source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1266

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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 "April">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81]>
82<?rfc toc="yes" ?>
83<?rfc symrefs="yes" ?>
84<?rfc sortrefs="yes" ?>
85<?rfc compact="yes"?>
86<?rfc subcompact="no" ?>
87<?rfc linkmailto="no" ?>
88<?rfc editing="no" ?>
89<?rfc comments="yes"?>
90<?rfc inline="yes"?>
91<?rfc rfcedstyle="yes"?>
92<?rfc-ext allow-markup-in-artwork="yes" ?>
93<?rfc-ext include-references-in-index="yes" ?>
94<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
95     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
96     xmlns:x='http://purl.org/net/xml2rfc/ext'
97     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
98<front>
99
100  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
101
102  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
103    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
104    <address>
105      <postal>
106        <street>345 Park Ave</street>
107        <city>San Jose</city>
108        <region>CA</region>
109        <code>95110</code>
110        <country>USA</country>
111      </postal>
112      <email>fielding@gbiv.com</email>
113      <uri>http://roy.gbiv.com/</uri>
114    </address>
115  </author>
116
117  <author initials="J." surname="Gettys" fullname="Jim Gettys">
118    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
119    <address>
120      <postal>
121        <street>21 Oak Knoll Road</street>
122        <city>Carlisle</city>
123        <region>MA</region>
124        <code>01741</code>
125        <country>USA</country>
126      </postal>
127      <email>jg@freedesktop.org</email>
128      <uri>http://gettys.wordpress.com/</uri>
129    </address>
130  </author>
131 
132  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
133    <organization abbrev="HP">Hewlett-Packard Company</organization>
134    <address>
135      <postal>
136        <street>HP Labs, Large Scale Systems Group</street>
137        <street>1501 Page Mill Road, MS 1177</street>
138        <city>Palo Alto</city>
139        <region>CA</region>
140        <code>94304</code>
141        <country>USA</country>
142      </postal>
143      <email>JeffMogul@acm.org</email>
144    </address>
145  </author>
146
147  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
148    <organization abbrev="Microsoft">Microsoft Corporation</organization>
149    <address>
150      <postal>
151        <street>1 Microsoft Way</street>
152        <city>Redmond</city>
153        <region>WA</region>
154        <code>98052</code>
155        <country>USA</country>
156      </postal>
157      <email>henrikn@microsoft.com</email>
158    </address>
159  </author>
160
161  <author initials="L." surname="Masinter" fullname="Larry Masinter">
162    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
163    <address>
164      <postal>
165        <street>345 Park Ave</street>
166        <city>San Jose</city>
167        <region>CA</region>
168        <code>95110</code>
169        <country>USA</country>
170      </postal>
171      <email>LMM@acm.org</email>
172      <uri>http://larry.masinter.net/</uri>
173    </address>
174  </author>
175 
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email>paulle@microsoft.com</email>
186    </address>
187  </author>
188   
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
199        <country>USA</country>
200      </postal>
201      <email>timbl@w3.org</email>
202      <uri>http://www.w3.org/People/Berners-Lee/</uri>
203    </address>
204  </author>
205
206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email>ylafon@w3.org</email>
218      <uri>http://www.raubacapeu.net/people/yves/</uri>
219    </address>
220  </author>
221
222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email>julian.reschke@greenbytes.de</email>
233      <uri>http://greenbytes.de/tech/webdav/</uri>
234    </address>
235  </author>
236
237  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
238  <workgroup>HTTPbis Working Group</workgroup>
239
240<abstract>
241<t>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
244   systems. HTTP has been in use by the World Wide Web global information
245   initiative since 1990. This document is Part 2 of the seven-part specification
246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
248   as expressed by request methods, request header fields, response status codes,
249   and response header fields.
250</t>
251</abstract>
252
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
256    mailing list (ietf-http-wg@w3.org). The current issues list is
257    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
258    and related documents (including fancy diffs) can be found at
259    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
260  </t>
261  <t>
262    The changes in this draft are summarized in <xref target="changes.since.13"/>.
263  </t>
264</note>
265</front>
266<middle>
267<section title="Introduction" anchor="introduction">
268<t>
269   This document defines HTTP/1.1 request and response semantics.  Each HTTP
270   message, as defined in &messaging;, is in the form of either a request or
271   a response.  An HTTP server listens on a connection for HTTP requests and
272   responds to each request, in the order received on that connection, with
273   one or more HTTP response messages.  This document defines the commonly
274   agreed upon semantics of the HTTP uniform interface, the intentions defined
275   by each request method, and the various response messages that might be
276   expected as a result of applying that method to the target resource.
277</t>
278<t>
279   This document is currently disorganized in order to minimize the changes
280   between drafts and enable reviewers to see the smaller errata changes.
281   A future draft will reorganize the sections to better reflect the content.
282   In particular, the sections will be ordered according to the typical
283   processing of an HTTP request message (after message parsing): resource
284   mapping, methods, request modifying header fields, response status,
285   status modifying header fields, and resource metadata.  The current mess
286   reflects how widely dispersed these topics and associated requirements
287   had become in <xref target="RFC2616"/>.
288</t>
289
290<section title="Requirements" anchor="intro.requirements">
291<t>
292   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
293   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
294   document are to be interpreted as described in <xref target="RFC2119"/>.
295</t>
296<t>
297   An implementation is not compliant if it fails to satisfy one or more
298   of the "MUST" or "REQUIRED" level requirements for the protocols it
299   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
300   level and all the "SHOULD" level requirements for its protocols is said
301   to be "unconditionally compliant"; one that satisfies all the "MUST"
302   level requirements but not all the "SHOULD" level requirements for its
303   protocols is said to be "conditionally compliant".
304</t>
305</section>
306
307<section title="Syntax Notation" anchor="notation">
308  <x:anchor-alias value="CR"/>
309  <x:anchor-alias value="DIGIT"/>
310  <x:anchor-alias value="LF"/>
311  <x:anchor-alias value="VCHAR"/>
312  <x:anchor-alias value="WSP"/>
313<t>
314  This specification uses the ABNF syntax defined in &notation; (which
315  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
316  <xref target="collected.abnf"/> shows the collected ABNF, with the list
317  rule expanded.
318</t>
319<t>
320  The following core rules are included by
321  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
322  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
323  DIGIT (decimal 0-9), DQUOTE (double quote),
324  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
325  OCTET (any 8-bit sequence of data), SP (space),
326  VCHAR (any visible USASCII character),
327  and WSP (whitespace).
328</t>
329
330<section title="Core Rules" anchor="core.rules">
331  <x:anchor-alias value="obs-text"/>
332  <x:anchor-alias value="quoted-string"/>
333  <x:anchor-alias value="token"/>
334  <x:anchor-alias value="OWS"/>
335  <x:anchor-alias value="RWS"/>
336<t>
337  The core rules below are defined in &basic-rules;:
338</t>
339<figure><artwork type="abnf2616">
340  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
341  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
342  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
343  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
344  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
345</artwork></figure>
346</section>
347
348<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
349  <x:anchor-alias value="absolute-URI"/>
350  <x:anchor-alias value="comment"/>
351  <x:anchor-alias value="HTTP-date"/>
352  <x:anchor-alias value="partial-URI"/>
353  <x:anchor-alias value="product"/>
354  <x:anchor-alias value="URI-reference"/>
355<t>
356  The ABNF rules below are defined in other parts:
357</t>
358<figure><!--Part1--><artwork type="abnf2616">
359  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
360  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
361  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
362  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
363  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
364  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
365</artwork></figure>
366</section>
367</section>
368</section>
369
370<section title="Method" anchor="method">
371  <x:anchor-alias value="Method"/>
372  <x:anchor-alias value="extension-method"/>
373<t>
374   The Method token indicates the request method to be performed on the target
375   resource (&effective-request-uri;). The method is case-sensitive.
376</t>
377<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
378  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
379</artwork></figure>
380<t>
381   The list of methods allowed by a resource can be specified in an
382   Allow header field (<xref target="header.allow"/>). The status code of the response
383   always notifies the client whether a method is currently allowed on a
384   resource, since the set of allowed methods can change dynamically. An
385   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
386   if the method is known by the origin server but not allowed for the
387   resource, and 501 (Not Implemented) if the method is
388   unrecognized or not implemented by the origin server. The methods GET
389   and HEAD &MUST; be supported by all general-purpose servers. All other
390   methods are &OPTIONAL;; however, if the above methods are implemented,
391   they &MUST; be implemented with the same semantics as those specified
392   in <xref target="method.definitions"/>.
393</t>
394
395<section title="Overview of Methods" anchor="overview.of.methods">
396<t>
397  The methods listed below are defined in <xref target="method.definitions"/>.
398</t>
399<texttable align="left">
400  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
401 
402  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
403  <c>GET</c> <c><xref target="GET"/></c>
404  <c>HEAD</c> <c><xref target="HEAD"/></c>
405  <c>POST</c> <c><xref target="POST"/></c>
406  <c>PUT</c> <c><xref target="PUT"/></c>
407  <c>DELETE</c> <c><xref target="DELETE"/></c>
408  <c>TRACE</c> <c><xref target="TRACE"/></c>
409  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
410</texttable>
411<t>
412  Note that this list is not exhaustive &mdash; it does not include request methods defined
413  in other specifications.
414</t>
415</section>
416
417<section title="Method Registry" anchor="method.registry">
418<t>
419  The HTTP Method Registry defines the name space for the Method token in the
420  Request line of an HTTP request.
421</t>
422<t>
423  Registrations &MUST; include the following fields:
424  <list style="symbols">
425    <t>Method Name (see <xref target="method"/>)</t>
426    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
427    <t>Pointer to specification text</t>
428  </list>
429</t>
430<t>
431  Values to be added to this name space are subject to IETF review
432  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
433</t>
434<t>
435  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
436</t>
437
438<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
439<t>
440   When it is necessary to express new semantics for a HTTP request that
441   aren't specific to a single application or media type, and currently defined
442   methods are inadequate, it may be appropriate to register a new method.
443</t>
444<t>
445   HTTP methods are generic; that is, they are potentially applicable to any
446   resource, not just one particular media type, "type" of resource, or
447   application. As such, it is preferred that new HTTP methods be registered
448   in a document that isn't specific to a single application, so that this is
449   clear.
450</t>
451<t>
452   Due to the parsing rules defined in &message-body;, definitions of HTTP
453   methods cannot prohibit the presence of a message-body on either the request
454   or the response message (with responses to HEAD requests being the single
455   exception). Definitions of new methods cannot change this rule, but they can
456   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
457</t>
458<t>
459   New method definitions need to indicate whether they are safe (<xref
460   target="safe.methods"/>), what semantics (if any) the request body has,
461   and whether they are idempotent (<xref target="idempotent.methods"/>).
462   They also need to state whether they can be cached (&caching;); in
463   particular what conditions a cache may store the response, and under what
464   conditions such a stored response may be used to satisfy a subsequent
465   request.
466</t>
467</section>
468
469</section>
470</section>
471
472<section title="Request Header Fields" anchor="request.header.fields">
473  <x:anchor-alias value="request-header"/>
474<t>
475   The request header fields allow the client to pass additional
476   information about the request, and about the client itself, to the
477   server. These fields act as request modifiers, with semantics
478   equivalent to the parameters on a programming language method
479   invocation.
480</t>
481<texttable align="left">
482  <ttcol>Header Field Name</ttcol>
483  <ttcol>Defined in...</ttcol>
484
485  <c>Accept</c> <c>&header-accept;</c>
486  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
487  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
488  <c>Accept-Language</c> <c>&header-accept-language;</c>
489  <c>Authorization</c> <c>&header-authorization;</c>
490  <c>Expect</c> <c><xref target="header.expect"/></c>
491  <c>From</c> <c><xref target="header.from"/></c>
492  <c>Host</c> <c>&header-host;</c>
493  <c>If-Match</c> <c>&header-if-match;</c>
494  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
495  <c>If-None-Match</c> <c>&header-if-none-match;</c>
496  <c>If-Range</c> <c>&header-if-range;</c>
497  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
498  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
499  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
500  <c>Range</c> <c>&header-range;</c>
501  <c>Referer</c> <c><xref target="header.referer"/></c>
502  <c>TE</c> <c>&header-te;</c>
503  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
504</texttable>
505</section>
506
507<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
508  <x:anchor-alias value="Reason-Phrase"/>
509  <x:anchor-alias value="Status-Code"/>
510  <x:anchor-alias value="extension-code"/>
511<t>
512   The Status-Code element is a 3-digit integer result code of the attempt to
513   understand and satisfy the request.
514</t>
515<t>
516   The Reason-Phrase is intended to give a short textual description of the
517   Status-Code and is intended for a human user. The client does not need
518   to examine or display the Reason-Phrase.
519</t>
520<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"/>
521  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
522  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
523</artwork></figure>
524<t>
525   HTTP status codes are extensible. HTTP applications are not required
526   to understand the meaning of all registered status codes, though such
527   understanding is obviously desirable. However, applications &MUST;
528   understand the class of any status code, as indicated by the first
529   digit, and treat any unrecognized response as being equivalent to the
530   x00 status code of that class, with the exception that an
531   unrecognized response &MUST-NOT; be cached. For example, if an
532   unrecognized status code of 431 is received by the client, it can
533   safely assume that there was something wrong with its request and
534   treat the response as if it had received a 400 status code. In such
535   cases, user agents &SHOULD; present to the user the representation enclosed
536   with the response, since that representation is likely to include human-readable
537   information which will explain the unusual status.
538</t>
539
540<section title="Overview of Status Codes" anchor="overview.of.status.codes">
541<t> 
542   The status codes listed below are defined in <xref target="status.codes"/>
543   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
544   The reason phrases listed here are only recommendations &mdash; they can be
545   replaced by local equivalents without affecting the protocol.
