source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1466

Last change on this file since 1466 was 1466, checked in by julian.reschke@…, 8 years ago

Mark issue as done (see #231)

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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 "October">
16  <!ENTITY ID-YEAR "2011">
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="draft"
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<front>
107
108  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
109
110  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
111    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
112    <address>
113      <postal>
114        <street>345 Park Ave</street>
115        <city>San Jose</city>
116        <region>CA</region>
117        <code>95110</code>
118        <country>USA</country>
119      </postal>
120      <email>fielding@gbiv.com</email>
121      <uri>http://roy.gbiv.com/</uri>
122    </address>
123  </author>
124
125  <author initials="J." surname="Gettys" fullname="Jim Gettys">
126    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
127    <address>
128      <postal>
129        <street>21 Oak Knoll Road</street>
130        <city>Carlisle</city>
131        <region>MA</region>
132        <code>01741</code>
133        <country>USA</country>
134      </postal>
135      <email>jg@freedesktop.org</email>
136      <uri>http://gettys.wordpress.com/</uri>
137    </address>
138  </author>
139 
140  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
141    <organization abbrev="HP">Hewlett-Packard Company</organization>
142    <address>
143      <postal>
144        <street>HP Labs, Large Scale Systems Group</street>
145        <street>1501 Page Mill Road, MS 1177</street>
146        <city>Palo Alto</city>
147        <region>CA</region>
148        <code>94304</code>
149        <country>USA</country>
150      </postal>
151      <email>JeffMogul@acm.org</email>
152    </address>
153  </author>
154
155  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
156    <organization abbrev="Microsoft">Microsoft Corporation</organization>
157    <address>
158      <postal>
159        <street>1 Microsoft Way</street>
160        <city>Redmond</city>
161        <region>WA</region>
162        <code>98052</code>
163        <country>USA</country>
164      </postal>
165      <email>henrikn@microsoft.com</email>
166    </address>
167  </author>
168
169  <author initials="L." surname="Masinter" fullname="Larry Masinter">
170    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
171    <address>
172      <postal>
173        <street>345 Park Ave</street>
174        <city>San Jose</city>
175        <region>CA</region>
176        <code>95110</code>
177        <country>USA</country>
178      </postal>
179      <email>LMM@acm.org</email>
180      <uri>http://larry.masinter.net/</uri>
181    </address>
182  </author>
183 
184  <author initials="P." surname="Leach" fullname="Paul J. Leach">
185    <organization abbrev="Microsoft">Microsoft Corporation</organization>
186    <address>
187      <postal>
188        <street>1 Microsoft Way</street>
189        <city>Redmond</city>
190        <region>WA</region>
191        <code>98052</code>
192      </postal>
193      <email>paulle@microsoft.com</email>
194    </address>
195  </author>
196   
197  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
198    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
199    <address>
200      <postal>
201        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
202        <street>The Stata Center, Building 32</street>
203        <street>32 Vassar Street</street>
204        <city>Cambridge</city>
205        <region>MA</region>
206        <code>02139</code>
207        <country>USA</country>
208      </postal>
209      <email>timbl@w3.org</email>
210      <uri>http://www.w3.org/People/Berners-Lee/</uri>
211    </address>
212  </author>
213
214  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
215    <organization abbrev="W3C">World Wide Web Consortium</organization>
216    <address>
217      <postal>
218        <street>W3C / ERCIM</street>
219        <street>2004, rte des Lucioles</street>
220        <city>Sophia-Antipolis</city>
221        <region>AM</region>
222        <code>06902</code>
223        <country>France</country>
224      </postal>
225      <email>ylafon@w3.org</email>
226      <uri>http://www.raubacapeu.net/people/yves/</uri>
227    </address>
228  </author>
229
230  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
231    <organization abbrev="greenbytes">greenbytes GmbH</organization>
232    <address>
233      <postal>
234        <street>Hafenweg 16</street>
235        <city>Muenster</city><region>NW</region><code>48155</code>
236        <country>Germany</country>
237      </postal>
238      <phone>+49 251 2807760</phone>
239      <facsimile>+49 251 2807761</facsimile>
240      <email>julian.reschke@greenbytes.de</email>
241      <uri>http://greenbytes.de/tech/webdav/</uri>
242    </address>
243  </author>
244
245  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
246  <workgroup>HTTPbis Working Group</workgroup>
247
248<abstract>
249<t>
250   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
251   distributed, collaborative, hypertext information systems. HTTP has been in
252   use by the World Wide Web global information initiative since 1990. This
253   document is Part 2 of the seven-part specification that defines the protocol
254   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
255</t>
256<t>
257   Part 2 defines the semantics of HTTP messages as expressed by request
258   methods, request header fields, response status codes, and response header
259   fields.
260</t>
261</abstract>
262
263<note title="Editorial Note (To be removed by RFC Editor)">
264  <t>
265    Discussion of this draft should take place on the HTTPBIS working group
266    mailing list (ietf-http-wg@w3.org), which is archived at
267    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
268  </t>
269  <t>
270    The current issues list is at
271    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
272    documents (including fancy diffs) can be found at
273    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
274  </t>
275  <t>
276    The changes in this draft are summarized in <xref target="changes.since.16"/>.
277  </t>
278</note>
279</front>
280<middle>
281<section title="Introduction" anchor="introduction">
282<t>
283   This document defines HTTP/1.1 request and response semantics.  Each HTTP
284   message, as defined in &messaging;, is in the form of either a request or
285   a response.  An HTTP server listens on a connection for HTTP requests and
286   responds to each request, in the order received on that connection, with
287   one or more HTTP response messages.  This document defines the commonly
288   agreed upon semantics of the HTTP uniform interface, the intentions defined
289   by each request method, and the various response messages that might be
290   expected as a result of applying that method to the target resource.
291</t>
292<t>
293   This document is currently disorganized in order to minimize the changes
294   between drafts and enable reviewers to see the smaller errata changes.
295   A future draft will reorganize the sections to better reflect the content.
296   In particular, the sections will be ordered according to the typical
297   processing of an HTTP request message (after message parsing): resource
298   mapping, methods, request modifying header fields, response status,
299   status modifying header fields, and resource metadata.  The current mess
300   reflects how widely dispersed these topics and associated requirements
301   had become in <xref target="RFC2616"/>.
302</t>
303
304<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
305<t>
306   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
307   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
308   document are to be interpreted as described in <xref target="RFC2119"/>.
309</t>
310<t>
311   This document defines conformance criteria for several roles in HTTP
312   communication, including Senders, Recipients, Clients, Servers, User-Agents,
313   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
314   for definitions of these terms.
315</t>
316<t>
317   An implementation is considered conformant if it complies with all of the
318   requirements associated with its role(s). Note that SHOULD-level requirements
319   are relevant here, unless one of the documented exceptions is applicable.
320</t>
321<t>
322   This document also uses ABNF to define valid protocol elements
323   (<xref target="notation"/>). In addition to the prose requirements placed
324   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
325</t>
326<t>
327   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
328   protocol element from an invalid construct. However, HTTP does not define
329   specific error handling mechanisms, except in cases where it has direct
330   impact on security. This is because different uses of the protocol require
331   different error handling strategies; for example, a Web browser may wish to
332   transparently recover from a response where the Location header field
333   doesn't parse according to the ABNF, whereby in a systems control protocol
334   using HTTP, this type of error recovery could lead to dangerous consequences.
335</t>
336</section>
337
338<section title="Syntax Notation" anchor="notation">
339  <x:anchor-alias value="CR"/>
340  <x:anchor-alias value="DIGIT"/>
341  <x:anchor-alias value="LF"/>
342  <x:anchor-alias value="HTAB"/>
343  <x:anchor-alias value="VCHAR"/>
344  <x:anchor-alias value="SP"/>
345<t>
346  This specification uses the ABNF syntax defined in &notation; (which
347  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
348  <xref target="collected.abnf"/> shows the collected ABNF, with the list
349  rule expanded.
350</t>
351<t>
352  The following core rules are included by
353  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
354  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
355  DIGIT (decimal 0-9), DQUOTE (double quote),
356  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
357  OCTET (any 8-bit sequence of data), SP (space), and
358  VCHAR (any visible US-ASCII character).
359</t>
360
361<section title="Core Rules" anchor="core.rules">
362  <x:anchor-alias value="obs-text"/>
363  <x:anchor-alias value="quoted-string"/>
364  <x:anchor-alias value="token"/>
365  <x:anchor-alias value="OWS"/>
366  <x:anchor-alias value="RWS"/>
367<t>
368  The core rules below are defined in <xref target="Part1"/>:
369</t>
370<figure><artwork type="abnf2616">
371  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
372  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
373  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
374  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
375  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
376</artwork></figure>
377</section>
378
379<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
380  <x:anchor-alias value="absolute-URI"/>
381  <x:anchor-alias value="comment"/>
382  <x:anchor-alias value="partial-URI"/>
383  <x:anchor-alias value="product"/>
384  <x:anchor-alias value="URI-reference"/>
385<t>
386  The ABNF rules below are defined in other parts:
387</t>
388<figure><!--Part1--><artwork type="abnf2616">
389  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
390  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
391  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
392  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
393  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
394</artwork></figure>
395</section>
396</section>
397</section>
398
399<section title="Method" anchor="method">
400  <x:anchor-alias value="Method"/>
401  <x:anchor-alias value="extension-method"/>
402<t>
403   The Method token indicates the request method to be performed on the target
404   resource (&effective-request-uri;). The method is case-sensitive.
405</t>
406<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
407  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
408</artwork></figure>
409<t>
410   The list of methods allowed by a resource can be specified in an
411   Allow header field (<xref target="header.allow"/>). The status code of the response
412   always notifies the client whether a method is currently allowed on a
413   resource, since the set of allowed methods can change dynamically. An
414   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
415   if the method is known by the origin server but not allowed for the
416   resource, and 501 (Not Implemented) if the method is
417   unrecognized or not implemented by the origin server. The methods GET
418   and HEAD &MUST; be supported by all general-purpose servers. All other
419   methods are &OPTIONAL;; however, if the above methods are implemented,
420   they &MUST; be implemented with the same semantics as those specified
421   in <xref target="method.definitions"/>.
422</t>
423
424<section title="Overview of Methods" anchor="overview.of.methods">
425<t>
426  The methods listed below are defined in <xref target="method.definitions"/>.
427</t>
428<texttable align="left">
429  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
430 
431  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
432  <c>GET</c> <c><xref target="GET"/></c>
433  <c>HEAD</c> <c><xref target="HEAD"/></c>
434  <c>POST</c> <c><xref target="POST"/></c>
435  <c>PUT</c> <c><xref target="PUT"/></c>
436  <c>DELETE</c> <c><xref target="DELETE"/></c>
437  <c>TRACE</c> <c><xref target="TRACE"/></c>
438  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
439</texttable>
440<t>
441  Note that this list is not exhaustive &mdash; it does not include request methods defined
442  in other specifications.
443</t>
444</section>
445
446<section title="Method Registry" anchor="method.registry">
447<t>
448  The HTTP Method Registry defines the name space for the Method token in the
449  Request line of an HTTP request.
450</t>
451<t>
452  Registrations &MUST; include the following fields:
453  <list style="symbols">
454    <t>Method Name (see <xref target="method"/>)</t>
455    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
456    <t>Pointer to specification text</t>
457  </list>
458</t>
459<t>
460  Values to be added to this name space are subject to IETF review
461  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
462</t>
463<t>
464  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
465</t>
466
467<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
468<t>
469   When it is necessary to express new semantics for a HTTP request that
470   aren't specific to a single application or media type, and currently defined
471   methods are inadequate, it may be appropriate to register a new method.
472</t>
473<t>
474   HTTP methods are generic; that is, they are potentially applicable to any
475   resource, not just one particular media type, "type" of resource, or
476   application. As such, it is preferred that new HTTP methods be registered
477   in a document that isn't specific to a single application, so that this is
478   clear.
479</t>
480<t>
481   Due to the parsing rules defined in &message-body;, definitions of HTTP
482   methods cannot prohibit the presence of a message-body on either the request
483   or the response message (with responses to HEAD requests being the single
484   exception). Definitions of new methods cannot change this rule, but they can
485   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
486</t>
487<t>
488   New method definitions need to indicate whether they are safe (<xref
489   target="safe.methods"/>), what semantics (if any) the request body has,
490   and whether they are idempotent (<xref target="idempotent.methods"/>).
491   They also need to state whether they can be cached (&caching;); in
492   particular what conditions a cache may store the response, and under what
493   conditions such a stored response may be used to satisfy a subsequent
494   request.
495</t>
496</section>
497
498</section>
499</section>
500
501<section title="Header Fields" anchor="header.fields">
502<t>
503   Header fields are key value pairs that can be used to communicate data about
504   the message, its payload, the target resource, or about the connection
505   itself (i.e., control data).  See &header-fields; for a general definition
506   of their syntax.
507</t>
508
509<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
510<t>
511   New header fields are registered using the procedures described in
512   <xref target="RFC3864"/>.
513</t>
514<t>
515   The requirements for header field names are defined in
516   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
517   defining new fields are advised to keep the name as short as practical, and
518   not to prefix them with "X-" if they are to be registered (either
519   immediately or in the future).
520</t>
521<t>
522   New header field values typically have their syntax defined using ABNF
523   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
524   as necessary, and are usually constrained to the range of ASCII characters.
525   Header fields needing a greater range of characters can use an encoding
526   such as the one defined in <xref target="RFC5987"/>.
527</t>
528<t>
529   Because commas (",") are used as a generic delimiter between field-values,
530   they need to be treated with care if they are allowed in the field-value's
531   payload. Typically, components that might contain a comma are protected with
532   double-quotes using the quoted-string ABNF production (&field-rules;).
533</t>
534<t>
535   For example, a textual date and a URI (either of which might contain a comma)
536   could be safely carried in field-values like these:
537</t>
538<figure><artwork type="example">
539  Example-URI-Field: "http://example.com/a.html,foo",
540                     "http://without-a-comma.example.com/"
541  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
542</artwork></figure>
543<t>
544   Many header fields use a format including (case-insensitively) named
545   parameters (for instance, Content-Type, defined in &header-content-type;).
546   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
547   parameter value enables recipients to use existing parser components. When
548   allowing both forms, the meaning of a parameter value ought to be
549   independent of the syntax used for it (for an example, see the notes on
550   parameter handling for media types in &media-types;).
551</t>
552<t>
553   Authors of specifications defining new header fields are advised to consider
554   documenting:
555  <list style="symbols">
556    <x:lt>
557      <t>Whether the field is a single value, or whether it can be a list
558      (delimited by commas; see &header-fields;).</t>
559      <t>If it does not use the list syntax, document how to treat messages
560      where the header field occurs multiple times (a sensible default would
561      be to ignore the header field, but this might not always be the right
562      choice).</t>
563      <t>Note that intermediaries and software libraries might combine
564      multiple header field instances into a single one, despite the header
565      field not allowing this. A robust format enables recipients to discover
566      these situations (good example: "Content-Type", as the comma can only
567      appear inside quoted strings; bad example: "Location", as a comma can
568      occur inside a URI).</t>
569    </x:lt>
570    <x:lt><t>Under what conditions the header field can be used; e.g., only in
571    responses or requests, in all messages, only on responses to a particular
572    request method.</t></x:lt>
573    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
574    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
575    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
576    field's value, insert or delete it.</t></x:lt>
577    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
578    <x:lt><t>Whether the header field is useful or allowable in trailers (see
579    &chunked-encoding;).</t></x:lt>
580    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
581  </list>
582</t>
583</section>
584
585<section title="Request Header Fields" anchor="request.header.fields">
586  <x:anchor-alias value="request-header"/>
587<t>
588   The request header fields allow the client to pass additional
589   information about the request, and about the client itself, to the
590   server. These fields act as request modifiers, with semantics
591   equivalent to the parameters on a programming language method
592   invocation.
593</t>
594<texttable align="left">
595  <ttcol>Header Field Name</ttcol>
596  <ttcol>Defined in...</ttcol>
597
598  <c>Accept</c> <c>&header-accept;</c>
599  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
600  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
601  <c>Accept-Language</c> <c>&header-accept-language;</c>
602  <c>Authorization</c> <c>&header-authorization;</c>
603  <c>Expect</c> <c><xref target="header.expect"/></c>
604  <c>From</c> <c><xref target="header.from"/></c>
605  <c>Host</c> <c>&header-host;</c>
606  <c>If-Match</c> <c>&header-if-match;</c>
607  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
608  <c>If-None-Match</c> <c>&header-if-none-match;</c>
609  <c>If-Range</c> <c>&header-if-range;</c>
610  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
611  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
612  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
613  <c>Range</c> <c>&header-range;</c>
614  <c>Referer</c> <c><xref target="header.referer"/></c>
615  <c>TE</c> <c>&header-te;</c>
616  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
617</texttable>
618</section>
619
620<section title="Response Header Fields" anchor="response.header.fields">
621  <x:anchor-alias value="response-header"/>
622<t>
623   The response header fields allow the server to pass additional
624   information about the response which cannot be placed in the Status-Line.
625   These header fields give information about the server and about
626   further access to the target resource (&effective-request-uri;).
