source: draft-ietf-httpbis/latest/p2-semantics.xml @ 563

Last change on this file since 563 was 563, checked in by julian.reschke@…, 11 years ago

replace <list> elements used for indentation by <x:note> elements

  • Property svn:eol-style set to native
File size: 151.8 KB
Line 
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 "March">
16  <!ENTITY ID-YEAR "2009">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64]>
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
77     ipr="pre5378Trust200902" 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  <workgroup>HTTPbis Working Group</workgroup>
223
224<abstract>
225<t>
226   The Hypertext Transfer Protocol (HTTP) is an application-level
227   protocol for distributed, collaborative, hypermedia information
228   systems. HTTP has been in use by the World Wide Web global information
229   initiative since 1990. This document is Part 2 of the seven-part specification
230   that defines the protocol referred to as "HTTP/1.1" and, taken together,
231   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
232   as expressed by request methods, request-header fields, response status codes,
233   and response-header fields.
234</t>
235</abstract>
236
237<note title="Editorial Note (To be removed by RFC Editor)">
238  <t>
239    Discussion of this draft should take place on the HTTPBIS working group
240    mailing list (ietf-http-wg@w3.org). The current issues list is
241    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
242    and related documents (including fancy diffs) can be found at
243    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
244  </t>
245  <t>
246    The changes in this draft are summarized in <xref target="changes.since.06"/>.
247  </t>
248</note>
249</front>
250<middle>
251<section title="Introduction" anchor="introduction">
252<t>
253   This document defines HTTP/1.1 request and response semantics.  Each HTTP
254   message, as defined in &messaging;, is in the form of either a request or
255   a response.  An HTTP server listens on a connection for HTTP requests and
256   responds to each request, in the order received on that connection, with
257   one or more HTTP response messages.  This document defines the commonly
258   agreed upon semantics of the HTTP uniform interface, the intentions defined
259   by each request method, and the various response messages that might be
260   expected as a result of applying that method for the requested resource.
261</t>
262<t>
263   This document is currently disorganized in order to minimize the changes
264   between drafts and enable reviewers to see the smaller errata changes.
265   The next draft will reorganize the sections to better reflect the content.
266   In particular, the sections will be ordered according to the typical
267   processing of an HTTP request message (after message parsing): resource
268   mapping, general header fields, methods, request modifiers, response
269   status, and resource metadata.  The current mess reflects how widely
270   dispersed these topics and associated requirements had become in
271   <xref target="RFC2616"/>.
272</t>
273
274<section title="Requirements" anchor="intro.requirements">
275<t>
276   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
277   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
278   document are to be interpreted as described in <xref target="RFC2119"/>.
279</t>
280<t>
281   An implementation is not compliant if it fails to satisfy one or more
282   of the &MUST; or &REQUIRED; level requirements for the protocols it
283   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
284   level and all the &SHOULD; level requirements for its protocols is said
285   to be "unconditionally compliant"; one that satisfies all the &MUST;
286   level requirements but not all the &SHOULD; level requirements for its
287   protocols is said to be "conditionally compliant."
288</t>
289</section>
290
291<section title="Syntax Notation" anchor="notation">
292  <x:anchor-alias value="CR"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="LF"/>
295  <x:anchor-alias value="VCHAR"/>
296  <x:anchor-alias value="WSP"/>
297<t>
298  This specification uses the ABNF syntax defined in &notation; (which
299  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
300  <xref target="collected.abnf"/> shows the collected ABNF, with the list
301  rule expanded.
302</t>
303<t>
304  The following core rules are included by
305  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
306  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
307  DIGIT (decimal 0-9), DQUOTE (double quote),
308  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
309  OCTET (any 8-bit sequence of data), SP (space),
310  VCHAR (any visible USASCII character),
311  and WSP (whitespace).
312</t>
313
314<section title="Core Rules" anchor="core.rules">
315  <x:anchor-alias value="comment"/>
316  <x:anchor-alias value="obs-text"/>
317  <x:anchor-alias value="quoted-string"/>
318  <x:anchor-alias value="token"/>
319  <x:anchor-alias value="OWS"/>
320  <x:anchor-alias value="RWS"/>
321<t>
322  The core rules below are defined in &basic-rules;:
323</t>
324<figure><artwork type="abnf2616">
325  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
326  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
327  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
328  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
329  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
330  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
331</artwork></figure>
332</section>
333
334<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
335  <x:anchor-alias value="absolute-URI"/>
336  <x:anchor-alias value="Accept"/>
337  <x:anchor-alias value="Accept-Charset"/>
338  <x:anchor-alias value="Accept-Encoding"/>
339  <x:anchor-alias value="Accept-Language"/>
340  <x:anchor-alias value="Accept-Ranges"/>
341  <x:anchor-alias value="Age"/>
342  <x:anchor-alias value="Authorization"/>
343  <x:anchor-alias value="ETag"/>
344  <x:anchor-alias value="fragment"/>
345  <x:anchor-alias value="Host"/>
346  <x:anchor-alias value="HTTP-date"/>
347  <x:anchor-alias value="If-Match"/>
348  <x:anchor-alias value="If-Modified-Since"/>
349  <x:anchor-alias value="If-None-Match"/>
350  <x:anchor-alias value="If-Range"/>
351  <x:anchor-alias value="If-Unmodified-Since"/>
352  <x:anchor-alias value="partial-URI"/>
353  <x:anchor-alias value="product"/>
354  <x:anchor-alias value="Proxy-Authenticate"/>
355  <x:anchor-alias value="Proxy-Authorization"/>
356  <x:anchor-alias value="Range"/>
357  <x:anchor-alias value="TE"/>
358  <x:anchor-alias value="Vary"/>
359  <x:anchor-alias value="WWW-Authenticate"/>
360<t>
361  The ABNF rules below are defined in other parts:
362</t>
363<figure><!--Part1--><artwork type="abnf2616">
364  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
365  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
366  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
367  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
368  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
369  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
370  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
371</artwork></figure>
372<figure><!--Part3--><artwork type="abnf2616">
373  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
374  <x:ref>Accept-Charset</x:ref> =
375             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
376  <x:ref>Accept-Encoding</x:ref> =
377             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
378  <x:ref>Accept-Language</x:ref> =
379             &lt;Accept-Language, defined in &header-accept-language;&gt;
380</artwork></figure>
381<figure><!--Part4--><artwork type="abnf2616">
382  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
383  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
384  <x:ref>If-Modified-Since</x:ref> =
385             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
386  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
387  <x:ref>If-Unmodified-Since</x:ref> =
388             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
389</artwork></figure>
390<figure><!--Part5--><artwork type="abnf2616">
391  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
392  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
393  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
394</artwork></figure>
395<figure><!--Part6--><artwork type="abnf2616">
396  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
397  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
398</artwork><!--Part7--></figure>
399<figure><artwork type="abnf2616">
400  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
401  <x:ref>Proxy-Authenticate</x:ref> =
402             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
403  <x:ref>Proxy-Authorization</x:ref> =
404             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
405  <x:ref>WWW-Authenticate</x:ref> =
406             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
407</artwork></figure>
408</section>
409</section>
410</section>
411
412<section title="Method" anchor="method">
413  <x:anchor-alias value="Method"/>
414  <x:anchor-alias value="extension-method"/>
415<t>
416   The Method  token indicates the method to be performed on the
417   resource identified by the request-target. The method is case-sensitive.
418</t>
419<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
420  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
421                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
422                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
423                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
424                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
425                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
426                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
427                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
428                 / <x:ref>extension-method</x:ref>
429  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
430</artwork></figure>
431<t>
432   The list of methods allowed by a resource can be specified in an
433   Allow header field (<xref target="header.allow"/>). The return code of the response
434   always notifies the client whether a method is currently allowed on a
435   resource, since the set of allowed methods can change dynamically. An
436   origin server &SHOULD; return the status code 405 (Method Not Allowed)
437   if the method is known by the origin server but not allowed for the
438   requested resource, and 501 (Not Implemented) if the method is
439   unrecognized or not implemented by the origin server. The methods GET
440   and HEAD &MUST; be supported by all general-purpose servers. All other
441   methods are &OPTIONAL;; however, if the above methods are implemented,
442   they &MUST; be implemented with the same semantics as those specified
443   in <xref target="method.definitions"/>.
444</t>
445
446<section title="Method Registry" anchor="method.registry">
447<t>
448  The HTTP Method Registry defines the name space for the Method token in the
449  Request line of an HTTP request.
450</t>
451<t>
452  Registrations &MUST; include the following fields:
453  <list style="symbols">
454    <t>Method Name (see <xref target="method"/>)</t>
455    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
456    <t>Pointer to specification text</t>
457  </list>
458</t>
459<t>
460  Values to be added to this name space are subject to IETF review
461  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
462  new method names should be traceable through statuses of either 'Obsoletes'
463  or 'Updates' to this document.
464</t>
465<t>
466  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
467</t>
468</section>
469</section>
470
471<section title="Request Header Fields" anchor="request.header.fields">
472  <x:anchor-alias value="request-header"/>
473<t>
474   The request-header fields allow the client to pass additional
475   information about the request, and about the client itself, to the
476   server. These fields act as request modifiers, with semantics
477   equivalent to the parameters on a programming language method
478   invocation.
479</t>
480<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
481  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
482                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
483                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
484                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
485                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
486                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
487                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
488                 / <x:ref>Host</x:ref>                     ; &header-host;
489                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
490                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
491                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
492                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
493                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
494                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
495                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
496                 / <x:ref>Range</x:ref>                    ; &header-range;
497                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
498                 / <x:ref>TE</x:ref>                       ; &header-te;
499                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
500</artwork></figure>
501<t>
502   Request-header field names can be extended reliably only in
503   combination with a change in the protocol version. However, new or
504   experimental header fields &MAY; be given the semantics of request-header
505   fields if all parties in the communication recognize them to
506   be request-header fields. Unrecognized header fields are treated as
507   entity-header fields.
508</t>
509</section>
510
511<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
512  <x:anchor-alias value="Reason-Phrase"/>
513  <x:anchor-alias value="Status-Code"/>
514  <x:anchor-alias value="extension-code"/>
515<t>
516   The Status-Code element is a 3-digit integer result code of the
517   attempt to understand and satisfy the request. The status codes listed
518   below are defined in <xref target="status.codes"/>.
519   The Reason-Phrase is intended to give a short
520   textual description of the Status-Code. The Status-Code is intended
521   for use by automata and the Reason-Phrase is intended for the human
522   user. The client is not required to examine or display the Reason-Phrase.
523</t>
524<t> 
525   The individual values of the numeric status codes defined for
526   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
527   presented below. The reason phrases listed here are only
528   recommendations -- they &MAY; be replaced by local equivalents without
529   affecting the protocol.
530</t>
531<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"/>
532  <x:ref>Status-Code</x:ref>    =
533         "100"  ; <xref target="status.100"/>: Continue
534       / "101"  ; <xref target="status.101"/>: Switching Protocols
535       / "200"  ; <xref target="status.200"/>: OK
536       / "201"  ; <xref target="status.201"/>: Created
537       / "202"  ; <xref target="status.202"/>: Accepted
538       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
539       / "204"  ; <xref target="status.204"/>: No Content
540       / "205"  ; <xref target="status.205"/>: Reset Content
541       / "206"  ; <xref target="status.206"/>: Partial Content
542       / "300"  ; <xref target="status.300"/>: Multiple Choices
543       / "301"  ; <xref target="status.301"/>: Moved Permanently
544       / "302"  ; <xref target="status.302"/>: Found
545       / "303"  ; <xref target="status.303"/>: See Other
546       / "304"  ; <xref target="status.304"/>: Not Modified
547       / "305"  ; <xref target="status.305"/>: Use Proxy
548       / "307"  ; <xref target="status.307"/>: Temporary Redirect
549       / "400"  ; <xref target="status.400"/>: Bad Request
550       / "401"  ; <xref target="status.401"/>: Unauthorized
551       / "402"  ; <xref target="status.402"/>: Payment Required
552       / "403"  ; <xref target="status.403"/>: Forbidden
553       / "404"  ; <xref target="status.404"/>: Not Found
554       / "405"  ; <xref target="status.405"/>: Method Not Allowed
555       / "406"  ; <xref target="status.406"/>: Not Acceptable
556       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
557       / "408"  ; <xref target="status.408"/>: Request Time-out
558       / "409"  ; <xref target="status.409"/>: Conflict
559       / "410"  ; <xref target="status.410"/>: Gone
560       / "411"  ; <xref target="status.411"/>: Length Required
561       / "412"  ; <xref target="status.412"/>: Precondition Failed
562       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
563       / "414"  ; <xref target="status.414"/>: URI Too Long
564       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
565       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
566       / "417"  ; <xref target="status.417"/>: Expectation Failed
567       / "500"  ; <xref target="status.500"/>: Internal Server Error
568       / "501"  ; <xref target="status.501"/>: Not Implemented
569       / "502"  ; <xref target="status.502"/>: Bad Gateway
570       / "503"  ; <xref target="status.503"/>: Service Unavailable
571       / "504"  ; <xref target="status.504"/>: Gateway Time-out
572       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
573       / <x:ref>extension-code</x:ref>
574
575  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
576  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
577</artwork></figure>
578<t>
579   HTTP status codes are extensible. HTTP applications are not required
580   to understand the meaning of all registered status codes, though such
581   understanding is obviously desirable. However, applications &MUST;
582   understand the class of any status code, as indicated by the first
583   digit, and treat any unrecognized response as being equivalent to the
584   x00 status code of that class, with the exception that an
585   unrecognized response &MUST-NOT; be cached. For example, if an
586   unrecognized status code of 431 is received by the client, it can
587   safely assume that there was something wrong with its request and
588   treat the response as if it had received a 400 status code. In such
589   cases, user agents &SHOULD; present to the user the entity returned
590   with the response, since that entity is likely to include human-readable
591   information which will explain the unusual status.
