source: draft-ietf-httpbis/latest/p2-semantics.xml @ 679

Last change on this file since 679 was 679, checked in by julian.reschke@…, 10 years ago

add tool for refreshing included stuff, use it throughout for collected ABNF

  • Property svn:eol-style set to native
File size: 153.8 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 "August">
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='#date.time.formats.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.07"/>.
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="Host"/>
345  <x:anchor-alias value="HTTP-date"/>
346  <x:anchor-alias value="If-Match"/>
347  <x:anchor-alias value="If-Modified-Since"/>
348  <x:anchor-alias value="If-None-Match"/>
349  <x:anchor-alias value="If-Range"/>
350  <x:anchor-alias value="If-Unmodified-Since"/>
351  <x:anchor-alias value="partial-URI"/>
352  <x:anchor-alias value="product"/>
353  <x:anchor-alias value="Proxy-Authenticate"/>
354  <x:anchor-alias value="Proxy-Authorization"/>
355  <x:anchor-alias value="Range"/>
356  <x:anchor-alias value="TE"/>
357  <x:anchor-alias value="URI"/>
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>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
366  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
367  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
368  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
369  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
370  <x:ref>URI</x:ref>           = &lt;URI, defined in &uri;&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"/>).
462</t>
463<t>
464  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
465</t>
466</section>
467</section>
468
469<section title="Request Header Fields" anchor="request.header.fields">
470  <x:anchor-alias value="request-header"/>
471<t>
472   The request-header fields allow the client to pass additional
473   information about the request, and about the client itself, to the
474   server. These fields act as request modifiers, with semantics
475   equivalent to the parameters on a programming language method
476   invocation.
477</t>
478<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
479  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
480                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
481                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
482                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
483                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
484                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
485                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
486                 / <x:ref>Host</x:ref>                     ; &header-host;
487                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
488                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
489                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
490                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
491                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
492                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
493                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
494                 / <x:ref>Range</x:ref>                    ; &header-range;
495                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
496                 / <x:ref>TE</x:ref>                       ; &header-te;
497                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
498</artwork></figure>
499<t>
500   Request-header field names can be extended reliably only in
501   combination with a change in the protocol version. However, new or
502   experimental header fields &MAY; be given the semantics of request-header
503   fields if all parties in the communication recognize them to
504   be request-header fields. Unrecognized header fields are treated as
505   entity-header fields.
506</t>
507</section>
508
509<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
510  <x:anchor-alias value="Reason-Phrase"/>
511  <x:anchor-alias value="Status-Code"/>
512  <x:anchor-alias value="extension-code"/>
513<t>
514   The Status-Code element is a 3-digit integer result code of the
515   attempt to understand and satisfy the request. The status codes listed
516   below are defined in <xref target="status.codes"/>.
517   The Reason-Phrase is intended to give a short
518   textual description of the Status-Code. The Status-Code is intended
519   for use by automata and the Reason-Phrase is intended for the human
520   user. The client is not required to examine or display the Reason-Phrase.
521</t>
522<t> 
523   The individual values of the numeric status codes defined for
524   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
525   presented below. The reason phrases listed here are only
526   recommendations -- they &MAY; be replaced by local equivalents without
527   affecting the protocol.
528</t>
529<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"/>
530  <x:ref>Status-Code</x:ref>    =
531         "100"  ; <xref target="status.100"/>: Continue
532       / "101"  ; <xref target="status.101"/>: Switching Protocols
533       / "200"  ; <xref target="status.200"/>: OK
534       / "201"  ; <xref target="status.201"/>: Created
535       / "202"  ; <xref target="status.202"/>: Accepted
536       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
537       / "204"  ; <xref target="status.204"/>: No Content
538       / "205"  ; <xref target="status.205"/>: Reset Content
539       / "206"  ; <xref target="status.206"/>: Partial Content
540       / "300"  ; <xref target="status.300"/>: Multiple Choices
541       / "301"  ; <xref target="status.301"/>: Moved Permanently
542       / "302"  ; <xref target="status.302"/>: Found
543       / "303"  ; <xref target="status.303"/>: See Other
544       / "304"  ; <xref target="status.304"/>: Not Modified
545       / "305"  ; <xref target="status.305"/>: Use Proxy
546       / "307"  ; <xref target="status.307"/>: Temporary Redirect
547       / "400"  ; <xref target="status.400"/>: Bad Request
548       / "401"  ; <xref target="status.401"/>: Unauthorized
549       / "402"  ; <xref target="status.402"/>: Payment Required
550       / "403"  ; <xref target="status.403"/>: Forbidden
551       / "404"  ; <xref target="status.404"/>: Not Found
552       / "405"  ; <xref target="status.405"/>: Method Not Allowed
553       / "406"  ; <xref target="status.406"/>: Not Acceptable
554       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
555       / "408"  ; <xref target="status.408"/>: Request Time-out
556       / "409"  ; <xref target="status.409"/>: Conflict
557       / "410"  ; <xref target="status.410"/>: Gone
558       / "411"  ; <xref target="status.411"/>: Length Required
559       / "412"  ; <xref target="status.412"/>: Precondition Failed
560       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
561       / "414"  ; <xref target="status.414"/>: URI Too Long
562       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
563       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
564       / "417"  ; <xref target="status.417"/>: Expectation Failed
565       / "500"  ; <xref target="status.500"/>: Internal Server Error
566       / "501"  ; <xref target="status.501"/>: Not Implemented
567       / "502"  ; <xref target="status.502"/>: Bad Gateway
568       / "503"  ; <xref target="status.503"/>: Service Unavailable
569       / "504"  ; <xref target="status.504"/>: Gateway Time-out
570       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
571       / <x:ref>extension-code</x:ref>
572
573  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
574  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
575</artwork></figure>
576<t>
577   HTTP status codes are extensible. HTTP applications are not required
578   to understand the meaning of all registered status codes, though such
579   understanding is obviously desirable. However, applications &MUST;
580   understand the class of any status code, as indicated by the first
581   digit, and treat any unrecognized response as being equivalent to the
582   x00 status code of that class, with the exception that an
583   unrecognized response &MUST-NOT; be cached. For example, if an
584   unrecognized status code of 431 is received by the client, it can
585   safely assume that there was something wrong with its request and
586   treat the response as if it had received a 400 status code. In such
587   cases, user agents &SHOULD; present to the user the entity returned
588   with the response, since that entity is likely to include human-readable
589   information which will explain the unusual status.
590</t>
591
592<section title="Status Code Registry" anchor="status.code.registry">
593<t>
594  The HTTP Status Code Registry defines the name space for the Status-Code
595  token in the Status line of an HTTP response.
596</t>
597<t>
598  Values to be added to this name space are subject to IETF review
599  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
600</t>
601<t>
602  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
603</t>
604</section>
605
606</section>
607
608<section title="Response Header Fields" anchor="response.header.fields">
609  <x:anchor-alias value="response-header"/>
610<t>
611   The response-header fields allow the server to pass additional
612   information about the response which cannot be placed in the Status-Line.
613   These header fields give information about the server and about
614   further access to the resource identified by the request-target.
615</t>
616<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
617  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
618                  / <x:ref>Age</x:ref>                     ; &header-age;
619                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
620                  / <x:ref>ETag</x:ref>                    ; &header-etag;
621                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
622                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
623                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
624                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
625                  / <x:ref>Vary</x:ref>                    ; &header-vary;
626                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
627</artwork></figure>
628<t>
629   Response-header field names can be extended reliably only in
630   combination with a change in the protocol version. However, new or
631   experimental header fields &MAY; be given the semantics of response-header
632   fields if all parties in the communication recognize them to
633   be response-header fields. Unrecognized header fields are treated as
634   entity-header fields.
635</t>
636</section>
637
638<section title="Entity" anchor="entity">
639<t>
640   Request and Response messages &MAY; transfer an entity if not otherwise
641   restricted by the request method or response status code. An entity
642   consists of entity-header fields and an entity-body, although some
643   responses will only include the entity-headers. HTTP entity-body and
644   entity-header fields are defined in &payload;.
645</t>
646<t>
647   An entity-body is only present in a message when a message-body is
648   present, as described in &message-body;. The entity-body is obtained
649   from the message-body by decoding any Transfer-Encoding that might
650   have been applied to ensure safe and proper transfer of the message.
651</t>
652</section>
653
654
655<section title="Method Definitions" anchor="method.definitions">
656<t>
657   The set of common methods for HTTP/1.1 is defined below. Although
658   this set can be expanded, additional methods cannot be assumed to
659   share the same semantics for separately extended clients and servers.
660</t>
661
662<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
663
664<section title="Safe Methods" anchor="safe.methods">
665<iref item="Safe Methods" primary="true"/>
666<t>
667   Implementors should be aware that the software represents the user in
668   their interactions over the Internet, and should be careful to allow
669   the user to be aware of any actions they might take which may have an
670   unexpected significance to themselves or others.
671</t>
672<t>
673   In particular, the convention has been established that the GET and
674   HEAD methods &SHOULD-NOT;  have the significance of taking an action
675   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
676   This allows user agents to represent other methods, such as POST, PUT
677   and DELETE, in a special way, so that the user is made aware of the
678   fact that a possibly unsafe action is being requested.
679</t>
680<t>
681   Naturally, it is not possible to ensure that the server does not
682   generate side-effects as a result of performing a GET request; in
683   fact, some dynamic resources consider that a feature. The important
684   distinction here is that the user did not request the side-effects,
685   so therefore cannot be held accountable for them.
686</t>
687</section>
688
689<section title="Idempotent Methods" anchor="idempotent.methods">
690<iref item="Idempotent Methods" primary="true"/>
691<t>
692   Methods can also have the property of "idempotence" in that, aside
693   from error or expiration issues, the intended effect of multiple
694   identical requests is the same as for a single request.
695   The methods PUT, DELETE, and all safe methods are idempotent.
696   It is important to note that idempotence refers only to changes
697   requested by the client: a server is free to change its state due
698   to multiple requests for the purpose of tracking those requests,
699   versioning of results, etc.
700</t>
701</section>
702</section>
703
704<section title="OPTIONS" anchor="OPTIONS">
705  <rdf:Description>
706    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
707  </rdf:Description>
708  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
709  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
710<t>
711   The OPTIONS method represents a request for information about the
712   communication options available on the request/response chain
713   identified by the request-target. This method allows the client to
714   determine the options and/or requirements associated with a resource,
715   or the capabilities of a server, without implying a resource action
716   or initiating a resource retrieval.
717</t>
718<t>
719   Responses to this method are not cacheable.
720</t>
721<t>
722   If the OPTIONS request includes an entity-body (as indicated by the
723   presence of Content-Length or Transfer-Encoding), then the media type
724   &MUST; be indicated by a Content-Type field. Although this
725   specification does not define any use for such a body, future
726   extensions to HTTP might use the OPTIONS body to make more detailed
727   queries on the server.
728</t>
729<t>
730   If the request-target is an asterisk ("*"), the OPTIONS request is
731   intended to apply to the server in general rather than to a specific
732   resource. Since a server's communication options typically depend on
733   the resource, the "*" request is only useful as a "ping" or "no-op"
734   type of method; it does nothing beyond allowing the client to test
735   the capabilities of the server. For example, this can be used to test
736   a proxy for HTTP/1.1 compliance (or lack thereof).
737</t>
738<t>
739   If the request-target is not an asterisk, the OPTIONS request applies
740   only to the options that are available when communicating with that
741   resource.
742</t>
743<t>
744   A 200 response &SHOULD; include any header fields that indicate
745   optional features implemented by the server and applicable to that
746   resource (e.g., Allow), possibly including extensions not defined by
747   this specification. The response body, if any, &SHOULD; also include
748   information about the communication options. The format for such a
749   body is not defined by this specification, but might be defined by
750   future extensions to HTTP. Content negotiation &MAY; be used to select
751   the appropriate response format. If no response body is included, the
752   response &MUST; include a Content-Length field with a field-value of
753   "0".
754</t>
755<t>
756   The Max-Forwards request-header field &MAY; be used to target a
757   specific proxy in the request chain. When a proxy receives an OPTIONS
758   request on an absolute-URI for which request forwarding is permitted,
759   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
760   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
761   instead, the proxy &SHOULD; respond with its own communication options.
762   If the Max-Forwards field-value is an integer greater than zero, the
763   proxy &MUST; decrement the field-value when it forwards the request. If
764   no Max-Forwards field is present in the request, then the forwarded
765   request &MUST-NOT; include a Max-Forwards field.