627</t>
628<texttable align="left">
629  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
630
631  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
632  <c>Age</c> <c>&header-age;</c>
633  <c>Allow</c> <c><xref target="header.allow"/></c>
634  <c>Date</c> <c><xref target="header.date"/></c>
635  <c>ETag</c> <c>&header-etag;</c>
636  <c>Location</c> <c><xref target="header.location"/></c>
637  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
638  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
639  <c>Server</c> <c><xref target="header.server"/></c>
640  <c>Vary</c> <c>&header-vary;</c>
641  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
642</texttable>
643</section>
644
645</section>
646
647<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
648  <x:anchor-alias value="Reason-Phrase"/>
649  <x:anchor-alias value="Status-Code"/>
650  <x:anchor-alias value="extension-code"/>
651<t>
652   The Status-Code element is a 3-digit integer result code of the attempt to
653   understand and satisfy the request.
654</t>
655<t>
656   The Reason-Phrase is intended to give a short textual description of the
657   Status-Code and is intended for a human user. The client does not need
658   to examine or display the Reason-Phrase.
659</t>
660<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"/>
661  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
662  <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> )
663</artwork></figure>
664<t>
665   HTTP status codes are extensible. HTTP applications are not required
666   to understand the meaning of all registered status codes, though such
667   understanding is obviously desirable. However, applications &MUST;
668   understand the class of any status code, as indicated by the first
669   digit, and treat any unrecognized response as being equivalent to the
670   x00 status code of that class, with the exception that an
671   unrecognized response &MUST-NOT; be cached. For example, if an
672   unrecognized status code of 431 is received by the client, it can
673   safely assume that there was something wrong with its request and
674   treat the response as if it had received a 400 status code. In such
675   cases, user agents &SHOULD; present to the user the representation enclosed
676   with the response, since that representation is likely to include human-readable
677   information which will explain the unusual status.
678</t>
679
680<section title="Overview of Status Codes" anchor="overview.of.status.codes">
681<t> 
682   The status codes listed below are defined in <xref target="status.codes"/>
683   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
684   The reason phrases listed here are only recommendations &mdash; they can be
685   replaced by local equivalents without affecting the protocol.
686</t>
687<texttable align="left">
688  <ttcol>Status-Code</ttcol>
689  <ttcol>Reason-Phrase</ttcol>
690  <ttcol>Defined in...</ttcol>
691 
692  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
693  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
694
695  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
696  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
697  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
698  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
699  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
700  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
701  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
702
703  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
704  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
705  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
706  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
707  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
708  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
709  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
710
711  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
712  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
713  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
714  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
715  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
716  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
717  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
718  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
719  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
720  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
721  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
722  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
723  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
724  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
725  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
726  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
727  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
728  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
729  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
730
731  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
732  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
733  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
734  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
735  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
736  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
737</texttable>
738<t>
739   Note that this list is not exhaustive &mdash; it does not include
740   extension status codes defined in other specifications.
741</t>
742</section>
743
744<section title="Status Code Registry" anchor="status.code.registry">
745<t>
746  The HTTP Status Code Registry defines the name space for the Status-Code
747  token in the Status-Line of an HTTP response.
748</t>
749<t>
750  Values to be added to this name space are subject to IETF review
751  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
752</t>
753<t>
754  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
755</t>
756
757<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
758<t>
759   When it is necessary to express new semantics for a HTTP response that
760   aren't specific to a single application or media type, and currently defined
761   status codes are inadequate, a new status code can be registered.
762</t>
763<t>
764   HTTP status codes are generic; that is, they are potentially applicable to
765   any resource, not just one particular media type, "type" of resource, or
766   application. As such, it is preferred that new HTTP status codes be
767   registered in a document that isn't specific to a single application, so
768   that this is clear.
769</t>
770<t>
771   Definitions of new HTTP status codes typically explain the request
772   conditions that produce a response containing the status code (e.g.,
773   combinations of request headers and/or method(s)), along with any
774   interactions with response headers (e.g., those that are required, those
775   that modify the semantics of the response).
776</t>
777<t>
778   New HTTP status codes are required to fall under one of the categories
779   defined in <xref target="status.codes"/>. To allow existing parsers to
780   properly handle them, new status codes cannot disallow a response body,
781   although they can mandate a zero-length response body. They can require the
782   presence of one or more particular HTTP response header(s).
783</t>
784<t>
785   Likewise, their definitions can specify that caches are allowed to use
786   heuristics to determine their freshness (see &caching;; by default, it is
787   not allowed), and can define how to determine the resource which they
788   carry a representation for (see <xref
789   target="identifying.response.associated.with.representation"/>; by default,
790   it is anonymous).
791</t>
792</section>
793
794</section>
795
796</section>
797
798<section title="Representation" anchor="representation">
799<t>
800   Request and Response messages &MAY; transfer a representation if not otherwise
801   restricted by the request method or response status code. A representation
802   consists of metadata (representation header fields) and data (representation
803   body).  When a complete or partial representation is enclosed in an HTTP message,
804   it is referred to as the payload of the message. HTTP representations
805   are defined in &payload;.
806</t>
807<t>
808   A representation body is only present in a message when a message-body is
809   present, as described in &message-body;. The representation body is obtained
810   from the message-body by decoding any Transfer-Encoding that might
811   have been applied to ensure safe and proper transfer of the message.
812</t>
813
814<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
815<t>
816   It is sometimes necessary to determine an identifier for the resource
817   associated with a representation.
818</t>
819<t>
820   An HTTP request representation, when present, is always associated with an
821   anonymous (i.e., unidentified) resource.
822</t>
823<t>
824   In the common case, an HTTP response is a representation of the target
825   resource (see &effective-request-uri;). However, this is not always the
826   case. To determine the URI of the resource a response is associated with,
827   the following rules are used (with the first applicable one being selected):
828</t>
829<t><list style="numbers">
830   <t>If the response status code is 200 or 203 and the request method was GET,
831   the response payload is a representation of the target resource.</t>
832   <t>If the response status code is 204, 206, or 304 and the request method was GET
833   or HEAD, the response payload is a partial representation of the target
834   resource.</t>
835   <t>If the response has a Content-Location header field, and that URI is the same
836   as the effective request URI, the response payload is a representation of the
837   target resource.</t>
838   <t>If the response has a Content-Location header field, and that URI is not the
839   same as the effective request URI, then the response asserts that its
840   payload is a representation of the resource identified by the
841   Content-Location URI. However, such an assertion cannot be trusted unless
842   it can be verified by other means (not defined by HTTP).</t>
843   <t>Otherwise, the response is a representation of an anonymous (i.e.,
844   unidentified) resource.</t>
845</list></t>
846<t>
847  <cref anchor="TODO-req-uri">
848   The comparison function is going to have to be defined somewhere,
849   because we already need to compare URIs for things like cache invalidation.</cref>
850</t>
851</section>
852
853</section>
854
855
856<section title="Method Definitions" anchor="method.definitions">
857<t>
858   The set of common request methods for HTTP/1.1 is defined below. Although
859   this set can be expanded, additional methods cannot be assumed to
860   share the same semantics for separately extended clients and servers.
861</t>
862
863<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
864
865<section title="Safe Methods" anchor="safe.methods">
866<iref item="Safe Methods" primary="true"/>
867<t>
868   Implementors need to be aware that the software represents the user in
869   their interactions over the Internet, and need to allow
870   the user to be aware of any actions they take which might have an
871   unexpected significance to themselves or others.
872</t>
873<t>
874   In particular, the convention has been established that the GET, HEAD,
875   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
876   of taking an action other than retrieval. These request methods ought
877   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
878   This allows user agents to represent other methods, such as POST, PUT
879   and DELETE, in a special way, so that the user is made aware of the
880   fact that a possibly unsafe action is being requested.
881</t>
882<t>
883   Naturally, it is not possible to ensure that the server does not
884   generate side-effects as a result of performing a GET request; in
885   fact, some dynamic resources consider that a feature. The important
886   distinction here is that the user did not request the side-effects,
887   so therefore cannot be held accountable for them.
888</t>
889</section>
890
891<section title="Idempotent Methods" anchor="idempotent.methods">
892<iref item="Idempotent Methods" primary="true"/>
893<t>
894   Request methods can also have the property of "idempotence" in that,
895   aside from error or expiration issues, the intended effect of multiple
896   identical requests is the same as for a single request.
897   PUT, DELETE, and all safe request methods are idempotent.
898   It is important to note that idempotence refers only to changes
899   requested by the client: a server is free to change its state due
900   to multiple requests for the purpose of tracking those requests,
901   versioning of results, etc.
902</t>
903</section>
904</section>
905
906<section title="OPTIONS" anchor="OPTIONS">
907  <rdf:Description>
908    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
909  </rdf:Description>
910  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
911  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
912<t>
913   The OPTIONS method requests information about the
914   communication options available on the request/response chain
915   identified by the effective request URI. This method allows a client to
916   determine the options and/or requirements associated with a resource,
917   or the capabilities of a server, without implying a resource action
918   or initiating a resource retrieval.
919</t>
920<t>
921   Responses to the OPTIONS method are not cacheable.
922</t>
923<t>
924   If the OPTIONS request includes a message-body (as indicated by the
925   presence of Content-Length or Transfer-Encoding), then the media type
926   &MUST; be indicated by a Content-Type field. Although this
927   specification does not define any use for such a body, future
928   extensions to HTTP might use the OPTIONS body to make more detailed
929   queries on the server.
930</t>
931<t>
932   If the request-target is an asterisk ("*"), the OPTIONS request is
933   intended to apply to the server in general rather than to a specific
934   resource. Since a server's communication options typically depend on
935   the resource, the "*" request is only useful as a "ping" or "no-op"
936   type of method; it does nothing beyond allowing the client to test
937   the capabilities of the server. For example, this can be used to test
938   a proxy for HTTP/1.1 compliance (or lack thereof).
939</t>
940<t>
941   If the request-target is not an asterisk, the OPTIONS request applies
942   only to the options that are available when communicating with that
943   resource.
944</t>
945<t>
946   A 200 response &SHOULD; include any header fields that indicate
947   optional features implemented by the server and applicable to that
948   resource (e.g., Allow), possibly including extensions not defined by
949   this specification. The response body, if any, &SHOULD; also include
950   information about the communication options. The format for such a
951   body is not defined by this specification, but might be defined by
952   future extensions to HTTP. Content negotiation &MAY; be used to select
953   the appropriate response format. If no response body is included, the
954   response &MUST; include a Content-Length field with a field-value of
955   "0".
956</t>
957<t>
958   The Max-Forwards header field &MAY; be used to target a
959   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
960   If no Max-Forwards field is present in the request, then the forwarded
961   request &MUST-NOT; include a Max-Forwards field.
962</t>
963</section>
964
965<section title="GET" anchor="GET">
966  <rdf:Description>
967    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
968  </rdf:Description>
969  <iref primary="true" item="GET method" x:for-anchor=""/>
970  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
971<t>
972   The GET method requests transfer of a current representation of
973   the target resource.
974</t>
975<t>   
976   If the target resource is a data-producing process, it is the
977   produced data which shall be returned as the representation in the response and not
978   the source text of the process, unless that text happens to be the output of
979   the process.
980</t>
981<t>
982   The semantics of the GET method change to a "conditional GET" if the
983   request message includes an If-Modified-Since, If-Unmodified-Since,
984   If-Match, If-None-Match, or If-Range header field. A conditional GET
985   requests that the representation be transferred only under the
986   circumstances described by the conditional header field(s). The
987   conditional GET request is intended to reduce unnecessary network
988   usage by allowing cached representations to be refreshed without requiring
989   multiple requests or transferring data already held by the client.
990</t>
991<t>
992   The semantics of the GET method change to a "partial GET" if the
993   request message includes a Range header field. A partial GET requests
994   that only part of the representation be transferred, as described in &header-range;.
995   The partial GET request is intended to reduce unnecessary
996   network usage by allowing partially-retrieved representations to be
997   completed without transferring data already held by the client.
998</t>
999<t>
1000   Bodies on GET requests have no defined semantics. Note that sending a body
1001   on a GET request might cause some existing implementations to reject the
1002   request.
1003</t>
1004<t>
1005   The response to a GET request is cacheable and &MAY; be used to satisfy
1006   subsequent GET and HEAD requests (see &caching;).
1007</t>
1008<t>
1009   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
1010</t>
1011</section>
1012
1013<section title="HEAD" anchor="HEAD">
1014  <rdf:Description>
1015    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1016  </rdf:Description>
1017  <iref primary="true" item="HEAD method" x:for-anchor=""/>
1018  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
1019<t>
1020   The HEAD method is identical to GET except that the server &MUST-NOT;
1021   return a message-body in the response. The metadata contained
1022   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
1023   to the information sent in response to a GET request. This method can
1024   be used for obtaining metadata about the representation implied by the
1025   request without transferring the representation body. This method is
1026   often used for testing hypertext links for validity, accessibility,
1027   and recent modification.
1028</t>
1029<t>
1030   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1031   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1032   representation from that resource; if the new field values
1033   indicate that the cached representation differs from the current representation (as
1034   would be indicated by a change in Content-Length, ETag
1035   or Last-Modified), then the cache &MUST; treat the cache entry as
1036   stale.
1037</t>
1038<t>
1039   Bodies on HEAD requests have no defined semantics. Note that sending a body
1040   on a HEAD request might cause some existing implementations to reject the
1041   request.
1042</t>
1043</section>
1044
1045<section title="POST" anchor="POST">
1046  <iref primary="true" item="POST method" x:for-anchor=""/>
1047  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1048<t>
1049   The POST method requests that the origin server accept the
1050   representation enclosed in the request as data to be processed by the
1051   target resource. POST is designed to allow a uniform method to cover the
1052   following functions:
1053  <list style="symbols">
1054    <t>
1055      Annotation of existing resources;
1056    </t>
1057    <t>
1058        Posting a message to a bulletin board, newsgroup, mailing list,
1059        or similar group of articles;
1060    </t>
1061    <t>
1062        Providing a block of data, such as the result of submitting a
1063        form, to a data-handling process;
1064    </t>
1065    <t>
1066        Extending a database through an append operation.
1067    </t>
1068  </list>
1069</t>
1070<t>
1071   The actual function performed by the POST method is determined by the
1072   server and is usually dependent on the effective request URI.
1073</t>
1074<t>
1075   The action performed by the POST method might not result in a
1076   resource that can be identified by a URI. In this case, either 200
1077   (OK) or 204 (No Content) is the appropriate response status code,
1078   depending on whether or not the response includes a representation that
1079   describes the result.
1080</t>
1081<t>
1082   If a resource has been created on the origin server, the response
1083   &SHOULD; be 201 (Created) and contain a representation which describes the
1084   status of the request and refers to the new resource, and a Location
1085   header field (see <xref target="header.location"/>).
1086</t>
1087<t>
1088   Responses to POST requests are only cacheable when they
1089   include explicit freshness information (see &p6-explicit;). A
1090   cached POST response with a Content-Location header field
1091   (see &header-content-location;) whose value is the effective
1092   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1093</t>
1094<t>
1095   Note that POST caching is not widely implemented.
1096   However, the 303 (See Other) response can be used to direct the
1097   user agent to retrieve a cacheable resource.
1098</t>
1099</section>
1100
1101<section title="PUT" anchor="PUT">
1102  <iref primary="true" item="PUT method" x:for-anchor=""/>
1103  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1104<t>
1105   The PUT method requests that the state of the target resource
1106   be created or replaced with the state defined by the representation
1107   enclosed in the request message payload.  A successful PUT of a given
1108   representation would suggest that a subsequent GET on that same target
1109   resource will result in an equivalent representation being returned in
1110   a 200 (OK) response.  However, there is no guarantee that such a state
1111   change will be observable, since the target resource might be acted
1112   upon by other user agents in parallel, or might be subject to dynamic
1113   processing by the origin server, before any subsequent GET is received.
1114   A successful response only implies that the user agent's intent was
1115   achieved at the time of its processing by the origin server.
1116</t>
1117<t>   
1118   If the target resource does not have a current representation and
1119   the PUT successfully creates one, then the origin server &MUST; inform
1120   the user agent by sending a 201 (Created) response.  If the target
1121   resource does have a current representation and that representation is
1122   successfully modified in accordance with the state of the enclosed
1123   representation, then either a 200 (OK) or 204 (No Content) response
1124   &SHOULD; be sent to indicate successful completion of the request.
1125</t>
1126<t>
1127   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1128   as part of the resource state).
1129</t>
1130<t>
1131   An origin server &SHOULD; verify that the PUT representation is
1132   consistent with any constraints which the server has for the target
1133   resource that cannot or will not be changed by the PUT.  This is
1134   particularly important when the origin server uses internal
1135   configuration information related to the URI in order to set the
1136   values for representation metadata on GET responses.  When a PUT
1137   representation is inconsistent with the target resource, the origin
1138   server &SHOULD; either make them consistent, by transforming the
1139   representation or changing the resource configuration, or respond
1140   with an appropriate error message containing sufficient information
1141   to explain why the representation is unsuitable.  The 409 (Conflict)
1142   or 415 (Unsupported Media Type) status codes are suggested, with the
1143   latter being specific to constraints on Content-Type values.
1144</t>
1145<t>
1146   For example, if the target resource is configured to always have a
1147   Content-Type of "text/html" and the representation being PUT has a
1148   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1149   (a) reconfigure the target resource to reflect the new media type;
1150   (b) transform the PUT representation to a format consistent with that
1151   of the resource before saving it as the new resource state; or,
1152   (c) reject the request with a 415 response indicating that the target
1153   resource is limited to "text/html", perhaps including a link to a
1154   different resource that would be a suitable target for the new
1155   representation.