592</t>
593
594<section title="Status Code Registry" anchor="status.code.registry">
595<t>
596  The HTTP Status Code Registry defines the name space for the Status-Code
597  token in the Status line of an HTTP response.
598</t>
599<t>
600  Values to be added to this name space are subject to IETF review
601  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
602  new status codes should be traceable through statuses of either 'Obsoletes'
603  or 'Updates' to this document.
604</t>
605<t>
606  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
607</t>
608</section>
609
610</section>
611
612<section title="Response Header Fields" anchor="response.header.fields">
613  <x:anchor-alias value="response-header"/>
614<t>
615   The response-header fields allow the server to pass additional
616   information about the response which cannot be placed in the Status-Line.
617   These header fields give information about the server and about
618   further access to the resource identified by the request-target.
619</t>
620<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
621  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
622                  / <x:ref>Age</x:ref>                     ; &header-age;
623                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
624                  / <x:ref>ETag</x:ref>                    ; &header-etag;
625                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
626                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
627                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
628                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
629                  / <x:ref>Vary</x:ref>                    ; &header-vary;
630                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
631</artwork></figure>
632<t>
633   Response-header field names can be extended reliably only in
634   combination with a change in the protocol version. However, new or
635   experimental header fields &MAY; be given the semantics of response-header
636   fields if all parties in the communication recognize them to
637   be response-header fields. Unrecognized header fields are treated as
638   entity-header fields.
639</t>
640</section>
641
642<section title="Entity" anchor="entity">
643<t>
644   Request and Response messages &MAY; transfer an entity if not otherwise
645   restricted by the request method or response status code. An entity
646   consists of entity-header fields and an entity-body, although some
647   responses will only include the entity-headers. HTTP entity-body and
648   entity-header fields are defined in &payload;.
649</t>
650<t>
651   An entity-body is only present in a message when a message-body is
652   present, as described in &message-body;. The entity-body is obtained
653   from the message-body by decoding any Transfer-Encoding that might
654   have been applied to ensure safe and proper transfer of the message.
655</t>
656</section>
657
658
659<section title="Method Definitions" anchor="method.definitions">
660<t>
661   The set of common methods for HTTP/1.1 is defined below. Although
662   this set can be expanded, additional methods cannot be assumed to
663   share the same semantics for separately extended clients and servers.
664</t>
665
666<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
667
668<section title="Safe Methods" anchor="safe.methods">
669<iref item="Safe Methods" primary="true"/>
670<t>
671   Implementors should be aware that the software represents the user in
672   their interactions over the Internet, and should be careful to allow
673   the user to be aware of any actions they might take which may have an
674   unexpected significance to themselves or others.
675</t>
676<t>
677   In particular, the convention has been established that the GET and
678   HEAD methods &SHOULD-NOT;  have the significance of taking an action
679   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
680   This allows user agents to represent other methods, such as POST, PUT
681   and DELETE, in a special way, so that the user is made aware of the
682   fact that a possibly unsafe action is being requested.
683</t>
684<t>
685   Naturally, it is not possible to ensure that the server does not
686   generate side-effects as a result of performing a GET request; in
687   fact, some dynamic resources consider that a feature. The important
688   distinction here is that the user did not request the side-effects,
689   so therefore cannot be held accountable for them.
690</t>
691</section>
692
693<section title="Idempotent Methods" anchor="idempotent.methods">
694<iref item="Idempotent Methods" primary="true"/>
695<t>
696   Methods can also have the property of "idempotence" in that (aside
697   from error or expiration issues) the side-effects of N &gt; 0 identical
698   requests is the same as for a single request. The methods GET, HEAD,
699   PUT and DELETE share this property. Also, the methods OPTIONS and
700   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
701</t>
702<t>
703   However, it is possible that a sequence of several requests is non-idempotent,
704   even if all of the methods executed in that sequence are
705   idempotent. (A sequence is idempotent if a single execution of the
706   entire sequence always yields a result that is not changed by a
707   reexecution of all, or part, of that sequence.) For example, a
708   sequence is non-idempotent if its result depends on a value that is
709   later modified in the same sequence.
710</t>
711<t>
712   A sequence that never has side effects is idempotent, by definition
713   (provided that no concurrent operations are being executed on the
714   same set of resources).
715</t>
716</section>
717</section>
718
719<section title="OPTIONS" anchor="OPTIONS">
720  <rdf:Description>
721    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
722  </rdf:Description>
723  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
724  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
725<t>
726   The OPTIONS method represents a request for information about the
727   communication options available on the request/response chain
728   identified by the request-target. This method allows the client to
729   determine the options and/or requirements associated with a resource,
730   or the capabilities of a server, without implying a resource action
731   or initiating a resource retrieval.
732</t>
733<t>
734   Responses to this method are not cacheable.
735</t>
736<t>
737   If the OPTIONS request includes an entity-body (as indicated by the
738   presence of Content-Length or Transfer-Encoding), then the media type
739   &MUST; be indicated by a Content-Type field. Although this
740   specification does not define any use for such a body, future
741   extensions to HTTP might use the OPTIONS body to make more detailed
742   queries on the server.
743</t>
744<t>
745   If the request-target is an asterisk ("*"), the OPTIONS request is
746   intended to apply to the server in general rather than to a specific
747   resource. Since a server's communication options typically depend on
748   the resource, the "*" request is only useful as a "ping" or "no-op"
749   type of method; it does nothing beyond allowing the client to test
750   the capabilities of the server. For example, this can be used to test
751   a proxy for HTTP/1.1 compliance (or lack thereof).
752</t>
753<t>
754   If the request-target is not an asterisk, the OPTIONS request applies
755   only to the options that are available when communicating with that
756   resource.
757</t>
758<t>
759   A 200 response &SHOULD; include any header fields that indicate
760   optional features implemented by the server and applicable to that
761   resource (e.g., Allow), possibly including extensions not defined by
762   this specification. The response body, if any, &SHOULD; also include
763   information about the communication options. The format for such a
764   body is not defined by this specification, but might be defined by
765   future extensions to HTTP. Content negotiation &MAY; be used to select
766   the appropriate response format. If no response body is included, the
767   response &MUST; include a Content-Length field with a field-value of
768   "0".
769</t>
770<t>
771   The Max-Forwards request-header field &MAY; be used to target a
772   specific proxy in the request chain. When a proxy receives an OPTIONS
773   request on an absolute-URI for which request forwarding is permitted,
774   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
775   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
776   instead, the proxy &SHOULD; respond with its own communication options.
777   If the Max-Forwards field-value is an integer greater than zero, the
778   proxy &MUST; decrement the field-value when it forwards the request. If
779   no Max-Forwards field is present in the request, then the forwarded
780   request &MUST-NOT; include a Max-Forwards field.
781</t>
782</section>
783
784<section title="GET" anchor="GET">
785  <rdf:Description>
786    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
787  </rdf:Description>
788  <iref primary="true" item="GET method" x:for-anchor=""/>
789  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
790<t>
791   The GET method means retrieve whatever information (in the form of an
792   entity) is identified by the request-target. If the request-target refers
793   to a data-producing process, it is the produced data which shall be
794   returned as the entity in the response and not the source text of the
795   process, unless that text happens to be the output of the process.
796</t>
797<t>
798   The semantics of the GET method change to a "conditional GET" if the
799   request message includes an If-Modified-Since, If-Unmodified-Since,
800   If-Match, If-None-Match, or If-Range header field. A conditional GET
801   method requests that the entity be transferred only under the
802   circumstances described by the conditional header field(s). The
803   conditional GET method is intended to reduce unnecessary network
804   usage by allowing cached entities to be refreshed without requiring
805   multiple requests or transferring data already held by the client.
806</t>
807<t>
808   The semantics of the GET method change to a "partial GET" if the
809   request message includes a Range header field. A partial GET requests
810   that only part of the entity be transferred, as described in &header-range;.
811   The partial GET method is intended to reduce unnecessary
812   network usage by allowing partially-retrieved entities to be
813   completed without transferring data already held by the client.
814</t>
815<t>
816   The response to a GET request is cacheable if and only if it meets
817   the requirements for HTTP caching described in &caching;.
818</t>
819<t>
820   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
821</t>
822</section>
823
824<section title="HEAD" anchor="HEAD">
825  <rdf:Description>
826    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
827  </rdf:Description>
828  <iref primary="true" item="HEAD method" x:for-anchor=""/>
829  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
830<t>
831   The HEAD method is identical to GET except that the server &MUST-NOT;
832   return a message-body in the response. The metainformation contained
833   in the HTTP headers in response to a HEAD request &SHOULD; be identical
834   to the information sent in response to a GET request. This method can
835   be used for obtaining metainformation about the entity implied by the
836   request without transferring the entity-body itself. This method is
837   often used for testing hypertext links for validity, accessibility,
838   and recent modification.
839</t>
840<t>
841   The response to a HEAD request &MAY; be cacheable in the sense that the
842   information contained in the response &MAY; be used to update a
843   previously cached entity from that resource. If the new field values
844   indicate that the cached entity differs from the current entity (as
845   would be indicated by a change in Content-Length, Content-MD5, ETag
846   or Last-Modified), then the cache &MUST; treat the cache entry as
847   stale.
848</t>
849</section>
850
851<section title="POST" anchor="POST">
852  <iref primary="true" item="POST method" x:for-anchor=""/>
853  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
854<t>
855   The POST method is used to request that the origin server accept the
856   entity enclosed in the request as data to be processed by the resource
857   identified by the request-target in the Request-Line. POST is designed
858   to allow a uniform method to cover the following functions:
859  <list style="symbols">
860    <t>
861      Annotation of existing resources;
862    </t>
863    <t>
864        Posting a message to a bulletin board, newsgroup, mailing list,
865        or similar group of articles;
866    </t>
867    <t>
868        Providing a block of data, such as the result of submitting a
869        form, to a data-handling process;
870    </t>
871    <t>
872        Extending a database through an append operation.
873    </t>
874  </list>
875</t>
876<t>
877   The actual function performed by the POST method is determined by the
878   server and is usually dependent on the request-target.
879</t>
880<t>
881   The action performed by the POST method might not result in a
882   resource that can be identified by a URI. In this case, either 200
883   (OK) or 204 (No Content) is the appropriate response status,
884   depending on whether or not the response includes an entity that
885   describes the result.
886</t>
887<t>
888   If a resource has been created on the origin server, the response
889   &SHOULD; be 201 (Created) and contain an entity which describes the
890   status of the request and refers to the new resource, and a Location
891   header (see <xref target="header.location"/>).
892</t>
893<t>
894   Responses to this method are not cacheable, unless the response
895   includes appropriate Cache-Control or Expires header fields. However,
896   the 303 (See Other) response can be used to direct the user agent to
897   retrieve a cacheable resource.
898</t>
899</section>
900
901<section title="PUT" anchor="PUT">
902  <iref primary="true" item="PUT method" x:for-anchor=""/>
903  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
904<t>
905   The PUT method requests that the enclosed entity be stored at the
906   supplied request-target. If the request-target refers to an already
907   existing resource, the enclosed entity &SHOULD; be considered as a
908   modified version of the one residing on the origin server. If the
909   request-target does not point to an existing resource, and that URI is
910   capable of being defined as a new resource by the requesting user
911   agent, the origin server can create the resource with that URI. If a
912   new resource is created at the request-target, the origin server &MUST;
913         inform the user agent
914   via the 201 (Created) response. If an existing resource is modified,
915   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
916   to indicate successful completion of the request. If the resource
917   could not be created or modified with the request-target, an appropriate
918   error response &SHOULD; be given that reflects the nature of the
919   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
920   headers (headers starting with the prefix 'Content-') that it does
921   not understand or implement
922   and &MUST; return a 501 (Not Implemented) response in such cases.
923</t>
924<t>
925   If the request passes through a cache and the request-target identifies
926   one or more currently cached entities, those entries &SHOULD; be
927   treated as stale. Responses to this method are not cacheable.
928</t>
929<t>
930   The fundamental difference between the POST and PUT requests is
931   reflected in the different meaning of the request-target. The URI in a
932   POST request identifies the resource that will handle the enclosed
933   entity. That resource might be a data-accepting process, a gateway to
934   some other protocol, or a separate entity that accepts annotations.
935   In contrast, the URI in a PUT request identifies the entity enclosed
936   with the request -- the user agent knows what URI is intended and the
937   server &MUST-NOT; attempt to apply the request to some other resource.
938   If the server desires that the request be applied to a different URI,
939   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
940   then make its own decision regarding whether or not to redirect the
941   request.
942</t>
943<t>
944   A single resource &MAY; be identified by many different URIs. For
945   example, an article might have a URI for identifying "the current
946   version" which is separate from the URI identifying each particular
947   version. In this case, a PUT request on a general URI might result in
948   several other URIs being defined by the origin server.