546</t>
547<texttable align="left">
548  <ttcol>Status-Code</ttcol>
549  <ttcol>Reason-Phrase</ttcol>
550  <ttcol>Defined in...</ttcol>
551 
552  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
553  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
554
555  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
556  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
557  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
558  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
559  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
560  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
561  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
562
563  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
564  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
565  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
566  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
567  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
568  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
569  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
570
571  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
572  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
573  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
574  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
575  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
576  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
577  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
578  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
579  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
580  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
581  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
582  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
583  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
584  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
585  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
586  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
587  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
588  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
589  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
590
591  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
592  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
593  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
594  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
595  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
596  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
597</texttable>
598<t>
599   Note that this list is not exhaustive &mdash; it does not include
600   extension status codes defined in other specifications.
601</t>
602</section>
603
604<section title="Status Code Registry" anchor="status.code.registry">
605<t>
606  The HTTP Status Code Registry defines the name space for the Status-Code
607  token in the Status-Line of an HTTP response.
608</t>
609<t>
610  Values to be added to this name space are subject to IETF review
611  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
612</t>
613<t>
614  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
615</t>
616
617<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
618<t>
619   When it is necessary to express new semantics for a HTTP response that
620   aren't specific to a single application or media type, and currently defined
621   status codes are inadequate, a new status code can be registered.
622</t>
623<t>
624   HTTP status codes are generic; that is, they are potentially applicable to
625   any resource, not just one particular media type, "type" of resource, or
626   application. As such, it is preferred that new HTTP status codes be
627   registered in a document that isn't specific to a single application, so
628   that this is clear.
629</t>
630<t>
631   Definitions of new HTTP status codes typically explain the request
632   conditions that produce a response containing the status code (e.g.,
633   combinations of request headers and/or method(s)), along with any
634   interactions with response headers (e.g., those that are required, those
635   that modify the semantics of the response).
636</t>
637<t>
638   New HTTP status codes are required to fall under one of the categories
639   defined in <xref target="status.codes"/>. To allow existing parsers to
640   properly handle them, new status codes cannot disallow a response body,
641   although they can mandate a zero-length response body. They can require the
642   presence of one or more particular HTTP response header(s).
643</t>
644<t>
645   Likewise, their definitions can specify that caches are allowed to use
646   heuristics to determine their freshness (see &caching;; by default, it is
647   not allowed), and can define how to determine the resource which they
648   carry a representation for (see <xref
649   target="identifying.response.associated.with.representation"/>; by default,
650   it is anonymous).
651</t>
652</section>
653
654</section>
655
656</section>
657
658<section title="Response Header Fields" anchor="response.header.fields">
659  <x:anchor-alias value="response-header"/>
660<t>
661   The response header fields allow the server to pass additional
662   information about the response which cannot be placed in the Status-Line.
663   These header fields give information about the server and about
664   further access to the target resource (&effective-request-uri;).
665</t>
666<texttable align="left">
667  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
668
669  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
670  <c>Age</c> <c>&header-age;</c>
671  <c>Allow</c> <c><xref target="header.allow"/></c>
672  <c>ETag</c> <c>&header-etag;</c>
673  <c>Location</c> <c><xref target="header.location"/></c>
674  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
675  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
676  <c>Server</c> <c><xref target="header.server"/></c>
677  <c>Vary</c> <c>&header-vary;</c>
678  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
679</texttable>
680</section>
681
682<section title="Representation" anchor="representation">
683<t>
684   Request and Response messages &MAY; transfer a representation if not otherwise
685   restricted by the request method or response status code. A representation
686   consists of metadata (representation header fields) and data (representation
687   body).  When a complete or partial representation is enclosed in an HTTP message,
688   it is referred to as the payload of the message. HTTP representations
689   are defined in &payload;.
690</t>
691<t>
692   A representation body is only present in a message when a message-body is
693   present, as described in &message-body;. The representation body is obtained
694   from the message-body by decoding any Transfer-Encoding that might
695   have been applied to ensure safe and proper transfer of the message.
696</t>
697
698<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
699<t>
700   It is sometimes necessary to determine an identifier for the resource
701   associated with a representation.
702</t>
703<t>
704   An HTTP request representation, when present, is always associated with an
705   anonymous (i.e., unidentified) resource.
706</t>
707<t>
708   In the common case, an HTTP response is a representation of the target
709   resource (see &effective-request-uri;). However, this is not always the
710   case. To determine the URI of the resource a response is associated with,
711   the following rules are used (with the first applicable one being selected):
712</t>
713<t><list style="numbers">
714   <t>If the response status code is 200 or 203 and the request method was GET,
715   the response payload is a representation of the target resource.</t>
716   <t>If the response status code is 204, 206, or 304 and the request method was GET
717   or HEAD, the response payload is a partial representation of the target
718   resource (see &combining-responses;).</t>
719   <t>If the response has a Content-Location header field, and that URI is the same
720   as the effective request URI, the response payload is a representation of the
721   target resource.</t>
722   <t>If the response has a Content-Location header field, and that URI is not the
723   same as the effective request URI, then the response asserts that its
724   payload is a representation of the resource identified by the
725   Content-Location URI. However, such an assertion cannot be trusted unless
726   it can be verified by other means (not defined by HTTP).</t>
727   <t>Otherwise, the response is a representation of an anonymous (i.e.,
728   unidentified) resource.</t>
729</list></t>
730<t>
731  <cref anchor="TODO-req-uri">
732   The comparison function is going to have to be defined somewhere,
733   because we already need to compare URIs for things like cache invalidation.</cref>
734</t>
735</section>
736
737</section>
738
739
740<section title="Method Definitions" anchor="method.definitions">
741<t>
742   The set of common request methods for HTTP/1.1 is defined below. Although
743   this set can be expanded, additional methods cannot be assumed to
744   share the same semantics for separately extended clients and servers.
745</t>
746
747<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
748
749<section title="Safe Methods" anchor="safe.methods">
750<iref item="Safe Methods" primary="true"/>
751<t>
752   Implementors need to be aware that the software represents the user in
753   their interactions over the Internet, and need to allow
754   the user to be aware of any actions they take which might have an
755   unexpected significance to themselves or others.
756</t>
757<t>
758   In particular, the convention has been established that the GET, HEAD,
759   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
760   of taking an action other than retrieval. These request methods ought
761   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
762   This allows user agents to represent other methods, such as POST, PUT
763   and DELETE, in a special way, so that the user is made aware of the
764   fact that a possibly unsafe action is being requested.
765</t>
766<t>
767   Naturally, it is not possible to ensure that the server does not
768   generate side-effects as a result of performing a GET request; in
769   fact, some dynamic resources consider that a feature. The important
770   distinction here is that the user did not request the side-effects,
771   so therefore cannot be held accountable for them.
772</t>
773</section>
774
775<section title="Idempotent Methods" anchor="idempotent.methods">
776<iref item="Idempotent Methods" primary="true"/>
777<t>
778   Request methods can also have the property of "idempotence" in that,
779   aside from error or expiration issues, the intended effect of multiple
780   identical requests is the same as for a single request.
781   PUT, DELETE, and all safe request methods are idempotent.
782   It is important to note that idempotence refers only to changes
783   requested by the client: a server is free to change its state due
784   to multiple requests for the purpose of tracking those requests,
785   versioning of results, etc.
786</t>
787</section>
788</section>
789
790<section title="OPTIONS" anchor="OPTIONS">
791  <rdf:Description>
792    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
793  </rdf:Description>
794  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
795  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
796<t>
797   The OPTIONS method requests information about the
798   communication options available on the request/response chain
799   identified by the effective request URI. This method allows a client to
800   determine the options and/or requirements associated with a resource,
801   or the capabilities of a server, without implying a resource action
802   or initiating a resource retrieval.
803</t>
804<t>
805   Responses to the OPTIONS method are not cacheable.
806</t>
807<t>
808   If the OPTIONS request includes a message-body (as indicated by the
809   presence of Content-Length or Transfer-Encoding), then the media type
810   &MUST; be indicated by a Content-Type field. Although this
811   specification does not define any use for such a body, future
812   extensions to HTTP might use the OPTIONS body to make more detailed
813   queries on the server.
814</t>
815<t>
816   If the request-target is an asterisk ("*"), the OPTIONS request is
817   intended to apply to the server in general rather than to a specific
818   resource. Since a server's communication options typically depend on
819   the resource, the "*" request is only useful as a "ping" or "no-op"
820   type of method; it does nothing beyond allowing the client to test
821   the capabilities of the server. For example, this can be used to test
822   a proxy for HTTP/1.1 compliance (or lack thereof).
823</t>
824<t>
825   If the request-target is not an asterisk, the OPTIONS request applies
826   only to the options that are available when communicating with that
827   resource.
828</t>
829<t>
830   A 200 response &SHOULD; include any header fields that indicate
831   optional features implemented by the server and applicable to that
832   resource (e.g., Allow), possibly including extensions not defined by
833   this specification. The response body, if any, &SHOULD; also include
834   information about the communication options. The format for such a
835   body is not defined by this specification, but might be defined by
836   future extensions to HTTP. Content negotiation &MAY; be used to select
837   the appropriate response format. If no response body is included, the
838   response &MUST; include a Content-Length field with a field-value of
839   "0".
840</t>
841<t>
842   The Max-Forwards header field &MAY; be used to target a
843   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
844   If no Max-Forwards field is present in the request, then the forwarded
845   request &MUST-NOT; include a Max-Forwards field.
846</t>
847</section>
848
849<section title="GET" anchor="GET">
850  <rdf:Description>
851    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
852  </rdf:Description>
853  <iref primary="true" item="GET method" x:for-anchor=""/>
854  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
855<t>
856   The GET method requests transfer of a current representation of
857   the target resource.
858</t>
859<t>   
860   If the target resource is a data-producing process, it is the
861   produced data which shall be returned as the representation in the response and not
862   the source text of the process, unless that text happens to be the output of
863   the process.
864</t>
865<t>
866   The semantics of the GET method change to a "conditional GET" if the
867   request message includes an If-Modified-Since, If-Unmodified-Since,
868   If-Match, If-None-Match, or If-Range header field. A conditional GET
869   requests that the representation be transferred only under the
870   circumstances described by the conditional header field(s). The
871   conditional GET request is intended to reduce unnecessary network
872   usage by allowing cached representations to be refreshed without requiring
873   multiple requests or transferring data already held by the client.
874</t>
875<t>
876   The semantics of the GET method change to a "partial GET" if the
877   request message includes a Range header field. A partial GET requests
878   that only part of the representation be transferred, as described in &header-range;.
879   The partial GET request is intended to reduce unnecessary
880   network usage by allowing partially-retrieved representations to be
881   completed without transferring data already held by the client.
882</t>
883<t>
884   Bodies on GET requests have no defined semantics. Note that sending a body
885   on a GET request might cause some existing implementations to reject the
886   request.
887</t>
888<t>
889   The response to a GET request is cacheable and &MAY; be used to satisfy
890   subsequent GET and HEAD requests (see &caching;).
891</t>
892<t>
893   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
894</t>
895</section>
896
897<section title="HEAD" anchor="HEAD">
898  <rdf:Description>
899    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
900  </rdf:Description>
901  <iref primary="true" item="HEAD method" x:for-anchor=""/>
902  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
903<t>
904   The HEAD method is identical to GET except that the server &MUST-NOT;
905   return a message-body in the response. The metadata contained
906   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
907   to the information sent in response to a GET request. This method can
908   be used for obtaining metadata about the representation implied by the
909   request without transferring the representation body. This method is
910   often used for testing hypertext links for validity, accessibility,
911   and recent modification.
912</t>
913<t>
914   The response to a HEAD request is cacheable and &MAY; be used to satisfy
915   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
916   representation from that resource; if the new field values
917   indicate that the cached representation differs from the current representation (as
918   would be indicated by a change in Content-Length, Content-MD5, ETag
919   or Last-Modified), then the cache &MUST; treat the cache entry as
920   stale.
921</t>
922<t>
923   Bodies on HEAD requests have no defined semantics. Note that sending a body
924   on a HEAD request might cause some existing implementations to reject the
925   request.
926</t>
927</section>
928
929<section title="POST" anchor="POST">
930  <iref primary="true" item="POST method" x:for-anchor=""/>
931  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
932<t>
933   The POST method requests that the origin server accept the
934   representation enclosed in the request as data to be processed by the
935   target resource. POST is designed to allow a uniform method to cover the
936   following functions:
937  <list style="symbols">
938    <t>
939      Annotation of existing resources;
940    </t>
941    <t>
942        Posting a message to a bulletin board, newsgroup, mailing list,
943        or similar group of articles;
944    </t>
945    <t>
946        Providing a block of data, such as the result of submitting a
947        form, to a data-handling process;
948    </t>
949    <t>
950        Extending a database through an append operation.
951    </t>
952  </list>
953</t>
954<t>
955   The actual function performed by the POST method is determined by the
956   server and is usually dependent on the effective request URI.
957</t>
958<t>
959   The action performed by the POST method might not result in a
960   resource that can be identified by a URI. In this case, either 200
961   (OK) or 204 (No Content) is the appropriate response status code,
962   depending on whether or not the response includes a representation that
963   describes the result.
964</t>
965<t>
966   If a resource has been created on the origin server, the response
967   &SHOULD; be 201 (Created) and contain a representation which describes the
968   status of the request and refers to the new resource, and a Location
969   header field (see <xref target="header.location"/>).
970</t>
971<t>
972   Responses to POST requests are only cacheable when they
973   include explicit freshness information (see &p6-explicit;). A
974   cached POST response with a Content-Location header field
975   (see &header-content-location;) whose value is the effective
976   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
977</t>
978<t>
979   Note that POST caching is not widely implemented.
980   However, the 303 (See Other) response can be used to direct the
981   user agent to retrieve a cacheable resource.
