source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1512

Last change on this file since 1512 was 1512, checked in by julian.reschke@…, 8 years ago

Add payload to 426 response example (resolves #333)

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 195.7 KB
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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "January">
16  <!ENTITY ID-YEAR "2012">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY architecture               "<xref target='Part1' x:rel='#architecture' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY agent-driven-negotiation   "<xref target='Part3' x:rel='#agent-driven.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-connection          "<xref target='Part1' x:rel='#header.connection' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-content-type        "<xref target='Part3' x:rel='#header.content-type' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY media-types                "<xref target='Part3' x:rel='#media.types' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
85  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
86  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
87  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
88  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
89]>
90<?rfc toc="yes" ?>
91<?rfc symrefs="yes" ?>
92<?rfc sortrefs="yes" ?>
93<?rfc compact="yes"?>
94<?rfc subcompact="no" ?>
95<?rfc linkmailto="no" ?>
96<?rfc editing="no" ?>
97<?rfc comments="yes"?>
98<?rfc inline="yes"?>
99<?rfc rfcedstyle="yes"?>
100<?rfc-ext allow-markup-in-artwork="yes" ?>
101<?rfc-ext include-references-in-index="yes" ?>
102<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="proposed"
103     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
104     xmlns:x='http://purl.org/net/xml2rfc/ext'
105     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
106<x:link rel="prev" basename="p1-messaging"/>
107<x:link rel="next" basename="p3-payload"/>
108<front>
109
110  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
111
112  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
113    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
114    <address>
115      <postal>
116        <street>345 Park Ave</street>
117        <city>San Jose</city>
118        <region>CA</region>
119        <code>95110</code>
120        <country>USA</country>
121      </postal>
122      <email>fielding@gbiv.com</email>
123      <uri>http://roy.gbiv.com/</uri>
124    </address>
125  </author>
126
127  <author initials="J." surname="Gettys" fullname="Jim Gettys">
128    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
129    <address>
130      <postal>
131        <street>21 Oak Knoll Road</street>
132        <city>Carlisle</city>
133        <region>MA</region>
134        <code>01741</code>
135        <country>USA</country>
136      </postal>
137      <email>jg@freedesktop.org</email>
138      <uri>http://gettys.wordpress.com/</uri>
139    </address>
140  </author>
141 
142  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
143    <organization abbrev="HP">Hewlett-Packard Company</organization>
144    <address>
145      <postal>
146        <street>HP Labs, Large Scale Systems Group</street>
147        <street>1501 Page Mill Road, MS 1177</street>
148        <city>Palo Alto</city>
149        <region>CA</region>
150        <code>94304</code>
151        <country>USA</country>
152      </postal>
153      <email>JeffMogul@acm.org</email>
154    </address>
155  </author>
156
157  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
158    <organization abbrev="Microsoft">Microsoft Corporation</organization>
159    <address>
160      <postal>
161        <street>1 Microsoft Way</street>
162        <city>Redmond</city>
163        <region>WA</region>
164        <code>98052</code>
165        <country>USA</country>
166      </postal>
167      <email>henrikn@microsoft.com</email>
168    </address>
169  </author>
170
171  <author initials="L." surname="Masinter" fullname="Larry Masinter">
172    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
173    <address>
174      <postal>
175        <street>345 Park Ave</street>
176        <city>San Jose</city>
177        <region>CA</region>
178        <code>95110</code>
179        <country>USA</country>
180      </postal>
181      <email>LMM@acm.org</email>
182      <uri>http://larry.masinter.net/</uri>
183    </address>
184  </author>
185 
186  <author initials="P." surname="Leach" fullname="Paul J. Leach">
187    <organization abbrev="Microsoft">Microsoft Corporation</organization>
188    <address>
189      <postal>
190        <street>1 Microsoft Way</street>
191        <city>Redmond</city>
192        <region>WA</region>
193        <code>98052</code>
194      </postal>
195      <email>paulle@microsoft.com</email>
196    </address>
197  </author>
198   
199  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
200    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
201    <address>
202      <postal>
203        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
204        <street>The Stata Center, Building 32</street>
205        <street>32 Vassar Street</street>
206        <city>Cambridge</city>
207        <region>MA</region>
208        <code>02139</code>
209        <country>USA</country>
210      </postal>
211      <email>timbl@w3.org</email>
212      <uri>http://www.w3.org/People/Berners-Lee/</uri>
213    </address>
214  </author>
215
216  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
217    <organization abbrev="W3C">World Wide Web Consortium</organization>
218    <address>
219      <postal>
220        <street>W3C / ERCIM</street>
221        <street>2004, rte des Lucioles</street>
222        <city>Sophia-Antipolis</city>
223        <region>AM</region>
224        <code>06902</code>
225        <country>France</country>
226      </postal>
227      <email>ylafon@w3.org</email>
228      <uri>http://www.raubacapeu.net/people/yves/</uri>
229    </address>
230  </author>
231
232  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
233    <organization abbrev="greenbytes">greenbytes GmbH</organization>
234    <address>
235      <postal>
236        <street>Hafenweg 16</street>
237        <city>Muenster</city><region>NW</region><code>48155</code>
238        <country>Germany</country>
239      </postal>
240      <phone>+49 251 2807760</phone>
241      <facsimile>+49 251 2807761</facsimile>
242      <email>julian.reschke@greenbytes.de</email>
243      <uri>http://greenbytes.de/tech/webdav/</uri>
244    </address>
245  </author>
246
247  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
248  <workgroup>HTTPbis Working Group</workgroup>
249
250<abstract>
251<t>
252   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
253   distributed, collaborative, hypertext information systems. HTTP has been in
254   use by the World Wide Web global information initiative since 1990. This
255   document is Part 2 of the seven-part specification that defines the protocol
256   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
257</t>
258<t>
259   Part 2 defines the semantics of HTTP messages as expressed by request
260   methods, request header fields, response status codes, and response header
261   fields.
262</t>
263</abstract>
264
265<note title="Editorial Note (To be removed by RFC Editor)">
266  <t>
267    Discussion of this draft should take place on the HTTPBIS working group
268    mailing list (ietf-http-wg@w3.org), which is archived at
269    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
270  </t>
271  <t>
272    The current issues list is at
273    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
274    documents (including fancy diffs) can be found at
275    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
276  </t>
277  <t>
278    The changes in this draft are summarized in <xref target="changes.since.18"/>.
279  </t>
280</note>
281</front>
282<middle>
283<section title="Introduction" anchor="introduction">
284<t>
285   This document defines HTTP/1.1 request and response semantics.  Each HTTP
286   message, as defined in &messaging;, is in the form of either a request or
287   a response.  An HTTP server listens on a connection for HTTP requests and
288   responds to each request, in the order received on that connection, with
289   one or more HTTP response messages.  This document defines the commonly
290   agreed upon semantics of the HTTP uniform interface, the intentions defined
291   by each request method, and the various response messages that might be
292   expected as a result of applying that method to the target resource.
293</t>
294<t>
295   This document is currently disorganized in order to minimize the changes
296   between drafts and enable reviewers to see the smaller errata changes.
297   A future draft will reorganize the sections to better reflect the content.
298   In particular, the sections will be ordered according to the typical
299   processing of an HTTP request message (after message parsing): resource
300   mapping, methods, request modifying header fields, response status,
301   status modifying header fields, and resource metadata.  The current mess
302   reflects how widely dispersed these topics and associated requirements
303   had become in <xref target="RFC2616"/>.
304</t>
305
306<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
307<t>
308   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
309   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
310   document are to be interpreted as described in <xref target="RFC2119"/>.
311</t>
312<t>
313   This document defines conformance criteria for several roles in HTTP
314   communication, including Senders, Recipients, Clients, Servers, User-Agents,
315   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
316   for definitions of these terms.
317</t>
318<t>
319   An implementation is considered conformant if it complies with all of the
320   requirements associated with its role(s). Note that SHOULD-level requirements
321   are relevant here, unless one of the documented exceptions is applicable.
322</t>
323<t>
324   This document also uses ABNF to define valid protocol elements
325   (<xref target="notation"/>). In addition to the prose requirements placed
326   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
327</t>
328<t>
329   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
330   protocol element from an invalid construct. However, HTTP does not define
331   specific error handling mechanisms, except in cases where it has direct
332   impact on security. This is because different uses of the protocol require
333   different error handling strategies; for example, a Web browser may wish to
334   transparently recover from a response where the Location header field
335   doesn't parse according to the ABNF, whereby in a systems control protocol
336   using HTTP, this type of error recovery could lead to dangerous consequences.
337</t>
338</section>
339
340<section title="Syntax Notation" anchor="notation">
341  <x:anchor-alias value="CR"/>
342  <x:anchor-alias value="DIGIT"/>
343  <x:anchor-alias value="LF"/>
344  <x:anchor-alias value="HTAB"/>
345  <x:anchor-alias value="VCHAR"/>
346  <x:anchor-alias value="SP"/>
347<t>
348  This specification uses the ABNF syntax defined in &notation; (which
349  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
350  <xref target="collected.abnf"/> shows the collected ABNF, with the list
351  rule expanded.
352</t>
353<t>
354  The following core rules are included by
355  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
356  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
357  DIGIT (decimal 0-9), DQUOTE (double quote),
358  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
359  OCTET (any 8-bit sequence of data), SP (space), and
360  VCHAR (any visible US-ASCII character).
361</t>
362
363<section title="Core Rules" anchor="core.rules">
364  <x:anchor-alias value="obs-text"/>
365  <x:anchor-alias value="quoted-string"/>
366  <x:anchor-alias value="token"/>
367  <x:anchor-alias value="BWS"/>
368  <x:anchor-alias value="OWS"/>
369  <x:anchor-alias value="RWS"/>
370<t>
371  The core rules below are defined in <xref target="Part1"/>:
372</t>
373<figure><artwork type="abnf2616">
374  <x:ref>BWS</x:ref>           = &lt;BWS, defined in &basic-rules;&gt;
375  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
376  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
377  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
378  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
379  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
380</artwork></figure>
381</section>
382
383<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
384  <x:anchor-alias value="absolute-URI"/>
385  <x:anchor-alias value="comment"/>
386  <x:anchor-alias value="partial-URI"/>
387  <x:anchor-alias value="product"/>
388  <x:anchor-alias value="URI-reference"/>
389<t>
390  The ABNF rules below are defined in other parts:
391</t>
392<figure><!--Part1--><artwork type="abnf2616">
393  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
394  <x:ref>comment</x:ref>       = &lt;comment, defined in &field-rules;&gt;
395  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
396  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
397  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
398</artwork></figure>
399</section>
400</section>
401</section>
402
403<section title="Method" anchor="method">
404  <x:anchor-alias value="Method"/>
405  <x:anchor-alias value="extension-method"/>
406<t>
407   The Method token indicates the request method to be performed on the target
408   resource (&effective-request-uri;). The method is case-sensitive.
409</t>
410<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
411  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
412</artwork></figure>
413<t>
414   The list of methods allowed by a resource can be specified in an
415   Allow header field (<xref target="header.allow"/>). The status code of the response
416   always notifies the client whether a method is currently allowed on a
417   resource, since the set of allowed methods can change dynamically. An
418   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
419   if the method is known by the origin server but not allowed for the
420   resource, and 501 (Not Implemented) if the method is
421   unrecognized or not implemented by the origin server. The methods GET
422   and HEAD &MUST; be supported by all general-purpose servers. All other
423   methods are &OPTIONAL;; however, if the above methods are implemented,
424   they &MUST; be implemented with the same semantics as those specified
425   in <xref target="method.definitions"/>.
426</t>
427
428<section title="Overview of Methods" anchor="overview.of.methods">
429<t>
430  The methods listed below are defined in <xref target="method.definitions"/>.
431</t>
432<texttable align="left">
433  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
434 
435  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
436  <c>GET</c> <c><xref target="GET"/></c>
437  <c>HEAD</c> <c><xref target="HEAD"/></c>
438  <c>POST</c> <c><xref target="POST"/></c>
439  <c>PUT</c> <c><xref target="PUT"/></c>
440  <c>DELETE</c> <c><xref target="DELETE"/></c>
441  <c>TRACE</c> <c><xref target="TRACE"/></c>
442  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
443</texttable>
444<t>
445  Note that this list is not exhaustive &mdash; it does not include request methods defined
446  in other specifications.
447</t>
448</section>
449
450<section title="Method Registry" anchor="method.registry">
451<t>
452  The HTTP Method Registry defines the name space for the Method token in the
453  Request line of an HTTP request.
454</t>
455<t>
456  Registrations &MUST; include the following fields:
457  <list style="symbols">
458    <t>Method Name (see <xref target="method"/>)</t>
459    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
460    <t>Pointer to specification text</t>
461  </list>
462</t>
463<t>
464  Values to be added to this name space are subject to IETF review
465  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
466</t>
467<t>
468  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
469</t>
470
471<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
472<t>
473   When it is necessary to express new semantics for a HTTP request that
474   aren't specific to a single application or media type, and currently defined
475   methods are inadequate, it may be appropriate to register a new method.
476</t>
477<t>
478   HTTP methods are generic; that is, they are potentially applicable to any
479   resource, not just one particular media type, "type" of resource, or
480   application. As such, it is preferred that new HTTP methods be registered
481   in a document that isn't specific to a single application, so that this is
482   clear.
483</t>
484<t>
485   Due to the parsing rules defined in &message-body;, definitions of HTTP
486   methods cannot prohibit the presence of a message-body on either the request
487   or the response message (with responses to HEAD requests being the single
488   exception). Definitions of new methods cannot change this rule, but they can
489   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
490</t>
491<t>
492   New method definitions need to indicate whether they are safe (<xref
493   target="safe.methods"/>), what semantics (if any) the request body has,
494   and whether they are idempotent (<xref target="idempotent.methods"/>).
495   They also need to state whether they can be cached (&caching;); in
496   particular what conditions a cache may store the response, and under what
497   conditions such a stored response may be used to satisfy a subsequent
498   request.
499</t>
500</section>
501
502</section>
503</section>
504
505<section title="Header Fields" anchor="header.fields">
506<t>
507   Header fields are key value pairs that can be used to communicate data about
508   the message, its payload, the target resource, or about the connection
509   itself (i.e., control data).  See &header-fields; for a general definition
510   of their syntax.
511</t>
512
513<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
514<t>
515   New header fields are registered using the procedures described in
516   <xref target="RFC3864"/>.
517</t>
518<t>
519   The requirements for header field names are defined in
520   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
521   defining new fields are advised to keep the name as short as practical, and
522   not to prefix them with "X-" if they are to be registered (either
523   immediately or in the future).
524</t>
525<t>
526   New header field values typically have their syntax defined using ABNF
527   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
528   as necessary, and are usually constrained to the range of ASCII characters.
529   Header fields needing a greater range of characters can use an encoding
530   such as the one defined in <xref target="RFC5987"/>.
531</t>
532<t>
533   Because commas (",") are used as a generic delimiter between field-values,
534   they need to be treated with care if they are allowed in the field-value's
535   payload. Typically, components that might contain a comma are protected with
536   double-quotes using the quoted-string ABNF production (&field-rules;).
537</t>
538<t>
539   For example, a textual date and a URI (either of which might contain a comma)
540   could be safely carried in field-values like these:
541</t>
542<figure><artwork type="example">
543  Example-URI-Field: "http://example.com/a.html,foo",
544                     "http://without-a-comma.example.com/"
545  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
546</artwork></figure>
547<t>
548   Note that double quote delimiters almost always are used with the
549   quoted-string production; using a different syntax inside double quotes
550   will likely cause unnecessary confusion.
551</t>
552<t>
553   Many header fields use a format including (case-insensitively) named
554   parameters (for instance, Content-Type, defined in &header-content-type;).
555   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
556   parameter value enables recipients to use existing parser components. When
557   allowing both forms, the meaning of a parameter value ought to be
558   independent of the syntax used for it (for an example, see the notes on
559   parameter handling for media types in &media-types;).
560</t>
561<t>
562   Authors of specifications defining new header fields are advised to consider
563   documenting:
564  <list style="symbols">
565    <x:lt>
566      <t>Whether the field is a single value, or whether it can be a list
567      (delimited by commas; see &header-fields;).</t>
568      <t>If it does not use the list syntax, document how to treat messages
569      where the header field occurs multiple times (a sensible default would
570      be to ignore the header field, but this might not always be the right
571      choice).</t>
572      <t>Note that intermediaries and software libraries might combine
573      multiple header field instances into a single one, despite the header
574      field not allowing this. A robust format enables recipients to discover
575      these situations (good example: "Content-Type", as the comma can only
576      appear inside quoted strings; bad example: "Location", as a comma can
577      occur inside a URI).</t>
578    </x:lt>
579    <x:lt><t>Under what conditions the header field can be used; e.g., only in
580    responses or requests, in all messages, only on responses to a particular
581    request method.</t></x:lt>
582    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
583    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
584    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
585    field's value, insert or delete it.</t></x:lt>
586    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
587    <x:lt><t>Whether the header field is useful or allowable in trailers (see
588    &chunked-encoding;).</t></x:lt>
589    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
590  </list>
591</t>
592</section>
593
594<section title="Request Header Fields" anchor="request.header.fields">
595  <x:anchor-alias value="request-header"/>
596<t>
597   The request header fields allow the client to pass additional
598   information about the request, and about the client itself, to the
599   server. These fields act as request modifiers, with semantics
600   equivalent to the parameters on a programming language method
601   invocation.
602</t>
603<texttable align="left">
604  <ttcol>Header Field Name</ttcol>
605  <ttcol>Defined in...</ttcol>
606
607  <c>Accept</c> <c>&header-accept;</c>
608  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
609  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
610  <c>Accept-Language</c> <c>&header-accept-language;</c>
611  <c>Authorization</c> <c>&header-authorization;</c>
612  <c>Expect</c> <c><xref target="header.expect"/></c>
613  <c>From</c> <c><xref target="header.from"/></c>
614  <c>Host</c> <c>&header-host;</c>
615  <c>If-Match</c> <c>&header-if-match;</c>
616  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
617  <c>If-None-Match</c> <c>&header-if-none-match;</c>
618  <c>If-Range</c> <c>&header-if-range;</c>
619  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
620  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
621  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
622  <c>Range</c> <c>&header-range;</c>
623  <c>Referer</c> <c><xref target="header.referer"/></c>
624  <c>TE</c> <c>&header-te;</c>
625  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
626</texttable>
627</section>
628
629<section title="Response Header Fields" anchor="response.header.fields">
630  <x:anchor-alias value="response-header"/>
631<t>
632   The response header fields allow the server to pass additional
633   information about the response which cannot be placed in the Status-Line.