949</t>
950<t>
951   HTTP/1.1 does not define how a PUT method affects the state of an
952   origin server.
953</t>
954<t>
955   Unless otherwise specified for a particular entity-header, the
956   entity-headers in the PUT request &SHOULD; be applied to the resource
957   created or modified by the PUT.
958</t>
959</section>
960
961<section title="DELETE" anchor="DELETE">
962  <iref primary="true" item="DELETE method" x:for-anchor=""/>
963  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
964<t>
965   The DELETE method requests that the origin server delete the resource
966   identified by the request-target. This method &MAY; be overridden by human
967   intervention (or other means) on the origin server. The client cannot
968   be guaranteed that the operation has been carried out, even if the
969   status code returned from the origin server indicates that the action
970   has been completed successfully. However, the server &SHOULD-NOT; 
971   indicate success unless, at the time the response is given, it
972   intends to delete the resource or move it to an inaccessible
973   location.
974</t>
975<t>
976   A successful response &SHOULD; be 200 (OK) if the response includes an
977   entity describing the status, 202 (Accepted) if the action has not
978   yet been enacted, or 204 (No Content) if the action has been enacted
979   but the response does not include an entity.
980</t>
981<t>
982   If the request passes through a cache and the request-target identifies
983   one or more currently cached entities, those entries &SHOULD; be
984   treated as stale. Responses to this method are not cacheable.
985</t>
986</section>
987
988<section title="TRACE" anchor="TRACE">
989  <rdf:Description>
990    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
991  </rdf:Description>
992  <iref primary="true" item="TRACE method" x:for-anchor=""/>
993  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
994<t>
995   The TRACE method is used to invoke a remote, application-layer loop-back
996   of the request message. The final recipient of the request
997   &SHOULD; reflect the message received back to the client as the
998   entity-body of a 200 (OK) response. The final recipient is either the
999   origin server or the first proxy or gateway to receive a Max-Forwards
1000   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1001   &MUST-NOT; include an entity.
1002</t>
1003<t>
1004   TRACE allows the client to see what is being received at the other
1005   end of the request chain and use that data for testing or diagnostic
1006   information. The value of the Via header field (&header-via;) is of
1007   particular interest, since it acts as a trace of the request chain.
1008   Use of the Max-Forwards header field allows the client to limit the
1009   length of the request chain, which is useful for testing a chain of
1010   proxies forwarding messages in an infinite loop.
1011</t>
1012<t>
1013   If the request is valid, the response &SHOULD; contain the entire
1014   request message in the entity-body, with a Content-Type of
1015   "message/http" (see &media-type-message-http;). Responses to this method
1016   &MUST-NOT; be cached.
1017</t>
1018</section>
1019
1020<section title="CONNECT" anchor="CONNECT">
1021  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1022  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1023<t>
1024   This specification reserves the method name CONNECT for use with a
1025   proxy that can dynamically switch to being a tunnel (e.g. SSL
1026   tunneling <xref target="RFC2817"/>).
1027</t>
1028</section>
1029</section>
1030
1031
1032<section title="Status Code Definitions" anchor="status.codes">
1033<t>
1034   Each Status-Code is described below, including a description of which
1035   method(s) it can follow and any metainformation required in the
1036   response.
1037</t>
1038
1039<section title="Informational 1xx" anchor="status.1xx">
1040<t>
1041   This class of status code indicates a provisional response,
1042   consisting only of the Status-Line and optional headers, and is
1043   terminated by an empty line. There are no required headers for this
1044   class of status code. Since HTTP/1.0 did not define any 1xx status
1045   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1046   except under experimental conditions.
1047</t>
1048<t>
1049   A client &MUST; be prepared to accept one or more 1xx status responses
1050   prior to a regular response, even if the client does not expect a 100
1051   (Continue) status message. Unexpected 1xx status responses &MAY; be
1052   ignored by a user agent.
1053</t>
1054<t>
1055   Proxies &MUST; forward 1xx responses, unless the connection between the
1056   proxy and its client has been closed, or unless the proxy itself
1057   requested the generation of the 1xx response. (For example, if a
1058   proxy adds a "Expect: 100-continue" field when it forwards a request,
1059   then it need not forward the corresponding 100 (Continue)
1060   response(s).)
1061</t>
1062
1063<section title="100 Continue" anchor="status.100">
1064  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1065  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1066<t>
1067   The client &SHOULD; continue with its request. This interim response is
1068   used to inform the client that the initial part of the request has
1069   been received and has not yet been rejected by the server. The client
1070   &SHOULD; continue by sending the remainder of the request or, if the
1071   request has already been completed, ignore this response. The server
1072   &MUST; send a final response after the request has been completed. See
1073   &use100; for detailed discussion of the use and handling of this
1074   status code.
1075</t>
1076</section>
1077
1078<section title="101 Switching Protocols" anchor="status.101">
1079  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1080  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1081<t>
1082   The server understands and is willing to comply with the client's
1083   request, via the Upgrade message header field (&header-upgrade;), for a
1084   change in the application protocol being used on this connection. The
1085   server will switch protocols to those defined by the response's
1086   Upgrade header field immediately after the empty line which
1087   terminates the 101 response.
1088</t>
1089<t>
1090   The protocol &SHOULD; be switched only when it is advantageous to do
1091   so. For example, switching to a newer version of HTTP is advantageous
1092   over older versions, and switching to a real-time, synchronous
1093   protocol might be advantageous when delivering resources that use
1094   such features.
1095</t>
1096</section>
1097</section>
1098
1099<section title="Successful 2xx" anchor="status.2xx">
1100<t>
1101   This class of status code indicates that the client's request was
1102   successfully received, understood, and accepted.
1103</t>
1104
1105<section title="200 OK" anchor="status.200">
1106  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1107  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1108<t>
1109   The request has succeeded. The information returned with the response
1110   is dependent on the method used in the request, for example:
1111  <list style="hanging">
1112    <t hangText="GET">
1113          an entity corresponding to the requested resource is sent in
1114          the response;
1115    </t>
1116    <t hangText="HEAD">
1117          the entity-header fields corresponding to the requested
1118          resource are sent in the response without any message-body;
1119    </t>
1120    <t hangText="POST">
1121      an entity describing or containing the result of the action;
1122    </t>
1123    <t hangText="TRACE">
1124      an entity containing the request message as received by the
1125      end server.
1126    </t>
1127  </list>
1128</t>
1129</section>
1130
1131<section title="201 Created" anchor="status.201">
1132  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1133  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1134<t>
1135   The request has been fulfilled and resulted in a new resource being
1136   created. The newly created resource can be referenced by the URI(s)
1137   returned in the entity of the response, with the most specific URI
1138   for the resource given by a Location header field. The response
1139   &SHOULD; include an entity containing a list of resource
1140   characteristics and location(s) from which the user or user agent can
1141   choose the one most appropriate. The entity format is specified by
1142   the media type given in the Content-Type header field. The origin
1143   server &MUST; create the resource before returning the 201 status code.
1144   If the action cannot be carried out immediately, the server &SHOULD;
1145   respond with 202 (Accepted) response instead.
1146</t>
1147<t>
1148   A 201 response &MAY; contain an ETag response header field indicating
1149   the current value of the entity tag for the requested variant just
1150   created, see &header-etag;.
1151</t>
1152</section>
1153
1154<section title="202 Accepted" anchor="status.202">
1155  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1156  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1157<t>
1158   The request has been accepted for processing, but the processing has
1159   not been completed.  The request might or might not eventually be
1160   acted upon, as it might be disallowed when processing actually takes
1161   place. There is no facility for re-sending a status code from an
1162   asynchronous operation such as this.
1163</t>
1164<t>
1165   The 202 response is intentionally non-committal. Its purpose is to
1166   allow a server to accept a request for some other process (perhaps a
1167   batch-oriented process that is only run once per day) without
1168   requiring that the user agent's connection to the server persist
1169   until the process is completed. The entity returned with this
1170   response &SHOULD; include an indication of the request's current status
1171   and either a pointer to a status monitor or some estimate of when the
1172   user can expect the request to be fulfilled.
1173</t>
1174</section>
1175
1176<section title="203 Non-Authoritative Information" anchor="status.203">
1177  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1178  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1179<t>
1180   The returned metainformation in the entity-header is not the
1181   definitive set as available from the origin server, but is gathered
1182   from a local or a third-party copy. The set presented &MAY; be a subset
1183   or superset of the original version. For example, including local
1184   annotation information about the resource might result in a superset
1185   of the metainformation known by the origin server. Use of this
1186   response code is not required and is only appropriate when the
1187   response would otherwise be 200 (OK).
1188</t>
1189</section>
1190
1191<section title="204 No Content" anchor="status.204">
1192  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1193  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1194<t>
1195   The server has fulfilled the request but does not need to return an
1196   entity-body, and might want to return updated metainformation. The
1197   response &MAY; include new or updated metainformation in the form of
1198   entity-headers, which if present &SHOULD; be associated with the
1199   requested variant.
1200</t>
1201<t>
1202   If the client is a user agent, it &SHOULD-NOT;  change its document view
1203   from that which caused the request to be sent. This response is
1204   primarily intended to allow input for actions to take place without
1205   causing a change to the user agent's active document view, although
1206   any new or updated metainformation &SHOULD; be applied to the document
1207   currently in the user agent's active view.
1208</t>
1209<t>
1210   The 204 response &MUST-NOT; include a message-body, and thus is always
1211   terminated by the first empty line after the header fields.
1212</t>
1213</section>
1214
1215<section title="205 Reset Content" anchor="status.205">
1216  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1217  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1218<t>
1219   The server has fulfilled the request and the user agent &SHOULD; reset
1220   the document view which caused the request to be sent. This response
1221   is primarily intended to allow input for actions to take place via
1222   user input, followed by a clearing of the form in which the input is
1223   given so that the user can easily initiate another input action. The
1224   response &MUST-NOT; include an entity.
1225</t>
1226</section>
1227
1228<section title="206 Partial Content" anchor="status.206">
1229  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1230  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1231<t>
1232   The server has fulfilled the partial GET request for the resource
1233   and the enclosed entity is a partial representation as defined in &range;.
1234</t>
1235</section>
1236</section>
1237
1238<section title="Redirection 3xx" anchor="status.3xx">
1239<t>
1240   This class of status code indicates that further action needs to be
1241   taken by the user agent in order to fulfill the request.  The action
1242   required &MAY; be carried out by the user agent without interaction
1243   with the user if and only if the method used in the second request is
1244   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1245   such loops generate network traffic for each redirection.
1246</t>
1247<x:note>
1248  <t>
1249    <x:h>Note:</x:h> previous versions of this specification recommended a
1250    maximum of five redirections. Content developers should be aware
1251    that there might be clients that implement such a fixed
1252    limitation.
1253  </t>
1254</x:note>
1255
1256<section title="300 Multiple Choices" anchor="status.300">
1257  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1258  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1259<t>
1260   The requested resource corresponds to any one of a set of
1261   representations, each with its own specific location, and agent-driven
1262   negotiation information (&content-negotiation;) is being provided so that
1263   the user (or user agent) can select a preferred representation and
1264   redirect its request to that location.
1265</t>
1266<t>
1267   Unless it was a HEAD request, the response &SHOULD; include an entity
1268   containing a list of resource characteristics and location(s) from
1269   which the user or user agent can choose the one most appropriate. The
1270   entity format is specified by the media type given in the Content-Type
1271   header field. Depending upon the format and the capabilities of
1272   the user agent, selection of the most appropriate choice &MAY; be
1273   performed automatically. However, this specification does not define
1274   any standard for such automatic selection.
1275</t>
1276<t>
1277   If the server has a preferred choice of representation, it &SHOULD;
1278   include the specific URI for that representation in the Location
1279   field; user agents &MAY; use the Location field value for automatic
1280   redirection. This response is cacheable unless indicated otherwise.
1281</t>
1282</section>
1283
1284<section title="301 Moved Permanently" anchor="status.301">
1285  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1286  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1287<t>
1288   The requested resource has been assigned a new permanent URI and any
1289   future references to this resource &SHOULD; use one of the returned
1290   URIs.  Clients with link editing capabilities ought to automatically
1291   re-link references to the request-target to one or more of the new
1292   references returned by the server, where possible. This response is
1293   cacheable unless indicated otherwise.
1294</t>
1295<t>
1296   The new permanent URI &SHOULD; be given by the Location field in the
1297   response. Unless the request method was HEAD, the entity of the
1298   response &SHOULD; contain a short hypertext note with a hyperlink to
1299   the new URI(s).
1300</t>
1301<t>
1302   If the 301 status code is received in response to a request method
1303   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1304   then the request &MAY; be automatically redirected by the user agent without
1305   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1306   request unless it can be confirmed by the user, since this might
1307   change the conditions under which the request was issued.
1308</t>
1309<x:note>
1310  <t>
1311    <x:h>Note:</x:h> When automatically redirecting a POST request after
1312    receiving a 301 status code, some existing HTTP/1.0 user agents
1313    will erroneously change it into a GET request.
1314  </t>
1315</x:note>
1316</section>
1317
1318<section title="302 Found" anchor="status.302">
1319  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1320  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1321<t>
1322   The requested resource resides temporarily under a different URI.
1323   Since the redirection might be altered on occasion, the client &SHOULD;
1324   continue to use the request-target for future requests.  This response
1325   is only cacheable if indicated by a Cache-Control or Expires header
1326   field.