1156</t>
1157<t>
1158   HTTP does not define exactly how a PUT method affects the state
1159   of an origin server beyond what can be expressed by the intent of
1160   the user agent request and the semantics of the origin server response.
1161   It does not define what a resource might be, in any sense of that
1162   word, beyond the interface provided via HTTP.  It does not define
1163   how resource state is "stored", nor how such storage might change
1164   as a result of a change in resource state, nor how the origin server
1165   translates resource state into representations.  Generally speaking,
1166   all implementation details behind the resource interface are
1167   intentionally hidden by the server.
1168</t>
1169<t>
1170   The fundamental difference between the POST and PUT methods is
1171   highlighted by the different intent for the target resource.
1172   The target resource in a POST request is intended to handle the
1173   enclosed representation as a data-accepting process, such as for
1174   a gateway to some other protocol or a document that accepts annotations.
1175   In contrast, the target resource in a PUT request is intended to
1176   take the enclosed representation as a new or replacement value.
1177   Hence, the intent of PUT is idempotent and visible to intermediaries,
1178   even though the exact effect is only known by the origin server.
1179</t>
1180<t>
1181   Proper interpretation of a PUT request presumes that the user agent
1182   knows what target resource is desired.  A service that is intended
1183   to select a proper URI on behalf of the client, after receiving
1184   a state-changing request, &SHOULD; be implemented using the POST
1185   method rather than PUT.  If the origin server will not make the
1186   requested PUT state change to the target resource and instead
1187   wishes to have it applied to a different resource, such as when the
1188   resource has been moved to a different URI, then the origin server
1189   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1190   then make its own decision regarding whether or not to redirect the
1191   request.
1192</t>
1193<t>
1194   A PUT request applied to the target resource &MAY; have side-effects
1195   on other resources.  For example, an article might have a URI for
1196   identifying "the current version" (a resource) which is separate
1197   from the URIs identifying each particular version (different
1198   resources that at one point shared the same state as the current version
1199   resource).  A successful PUT request on "the current version" URI might
1200   therefore create a new version resource in addition to changing the
1201   state of the target resource, and might also cause links to be added
1202   between the related resources.
1203</t>
1204<t>
1205   An origin server &SHOULD; reject any PUT request that contains a
1206   Content-Range header field, since it might be misinterpreted as
1207   partial content (or might be partial content that is being mistakenly
1208   PUT as a full representation).  Partial content updates are
1209   possible by targeting a separately identified resource with state
1210   that overlaps a portion of the larger resource, or by using a
1211   different method that has been specifically defined for partial
1212   updates (for example, the PATCH method defined in
1213   <xref target="RFC5789"/>).
1214</t>
1215<t>
1216   Responses to the PUT method are not cacheable. If a PUT request passes
1217   through a cache that has one or more stored responses for the effective
1218   request URI, those stored responses will be invalidated (see
1219   &p6-invalid;).
1220</t>
1221</section>
1222
1223<section title="DELETE" anchor="DELETE">
1224  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1225  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1226<t>
1227   The DELETE method requests that the origin server delete the target
1228   resource. This method &MAY; be overridden by
1229   human intervention (or other means) on the origin server. The client cannot
1230   be guaranteed that the operation has been carried out, even if the
1231   status code returned from the origin server indicates that the action
1232   has been completed successfully. However, the server &SHOULD-NOT; 
1233   indicate success unless, at the time the response is given, it
1234   intends to delete the resource or move it to an inaccessible
1235   location.
1236</t>
1237<t>
1238   A successful response &SHOULD; be 200 (OK) if the response includes an
1239   representation describing the status, 202 (Accepted) if the action has not
1240   yet been enacted, or 204 (No Content) if the action has been enacted
1241   but the response does not include a representation.
1242</t>
1243<t>
1244   Bodies on DELETE requests have no defined semantics. Note that sending a body
1245   on a DELETE request might cause some existing implementations to reject the
1246   request.
1247</t>
1248<t>
1249   Responses to the DELETE method are not cacheable. If a DELETE request
1250   passes through a cache that has one or more stored responses for the
1251   effective request URI, those stored responses will be invalidated (see
1252   &p6-invalid;).
1253</t>
1254</section>
1255
1256<section title="TRACE" anchor="TRACE">
1257  <rdf:Description>
1258    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1259  </rdf:Description>
1260  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1261  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1262<t>
1263   The TRACE method requests a remote, application-layer loop-back
1264   of the request message. The final recipient of the request
1265   &SHOULD; reflect the message received back to the client as the
1266   message-body of a 200 (OK) response. The final recipient is either the
1267   origin server or the first proxy to receive a Max-Forwards
1268   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1269   A TRACE request &MUST-NOT; include a message-body.
1270</t>
1271<t>
1272   TRACE allows the client to see what is being received at the other
1273   end of the request chain and use that data for testing or diagnostic
1274   information. The value of the Via header field (&header-via;) is of
1275   particular interest, since it acts as a trace of the request chain.
1276   Use of the Max-Forwards header field allows the client to limit the
1277   length of the request chain, which is useful for testing a chain of
1278   proxies forwarding messages in an infinite loop.
1279</t>
1280<t>
1281   If the request is valid, the response &SHOULD; have a Content-Type of
1282   "message/http" (see &media-type-message-http;) and contain a message-body
1283   that encloses a copy of the entire request message.
1284   Responses to the TRACE method are not cacheable.
1285</t>
1286</section>
1287
1288<section title="CONNECT" anchor="CONNECT">
1289  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1290  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1291<t>
1292   The CONNECT method requests that the proxy establish a tunnel
1293   to the request-target and then restrict its behavior to blind
1294   forwarding of packets until the connection is closed.
1295</t>
1296<t>
1297   When using CONNECT, the request-target &MUST; use the authority form
1298   (&request-target;); i.e., the request-target consists of only the
1299   host name and port number of the tunnel destination, separated by a colon.
1300   For example,
1301</t>
1302<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1303CONNECT server.example.com:80 HTTP/1.1
1304Host: server.example.com:80
1305
1306</artwork></figure>
1307<t>
1308   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1309   except end-to-end protocol Upgrade requests, since the
1310   tunnel must be established first.
1311</t>
1312<t>
1313   For example, proxy authentication might be used to establish the
1314   authority to create a tunnel:
1315</t>
1316<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1317CONNECT server.example.com:80 HTTP/1.1
1318Host: server.example.com:80
1319Proxy-Authorization: basic aGVsbG86d29ybGQ=
1320
1321</artwork></figure>
1322<t>
1323   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1324   on a CONNECT request might cause some existing implementations to reject the
1325   request.
1326</t>
1327<t>
1328   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1329   sent immediately after the blank line. The usual caveats also apply:
1330   data may be discarded if the eventual response is negative, and the
1331   connection may be reset with no response if more than one TCP segment
1332   is outstanding.
1333</t>
1334
1335<section title="Establishing a Tunnel with CONNECT">
1336<t>
1337   Any successful (2xx) response to a CONNECT request indicates that the
1338   proxy has established a connection to the requested host and port,
1339   and has switched to tunneling the current connection to that server
1340   connection.
1341</t>
1342<t>
1343   It may be the case that the proxy itself can only reach the requested
1344   origin server through another proxy.  In this case, the first proxy
1345   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1346   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1347   unless it has either a direct or tunnel connection established to the
1348   authority.
1349</t>
1350<t>
1351   An origin server which receives a CONNECT request for itself &MAY;
1352   respond with a 2xx status code to indicate that a connection is
1353   established.
1354</t>
1355<t>
1356   If at any point either one of the peers gets disconnected, any
1357   outstanding data that came from that peer will be passed to the other
1358   one, and after that also the other connection will be terminated by
1359   the proxy. If there is outstanding data to that peer undelivered,
1360   that data will be discarded.
1361</t>
1362
1363</section>
1364</section>
1365</section>
1366
1367
1368<section title="Status Code Definitions" anchor="status.codes">
1369<t>
1370   The first digit of the Status-Code defines the class of response. The
1371   last two digits do not have any categorization role. There are 5
1372   values for the first digit:
1373  <list style="symbols">
1374    <t>
1375      1xx: Informational - Request received, continuing process
1376    </t>
1377    <t>
1378      2xx: Success - The action was successfully received,
1379        understood, and accepted
1380    </t>
1381    <t>
1382      3xx: Redirection - Further action must be taken in order to
1383        complete the request
1384    </t>
1385    <t>
1386      4xx: Client Error - The request contains bad syntax or cannot
1387        be fulfilled
1388    </t>
1389    <t>
1390      5xx: Server Error - The server failed to fulfill an apparently
1391        valid request
1392    </t>
1393  </list>
1394</t>
1395<t>
1396   Each Status-Code is described below, including any metadata required
1397   in the response.
1398</t>
1399
1400<section title="Informational 1xx" anchor="status.1xx">
1401<t>
1402   This class of status code indicates a provisional response,
1403   consisting only of the Status-Line and optional header fields, and is
1404   terminated by an empty line. There are no required header fields for this
1405   class of status code. Since HTTP/1.0 did not define any 1xx status
1406   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1407   except under experimental conditions.
1408</t>
1409<t>
1410   A client &MUST; be prepared to accept one or more 1xx status responses
1411   prior to a regular response, even if the client does not expect a 100
1412   (Continue) status message. Unexpected 1xx status responses &MAY; be
1413   ignored by a user agent.
1414</t>
1415<t>
1416   Proxies &MUST; forward 1xx responses, unless the connection between the
1417   proxy and its client has been closed, or unless the proxy itself
1418   requested the generation of the 1xx response. (For example, if a
1419   proxy adds a "Expect: 100-continue" field when it forwards a request,
1420   then it need not forward the corresponding 100 (Continue)
1421   response(s).)
1422</t>
1423
1424<section title="100 Continue" anchor="status.100">
1425  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1426  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1427<t>
1428   The client &SHOULD; continue with its request. This interim response is
1429   used to inform the client that the initial part of the request has
1430   been received and has not yet been rejected by the server. The client
1431   &SHOULD; continue by sending the remainder of the request or, if the
1432   request has already been completed, ignore this response. The server
1433   &MUST; send a final response after the request has been completed. See
1434   &use100; for detailed discussion of the use and handling of this
1435   status code.
1436</t>
1437</section>
1438
1439<section title="101 Switching Protocols" anchor="status.101">
1440  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1442<t>
1443   The server understands and is willing to comply with the client's
1444   request, via the Upgrade message header field (&header-upgrade;), for a
1445   change in the application protocol being used on this connection. The
1446   server will switch protocols to those defined by the response's
1447   Upgrade header field immediately after the empty line which
1448   terminates the 101 response.
1449</t>
1450<t>
1451   The protocol &SHOULD; be switched only when it is advantageous to do
1452   so. For example, switching to a newer version of HTTP is advantageous
1453   over older versions, and switching to a real-time, synchronous
1454   protocol might be advantageous when delivering resources that use
1455   such features.
1456</t>
1457</section>
1458</section>
1459
1460<section title="Successful 2xx" anchor="status.2xx">
1461<t>
1462   This class of status code indicates that the client's request was
1463   successfully received, understood, and accepted.
1464</t>
1465
1466<section title="200 OK" anchor="status.200">
1467  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1468  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1469<t>
1470   The request has succeeded. The payload returned with the response
1471   is dependent on the method used in the request, for example:
1472  <list style="hanging">
1473    <t hangText="GET">
1474      a representation of the target resource is sent in the response;
1475    </t>
1476    <t hangText="HEAD">
1477      the same representation as GET, except without the message-body;
1478    </t>
1479    <t hangText="POST">
1480      a representation describing or containing the result of the action;
1481    </t>
1482    <t hangText="TRACE">
1483      a representation containing the request message as received by the
1484      end server.
1485    </t>
1486  </list>
1487</t>
1488<t>
1489   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1490   freshness for 200 responses.
1491</t>
1492</section>
1493
1494<section title="201 Created" anchor="status.201">
1495  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1496  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1497<t>
1498   The request has been fulfilled and has resulted in a new resource being
1499   created. The newly created resource can be referenced by the URI(s)
1500   returned in the payload of the response, with the most specific URI
1501   for the resource given by a Location header field. The response
1502   &SHOULD; include a payload containing a list of resource
1503   characteristics and location(s) from which the user or user agent can
1504   choose the one most appropriate. The payload format is specified by
1505   the media type given in the Content-Type header field. The origin
1506   server &MUST; create the resource before returning the 201 status code.
1507   If the action cannot be carried out immediately, the server &SHOULD;
1508   respond with 202 (Accepted) response instead.
1509</t>
1510<t>
1511   A 201 response &MAY; contain an ETag response header field indicating
1512   the current value of the entity-tag for the representation of the resource
1513   just created (see &header-etag;).
1514</t>
1515</section>
1516
1517<section title="202 Accepted" anchor="status.202">
1518  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1519  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1520<t>
1521   The request has been accepted for processing, but the processing has
1522   not been completed.  The request might or might not eventually be
1523   acted upon, as it might be disallowed when processing actually takes
1524   place. There is no facility for re-sending a status code from an
1525   asynchronous operation such as this.
1526</t>
1527<t>
1528   The 202 response is intentionally non-committal. Its purpose is to
1529   allow a server to accept a request for some other process (perhaps a
1530   batch-oriented process that is only run once per day) without
1531   requiring that the user agent's connection to the server persist
1532   until the process is completed. The representation returned with this
1533   response &SHOULD; include an indication of the request's current status
1534   and either a pointer to a status monitor or some estimate of when the
1535   user can expect the request to be fulfilled.
1536</t>
1537</section>
1538
1539<section title="203 Non-Authoritative Information" anchor="status.203">
1540  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1541  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1542<t>
1543   The representation in the response has been transformed or otherwise
1544   modified by a transforming proxy (&intermediaries;).  Note that the
1545   behaviour of transforming intermediaries is controlled by the no-transform
1546   Cache-Control directive (&header-cache-control;).
1547</t>
1548<t>
1549   This status code is only appropriate when the response status code would
1550   have been 200 (OK) otherwise. When the status code before transformation
1551   would have been different, the 214 Transformation Applied warn-code
1552   (&header-warning;) is appropriate.
1553</t>
1554<t>
1555   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1556   freshness for 203 responses.
1557</t>
1558</section>
1559
1560<section title="204 No Content" anchor="status.204">
1561  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1562  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1563<t>
1564   The 204 (No Content) status code indicates that the server has
1565   successfully fulfilled the request and that there is no additional
1566   content to return in the response payload body.  Metadata in the
1567   response header fields refer to the target resource and its current
1568   representation after the requested action.
1569</t>
1570<t>
1571   For example, if a 204 status code is received in response to a PUT
1572   request and the response contains an ETag header field, then the PUT
1573   was successful and the ETag field-value contains the entity-tag for
1574   the new representation of that target resource.
1575</t>
1576<t>
1577   The 204 response allows a server to indicate that the action has been
1578   successfully applied to the target resource while implying that the
1579   user agent &SHOULD-NOT; traverse away from its current "document view"
1580   (if any).  The server assumes that the user agent will provide some
1581   indication of the success to its user, in accord with its own interface,
1582   and apply any new or updated metadata in the response to the active
1583   representation.
1584</t>
1585<t>
1586   For example, a 204 status code is commonly used with document editing
1587   interfaces corresponding to a "save" action, such that the document
1588   being saved remains available to the user for editing. It is also
1589   frequently used with interfaces that expect automated data transfers
1590   to be prevalent, such as within distributed version control systems.
1591</t>
1592<t>
1593   The 204 response &MUST-NOT; include a message-body, and thus is always
1594   terminated by the first empty line after the header fields.
1595</t>
1596</section>
1597
1598<section title="205 Reset Content" anchor="status.205">
1599  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1600  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1601<t>
1602   The server has fulfilled the request and the user agent &SHOULD; reset
1603   the document view which caused the request to be sent. This response
1604   is primarily intended to allow input for actions to take place via
1605   user input, followed by a clearing of the form in which the input is
1606   given so that the user can easily initiate another input action.
1607</t>
1608<t>   
1609   The message-body included with the response &MUST; be empty. Note that
1610   receivers still need to parse the response according to the algorithm defined
1611   in &message-body;.
1612</t>
1613</section>
1614
1615<section title="206 Partial Content" anchor="status.206">
1616  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1617  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1618  <rdf:Description>
1619    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1620  </rdf:Description>
1621<t>
1622   The server has fulfilled the partial GET request for the resource
1623   and the enclosed payload is a partial representation as defined in &status-206;.
1624</t>
1625<t>
1626   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1627   freshness for 206 responses.
1628</t>
1629</section>
1630</section>
1631
1632<section title="Redirection 3xx" anchor="status.3xx">
1633<t>
1634   This class of status code indicates that further action needs to be
1635   taken by the user agent in order to fulfill the request.  If the required
1636   action involves a subsequent HTTP request, it &MAY; be carried out by the
1637   user agent without interaction with the user if and only if the method used
1638   in the second request is known to be "safe", as defined in
1639   <xref target="safe.methods"/>.
1640</t>
1641<t>
1642   There are several types of redirects:
1643   <list style="numbers">
1644      <x:lt>
1645        <t>
1646          Redirects of the request to another URI, either temporarily or
1647          permanently. The new URI is specified in the Location header field.
1648          In this specification, the status codes 301 (Moved Permanently),
1649          302 (Found), and 307 (Temporary Redirect) fall under this category.