766</t>
767</section>
768
769<section title="GET" anchor="GET">
770  <rdf:Description>
771    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
772  </rdf:Description>
773  <iref primary="true" item="GET method" x:for-anchor=""/>
774  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
775<t>
776   The GET method means retrieve whatever information (in the form of an
777   entity) is identified by the request-target. If the request-target refers
778   to a data-producing process, it is the produced data which shall be
779   returned as the entity in the response and not the source text of the
780   process, unless that text happens to be the output of the process.
781</t>
782<t>
783   The semantics of the GET method change to a "conditional GET" if the
784   request message includes an If-Modified-Since, If-Unmodified-Since,
785   If-Match, If-None-Match, or If-Range header field. A conditional GET
786   method requests that the entity be transferred only under the
787   circumstances described by the conditional header field(s). The
788   conditional GET method is intended to reduce unnecessary network
789   usage by allowing cached entities to be refreshed without requiring
790   multiple requests or transferring data already held by the client.
791</t>
792<t>
793   The semantics of the GET method change to a "partial GET" if the
794   request message includes a Range header field. A partial GET requests
795   that only part of the entity be transferred, as described in &header-range;.
796   The partial GET method is intended to reduce unnecessary
797   network usage by allowing partially-retrieved entities to be
798   completed without transferring data already held by the client.
799</t>
800<t>
801   The response to a GET request is cacheable if and only if it meets
802   the requirements for HTTP caching described in &caching;.
803</t>
804<t>
805   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
806</t>
807</section>
808
809<section title="HEAD" anchor="HEAD">
810  <rdf:Description>
811    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
812  </rdf:Description>
813  <iref primary="true" item="HEAD method" x:for-anchor=""/>
814  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
815<t>
816   The HEAD method is identical to GET except that the server &MUST-NOT;
817   return a message-body in the response. The metainformation contained
818   in the HTTP headers in response to a HEAD request &SHOULD; be identical
819   to the information sent in response to a GET request. This method can
820   be used for obtaining metainformation about the entity implied by the
821   request without transferring the entity-body itself. This method is
822   often used for testing hypertext links for validity, accessibility,
823   and recent modification.
824</t>
825<t>
826   The response to a HEAD request &MAY; be cacheable in the sense that the
827   information contained in the response &MAY; be used to update a
828   previously cached entity from that resource. If the new field values
829   indicate that the cached entity differs from the current entity (as
830   would be indicated by a change in Content-Length, Content-MD5, ETag
831   or Last-Modified), then the cache &MUST; treat the cache entry as
832   stale.
833</t>
834</section>
835
836<section title="POST" anchor="POST">
837  <iref primary="true" item="POST method" x:for-anchor=""/>
838  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
839<t>
840   The POST method is used to request that the origin server accept the
841   entity enclosed in the request as data to be processed by the resource
842   identified by the request-target in the Request-Line. POST is designed
843   to allow a uniform method to cover the following functions:
844  <list style="symbols">
845    <t>
846      Annotation of existing resources;
847    </t>
848    <t>
849        Posting a message to a bulletin board, newsgroup, mailing list,
850        or similar group of articles;
851    </t>
852    <t>
853        Providing a block of data, such as the result of submitting a
854        form, to a data-handling process;
855    </t>
856    <t>
857        Extending a database through an append operation.
858    </t>
859  </list>
860</t>
861<t>
862   The actual function performed by the POST method is determined by the
863   server and is usually dependent on the request-target.
864</t>
865<t>
866   The action performed by the POST method might not result in a
867   resource that can be identified by a URI. In this case, either 200
868   (OK) or 204 (No Content) is the appropriate response status,
869   depending on whether or not the response includes an entity that
870   describes the result.
871</t>
872<t>
873   If a resource has been created on the origin server, the response
874   &SHOULD; be 201 (Created) and contain an entity which describes the
875   status of the request and refers to the new resource, and a Location
876   header (see <xref target="header.location"/>).
877</t>
878<t>
879   Responses to this method are not cacheable, unless the response
880   includes appropriate Cache-Control or Expires header fields. However,
881   the 303 (See Other) response can be used to direct the user agent to
882   retrieve a cacheable resource.
883</t>
884</section>
885
886<section title="PUT" anchor="PUT">
887  <iref primary="true" item="PUT method" x:for-anchor=""/>
888  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
889<t>
890   The PUT method requests that the enclosed entity be stored at the
891   supplied request-target. If the request-target refers to an already
892   existing resource, the enclosed entity &SHOULD; be considered as a
893   modified version of the one residing on the origin server. If the
894   request-target does not point to an existing resource, and that URI is
895   capable of being defined as a new resource by the requesting user
896   agent, the origin server can create the resource with that URI. If a
897   new resource is created at the request-target, the origin server &MUST;
898   inform the user agent
899   via the 201 (Created) response. If an existing resource is modified,
900   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
901   to indicate successful completion of the request. If the resource
902   could not be created or modified with the request-target, an appropriate
903   error response &SHOULD; be given that reflects the nature of the
904   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
905   headers (headers starting with the prefix 'Content-') that it does
906   not understand or implement
907   and &MUST; return a 501 (Not Implemented) response in such cases.
908</t>
909<t>
910   If the request passes through a cache and the request-target identifies
911   one or more currently cached entities, those entries &SHOULD; be
912   treated as stale. Responses to this method are not cacheable.
913</t>
914<t>
915   The fundamental difference between the POST and PUT requests is
916   reflected in the different meaning of the request-target. The URI in a
917   POST request identifies the resource that will handle the enclosed
918   entity. That resource might be a data-accepting process, a gateway to
919   some other protocol, or a separate entity that accepts annotations.
920   In contrast, the URI in a PUT request identifies the entity enclosed
921   with the request -- the user agent knows what URI is intended and the
922   server &MUST-NOT; attempt to apply the request to some other resource.
923   If the server desires that the request be applied to a different URI,
924   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
925   then make its own decision regarding whether or not to redirect the
926   request.
927</t>
928<t>
929   A single resource &MAY; be identified by many different URIs. For
930   example, an article might have a URI for identifying "the current
931   version" which is separate from the URI identifying each particular
932   version. In this case, a PUT request on a general URI might result in
933   several other URIs being defined by the origin server.
934</t>
935<t>
936   HTTP/1.1 does not define how a PUT method affects the state of an
937   origin server.
938</t>
939<t>
940   Unless otherwise specified for a particular entity-header, the
941   entity-headers in the PUT request &SHOULD; be applied to the resource
942   created or modified by the PUT.
943</t>
944</section>
945
946<section title="DELETE" anchor="DELETE">
947  <iref primary="true" item="DELETE method" x:for-anchor=""/>
948  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
949<t>
950   The DELETE method requests that the origin server delete the resource
951   identified by the request-target. This method &MAY; be overridden by human
952   intervention (or other means) on the origin server. The client cannot
953   be guaranteed that the operation has been carried out, even if the
954   status code returned from the origin server indicates that the action
955   has been completed successfully. However, the server &SHOULD-NOT; 
956   indicate success unless, at the time the response is given, it
957   intends to delete the resource or move it to an inaccessible
958   location.
959</t>
960<t>
961   A successful response &SHOULD; be 200 (OK) if the response includes an
962   entity describing the status, 202 (Accepted) if the action has not
963   yet been enacted, or 204 (No Content) if the action has been enacted
964   but the response does not include an entity.
965</t>
966<t>
967   If the request passes through a cache and the request-target identifies
968   one or more currently cached entities, those entries &SHOULD; be
969   treated as stale. Responses to this method are not cacheable.
970</t>
971</section>
972
973<section title="TRACE" anchor="TRACE">
974  <rdf:Description>
975    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
976  </rdf:Description>
977  <iref primary="true" item="TRACE method" x:for-anchor=""/>
978  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
979<t>
980   The TRACE method is used to invoke a remote, application-layer loop-back
981   of the request message. The final recipient of the request
982   &SHOULD; reflect the message received back to the client as the
983   entity-body of a 200 (OK) response. The final recipient is either the
984   origin server or the first proxy or gateway to receive a Max-Forwards
985   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
986   &MUST-NOT; include an entity.
987</t>
988<t>
989   TRACE allows the client to see what is being received at the other
990   end of the request chain and use that data for testing or diagnostic
991   information. The value of the Via header field (&header-via;) is of
992   particular interest, since it acts as a trace of the request chain.
993   Use of the Max-Forwards header field allows the client to limit the
994   length of the request chain, which is useful for testing a chain of
995   proxies forwarding messages in an infinite loop.
996</t>
997<t>
998   If the request is valid, the response &SHOULD; contain the entire
999   request message in the entity-body, with a Content-Type of
1000   "message/http" (see &media-type-message-http;). Responses to this method
1001   &MUST-NOT; be cached.
1002</t>
1003</section>
1004
1005<section title="CONNECT" anchor="CONNECT">
1006  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1007  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1008<t>
1009   This specification reserves the method name CONNECT for use with a
1010   proxy that can dynamically switch to being a tunnel (e.g. SSL
1011   tunneling <xref target="RFC2817"/>).
1012</t>
1013</section>
1014</section>
1015
1016
1017<section title="Status Code Definitions" anchor="status.codes">
1018<t>
1019   Each Status-Code is described below, including any metainformation required
1020   in the response.
1021</t>
1022
1023<section title="Informational 1xx" anchor="status.1xx">
1024<t>
1025   This class of status code indicates a provisional response,
1026   consisting only of the Status-Line and optional headers, and is
1027   terminated by an empty line. There are no required headers for this
1028   class of status code. Since HTTP/1.0 did not define any 1xx status
1029   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1030   except under experimental conditions.
1031</t>
1032<t>
1033   A client &MUST; be prepared to accept one or more 1xx status responses
1034   prior to a regular response, even if the client does not expect a 100
1035   (Continue) status message. Unexpected 1xx status responses &MAY; be
1036   ignored by a user agent.
1037</t>
1038<t>
1039   Proxies &MUST; forward 1xx responses, unless the connection between the
1040   proxy and its client has been closed, or unless the proxy itself
1041   requested the generation of the 1xx response. (For example, if a
1042   proxy adds a "Expect: 100-continue" field when it forwards a request,
1043   then it need not forward the corresponding 100 (Continue)
1044   response(s).)
1045</t>
1046
1047<section title="100 Continue" anchor="status.100">
1048  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1049  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1050<t>
1051   The client &SHOULD; continue with its request. This interim response is
1052   used to inform the client that the initial part of the request has
1053   been received and has not yet been rejected by the server. The client
1054   &SHOULD; continue by sending the remainder of the request or, if the
1055   request has already been completed, ignore this response. The server
1056   &MUST; send a final response after the request has been completed. See
1057   &use100; for detailed discussion of the use and handling of this
1058   status code.
1059</t>
1060</section>
1061
1062<section title="101 Switching Protocols" anchor="status.101">
1063  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1064  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1065<t>
1066   The server understands and is willing to comply with the client's
1067   request, via the Upgrade message header field (&header-upgrade;), for a
1068   change in the application protocol being used on this connection. The
1069   server will switch protocols to those defined by the response's
1070   Upgrade header field immediately after the empty line which
1071   terminates the 101 response.
1072</t>
1073<t>
1074   The protocol &SHOULD; be switched only when it is advantageous to do
1075   so. For example, switching to a newer version of HTTP is advantageous
1076   over older versions, and switching to a real-time, synchronous
1077   protocol might be advantageous when delivering resources that use
1078   such features.
1079</t>
1080</section>
1081</section>
1082
1083<section title="Successful 2xx" anchor="status.2xx">
1084<t>
1085   This class of status code indicates that the client's request was
1086   successfully received, understood, and accepted.
1087</t>
1088
1089<section title="200 OK" anchor="status.200">
1090  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1091  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1092<t>
1093   The request has succeeded. The information returned with the response
1094   is dependent on the method used in the request, for example:
1095  <list style="hanging">
1096    <t hangText="GET">
1097          an entity corresponding to the requested resource is sent in
1098          the response;
1099    </t>
1100    <t hangText="HEAD">
1101          the entity-header fields corresponding to the requested
1102          resource are sent in the response without any message-body;
1103    </t>
1104    <t hangText="POST">
1105      an entity describing or containing the result of the action;
1106    </t>
1107    <t hangText="TRACE">
1108      an entity containing the request message as received by the
1109      end server.
1110    </t>
1111  </list>
1112</t>
1113</section>
1114
1115<section title="201 Created" anchor="status.201">
1116  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1117  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1118<t>
1119   The request has been fulfilled and resulted in a new resource being
1120   created. The newly created resource can be referenced by the URI(s)
1121   returned in the entity of the response, with the most specific URI
1122   for the resource given by a Location header field. The response
1123   &SHOULD; include an entity containing a list of resource
1124   characteristics and location(s) from which the user or user agent can
1125   choose the one most appropriate. The entity format is specified by
1126   the media type given in the Content-Type header field. The origin
1127   server &MUST; create the resource before returning the 201 status code.