634   These header fields give information about the server and about
635   further access to the target resource (&effective-request-uri;).
636</t>
637<texttable align="left">
638  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
639
640  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
641  <c>Age</c> <c>&header-age;</c>
642  <c>Allow</c> <c><xref target="header.allow"/></c>
643  <c>Date</c> <c><xref target="header.date"/></c>
644  <c>ETag</c> <c>&header-etag;</c>
645  <c>Location</c> <c><xref target="header.location"/></c>
646  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
647  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
648  <c>Server</c> <c><xref target="header.server"/></c>
649  <c>Vary</c> <c>&header-vary;</c>
650  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
651</texttable>
652</section>
653
654</section>
655
656<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
657  <x:anchor-alias value="Reason-Phrase"/>
658  <x:anchor-alias value="Status-Code"/>
659  <x:anchor-alias value="extension-code"/>
660<t>
661   The Status-Code element is a 3-digit integer result code of the attempt to
662   understand and satisfy the request.
663</t>
664<t>
665   The Reason-Phrase is intended to give a short textual description of the
666   Status-Code and is intended for a human user. The client does not need
667   to examine or display the Reason-Phrase.
668</t>
669<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"/>
670  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
671  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>HTAB</x:ref> / <x:ref>SP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
672</artwork></figure>
673<t>
674   HTTP status codes are extensible. HTTP applications are not required
675   to understand the meaning of all registered status codes, though such
676   understanding is obviously desirable. However, applications &MUST;
677   understand the class of any status code, as indicated by the first
678   digit, and treat any unrecognized response as being equivalent to the
679   x00 status code of that class, with the exception that an
680   unrecognized response &MUST-NOT; be cached. For example, if an
681   unrecognized status code of 431 is received by the client, it can
682   safely assume that there was something wrong with its request and
683   treat the response as if it had received a 400 status code. In such
684   cases, user agents &SHOULD; present to the user the representation enclosed
685   with the response, since that representation is likely to include human-readable
686   information which will explain the unusual status.
687</t>
688
689<section title="Overview of Status Codes" anchor="overview.of.status.codes">
690<t> 
691   The status codes listed below are defined in <xref target="status.codes"/>
692   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
693   The reason phrases listed here are only recommendations &mdash; they can be
694   replaced by local equivalents without affecting the protocol.
695</t>
696<texttable align="left">
697  <ttcol>Status-Code</ttcol>
698  <ttcol>Reason-Phrase</ttcol>
699  <ttcol>Defined in...</ttcol>
700 
701  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
702  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
703
704  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
705  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
706  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
707  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
708  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
709  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
710  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
711
712  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
713  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
714  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
715  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
716  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
717  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
718  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
719
720  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
721  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
722  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
723  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
724  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
725  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
726  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
727  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
728  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
729  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
730  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
731  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
732  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
733  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
734  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
735  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
736  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
737  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
738  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
739
740  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
741  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
742  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
743  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
744  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
745  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
746</texttable>
747<t>
748   Note that this list is not exhaustive &mdash; it does not include
749   extension status codes defined in other specifications.
750</t>
751</section>
752
753<section title="Status Code Registry" anchor="status.code.registry">
754<t>
755  The HTTP Status Code Registry defines the name space for the Status-Code
756  token in the Status-Line of an HTTP response.
757</t>
758<t>
759  Values to be added to this name space are subject to IETF review
760  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
761</t>
762<t>
763  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
764</t>
765
766<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
767<t>
768   When it is necessary to express new semantics for a HTTP response that
769   aren't specific to a single application or media type, and currently defined
770   status codes are inadequate, a new status code can be registered.
771</t>
772<t>
773   HTTP status codes are generic; that is, they are potentially applicable to
774   any resource, not just one particular media type, "type" of resource, or
775   application. As such, it is preferred that new HTTP status codes be
776   registered in a document that isn't specific to a single application, so
777   that this is clear.
778</t>
779<t>
780   Definitions of new HTTP status codes typically explain the request
781   conditions that produce a response containing the status code (e.g.,
782   combinations of request headers and/or method(s)), along with any
783   interactions with response headers (e.g., those that are required, those
784   that modify the semantics of the response).
785</t>
786<t>
787   New HTTP status codes are required to fall under one of the categories
788   defined in <xref target="status.codes"/>. To allow existing parsers to
789   properly handle them, new status codes cannot disallow a response body,
790   although they can mandate a zero-length response body. They can require the
791   presence of one or more particular HTTP response header(s).
792</t>
793<t>
794   Likewise, their definitions can specify that caches are allowed to use
795   heuristics to determine their freshness (see &caching;; by default, it is
796   not allowed), and can define how to determine the resource which they
797   carry a representation for (see <xref
798   target="identifying.response.associated.with.representation"/>; by default,
799   it is anonymous).
800</t>
801</section>
802
803</section>
804
805</section>
806
807<section title="Representation" anchor="representation">
808<t>
809   Request and Response messages &MAY; transfer a representation if not otherwise
810   restricted by the request method or response status code. A representation
811   consists of metadata (representation header fields) and data (representation
812   body).  When a complete or partial representation is enclosed in an HTTP message,
813   it is referred to as the payload of the message. HTTP representations
814   are defined in &payload;.
815</t>
816<t>
817   A representation body is only present in a message when a message-body is
818   present, as described in &message-body;. The representation body is obtained
819   from the message-body by decoding any Transfer-Encoding that might
820   have been applied to ensure safe and proper transfer of the message.
821</t>
822
823<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
824<t>
825   It is sometimes necessary to determine an identifier for the resource
826   associated with a representation.
827</t>
828<t>
829   An HTTP request representation, when present, is always associated with an
830   anonymous (i.e., unidentified) resource.
831</t>
832<t>
833   In the common case, an HTTP response is a representation of the target
834   resource (see &effective-request-uri;). However, this is not always the
835   case. To determine the URI of the resource a response is associated with,
836   the following rules are used (with the first applicable one being selected):
837</t>
838<t><list style="numbers">
839   <t>If the response status code is 200 or 203 and the request method was GET,
840   the response payload is a representation of the target resource.</t>
841   <t>If the response status code is 204, 206, or 304 and the request method was GET
842   or HEAD, the response payload is a partial representation of the target
843   resource.</t>
844   <t>If the response has a Content-Location header field, and that URI is the same
845   as the effective request URI, the response payload is a representation of the
846   target resource.</t>
847   <t>If the response has a Content-Location header field, and that URI is not the
848   same as the effective request URI, then the response asserts that its
849   payload is a representation of the resource identified by the
850   Content-Location URI. However, such an assertion cannot be trusted unless
851   it can be verified by other means (not defined by HTTP).</t>
852   <t>Otherwise, the response is a representation of an anonymous (i.e.,
853   unidentified) resource.</t>
854</list></t>
855<t>
856  <cref anchor="TODO-req-uri">
857   The comparison function is going to have to be defined somewhere,
858   because we already need to compare URIs for things like cache invalidation.</cref>
859</t>
860</section>
861
862</section>
863
864
865<section title="Method Definitions" anchor="method.definitions">
866<t>
867   The set of common request methods for HTTP/1.1 is defined below. Although
868   this set can be expanded, additional methods cannot be assumed to
869   share the same semantics for separately extended clients and servers.
870</t>
871
872<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
873
874<section title="Safe Methods" anchor="safe.methods">
875<iref item="Safe Methods" primary="true"/>
876<t>
877   Implementors need to be aware that the software represents the user in
878   their interactions over the Internet, and need to allow
879   the user to be aware of any actions they take which might have an
880   unexpected significance to themselves or others.
881</t>
882<t>
883   In particular, the convention has been established that the GET, HEAD,
884   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
885   of taking an action other than retrieval. These request methods ought
886   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
887   This allows user agents to represent other methods, such as POST, PUT
888   and DELETE, in a special way, so that the user is made aware of the
889   fact that a possibly unsafe action is being requested.
890</t>
891<t>
892   Naturally, it is not possible to ensure that the server does not
893   generate side-effects as a result of performing a GET request; in
894   fact, some dynamic resources consider that a feature. The important
895   distinction here is that the user did not request the side-effects,
896   so therefore cannot be held accountable for them.
897</t>
898</section>
899
900<section title="Idempotent Methods" anchor="idempotent.methods">
901<iref item="Idempotent Methods" primary="true"/>
902<t>
903   Request methods can also have the property of "idempotence" in that,
904   aside from error or expiration issues, the intended effect of multiple
905   identical requests is the same as for a single request.
906   PUT, DELETE, and all safe request methods are idempotent.
907   It is important to note that idempotence refers only to changes
908   requested by the client: a server is free to change its state due
909   to multiple requests for the purpose of tracking those requests,
910   versioning of results, etc.
911</t>
912</section>
913</section>
914
915<section title="OPTIONS" anchor="OPTIONS">
916  <rdf:Description>
917    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
918  </rdf:Description>
919  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
920  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
921<t>
922   The OPTIONS method requests information about the
923   communication options available on the request/response chain
924   identified by the effective request URI. This method allows a client to
925   determine the options and/or requirements associated with a resource,
926   or the capabilities of a server, without implying a resource action
927   or initiating a resource retrieval.
928</t>
929<t>
930   Responses to the OPTIONS method are not cacheable.
931</t>
932<t>
933   If the OPTIONS request includes a message-body (as indicated by the
934   presence of Content-Length or Transfer-Encoding), then the media type
935   &MUST; be indicated by a Content-Type field. Although this
936   specification does not define any use for such a body, future
937   extensions to HTTP might use the OPTIONS body to make more detailed
938   queries on the server.
939</t>
940<t>
941   If the request-target is an asterisk ("*"), the OPTIONS request is
942   intended to apply to the server in general rather than to a specific
943   resource. Since a server's communication options typically depend on
944   the resource, the "*" request is only useful as a "ping" or "no-op"
945   type of method; it does nothing beyond allowing the client to test
946   the capabilities of the server. For example, this can be used to test
947   a proxy for HTTP/1.1 compliance (or lack thereof).
948</t>
949<t>
950   If the request-target is not an asterisk, the OPTIONS request applies
951   only to the options that are available when communicating with that
952   resource.
953</t>
954<t>
955   A 200 response &SHOULD; include any header fields that indicate
956   optional features implemented by the server and applicable to that
957   resource (e.g., Allow), possibly including extensions not defined by
958   this specification. The response body, if any, &SHOULD; also include
959   information about the communication options. The format for such a
960   body is not defined by this specification, but might be defined by
961   future extensions to HTTP. Content negotiation &MAY; be used to select
962   the appropriate response format. If no response body is included, the
963   response &MUST; include a Content-Length field with a field-value of
964   "0".
965</t>
966<t>
967   The Max-Forwards header field &MAY; be used to target a
968   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
969   If no Max-Forwards field is present in the request, then the forwarded
970   request &MUST-NOT; include a Max-Forwards field.
971</t>
972</section>
973
974<section title="GET" anchor="GET">
975  <rdf:Description>
976    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
977  </rdf:Description>
978  <iref primary="true" item="GET method" x:for-anchor=""/>
979  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
980<t>
981   The GET method requests transfer of a current representation of
982   the target resource.
983</t>
984<t>   
985   If the target resource is a data-producing process, it is the
986   produced data which shall be returned as the representation in the response and not
987   the source text of the process, unless that text happens to be the output of
988   the process.
989</t>
990<t>
991   The semantics of the GET method change to a "conditional GET" if the
992   request message includes an If-Modified-Since, If-Unmodified-Since,
993   If-Match, If-None-Match, or If-Range header field. A conditional GET
994   requests that the representation be transferred only under the
995   circumstances described by the conditional header field(s). The
996   conditional GET request is intended to reduce unnecessary network
997   usage by allowing cached representations to be refreshed without requiring
998   multiple requests or transferring data already held by the client.
999</t>
1000<t>
1001   The semantics of the GET method change to a "partial GET" if the
1002   request message includes a Range header field. A partial GET requests
1003   that only part of the representation be transferred, as described in &header-range;.
1004   The partial GET request is intended to reduce unnecessary
1005   network usage by allowing partially-retrieved representations to be
1006   completed without transferring data already held by the client.
1007</t>
1008<t>
1009   Bodies on GET requests have no defined semantics. Note that sending a body
1010   on a GET request might cause some existing implementations to reject the
1011   request.
1012</t>
1013<t>
1014   The response to a GET request is cacheable and &MAY; be used to satisfy
1015   subsequent GET and HEAD requests (see &caching;).
1016</t>
1017<t>
1018   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
1019</t>
1020</section>
1021
1022<section title="HEAD" anchor="HEAD">
1023  <rdf:Description>
1024    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1025  </rdf:Description>
1026  <iref primary="true" item="HEAD method" x:for-anchor=""/>
1027  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
1028<t>
1029   The HEAD method is identical to GET except that the server &MUST-NOT;
1030   return a message-body in the response. The metadata contained
1031   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
1032   to the information sent in response to a GET request. This method can
1033   be used for obtaining metadata about the representation implied by the
1034   request without transferring the representation body. This method is
1035   often used for testing hypertext links for validity, accessibility,
1036   and recent modification.
1037</t>
1038<t>
1039   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1040   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1041   representation from that resource; if the new field values
1042   indicate that the cached representation differs from the current representation (as
1043   would be indicated by a change in Content-Length, ETag
1044   or Last-Modified), then the cache &MUST; treat the cache entry as
1045   stale.
1046</t>
1047<t>
1048   Bodies on HEAD requests have no defined semantics. Note that sending a body
1049   on a HEAD request might cause some existing implementations to reject the
1050   request.
1051</t>
1052</section>
1053
1054<section title="POST" anchor="POST">
1055  <iref primary="true" item="POST method" x:for-anchor=""/>
1056  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1057<t>
1058   The POST method requests that the origin server accept the
1059   representation enclosed in the request as data to be processed by the
1060   target resource. POST is designed to allow a uniform method to cover the
1061   following functions:
1062  <list style="symbols">
1063    <t>
1064      Annotation of existing resources;
1065    </t>
1066    <t>
1067        Posting a message to a bulletin board, newsgroup, mailing list,
1068        or similar group of articles;
1069    </t>
1070    <t>
1071        Providing a block of data, such as the result of submitting a
1072        form, to a data-handling process;
1073    </t>
1074    <t>
1075        Extending a database through an append operation.
1076    </t>
1077  </list>
1078</t>
1079<t>
1080   The actual function performed by the POST method is determined by the
1081   server and is usually dependent on the effective request URI.
1082</t>
1083<t>
1084   The action performed by the POST method might not result in a
1085   resource that can be identified by a URI. In this case, either 200
1086   (OK) or 204 (No Content) is the appropriate response status code,
1087   depending on whether or not the response includes a representation that
1088   describes the result.
1089</t>
1090<t>
1091   If a resource has been created on the origin server, the response
1092   &SHOULD; be 201 (Created) and contain a representation which describes the
1093   status of the request and refers to the new resource, and a Location
1094   header field (see <xref target="header.location"/>).
1095</t>
1096<t>
1097   Responses to POST requests are only cacheable when they
1098   include explicit freshness information (see &p6-explicit;). A
1099   cached POST response with a Content-Location header field
1100   (see &header-content-location;) whose value is the effective
1101   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1102</t>
1103<t>
1104   Note that POST caching is not widely implemented.
1105   However, the 303 (See Other) response can be used to direct the
1106   user agent to retrieve a cacheable resource.
1107</t>
1108</section>
1109
1110<section title="PUT" anchor="PUT">
1111  <iref primary="true" item="PUT method" x:for-anchor=""/>
1112  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1113<t>
1114   The PUT method requests that the state of the target resource
1115   be created or replaced with the state defined by the representation
1116   enclosed in the request message payload.  A successful PUT of a given
1117   representation would suggest that a subsequent GET on that same target
1118   resource will result in an equivalent representation being returned in
1119   a 200 (OK) response.  However, there is no guarantee that such a state
1120   change will be observable, since the target resource might be acted
1121   upon by other user agents in parallel, or might be subject to dynamic
1122   processing by the origin server, before any subsequent GET is received.
1123   A successful response only implies that the user agent's intent was
1124   achieved at the time of its processing by the origin server.
1125</t>
1126<t>   
1127   If the target resource does not have a current representation and
1128   the PUT successfully creates one, then the origin server &MUST; inform
1129   the user agent by sending a 201 (Created) response.  If the target
1130   resource does have a current representation and that representation is
1131   successfully modified in accordance with the state of the enclosed
1132   representation, then either a 200 (OK) or 204 (No Content) response
1133   &SHOULD; be sent to indicate successful completion of the request.
1134</t>
1135<t>
1136   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1137   as part of the resource state).
1138</t>
1139<t>
1140   An origin server &SHOULD; verify that the PUT representation is
1141   consistent with any constraints which the server has for the target
1142   resource that cannot or will not be changed by the PUT.  This is
1143   particularly important when the origin server uses internal
1144   configuration information related to the URI in order to set the
1145   values for representation metadata on GET responses.  When a PUT
1146   representation is inconsistent with the target resource, the origin
1147   server &SHOULD; either make them consistent, by transforming the
1148   representation or changing the resource configuration, or respond
1149   with an appropriate error message containing sufficient information
1150   to explain why the representation is unsuitable.  The 409 (Conflict)
1151   or 415 (Unsupported Media Type) status codes are suggested, with the
1152   latter being specific to constraints on Content-Type values.
1153</t>
1154<t>
1155   For example, if the target resource is configured to always have a
1156   Content-Type of "text/html" and the representation being PUT has a
1157   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1158   (a) reconfigure the target resource to reflect the new media type;
1159   (b) transform the PUT representation to a format consistent with that
1160   of the resource before saving it as the new resource state; or,
1161   (c) reject the request with a 415 response indicating that the target
1162   resource is limited to "text/html", perhaps including a link to a
1163   different resource that would be a suitable target for the new
1164   representation.