982</t>
983</section>
984
985<section title="PUT" anchor="PUT">
986  <iref primary="true" item="PUT method" x:for-anchor=""/>
987  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
988<t>
989   The PUT method requests that the state of the target resource
990   be created or replaced with the state defined by the representation
991   enclosed in the request message payload.  A successful PUT of a given
992   representation would suggest that a subsequent GET on that same target
993   resource will result in an equivalent representation being returned in
994   a 200 (OK) response.  However, there is no guarantee that such a state
995   change will be observable, since the target resource might be acted
996   upon by other user agents in parallel, or might be subject to dynamic
997   processing by the origin server, before any subsequent GET is received.
998   A successful response only implies that the user agent's intent was
999   achieved at the time of its processing by the origin server.
1000</t>
1001<t>   
1002   If the target resource does not have a current representation and
1003   the PUT successfully creates one, then the origin server &MUST; inform
1004   the user agent by sending a 201 (Created) response.  If the target
1005   resource does have a current representation and that representation is
1006   successfully modified in accordance with the state of the enclosed
1007   representation, then either a 200 (OK) or 204 (No Content) response
1008   &SHOULD; be sent to indicate successful completion of the request.
1009</t>
1010<t>
1011   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1012   as part of the resource state).
1013</t>
1014<t>
1015   An origin server &SHOULD; verify that the PUT representation is
1016   consistent with any constraints which the server has for the target
1017   resource that cannot or will not be changed by the PUT.  This is
1018   particularly important when the origin server uses internal
1019   configuration information related to the URI in order to set the
1020   values for representation metadata on GET responses.  When a PUT
1021   representation is inconsistent with the target resource, the origin
1022   server &SHOULD; either make them consistent, by transforming the
1023   representation or changing the resource configuration, or respond
1024   with an appropriate error message containing sufficient information
1025   to explain why the representation is unsuitable.  The 409 (Conflict)
1026   or 415 (Unsupported Media Type) status codes are suggested, with the
1027   latter being specific to constraints on Content-Type values.
1028</t>
1029<t>
1030   For example, if the target resource is configured to always have a
1031   Content-Type of "text/html" and the representation being PUT has a
1032   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1033   (a) reconfigure the target resource to reflect the new media type;
1034   (b) transform the PUT representation to a format consistent with that
1035   of the resource before saving it as the new resource state; or,
1036   (c) reject the request with a 415 response indicating that the target
1037   resource is limited to "text/html", perhaps including a link to a
1038   different resource that would be a suitable target for the new
1039   representation.
1040</t>
1041<t>
1042   HTTP does not define exactly how a PUT method affects the state
1043   of an origin server beyond what can be expressed by the intent of
1044   the user agent request and the semantics of the origin server response.
1045   It does not define what a resource might be, in any sense of that
1046   word, beyond the interface provided via HTTP.  It does not define
1047   how resource state is "stored", nor how such storage might change
1048   as a result of a change in resource state, nor how the origin server
1049   translates resource state into representations.  Generally speaking,
1050   all implementation details behind the resource interface are
1051   intentionally hidden by the server.
1052</t>
1053<t>
1054   The fundamental difference between the POST and PUT methods is
1055   highlighted by the different intent for the target resource.
1056   The target resource in a POST request is intended to handle the
1057   enclosed representation as a data-accepting process, such as for
1058   a gateway to some other protocol or a document that accepts annotations.
1059   In contrast, the target resource in a PUT request is intended to
1060   take the enclosed representation as a new or replacement value.
1061   Hence, the intent of PUT is idempotent and visible to intermediaries,
1062   even though the exact effect is only known by the origin server.
1063</t>
1064<t>
1065   Proper interpretation of a PUT request presumes that the user agent
1066   knows what target resource is desired.  A service that is intended
1067   to select a proper URI on behalf of the client, after receiving
1068   a state-changing request, &SHOULD; be implemented using the POST
1069   method rather than PUT.  If the origin server will not make the
1070   requested PUT state change to the target resource and instead
1071   wishes to have it applied to a different resource, such as when the
1072   resource has been moved to a different URI, then the origin server
1073   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1074   then make its own decision regarding whether or not to redirect the
1075   request.
1076</t>
1077<t>
1078   A PUT request applied to the target resource &MAY; have side-effects
1079   on other resources.  For example, an article might have a URI for
1080   identifying "the current version" (a resource) which is separate
1081   from the URIs identifying each particular version (different
1082   resources that at one point shared the same state as the current version
1083   resource).  A successful PUT request on "the current version" URI might
1084   therefore create a new version resource in addition to changing the
1085   state of the target resource, and might also cause links to be added
1086   between the related resources.
1087</t>
1088<t>
1089   An origin server &SHOULD; reject any PUT request that contains a
1090   Content-Range header field, since it might be misinterpreted as
1091   partial content (or might be partial content that is being mistakenly
1092   PUT as a full representation).  Partial content updates are
1093   possible by targeting a separately identified resource with state
1094   that overlaps a portion of the larger resource, or by using a
1095   different method that has been specifically defined for partial
1096   updates (for example, the PATCH method defined in
1097   <xref target="RFC5789"/>).
1098</t>
1099<t>
1100   Responses to the PUT method are not cacheable. If a PUT request passes
1101   through a cache that has one or more stored responses for the effective
1102   request URI, those stored responses will be invalidated (see
1103   &p6-invalid;).
1104</t>
1105</section>
1106
1107<section title="DELETE" anchor="DELETE">
1108  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1109  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1110<t>
1111   The DELETE method requests that the origin server delete the target
1112   resource. This method &MAY; be overridden by
1113   human intervention (or other means) on the origin server. The client cannot
1114   be guaranteed that the operation has been carried out, even if the
1115   status code returned from the origin server indicates that the action
1116   has been completed successfully. However, the server &SHOULD-NOT; 
1117   indicate success unless, at the time the response is given, it
1118   intends to delete the resource or move it to an inaccessible
1119   location.
1120</t>
1121<t>
1122   A successful response &SHOULD; be 200 (OK) if the response includes an
1123   representation describing the status, 202 (Accepted) if the action has not
1124   yet been enacted, or 204 (No Content) if the action has been enacted
1125   but the response does not include a representation.
1126</t>
1127<t>
1128   Bodies on DELETE requests have no defined semantics. Note that sending a body
1129   on a DELETE request might cause some existing implementations to reject the
1130   request.
1131</t>
1132<t>
1133   Responses to the DELETE method are not cacheable. If a DELETE request
1134   passes through a cache that has one or more stored responses for the
1135   effective request URI, those stored responses will be invalidated (see
1136   &p6-invalid;).
1137</t>
1138</section>
1139
1140<section title="TRACE" anchor="TRACE">
1141  <rdf:Description>
1142    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1143  </rdf:Description>
1144  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1145  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1146<t>
1147   The TRACE method requests a remote, application-layer loop-back
1148   of the request message. The final recipient of the request
1149   &SHOULD; reflect the message received back to the client as the
1150   message-body of a 200 (OK) response. The final recipient is either the
1151   origin server or the first proxy to receive a Max-Forwards
1152   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1153   A TRACE request &MUST-NOT; include a message-body.
1154</t>
1155<t>
1156   TRACE allows the client to see what is being received at the other
1157   end of the request chain and use that data for testing or diagnostic
1158   information. The value of the Via header field (&header-via;) is of
1159   particular interest, since it acts as a trace of the request chain.
1160   Use of the Max-Forwards header field allows the client to limit the
1161   length of the request chain, which is useful for testing a chain of
1162   proxies forwarding messages in an infinite loop.
1163</t>
1164<t>
1165   If the request is valid, the response &SHOULD; have a Content-Type of
1166   "message/http" (see &media-type-message-http;) and contain a message-body
1167   that encloses a copy of the entire request message.
1168   Responses to the TRACE method are not cacheable.
1169</t>
1170</section>
1171
1172<section title="CONNECT" anchor="CONNECT">
1173  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1174  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1175<t>
1176   The CONNECT method requests that the proxy establish a tunnel
1177   to the request-target and then restrict its behavior to blind
1178   forwarding of packets until the connection is closed.
1179</t>
1180<t>
1181   When using CONNECT, the request-target &MUST; use the authority form
1182   (&request-target;); i.e., the request-target consists of only the
1183   host name and port number of the tunnel destination, separated by a colon.
1184   For example,
1185</t>
1186<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1187CONNECT server.example.com:80 HTTP/1.1
1188Host: server.example.com:80
1189
1190</artwork></figure>
1191<t>
1192   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1193   except end-to-end protocol Upgrade requests, since the
1194   tunnel must be established first.
1195</t>
1196<t>
1197   For example, proxy authentication might be used to establish the
1198   authority to create a tunnel:
1199</t>
1200<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1201CONNECT server.example.com:80 HTTP/1.1
1202Host: server.example.com:80
1203Proxy-Authorization: basic aGVsbG86d29ybGQ=
1204
1205</artwork></figure>
1206<t>
1207   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1208   on a CONNECT request might cause some existing implementations to reject the
1209   request.
1210</t>
1211<t>
1212   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1213   sent immediately after the blank line. The usual caveats also apply:
1214   data may be discarded if the eventual response is negative, and the
1215   connection may be reset with no response if more than one TCP segment
1216   is outstanding.
1217</t>
1218
1219<section title="Establishing a Tunnel with CONNECT">
1220<t>
1221   Any successful (2xx) response to a CONNECT request indicates that the
1222   proxy has established a connection to the requested host and port,
1223   and has switched to tunneling the current connection to that server
1224   connection.
1225</t>
1226<t>
1227   It may be the case that the proxy itself can only reach the requested
1228   origin server through another proxy.  In this case, the first proxy
1229   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1230   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1231   unless it has either a direct or tunnel connection established to the
1232   authority.
1233</t>
1234<t>
1235   An origin server which receives a CONNECT request for itself &MAY;
1236   respond with a 2xx status code to indicate that a connection is
1237   established.
1238</t>
1239<t>
1240   If at any point either one of the peers gets disconnected, any
1241   outstanding data that came from that peer will be passed to the other
1242   one, and after that also the other connection will be terminated by
1243   the proxy. If there is outstanding data to that peer undelivered,
1244   that data will be discarded.
1245</t>
1246
1247</section>
1248</section>
1249</section>
1250
1251
1252<section title="Status Code Definitions" anchor="status.codes">
1253<t>
1254   Each Status-Code is described below, including any metadata required
1255   in the response.
1256</t>
1257
1258<section title="Informational 1xx" anchor="status.1xx">
1259<t>
1260   This class of status code indicates a provisional response,
1261   consisting only of the Status-Line and optional header fields, and is
1262   terminated by an empty line. There are no required header fields for this
1263   class of status code. Since HTTP/1.0 did not define any 1xx status
1264   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1265   except under experimental conditions.
1266</t>
1267<t>
1268   A client &MUST; be prepared to accept one or more 1xx status responses
1269   prior to a regular response, even if the client does not expect a 100
1270   (Continue) status message. Unexpected 1xx status responses &MAY; be
1271   ignored by a user agent.
1272</t>
1273<t>
1274   Proxies &MUST; forward 1xx responses, unless the connection between the
1275   proxy and its client has been closed, or unless the proxy itself
1276   requested the generation of the 1xx response. (For example, if a
1277   proxy adds a "Expect: 100-continue" field when it forwards a request,
1278   then it need not forward the corresponding 100 (Continue)
1279   response(s).)
1280</t>
1281
1282<section title="100 Continue" anchor="status.100">
1283  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1284  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1285<t>
1286   The client &SHOULD; continue with its request. This interim response is
1287   used to inform the client that the initial part of the request has
1288   been received and has not yet been rejected by the server. The client
1289   &SHOULD; continue by sending the remainder of the request or, if the
1290   request has already been completed, ignore this response. The server
1291   &MUST; send a final response after the request has been completed. See
1292   &use100; for detailed discussion of the use and handling of this
1293   status code.
1294</t>
1295</section>
1296
1297<section title="101 Switching Protocols" anchor="status.101">
1298  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1299  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1300<t>
1301   The server understands and is willing to comply with the client's
1302   request, via the Upgrade message header field (&header-upgrade;), for a
1303   change in the application protocol being used on this connection. The
1304   server will switch protocols to those defined by the response's
1305   Upgrade header field immediately after the empty line which
1306   terminates the 101 response.
1307</t>
1308<t>
1309   The protocol &SHOULD; be switched only when it is advantageous to do
1310   so. For example, switching to a newer version of HTTP is advantageous
1311   over older versions, and switching to a real-time, synchronous
1312   protocol might be advantageous when delivering resources that use
1313   such features.
1314</t>
1315</section>
1316</section>
1317
1318<section title="Successful 2xx" anchor="status.2xx">
1319<t>
1320   This class of status code indicates that the client's request was
1321   successfully received, understood, and accepted.
1322</t>
1323
1324<section title="200 OK" anchor="status.200">
1325  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1326  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1327<t>
1328   The request has succeeded. The payload returned with the response
1329   is dependent on the method used in the request, for example:
1330  <list style="hanging">
1331    <t hangText="GET">
1332          a representation of the target resource is sent in the response;
1333    </t>
1334    <t hangText="HEAD">
1335          the same representation as GET, except without the message-body;
1336    </t>
1337    <t hangText="POST">
1338      a representation describing or containing the result of the action;
1339    </t>
1340    <t hangText="TRACE">
1341      a representation containing the request message as received by the
1342      end server.
1343    </t>
1344  </list>
1345</t>
1346<t>
1347   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1348   freshness for 200 responses.
1349</t>
1350</section>
1351
1352<section title="201 Created" anchor="status.201">
1353  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1354  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1355<t>
1356   The request has been fulfilled and has resulted in a new resource being
1357   created. The newly created resource can be referenced by the URI(s)
1358   returned in the payload of the response, with the most specific URI
1359   for the resource given by a Location header field. The response
1360   &SHOULD; include a payload containing a list of resource
1361   characteristics and location(s) from which the user or user agent can
1362   choose the one most appropriate. The payload format is specified by
1363   the media type given in the Content-Type header field. The origin
1364   server &MUST; create the resource before returning the 201 status code.