1128   If the action cannot be carried out immediately, the server &SHOULD;
1129   respond with 202 (Accepted) response instead.
1130</t>
1131<t>
1132   A 201 response &MAY; contain an ETag response header field indicating
1133   the current value of the entity tag for the requested variant just
1134   created, see &header-etag;.
1135</t>
1136</section>
1137
1138<section title="202 Accepted" anchor="status.202">
1139  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1140  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1141<t>
1142   The request has been accepted for processing, but the processing has
1143   not been completed.  The request might or might not eventually be
1144   acted upon, as it might be disallowed when processing actually takes
1145   place. There is no facility for re-sending a status code from an
1146   asynchronous operation such as this.
1147</t>
1148<t>
1149   The 202 response is intentionally non-committal. Its purpose is to
1150   allow a server to accept a request for some other process (perhaps a
1151   batch-oriented process that is only run once per day) without
1152   requiring that the user agent's connection to the server persist
1153   until the process is completed. The entity returned with this
1154   response &SHOULD; include an indication of the request's current status
1155   and either a pointer to a status monitor or some estimate of when the
1156   user can expect the request to be fulfilled.
1157</t>
1158</section>
1159
1160<section title="203 Non-Authoritative Information" anchor="status.203">
1161  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1162  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1163<t>
1164   The returned metainformation in the entity-header is not the
1165   definitive set as available from the origin server, but is gathered
1166   from a local or a third-party copy. The set presented &MAY; be a subset
1167   or superset of the original version. For example, including local
1168   annotation information about the resource might result in a superset
1169   of the metainformation known by the origin server. Use of this
1170   response code is not required and is only appropriate when the
1171   response would otherwise be 200 (OK).
1172</t>
1173</section>
1174
1175<section title="204 No Content" anchor="status.204">
1176  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1177  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1178<t>
1179   The server has fulfilled the request but does not need to return an
1180   entity-body, and might want to return updated metainformation. The
1181   response &MAY; include new or updated metainformation in the form of
1182   entity-headers, which if present &SHOULD; be associated with the
1183   requested variant.
1184</t>
1185<t>
1186   If the client is a user agent, it &SHOULD-NOT;  change its document view
1187   from that which caused the request to be sent. This response is
1188   primarily intended to allow input for actions to take place without
1189   causing a change to the user agent's active document view, although
1190   any new or updated metainformation &SHOULD; be applied to the document
1191   currently in the user agent's active view.
1192</t>
1193<t>
1194   The 204 response &MUST-NOT; include a message-body, and thus is always
1195   terminated by the first empty line after the header fields.
1196</t>
1197</section>
1198
1199<section title="205 Reset Content" anchor="status.205">
1200  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1201  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1202<t>
1203   The server has fulfilled the request and the user agent &SHOULD; reset
1204   the document view which caused the request to be sent. This response
1205   is primarily intended to allow input for actions to take place via
1206   user input, followed by a clearing of the form in which the input is
1207   given so that the user can easily initiate another input action. The
1208   response &MUST-NOT; include an entity.
1209</t>
1210</section>
1211
1212<section title="206 Partial Content" anchor="status.206">
1213  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1214  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1215<t>
1216   The server has fulfilled the partial GET request for the resource
1217   and the enclosed entity is a partial representation as defined in &range;.
1218</t>
1219</section>
1220</section>
1221
1222<section title="Redirection 3xx" anchor="status.3xx">
1223<t>
1224   This class of status code indicates that further action needs to be
1225   taken by the user agent in order to fulfill the request.  The action
1226   required &MAY; be carried out by the user agent without interaction
1227   with the user if and only if the method used in the second request is
1228   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1229   such loops generate network traffic for each redirection.
1230</t>
1231<x:note>
1232  <t>
1233    <x:h>Note:</x:h> an earlier version of this specification recommended a
1234    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1235    Content developers should be aware that there might be clients that
1236    implement such a fixed limitation.
1237  </t>
1238</x:note>
1239
1240<section title="300 Multiple Choices" anchor="status.300">
1241  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1242  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1243<t>
1244   The requested resource corresponds to any one of a set of
1245   representations, each with its own specific location, and agent-driven
1246   negotiation information (&content-negotiation;) is being provided so that
1247   the user (or user agent) can select a preferred representation and
1248   redirect its request to that location.
1249</t>
1250<t>
1251   Unless it was a HEAD request, the response &SHOULD; include an entity
1252   containing a list of resource characteristics and location(s) from
1253   which the user or user agent can choose the one most appropriate. The
1254   entity format is specified by the media type given in the Content-Type
1255   header field. Depending upon the format and the capabilities of
1256   the user agent, selection of the most appropriate choice &MAY; be
1257   performed automatically. However, this specification does not define
1258   any standard for such automatic selection.
1259</t>
1260<t>
1261   If the server has a preferred choice of representation, it &SHOULD;
1262   include the specific URI for that representation in the Location
1263   field; user agents &MAY; use the Location field value for automatic
1264   redirection. This response is cacheable unless indicated otherwise.
1265</t>
1266</section>
1267
1268<section title="301 Moved Permanently" anchor="status.301">
1269  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1270  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1271<t>
1272   The requested resource has been assigned a new permanent URI and any
1273   future references to this resource &SHOULD; use one of the returned
1274   URIs.  Clients with link editing capabilities ought to automatically
1275   re-link references to the request-target to one or more of the new
1276   references returned by the server, where possible. This response is
1277   cacheable unless indicated otherwise.
1278</t>
1279<t>
1280   The new permanent URI &SHOULD; be given by the Location field in the
1281   response. Unless the request method was HEAD, the entity of the
1282   response &SHOULD; contain a short hypertext note with a hyperlink to
1283   the new URI(s).
1284</t>
1285<t>
1286   If the 301 status code is received in response to a request method
1287   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1288   then the request &MAY; be automatically redirected by the user agent without
1289   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1290   request unless it can be confirmed by the user, since this might
1291   change the conditions under which the request was issued.
1292</t>
1293<x:note>
1294  <t>
1295    <x:h>Note:</x:h> When automatically redirecting a POST request after
1296    receiving a 301 status code, some existing HTTP/1.0 user agents
1297    will erroneously change it into a GET request.
1298  </t>
1299</x:note>
1300</section>
1301
1302<section title="302 Found" anchor="status.302">
1303  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1304  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1305<t>
1306   The requested resource resides temporarily under a different URI.
1307   Since the redirection might be altered on occasion, the client &SHOULD;
1308   continue to use the request-target for future requests.  This response
1309   is only cacheable if indicated by a Cache-Control or Expires header
1310   field.
1311</t>
1312<t>
1313   The temporary URI &SHOULD; be given by the Location field in the
1314   response. Unless the request method was HEAD, the entity of the
1315   response &SHOULD; contain a short hypertext note with a hyperlink to
1316   the new URI(s).
1317</t>
1318<t>
1319   If the 302 status code is received in response to a request method
1320   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1321   then the request &MAY; be automatically redirected by the user agent without
1322   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1323   request unless it can be confirmed by the user, since this might
1324   change the conditions under which the request was issued.
1325</t>
1326<x:note>
1327  <t>
1328    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1329    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1330    specify that the client is not allowed to change the method on the
1331    redirected request.  However, most existing user agent implementations
1332    treat 302 as if it were a 303 response, performing a GET on the Location
1333    field-value regardless of the original request method. Therefore, a
1334    previous version of this specification
1335    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1336    status codes
1337    <xref target="status.303" format="none">303</xref> and
1338    <xref target="status.307" format="none">307</xref> for servers that wish
1339    to make unambiguously clear which kind of reaction is expected of the
1340    client.
1341  </t>
1342</x:note>
1343</section>
1344
1345<section title="303 See Other" anchor="status.303">
1346  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1347  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1348<t>
1349   The server directs the user agent to a different resource, indicated
1350   by a URI in the Location header field, that provides an indirect
1351   response to the original request.  The user agent &MAY; perform a GET
1352   request on the URI in the Location field in order to obtain a
1353   representation corresponding to the response, be redirected again,
1354   or end with an error status.  The Location URI is not a substitute
1355   reference for the originally requested resource.
1356</t>
1357<t>
1358   The 303 status is generally applicable to any HTTP method.  It is
1359   primarily used to allow the output of a POST action to redirect
1360   the user agent to a selected resource, since doing so provides the
1361   information corresponding to the POST response in a form that
1362   can be separately identified, bookmarked, and cached independent
1363   of the original request.
1364</t>
1365<t>
1366   A 303 response to a GET request indicates that the requested
1367   resource does not have a representation of its own that can be
1368   transferred by the server over HTTP.  The Location URI indicates a
1369   resource that is descriptive of the requested resource such that
1370   the follow-on representation may be useful without implying that
1371   it adequately represents the previously requested resource.
1372   Note that answers to the questions of what can be represented, what
1373   representations are adequate, and what might be a useful description
1374   are outside the scope of HTTP and thus entirely determined by the
1375   URI owner(s).
1376</t>
1377<t>
1378   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1379   cacheable by Cache-Control or Expires header fields.  Except for
1380   responses to a HEAD request, the entity of a 303 response &SHOULD;
1381   contain a short hypertext note with a hyperlink to the Location URI.
1382</t>
1383</section>
1384
1385<section title="304 Not Modified" anchor="status.304">
1386  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1387  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1388<t>
1389   The response to the request has not been modified since the conditions
1390   indicated by the client's conditional GET request, as defined in &conditional;.
1391</t>
1392</section>
1393
1394<section title="305 Use Proxy" anchor="status.305">
1395  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1396  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1397<t>
1398   The 305 status was defined in a previous version of this specification
1399   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1400</t>
1401</section>
1402
1403<section title="306 (Unused)" anchor="status.306">
1404  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1405  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1406<t>
1407   The 306 status code was used in a previous version of the
1408   specification, is no longer used, and the code is reserved.
1409</t>
1410</section>
1411
1412<section title="307 Temporary Redirect" anchor="status.307">
1413  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1414  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1415<t>
1416   The requested resource resides temporarily under a different URI.
1417   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1418   continue to use the request-target for future requests.  This response
1419   is only cacheable if indicated by a Cache-Control or Expires header
1420   field.
1421</t>
1422<t>
1423   The temporary URI &SHOULD; be given by the Location field in the
1424   response. Unless the request method was HEAD, the entity of the
1425   response &SHOULD; contain a short hypertext note with a hyperlink to
1426   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1427   understand the 307 status. Therefore, the note &SHOULD; contain the
1428   information necessary for a user to repeat the original request on
1429   the new URI.
1430</t>
1431<t>
1432   If the 307 status code is received in response to a request method
1433   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1434   then the request &MAY; be automatically redirected by the user agent without
1435   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1436   request unless it can be confirmed by the user, since this might
1437   change the conditions under which the request was issued.
1438</t>
1439</section>
1440</section>
1441
1442<section title="Client Error 4xx" anchor="status.4xx">
1443<t>
1444   The 4xx class of status code is intended for cases in which the
1445   client seems to have erred. Except when responding to a HEAD request,
1446   the server &SHOULD; include an entity containing an explanation of the
1447   error situation, and whether it is a temporary or permanent
1448   condition. These status codes are applicable to any request method.
1449   User agents &SHOULD; display any included entity to the user.
1450</t>
1451<t>
1452   If the client is sending data, a server implementation using TCP
1453   &SHOULD; be careful to ensure that the client acknowledges receipt of
1454   the packet(s) containing the response, before the server closes the
1455   input connection. If the client continues sending data to the server
1456   after the close, the server's TCP stack will send a reset packet to
1457   the client, which may erase the client's unacknowledged input buffers
1458   before they can be read and interpreted by the HTTP application.
1459</t>
1460
1461<section title="400 Bad Request" anchor="status.400">
1462  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1463  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1464<t>
1465   The request could not be understood by the server due to malformed
1466   syntax. The client &SHOULD-NOT;  repeat the request without
1467   modifications.
1468</t>
1469</section>
1470
1471<section title="401 Unauthorized" anchor="status.401">
1472  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1473  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1474<t>
1475   The request requires user authentication (see &auth;).
1476</t>
1477</section>
1478
1479<section title="402 Payment Required" anchor="status.402">
1480  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1481  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1482<t>
1483   This code is reserved for future use.
1484</t>
1485</section>
1486
1487<section title="403 Forbidden" anchor="status.403">
1488  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1489  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1490<t>
1491   The server understood the request, but is refusing to fulfill it.
1492   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1493   If the request method was not HEAD and the server wishes to make
1494   public why the request has not been fulfilled, it &SHOULD; describe the
1495   reason for the refusal in the entity.  If the server does not wish to
1496   make this information available to the client, the status code 404
1497   (Not Found) can be used instead.