1165</t>
1166<t>
1167   HTTP does not define exactly how a PUT method affects the state
1168   of an origin server beyond what can be expressed by the intent of
1169   the user agent request and the semantics of the origin server response.
1170   It does not define what a resource might be, in any sense of that
1171   word, beyond the interface provided via HTTP.  It does not define
1172   how resource state is "stored", nor how such storage might change
1173   as a result of a change in resource state, nor how the origin server
1174   translates resource state into representations.  Generally speaking,
1175   all implementation details behind the resource interface are
1176   intentionally hidden by the server.
1177</t>
1178<t>
1179   The fundamental difference between the POST and PUT methods is
1180   highlighted by the different intent for the target resource.
1181   The target resource in a POST request is intended to handle the
1182   enclosed representation as a data-accepting process, such as for
1183   a gateway to some other protocol or a document that accepts annotations.
1184   In contrast, the target resource in a PUT request is intended to
1185   take the enclosed representation as a new or replacement value.
1186   Hence, the intent of PUT is idempotent and visible to intermediaries,
1187   even though the exact effect is only known by the origin server.
1188</t>
1189<t>
1190   Proper interpretation of a PUT request presumes that the user agent
1191   knows what target resource is desired.  A service that is intended
1192   to select a proper URI on behalf of the client, after receiving
1193   a state-changing request, &SHOULD; be implemented using the POST
1194   method rather than PUT.  If the origin server will not make the
1195   requested PUT state change to the target resource and instead
1196   wishes to have it applied to a different resource, such as when the
1197   resource has been moved to a different URI, then the origin server
1198   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1199   then make its own decision regarding whether or not to redirect the
1200   request.
1201</t>
1202<t>
1203   A PUT request applied to the target resource &MAY; have side-effects
1204   on other resources.  For example, an article might have a URI for
1205   identifying "the current version" (a resource) which is separate
1206   from the URIs identifying each particular version (different
1207   resources that at one point shared the same state as the current version
1208   resource).  A successful PUT request on "the current version" URI might
1209   therefore create a new version resource in addition to changing the
1210   state of the target resource, and might also cause links to be added
1211   between the related resources.
1212</t>
1213<t>
1214   An origin server &SHOULD; reject any PUT request that contains a
1215   Content-Range header field, since it might be misinterpreted as
1216   partial content (or might be partial content that is being mistakenly
1217   PUT as a full representation).  Partial content updates are
1218   possible by targeting a separately identified resource with state
1219   that overlaps a portion of the larger resource, or by using a
1220   different method that has been specifically defined for partial
1221   updates (for example, the PATCH method defined in
1222   <xref target="RFC5789"/>).
1223</t>
1224<t>
1225   Responses to the PUT method are not cacheable. If a PUT request passes
1226   through a cache that has one or more stored responses for the effective
1227   request URI, those stored responses will be invalidated (see
1228   &p6-invalid;).
1229</t>
1230</section>
1231
1232<section title="DELETE" anchor="DELETE">
1233  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1234  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1235<t>
1236   The DELETE method requests that the origin server delete the target
1237   resource. This method &MAY; be overridden by
1238   human intervention (or other means) on the origin server. The client cannot
1239   be guaranteed that the operation has been carried out, even if the
1240   status code returned from the origin server indicates that the action
1241   has been completed successfully. However, the server &SHOULD-NOT; 
1242   indicate success unless, at the time the response is given, it
1243   intends to delete the resource or move it to an inaccessible
1244   location.
1245</t>
1246<t>
1247   A successful response &SHOULD; be 200 (OK) if the response includes an
1248   representation describing the status, 202 (Accepted) if the action has not
1249   yet been enacted, or 204 (No Content) if the action has been enacted
1250   but the response does not include a representation.
1251</t>
1252<t>
1253   Bodies on DELETE requests have no defined semantics. Note that sending a body
1254   on a DELETE request might cause some existing implementations to reject the
1255   request.
1256</t>
1257<t>
1258   Responses to the DELETE method are not cacheable. If a DELETE request
1259   passes through a cache that has one or more stored responses for the
1260   effective request URI, those stored responses will be invalidated (see
1261   &p6-invalid;).
1262</t>
1263</section>
1264
1265<section title="TRACE" anchor="TRACE">
1266  <rdf:Description>
1267    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1268  </rdf:Description>
1269  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1270  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1271<t>
1272   The TRACE method requests a remote, application-layer loop-back
1273   of the request message. The final recipient of the request
1274   &SHOULD; reflect the message received back to the client as the
1275   message-body of a 200 (OK) response. The final recipient is either the
1276   origin server or the first proxy to receive a Max-Forwards
1277   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1278   A TRACE request &MUST-NOT; include a message-body.
1279</t>
1280<t>
1281   TRACE allows the client to see what is being received at the other
1282   end of the request chain and use that data for testing or diagnostic
1283   information. The value of the Via header field (&header-via;) is of
1284   particular interest, since it acts as a trace of the request chain.
1285   Use of the Max-Forwards header field allows the client to limit the
1286   length of the request chain, which is useful for testing a chain of
1287   proxies forwarding messages in an infinite loop.
1288</t>
1289<t>
1290   If the request is valid, the response &SHOULD; have a Content-Type of
1291   "message/http" (see &media-type-message-http;) and contain a message-body
1292   that encloses a copy of the entire request message.
1293   Responses to the TRACE method are not cacheable.
1294</t>
1295</section>
1296
1297<section title="CONNECT" anchor="CONNECT">
1298  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1299  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1300<t>
1301   The CONNECT method requests that the proxy establish a tunnel
1302   to the request-target and then restrict its behavior to blind
1303   forwarding of packets until the connection is closed.
1304</t>
1305<t>
1306   When using CONNECT, the request-target &MUST; use the authority form
1307   (&request-target;); i.e., the request-target consists of only the
1308   host name and port number of the tunnel destination, separated by a colon.
1309   For example,
1310</t>
1311<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1312CONNECT server.example.com:80 HTTP/1.1
1313Host: server.example.com:80
1314
1315</artwork></figure>
1316<t>
1317   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1318   except end-to-end protocol Upgrade requests, since the
1319   tunnel must be established first.
1320</t>
1321<t>
1322   For example, proxy authentication might be used to establish the
1323   authority to create a tunnel:
1324</t>
1325<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1326CONNECT server.example.com:80 HTTP/1.1
1327Host: server.example.com:80
1328Proxy-Authorization: basic aGVsbG86d29ybGQ=
1329
1330</artwork></figure>
1331<t>
1332   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1333   on a CONNECT request might cause some existing implementations to reject the
1334   request.
1335</t>
1336<t>
1337   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1338   sent immediately after the blank line. The usual caveats also apply:
1339   data may be discarded if the eventual response is negative, and the
1340   connection may be reset with no response if more than one TCP segment
1341   is outstanding.
1342</t>
1343
1344<section title="Establishing a Tunnel with CONNECT">
1345<t>
1346   Any successful (2xx) response to a CONNECT request indicates that the
1347   proxy has established a connection to the requested host and port,
1348   and has switched to tunneling the current connection to that server
1349   connection.
1350</t>
1351<t>
1352   It may be the case that the proxy itself can only reach the requested
1353   origin server through another proxy.  In this case, the first proxy
1354   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1355   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1356   unless it has either a direct or tunnel connection established to the
1357   authority.
1358</t>
1359<t>
1360   An origin server which receives a CONNECT request for itself &MAY;
1361   respond with a 2xx status code to indicate that a connection is
1362   established.
1363</t>
1364<t>
1365   If at any point either one of the peers gets disconnected, any
1366   outstanding data that came from that peer will be passed to the other
1367   one, and after that also the other connection will be terminated by
1368   the proxy. If there is outstanding data to that peer undelivered,
1369   that data will be discarded.
1370</t>
1371
1372</section>
1373</section>
1374</section>
1375
1376
1377<section title="Status Code Definitions" anchor="status.codes">
1378<t>
1379   The first digit of the Status-Code defines the class of response. The
1380   last two digits do not have any categorization role. There are 5
1381   values for the first digit:
1382  <list style="symbols">
1383    <t>
1384      1xx: Informational - Request received, continuing process
1385    </t>
1386    <t>
1387      2xx: Success - The action was successfully received,
1388        understood, and accepted
1389    </t>
1390    <t>
1391      3xx: Redirection - Further action must be taken in order to
1392        complete the request
1393    </t>
1394    <t>
1395      4xx: Client Error - The request contains bad syntax or cannot
1396        be fulfilled
1397    </t>
1398    <t>
1399      5xx: Server Error - The server failed to fulfill an apparently
1400        valid request
1401    </t>
1402  </list>
1403</t>
1404<t>
1405   Each Status-Code is described below, including any metadata required
1406   in the response.
1407</t>
1408
1409<section title="Informational 1xx" anchor="status.1xx">
1410<t>
1411   This class of status code indicates a provisional response,
1412   consisting only of the Status-Line and optional header fields, and is
1413   terminated by an empty line. There are no required header fields for this
1414   class of status code. Since HTTP/1.0 did not define any 1xx status
1415   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1416   except under experimental conditions.
1417</t>
1418<t>
1419   A client &MUST; be prepared to accept one or more 1xx status responses
1420   prior to a regular response, even if the client does not expect a 100
1421   (Continue) status message. Unexpected 1xx status responses &MAY; be
1422   ignored by a user agent.
1423</t>
1424<t>
1425   Proxies &MUST; forward 1xx responses, unless the connection between the
1426   proxy and its client has been closed, or unless the proxy itself
1427   requested the generation of the 1xx response. (For example, if a
1428   proxy adds a "Expect: 100-continue" field when it forwards a request,
1429   then it need not forward the corresponding 100 (Continue)
1430   response(s).)
1431</t>
1432
1433<section title="100 Continue" anchor="status.100">
1434  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1435  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1436<t>
1437   The client &SHOULD; continue with its request. This interim response is
1438   used to inform the client that the initial part of the request has
1439   been received and has not yet been rejected by the server. The client
1440   &SHOULD; continue by sending the remainder of the request or, if the
1441   request has already been completed, ignore this response. The server
1442   &MUST; send a final response after the request has been completed. See
1443   &use100; for detailed discussion of the use and handling of this
1444   status code.
1445</t>
1446</section>
1447
1448<section title="101 Switching Protocols" anchor="status.101">
1449  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1450  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1451<t>
1452   The server understands and is willing to comply with the client's
1453   request, via the Upgrade message header field (&header-upgrade;), for a
1454   change in the application protocol being used on this connection. The
1455   server will switch protocols to those defined by the response's
1456   Upgrade header field immediately after the empty line which
1457   terminates the 101 response.
1458</t>
1459<t>
1460   The protocol &SHOULD; be switched only when it is advantageous to do
1461   so. For example, switching to a newer version of HTTP is advantageous
1462   over older versions, and switching to a real-time, synchronous
1463   protocol might be advantageous when delivering resources that use
1464   such features.
1465</t>
1466</section>
1467</section>
1468
1469<section title="Successful 2xx" anchor="status.2xx">
1470<t>
1471   This class of status code indicates that the client's request was
1472   successfully received, understood, and accepted.
1473</t>
1474
1475<section title="200 OK" anchor="status.200">
1476  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1477  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1478<t>
1479   The request has succeeded. The payload returned with the response
1480   is dependent on the method used in the request, for example:
1481  <list style="hanging">
1482    <t hangText="GET">
1483      a representation of the target resource is sent in the response;
1484    </t>
1485    <t hangText="HEAD">
1486      the same representation as GET, except without the message-body;
1487    </t>
1488    <t hangText="POST">
1489      a representation describing or containing the result of the action;
1490    </t>
1491    <t hangText="TRACE">
1492      a representation containing the request message as received by the
1493      end server.
1494    </t>
1495  </list>
1496</t>
1497<t>
1498   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1499   freshness for 200 responses.
1500</t>
1501</section>
1502
1503<section title="201 Created" anchor="status.201">
1504  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1505  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1506<t>
1507   The request has been fulfilled and has resulted in a new resource being
1508   created. The newly created resource can be referenced by the URI(s)
1509   returned in the payload of the response, with the most specific URI
1510   for the resource given by a Location header field. The response
1511   &SHOULD; include a payload containing a list of resource
1512   characteristics and location(s) from which the user or user agent can
1513   choose the one most appropriate. The payload format is specified by
1514   the media type given in the Content-Type header field.
1515</t>
1516<t>
1517   The origin server &MUST; create the resource before returning the 201 status
1518   code. If the action cannot be carried out immediately, the server &SHOULD;
1519   respond with 202 (Accepted) response instead.
1520</t>
1521<t>
1522   A 201 response &MAY; contain an ETag response header field indicating
1523   the current value of the entity-tag for the representation of the resource
1524   just created (see &header-etag;).
1525</t>
1526</section>
1527
1528<section title="202 Accepted" anchor="status.202">
1529  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1530  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1531<t>
1532   The request has been accepted for processing, but the processing has
1533   not been completed.  The request might or might not eventually be
1534   acted upon, as it might be disallowed when processing actually takes
1535   place. There is no facility for re-sending a status code from an
1536   asynchronous operation such as this.
1537</t>
1538<t>
1539   The 202 response is intentionally non-committal. Its purpose is to
1540   allow a server to accept a request for some other process (perhaps a
1541   batch-oriented process that is only run once per day) without
1542   requiring that the user agent's connection to the server persist
1543   until the process is completed. The representation returned with this
1544   response &SHOULD; include an indication of the request's current status
1545   and either a pointer to a status monitor or some estimate of when the
1546   user can expect the request to be fulfilled.
1547</t>
1548</section>
1549
1550<section title="203 Non-Authoritative Information" anchor="status.203">
1551  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1552  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1553<t>
1554   The representation in the response has been transformed or otherwise
1555   modified by a transforming proxy (&intermediaries;).  Note that the
1556   behavior of transforming intermediaries is controlled by the no-transform
1557   Cache-Control directive (&header-cache-control;).
1558</t>
1559<t>
1560   This status code is only appropriate when the response status code would
1561   have been 200 (OK) otherwise. When the status code before transformation
1562   would have been different, the 214 Transformation Applied warn-code
1563   (&header-warning;) is appropriate.
1564</t>
1565<t>
1566   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1567   freshness for 203 responses.
1568</t>
1569</section>
1570
1571<section title="204 No Content" anchor="status.204">
1572  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1573  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1574<t>
1575   The 204 (No Content) status code indicates that the server has
1576   successfully fulfilled the request and that there is no additional
1577   content to return in the response payload body.  Metadata in the
1578   response header fields refer to the target resource and its current
1579   representation after the requested action.
1580</t>
1581<t>
1582   For example, if a 204 status code is received in response to a PUT
1583   request and the response contains an ETag header field, then the PUT
1584   was successful and the ETag field-value contains the entity-tag for
1585   the new representation of that target resource.
1586</t>
1587<t>
1588   The 204 response allows a server to indicate that the action has been
1589   successfully applied to the target resource while implying that the
1590   user agent &SHOULD-NOT; traverse away from its current "document view"
1591   (if any).  The server assumes that the user agent will provide some
1592   indication of the success to its user, in accord with its own interface,
1593   and apply any new or updated metadata in the response to the active
1594   representation.
1595</t>
1596<t>
1597   For example, a 204 status code is commonly used with document editing
1598   interfaces corresponding to a "save" action, such that the document
1599   being saved remains available to the user for editing. It is also
1600   frequently used with interfaces that expect automated data transfers
1601   to be prevalent, such as within distributed version control systems.
1602</t>
1603<t>
1604   The 204 response &MUST-NOT; include a message-body, and thus is always
1605   terminated by the first empty line after the header fields.
1606</t>
1607</section>
1608
1609<section title="205 Reset Content" anchor="status.205">
1610  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1611  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1612<t>
1613   The server has fulfilled the request and the user agent &SHOULD; reset
1614   the document view which caused the request to be sent. This response
1615   is primarily intended to allow input for actions to take place via
1616   user input, followed by a clearing of the form in which the input is
1617   given so that the user can easily initiate another input action.
1618</t>
1619<t>   
1620   The message-body included with the response &MUST; be empty. Note that
1621   receivers still need to parse the response according to the algorithm defined
1622   in &message-body;.
1623</t>
1624</section>
1625
1626<section title="206 Partial Content" anchor="status.206">
1627  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1628  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1629  <rdf:Description>
1630    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1631  </rdf:Description>
1632<t>
1633   The server has fulfilled the partial GET request for the resource
1634   and the enclosed payload is a partial representation as defined in &status-206;.
1635</t>
1636<t>
1637   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1638   freshness for 206 responses.
1639</t>
1640</section>
1641</section>
1642
1643<section title="Redirection 3xx" anchor="status.3xx">
1644<t>
1645   This class of status code indicates that further action needs to be
1646   taken by the user agent in order to fulfill the request.  If the required
1647   action involves a subsequent HTTP request, it &MAY; be carried out by the
1648   user agent without interaction with the user if and only if the method used
1649   in the second request is known to be "safe", as defined in
1650   <xref target="safe.methods"/>.
1651</t>
1652<t>
1653   There are several types of redirects:
1654   <list style="numbers">
1655      <x:lt>
1656        <t>
1657          Redirects of the request to another URI, either temporarily or
1658          permanently. The new URI is specified in the Location header field.
1659          In this specification, the status codes 301 (Moved Permanently),
1660          302 (Found), and 307 (Temporary Redirect) fall under this category.
1661        </t>
1662      </x:lt>
1663      <x:lt>
1664        <t>
1665          Redirection to a new location that represents an indirect response to
1666          the request, such as the result of a POST operation to be retrieved
1667          with a subsequent GET request. This is status code 303 (See Other).
1668        </t>
1669      </x:lt>
1670      <x:lt>
1671        <t>
1672          Redirection offering a choice of matching resources for use by
1673          agent-driven content negotiation (&agent-driven-negotiation;). This
1674          is status code 300 (Multiple Choices).
1675        </t>
1676      </x:lt>
1677      <x:lt>
1678        <t>
1679          Other kinds of redirection, such as to a cached result (status code 304
1680          (Not Modified)).
