source: draft-ietf-httpbis/latest/p2-semantics.xml @ 424

Last change on this file since 424 was 424, checked in by julian.reschke@…, 11 years ago

reorganize ABNF introductions to match Part1 (related to #36)

  • Property svn:eol-style set to native
File size: 150.2 KB
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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 "November">
16  <!ENTITY ID-YEAR "2008">
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<t>
292  This specification uses the ABNF syntax defined in &notation;.
293</t>
294
295<section title="Core Rules" anchor="core.rules">
296  <x:anchor-alias value="comment"/>
297  <x:anchor-alias value="CR"/>
298  <x:anchor-alias value="DIGIT"/>
299  <x:anchor-alias value="LF"/>
300  <x:anchor-alias value="obs-text"/>
301  <x:anchor-alias value="quoted-string"/>
302  <x:anchor-alias value="token"/>
303  <x:anchor-alias value="OWS"/>
304  <x:anchor-alias value="RWS"/>
305  <x:anchor-alias value="VCHAR"/>
306  <x:anchor-alias value="WSP"/>
307<t>
308  The core rules below are defined in &basic-rules;:
309</t>
310<figure><artwork type="abnf2616">
311  <x:ref>CR</x:ref>            = &lt;CR, defined in &basic-rules;&gt;
312  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
313  <x:ref>LF</x:ref>            = &lt;LF, defined in &basic-rules;&gt;
314  <x:ref>VCHAR</x:ref>         = &lt;VCHAR, defined in &basic-rules;&gt;
315  <x:ref>WSP</x:ref>           = &lt;WSP, defined in &basic-rules;&gt;
316</artwork></figure>
317<figure><artwork type="abnf2616">
318  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
319  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
320  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
321  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
322  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
323  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
324</artwork></figure>
325</section>
326
327<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
328  <x:anchor-alias value="absolute-URI"/>
329  <x:anchor-alias value="Accept"/>
330  <x:anchor-alias value="Accept-Charset"/>
331  <x:anchor-alias value="Accept-Encoding"/>
332  <x:anchor-alias value="Accept-Language"/>
333  <x:anchor-alias value="Accept-Ranges"/>
334  <x:anchor-alias value="Age"/>
335  <x:anchor-alias value="Authorization"/>
336  <x:anchor-alias value="ETag"/>
337  <x:anchor-alias value="fragment"/>
338  <x:anchor-alias value="Host"/>
339  <x:anchor-alias value="HTTP-date"/>
340  <x:anchor-alias value="If-Match"/>
341  <x:anchor-alias value="If-Modified-Since"/>
342  <x:anchor-alias value="If-None-Match"/>
343  <x:anchor-alias value="If-Range"/>
344  <x:anchor-alias value="If-Unmodified-Since"/>
345  <x:anchor-alias value="partial-URI"/>
346  <x:anchor-alias value="product"/>
347  <x:anchor-alias value="Proxy-Authenticate"/>
348  <x:anchor-alias value="Proxy-Authorization"/>
349  <x:anchor-alias value="Range"/>
350  <x:anchor-alias value="TE"/>
351  <x:anchor-alias value="Vary"/>
352  <x:anchor-alias value="WWW-Authenticate"/>
353<t>
354  The ABNF rules below are defined in other parts:
355</t>
356<figure><!--Part1--><artwork type="abnf2616">
357  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
358  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
359  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
360  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
361  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
362  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
363  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
364</artwork></figure>
365<figure><!--Part3--><artwork type="abnf2616">
366  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
367  <x:ref>Accept-Charset</x:ref> =
368             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
369  <x:ref>Accept-Encoding</x:ref> =
370             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
371  <x:ref>Accept-Language</x:ref> =
372             &lt;Accept-Language, defined in &header-accept-language;&gt;
373</artwork></figure>
374<figure><!--Part4--><artwork type="abnf2616">
375  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
376  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
377  <x:ref>If-Modified-Since</x:ref> =
378             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
379  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
380  <x:ref>If-Unmodified-Since</x:ref> =
381             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
382</artwork></figure>
383<figure><!--Part5--><artwork type="abnf2616">
384  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
385  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
386  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
387</artwork></figure>
388<figure><!--Part6--><artwork type="abnf2616">
389  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
390  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
391</artwork><!--Part7--></figure>
392<figure><artwork type="abnf2616">
393  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
394  <x:ref>Proxy-Authenticate</x:ref> =
395             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
396  <x:ref>Proxy-Authorization</x:ref> =
397             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
398  <x:ref>WWW-Authenticate</x:ref> =
399             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
400</artwork></figure>
401</section>
402</section>
403</section>
404
405<section title="Method" anchor="method">
406  <x:anchor-alias value="Method"/>
407  <x:anchor-alias value="extension-method"/>
408<t>
409   The Method  token indicates the method to be performed on the
410   resource identified by the request-target. The method is case-sensitive.
411</t>
412<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
413  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
414                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
415                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
416                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
417                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
418                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
419                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
420                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
421                 / <x:ref>extension-method</x:ref>
422  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
423</artwork></figure>
424<t>
425   The list of methods allowed by a resource can be specified in an
426   Allow header field (<xref target="header.allow"/>). The return code of the response
427   always notifies the client whether a method is currently allowed on a
428   resource, since the set of allowed methods can change dynamically. An
429   origin server &SHOULD; return the status code 405 (Method Not Allowed)
430   if the method is known by the origin server but not allowed for the
431   requested resource, and 501 (Not Implemented) if the method is
432   unrecognized or not implemented by the origin server. The methods GET
433   and HEAD &MUST; be supported by all general-purpose servers. All other
434   methods are &OPTIONAL;; however, if the above methods are implemented,
435   they &MUST; be implemented with the same semantics as those specified
436   in <xref target="method.definitions"/>.
437</t>
438
439<section title="Method Registry" anchor="method.registry">
440<t>
441  The HTTP Method Registry defines the name space for the Method token in the
442  Request line of an HTTP request.
443</t>
444<t>
445  Registrations &MUST; include the following fields:
446  <list style="symbols">
447    <t>Method Name (see <xref target="method"/>)</t>
448    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
449    <t>Pointer to specification text</t>
450  </list>
451</t>
452<t>
453  Values to be added to this name space are subject to IETF review
454  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
455  new method names should be traceable through statuses of either 'Obsoletes'
456  or 'Updates' to this document.
457</t>
458<t>
459  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
460</t>
461</section>
462</section>
463
464<section title="Request Header Fields" anchor="request.header.fields">
465  <x:anchor-alias value="extension-code"/>
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<t>
509   The Status-Code element is a 3-digit integer result code of the
510   attempt to understand and satisfy the request. The status codes listed
511   below are defined in <xref target="status.codes"/>.
512   The Reason-Phrase is intended to give a short
513   textual description of the Status-Code. The Status-Code is intended
514   for use by automata and the Reason-Phrase is intended for the human
515   user. The client is not required to examine or display the Reason-Phrase.
516</t>
517<t> 
518   The individual values of the numeric status codes defined for
519   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
520   presented below. The reason phrases listed here are only
521   recommendations -- they &MAY; be replaced by local equivalents without
522   affecting the protocol.
523</t>
524<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"/>
525  <x:ref>Status-Code</x:ref>    =
526         "100"  ; <xref target="status.100"/>: Continue
527       / "101"  ; <xref target="status.101"/>: Switching Protocols
528       / "200"  ; <xref target="status.200"/>: OK
529       / "201"  ; <xref target="status.201"/>: Created
530       / "202"  ; <xref target="status.202"/>: Accepted
531       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
532       / "204"  ; <xref target="status.204"/>: No Content
533       / "205"  ; <xref target="status.205"/>: Reset Content
534       / "206"  ; <xref target="status.206"/>: Partial Content
535       / "300"  ; <xref target="status.300"/>: Multiple Choices
536       / "301"  ; <xref target="status.301"/>: Moved Permanently
537       / "302"  ; <xref target="status.302"/>: Found
538       / "303"  ; <xref target="status.303"/>: See Other
539       / "304"  ; <xref target="status.304"/>: Not Modified
540       / "305"  ; <xref target="status.305"/>: Use Proxy
541       / "307"  ; <xref target="status.307"/>: Temporary Redirect
542       / "400"  ; <xref target="status.400"/>: Bad Request
543       / "401"  ; <xref target="status.401"/>: Unauthorized
544       / "402"  ; <xref target="status.402"/>: Payment Required
545       / "403"  ; <xref target="status.403"/>: Forbidden
546       / "404"  ; <xref target="status.404"/>: Not Found
547       / "405"  ; <xref target="status.405"/>: Method Not Allowed
548       / "406"  ; <xref target="status.406"/>: Not Acceptable
549       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
550       / "408"  ; <xref target="status.408"/>: Request Time-out
551       / "409"  ; <xref target="status.409"/>: Conflict
552       / "410"  ; <xref target="status.410"/>: Gone
553       / "411"  ; <xref target="status.411"/>: Length Required
554       / "412"  ; <xref target="status.412"/>: Precondition Failed
555       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
556       / "414"  ; <xref target="status.414"/>: Request-target Too Long
557       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
558       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
559       / "417"  ; <xref target="status.417"/>: Expectation Failed
560       / "500"  ; <xref target="status.500"/>: Internal Server Error
561       / "501"  ; <xref target="status.501"/>: Not Implemented
562       / "502"  ; <xref target="status.502"/>: Bad Gateway
563       / "503"  ; <xref target="status.503"/>: Service Unavailable
564       / "504"  ; <xref target="status.504"/>: Gateway Time-out
565       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
566       / <x:ref>extension-code</x:ref>
567
568  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
569  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
570</artwork></figure>
571<t>
572   HTTP status codes are extensible. HTTP applications are not required
573   to understand the meaning of all registered status codes, though such
574   understanding is obviously desirable. However, applications &MUST;
575   understand the class of any status code, as indicated by the first
576   digit, and treat any unrecognized response as being equivalent to the
577   x00 status code of that class, with the exception that an
578   unrecognized response &MUST-NOT; be cached. For example, if an
579   unrecognized status code of 431 is received by the client, it can
580   safely assume that there was something wrong with its request and
581   treat the response as if it had received a 400 status code. In such
582   cases, user agents &SHOULD; present to the user the entity returned
583   with the response, since that entity is likely to include human-readable
584   information which will explain the unusual status.
585</t>
586
587<section title="Status Code Registry" anchor="status.code.registry">
588<t>
589  The HTTP Status Code Registry defines the name space for the Status-Code
590  token in the Status line of an HTTP response.
591</t>
592<t>
593  Values to be added to this name space are subject to IETF review
594  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
595  new status codes should be traceable through statuses of either 'Obsoletes'
596  or 'Updates' to this document.
597</t>
598<t>
599  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
600</t>
601</section>
602
603</section>
604
605<section title="Response Header Fields" anchor="response.header.fields">
606  <x:anchor-alias value="response-header"/>
607<t>
608   The response-header fields allow the server to pass additional
609   information about the response which cannot be placed in the Status-Line.
610   These header fields give information about the server and about
611   further access to the resource identified by the request-target.
612</t>
613<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
614  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
615                  / <x:ref>Age</x:ref>                     ; &header-age;
616                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
617                  / <x:ref>ETag</x:ref>                    ; &header-etag;
618                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
619                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
620                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
621                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
622                  / <x:ref>Vary</x:ref>                    ; &header-vary;
623                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
624</artwork></figure>
625<t>
626   Response-header field names can be extended reliably only in
627   combination with a change in the protocol version. However, new or
628   experimental header fields &MAY; be given the semantics of response-header
629   fields if all parties in the communication recognize them to
630   be response-header fields. Unrecognized header fields are treated as
631   entity-header fields.
632</t>
633</section>
634
635<section title="Entity" anchor="entity">
636<t>
637   Request and Response messages &MAY; transfer an entity if not otherwise
638   restricted by the request method or response status code. An entity
639   consists of entity-header fields and an entity-body, although some
640   responses will only include the entity-headers. HTTP entity-body and
641   entity-header fields are defined in &payload;.
642</t>
643<t>
644   An entity-body is only present in a message when a message-body is
645   present, as described in &message-body;. The entity-body is obtained
646   from the message-body by decoding any Transfer-Encoding that might
647   have been applied to ensure safe and proper transfer of the message.
648</t>
649</section>
650
651
652<section title="Method Definitions" anchor="method.definitions">
653<t>
654   The set of common methods for HTTP/1.1 is defined below. Although
655   this set can be expanded, additional methods cannot be assumed to
656   share the same semantics for separately extended clients and servers.
657</t>
658
659<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
660
661<section title="Safe Methods" anchor="safe.methods">
662<iref item="Safe Methods" primary="true"/>
663<t>
664   Implementors should be aware that the software represents the user in
665   their interactions over the Internet, and should be careful to allow
666   the user to be aware of any actions they might take which may have an
667   unexpected significance to themselves or others.
668</t>
669<t>
670   In particular, the convention has been established that the GET and
671   HEAD methods &SHOULD-NOT;  have the significance of taking an action
672   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
673   This allows user agents to represent other methods, such as POST, PUT
674   and DELETE, in a special way, so that the user is made aware of the
675   fact that a possibly unsafe action is being requested.