1650        </t>
1651      </x:lt>
1652      <x:lt>
1653        <t>
1654          Redirection to a new location that represents an indirect response to
1655          the request, such as the result of a POST operation to be retrieved
1656          with a subsequent GET request. This is status code 303 (See Other).
1657        </t>
1658      </x:lt>
1659      <x:lt>
1660        <t>
1661          Redirection offering a choice of matching resources for use by
1662          agent-driven content negotiation (&agent-driven-negotiation;). This
1663          is status code 300 (Multiple Choices).
1664        </t>
1665      </x:lt>
1666      <x:lt>
1667        <t>
1668          Other kinds of redirection, such as to a cached result (status code 304
1669          (Not Modified)).
1670        </t>
1671      </x:lt>
1672   </list>
1673</t>
1674<x:note>
1675  <t>
1676    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1677    and 302 (Found) were defined for the first type of redirect, and the second
1678    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1679    However it turned out that web forms using POST expected redirects to change
1680    the operation for the subsequent request to retrieval (GET). To address this
1681    use case, HTTP/1.1 introduced the second type of redirect with the status
1682    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1683    As user agents did not change their behavior to maintain backwards
1684    compatibility, the first revision of HTTP/1.1 added yet another status code,
1685    307 (Temporary Redirect), for which the backwards compatibility problems did
1686    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1687    Over 10 years later, most user agents still do method rewriting for
1688    status codes 301 and 302, therefore this specification makes that behavior
1689    compliant in case the original request was POST.
1690  </t>
1691</x:note>
1692<t>
1693   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1694   "infinite" redirection loops).
1695</t>
1696<x:note>
1697  <t>
1698    <x:h>Note:</x:h> An earlier version of this specification recommended a
1699    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1700    Content developers need to be aware that some clients might
1701    implement such a fixed limitation.
1702  </t>
1703</x:note>
1704
1705<section title="300 Multiple Choices" anchor="status.300">
1706  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1707  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1708<t>
1709   The target resource has more than one
1710   representation, each with its own specific location, and agent-driven
1711   negotiation information (&content-negotiation;) is being provided so that
1712   the user (or user agent) can select a preferred representation by
1713   redirecting its request to that location.
1714</t>
1715<t>
1716   Unless it was a HEAD request, the response &SHOULD; include a representation
1717   containing a list of representation metadata and location(s) from
1718   which the user or user agent can choose the one most appropriate. The
1719   data format is specified by the media type given in the Content-Type
1720   header field. Depending upon the format and the capabilities of
1721   the user agent, selection of the most appropriate choice &MAY; be
1722   performed automatically. However, this specification does not define
1723   any standard for such automatic selection.
1724</t>
1725<t>
1726   If the server has a preferred choice of representation, it &SHOULD;
1727   include the specific URI for that representation in the Location
1728   field; user agents &MAY; use the Location field value for automatic
1729   redirection.
1730</t>
1731<t>
1732   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1733   freshness for 300 responses.
1734</t>
1735
1736</section>
1737
1738<section title="301 Moved Permanently" anchor="status.301">
1739  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1740  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1741<t>
1742   The target resource has been assigned a new permanent URI and any
1743   future references to this resource &SHOULD; use one of the returned
1744   URIs.  Clients with link editing capabilities ought to automatically
1745   re-link references to the effective request URI to one or more of the new
1746   references returned by the server, where possible.
1747</t>
1748<t>
1749   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1750   freshness for 301 responses.
1751</t>
1752<t>
1753   The new permanent URI &SHOULD; be given by the Location field in the
1754   response. Unless the request method was HEAD, the representation of the
1755   response &SHOULD; contain a short hypertext note with a hyperlink to
1756   the new URI(s).
1757</t>
1758<t>
1759   If the 301 status code is received in response to a request method
1760   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1761   then the request &MAY; be automatically redirected by the user agent without
1762   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1763   request unless it can be confirmed by the user, since this might
1764   change the conditions under which the request was issued.
1765</t>
1766<x:note>
1767  <t>
1768    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1769    request method from POST to GET for the subsequent request. If this
1770    behavior is undesired, status code 307 (Temporary Redirect) can be used
1771    instead.
1772  </t>
1773</x:note>
1774</section>
1775
1776<section title="302 Found" anchor="status.302">
1777  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1778  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1779<t>
1780   The target resource resides temporarily under a different URI.
1781   Since the redirection might be altered on occasion, the client &SHOULD;
1782   continue to use the effective request URI for future requests.
1783</t>
1784<t>
1785   The temporary URI &SHOULD; be given by the Location field in the
1786   response. Unless the request method was HEAD, the representation of the
1787   response &SHOULD; contain a short hypertext note with a hyperlink to
1788   the new URI(s).
1789</t>
1790<t>
1791   If the 302 status code is received in response to a request method
1792   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1793   then the request &MAY; be automatically redirected by the user agent without
1794   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1795   request unless it can be confirmed by the user, since this might
1796   change the conditions under which the request was issued.
1797</t>
1798<x:note>
1799  <t>
1800    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1801    request method from POST to GET for the subsequent request. If this
1802    behavior is undesired, status code 307 (Temporary Redirect) can be used
1803    instead.
1804    <cref anchor="issue312">but see <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312"/></cref>
1805  </t>
1806</x:note>
1807</section>
1808
1809<section title="303 See Other" anchor="status.303">
1810  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1811  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1812<t>
1813   The 303 status code indicates that the server is redirecting the
1814   user agent to a different resource, as indicated by a URI in the
1815   Location header field, that is intended to provide an indirect
1816   response to the original request.  In order to satisfy the original
1817   request, a user agent &SHOULD; perform a retrieval request using the
1818   Location URI (a GET or HEAD request if using HTTP), which
1819   may itself be redirected further, and present the eventual result as an
1820   answer to the original request.
1821   Note that the new URI in the Location header field is not considered
1822   equivalent to the effective request URI.
1823</t>
1824<t>
1825   This status code is generally applicable to any HTTP method.  It is
1826   primarily used to allow the output of a POST action to redirect
1827   the user agent to a selected resource, since doing so provides the
1828   information corresponding to the POST response in a form that
1829   can be separately identified, bookmarked, and cached independent
1830   of the original request.
1831</t>
1832<t>
1833   A 303 response to a GET request indicates that the requested
1834   resource does not have a representation of its own that can be
1835   transferred by the server over HTTP.  The Location URI indicates a
1836   resource that is descriptive of the target resource, such that the
1837   follow-on representation might be useful to recipients without
1838   implying that it adequately represents the target resource.
1839   Note that answers to the questions of what can be represented, what
1840   representations are adequate, and what might be a useful description
1841   are outside the scope of HTTP and thus entirely determined by the
1842   URI owner(s).
1843</t>
1844<t>
1845   Except for responses to a HEAD request, the representation of a 303
1846   response &SHOULD; contain a short hypertext note with a hyperlink
1847   to the Location URI.
1848</t>
1849</section>
1850
1851<section title="304 Not Modified" anchor="status.304">
1852  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1853  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1854  <rdf:Description>
1855    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1856  </rdf:Description>
1857<t>
1858   The response to the request has not been modified since the conditions
1859   indicated by the client's conditional GET request, as defined in &status-304;.
1860</t>
1861</section>
1862
1863<section title="305 Use Proxy" anchor="status.305">
1864  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1865  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1866<t>
1867   The 305 status code was defined in a previous version of this specification
1868   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1869</t>
1870</section>
1871
1872<section title="306 (Unused)" anchor="status.306">
1873  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1874  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1875<t>
1876   The 306 status code was used in a previous version of the
1877   specification, is no longer used, and the code is reserved.
1878</t>
1879</section>
1880
1881<section title="307 Temporary Redirect" anchor="status.307">
1882  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1883  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1884<t>
1885   The target resource resides temporarily under a different URI.
1886   Since the redirection can change over time, the client &SHOULD;
1887   continue to use the effective request URI for future requests.
1888</t>
1889<t>
1890   The temporary URI &SHOULD; be given by the Location field in the
1891   response. Unless the request method was HEAD, the representation of the
1892   response &SHOULD; contain a short hypertext note with a hyperlink to
1893   the new URI(s), since many pre-HTTP/1.1 user agents do not
1894   understand the 307 status code. Therefore, the note &SHOULD; contain the
1895   information necessary for a user to repeat the original request on
1896   the new URI.
1897</t>
1898<t>
1899   If the 307 status code is received in response to a request method
1900   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1901   then the request &MAY; be automatically redirected by the user agent without
1902   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1903   request unless it can be confirmed by the user, since this might
1904   change the conditions under which the request was issued.
1905</t>
1906</section>
1907</section>
1908
1909<section title="Client Error 4xx" anchor="status.4xx">
1910<t>
1911   The 4xx class of status code is intended for cases in which the
1912   client seems to have erred. Except when responding to a HEAD request,
1913   the server &SHOULD; include a representation containing an explanation of the
1914   error situation, and whether it is a temporary or permanent
1915   condition. These status codes are applicable to any request method.
1916   User agents &SHOULD; display any included representation to the user.
1917</t>
1918<t>
1919   If the client is sending data, a server implementation using TCP
1920   &SHOULD; be careful to ensure that the client acknowledges receipt of
1921   the packet(s) containing the response, before the server closes the
1922   input connection. If the client continues sending data to the server
1923   after the close, the server's TCP stack will send a reset packet to
1924   the client, which might erase the client's unacknowledged input buffers
1925   before they can be read and interpreted by the HTTP application.
1926</t>
1927
1928<section title="400 Bad Request" anchor="status.400">
1929  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1930  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1931<t>
1932   The server cannot or will not process the request, due to a client error (e.g.,
1933   malformed syntax).</t>
1934</section>
1935
1936<section title="401 Unauthorized" anchor="status.401">
1937  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1938  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1939  <rdf:Description>
1940    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1941  </rdf:Description>
1942<t>
1943   The request requires user authentication (see &status-401;).
1944</t>
1945</section>
1946
1947<section title="402 Payment Required" anchor="status.402">
1948  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1950<t>
1951   This code is reserved for future use.
1952</t>
1953</section>
1954
1955<section title="403 Forbidden" anchor="status.403">
1956  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1957  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1958<t>
1959   The server understood the request, but refuses to authorize it. Providing
1960   different user authentication credentials might be successful, but any
1961   credentials that were provided in the request are insufficient. The request
1962   &SHOULD-NOT; be repeated with the same credentials.
1963</t>
1964<t>
1965   If the request method was not HEAD and the server wishes to make
1966   public why the request has not been fulfilled, it &SHOULD; describe the
1967   reason for the refusal in the representation.  If the server does not wish to
1968   make this information available to the client, the status code 404
1969   (Not Found) &MAY; be used instead.
1970</t>
1971</section>
1972
1973<section title="404 Not Found" anchor="status.404">
1974  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1975  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1976<t>
1977   The server has not found anything matching the effective request URI. No
1978   indication is given of whether the condition is temporary or
1979   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1980   knows, through some internally configurable mechanism, that an old
1981   resource is permanently unavailable and has no forwarding address.
1982   This status code is commonly used when the server does not wish to
1983   reveal exactly why the request has been refused, or when no other
1984   response is applicable.
1985</t>
1986</section>
1987
1988<section title="405 Method Not Allowed" anchor="status.405">
1989  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1990  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1991<t>
1992   The method specified in the Request-Line is not allowed for the target
1993   resource. The response &MUST; include an Allow header field containing a
1994   list of valid methods for the requested resource.
1995</t>
1996</section>
1997
1998<section title="406 Not Acceptable" anchor="status.406">
1999  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
2000  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
2001<t>
2002   The resource identified by the request is only capable of generating
2003   response representations which have content characteristics not acceptable
2004   according to the Accept and Accept-* header fields sent in the request
2005   (see &p3-header-fields;).
2006</t>
2007<t>
2008   Unless it was a HEAD request, the response &SHOULD; include a representation
2009   containing a list of available representation characteristics and location(s)
2010   from which the user or user agent can choose the one most
2011   appropriate. The data format is specified by the media type given
2012   in the Content-Type header field. Depending upon the format and the
2013   capabilities of the user agent, selection of the most appropriate
2014   choice &MAY; be performed automatically. However, this specification
2015   does not define any standard for such automatic selection.
2016</t>
2017<x:note>
2018  <t>
2019    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
2020    not acceptable according to the accept header fields sent in the
2021    request. In some cases, this might even be preferable to sending a
2022    406 response. User agents are encouraged to inspect the header fields of
2023    an incoming response to determine if it is acceptable.
2024  </t>
2025</x:note>
2026<t>
2027   If the response could be unacceptable, a user agent &SHOULD;
2028   temporarily stop receipt of more data and query the user for a
2029   decision on further actions.
2030</t>
2031</section>
2032
2033<section title="407 Proxy Authentication Required" anchor="status.407">
2034  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2035  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2036<t>
2037   This code is similar to 401 (Unauthorized), but indicates that the
2038   client must first authenticate itself with the proxy (see &status-407;).
2039</t>
2040</section>
2041
2042<section title="408 Request Timeout" anchor="status.408">
2043  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2044  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2045<t>
2046   The client did not produce a request within the time that the server
2047   was prepared to wait. The client &MAY; repeat the request without
2048   modifications at any later time.
2049</t>
2050</section>
2051
2052<section title="409 Conflict" anchor="status.409">
2053  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2054  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2055<t>
2056   The request could not be completed due to a conflict with the current
2057   state of the resource. This code is only allowed in situations where
2058   it is expected that the user might be able to resolve the conflict
2059   and resubmit the request. The response body &SHOULD; include enough
2060   information for the user to recognize the source of the conflict.
2061   Ideally, the response representation would include enough information for the
2062   user or user agent to fix the problem; however, that might not be
2063   possible and is not required.
2064</t>
2065<t>
2066   Conflicts are most likely to occur in response to a PUT request. For
2067   example, if versioning were being used and the representation being PUT
2068   included changes to a resource which conflict with those made by an
2069   earlier (third-party) request, the server might use the 409 response
2070   to indicate that it can't complete the request. In this case, the
2071   response representation would likely contain a list of the differences
2072   between the two versions in a format defined by the response
2073   Content-Type.
2074</t>
2075</section>
2076
2077<section title="410 Gone" anchor="status.410">
2078  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2079  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2080<t>
2081   The target resource is no longer available at the server and no
2082   forwarding address is known. This condition is expected to be
2083   considered permanent. Clients with link editing capabilities &SHOULD;
2084   delete references to the effective request URI after user approval. If the
2085   server does not know, or has no facility to determine, whether or not
2086   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2087   used instead.
2088</t>
2089<t>
2090   The 410 response is primarily intended to assist the task of web
2091   maintenance by notifying the recipient that the resource is
2092   intentionally unavailable and that the server owners desire that
2093   remote links to that resource be removed. Such an event is common for
2094   limited-time, promotional services and for resources belonging to
2095   individuals no longer working at the server's site. It is not
2096   necessary to mark all permanently unavailable resources as "gone" or
2097   to keep the mark for any length of time &mdash; that is left to the
2098   discretion of the server owner.
2099</t>
2100<t>
2101   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2102   for 410 responses.
2103</t>
2104
2105</section>
2106
2107<section title="411 Length Required" anchor="status.411">
2108  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2109  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2110<t>
2111   The server refuses to accept the request without a defined Content-Length.
2112   The client &MAY; repeat the request if it adds a valid
2113   Content-Length header field containing the length of the message-body
2114   in the request message.
2115</t>
2116</section>
2117
2118<section title="412 Precondition Failed" anchor="status.412">
2119  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2120  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2121  <rdf:Description>
2122    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2123  </rdf:Description>
2124<t>
2125   The precondition given in one or more of the header fields
2126   evaluated to false when it was tested on the server, as defined in
2127   &status-412;.
2128</t>
2129</section>
2130
2131<section title="413 Request Representation Too Large" anchor="status.413">
2132  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2133  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2134<t>
2135   The server is refusing to process a request because the request
2136   representation is larger than the server is willing or able to process. The
2137   server &MAY; close the connection to prevent the client from continuing
2138   the request.
2139</t>
2140<t>
2141   If the condition is temporary, the server &SHOULD; include a Retry-After
2142   header field to indicate that it is temporary and after what
2143   time the client &MAY; try again.
2144</t>
2145</section>
2146
2147<section title="414 URI Too Long" anchor="status.414">
2148  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2149  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2150<t>
2151   The server is refusing to service the request because the effective request URI
2152   is longer than the server is willing to interpret. This rare
2153   condition is only likely to occur when a client has improperly
2154   converted a POST request to a GET request with long query
2155   information, when the client has descended into a URI "black hole" of
2156   redirection (e.g., a redirected URI prefix that points to a suffix of
2157   itself), or when the server is under attack by a client attempting to
2158   exploit security holes present in some servers using fixed-length
2159   buffers for reading or manipulating the effective request URI.
2160</t>
2161</section>
2162
2163<section title="415 Unsupported Media Type" anchor="status.415">
2164  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2165  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2166<t>
2167   The server is refusing to service the request because the request
2168   payload is in a format not supported by this request method on the
2169   target resource.
2170</t>
2171</section>
2172
2173<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2174  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2175  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2176  <rdf:Description>
2177    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2178  </rdf:Description>
2179<t>
2180   The request included a Range header field (&header-range;) and none of
2181   the range-specifier values in this field overlap the current extent
2182   of the selected resource. See &status-416;.