1365   If the action cannot be carried out immediately, the server &SHOULD;
1366   respond with 202 (Accepted) response instead.
1367</t>
1368<t>
1369   A 201 response &MAY; contain an ETag response header field indicating
1370   the current value of the entity-tag for the representation of the resource
1371   just created (see &header-etag;).
1372</t>
1373</section>
1374
1375<section title="202 Accepted" anchor="status.202">
1376  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1377  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1378<t>
1379   The request has been accepted for processing, but the processing has
1380   not been completed.  The request might or might not eventually be
1381   acted upon, as it might be disallowed when processing actually takes
1382   place. There is no facility for re-sending a status code from an
1383   asynchronous operation such as this.
1384</t>
1385<t>
1386   The 202 response is intentionally non-committal. Its purpose is to
1387   allow a server to accept a request for some other process (perhaps a
1388   batch-oriented process that is only run once per day) without
1389   requiring that the user agent's connection to the server persist
1390   until the process is completed. The representation returned with this
1391   response &SHOULD; include an indication of the request's current status
1392   and either a pointer to a status monitor or some estimate of when the
1393   user can expect the request to be fulfilled.
1394</t>
1395</section>
1396
1397<section title="203 Non-Authoritative Information" anchor="status.203">
1398  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1399  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1400<t>
1401   The returned metadata in the header fields is not the
1402   definitive set as available from the origin server, but is gathered
1403   from a local or a third-party copy. The set presented &MAY; be a subset
1404   or superset of the original version. For example, including local
1405   annotation information about the resource might result in a superset
1406   of the metadata known by the origin server. Use of this
1407   response code is not required and is only appropriate when the
1408   response would otherwise be 200 (OK).
1409</t>
1410<t>
1411   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1412   freshness for 203 responses.
1413</t>
1414
1415</section>
1416
1417<section title="204 No Content" anchor="status.204">
1418  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1419  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1420<t>
1421   The 204 (No Content) status code indicates that the server has
1422   successfully fulfilled the request and that there is no additional
1423   content to return in the response payload body.  Metadata in the
1424   response header fields refer to the target resource and its current
1425   representation after the requested action.
1426</t>
1427<t>
1428   For example, if a 204 status code is received in response to a PUT
1429   request and the response contains an ETag header field, then the PUT
1430   was successful and the ETag field-value contains the entity-tag for
1431   the new representation of that target resource.
1432</t>
1433<t>
1434   The 204 response allows a server to indicate that the action has been
1435   successfully applied to the target resource while implying that the
1436   user agent &SHOULD-NOT; traverse away from its current "document view"
1437   (if any).  The server assumes that the user agent will provide some
1438   indication of the success to its user, in accord with its own interface,
1439   and apply any new or updated metadata in the response to the active
1440   representation.
1441   For example, a 204 status code is commonly used with document editing
1442   interfaces corresponding to a "save" action, such that the document
1443   being saved remains available to the user for editing. It is also
1444   frequently used with interfaces that expect automated data transfers
1445   to be prevalent, such as within distributed version control systems.
1446</t>
1447<t>
1448   The 204 response &MUST-NOT; include a message-body, and thus is always
1449   terminated by the first empty line after the header fields.
1450</t>
1451</section>
1452
1453<section title="205 Reset Content" anchor="status.205">
1454  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1455  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1456<t>
1457   The server has fulfilled the request and the user agent &SHOULD; reset
1458   the document view which caused the request to be sent. This response
1459   is primarily intended to allow input for actions to take place via
1460   user input, followed by a clearing of the form in which the input is
1461   given so that the user can easily initiate another input action.
1462</t>
1463<t>   
1464   The message-body included with the response &MUST; be empty. Note that
1465   receivers still need to parse the response according to the algorithm defined
1466   in &message-body;.
1467</t>
1468</section>
1469
1470<section title="206 Partial Content" anchor="status.206">
1471  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1472  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1473  <rdf:Description>
1474    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1475  </rdf:Description>
1476<t>
1477   The server has fulfilled the partial GET request for the resource
1478   and the enclosed payload is a partial representation as defined in &status-206;.
1479</t>
1480<t>
1481   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1482   freshness for 206 responses.
1483</t>
1484</section>
1485</section>
1486
1487<section title="Redirection 3xx" anchor="status.3xx">
1488<t>
1489   This class of status code indicates that further action needs to be
1490   taken by the user agent in order to fulfill the request.  The action
1491   required &MAY; be carried out by the user agent without interaction
1492   with the user if and only if the method used in the second request is
1493   known to be "safe", as defined in <xref target="safe.methods"/>.
1494   A client &SHOULD; detect infinite redirection loops, since such loops
1495   generate network traffic for each redirection.
1496</t>
1497<x:note>
1498  <t>
1499    <x:h>Note:</x:h> An earlier version of this specification recommended a
1500    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1501    Content developers need to be aware that some clients might
1502    implement such a fixed limitation.
1503  </t>
1504</x:note>
1505
1506<section title="300 Multiple Choices" anchor="status.300">
1507  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1508  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1509<t>
1510   The target resource has more than one
1511   representation, each with its own specific location, and agent-driven
1512   negotiation information (&content-negotiation;) is being provided so that
1513   the user (or user agent) can select a preferred representation by
1514   redirecting its request to that location.
1515</t>
1516<t>
1517   Unless it was a HEAD request, the response &SHOULD; include a representation
1518   containing a list of representation metadata and location(s) from
1519   which the user or user agent can choose the one most appropriate. The
1520   data format is specified by the media type given in the Content-Type
1521   header field. Depending upon the format and the capabilities of
1522   the user agent, selection of the most appropriate choice &MAY; be
1523   performed automatically. However, this specification does not define
1524   any standard for such automatic selection.
1525</t>
1526<t>
1527   If the server has a preferred choice of representation, it &SHOULD;
1528   include the specific URI for that representation in the Location
1529   field; user agents &MAY; use the Location field value for automatic
1530   redirection.
1531</t>
1532<t>
1533   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1534   freshness for 300 responses.
1535</t>
1536
1537</section>
1538
1539<section title="301 Moved Permanently" anchor="status.301">
1540  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1541  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1542<t>
1543   The target resource has been assigned a new permanent URI and any
1544   future references to this resource &SHOULD; use one of the returned
1545   URIs.  Clients with link editing capabilities ought to automatically
1546   re-link references to the effective request URI to one or more of the new
1547   references returned by the server, where possible.
1548</t>
1549<t>
1550   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1551   freshness for 301 responses.
1552</t>
1553<t>
1554   The new permanent URI &SHOULD; be given by the Location field in the
1555   response. Unless the request method was HEAD, the representation of the
1556   response &SHOULD; contain a short hypertext note with a hyperlink to
1557   the new URI(s).
1558</t>
1559<t>
1560   If the 301 status code is received in response to a request method
1561   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1562   then the request &MAY; be automatically redirected by the user agent without
1563   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1564   request unless it can be confirmed by the user, since this might
1565   change the conditions under which the request was issued.
1566</t>
1567<x:note>
1568  <t>
1569    <x:h>Note:</x:h> When automatically redirecting a POST request after
1570    receiving a 301 status code, some existing HTTP/1.0 user agents
1571    will erroneously change it into a GET request.
1572  </t>
1573</x:note>
1574</section>
1575
1576<section title="302 Found" anchor="status.302">
1577  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1578  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1579<t>
1580   The target resource resides temporarily under a different URI.
1581   Since the redirection might be altered on occasion, the client &SHOULD;
1582   continue to use the effective request URI for future requests.
1583</t>
1584<t>
1585   The temporary URI &SHOULD; be given by the Location field in the
1586   response. Unless the request method was HEAD, the representation of the
1587   response &SHOULD; contain a short hypertext note with a hyperlink to
1588   the new URI(s).
1589</t>
1590<t>
1591   If the 302 status code is received in response to a request method
1592   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1593   then the request &MAY; be automatically redirected by the user agent without
1594   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1595   request unless it can be confirmed by the user, since this might
1596   change the conditions under which the request was issued.
1597</t>
1598<x:note>
1599  <t>
1600    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1601    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1602    specify that the client is not allowed to change the method on the
1603    redirected request.  However, most existing user agent implementations
1604    treat 302 as if it were a 303 response, performing a GET on the Location
1605    field-value regardless of the original request method. Therefore, a
1606    previous version of this specification
1607    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1608    status codes
1609    <xref target="status.303" format="none">303</xref> and
1610    <xref target="status.307" format="none">307</xref> for servers that wish
1611    to make unambiguously clear which kind of reaction is expected of the
1612    client.
1613  </t>
1614</x:note>
1615</section>
1616
1617<section title="303 See Other" anchor="status.303">
1618  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1619  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1620<t>
1621   The server directs the user agent to a different resource, indicated
1622   by a URI in the Location header field, that provides an indirect
1623   response to the original request.  The user agent &MAY; perform a GET
1624   request on the URI in the Location field in order to obtain a
1625   representation corresponding to the response, be redirected again,
1626   or end with an error status.  The Location URI is not a substitute
1627   reference for the effective request URI.
1628</t>
1629<t>
1630   The 303 status code is generally applicable to any HTTP method.  It is
1631   primarily used to allow the output of a POST action to redirect
1632   the user agent to a selected resource, since doing so provides the
1633   information corresponding to the POST response in a form that
1634   can be separately identified, bookmarked, and cached independent
1635   of the original request.
1636</t>
1637<t>
1638   A 303 response to a GET request indicates that the requested
1639   resource does not have a representation of its own that can be
1640   transferred by the server over HTTP.  The Location URI indicates a
1641   resource that is descriptive of the target resource, such that the
1642   follow-on representation might be useful to recipients without
1643   implying that it adequately represents the target resource.
1644   Note that answers to the questions of what can be represented, what
1645   representations are adequate, and what might be a useful description
1646   are outside the scope of HTTP and thus entirely determined by the
1647   URI owner(s).
1648</t>
1649<t>
1650   Except for responses to a HEAD request, the representation of a 303
1651   response &SHOULD; contain a short hypertext note with a hyperlink
1652   to the Location URI.
1653</t>
1654</section>
1655
1656<section title="304 Not Modified" anchor="status.304">
1657  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1658  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1659  <rdf:Description>
1660    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1661  </rdf:Description>
1662<t>
1663   The response to the request has not been modified since the conditions
1664   indicated by the client's conditional GET request, as defined in &status-304;.
1665</t>
1666</section>
1667
1668<section title="305 Use Proxy" anchor="status.305">
1669  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1670  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1671<t>
1672   The 305 status code was defined in a previous version of this specification
1673   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1674</t>
1675</section>
1676
1677<section title="306 (Unused)" anchor="status.306">
1678  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1679  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1680<t>
1681   The 306 status code was used in a previous version of the
1682   specification, is no longer used, and the code is reserved.
1683</t>
1684</section>
1685
1686<section title="307 Temporary Redirect" anchor="status.307">
1687  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1688  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1689<t>
1690   The target resource resides temporarily under a different URI.
1691   Since the redirection can change over time, the client &SHOULD;
1692   continue to use the effective request URI for future requests.
1693</t>
1694<t>
1695   The temporary URI &SHOULD; be given by the Location field in the
1696   response. Unless the request method was HEAD, the representation of the
1697   response &SHOULD; contain a short hypertext note with a hyperlink to
1698   the new URI(s), since many pre-HTTP/1.1 user agents do not
1699   understand the 307 status code. Therefore, the note &SHOULD; contain the
1700   information necessary for a user to repeat the original request on
1701   the new URI.
1702</t>
1703<t>
1704   If the 307 status code is received in response to a request method
1705   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1706   then the request &MAY; be automatically redirected by the user agent without
1707   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1708   request unless it can be confirmed by the user, since this might
1709   change the conditions under which the request was issued.
1710</t>
1711</section>
1712</section>
1713
1714<section title="Client Error 4xx" anchor="status.4xx">
1715<t>
1716   The 4xx class of status code is intended for cases in which the
1717   client seems to have erred. Except when responding to a HEAD request,
1718   the server &SHOULD; include a representation containing an explanation of the
1719   error situation, and whether it is a temporary or permanent
1720   condition. These status codes are applicable to any request method.
1721   User agents &SHOULD; display any included representation to the user.
1722</t>
1723<t>
1724   If the client is sending data, a server implementation using TCP
1725   &SHOULD; be careful to ensure that the client acknowledges receipt of
1726   the packet(s) containing the response, before the server closes the
1727   input connection. If the client continues sending data to the server
1728   after the close, the server's TCP stack will send a reset packet to
1729   the client, which might erase the client's unacknowledged input buffers
1730   before they can be read and interpreted by the HTTP application.
1731</t>
1732
1733<section title="400 Bad Request" anchor="status.400">
1734  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1735  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1736<t>
1737   The request could not be understood by the server due to malformed
1738   syntax. The client &SHOULD-NOT; repeat the request without
1739   modifications.
1740</t>
1741</section>
1742
1743<section title="401 Unauthorized" anchor="status.401">
1744  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1745  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1746  <rdf:Description>
1747    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1748  </rdf:Description>
1749<t>
1750   The request requires user authentication (see &status-401;).
1751</t>
1752</section>
1753
1754<section title="402 Payment Required" anchor="status.402">
1755  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1756  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1757<t>
1758   This code is reserved for future use.
1759</t>
1760</section>
1761
1762<section title="403 Forbidden" anchor="status.403">
1763  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1764  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1765<t>
1766   The server understood the request, but is refusing to fulfill it.
1767   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1768   If the request method was not HEAD and the server wishes to make
1769   public why the request has not been fulfilled, it &SHOULD; describe the
1770   reason for the refusal in the representation.  If the server does not wish to
1771   make this information available to the client, the status code 404
1772   (Not Found) can be used instead.