676</t>
677<t>
678   Naturally, it is not possible to ensure that the server does not
679   generate side-effects as a result of performing a GET request; in
680   fact, some dynamic resources consider that a feature. The important
681   distinction here is that the user did not request the side-effects,
682   so therefore cannot be held accountable for them.
683</t>
684</section>
685
686<section title="Idempotent Methods" anchor="idempotent.methods">
687<iref item="Idempotent Methods" primary="true"/>
688<t>
689   Methods can also have the property of "idempotence" in that (aside
690   from error or expiration issues) the side-effects of N &gt; 0 identical
691   requests is the same as for a single request. The methods GET, HEAD,
692   PUT and DELETE share this property. Also, the methods OPTIONS and
693   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
694</t>
695<t>
696   However, it is possible that a sequence of several requests is non-idempotent,
697   even if all of the methods executed in that sequence are
698   idempotent. (A sequence is idempotent if a single execution of the
699   entire sequence always yields a result that is not changed by a
700   reexecution of all, or part, of that sequence.) For example, a
701   sequence is non-idempotent if its result depends on a value that is
702   later modified in the same sequence.
703</t>
704<t>
705   A sequence that never has side effects is idempotent, by definition
706   (provided that no concurrent operations are being executed on the
707   same set of resources).
708</t>
709</section>
710</section>
711
712<section title="OPTIONS" anchor="OPTIONS">
713  <rdf:Description>
714    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
715  </rdf:Description>
716  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
717  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
718<t>
719   The OPTIONS method represents a request for information about the
720   communication options available on the request/response chain
721   identified by the request-target. This method allows the client to
722   determine the options and/or requirements associated with a resource,
723   or the capabilities of a server, without implying a resource action
724   or initiating a resource retrieval.
725</t>
726<t>
727   Responses to this method are not cacheable.
728</t>
729<t>
730   If the OPTIONS request includes an entity-body (as indicated by the
731   presence of Content-Length or Transfer-Encoding), then the media type
732   &MUST; be indicated by a Content-Type field. Although this
733   specification does not define any use for such a body, future
734   extensions to HTTP might use the OPTIONS body to make more detailed
735   queries on the server.
736</t>
737<t>
738   If the request-target is an asterisk ("*"), the OPTIONS request is
739   intended to apply to the server in general rather than to a specific
740   resource. Since a server's communication options typically depend on
741   the resource, the "*" request is only useful as a "ping" or "no-op"
742   type of method; it does nothing beyond allowing the client to test
743   the capabilities of the server. For example, this can be used to test
744   a proxy for HTTP/1.1 compliance (or lack thereof).
745</t>
746<t>
747   If the request-target is not an asterisk, the OPTIONS request applies
748   only to the options that are available when communicating with that
749   resource.
750</t>
751<t>
752   A 200 response &SHOULD; include any header fields that indicate
753   optional features implemented by the server and applicable to that
754   resource (e.g., Allow), possibly including extensions not defined by
755   this specification. The response body, if any, &SHOULD; also include
756   information about the communication options. The format for such a
757   body is not defined by this specification, but might be defined by
758   future extensions to HTTP. Content negotiation &MAY; be used to select
759   the appropriate response format. If no response body is included, the
760   response &MUST; include a Content-Length field with a field-value of
761   "0".
762</t>
763<t>
764   The Max-Forwards request-header field &MAY; be used to target a
765   specific proxy in the request chain. When a proxy receives an OPTIONS
766   request on an absolute-URI for which request forwarding is permitted,
767   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
768   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
769   instead, the proxy &SHOULD; respond with its own communication options.
770   If the Max-Forwards field-value is an integer greater than zero, the
771   proxy &MUST; decrement the field-value when it forwards the request. If
772   no Max-Forwards field is present in the request, then the forwarded
773   request &MUST-NOT; include a Max-Forwards field.
774</t>
775</section>
776
777<section title="GET" anchor="GET">
778  <rdf:Description>
779    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
780  </rdf:Description>
781  <iref primary="true" item="GET method" x:for-anchor=""/>
782  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
783<t>
784   The GET method means retrieve whatever information (in the form of an
785   entity) is identified by the request-target. If the request-target refers
786   to a data-producing process, it is the produced data which shall be
787   returned as the entity in the response and not the source text of the
788   process, unless that text happens to be the output of the process.
789</t>
790<t>
791   The semantics of the GET method change to a "conditional GET" if the
792   request message includes an If-Modified-Since, If-Unmodified-Since,
793   If-Match, If-None-Match, or If-Range header field. A conditional GET
794   method requests that the entity be transferred only under the
795   circumstances described by the conditional header field(s). The
796   conditional GET method is intended to reduce unnecessary network
797   usage by allowing cached entities to be refreshed without requiring
798   multiple requests or transferring data already held by the client.
799</t>
800<t>
801   The semantics of the GET method change to a "partial GET" if the
802   request message includes a Range header field. A partial GET requests
803   that only part of the entity be transferred, as described in &header-range;.
804   The partial GET method is intended to reduce unnecessary
805   network usage by allowing partially-retrieved entities to be
806   completed without transferring data already held by the client.
807</t>
808<t>
809   The response to a GET request is cacheable if and only if it meets
810   the requirements for HTTP caching described in &caching;.
811</t>
812<t>
813   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
814</t>
815</section>
816
817<section title="HEAD" anchor="HEAD">
818  <rdf:Description>
819    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
820  </rdf:Description>
821  <iref primary="true" item="HEAD method" x:for-anchor=""/>
822  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
823<t>
824   The HEAD method is identical to GET except that the server &MUST-NOT;
825   return a message-body in the response. The metainformation contained
826   in the HTTP headers in response to a HEAD request &SHOULD; be identical
827   to the information sent in response to a GET request. This method can
828   be used for obtaining metainformation about the entity implied by the
829   request without transferring the entity-body itself. This method is
830   often used for testing hypertext links for validity, accessibility,
831   and recent modification.
832</t>
833<t>
834   The response to a HEAD request &MAY; be cacheable in the sense that the
835   information contained in the response &MAY; be used to update a
836   previously cached entity from that resource. If the new field values
837   indicate that the cached entity differs from the current entity (as
838   would be indicated by a change in Content-Length, Content-MD5, ETag
839   or Last-Modified), then the cache &MUST; treat the cache entry as
840   stale.
841</t>
842</section>
843
844<section title="POST" anchor="POST">
845  <iref primary="true" item="POST method" x:for-anchor=""/>
846  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
847<t>
848   The POST method is used to request that the origin server accept the
849   entity enclosed in the request as data to be processed by the resource
850   identified by the request-target in the Request-Line. POST is designed
851   to allow a uniform method to cover the following functions:
852  <list style="symbols">
853    <t>
854      Annotation of existing resources;
855    </t>
856    <t>
857        Posting a message to a bulletin board, newsgroup, mailing list,
858        or similar group of articles;
859    </t>
860    <t>
861        Providing a block of data, such as the result of submitting a
862        form, to a data-handling process;
863    </t>
864    <t>
865        Extending a database through an append operation.
866    </t>
867  </list>
868</t>
869<t>
870   The actual function performed by the POST method is determined by the
871   server and is usually dependent on the request-target.
872</t>
873<t>
874   The action performed by the POST method might not result in a
875   resource that can be identified by a URI. In this case, either 200
876   (OK) or 204 (No Content) is the appropriate response status,
877   depending on whether or not the response includes an entity that
878   describes the result.
879</t>
880<t>
881   If a resource has been created on the origin server, the response
882   &SHOULD; be 201 (Created) and contain an entity which describes the
883   status of the request and refers to the new resource, and a Location
884   header (see <xref target="header.location"/>).
885</t>
886<t>
887   Responses to this method are not cacheable, unless the response
888   includes appropriate Cache-Control or Expires header fields. However,
889   the 303 (See Other) response can be used to direct the user agent to
890   retrieve a cacheable resource.
891</t>
892</section>
893
894<section title="PUT" anchor="PUT">
895  <iref primary="true" item="PUT method" x:for-anchor=""/>
896  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
897<t>
898   The PUT method requests that the enclosed entity be stored at the
899   supplied request-target. If the request-target refers to an already
900   existing resource, the enclosed entity &SHOULD; be considered as a
901   modified version of the one residing on the origin server. If the
902   request-target does not point to an existing resource, and that URI is
903   capable of being defined as a new resource by the requesting user
904   agent, the origin server can create the resource with that URI. If a
905   new resource is created at the request-target, the origin server &MUST;
906         inform the user agent
907   via the 201 (Created) response. If an existing resource is modified,
908   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
909   to indicate successful completion of the request. If the resource
910   could not be created or modified with the request-target, an appropriate
911   error response &SHOULD; be given that reflects the nature of the
912   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
913   headers (headers starting with the prefix 'Content-') that it does
914   not understand or implement
915   and &MUST; return a 501 (Not Implemented) response in such cases.
916</t>
917<t>
918   If the request passes through a cache and the request-target identifies
919   one or more currently cached entities, those entries &SHOULD; be
920   treated as stale. Responses to this method are not cacheable.
921</t>
922<t>
923   The fundamental difference between the POST and PUT requests is
924   reflected in the different meaning of the request-target. The URI in a
925   POST request identifies the resource that will handle the enclosed
926   entity. That resource might be a data-accepting process, a gateway to
927   some other protocol, or a separate entity that accepts annotations.
928   In contrast, the URI in a PUT request identifies the entity enclosed
929   with the request -- the user agent knows what URI is intended and the
930   server &MUST-NOT; attempt to apply the request to some other resource.
931   If the server desires that the request be applied to a different URI,
932   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
933   then make its own decision regarding whether or not to redirect the
934   request.
935</t>
936<t>
937   A single resource &MAY; be identified by many different URIs. For
938   example, an article might have a URI for identifying "the current
939   version" which is separate from the URI identifying each particular
940   version. In this case, a PUT request on a general URI might result in
941   several other URIs being defined by the origin server.
942</t>
943<t>
944   HTTP/1.1 does not define how a PUT method affects the state of an
945   origin server.
946</t>
947<t>
948   Unless otherwise specified for a particular entity-header, the
949   entity-headers in the PUT request &SHOULD; be applied to the resource
950   created or modified by the PUT.
951</t>
952</section>
953
954<section title="DELETE" anchor="DELETE">
955  <iref primary="true" item="DELETE method" x:for-anchor=""/>
956  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
957<t>
958   The DELETE method requests that the origin server delete the resource
959   identified by the request-target. This method &MAY; be overridden by human
960   intervention (or other means) on the origin server. The client cannot
961   be guaranteed that the operation has been carried out, even if the
962   status code returned from the origin server indicates that the action
963   has been completed successfully. However, the server &SHOULD-NOT; 
964   indicate success unless, at the time the response is given, it
965   intends to delete the resource or move it to an inaccessible
966   location.
967</t>
968<t>
969   A successful response &SHOULD; be 200 (OK) if the response includes an
970   entity describing the status, 202 (Accepted) if the action has not
971   yet been enacted, or 204 (No Content) if the action has been enacted
972   but the response does not include an entity.
973</t>
974<t>
975   If the request passes through a cache and the request-target identifies
976   one or more currently cached entities, those entries &SHOULD; be
977   treated as stale. Responses to this method are not cacheable.
978</t>
979</section>
980
981<section title="TRACE" anchor="TRACE">
982  <rdf:Description>
983    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
984  </rdf:Description>
985  <iref primary="true" item="TRACE method" x:for-anchor=""/>
986  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
987<t>
988   The TRACE method is used to invoke a remote, application-layer loop-back
989   of the request message. The final recipient of the request
990   &SHOULD; reflect the message received back to the client as the
991   entity-body of a 200 (OK) response. The final recipient is either the
992   origin server or the first proxy or gateway to receive a Max-Forwards
993   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
994   &MUST-NOT; include an entity.
995</t>
996<t>
997   TRACE allows the client to see what is being received at the other
998   end of the request chain and use that data for testing or diagnostic
999   information. The value of the Via header field (&header-via;) is of
1000   particular interest, since it acts as a trace of the request chain.
1001   Use of the Max-Forwards header field allows the client to limit the
1002   length of the request chain, which is useful for testing a chain of
1003   proxies forwarding messages in an infinite loop.
1004</t>
1005<t>
1006   If the request is valid, the response &SHOULD; contain the entire
1007   request message in the entity-body, with a Content-Type of
1008   "message/http" (see &media-type-message-http;). Responses to this method
1009   &MUST-NOT; be cached.
1010</t>
1011</section>
1012
1013<section title="CONNECT" anchor="CONNECT">
1014  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1015  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1016<t>
1017   This specification reserves the method name CONNECT for use with a
1018   proxy that can dynamically switch to being a tunnel (e.g. SSL
1019   tunneling <xref target="RFC2817"/>).
1020</t>
1021</section>
1022</section>
1023
1024
1025<section title="Status Code Definitions" anchor="status.codes">
1026<t>
1027   Each Status-Code is described below, including a description of which
1028   method(s) it can follow and any metainformation required in the
1029   response.
1030</t>
1031
1032<section title="Informational 1xx" anchor="status.1xx">
1033<t>
1034   This class of status code indicates a provisional response,
1035   consisting only of the Status-Line and optional headers, and is
1036   terminated by an empty line. There are no required headers for this
1037   class of status code. Since HTTP/1.0 did not define any 1xx status
1038   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1039   except under experimental conditions.