1498</t>
1499</section>
1500
1501<section title="404 Not Found" anchor="status.404">
1502  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1503  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1504<t>
1505   The server has not found anything matching the request-target. No
1506   indication is given of whether the condition is temporary or
1507   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1508   knows, through some internally configurable mechanism, that an old
1509   resource is permanently unavailable and has no forwarding address.
1510   This status code is commonly used when the server does not wish to
1511   reveal exactly why the request has been refused, or when no other
1512   response is applicable.
1513</t>
1514</section>
1515
1516<section title="405 Method Not Allowed" anchor="status.405">
1517  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1518  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1519<t>
1520   The method specified in the Request-Line is not allowed for the
1521   resource identified by the request-target. The response &MUST; include an
1522   Allow header containing a list of valid methods for the requested
1523   resource.
1524</t>
1525</section>
1526
1527<section title="406 Not Acceptable" anchor="status.406">
1528  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1529  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1530<t>
1531   The resource identified by the request is only capable of generating
1532   response entities which have content characteristics not acceptable
1533   according to the accept headers sent in the request.
1534</t>
1535<t>
1536   Unless it was a HEAD request, the response &SHOULD; include an entity
1537   containing a list of available entity characteristics and location(s)
1538   from which the user or user agent can choose the one most
1539   appropriate. The entity format is specified by the media type given
1540   in the Content-Type header field. Depending upon the format and the
1541   capabilities of the user agent, selection of the most appropriate
1542   choice &MAY; be performed automatically. However, this specification
1543   does not define any standard for such automatic selection.
1544</t>
1545<x:note>
1546  <t>
1547    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1548    not acceptable according to the accept headers sent in the
1549    request. In some cases, this may even be preferable to sending a
1550    406 response. User agents are encouraged to inspect the headers of
1551    an incoming response to determine if it is acceptable.
1552  </t>
1553</x:note>
1554<t>
1555   If the response could be unacceptable, a user agent &SHOULD;
1556   temporarily stop receipt of more data and query the user for a
1557   decision on further actions.
1558</t>
1559</section>
1560
1561<section title="407 Proxy Authentication Required" anchor="status.407">
1562  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1563  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1564<t>
1565   This code is similar to 401 (Unauthorized), but indicates that the
1566   client must first authenticate itself with the proxy (see &auth;).
1567</t>
1568</section>
1569
1570<section title="408 Request Timeout" anchor="status.408">
1571  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1572  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1573<t>
1574   The client did not produce a request within the time that the server
1575   was prepared to wait. The client &MAY; repeat the request without
1576   modifications at any later time.
1577</t>
1578</section>
1579
1580<section title="409 Conflict" anchor="status.409">
1581  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1583<t>
1584   The request could not be completed due to a conflict with the current
1585   state of the resource. This code is only allowed in situations where
1586   it is expected that the user might be able to resolve the conflict
1587   and resubmit the request. The response body &SHOULD; include enough
1588   information for the user to recognize the source of the conflict.
1589   Ideally, the response entity would include enough information for the
1590   user or user agent to fix the problem; however, that might not be
1591   possible and is not required.
1592</t>
1593<t>
1594   Conflicts are most likely to occur in response to a PUT request. For
1595   example, if versioning were being used and the entity being PUT
1596   included changes to a resource which conflict with those made by an
1597   earlier (third-party) request, the server might use the 409 response
1598   to indicate that it can't complete the request. In this case, the
1599   response entity would likely contain a list of the differences
1600   between the two versions in a format defined by the response
1601   Content-Type.
1602</t>
1603</section>
1604
1605<section title="410 Gone" anchor="status.410">
1606  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1607  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1608<t>
1609   The requested resource is no longer available at the server and no
1610   forwarding address is known. This condition is expected to be
1611   considered permanent. Clients with link editing capabilities &SHOULD;
1612   delete references to the request-target after user approval. If the
1613   server does not know, or has no facility to determine, whether or not
1614   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1615   used instead. This response is cacheable unless indicated otherwise.
1616</t>
1617<t>
1618   The 410 response is primarily intended to assist the task of web
1619   maintenance by notifying the recipient that the resource is
1620   intentionally unavailable and that the server owners desire that
1621   remote links to that resource be removed. Such an event is common for
1622   limited-time, promotional services and for resources belonging to
1623   individuals no longer working at the server's site. It is not
1624   necessary to mark all permanently unavailable resources as "gone" or
1625   to keep the mark for any length of time -- that is left to the
1626   discretion of the server owner.
1627</t>
1628</section>
1629
1630<section title="411 Length Required" anchor="status.411">
1631  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1632  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1633<t>
1634   The server refuses to accept the request without a defined Content-Length.
1635   The client &MAY; repeat the request if it adds a valid
1636   Content-Length header field containing the length of the message-body
1637   in the request message.
1638</t>
1639</section>
1640
1641<section title="412 Precondition Failed" anchor="status.412">
1642  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1643  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1644<t>
1645   The precondition given in one or more of the request-header fields
1646   evaluated to false when it was tested on the server, as defined in
1647   &conditional;.
1648</t>
1649</section>
1650
1651<section title="413 Request Entity Too Large" anchor="status.413">
1652  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1653  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1654<t>
1655   The server is refusing to process a request because the request
1656   entity is larger than the server is willing or able to process. The
1657   server &MAY; close the connection to prevent the client from continuing
1658   the request.
1659</t>
1660<t>
1661   If the condition is temporary, the server &SHOULD; include a Retry-After
1662   header field to indicate that it is temporary and after what
1663   time the client &MAY; try again.
1664</t>
1665</section>
1666
1667<section title="414 URI Too Long" anchor="status.414">
1668  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1669  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1670<t>
1671   The server is refusing to service the request because the request-target
1672   is longer than the server is willing to interpret. This rare
1673   condition is only likely to occur when a client has improperly
1674   converted a POST request to a GET request with long query
1675   information, when the client has descended into a URI "black hole" of
1676   redirection (e.g., a redirected URI prefix that points to a suffix of
1677   itself), or when the server is under attack by a client attempting to
1678   exploit security holes present in some servers using fixed-length
1679   buffers for reading or manipulating the request-target.
1680</t>
1681</section>
1682
1683<section title="415 Unsupported Media Type" anchor="status.415">
1684  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1685  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1686<t>
1687   The server is refusing to service the request because the entity of
1688   the request is in a format not supported by the requested resource
1689   for the requested method.
1690</t>
1691</section>
1692
1693<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1694  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1695  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1696<t>
1697   The request included a Range request-header field (&header-range;) and none of
1698   the range-specifier values in this field overlap the current extent
1699   of the selected resource.
1700</t>
1701</section>
1702
1703<section title="417 Expectation Failed" anchor="status.417">
1704  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1705  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1706<t>
1707   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1708   could not be met by this server, or, if the server is a proxy,
1709   the server has unambiguous evidence that the request could not be met
1710   by the next-hop server.
1711</t>
1712</section>
1713</section>
1714
1715<section title="Server Error 5xx" anchor="status.5xx">
1716<t>
1717   Response status codes beginning with the digit "5" indicate cases in
1718   which the server is aware that it has erred or is incapable of
1719   performing the request. Except when responding to a HEAD request, the
1720   server &SHOULD; include an entity containing an explanation of the
1721   error situation, and whether it is a temporary or permanent
1722   condition. User agents &SHOULD; display any included entity to the
1723   user. These response codes are applicable to any request method.
1724</t>
1725
1726<section title="500 Internal Server Error" anchor="status.500">
1727  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1728  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1729<t>
1730   The server encountered an unexpected condition which prevented it
1731   from fulfilling the request.
1732</t>
1733</section>
1734
1735<section title="501 Not Implemented" anchor="status.501">
1736  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1737  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1738<t>
1739   The server does not support the functionality required to fulfill the
1740   request. This is the appropriate response when the server does not
1741   recognize the request method and is not capable of supporting it for
1742   any resource.
1743</t>
1744</section>
1745
1746<section title="502 Bad Gateway" anchor="status.502">
1747  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1748  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1749<t>
1750   The server, while acting as a gateway or proxy, received an invalid
1751   response from the upstream server it accessed in attempting to
1752   fulfill the request.
1753</t>
1754</section>
1755
1756<section title="503 Service Unavailable" anchor="status.503">
1757  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1759<t>
1760   The server is currently unable to handle the request due to a
1761   temporary overloading or maintenance of the server. The implication
1762   is that this is a temporary condition which will be alleviated after
1763   some delay. If known, the length of the delay &MAY; be indicated in a
1764   Retry-After header. If no Retry-After is given, the client &SHOULD;
1765   handle the response as it would for a 500 response.
1766</t>
1767<x:note>
1768  <t>
1769    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1770    server must use it when becoming overloaded. Some servers may wish
1771    to simply refuse the connection.
1772  </t>
1773</x:note>
1774</section>
1775
1776<section title="504 Gateway Timeout" anchor="status.504">
1777  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1778  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1779<t>
1780   The server, while acting as a gateway or proxy, did not receive a
1781   timely response from the upstream server specified by the URI (e.g.
1782   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1783   to access in attempting to complete the request.
1784</t>
1785<x:note>
1786  <t>
1787    <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1788    return 400 or 500 when DNS lookups time out.
1789  </t>
1790</x:note>
1791</section>
1792
1793<section title="505 HTTP Version Not Supported" anchor="status.505">
1794  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1795  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1796<t>
1797   The server does not support, or refuses to support, the protocol
1798   version that was used in the request message. The server is
1799   indicating that it is unable or unwilling to complete the request
1800   using the same major version as the client, as described in &http-version;,
1801   other than with this error message. The response &SHOULD; contain
1802   an entity describing why that version is not supported and what other
1803   protocols are supported by that server.
1804</t>
1805
1806</section>
1807</section>
1808</section>
1809
1810
1811<section title="Header Field Definitions" anchor="header.fields">
1812<t>
1813   This section defines the syntax and semantics of HTTP/1.1 header fields
1814   related to request and response semantics.
1815</t>
1816<t>
1817   For entity-header fields, both sender and recipient refer to either the
1818   client or the server, depending on who sends and who receives the entity.
1819</t>
1820
1821<section title="Allow" anchor="header.allow">
1822  <iref primary="true" item="Allow header" x:for-anchor=""/>
1823  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1824  <x:anchor-alias value="Allow"/>
1825  <x:anchor-alias value="Allow-v"/>
1826<t>
1827      The response-header field "Allow" lists the set of methods advertised as
1828      supported by the resource identified by the request-target. The purpose of
1829      this field is strictly to inform the recipient of valid methods
1830      associated with the resource. An Allow header field &MUST; be
1831      present in a 405 (Method Not Allowed) response.
1832</t>
1833<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1834  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1835  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1836</artwork></figure>
1837<t>
1838      Example of use:
1839</t>
1840<figure><artwork type="example">
1841  Allow: GET, HEAD, PUT
1842</artwork></figure>
1843<t>
1844      The actual set of allowed methods is defined
1845      by the origin server at the time of each request.
1846</t>
1847<t>
1848      A proxy &MUST-NOT; modify the Allow header field even if it does not
1849      understand all the methods specified, since the user agent might
1850      have other means of communicating with the origin server.
1851</t>
1852</section>
1853
1854<section title="Expect" anchor="header.expect">
1855  <iref primary="true" item="Expect header" x:for-anchor=""/>
1856  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1857  <x:anchor-alias value="Expect"/>
1858  <x:anchor-alias value="Expect-v"/>
1859  <x:anchor-alias value="expectation"/>
1860  <x:anchor-alias value="expectation-extension"/>
1861  <x:anchor-alias value="expect-params"/>
1862<t>
1863   The request-header field "Expect" is used to indicate that particular
1864   server behaviors are required by the client.
1865</t>
1866<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"/>
1867  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1868  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1869 
1870  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1871  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1872                           *<x:ref>expect-params</x:ref> ]
1873  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1874</artwork></figure>
1875<t>
1876   A server that does not understand or is unable to comply with any of
1877   the expectation values in the Expect field of a request &MUST; respond
1878   with appropriate error status. The server &MUST; respond with a 417
1879   (Expectation Failed) status if any of the expectations cannot be met
1880   or, if there are other problems with the request, some other 4xx
1881   status.
1882</t>
1883<t>
1884   This header field is defined with extensible syntax to allow for
1885   future extensions. If a server receives a request containing an
1886   Expect field that includes an expectation-extension that it does not
1887   support, it &MUST; respond with a 417 (Expectation Failed) status.