1773</t>
1774</section>
1775
1776<section title="404 Not Found" anchor="status.404">
1777  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1778  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1779<t>
1780   The server has not found anything matching the effective request URI. No
1781   indication is given of whether the condition is temporary or
1782   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1783   knows, through some internally configurable mechanism, that an old
1784   resource is permanently unavailable and has no forwarding address.
1785   This status code is commonly used when the server does not wish to
1786   reveal exactly why the request has been refused, or when no other
1787   response is applicable.
1788</t>
1789</section>
1790
1791<section title="405 Method Not Allowed" anchor="status.405">
1792  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1793  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1794<t>
1795   The method specified in the Request-Line is not allowed for the target
1796   resource. The response &MUST; include an
1797   Allow header field containing a list of valid methods for the requested
1798   resource.
1799</t>
1800</section>
1801
1802<section title="406 Not Acceptable" anchor="status.406">
1803  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1804  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1805<t>
1806   The resource identified by the request is only capable of generating
1807   response representations which have content characteristics not acceptable
1808   according to the accept header fields sent in the request.
1809</t>
1810<t>
1811   Unless it was a HEAD request, the response &SHOULD; include a representation
1812   containing a list of available representation characteristics and location(s)
1813   from which the user or user agent can choose the one most
1814   appropriate. The data format is specified by the media type given
1815   in the Content-Type header field. Depending upon the format and the
1816   capabilities of the user agent, selection of the most appropriate
1817   choice &MAY; be performed automatically. However, this specification
1818   does not define any standard for such automatic selection.
1819</t>
1820<x:note>
1821  <t>
1822    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1823    not acceptable according to the accept header fields sent in the
1824    request. In some cases, this might even be preferable to sending a
1825    406 response. User agents are encouraged to inspect the header fields of
1826    an incoming response to determine if it is acceptable.
1827  </t>
1828</x:note>
1829<t>
1830   If the response could be unacceptable, a user agent &SHOULD;
1831   temporarily stop receipt of more data and query the user for a
1832   decision on further actions.
1833</t>
1834</section>
1835
1836<section title="407 Proxy Authentication Required" anchor="status.407">
1837  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1838  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1839<t>
1840   This code is similar to 401 (Unauthorized), but indicates that the
1841   client must first authenticate itself with the proxy (see &status-407;).
1842</t>
1843</section>
1844
1845<section title="408 Request Timeout" anchor="status.408">
1846  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1847  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1848<t>
1849   The client did not produce a request within the time that the server
1850   was prepared to wait. The client &MAY; repeat the request without
1851   modifications at any later time.
1852</t>
1853</section>
1854
1855<section title="409 Conflict" anchor="status.409">
1856  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1857  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1858<t>
1859   The request could not be completed due to a conflict with the current
1860   state of the resource. This code is only allowed in situations where
1861   it is expected that the user might be able to resolve the conflict
1862   and resubmit the request. The response body &SHOULD; include enough
1863   information for the user to recognize the source of the conflict.
1864   Ideally, the response representation would include enough information for the
1865   user or user agent to fix the problem; however, that might not be
1866   possible and is not required.
1867</t>
1868<t>
1869   Conflicts are most likely to occur in response to a PUT request. For
1870   example, if versioning were being used and the representation being PUT
1871   included changes to a resource which conflict with those made by an
1872   earlier (third-party) request, the server might use the 409 response
1873   to indicate that it can't complete the request. In this case, the
1874   response representation would likely contain a list of the differences
1875   between the two versions in a format defined by the response
1876   Content-Type.
1877</t>
1878</section>
1879
1880<section title="410 Gone" anchor="status.410">
1881  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1882  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1883<t>
1884   The target resource is no longer available at the server and no
1885   forwarding address is known. This condition is expected to be
1886   considered permanent. Clients with link editing capabilities &SHOULD;
1887   delete references to the effective request URI after user approval. If the
1888   server does not know, or has no facility to determine, whether or not
1889   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1890   used instead.
1891</t>
1892<t>
1893   The 410 response is primarily intended to assist the task of web
1894   maintenance by notifying the recipient that the resource is
1895   intentionally unavailable and that the server owners desire that
1896   remote links to that resource be removed. Such an event is common for
1897   limited-time, promotional services and for resources belonging to
1898   individuals no longer working at the server's site. It is not
1899   necessary to mark all permanently unavailable resources as "gone" or
1900   to keep the mark for any length of time &mdash; that is left to the
1901   discretion of the server owner.
1902</t>
1903<t>
1904   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1905   for 410 responses.
1906</t>
1907
1908</section>
1909
1910<section title="411 Length Required" anchor="status.411">
1911  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1912  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1913<t>
1914   The server refuses to accept the request without a defined Content-Length.
1915   The client &MAY; repeat the request if it adds a valid
1916   Content-Length header field containing the length of the message-body
1917   in the request message.
1918</t>
1919</section>
1920
1921<section title="412 Precondition Failed" anchor="status.412">
1922  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1923  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1924  <rdf:Description>
1925    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1926  </rdf:Description>
1927<t>
1928   The precondition given in one or more of the header fields
1929   evaluated to false when it was tested on the server, as defined in
1930   &status-412;.
1931</t>
1932</section>
1933
1934<section title="413 Request Entity Too Large" anchor="status.413">
1935  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1936  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1937<t>
1938   The server is refusing to process a request because the request
1939   representation is larger than the server is willing or able to process. The
1940   server &MAY; close the connection to prevent the client from continuing
1941   the request.
1942</t>
1943<t>
1944   If the condition is temporary, the server &SHOULD; include a Retry-After
1945   header field to indicate that it is temporary and after what
1946   time the client &MAY; try again.
1947</t>
1948</section>
1949
1950<section title="414 URI Too Long" anchor="status.414">
1951  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1952  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1953<t>
1954   The server is refusing to service the request because the effective request URI
1955   is longer than the server is willing to interpret. This rare
1956   condition is only likely to occur when a client has improperly
1957   converted a POST request to a GET request with long query
1958   information, when the client has descended into a URI "black hole" of
1959   redirection (e.g., a redirected URI prefix that points to a suffix of
1960   itself), or when the server is under attack by a client attempting to
1961   exploit security holes present in some servers using fixed-length
1962   buffers for reading or manipulating the effective request URI.
1963</t>
1964</section>
1965
1966<section title="415 Unsupported Media Type" anchor="status.415">
1967  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1968  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1969<t>
1970   The server is refusing to service the request because the request
1971   payload is in a format not supported by this request method on the
1972   target resource.
1973</t>
1974</section>
1975
1976<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1977  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1978  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1979  <rdf:Description>
1980    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1981  </rdf:Description>
1982<t>
1983   The request included a Range header field (&header-range;) and none of
1984   the range-specifier values in this field overlap the current extent
1985   of the selected resource. See &status-416;.
1986</t>
1987</section>
1988
1989<section title="417 Expectation Failed" anchor="status.417">
1990  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1991  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1992<t>
1993   The expectation given in an Expect header field (see <xref target="header.expect"/>)
1994   could not be met by this server, or, if the server is a proxy,
1995   the server has unambiguous evidence that the request could not be met
1996   by the next-hop server.
1997</t>
1998</section>
1999
2000<section title="426 Upgrade Required" anchor="status.426">
2001  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2002  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2003<t>
2004   The request can not be completed without a prior protocol upgrade. This
2005   response &MUST; include an Upgrade header field (&header-upgrade;)
2006   specifying the required protocols.
2007</t>
2008<figure>
2009<preamble>Example:</preamble>
2010<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2011HTTP/1.1 426 Upgrade Required
2012Upgrade: HTTP/2.0
2013Connection: Upgrade
2014
2015</artwork></figure>
2016<t>
2017   The server &SHOULD; include a message body in the 426 response which
2018   indicates in human readable form the reason for the error and describes any
2019   alternative courses which may be available to the user.
2020</t>
2021</section>
2022</section>
2023
2024<section title="Server Error 5xx" anchor="status.5xx">
2025<t>
2026   Response status codes beginning with the digit "5" indicate cases in
2027   which the server is aware that it has erred or is incapable of
2028   performing the request. Except when responding to a HEAD request, the
2029   server &SHOULD; include a representation containing an explanation of the
2030   error situation, and whether it is a temporary or permanent
2031   condition. User agents &SHOULD; display any included representation to the
2032   user. These response codes are applicable to any request method.
2033</t>
2034
2035<section title="500 Internal Server Error" anchor="status.500">
2036  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2037  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2038<t>
2039   The server encountered an unexpected condition which prevented it
2040   from fulfilling the request.
2041</t>
2042</section>
2043
2044<section title="501 Not Implemented" anchor="status.501">
2045  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2046  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2047<t>
2048   The server does not support the functionality required to fulfill the
2049   request. This is the appropriate response when the server does not
2050   recognize the request method and is not capable of supporting it for
2051   any resource.
2052</t>
2053</section>
2054
2055<section title="502 Bad Gateway" anchor="status.502">
2056  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2057  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2058<t>
2059   The server, while acting as a gateway or proxy, received an invalid
2060   response from the upstream server it accessed in attempting to
2061   fulfill the request.
2062</t>
2063</section>
2064
2065<section title="503 Service Unavailable" anchor="status.503">
2066  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2067  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2068<t>
2069   The server is currently unable to handle the request due to a
2070   temporary overloading or maintenance of the server. The implication
2071   is that this is a temporary condition which will be alleviated after
2072   some delay. If known, the length of the delay &MAY; be indicated in a
2073   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2074   handle the response as it would for a 500 response.
2075</t>
2076<x:note>
2077  <t>
2078    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2079    server must use it when becoming overloaded. Some servers might wish
2080    to simply refuse the connection.
2081  </t>
2082</x:note>
2083</section>
2084
2085<section title="504 Gateway Timeout" anchor="status.504">
2086  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2087  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2088<t>
2089   The server, while acting as a gateway or proxy, did not receive a
2090   timely response from the upstream server specified by the URI (e.g.,
2091   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2092   to access in attempting to complete the request.
2093</t>
2094<x:note>
2095  <t>
2096    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2097    return 400 or 500 when DNS lookups time out.
2098  </t>
2099</x:note>
2100</section>
2101
2102<section title="505 HTTP Version Not Supported" anchor="status.505">
2103  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2104  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2105<t>
2106   The server does not support, or refuses to support, the protocol
2107   version that was used in the request message. The server is
2108   indicating that it is unable or unwilling to complete the request
2109   using the same major version as the client, as described in &http-version;,
2110   other than with this error message. The response &SHOULD; contain
2111   a representation describing why that version is not supported and what other
2112   protocols are supported by that server.
2113</t>
2114
2115</section>
2116</section>
2117</section>
2118
2119
2120<section title="Header Field Definitions" anchor="header.fields">
2121<t>
2122   This section defines the syntax and semantics of HTTP/1.1 header fields
2123   related to request and response semantics.
2124</t>
2125
2126<section title="Allow" anchor="header.allow">
2127  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2128  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2129  <x:anchor-alias value="Allow"/>
2130<t>
2131   The "Allow" header field lists the set of methods advertised as
2132   supported by the target resource. The purpose of this field is strictly to
2133   inform the recipient of valid request methods associated with the resource.
2134</t>
2135<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2136  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2137</artwork></figure>
2138<t>
2139   Example of use:
2140</t>
2141<figure><artwork type="example">
2142  Allow: GET, HEAD, PUT
2143</artwork></figure>
2144<t>
2145   The actual set of allowed methods is defined by the origin server at the
2146   time of each request.
2147</t>
2148<t>
2149   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2150   understand all the methods specified in order to handle them according to
2151   the generic message handling rules.
2152</t>
2153</section>
2154
2155<section title="Expect" anchor="header.expect">
2156  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2157  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2158  <x:anchor-alias value="Expect"/>
2159  <x:anchor-alias value="expectation"/>
2160  <x:anchor-alias value="expectation-extension"/>
2161  <x:anchor-alias value="expect-params"/>
2162<t>
2163   The "Expect" header field is used to indicate that particular
2164   server behaviors are required by the client.
2165</t>
2166<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"/>
2167  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2168 
2169  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2170  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2171                           *<x:ref>expect-params</x:ref> ]
2172  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2173</artwork></figure>
2174<t>
2175   A server that does not understand or is unable to comply with any of
2176   the expectation values in the Expect field of a request &MUST; respond
2177   with appropriate error status code. The server &MUST; respond with a 417
2178   (Expectation Failed) status code if any of the expectations cannot be met
2179   or, if there are other problems with the request, some other 4xx
2180   status code.
2181</t>
2182<t>
2183   This header field is defined with extensible syntax to allow for
2184   future extensions. If a server receives a request containing an
2185   Expect field that includes an expectation-extension that it does not
2186   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2187</t>
2188<t>
2189   Comparison of expectation values is case-insensitive for unquoted
2190   tokens (including the 100-continue token), and is case-sensitive for
2191   quoted-string expectation-extensions.
2192</t>
2193<t>
2194   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2195   return a 417 (Expectation Failed) status code if it receives a request
2196   with an expectation that it cannot meet. However, the Expect
2197   header field itself is end-to-end; it &MUST; be forwarded if the
2198   request is forwarded.
2199</t>
2200<t>
2201   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2202   Expect header field.
2203</t>
2204<t>
2205   See &use100; for the use of the 100 (Continue) status code.
2206</t>
2207</section>
2208
2209<section title="From" anchor="header.from">
2210  <iref primary="true" item="From header field" x:for-anchor=""/>
2211  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2212  <x:anchor-alias value="From"/>
2213  <x:anchor-alias value="mailbox"/>
2214<t>
2215   The "From" header field, if given, &SHOULD; contain an Internet
2216   e-mail address for the human user who controls the requesting user
2217   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2218   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2219</t>
2220<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2221  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2222 
2223  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2224</artwork></figure>
2225<t>
2226   An example is:
2227</t>
2228<figure><artwork type="example">
2229  From: webmaster@example.org
2230</artwork></figure>
2231<t>
2232   This header field &MAY; be used for logging purposes and as a means for
2233   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2234   be used as an insecure form of access protection. The interpretation
2235   of this field is that the request is being performed on behalf of the
2236   person given, who accepts responsibility for the method performed. In
2237   particular, robot agents &SHOULD; include this header field so that the
2238   person responsible for running the robot can be contacted if problems
2239   occur on the receiving end.
