205"/>
2286   </c>
2287   <c>206</c>
2288   <c>Partial Content</c>
2289   <c>
2290      <xref target="status.206"/>
2291   </c>
2292   <c>300</c>
2293   <c>Multiple Choices</c>
2294   <c>
2295      <xref target="status.300"/>
2296   </c>
2297   <c>301</c>
2298   <c>Moved Permanently</c>
2299   <c>
2300      <xref target="status.301"/>
2301   </c>
2302   <c>302</c>
2303   <c>Found</c>
2304   <c>
2305      <xref target="status.302"/>
2306   </c>
2307   <c>303</c>
2308   <c>See Other</c>
2309   <c>
2310      <xref target="status.303"/>
2311   </c>
2312   <c>304</c>
2313   <c>Not Modified</c>
2314   <c>
2315      <xref target="status.304"/>
2316   </c>
2317   <c>305</c>
2318   <c>Use Proxy</c>
2319   <c>
2320      <xref target="status.305"/>
2321   </c>
2322   <c>306</c>
2323   <c>(Unused)</c>
2324   <c>
2325      <xref target="status.306"/>
2326   </c>
2327   <c>307</c>
2328   <c>Temporary Redirect</c>
2329   <c>
2330      <xref target="status.307"/>
2331   </c>
2332   <c>400</c>
2333   <c>Bad Request</c>
2334   <c>
2335      <xref target="status.400"/>
2336   </c>
2337   <c>401</c>
2338   <c>Unauthorized</c>
2339   <c>
2340      <xref target="status.401"/>
2341   </c>
2342   <c>402</c>
2343   <c>Payment Required</c>
2344   <c>
2345      <xref target="status.402"/>
2346   </c>
2347   <c>403</c>
2348   <c>Forbidden</c>
2349   <c>
2350      <xref target="status.403"/>
2351   </c>
2352   <c>404</c>
2353   <c>Not Found</c>
2354   <c>
2355      <xref target="status.404"/>
2356   </c>
2357   <c>405</c>
2358   <c>Method Not Allowed</c>
2359   <c>
2360      <xref target="status.405"/>
2361   </c>
2362   <c>406</c>
2363   <c>Not Acceptable</c>
2364   <c>
2365      <xref target="status.406"/>
2366   </c>
2367   <c>407</c>
2368   <c>Proxy Authentication Required</c>
2369   <c>
2370      <xref target="status.407"/>
2371   </c>
2372   <c>408</c>
2373   <c>Request Timeout</c>
2374   <c>
2375      <xref target="status.408"/>
2376   </c>
2377   <c>409</c>
2378   <c>Conflict</c>
2379   <c>
2380      <xref target="status.409"/>
2381   </c>
2382   <c>410</c>
2383   <c>Gone</c>
2384   <c>
2385      <xref target="status.410"/>
2386   </c>
2387   <c>411</c>
2388   <c>Length Required</c>
2389   <c>
2390      <xref target="status.411"/>
2391   </c>
2392   <c>412</c>
2393   <c>Precondition Failed</c>
2394   <c>
2395      <xref target="status.412"/>
2396   </c>
2397   <c>413</c>
2398   <c>Request Entity Too Large</c>
2399   <c>
2400      <xref target="status.413"/>
2401   </c>
2402   <c>414</c>
2403   <c>Request-target Too Long</c>
2404   <c>
2405      <xref target="status.414"/>
2406   </c>
2407   <c>415</c>
2408   <c>Unsupported Media Type</c>
2409   <c>
2410      <xref target="status.415"/>
2411   </c>
2412   <c>416</c>
2413   <c>Requested Range Not Satisfiable</c>
2414   <c>
2415      <xref target="status.416"/>
2416   </c>
2417   <c>417</c>
2418   <c>Expectation Failed</c>
2419   <c>
2420      <xref target="status.417"/>
2421   </c>
2422   <c>500</c>
2423   <c>Internal Server Error</c>
2424   <c>
2425      <xref target="status.500"/>
2426   </c>
2427   <c>501</c>
2428   <c>Not Implemented</c>
2429   <c>
2430      <xref target="status.501"/>
2431   </c>
2432   <c>502</c>
2433   <c>Bad Gateway</c>
2434   <c>
2435      <xref target="status.502"/>
2436   </c>
2437   <c>503</c>
2438   <c>Service Unavailable</c>
2439   <c>
2440      <xref target="status.503"/>
2441   </c>
2442   <c>504</c>
2443   <c>Gateway Timeout</c>
2444   <c>
2445      <xref target="status.504"/>
2446   </c>
2447   <c>505</c>
2448   <c>HTTP Version Not Supported</c>
2449   <c>
2450      <xref target="status.505"/>
2451   </c>
2452</texttable>
2453<!--(END)-->
2454</section>
2455<section title="Message Header Registration" anchor="message.header.registration">
2456<t>
2457   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2458   with the permanent registrations below (see <xref target="RFC3864"/>):
2459</t>
2460<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2461<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2462   <ttcol>Header Field Name</ttcol>
2463   <ttcol>Protocol</ttcol>
2464   <ttcol>Status</ttcol>
2465   <ttcol>Reference</ttcol>
2466   <c>Allow</c>
2467   <c>http</c>
2468   <c>standard</c>