1327</t>
1328<t>
1329   The temporary URI &SHOULD; be given by the Location field in the
1330   response. Unless the request method was HEAD, the entity of the
1331   response &SHOULD; contain a short hypertext note with a hyperlink to
1332   the new URI(s).
1333</t>
1334<t>
1335   If the 302 status code is received in response to a request method
1336   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1337   then the request &MAY; be automatically redirected by the user agent without
1338   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1339   request unless it can be confirmed by the user, since this might
1340   change the conditions under which the request was issued.
1341</t>
1342<x:note>
1343  <t>
1344    <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1345    to change the method on the redirected request.  However, most
1346    existing user agent implementations treat 302 as if it were a 303
1347    response, performing a GET on the Location field-value regardless
1348    of the original request method. The status codes 303 and 307 have
1349    been added for servers that wish to make unambiguously clear which
1350    kind of reaction is expected of the client.
1351  </t>
1352</x:note>
1353</section>
1354
1355<section title="303 See Other" anchor="status.303">
1356  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1357  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1358<t>
1359   The server directs the user agent to a different resource, indicated
1360   by a URI in the Location header field, that provides an indirect
1361   response to the original request.  The user agent &MAY; perform a GET
1362   request on the URI in the Location field in order to obtain a
1363   representation corresponding to the response, be redirected again,
1364   or end with an error status.  The Location URI is not a substitute
1365   reference for the originally requested resource.
1366</t>
1367<t>
1368   The 303 status is generally applicable to any HTTP method.  It is
1369   primarily used to allow the output of a POST action to redirect
1370   the user agent to a selected resource, since doing so provides the
1371   information corresponding to the POST response in a form that
1372   can be separately identified, bookmarked, and cached independent
1373   of the original request.
1374</t>
1375<t>
1376   A 303 response to a GET request indicates that the requested
1377   resource does not have a representation of its own that can be
1378   transferred by the server over HTTP.  The Location URI indicates a
1379   resource that is descriptive of the requested resource such that
1380   the follow-on representation may be useful without implying that
1381   it adequately represents the previously requested resource.
1382   Note that answers to the questions of what can be represented, what
1383   representations are adequate, and what might be a useful description
1384   are outside the scope of HTTP and thus entirely determined by the
1385   resource owner(s).
1386</t>
1387<t>
1388   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1389   cacheable by Cache-Control or Expires header fields.  Except for
1390   responses to a HEAD request, the entity of a 303 response &SHOULD;
1391   contain a short hypertext note with a hyperlink to the Location URI.
1392</t>
1393</section>
1394
1395<section title="304 Not Modified" anchor="status.304">
1396  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1397  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1398<t>
1399   The response to the request has not been modified since the conditions
1400   indicated by the client's conditional GET request, as defined in &conditional;.
1401</t>
1402</section>
1403
1404<section title="305 Use Proxy" anchor="status.305">
1405  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1406  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1407<t>
1408   The 305 status was defined in a previous version of this specification
1409   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1410</t>
1411</section>
1412
1413<section title="306 (Unused)" anchor="status.306">
1414  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1415  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1416<t>
1417   The 306 status code was used in a previous version of the
1418   specification, is no longer used, and the code is reserved.
1419</t>
1420</section>
1421
1422<section title="307 Temporary Redirect" anchor="status.307">
1423  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1424  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1425<t>
1426   The requested resource resides temporarily under a different URI.
1427   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1428   continue to use the request-target for future requests.  This response
1429   is only cacheable if indicated by a Cache-Control or Expires header
1430   field.
1431</t>
1432<t>
1433   The temporary URI &SHOULD; be given by the Location field in the
1434   response. Unless the request method was HEAD, the entity of the
1435   response &SHOULD; contain a short hypertext note with a hyperlink to
1436   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1437   understand the 307 status. Therefore, the note &SHOULD; contain the
1438   information necessary for a user to repeat the original request on
1439   the new URI.
1440</t>
1441<t>
1442   If the 307 status code is received in response to a request method
1443   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1444   then the request &MAY; be automatically redirected by the user agent without
1445   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1446   request unless it can be confirmed by the user, since this might
1447   change the conditions under which the request was issued.
1448</t>
1449</section>
1450</section>
1451
1452<section title="Client Error 4xx" anchor="status.4xx">
1453<t>
1454   The 4xx class of status code is intended for cases in which the
1455   client seems to have erred. Except when responding to a HEAD request,
1456   the server &SHOULD; include an entity containing an explanation of the
1457   error situation, and whether it is a temporary or permanent
1458   condition. These status codes are applicable to any request method.
1459   User agents &SHOULD; display any included entity to the user.
1460</t>
1461<t>
1462   If the client is sending data, a server implementation using TCP
1463   &SHOULD; be careful to ensure that the client acknowledges receipt of
1464   the packet(s) containing the response, before the server closes the
1465   input connection. If the client continues sending data to the server
1466   after the close, the server's TCP stack will send a reset packet to
1467   the client, which may erase the client's unacknowledged input buffers
1468   before they can be read and interpreted by the HTTP application.
1469</t>
1470
1471<section title="400 Bad Request" anchor="status.400">
1472  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1473  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1474<t>
1475   The request could not be understood by the server due to malformed
1476   syntax. The client &SHOULD-NOT;  repeat the request without
1477   modifications.
1478</t>
1479</section>
1480
1481<section title="401 Unauthorized" anchor="status.401">
1482  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1483  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1484<t>
1485   The request requires user authentication (see &auth;).
1486</t>
1487</section>
1488
1489<section title="402 Payment Required" anchor="status.402">
1490  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1491  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1492<t>
1493   This code is reserved for future use.
1494</t>
1495</section>
1496
1497<section title="403 Forbidden" anchor="status.403">
1498  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1499  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1500<t>
1501   The server understood the request, but is refusing to fulfill it.
1502   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1503   If the request method was not HEAD and the server wishes to make
1504   public why the request has not been fulfilled, it &SHOULD; describe the
1505   reason for the refusal in the entity.  If the server does not wish to
1506   make this information available to the client, the status code 404
1507   (Not Found) can be used instead.
1508</t>
1509</section>
1510
1511<section title="404 Not Found" anchor="status.404">
1512  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1513  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1514<t>
1515   The server has not found anything matching the request-target. No
1516   indication is given of whether the condition is temporary or
1517   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1518   knows, through some internally configurable mechanism, that an old
1519   resource is permanently unavailable and has no forwarding address.
1520   This status code is commonly used when the server does not wish to
1521   reveal exactly why the request has been refused, or when no other
1522   response is applicable.
1523</t>
1524</section>
1525
1526<section title="405 Method Not Allowed" anchor="status.405">
1527  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1528  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1529<t>
1530   The method specified in the Request-Line is not allowed for the
1531   resource identified by the request-target. The response &MUST; include an
1532   Allow header containing a list of valid methods for the requested
1533   resource.
1534</t>
1535</section>
1536
1537<section title="406 Not Acceptable" anchor="status.406">
1538  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1539  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1540<t>
1541   The resource identified by the request is only capable of generating
1542   response entities which have content characteristics not acceptable
1543   according to the accept headers sent in the request.
1544</t>
1545<t>
1546   Unless it was a HEAD request, the response &SHOULD; include an entity
1547   containing a list of available entity characteristics and location(s)
1548   from which the user or user agent can choose the one most
1549   appropriate. The entity format is specified by the media type given
1550   in the Content-Type header field. Depending upon the format and the
1551   capabilities of the user agent, selection of the most appropriate
1552   choice &MAY; be performed automatically. However, this specification
1553   does not define any standard for such automatic selection.
1554</t>
1555<x:note>
1556  <t>
1557    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1558    not acceptable according to the accept headers sent in the
1559    request. In some cases, this may even be preferable to sending a
1560    406 response. User agents are encouraged to inspect the headers of
1561    an incoming response to determine if it is acceptable.
1562  </t>
1563</x:note>
1564<t>
1565   If the response could be unacceptable, a user agent &SHOULD;
1566   temporarily stop receipt of more data and query the user for a
1567   decision on further actions.
1568</t>
1569</section>
1570
1571<section title="407 Proxy Authentication Required" anchor="status.407">
1572  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1573  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1574<t>
1575   This code is similar to 401 (Unauthorized), but indicates that the
1576   client must first authenticate itself with the proxy (see &auth;).
1577</t>
1578</section>
1579
1580<section title="408 Request Timeout" anchor="status.408">
1581  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1583<t>
1584   The client did not produce a request within the time that the server
1585   was prepared to wait. The client &MAY; repeat the request without
1586   modifications at any later time.
1587</t>
1588</section>
1589
1590<section title="409 Conflict" anchor="status.409">
1591  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1592  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1593<t>
1594   The request could not be completed due to a conflict with the current
1595   state of the resource. This code is only allowed in situations where
1596   it is expected that the user might be able to resolve the conflict
1597   and resubmit the request. The response body &SHOULD; include enough
1598   information for the user to recognize the source of the conflict.
1599   Ideally, the response entity would include enough information for the
1600   user or user agent to fix the problem; however, that might not be
1601   possible and is not required.
1602</t>
1603<t>
1604   Conflicts are most likely to occur in response to a PUT request. For
1605   example, if versioning were being used and the entity being PUT
1606   included changes to a resource which conflict with those made by an
1607   earlier (third-party) request, the server might use the 409 response
1608   to indicate that it can't complete the request. In this case, the
1609   response entity would likely contain a list of the differences
1610   between the two versions in a format defined by the response
1611   Content-Type.
1612</t>
1613</section>
1614
1615<section title="410 Gone" anchor="status.410">
1616  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1617  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1618<t>
1619   The requested resource is no longer available at the server and no
1620   forwarding address is known. This condition is expected to be
1621   considered permanent. Clients with link editing capabilities &SHOULD;
1622   delete references to the request-target after user approval. If the
1623   server does not know, or has no facility to determine, whether or not
1624   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1625   used instead. This response is cacheable unless indicated otherwise.
1626</t>
1627<t>
1628   The 410 response is primarily intended to assist the task of web
1629   maintenance by notifying the recipient that the resource is
1630   intentionally unavailable and that the server owners desire that
1631   remote links to that resource be removed. Such an event is common for
1632   limited-time, promotional services and for resources belonging to
1633   individuals no longer working at the server's site. It is not
1634   necessary to mark all permanently unavailable resources as "gone" or
1635   to keep the mark for any length of time -- that is left to the
1636   discretion of the server owner.
1637</t>
1638</section>
1639
1640<section title="411 Length Required" anchor="status.411">
1641  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1642  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1643<t>
1644   The server refuses to accept the request without a defined Content-Length.
1645   The client &MAY; repeat the request if it adds a valid
1646   Content-Length header field containing the length of the message-body
1647   in the request message.
1648</t>
1649</section>
1650
1651<section title="412 Precondition Failed" anchor="status.412">
1652  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1653  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1654<t>
1655   The precondition given in one or more of the request-header fields
1656   evaluated to false when it was tested on the server, as defined in
1657   &conditional;.
1658</t>
1659</section>
1660
1661<section title="413 Request Entity Too Large" anchor="status.413">
1662  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1663  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1664<t>
1665   The server is refusing to process a request because the request
1666   entity is larger than the server is willing or able to process. The
1667   server &MAY; close the connection to prevent the client from continuing
1668   the request.
1669</t>
1670<t>
1671   If the condition is temporary, the server &SHOULD; include a Retry-After
1672   header field to indicate that it is temporary and after what
1673   time the client &MAY; try again.
1674</t>
1675</section>
1676
1677<section title="414 URI Too Long" anchor="status.414">
1678  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1679  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1680<t>
1681   The server is refusing to service the request because the request-target
1682   is longer than the server is willing to interpret. This rare
1683   condition is only likely to occur when a client has improperly
1684   converted a POST request to a GET request with long query
1685   information, when the client has descended into a URI "black hole" of
1686   redirection (e.g., a redirected URI prefix that points to a suffix of
1687   itself), or when the server is under attack by a client attempting to
1688   exploit security holes present in some servers using fixed-length
1689   buffers for reading or manipulating the request-target.
1690</t>
1691</section>
1692
1693<section title="415 Unsupported Media Type" anchor="status.415">
1694  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1695  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1696<t>
1697   The server is refusing to service the request because the entity of
1698   the request is in a format not supported by the requested resource
1699   for the requested method.
1700</t>
1701</section>
1702
1703<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1704  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1705  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1706<t>
1707   The request included a Range request-header field (&header-range;) and none of
1708   the range-specifier values in this field overlap the current extent
1709   of the selected resource.
1710</t>
1711</section>
1712
1713<section title="417 Expectation Failed" anchor="status.417">
1714  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1715  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1716<t>
1717   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1718   could not be met by this server, or, if the server is a proxy,
1719   the server has unambiguous evidence that the request could not be met
1720   by the next-hop server.
1721</t>
1722</section>
1723</section>
1724
1725<section title="Server Error 5xx" anchor="status.5xx">
1726<t>
1727   Response status codes beginning with the digit "5" indicate cases in
1728   which the server is aware that it has erred or is incapable of
1729   performing the request. Except when responding to a HEAD request, the
1730   server &SHOULD; include an entity containing an explanation of the
1731   error situation, and whether it is a temporary or permanent
1732   condition. User agents &SHOULD; display any included entity to the
1733   user. These response codes are applicable to any request method.