2240</t>
2241<t>
2242   The Internet e-mail address in this field &MAY; be separate from the
2243   Internet host which issued the request. For example, when a request
2244   is passed through a proxy the original issuer's address &SHOULD; be
2245   used.
2246</t>
2247<t>
2248   The client &SHOULD-NOT;  send the From header field without the user's
2249   approval, as it might conflict with the user's privacy interests or
2250   their site's security policy. It is strongly recommended that the
2251   user be able to disable, enable, and modify the value of this field
2252   at any time prior to a request.
2253</t>
2254</section>
2255
2256<section title="Location" anchor="header.location">
2257  <iref primary="true" item="Location header field" x:for-anchor=""/>
2258  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2259  <x:anchor-alias value="Location"/>
2260<t>
2261   The "Location" header field is used to identify a newly created
2262   resource, or to redirect the recipient to a different location for
2263   completion of the request.
2264</t>
2265<t>
2266   For 201 (Created) responses, the Location is the URI of the new resource
2267   which was created by the request. For 3xx responses, the location &SHOULD;
2268   indicate the server's preferred URI for automatic redirection to the
2269   resource.
2270</t>
2271<t>
2272   The field value consists of a single URI-reference. When it has the form
2273   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2274   the final value is computed by resolving it against the effective request
2275   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2276</t>
2277<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2278  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2279</artwork></figure>
2280<figure>
2281<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2282<artwork type="example">
2283  Location: http://www.example.org/pub/WWW/People.html#tim
2284</artwork></figure><figure><artwork type="example">  Location: /index.html
2285</artwork></figure>
2286<t>
2287   There are circumstances in which a fragment identifier in a Location URI
2288   would not be appropriate:
2289   <list style="symbols">
2290      <t>With a 201 Created response, because in this usage the Location header
2291      field specifies the URI for the entire created resource.</t>
2292      <t>With 305 Use Proxy.</t>
2293   </list>
2294</t>
2295<x:note>
2296  <t>
2297    <x:h>Note:</x:h> This specification does not define precedence rules
2298    for the case where the original URI, as navigated to by the user
2299    agent, and the Location header field value both contain fragment
2300    identifiers. Thus be aware that including fragment identifiers might
2301    inconvenience anyone relying on the semantics of the original URI's
2302    fragment identifier.
2303  </t>
2304</x:note>
2305<x:note>
2306  <t>
2307    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2308    from Location in that the Content-Location identifies the most specific
2309    resource corresponding to the enclosed representation.
2310    It is therefore possible for a response to contain header fields for
2311    both Location and Content-Location.
2312  </t>
2313</x:note>
2314</section>
2315
2316<section title="Max-Forwards" anchor="header.max-forwards">
2317  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2318  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2319  <x:anchor-alias value="Max-Forwards"/>
2320<t>
2321   The "Max-Forwards" header field provides a mechanism with the
2322   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2323   methods to limit the number of times that the request is forwarded by
2324   proxies. This can be useful when the client is attempting to
2325   trace a request which appears to be failing or looping in mid-chain.
2326</t>
2327<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2328  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2329</artwork></figure>
2330<t>
2331   The Max-Forwards value is a decimal integer indicating the remaining
2332   number of times this request message can be forwarded.
2333</t>
2334<t>
2335   Each recipient of a TRACE or OPTIONS request
2336   containing a Max-Forwards header field &MUST; check and update its
2337   value prior to forwarding the request. If the received value is zero
2338   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2339   respond as the final recipient. If the received Max-Forwards value is
2340   greater than zero, then the forwarded message &MUST; contain an updated
2341   Max-Forwards field with a value decremented by one (1).
2342</t>
2343<t>
2344   The Max-Forwards header field &MAY; be ignored for all other request
2345   methods.
2346</t>
2347</section>
2348
2349<section title="Referer" anchor="header.referer">
2350  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2351  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2352  <x:anchor-alias value="Referer"/>
2353<t>
2354   The "Referer" [sic] header field allows the client to specify the
2355   URI of the resource from which the effective request URI was obtained (the
2356   "referrer", although the header field is misspelled.).
2357</t>
2358<t>
2359   The Referer header field allows servers to generate lists of back-links to
2360   resources for interest, logging, optimized caching, etc. It also allows
2361   obsolete or mistyped links to be traced for maintenance. Some servers use
2362   Referer as a means of controlling where they allow links from (so-called
2363   "deep linking"), but legitimate requests do not always
2364   contain a Referer header field.
2365</t>
2366<t>
2367   If the effective request URI was obtained from a source that does not have its own
2368   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2369   sent with the value "about:blank", or not be sent at all. Note that this
2370   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2371</t>
2372<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2373  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2374</artwork></figure>
2375<t>
2376   Example:
2377</t>
2378<figure><artwork type="example">
2379  Referer: http://www.example.org/hypertext/Overview.html
2380</artwork></figure>
2381<t>
2382   If the field value is a relative URI, it &SHOULD; be interpreted
2383   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2384   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2385</t>
2386</section>
2387
2388<section title="Retry-After" anchor="header.retry-after">
2389  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2390  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2391  <x:anchor-alias value="Retry-After"/>
2392<t>
2393   The header "Retry-After" field can be used with a 503 (Service
2394   Unavailable) response to indicate how long the service is expected to
2395   be unavailable to the requesting client. This field &MAY; also be used
2396   with any 3xx (Redirection) response to indicate the minimum time the
2397   user-agent is asked wait before issuing the redirected request.
2398</t>
2399<t>
2400   The value of this field can be either an HTTP-date or an integer number
2401   of seconds (in decimal) after the time of the response.
2402</t>
2403<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2404  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2405</artwork></figure>
2406<t anchor="rule.delta-seconds">
2407  <x:anchor-alias value="delta-seconds"/>
2408   Time spans are non-negative decimal integers, representing time in
2409   seconds.
2410</t>
2411<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2412  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2413</artwork></figure>
2414<t>
2415   Two examples of its use are
2416</t>
2417<figure><artwork type="example">
2418  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2419  Retry-After: 120
2420</artwork></figure>
2421<t>
2422   In the latter example, the delay is 2 minutes.
2423</t>
2424</section>
2425
2426<section title="Server" anchor="header.server">
2427  <iref primary="true" item="Server header field" x:for-anchor=""/>
2428  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2429  <x:anchor-alias value="Server"/>
2430<t>
2431   The "Server" header field contains information about the
2432   software used by the origin server to handle the request.
2433</t>
2434<t>
2435   The field can contain multiple product tokens (&product-tokens;) and
2436   comments (&header-fields;) identifying the server and any significant
2437   subproducts. The product tokens are listed in order of their significance
2438   for identifying the application.
2439</t>
2440<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2441  <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> ) )
2442</artwork></figure>
2443<t>
2444   Example:
2445</t>
2446<figure><artwork type="example">
2447  Server: CERN/3.0 libwww/2.17
2448</artwork></figure>
2449<t>
2450   If the response is being forwarded through a proxy, the proxy
2451   application &MUST-NOT; modify the Server header field. Instead, it
2452   &MUST; include a Via field (as described in &header-via;).
2453</t>
2454<x:note>
2455  <t>
2456    <x:h>Note:</x:h> Revealing the specific software version of the server might
2457    allow the server machine to become more vulnerable to attacks
2458    against software that is known to contain security holes. Server
2459    implementors are encouraged to make this field a configurable
2460    option.
2461  </t>
2462</x:note>
2463</section>
2464
2465<section title="User-Agent" anchor="header.user-agent">
2466  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2467  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2468  <x:anchor-alias value="User-Agent"/>
2469<t>
2470   The "User-Agent" header field contains information about the user
2471   agent originating the request. User agents &SHOULD; include this field with
2472   requests.
2473</t>
2474<t>
2475   Typically, it is used for statistical purposes, the tracing of protocol
2476   violations, and tailoring responses to avoid particular user agent
2477   limitations.
2478</t>
2479<t>
2480   The field can contain multiple product tokens (&product-tokens;)
2481   and comments (&header-fields;) identifying the agent and its
2482   significant subproducts. By convention, the product tokens are listed in
2483   order of their significance for identifying the application.
2484</t>
2485<t>
2486   Because this field is usually sent on every request a user agent makes,
2487   implementations are encouraged not to include needlessly fine-grained
2488   detail, and to limit (or even prohibit) the addition of subproducts by third
2489   parties. Overly long and detailed User-Agent field values make requests
2490   larger and can also be used to identify ("fingerprint") the user against
2491   their wishes.
2492</t>
2493<t>
2494   Likewise, implementations are encouraged not to use the product tokens of
2495   other implementations in order to declare compatibility with them, as this
2496   circumvents the purpose of the field. Finally, they are encouraged not to
2497   use comments to identify products; doing so makes the field value more
2498   difficult to parse.
2499</t>
2500<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2501  <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> ) )
2502</artwork></figure>
2503<t>
2504   Example:
2505</t>
2506<figure><artwork type="example">
2507  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2508</artwork></figure>
2509</section>
2510
2511</section>
2512
2513<section title="IANA Considerations" anchor="IANA.considerations">
2514
2515<section title="Method Registry" anchor="method.registration">
2516<t>
2517  The registration procedure for HTTP request methods is defined by
2518  <xref target="method.registry"/> of this document.
2519</t>
2520<t>
2521   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2522   and be populated with the registrations below:
2523</t>
2524<?BEGININC p2-semantics.iana-methods ?>
2525<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2526<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2527   <ttcol>Method</ttcol>
2528   <ttcol>Safe</ttcol>
2529   <ttcol>Reference</ttcol>
2530   <c>CONNECT</c>
2531   <c>no</c>
2532   <c>
2533      <xref target="CONNECT"/>
2534   </c>
2535   <c>DELETE</c>
2536   <c>no</c>
2537   <c>
2538      <xref target="DELETE"/>
2539   </c>
2540   <c>GET</c>
2541   <c>yes</c>
2542   <c>
2543      <xref target="GET"/>
2544   </c>
2545   <c>HEAD</c>
2546   <c>yes</c>
2547   <c>
2548      <xref target="HEAD"/>
2549   </c>
2550   <c>OPTIONS</c>
2551   <c>yes</c>
2552   <c>
2553      <xref target="OPTIONS"/>
2554   </c>
2555   <c>POST</c>
2556   <c>no</c>
2557   <c>
2558      <xref target="POST"/>
2559   </c>
2560   <c>PUT</c>
2561   <c>no</c>
2562   <c>
2563      <xref target="PUT"/>
2564   </c>
2565   <c>TRACE</c>
2566   <c>yes</c>
2567   <c>
2568      <xref target="TRACE"/>
2569   </c>
2570</texttable>
2571<!--(END)-->
2572<?ENDINC p2-semantics.iana-methods ?>
2573</section>
2574
2575<section title="Status Code Registry" anchor="status.code.registration">
2576<t>
2577   The registration procedure for HTTP Status Codes &mdash; previously defined
2578   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2579   by <xref target="status.code.registry"/> of this document.