2469   <c>
2470      <xref target="header.allow"/>
2471   </c>
2472   <c>Expect</c>
2473   <c>http</c>
2474   <c>standard</c>
2475   <c>
2476      <xref target="header.expect"/>
2477   </c>
2478   <c>From</c>
2479   <c>http</c>
2480   <c>standard</c>
2481   <c>
2482      <xref target="header.from"/>
2483   </c>
2484   <c>Location</c>
2485   <c>http</c>
2486   <c>standard</c>
2487   <c>
2488      <xref target="header.location"/>
2489   </c>
2490   <c>Max-Forwards</c>
2491   <c>http</c>
2492   <c>standard</c>
2493   <c>
2494      <xref target="header.max-forwards"/>
2495   </c>
2496   <c>Referer</c>
2497   <c>http</c>
2498   <c>standard</c>
2499   <c>
2500      <xref target="header.referer"/>
2501   </c>
2502   <c>Retry-After</c>
2503   <c>http</c>
2504   <c>standard</c>
2505   <c>
2506      <xref target="header.retry-after"/>
2507   </c>
2508   <c>Server</c>
2509   <c>http</c>
2510   <c>standard</c>
2511   <c>
2512      <xref target="header.server"/>
2513   </c>
2514   <c>User-Agent</c>
2515   <c>http</c>
2516   <c>standard</c>
2517   <c>
2518      <xref target="header.user-agent"/>
2519   </c>
2520</texttable>
2521<!--(END)-->
2522<t>
2523   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2524</t>
2525</section>
2526</section>
2527
2528<section title="Security Considerations" anchor="security.considerations">
2529<t>
2530   This section is meant to inform application developers, information
2531   providers, and users of the security limitations in HTTP/1.1 as
2532   described by this document. The discussion does not include
2533   definitive solutions to the problems revealed, though it does make
2534   some suggestions for reducing security risks.
2535</t>
2536
2537<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2538<t>
2539   Like any generic data transfer protocol, HTTP cannot regulate the
2540   content of the data that is transferred, nor is there any a priori
2541   method of determining the sensitivity of any particular piece of
2542   information within the context of any given request. Therefore,
2543   applications &SHOULD; supply as much control over this information as
2544   possible to the provider of that information. Four header fields are
2545   worth special mention in this context: Server, Via, Referer and From.
2546</t>
2547<t>
2548   Revealing the specific software version of the server might allow the
2549   server machine to become more vulnerable to attacks against software
2550   that is known to contain security holes. Implementors &SHOULD; make the
2551   Server header field a configurable option.
2552</t>
2553<t>
2554   Proxies which serve as a portal through a network firewall &SHOULD;
2555   take special precautions regarding the transfer of header information
2556   that identifies the hosts behind the firewall. In particular, they
2557   &SHOULD; remove, or replace with sanitized versions, any Via fields
2558   generated behind the firewall.
2559</t>
2560<t>
2561   The Referer header allows reading patterns to be studied and reverse
2562   links drawn. Although it can be very useful, its power can be abused
2563   if user details are not separated from the information contained in
2564   the Referer. Even when the personal information has been removed, the
2565   Referer header might indicate a private document's URI whose
2566   publication would be inappropriate.
2567</t>
2568<t>
2569   The information sent in the From field might conflict with the user's
2570   privacy interests or their site's security policy, and hence it
2571   &SHOULD-NOT;  be transmitted without the user being able to disable,
2572   enable, and modify the contents of the field. The user &MUST; be able
2573   to set the contents of this field within a user preference or
2574   application defaults configuration.
2575</t>
2576<t>
2577   We suggest, though do not require, that a convenient toggle interface
2578   be provided for the user to enable or disable the sending of From and
2579   Referer information.
2580</t>
2581<t>
2582   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2583   fields can sometimes be used to determine that a specific client or
2584   server have a particular security hole which might be exploited.