1681        </t>
1682      </x:lt>
1683   </list>
1684</t>
1685<x:note>
1686  <t>
1687    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1688    and 302 (Found) were defined for the first type of redirect, and the second
1689    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1690    However it turned out that web forms using POST expected redirects to change
1691    the operation for the subsequent request to retrieval (GET). To address this
1692    use case, HTTP/1.1 introduced the second type of redirect with the status
1693    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1694    As user agents did not change their behavior to maintain backwards
1695    compatibility, the first revision of HTTP/1.1 added yet another status code,
1696    307 (Temporary Redirect), for which the backwards compatibility problems did
1697    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1698    Over 10 years later, most user agents still do method rewriting for
1699    status codes 301 and 302, therefore this specification makes that behavior
1700    compliant in case the original request was POST.
1701  </t>
1702</x:note>
1703<t>
1704   A Location header field on a 3xx response indicates that a client &MAY;
1705   automatically redirect to the URI provided; see <xref target="header.location"/>.
1706</t>
1707<t>
1708   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1709   "infinite" redirection loops).
1710</t>
1711<x:note>
1712  <t>
1713    <x:h>Note:</x:h> An earlier version of this specification recommended a
1714    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1715    Content developers need to be aware that some clients might
1716    implement such a fixed limitation.
1717  </t>
1718</x:note>
1719
1720<section title="300 Multiple Choices" anchor="status.300">
1721  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1722  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1723<t>
1724   The target resource has more than one
1725   representation, each with its own specific location, and agent-driven
1726   negotiation information (&content-negotiation;) is being provided so that
1727   the user (or user agent) can select a preferred representation by
1728   redirecting its request to that location.
1729</t>
1730<t>
1731   Unless it was a HEAD request, the response &SHOULD; include a representation
1732   containing a list of representation metadata and location(s) from
1733   which the user or user agent can choose the one most appropriate. The
1734   data format is specified by the media type given in the Content-Type
1735   header field. Depending upon the format and the capabilities of
1736   the user agent, selection of the most appropriate choice &MAY; be
1737   performed automatically. However, this specification does not define
1738   any standard for such automatic selection.
1739</t>
1740<t>
1741   If the server has a preferred choice of representation, it &SHOULD;
1742   include the specific URI for that representation in the Location
1743   field; user agents &MAY; use the Location field value for automatic
1744   redirection.
1745</t>
1746<t>
1747   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1748   freshness for 300 responses.
1749</t>
1750
1751</section>
1752
1753<section title="301 Moved Permanently" anchor="status.301">
1754  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1755  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1756<t>
1757   The target resource has been assigned a new permanent URI and any
1758   future references to this resource &SHOULD; use one of the returned
1759   URIs.  Clients with link editing capabilities ought to automatically
1760   re-link references to the effective request URI to one or more of the new
1761   references returned by the server, where possible.
1762</t>
1763<t>
1764   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1765   freshness for 301 responses.
1766</t>
1767<t>
1768   The new permanent URI &SHOULD; be given by the Location field in the
1769   response. Unless the request method was HEAD, the representation of the
1770   response &SHOULD; contain a short hypertext note with a hyperlink to
1771   the new URI(s).
1772</t>
1773<t>
1774   If the 301 status code is received in response to a request method
1775   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1776   then the request &MAY; be automatically redirected by the user agent without
1777   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1778   request unless it can be confirmed by the user, since this might
1779   change the conditions under which the request was issued.
1780</t>
1781<x:note>
1782  <t>
1783    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1784    request method from POST to GET for the subsequent request. If this
1785    behavior is undesired, status code 307 (Temporary Redirect) can be used
1786    instead.
1787  </t>
1788</x:note>
1789</section>
1790
1791<section title="302 Found" anchor="status.302">
1792  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1793  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1794<t>
1795   The target resource resides temporarily under a different URI.
1796   Since the redirection might be altered on occasion, the client &SHOULD;
1797   continue to use the effective request URI for future requests.
1798</t>
1799<t>
1800   The temporary URI &SHOULD; be given by the Location field in the
1801   response. Unless the request method was HEAD, the representation of the
1802   response &SHOULD; contain a short hypertext note with a hyperlink to
1803   the new URI(s).
1804</t>
1805<t>
1806   If the 302 status code is received in response to a request method
1807   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1808   then the request &MAY; be automatically redirected by the user agent without
1809   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1810   request unless it can be confirmed by the user, since this might
1811   change the conditions under which the request was issued.
1812</t>
1813<x:note>
1814  <t>
1815    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1816    request method from POST to GET for the subsequent request. If this
1817    behavior is undesired, status code 307 (Temporary Redirect) can be used
1818    instead.
1819  </t>
1820</x:note>
1821</section>
1822
1823<section title="303 See Other" anchor="status.303">
1824  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1825  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1826<t>
1827   The 303 status code indicates that the server is redirecting the
1828   user agent to a different resource, as indicated by a URI in the
1829   Location header field, that is intended to provide an indirect
1830   response to the original request.  In order to satisfy the original
1831   request, a user agent &SHOULD; perform a retrieval request using the
1832   Location URI (a GET or HEAD request if using HTTP), which
1833   may itself be redirected further, and present the eventual result as an
1834   answer to the original request.
1835   Note that the new URI in the Location header field is not considered
1836   equivalent to the effective request URI.
1837</t>
1838<t>
1839   This status code is generally applicable to any HTTP method.  It is
1840   primarily used to allow the output of a POST action to redirect
1841   the user agent to a selected resource, since doing so provides the
1842   information corresponding to the POST response in a form that
1843   can be separately identified, bookmarked, and cached independent
1844   of the original request.
1845</t>
1846<t>
1847   A 303 response to a GET request indicates that the requested
1848   resource does not have a representation of its own that can be
1849   transferred by the server over HTTP.  The Location URI indicates a
1850   resource that is descriptive of the target resource, such that the
1851   follow-on representation might be useful to recipients without
1852   implying that it adequately represents the target resource.
1853   Note that answers to the questions of what can be represented, what
1854   representations are adequate, and what might be a useful description
1855   are outside the scope of HTTP and thus entirely determined by the
1856   URI owner(s).
1857</t>
1858<t>
1859   Except for responses to a HEAD request, the representation of a 303
1860   response &SHOULD; contain a short hypertext note with a hyperlink
1861   to the Location URI.
1862</t>
1863</section>
1864
1865<section title="304 Not Modified" anchor="status.304">
1866  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1867  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1868  <rdf:Description>
1869    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1870  </rdf:Description>
1871<t>
1872   The response to the request has not been modified since the conditions
1873   indicated by the client's conditional GET request, as defined in &status-304;.
1874</t>
1875</section>
1876
1877<section title="305 Use Proxy" anchor="status.305">
1878  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1879  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1880<t>
1881   The 305 status code was defined in a previous version of this specification
1882   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1883</t>
1884</section>
1885
1886<section title="306 (Unused)" anchor="status.306">
1887  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1888  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1889<t>
1890   The 306 status code was used in a previous version of the
1891   specification, is no longer used, and the code is reserved.
1892</t>
1893</section>
1894
1895<section title="307 Temporary Redirect" anchor="status.307">
1896  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1897  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1898<t>
1899   The target resource resides temporarily under a different URI.
1900   Since the redirection can change over time, the client &SHOULD;
1901   continue to use the effective request URI for future requests.
1902</t>
1903<t>
1904   The temporary URI &SHOULD; be given by the Location field in the
1905   response. Unless the request method was HEAD, the representation of the
1906   response &SHOULD; contain a short hypertext note with a hyperlink to
1907   the new URI(s).
1908</t>
1909<t>
1910   If the 307 status code is received in response to a request method
1911   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1912   then the request &MAY; be automatically redirected by the user agent without
1913   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1914   request unless it can be confirmed by the user, since this might
1915   change the conditions under which the request was issued.
1916</t>
1917<x:note>
1918  <t>
1919    <x:h>Note:</x:h> This status code is similar to 302 Found, except that
1920    it does not allow rewriting the request method from POST to GET. This
1921    specification defines no equivalent counterpart for 301 Moved Permanently.
1922  </t>
1923</x:note>
1924</section>
1925</section>
1926
1927<section title="Client Error 4xx" anchor="status.4xx">
1928<t>
1929   The 4xx class of status code is intended for cases in which the
1930   client seems to have erred. Except when responding to a HEAD request,
1931   the server &SHOULD; include a representation containing an explanation of the
1932   error situation, and whether it is a temporary or permanent
1933   condition. These status codes are applicable to any request method.
1934   User agents &SHOULD; display any included representation to the user.
1935</t>
1936<t>
1937   If the client is sending data, a server implementation using TCP
1938   &SHOULD; be careful to ensure that the client acknowledges receipt of
1939   the packet(s) containing the response, before the server closes the
1940   input connection. If the client continues sending data to the server
1941   after the close, the server's TCP stack will send a reset packet to
1942   the client, which might erase the client's unacknowledged input buffers
1943   before they can be read and interpreted by the HTTP application.
1944</t>
1945
1946<section title="400 Bad Request" anchor="status.400">
1947  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1948  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1949<t>
1950   The server cannot or will not process the request, due to a client error (e.g.,
1951   malformed syntax).</t>
1952</section>
1953
1954<section title="401 Unauthorized" anchor="status.401">
1955  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1956  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1957  <rdf:Description>
1958    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1959  </rdf:Description>
1960<t>
1961   The request requires user authentication (see &status-401;).
1962</t>
1963</section>
1964
1965<section title="402 Payment Required" anchor="status.402">
1966  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1967  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1968<t>
1969   This code is reserved for future use.
1970</t>
1971</section>
1972
1973<section title="403 Forbidden" anchor="status.403">
1974  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1975  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1976<t>
1977   The server understood the request, but refuses to authorize it. Providing
1978   different user authentication credentials might be successful, but any
1979   credentials that were provided in the request are insufficient. The request
1980   &SHOULD-NOT; be repeated with the same credentials.
1981</t>
1982<t>
1983   If the request method was not HEAD and the server wishes to make
1984   public why the request has not been fulfilled, it &SHOULD; describe the
1985   reason for the refusal in the representation.  If the server does not wish to
1986   make this information available to the client, the status code 404
1987   (Not Found) &MAY; be used instead.
1988</t>
1989</section>
1990
1991<section title="404 Not Found" anchor="status.404">
1992  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1993  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1994<t>
1995   The server has not found anything matching the effective request URI. No
1996   indication is given of whether the condition is temporary or
1997   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1998   knows, through some internally configurable mechanism, that an old
1999   resource is permanently unavailable and has no forwarding address.
2000   This status code is commonly used when the server does not wish to
2001   reveal exactly why the request has been refused, or when no other
2002   response is applicable.
2003</t>
2004</section>
2005
2006<section title="405 Method Not Allowed" anchor="status.405">
2007  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
2008  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
2009<t>
2010   The method specified in the Request-Line is not allowed for the target
2011   resource. The response &MUST; include an Allow header field containing a
2012   list of valid methods for the requested resource.
2013</t>
2014</section>
2015
2016<section title="406 Not Acceptable" anchor="status.406">
2017  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
2018  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
2019<t>
2020   The resource identified by the request is only capable of generating
2021   response representations which have content characteristics not acceptable
2022   according to the Accept and Accept-* header fields sent in the request
2023   (see &p3-header-fields;).
2024</t>
2025<t>
2026   Unless it was a HEAD request, the response &SHOULD; include a representation
2027   containing a list of available representation characteristics and location(s)
2028   from which the user or user agent can choose the one most
2029   appropriate. The data format is specified by the media type given
2030   in the Content-Type header field. Depending upon the format and the
2031   capabilities of the user agent, selection of the most appropriate
2032   choice &MAY; be performed automatically. However, this specification
2033   does not define any standard for such automatic selection.
2034</t>
2035<x:note>
2036  <t>
2037    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
2038    not acceptable according to the accept header fields sent in the
2039    request. In some cases, this might even be preferable to sending a
2040    406 response. User agents are encouraged to inspect the header fields of
2041    an incoming response to determine if it is acceptable.
2042  </t>
2043</x:note>
2044<t>
2045   If the response could be unacceptable, a user agent &SHOULD;
2046   temporarily stop receipt of more data and query the user for a
2047   decision on further actions.
2048</t>
2049</section>
2050
2051<section title="407 Proxy Authentication Required" anchor="status.407">
2052  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2053  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2054<t>
2055   This code is similar to 401 (Unauthorized), but indicates that the
2056   client must first authenticate itself with the proxy (see &status-407;).
2057</t>
2058</section>
2059
2060<section title="408 Request Timeout" anchor="status.408">
2061  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2062  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2063<t>
2064   The client did not produce a request within the time that the server
2065   was prepared to wait. The client &MAY; repeat the request without
2066   modifications at any later time.
2067</t>
2068</section>
2069
2070<section title="409 Conflict" anchor="status.409">
2071  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2072  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2073<t>
2074   The request could not be completed due to a conflict with the current
2075   state of the resource. This code is only allowed in situations where
2076   it is expected that the user might be able to resolve the conflict
2077   and resubmit the request. The response body &SHOULD; include enough
2078   information for the user to recognize the source of the conflict.
2079   Ideally, the response representation would include enough information for the
2080   user or user agent to fix the problem; however, that might not be
2081   possible and is not required.
2082</t>
2083<t>
2084   Conflicts are most likely to occur in response to a PUT request. For
2085   example, if versioning were being used and the representation being PUT
2086   included changes to a resource which conflict with those made by an
2087   earlier (third-party) request, the server might use the 409 response
2088   to indicate that it can't complete the request. In this case, the
2089   response representation would likely contain a list of the differences
2090   between the two versions in a format defined by the response
2091   Content-Type.
2092</t>
2093</section>
2094
2095<section title="410 Gone" anchor="status.410">
2096  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2097  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2098<t>
2099   The target resource is no longer available at the server and no
2100   forwarding address is known. This condition is expected to be
2101   considered permanent. Clients with link editing capabilities &SHOULD;
2102   delete references to the effective request URI after user approval. If the
2103   server does not know, or has no facility to determine, whether or not
2104   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2105   used instead.
2106</t>
2107<t>
2108   The 410 response is primarily intended to assist the task of web
2109   maintenance by notifying the recipient that the resource is
2110   intentionally unavailable and that the server owners desire that
2111   remote links to that resource be removed. Such an event is common for
2112   limited-time, promotional services and for resources belonging to
2113   individuals no longer working at the server's site. It is not
2114   necessary to mark all permanently unavailable resources as "gone" or
2115   to keep the mark for any length of time &mdash; that is left to the
2116   discretion of the server owner.
2117</t>
2118<t>
2119   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2120   for 410 responses.
2121</t>
2122
2123</section>
2124
2125<section title="411 Length Required" anchor="status.411">
2126  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2127  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2128<t>
2129   The server refuses to accept the request without a defined Content-Length.
2130   The client &MAY; repeat the request if it adds a valid
2131   Content-Length header field containing the length of the message-body
2132   in the request message.
2133</t>
2134</section>
2135
2136<section title="412 Precondition Failed" anchor="status.412">
2137  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2138  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2139  <rdf:Description>
2140    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2141  </rdf:Description>
2142<t>
2143   The precondition given in one or more of the header fields
2144   evaluated to false when it was tested on the server, as defined in
2145   &status-412;.
2146</t>
2147</section>
2148
2149<section title="413 Request Representation Too Large" anchor="status.413">
2150  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2151  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2152<t>
2153   The server is refusing to process a request because the request
2154   representation is larger than the server is willing or able to process. The
2155   server &MAY; close the connection to prevent the client from continuing
2156   the request.
2157</t>
2158<t>
2159   If the condition is temporary, the server &SHOULD; include a Retry-After
2160   header field to indicate that it is temporary and after what
2161   time the client &MAY; try again.
2162</t>
2163</section>
2164
2165<section title="414 URI Too Long" anchor="status.414">
2166  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2167  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2168<t>
2169   The server is refusing to service the request because the effective request URI
2170   is longer than the server is willing to interpret. This rare
2171   condition is only likely to occur when a client has improperly
2172   converted a POST request to a GET request with long query
2173   information, when the client has descended into a URI "black hole" of
2174   redirection (e.g., a redirected URI prefix that points to a suffix of
2175   itself), or when the server is under attack by a client attempting to
2176   exploit security holes present in some servers using fixed-length
2177   buffers for reading or manipulating the effective request URI.
2178</t>
2179</section>
2180
2181<section title="415 Unsupported Media Type" anchor="status.415">
2182  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2183  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2184<t>
2185   The server is refusing to service the request because the request
2186   payload is in a format not supported by this request method on the
2187   target resource.
2188</t>
2189</section>
2190
2191<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2192  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2193  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2194  <rdf:Description>
2195    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2196  </rdf:Description>
2197<t>
2198   The request included a Range header field (&header-range;) and none of
2199   the range-specifier values in this field overlap the current extent
2200   of the selected resource. See &status-416;.
2201</t>
2202</section>
2203
2204<section title="417 Expectation Failed" anchor="status.417">
2205  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2206  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2207<t>
2208   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2209   could not be met by this server, or, if the server is a proxy,
2210   the server has unambiguous evidence that the request could not be met
2211   by the next-hop server.
2212</t>
2213</section>
2214
2215<section title="426 Upgrade Required" anchor="status.426">
2216  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2217  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2218<t>
2219   The request can not be completed without a prior protocol upgrade. This
2220   response &MUST; include an Upgrade header field (&header-upgrade;)
2221   specifying the required protocols.
2222</t>
2223<figure>
2224<preamble>Example:</preamble>
2225<artwork type="message/http; msgtype=&#34;response&#34;" x:indent-with="  ">
2226HTTP/1.1 426 Upgrade Required
2227Upgrade: HTTP/3.0
2228Connection: Upgrade
2229Content-Length: <x:length-of target="s426body"/>
2230Content-Type: text/plain
2231
2232<x:span anchor="s426body">This service requires use of the HTTP/3.0 protocol.
2233</x:span></artwork></figure>
2234<t>
2235   The server &SHOULD; include a message body in the 426 response which
2236   indicates in human readable form the reason for the error and describes any
2237   alternative courses which may be available to the user.