1040</t>
1041<t>
1042   A client &MUST; be prepared to accept one or more 1xx status responses
1043   prior to a regular response, even if the client does not expect a 100
1044   (Continue) status message. Unexpected 1xx status responses &MAY; be
1045   ignored by a user agent.
1046</t>
1047<t>
1048   Proxies &MUST; forward 1xx responses, unless the connection between the
1049   proxy and its client has been closed, or unless the proxy itself
1050   requested the generation of the 1xx response. (For example, if a
1051   proxy adds a "Expect: 100-continue" field when it forwards a request,
1052   then it need not forward the corresponding 100 (Continue)
1053   response(s).)
1054</t>
1055
1056<section title="100 Continue" anchor="status.100">
1057  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1058  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1059<t>
1060   The client &SHOULD; continue with its request. This interim response is
1061   used to inform the client that the initial part of the request has
1062   been received and has not yet been rejected by the server. The client
1063   &SHOULD; continue by sending the remainder of the request or, if the
1064   request has already been completed, ignore this response. The server
1065   &MUST; send a final response after the request has been completed. See
1066   &use100; for detailed discussion of the use and handling of this
1067   status code.
1068</t>
1069</section>
1070
1071<section title="101 Switching Protocols" anchor="status.101">
1072  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1073  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1074<t>
1075   The server understands and is willing to comply with the client's
1076   request, via the Upgrade message header field (&header-upgrade;), for a
1077   change in the application protocol being used on this connection. The
1078   server will switch protocols to those defined by the response's
1079   Upgrade header field immediately after the empty line which
1080   terminates the 101 response.
1081</t>
1082<t>
1083   The protocol &SHOULD; be switched only when it is advantageous to do
1084   so. For example, switching to a newer version of HTTP is advantageous
1085   over older versions, and switching to a real-time, synchronous
1086   protocol might be advantageous when delivering resources that use
1087   such features.
1088</t>
1089</section>
1090</section>
1091
1092<section title="Successful 2xx" anchor="status.2xx">
1093<t>
1094   This class of status code indicates that the client's request was
1095   successfully received, understood, and accepted.
1096</t>
1097
1098<section title="200 OK" anchor="status.200">
1099  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1100  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1101<t>
1102   The request has succeeded. The information returned with the response
1103   is dependent on the method used in the request, for example:
1104  <list style="hanging">
1105    <t hangText="GET">
1106          an entity corresponding to the requested resource is sent in
1107          the response;
1108    </t>
1109    <t hangText="HEAD">
1110          the entity-header fields corresponding to the requested
1111          resource are sent in the response without any message-body;
1112    </t>
1113    <t hangText="POST">
1114      an entity describing or containing the result of the action;
1115    </t>
1116    <t hangText="TRACE">
1117      an entity containing the request message as received by the
1118      end server.
1119    </t>
1120  </list>
1121</t>
1122</section>
1123
1124<section title="201 Created" anchor="status.201">
1125  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1126  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1127<t>
1128   The request has been fulfilled and resulted in a new resource being
1129   created. The newly created resource can be referenced by the URI(s)
1130   returned in the entity of the response, with the most specific URI
1131   for the resource given by a Location header field. The response
1132   &SHOULD; include an entity containing a list of resource
1133   characteristics and location(s) from which the user or user agent can
1134   choose the one most appropriate. The entity format is specified by
1135   the media type given in the Content-Type header field. The origin
1136   server &MUST; create the resource before returning the 201 status code.
1137   If the action cannot be carried out immediately, the server &SHOULD;
1138   respond with 202 (Accepted) response instead.
1139</t>
1140<t>
1141   A 201 response &MAY; contain an ETag response header field indicating
1142   the current value of the entity tag for the requested variant just
1143   created, see &header-etag;.
1144</t>
1145</section>
1146
1147<section title="202 Accepted" anchor="status.202">
1148  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1149  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1150<t>
1151   The request has been accepted for processing, but the processing has
1152   not been completed.  The request might or might not eventually be
1153   acted upon, as it might be disallowed when processing actually takes
1154   place. There is no facility for re-sending a status code from an
1155   asynchronous operation such as this.
1156</t>
1157<t>
1158   The 202 response is intentionally non-committal. Its purpose is to
1159   allow a server to accept a request for some other process (perhaps a
1160   batch-oriented process that is only run once per day) without
1161   requiring that the user agent's connection to the server persist
1162   until the process is completed. The entity returned with this
1163   response &SHOULD; include an indication of the request's current status
1164   and either a pointer to a status monitor or some estimate of when the
1165   user can expect the request to be fulfilled.
1166</t>
1167</section>
1168
1169<section title="203 Non-Authoritative Information" anchor="status.203">
1170  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1171  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1172<t>
1173   The returned metainformation in the entity-header is not the
1174   definitive set as available from the origin server, but is gathered
1175   from a local or a third-party copy. The set presented &MAY; be a subset
1176   or superset of the original version. For example, including local
1177   annotation information about the resource might result in a superset
1178   of the metainformation known by the origin server. Use of this
1179   response code is not required and is only appropriate when the
1180   response would otherwise be 200 (OK).
1181</t>
1182</section>
1183
1184<section title="204 No Content" anchor="status.204">
1185  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1186  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1187<t>
1188   The server has fulfilled the request but does not need to return an
1189   entity-body, and might want to return updated metainformation. The
1190   response &MAY; include new or updated metainformation in the form of
1191   entity-headers, which if present &SHOULD; be associated with the
1192   requested variant.
1193</t>
1194<t>
1195   If the client is a user agent, it &SHOULD-NOT;  change its document view
1196   from that which caused the request to be sent. This response is
1197   primarily intended to allow input for actions to take place without
1198   causing a change to the user agent's active document view, although
1199   any new or updated metainformation &SHOULD; be applied to the document
1200   currently in the user agent's active view.
1201</t>
1202<t>
1203   The 204 response &MUST-NOT; include a message-body, and thus is always
1204   terminated by the first empty line after the header fields.
1205</t>
1206</section>
1207
1208<section title="205 Reset Content" anchor="status.205">
1209  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1210  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1211<t>
1212   The server has fulfilled the request and the user agent &SHOULD; reset
1213   the document view which caused the request to be sent. This response
1214   is primarily intended to allow input for actions to take place via
1215   user input, followed by a clearing of the form in which the input is
1216   given so that the user can easily initiate another input action. The
1217   response &MUST-NOT; include an entity.
1218</t>
1219</section>
1220
1221<section title="206 Partial Content" anchor="status.206">
1222  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1223  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1224<t>
1225   The server has fulfilled the partial GET request for the resource
1226   and the enclosed entity is a partial representation as defined in &range;.
1227</t>
1228</section>
1229</section>
1230
1231<section title="Redirection 3xx" anchor="status.3xx">
1232<t>
1233   This class of status code indicates that further action needs to be
1234   taken by the user agent in order to fulfill the request.  The action
1235   required &MAY; be carried out by the user agent without interaction
1236   with the user if and only if the method used in the second request is
1237   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1238   such loops generate network traffic for each redirection.
1239  <list><t>
1240      <x:h>Note:</x:h> previous versions of this specification recommended a
1241      maximum of five redirections. Content developers should be aware
1242      that there might be clients that implement such a fixed
1243      limitation.
1244  </t></list>
1245</t>
1246
1247<section title="300 Multiple Choices" anchor="status.300">
1248  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1249  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1250<t>
1251   The requested resource corresponds to any one of a set of
1252   representations, each with its own specific location, and agent-driven
1253   negotiation information (&content-negotiation;) is being provided so that
1254   the user (or user agent) can select a preferred representation and
1255   redirect its request to that location.
1256</t>
1257<t>
1258   Unless it was a HEAD request, the response &SHOULD; include an entity
1259   containing a list of resource characteristics and location(s) from
1260   which the user or user agent can choose the one most appropriate. The
1261   entity format is specified by the media type given in the Content-Type
1262   header field. Depending upon the format and the capabilities of
1263   the user agent, selection of the most appropriate choice &MAY; be
1264   performed automatically. However, this specification does not define
1265   any standard for such automatic selection.
1266</t>
1267<t>
1268   If the server has a preferred choice of representation, it &SHOULD;
1269   include the specific URI for that representation in the Location
1270   field; user agents &MAY; use the Location field value for automatic
1271   redirection. This response is cacheable unless indicated otherwise.
1272</t>
1273</section>
1274
1275<section title="301 Moved Permanently" anchor="status.301">
1276  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1277  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1278<t>
1279   The requested resource has been assigned a new permanent URI and any
1280   future references to this resource &SHOULD; use one of the returned
1281   URIs.  Clients with link editing capabilities ought to automatically
1282   re-link references to the request-target to one or more of the new
1283   references returned by the server, where possible. This response is
1284   cacheable unless indicated otherwise.
1285</t>
1286<t>
1287   The new permanent URI &SHOULD; be given by the Location field in the
1288   response. Unless the request method was HEAD, the entity of the
1289   response &SHOULD; contain a short hypertext note with a hyperlink to
1290   the new URI(s).
1291</t>
1292<t>
1293   If the 301 status code is received in response to a request method
1294   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1295   then the request &MAY; be automatically redirected by the user agent without
1296   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1297   request unless it can be confirmed by the user, since this might
1298   change the conditions under which the request was issued.
1299  <list><t>
1300      <x:h>Note:</x:h> When automatically redirecting a POST request after
1301      receiving a 301 status code, some existing HTTP/1.0 user agents
1302      will erroneously change it into a GET request.
1303  </t></list>
1304</t>
1305</section>
1306
1307<section title="302 Found" anchor="status.302">
1308  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1309  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1310<t>
1311   The requested resource resides temporarily under a different URI.
1312   Since the redirection might be altered on occasion, the client &SHOULD;
1313   continue to use the request-target for future requests.  This response
1314   is only cacheable if indicated by a Cache-Control or Expires header
1315   field.
1316</t>
1317<t>
1318   The temporary URI &SHOULD; be given by the Location field in the
1319   response. Unless the request method was HEAD, the entity of the
1320   response &SHOULD; contain a short hypertext note with a hyperlink to
1321   the new URI(s).
1322</t>
1323<t>
1324   If the 302 status code is received in response to a request method
1325   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1326   then the request &MAY; be automatically redirected by the user agent without
1327   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1328   request unless it can be confirmed by the user, since this might
1329   change the conditions under which the request was issued.
1330  <list><t>
1331      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1332      to change the method on the redirected request.  However, most
1333      existing user agent implementations treat 302 as if it were a 303
1334      response, performing a GET on the Location field-value regardless
1335      of the original request method. The status codes 303 and 307 have
1336      been added for servers that wish to make unambiguously clear which
1337      kind of reaction is expected of the client.
1338  </t></list>
1339</t>
1340</section>
1341
1342<section title="303 See Other" anchor="status.303">
1343  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1344  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1345<t>
1346   The server directs the user agent to a different resource, indicated
1347   by a URI in the Location header field, that provides an indirect
1348   response to the original request.  The user agent &MAY; perform a GET
1349   request on the URI in the Location field in order to obtain a
1350   representation corresponding to the response, be redirected again,
1351   or end with an error status.  The Location URI is not a substitute
1352   reference for the originally requested resource.
1353</t>
1354<t>
1355   The 303 status is generally applicable to any HTTP method.  It is
1356   primarily used to allow the output of a POST action to redirect
1357   the user agent to a selected resource, since doing so provides the
1358   information corresponding to the POST response in a form that
1359   can be separately identified, bookmarked, and cached independent
1360   of the original request.
1361</t>
1362<t>
1363   A 303 response to a GET request indicates that the requested
1364   resource does not have a representation of its own that can be
1365   transferred by the server over HTTP.  The Location URI indicates a
1366   resource that is descriptive of the requested resource such that
1367   the follow-on representation may be useful without implying that
1368   it adequately represents the previously requested resource.
1369   Note that answers to the questions of what can be represented, what
1370   representations are adequate, and what might be a useful description
1371   are outside the scope of HTTP and thus entirely determined by the
1372   resource owner(s).
1373</t>
1374<t>
1375   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1376   cacheable by Cache-Control or Expires header fields.  Except for
1377   responses to a HEAD request, the entity of a 303 response &SHOULD;
1378   contain a short hypertext note with a hyperlink to the Location URI.
1379</t>
1380</section>
1381
1382<section title="304 Not Modified" anchor="status.304">
1383  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1384  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1385<t>
1386   The response to the request has not been modified since the conditions
1387   indicated by the client's conditional GET request, as defined in &conditional;.
1388</t>
1389</section>
1390
1391<section title="305 Use Proxy" anchor="status.305">
1392  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1393  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1394<t>
1395   The 305 status was defined in a previous version of this specification
1396   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1397</t>
1398</section>
1399
1400<section title="306 (Unused)" anchor="status.306">
1401  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1402  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1403<t>
1404   The 306 status code was used in a previous version of the
1405   specification, is no longer used, and the code is reserved.