2585   Unfortunately, this same information is often used for other valuable
2586   purposes for which HTTP currently has no better mechanism.
2587</t>
2588</section>
2589
2590<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2591<t>
2592   Because the source of a link might be private information or might
2593   reveal an otherwise private information source, it is strongly
2594   recommended that the user be able to select whether or not the
2595   Referer field is sent. For example, a browser client could have a
2596   toggle switch for browsing openly/anonymously, which would
2597   respectively enable/disable the sending of Referer and From
2598   information.
2599</t>
2600<t>
2601   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2602   HTTP request if the referring page was transferred with a secure
2603   protocol.
2604</t>
2605<t>
2606   Authors of services should not use
2607   GET-based forms for the submission of sensitive data because that
2608   data will be encoded in the Request-target. Many existing
2609   servers, proxies, and user agents log or display the Request-target in
2610   places where it might be visible to third parties. Such services can
2611   use POST-based form submission instead.
2612</t>
2613</section>
2614
2615<section title="Location Headers and Spoofing" anchor="location.spoofing">
2616<t>
2617   If a single server supports multiple organizations that do not trust
2618   one another, then it &MUST; check the values of Location and Content-Location
2619   headers in responses that are generated under control of
2620   said organizations to make sure that they do not attempt to
2621   invalidate resources over which they have no authority.
2622</t>
2623</section>
2624
2625</section>
2626
2627<section title="Acknowledgments" anchor="ack">
2628</section>
2629</middle>
2630<back>
2631
2632<references title="Normative References">
2633
2634<reference anchor="Part1">
2635  <front>
2636    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2637    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2638      <organization abbrev="Day Software">Day Software</organization>
2639      <address><email>fielding@gbiv.com</email></address>
2640    </author>
2641    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2642      <organization>One Laptop per Child</organization>
2643      <address><email>jg@laptop.org</email></address>
2644    </author>
2645    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2646      <organization abbrev="HP">Hewlett-Packard Company</organization>
2647      <address><email>JeffMogul@acm.org</email></address>
2648    </author>
2649    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2650      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2651      <address><email>henrikn@microsoft.com</email></address>
2652    </author>
2653    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2654      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2655      <address><email>LMM@acm.org</email></address>
2656    </author>
2657    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2658      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2659      <address><email>paulle@microsoft.com</email></address>
2660    </author>
2661    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2662      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2663      <address><email>timbl@w3.org</email></address>
2664    </author>
2665    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2666      <organization abbrev="W3C">World Wide Web Consortium</organization>
2667      <address><email>ylafon@w3.org</email></address>
2668    </author>
2669    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2670      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2671      <address><email>julian.reschke@greenbytes.de</email></address>
2672    </author>
2673    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2674  </front>
2675  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2676  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2677</reference>
2678
2679<reference anchor="Part3">
2680  <front>
2681    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2682    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2683      <organization abbrev="Day Software">Day Software</organization>
2684      <address><email>fielding@gbiv.com</email></address>
2685    </author>
2686    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2687      <organization>One Laptop per Child</organization>
2688      <address><email>jg@laptop.org</email></address>
2689    </author>
2690    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2691      <organization abbrev="HP">Hewlett-Packard Company</organization>
2692      <address><email>JeffMogul@acm.org</email></address>
2693    </author>
2694    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2695      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2696      <address><email>henrikn@microsoft.com</email></address>
2697    </author>
2698    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2699      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2700      <address><email>LMM@acm.org</email></address>
2701    </author>
2702    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2703      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2704      <address><email>paulle@microsoft.com</email></address>
2705    </author>
2706    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2707      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2708      <address><email>timbl@w3.org</email></address>
2709    </author>
2710    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2711      <organization abbrev="W3C">World Wide Web Consortium</organization>
2712      <address><email>ylafon@w3.org</email></address>
2713    </author>
2714    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2715      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2716      <address><email>julian.reschke@greenbytes.de</email></address>
2717    </author>
2718    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2719  </front>
2720  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2721  <x:source href="p3-payload.xml" basename="p3-payload"/>
2722</reference>
2723
2724<reference anchor="Part4">
2725  <front>
2726    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2727    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2728      <organization abbrev="Day Software">Day Software</organization>