2238</t>
2239</section>
2240</section>
2241
2242<section title="Server Error 5xx" anchor="status.5xx">
2243<t>
2244   Response status codes beginning with the digit "5" indicate cases in
2245   which the server is aware that it has erred or is incapable of
2246   performing the request. Except when responding to a HEAD request, the
2247   server &SHOULD; include a representation containing an explanation of the
2248   error situation, and whether it is a temporary or permanent
2249   condition. User agents &SHOULD; display any included representation to the
2250   user. These response codes are applicable to any request method.
2251</t>
2252
2253<section title="500 Internal Server Error" anchor="status.500">
2254  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2255  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2256<t>
2257   The server encountered an unexpected condition which prevented it
2258   from fulfilling the request.
2259</t>
2260</section>
2261
2262<section title="501 Not Implemented" anchor="status.501">
2263  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2264  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2265<t>
2266   The server does not support the functionality required to fulfill the
2267   request. This is the appropriate response when the server does not
2268   recognize the request method and is not capable of supporting it for
2269   any resource.
2270</t>
2271</section>
2272
2273<section title="502 Bad Gateway" anchor="status.502">
2274  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2275  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2276<t>
2277   The server, while acting as a gateway or proxy, received an invalid
2278   response from the upstream server it accessed in attempting to
2279   fulfill the request.
2280</t>
2281</section>
2282
2283<section title="503 Service Unavailable" anchor="status.503">
2284  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2285  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2286<t>
2287   The server is currently unable to handle the request due to a
2288   temporary overloading or maintenance of the server.
2289</t>
2290<t>
2291   The implication is that this is a temporary condition which will be
2292   alleviated after some delay. If known, the length of the delay &MAY; be
2293   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2294   If no Retry-After is given, the client &SHOULD; handle the response as it
2295   would for a 500 response.
2296</t>
2297<x:note>
2298  <t>
2299    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2300    server must use it when becoming overloaded. Some servers might wish
2301    to simply refuse the connection.
2302  </t>
2303</x:note>
2304</section>
2305
2306<section title="504 Gateway Timeout" anchor="status.504">
2307  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2308  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2309<t>
2310   The server, while acting as a gateway or proxy, did not receive a
2311   timely response from the upstream server specified by the URI (e.g.,
2312   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2313   to access in attempting to complete the request.
2314</t>
2315<x:note>
2316  <t>
2317    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2318    return 400 or 500 when DNS lookups time out.
2319  </t>
2320</x:note>
2321</section>
2322
2323<section title="505 HTTP Version Not Supported" anchor="status.505">
2324  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2325  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2326<t>
2327   The server does not support, or refuses to support, the protocol
2328   version that was used in the request message. The server is
2329   indicating that it is unable or unwilling to complete the request
2330   using the same major version as the client, as described in &http-version;,
2331   other than with this error message. The response &SHOULD; contain
2332   a representation describing why that version is not supported and what other
2333   protocols are supported by that server.
2334</t>
2335
2336</section>
2337</section>
2338</section>
2339
2340
2341<section title="Date/Time Formats" anchor="http.date">
2342  <x:anchor-alias value="HTTP-date"/>
2343<t>
2344   HTTP applications have historically allowed three different formats
2345   for date/time stamps. However, the preferred format is a fixed-length subset
2346   of that defined by <xref target="RFC1123"/>:
2347</t>
2348<figure><artwork type="example" x:indent-with="  ">
2349Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2350</artwork></figure>
2351<t>
2352   The other formats are described here only for compatibility with obsolete
2353   implementations.
2354</t>
2355<figure><artwork type="example" x:indent-with="  ">
2356Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2357Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2358</artwork></figure>
2359<t>
2360   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2361   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2362   only generate the RFC 1123 format for representing HTTP-date values
2363   in header fields.
2364</t>
2365<t>
2366   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2367   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2368   equal to UTC (Coordinated Universal Time). This is indicated in the
2369   first two formats by the inclusion of "GMT" as the three-letter
2370   abbreviation for time zone, and &MUST; be assumed when reading the
2371   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2372   additional whitespace beyond that specifically included as SP in the
2373   grammar.
2374</t>
2375<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2376  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2377</artwork></figure>
2378<t anchor="preferred.date.format">
2379  <x:anchor-alias value="rfc1123-date"/>
2380  <x:anchor-alias value="time-of-day"/>
2381  <x:anchor-alias value="hour"/>
2382  <x:anchor-alias value="minute"/>
2383  <x:anchor-alias value="second"/>
2384  <x:anchor-alias value="day-name"/>
2385  <x:anchor-alias value="day"/>
2386  <x:anchor-alias value="month"/>
2387  <x:anchor-alias value="year"/>
2388  <x:anchor-alias value="GMT"/>
2389  Preferred format:
2390</t>
2391<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc1123-date"/><iref primary="true" item="Grammar" subitem="date1"/><iref primary="true" item="Grammar" subitem="time-of-day"/><iref primary="true" item="Grammar" subitem="hour"/><iref primary="true" item="Grammar" subitem="minute"/><iref primary="true" item="Grammar" subitem="second"/><iref primary="true" item="Grammar" subitem="day-name"/><iref primary="true" item="Grammar" subitem="day-name-l"/><iref primary="true" item="Grammar" subitem="day"/><iref primary="true" item="Grammar" subitem="month"/><iref primary="true" item="Grammar" subitem="year"/><iref primary="true" item="Grammar" subitem="GMT"/>
2392  <x:ref>rfc1123-date</x:ref> = <x:ref>day-name</x:ref> "," <x:ref>SP</x:ref> date1 <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2393  ; fixed length subset of the format defined in
2394  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2395 
2396  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2397               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2398               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2399               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2400               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2401               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2402               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2403               
2404  <x:ref>date1</x:ref>        = <x:ref>day</x:ref> <x:ref>SP</x:ref> <x:ref>month</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2405               ; e.g., 02 Jun 1982
2406
2407  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2408  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2409               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2410               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2411               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2412               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2413               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2414               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2415               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2416               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2417               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2418               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2419               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2420  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2421
2422  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2423
2424  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2425                 ; 00:00:00 - 23:59:59
2426                 
2427  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2428  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2429  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2430</artwork></figure>
2431<t>
2432  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2433  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2434  same as those defined for the RFC 5322 constructs
2435  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2436</t>
2437<t anchor="obsolete.date.formats">
2438  <x:anchor-alias value="obs-date"/>
2439  <x:anchor-alias value="rfc850-date"/>
2440  <x:anchor-alias value="asctime-date"/>
2441  <x:anchor-alias value="date1"/>
2442  <x:anchor-alias value="date2"/>
2443  <x:anchor-alias value="date3"/>
2444  <x:anchor-alias value="rfc1123-date"/>
2445  <x:anchor-alias value="day-name-l"/>
2446  Obsolete formats:
2447</t>
2448<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2449  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2450</artwork></figure>
2451<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2452  <x:ref>rfc850-date</x:ref>  = <x:ref>day-name-l</x:ref> "," <x:ref>SP</x:ref> <x:ref>date2</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2453  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2454                 ; day-month-year (e.g., 02-Jun-82)
2455
2456  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2457         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2458         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2459         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2460         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2461         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2462         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2463</artwork></figure>
2464<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2465  <x:ref>asctime-date</x:ref> = <x:ref>day-name</x:ref> <x:ref>SP</x:ref> <x:ref>date3</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2466  <x:ref>date3</x:ref>        = <x:ref>month</x:ref> <x:ref>SP</x:ref> ( 2<x:ref>DIGIT</x:ref> / ( <x:ref>SP</x:ref> 1<x:ref>DIGIT</x:ref> ))
2467                 ; month day (e.g., Jun  2)
2468</artwork></figure>
2469<x:note>
2470  <t>
2471    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2472    accepting date values that might have been sent by non-HTTP
2473    applications, as is sometimes the case when retrieving or posting
2474    messages via proxies/gateways to SMTP or NNTP.
2475  </t>
2476</x:note>
2477<x:note>
2478  <t>
2479    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2480    to their usage within the protocol stream. Clients and servers are
2481    not required to use these formats for user presentation, request
2482    logging, etc.
2483  </t>
2484</x:note>
2485</section>
2486
2487
2488<section title="Header Field Definitions" anchor="header.field.definitions">
2489<t>
2490   This section defines the syntax and semantics of HTTP/1.1 header fields
2491   related to request and response semantics.
2492</t>
2493
2494<section title="Allow" anchor="header.allow">
2495  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2496  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2497  <x:anchor-alias value="Allow"/>
2498<t>
2499   The "Allow" header field lists the set of methods advertised as
2500   supported by the target resource. The purpose of this field is strictly to
2501   inform the recipient of valid request methods associated with the resource.
2502</t>
2503<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2504  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2505</artwork></figure>
2506<t>
2507   Example of use:
2508</t>
2509<figure><artwork type="example">
2510  Allow: GET, HEAD, PUT
2511</artwork></figure>
2512<t>
2513   The actual set of allowed methods is defined by the origin server at the
2514   time of each request.
2515</t>
2516<t>
2517   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2518   understand all the methods specified in order to handle them according to
2519   the generic message handling rules.
2520</t>
2521</section>
2522
2523<section title="Date" anchor="header.date">
2524  <iref primary="true" item="Date header field" x:for-anchor=""/>
2525  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2526  <x:anchor-alias value="Date"/>
2527<t>
2528   The "Date" header field represents the date and time at which
2529   the message was originated, having the same semantics as the Origination
2530   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2531   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2532   it &MUST; be sent in rfc1123-date format.
2533</t>
2534<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2535  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2536</artwork></figure>
2537<t>
2538   An example is
2539</t>
2540<figure><artwork type="example">
2541  Date: Tue, 15 Nov 1994 08:12:31 GMT
2542</artwork></figure>
2543<t>
2544   Origin servers &MUST; include a Date header field in all responses,
2545   except in these cases:
2546  <list style="numbers">
2547      <t>If the response status code is 100 (Continue) or 101 (Switching
2548         Protocols), the response &MAY; include a Date header field, at
2549         the server's option.</t>
2550
2551      <t>If the response status code conveys a server error, e.g., 500
2552         (Internal Server Error) or 503 (Service Unavailable), and it is
2553         inconvenient or impossible to generate a valid Date.</t>
2554
2555      <t>If the server does not have a clock that can provide a
2556         reasonable approximation of the current time, its responses
2557         &MUST-NOT; include a Date header field.</t>
2558  </list>
2559</t>
2560<t>
2561   A received message that does not have a Date header field &MUST; be
2562   assigned one by the recipient if the message will be cached by that
2563   recipient.
2564</t>
2565<t>
2566   Clients can use the Date header field as well; in order to keep request
2567   messages small, they are advised not to include it when it doesn't convey
2568   any useful information (as it is usually the case for requests that do not
2569   contain a payload).
2570</t>
2571<t>
2572   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2573   time subsequent to the generation of the message. It &SHOULD; represent
2574   the best available approximation of the date and time of message
2575   generation, unless the implementation has no means of generating a
2576   reasonably accurate date and time. In theory, the date ought to
2577   represent the moment just before the payload is generated. In
2578   practice, the date can be generated at any time during the message
2579   origination without affecting its semantic value.
2580</t>
2581</section>
2582
2583<section title="Expect" anchor="header.expect">
2584  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2585  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2586  <x:anchor-alias value="Expect"/>
2587  <x:anchor-alias value="expectation"/>
2588  <x:anchor-alias value="expect-param"/>
2589  <x:anchor-alias value="expect-name"/>
2590  <x:anchor-alias value="expect-value"/>
2591<t>
2592   The "Expect" header field is used to indicate that particular
2593   server behaviors are required by the client.
2594</t>
2595<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expect-param"/><iref primary="true" item="Grammar" subitem="expect-value"/><iref primary="true" item="Grammar" subitem="expect-name"/>
2596  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2597 
2598  <x:ref>expectation</x:ref>  = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2599                             *( <x:ref>OWS</x:ref> ";" [ <x:ref>OWS</x:ref> <x:ref>expect-param</x:ref> ] )
2600  <x:ref>expect-param</x:ref> = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2601 
2602  <x:ref>expect-name</x:ref>  = <x:ref>token</x:ref>
2603  <x:ref>expect-value</x:ref> = <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref>
2604</artwork></figure>
2605<t>
2606   If all received Expect header field(s) are syntactically valid but contain
2607   an expectation that the recipient does not understand or cannot comply with,
2608   the recipient &MUST; respond with a 417 (Expectation Failed) status code. A
2609   recipient of a syntactically invalid Expectation header field &MUST; respond
2610   with a 4xx status code other than 417.
2611</t>
2612<t>
2613   The only expectation defined by this specification is:
2614</t>
2615<t><iref primary="true" item="100-continue (expect value)"/><iref primary="true" item="Expect Values" subitem="100-continue"/>
2616  100-continue
2617   <list>
2618      <t>
2619        The "100-continue" expectation is defined &use100;. It does not support
2620        any expect-params.
2621      </t>
2622   </list>
2623</t>
2624<t>
2625   Comparison is case-insensitive for names (expect-name), and case-sensitive
2626   for values (expect-value).
2627</t>
2628<t>
2629   The Expect mechanism is hop-by-hop: the above requirements apply to any
2630   server, including proxies. However, the Expect header field itself is
2631   end-to-end; it &MUST; be forwarded if the request is forwarded.
2632</t>
2633<t>
2634   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect
2635   header field.
2636</t>
2637</section>
2638
2639<section title="From" anchor="header.from">
2640  <iref primary="true" item="From header field" x:for-anchor=""/>
2641  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2642  <x:anchor-alias value="From"/>
2643  <x:anchor-alias value="mailbox"/>
2644<t>
2645   The "From" header field, if given, &SHOULD; contain an Internet
2646   e-mail address for the human user who controls the requesting user
2647   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2648   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2649</t>
2650<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2651  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2652 
2653  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2654</artwork></figure>
2655<t>
2656   An example is:
2657</t>
2658<figure><artwork type="example">
2659  From: webmaster@example.org
2660</artwork></figure>
2661<t>
2662   This header field &MAY; be used for logging purposes and as a means for
2663   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2664   be used as an insecure form of access protection. The interpretation
2665   of this field is that the request is being performed on behalf of the
2666   person given, who accepts responsibility for the method performed. In
2667   particular, robot agents &SHOULD; include this header field so that the
2668   person responsible for running the robot can be contacted if problems
2669   occur on the receiving end.
2670</t>
2671<t>
2672   The Internet e-mail address in this field &MAY; be separate from the
2673   Internet host which issued the request. For example, when a request
2674   is passed through a proxy the original issuer's address &SHOULD; be
2675   used.
2676</t>
2677<t>
2678   The client &SHOULD-NOT;  send the From header field without the user's
2679   approval, as it might conflict with the user's privacy interests or
2680   their site's security policy. It is strongly recommended that the
2681   user be able to disable, enable, and modify the value of this field
2682   at any time prior to a request.
2683</t>
2684</section>
2685
2686<section title="Location" anchor="header.location">
2687  <iref primary="true" item="Location header field" x:for-anchor=""/>
2688  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2689  <x:anchor-alias value="Location"/>
2690<t>
2691   The "Location" header field is used to identify a newly created
2692   resource, or to redirect the recipient to a different location for
2693   completion of the request.
2694</t>
2695<t>
2696   For 201 (Created) responses, the Location is the URI of the new resource
2697   which was created by the request. For 3xx responses, the location &SHOULD;
2698   indicate the server's preferred URI for automatic redirection to the
2699   resource.
2700</t>
2701<t>
2702   The field value consists of a single URI-reference. When it has the form
2703   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2704   the final value is computed by resolving it against the effective request
2705   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2706</t>
2707<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2708  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2709</artwork></figure>
2710<figure>
2711<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2712<artwork type="example">
2713  Location: http://www.example.org/pub/WWW/People.html#tim
2714</artwork></figure><figure><artwork type="example">  Location: /index.html
2715</artwork></figure>
2716<x:note>
2717  <t>
2718    <x:h>Note:</x:h> Some recipients attempt to recover from Location fields
2719    that are not valid URI references. This specification does not mandate or
2720    define such processing, but does allow it (see <xref target="intro.conformance.and.error.handling"/>).
2721  </t>
2722</x:note>
2723<t>
2724   There are circumstances in which a fragment identifier in a Location URI
2725   would not be appropriate. For instance, when it appears in a 201 Created
2726   response, where the Location header field specifies the URI for the entire
2727   created resource.
2728</t>
2729<x:note>
2730  <t>
2731    <x:h>Note:</x:h> This specification does not define precedence rules
2732    for the case where the original URI, as navigated to by the user
2733    agent, and the Location header field value both contain fragment
2734    identifiers. Thus be aware that including fragment identifiers might
2735    inconvenience anyone relying on the semantics of the original URI's
2736    fragment identifier.
2737  </t>
2738</x:note>
2739<x:note>
2740  <t>
2741    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2742    from Location in that the Content-Location identifies the most specific
2743    resource corresponding to the enclosed representation.
2744    It is therefore possible for a response to contain header fields for
2745    both Location and Content-Location.
2746  </t>
2747</x:note>
2748</section>
2749
2750<section title="Max-Forwards" anchor="header.max-forwards">
2751  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2752  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2753  <x:anchor-alias value="Max-Forwards"/>
2754<t>
2755   The "Max-Forwards" header field provides a mechanism with the
2756   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2757   methods to limit the number of times that the request is forwarded by
2758   proxies. This can be useful when the client is attempting to
2759   trace a request which appears to be failing or looping in mid-chain.
2760</t>
2761<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2762  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2763</artwork></figure>
2764<t>
2765   The Max-Forwards value is a decimal integer indicating the remaining
2766   number of times this request message can be forwarded.
2767</t>
2768<t>
2769   Each recipient of a TRACE or OPTIONS request
2770   containing a Max-Forwards header field &MUST; check and update its
2771   value prior to forwarding the request. If the received value is zero
2772   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2773   respond as the final recipient. If the received Max-Forwards value is
2774   greater than zero, then the forwarded message &MUST; contain an updated
2775   Max-Forwards field with a value decremented by one (1).
2776</t>
2777<t>
2778   The Max-Forwards header field &MAY; be ignored for all other request
2779   methods.