2183</t>
2184</section>
2185
2186<section title="417 Expectation Failed" anchor="status.417">
2187  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2188  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2189<t>
2190   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2191   could not be met by this server, or, if the server is a proxy,
2192   the server has unambiguous evidence that the request could not be met
2193   by the next-hop server.
2194</t>
2195</section>
2196
2197<section title="426 Upgrade Required" anchor="status.426">
2198  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2199  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2200<t>
2201   The request can not be completed without a prior protocol upgrade. This
2202   response &MUST; include an Upgrade header field (&header-upgrade;)
2203   specifying the required protocols.
2204</t>
2205<figure>
2206<preamble>Example:</preamble>
2207<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2208HTTP/1.1 426 Upgrade Required
2209Upgrade: HTTP/2.0
2210Connection: Upgrade
2211
2212</artwork></figure>
2213<t>
2214   The server &SHOULD; include a message body in the 426 response which
2215   indicates in human readable form the reason for the error and describes any
2216   alternative courses which may be available to the user.
2217</t>
2218</section>
2219</section>
2220
2221<section title="Server Error 5xx" anchor="status.5xx">
2222<t>
2223   Response status codes beginning with the digit "5" indicate cases in
2224   which the server is aware that it has erred or is incapable of
2225   performing the request. Except when responding to a HEAD request, the
2226   server &SHOULD; include a representation containing an explanation of the
2227   error situation, and whether it is a temporary or permanent
2228   condition. User agents &SHOULD; display any included representation to the
2229   user. These response codes are applicable to any request method.
2230</t>
2231
2232<section title="500 Internal Server Error" anchor="status.500">
2233  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2234  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2235<t>
2236   The server encountered an unexpected condition which prevented it
2237   from fulfilling the request.
2238</t>
2239</section>
2240
2241<section title="501 Not Implemented" anchor="status.501">
2242  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2243  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2244<t>
2245   The server does not support the functionality required to fulfill the
2246   request. This is the appropriate response when the server does not
2247   recognize the request method and is not capable of supporting it for
2248   any resource.
2249</t>
2250</section>
2251
2252<section title="502 Bad Gateway" anchor="status.502">
2253  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2254  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2255<t>
2256   The server, while acting as a gateway or proxy, received an invalid
2257   response from the upstream server it accessed in attempting to
2258   fulfill the request.
2259</t>
2260</section>
2261
2262<section title="503 Service Unavailable" anchor="status.503">
2263  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2264  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2265<t>
2266   The server is currently unable or unwilling to handle the request due to
2267   reasons such as temporary overloading, maintenance of the server, or rate
2268   limiting of the client.
2269</t>
2270<t>
2271   The implication is that this is a temporary condition which will be
2272   alleviated after some delay. If known, the length of the delay &MAY; be
2273   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2274   If no Retry-After is given, the client &SHOULD; handle the response as it
2275   would for a 500 response.
2276</t>
2277<x:note>
2278  <t>
2279    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2280    server must use it when becoming overloaded. Some servers might wish
2281    to simply refuse the connection.
2282  </t>
2283</x:note>
2284</section>
2285
2286<section title="504 Gateway Timeout" anchor="status.504">
2287  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2288  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2289<t>
2290   The server, while acting as a gateway or proxy, did not receive a
2291   timely response from the upstream server specified by the URI (e.g.,
2292   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2293   to access in attempting to complete the request.
2294</t>
2295<x:note>
2296  <t>
2297    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2298    return 400 or 500 when DNS lookups time out.
2299  </t>
2300</x:note>
2301</section>
2302
2303<section title="505 HTTP Version Not Supported" anchor="status.505">
2304  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2305  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2306<t>
2307   The server does not support, or refuses to support, the protocol
2308   version that was used in the request message. The server is
2309   indicating that it is unable or unwilling to complete the request
2310   using the same major version as the client, as described in &http-version;,
2311   other than with this error message. The response &SHOULD; contain
2312   a representation describing why that version is not supported and what other
2313   protocols are supported by that server.
2314</t>
2315
2316</section>
2317</section>
2318</section>
2319
2320
2321<section title="Date/Time Formats" anchor="http.date">
2322  <x:anchor-alias value="HTTP-date"/>
2323<t>
2324   HTTP applications have historically allowed three different formats
2325   for date/time stamps. However, the preferred format is a fixed-length subset
2326   of that defined by <xref target="RFC1123"/>:
2327</t>
2328<figure><artwork type="example" x:indent-with="  ">
2329Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2330</artwork></figure>
2331<t>
2332   The other formats are described here only for compatibility with obsolete
2333   implementations.
2334</t>
2335<figure><artwork type="example" x:indent-with="  ">
2336Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2337Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2338</artwork></figure>
2339<t>
2340   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2341   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2342   only generate the RFC 1123 format for representing HTTP-date values
2343   in header fields.
2344</t>
2345<t>
2346   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2347   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2348   equal to UTC (Coordinated Universal Time). This is indicated in the
2349   first two formats by the inclusion of "GMT" as the three-letter
2350   abbreviation for time zone, and &MUST; be assumed when reading the
2351   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2352   additional whitespace beyond that specifically included as SP in the
2353   grammar.
2354</t>
2355<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2356  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2357</artwork></figure>
2358<t anchor="preferred.date.format">
2359  <x:anchor-alias value="rfc1123-date"/>
2360  <x:anchor-alias value="time-of-day"/>
2361  <x:anchor-alias value="hour"/>
2362  <x:anchor-alias value="minute"/>
2363  <x:anchor-alias value="second"/>
2364  <x:anchor-alias value="day-name"/>
2365  <x:anchor-alias value="day"/>
2366  <x:anchor-alias value="month"/>
2367  <x:anchor-alias value="year"/>
2368  <x:anchor-alias value="GMT"/>
2369  Preferred format:
2370</t>
2371<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"/>
2372  <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>
2373  ; fixed length subset of the format defined in
2374  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2375 
2376  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2377               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2378               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2379               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2380               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2381               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2382               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2383               
2384  <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>
2385               ; e.g., 02 Jun 1982
2386
2387  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2388  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2389               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2390               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2391               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2392               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2393               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2394               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2395               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2396               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2397               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2398               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2399               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2400  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2401
2402  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2403
2404  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2405                 ; 00:00:00 - 23:59:59
2406                 
2407  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2408  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2409  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2410</artwork></figure>
2411<t>
2412  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2413  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2414  same as those defined for the RFC 5322 constructs
2415  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2416</t>
2417<t anchor="obsolete.date.formats">
2418  <x:anchor-alias value="obs-date"/>
2419  <x:anchor-alias value="rfc850-date"/>
2420  <x:anchor-alias value="asctime-date"/>
2421  <x:anchor-alias value="date1"/>
2422  <x:anchor-alias value="date2"/>
2423  <x:anchor-alias value="date3"/>
2424  <x:anchor-alias value="rfc1123-date"/>
2425  <x:anchor-alias value="day-name-l"/>
2426  Obsolete formats:
2427</t>
2428<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2429  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2430</artwork></figure>
2431<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2432  <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>
2433  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2434                 ; day-month-year (e.g., 02-Jun-82)
2435
2436  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2437         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2438         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2439         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2440         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2441         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2442         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2443</artwork></figure>
2444<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2445  <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>
2446  <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> ))
2447                 ; month day (e.g., Jun  2)
2448</artwork></figure>
2449<x:note>
2450  <t>
2451    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2452    accepting date values that might have been sent by non-HTTP
2453    applications, as is sometimes the case when retrieving or posting
2454    messages via proxies/gateways to SMTP or NNTP.
2455  </t>
2456</x:note>
2457<x:note>
2458  <t>
2459    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2460    to their usage within the protocol stream. Clients and servers are
2461    not required to use these formats for user presentation, request
2462    logging, etc.
2463  </t>
2464</x:note>
2465</section>
2466
2467
2468<section title="Header Field Definitions" anchor="header.field.definitions">
2469<t>
2470   This section defines the syntax and semantics of HTTP/1.1 header fields
2471   related to request and response semantics.
2472</t>
2473
2474<section title="Allow" anchor="header.allow">
2475  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2476  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2477  <x:anchor-alias value="Allow"/>
2478<t>
2479   The "Allow" header field lists the set of methods advertised as
2480   supported by the target resource. The purpose of this field is strictly to
2481   inform the recipient of valid request methods associated with the resource.
2482</t>
2483<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2484  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2485</artwork></figure>
2486<t>
2487   Example of use:
2488</t>
2489<figure><artwork type="example">
2490  Allow: GET, HEAD, PUT
2491</artwork></figure>
2492<t>
2493   The actual set of allowed methods is defined by the origin server at the
2494   time of each request.
2495</t>
2496<t>
2497   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2498   understand all the methods specified in order to handle them according to
2499   the generic message handling rules.
2500</t>
2501</section>
2502
2503<section title="Date" anchor="header.date">
2504  <iref primary="true" item="Date header field" x:for-anchor=""/>
2505  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2506  <x:anchor-alias value="Date"/>
2507<t>
2508   The "Date" header field represents the date and time at which
2509   the message was originated, having the same semantics as the Origination
2510   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2511   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2512   it &MUST; be sent in rfc1123-date format.
2513</t>
2514<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2515  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2516</artwork></figure>
2517<t>
2518   An example is
2519</t>
2520<figure><artwork type="example">
2521  Date: Tue, 15 Nov 1994 08:12:31 GMT
2522</artwork></figure>
2523<t>
2524   Origin servers &MUST; include a Date header field in all responses,
2525   except in these cases:
2526  <list style="numbers">
2527      <t>If the response status code is 100 (Continue) or 101 (Switching
2528         Protocols), the response &MAY; include a Date header field, at
2529         the server's option.</t>
2530
2531      <t>If the response status code conveys a server error, e.g., 500
2532         (Internal Server Error) or 503 (Service Unavailable), and it is
2533         inconvenient or impossible to generate a valid Date.</t>
2534
2535      <t>If the server does not have a clock that can provide a
2536         reasonable approximation of the current time, its responses
2537         &MUST-NOT; include a Date header field.</t>
2538  </list>
2539</t>
2540<t>
2541   A received message that does not have a Date header field &MUST; be
2542   assigned one by the recipient if the message will be cached by that
2543   recipient.
2544</t>
2545<t>
2546   Clients can use the Date header field as well; in order to keep request
2547   messages small, they are advised not to include it when it doesn't convey
2548   any useful information (as it is usually the case for requests that do not
2549   contain a payload).
2550</t>
2551<t>
2552   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2553   time subsequent to the generation of the message. It &SHOULD; represent
2554   the best available approximation of the date and time of message
2555   generation, unless the implementation has no means of generating a
2556   reasonably accurate date and time. In theory, the date ought to
2557   represent the moment just before the payload is generated. In
2558   practice, the date can be generated at any time during the message
2559   origination without affecting its semantic value.
2560</t>
2561</section>
2562
2563<section title="Expect" anchor="header.expect">
2564  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2565  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2566  <x:anchor-alias value="Expect"/>
2567  <x:anchor-alias value="expectation"/>
2568  <x:anchor-alias value="expectation-extension"/>
2569  <x:anchor-alias value="expect-params"/>
2570<t>
2571   The "Expect" header field is used to indicate that particular
2572   server behaviors are required by the client.
2573</t>
2574<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2575  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2576 
2577  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2578  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2579                           *<x:ref>expect-params</x:ref> ]
2580  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2581</artwork></figure>
2582<t>
2583   A server that does not understand or is unable to comply with any of
2584   the expectation values in the Expect field of a request &MUST; respond
2585   with appropriate error status code. The server &MUST; respond with a 417
2586   (Expectation Failed) status code if any of the expectations cannot be met
2587   or, if there are other problems with the request, some other 4xx
2588   status code.
2589</t>
2590<t>
2591   This header field is defined with extensible syntax to allow for
2592   future extensions. If a server receives a request containing an
2593   Expect field that includes an expectation-extension that it does not
2594   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2595</t>
2596<t>
2597   Comparison of expectation values is case-insensitive for unquoted
2598   tokens (including the 100-continue token), and is case-sensitive for
2599   quoted-string expectation-extensions.
2600</t>
2601<t>
2602   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2603   return a 417 (Expectation Failed) status code if it receives a request
2604   with an expectation that it cannot meet. However, the Expect
2605   header field itself is end-to-end; it &MUST; be forwarded if the
2606   request is forwarded.
2607</t>
2608<t>
2609   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2610   Expect header field.
2611</t>
2612<t>
2613   See &use100; for the use of the 100 (Continue) status code.
2614</t>
2615</section>
2616
2617<section title="From" anchor="header.from">
2618  <iref primary="true" item="From header field" x:for-anchor=""/>
2619  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2620  <x:anchor-alias value="From"/>
2621  <x:anchor-alias value="mailbox"/>
2622<t>
2623   The "From" header field, if given, &SHOULD; contain an Internet
2624   e-mail address for the human user who controls the requesting user
2625   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2626   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2627</t>
2628<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2629  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2630 
2631  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2632</artwork></figure>
2633<t>
2634   An example is:
2635</t>
2636<figure><artwork type="example">
2637  From: webmaster@example.org
2638</artwork></figure>
2639<t>
2640   This header field &MAY; be used for logging purposes and as a means for
2641   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2642   be used as an insecure form of access protection. The interpretation
2643   of this field is that the request is being performed on behalf of the
2644   person given, who accepts responsibility for the method performed. In
2645   particular, robot agents &SHOULD; include this header field so that the
2646   person responsible for running the robot can be contacted if problems
2647   occur on the receiving end.
2648</t>
2649<t>
2650   The Internet e-mail address in this field &MAY; be separate from the
2651   Internet host which issued the request. For example, when a request
2652   is passed through a proxy the original issuer's address &SHOULD; be
2653   used.
2654</t>
2655<t>
2656   The client &SHOULD-NOT;  send the From header field without the user's
2657   approval, as it might conflict with the user's privacy interests or
2658   their site's security policy. It is strongly recommended that the
2659   user be able to disable, enable, and modify the value of this field
2660   at any time prior to a request.
2661</t>
2662</section>
2663
2664<section title="Location" anchor="header.location">
2665  <iref primary="true" item="Location header field" x:for-anchor=""/>
2666  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2667  <x:anchor-alias value="Location"/>
2668<t>
2669   The "Location" header field is used to identify a newly created
2670   resource, or to redirect the recipient to a different location for
2671   completion of the request.
2672</t>
2673<t>
2674   For 201 (Created) responses, the Location is the URI of the new resource
2675   which was created by the request. For 3xx responses, the location &SHOULD;
2676   indicate the server's preferred URI for automatic redirection to the
2677   resource.
2678</t>
2679<t>
2680   The field value consists of a single URI-reference. When it has the form
2681   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2682   the final value is computed by resolving it against the effective request
2683   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2684</t>
2685<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2686  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2687</artwork></figure>
2688<figure>
2689<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2690<artwork type="example">
2691  Location: http://www.example.org/pub/WWW/People.html#tim
2692</artwork></figure><figure><artwork type="example">  Location: /index.html
2693</artwork></figure>
2694<t>
2695   There are circumstances in which a fragment identifier in a Location URI
2696   would not be appropriate. For instance, when it appears in a 201 Created
2697   response, where the Location header field specifies the URI for the entire
2698   created resource.
2699</t>
2700<x:note>
2701  <t>
2702    <x:h>Note:</x:h> This specification does not define precedence rules
2703    for the case where the original URI, as navigated to by the user
2704    agent, and the Location header field value both contain fragment
2705    identifiers. Thus be aware that including fragment identifiers might
2706    inconvenience anyone relying on the semantics of the original URI's
2707    fragment identifier.
2708  </t>
2709</x:note>
2710<x:note>
2711  <t>
2712    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2713    from Location in that the Content-Location identifies the most specific
2714    resource corresponding to the enclosed representation.
2715    It is therefore possible for a response to contain header fields for
2716    both Location and Content-Location.
2717  </t>
2718</x:note>
2719</section>
2720
2721<section title="Max-Forwards" anchor="header.max-forwards">
2722  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2723  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2724  <x:anchor-alias value="Max-Forwards"/>
2725<t>
2726   The "Max-Forwards" header field provides a mechanism with the
2727   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2728   methods to limit the number of times that the request is forwarded by
2729   proxies. This can be useful when the client is attempting to
2730   trace a request which appears to be failing or looping in mid-chain.
2731</t>
2732<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2733  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2734</artwork></figure>
2735<t>
2736   The Max-Forwards value is a decimal integer indicating the remaining
2737   number of times this request message can be forwarded.
2738</t>
2739<t>
2740   Each recipient of a TRACE or OPTIONS request
2741   containing a Max-Forwards header field &MUST; check and update its
2742   value prior to forwarding the request. If the received value is zero
2743   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2744   respond as the final recipient. If the received Max-Forwards value is
2745   greater than zero, then the forwarded message &MUST; contain an updated
2746   Max-Forwards field with a value decremented by one (1).
2747</t>
2748<t>
2749   The Max-Forwards header field &MAY; be ignored for all other request
2750   methods.
2751</t>
2752</section>
2753
2754<section title="Referer" anchor="header.referer">
2755  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2756  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2757  <x:anchor-alias value="Referer"/>
2758<t>
2759   The "Referer" [sic] header field allows the client to specify the
2760   URI of the resource from which the effective request URI was obtained (the
2761   "referrer", although the header field is misspelled.).