1734</t>
1735
1736<section title="500 Internal Server Error" anchor="status.500">
1737  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1738  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1739<t>
1740   The server encountered an unexpected condition which prevented it
1741   from fulfilling the request.
1742</t>
1743</section>
1744
1745<section title="501 Not Implemented" anchor="status.501">
1746  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1747  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1748<t>
1749   The server does not support the functionality required to fulfill the
1750   request. This is the appropriate response when the server does not
1751   recognize the request method and is not capable of supporting it for
1752   any resource.
1753</t>
1754</section>
1755
1756<section title="502 Bad Gateway" anchor="status.502">
1757  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1759<t>
1760   The server, while acting as a gateway or proxy, received an invalid
1761   response from the upstream server it accessed in attempting to
1762   fulfill the request.
1763</t>
1764</section>
1765
1766<section title="503 Service Unavailable" anchor="status.503">
1767  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1768  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1769<t>
1770   The server is currently unable to handle the request due to a
1771   temporary overloading or maintenance of the server. The implication
1772   is that this is a temporary condition which will be alleviated after
1773   some delay. If known, the length of the delay &MAY; be indicated in a
1774   Retry-After header. If no Retry-After is given, the client &SHOULD;
1775   handle the response as it would for a 500 response.
1776</t>
1777<x:note>
1778  <t>
1779    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1780    server must use it when becoming overloaded. Some servers may wish
1781    to simply refuse the connection.
1782  </t>
1783</x:note>
1784</section>
1785
1786<section title="504 Gateway Timeout" anchor="status.504">
1787  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1788  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1789<t>
1790   The server, while acting as a gateway or proxy, did not receive a
1791   timely response from the upstream server specified by the URI (e.g.
1792   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1793   to access in attempting to complete the request.
1794</t>
1795<x:note>
1796  <t>
1797    <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1798    return 400 or 500 when DNS lookups time out.
1799  </t>
1800</x:note>
1801</section>
1802
1803<section title="505 HTTP Version Not Supported" anchor="status.505">
1804  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1805  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1806<t>
1807   The server does not support, or refuses to support, the protocol
1808   version that was used in the request message. The server is
1809   indicating that it is unable or unwilling to complete the request
1810   using the same major version as the client, as described in &http-version;,
1811   other than with this error message. The response &SHOULD; contain
1812   an entity describing why that version is not supported and what other
1813   protocols are supported by that server.
1814</t>
1815
1816</section>
1817</section>
1818</section>
1819
1820
1821<section title="Header Field Definitions" anchor="header.fields">
1822<t>
1823   This section defines the syntax and semantics of HTTP/1.1 header fields
1824   related to request and response semantics.
1825</t>
1826<t>
1827   For entity-header fields, both sender and recipient refer to either the
1828   client or the server, depending on who sends and who receives the entity.
1829</t>
1830
1831<section title="Allow" anchor="header.allow">
1832  <iref primary="true" item="Allow header" x:for-anchor=""/>
1833  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1834  <x:anchor-alias value="Allow"/>
1835  <x:anchor-alias value="Allow-v"/>
1836<t>
1837      The response-header field "Allow" lists the set of methods advertised as
1838      supported by the resource identified by the request-target. The purpose of
1839      this field is strictly to inform the recipient of valid methods
1840      associated with the resource. An Allow header field &MUST; be
1841      present in a 405 (Method Not Allowed) response.
1842</t>
1843<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1844  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1845  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1846</artwork></figure>
1847<t>
1848      Example of use:
1849</t>
1850<figure><artwork type="example">
1851  Allow: GET, HEAD, PUT
1852</artwork></figure>
1853<t>
1854      The actual set of allowed methods is defined
1855      by the origin server at the time of each request.
1856</t>
1857<t>
1858      A proxy &MUST-NOT; modify the Allow header field even if it does not
1859      understand all the methods specified, since the user agent might
1860      have other means of communicating with the origin server.
1861</t>
1862</section>
1863
1864<section title="Expect" anchor="header.expect">
1865  <iref primary="true" item="Expect header" x:for-anchor=""/>
1866  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1867  <x:anchor-alias value="Expect"/>
1868  <x:anchor-alias value="Expect-v"/>
1869  <x:anchor-alias value="expectation"/>
1870  <x:anchor-alias value="expectation-extension"/>
1871  <x:anchor-alias value="expect-params"/>
1872<t>
1873   The request-header field "Expect" is used to indicate that particular
1874   server behaviors are required by the client.
1875</t>
1876<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"/>
1877  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1878  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1879 
1880  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1881  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1882                           *<x:ref>expect-params</x:ref> ]
1883  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1884</artwork></figure>
1885<t>
1886   A server that does not understand or is unable to comply with any of
1887   the expectation values in the Expect field of a request &MUST; respond
1888   with appropriate error status. The server &MUST; respond with a 417
1889   (Expectation Failed) status if any of the expectations cannot be met
1890   or, if there are other problems with the request, some other 4xx
1891   status.
1892</t>
1893<t>
1894   This header field is defined with extensible syntax to allow for
1895   future extensions. If a server receives a request containing an
1896   Expect field that includes an expectation-extension that it does not
1897   support, it &MUST; respond with a 417 (Expectation Failed) status.
1898</t>
1899<t>
1900   Comparison of expectation values is case-insensitive for unquoted
1901   tokens (including the 100-continue token), and is case-sensitive for
1902   quoted-string expectation-extensions.
1903</t>
1904<t>
1905   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1906   return a 417 (Expectation Failed) status if it receives a request
1907   with an expectation that it cannot meet. However, the Expect
1908   request-header itself is end-to-end; it &MUST; be forwarded if the
1909   request is forwarded.
1910</t>
1911<t>
1912   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1913   Expect header.
1914</t>
1915<t>
1916   See &use100; for the use of the 100 (Continue) status.
1917</t>
1918</section>
1919
1920<section title="From" anchor="header.from">
1921  <iref primary="true" item="From header" x:for-anchor=""/>
1922  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1923  <x:anchor-alias value="From"/>
1924  <x:anchor-alias value="From-v"/>
1925  <x:anchor-alias value="mailbox"/>
1926<t>
1927   The request-header field "From", if given, &SHOULD; contain an Internet
1928   e-mail address for the human user who controls the requesting user
1929   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1930   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1931</t>
1932<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1933  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1934  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1935 
1936  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1937</artwork></figure>
1938<t>
1939   An example is:
1940</t>
1941<figure><artwork type="example">
1942  From: webmaster@example.org
1943</artwork></figure>
1944<t>
1945   This header field &MAY; be used for logging purposes and as a means for
1946   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1947   be used as an insecure form of access protection. The interpretation
1948   of this field is that the request is being performed on behalf of the
1949   person given, who accepts responsibility for the method performed. In
1950   particular, robot agents &SHOULD; include this header so that the
1951   person responsible for running the robot can be contacted if problems
1952   occur on the receiving end.
1953</t>
1954<t>
1955   The Internet e-mail address in this field &MAY; be separate from the
1956   Internet host which issued the request. For example, when a request
1957   is passed through a proxy the original issuer's address &SHOULD; be
1958   used.
1959</t>
1960<t>
1961   The client &SHOULD-NOT;  send the From header field without the user's
1962   approval, as it might conflict with the user's privacy interests or
1963   their site's security policy. It is strongly recommended that the
1964   user be able to disable, enable, and modify the value of this field
1965   at any time prior to a request.
1966</t>
1967</section>
1968
1969<section title="Location" anchor="header.location">
1970  <iref primary="true" item="Location header" x:for-anchor=""/>
1971  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1972  <x:anchor-alias value="Location"/>
1973  <x:anchor-alias value="Location-v"/>
1974<t>
1975   The response-header field "Location" is used for the identification of a
1976   new resource or to redirect the recipient to a location other than the
1977   request-target for completion of the request.  For 201 (Created)
1978   responses, the Location is that of the new resource which was created
1979   by the request. For 3xx responses, the location &SHOULD; indicate the
1980   server's preferred URI for automatic redirection to the resource. The
1981   field value consists of a single absolute URI.
1982</t>
1983<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1984  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1985  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1986</artwork></figure>
1987<t>
1988   An example is:
1989</t>
1990<figure><artwork type="example">
1991  Location: http://www.example.org/pub/WWW/People.html
1992</artwork></figure>
1993<x:note>
1994  <t>
1995    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1996    from Location in that the Content-Location identifies the original
1997    location of the entity enclosed in the response. It is therefore
1998    possible for a response to contain header fields for both Location
1999    and Content-Location.
2000  </t>
2001</x:note>
2002<t>
2003   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
2004   <list style="symbols">
2005      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
2006      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
2007      <t>With 305 Use Proxy.</t>
2008   </list>
2009</t>
2010</section>
2011
2012<section title="Max-Forwards" anchor="header.max-forwards">
2013  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2014  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2015  <x:anchor-alias value="Max-Forwards"/>
2016  <x:anchor-alias value="Max-Forwards-v"/>
2017<t>
2018   The request-header "Max-Forwards" field provides a mechanism with the
2019   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2020   number of proxies or gateways that can forward the request to the
2021   next inbound server. This can be useful when the client is attempting
2022   to trace a request chain which appears to be failing or looping in
2023   mid-chain.
2024</t>
2025<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2026  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2027  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2028</artwork></figure>
2029<t>
2030   The Max-Forwards value is a decimal integer indicating the remaining
2031   number of times this request message may be forwarded.
2032</t>
2033<t>
2034   Each proxy or gateway recipient of a TRACE or OPTIONS request
2035   containing a Max-Forwards header field &MUST; check and update its
2036   value prior to forwarding the request. If the received value is zero
2037   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2038   respond as the final recipient. If the received Max-Forwards value is
2039   greater than zero, then the forwarded message &MUST; contain an updated
2040   Max-Forwards field with a value decremented by one (1).
2041</t>
2042<t>
2043   The Max-Forwards header field &MAY; be ignored for all other methods
2044   defined by this specification and for any extension methods for which
2045   it is not explicitly referred to as part of that method definition.
2046</t>
2047</section>
2048
2049<section title="Referer" anchor="header.referer">
2050  <iref primary="true" item="Referer header" x:for-anchor=""/>
2051  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2052  <x:anchor-alias value="Referer"/>
2053  <x:anchor-alias value="Referer-v"/>
2054<t>
2055   The request-header field "Referer" [sic] allows the client to specify,
2056   for the server's benefit, the address (URI) of the resource from
2057   which the request-target was obtained (the "referrer", although the
2058   header field is misspelled.) The Referer request-header allows a
2059   server to generate lists of back-links to resources for interest,
2060   logging, optimized caching, etc. It also allows obsolete or mistyped
2061   links to be traced for maintenance. The Referer field &MUST-NOT; be
2062   sent if the request-target was obtained from a source that does not have
2063   its own URI, such as input from the user keyboard.
2064</t>
2065<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2066  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2067  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2068</artwork></figure>
2069<t>
2070   Example:
2071</t>
2072<figure><artwork type="example">
2073  Referer: http://www.example.org/hypertext/Overview.html
2074</artwork></figure>
2075<t>
2076   If the field value is a relative URI, it &SHOULD; be interpreted
2077   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2078   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2079</t>
2080</section>
2081
2082<section title="Retry-After" anchor="header.retry-after">
2083  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2084  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2085  <x:anchor-alias value="Retry-After"/>
2086  <x:anchor-alias value="Retry-After-v"/>
2087<t>
2088   The response-header "Retry-After" field can be used with a 503 (Service
2089   Unavailable) response to indicate how long the service is expected to
2090   be unavailable to the requesting client. This field &MAY; also be used
2091   with any 3xx (Redirection) response to indicate the minimum time the
2092   user-agent is asked wait before issuing the redirected request. The
2093   value of this field can be either an HTTP-date or an integer number
2094   of seconds (in decimal) after the time of the response.
2095</t>
2096<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2097  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2098  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2099</artwork></figure>
2100<t anchor="rule.delta-seconds">
2101  <x:anchor-alias value="delta-seconds"/>
2102   Time spans are non-negative decimal integers, representing time in
2103   seconds.
2104</t>
2105<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2106  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2107</artwork></figure>
2108<t>
2109   Two examples of its use are
2110</t>
2111<figure><artwork type="example">
2112  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2113  Retry-After: 120
2114</artwork></figure>
2115<t>
2116   In the latter example, the delay is 2 minutes.
2117</t>
2118</section>
2119
2120<section title="Server" anchor="header.server">
2121  <iref primary="true" item="Server header" x:for-anchor=""/>
2122  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2123  <x:anchor-alias value="Server"/>
2124  <x:anchor-alias value="Server-v"/>
2125<t>
2126   The response-header field "Server" contains information about the
2127   software used by the origin server to handle the request. The field
2128   can contain multiple product tokens (&product-tokens;) and comments
2129   identifying the server and any significant subproducts. The product
2130   tokens are listed in order of their significance for identifying the
2131   application.
2132</t>
2133<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2134  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2135  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2136                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2137</artwork></figure>
2138<t>
2139   Example:
2140</t>
2141<figure><artwork type="example">
2142  Server: CERN/3.0 libwww/2.17
2143</artwork></figure>
2144<t>
2145   If the response is being forwarded through a proxy, the proxy
2146   application &MUST-NOT; modify the Server response-header. Instead, it
2147   &MUST; include a Via field (as described in &header-via;).