2780</t>
2781</section>
2782
2783<section title="Referer" anchor="header.referer">
2784  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2785  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2786  <x:anchor-alias value="Referer"/>
2787<t>
2788   The "Referer" [sic] header field allows the client to specify the
2789   URI of the resource from which the effective request URI was obtained (the
2790   "referrer", although the header field is misspelled.).
2791</t>
2792<t>
2793   The Referer header field allows servers to generate lists of back-links to
2794   resources for interest, logging, optimized caching, etc. It also allows
2795   obsolete or mistyped links to be traced for maintenance. Some servers use
2796   Referer as a means of controlling where they allow links from (so-called
2797   "deep linking"), but legitimate requests do not always
2798   contain a Referer header field.
2799</t>
2800<t>
2801   If the effective request URI was obtained from a source that does not have its own
2802   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2803   sent with the value "about:blank", or not be sent at all. Note that this
2804   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2805</t>
2806<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2807  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2808</artwork></figure>
2809<t>
2810   Example:
2811</t>
2812<figure><artwork type="example">
2813  Referer: http://www.example.org/hypertext/Overview.html
2814</artwork></figure>
2815<t>
2816   If the field value is a relative URI, it &SHOULD; be interpreted
2817   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2818   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2819</t>
2820</section>
2821
2822<section title="Retry-After" anchor="header.retry-after">
2823  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2824  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2825  <x:anchor-alias value="Retry-After"/>
2826<t>
2827   The header "Retry-After" field can be used with a 503 (Service
2828   Unavailable) response to indicate how long the service is expected to
2829   be unavailable to the requesting client. This field &MAY; also be used
2830   with any 3xx (Redirection) response to indicate the minimum time the
2831   user-agent is asked wait before issuing the redirected request.
2832</t>
2833<t>
2834   The value of this field can be either an HTTP-date or an integer number
2835   of seconds (in decimal) after the time of the response.
2836</t>
2837<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2838  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2839</artwork></figure>
2840<t anchor="rule.delta-seconds">
2841  <x:anchor-alias value="delta-seconds"/>
2842   Time spans are non-negative decimal integers, representing time in
2843   seconds.
2844</t>
2845<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2846  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2847</artwork></figure>
2848<t>
2849   Two examples of its use are
2850</t>
2851<figure><artwork type="example">
2852  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2853  Retry-After: 120
2854</artwork></figure>
2855<t>
2856   In the latter example, the delay is 2 minutes.
2857</t>
2858</section>
2859
2860<section title="Server" anchor="header.server">
2861  <iref primary="true" item="Server header field" x:for-anchor=""/>
2862  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2863  <x:anchor-alias value="Server"/>
2864<t>
2865   The "Server" header field contains information about the
2866   software used by the origin server to handle the request.
2867</t>
2868<t>
2869   The field can contain multiple product tokens (&product-tokens;) and
2870   comments (&header-fields;) identifying the server and any significant
2871   subproducts. The product tokens are listed in order of their significance
2872   for identifying the application.
2873</t>
2874<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2875  <x:ref>Server</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2876</artwork></figure>
2877<t>
2878   Example:
2879</t>
2880<figure><artwork type="example">
2881  Server: CERN/3.0 libwww/2.17
2882</artwork></figure>
2883<t>
2884   If the response is being forwarded through a proxy, the proxy
2885   application &MUST-NOT; modify the Server header field. Instead, it
2886   &MUST; include a Via field (as described in &header-via;).
2887</t>
2888<x:note>
2889  <t>
2890    <x:h>Note:</x:h> Revealing the specific software version of the server might
2891    allow the server machine to become more vulnerable to attacks
2892    against software that is known to contain security holes. Server
2893    implementors are encouraged to make this field a configurable
2894    option.
2895  </t>
2896</x:note>
2897</section>
2898
2899<section title="User-Agent" anchor="header.user-agent">
2900  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2901  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2902  <x:anchor-alias value="User-Agent"/>
2903<t>
2904   The "User-Agent" header field contains information about the user
2905   agent originating the request. User agents &SHOULD; include this field with
2906   requests.
2907</t>
2908<t>
2909   Typically, it is used for statistical purposes, the tracing of protocol
2910   violations, and tailoring responses to avoid particular user agent
2911   limitations.
2912</t>
2913<t>
2914   The field can contain multiple product tokens (&product-tokens;)
2915   and comments (&header-fields;) identifying the agent and its
2916   significant subproducts. By convention, the product tokens are listed in
2917   order of their significance for identifying the application.
2918</t>
2919<t>
2920   Because this field is usually sent on every request a user agent makes,
2921   implementations are encouraged not to include needlessly fine-grained
2922   detail, and to limit (or even prohibit) the addition of subproducts by third
2923   parties. Overly long and detailed User-Agent field values make requests
2924   larger and can also be used to identify ("fingerprint") the user against
2925   their wishes.
2926</t>
2927<t>
2928   Likewise, implementations are encouraged not to use the product tokens of
2929   other implementations in order to declare compatibility with them, as this
2930   circumvents the purpose of the field. Finally, they are encouraged not to
2931   use comments to identify products; doing so makes the field value more
2932   difficult to parse.
2933</t>
2934<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2935  <x:ref>User-Agent</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2936</artwork></figure>
2937<t>
2938   Example:
2939</t>
2940<figure><artwork type="example">
2941  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2942</artwork></figure>
2943</section>
2944
2945</section>
2946
2947<section title="IANA Considerations" anchor="IANA.considerations">
2948
2949<section title="Method Registry" anchor="method.registration">
2950<t>
2951  The registration procedure for HTTP request methods is defined by
2952  <xref target="method.registry"/> of this document.
2953</t>
2954<t>
2955   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2956   and be populated with the registrations below:
2957</t>
2958<?BEGININC p2-semantics.iana-methods ?>
2959<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2960<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2961   <ttcol>Method</ttcol>
2962   <ttcol>Safe</ttcol>
2963   <ttcol>Reference</ttcol>
2964   <c>CONNECT</c>
2965   <c>no</c>
2966   <c>
2967      <xref target="CONNECT"/>
2968   </c>
2969   <c>DELETE</c>
2970   <c>no</c>
2971   <c>
2972      <xref target="DELETE"/>
2973   </c>
2974   <c>GET</c>
2975   <c>yes</c>
2976   <c>
2977      <xref target="GET"/>
2978   </c>
2979   <c>HEAD</c>
2980   <c>yes</c>
2981   <c>
2982      <xref target="HEAD"/>
2983   </c>
2984   <c>OPTIONS</c>
2985   <c>yes</c>
2986   <c>
2987      <xref target="OPTIONS"/>
2988   </c>
2989   <c>POST</c>
2990   <c>no</c>
2991   <c>
2992      <xref target="POST"/>
2993   </c>
2994   <c>PUT</c>
2995   <c>no</c>
2996   <c>
2997      <xref target="PUT"/>
2998   </c>
2999   <c>TRACE</c>
3000   <c>yes</c>
3001   <c>
3002      <xref target="TRACE"/>
3003   </c>
3004</texttable>
3005<!--(END)-->
3006<?ENDINC p2-semantics.iana-methods ?>
3007</section>
3008
3009<section title="Status Code Registry" anchor="status.code.registration">
3010<t>
3011   The registration procedure for HTTP Status Codes &mdash; previously defined
3012   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
3013   by <xref target="status.code.registry"/> of this document.
3014</t>
3015<t>
3016   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
3017   shall be updated with the registrations below:
3018</t>
3019<?BEGININC p2-semantics.iana-status-codes ?>
3020<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
3021<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
3022   <ttcol>Value</ttcol>
3023   <ttcol>Description</ttcol>
3024   <ttcol>Reference</ttcol>
3025   <c>100</c>
3026   <c>Continue</c>
3027   <c>
3028      <xref target="status.100"/>
3029   </c>
3030   <c>101</c>
3031   <c>Switching Protocols</c>
3032   <c>
3033      <xref target="status.101"/>
3034   </c>
3035   <c>200</c>
3036   <c>OK</c>
3037   <c>
3038      <xref target="status.200"/>
3039   </c>
3040   <c>201</c>
3041   <c>Created</c>
3042   <c>
3043      <xref target="status.201"/>
3044   </c>
3045   <c>202</c>
3046   <c>Accepted</c>
3047   <c>
3048      <xref target="status.202"/>
3049   </c>
3050   <c>203</c>
3051   <c>Non-Authoritative Information</c>
3052   <c>
3053      <xref target="status.203"/>
3054   </c>
3055   <c>204</c>
3056   <c>No Content</c>
3057   <c>
3058      <xref target="status.204"/>
3059   </c>
3060   <c>205</c>
3061   <c>Reset Content</c>
3062   <c>
3063      <xref target="status.205"/>
3064   </c>
3065   <c>300</c>
3066   <c>Multiple Choices</c>
3067   <c>
3068      <xref target="status.300"/>
3069   </c>
3070   <c>301</c>
3071   <c>Moved Permanently</c>
3072   <c>
3073      <xref target="status.301"/>
3074   </c>
3075   <c>302</c>
3076   <c>Found</c>
3077   <c>
3078      <xref target="status.302"/>
3079   </c>
3080   <c>303</c>
3081   <c>See Other</c>
3082   <c>
3083      <xref target="status.303"/>
3084   </c>
3085   <c>305</c>
3086   <c>Use Proxy</c>
3087   <c>
3088      <xref target="status.305"/>
3089   </c>
3090   <c>306</c>
3091   <c>(Unused)</c>
3092   <c>
3093      <xref target="status.306"/>
3094   </c>
3095   <c>307</c>
3096   <c>Temporary Redirect</c>
3097   <c>
3098      <xref target="status.307"/>
3099   </c>
3100   <c>400</c>
3101   <c>Bad Request</c>
3102   <c>
3103      <xref target="status.400"/>
3104   </c>
3105   <c>402</c>
3106   <c>Payment Required</c>
3107   <c>
3108      <xref target="status.402"/>
3109   </c>
3110   <c>403</c>
3111   <c>Forbidden</c>
3112   <c>
3113      <xref target="status.403"/>
3114   </c>
3115   <c>404</c>
3116   <c>Not Found</c>
3117   <c>
3118      <xref target="status.404"/>
3119   </c>
3120   <c>405</c>
3121   <c>Method Not Allowed</c>
3122   <c>
3123      <xref target="status.405"/>
3124   </c>
3125   <c>406</c>
3126   <c>Not Acceptable</c>
3127   <c>
3128      <xref target="status.406"/>
3129   </c>
3130   <c>407</c>
3131   <c>Proxy Authentication Required</c>
3132   <c>
3133      <xref target="status.407"/>
3134   </c>
3135   <c>408</c>
3136   <c>Request Timeout</c>
3137   <c>
3138      <xref target="status.408"/>
3139   </c>
3140   <c>409</c>
3141   <c>Conflict</c>
3142   <c>
3143      <xref target="status.409"/>
3144   </c>
3145   <c>410</c>
3146   <c>Gone</c>
3147   <c>
3148      <xref target="status.410"/>
3149   </c>
3150   <c>411</c>
3151   <c>Length Required</c>
3152   <c>
3153      <xref target="status.411"/>
3154   </c>
3155   <c>413</c>
3156   <c>Request Representation Too Large</c>
3157   <c>
3158      <xref target="status.413"/>
3159   </c>
3160   <c>414</c>
3161   <c>URI Too Long</c>
3162   <c>
3163      <xref target="status.414"/>
3164   </c>
3165   <c>415</c>
3166   <c>Unsupported Media Type</c>
3167   <c>
3168      <xref target="status.415"/>
3169   </c>
3170   <c>417</c>
3171   <c>Expectation Failed</c>
3172   <c>
3173      <xref target="status.417"/>
3174   </c>
3175   <c>426</c>
3176   <c>Upgrade Required</c>
3177   <c>
3178      <xref target="status.426"/>
3179   </c>
3180   <c>500</c>
3181   <c>Internal Server Error</c>
3182   <c>
3183      <xref target="status.500"/>
3184   </c>
3185   <c>501</c>
3186   <c>Not Implemented</c>
3187   <c>
3188      <xref target="status.501"/>
3189   </c>
3190   <c>502</c>
3191   <c>Bad Gateway</c>
3192   <c>
3193      <xref target="status.502"/>
3194   </c>
3195   <c>503</c>
3196   <c>Service Unavailable</c>
3197   <c>
3198      <xref target="status.503"/>
3199   </c>
3200   <c>504</c>
3201   <c>Gateway Timeout</c>
3202   <c>
3203      <xref target="status.504"/>
3204   </c>
3205   <c>505</c>
3206   <c>HTTP Version Not Supported</c>
3207   <c>
3208      <xref target="status.505"/>
3209   </c>
3210</texttable>
3211<!--(END)-->
3212<?ENDINC p2-semantics.iana-status-codes ?>
3213</section>
3214<section title="Header Field Registration" anchor="header.field.registration">
3215<t>
3216   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3217   with the permanent registrations below (see <xref target="RFC3864"/>):
3218</t>
3219<?BEGININC p2-semantics.iana-headers ?>
3220<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3221<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3222   <ttcol>Header Field Name</ttcol>
3223   <ttcol>Protocol</ttcol>
3224   <ttcol>Status</ttcol>
3225   <ttcol>Reference</ttcol>
3226
3227   <c>Allow</c>
3228   <c>http</c>
3229   <c>standard</c>
3230   <c>
3231      <xref target="header.allow"/>
3232   </c>
3233   <c>Date</c>
3234   <c>http</c>
3235   <c>standard</c>
3236   <c>
3237      <xref target="header.date"/>
3238   </c>
3239   <c>Expect</c>
3240   <c>http</c>
3241   <c>standard</c>
3242   <c>
3243      <xref target="header.expect"/>
3244   </c>
3245   <c>From</c>
3246   <c>http</c>
3247   <c>standard</c>
3248   <c>
3249      <xref target="header.from"/>
3250   </c>
3251   <c>Location</c>
3252   <c>http</c>
3253   <c>standard</c>
3254   <c>
3255      <xref target="header.location"/>
3256   </c>
3257   <c>Max-Forwards</c>
3258   <c>http</c>
3259   <c>standard</c>
3260   <c>
3261      <xref target="header.max-forwards"/>
3262   </c>
3263   <c>Referer</c>
3264   <c>http</c>
3265   <c>standard</c>
3266   <c>
3267      <xref target="header.referer"/>
3268   </c>
3269   <c>Retry-After</c>
3270   <c>http</c>
3271   <c>standard</c>
3272   <c>
3273      <xref target="header.retry-after"/>
3274   </c>
3275   <c>Server</c>
3276   <c>http</c>
3277   <c>standard</c>
3278   <c>
3279      <xref target="header.server"/>
3280   </c>
3281   <c>User-Agent</c>
3282   <c>http</c>
3283   <c>standard</c>
3284   <c>
3285      <xref target="header.user-agent"/>
3286   </c>
3287</texttable>
3288<!--(END)-->
3289<?ENDINC p2-semantics.iana-headers ?>
3290<t>
3291   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3292</t>
3293</section>
3294</section>
3295
3296<section title="Security Considerations" anchor="security.considerations">
3297<t>
3298   This section is meant to inform application developers, information
3299   providers, and users of the security limitations in HTTP/1.1 as
3300   described by this document. The discussion does not include
3301   definitive solutions to the problems revealed, though it does make
3302   some suggestions for reducing security risks.
3303</t>
3304
3305<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3306<t>
3307   Like any generic data transfer protocol, HTTP cannot regulate the
3308   content of the data that is transferred, nor is there any a priori
3309   method of determining the sensitivity of any particular piece of
3310   information within the context of any given request. Therefore,
3311   applications &SHOULD; supply as much control over this information as
3312   possible to the provider of that information. Four header fields are
3313   worth special mention in this context: Server, Via, Referer and From.
3314</t>
3315<t>
3316   Revealing the specific software version of the server might allow the
3317   server machine to become more vulnerable to attacks against software
3318   that is known to contain security holes. Implementors &SHOULD; make the
3319   Server header field a configurable option.
3320</t>
3321<t>
3322   Proxies which serve as a portal through a network firewall &SHOULD;
3323   take special precautions regarding the transfer of header information
3324   that identifies the hosts behind the firewall. In particular, they
3325   &SHOULD; remove, or replace with sanitized versions, any Via fields
3326   generated behind the firewall.
3327</t>
3328<t>
3329   The Referer header field allows reading patterns to be studied and reverse
3330   links drawn. Although it can be very useful, its power can be abused
3331   if user details are not separated from the information contained in
3332   the Referer. Even when the personal information has been removed, the
3333   Referer header field might indicate a private document's URI whose
3334   publication would be inappropriate.
3335</t>
3336<t>
3337   The information sent in the From field might conflict with the user's
3338   privacy interests or their site's security policy, and hence it
3339   &SHOULD-NOT;  be transmitted without the user being able to disable,
3340   enable, and modify the contents of the field. The user &MUST; be able
3341   to set the contents of this field within a user preference or
3342   application defaults configuration.
3343</t>
3344<t>
3345   We suggest, though do not require, that a convenient toggle interface
3346   be provided for the user to enable or disable the sending of From and
3347   Referer information.
3348</t>
3349<t>
3350   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3351   target="header.server"/>) header fields can sometimes be used to determine
3352   that a specific client or server have a particular security hole which might
3353   be exploited. Unfortunately, this same information is often used for other
3354   valuable purposes for which HTTP currently has no better mechanism.
3355</t>
3356<t>
3357   Furthermore, the User-Agent header field may contain enough entropy to be
3358   used, possibly in conjunction with other material, to uniquely identify the
3359   user.
3360</t>
3361<t>
3362   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3363   that was sent in request header fields within the body of their response.
3364   Clients &SHOULD; be careful with sensitive information, like Cookies,
3365   Authorization credentials, and other header fields that might be used to
3366   collect data from the client.
3367</t> 
3368</section>
3369
3370<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3371<t>
3372   Because the source of a link might be private information or might
3373   reveal an otherwise private information source, it is strongly
3374   recommended that the user be able to select whether or not the
3375   Referer field is sent. For example, a browser client could have a
3376   toggle switch for browsing openly/anonymously, which would
3377   respectively enable/disable the sending of Referer and From
3378   information.