2580</t>
2581<t>
2582   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2583   shall be updated with the registrations below:
2584</t>
2585<?BEGININC p2-semantics.iana-status-codes ?>
2586<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2587<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2588   <ttcol>Value</ttcol>
2589   <ttcol>Description</ttcol>
2590   <ttcol>Reference</ttcol>
2591   <c>100</c>
2592   <c>Continue</c>
2593   <c>
2594      <xref target="status.100"/>
2595   </c>
2596   <c>101</c>
2597   <c>Switching Protocols</c>
2598   <c>
2599      <xref target="status.101"/>
2600   </c>
2601   <c>200</c>
2602   <c>OK</c>
2603   <c>
2604      <xref target="status.200"/>
2605   </c>
2606   <c>201</c>
2607   <c>Created</c>
2608   <c>
2609      <xref target="status.201"/>
2610   </c>
2611   <c>202</c>
2612   <c>Accepted</c>
2613   <c>
2614      <xref target="status.202"/>
2615   </c>
2616   <c>203</c>
2617   <c>Non-Authoritative Information</c>
2618   <c>
2619      <xref target="status.203"/>
2620   </c>
2621   <c>204</c>
2622   <c>No Content</c>
2623   <c>
2624      <xref target="status.204"/>
2625   </c>
2626   <c>205</c>
2627   <c>Reset Content</c>
2628   <c>
2629      <xref target="status.205"/>
2630   </c>
2631   <c>300</c>
2632   <c>Multiple Choices</c>
2633   <c>
2634      <xref target="status.300"/>
2635   </c>
2636   <c>301</c>
2637   <c>Moved Permanently</c>
2638   <c>
2639      <xref target="status.301"/>
2640   </c>
2641   <c>302</c>
2642   <c>Found</c>
2643   <c>
2644      <xref target="status.302"/>
2645   </c>
2646   <c>303</c>
2647   <c>See Other</c>
2648   <c>
2649      <xref target="status.303"/>
2650   </c>
2651   <c>305</c>
2652   <c>Use Proxy</c>
2653   <c>
2654      <xref target="status.305"/>
2655   </c>
2656   <c>306</c>
2657   <c>(Unused)</c>
2658   <c>
2659      <xref target="status.306"/>
2660   </c>
2661   <c>307</c>
2662   <c>Temporary Redirect</c>
2663   <c>
2664      <xref target="status.307"/>
2665   </c>
2666   <c>400</c>
2667   <c>Bad Request</c>
2668   <c>
2669      <xref target="status.400"/>
2670   </c>
2671   <c>402</c>
2672   <c>Payment Required</c>
2673   <c>
2674      <xref target="status.402"/>
2675   </c>
2676   <c>403</c>
2677   <c>Forbidden</c>
2678   <c>
2679      <xref target="status.403"/>
2680   </c>
2681   <c>404</c>
2682   <c>Not Found</c>
2683   <c>
2684      <xref target="status.404"/>
2685   </c>
2686   <c>405</c>
2687   <c>Method Not Allowed</c>
2688   <c>
2689      <xref target="status.405"/>
2690   </c>
2691   <c>406</c>
2692   <c>Not Acceptable</c>
2693   <c>
2694      <xref target="status.406"/>
2695   </c>
2696   <c>407</c>
2697   <c>Proxy Authentication Required</c>
2698   <c>
2699      <xref target="status.407"/>
2700   </c>
2701   <c>408</c>
2702   <c>Request Timeout</c>
2703   <c>
2704      <xref target="status.408"/>
2705   </c>
2706   <c>409</c>
2707   <c>Conflict</c>
2708   <c>
2709      <xref target="status.409"/>
2710   </c>
2711   <c>410</c>
2712   <c>Gone</c>
2713   <c>
2714      <xref target="status.410"/>
2715   </c>
2716   <c>411</c>
2717   <c>Length Required</c>
2718   <c>
2719      <xref target="status.411"/>
2720   </c>
2721   <c>413</c>
2722   <c>Request Entity Too Large</c>
2723   <c>
2724      <xref target="status.413"/>
2725   </c>
2726   <c>414</c>
2727   <c>URI Too Long</c>
2728   <c>
2729      <xref target="status.414"/>
2730   </c>
2731   <c>415</c>
2732   <c>Unsupported Media Type</c>
2733   <c>
2734      <xref target="status.415"/>
2735   </c>
2736   <c>417</c>
2737   <c>Expectation Failed</c>
2738   <c>
2739      <xref target="status.417"/>
2740   </c>
2741   <c>426</c>
2742   <c>Upgrade Required</c>
2743   <c>
2744      <xref target="status.426"/>
2745   </c>
2746   <c>500</c>
2747   <c>Internal Server Error</c>
2748   <c>
2749      <xref target="status.500"/>
2750   </c>
2751   <c>501</c>
2752   <c>Not Implemented</c>
2753   <c>
2754      <xref target="status.501"/>
2755   </c>
2756   <c>502</c>
2757   <c>Bad Gateway</c>
2758   <c>
2759      <xref target="status.502"/>
2760   </c>
2761   <c>503</c>
2762   <c>Service Unavailable</c>
2763   <c>
2764      <xref target="status.503"/>
2765   </c>
2766   <c>504</c>
2767   <c>Gateway Timeout</c>
2768   <c>
2769      <xref target="status.504"/>
2770   </c>
2771   <c>505</c>
2772   <c>HTTP Version Not Supported</c>
2773   <c>
2774      <xref target="status.505"/>
2775   </c>
2776</texttable>
2777<!--(END)-->
2778<?ENDINC p2-semantics.iana-status-codes ?>
2779</section>
2780<section title="Header Field Registration" anchor="header.field.registration">
2781<t>
2782   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2783   with the permanent registrations below (see <xref target="RFC3864"/>):
2784</t>
2785<?BEGININC p2-semantics.iana-headers ?>
2786<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2787<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2788   <ttcol>Header Field Name</ttcol>
2789   <ttcol>Protocol</ttcol>
2790   <ttcol>Status</ttcol>
2791   <ttcol>Reference</ttcol>
2792
2793   <c>Allow</c>
2794   <c>http</c>
2795   <c>standard</c>
2796   <c>
2797      <xref target="header.allow"/>
2798   </c>
2799   <c>Expect</c>
2800   <c>http</c>
2801   <c>standard</c>
2802   <c>
2803      <xref target="header.expect"/>
2804   </c>
2805   <c>From</c>
2806   <c>http</c>
2807   <c>standard</c>
2808   <c>
2809      <xref target="header.from"/>
2810   </c>
2811   <c>Location</c>
2812   <c>http</c>
2813   <c>standard</c>
2814   <c>
2815      <xref target="header.location"/>
2816   </c>
2817   <c>Max-Forwards</c>
2818   <c>http</c>
2819   <c>standard</c>
2820   <c>
2821      <xref target="header.max-forwards"/>
2822   </c>
2823   <c>Referer</c>
2824   <c>http</c>
2825   <c>standard</c>
2826   <c>
2827      <xref target="header.referer"/>
2828   </c>
2829   <c>Retry-After</c>
2830   <c>http</c>
2831   <c>standard</c>
2832   <c>
2833      <xref target="header.retry-after"/>
2834   </c>
2835   <c>Server</c>
2836   <c>http</c>
2837   <c>standard</c>
2838   <c>
2839      <xref target="header.server"/>
2840   </c>
2841   <c>User-Agent</c>
2842   <c>http</c>
2843   <c>standard</c>
2844   <c>
2845      <xref target="header.user-agent"/>
2846   </c>
2847</texttable>
2848<!--(END)-->
2849<?ENDINC p2-semantics.iana-headers ?>
2850<t>
2851   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2852</t>
2853</section>
2854</section>
2855
2856<section title="Security Considerations" anchor="security.considerations">
2857<t>
2858   This section is meant to inform application developers, information
2859   providers, and users of the security limitations in HTTP/1.1 as
2860   described by this document. The discussion does not include
2861   definitive solutions to the problems revealed, though it does make
2862   some suggestions for reducing security risks.
2863</t>
2864
2865<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2866<t>
2867   Like any generic data transfer protocol, HTTP cannot regulate the
2868   content of the data that is transferred, nor is there any a priori
2869   method of determining the sensitivity of any particular piece of
2870   information within the context of any given request. Therefore,
2871   applications &SHOULD; supply as much control over this information as
2872   possible to the provider of that information. Four header fields are
2873   worth special mention in this context: Server, Via, Referer and From.
2874</t>
2875<t>
2876   Revealing the specific software version of the server might allow the
2877   server machine to become more vulnerable to attacks against software
2878   that is known to contain security holes. Implementors &SHOULD; make the
2879   Server header field a configurable option.
2880</t>
2881<t>
2882   Proxies which serve as a portal through a network firewall &SHOULD;
2883   take special precautions regarding the transfer of header information
2884   that identifies the hosts behind the firewall. In particular, they
2885   &SHOULD; remove, or replace with sanitized versions, any Via fields
2886   generated behind the firewall.
2887</t>
2888<t>
2889   The Referer header field allows reading patterns to be studied and reverse
2890   links drawn. Although it can be very useful, its power can be abused
2891   if user details are not separated from the information contained in
2892   the Referer. Even when the personal information has been removed, the
2893   Referer header field might indicate a private document's URI whose
2894   publication would be inappropriate.
2895</t>
2896<t>
2897   The information sent in the From field might conflict with the user's
2898   privacy interests or their site's security policy, and hence it
2899   &SHOULD-NOT;  be transmitted without the user being able to disable,
2900   enable, and modify the contents of the field. The user &MUST; be able
2901   to set the contents of this field within a user preference or
2902   application defaults configuration.
2903</t>
2904<t>
2905   We suggest, though do not require, that a convenient toggle interface
2906   be provided for the user to enable or disable the sending of From and
2907   Referer information.
2908</t>
2909<t>
2910   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2911   target="header.server"/>) header fields can sometimes be used to determine
2912   that a specific client or server have a particular security hole which might
2913   be exploited. Unfortunately, this same information is often used for other
2914   valuable purposes for which HTTP currently has no better mechanism.
2915</t>
2916<t>
2917   Furthermore, the User-Agent header field may contain enough entropy to be
2918   used, possibly in conjunction with other material, to uniquely identify the
2919   user.
2920</t>
2921<t>
2922   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2923   that was sent in request header fields within the body of their response.
2924   Clients &SHOULD; be careful with sensitive information, like Cookies,
2925   Authorization credentials, and other header fields that might be used to
2926   collect data from the client.
2927</t> 
2928</section>
2929
2930<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2931<t>
2932   Because the source of a link might be private information or might
2933   reveal an otherwise private information source, it is strongly
2934   recommended that the user be able to select whether or not the
2935   Referer field is sent. For example, a browser client could have a
2936   toggle switch for browsing openly/anonymously, which would
2937   respectively enable/disable the sending of Referer and From
2938   information.
2939</t>
2940<t>
2941   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2942   HTTP request if the referring page was transferred with a secure
2943   protocol.
2944</t>
2945<t>
2946   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2947   sensitive data because that data will be placed in the request-target. Many
2948   existing servers, proxies, and user agents log or display the request-target
2949   in places where it might be visible to third parties. Such services can
2950   use POST-based form submission instead.
2951</t>
2952</section>
2953
2954<section title="Location Headers and Spoofing" anchor="location.spoofing">
2955<t>
2956   If a single server supports multiple organizations that do not trust
2957   one another, then it &MUST; check the values of Location and Content-Location
2958   header fields in responses that are generated under control of
2959   said organizations to make sure that they do not attempt to
2960   invalidate resources over which they have no authority.
2961</t>
2962</section>
2963
2964<section title="Security Considerations for CONNECT">
2965<t>
2966   Since tunneled data is opaque to the proxy, there are additional
2967   risks to tunneling to other well-known or reserved ports.
2968   A HTTP client CONNECTing to port 25 could relay spam
2969   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2970   access to a small number of known ports.
2971</t>
2972</section>
2973
2974</section>
2975
2976<section title="Acknowledgments" anchor="ack">
2977</section>
2978</middle>
2979<back>
2980
2981<references title="Normative References">
2982
2983<reference anchor="Part1">
2984  <front>
2985    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2986    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2987      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2988      <address><email>fielding@gbiv.com</email></address>
2989    </author>
2990    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2991      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2992      <address><email>jg@freedesktop.org</email></address>
2993    </author>
2994    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2995      <organization abbrev="HP">Hewlett-Packard Company</organization>
2996      <address><email>JeffMogul@acm.org</email></address>
2997    </author>
2998    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2999      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3000      <address><email>henrikn@microsoft.com</email></address>
3001    </author>
3002    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3003      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3004      <address><email>LMM@acm.org</email></address>
3005    </author>
3006    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3007      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3008      <address><email>paulle@microsoft.com</email></address>
3009    </author>
3010    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3011      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3012      <address><email>timbl@w3.org</email></address>
3013    </author>
3014    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3015      <organization abbrev="W3C">World Wide Web Consortium</organization>
3016      <address><email>ylafon@w3.org</email></address>
3017    </author>
3018    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3019      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3020      <address><email>julian.reschke@greenbytes.de</email></address>
3021    </author>
3022    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3023  </front>
3024  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3025  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3026</reference>
3027
3028<reference anchor="Part3">
3029  <front>
3030    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3031    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3032      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3033      <address><email>fielding@gbiv.com</email></address>
3034    </author>
3035    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3036      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3037      <address><email>jg@freedesktop.org</email></address>
3038    </author>
3039    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3040      <organization abbrev="HP">Hewlett-Packard Company</organization>
3041      <address><email>JeffMogul@acm.org</email></address>
3042    </author>
3043    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3044      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3045      <address><email>henrikn@microsoft.com</email></address>
3046    </author>
3047    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3048      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3049      <address><email>LMM@acm.org</email></address>
3050    </author>
3051    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3052      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3053      <address><email>paulle@microsoft.com</email></address>
3054    </author>
3055    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3056      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3057      <address><email>timbl@w3.org</email></address>
3058    </author>
3059    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3060      <organization abbrev="W3C">World Wide Web Consortium</organization>
3061      <address><email>ylafon@w3.org</email></address>
3062    </author>
3063    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3064      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3065      <address><email>julian.reschke@greenbytes.de</email></address>
3066    </author>
3067    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3068  </front>
3069  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3070  <x:source href="p3-payload.xml" basename="p3-payload"/>
3071</reference>
3072
3073<reference anchor="Part4">
3074  <front>
3075    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3076    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3077      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3078      <address><email>fielding@gbiv.com</email></address>
3079    </author>
3080    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3081      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3082      <address><email>jg@freedesktop.org</email></address>
3083    </author>
3084    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3085      <organization abbrev="HP">Hewlett-Packard Company</organization>
3086      <address><email>JeffMogul@acm.org</email></address>
3087    </author>
3088    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3089      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3090      <address><email>henrikn@microsoft.com</email></address>
3091    </author>
3092    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3093      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3094      <address><email>LMM@acm.org</email></address>
3095    </author>
3096    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3097      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3098      <address><email>paulle@microsoft.com</email></address>
3099    </author>
3100    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3101      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3102      <address><email>timbl@w3.org</email></address>
3103    </author>
3104    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3105      <organization abbrev="W3C">World Wide Web Consortium</organization>
3106      <address><email>ylafon@w3.org</email></address>
3107    </author>
3108    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3109      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3110      <address><email>julian.reschke@greenbytes.de</email></address>
3111    </author>
3112    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3113  </front>
3114  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3115  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3116</reference>
3117
3118<reference anchor="Part5">
3119  <front>
3120    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3121    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3122      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3123      <address><email>fielding@gbiv.com</email></address>
3124    </author>
3125    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3126      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3127      <address><email>jg@freedesktop.org</email></address>
3128    </author>
3129    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3130      <organization abbrev="HP">Hewlett-Packard Company</organization>
3131      <address><email>JeffMogul@acm.org</email></address>
3132    </author>
3133    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3134      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3135      <address><email>henrikn@microsoft.com</email></address>
3136    </author>