2762</t>
2763<t>
2764   The Referer header field allows servers to generate lists of back-links to
2765   resources for interest, logging, optimized caching, etc. It also allows
2766   obsolete or mistyped links to be traced for maintenance. Some servers use
2767   Referer as a means of controlling where they allow links from (so-called
2768   "deep linking"), but legitimate requests do not always
2769   contain a Referer header field.
2770</t>
2771<t>
2772   If the effective request URI was obtained from a source that does not have its own
2773   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2774   sent with the value "about:blank", or not be sent at all. Note that this
2775   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2776</t>
2777<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2778  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2779</artwork></figure>
2780<t>
2781   Example:
2782</t>
2783<figure><artwork type="example">
2784  Referer: http://www.example.org/hypertext/Overview.html
2785</artwork></figure>
2786<t>
2787   If the field value is a relative URI, it &SHOULD; be interpreted
2788   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2789   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2790</t>
2791</section>
2792
2793<section title="Retry-After" anchor="header.retry-after">
2794  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2795  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2796  <x:anchor-alias value="Retry-After"/>
2797<t>
2798   The header "Retry-After" field can be used with a 503 (Service
2799   Unavailable) response to indicate how long the service is expected to
2800   be unavailable to the requesting client. This field &MAY; also be used
2801   with any 3xx (Redirection) response to indicate the minimum time the
2802   user-agent is asked wait before issuing the redirected request.
2803</t>
2804<t>
2805   The value of this field can be either an HTTP-date or an integer number
2806   of seconds (in decimal) after the time of the response.
2807</t>
2808<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2809  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2810</artwork></figure>
2811<t anchor="rule.delta-seconds">
2812  <x:anchor-alias value="delta-seconds"/>
2813   Time spans are non-negative decimal integers, representing time in
2814   seconds.
2815</t>
2816<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2817  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2818</artwork></figure>
2819<t>
2820   Two examples of its use are
2821</t>
2822<figure><artwork type="example">
2823  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2824  Retry-After: 120
2825</artwork></figure>
2826<t>
2827   In the latter example, the delay is 2 minutes.
2828</t>
2829</section>
2830
2831<section title="Server" anchor="header.server">
2832  <iref primary="true" item="Server header field" x:for-anchor=""/>
2833  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2834  <x:anchor-alias value="Server"/>
2835<t>
2836   The "Server" header field contains information about the
2837   software used by the origin server to handle the request.
2838</t>
2839<t>
2840   The field can contain multiple product tokens (&product-tokens;) and
2841   comments (&header-fields;) identifying the server and any significant
2842   subproducts. The product tokens are listed in order of their significance
2843   for identifying the application.
2844</t>
2845<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2846  <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> ) )
2847</artwork></figure>
2848<t>
2849   Example:
2850</t>
2851<figure><artwork type="example">
2852  Server: CERN/3.0 libwww/2.17
2853</artwork></figure>
2854<t>
2855   If the response is being forwarded through a proxy, the proxy
2856   application &MUST-NOT; modify the Server header field. Instead, it
2857   &MUST; include a Via field (as described in &header-via;).
2858</t>
2859<x:note>
2860  <t>
2861    <x:h>Note:</x:h> Revealing the specific software version of the server might
2862    allow the server machine to become more vulnerable to attacks
2863    against software that is known to contain security holes. Server
2864    implementors are encouraged to make this field a configurable
2865    option.
2866  </t>
2867</x:note>
2868</section>
2869
2870<section title="User-Agent" anchor="header.user-agent">
2871  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2872  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2873  <x:anchor-alias value="User-Agent"/>
2874<t>
2875   The "User-Agent" header field contains information about the user
2876   agent originating the request. User agents &SHOULD; include this field with
2877   requests.
2878</t>
2879<t>
2880   Typically, it is used for statistical purposes, the tracing of protocol
2881   violations, and tailoring responses to avoid particular user agent
2882   limitations.
2883</t>
2884<t>
2885   The field can contain multiple product tokens (&product-tokens;)
2886   and comments (&header-fields;) identifying the agent and its
2887   significant subproducts. By convention, the product tokens are listed in
2888   order of their significance for identifying the application.
2889</t>
2890<t>
2891   Because this field is usually sent on every request a user agent makes,
2892   implementations are encouraged not to include needlessly fine-grained
2893   detail, and to limit (or even prohibit) the addition of subproducts by third
2894   parties. Overly long and detailed User-Agent field values make requests
2895   larger and can also be used to identify ("fingerprint") the user against
2896   their wishes.
2897</t>
2898<t>
2899   Likewise, implementations are encouraged not to use the product tokens of
2900   other implementations in order to declare compatibility with them, as this
2901   circumvents the purpose of the field. Finally, they are encouraged not to
2902   use comments to identify products; doing so makes the field value more
2903   difficult to parse.
2904</t>
2905<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2906  <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> ) )
2907</artwork></figure>
2908<t>
2909   Example:
2910</t>
2911<figure><artwork type="example">
2912  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2913</artwork></figure>
2914</section>
2915
2916</section>
2917
2918<section title="IANA Considerations" anchor="IANA.considerations">
2919
2920<section title="Method Registry" anchor="method.registration">
2921<t>
2922  The registration procedure for HTTP request methods is defined by
2923  <xref target="method.registry"/> of this document.
2924</t>
2925<t>
2926   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2927   and be populated with the registrations below:
2928</t>
2929<?BEGININC p2-semantics.iana-methods ?>
2930<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2931<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2932   <ttcol>Method</ttcol>
2933   <ttcol>Safe</ttcol>
2934   <ttcol>Reference</ttcol>
2935   <c>CONNECT</c>
2936   <c>no</c>
2937   <c>
2938      <xref target="CONNECT"/>
2939   </c>
2940   <c>DELETE</c>
2941   <c>no</c>
2942   <c>
2943      <xref target="DELETE"/>
2944   </c>
2945   <c>GET</c>
2946   <c>yes</c>
2947   <c>
2948      <xref target="GET"/>
2949   </c>
2950   <c>HEAD</c>
2951   <c>yes</c>
2952   <c>
2953      <xref target="HEAD"/>
2954   </c>
2955   <c>OPTIONS</c>
2956   <c>yes</c>
2957   <c>
2958      <xref target="OPTIONS"/>
2959   </c>
2960   <c>POST</c>
2961   <c>no</c>
2962   <c>
2963      <xref target="POST"/>
2964   </c>
2965   <c>PUT</c>
2966   <c>no</c>
2967   <c>
2968      <xref target="PUT"/>
2969   </c>
2970   <c>TRACE</c>
2971   <c>yes</c>
2972   <c>
2973      <xref target="TRACE"/>
2974   </c>
2975</texttable>
2976<!--(END)-->
2977<?ENDINC p2-semantics.iana-methods ?>
2978</section>
2979
2980<section title="Status Code Registry" anchor="status.code.registration">
2981<t>
2982   The registration procedure for HTTP Status Codes &mdash; previously defined
2983   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2984   by <xref target="status.code.registry"/> of this document.
2985</t>
2986<t>
2987   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2988   shall be updated with the registrations below:
2989</t>
2990<?BEGININC p2-semantics.iana-status-codes ?>
2991<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2992<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2993   <ttcol>Value</ttcol>
2994   <ttcol>Description</ttcol>
2995   <ttcol>Reference</ttcol>
2996   <c>100</c>
2997   <c>Continue</c>
2998   <c>
2999      <xref target="status.100"/>
3000   </c>
3001   <c>101</c>
3002   <c>Switching Protocols</c>
3003   <c>
3004      <xref target="status.101"/>
3005   </c>
3006   <c>200</c>
3007   <c>OK</c>
3008   <c>
3009      <xref target="status.200"/>
3010   </c>
3011   <c>201</c>
3012   <c>Created</c>
3013   <c>
3014      <xref target="status.201"/>
3015   </c>
3016   <c>202</c>
3017   <c>Accepted</c>
3018   <c>
3019      <xref target="status.202"/>
3020   </c>
3021   <c>203</c>
3022   <c>Non-Authoritative Information</c>
3023   <c>
3024      <xref target="status.203"/>
3025   </c>
3026   <c>204</c>
3027   <c>No Content</c>
3028   <c>
3029      <xref target="status.204"/>
3030   </c>
3031   <c>205</c>
3032   <c>Reset Content</c>
3033   <c>
3034      <xref target="status.205"/>
3035   </c>
3036   <c>300</c>
3037   <c>Multiple Choices</c>
3038   <c>
3039      <xref target="status.300"/>
3040   </c>
3041   <c>301</c>
3042   <c>Moved Permanently</c>
3043   <c>
3044      <xref target="status.301"/>
3045   </c>
3046   <c>302</c>
3047   <c>Found</c>
3048   <c>
3049      <xref target="status.302"/>
3050   </c>
3051   <c>303</c>
3052   <c>See Other</c>
3053   <c>
3054      <xref target="status.303"/>
3055   </c>
3056   <c>305</c>
3057   <c>Use Proxy</c>
3058   <c>
3059      <xref target="status.305"/>
3060   </c>
3061   <c>306</c>
3062   <c>(Unused)</c>
3063   <c>
3064      <xref target="status.306"/>
3065   </c>
3066   <c>307</c>
3067   <c>Temporary Redirect</c>
3068   <c>
3069      <xref target="status.307"/>
3070   </c>
3071   <c>400</c>
3072   <c>Bad Request</c>
3073   <c>
3074      <xref target="status.400"/>
3075   </c>
3076   <c>402</c>
3077   <c>Payment Required</c>
3078   <c>
3079      <xref target="status.402"/>
3080   </c>
3081   <c>403</c>
3082   <c>Forbidden</c>
3083   <c>
3084      <xref target="status.403"/>
3085   </c>
3086   <c>404</c>
3087   <c>Not Found</c>
3088   <c>
3089      <xref target="status.404"/>
3090   </c>
3091   <c>405</c>
3092   <c>Method Not Allowed</c>
3093   <c>
3094      <xref target="status.405"/>
3095   </c>
3096   <c>406</c>
3097   <c>Not Acceptable</c>
3098   <c>
3099      <xref target="status.406"/>
3100   </c>
3101   <c>407</c>
3102   <c>Proxy Authentication Required</c>
3103   <c>
3104      <xref target="status.407"/>
3105   </c>
3106   <c>408</c>
3107   <c>Request Timeout</c>
3108   <c>
3109      <xref target="status.408"/>
3110   </c>
3111   <c>409</c>
3112   <c>Conflict</c>
3113   <c>
3114      <xref target="status.409"/>
3115   </c>
3116   <c>410</c>
3117   <c>Gone</c>
3118   <c>
3119      <xref target="status.410"/>
3120   </c>
3121   <c>411</c>
3122   <c>Length Required</c>
3123   <c>
3124      <xref target="status.411"/>
3125   </c>
3126   <c>413</c>
3127   <c>Request Representation Too Large</c>
3128   <c>
3129      <xref target="status.413"/>
3130   </c>
3131   <c>414</c>
3132   <c>URI Too Long</c>
3133   <c>
3134      <xref target="status.414"/>
3135   </c>
3136   <c>415</c>
3137   <c>Unsupported Media Type</c>
3138   <c>
3139      <xref target="status.415"/>
3140   </c>
3141   <c>417</c>
3142   <c>Expectation Failed</c>
3143   <c>
3144      <xref target="status.417"/>
3145   </c>
3146   <c>426</c>
3147   <c>Upgrade Required</c>
3148   <c>
3149      <xref target="status.426"/>
3150   </c>
3151   <c>500</c>
3152   <c>Internal Server Error</c>
3153   <c>
3154      <xref target="status.500"/>
3155   </c>
3156   <c>501</c>
3157   <c>Not Implemented</c>
3158   <c>
3159      <xref target="status.501"/>
3160   </c>
3161   <c>502</c>
3162   <c>Bad Gateway</c>
3163   <c>
3164      <xref target="status.502"/>
3165   </c>
3166   <c>503</c>
3167   <c>Service Unavailable</c>
3168   <c>
3169      <xref target="status.503"/>
3170   </c>
3171   <c>504</c>
3172   <c>Gateway Timeout</c>
3173   <c>
3174      <xref target="status.504"/>
3175   </c>
3176   <c>505</c>
3177   <c>HTTP Version Not Supported</c>
3178   <c>
3179      <xref target="status.505"/>
3180   </c>
3181</texttable>
3182<!--(END)-->
3183<?ENDINC p2-semantics.iana-status-codes ?>
3184</section>
3185<section title="Header Field Registration" anchor="header.field.registration">
3186<t>
3187   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3188   with the permanent registrations below (see <xref target="RFC3864"/>):
3189</t>
3190<?BEGININC p2-semantics.iana-headers ?>
3191<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3192<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3193   <ttcol>Header Field Name</ttcol>
3194   <ttcol>Protocol</ttcol>
3195   <ttcol>Status</ttcol>
3196   <ttcol>Reference</ttcol>
3197
3198   <c>Allow</c>
3199   <c>http</c>
3200   <c>standard</c>
3201   <c>
3202      <xref target="header.allow"/>
3203   </c>
3204   <c>Date</c>
3205   <c>http</c>
3206   <c>standard</c>
3207   <c>
3208      <xref target="header.date"/>
3209   </c>
3210   <c>Expect</c>
3211   <c>http</c>
3212   <c>standard</c>
3213   <c>
3214      <xref target="header.expect"/>
3215   </c>
3216   <c>From</c>
3217   <c>http</c>
3218   <c>standard</c>
3219   <c>
3220      <xref target="header.from"/>
3221   </c>
3222   <c>Location</c>
3223   <c>http</c>
3224   <c>standard</c>
3225   <c>
3226      <xref target="header.location"/>
3227   </c>
3228   <c>Max-Forwards</c>
3229   <c>http</c>
3230   <c>standard</c>
3231   <c>
3232      <xref target="header.max-forwards"/>
3233   </c>
3234   <c>Referer</c>
3235   <c>http</c>
3236   <c>standard</c>
3237   <c>
3238      <xref target="header.referer"/>
3239   </c>
3240   <c>Retry-After</c>
3241   <c>http</c>
3242   <c>standard</c>
3243   <c>
3244      <xref target="header.retry-after"/>
3245   </c>
3246   <c>Server</c>
3247   <c>http</c>
3248   <c>standard</c>
3249   <c>
3250      <xref target="header.server"/>
3251   </c>
3252   <c>User-Agent</c>
3253   <c>http</c>
3254   <c>standard</c>
3255   <c>
3256      <xref target="header.user-agent"/>
3257   </c>
3258</texttable>
3259<!--(END)-->
3260<?ENDINC p2-semantics.iana-headers ?>
3261<t>
3262   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3263</t>
3264</section>
3265</section>
3266
3267<section title="Security Considerations" anchor="security.considerations">
3268<t>
3269   This section is meant to inform application developers, information
3270   providers, and users of the security limitations in HTTP/1.1 as
3271   described by this document. The discussion does not include
3272   definitive solutions to the problems revealed, though it does make
3273   some suggestions for reducing security risks.
3274</t>
3275
3276<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3277<t>
3278   Like any generic data transfer protocol, HTTP cannot regulate the
3279   content of the data that is transferred, nor is there any a priori
3280   method of determining the sensitivity of any particular piece of
3281   information within the context of any given request. Therefore,
3282   applications &SHOULD; supply as much control over this information as
3283   possible to the provider of that information. Four header fields are
3284   worth special mention in this context: Server, Via, Referer and From.
3285</t>
3286<t>
3287   Revealing the specific software version of the server might allow the
3288   server machine to become more vulnerable to attacks against software
3289   that is known to contain security holes. Implementors &SHOULD; make the
3290   Server header field a configurable option.
3291</t>
3292<t>
3293   Proxies which serve as a portal through a network firewall &SHOULD;
3294   take special precautions regarding the transfer of header information
3295   that identifies the hosts behind the firewall. In particular, they
3296   &SHOULD; remove, or replace with sanitized versions, any Via fields
3297   generated behind the firewall.
3298</t>
3299<t>
3300   The Referer header field allows reading patterns to be studied and reverse
3301   links drawn. Although it can be very useful, its power can be abused
3302   if user details are not separated from the information contained in
3303   the Referer. Even when the personal information has been removed, the
3304   Referer header field might indicate a private document's URI whose
3305   publication would be inappropriate.
3306</t>
3307<t>
3308   The information sent in the From field might conflict with the user's
3309   privacy interests or their site's security policy, and hence it
3310   &SHOULD-NOT;  be transmitted without the user being able to disable,
3311   enable, and modify the contents of the field. The user &MUST; be able
3312   to set the contents of this field within a user preference or
3313   application defaults configuration.
3314</t>
3315<t>
3316   We suggest, though do not require, that a convenient toggle interface
3317   be provided for the user to enable or disable the sending of From and
3318   Referer information.
3319</t>
3320<t>
3321   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3322   target="header.server"/>) header fields can sometimes be used to determine
3323   that a specific client or server have a particular security hole which might
3324   be exploited. Unfortunately, this same information is often used for other
3325   valuable purposes for which HTTP currently has no better mechanism.
3326</t>
3327<t>
3328   Furthermore, the User-Agent header field may contain enough entropy to be
3329   used, possibly in conjunction with other material, to uniquely identify the
3330   user.
3331</t>
3332<t>
3333   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3334   that was sent in request header fields within the body of their response.
3335   Clients &SHOULD; be careful with sensitive information, like Cookies,
3336   Authorization credentials, and other header fields that might be used to
3337   collect data from the client.