1406</t>
1407</section>
1408
1409<section title="307 Temporary Redirect" anchor="status.307">
1410  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1411  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1412<t>
1413   The requested resource resides temporarily under a different URI.
1414   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1415   continue to use the request-target for future requests.  This response
1416   is only cacheable if indicated by a Cache-Control or Expires header
1417   field.
1418</t>
1419<t>
1420   The temporary URI &SHOULD; be given by the Location field in the
1421   response. Unless the request method was HEAD, the entity of the
1422   response &SHOULD; contain a short hypertext note with a hyperlink to
1423   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1424   understand the 307 status. Therefore, the note &SHOULD; contain the
1425   information necessary for a user to repeat the original request on
1426   the new URI.
1427</t>
1428<t>
1429   If the 307 status code is received in response to a request method
1430   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1431   then the request &MAY; be automatically redirected by the user agent without
1432   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1433   request unless it can be confirmed by the user, since this might
1434   change the conditions under which the request was issued.
1435</t>
1436</section>
1437</section>
1438
1439<section title="Client Error 4xx" anchor="status.4xx">
1440<t>
1441   The 4xx class of status code is intended for cases in which the
1442   client seems to have erred. Except when responding to a HEAD request,
1443   the server &SHOULD; include an entity containing an explanation of the
1444   error situation, and whether it is a temporary or permanent
1445   condition. These status codes are applicable to any request method.
1446   User agents &SHOULD; display any included entity to the user.
1447</t>
1448<t>
1449   If the client is sending data, a server implementation using TCP
1450   &SHOULD; be careful to ensure that the client acknowledges receipt of
1451   the packet(s) containing the response, before the server closes the
1452   input connection. If the client continues sending data to the server
1453   after the close, the server's TCP stack will send a reset packet to
1454   the client, which may erase the client's unacknowledged input buffers
1455   before they can be read and interpreted by the HTTP application.
1456</t>
1457
1458<section title="400 Bad Request" anchor="status.400">
1459  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1460  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1461<t>
1462   The request could not be understood by the server due to malformed
1463   syntax. The client &SHOULD-NOT;  repeat the request without
1464   modifications.
1465</t>
1466</section>
1467
1468<section title="401 Unauthorized" anchor="status.401">
1469  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1470  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1471<t>
1472   The request requires user authentication (see &auth;).
1473</t>
1474</section>
1475
1476<section title="402 Payment Required" anchor="status.402">
1477  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1478  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1479<t>
1480   This code is reserved for future use.
1481</t>
1482</section>
1483
1484<section title="403 Forbidden" anchor="status.403">
1485  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1486  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1487<t>
1488   The server understood the request, but is refusing to fulfill it.
1489   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1490   If the request method was not HEAD and the server wishes to make
1491   public why the request has not been fulfilled, it &SHOULD; describe the
1492   reason for the refusal in the entity.  If the server does not wish to
1493   make this information available to the client, the status code 404
1494   (Not Found) can be used instead.
1495</t>
1496</section>
1497
1498<section title="404 Not Found" anchor="status.404">
1499  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1500  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1501<t>
1502   The server has not found anything matching the request-target. No
1503   indication is given of whether the condition is temporary or
1504   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1505   knows, through some internally configurable mechanism, that an old
1506   resource is permanently unavailable and has no forwarding address.
1507   This status code is commonly used when the server does not wish to
1508   reveal exactly why the request has been refused, or when no other
1509   response is applicable.
1510</t>
1511</section>
1512
1513<section title="405 Method Not Allowed" anchor="status.405">
1514  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1515  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1516<t>
1517   The method specified in the Request-Line is not allowed for the
1518   resource identified by the request-target. The response &MUST; include an
1519   Allow header containing a list of valid methods for the requested
1520   resource.
1521</t>
1522</section>
1523
1524<section title="406 Not Acceptable" anchor="status.406">
1525  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1526  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1527<t>
1528   The resource identified by the request is only capable of generating
1529   response entities which have content characteristics not acceptable
1530   according to the accept headers sent in the request.
1531</t>
1532<t>
1533   Unless it was a HEAD request, the response &SHOULD; include an entity
1534   containing a list of available entity characteristics and location(s)
1535   from which the user or user agent can choose the one most
1536   appropriate. The entity format is specified by the media type given
1537   in the Content-Type header field. Depending upon the format and the
1538   capabilities of the user agent, selection of the most appropriate
1539   choice &MAY; be performed automatically. However, this specification
1540   does not define any standard for such automatic selection.
1541  <list><t>
1542      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1543      not acceptable according to the accept headers sent in the
1544      request. In some cases, this may even be preferable to sending a
1545      406 response. User agents are encouraged to inspect the headers of
1546      an incoming response to determine if it is acceptable.
1547  </t></list>
1548</t>
1549<t>
1550   If the response could be unacceptable, a user agent &SHOULD;
1551   temporarily stop receipt of more data and query the user for a
1552   decision on further actions.
1553</t>
1554</section>
1555
1556<section title="407 Proxy Authentication Required" anchor="status.407">
1557  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1558  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1559<t>
1560   This code is similar to 401 (Unauthorized), but indicates that the
1561   client must first authenticate itself with the proxy (see &auth;).
1562</t>
1563</section>
1564
1565<section title="408 Request Timeout" anchor="status.408">
1566  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1567  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1568<t>
1569   The client did not produce a request within the time that the server
1570   was prepared to wait. The client &MAY; repeat the request without
1571   modifications at any later time.
1572</t>
1573</section>
1574
1575<section title="409 Conflict" anchor="status.409">
1576  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1577  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1578<t>
1579   The request could not be completed due to a conflict with the current
1580   state of the resource. This code is only allowed in situations where
1581   it is expected that the user might be able to resolve the conflict
1582   and resubmit the request. The response body &SHOULD; include enough
1583   information for the user to recognize the source of the conflict.
1584   Ideally, the response entity would include enough information for the
1585   user or user agent to fix the problem; however, that might not be
1586   possible and is not required.
1587</t>
1588<t>
1589   Conflicts are most likely to occur in response to a PUT request. For
1590   example, if versioning were being used and the entity being PUT
1591   included changes to a resource which conflict with those made by an
1592   earlier (third-party) request, the server might use the 409 response
1593   to indicate that it can't complete the request. In this case, the
1594   response entity would likely contain a list of the differences
1595   between the two versions in a format defined by the response
1596   Content-Type.
1597</t>
1598</section>
1599
1600<section title="410 Gone" anchor="status.410">
1601  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1602  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1603<t>
1604   The requested resource is no longer available at the server and no
1605   forwarding address is known. This condition is expected to be
1606   considered permanent. Clients with link editing capabilities &SHOULD;
1607   delete references to the request-target after user approval. If the
1608   server does not know, or has no facility to determine, whether or not
1609   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1610   used instead. This response is cacheable unless indicated otherwise.
1611</t>
1612<t>
1613   The 410 response is primarily intended to assist the task of web
1614   maintenance by notifying the recipient that the resource is
1615   intentionally unavailable and that the server owners desire that
1616   remote links to that resource be removed. Such an event is common for
1617   limited-time, promotional services and for resources belonging to
1618   individuals no longer working at the server's site. It is not
1619   necessary to mark all permanently unavailable resources as "gone" or
1620   to keep the mark for any length of time -- that is left to the
1621   discretion of the server owner.
1622</t>
1623</section>
1624
1625<section title="411 Length Required" anchor="status.411">
1626  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1627  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1628<t>
1629   The server refuses to accept the request without a defined Content-Length.
1630   The client &MAY; repeat the request if it adds a valid
1631   Content-Length header field containing the length of the message-body
1632   in the request message.
1633</t>
1634</section>
1635
1636<section title="412 Precondition Failed" anchor="status.412">
1637  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1638  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1639<t>
1640   The precondition given in one or more of the request-header fields
1641   evaluated to false when it was tested on the server, as defined in
1642   &conditional;.
1643</t>
1644</section>
1645
1646<section title="413 Request Entity Too Large" anchor="status.413">
1647  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1648  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1649<t>
1650   The server is refusing to process a request because the request
1651   entity is larger than the server is willing or able to process. The
1652   server &MAY; close the connection to prevent the client from continuing
1653   the request.
1654</t>
1655<t>
1656   If the condition is temporary, the server &SHOULD; include a Retry-After
1657   header field to indicate that it is temporary and after what
1658   time the client &MAY; try again.
1659</t>
1660</section>
1661
1662<section title="414 Request-target Too Long" anchor="status.414">
1663  <iref primary="true" item="414 Request-target Too Long (status code)" x:for-anchor=""/>
1664  <iref primary="true" item="Status Codes" subitem="414 Request-target Too Long" x:for-anchor=""/>
1665<t>
1666   The server is refusing to service the request because the request-target
1667   is longer than the server is willing to interpret. This rare
1668   condition is only likely to occur when a client has improperly
1669   converted a POST request to a GET request with long query
1670   information, when the client has descended into a URI "black hole" of
1671   redirection (e.g., a redirected URI prefix that points to a suffix of
1672   itself), or when the server is under attack by a client attempting to
1673   exploit security holes present in some servers using fixed-length
1674   buffers for reading or manipulating the request-target.
1675</t>
1676</section>
1677
1678<section title="415 Unsupported Media Type" anchor="status.415">
1679  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1680  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1681<t>
1682   The server is refusing to service the request because the entity of
1683   the request is in a format not supported by the requested resource
1684   for the requested method.
1685</t>
1686</section>
1687
1688<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1689  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1690  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1691<t>
1692   The request included a Range request-header field (&header-range;) and none of
1693   the range-specifier values in this field overlap the current extent
1694   of the selected resource.
1695</t>
1696</section>
1697
1698<section title="417 Expectation Failed" anchor="status.417">
1699  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1700  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1701<t>
1702   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1703   could not be met by this server, or, if the server is a proxy,
1704   the server has unambiguous evidence that the request could not be met
1705   by the next-hop server.
1706</t>
1707</section>
1708</section>
1709
1710<section title="Server Error 5xx" anchor="status.5xx">
1711<t>
1712   Response status codes beginning with the digit "5" indicate cases in
1713   which the server is aware that it has erred or is incapable of
1714   performing the request. Except when responding to a HEAD request, the
1715   server &SHOULD; include an entity containing an explanation of the
1716   error situation, and whether it is a temporary or permanent
1717   condition. User agents &SHOULD; display any included entity to the
1718   user. These response codes are applicable to any request method.
1719</t>
1720
1721<section title="500 Internal Server Error" anchor="status.500">
1722  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1723  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1724<t>
1725   The server encountered an unexpected condition which prevented it
1726   from fulfilling the request.
1727</t>
1728</section>
1729
1730<section title="501 Not Implemented" anchor="status.501">
1731  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1732  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1733<t>
1734   The server does not support the functionality required to fulfill the
1735   request. This is the appropriate response when the server does not
1736   recognize the request method and is not capable of supporting it for
1737   any resource.
1738</t>
1739</section>
1740
1741<section title="502 Bad Gateway" anchor="status.502">
1742  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1743  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1744<t>
1745   The server, while acting as a gateway or proxy, received an invalid
1746   response from the upstream server it accessed in attempting to
1747   fulfill the request.
1748</t>
1749</section>
1750
1751<section title="503 Service Unavailable" anchor="status.503">
1752  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1753  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1754<t>
1755   The server is currently unable to handle the request due to a
1756   temporary overloading or maintenance of the server. The implication
1757   is that this is a temporary condition which will be alleviated after
1758   some delay. If known, the length of the delay &MAY; be indicated in a
1759   Retry-After header. If no Retry-After is given, the client &SHOULD;
1760   handle the response as it would for a 500 response.
1761  <list><t>
1762      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1763      server must use it when becoming overloaded. Some servers may wish
1764      to simply refuse the connection.
1765  </t></list>
1766</t>
1767</section>
1768
1769<section title="504 Gateway Timeout" anchor="status.504">
1770  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1771  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1772<t>
1773   The server, while acting as a gateway or proxy, did not receive a
1774   timely response from the upstream server specified by the URI (e.g.
1775   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1776   to access in attempting to complete the request.
1777  <list><t>
1778      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1779      return 400 or 500 when DNS lookups time out.
1780  </t></list>
1781</t>
1782</section>
1783
1784<section title="505 HTTP Version Not Supported" anchor="status.505">
1785  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1786  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1787<t>
1788   The server does not support, or refuses to support, the protocol
1789   version that was used in the request message. The server is
1790   indicating that it is unable or unwilling to complete the request
1791   using the same major version as the client, as described in &http-version;,
1792   other than with this error message. The response &SHOULD; contain
1793   an entity describing why that version is not supported and what other
1794   protocols are supported by that server.
1795</t>
1796
1797</section>
1798</section>
1799</section>
1800
1801
1802<section title="Header Field Definitions" anchor="header.fields">
1803<t>
1804   This section defines the syntax and semantics of HTTP/1.1 header fields
1805   related to request and response semantics.
1806</t>
1807<t>
1808   For entity-header fields, both sender and recipient refer to either the
1809   client or the server, depending on who sends and who receives the entity.