2729      <address><email>fielding@gbiv.com</email></address>
2730    </author>
2731    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2732      <organization>One Laptop per Child</organization>
2733      <address><email>jg@laptop.org</email></address>
2734    </author>
2735    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2736      <organization abbrev="HP">Hewlett-Packard Company</organization>
2737      <address><email>JeffMogul@acm.org</email></address>
2738    </author>
2739    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2740      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2741      <address><email>henrikn@microsoft.com</email></address>
2742    </author>
2743    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2744      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2745      <address><email>LMM@acm.org</email></address>
2746    </author>
2747    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2748      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2749      <address><email>paulle@microsoft.com</email></address>
2750    </author>
2751    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2752      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2753      <address><email>timbl@w3.org</email></address>
2754    </author>
2755    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2756      <organization abbrev="W3C">World Wide Web Consortium</organization>
2757      <address><email>ylafon@w3.org</email></address>
2758    </author>
2759    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2760      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2761      <address><email>julian.reschke@greenbytes.de</email></address>
2762    </author>
2763    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2764  </front>
2765  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2766  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2767</reference>
2768
2769<reference anchor="Part5">
2770  <front>
2771    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2772    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2773      <organization abbrev="Day Software">Day Software</organization>
2774      <address><email>fielding@gbiv.com</email></address>
2775    </author>
2776    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2777      <organization>One Laptop per Child</organization>
2778      <address><email>jg@laptop.org</email></address>
2779    </author>
2780    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2781      <organization abbrev="HP">Hewlett-Packard Company</organization>
2782      <address><email>JeffMogul@acm.org</email></address>
2783    </author>
2784    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2785      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2786      <address><email>henrikn@microsoft.com</email></address>
2787    </author>
2788    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2789      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2790      <address><email>LMM@acm.org</email></address>
2791    </author>
2792    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2793      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2794      <address><email>paulle@microsoft.com</email></address>
2795    </author>
2796    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2797      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2798      <address><email>timbl@w3.org</email></address>
2799    </author>
2800    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2801      <organization abbrev="W3C">World Wide Web Consortium</organization>
2802      <address><email>ylafon@w3.org</email></address>
2803    </author>
2804    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2805      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2806      <address><email>julian.reschke@greenbytes.de</email></address>
2807    </author>
2808    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2809  </front>
2810  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2811  <x:source href="p5-range.xml" basename="p5-range"/>
2812</reference>
2813
2814<reference anchor="Part6">
2815  <front>
2816    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2817    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2818      <organization abbrev="Day Software">Day Software</organization>
2819      <address><email>fielding@gbiv.com</email></address>
2820    </author>
2821    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2822      <organization>One Laptop per Child</organization>
2823      <address><email>jg@laptop.org</email></address>
2824    </author>
2825    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2826      <organization abbrev="HP">Hewlett-Packard Company</organization>
2827      <address><email>JeffMogul@acm.org</email></address>
2828    </author>
2829    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2830      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2831      <address><email>henrikn@microsoft.com</email></address>
2832    </author>
2833    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2834      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2835      <address><email>LMM@acm.org</email></address>
2836    </author>
2837    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2838      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2839      <address><email>paulle@microsoft.com</email></address>
2840    </author>
2841    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2842      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2843      <address><email>timbl@w3.org</email></address>
2844    </author>
2845    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2846      <organization abbrev="W3C">World Wide Web Consortium</organization>
2847      <address><email>ylafon@w3.org</email></address>
2848    </author>
2849    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2850      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2851      <address><email>julian.reschke@greenbytes.de</email></address>
2852    </author>
2853    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2854  </front>
2855  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2856  <x:source href="p6-cache.xml" basename="p6-cache"/>
2857</reference>
2858
2859<reference anchor="Part7">
2860  <front>