2148</t>
2149<x:note>
2150  <t>
2151    <x:h>Note:</x:h> Revealing the specific software version of the server might
2152    allow the server machine to become more vulnerable to attacks
2153    against software that is known to contain security holes. Server
2154    implementors are encouraged to make this field a configurable
2155    option.
2156  </t>
2157</x:note>
2158</section>
2159
2160<section title="User-Agent" anchor="header.user-agent">
2161  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2162  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2163  <x:anchor-alias value="User-Agent"/>
2164  <x:anchor-alias value="User-Agent-v"/>
2165<t>
2166   The request-header field "User-Agent" contains information about the
2167   user agent originating the request. This is for statistical purposes,
2168   the tracing of protocol violations, and automated recognition of user
2169   agents for the sake of tailoring responses to avoid particular user
2170   agent limitations. User agents &SHOULD; include this field with
2171   requests. The field can contain multiple product tokens (&product-tokens;)
2172   and comments identifying the agent and any subproducts which form a
2173   significant part of the user agent. By convention, the product tokens
2174   are listed in order of their significance for identifying the
2175   application.
2176</t>
2177<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2178  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2179  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2180                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2181</artwork></figure>
2182<t>
2183   Example:
2184</t>
2185<figure><artwork type="example">
2186  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2187</artwork></figure>
2188</section>
2189
2190</section>
2191
2192<section title="IANA Considerations" anchor="IANA.considerations">
2193
2194<section title="Method Registry" anchor="method.registration">
2195<t>
2196  The registration procedure for HTTP Methods is defined by
2197  <xref target="method.registry"/> of this document.
2198</t>
2199<t>
2200   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2201   should be populated with the registrations below:
2202</t>
2203<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2204<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2205   <ttcol>Method</ttcol>
2206   <ttcol>Safe</ttcol>
2207   <ttcol>Reference</ttcol>
2208   <c>CONNECT</c>
2209   <c>no</c>
2210   <c>
2211      <xref target="CONNECT"/>
2212   </c>
2213   <c>DELETE</c>
2214   <c>no</c>
2215   <c>
2216      <xref target="DELETE"/>
2217   </c>
2218   <c>GET</c>
2219   <c>yes</c>
2220   <c>
2221      <xref target="GET"/>
2222   </c>
2223   <c>HEAD</c>
2224   <c>yes</c>
2225   <c>
2226      <xref target="HEAD"/>
2227   </c>
2228   <c>OPTIONS</c>
2229   <c>yes</c>
2230   <c>
2231      <xref target="OPTIONS"/>
2232   </c>
2233   <c>POST</c>
2234   <c>no</c>
2235   <c>
2236      <xref target="POST"/>
2237   </c>
2238   <c>PUT</c>
2239   <c>no</c>
2240   <c>
2241      <xref target="PUT"/>
2242   </c>
2243   <c>TRACE</c>
2244   <c>yes</c>
2245   <c>
2246      <xref target="TRACE"/>
2247   </c>
2248</texttable>
2249<!--(END)-->
2250</section>
2251
2252<section title="Status Code Registry" anchor="status.code.registration">
2253<t>
2254   The registration procedure for HTTP Status Codes -- previously defined
2255   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2256   by <xref target="status.code.registry"/> of this document.
2257</t>
2258<t>
2259   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2260   should be updated with the registrations below:
2261</t>
2262<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2263<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2264   <ttcol>Value</ttcol>
2265   <ttcol>Description</ttcol>
2266   <ttcol>Reference</ttcol>
2267   <c>100</c>
2268   <c>Continue</c>
2269   <c>
2270      <xref target="status.100"/>
2271   </c>
2272   <c>101</c>
2273   <c>Switching Protocols</c>
2274   <c>
2275      <xref target="status.101"/>
2276   </c>
2277   <c>200</c>
2278   <c>OK</c>
2279   <c>
2280      <xref target="status.200"/>
2281   </c>
2282   <c>201</c>
2283   <c>Created</c>
2284   <c>
2285      <xref target="status.201"/>
2286   </c>
2287   <c>202</c>
2288   <c>Accepted</c>
2289   <c>
2290      <xref target="status.202"/>
2291   </c>
2292   <c>203</c>
2293   <c>Non-Authoritative Information</c>
2294   <c>
2295      <xref target="status.203"/>
2296   </c>
2297   <c>204</c>
2298   <c>No Content</c>
2299   <c>
2300      <xref target="status.204"/>
2301   </c>
2302   <c>205</c>
2303   <c>Reset Content</c>
2304   <c>
2305      <xref target="status.205"/>
2306   </c>
2307   <c>206</c>
2308   <c>Partial Content</c>
2309   <c>
2310      <xref target="status.206"/>
2311   </c>
2312   <c>300</c>
2313   <c>Multiple Choices</c>
2314   <c>
2315      <xref target="status.300"/>
2316   </c>
2317   <c>301</c>
2318   <c>Moved Permanently</c>
2319   <c>
2320      <xref target="status.301"/>
2321   </c>
2322   <c>302</c>
2323   <c>Found</c>
2324   <c>
2325      <xref target="status.302"/>
2326   </c>
2327   <c>303</c>
2328   <c>See Other</c>
2329   <c>
2330      <xref target="status.303"/>
2331   </c>
2332   <c>304</c>
2333   <c>Not Modified</c>
2334   <c>
2335      <xref target="status.304"/>
2336   </c>
2337   <c>305</c>
2338   <c>Use Proxy</c>
2339   <c>
2340      <xref target="status.305"/>
2341   </c>
2342   <c>306</c>
2343   <c>(Unused)</c>
2344   <c>
2345      <xref target="status.306"/>
2346   </c>
2347   <c>307</c>
2348   <c>Temporary Redirect</c>
2349   <c>
2350      <xref target="status.307"/>
2351   </c>
2352   <c>400</c>
2353   <c>Bad Request</c>
2354   <c>
2355      <xref target="status.400"/>
2356   </c>
2357   <c>401</c>
2358   <c>Unauthorized</c>
2359   <c>
2360      <xref target="status.401"/>
2361   </c>
2362   <c>402</c>
2363   <c>Payment Required</c>
2364   <c>
2365      <xref target="status.402"/>
2366   </c>
2367   <c>403</c>
2368   <c>Forbidden</c>
2369   <c>
2370      <xref target="status.403"/>
2371   </c>
2372   <c>404</c>
2373   <c>Not Found</c>
2374   <c>
2375      <xref target="status.404"/>
2376   </c>
2377   <c>405</c>
2378   <c>Method Not Allowed</c>
2379   <c>
2380      <xref target="status.405"/>
2381   </c>
2382   <c>406</c>
2383   <c>Not Acceptable</c>
2384   <c>
2385      <xref target="status.406"/>
2386   </c>
2387   <c>407</c>
2388   <c>Proxy Authentication Required</c>
2389   <c>
2390      <xref target="status.407"/>
2391   </c>
2392   <c>408</c>
2393   <c>Request Timeout</c>
2394   <c>
2395      <xref target="status.408"/>
2396   </c>
2397   <c>409</c>
2398   <c>Conflict</c>
2399   <c>
2400      <xref target="status.409"/>
2401   </c>
2402   <c>410</c>
2403   <c>Gone</c>
2404   <c>
2405      <xref target="status.410"/>
2406   </c>
2407   <c>411</c>
2408   <c>Length Required</c>
2409   <c>
2410      <xref target="status.411"/>
2411   </c>
2412   <c>412</c>
2413   <c>Precondition Failed</c>
2414   <c>
2415      <xref target="status.412"/>
2416   </c>
2417   <c>413</c>
2418   <c>Request Entity Too Large</c>
2419   <c>
2420      <xref target="status.413"/>
2421   </c>
2422   <c>414</c>
2423   <c>URI Too Long</c>
2424   <c>
2425      <xref target="status.414"/>
2426   </c>
2427   <c>415</c>
2428   <c>Unsupported Media Type</c>
2429   <c>
2430      <xref target="status.415"/>
2431   </c>
2432   <c>416</c>
2433   <c>Requested Range Not Satisfiable</c>
2434   <c>
2435      <xref target="status.416"/>
2436   </c>
2437   <c>417</c>
2438   <c>Expectation Failed</c>
2439   <c>
2440      <xref target="status.417"/>
2441   </c>
2442   <c>500</c>
2443   <c>Internal Server Error</c>
2444   <c>
2445      <xref target="status.500"/>
2446   </c>
2447   <c>501</c>
2448   <c>Not Implemented</c>
2449   <c>
2450      <xref target="status.501"/>
2451   </c>
2452   <c>502</c>
2453   <c>Bad Gateway</c>
2454   <c>
2455      <xref target="status.502"/>
2456   </c>
2457   <c>503</c>
2458   <c>Service Unavailable</c>
2459   <c>
2460      <xref target="status.503"/>
2461   </c>
2462   <c>504</c>
2463   <c>Gateway Timeout</c>
2464   <c>
2465      <xref target="status.504"/>
2466   </c>
2467   <c>505</c>
2468   <c>HTTP Version Not Supported</c>
2469   <c>
2470      <xref target="status.505"/>
2471   </c>
2472</texttable>
2473<!--(END)-->
2474</section>
2475<section title="Message Header Registration" anchor="message.header.registration">
2476<t>
2477   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2478   with the permanent registrations below (see <xref target="RFC3864"/>):
2479</t>
2480<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2481<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2482   <ttcol>Header Field Name</ttcol>
2483   <ttcol>Protocol</ttcol>
2484   <ttcol>Status</ttcol>
2485   <ttcol>Reference</ttcol>
2486   <c>Allow</c>
2487   <c>http</c>
2488   <c>standard</c>
2489   <c>
2490      <xref target="header.allow"/>
2491   </c>
2492   <c>Expect</c>
2493   <c>http</c>
2494   <c>standard</c>
2495   <c>
2496      <xref target="header.expect"/>
2497   </c>
2498   <c>From</c>
2499   <c>http</c>
2500   <c>standard</c>
2501   <c>
2502      <xref target="header.from"/>
2503   </c>
2504   <c>Location</c>
2505   <c>http</c>
2506   <c>standard</c>
2507   <c>
2508      <xref target="header.location"/>
2509   </c>
2510   <c>Max-Forwards</c>
2511   <c>http</c>
2512   <c>standard</c>
2513   <c>
2514      <xref target="header.max-forwards"/>
2515   </c>
2516   <c>Referer</c>
2517   <c>http</c>
2518   <c>standard</c>
2519   <c>
2520      <xref target="header.referer"/>
2521   </c>
2522   <c>Retry-After</c>
2523   <c>http</c>
2524   <c>standard</c>
2525   <c>
2526      <xref target="header.retry-after"/>
2527   </c>
2528   <c>Server</c>
2529   <c>http</c>
2530   <c>standard</c>
2531   <c>
2532      <xref target="header.server"/>
2533   </c>
2534   <c>User-Agent</c>
2535   <c>http</c>
2536   <c>standard</c>
2537   <c>
2538      <xref target="header.user-agent"/>
2539   </c>
2540</texttable>
2541<!--(END)-->
2542<t>
2543   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2544</t>
2545</section>
2546</section>
2547
2548<section title="Security Considerations" anchor="security.considerations">
2549<t>
2550   This section is meant to inform application developers, information
2551   providers, and users of the security limitations in HTTP/1.1 as
2552   described by this document. The discussion does not include
2553   definitive solutions to the problems revealed, though it does make
2554   some suggestions for reducing security risks.
2555</t>
2556
2557<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2558<t>
2559   Like any generic data transfer protocol, HTTP cannot regulate the
2560   content of the data that is transferred, nor is there any a priori
2561   method of determining the sensitivity of any particular piece of
2562   information within the context of any given request. Therefore,
2563   applications &SHOULD; supply as much control over this information as
2564   possible to the provider of that information. Four header fields are
2565   worth special mention in this context: Server, Via, Referer and From.
2566</t>
2567<t>
2568   Revealing the specific software version of the server might allow the
2569   server machine to become more vulnerable to attacks against software
2570   that is known to contain security holes. Implementors &SHOULD; make the
2571   Server header field a configurable option.
2572</t>
2573<t>
2574   Proxies which serve as a portal through a network firewall &SHOULD;
2575   take special precautions regarding the transfer of header information
2576   that identifies the hosts behind the firewall. In particular, they
2577   &SHOULD; remove, or replace with sanitized versions, any Via fields
2578   generated behind the firewall.
2579</t>
2580<t>
2581   The Referer header allows reading patterns to be studied and reverse
2582   links drawn. Although it can be very useful, its power can be abused
2583   if user details are not separated from the information contained in
2584   the Referer. Even when the personal information has been removed, the
2585   Referer header might indicate a private document's URI whose
2586   publication would be inappropriate.
2587</t>
2588<t>
2589   The information sent in the From field might conflict with the user's
2590   privacy interests or their site's security policy, and hence it
2591   &SHOULD-NOT;  be transmitted without the user being able to disable,
2592   enable, and modify the contents of the field. The user &MUST; be able
2593   to set the contents of this field within a user preference or
2594   application defaults configuration.