1810</t>
1811
1812<section title="Allow" anchor="header.allow">
1813  <iref primary="true" item="Allow header" x:for-anchor=""/>
1814  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1815  <x:anchor-alias value="Allow"/>
1816  <x:anchor-alias value="Allow-v"/>
1817<t>
1818      The response-header field "Allow" lists the set of methods advertised as
1819      supported by the resource identified by the request-target. The purpose of
1820      this field is strictly to inform the recipient of valid methods
1821      associated with the resource. An Allow header field &MUST; be
1822      present in a 405 (Method Not Allowed) response.
1823</t>
1824<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1825  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1826  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1827</artwork></figure>
1828<t>
1829      Example of use:
1830</t>
1831<figure><artwork type="example">
1832  Allow: GET, HEAD, PUT
1833</artwork></figure>
1834<t>
1835      The actual set of allowed methods is defined
1836      by the origin server at the time of each request.
1837</t>
1838<t>
1839      A proxy &MUST-NOT; modify the Allow header field even if it does not
1840      understand all the methods specified, since the user agent might
1841      have other means of communicating with the origin server.
1842</t>
1843</section>
1844
1845<section title="Expect" anchor="header.expect">
1846  <iref primary="true" item="Expect header" x:for-anchor=""/>
1847  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1848  <x:anchor-alias value="Expect"/>
1849  <x:anchor-alias value="Expect-v"/>
1850  <x:anchor-alias value="expectation"/>
1851  <x:anchor-alias value="expectation-extension"/>
1852  <x:anchor-alias value="expect-params"/>
1853<t>
1854   The request-header field "Expect" is used to indicate that particular
1855   server behaviors are required by the client.
1856</t>
1857<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"/>
1858  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1859  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1860 
1861  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1862  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1863                           *<x:ref>expect-params</x:ref> ]
1864  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1865</artwork></figure>
1866<t>
1867   A server that does not understand or is unable to comply with any of
1868   the expectation values in the Expect field of a request &MUST; respond
1869   with appropriate error status. The server &MUST; respond with a 417
1870   (Expectation Failed) status if any of the expectations cannot be met
1871   or, if there are other problems with the request, some other 4xx
1872   status.
1873</t>
1874<t>
1875   This header field is defined with extensible syntax to allow for
1876   future extensions. If a server receives a request containing an
1877   Expect field that includes an expectation-extension that it does not
1878   support, it &MUST; respond with a 417 (Expectation Failed) status.
1879</t>
1880<t>
1881   Comparison of expectation values is case-insensitive for unquoted
1882   tokens (including the 100-continue token), and is case-sensitive for
1883   quoted-string expectation-extensions.
1884</t>
1885<t>
1886   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1887   return a 417 (Expectation Failed) status if it receives a request
1888   with an expectation that it cannot meet. However, the Expect
1889   request-header itself is end-to-end; it &MUST; be forwarded if the
1890   request is forwarded.
1891</t>
1892<t>
1893   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1894   Expect header.
1895</t>
1896<t>
1897   See &use100; for the use of the 100 (Continue) status.
1898</t>
1899</section>
1900
1901<section title="From" anchor="header.from">
1902  <iref primary="true" item="From header" x:for-anchor=""/>
1903  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1904  <x:anchor-alias value="From"/>
1905  <x:anchor-alias value="From-v"/>
1906  <x:anchor-alias value="mailbox"/>
1907<t>
1908   The request-header field "From", if given, &SHOULD; contain an Internet
1909   e-mail address for the human user who controls the requesting user
1910   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1911   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1912</t>
1913<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1914  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1915  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1916 
1917  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1918</artwork></figure>
1919<t>
1920   An example is:
1921</t>
1922<figure><artwork type="example">
1923  From: webmaster@example.org
1924</artwork></figure>
1925<t>
1926   This header field &MAY; be used for logging purposes and as a means for
1927   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1928   be used as an insecure form of access protection. The interpretation
1929   of this field is that the request is being performed on behalf of the
1930   person given, who accepts responsibility for the method performed. In
1931   particular, robot agents &SHOULD; include this header so that the
1932   person responsible for running the robot can be contacted if problems
1933   occur on the receiving end.
1934</t>
1935<t>
1936   The Internet e-mail address in this field &MAY; be separate from the
1937   Internet host which issued the request. For example, when a request
1938   is passed through a proxy the original issuer's address &SHOULD; be
1939   used.
1940</t>
1941<t>
1942   The client &SHOULD-NOT;  send the From header field without the user's
1943   approval, as it might conflict with the user's privacy interests or
1944   their site's security policy. It is strongly recommended that the
1945   user be able to disable, enable, and modify the value of this field
1946   at any time prior to a request.
1947</t>
1948</section>
1949
1950<section title="Location" anchor="header.location">
1951  <iref primary="true" item="Location header" x:for-anchor=""/>
1952  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1953  <x:anchor-alias value="Location"/>
1954  <x:anchor-alias value="Location-v"/>
1955<t>
1956   The response-header field "Location" is used for the identification of a
1957   new resource or to redirect the recipient to a location other than the
1958   request-target for completion of the request.  For 201 (Created)
1959   responses, the Location is that of the new resource which was created
1960   by the request. For 3xx responses, the location &SHOULD; indicate the
1961   server's preferred URI for automatic redirection to the resource. The
1962   field value consists of a single absolute URI.
1963</t>
1964<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1965  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1966  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1967</artwork></figure>
1968<t>
1969   An example is:
1970</t>
1971<figure><artwork type="example">
1972  Location: http://www.example.org/pub/WWW/People.html
1973</artwork></figure>
1974<t>
1975  <list><t>
1976      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1977      from Location in that the Content-Location identifies the original
1978      location of the entity enclosed in the response. It is therefore
1979      possible for a response to contain header fields for both Location
1980      and Content-Location.
1981  </t></list>
1982</t>
1983<t>
1984   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1985   <list style="symbols">
1986      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1987      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1988      <t>With 305 Use Proxy.</t>
1989   </list>
1990</t>
1991</section>
1992
1993<section title="Max-Forwards" anchor="header.max-forwards">
1994  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1995  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1996  <x:anchor-alias value="Max-Forwards"/>
1997  <x:anchor-alias value="Max-Forwards-v"/>
1998<t>
1999   The request-header "Max-Forwards" field provides a mechanism with the
2000   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2001   number of proxies or gateways that can forward the request to the
2002   next inbound server. This can be useful when the client is attempting
2003   to trace a request chain which appears to be failing or looping in
2004   mid-chain.
2005</t>
2006<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2007  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2008  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2009</artwork></figure>
2010<t>
2011   The Max-Forwards value is a decimal integer indicating the remaining
2012   number of times this request message may be forwarded.
2013</t>
2014<t>
2015   Each proxy or gateway recipient of a TRACE or OPTIONS request
2016   containing a Max-Forwards header field &MUST; check and update its
2017   value prior to forwarding the request. If the received value is zero
2018   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2019   respond as the final recipient. If the received Max-Forwards value is
2020   greater than zero, then the forwarded message &MUST; contain an updated
2021   Max-Forwards field with a value decremented by one (1).
2022</t>
2023<t>
2024   The Max-Forwards header field &MAY; be ignored for all other methods
2025   defined by this specification and for any extension methods for which
2026   it is not explicitly referred to as part of that method definition.
2027</t>
2028</section>
2029
2030<section title="Referer" anchor="header.referer">
2031  <iref primary="true" item="Referer header" x:for-anchor=""/>
2032  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2033  <x:anchor-alias value="Referer"/>
2034  <x:anchor-alias value="Referer-v"/>
2035<t>
2036   The request-header field "Referer" [sic] allows the client to specify,
2037   for the server's benefit, the address (URI) of the resource from
2038   which the request-target was obtained (the "referrer", although the
2039   header field is misspelled.) The Referer request-header allows a
2040   server to generate lists of back-links to resources for interest,
2041   logging, optimized caching, etc. It also allows obsolete or mistyped
2042   links to be traced for maintenance. The Referer field &MUST-NOT; be
2043   sent if the request-target was obtained from a source that does not have
2044   its own URI, such as input from the user keyboard.
2045</t>
2046<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2047  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2048  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2049</artwork></figure>
2050<t>
2051   Example:
2052</t>
2053<figure><artwork type="example">
2054  Referer: http://www.example.org/hypertext/Overview.html
2055</artwork></figure>
2056<t>
2057   If the field value is a relative URI, it &SHOULD; be interpreted
2058   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2059   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2060</t>
2061</section>
2062
2063<section title="Retry-After" anchor="header.retry-after">
2064  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2065  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2066  <x:anchor-alias value="Retry-After"/>
2067  <x:anchor-alias value="Retry-After-v"/>
2068<t>
2069   The response-header "Retry-After" field can be used with a 503 (Service
2070   Unavailable) response to indicate how long the service is expected to
2071   be unavailable to the requesting client. This field &MAY; also be used
2072   with any 3xx (Redirection) response to indicate the minimum time the
2073   user-agent is asked wait before issuing the redirected request. The
2074   value of this field can be either an HTTP-date or an integer number
2075   of seconds (in decimal) after the time of the response.
2076</t>
2077<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2078  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2079  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2080</artwork></figure>
2081<t anchor="rule.delta-seconds">
2082  <x:anchor-alias value="delta-seconds"/>
2083   Time spans are non-negative decimal integers, representing time in
2084   seconds.
2085</t>
2086<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2087  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2088</artwork></figure>
2089<t>
2090   Two examples of its use are
2091</t>
2092<figure><artwork type="example">
2093  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2094  Retry-After: 120
2095</artwork></figure>
2096<t>
2097   In the latter example, the delay is 2 minutes.
2098</t>
2099</section>
2100
2101<section title="Server" anchor="header.server">
2102  <iref primary="true" item="Server header" x:for-anchor=""/>
2103  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2104  <x:anchor-alias value="Server"/>
2105  <x:anchor-alias value="Server-v"/>
2106<t>
2107   The response-header field "Server" contains information about the
2108   software used by the origin server to handle the request. The field
2109   can contain multiple product tokens (&product-tokens;) and comments
2110   identifying the server and any significant subproducts. The product
2111   tokens are listed in order of their significance for identifying the
2112   application.
2113</t>
2114<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2115  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2116  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2117                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2118</artwork></figure>
2119<t>
2120   Example:
2121</t>
2122<figure><artwork type="example">
2123  Server: CERN/3.0 libwww/2.17
2124</artwork></figure>
2125<t>
2126   If the response is being forwarded through a proxy, the proxy
2127   application &MUST-NOT; modify the Server response-header. Instead, it
2128   &MUST; include a Via field (as described in &header-via;).
2129  <list><t>
2130      <x:h>Note:</x:h> Revealing the specific software version of the server might
2131      allow the server machine to become more vulnerable to attacks
2132      against software that is known to contain security holes. Server
2133      implementors are encouraged to make this field a configurable
2134      option.
2135  </t></list>
2136</t>
2137</section>
2138
2139<section title="User-Agent" anchor="header.user-agent">
2140  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2141  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2142  <x:anchor-alias value="User-Agent"/>
2143  <x:anchor-alias value="User-Agent-v"/>
2144<t>
2145   The request-header field "User-Agent" contains information about the
2146   user agent originating the request. This is for statistical purposes,
2147   the tracing of protocol violations, and automated recognition of user
2148   agents for the sake of tailoring responses to avoid particular user
2149   agent limitations. User agents &SHOULD; include this field with
2150   requests. The field can contain multiple product tokens (&product-tokens;)
2151   and comments identifying the agent and any subproducts which form a
2152   significant part of the user agent. By convention, the product tokens
2153   are listed in order of their significance for identifying the
2154   application.
2155</t>
2156<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2157  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2158  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2159                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2160</artwork></figure>
2161<t>
2162   Example:
2163</t>
2164<figure><artwork type="example">
2165  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2166</artwork></figure>
2167</section>
2168
2169</section>
2170
2171<section title="IANA Considerations" anchor="IANA.considerations">
2172
2173<section title="Method Registry" anchor="method.registration">
2174<t>
2175  The registration procedure for HTTP Methods is defined by
2176  <xref target="method.registry"/> of this document.
2177</t>
2178<t>
2179   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2180   should be populated with the registrations below:
2181</t>
2182<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2183<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2184   <ttcol>Method</ttcol>
2185   <ttcol>Safe</ttcol>
2186   <ttcol>Reference</ttcol>
2187   <c>CONNECT</c>
2188   <c>no</c>
2189   <c>
2190      <xref target="CONNECT"/>
2191   </c>
2192   <c>DELETE</c>
2193   <c>no</c>
2194   <c>
2195      <xref target="DELETE"/>
2196   </c>
2197   <c>GET</c>
2198   <c>yes</c>
2199   <c>
2200      <xref target="GET"/>
2201   </c>
2202   <c>HEAD</c>
2203   <c>yes</c>
2204   <c>
2205      <xref target="HEAD"/>
2206   </c>
2207   <c>OPTIONS</c>
2208   <c>yes</c>
2209   <c>
2210      <xref target="OPTIONS"/>
2211   </c>
2212   <c>POST</c>
2213   <c>no</c>
2214   <c>
2215      <xref target="POST"/>
2216   </c>
2217   <c>PUT</c>
2218   <c>no</c>
2219   <c>
2220      <xref target="PUT"/>
2221   </c>
2222   <c>TRACE</c>
2223   <c>yes</c>
2224   <c>
2225      <xref target="TRACE"/>
2226   </c>
2227</texttable>
2228<!--(END)-->
2229</section>
2230
2231<section title="Status Code Registry" anchor="status.code.registration">
2232<t>
2233   The registration procedure for HTTP Status Codes -- previously defined
2234   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2235   by <xref target="status.code.registry"/> of this document.