3338</t> 
3339</section>
3340
3341<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3342<t>
3343   Because the source of a link might be private information or might
3344   reveal an otherwise private information source, it is strongly
3345   recommended that the user be able to select whether or not the
3346   Referer field is sent. For example, a browser client could have a
3347   toggle switch for browsing openly/anonymously, which would
3348   respectively enable/disable the sending of Referer and From
3349   information.
3350</t>
3351<t>
3352   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3353   HTTP request if the referring page was transferred with a secure
3354   protocol.
3355</t>
3356<t>
3357   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3358   sensitive data because that data will be placed in the request-target. Many
3359   existing servers, proxies, and user agents log or display the request-target
3360   in places where it might be visible to third parties. Such services can
3361   use POST-based form submission instead.
3362</t>
3363</section>
3364
3365<section title="Location Headers and Spoofing" anchor="location.spoofing">
3366<t>
3367   If a single server supports multiple organizations that do not trust
3368   one another, then it &MUST; check the values of Location and Content-Location
3369   header fields in responses that are generated under control of
3370   said organizations to make sure that they do not attempt to
3371   invalidate resources over which they have no authority.
3372</t>
3373</section>
3374
3375<section title="Security Considerations for CONNECT">
3376<t>
3377   Since tunneled data is opaque to the proxy, there are additional
3378   risks to tunneling to other well-known or reserved ports.
3379   A HTTP client CONNECTing to port 25 could relay spam
3380   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3381   access to a small number of known ports.
3382</t>
3383</section>
3384
3385</section>
3386
3387<section title="Acknowledgments" anchor="acks">
3388<t>
3389  See &acks;.
3390</t>
3391</section>
3392</middle>
3393<back>
3394
3395<references title="Normative References">
3396
3397<reference anchor="Part1">
3398  <front>
3399    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3400    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3401      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3402      <address><email>fielding@gbiv.com</email></address>
3403    </author>
3404    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3405      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3406      <address><email>jg@freedesktop.org</email></address>
3407    </author>
3408    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3409      <organization abbrev="HP">Hewlett-Packard Company</organization>
3410      <address><email>JeffMogul@acm.org</email></address>
3411    </author>
3412    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3413      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3414      <address><email>henrikn@microsoft.com</email></address>
3415    </author>
3416    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3417      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3418      <address><email>LMM@acm.org</email></address>
3419    </author>
3420    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3421      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3422      <address><email>paulle@microsoft.com</email></address>
3423    </author>
3424    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3425      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3426      <address><email>timbl@w3.org</email></address>
3427    </author>
3428    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3429      <organization abbrev="W3C">World Wide Web Consortium</organization>
3430      <address><email>ylafon@w3.org</email></address>
3431    </author>
3432    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3433      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3434      <address><email>julian.reschke@greenbytes.de</email></address>
3435    </author>
3436    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3437  </front>
3438  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3439  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3440</reference>
3441
3442<reference anchor="Part3">
3443  <front>
3444    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3445    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3446      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3447      <address><email>fielding@gbiv.com</email></address>
3448    </author>
3449    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3450      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3451      <address><email>jg@freedesktop.org</email></address>
3452    </author>
3453    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3454      <organization abbrev="HP">Hewlett-Packard Company</organization>
3455      <address><email>JeffMogul@acm.org</email></address>
3456    </author>
3457    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3458      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3459      <address><email>henrikn@microsoft.com</email></address>
3460    </author>
3461    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3462      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3463      <address><email>LMM@acm.org</email></address>
3464    </author>
3465    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3466      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3467      <address><email>paulle@microsoft.com</email></address>
3468    </author>
3469    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3470      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3471      <address><email>timbl@w3.org</email></address>
3472    </author>
3473    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3474      <organization abbrev="W3C">World Wide Web Consortium</organization>
3475      <address><email>ylafon@w3.org</email></address>
3476    </author>
3477    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3478      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3479      <address><email>julian.reschke@greenbytes.de</email></address>
3480    </author>
3481    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3482  </front>
3483  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3484  <x:source href="p3-payload.xml" basename="p3-payload"/>
3485</reference>
3486
3487<reference anchor="Part4">
3488  <front>
3489    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3490    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3491      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3492      <address><email>fielding@gbiv.com</email></address>
3493    </author>
3494    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3495      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3496      <address><email>jg@freedesktop.org</email></address>
3497    </author>
3498    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3499      <organization abbrev="HP">Hewlett-Packard Company</organization>
3500      <address><email>JeffMogul@acm.org</email></address>
3501    </author>
3502    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3503      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3504      <address><email>henrikn@microsoft.com</email></address>
3505    </author>
3506    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3507      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3508      <address><email>LMM@acm.org</email></address>
3509    </author>
3510    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3511      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3512      <address><email>paulle@microsoft.com</email></address>
3513    </author>
3514    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3515      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3516      <address><email>timbl@w3.org</email></address>
3517    </author>
3518    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3519      <organization abbrev="W3C">World Wide Web Consortium</organization>
3520      <address><email>ylafon@w3.org</email></address>
3521    </author>
3522    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3523      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3524      <address><email>julian.reschke@greenbytes.de</email></address>
3525    </author>
3526    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3527  </front>
3528  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3529  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3530</reference>
3531
3532<reference anchor="Part5">
3533  <front>
3534    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3535    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3536      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3537      <address><email>fielding@gbiv.com</email></address>
3538    </author>
3539    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3540      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3541      <address><email>jg@freedesktop.org</email></address>
3542    </author>
3543    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3544      <organization abbrev="HP">Hewlett-Packard Company</organization>
3545      <address><email>JeffMogul@acm.org</email></address>
3546    </author>
3547    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3548      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3549      <address><email>henrikn@microsoft.com</email></address>
3550    </author>
3551    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3552      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3553      <address><email>LMM@acm.org</email></address>
3554    </author>
3555    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3556      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3557      <address><email>paulle@microsoft.com</email></address>
3558    </author>
3559    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3560      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3561      <address><email>timbl@w3.org</email></address>
3562    </author>
3563    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3564      <organization abbrev="W3C">World Wide Web Consortium</organization>
3565      <address><email>ylafon@w3.org</email></address>
3566    </author>
3567    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3568      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3569      <address><email>julian.reschke@greenbytes.de</email></address>
3570    </author>
3571    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3572  </front>
3573  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3574  <x:source href="p5-range.xml" basename="p5-range"/>
3575</reference>
3576
3577<reference anchor="Part6">
3578  <front>
3579    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3580    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3581      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3582      <address><email>fielding@gbiv.com</email></address>
3583    </author>
3584    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3585      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3586      <address><email>jg@freedesktop.org</email></address>
3587    </author>
3588    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3589      <organization abbrev="HP">Hewlett-Packard Company</organization>
3590      <address><email>JeffMogul@acm.org</email></address>
3591    </author>
3592    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3593      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3594      <address><email>henrikn@microsoft.com</email></address>
3595    </author>
3596    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3597      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3598      <address><email>LMM@acm.org</email></address>
3599    </author>
3600    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3601      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3602      <address><email>paulle@microsoft.com</email></address>
3603    </author>
3604    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3605      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3606      <address><email>timbl@w3.org</email></address>
3607    </author>
3608    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3609      <organization abbrev="W3C">World Wide Web Consortium</organization>
3610      <address><email>ylafon@w3.org</email></address>
3611    </author>
3612    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3613      <organization>Rackspace</organization>
3614      <address><email>mnot@mnot.net</email></address>
3615    </author>
3616    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3617      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3618      <address><email>julian.reschke@greenbytes.de</email></address>
3619    </author>
3620    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3621  </front>
3622  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3623  <x:source href="p6-cache.xml" basename="p6-cache"/>
3624</reference>
3625
3626<reference anchor="Part7">
3627  <front>
3628    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3629    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3630      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3631      <address><email>fielding@gbiv.com</email></address>
3632    </author>
3633    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3634      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3635      <address><email>jg@freedesktop.org</email></address>
3636    </author>
3637    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3638      <organization abbrev="HP">Hewlett-Packard Company</organization>
3639      <address><email>JeffMogul@acm.org</email></address>
3640    </author>
3641    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3642      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3643      <address><email>henrikn@microsoft.com</email></address>
3644    </author>
3645    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3646      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3647      <address><email>LMM@acm.org</email></address>
3648    </author>
3649    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3650      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3651      <address><email>paulle@microsoft.com</email></address>
3652    </author>
3653    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3654      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3655      <address><email>timbl@w3.org</email></address>
3656    </author>
3657    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3658      <organization abbrev="W3C">World Wide Web Consortium</organization>
3659      <address><email>ylafon@w3.org</email></address>
3660    </author>
3661    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3662      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3663      <address><email>julian.reschke@greenbytes.de</email></address>
3664    </author>
3665    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3666  </front>
3667  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3668  <x:source href="p7-auth.xml" basename="p7-auth"/>
3669</reference>
3670
3671<reference anchor="RFC2119">
3672  <front>
3673    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3674    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3675      <organization>Harvard University</organization>
3676      <address><email>sob@harvard.edu</email></address>
3677    </author>
3678    <date month="March" year="1997"/>
3679  </front>
3680  <seriesInfo name="BCP" value="14"/>
3681  <seriesInfo name="RFC" value="2119"/>
3682</reference>
3683
3684<reference anchor="RFC3986">
3685 <front>
3686  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3687  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3688    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3689    <address>
3690       <email>timbl@w3.org</email>
3691       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3692    </address>
3693  </author>
3694  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3695    <organization abbrev="Day Software">Day Software</organization>
3696    <address>
3697      <email>fielding@gbiv.com</email>
3698      <uri>http://roy.gbiv.com/</uri>
3699    </address>
3700  </author>
3701  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3702    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3703    <address>
3704      <email>LMM@acm.org</email>
3705      <uri>http://larry.masinter.net/</uri>
3706    </address>
3707  </author>
3708  <date month='January' year='2005'></date>
3709 </front>
3710 <seriesInfo name="STD" value="66"/>
3711 <seriesInfo name="RFC" value="3986"/>
3712</reference>
3713
3714<reference anchor="RFC5234">
3715  <front>
3716    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3717    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3718      <organization>Brandenburg InternetWorking</organization>
3719      <address>
3720        <email>dcrocker@bbiw.net</email>
3721      </address> 
3722    </author>
3723    <author initials="P." surname="Overell" fullname="Paul Overell">
3724      <organization>THUS plc.</organization>
3725      <address>
3726        <email>paul.overell@thus.net</email>
3727      </address>
3728    </author>
3729    <date month="January" year="2008"/>
3730  </front>
3731  <seriesInfo name="STD" value="68"/>
3732  <seriesInfo name="RFC" value="5234"/>
3733</reference>
3734
3735</references>
3736
3737<references title="Informative References">
3738
3739<reference anchor="RFC1123">
3740  <front>
3741    <title>Requirements for Internet Hosts - Application and Support</title>
3742    <author initials="R." surname="Braden" fullname="Robert Braden">
3743      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3744      <address><email>Braden@ISI.EDU</email></address>
3745    </author>
3746    <date month="October" year="1989"/>
3747  </front>
3748  <seriesInfo name="STD" value="3"/>
3749  <seriesInfo name="RFC" value="1123"/>
3750</reference>
3751
3752<reference anchor="RFC1945">
3753  <front>
3754    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3755    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3756      <organization>MIT, Laboratory for Computer Science</organization>
3757      <address><email>timbl@w3.org</email></address>
3758    </author>
3759    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3760      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3761      <address><email>fielding@ics.uci.edu</email></address>
3762    </author>
3763    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3764      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3765      <address><email>frystyk@w3.org</email></address>
3766    </author>
3767    <date month="May" year="1996"/>
3768  </front>
3769  <seriesInfo name="RFC" value="1945"/>
3770</reference>
3771
3772<reference anchor="RFC2068">
3773  <front>
3774    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3775    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3776      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3777      <address><email>fielding@ics.uci.edu</email></address>
3778    </author>
3779    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3780      <organization>MIT Laboratory for Computer Science</organization>
3781      <address><email>jg@w3.org</email></address>
3782    </author>
3783    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3784      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3785      <address><email>mogul@wrl.dec.com</email></address>
3786    </author>
3787    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3788      <organization>MIT Laboratory for Computer Science</organization>
3789      <address><email>frystyk@w3.org</email></address>
3790    </author>
3791    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3792      <organization>MIT Laboratory for Computer Science</organization>
3793      <address><email>timbl@w3.org</email></address>
3794    </author>
3795    <date month="January" year="1997"/>
3796  </front>
3797  <seriesInfo name="RFC" value="2068"/>
3798</reference>
3799
3800<reference anchor="RFC2616">
3801  <front>
3802    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3803    <author initials="R." surname="Fielding" fullname="R. Fielding">
3804      <organization>University of California, Irvine</organization>
3805      <address><email>fielding@ics.uci.edu</email></address>
3806    </author>
3807    <author initials="J." surname="Gettys" fullname="J. Gettys">
3808      <organization>W3C</organization>
3809      <address><email>jg@w3.org</email></address>
3810    </author>
3811    <author initials="J." surname="Mogul" fullname="J. Mogul">
3812      <organization>Compaq Computer Corporation</organization>
3813      <address><email>mogul@wrl.dec.com</email></address>
3814    </author>
3815    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3816      <organization>MIT Laboratory for Computer Science</organization>
3817      <address><email>frystyk@w3.org</email></address>
3818    </author>
3819    <author initials="L." surname="Masinter" fullname="L. Masinter">
3820      <organization>Xerox Corporation</organization>
3821      <address><email>masinter@parc.xerox.com</email></address>
3822    </author>
3823    <author initials="P." surname="Leach" fullname="P. Leach">
3824      <organization>Microsoft Corporation</organization>
3825      <address><email>paulle@microsoft.com</email></address>
3826    </author>
3827    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3828      <organization>W3C</organization>
3829      <address><email>timbl@w3.org</email></address>
3830    </author>
3831    <date month="June" year="1999"/>
3832  </front>
3833  <seriesInfo name="RFC" value="2616"/>
3834</reference>
3835
3836<reference anchor='RFC2817'>
3837  <front>
3838    <title>Upgrading to TLS Within HTTP/1.1</title>
3839    <author initials='R.' surname='Khare' fullname='R. Khare'>
3840      <organization>4K Associates / UC Irvine</organization>
3841      <address><email>rohit@4K-associates.com</email></address>
3842    </author>
3843    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3844      <organization>Agranat Systems, Inc.</organization>
3845      <address><email>lawrence@agranat.com</email></address>
3846    </author>
3847    <date year='2000' month='May' />
3848  </front>
3849  <seriesInfo name='RFC' value='2817' />
3850</reference>
3851
3852<reference anchor='RFC3864'>
3853  <front>
3854    <title>Registration Procedures for Message Header Fields</title>
3855    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3856      <organization>Nine by Nine</organization>
3857      <address><email>GK-IETF@ninebynine.org</email></address>
3858    </author>
3859    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3860      <organization>BEA Systems</organization>
3861      <address><email>mnot@pobox.com</email></address>
3862    </author>
3863    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3864      <organization>HP Labs</organization>
3865      <address><email>JeffMogul@acm.org</email></address>
3866    </author>
3867    <date year='2004' month='September' />
3868  </front>
3869  <seriesInfo name='BCP' value='90' />
3870  <seriesInfo name='RFC' value='3864' />
3871</reference>
3872
3873<reference anchor='RFC5226'>
3874  <front>
3875    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3876    <author initials='T.' surname='Narten' fullname='T. Narten'>
3877      <organization>IBM</organization>
3878      <address><email>narten@us.ibm.com</email></address>
3879    </author>
3880    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3881      <organization>Google</organization>
3882      <address><email>Harald@Alvestrand.no</email></address>
3883    </author>
3884    <date year='2008' month='May' />
3885  </front>
3886  <seriesInfo name='BCP' value='26' />
3887  <seriesInfo name='RFC' value='5226' />
3888</reference>
3889
3890<reference anchor="RFC5322">
3891  <front>
3892    <title>Internet Message Format</title>
3893    <author initials="P." surname="Resnick" fullname="P. Resnick">
3894      <organization>Qualcomm Incorporated</organization>
3895    </author>
3896    <date year="2008" month="October"/>
3897  </front> 
3898  <seriesInfo name="RFC" value="5322"/>
3899</reference>
3900
3901<reference anchor='RFC5789'>
3902  <front>
3903    <title>PATCH Method for HTTP</title>
3904    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3905      <organization>Linden Lab</organization>
3906    </author>
3907    <author initials='J.' surname='Snell' fullname='J. Snell' />
3908    <date year='2010' month='March' />
3909  </front>
3910  <seriesInfo name='RFC' value='5789' />
3911</reference>
3912
3913<reference anchor="RFC5987">
3914        <front>
3915    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3916    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3917      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3918      <address>
3919        <postal>
3920          <street>Hafenweg 16</street>
3921          <city>Muenster</city><region>NW</region><code>48155</code>
3922          <country>Germany</country>
3923        </postal>
3924        <email>julian.reschke@greenbytes.de</email>     
3925        <uri>http://greenbytes.de/tech/webdav/</uri>   
3926      </address>
3927    </author>
3928    <date month="August" year="2010"/>
3929  </front>
3930  <seriesInfo name="RFC" value="5987"/>
3931</reference>
3932
3933</references>
3934
3935<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3936<t>
3937  This document takes over the Status Code Registry, previously defined
3938  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3939  (<xref target="status.code.registry"/>)
3940</t>
3941<t>
3942  Clarify definition of POST.
3943  (<xref target="POST"/>)
3944</t>
3945<t>
3946  Remove requirement to handle all Content-* header fields; ban use of
3947  Content-Range with PUT.
3948  (<xref target="PUT"/>)
3949</t>
3950<t>
3951  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3952  (<xref target="CONNECT"/>)
3953</t>
3954<t>
3955  Broadened the definition of 203 (Non-Authoritative Information) to include
3956  cases of payload transformations as well.