2595</t>
2596<t>
2597   We suggest, though do not require, that a convenient toggle interface
2598   be provided for the user to enable or disable the sending of From and
2599   Referer information.
2600</t>
2601<t>
2602   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2603   fields can sometimes be used to determine that a specific client or
2604   server have a particular security hole which might be exploited.
2605   Unfortunately, this same information is often used for other valuable
2606   purposes for which HTTP currently has no better mechanism.
2607</t>
2608</section>
2609
2610<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2611<t>
2612   Because the source of a link might be private information or might
2613   reveal an otherwise private information source, it is strongly
2614   recommended that the user be able to select whether or not the
2615   Referer field is sent. For example, a browser client could have a
2616   toggle switch for browsing openly/anonymously, which would
2617   respectively enable/disable the sending of Referer and From
2618   information.
2619</t>
2620<t>
2621   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2622   HTTP request if the referring page was transferred with a secure
2623   protocol.
2624</t>
2625<t>
2626   Authors of services should not use
2627   GET-based forms for the submission of sensitive data because that
2628   data will be encoded in the Request-target. Many existing
2629   servers, proxies, and user agents log or display the Request-target in
2630   places where it might be visible to third parties. Such services can
2631   use POST-based form submission instead.
2632</t>
2633</section>
2634
2635<section title="Location Headers and Spoofing" anchor="location.spoofing">
2636<t>
2637   If a single server supports multiple organizations that do not trust
2638   one another, then it &MUST; check the values of Location and Content-Location
2639   headers in responses that are generated under control of
2640   said organizations to make sure that they do not attempt to
2641   invalidate resources over which they have no authority.
2642</t>
2643</section>
2644
2645</section>
2646
2647<section title="Acknowledgments" anchor="ack">
2648</section>
2649</middle>
2650<back>
2651
2652<references title="Normative References">
2653
2654<reference anchor="Part1">
2655  <front>
2656    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2657    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2658      <organization abbrev="Day Software">Day Software</organization>
2659      <address><email>fielding@gbiv.com</email></address>
2660    </author>
2661    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2662      <organization>One Laptop per Child</organization>
2663      <address><email>jg@laptop.org</email></address>
2664    </author>
2665    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2666      <organization abbrev="HP">Hewlett-Packard Company</organization>
2667      <address><email>JeffMogul@acm.org</email></address>
2668    </author>
2669    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2670      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2671      <address><email>henrikn@microsoft.com</email></address>
2672    </author>
2673    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2674      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2675      <address><email>LMM@acm.org</email></address>
2676    </author>
2677    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2678      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2679      <address><email>paulle@microsoft.com</email></address>
2680    </author>
2681    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2682      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2683      <address><email>timbl@w3.org</email></address>
2684    </author>
2685    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2686      <organization abbrev="W3C">World Wide Web Consortium</organization>
2687      <address><email>ylafon@w3.org</email></address>
2688    </author>
2689    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2690      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2691      <address><email>julian.reschke@greenbytes.de</email></address>
2692    </author>
2693    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2694  </front>
2695  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2696  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2697</reference>
2698
2699<reference anchor="Part3">
2700  <front>
2701    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2702    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2703      <organization abbrev="Day Software">Day Software</organization>
2704      <address><email>fielding@gbiv.com</email></address>
2705    </author>
2706    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2707      <organization>One Laptop per Child</organization>
2708      <address><email>jg@laptop.org</email></address>
2709    </author>
2710    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2711      <organization abbrev="HP">Hewlett-Packard Company</organization>
2712      <address><email>JeffMogul@acm.org</email></address>
2713    </author>
2714    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2715      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2716      <address><email>henrikn@microsoft.com</email></address>
2717    </author>
2718    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2719      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2720      <address><email>LMM@acm.org</email></address>
2721    </author>
2722    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2723      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2724      <address><email>paulle@microsoft.com</email></address>
2725    </author>
2726    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2727      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2728      <address><email>timbl@w3.org</email></address>
2729    </author>
2730    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2731      <organization abbrev="W3C">World Wide Web Consortium</organization>
2732      <address><email>ylafon@w3.org</email></address>
2733    </author>
2734    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2735      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2736      <address><email>julian.reschke@greenbytes.de</email></address>
2737    </author>
2738    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2739  </front>
2740  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2741  <x:source href="p3-payload.xml" basename="p3-payload"/>
2742</reference>
2743
2744<reference anchor="Part4">
2745  <front>
2746    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2747    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2748      <organization abbrev="Day Software">Day Software</organization>
2749      <address><email>fielding@gbiv.com</email></address>
2750    </author>
2751    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2752      <organization>One Laptop per Child</organization>
2753      <address><email>jg@laptop.org</email></address>
2754    </author>
2755    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2756      <organization abbrev="HP">Hewlett-Packard Company</organization>
2757      <address><email>JeffMogul@acm.org</email></address>
2758    </author>
2759    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2760      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2761      <address><email>henrikn@microsoft.com</email></address>
2762    </author>
2763    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2764      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2765      <address><email>LMM@acm.org</email></address>
2766    </author>
2767    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2768      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2769      <address><email>paulle@microsoft.com</email></address>
2770    </author>
2771    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2772      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2773      <address><email>timbl@w3.org</email></address>
2774    </author>
2775    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2776      <organization abbrev="W3C">World Wide Web Consortium</organization>
2777      <address><email>ylafon@w3.org</email></address>
2778    </author>
2779    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2780      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2781      <address><email>julian.reschke@greenbytes.de</email></address>
2782    </author>
2783    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2784  </front>
2785  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2786  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2787</reference>
2788
2789<reference anchor="Part5">
2790  <front>
2791    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2792    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2793      <organization abbrev="Day Software">Day Software</organization>
2794      <address><email>fielding@gbiv.com</email></address>
2795    </author>
2796    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2797      <organization>One Laptop per Child</organization>
2798      <address><email>jg@laptop.org</email></address>
2799    </author>
2800    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2801      <organization abbrev="HP">Hewlett-Packard Company</organization>
2802      <address><email>JeffMogul@acm.org</email></address>
2803    </author>
2804    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2805      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2806      <address><email>henrikn@microsoft.com</email></address>
2807    </author>
2808    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2809      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2810      <address><email>LMM@acm.org</email></address>
2811    </author>
2812    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2813      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2814      <address><email>paulle@microsoft.com</email></address>
2815    </author>
2816    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2817      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2818      <address><email>timbl@w3.org</email></address>
2819    </author>
2820    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2821      <organization abbrev="W3C">World Wide Web Consortium</organization>
2822      <address><email>ylafon@w3.org</email></address>
2823    </author>
2824    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2825      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2826      <address><email>julian.reschke@greenbytes.de</email></address>
2827    </author>
2828    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2829  </front>
2830  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2831  <x:source href="p5-range.xml" basename="p5-range"/>
2832</reference>
2833
2834<reference anchor="Part6">
2835  <front>
2836    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2837    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2838      <organization abbrev="Day Software">Day Software</organization>
2839      <address><email>fielding@gbiv.com</email></address>
2840    </author>
2841    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2842      <organization>One Laptop per Child</organization>
2843      <address><email>jg@laptop.org</email></address>
2844    </author>
2845    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2846      <organization abbrev="HP">Hewlett-Packard Company</organization>
2847      <address><email>JeffMogul@acm.org</email></address>
2848    </author>
2849    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2850      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2851      <address><email>henrikn@microsoft.com</email></address>
2852    </author>
2853    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2854      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2855      <address><email>LMM@acm.org</email></address>
2856    </author>
2857    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2858      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2859      <address><email>paulle@microsoft.com</email></address>
2860    </author>
2861    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2862      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2863      <address><email>timbl@w3.org</email></address>
2864    </author>
2865    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2866      <organization abbrev="W3C">World Wide Web Consortium</organization>
2867      <address><email>ylafon@w3.org</email></address>
2868    </author>
2869    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2870      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2871      <address><email>julian.reschke@greenbytes.de</email></address>
2872    </author>
2873    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2874  </front>
2875  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2876  <x:source href="p6-cache.xml" basename="p6-cache"/>
2877</reference>
2878
2879<reference anchor="Part7">
2880  <front>
2881    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2882    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2883      <organization abbrev="Day Software">Day Software</organization>
2884      <address><email>fielding@gbiv.com</email></address>
2885    </author>
2886    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2887      <organization>One Laptop per Child</organization>
2888      <address><email>jg@laptop.org</email></address>
2889    </author>
2890    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2891      <organization abbrev="HP">Hewlett-Packard Company</organization>
2892      <address><email>JeffMogul@acm.org</email></address>
2893    </author>
2894    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2895      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2896      <address><email>henrikn@microsoft.com</email></address>
2897    </author>
2898    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2899      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2900      <address><email>LMM@acm.org</email></address>
2901    </author>
2902    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2903      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2904      <address><email>paulle@microsoft.com</email></address>
2905    </author>
2906    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2907      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2908      <address><email>timbl@w3.org</email></address>
2909    </author>
2910    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2911      <organization abbrev="W3C">World Wide Web Consortium</organization>
2912      <address><email>ylafon@w3.org</email></address>
2913    </author>
2914    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2915      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2916      <address><email>julian.reschke@greenbytes.de</email></address>
2917    </author>
2918    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2919  </front>
2920  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2921  <x:source href="p7-auth.xml" basename="p7-auth"/>
2922</reference>
2923
2924<reference anchor="RFC2119">
2925  <front>
2926    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2927    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2928      <organization>Harvard University</organization>
2929      <address><email>sob@harvard.edu</email></address>
2930    </author>
2931    <date month="March" year="1997"/>
2932  </front>
2933  <seriesInfo name="BCP" value="14"/>
2934  <seriesInfo name="RFC" value="2119"/>
2935</reference>
2936
2937<reference anchor="RFC5234">
2938  <front>
2939    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2940    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2941      <organization>Brandenburg InternetWorking</organization>
2942      <address>
2943      <postal>
2944      <street>675 Spruce Dr.</street>
2945      <city>Sunnyvale</city>
2946      <region>CA</region>
2947      <code>94086</code>
2948      <country>US</country></postal>
2949      <phone>+1.408.246.8253</phone>
2950      <email>dcrocker@bbiw.net</email></address> 
2951    </author>
2952    <author initials="P." surname="Overell" fullname="Paul Overell">
2953      <organization>THUS plc.</organization>
2954      <address>
2955      <postal>
2956      <street>1/2 Berkeley Square</street>
2957      <street>99 Berkely Street</street>
2958      <city>Glasgow</city>
2959      <code>G3 7HR</code>
2960      <country>UK</country></postal>
2961      <email>paul.overell@thus.net</email></address>
2962    </author>
2963    <date month="January" year="2008"/>
2964  </front>
2965  <seriesInfo name="STD" value="68"/>
2966  <seriesInfo name="RFC" value="5234"/>
2967</reference>
2968
2969</references>
2970
2971<references title="Informative References">
2972
2973<reference anchor="RFC1945">
2974  <front>
2975    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2976    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2977      <organization>MIT, Laboratory for Computer Science</organization>
2978      <address><email>timbl@w3.org</email></address>
2979    </author>
2980    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2981      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2982      <address><email>fielding@ics.uci.edu</email></address>
2983    </author>
2984    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2985      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2986      <address><email>frystyk@w3.org</email></address>
2987    </author>
2988    <date month="May" year="1996"/>
2989  </front>
2990  <seriesInfo name="RFC" value="1945"/>
2991</reference>
2992
2993<reference anchor="RFC2068">
2994  <front>
2995    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2996    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2997      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2998      <address><email>fielding@ics.uci.edu</email></address>
2999    </author>
3000    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3001      <organization>MIT Laboratory for Computer Science</organization>
3002      <address><email>jg@w3.org</email></address>
3003    </author>
3004    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3005      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3006      <address><email>mogul@wrl.dec.com</email></address>
3007    </author>
3008    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3009      <organization>MIT Laboratory for Computer Science</organization>
3010      <address><email>frystyk@w3.org</email></address>
3011    </author>
3012    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3013      <organization>MIT Laboratory for Computer Science</organization>
3014      <address><email>timbl@w3.org</email></address>
3015    </author>
3016    <date month="January" year="1997"/>
3017  </front>
3018  <seriesInfo name="RFC" value="2068"/>
3019</reference>
3020
3021<reference anchor="RFC2616">
3022  <front>
3023    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3024    <author initials="R." surname="Fielding" fullname="R. Fielding">
3025      <organization>University of California, Irvine</organization>
3026      <address><email>fielding@ics.uci.edu</email></address>
3027    </author>
3028    <author initials="J." surname="Gettys" fullname="J. Gettys">
3029      <organization>W3C</organization>
3030      <address><email>jg@w3.org</email></address>
3031    </author>
3032    <author initials="J." surname="Mogul" fullname="J. Mogul">
3033      <organization>Compaq Computer Corporation</organization>
3034      <address><email>mogul@wrl.dec.com</email></address>
3035    </author>
3036    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3037      <organization>MIT Laboratory for Computer Science</organization>
3038      <address><email>frystyk@w3.org</email></address>
3039    </author>
3040    <author initials="L." surname="Masinter" fullname="L. Masinter">
3041      <organization>Xerox Corporation</organization>
3042      <address><email>masinter@parc.xerox.com</email></address>
3043    </author>
3044    <author initials="P." surname="Leach" fullname="P. Leach">
3045      <organization>Microsoft Corporation</organization>
3046      <address><email>paulle@microsoft.com</email></address>
3047    </author>
3048    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3049      <organization>W3C</organization>
3050      <address><email>timbl@w3.org</email></address>
3051    </author>
3052    <date month="June" year="1999"/>
3053  </front>
3054  <seriesInfo name="RFC" value="2616"/>
3055</reference>
3056
3057<reference anchor='RFC2817'>
3058  <front>
3059    <title>Upgrading to TLS Within HTTP/1.1</title>
3060    <author initials='R.' surname='Khare' fullname='R. Khare'>
3061      <organization>4K Associates / UC Irvine</organization>
3062      <address><email>rohit@4K-associates.com</email></address>
3063    </author>
3064    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3065      <organization>Agranat Systems, Inc.</organization>
3066      <address><email>lawrence@agranat.com</email></address>
3067    </author>
3068    <date year='2000' month='May' />
3069  </front>
3070  <seriesInfo name='RFC' value='2817' />
3071</reference>
3072
3073<reference anchor='RFC3864'>
3074  <front>
3075    <title>Registration Procedures for Message Header Fields</title>
3076    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3077      <organization>Nine by Nine</organization>
3078      <address><email>GK-IETF@ninebynine.org</email></address>
3079    </author>
3080    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3081      <organization>BEA Systems</organization>
3082      <address><email>mnot@pobox.com</email></address>
3083    </author>
3084    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3085      <organization>HP Labs</organization>
3086      <address><email>JeffMogul@acm.org</email></address>
3087    </author>
3088    <date year='2004' month='September' />
3089  </front>
3090  <seriesInfo name='BCP' value='90' />
3091  <seriesInfo name='RFC' value='3864' />
3092</reference>
3093
3094<reference anchor='RFC5226'>
3095  <front>
3096    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3097    <author initials='T.' surname='Narten' fullname='T. Narten'>
3098      <organization>IBM</organization>
3099      <address><email>narten@us.ibm.com</email></address>
3100    </author>
3101    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3102      <organization>Google</organization>
3103      <address><email>Harald@Alvestrand.no</email></address>
3104    </author>
3105    <date year='2008' month='May' />
3106  </front>
3107  <seriesInfo name='BCP' value='26' />
3108  <seriesInfo name='RFC' value='5226' />
3109</reference>
3110
3111<reference anchor="RFC5322">
3112  <front>
3113    <title>Internet Message Format</title>
3114    <author initials="P." surname="Resnick" fullname="P. Resnick">
3115      <organization>Qualcomm Incorporated</organization>
3116    </author>
3117    <date year="2008" month="October"/>
3118  </front> 
3119  <seriesInfo name="RFC" value="5322"/>
3120</reference>
3121
3122</references>
3123
3124<section title="Compatibility with Previous Versions" anchor="compatibility">
3125<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3126<t>
3127   Clarified which error code should be used for inbound server failures
3128   (e.g. DNS failures). (<xref target="status.504"/>).