1888</t>
1889<t>
1890   Comparison of expectation values is case-insensitive for unquoted
1891   tokens (including the 100-continue token), and is case-sensitive for
1892   quoted-string expectation-extensions.
1893</t>
1894<t>
1895   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1896   return a 417 (Expectation Failed) status if it receives a request
1897   with an expectation that it cannot meet. However, the Expect
1898   request-header itself is end-to-end; it &MUST; be forwarded if the
1899   request is forwarded.
1900</t>
1901<t>
1902   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1903   Expect header.
1904</t>
1905<t>
1906   See &use100; for the use of the 100 (Continue) status.
1907</t>
1908</section>
1909
1910<section title="From" anchor="header.from">
1911  <iref primary="true" item="From header" x:for-anchor=""/>
1912  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1913  <x:anchor-alias value="From"/>
1914  <x:anchor-alias value="From-v"/>
1915  <x:anchor-alias value="mailbox"/>
1916<t>
1917   The request-header field "From", if given, &SHOULD; contain an Internet
1918   e-mail address for the human user who controls the requesting user
1919   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1920   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1921</t>
1922<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1923  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1924  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1925 
1926  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1927</artwork></figure>
1928<t>
1929   An example is:
1930</t>
1931<figure><artwork type="example">
1932  From: webmaster@example.org
1933</artwork></figure>
1934<t>
1935   This header field &MAY; be used for logging purposes and as a means for
1936   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1937   be used as an insecure form of access protection. The interpretation
1938   of this field is that the request is being performed on behalf of the
1939   person given, who accepts responsibility for the method performed. In
1940   particular, robot agents &SHOULD; include this header so that the
1941   person responsible for running the robot can be contacted if problems
1942   occur on the receiving end.
1943</t>
1944<t>
1945   The Internet e-mail address in this field &MAY; be separate from the
1946   Internet host which issued the request. For example, when a request
1947   is passed through a proxy the original issuer's address &SHOULD; be
1948   used.
1949</t>
1950<t>
1951   The client &SHOULD-NOT;  send the From header field without the user's
1952   approval, as it might conflict with the user's privacy interests or
1953   their site's security policy. It is strongly recommended that the
1954   user be able to disable, enable, and modify the value of this field
1955   at any time prior to a request.
1956</t>
1957</section>
1958
1959<section title="Location" anchor="header.location">
1960  <iref primary="true" item="Location header" x:for-anchor=""/>
1961  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1962  <x:anchor-alias value="Location"/>
1963  <x:anchor-alias value="Location-v"/>
1964<t>
1965   The response-header field "Location" is used for the identification of a
1966   new resource or to redirect the recipient to a location other than the
1967   request-target for completion of the request.  For 201 (Created)
1968   responses, the Location is that of the new resource which was created
1969   by the request. For 3xx responses, the location &SHOULD; indicate the
1970   server's preferred URI for automatic redirection to the resource. The
1971   field value consists of a single URI.
1972</t>
1973<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1974  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1975  <x:ref>Location-v</x:ref>     = <x:ref>URI</x:ref>
1976</artwork></figure>
1977<t>
1978   An example is:
1979</t>
1980<figure><artwork type="example">
1981  Location: http://www.example.org/pub/WWW/People.html
1982</artwork></figure>
1983<t>
1984   There are circumstances in which a fragment identifier in a Location URI would not be appropriate:
1985   <list style="symbols">
1986      <t>With a 201 Created response, because in this usage the Location header specifies the URI for the entire created resource.</t>
1987      <t>With 305 Use Proxy.</t>
1988   </list>
1989</t>
1990<x:note>
1991  <t>
1992    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1993    from Location in that the Content-Location identifies the original
1994    location of the entity enclosed in the response. It is therefore
1995    possible for a response to contain header fields for both Location
1996    and Content-Location.
1997  </t>
1998</x:note>
1999</section>
2000
2001<section title="Max-Forwards" anchor="header.max-forwards">
2002  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2003  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2004  <x:anchor-alias value="Max-Forwards"/>
2005  <x:anchor-alias value="Max-Forwards-v"/>
2006<t>
2007   The request-header "Max-Forwards" field provides a mechanism with the
2008   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2009   number of proxies or gateways that can forward the request to the
2010   next inbound server. This can be useful when the client is attempting
2011   to trace a request chain which appears to be failing or looping in
2012   mid-chain.
2013</t>
2014<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2015  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2016  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2017</artwork></figure>
2018<t>
2019   The Max-Forwards value is a decimal integer indicating the remaining
2020   number of times this request message may be forwarded.
2021</t>
2022<t>
2023   Each proxy or gateway recipient of a TRACE or OPTIONS request
2024   containing a Max-Forwards header field &MUST; check and update its
2025   value prior to forwarding the request. If the received value is zero
2026   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2027   respond as the final recipient. If the received Max-Forwards value is
2028   greater than zero, then the forwarded message &MUST; contain an updated
2029   Max-Forwards field with a value decremented by one (1).
2030</t>
2031<t>
2032   The Max-Forwards header field &MAY; be ignored for all other methods
2033   defined by this specification and for any extension methods for which
2034   it is not explicitly referred to as part of that method definition.
2035</t>
2036</section>
2037
2038<section title="Referer" anchor="header.referer">
2039  <iref primary="true" item="Referer header" x:for-anchor=""/>
2040  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2041  <x:anchor-alias value="Referer"/>
2042  <x:anchor-alias value="Referer-v"/>
2043<t>
2044   The request-header field "Referer" [sic] allows the client to specify, for
2045   the server's benefit, the address (URI) of the resource from which the
2046   request-target was obtained (the "referrer", although the header field is
2047   misspelled.).
2048</t>
2049<t>
2050   The Referer header allows servers to generate lists of back-links to
2051   resources for interest, logging, optimized caching, etc. It also allows
2052   obsolete or mistyped links to be traced for maintenance. Some servers use
2053   Referer as a means of controlling where they allow links from (so-called
2054   "deep linking"), but it should be noted that legitimate requests are not
2055   required to contain a Referer header field.
2056</t>
2057<t>
2058   If the request-target was obtained from a source that does not have its own
2059   URI (e.g., input from the user keyboard), the Referer field MUST either be
2060   sent with the value "about:blank", or not be sent at all. Note that this
2061   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2062</t>
2063<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2064  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2065  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2066</artwork></figure>
2067<t>
2068   Example:
2069</t>
2070<figure><artwork type="example">
2071  Referer: http://www.example.org/hypertext/Overview.html
2072</artwork></figure>
2073<t>
2074   If the field value is a relative URI, it &SHOULD; be interpreted
2075   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2076   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2077</t>
2078</section>
2079
2080<section title="Retry-After" anchor="header.retry-after">
2081  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2082  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2083  <x:anchor-alias value="Retry-After"/>
2084  <x:anchor-alias value="Retry-After-v"/>
2085<t>
2086   The response-header "Retry-After" field can be used with a 503 (Service
2087   Unavailable) response to indicate how long the service is expected to
2088   be unavailable to the requesting client. This field &MAY; also be used
2089   with any 3xx (Redirection) response to indicate the minimum time the
2090   user-agent is asked wait before issuing the redirected request. The
2091   value of this field can be either an HTTP-date or an integer number
2092   of seconds (in decimal) after the time of the response.
2093</t>
2094<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2095  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2096  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2097</artwork></figure>
2098<t anchor="rule.delta-seconds">
2099  <x:anchor-alias value="delta-seconds"/>
2100   Time spans are non-negative decimal integers, representing time in
2101   seconds.
2102</t>
2103<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2104  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2105</artwork></figure>
2106<t>
2107   Two examples of its use are
2108</t>
2109<figure><artwork type="example">
2110  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2111  Retry-After: 120
2112</artwork></figure>
2113<t>
2114   In the latter example, the delay is 2 minutes.
2115</t>
2116</section>
2117
2118<section title="Server" anchor="header.server">
2119  <iref primary="true" item="Server header" x:for-anchor=""/>
2120  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2121  <x:anchor-alias value="Server"/>
2122  <x:anchor-alias value="Server-v"/>
2123<t>
2124   The response-header field "Server" contains information about the
2125   software used by the origin server to handle the request. The field
2126   can contain multiple product tokens (&product-tokens;) and comments
2127   identifying the server and any significant subproducts. The product
2128   tokens are listed in order of their significance for identifying the
2129   application.
2130</t>
2131<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2132  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2133  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2134                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2135</artwork></figure>
2136<t>
2137   Example:
2138</t>
2139<figure><artwork type="example">
2140  Server: CERN/3.0 libwww/2.17
2141</artwork></figure>
2142<t>
2143   If the response is being forwarded through a proxy, the proxy
2144   application &MUST-NOT; modify the Server response-header. Instead, it
2145   &MUST; include a Via field (as described in &header-via;).
2146</t>
2147<x:note>
2148  <t>
2149    <x:h>Note:</x:h> Revealing the specific software version of the server might
2150    allow the server machine to become more vulnerable to attacks
2151    against software that is known to contain security holes. Server
2152    implementors are encouraged to make this field a configurable
2153    option.
2154  </t>
2155</x:note>
2156</section>
2157
2158<section title="User-Agent" anchor="header.user-agent">
2159  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2160  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2161  <x:anchor-alias value="User-Agent"/>
2162  <x:anchor-alias value="User-Agent-v"/>
2163<t>
2164   The request-header field "User-Agent" contains information about the
2165   user agent originating the request. This is for statistical purposes,
2166   the tracing of protocol violations, and automated recognition of user
2167   agents for the sake of tailoring responses to avoid particular user
2168   agent limitations. User agents &SHOULD; include this field with
2169   requests. The field can contain multiple product tokens (&product-tokens;)
2170   and comments identifying the agent and any subproducts which form a
2171   significant part of the user agent. By convention, the product tokens
2172   are listed in order of their significance for identifying the
2173   application.
2174</t>
2175<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2176  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2177  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2178                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2179</artwork></figure>
2180<t>
2181   Example:
2182</t>
2183<figure><artwork type="example">
2184  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2185</artwork></figure>
2186</section>
2187
2188</section>
2189
2190<section title="IANA Considerations" anchor="IANA.considerations">
2191
2192<section title="Method Registry" anchor="method.registration">
2193<t>
2194  The registration procedure for HTTP Methods is defined by
2195  <xref target="method.registry"/> of this document.
2196</t>
2197<t>
2198   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2199   should be populated with the registrations below:
2200</t>
2201<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2202<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2203   <ttcol>Method</ttcol>
2204   <ttcol>Safe</ttcol>
2205   <ttcol>Reference</ttcol>
2206   <c>CONNECT</c>
2207   <c>no</c>
2208   <c>
2209      <xref target="CONNECT"/>
2210   </c>
2211   <c>DELETE</c>
2212   <c>no</c>
2213   <c>
2214      <xref target="DELETE"/>
2215   </c>
2216   <c>GET</c>
2217   <c>yes</c>
2218   <c>
2219      <xref target="GET"/>
2220   </c>
2221   <c>HEAD</c>
2222   <c>yes</c>
2223   <c>
2224      <xref target="HEAD"/>
2225   </c>
2226   <c>OPTIONS</c>
2227   <c>yes</c>
2228   <c>
2229      <xref target="OPTIONS"/>
2230   </c>
2231   <c>POST</c>
2232   <c>no</c>
2233   <c>
2234      <xref target="POST"/>
2235   </c>
2236   <c>PUT</c>
2237   <c>no</c>
2238   <c>
2239      <xref target="PUT"/>
2240   </c>
2241   <c>TRACE</c>
2242   <c>yes</c>
2243   <c>
2244      <xref target="TRACE"/>
2245   </c>
2246</texttable>
2247<!--(END)-->
2248</section>
2249
2250<section title="Status Code Registry" anchor="status.code.registration">
2251<t>
2252   The registration procedure for HTTP Status Codes -- previously defined
2253   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2254   by <xref target="status.code.registry"/> of this document.