2861    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2862    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2863      <organization abbrev="Day Software">Day Software</organization>
2864      <address><email>fielding@gbiv.com</email></address>
2865    </author>
2866    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2867      <organization>One Laptop per Child</organization>
2868      <address><email>jg@laptop.org</email></address>
2869    </author>
2870    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2871      <organization abbrev="HP">Hewlett-Packard Company</organization>
2872      <address><email>JeffMogul@acm.org</email></address>
2873    </author>
2874    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2875      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2876      <address><email>henrikn@microsoft.com</email></address>
2877    </author>
2878    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2879      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2880      <address><email>LMM@acm.org</email></address>
2881    </author>
2882    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2883      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2884      <address><email>paulle@microsoft.com</email></address>
2885    </author>
2886    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2887      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2888      <address><email>timbl@w3.org</email></address>
2889    </author>
2890    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2891      <organization abbrev="W3C">World Wide Web Consortium</organization>
2892      <address><email>ylafon@w3.org</email></address>
2893    </author>
2894    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2895      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2896      <address><email>julian.reschke@greenbytes.de</email></address>
2897    </author>
2898    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2899  </front>
2900  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2901  <x:source href="p7-auth.xml" basename="p7-auth"/>
2902</reference>
2903
2904<reference anchor="RFC2119">
2905  <front>
2906    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2907    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2908      <organization>Harvard University</organization>
2909      <address><email>sob@harvard.edu</email></address>
2910    </author>
2911    <date month="March" year="1997"/>
2912  </front>
2913  <seriesInfo name="BCP" value="14"/>
2914  <seriesInfo name="RFC" value="2119"/>
2915</reference>
2916
2917<reference anchor="RFC5234">
2918  <front>
2919    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2920    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2921      <organization>Brandenburg InternetWorking</organization>
2922      <address>
2923      <postal>
2924      <street>675 Spruce Dr.</street>
2925      <city>Sunnyvale</city>
2926      <region>CA</region>
2927      <code>94086</code>
2928      <country>US</country></postal>
2929      <phone>+1.408.246.8253</phone>
2930      <email>dcrocker@bbiw.net</email></address> 
2931    </author>
2932    <author initials="P." surname="Overell" fullname="Paul Overell">
2933      <organization>THUS plc.</organization>
2934      <address>
2935      <postal>
2936      <street>1/2 Berkeley Square</street>
2937      <street>99 Berkely Street</street>
2938      <city>Glasgow</city>
2939      <code>G3 7HR</code>
2940      <country>UK</country></postal>
2941      <email>paul.overell@thus.net</email></address>
2942    </author>
2943    <date month="January" year="2008"/>
2944  </front>
2945  <seriesInfo name="STD" value="68"/>
2946  <seriesInfo name="RFC" value="5234"/>
2947</reference>
2948
2949</references>
2950
2951<references title="Informative References">
2952
2953<reference anchor="RFC1945">
2954  <front>
2955    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2956    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2957      <organization>MIT, Laboratory for Computer Science</organization>
2958      <address><email>timbl@w3.org</email></address>
2959    </author>
2960    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2961      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2962      <address><email>fielding@ics.uci.edu</email></address>
2963    </author>
2964    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2965      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2966      <address><email>frystyk@w3.org</email></address>
2967    </author>
2968    <date month="May" year="1996"/>
2969  </front>
2970  <seriesInfo name="RFC" value="1945"/>
2971</reference>
2972
2973<reference anchor="RFC2068">
2974  <front>
2975    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2976    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2977      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2978      <address><email>fielding@ics.uci.edu</email></address>
2979    </author>
2980    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2981      <organization>MIT Laboratory for Computer Science</organization>
2982      <address><email>jg@w3.org</email></address>
2983    </author>
2984    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2985      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2986      <address><email>mogul@wrl.dec.com</email></address>
2987    </author>
2988    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2989      <organization>MIT Laboratory for Computer Science</organization>
2990      <address><email>frystyk@w3.org</email></address>
2991    </author>
2992    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2993      <organization>MIT Laboratory for Computer Science</organization>
2994      <address><email>timbl@w3.org</email></address>
2995    </author>
2996    <date month="January" year="1997"/>
2997  </front>
2998  <seriesInfo name="RFC" value="2068"/>
2999</reference>
3000
3001<reference anchor="RFC2616">
3002  <front>
3003    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3004    <author initials="R." surname="Fielding" fullname="R. Fielding">
3005      <organization>University of California, Irvine</organization>
3006      <address><email>fielding@ics.uci.edu</email></address>
3007    </author>
3008    <author initials="J." surname="Gettys" fullname="J. Gettys">
3009      <organization>W3C</organization>
3010      <address><email>jg@w3.org</email></address>
3011    </author>
3012    <author initials="J." surname="Mogul" fullname="J. Mogul">