3129</t>
3130<t>
3131   201 (Created) had a race that required an Etag be sent when a resource is
3132   first created. (<xref target="status.201"/>).
3133</t>
3134<t>
3135   Rewrite of message transmission requirements to make it much harder
3136   for implementors to get it wrong, as the consequences of errors here
3137   can have significant impact on the Internet, and to deal with the
3138   following problems:
3139  <list style="numbers">
3140      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3141         this was incorrectly placing a requirement on the behavior of
3142         an implementation of a future version of HTTP/1.x</t>
3143
3144      <t>Made it clear that user-agents should retry requests, not
3145         "clients" in general.</t>
3146
3147      <t>Converted requirements for clients to ignore unexpected 100
3148         (Continue) responses, and for proxies to forward 100 responses,
3149         into a general requirement for 1xx responses.</t>
3150
3151      <t>Modified some TCP-specific language, to make it clearer that
3152         non-TCP transports are possible for HTTP.</t>
3153
3154      <t>Require that the origin server &MUST-NOT; wait for the request
3155         body before it sends a required 100 (Continue) response.</t>
3156
3157      <t>Allow, rather than require, a server to omit 100 (Continue) if
3158         it has already seen some of the request body.</t>
3159
3160      <t>Allow servers to defend against denial-of-service attacks and
3161         broken clients.</t>
3162  </list>
3163</t>
3164<t>
3165   This change adds the Expect header and 417 status code.
3166</t>
3167<t>
3168   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3169   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3170</t>
3171<t>
3172   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
3173   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3174</t>
3175</section>
3176
3177<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3178<t>
3179  This document takes over the Status Code Registry, previously defined
3180  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3181  (<xref target="status.code.registry"/>)
3182</t>
3183<t>
3184  Clarify definition of POST.
3185  (<xref target="POST"/>)
3186</t>
3187<t>
3188  Failed to consider that there are
3189  many other request methods that are safe to automatically redirect,
3190  and further that the user agent is able to make that determination
3191  based on the request method semantics.
3192  (Sections <xref format="counter" target="status.301"/>,
3193  <xref format="counter" target="status.302"/> and
3194  <xref format="counter" target="status.307"/>)
3195</t>
3196<t>
3197  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3198  It used to indicate that the requested resource must be accessed through the
3199  proxy given by the Location field. The Location field gave the URI of the
3200  proxy. The recipient was expected to repeat this single request via the proxy.
3201  (<xref target="status.305"/>)
3202</t>
3203<t>
3204  Reclassify Allow header as response header, removing the option to
3205  specify it in a PUT request.
3206  Relax the server requirement on the contents of the Allow header and
3207  remove requirement on clients to always trust the header value.
3208  (<xref target="header.allow"/>)
3209</t>
3210<t>
3211  Correct syntax of Location header to allow fragment,
3212  as referred symbol wasn't what was expected, and add some
3213  clarifications as to when it would not be appropriate.
3214  (<xref target="header.location"/>)
3215</t>
3216<t>
3217  In the description of the Server header, the Via field
3218  was described as a SHOULD. The requirement was and is stated
3219  correctly in the description of the Via header in &header-via;.
3220  (<xref target="header.server"/>)
3221</t>
3222</section>
3223
3224</section>
3225
3226<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3227<figure>
3228<artwork type="abnf" name="p2-semantics.parsed-abnf">
3229<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3230<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3231<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3232<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3233<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3234<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3235<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3236<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3237<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3238
3239<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3240<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3241<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3242
3243<x:ref>From</x:ref> = "From:" OWS From-v
3244<x:ref>From-v</x:ref> = mailbox
3245
3246<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;
3247<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.1&gt;
3248
3249<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3250If-Modified-Since =
3251 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3252<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3253<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3254If-Unmodified-Since =
3255 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3256
3257<x:ref>Location</x:ref> = "Location:" OWS Location-v
3258<x:ref>Location-v</x:ref> = absolute-URI [ "#" fragment ]
3259
3260<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3261<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3262<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 /
3263 %x50.4F.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45 /
3264 %x43.4E.4E.45.43.54 / extension-method
3265
3266<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3267
3268Proxy-Authenticate =
3269 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3270Proxy-Authorization =
3271 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3272
3273<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3274<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3275<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3276<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3277<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3278<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3279<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3280
3281<x:ref>Server</x:ref> = "Server:" OWS Server-v
3282<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3283<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3284 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3285 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3286 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3287 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3288 "505" / extension-code
3289
3290<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 8.8&gt;
3291
3292<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3293<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3294
3295<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3296
3297WWW-Authenticate =
3298 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3299
3300<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;
3301
3302<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 1.2.2&gt;
3303
3304<x:ref>delta-seconds</x:ref> = 1*DIGIT
3305
3306<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3307<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3308<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3309 *expect-params ]
3310<x:ref>extension-code</x:ref> = 3DIGIT
3311<x:ref>extension-method</x:ref> = token
3312
3313<x:ref>fragment</x:ref> = &lt;fragment, defined in [Part1], Section 2.1&gt;
3314
3315<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3316
3317<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3318
3319<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.1&gt;
3320<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 3.4&gt;
3321
3322<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3323
3324<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3325 Accept-Language / Authorization / Expect / From / Host / If-Match /
3326 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3327 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3328 User-Agent
3329<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3330 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3331
3332<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3333
3334
3335</artwork>
3336</figure>
3337<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3338; Reason-Phrase defined but not used
3339; Status-Code defined but not used
3340; request-header defined but not used
3341; response-header defined but not used
3342</artwork></figure></section>
3343
3344<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3345
3346<section title="Since RFC2616">
3347<t>
3348  Extracted relevant partitions from <xref target="RFC2616"/>.
3349</t>
3350</section>
3351
3352<section title="Since draft-ietf-httpbis-p2-semantics-00">
3353<t>
3354  Closed issues:
3355  <list style="symbols"> 
3356    <t>
3357      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3358      "Via is a MUST"
3359      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3360    </t>
3361    <t>
3362      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3363      "Fragments allowed in Location"
3364      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3365    </t>
3366    <t>
3367      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3368      "Safe Methods vs Redirection"
3369      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3370    </t>
3371    <t>
3372      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3373      "Revise description of the POST method"
3374      (<eref target="http://purl.org/NET/http-errata#post"/>)
3375    </t>
3376    <t>
3377      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3378      "Normative and Informative references"
3379    </t>
3380    <t>
3381      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3382      "RFC2606 Compliance"
3383    </t>
3384    <t>
3385      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3386      "Informative references"
3387    </t>
3388    <t>
3389      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3390      "Redundant cross-references"
3391    </t>
3392  </list>
3393</t>
3394<t>
3395  Other changes:
3396  <list style="symbols"> 
3397    <t>
3398      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3399    </t>
3400  </list>
3401</t>
3402</section>
3403
3404<section title="Since draft-ietf-httpbis-p2-semantics-01">
3405<t>
3406  Closed issues:
3407  <list style="symbols"> 
3408    <t>
3409      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3410      "PUT side effects"
3411    </t>
3412    <t>
3413      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3414      "Duplicate Host header requirements"
3415    </t>
3416  </list>
3417</t>
3418<t>
3419  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3420  <list style="symbols"> 
3421    <t>
3422      Move "Product Tokens" section (back) into Part 1, as "token" is used
3423      in the definition of the Upgrade header.
3424    </t>
3425    <t>
3426      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3427    </t>
3428    <t>
3429      Copy definition of delta-seconds from Part6 instead of referencing it.
3430    </t>
3431  </list>
3432</t>
3433</section>
3434
3435<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3436<t>
3437  Closed issues:
3438  <list style="symbols"> 
3439    <t>
3440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3441      "Requiring Allow in 405 responses"
3442    </t>
3443    <t>
3444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3445      "Status Code Registry"
3446    </t>
3447    <t>
3448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3449      "Redirection vs. Location"
3450    </t>
3451    <t>
3452      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3453      "Cacheability of 303 response"
3454    </t>
3455    <t>
3456      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3457      "305 Use Proxy"
3458    </t>
3459    <t>
3460      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3461      "Classification for Allow header"
3462    </t>
3463    <t>
3464      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3465      "PUT - 'store under' vs 'store at'"
3466    </t>
3467  </list>
3468</t>
3469<t>
3470  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3471  <list style="symbols"> 
3472    <t>
3473      Reference RFC 3984, and update header registrations for headers defined
3474      in this document.
3475    </t>
3476  </list>
3477</t>
3478<t>
3479  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3480  <list style="symbols"> 
3481    <t>
3482      Replace string literals when the string really is case-sensitive (method).
3483    </t>
3484  </list>
3485</t>
3486</section>
3487
3488<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3489<t>
3490  Closed issues:
3491  <list style="symbols"> 
3492    <t>
3493      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3494      "OPTIONS request bodies"
3495    </t>
3496    <t>
3497      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3498      "Description of CONNECT should refer to RFC2817"
3499    </t>
3500    <t>
3501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3502      "Location Content-Location reference request/response mixup"
3503    </t>
3504  </list>
3505</t>
3506<t>
3507  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3508  <list style="symbols"> 
3509    <t>
3510      Added initial proposal for registration process, plus initial
3511      content (non-HTTP/1.1 methods to be added by a separate specification).
3512    </t>
3513  </list>
3514</t>
3515</section>
3516
3517<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3518<t>
3519  Closed issues:
3520  <list style="symbols"> 
3521    <t>
3522      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3523      "Content-*"
3524    </t>
3525    <t>
3526      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3527      "RFC 2822 is updated by RFC 5322"
3528    </t>
3529  </list>
3530</t>
3531<t>
3532  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3533  <list style="symbols"> 
3534    <t>
3535      Use "/" instead of "|" for alternatives.
3536    </t>
3537    <t>
3538      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3539      whitespace ("OWS") and required whitespace ("RWS").
3540    </t>
3541    <t>
3542      Rewrite ABNFs to spell out whitespace rules, factor out
3543      header value format definitions.
3544    </t>
3545  </list>
3546</t>
3547</section>
3548
3549<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3550<t>
3551  Closed issues:
3552  <list style="symbols"> 
3553    <t>
3554      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3555      "Reason-Phrase BNF"
3556    </t>
3557  </list>
3558</t>
3559<t>
3560  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3561  <list style="symbols"> 
3562    <t>
3563      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3564    </t>
3565  </list>
3566</t>
3567</section>
3568
3569<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3570<t>
3571</t>
3572</section>
3573
3574</section>
3575
3576</back>
3577</rfc>
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