3379</t>
3380<t>
3381   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3382   HTTP request if the referring page was transferred with a secure
3383   protocol.
3384</t>
3385<t>
3386   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3387   sensitive data because that data will be placed in the request-target. Many
3388   existing servers, proxies, and user agents log or display the request-target
3389   in places where it might be visible to third parties. Such services can
3390   use POST-based form submission instead.
3391</t>
3392</section>
3393
3394<section title="Location Headers and Spoofing" anchor="location.spoofing">
3395<t>
3396   If a single server supports multiple organizations that do not trust
3397   one another, then it &MUST; check the values of Location and Content-Location
3398   header fields in responses that are generated under control of
3399   said organizations to make sure that they do not attempt to
3400   invalidate resources over which they have no authority.
3401</t>
3402</section>
3403
3404<section title="Security Considerations for CONNECT">
3405<t>
3406   Since tunneled data is opaque to the proxy, there are additional
3407   risks to tunneling to other well-known or reserved ports.
3408   A HTTP client CONNECTing to port 25 could relay spam
3409   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3410   access to a small number of known ports.
3411</t>
3412</section>
3413
3414</section>
3415
3416<section title="Acknowledgments" anchor="acks">
3417<t>
3418  See &acks;.
3419</t>
3420</section>
3421</middle>
3422<back>
3423
3424<references title="Normative References">
3425
3426<reference anchor="Part1">
3427  <front>
3428    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3429    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3430      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3431      <address><email>fielding@gbiv.com</email></address>
3432    </author>
3433    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3434      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3435      <address><email>jg@freedesktop.org</email></address>
3436    </author>
3437    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3438      <organization abbrev="HP">Hewlett-Packard Company</organization>
3439      <address><email>JeffMogul@acm.org</email></address>
3440    </author>
3441    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3442      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3443      <address><email>henrikn@microsoft.com</email></address>
3444    </author>
3445    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3446      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3447      <address><email>LMM@acm.org</email></address>
3448    </author>
3449    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3450      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3451      <address><email>paulle@microsoft.com</email></address>
3452    </author>
3453    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3454      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3455      <address><email>timbl@w3.org</email></address>
3456    </author>
3457    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3458      <organization abbrev="W3C">World Wide Web Consortium</organization>
3459      <address><email>ylafon@w3.org</email></address>
3460    </author>
3461    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3462      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3463      <address><email>julian.reschke@greenbytes.de</email></address>
3464    </author>
3465    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3466  </front>
3467  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3468  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3469</reference>
3470
3471<reference anchor="Part3">
3472  <front>
3473    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3474    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3475      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3476      <address><email>fielding@gbiv.com</email></address>
3477    </author>
3478    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3479      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3480      <address><email>jg@freedesktop.org</email></address>
3481    </author>
3482    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3483      <organization abbrev="HP">Hewlett-Packard Company</organization>
3484      <address><email>JeffMogul@acm.org</email></address>
3485    </author>
3486    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3487      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3488      <address><email>henrikn@microsoft.com</email></address>
3489    </author>
3490    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3491      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3492      <address><email>LMM@acm.org</email></address>
3493    </author>
3494    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3495      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3496      <address><email>paulle@microsoft.com</email></address>
3497    </author>
3498    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3499      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3500      <address><email>timbl@w3.org</email></address>
3501    </author>
3502    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3503      <organization abbrev="W3C">World Wide Web Consortium</organization>
3504      <address><email>ylafon@w3.org</email></address>
3505    </author>
3506    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3507      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3508      <address><email>julian.reschke@greenbytes.de</email></address>
3509    </author>
3510    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3511  </front>
3512  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3513  <x:source href="p3-payload.xml" basename="p3-payload"/>
3514</reference>
3515
3516<reference anchor="Part4">
3517  <front>
3518    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3519    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3520      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3521      <address><email>fielding@gbiv.com</email></address>
3522    </author>
3523    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3524      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3525      <address><email>jg@freedesktop.org</email></address>
3526    </author>
3527    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3528      <organization abbrev="HP">Hewlett-Packard Company</organization>
3529      <address><email>JeffMogul@acm.org</email></address>
3530    </author>
3531    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3532      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3533      <address><email>henrikn@microsoft.com</email></address>
3534    </author>
3535    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3536      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3537      <address><email>LMM@acm.org</email></address>
3538    </author>
3539    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3540      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3541      <address><email>paulle@microsoft.com</email></address>
3542    </author>
3543    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3544      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3545      <address><email>timbl@w3.org</email></address>
3546    </author>
3547    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3548      <organization abbrev="W3C">World Wide Web Consortium</organization>
3549      <address><email>ylafon@w3.org</email></address>
3550    </author>
3551    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3552      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3553      <address><email>julian.reschke@greenbytes.de</email></address>
3554    </author>
3555    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3556  </front>
3557  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3558  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3559</reference>
3560
3561<reference anchor="Part5">
3562  <front>
3563    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3564    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3565      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3566      <address><email>fielding@gbiv.com</email></address>
3567    </author>
3568    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3569      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3570      <address><email>jg@freedesktop.org</email></address>
3571    </author>
3572    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3573      <organization abbrev="HP">Hewlett-Packard Company</organization>
3574      <address><email>JeffMogul@acm.org</email></address>
3575    </author>
3576    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3577      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3578      <address><email>henrikn@microsoft.com</email></address>
3579    </author>
3580    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3581      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3582      <address><email>LMM@acm.org</email></address>
3583    </author>
3584    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3585      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3586      <address><email>paulle@microsoft.com</email></address>
3587    </author>
3588    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3589      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3590      <address><email>timbl@w3.org</email></address>
3591    </author>
3592    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3593      <organization abbrev="W3C">World Wide Web Consortium</organization>
3594      <address><email>ylafon@w3.org</email></address>
3595    </author>
3596    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3597      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3598      <address><email>julian.reschke@greenbytes.de</email></address>
3599    </author>
3600    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3601  </front>
3602  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3603  <x:source href="p5-range.xml" basename="p5-range"/>
3604</reference>
3605
3606<reference anchor="Part6">
3607  <front>
3608    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3609    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3610      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3611      <address><email>fielding@gbiv.com</email></address>
3612    </author>
3613    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3614      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3615      <address><email>jg@freedesktop.org</email></address>
3616    </author>
3617    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3618      <organization abbrev="HP">Hewlett-Packard Company</organization>
3619      <address><email>JeffMogul@acm.org</email></address>
3620    </author>
3621    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3622      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3623      <address><email>henrikn@microsoft.com</email></address>
3624    </author>
3625    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3626      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3627      <address><email>LMM@acm.org</email></address>
3628    </author>
3629    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3630      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3631      <address><email>paulle@microsoft.com</email></address>
3632    </author>
3633    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3634      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3635      <address><email>timbl@w3.org</email></address>
3636    </author>
3637    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3638      <organization abbrev="W3C">World Wide Web Consortium</organization>
3639      <address><email>ylafon@w3.org</email></address>
3640    </author>
3641    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3642      <organization>Rackspace</organization>
3643      <address><email>mnot@mnot.net</email></address>
3644    </author>
3645    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3646      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3647      <address><email>julian.reschke@greenbytes.de</email></address>
3648    </author>
3649    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3650  </front>
3651  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3652  <x:source href="p6-cache.xml" basename="p6-cache"/>
3653</reference>
3654
3655<reference anchor="Part7">
3656  <front>
3657    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3658    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3659      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3660      <address><email>fielding@gbiv.com</email></address>
3661    </author>
3662    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3663      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3664      <address><email>jg@freedesktop.org</email></address>
3665    </author>
3666    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3667      <organization abbrev="HP">Hewlett-Packard Company</organization>
3668      <address><email>JeffMogul@acm.org</email></address>
3669    </author>
3670    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3671      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3672      <address><email>henrikn@microsoft.com</email></address>
3673    </author>
3674    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3675      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3676      <address><email>LMM@acm.org</email></address>
3677    </author>
3678    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3679      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3680      <address><email>paulle@microsoft.com</email></address>
3681    </author>
3682    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3683      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3684      <address><email>timbl@w3.org</email></address>
3685    </author>
3686    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3687      <organization abbrev="W3C">World Wide Web Consortium</organization>
3688      <address><email>ylafon@w3.org</email></address>
3689    </author>
3690    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3691      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3692      <address><email>julian.reschke@greenbytes.de</email></address>
3693    </author>
3694    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3695  </front>
3696  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3697  <x:source href="p7-auth.xml" basename="p7-auth"/>
3698</reference>
3699
3700<reference anchor="RFC2119">
3701  <front>
3702    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3703    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3704      <organization>Harvard University</organization>
3705      <address><email>sob@harvard.edu</email></address>
3706    </author>
3707    <date month="March" year="1997"/>
3708  </front>
3709  <seriesInfo name="BCP" value="14"/>
3710  <seriesInfo name="RFC" value="2119"/>
3711</reference>
3712
3713<reference anchor="RFC3986">
3714 <front>
3715  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3716  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3717    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3718    <address>
3719       <email>timbl@w3.org</email>
3720       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3721    </address>
3722  </author>
3723  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3724    <organization abbrev="Day Software">Day Software</organization>
3725    <address>
3726      <email>fielding@gbiv.com</email>
3727      <uri>http://roy.gbiv.com/</uri>
3728    </address>
3729  </author>
3730  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3731    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3732    <address>
3733      <email>LMM@acm.org</email>
3734      <uri>http://larry.masinter.net/</uri>
3735    </address>
3736  </author>
3737  <date month='January' year='2005'></date>
3738 </front>
3739 <seriesInfo name="STD" value="66"/>
3740 <seriesInfo name="RFC" value="3986"/>
3741</reference>
3742
3743<reference anchor="RFC5234">
3744  <front>
3745    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3746    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3747      <organization>Brandenburg InternetWorking</organization>
3748      <address>
3749        <email>dcrocker@bbiw.net</email>
3750      </address> 
3751    </author>
3752    <author initials="P." surname="Overell" fullname="Paul Overell">
3753      <organization>THUS plc.</organization>
3754      <address>
3755        <email>paul.overell@thus.net</email>
3756      </address>
3757    </author>
3758    <date month="January" year="2008"/>
3759  </front>
3760  <seriesInfo name="STD" value="68"/>
3761  <seriesInfo name="RFC" value="5234"/>
3762</reference>
3763
3764</references>
3765
3766<references title="Informative References">
3767
3768<reference anchor="RFC1123">
3769  <front>
3770    <title>Requirements for Internet Hosts - Application and Support</title>
3771    <author initials="R." surname="Braden" fullname="Robert Braden">
3772      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3773      <address><email>Braden@ISI.EDU</email></address>
3774    </author>
3775    <date month="October" year="1989"/>
3776  </front>
3777  <seriesInfo name="STD" value="3"/>
3778  <seriesInfo name="RFC" value="1123"/>
3779</reference>
3780
3781<reference anchor="RFC1945">
3782  <front>
3783    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3784    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3785      <organization>MIT, Laboratory for Computer Science</organization>
3786      <address><email>timbl@w3.org</email></address>
3787    </author>
3788    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3789      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3790      <address><email>fielding@ics.uci.edu</email></address>
3791    </author>
3792    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3793      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3794      <address><email>frystyk@w3.org</email></address>
3795    </author>
3796    <date month="May" year="1996"/>
3797  </front>
3798  <seriesInfo name="RFC" value="1945"/>
3799</reference>
3800
3801<reference anchor="RFC2068">
3802  <front>
3803    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3804    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3805      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3806      <address><email>fielding@ics.uci.edu</email></address>
3807    </author>
3808    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3809      <organization>MIT Laboratory for Computer Science</organization>
3810      <address><email>jg@w3.org</email></address>
3811    </author>
3812    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3813      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3814      <address><email>mogul@wrl.dec.com</email></address>
3815    </author>
3816    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3817      <organization>MIT Laboratory for Computer Science</organization>
3818      <address><email>frystyk@w3.org</email></address>
3819    </author>
3820    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3821      <organization>MIT Laboratory for Computer Science</organization>
3822      <address><email>timbl@w3.org</email></address>
3823    </author>
3824    <date month="January" year="1997"/>
3825  </front>
3826  <seriesInfo name="RFC" value="2068"/>
3827</reference>
3828
3829<reference anchor="RFC2616">
3830  <front>
3831    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3832    <author initials="R." surname="Fielding" fullname="R. Fielding">
3833      <organization>University of California, Irvine</organization>
3834      <address><email>fielding@ics.uci.edu</email></address>
3835    </author>
3836    <author initials="J." surname="Gettys" fullname="J. Gettys">
3837      <organization>W3C</organization>
3838      <address><email>jg@w3.org</email></address>
3839    </author>
3840    <author initials="J." surname="Mogul" fullname="J. Mogul">
3841      <organization>Compaq Computer Corporation</organization>
3842      <address><email>mogul@wrl.dec.com</email></address>
3843    </author>
3844    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3845      <organization>MIT Laboratory for Computer Science</organization>
3846      <address><email>frystyk@w3.org</email></address>
3847    </author>
3848    <author initials="L." surname="Masinter" fullname="L. Masinter">
3849      <organization>Xerox Corporation</organization>
3850      <address><email>masinter@parc.xerox.com</email></address>
3851    </author>
3852    <author initials="P." surname="Leach" fullname="P. Leach">
3853      <organization>Microsoft Corporation</organization>
3854      <address><email>paulle@microsoft.com</email></address>
3855    </author>
3856    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3857      <organization>W3C</organization>
3858      <address><email>timbl@w3.org</email></address>
3859    </author>
3860    <date month="June" year="1999"/>
3861  </front>
3862  <seriesInfo name="RFC" value="2616"/>
3863</reference>
3864
3865<reference anchor='RFC2817'>
3866  <front>
3867    <title>Upgrading to TLS Within HTTP/1.1</title>
3868    <author initials='R.' surname='Khare' fullname='R. Khare'>
3869      <organization>4K Associates / UC Irvine</organization>
3870      <address><email>rohit@4K-associates.com</email></address>
3871    </author>
3872    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3873      <organization>Agranat Systems, Inc.</organization>
3874      <address><email>lawrence@agranat.com</email></address>
3875    </author>
3876    <date year='2000' month='May' />
3877  </front>
3878  <seriesInfo name='RFC' value='2817' />
3879</reference>
3880
3881<reference anchor='RFC3864'>
3882  <front>
3883    <title>Registration Procedures for Message Header Fields</title>
3884    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3885      <organization>Nine by Nine</organization>
3886      <address><email>GK-IETF@ninebynine.org</email></address>
3887    </author>
3888    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3889      <organization>BEA Systems</organization>
3890      <address><email>mnot@pobox.com</email></address>
3891    </author>
3892    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3893      <organization>HP Labs</organization>
3894      <address><email>JeffMogul@acm.org</email></address>
3895    </author>
3896    <date year='2004' month='September' />
3897  </front>
3898  <seriesInfo name='BCP' value='90' />
3899  <seriesInfo name='RFC' value='3864' />
3900</reference>
3901
3902<reference anchor='RFC5226'>
3903  <front>
3904    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3905    <author initials='T.' surname='Narten' fullname='T. Narten'>
3906      <organization>IBM</organization>
3907      <address><email>narten@us.ibm.com</email></address>
3908    </author>
3909    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3910      <organization>Google</organization>
3911      <address><email>Harald@Alvestrand.no</email></address>
3912    </author>
3913    <date year='2008' month='May' />
3914  </front>
3915  <seriesInfo name='BCP' value='26' />
3916  <seriesInfo name='RFC' value='5226' />
3917</reference>
3918
3919<reference anchor="RFC5322">
3920  <front>
3921    <title>Internet Message Format</title>
3922    <author initials="P." surname="Resnick" fullname="P. Resnick">
3923      <organization>Qualcomm Incorporated</organization>
3924    </author>
3925    <date year="2008" month="October"/>
3926  </front> 
3927  <seriesInfo name="RFC" value="5322"/>
3928</reference>
3929
3930<reference anchor='RFC5789'>
3931  <front>
3932    <title>PATCH Method for HTTP</title>
3933    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3934      <organization>Linden Lab</organization>
3935    </author>
3936    <author initials='J.' surname='Snell' fullname='J. Snell' />
3937    <date year='2010' month='March' />
3938  </front>
3939  <seriesInfo name='RFC' value='5789' />
3940</reference>
3941
3942<reference anchor="RFC5987">
3943        <front>
3944    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3945    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3946      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3947      <address>
3948        <postal>
3949          <street>Hafenweg 16</street>
3950          <city>Muenster</city><region>NW</region><code>48155</code>
3951          <country>Germany</country>
3952        </postal>
3953        <email>julian.reschke@greenbytes.de</email>     
3954        <uri>http://greenbytes.de/tech/webdav/</uri>   
3955      </address>
3956    </author>
3957    <date month="August" year="2010"/>
3958  </front>
3959  <seriesInfo name="RFC" value="5987"/>
3960</reference>
3961
3962</references>
3963
3964<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3965<t>
3966  This document takes over the Status Code Registry, previously defined
3967  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3968  (<xref target="status.code.registry"/>)
3969</t>
3970<t>
3971  Clarify definition of POST.
3972  (<xref target="POST"/>)
3973</t>
3974<t>
3975  Remove requirement to handle all Content-* header fields; ban use of
3976  Content-Range with PUT.
3977  (<xref target="PUT"/>)
3978</t>
3979<t>
3980  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3981  (<xref target="CONNECT"/>)
3982</t>
3983<t>
3984  Broadened the definition of 203 (Non-Authoritative Information) to include
3985  cases of payload transformations as well.
3986  (<xref target="status.203"/>)
3987</t>
3988<t>
3989  Failed to consider that there are many other request methods that are safe
3990  to automatically redirect, and further that the user agent is able to make
3991  that determination based on the request method semantics.
3992  Furthermore, allow user agents to rewrite the method from POST to GET
3993  for status codes 301 and 302.
3994  (Sections <xref format="counter" target="status.301"/>,
3995  <xref format="counter" target="status.302"/> and
3996  <xref format="counter" target="status.307"/>)
3997</t>
3998<t>
3999  Deprecate 305 Use Proxy status code, because user agents did not implement it.
4000  It used to indicate that the target resource must be accessed through the
4001  proxy given by the Location field. The Location field gave the URI of the
4002  proxy. The recipient was expected to repeat this single request via the proxy.