3013      <organization>Compaq Computer Corporation</organization>
3014      <address><email>mogul@wrl.dec.com</email></address>
3015    </author>
3016    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3017      <organization>MIT Laboratory for Computer Science</organization>
3018      <address><email>frystyk@w3.org</email></address>
3019    </author>
3020    <author initials="L." surname="Masinter" fullname="L. Masinter">
3021      <organization>Xerox Corporation</organization>
3022      <address><email>masinter@parc.xerox.com</email></address>
3023    </author>
3024    <author initials="P." surname="Leach" fullname="P. Leach">
3025      <organization>Microsoft Corporation</organization>
3026      <address><email>paulle@microsoft.com</email></address>
3027    </author>
3028    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3029      <organization>W3C</organization>
3030      <address><email>timbl@w3.org</email></address>
3031    </author>
3032    <date month="June" year="1999"/>
3033  </front>
3034  <seriesInfo name="RFC" value="2616"/>
3035</reference>
3036
3037<reference anchor='RFC2817'>
3038  <front>
3039    <title>Upgrading to TLS Within HTTP/1.1</title>
3040    <author initials='R.' surname='Khare' fullname='R. Khare'>
3041      <organization>4K Associates / UC Irvine</organization>
3042      <address><email>rohit@4K-associates.com</email></address>
3043    </author>
3044    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3045      <organization>Agranat Systems, Inc.</organization>
3046      <address><email>lawrence@agranat.com</email></address>
3047    </author>
3048    <date year='2000' month='May' />
3049  </front>
3050  <seriesInfo name='RFC' value='2817' />
3051</reference>
3052
3053<reference anchor='RFC3864'>
3054  <front>
3055    <title>Registration Procedures for Message Header Fields</title>
3056    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3057      <organization>Nine by Nine</organization>
3058      <address><email>GK-IETF@ninebynine.org</email></address>
3059    </author>
3060    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3061      <organization>BEA Systems</organization>
3062      <address><email>mnot@pobox.com</email></address>
3063    </author>
3064    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3065      <organization>HP Labs</organization>
3066      <address><email>JeffMogul@acm.org</email></address>
3067    </author>
3068    <date year='2004' month='September' />
3069  </front>
3070  <seriesInfo name='BCP' value='90' />
3071  <seriesInfo name='RFC' value='3864' />
3072</reference>
3073
3074<reference anchor='RFC5226'>
3075  <front>
3076    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3077    <author initials='T.' surname='Narten' fullname='T. Narten'>
3078      <organization>IBM</organization>
3079      <address><email>narten@us.ibm.com</email></address>
3080    </author>
3081    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3082      <organization>Google</organization>
3083      <address><email>Harald@Alvestrand.no</email></address>
3084    </author>
3085    <date year='2008' month='May' />
3086  </front>
3087  <seriesInfo name='BCP' value='26' />
3088  <seriesInfo name='RFC' value='5226' />
3089</reference>
3090
3091<reference anchor="RFC5322">
3092  <front>
3093    <title>Internet Message Format</title>
3094    <author initials="P." surname="Resnick" fullname="P. Resnick">
3095      <organization>Qualcomm Incorporated</organization>
3096    </author>
3097    <date year="2008" month="October"/>
3098  </front> 
3099  <seriesInfo name="RFC" value="5322"/>
3100</reference>
3101
3102</references>
3103
3104<section title="Compatibility with Previous Versions" anchor="compatibility">
3105<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3106<t>
3107   Clarified which error code should be used for inbound server failures
3108   (e.g. DNS failures). (<xref target="status.504"/>).
3109</t>
3110<t>
3111   201 (Created) had a race that required an Etag be sent when a resource is
3112   first created. (<xref target="status.201"/>).
3113</t>
3114<t>
3115   Rewrite of message transmission requirements to make it much harder
3116   for implementors to get it wrong, as the consequences of errors here
3117   can have significant impact on the Internet, and to deal with the
3118   following problems:
3119  <list style="numbers">
3120      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3121         this was incorrectly placing a requirement on the behavior of
3122         an implementation of a future version of HTTP/1.x</t>
3123
3124      <t>Made it clear that user-agents should retry requests, not
3125         "clients" in general.</t>
3126
3127      <t>Converted requirements for clients to ignore unexpected 100
3128         (Continue) responses, and for proxies to forward 100 responses,
3129         into a general requirement for 1xx responses.</t>
3130
3131      <t>Modified some TCP-specific language, to make it clearer that
3132         non-TCP transports are possible for HTTP.</t>
3133
3134      <t>Require that the origin server &MUST-NOT; wait for the request
3135         body before it sends a required 100 (Continue) response.</t>
3136
3137      <t>Allow, rather than require, a server to omit 100 (Continue) if
3138         it has already seen some of the request body.</t>
3139
3140      <t>Allow servers to defend against denial-of-service attacks and
3141         broken clients.</t>
3142  </list>
3143</t>
3144<t>
3145   This change adds the Expect header and 417 status code.
3146</t>
3147<t>
3148   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3149   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3150</t>
3151<t>
3152   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
3153   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3154</t>
3155</section>
3156
3157<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3158<t>
3159  This document takes over the Status Code Registry, previously defined
3160  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3161  (<xref target="status.code.registry"/>)
3162</t>
3163<t>
3164  Clarify definition of POST.
3165  (<xref target="POST"/>)
3166</t>
3167<t>
3168  Failed to consider that there are
3169  many other request methods that are safe to automatically redirect,
3170  and further that the user agent is able to make that determination
3171  based on the request method semantics.