2236</t>
2237<t>
2238   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2239   should be updated with the registrations below:
2240</t>
2241<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2242<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2243   <ttcol>Value</ttcol>
2244   <ttcol>Description</ttcol>
2245   <ttcol>Reference</ttcol>
2246   <c>100</c>
2247   <c>Continue</c>
2248   <c>
2249      <xref target="status.100"/>
2250   </c>
2251   <c>101</c>
2252   <c>Switching Protocols</c>
2253   <c>
2254      <xref target="status.101"/>
2255   </c>
2256   <c>200</c>
2257   <c>OK</c>
2258   <c>
2259      <xref target="status.200"/>
2260   </c>
2261   <c>201</c>
2262   <c>Created</c>
2263   <c>
2264      <xref target="status.201"/>
2265   </c>
2266   <c>202</c>
2267   <c>Accepted</c>
2268   <c>
2269      <xref target="status.202"/>
2270   </c>
2271   <c>203</c>
2272   <c>Non-Authoritative Information</c>
2273   <c>
2274      <xref target="status.203"/>
2275   </c>
2276   <c>204</c>
2277   <c>No Content</c>
2278   <c>
2279      <xref target="status.204"/>
2280   </c>
2281   <c>205</c>
2282   <c>Reset Content</c>
2283   <c>
2284      <xref target="status.205"/>
2285   </c>
2286   <c>206</c>
2287   <c>Partial Content</c>
2288   <c>
2289      <xref target="status.206"/>
2290   </c>
2291   <c>300</c>
2292   <c>Multiple Choices</c>
2293   <c>
2294      <xref target="status.300"/>
2295   </c>
2296   <c>301</c>
2297   <c>Moved Permanently</c>
2298   <c>
2299      <xref target="status.301"/>
2300   </c>
2301   <c>302</c>
2302   <c>Found</c>
2303   <c>
2304      <xref target="status.302"/>
2305   </c>
2306   <c>303</c>
2307   <c>See Other</c>
2308   <c>
2309      <xref target="status.303"/>
2310   </c>
2311   <c>304</c>
2312   <c>Not Modified</c>
2313   <c>
2314      <xref target="status.304"/>
2315   </c>
2316   <c>305</c>
2317   <c>Use Proxy</c>
2318   <c>
2319      <xref target="status.305"/>
2320   </c>
2321   <c>306</c>
2322   <c>(Unused)</c>
2323   <c>
2324      <xref target="status.306"/>
2325   </c>
2326   <c>307</c>
2327   <c>Temporary Redirect</c>
2328   <c>
2329      <xref target="status.307"/>
2330   </c>
2331   <c>400</c>
2332   <c>Bad Request</c>
2333   <c>
2334      <xref target="status.400"/>
2335   </c>
2336   <c>401</c>
2337   <c>Unauthorized</c>
2338   <c>
2339      <xref target="status.401"/>
2340   </c>
2341   <c>402</c>
2342   <c>Payment Required</c>
2343   <c>
2344      <xref target="status.402"/>
2345   </c>
2346   <c>403</c>
2347   <c>Forbidden</c>
2348   <c>
2349      <xref target="status.403"/>
2350   </c>
2351   <c>404</c>
2352   <c>Not Found</c>
2353   <c>
2354      <xref target="status.404"/>
2355   </c>
2356   <c>405</c>
2357   <c>Method Not Allowed</c>
2358   <c>
2359      <xref target="status.405"/>
2360   </c>
2361   <c>406</c>
2362   <c>Not Acceptable</c>
2363   <c>
2364      <xref target="status.406"/>
2365   </c>
2366   <c>407</c>
2367   <c>Proxy Authentication Required</c>
2368   <c>
2369      <xref target="status.407"/>
2370   </c>
2371   <c>408</c>
2372   <c>Request Timeout</c>
2373   <c>
2374      <xref target="status.408"/>
2375   </c>
2376   <c>409</c>
2377   <c>Conflict</c>
2378   <c>
2379      <xref target="status.409"/>
2380   </c>
2381   <c>410</c>
2382   <c>Gone</c>
2383   <c>
2384      <xref target="status.410"/>
2385   </c>
2386   <c>411</c>
2387   <c>Length Required</c>
2388   <c>
2389      <xref target="status.411"/>
2390   </c>
2391   <c>412</c>
2392   <c>Precondition Failed</c>
2393   <c>
2394      <xref target="status.412"/>
2395   </c>
2396   <c>413</c>
2397   <c>Request Entity Too Large</c>
2398   <c>
2399      <xref target="status.413"/>
2400   </c>
2401   <c>414</c>
2402   <c>Request-target Too Long</c>
2403   <c>
2404      <xref target="status.414"/>
2405   </c>
2406   <c>415</c>
2407   <c>Unsupported Media Type</c>
2408   <c>
2409      <xref target="status.415"/>
2410   </c>
2411   <c>416</c>
2412   <c>Requested Range Not Satisfiable</c>
2413   <c>
2414      <xref target="status.416"/>
2415   </c>
2416   <c>417</c>
2417   <c>Expectation Failed</c>
2418   <c>
2419      <xref target="status.417"/>
2420   </c>
2421   <c>500</c>
2422   <c>Internal Server Error</c>
2423   <c>
2424      <xref target="status.500"/>
2425   </c>
2426   <c>501</c>
2427   <c>Not Implemented</c>
2428   <c>
2429      <xref target="status.501"/>
2430   </c>
2431   <c>502</c>
2432   <c>Bad Gateway</c>
2433   <c>
2434      <xref target="status.502"/>
2435   </c>
2436   <c>503</c>
2437   <c>Service Unavailable</c>
2438   <c>
2439      <xref target="status.503"/>
2440   </c>
2441   <c>504</c>
2442   <c>Gateway Timeout</c>
2443   <c>
2444      <xref target="status.504"/>
2445   </c>
2446   <c>505</c>
2447   <c>HTTP Version Not Supported</c>
2448   <c>
2449      <xref target="status.505"/>
2450   </c>
2451</texttable>
2452<!--(END)-->
2453</section>
2454<section title="Message Header Registration" anchor="message.header.registration">
2455<t>
2456   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2457   with the permanent registrations below (see <xref target="RFC3864"/>):
2458</t>
2459<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2460<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2461   <ttcol>Header Field Name</ttcol>
2462   <ttcol>Protocol</ttcol>
2463   <ttcol>Status</ttcol>
2464   <ttcol>Reference</ttcol>
2465   <c>Allow</c>
2466   <c>http</c>
2467   <c>standard</c>
2468   <c>
2469      <xref target="header.allow"/>
2470   </c>
2471   <c>Expect</c>
2472   <c>http</c>
2473   <c>standard</c>
2474   <c>
2475      <xref target="header.expect"/>
2476   </c>
2477   <c>From</c>
2478   <c>http</c>
2479   <c>standard</c>
2480   <c>
2481      <xref target="header.from"/>
2482   </c>
2483   <c>Location</c>
2484   <c>http</c>
2485   <c>standard</c>
2486   <c>
2487      <xref target="header.location"/>
2488   </c>
2489   <c>Max-Forwards</c>
2490   <c>http</c>
2491   <c>standard</c>
2492   <c>
2493      <xref target="header.max-forwards"/>
2494   </c>
2495   <c>Referer</c>
2496   <c>http</c>
2497   <c>standard</c>
2498   <c>
2499      <xref target="header.referer"/>
2500   </c>
2501   <c>Retry-After</c>
2502   <c>http</c>
2503   <c>standard</c>
2504   <c>
2505      <xref target="header.retry-after"/>
2506   </c>
2507   <c>Server</c>
2508   <c>http</c>
2509   <c>standard</c>
2510   <c>
2511      <xref target="header.server"/>
2512   </c>
2513   <c>User-Agent</c>
2514   <c>http</c>
2515   <c>standard</c>
2516   <c>
2517      <xref target="header.user-agent"/>
2518   </c>
2519</texttable>
2520<!--(END)-->
2521<t>
2522   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2523</t>
2524</section>
2525</section>
2526
2527<section title="Security Considerations" anchor="security.considerations">
2528<t>
2529   This section is meant to inform application developers, information
2530   providers, and users of the security limitations in HTTP/1.1 as
2531   described by this document. The discussion does not include
2532   definitive solutions to the problems revealed, though it does make
2533   some suggestions for reducing security risks.
2534</t>
2535
2536<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2537<t>
2538   Like any generic data transfer protocol, HTTP cannot regulate the
2539   content of the data that is transferred, nor is there any a priori
2540   method of determining the sensitivity of any particular piece of
2541   information within the context of any given request. Therefore,
2542   applications &SHOULD; supply as much control over this information as
2543   possible to the provider of that information. Four header fields are
2544   worth special mention in this context: Server, Via, Referer and From.
2545</t>
2546<t>
2547   Revealing the specific software version of the server might allow the
2548   server machine to become more vulnerable to attacks against software
2549   that is known to contain security holes. Implementors &SHOULD; make the
2550   Server header field a configurable option.
2551</t>
2552<t>
2553   Proxies which serve as a portal through a network firewall &SHOULD;
2554   take special precautions regarding the transfer of header information
2555   that identifies the hosts behind the firewall. In particular, they
2556   &SHOULD; remove, or replace with sanitized versions, any Via fields
2557   generated behind the firewall.
2558</t>
2559<t>
2560   The Referer header allows reading patterns to be studied and reverse
2561   links drawn. Although it can be very useful, its power can be abused
2562   if user details are not separated from the information contained in
2563   the Referer. Even when the personal information has been removed, the
2564   Referer header might indicate a private document's URI whose
2565   publication would be inappropriate.
2566</t>
2567<t>
2568   The information sent in the From field might conflict with the user's
2569   privacy interests or their site's security policy, and hence it
2570   &SHOULD-NOT;  be transmitted without the user being able to disable,
2571   enable, and modify the contents of the field. The user &MUST; be able
2572   to set the contents of this field within a user preference or
2573   application defaults configuration.
2574</t>
2575<t>
2576   We suggest, though do not require, that a convenient toggle interface
2577   be provided for the user to enable or disable the sending of From and
2578   Referer information.
2579</t>
2580<t>
2581   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2582   fields can sometimes be used to determine that a specific client or
2583   server have a particular security hole which might be exploited.
2584   Unfortunately, this same information is often used for other valuable
2585   purposes for which HTTP currently has no better mechanism.
2586</t>
2587</section>
2588
2589<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2590<t>
2591   Because the source of a link might be private information or might
2592   reveal an otherwise private information source, it is strongly
2593   recommended that the user be able to select whether or not the
2594   Referer field is sent. For example, a browser client could have a
2595   toggle switch for browsing openly/anonymously, which would
2596   respectively enable/disable the sending of Referer and From
2597   information.
2598</t>
2599<t>
2600   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2601   HTTP request if the referring page was transferred with a secure
2602   protocol.
2603</t>
2604<t>
2605   Authors of services should not use
2606   GET-based forms for the submission of sensitive data because that
2607   data will be encoded in the Request-target. Many existing
2608   servers, proxies, and user agents log or display the Request-target in
2609   places where it might be visible to third parties. Such services can
2610   use POST-based form submission instead.
2611</t>
2612</section>
2613
2614<section title="Location Headers and Spoofing" anchor="location.spoofing">
2615<t>
2616   If a single server supports multiple organizations that do not trust
2617   one another, then it &MUST; check the values of Location and Content-Location
2618   headers in responses that are generated under control of
2619   said organizations to make sure that they do not attempt to
2620   invalidate resources over which they have no authority.