4003  (<xref target="status.305"/>)
4004</t>
4005<t>
4006  Define status 426 (Upgrade Required) (this was incorporated from
4007  <xref target="RFC2817"/>).
4008  (<xref target="status.426"/>)
4009</t>
4010<t>
4011  Change ABNF productions for header fields to only define the field value.
4012  (<xref target="header.field.definitions"/>)
4013</t>
4014<t>
4015  Reclassify "Allow" as response header field, removing the option to
4016  specify it in a PUT request.
4017  Relax the server requirement on the contents of the Allow header field and
4018  remove requirement on clients to always trust the header field value.
4019  (<xref target="header.allow"/>)
4020</t>
4021<t>
4022  The ABNF for the Expect header field has been both fixed (allowing parameters
4023  for value-less expectations as well) and simplified (allowing trailing
4024  semicolons after "100-continue" when they were invalid before).
4025  (<xref target="header.expect"/>)
4026</t>
4027<t>
4028  Correct syntax of Location header field to allow URI references (including
4029  relative references and fragments), as referred symbol "absoluteURI" wasn't
4030  what was expected, and add some clarifications as to when use of fragments
4031  would not be appropriate.
4032  (<xref target="header.location"/>)
4033</t>
4034<t>
4035  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
4036  extension methods could have used it as well).
4037  (<xref target="header.max-forwards"/>)
4038</t>
4039<t>
4040  Allow Referer field value of "about:blank" as alternative to not specifying it.
4041  (<xref target="header.referer"/>)
4042</t>
4043<t>
4044  In the description of the Server header field, the Via field
4045  was described as a SHOULD. The requirement was and is stated
4046  correctly in the description of the Via header field in &header-via;.
4047  (<xref target="header.server"/>)
4048</t>
4049</section>
4050
4051<?BEGININC p2-semantics.abnf-appendix ?>
4052<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
4053<figure>
4054<artwork type="abnf" name="p2-semantics.parsed-abnf">
4055<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
4056
4057<x:ref>BWS</x:ref> = &lt;BWS, defined in [Part1], Section 1.2.2&gt;
4058
4059<x:ref>Date</x:ref> = HTTP-date
4060
4061<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
4062
4063<x:ref>From</x:ref> = mailbox
4064
4065<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4066
4067<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4068
4069<x:ref>Location</x:ref> = URI-reference
4070
4071<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4072<x:ref>Method</x:ref> = token
4073
4074<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
4075
4076<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
4077<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4078<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4079<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4080
4081<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4082<x:ref>Status-Code</x:ref> = 3DIGIT
4083
4084<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4085<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4086
4087<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4088<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4089
4090<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2.3&gt;
4091
4092<x:ref>date1</x:ref> = day SP month SP year
4093<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4094<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4095<x:ref>day</x:ref> = 2DIGIT
4096<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4097 / %x54.75.65 ; Tue
4098 / %x57.65.64 ; Wed
4099 / %x54.68.75 ; Thu
4100 / %x46.72.69 ; Fri
4101 / %x53.61.74 ; Sat
4102 / %x53.75.6E ; Sun
4103<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4104 / %x54.75.65.73.64.61.79 ; Tuesday
4105 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4106 / %x54.68.75.72.73.64.61.79 ; Thursday
4107 / %x46.72.69.64.61.79 ; Friday
4108 / %x53.61.74.75.72.64.61.79 ; Saturday
4109 / %x53.75.6E.64.61.79 ; Sunday
4110<x:ref>delta-seconds</x:ref> = 1*DIGIT
4111
4112<x:ref>expect-name</x:ref> = token
4113<x:ref>expect-param</x:ref> = expect-name [ BWS "=" BWS expect-value ]
4114<x:ref>expect-value</x:ref> = token / quoted-string
4115<x:ref>expectation</x:ref> = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
4116 OWS expect-param ] )
4117
4118<x:ref>hour</x:ref> = 2DIGIT
4119
4120<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4121<x:ref>minute</x:ref> = 2DIGIT
4122<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4123 / %x46.65.62 ; Feb
4124 / %x4D.61.72 ; Mar
4125 / %x41.70.72 ; Apr
4126 / %x4D.61.79 ; May
4127 / %x4A.75.6E ; Jun
4128 / %x4A.75.6C ; Jul
4129 / %x41.75.67 ; Aug
4130 / %x53.65.70 ; Sep
4131 / %x4F.63.74 ; Oct
4132 / %x4E.6F.76 ; Nov
4133 / %x44.65.63 ; Dec
4134
4135<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4136<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4137
4138<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4139<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4140
4141<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4142
4143<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4144<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4145
4146<x:ref>second</x:ref> = 2DIGIT
4147
4148<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4149<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4150
4151<x:ref>year</x:ref> = 4DIGIT
4152</artwork>
4153</figure>
4154<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4155; Allow defined but not used
4156; Date defined but not used
4157; Expect defined but not used
4158; From defined but not used
4159; Location defined but not used
4160; Max-Forwards defined but not used
4161; Reason-Phrase defined but not used
4162; Referer defined but not used
4163; Retry-After defined but not used
4164; Server defined but not used
4165; Status-Code defined but not used
4166; User-Agent defined but not used
4167</artwork></figure></section>
4168<?ENDINC p2-semantics.abnf-appendix ?>
4169
4170<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4171
4172<section title="Since RFC 2616">
4173<t>
4174  Extracted relevant partitions from <xref target="RFC2616"/>.
4175</t>
4176</section>
4177
4178<section title="Since draft-ietf-httpbis-p2-semantics-00">
4179<t>
4180  Closed issues:
4181  <list style="symbols"> 
4182    <t>
4183      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4184      "Via is a MUST"
4185      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4186    </t>
4187    <t>
4188      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4189      "Fragments allowed in Location"
4190      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4191    </t>
4192    <t>
4193      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4194      "Safe Methods vs Redirection"
4195      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4196    </t>
4197    <t>
4198      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4199      "Revise description of the POST method"
4200      (<eref target="http://purl.org/NET/http-errata#post"/>)
4201    </t>
4202    <t>
4203      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4204      "Normative and Informative references"
4205    </t>
4206    <t>
4207      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4208      "RFC2606 Compliance"
4209    </t>
4210    <t>
4211      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4212      "Informative references"
4213    </t>
4214    <t>
4215      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4216      "Redundant cross-references"
4217    </t>
4218  </list>
4219</t>
4220<t>
4221  Other changes:
4222  <list style="symbols"> 
4223    <t>
4224      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4225    </t>
4226  </list>
4227</t>
4228</section>
4229
4230<section title="Since draft-ietf-httpbis-p2-semantics-01">
4231<t>
4232  Closed issues:
4233  <list style="symbols"> 
4234    <t>
4235      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4236      "PUT side effects"
4237    </t>
4238    <t>
4239      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4240      "Duplicate Host header requirements"
4241    </t>
4242  </list>
4243</t>
4244<t>
4245  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4246  <list style="symbols"> 
4247    <t>
4248      Move "Product Tokens" section (back) into Part 1, as "token" is used
4249      in the definition of the Upgrade header field.
4250    </t>
4251    <t>
4252      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4253    </t>
4254    <t>
4255      Copy definition of delta-seconds from Part6 instead of referencing it.
4256    </t>
4257  </list>
4258</t>
4259</section>
4260
4261<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4262<t>
4263  Closed issues:
4264  <list style="symbols"> 
4265    <t>
4266      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4267      "Requiring Allow in 405 responses"
4268    </t>
4269    <t>
4270      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4271      "Status Code Registry"
4272    </t>
4273    <t>
4274      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4275      "Redirection vs. Location"
4276    </t>
4277    <t>
4278      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4279      "Cacheability of 303 response"
4280    </t>
4281    <t>
4282      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4283      "305 Use Proxy"
4284    </t>
4285    <t>
4286      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4287      "Classification for Allow header"
4288    </t>
4289    <t>
4290      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4291      "PUT - 'store under' vs 'store at'"
4292    </t>
4293  </list>
4294</t>
4295<t>
4296  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4297  <list style="symbols"> 
4298    <t>
4299      Reference RFC 3984, and update header field registrations for headers defined
4300      in this document.
4301    </t>
4302  </list>
4303</t>
4304<t>
4305  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4306  <list style="symbols"> 
4307    <t>
4308      Replace string literals when the string really is case-sensitive (method).
4309    </t>
4310  </list>
4311</t>
4312</section>
4313
4314<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4315<t>
4316  Closed issues:
4317  <list style="symbols"> 
4318    <t>
4319      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4320      "OPTIONS request bodies"
4321    </t>
4322    <t>
4323      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4324      "Description of CONNECT should refer to RFC2817"
4325    </t>
4326    <t>
4327      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4328      "Location Content-Location reference request/response mixup"
4329    </t>
4330  </list>
4331</t>
4332<t>
4333  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4334  <list style="symbols"> 
4335    <t>
4336      Added initial proposal for registration process, plus initial
4337      content (non-HTTP/1.1 methods to be added by a separate specification).
4338    </t>
4339  </list>
4340</t>
4341</section>
4342
4343<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4344<t>
4345  Closed issues:
4346  <list style="symbols"> 
4347    <t>
4348      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4349      "Content-*"
4350    </t>
4351    <t>
4352      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4353      "RFC 2822 is updated by RFC 5322"
4354    </t>
4355  </list>
4356</t>
4357<t>
4358  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4359  <list style="symbols"> 
4360    <t>
4361      Use "/" instead of "|" for alternatives.
4362    </t>
4363    <t>
4364      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4365      whitespace ("OWS") and required whitespace ("RWS").
4366    </t>
4367    <t>
4368      Rewrite ABNFs to spell out whitespace rules, factor out
4369      header field value format definitions.
4370    </t>
4371  </list>
4372</t>
4373</section>
4374
4375<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4376<t>
4377  Closed issues:
4378  <list style="symbols"> 
4379    <t>
4380      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4381      "Reason-Phrase BNF"
4382    </t>
4383  </list>
4384</t>
4385<t>
4386  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4387  <list style="symbols"> 
4388    <t>
4389      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4390    </t>
4391  </list>
4392</t>
4393</section>
4394
4395<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4396<t>
4397  Closed issues:
4398  <list style="symbols"> 
4399    <t>
4400      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4401      "Clarify when Referer is sent"
4402    </t>
4403    <t>
4404      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4405      "status codes vs methods"
4406    </t>
4407    <t>
4408      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4409      "Do not require "updates" relation for specs that register status codes or method names"
4410    </t>
4411  </list>
4412</t>
4413</section>
4414
4415<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4416<t>
4417  Closed issues:
4418  <list style="symbols"> 
4419    <t>
4420      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4421      "Idempotency"
4422    </t>
4423    <t>
4424      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4425      "TRACE security considerations"
4426    </t>
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4429      "Clarify rules for determining what entities a response carries"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4433      "update note citing RFC 1945 and 2068"
4434    </t>
4435    <t>
4436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4437      "update note about redirect limit"
4438    </t>
4439    <t>
4440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4441      "Location header ABNF should use 'URI'"
4442    </t>
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4445      "fragments in Location vs status 303"
4446    </t>
4447    <t>
4448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4449      "move IANA registrations for optional status codes"
4450    </t>
4451  </list>
4452</t>
4453<t>
4454  Partly resolved issues:
4455  <list style="symbols"> 
4456    <t>
4457      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4458      "Are OPTIONS and TRACE safe?"
4459    </t>
4460  </list>
4461</t>
4462</section>
4463
4464<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4465<t>
4466  Closed issues:
4467  <list style="symbols"> 
4468    <t>
4469      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4470      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4471      status codes when fixing this previously)
4472    </t>
4473  </list>
4474</t>
4475</section>
4476
4477<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4478<t>
4479  Closed issues:
4480  <list style="symbols"> 
4481    <t>
4482      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4483      "Fragment combination / precedence during redirects"
4484    </t>
4485  </list>
4486</t>
4487<t>
4488  Partly resolved issues:
4489  <list style="symbols"> 
4490    <t>
4491      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4492      "Location header payload handling"
4493    </t>
4494    <t>
4495      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4496      "Term for the requested resource's URI"
4497    </t>
4498  </list>
4499</t>
4500</section>
4501
4502<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4503<t>
4504  Closed issues:
4505  <list style="symbols"> 
4506    <t>
4507      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4508      "Clarify 'Requested Variant'"
4509    </t>
4510    <t>
4511      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4512      "Clarify entity / representation / variant terminology"
4513    </t>
4514    <t>
4515      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4516      "Methods and Caching"
4517    </t>
4518    <t>
4519      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4520      "OPTIONS vs Max-Forwards"
4521    </t>
4522    <t>
4523      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4524      "Status codes and caching"
4525    </t>
4526    <t>
4527      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4528      "consider removing the 'changes from 2068' sections"
4529    </t>
4530  </list>
4531</t>
4532</section>
4533
4534<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4535<t>
4536  Closed issues:
4537  <list style="symbols"> 
4538    <t>
4539      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4540      "Considerations for new status codes"
4541    </t>
4542    <t>
4543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4544      "Considerations for new methods"
4545    </t>
4546    <t>
4547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4548      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4549    </t>
4550  </list>
4551</t>
4552</section>
4553
4554<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4555<t>
4556  Closed issues:
4557  <list style="symbols"> 
4558    <t>
4559      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4560      "Fragment combination / precedence during redirects" (added warning
4561      about having a fragid on the redirect may cause inconvenience in
4562      some cases)
4563    </t>
4564    <t>
4565      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4566      "Content-* vs. PUT"
4567    </t>
4568    <t>
4569      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4570      "205 Bodies"
4571    </t>
4572    <t>
4573      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4574      "Understanding Content-* on non-PUT requests"
4575    </t>
4576    <t>
4577      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4578      "Content-*"
4579    </t>
4580    <t>
4581      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4582      "Header type defaulting"
4583    </t>
4584    <t>
4585      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4586      "PUT - 'store under' vs 'store at'"
4587    </t>
4588    <t>
4589      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4590      "duplicate ABNF for Reason-Phrase"
4591    </t>
4592    <t>
4593      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4594      "Note special status of Content-* prefix in header registration procedures"
4595    </t>
4596    <t>
4597      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4598      "Max-Forwards vs extension methods"
4599    </t>
4600    <t>
4601      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4602      "What is the value space of HTTP status codes?" (actually fixed in
4603      draft-ietf-httpbis-p2-semantics-11)
4604    </t>
4605    <t>
4606      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4607      "Header Classification"
4608    </t>
4609    <t>
4610      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4611      "PUT side effect: invalidation or just stale?"
4612    </t>
4613    <t>
4614      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4615      "proxies not supporting certain methods"
4616    </t>
4617    <t>
4618      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4619      "Migrate CONNECT from RFC2817 to p2"
4620    </t>
4621    <t>
4622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4623      "Migrate Upgrade details from RFC2817"
4624    </t>
4625    <t>
4626      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4627      "clarify PUT semantics'"
4628    </t>
4629    <t>
4630      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4631      "duplicate ABNF for 'Method'"
4632    </t>
4633    <t>
4634      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4635      "untangle ABNFs for header fields"
4636    </t>
4637  </list>
4638</t>
4639</section>
4640
4641<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4642<t>
4643  Closed issues:
4644  <list style="symbols"> 
4645    <t>
4646      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4647      "untangle ABNFs for header fields"
4648    </t>
4649    <t>
4650      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4651      "message-body in CONNECT request"
4652    </t>
4653  </list>
4654</t>
4655</section>
4656
4657<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4658<t>
4659  Closed issues:
4660  <list style="symbols"> 
4661    <t>
4662      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4663      "Clarify status code for rate limiting"
4664    </t>
4665    <t>
4666      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4667      "clarify 403 forbidden"
4668    </t>
4669    <t>
4670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4671      "Clarify 203 Non-Authoritative Information"
4672    </t>
4673    <t>
4674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4675      "update default reason phrase for 413"
4676    </t>
4677  </list>
4678</t>
4679</section>
4680
4681<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4682<t>
4683  Closed issues:
4684  <list style="symbols"> 
4685    <t>
4686      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4687      "Strength of requirements on Accept re: 406"
4688    </t>
4689    <t>
4690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4691      "400 response isn't generic"
4692    </t>
4693  </list>
4694</t>
4695</section>
4696
4697<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4698<t>
4699  Closed issues:
4700  <list style="symbols"> 
4701    <t>
4702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4703      "Redirects and non-GET methods"
4704    </t>
4705    <t>
4706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4707      "Document HTTP's error-handling philosophy"
4708    </t>
4709    <t>
4710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4711      "Considerations for new headers"
4712    </t>
4713    <t>
4714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4715      "clarify 303 redirect on HEAD"
4716    </t>
4717  </list>
4718</t>
4719</section>
4720
4721<section title="Since draft-ietf-httpbis-p2-semantics-17" anchor="changes.since.17">
4722<t>
4723  Closed issues:
4724  <list style="symbols"> 
4725    <t>
4726      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4727      "Location header payload handling"
4728    </t>
4729    <t>
4730      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4731      "Clarify status code for rate limiting" (change backed out because
4732      a new status code is being defined for this purpose)
4733    </t>
4734    <t>
4735      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/312"/>:
4736      "should there be a permanent variant of 307"
4737    </t>
4738    <t>
4739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/325"/>:
4740      "When are Location's semantics triggered?"
4741    </t>
4742    <t>
4743      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/327"/>:
4744      "'expect' grammar missing OWS"
4745    </t>
4746    <t>
4747      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/329"/>:
4748      "header field considerations: quoted-string vs use of double quotes"
4749    </t>
4750  </list>
4751</t>
4752</section>
4753
4754<section title="Since draft-ietf-httpbis-p2-semantics-18" anchor="changes.since.18">
4755<t>
4756  Closed issues:
4757  <list style="symbols"> 
4758    <t>
4759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/333"/>:
4760      "example for 426 response should have a payload"
4761    </t>
4762  </list>
4763</t>
4764</section>
4765
4766</section>
4767
4768</back>
4769</rfc>
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