3172  (Sections <xref format="counter" target="status.301"/>,
3173  <xref format="counter" target="status.302"/> and
3174  <xref format="counter" target="status.307"/>)
3175</t>
3176<t>
3177  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3178  It used to indicate that the requested resource must be accessed through the
3179  proxy given by the Location field. The Location field gave the URI of the
3180  proxy. The recipient was expected to repeat this single request via the proxy.
3181  (<xref target="status.305"/>)
3182</t>
3183<t>
3184  Reclassify Allow header as response header, removing the option to
3185  specify it in a PUT request.
3186  Relax the server requirement on the contents of the Allow header and
3187  remove requirement on clients to always trust the header value.
3188  (<xref target="header.allow"/>)
3189</t>
3190<t>
3191  Correct syntax of Location header to allow fragment,
3192  as referred symbol wasn't what was expected, and add some
3193  clarifications as to when it would not be appropriate.
3194  (<xref target="header.location"/>)
3195</t>
3196<t>
3197  In the description of the Server header, the Via field
3198  was described as a SHOULD. The requirement was and is stated
3199  correctly in the description of the Via header in &header-via;.
3200  (<xref target="header.server"/>)
3201</t>
3202</section>
3203
3204</section>
3205
3206<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3207<figure>
3208<artwork type="abnf" name="p2-semantics.parsed-abnf">
3209<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3210<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3211<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3212<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3213<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3214<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 15.1&gt;
3215<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3216<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3217<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3218
3219<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3220<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3221<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3222
3223<x:ref>From</x:ref> = "From:" OWS From-v
3224<x:ref>From-v</x:ref> = mailbox
3225
3226<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;
3227<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.1&gt;
3228
3229<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3230<x:ref>If-Modified-Since</x:ref> = &lt;If-Modified-Since, defined in [Part4], Section
3231 6.3&gt;
3232<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3233<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3234<x:ref>If-Unmodified-Since</x:ref> = &lt;If-Unmodified-Since, defined in [Part4],
3235 Section 6.5&gt;
3236
3237<x:ref>Location</x:ref> = "Location:" OWS Location-v
3238<x:ref>Location-v</x:ref> = absolute-URI [ "#" fragment ]
3239
3240<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3241<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3242<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 /
3243 %x50.4F.53.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45
3244 / %x43.4F.4E.4E.45.43.54 / extension-method
3245
3246<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3247
3248<x:ref>Proxy-Authenticate</x:ref> = &lt;Proxy-Authenticate, defined in [Part7], Section
3249 3.2&gt;
3250<x:ref>Proxy-Authorization</x:ref> = &lt;Proxy-Authorization, defined in [Part7],
3251 Section 3.3&gt;
3252
3253<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3254<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3255<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3256<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3257<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3258<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3259<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3260
3261<x:ref>Server</x:ref> = "Server:" OWS Server-v
3262<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3263<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3264 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3265 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3266 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3267 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3268 "505" / extension-code
3269
3270<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 8.8&gt;
3271
3272<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3273<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3274
3275<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 15.5&gt;
3276
3277<x:ref>WWW-Authenticate</x:ref> = &lt;WWW-Authenticate, defined in [Part7], Section
3278 3.4&gt;
3279
3280<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;
3281
3282<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 1.2.2&gt;
3283
3284<x:ref>delta-seconds</x:ref> = 1*DIGIT
3285
3286<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3287<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3288<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3289 *expect-params ]
3290<x:ref>extension-code</x:ref> = 3DIGIT
3291<x:ref>extension-method</x:ref> = token
3292
3293<x:ref>fragment</x:ref> = &lt;fragment, defined in [Part1], Section 2.1&gt;
3294
3295<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3296
3297<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3298
3299<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.1&gt;
3300<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 3.4&gt;
3301
3302<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3303
3304<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3305 Accept-Language / Authorization / Expect / From / Host / If-Match /
3306 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3307 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3308 User-Agent
3309<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3310 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3311