2621</t>
2622</section>
2623
2624</section>
2625
2626<section title="Acknowledgments" anchor="ack">
2627</section>
2628</middle>
2629<back>
2630
2631<references title="Normative References">
2632
2633<reference anchor="Part1">
2634  <front>
2635    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2636    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2637      <organization abbrev="Day Software">Day Software</organization>
2638      <address><email>fielding@gbiv.com</email></address>
2639    </author>
2640    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2641      <organization>One Laptop per Child</organization>
2642      <address><email>jg@laptop.org</email></address>
2643    </author>
2644    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2645      <organization abbrev="HP">Hewlett-Packard Company</organization>
2646      <address><email>JeffMogul@acm.org</email></address>
2647    </author>
2648    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2649      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2650      <address><email>henrikn@microsoft.com</email></address>
2651    </author>
2652    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2653      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2654      <address><email>LMM@acm.org</email></address>
2655    </author>
2656    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2657      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2658      <address><email>paulle@microsoft.com</email></address>
2659    </author>
2660    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2661      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2662      <address><email>timbl@w3.org</email></address>
2663    </author>
2664    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2665      <organization abbrev="W3C">World Wide Web Consortium</organization>
2666      <address><email>ylafon@w3.org</email></address>
2667    </author>
2668    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2669      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2670      <address><email>julian.reschke@greenbytes.de</email></address>
2671    </author>
2672    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2673  </front>
2674  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2675  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2676</reference>
2677
2678<reference anchor="Part3">
2679  <front>
2680    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2681    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2682      <organization abbrev="Day Software">Day Software</organization>
2683      <address><email>fielding@gbiv.com</email></address>
2684    </author>
2685    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2686      <organization>One Laptop per Child</organization>
2687      <address><email>jg@laptop.org</email></address>
2688    </author>
2689    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2690      <organization abbrev="HP">Hewlett-Packard Company</organization>
2691      <address><email>JeffMogul@acm.org</email></address>
2692    </author>
2693    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2694      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2695      <address><email>henrikn@microsoft.com</email></address>
2696    </author>
2697    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2698      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2699      <address><email>LMM@acm.org</email></address>
2700    </author>
2701    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2702      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2703      <address><email>paulle@microsoft.com</email></address>
2704    </author>
2705    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2706      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2707      <address><email>timbl@w3.org</email></address>
2708    </author>
2709    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2710      <organization abbrev="W3C">World Wide Web Consortium</organization>
2711      <address><email>ylafon@w3.org</email></address>
2712    </author>
2713    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2714      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2715      <address><email>julian.reschke@greenbytes.de</email></address>
2716    </author>
2717    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2718  </front>
2719  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2720  <x:source href="p3-payload.xml" basename="p3-payload"/>
2721</reference>
2722
2723<reference anchor="Part4">
2724  <front>
2725    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2726    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2727      <organization abbrev="Day Software">Day Software</organization>
2728      <address><email>fielding@gbiv.com</email></address>
2729    </author>
2730    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2731      <organization>One Laptop per Child</organization>
2732      <address><email>jg@laptop.org</email></address>
2733    </author>
2734    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2735      <organization abbrev="HP">Hewlett-Packard Company</organization>
2736      <address><email>JeffMogul@acm.org</email></address>
2737    </author>
2738    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2739      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2740      <address><email>henrikn@microsoft.com</email></address>
2741    </author>
2742    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2743      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2744      <address><email>LMM@acm.org</email></address>
2745    </author>
2746    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2747      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2748      <address><email>paulle@microsoft.com</email></address>
2749    </author>
2750    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2751      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2752      <address><email>timbl@w3.org</email></address>
2753    </author>
2754    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2755      <organization abbrev="W3C">World Wide Web Consortium</organization>
2756      <address><email>ylafon@w3.org</email></address>
2757    </author>
2758    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2759      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2760      <address><email>julian.reschke@greenbytes.de</email></address>
2761    </author>
2762    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2763  </front>
2764  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2765  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2766</reference>
2767
2768<reference anchor="Part5">
2769  <front>
2770    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2771    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2772      <organization abbrev="Day Software">Day Software</organization>
2773      <address><email>fielding@gbiv.com</email></address>
2774    </author>
2775    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2776      <organization>One Laptop per Child</organization>
2777      <address><email>jg@laptop.org</email></address>
2778    </author>
2779    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2780      <organization abbrev="HP">Hewlett-Packard Company</organization>
2781      <address><email>JeffMogul@acm.org</email></address>
2782    </author>
2783    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2784      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2785      <address><email>henrikn@microsoft.com</email></address>
2786    </author>
2787    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2788      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2789      <address><email>LMM@acm.org</email></address>
2790    </author>
2791    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2792      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2793      <address><email>paulle@microsoft.com</email></address>
2794    </author>
2795    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2796      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2797      <address><email>timbl@w3.org</email></address>
2798    </author>
2799    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2800      <organization abbrev="W3C">World Wide Web Consortium</organization>
2801      <address><email>ylafon@w3.org</email></address>
2802    </author>
2803    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2804      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2805      <address><email>julian.reschke@greenbytes.de</email></address>
2806    </author>
2807    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2808  </front>
2809  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2810  <x:source href="p5-range.xml" basename="p5-range"/>
2811</reference>
2812
2813<reference anchor="Part6">
2814  <front>
2815    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2816    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2817      <organization abbrev="Day Software">Day Software</organization>
2818      <address><email>fielding@gbiv.com</email></address>
2819    </author>
2820    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2821      <organization>One Laptop per Child</organization>
2822      <address><email>jg@laptop.org</email></address>
2823    </author>
2824    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2825      <organization abbrev="HP">Hewlett-Packard Company</organization>
2826      <address><email>JeffMogul@acm.org</email></address>
2827    </author>
2828    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2829      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2830      <address><email>henrikn@microsoft.com</email></address>
2831    </author>
2832    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2833      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2834      <address><email>LMM@acm.org</email></address>
2835    </author>
2836    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2837      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2838      <address><email>paulle@microsoft.com</email></address>
2839    </author>
2840    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2841      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2842      <address><email>timbl@w3.org</email></address>
2843    </author>
2844    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2845      <organization abbrev="W3C">World Wide Web Consortium</organization>
2846      <address><email>ylafon@w3.org</email></address>
2847    </author>
2848    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2849      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2850      <address><email>julian.reschke@greenbytes.de</email></address>
2851    </author>
2852    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2853  </front>
2854  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2855  <x:source href="p6-cache.xml" basename="p6-cache"/>
2856</reference>
2857
2858<reference anchor="Part7">
2859  <front>
2860    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2861    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2862      <organization abbrev="Day Software">Day Software</organization>
2863      <address><email>fielding@gbiv.com</email></address>
2864    </author>
2865    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2866      <organization>One Laptop per Child</organization>
2867      <address><email>jg@laptop.org</email></address>
2868    </author>
2869    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2870      <organization abbrev="HP">Hewlett-Packard Company</organization>
2871      <address><email>JeffMogul@acm.org</email></address>
2872    </author>
2873    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2874      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2875      <address><email>henrikn@microsoft.com</email></address>
2876    </author>
2877    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2878      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2879      <address><email>LMM@acm.org</email></address>
2880    </author>
2881    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2882      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2883      <address><email>paulle@microsoft.com</email></address>
2884    </author>
2885    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2886      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2887      <address><email>timbl@w3.org</email></address>
2888    </author>
2889    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2890      <organization abbrev="W3C">World Wide Web Consortium</organization>
2891      <address><email>ylafon@w3.org</email></address>
2892    </author>
2893    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2894      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2895      <address><email>julian.reschke@greenbytes.de</email></address>
2896    </author>
2897    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2898  </front>
2899  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2900  <x:source href="p7-auth.xml" basename="p7-auth"/>
2901</reference>
2902
2903<reference anchor="RFC2119">
2904  <front>
2905    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2906    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2907      <organization>Harvard University</organization>
2908      <address><email>sob@harvard.edu</email></address>
2909    </author>
2910    <date month="March" year="1997"/>
2911  </front>
2912  <seriesInfo name="BCP" value="14"/>
2913  <seriesInfo name="RFC" value="2119"/>
2914</reference>
2915
2916</references>
2917
2918<references title="Informative References">
2919
2920<reference anchor="RFC1945">
2921  <front>
2922    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2923    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2924      <organization>MIT, Laboratory for Computer Science</organization>
2925      <address><email>timbl@w3.org</email></address>
2926    </author>
2927    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2928      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2929      <address><email>fielding@ics.uci.edu</email></address>
2930    </author>
2931    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2932      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2933      <address><email>frystyk@w3.org</email></address>
2934    </author>
2935    <date month="May" year="1996"/>
2936  </front>
2937  <seriesInfo name="RFC" value="1945"/>
2938</reference>
2939
2940<reference anchor="RFC2068">
2941  <front>
2942    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2943    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2944      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2945      <address><email>fielding@ics.uci.edu</email></address>
2946    </author>
2947    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2948      <organization>MIT Laboratory for Computer Science</organization>
2949      <address><email>jg@w3.org</email></address>
2950    </author>
2951    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2952      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2953      <address><email>mogul@wrl.dec.com</email></address>
2954    </author>
2955    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2956      <organization>MIT Laboratory for Computer Science</organization>
2957      <address><email>frystyk@w3.org</email></address>
2958    </author>
2959    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2960      <organization>MIT Laboratory for Computer Science</organization>
2961      <address><email>timbl@w3.org</email></address>
2962    </author>
2963    <date month="January" year="1997"/>
2964  </front>
2965  <seriesInfo name="RFC" value="2068"/>
2966</reference>
2967
2968<reference anchor="RFC2616">
2969  <front>
2970    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2971    <author initials="R." surname="Fielding" fullname="R. Fielding">
2972      <organization>University of California, Irvine</organization>
2973      <address><email>fielding@ics.uci.edu</email></address>
2974    </author>
2975    <author initials="J." surname="Gettys" fullname="J. Gettys">
2976      <organization>W3C</organization>
2977      <address><email>jg@w3.org</email></address>
2978    </author>
2979    <author initials="J." surname="Mogul" fullname="J. Mogul">
2980      <organization>Compaq Computer Corporation</organization>
2981      <address><email>mogul@wrl.dec.com</email></address>
2982    </author>
2983    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2984      <organization>MIT Laboratory for Computer Science</organization>
2985      <address><email>frystyk@w3.org</email></address>
2986    </author>
2987    <author initials="L." surname="Masinter" fullname="L. Masinter">
2988      <organization>Xerox Corporation</organization>
2989      <address><email>masinter@parc.xerox.com</email></address>
2990    </author>
2991    <author initials="P." surname="Leach" fullname="P. Leach">
2992      <organization>Microsoft Corporation</organization>
2993      <address><email>paulle@microsoft.com</email></address>
2994    </author>
2995    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2996      <organization>W3C</organization>
2997      <address><email>timbl@w3.org</email></address>
2998    </author>
2999    <date month="June" year="1999"/>
3000  </front>
3001  <seriesInfo name="RFC" value="2616"/>
3002</reference>
3003
3004<reference anchor='RFC2817'>
3005  <front>
3006    <title>Upgrading to TLS Within HTTP/1.1</title>
3007    <author initials='R.' surname='Khare' fullname='R. Khare'>
3008      <organization>4K Associates / UC Irvine</organization>
3009      <address><email>rohit@4K-associates.com</email></address>
3010    </author>
3011    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3012      <organization>Agranat Systems, Inc.</organization>
3013      <address><email>lawrence@agranat.com</email></address>
3014    </author>
3015    <date year='2000' month='May' />
3016  </front>
3017  <seriesInfo name='RFC' value='2817' />
3018</reference>
3019
3020<reference anchor='RFC3864'>
3021  <front>
3022    <title>Registration Procedures for Message Header Fields</title>
3023    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3024      <organization>Nine by Nine</organization>
3025      <address><email>GK-IETF@ninebynine.org</email></address>
3026    </author>
3027    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3028      <organization>BEA Systems</organization>
3029      <address><email>mnot@pobox.com</email></address>
3030    </author>
3031    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3032      <organization>HP Labs</organization>
3033      <address><email>JeffMogul@acm.org</email></address>
3034    </author>
3035    <date year='2004' month='September' />
3036  </front>
3037  <seriesInfo name='BCP' value='90' />
3038  <seriesInfo name='RFC' value='3864' />
3039</reference>
3040
3041<reference anchor='RFC5226'>
3042  <front>
3043    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3044    <author initials='T.' surname='Narten' fullname='T. Narten'>
3045      <organization>IBM</organization>
3046      <address><email>narten@us.ibm.com</email></address>
3047    </author>
3048    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3049      <organization>Google</organization>
3050      <address><email>Harald@Alvestrand.no</email></address>
3051    </author>
3052    <date year='2008' month='May' />
3053  </front>
3054  <seriesInfo name='BCP' value='26' />
3055  <seriesInfo name='RFC' value='5226' />
3056</reference>
3057
3058<reference anchor="RFC5322">
3059  <front>
3060    <title>Internet Message Format</title>
3061    <author initials="P." surname="Resnick" fullname="P. Resnick">
3062      <organization>Qualcomm Incorporated</organization>
3063    </author>
3064    <date year="2008" month="October"/>
3065  </front> 
3066  <seriesInfo name="RFC" value="5322"/>
3067</reference>
3068
3069</references>
3070
3071<section title="Compatibility with Previous Versions" anchor="compatibility">
3072<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3073<t>
3074   Clarified which error code should be used for inbound server failures
3075   (e.g. DNS failures). (<xref target="status.504"/>).
3076</t>
3077<t>
3078   201 (Created) had a race that required an Etag be sent when a resource is
3079   first created. (<xref target="status.201"/>).