2255</t>
2256<t>
2257   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2258   should be updated with the registrations below:
2259</t>
2260<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2261<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2262   <ttcol>Value</ttcol>
2263   <ttcol>Description</ttcol>
2264   <ttcol>Reference</ttcol>
2265   <c>100</c>
2266   <c>Continue</c>
2267   <c>
2268      <xref target="status.100"/>
2269   </c>
2270   <c>101</c>
2271   <c>Switching Protocols</c>
2272   <c>
2273      <xref target="status.101"/>
2274   </c>
2275   <c>200</c>
2276   <c>OK</c>
2277   <c>
2278      <xref target="status.200"/>
2279   </c>
2280   <c>201</c>
2281   <c>Created</c>
2282   <c>
2283      <xref target="status.201"/>
2284   </c>
2285   <c>202</c>
2286   <c>Accepted</c>
2287   <c>
2288      <xref target="status.202"/>
2289   </c>
2290   <c>203</c>
2291   <c>Non-Authoritative Information</c>
2292   <c>
2293      <xref target="status.203"/>
2294   </c>
2295   <c>204</c>
2296   <c>No Content</c>
2297   <c>
2298      <xref target="status.204"/>
2299   </c>
2300   <c>205</c>
2301   <c>Reset Content</c>
2302   <c>
2303      <xref target="status.205"/>
2304   </c>
2305   <c>206</c>
2306   <c>Partial Content</c>
2307   <c>
2308      <xref target="status.206"/>
2309   </c>
2310   <c>300</c>
2311   <c>Multiple Choices</c>
2312   <c>
2313      <xref target="status.300"/>
2314   </c>
2315   <c>301</c>
2316   <c>Moved Permanently</c>
2317   <c>
2318      <xref target="status.301"/>
2319   </c>
2320   <c>302</c>
2321   <c>Found</c>
2322   <c>
2323      <xref target="status.302"/>
2324   </c>
2325   <c>303</c>
2326   <c>See Other</c>
2327   <c>
2328      <xref target="status.303"/>
2329   </c>
2330   <c>304</c>
2331   <c>Not Modified</c>
2332   <c>
2333      <xref target="status.304"/>
2334   </c>
2335   <c>305</c>
2336   <c>Use Proxy</c>
2337   <c>
2338      <xref target="status.305"/>
2339   </c>
2340   <c>306</c>
2341   <c>(Unused)</c>
2342   <c>
2343      <xref target="status.306"/>
2344   </c>
2345   <c>307</c>
2346   <c>Temporary Redirect</c>
2347   <c>
2348      <xref target="status.307"/>
2349   </c>
2350   <c>400</c>
2351   <c>Bad Request</c>
2352   <c>
2353      <xref target="status.400"/>
2354   </c>
2355   <c>401</c>
2356   <c>Unauthorized</c>
2357   <c>
2358      <xref target="status.401"/>
2359   </c>
2360   <c>402</c>
2361   <c>Payment Required</c>
2362   <c>
2363      <xref target="status.402"/>
2364   </c>
2365   <c>403</c>
2366   <c>Forbidden</c>
2367   <c>
2368      <xref target="status.403"/>
2369   </c>
2370   <c>404</c>
2371   <c>Not Found</c>
2372   <c>
2373      <xref target="status.404"/>
2374   </c>
2375   <c>405</c>
2376   <c>Method Not Allowed</c>
2377   <c>
2378      <xref target="status.405"/>
2379   </c>
2380   <c>406</c>
2381   <c>Not Acceptable</c>
2382   <c>
2383      <xref target="status.406"/>
2384   </c>
2385   <c>407</c>
2386   <c>Proxy Authentication Required</c>
2387   <c>
2388      <xref target="status.407"/>
2389   </c>
2390   <c>408</c>
2391   <c>Request Timeout</c>
2392   <c>
2393      <xref target="status.408"/>
2394   </c>
2395   <c>409</c>
2396   <c>Conflict</c>
2397   <c>
2398      <xref target="status.409"/>
2399   </c>
2400   <c>410</c>
2401   <c>Gone</c>
2402   <c>
2403      <xref target="status.410"/>
2404   </c>
2405   <c>411</c>
2406   <c>Length Required</c>
2407   <c>
2408      <xref target="status.411"/>
2409   </c>
2410   <c>412</c>
2411   <c>Precondition Failed</c>
2412   <c>
2413      <xref target="status.412"/>
2414   </c>
2415   <c>413</c>
2416   <c>Request Entity Too Large</c>
2417   <c>
2418      <xref target="status.413"/>
2419   </c>
2420   <c>414</c>
2421   <c>URI Too Long</c>
2422   <c>
2423      <xref target="status.414"/>
2424   </c>
2425   <c>415</c>
2426   <c>Unsupported Media Type</c>
2427   <c>
2428      <xref target="status.415"/>
2429   </c>
2430   <c>416</c>
2431   <c>Requested Range Not Satisfiable</c>
2432   <c>
2433      <xref target="status.416"/>
2434   </c>
2435   <c>417</c>
2436   <c>Expectation Failed</c>
2437   <c>
2438      <xref target="status.417"/>
2439   </c>
2440   <c>500</c>
2441   <c>Internal Server Error</c>
2442   <c>
2443      <xref target="status.500"/>
2444   </c>
2445   <c>501</c>
2446   <c>Not Implemented</c>
2447   <c>
2448      <xref target="status.501"/>
2449   </c>
2450   <c>502</c>
2451   <c>Bad Gateway</c>
2452   <c>
2453      <xref target="status.502"/>
2454   </c>
2455   <c>503</c>
2456   <c>Service Unavailable</c>
2457   <c>
2458      <xref target="status.503"/>
2459   </c>
2460   <c>504</c>
2461   <c>Gateway Timeout</c>
2462   <c>
2463      <xref target="status.504"/>
2464   </c>
2465   <c>505</c>
2466   <c>HTTP Version Not Supported</c>
2467   <c>
2468      <xref target="status.505"/>
2469   </c>
2470</texttable>
2471<!--(END)-->
2472</section>
2473<section title="Message Header Registration" anchor="message.header.registration">
2474<t>
2475   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2476   with the permanent registrations below (see <xref target="RFC3864"/>):
2477</t>
2478<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2479<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2480   <ttcol>Header Field Name</ttcol>
2481   <ttcol>Protocol</ttcol>
2482   <ttcol>Status</ttcol>
2483   <ttcol>Reference</ttcol>
2484   <c>Allow</c>
2485   <c>http</c>
2486   <c>standard</c>
2487   <c>
2488      <xref target="header.allow"/>
2489   </c>
2490   <c>Expect</c>
2491   <c>http</c>
2492   <c>standard</c>
2493   <c>
2494      <xref target="header.expect"/>
2495   </c>
2496   <c>From</c>
2497   <c>http</c>
2498   <c>standard</c>
2499   <c>
2500      <xref target="header.from"/>
2501   </c>
2502   <c>Location</c>
2503   <c>http</c>
2504   <c>standard</c>
2505   <c>
2506      <xref target="header.location"/>
2507   </c>
2508   <c>Max-Forwards</c>
2509   <c>http</c>
2510   <c>standard</c>
2511   <c>
2512      <xref target="header.max-forwards"/>
2513   </c>
2514   <c>Referer</c>
2515   <c>http</c>
2516   <c>standard</c>
2517   <c>
2518      <xref target="header.referer"/>
2519   </c>
2520   <c>Retry-After</c>
2521   <c>http</c>
2522   <c>standard</c>
2523   <c>
2524      <xref target="header.retry-after"/>
2525   </c>
2526   <c>Server</c>
2527   <c>http</c>
2528   <c>standard</c>
2529   <c>
2530      <xref target="header.server"/>
2531   </c>
2532   <c>User-Agent</c>
2533   <c>http</c>
2534   <c>standard</c>
2535   <c>
2536      <xref target="header.user-agent"/>
2537   </c>
2538</texttable>
2539<!--(END)-->
2540<t>
2541   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2542</t>
2543</section>
2544</section>
2545
2546<section title="Security Considerations" anchor="security.considerations">
2547<t>
2548   This section is meant to inform application developers, information
2549   providers, and users of the security limitations in HTTP/1.1 as
2550   described by this document. The discussion does not include
2551   definitive solutions to the problems revealed, though it does make
2552   some suggestions for reducing security risks.
2553</t>
2554
2555<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2556<t>
2557   Like any generic data transfer protocol, HTTP cannot regulate the
2558   content of the data that is transferred, nor is there any a priori
2559   method of determining the sensitivity of any particular piece of
2560   information within the context of any given request. Therefore,
2561   applications &SHOULD; supply as much control over this information as
2562   possible to the provider of that information. Four header fields are
2563   worth special mention in this context: Server, Via, Referer and From.
2564</t>
2565<t>
2566   Revealing the specific software version of the server might allow the
2567   server machine to become more vulnerable to attacks against software
2568   that is known to contain security holes. Implementors &SHOULD; make the
2569   Server header field a configurable option.
2570</t>
2571<t>
2572   Proxies which serve as a portal through a network firewall &SHOULD;
2573   take special precautions regarding the transfer of header information
2574   that identifies the hosts behind the firewall. In particular, they
2575   &SHOULD; remove, or replace with sanitized versions, any Via fields
2576   generated behind the firewall.
2577</t>
2578<t>
2579   The Referer header allows reading patterns to be studied and reverse
2580   links drawn. Although it can be very useful, its power can be abused
2581   if user details are not separated from the information contained in
2582   the Referer. Even when the personal information has been removed, the
2583   Referer header might indicate a private document's URI whose
2584   publication would be inappropriate.
2585</t>
2586<t>
2587   The information sent in the From field might conflict with the user's
2588   privacy interests or their site's security policy, and hence it
2589   &SHOULD-NOT;  be transmitted without the user being able to disable,
2590   enable, and modify the contents of the field. The user &MUST; be able
2591   to set the contents of this field within a user preference or
2592   application defaults configuration.
2593</t>
2594<t>
2595   We suggest, though do not require, that a convenient toggle interface
2596   be provided for the user to enable or disable the sending of From and
2597   Referer information.
2598</t>
2599<t>
2600   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2601   fields can sometimes be used to determine that a specific client or
2602   server have a particular security hole which might be exploited.
2603   Unfortunately, this same information is often used for other valuable
2604   purposes for which HTTP currently has no better mechanism.
2605</t>
2606<t>
2607   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2608   information sent in request headers in the response entity.
2609   Clients &SHOULD; be careful with sensitive information, like Cookies,
2610   Authorization credentials and other headers that might be used to
2611   collect data from the client.
2612</t> 
2613</section>
2614
2615<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2616<t>
2617   Because the source of a link might be private information or might
2618   reveal an otherwise private information source, it is strongly
2619   recommended that the user be able to select whether or not the
2620   Referer field is sent. For example, a browser client could have a
2621   toggle switch for browsing openly/anonymously, which would
2622   respectively enable/disable the sending of Referer and From
2623   information.
2624</t>
2625<t>
2626   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2627   HTTP request if the referring page was transferred with a secure
2628   protocol.
2629</t>
2630<t>
2631   Authors of services should not use
2632   GET-based forms for the submission of sensitive data because that
2633   data will be encoded in the Request-target. Many existing
2634   servers, proxies, and user agents log or display the Request-target in
2635   places where it might be visible to third parties. Such services can
2636   use POST-based form submission instead.
2637</t>
2638</section>
2639
2640<section title="Location Headers and Spoofing" anchor="location.spoofing">
2641<t>
2642   If a single server supports multiple organizations that do not trust
2643   one another, then it &MUST; check the values of Location and Content-Location
2644   headers in responses that are generated under control of
2645   said organizations to make sure that they do not attempt to
2646   invalidate resources over which they have no authority.