3957  (<xref target="status.203"/>)
3958</t>
3959<t>
3960  Failed to consider that there are many other request methods that are safe
3961  to automatically redirect, and further that the user agent is able to make
3962  that determination based on the request method semantics.
3963  Furthermore, allow user agents to rewrite the method from POST to GET
3964  for status codes 301 and 302.
3965  (Sections <xref format="counter" target="status.301"/>,
3966  <xref format="counter" target="status.302"/> and
3967  <xref format="counter" target="status.307"/>)
3968</t>
3969<t>
3970  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3971  It used to indicate that the target resource must be accessed through the
3972  proxy given by the Location field. The Location field gave the URI of the
3973  proxy. The recipient was expected to repeat this single request via the proxy.
3974  (<xref target="status.305"/>)
3975</t>
3976<t>
3977  Define status 426 (Upgrade Required) (this was incorporated from
3978  <xref target="RFC2817"/>).
3979  (<xref target="status.426"/>)
3980</t>
3981<t>
3982  Change ABNF productions for header fields to only define the field value.
3983  (<xref target="header.field.definitions"/>)
3984</t>
3985<t>
3986  Reclassify "Allow" as response header field, removing the option to
3987  specify it in a PUT request.
3988  Relax the server requirement on the contents of the Allow header field and
3989  remove requirement on clients to always trust the header field value.
3990  (<xref target="header.allow"/>)
3991</t>
3992<t>
3993  Correct syntax of Location header field to allow URI references (including
3994  relative references and fragments), as referred symbol "absoluteURI" wasn't
3995  what was expected, and add some clarifications as to when use of fragments
3996  would not be appropriate.
3997  (<xref target="header.location"/>)
3998</t>
3999<t>
4000  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
4001  extension methods could have used it as well).
4002  (<xref target="header.max-forwards"/>)
4003</t>
4004<t>
4005  Allow Referer field value of "about:blank" as alternative to not specifying it.
4006  (<xref target="header.referer"/>)
4007</t>
4008<t>
4009  In the description of the Server header field, the Via field
4010  was described as a SHOULD. The requirement was and is stated
4011  correctly in the description of the Via header field in &header-via;.
4012  (<xref target="header.server"/>)
4013</t>
4014</section>
4015
4016<?BEGININC p2-semantics.abnf-appendix ?>
4017<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
4018<figure>
4019<artwork type="abnf" name="p2-semantics.parsed-abnf">
4020<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
4021
4022<x:ref>Date</x:ref> = HTTP-date
4023
4024<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
4025
4026<x:ref>From</x:ref> = mailbox
4027
4028<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4029
4030<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4031
4032<x:ref>Location</x:ref> = URI-reference
4033
4034<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4035<x:ref>Method</x:ref> = token
4036
4037<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
4038
4039<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
4040<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4041<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4042<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4043
4044<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4045<x:ref>Status-Code</x:ref> = 3DIGIT
4046
4047<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4048<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4049
4050<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4051<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4052
4053<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
4054
4055<x:ref>date1</x:ref> = day SP month SP year
4056<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4057<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4058<x:ref>day</x:ref> = 2DIGIT
4059<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4060 / %x54.75.65 ; Tue
4061 / %x57.65.64 ; Wed
4062 / %x54.68.75 ; Thu
4063 / %x46.72.69 ; Fri
4064 / %x53.61.74 ; Sat
4065 / %x53.75.6E ; Sun
4066<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4067 / %x54.75.65.73.64.61.79 ; Tuesday
4068 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4069 / %x54.68.75.72.73.64.61.79 ; Thursday
4070 / %x46.72.69.64.61.79 ; Friday
4071 / %x53.61.74.75.72.64.61.79 ; Saturday
4072 / %x53.75.6E.64.61.79 ; Sunday
4073<x:ref>delta-seconds</x:ref> = 1*DIGIT
4074
4075<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
4076<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
4077<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
4078 *expect-params ]
4079
4080<x:ref>hour</x:ref> = 2DIGIT
4081
4082<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4083<x:ref>minute</x:ref> = 2DIGIT
4084<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4085 / %x46.65.62 ; Feb
4086 / %x4D.61.72 ; Mar
4087 / %x41.70.72 ; Apr
4088 / %x4D.61.79 ; May
4089 / %x4A.75.6E ; Jun
4090 / %x4A.75.6C ; Jul
4091 / %x41.75.67 ; Aug
4092 / %x53.65.70 ; Sep
4093 / %x4F.63.74 ; Oct
4094 / %x4E.6F.76 ; Nov
4095 / %x44.65.63 ; Dec
4096
4097<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4098<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4099
4100<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4101<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4102
4103<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4104
4105<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4106<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4107
4108<x:ref>second</x:ref> = 2DIGIT
4109
4110<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4111<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4112
4113<x:ref>year</x:ref> = 4DIGIT
4114</artwork>
4115</figure>
4116<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4117; Allow defined but not used
4118; Date defined but not used
4119; Expect defined but not used
4120; From defined but not used
4121; Location defined but not used
4122; Max-Forwards defined but not used
4123; Reason-Phrase defined but not used
4124; Referer defined but not used
4125; Retry-After defined but not used
4126; Server defined but not used
4127; Status-Code defined but not used
4128; User-Agent defined but not used
4129</artwork></figure></section>
4130<?ENDINC p2-semantics.abnf-appendix ?>
4131
4132<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4133
4134<section title="Since RFC 2616">
4135<t>
4136  Extracted relevant partitions from <xref target="RFC2616"/>.
4137</t>
4138</section>
4139
4140<section title="Since draft-ietf-httpbis-p2-semantics-00">
4141<t>
4142  Closed issues:
4143  <list style="symbols"> 
4144    <t>
4145      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4146      "Via is a MUST"
4147      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4148    </t>
4149    <t>
4150      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4151      "Fragments allowed in Location"
4152      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4153    </t>
4154    <t>
4155      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4156      "Safe Methods vs Redirection"
4157      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4158    </t>
4159    <t>
4160      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4161      "Revise description of the POST method"
4162      (<eref target="http://purl.org/NET/http-errata#post"/>)
4163    </t>
4164    <t>
4165      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4166      "Normative and Informative references"
4167    </t>
4168    <t>
4169      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4170      "RFC2606 Compliance"
4171    </t>
4172    <t>
4173      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4174      "Informative references"
4175    </t>
4176    <t>
4177      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4178      "Redundant cross-references"
4179    </t>
4180  </list>
4181</t>
4182<t>
4183  Other changes:
4184  <list style="symbols"> 
4185    <t>
4186      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4187    </t>
4188  </list>
4189</t>
4190</section>
4191
4192<section title="Since draft-ietf-httpbis-p2-semantics-01">
4193<t>
4194  Closed issues:
4195  <list style="symbols"> 
4196    <t>
4197      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4198      "PUT side effects"
4199    </t>
4200    <t>
4201      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4202      "Duplicate Host header requirements"
4203    </t>
4204  </list>
4205</t>
4206<t>
4207  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4208  <list style="symbols"> 
4209    <t>
4210      Move "Product Tokens" section (back) into Part 1, as "token" is used
4211      in the definition of the Upgrade header field.
4212    </t>
4213    <t>
4214      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4215    </t>
4216    <t>
4217      Copy definition of delta-seconds from Part6 instead of referencing it.
4218    </t>
4219  </list>
4220</t>
4221</section>
4222
4223<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4224<t>
4225  Closed issues:
4226  <list style="symbols"> 
4227    <t>
4228      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4229      "Requiring Allow in 405 responses"
4230    </t>
4231    <t>
4232      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4233      "Status Code Registry"
4234    </t>
4235    <t>
4236      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4237      "Redirection vs. Location"
4238    </t>
4239    <t>
4240      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4241      "Cacheability of 303 response"
4242    </t>
4243    <t>
4244      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4245      "305 Use Proxy"
4246    </t>
4247    <t>
4248      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4249      "Classification for Allow header"
4250    </t>
4251    <t>
4252      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4253      "PUT - 'store under' vs 'store at'"
4254    </t>
4255  </list>
4256</t>
4257<t>
4258  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4259  <list style="symbols"> 
4260    <t>
4261      Reference RFC 3984, and update header field registrations for headers defined
4262      in this document.
4263    </t>
4264  </list>
4265</t>
4266<t>
4267  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4268  <list style="symbols"> 
4269    <t>
4270      Replace string literals when the string really is case-sensitive (method).
4271    </t>
4272  </list>
4273</t>
4274</section>
4275
4276<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4277<t>
4278  Closed issues:
4279  <list style="symbols"> 
4280    <t>
4281      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4282      "OPTIONS request bodies"
4283    </t>
4284    <t>
4285      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4286      "Description of CONNECT should refer to RFC2817"
4287    </t>
4288    <t>
4289      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4290      "Location Content-Location reference request/response mixup"
4291    </t>
4292  </list>
4293</t>
4294<t>
4295  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4296  <list style="symbols"> 
4297    <t>
4298      Added initial proposal for registration process, plus initial
4299      content (non-HTTP/1.1 methods to be added by a separate specification).
4300    </t>
4301  </list>
4302</t>
4303</section>
4304
4305<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4306<t>
4307  Closed issues:
4308  <list style="symbols"> 
4309    <t>
4310      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4311      "Content-*"
4312    </t>
4313    <t>
4314      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4315      "RFC 2822 is updated by RFC 5322"
4316    </t>
4317  </list>
4318</t>
4319<t>
4320  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4321  <list style="symbols"> 
4322    <t>
4323      Use "/" instead of "|" for alternatives.
4324    </t>
4325    <t>
4326      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4327      whitespace ("OWS") and required whitespace ("RWS").
4328    </t>
4329    <t>
4330      Rewrite ABNFs to spell out whitespace rules, factor out
4331      header field value format definitions.
4332    </t>
4333  </list>
4334</t>
4335</section>
4336
4337<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4338<t>
4339  Closed issues:
4340  <list style="symbols"> 
4341    <t>
4342      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4343      "Reason-Phrase BNF"
4344    </t>
4345  </list>
4346</t>
4347<t>
4348  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4349  <list style="symbols"> 
4350    <t>
4351      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4352    </t>
4353  </list>
4354</t>
4355</section>
4356
4357<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4358<t>
4359  Closed issues:
4360  <list style="symbols"> 
4361    <t>
4362      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4363      "Clarify when Referer is sent"
4364    </t>
4365    <t>
4366      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4367      "status codes vs methods"
4368    </t>
4369    <t>
4370      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4371      "Do not require "updates" relation for specs that register status codes or method names"
4372    </t>
4373  </list>
4374</t>
4375</section>
4376
4377<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4378<t>
4379  Closed issues:
4380  <list style="symbols"> 
4381    <t>
4382      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4383      "Idempotency"
4384    </t>
4385    <t>
4386      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4387      "TRACE security considerations"
4388    </t>
4389    <t>
4390      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4391      "Clarify rules for determining what entities a response carries"
4392    </t>
4393    <t>
4394      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4395      "update note citing RFC 1945 and 2068"
4396    </t>
4397    <t>
4398      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4399      "update note about redirect limit"
4400    </t>
4401    <t>
4402      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4403      "Location header ABNF should use 'URI'"
4404    </t>
4405    <t>
4406      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4407      "fragments in Location vs status 303"
4408    </t>
4409    <t>
4410      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4411      "move IANA registrations for optional status codes"
4412    </t>
4413  </list>
4414</t>
4415<t>
4416  Partly resolved issues:
4417  <list style="symbols"> 
4418    <t>
4419      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4420      "Are OPTIONS and TRACE safe?"
4421    </t>
4422  </list>
4423</t>
4424</section>
4425
4426<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4427<t>
4428  Closed issues:
4429  <list style="symbols"> 
4430    <t>
4431      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4432      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4433      status codes when fixing this previously)
4434    </t>
4435  </list>
4436</t>
4437</section>
4438
4439<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4440<t>
4441  Closed issues:
4442  <list style="symbols"> 
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4445      "Fragment combination / precedence during redirects"
4446    </t>
4447  </list>
4448</t>
4449<t>
4450  Partly resolved issues:
4451  <list style="symbols"> 
4452    <t>
4453      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4454      "Location header payload handling"
4455    </t>
4456    <t>
4457      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4458      "Term for the requested resource's URI"
4459    </t>
4460  </list>
4461</t>
4462</section>
4463
4464<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4465<t>
4466  Closed issues:
4467  <list style="symbols"> 
4468    <t>
4469      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4470      "Clarify 'Requested Variant'"
4471    </t>
4472    <t>
4473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4474      "Clarify entity / representation / variant terminology"
4475    </t>
4476    <t>
4477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4478      "Methods and Caching"
4479    </t>
4480    <t>
4481      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4482      "OPTIONS vs Max-Forwards"
4483    </t>
4484    <t>
4485      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4486      "Status codes and caching"
4487    </t>
4488    <t>
4489      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4490      "consider removing the 'changes from 2068' sections"
4491    </t>
4492  </list>
4493</t>
4494</section>
4495
4496<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4497<t>
4498  Closed issues:
4499  <list style="symbols"> 
4500    <t>
4501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4502      "Considerations for new status codes"
4503    </t>
4504    <t>
4505      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4506      "Considerations for new methods"
4507    </t>
4508    <t>
4509      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4510      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4511    </t>
4512  </list>
4513</t>
4514</section>
4515
4516<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4517<t>
4518  Closed issues:
4519  <list style="symbols"> 
4520    <t>
4521      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4522      "Fragment combination / precedence during redirects" (added warning
4523      about having a fragid on the redirect may cause inconvenience in
4524      some cases)
4525    </t>
4526    <t>
4527      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4528      "Content-* vs. PUT"
4529    </t>
4530    <t>
4531      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4532      "205 Bodies"
4533    </t>
4534    <t>
4535      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4536      "Understanding Content-* on non-PUT requests"
4537    </t>
4538    <t>
4539      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4540      "Content-*"
4541    </t>
4542    <t>
4543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4544      "Header type defaulting"
4545    </t>
4546    <t>
4547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4548      "PUT - 'store under' vs 'store at'"
4549    </t>
4550    <t>
4551      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4552      "duplicate ABNF for Reason-Phrase"
4553    </t>
4554    <t>
4555      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4556      "Note special status of Content-* prefix in header registration procedures"
4557    </t>
4558    <t>
4559      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4560      "Max-Forwards vs extension methods"
4561    </t>
4562    <t>
4563      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4564      "What is the value space of HTTP status codes?" (actually fixed in
4565      draft-ietf-httpbis-p2-semantics-11)
4566    </t>
4567    <t>
4568      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4569      "Header Classification"
4570    </t>
4571    <t>
4572      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4573      "PUT side effect: invalidation or just stale?"
4574    </t>
4575    <t>
4576      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4577      "proxies not supporting certain methods"
4578    </t>
4579    <t>
4580      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4581      "Migrate CONNECT from RFC2817 to p2"
4582    </t>
4583    <t>
4584      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4585      "Migrate Upgrade details from RFC2817"
4586    </t>
4587    <t>
4588      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4589      "clarify PUT semantics'"
4590    </t>
4591    <t>
4592      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4593      "duplicate ABNF for 'Method'"
4594    </t>
4595    <t>
4596      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4597      "untangle ABNFs for header fields"
4598    </t>
4599  </list>
4600</t>
4601</section>
4602
4603<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4604<t>
4605  Closed issues:
4606  <list style="symbols"> 
4607    <t>
4608      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4609      "untangle ABNFs for header fields"
4610    </t>
4611    <t>
4612      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4613      "message-body in CONNECT request"
4614    </t>
4615  </list>
4616</t>
4617</section>
4618
4619<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4620<t>
4621  Closed issues:
4622  <list style="symbols"> 
4623    <t>
4624      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4625      "Clarify status code for rate limiting"
4626    </t>
4627    <t>
4628      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4629      "clarify 403 forbidden"
4630    </t>
4631    <t>
4632      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4633      "Clarify 203 Non-Authoritative Information"
4634    </t>
4635    <t>
4636      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4637      "update default reason phrase for 413"
4638    </t>
4639  </list>
4640</t>
4641</section>
4642
4643<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4644<t>
4645  Closed issues:
4646  <list style="symbols"> 
4647    <t>
4648      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4649      "Strength of requirements on Accept re: 406"
4650    </t>
4651    <t>
4652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4653      "400 response isn't generic"
4654    </t>
4655  </list>
4656</t>
4657</section>
4658
4659<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4660<t>
4661  Closed issues:
4662  <list style="symbols"> 
4663    <t>
4664      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4665      "Redirects and non-GET methods"
4666    </t>
4667    <t>
4668      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4669      "Document HTTP's error-handling philosophy"
4670    </t>
4671    <t>
4672      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4673      "Considerations for new headers"
4674    </t>
4675    <t>
4676      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4677      "clarify 303 redirect on HEAD"
4678    </t>
4679  </list>
4680</t>
4681</section>
4682
4683</section>
4684
4685</back>
4686</rfc>
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