3080</t>
3081<t>
3082   Rewrite of message transmission requirements to make it much harder
3083   for implementors to get it wrong, as the consequences of errors here
3084   can have significant impact on the Internet, and to deal with the
3085   following problems:
3086  <list style="numbers">
3087      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3088         this was incorrectly placing a requirement on the behavior of
3089         an implementation of a future version of HTTP/1.x</t>
3090
3091      <t>Made it clear that user-agents should retry requests, not
3092         "clients" in general.</t>
3093
3094      <t>Converted requirements for clients to ignore unexpected 100
3095         (Continue) responses, and for proxies to forward 100 responses,
3096         into a general requirement for 1xx responses.</t>
3097
3098      <t>Modified some TCP-specific language, to make it clearer that
3099         non-TCP transports are possible for HTTP.</t>
3100
3101      <t>Require that the origin server &MUST-NOT; wait for the request
3102         body before it sends a required 100 (Continue) response.</t>
3103
3104      <t>Allow, rather than require, a server to omit 100 (Continue) if
3105         it has already seen some of the request body.</t>
3106
3107      <t>Allow servers to defend against denial-of-service attacks and
3108         broken clients.</t>
3109  </list>
3110</t>
3111<t>
3112   This change adds the Expect header and 417 status code.
3113</t>
3114<t>
3115   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3116   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3117</t>
3118<t>
3119   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
3120   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3121</t>
3122</section>
3123
3124<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3125<t>
3126  This document takes over the Status Code Registry, previously defined
3127  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3128  (<xref target="status.code.registry"/>)
3129</t>
3130<t>
3131  Clarify definition of POST.
3132  (<xref target="POST"/>)
3133</t>
3134<t>
3135  Failed to consider that there are
3136  many other request methods that are safe to automatically redirect,
3137  and further that the user agent is able to make that determination
3138  based on the request method semantics.
3139  (Sections <xref format="counter" target="status.301"/>,
3140  <xref format="counter" target="status.302"/> and
3141  <xref format="counter" target="status.307"/>)
3142</t>
3143<t>
3144  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3145  It used to indicate that the requested resource must be accessed through the
3146  proxy given by the Location field. The Location field gave the URI of the
3147  proxy. The recipient was expected to repeat this single request via the proxy.
3148  (<xref target="status.305"/>)
3149</t>
3150<t>
3151  Reclassify Allow header as response header, removing the option to
3152  specify it in a PUT request.
3153  Relax the server requirement on the contents of the Allow header and
3154  remove requirement on clients to always trust the header value.
3155  (<xref target="header.allow"/>)
3156</t>
3157<t>
3158  Correct syntax of Location header to allow fragment,
3159  as referred symbol wasn't what was expected, and add some
3160  clarifications as to when it would not be appropriate.
3161  (<xref target="header.location"/>)
3162</t>
3163<t>
3164  In the description of the Server header, the Via field
3165  was described as a SHOULD. The requirement was and is stated
3166  correctly in the description of the Via header in &header-via;.
3167  (<xref target="header.server"/>)
3168</t>
3169</section>
3170
3171</section>
3172
3173<section title="Collected ABNF" anchor="collected.abnf">
3174   <figure>
3175      <artwork type="abnf" name="p2-semantics.parsed-abnf">Accept = &lt;Accept, defined in [Part3], Section 5.1&gt;&#xD;
3176Accept-Charset = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;&#xD;
3177Accept-Encoding = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;&#xD;
3178Accept-Language = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;&#xD;
3179Accept-Ranges = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;&#xD;
3180Age = &lt;Age, defined in [Part6], Section 15.1&gt;&#xD;
3181Allow = "Allow:" OWS Allow-v&#xD;
3182Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]&#xD;
3183Authorization = &lt;Authorization, defined in [Part7], Section 3.1&gt;&#xD;
3184CR = &lt;CR, defined in [Part1], Section 1.2.2&gt;&#xD;
3185DIGIT = &lt;DIGIT, defined in [Part1], Section 1.2.2&gt;&#xD;
3186ETag = &lt;ETag, defined in [Part4], Section 6.1&gt;&#xD;
3187Expect = "Expect:" OWS Expect-v&#xD;
3188Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )&#xD;
3189From = "From:" OWS From-v&#xD;
3190From-v = mailbox&#xD;
3191HTTP-date = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;&#xD;
3192Host = &lt;Host, defined in [Part1], Section 2.1&gt;&#xD;
3193If-Match = &lt;If-Match, defined in [Part4], Section 6.2&gt;&#xD;
3194If-Modified-Since = &lt;If-Modified-Since, defined in [Part4], Section&#xD;
3195 6.3&gt;&#xD;
3196If-None-Match = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;&#xD;
3197If-Range = &lt;If-Range, defined in [Part5], Section 5.3&gt;&#xD;
3198If-Unmodified-Since = &lt;If-Unmodified-Since, defined in [Part4],&#xD;
3199 Section 6.5&gt;&#xD;
3200LF = &lt;LF, defined in [Part1], Section 1.2.2&gt;&#xD;
3201Location = "Location:" OWS Location-v&#xD;
3202Location-v = absolute-URI [ "#" fragment ]&#xD;
3203Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v&#xD;
3204Max-Forwards-v = 1*DIGIT&#xD;
3205Method = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 /&#xD;
3206 %x50.4F.53.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45&#xD;
3207 / %x43.4F.4E.4E.45.43.54 / extension-method&#xD;
3208OWS = &lt;OWS, defined in [Part1], Section 1.2.2&gt;&#xD;
3209Proxy-Authenticate = &lt;Proxy-Authenticate, defined in [Part7], Section&#xD;
3210 3.2&gt;&#xD;
3211Proxy-Authorization = &lt;Proxy-Authorization, defined in [Part7],&#xD;
3212 Section 3.3&gt;&#xD;
3213RWS = &lt;RWS, defined in [Part1], Section 1.2.2&gt;&#xD;
3214Range = &lt;Range, defined in [Part5], Section 5.4&gt;&#xD;
3215Reason-Phrase = *( WSP / VCHAR / obs-text )&#xD;
3216Referer = "Referer:" OWS Referer-v&#xD;
3217Referer-v = absolute-URI / partial-URI&#xD;
3218Retry-After = "Retry-After:" OWS Retry-After-v&#xD;
3219Retry-After-v = HTTP-date / delta-seconds&#xD;
3220Server = "Server:" OWS Server-v&#xD;
3221Server-v = product *( RWS ( product / comment ) )&#xD;
3222Status-Code = "100" / "101" / "200" / "201" / "202" / "203" / "204" /&#xD;
3223 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /&#xD;
3224 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /&#xD;
3225 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /&#xD;
3226 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /&#xD;
3227 "505" / extension-code&#xD;
3228TE = &lt;TE, defined in [Part1], Section 8.8&gt;&#xD;
3229User-Agent = "User-Agent:" OWS User-Agent-v&#xD;
3230User-Agent-v = product *( RWS ( product / comment ) )&#xD;
3231VCHAR = &lt;VCHAR, defined in [Part1], Section 1.2.2&gt;&#xD;
3232Vary = &lt;Vary, defined in [Part6], Section 15.5&gt;&#xD;
3233WSP = &lt;WSP, defined in [Part1], Section 1.2.2&gt;&#xD;
3234WWW-Authenticate = &lt;WWW-Authenticate, defined in [Part7], Section&#xD;
3235 3.4&gt;&#xD;
3236absolute-URI = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;&#xD;
3237comment = &lt;comment, defined in [Part1], Section 1.2.2&gt;&#xD;
3238delta-seconds = 1*DIGIT&#xD;
3239expect-params = ";" token [ "=" ( token / quoted-string ) ]&#xD;
3240expectation = "100-continue" / expectation-extension&#xD;
3241expectation-extension = token [ "=" ( token / quoted-string )&#xD;
3242 *expect-params ]&#xD;
3243extension-code = 3DIGIT&#xD;
3244extension-method = token&#xD;
3245fragment = &lt;fragment, defined in [Part1], Section 2.1&gt;&#xD;
3246mailbox = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;&#xD;
3247obs-text = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;&#xD;
3248partial-URI = &lt;partial-URI, defined in [Part1], Section 2.1&gt;&#xD;
3249product = &lt;product, defined in [Part1], Section 3.4&gt;&#xD;
3250quoted-string = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;&#xD;
3251request-header = Accept / Accept-Charset / Accept-Encoding /&#xD;
3252 Accept-Language / Authorization / Expect / From / Host / If-Match /&#xD;
3253 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /&#xD;
3254 Max-Forwards / Proxy-Authorization / Range / Referer / TE /&#xD;
3255 User-Agent&#xD;
3256response-header = Accept-Ranges / Age / Allow / ETag / Location /&#xD;
3257 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate&#xD;
3258token = &lt;token, defined in [Part1], Section 1.2.2&gt;&#xD;
3259; CR defined but not used&#xD;
3260; LF defined but not used&#xD;
3261; Reason-Phrase defined but not used&#xD;
3262; Status-Code defined but not used&#xD;
3263; request-header defined but not used&#xD;
3264; response-header defined but not used&#xD;
3265</artwork>
3266   </figure>
3267</section>
3268
3269<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3270
3271<section title="Since RFC2616">
3272<t>
3273  Extracted relevant partitions from <xref target="RFC2616"/>.
3274</t>
3275</section>
3276
3277<section title="Since draft-ietf-httpbis-p2-semantics-00">
3278<t>
3279  Closed issues:
3280  <list style="symbols"> 
3281    <t>
3282      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3283      "Via is a MUST"
3284      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3285    </t>
3286    <t>
3287      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3288      "Fragments allowed in Location"
3289      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3290    </t>
3291    <t>
3292      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3293      "Safe Methods vs Redirection"
3294      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3295    </t>
3296    <t>
3297      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3298      "Revise description of the POST method"
3299      (<eref target="http://purl.org/NET/http-errata#post"/>)
3300    </t>
3301    <t>
3302      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3303      "Normative and Informative references"
3304    </t>
3305    <t>
3306      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3307      "RFC2606 Compliance"
3308    </t>
3309    <t>
3310      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3311      "Informative references"
3312    </t>
3313    <t>
3314      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3315      "Redundant cross-references"
3316    </t>
3317  </list>
3318</t>
3319<t>
3320  Other changes:
3321  <list style="symbols"> 
3322    <t>
3323      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3324    </t>
3325  </list>
3326</t>
3327</section>
3328
3329<section title="Since draft-ietf-httpbis-p2-semantics-01">
3330<t>
3331  Closed issues:
3332  <list style="symbols"> 
3333    <t>
3334      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3335      "PUT side effects"
3336    </t>
3337    <t>
3338      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3339      "Duplicate Host header requirements"
3340    </t>
3341  </list>
3342</t>
3343<t>
3344  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3345  <list style="symbols"> 
3346    <t>
3347      Move "Product Tokens" section (back) into Part 1, as "token" is used
3348      in the definition of the Upgrade header.
3349    </t>
3350    <t>
3351      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3352    </t>
3353    <t>
3354      Copy definition of delta-seconds from Part6 instead of referencing it.
3355    </t>
3356  </list>
3357</t>
3358</section>
3359
3360<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3361<t>
3362  Closed issues:
3363  <list style="symbols"> 
3364    <t>
3365      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3366      "Requiring Allow in 405 responses"
3367    </t>
3368    <t>
3369      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3370      "Status Code Registry"
3371    </t>
3372    <t>
3373      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3374      "Redirection vs. Location"
3375    </t>
3376    <t>
3377      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3378      "Cacheability of 303 response"
3379    </t>
3380    <t>
3381      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3382      "305 Use Proxy"
3383    </t>
3384    <t>
3385      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3386      "Classification for Allow header"
3387    </t>
3388    <t>
3389      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3390      "PUT - 'store under' vs 'store at'"
3391    </t>
3392  </list>
3393</t>
3394<t>
3395  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3396  <list style="symbols"> 
3397    <t>
3398      Reference RFC 3984, and update header registrations for headers defined
3399      in this document.
3400    </t>
3401  </list>
3402</t>
3403<t>
3404  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3405  <list style="symbols"> 
3406    <t>
3407      Replace string literals when the string really is case-sensitive (method).
3408    </t>
3409  </list>
3410</t>
3411</section>
3412
3413<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3414<t>
3415  Closed issues:
3416  <list style="symbols"> 
3417    <t>
3418      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3419      "OPTIONS request bodies"
3420    </t>
3421    <t>
3422      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3423      "Description of CONNECT should refer to RFC2817"
3424    </t>
3425    <t>
3426      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3427      "Location Content-Location reference request/response mixup"
3428    </t>
3429  </list>
3430</t>
3431<t>
3432  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3433  <list style="symbols"> 
3434    <t>
3435      Added initial proposal for registration process, plus initial
3436      content (non-HTTP/1.1 methods to be added by a separate specification).
3437    </t>
3438  </list>
3439</t>
3440</section>
3441
3442<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3443<t>
3444  Closed issues:
3445  <list style="symbols"> 
3446    <t>
3447      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3448      "Content-*"
3449    </t>
3450    <t>
3451      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3452      "RFC 2822 is updated by RFC 5322"
3453    </t>
3454  </list>
3455</t>
3456<t>
3457  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3458  <list style="symbols"> 
3459    <t>
3460      Use "/" instead of "|" for alternatives.
3461    </t>
3462    <t>
3463      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3464      whitespace ("OWS") and required whitespace ("RWS").
3465    </t>
3466    <t>
3467      Rewrite ABNFs to spell out whitespace rules, factor out
3468      header value format definitions.
3469    </t>
3470  </list>
3471</t>
3472</section>
3473
3474<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3475<t>
3476  Closed issues:
3477  <list style="symbols"> 
3478    <t>
3479      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3480      "Reason-Phrase BNF"
3481    </t>
3482  </list>
3483</t>
3484<t>
3485  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3486  <list style="symbols"> 
3487    <t>
3488      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3489    </t>
3490  </list>
3491</t>
3492</section>
3493
3494</section>
3495
3496</back>
3497</rfc>
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