2647</t>
2648</section>
2649
2650</section>
2651
2652<section title="Acknowledgments" anchor="ack">
2653</section>
2654</middle>
2655<back>
2656
2657<references title="Normative References">
2658
2659<reference anchor="Part1">
2660  <front>
2661    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2662    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2663      <organization abbrev="Day Software">Day Software</organization>
2664      <address><email>fielding@gbiv.com</email></address>
2665    </author>
2666    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2667      <organization>One Laptop per Child</organization>
2668      <address><email>jg@laptop.org</email></address>
2669    </author>
2670    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2671      <organization abbrev="HP">Hewlett-Packard Company</organization>
2672      <address><email>JeffMogul@acm.org</email></address>
2673    </author>
2674    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2675      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2676      <address><email>henrikn@microsoft.com</email></address>
2677    </author>
2678    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2679      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2680      <address><email>LMM@acm.org</email></address>
2681    </author>
2682    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2683      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2684      <address><email>paulle@microsoft.com</email></address>
2685    </author>
2686    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2687      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2688      <address><email>timbl@w3.org</email></address>
2689    </author>
2690    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2691      <organization abbrev="W3C">World Wide Web Consortium</organization>
2692      <address><email>ylafon@w3.org</email></address>
2693    </author>
2694    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2695      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2696      <address><email>julian.reschke@greenbytes.de</email></address>
2697    </author>
2698    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2699  </front>
2700  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2701  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2702</reference>
2703
2704<reference anchor="Part3">
2705  <front>
2706    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2707    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2708      <organization abbrev="Day Software">Day Software</organization>
2709      <address><email>fielding@gbiv.com</email></address>
2710    </author>
2711    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2712      <organization>One Laptop per Child</organization>
2713      <address><email>jg@laptop.org</email></address>
2714    </author>
2715    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2716      <organization abbrev="HP">Hewlett-Packard Company</organization>
2717      <address><email>JeffMogul@acm.org</email></address>
2718    </author>
2719    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2720      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2721      <address><email>henrikn@microsoft.com</email></address>
2722    </author>
2723    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2724      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2725      <address><email>LMM@acm.org</email></address>
2726    </author>
2727    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2728      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2729      <address><email>paulle@microsoft.com</email></address>
2730    </author>
2731    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2732      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2733      <address><email>timbl@w3.org</email></address>
2734    </author>
2735    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2736      <organization abbrev="W3C">World Wide Web Consortium</organization>
2737      <address><email>ylafon@w3.org</email></address>
2738    </author>
2739    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2740      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2741      <address><email>julian.reschke@greenbytes.de</email></address>
2742    </author>
2743    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2744  </front>
2745  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2746  <x:source href="p3-payload.xml" basename="p3-payload"/>
2747</reference>
2748
2749<reference anchor="Part4">
2750  <front>
2751    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2752    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2753      <organization abbrev="Day Software">Day Software</organization>
2754      <address><email>fielding@gbiv.com</email></address>
2755    </author>
2756    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2757      <organization>One Laptop per Child</organization>
2758      <address><email>jg@laptop.org</email></address>
2759    </author>
2760    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2761      <organization abbrev="HP">Hewlett-Packard Company</organization>
2762      <address><email>JeffMogul@acm.org</email></address>
2763    </author>
2764    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2765      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2766      <address><email>henrikn@microsoft.com</email></address>
2767    </author>
2768    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2769      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2770      <address><email>LMM@acm.org</email></address>
2771    </author>
2772    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2773      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2774      <address><email>paulle@microsoft.com</email></address>
2775    </author>
2776    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2777      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2778      <address><email>timbl@w3.org</email></address>
2779    </author>
2780    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2781      <organization abbrev="W3C">World Wide Web Consortium</organization>
2782      <address><email>ylafon@w3.org</email></address>
2783    </author>
2784    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2785      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2786      <address><email>julian.reschke@greenbytes.de</email></address>
2787    </author>
2788    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2789  </front>
2790  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2791  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2792</reference>
2793
2794<reference anchor="Part5">
2795  <front>
2796    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2797    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2798      <organization abbrev="Day Software">Day Software</organization>
2799      <address><email>fielding@gbiv.com</email></address>
2800    </author>
2801    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2802      <organization>One Laptop per Child</organization>
2803      <address><email>jg@laptop.org</email></address>
2804    </author>
2805    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2806      <organization abbrev="HP">Hewlett-Packard Company</organization>
2807      <address><email>JeffMogul@acm.org</email></address>
2808    </author>
2809    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2810      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2811      <address><email>henrikn@microsoft.com</email></address>
2812    </author>
2813    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2814      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2815      <address><email>LMM@acm.org</email></address>
2816    </author>
2817    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2818      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2819      <address><email>paulle@microsoft.com</email></address>
2820    </author>
2821    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2822      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2823      <address><email>timbl@w3.org</email></address>
2824    </author>
2825    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2826      <organization abbrev="W3C">World Wide Web Consortium</organization>
2827      <address><email>ylafon@w3.org</email></address>
2828    </author>
2829    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2830      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2831      <address><email>julian.reschke@greenbytes.de</email></address>
2832    </author>
2833    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2834  </front>
2835  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2836  <x:source href="p5-range.xml" basename="p5-range"/>
2837</reference>
2838
2839<reference anchor="Part6">
2840  <front>
2841    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2842    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2843      <organization abbrev="Day Software">Day Software</organization>
2844      <address><email>fielding@gbiv.com</email></address>
2845    </author>
2846    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2847      <organization>One Laptop per Child</organization>
2848      <address><email>jg@laptop.org</email></address>
2849    </author>
2850    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2851      <organization abbrev="HP">Hewlett-Packard Company</organization>
2852      <address><email>JeffMogul@acm.org</email></address>
2853    </author>
2854    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2855      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2856      <address><email>henrikn@microsoft.com</email></address>
2857    </author>
2858    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2859      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2860      <address><email>LMM@acm.org</email></address>
2861    </author>
2862    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2863      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2864      <address><email>paulle@microsoft.com</email></address>
2865    </author>
2866    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2867      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2868      <address><email>timbl@w3.org</email></address>
2869    </author>
2870    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2871      <organization abbrev="W3C">World Wide Web Consortium</organization>
2872      <address><email>ylafon@w3.org</email></address>
2873    </author>
2874    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2875      <organization />
2876      <address><email>mnot@mnot.net</email></address>
2877    </author>
2878    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2879      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2880      <address><email>julian.reschke@greenbytes.de</email></address>
2881    </author>
2882    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2883  </front>
2884  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2885  <x:source href="p6-cache.xml" basename="p6-cache"/>
2886</reference>
2887
2888<reference anchor="Part7">
2889  <front>
2890    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2891    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2892      <organization abbrev="Day Software">Day Software</organization>
2893      <address><email>fielding@gbiv.com</email></address>
2894    </author>
2895    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2896      <organization>One Laptop per Child</organization>
2897      <address><email>jg@laptop.org</email></address>
2898    </author>
2899    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2900      <organization abbrev="HP">Hewlett-Packard Company</organization>
2901      <address><email>JeffMogul@acm.org</email></address>
2902    </author>
2903    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2904      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2905      <address><email>henrikn@microsoft.com</email></address>
2906    </author>
2907    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2908      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2909      <address><email>LMM@acm.org</email></address>
2910    </author>
2911    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2912      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2913      <address><email>paulle@microsoft.com</email></address>
2914    </author>
2915    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2916      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2917      <address><email>timbl@w3.org</email></address>
2918    </author>
2919    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2920      <organization abbrev="W3C">World Wide Web Consortium</organization>
2921      <address><email>ylafon@w3.org</email></address>
2922    </author>
2923    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2924      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2925      <address><email>julian.reschke@greenbytes.de</email></address>
2926    </author>
2927    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2928  </front>
2929  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2930  <x:source href="p7-auth.xml" basename="p7-auth"/>
2931</reference>
2932
2933<reference anchor="RFC2119">
2934  <front>
2935    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2936    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2937      <organization>Harvard University</organization>
2938      <address><email>sob@harvard.edu</email></address>
2939    </author>
2940    <date month="March" year="1997"/>
2941  </front>
2942  <seriesInfo name="BCP" value="14"/>
2943  <seriesInfo name="RFC" value="2119"/>
2944</reference>
2945
2946<reference anchor="RFC5234">
2947  <front>
2948    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2949    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2950      <organization>Brandenburg InternetWorking</organization>
2951      <address>
2952      <postal>
2953      <street>675 Spruce Dr.</street>
2954      <city>Sunnyvale</city>
2955      <region>CA</region>
2956      <code>94086</code>
2957      <country>US</country></postal>
2958      <phone>+1.408.246.8253</phone>
2959      <email>dcrocker@bbiw.net</email></address> 
2960    </author>
2961    <author initials="P." surname="Overell" fullname="Paul Overell">
2962      <organization>THUS plc.</organization>
2963      <address>
2964      <postal>
2965      <street>1/2 Berkeley Square</street>
2966      <street>99 Berkely Street</street>
2967      <city>Glasgow</city>
2968      <code>G3 7HR</code>
2969      <country>UK</country></postal>
2970      <email>paul.overell@thus.net</email></address>
2971    </author>
2972    <date month="January" year="2008"/>
2973  </front>
2974  <seriesInfo name="STD" value="68"/>
2975  <seriesInfo name="RFC" value="5234"/>
2976</reference>
2977
2978</references>
2979
2980<references title="Informative References">
2981
2982<reference anchor="RFC1945">
2983  <front>
2984    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2985    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2986      <organization>MIT, Laboratory for Computer Science</organization>
2987      <address><email>timbl@w3.org</email></address>
2988    </author>
2989    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2990      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2991      <address><email>fielding@ics.uci.edu</email></address>
2992    </author>
2993    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2994      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2995      <address><email>frystyk@w3.org</email></address>
2996    </author>
2997    <date month="May" year="1996"/>
2998  </front>
2999  <seriesInfo name="RFC" value="1945"/>
3000</reference>
3001
3002<reference anchor="RFC2068">
3003  <front>
3004    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3005    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3006      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3007      <address><email>fielding@ics.uci.edu</email></address>
3008    </author>
3009    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3010      <organization>MIT Laboratory for Computer Science</organization>
3011      <address><email>jg@w3.org</email></address>
3012    </author>
3013    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3014      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3015      <address><email>mogul@wrl.dec.com</email></address>
3016    </author>
3017    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3018      <organization>MIT Laboratory for Computer Science</organization>
3019      <address><email>frystyk@w3.org</email></address>
3020    </author>
3021    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3022      <organization>MIT Laboratory for Computer Science</organization>
3023      <address><email>timbl@w3.org</email></address>
3024    </author>
3025    <date month="January" year="1997"/>
3026  </front>
3027  <seriesInfo name="RFC" value="2068"/>
3028</reference>
3029
3030<reference anchor="RFC2616">
3031  <front>
3032    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3033    <author initials="R." surname="Fielding" fullname="R. Fielding">
3034      <organization>University of California, Irvine</organization>
3035      <address><email>fielding@ics.uci.edu</email></address>
3036    </author>
3037    <author initials="J." surname="Gettys" fullname="J. Gettys">
3038      <organization>W3C</organization>
3039      <address><email>jg@w3.org</email></address>
3040    </author>
3041    <author initials="J." surname="Mogul" fullname="J. Mogul">
3042      <organization>Compaq Computer Corporation</organization>
3043      <address><email>mogul@wrl.dec.com</email></address>
3044    </author>
3045    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3046      <organization>MIT Laboratory for Computer Science</organization>
3047      <address><email>frystyk@w3.org</email></address>
3048    </author>
3049    <author initials="L." surname="Masinter" fullname="L. Masinter">
3050      <organization>Xerox Corporation</organization>
3051      <address><email>masinter@parc.xerox.com</email></address>
3052    </author>
3053    <author initials="P." surname="Leach" fullname="P. Leach">
3054      <organization>Microsoft Corporation</organization>
3055      <address><email>paulle@microsoft.com</email></address>
3056    </author>
3057    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3058      <organization>W3C</organization>
3059      <address><email>timbl@w3.org</email></address>
3060    </author>
3061    <date month="June" year="1999"/>
3062  </front>
3063  <seriesInfo name="RFC" value="2616"/>
3064</reference>
3065
3066<reference anchor='RFC2817'>
3067  <front>
3068    <title>Upgrading to TLS Within HTTP/1.1</title>
3069    <author initials='R.' surname='Khare' fullname='R. Khare'>
3070      <organization>4K Associates / UC Irvine</organization>
3071      <address><email>rohit@4K-associates.com</email></address>
3072    </author>
3073    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3074      <organization>Agranat Systems, Inc.</organization>
3075      <address><email>lawrence@agranat.com</email></address>
3076    </author>
3077    <date year='2000' month='May' />
3078  </front>
3079  <seriesInfo name='RFC' value='2817' />
3080</reference>
3081
3082<reference anchor='RFC3864'>
3083  <front>
3084    <title>Registration Procedures for Message Header Fields</title>
3085    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3086      <organization>Nine by Nine</organization>
3087      <address><email>GK-IETF@ninebynine.org</email></address>
3088    </author>
3089    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3090      <organization>BEA Systems</organization>
3091      <address><email>mnot@pobox.com</email></address>
3092    </author>
3093    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3094      <organization>HP Labs</organization>
3095      <address><email>JeffMogul@acm.org</email></address>
3096    </author>
3097    <date year='2004' month='September' />
3098  </front>
3099  <seriesInfo name='BCP' value='90' />
3100  <seriesInfo name='RFC' value='3864' />
3101</reference>
3102
3103<reference anchor='RFC5226'>
3104  <front>
3105    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3106    <author initials='T.' surname='Narten' fullname='T. Narten'>
3107      <organization>IBM</organization>
3108      <address><email>narten@us.ibm.com</email></address>
3109    </author>
3110    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3111      <organization>Google</organization>
3112      <address><email>Harald@Alvestrand.no</email></address>
3113    </author>
3114    <date year='2008' month='May' />
3115  </front>
3116  <seriesInfo name='BCP' value='26' />
3117  <seriesInfo name='RFC' value='5226' />
3118</reference>
3119
3120<reference anchor="RFC5322">
3121  <front>
3122    <title>Internet Message Format</title>
3123    <author initials="P." surname="Resnick" fullname="P. Resnick">
3124      <organization>Qualcomm Incorporated</organization>
3125    </author>
3126    <date year="2008" month="October"/>
3127  </front> 
3128  <seriesInfo name="RFC" value="5322"/>
3129</reference>
3130
3131</references>
3132
3133<section title="Compatibility with Previous Versions" anchor="compatibility">
3134<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3135<t>
3136   Clarified which error code should be used for inbound server failures
3137   (e.g. DNS failures). (<xref target="status.504"/>).