3312<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3313
3314; Reason-Phrase defined but not used
3315; Status-Code defined but not used
3316; request-header defined but not used
3317; response-header defined but not used
3318
3319
3320</artwork>
3321</figure>
3322</section>
3323
3324<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3325
3326<section title="Since RFC2616">
3327<t>
3328  Extracted relevant partitions from <xref target="RFC2616"/>.
3329</t>
3330</section>
3331
3332<section title="Since draft-ietf-httpbis-p2-semantics-00">
3333<t>
3334  Closed issues:
3335  <list style="symbols"> 
3336    <t>
3337      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3338      "Via is a MUST"
3339      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3340    </t>
3341    <t>
3342      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3343      "Fragments allowed in Location"
3344      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3345    </t>
3346    <t>
3347      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3348      "Safe Methods vs Redirection"
3349      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3350    </t>
3351    <t>
3352      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3353      "Revise description of the POST method"
3354      (<eref target="http://purl.org/NET/http-errata#post"/>)
3355    </t>
3356    <t>
3357      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3358      "Normative and Informative references"
3359    </t>
3360    <t>
3361      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3362      "RFC2606 Compliance"
3363    </t>
3364    <t>
3365      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3366      "Informative references"
3367    </t>
3368    <t>
3369      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3370      "Redundant cross-references"
3371    </t>
3372  </list>
3373</t>
3374<t>
3375  Other changes:
3376  <list style="symbols"> 
3377    <t>
3378      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3379    </t>
3380  </list>
3381</t>
3382</section>
3383
3384<section title="Since draft-ietf-httpbis-p2-semantics-01">
3385<t>
3386  Closed issues:
3387  <list style="symbols"> 
3388    <t>
3389      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3390      "PUT side effects"
3391    </t>
3392    <t>
3393      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3394      "Duplicate Host header requirements"
3395    </t>
3396  </list>
3397</t>
3398<t>
3399  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3400  <list style="symbols"> 
3401    <t>
3402      Move "Product Tokens" section (back) into Part 1, as "token" is used
3403      in the definition of the Upgrade header.
3404    </t>
3405    <t>
3406      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3407    </t>
3408    <t>
3409      Copy definition of delta-seconds from Part6 instead of referencing it.
3410    </t>
3411  </list>
3412</t>
3413</section>
3414
3415<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3416<t>
3417  Closed issues:
3418  <list style="symbols"> 
3419    <t>
3420      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3421      "Requiring Allow in 405 responses"
3422    </t>
3423    <t>
3424      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3425      "Status Code Registry"
3426    </t>
3427    <t>
3428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3429      "Redirection vs. Location"
3430    </t>
3431    <t>
3432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3433      "Cacheability of 303 response"
3434    </t>
3435    <t>
3436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3437      "305 Use Proxy"
3438    </t>
3439    <t>
3440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3441      "Classification for Allow header"
3442    </t>
3443    <t>
3444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3445      "PUT - 'store under' vs 'store at'"
3446    </t>
3447  </list>
3448</t>
3449<t>
3450  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3451  <list style="symbols"> 
3452    <t>
3453      Reference RFC 3984, and update header registrations for headers defined
3454      in this document.
3455    </t>
3456  </list>
3457</t>
3458<t>
3459  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3460  <list style="symbols"> 
3461    <t>
3462      Replace string literals when the string really is case-sensitive (method).
3463    </t>
3464  </list>
3465</t>
3466</section>
3467
3468<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3469<t>
3470  Closed issues:
3471  <list style="symbols"> 
3472    <t>
3473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3474      "OPTIONS request bodies"
3475    </t>
3476    <t>
3477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3478      "Description of CONNECT should refer to RFC2817"
3479    </t>
3480    <t>
3481      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3482      "Location Content-Location reference request/response mixup"
3483    </t>
3484  </list>
3485</t>
3486<t>
3487  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3488  <list style="symbols"> 
3489    <t>
3490      Added initial proposal for registration process, plus initial
3491      content (non-HTTP/1.1 methods to be added by a separate specification).
3492    </t>
3493  </list>
3494</t>
3495</section>
3496
3497<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3498<t>
3499  Closed issues:
3500  <list style="symbols"> 
3501    <t>
3502      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3503      "Content-*"
3504    </t>
3505    <t>
3506      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3507      "RFC 2822 is updated by RFC 5322"
3508    </t>
3509  </list>
3510</t>
3511<t>
3512  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3513  <list style="symbols"> 
3514    <t>
3515      Use "/" instead of "|" for alternatives.
3516    </t>
3517    <t>
3518      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3519      whitespace ("OWS") and required whitespace ("RWS").
3520    </t>
3521    <t>
3522      Rewrite ABNFs to spell out whitespace rules, factor out
3523      header value format definitions.
3524    </t>
3525  </list>
3526</t>
3527</section>
3528
3529<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3530<t>
3531  Closed issues:
3532  <list style="symbols"> 
3533    <t>
3534      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3535      "Reason-Phrase BNF"
3536    </t>
3537  </list>
3538</t>
3539<t>
3540  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3541  <list style="symbols"> 
3542    <t>
3543      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3544    </t>
3545  </list>
3546</t>
3547</section>
3548
3549</section>
3550
3551</back>
3552</rfc>
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