3138</t>
3139<t>
3140   201 (Created) had a race that required an Etag be sent when a resource is
3141   first created. (<xref target="status.201"/>).
3142</t>
3143<t>
3144   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3145   failure to implement status code 302 properly.
3146   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
3147</t>
3148<t>
3149   Rewrite of message transmission requirements to make it much harder
3150   for implementors to get it wrong, as the consequences of errors here
3151   can have significant impact on the Internet, and to deal with the
3152   following problems:
3153  <list style="numbers">
3154      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3155         this was incorrectly placing a requirement on the behavior of
3156         an implementation of a future version of HTTP/1.x</t>
3157
3158      <t>Made it clear that user-agents should retry requests, not
3159         "clients" in general.</t>
3160
3161      <t>Converted requirements for clients to ignore unexpected 100
3162         (Continue) responses, and for proxies to forward 100 responses,
3163         into a general requirement for 1xx responses.</t>
3164
3165      <t>Modified some TCP-specific language, to make it clearer that
3166         non-TCP transports are possible for HTTP.</t>
3167
3168      <t>Require that the origin server &MUST-NOT; wait for the request
3169         body before it sends a required 100 (Continue) response.</t>
3170
3171      <t>Allow, rather than require, a server to omit 100 (Continue) if
3172         it has already seen some of the request body.</t>
3173
3174      <t>Allow servers to defend against denial-of-service attacks and
3175         broken clients.</t>
3176  </list>
3177</t>
3178<t>
3179   This change adds the Expect header and 417 status code.
3180</t>
3181<t>
3182   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3183   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3184</t>
3185<t>
3186   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
3187   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3188</t>
3189</section>
3190
3191<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3192<t>
3193  This document takes over the Status Code Registry, previously defined
3194  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3195  (<xref target="status.code.registry"/>)
3196</t>
3197<t>
3198  Clarify definition of POST.
3199  (<xref target="POST"/>)
3200</t>
3201<t>
3202  Failed to consider that there are
3203  many other request methods that are safe to automatically redirect,
3204  and further that the user agent is able to make that determination
3205  based on the request method semantics.
3206  (Sections <xref format="counter" target="status.301"/>,
3207  <xref format="counter" target="status.302"/> and
3208  <xref format="counter" target="status.307"/>)
3209</t>
3210<t>
3211  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3212  It used to indicate that the requested resource must be accessed through the
3213  proxy given by the Location field. The Location field gave the URI of the
3214  proxy. The recipient was expected to repeat this single request via the proxy.
3215  (<xref target="status.305"/>)
3216</t>
3217<t>
3218  Reclassify Allow header as response header, removing the option to
3219  specify it in a PUT request.
3220  Relax the server requirement on the contents of the Allow header and
3221  remove requirement on clients to always trust the header value.
3222  (<xref target="header.allow"/>)
3223</t>
3224<t>
3225  Correct syntax of Location header to allow fragment,
3226  as referred symbol wasn't what was expected, and add some
3227  clarifications as to when it would not be appropriate.
3228  (<xref target="header.location"/>)
3229</t>
3230<t>
3231  Allow Referer value of "about:blank" as alternative to not specifying it.
3232  (<xref target="header.referer"/>)
3233</t>
3234<t>
3235  In the description of the Server header, the Via field
3236  was described as a SHOULD. The requirement was and is stated
3237  correctly in the description of the Via header in &header-via;.
3238  (<xref target="header.server"/>)
3239</t>
3240</section>
3241
3242</section>
3243
3244<!-- BEGININC p2-semantics.abnf-appendix -->
3245<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3246<figure>
3247<artwork type="abnf" name="p2-semantics.parsed-abnf">
3248<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3249<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3250<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3251<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3252<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3253<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3254<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3255<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3256<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3257
3258<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3259<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3260<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3261
3262<x:ref>From</x:ref> = "From:" OWS From-v
3263<x:ref>From-v</x:ref> = mailbox
3264
3265<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3266<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3267
3268<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3269If-Modified-Since =
3270 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3271<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3272<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3273If-Unmodified-Since =
3274 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3275
3276<x:ref>Location</x:ref> = "Location:" OWS Location-v
3277<x:ref>Location-v</x:ref> = URI
3278
3279<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3280<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3281<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3282 / %x47.45.54 ; GET
3283 / %x48.45.41.44 ; HEAD
3284 / %x50.4F.53.54 ; POST
3285 / %x50.55.54 ; PUT
3286 / %x44.45.4C.45.54.45 ; DELETE
3287 / %x54.52.41.43.45 ; TRACE
3288 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3289 / extension-method
3290
3291<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3292
3293Proxy-Authenticate =
3294 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3295Proxy-Authorization =
3296 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3297
3298<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3299<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3300<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3301<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3302<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3303<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3304<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3305
3306<x:ref>Server</x:ref> = "Server:" OWS Server-v
3307<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3308<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3309 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3310 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3311 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3312 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3313 "505" / extension-code
3314
3315<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.8&gt;
3316
3317<x:ref>URI</x:ref> = &lt;URI, defined in [Part1], Section 2.6&gt;
3318<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3319<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3320
3321<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3322
3323WWW-Authenticate =
3324 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3325
3326<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3327
3328<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 1.2.2&gt;
3329
3330<x:ref>delta-seconds</x:ref> = 1*DIGIT
3331
3332<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3333<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3334<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3335 *expect-params ]
3336<x:ref>extension-code</x:ref> = 3DIGIT
3337<x:ref>extension-method</x:ref> = token
3338
3339<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3340
3341<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3342
3343<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3344<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3345
3346<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3347
3348<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3349 Accept-Language / Authorization / Expect / From / Host / If-Match /
3350 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3351 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3352 User-Agent
3353<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3354 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3355
3356<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3357</artwork>
3358</figure>
3359<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3360; Reason-Phrase defined but not used
3361; Status-Code defined but not used
3362; request-header defined but not used
3363; response-header defined but not used
3364</artwork></figure></section>
3365<!-- ENDINC p2-semantics.abnf-appendix -->
3366
3367<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3368
3369<section title="Since RFC2616">
3370<t>
3371  Extracted relevant partitions from <xref target="RFC2616"/>.
3372</t>
3373</section>
3374
3375<section title="Since draft-ietf-httpbis-p2-semantics-00">
3376<t>
3377  Closed issues:
3378  <list style="symbols"> 
3379    <t>
3380      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3381      "Via is a MUST"
3382      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3383    </t>
3384    <t>
3385      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3386      "Fragments allowed in Location"
3387      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3388    </t>
3389    <t>
3390      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3391      "Safe Methods vs Redirection"
3392      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3393    </t>
3394    <t>
3395      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3396      "Revise description of the POST method"
3397      (<eref target="http://purl.org/NET/http-errata#post"/>)
3398    </t>
3399    <t>
3400      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3401      "Normative and Informative references"
3402    </t>
3403    <t>
3404      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3405      "RFC2606 Compliance"
3406    </t>
3407    <t>
3408      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3409      "Informative references"
3410    </t>
3411    <t>
3412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3413      "Redundant cross-references"
3414    </t>
3415  </list>
3416</t>
3417<t>
3418  Other changes:
3419  <list style="symbols"> 
3420    <t>
3421      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3422    </t>
3423  </list>
3424</t>
3425</section>
3426
3427<section title="Since draft-ietf-httpbis-p2-semantics-01">
3428<t>
3429  Closed issues:
3430  <list style="symbols"> 
3431    <t>
3432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3433      "PUT side effects"
3434    </t>
3435    <t>
3436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3437      "Duplicate Host header requirements"
3438    </t>
3439  </list>
3440</t>
3441<t>
3442  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3443  <list style="symbols"> 
3444    <t>
3445      Move "Product Tokens" section (back) into Part 1, as "token" is used
3446      in the definition of the Upgrade header.
3447    </t>
3448    <t>
3449      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3450    </t>
3451    <t>
3452      Copy definition of delta-seconds from Part6 instead of referencing it.
3453    </t>
3454  </list>
3455</t>
3456</section>
3457
3458<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3459<t>
3460  Closed issues:
3461  <list style="symbols"> 
3462    <t>
3463      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3464      "Requiring Allow in 405 responses"
3465    </t>
3466    <t>
3467      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3468      "Status Code Registry"
3469    </t>
3470    <t>
3471      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3472      "Redirection vs. Location"
3473    </t>
3474    <t>
3475      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3476      "Cacheability of 303 response"
3477    </t>
3478    <t>
3479      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3480      "305 Use Proxy"
3481    </t>
3482    <t>
3483      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3484      "Classification for Allow header"
3485    </t>
3486    <t>
3487      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3488      "PUT - 'store under' vs 'store at'"
3489    </t>
3490  </list>
3491</t>
3492<t>
3493  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3494  <list style="symbols"> 
3495    <t>
3496      Reference RFC 3984, and update header registrations for headers defined
3497      in this document.
3498    </t>
3499  </list>
3500</t>
3501<t>
3502  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3503  <list style="symbols"> 
3504    <t>
3505      Replace string literals when the string really is case-sensitive (method).
3506    </t>
3507  </list>
3508</t>
3509</section>
3510
3511<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3512<t>
3513  Closed issues:
3514  <list style="symbols"> 
3515    <t>
3516      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3517      "OPTIONS request bodies"
3518    </t>
3519    <t>
3520      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3521      "Description of CONNECT should refer to RFC2817"
3522    </t>
3523    <t>
3524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3525      "Location Content-Location reference request/response mixup"
3526    </t>
3527  </list>
3528</t>
3529<t>
3530  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3531  <list style="symbols"> 
3532    <t>
3533      Added initial proposal for registration process, plus initial
3534      content (non-HTTP/1.1 methods to be added by a separate specification).
3535    </t>
3536  </list>
3537</t>
3538</section>
3539
3540<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3541<t>
3542  Closed issues:
3543  <list style="symbols"> 
3544    <t>
3545      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3546      "Content-*"
3547    </t>
3548    <t>
3549      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3550      "RFC 2822 is updated by RFC 5322"
3551    </t>
3552  </list>
3553</t>
3554<t>
3555  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3556  <list style="symbols"> 
3557    <t>
3558      Use "/" instead of "|" for alternatives.
3559    </t>
3560    <t>
3561      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3562      whitespace ("OWS") and required whitespace ("RWS").
3563    </t>
3564    <t>
3565      Rewrite ABNFs to spell out whitespace rules, factor out
3566      header value format definitions.
3567    </t>
3568  </list>
3569</t>
3570</section>
3571
3572<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3573<t>
3574  Closed issues:
3575  <list style="symbols"> 
3576    <t>
3577      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3578      "Reason-Phrase BNF"
3579    </t>
3580  </list>
3581</t>
3582<t>
3583  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3584  <list style="symbols"> 
3585    <t>
3586      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3587    </t>
3588  </list>
3589</t>
3590</section>
3591
3592<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3593<t>
3594  Closed issues:
3595  <list style="symbols"> 
3596    <t>
3597      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3598      "Clarify when Referer is sent"
3599    </t>
3600    <t>
3601      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3602      "status codes vs methods"
3603    </t>
3604    <t>
3605      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3606      "Do not require "updates" relation for specs that register status codes or method names"
3607    </t>
3608  </list>
3609</t>
3610</section>
3611
3612<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3613<t>
3614  Closed issues:
3615  <list style="symbols"> 
3616    <t>
3617      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3618      "Idempotency"
3619    </t>
3620    <t>
3621      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3622      "TRACE security considerations"
3623    </t>
3624    <t>
3625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3626      "update note citing RFC 1945 and 2068"
3627    </t>
3628    <t>
3629      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3630      "update note about redirect limit"
3631    </t>
3632    <t>
3633      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3634      "Location header ABNF should use 'URI'"
3635    </t>
3636    <t>
3637      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3638      "fragments in Location vs status 303"
3639    </t>
3640  </list>
3641</t>
3642</section>
3643
3644</section>
3645
3646</back>
3647</rfc>
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