3137    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3138      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3139      <address><email>LMM@acm.org</email></address>
3140    </author>
3141    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3142      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3143      <address><email>paulle@microsoft.com</email></address>
3144    </author>
3145    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3146      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3147      <address><email>timbl@w3.org</email></address>
3148    </author>
3149    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3150      <organization abbrev="W3C">World Wide Web Consortium</organization>
3151      <address><email>ylafon@w3.org</email></address>
3152    </author>
3153    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3154      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3155      <address><email>julian.reschke@greenbytes.de</email></address>
3156    </author>
3157    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3158  </front>
3159  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3160  <x:source href="p5-range.xml" basename="p5-range"/>
3161</reference>
3162
3163<reference anchor="Part6">
3164  <front>
3165    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3166    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3167      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3168      <address><email>fielding@gbiv.com</email></address>
3169    </author>
3170    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3171      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3172      <address><email>jg@freedesktop.org</email></address>
3173    </author>
3174    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3175      <organization abbrev="HP">Hewlett-Packard Company</organization>
3176      <address><email>JeffMogul@acm.org</email></address>
3177    </author>
3178    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3179      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3180      <address><email>henrikn@microsoft.com</email></address>
3181    </author>
3182    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3183      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3184      <address><email>LMM@acm.org</email></address>
3185    </author>
3186    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3187      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3188      <address><email>paulle@microsoft.com</email></address>
3189    </author>
3190    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3191      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3192      <address><email>timbl@w3.org</email></address>
3193    </author>
3194    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3195      <organization abbrev="W3C">World Wide Web Consortium</organization>
3196      <address><email>ylafon@w3.org</email></address>
3197    </author>
3198    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3199      <address><email>mnot@mnot.net</email></address>
3200    </author>
3201    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3202      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3203      <address><email>julian.reschke@greenbytes.de</email></address>
3204    </author>
3205    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3206  </front>
3207  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3208  <x:source href="p6-cache.xml" basename="p6-cache"/>
3209</reference>
3210
3211<reference anchor="Part7">
3212  <front>
3213    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3214    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3215      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3216      <address><email>fielding@gbiv.com</email></address>
3217    </author>
3218    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3219      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3220      <address><email>jg@freedesktop.org</email></address>
3221    </author>
3222    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3223      <organization abbrev="HP">Hewlett-Packard Company</organization>
3224      <address><email>JeffMogul@acm.org</email></address>
3225    </author>
3226    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3227      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3228      <address><email>henrikn@microsoft.com</email></address>
3229    </author>
3230    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3231      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3232      <address><email>LMM@acm.org</email></address>
3233    </author>
3234    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3235      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3236      <address><email>paulle@microsoft.com</email></address>
3237    </author>
3238    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3239      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3240      <address><email>timbl@w3.org</email></address>
3241    </author>
3242    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3243      <organization abbrev="W3C">World Wide Web Consortium</organization>
3244      <address><email>ylafon@w3.org</email></address>
3245    </author>
3246    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3247      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3248      <address><email>julian.reschke@greenbytes.de</email></address>
3249    </author>
3250    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3251  </front>
3252  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3253  <x:source href="p7-auth.xml" basename="p7-auth"/>
3254</reference>
3255
3256<reference anchor="RFC2119">
3257  <front>
3258    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3259    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3260      <organization>Harvard University</organization>
3261      <address><email>sob@harvard.edu</email></address>
3262    </author>
3263    <date month="March" year="1997"/>
3264  </front>
3265  <seriesInfo name="BCP" value="14"/>
3266  <seriesInfo name="RFC" value="2119"/>
3267</reference>
3268
3269<reference anchor="RFC3986">
3270 <front>
3271  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3272  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3273    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3274    <address>
3275       <email>timbl@w3.org</email>
3276       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3277    </address>
3278  </author>
3279  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3280    <organization abbrev="Day Software">Day Software</organization>
3281    <address>
3282      <email>fielding@gbiv.com</email>
3283      <uri>http://roy.gbiv.com/</uri>
3284    </address>
3285  </author>
3286  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3287    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3288    <address>
3289      <email>LMM@acm.org</email>
3290      <uri>http://larry.masinter.net/</uri>
3291    </address>
3292  </author>
3293  <date month='January' year='2005'></date>
3294 </front>
3295 <seriesInfo name="STD" value="66"/>
3296 <seriesInfo name="RFC" value="3986"/>
3297</reference>
3298
3299<reference anchor="RFC5234">
3300  <front>
3301    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3302    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3303      <organization>Brandenburg InternetWorking</organization>
3304      <address>
3305        <email>dcrocker@bbiw.net</email>
3306      </address> 
3307    </author>
3308    <author initials="P." surname="Overell" fullname="Paul Overell">
3309      <organization>THUS plc.</organization>
3310      <address>
3311        <email>paul.overell@thus.net</email>
3312      </address>
3313    </author>
3314    <date month="January" year="2008"/>
3315  </front>
3316  <seriesInfo name="STD" value="68"/>
3317  <seriesInfo name="RFC" value="5234"/>
3318</reference>
3319
3320</references>
3321
3322<references title="Informative References">
3323
3324<reference anchor="RFC1945">
3325  <front>
3326    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3327    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3328      <organization>MIT, Laboratory for Computer Science</organization>
3329      <address><email>timbl@w3.org</email></address>
3330    </author>
3331    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3332      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3333      <address><email>fielding@ics.uci.edu</email></address>
3334    </author>
3335    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3336      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3337      <address><email>frystyk@w3.org</email></address>
3338    </author>
3339    <date month="May" year="1996"/>
3340  </front>
3341  <seriesInfo name="RFC" value="1945"/>
3342</reference>
3343
3344<reference anchor="RFC2068">
3345  <front>
3346    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3347    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3348      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3349      <address><email>fielding@ics.uci.edu</email></address>
3350    </author>
3351    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3352      <organization>MIT Laboratory for Computer Science</organization>
3353      <address><email>jg@w3.org</email></address>
3354    </author>
3355    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3356      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3357      <address><email>mogul@wrl.dec.com</email></address>
3358    </author>
3359    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3360      <organization>MIT Laboratory for Computer Science</organization>
3361      <address><email>frystyk@w3.org</email></address>
3362    </author>
3363    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3364      <organization>MIT Laboratory for Computer Science</organization>
3365      <address><email>timbl@w3.org</email></address>
3366    </author>
3367    <date month="January" year="1997"/>
3368  </front>
3369  <seriesInfo name="RFC" value="2068"/>
3370</reference>
3371
3372<reference anchor="RFC2616">
3373  <front>
3374    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3375    <author initials="R." surname="Fielding" fullname="R. Fielding">
3376      <organization>University of California, Irvine</organization>
3377      <address><email>fielding@ics.uci.edu</email></address>
3378    </author>
3379    <author initials="J." surname="Gettys" fullname="J. Gettys">
3380      <organization>W3C</organization>
3381      <address><email>jg@w3.org</email></address>
3382    </author>
3383    <author initials="J." surname="Mogul" fullname="J. Mogul">
3384      <organization>Compaq Computer Corporation</organization>
3385      <address><email>mogul@wrl.dec.com</email></address>
3386    </author>
3387    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3388      <organization>MIT Laboratory for Computer Science</organization>
3389      <address><email>frystyk@w3.org</email></address>
3390    </author>
3391    <author initials="L." surname="Masinter" fullname="L. Masinter">
3392      <organization>Xerox Corporation</organization>
3393      <address><email>masinter@parc.xerox.com</email></address>
3394    </author>
3395    <author initials="P." surname="Leach" fullname="P. Leach">
3396      <organization>Microsoft Corporation</organization>
3397      <address><email>paulle@microsoft.com</email></address>
3398    </author>
3399    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3400      <organization>W3C</organization>
3401      <address><email>timbl@w3.org</email></address>
3402    </author>
3403    <date month="June" year="1999"/>
3404  </front>
3405  <seriesInfo name="RFC" value="2616"/>
3406</reference>
3407
3408<reference anchor='RFC2817'>
3409  <front>
3410    <title>Upgrading to TLS Within HTTP/1.1</title>
3411    <author initials='R.' surname='Khare' fullname='R. Khare'>
3412      <organization>4K Associates / UC Irvine</organization>
3413      <address><email>rohit@4K-associates.com</email></address>
3414    </author>
3415    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3416      <organization>Agranat Systems, Inc.</organization>
3417      <address><email>lawrence@agranat.com</email></address>
3418    </author>
3419    <date year='2000' month='May' />
3420  </front>
3421  <seriesInfo name='RFC' value='2817' />
3422</reference>
3423
3424<reference anchor='RFC3864'>
3425  <front>
3426    <title>Registration Procedures for Message Header Fields</title>
3427    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3428      <organization>Nine by Nine</organization>
3429      <address><email>GK-IETF@ninebynine.org</email></address>
3430    </author>
3431    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3432      <organization>BEA Systems</organization>
3433      <address><email>mnot@pobox.com</email></address>
3434    </author>
3435    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3436      <organization>HP Labs</organization>
3437      <address><email>JeffMogul@acm.org</email></address>
3438    </author>
3439    <date year='2004' month='September' />
3440  </front>
3441  <seriesInfo name='BCP' value='90' />
3442  <seriesInfo name='RFC' value='3864' />
3443</reference>
3444
3445<reference anchor='RFC5226'>
3446  <front>
3447    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3448    <author initials='T.' surname='Narten' fullname='T. Narten'>
3449      <organization>IBM</organization>
3450      <address><email>narten@us.ibm.com</email></address>
3451    </author>
3452    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3453      <organization>Google</organization>
3454      <address><email>Harald@Alvestrand.no</email></address>
3455    </author>
3456    <date year='2008' month='May' />
3457  </front>
3458  <seriesInfo name='BCP' value='26' />
3459  <seriesInfo name='RFC' value='5226' />
3460</reference>
3461
3462<reference anchor="RFC5322">
3463  <front>
3464    <title>Internet Message Format</title>
3465    <author initials="P." surname="Resnick" fullname="P. Resnick">
3466      <organization>Qualcomm Incorporated</organization>
3467    </author>
3468    <date year="2008" month="October"/>
3469  </front> 
3470  <seriesInfo name="RFC" value="5322"/>
3471</reference>
3472
3473<reference anchor='RFC5789'>
3474  <front>
3475    <title>PATCH Method for HTTP</title>
3476    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3477      <organization>Linden Lab</organization>
3478    </author>
3479    <author initials='J.' surname='Snell' fullname='J. Snell' />
3480    <date year='2010' month='March' />
3481  </front>
3482  <seriesInfo name='RFC' value='5789' />
3483</reference>
3484
3485</references>
3486
3487<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3488<t>
3489  This document takes over the Status Code Registry, previously defined
3490  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3491  (<xref target="status.code.registry"/>)
3492</t>
3493<t>
3494  Clarify definition of POST.
3495  (<xref target="POST"/>)
3496</t>
3497<t>
3498  Remove requirement to handle all Content-* header fields; ban use of
3499  Content-Range with PUT.
3500  (<xref target="PUT"/>)
3501</t>
3502<t>
3503  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3504  (<xref target="CONNECT"/>)
3505</t>
3506<t>
3507  Failed to consider that there are
3508  many other request methods that are safe to automatically redirect,
3509  and further that the user agent is able to make that determination
3510  based on the request method semantics.
3511  (Sections <xref format="counter" target="status.301"/>,
3512  <xref format="counter" target="status.302"/> and
3513  <xref format="counter" target="status.307"/>)
3514</t>
3515<t>
3516  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3517  It used to indicate that the target resource must be accessed through the
3518  proxy given by the Location field. The Location field gave the URI of the
3519  proxy. The recipient was expected to repeat this single request via the proxy.
3520  (<xref target="status.305"/>)
3521</t>
3522<t>
3523  Define status 426 (Upgrade Required) (this was incorporated from
3524  <xref target="RFC2817"/>).
3525  (<xref target="status.426"/>)
3526</t>
3527<t>
3528  Change ABNF productions for header fields to only define the field value.
3529  (<xref target="header.fields"/>)
3530</t>
3531<t>
3532  Reclassify "Allow" as response header field, removing the option to
3533  specify it in a PUT request.
3534  Relax the server requirement on the contents of the Allow header field and
3535  remove requirement on clients to always trust the header field value.
3536  (<xref target="header.allow"/>)
3537</t>
3538<t>
3539  Correct syntax of Location header field to allow URI references (including
3540  relative references and fragments), as referred symbol "absoluteURI" wasn't
3541  what was expected, and add some clarifications as to when use of fragments
3542  would not be appropriate.
3543  (<xref target="header.location"/>)
3544</t>
3545<t>
3546  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3547  extension methods could have used it as well).
3548  (<xref target="header.max-forwards"/>)
3549</t>
3550<t>
3551  Allow Referer field value of "about:blank" as alternative to not specifying it.
3552  (<xref target="header.referer"/>)
3553</t>
3554<t>
3555  In the description of the Server header field, the Via field
3556  was described as a SHOULD. The requirement was and is stated
3557  correctly in the description of the Via header field in &header-via;.
3558  (<xref target="header.server"/>)
3559</t>
3560</section>
3561
3562<?BEGININC p2-semantics.abnf-appendix ?>
3563<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3564<figure>
3565<artwork type="abnf" name="p2-semantics.parsed-abnf">
3566<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3567
3568<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3569
3570<x:ref>From</x:ref> = mailbox
3571
3572<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3573
3574<x:ref>Location</x:ref> = URI-reference
3575
3576<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3577<x:ref>Method</x:ref> = token
3578
3579<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3580
3581<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3582<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3583<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3584<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3585
3586<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3587<x:ref>Status-Code</x:ref> = 3DIGIT
3588
3589<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3590<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3591
3592<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3593
3594<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3595
3596<x:ref>delta-seconds</x:ref> = 1*DIGIT
3597
3598<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3599<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3600<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3601 *expect-params ]
3602
3603<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3604
3605<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3606
3607<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3608<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3609
3610<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3611
3612<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3613</artwork>
3614</figure>
3615<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3616; Allow defined but not used
3617; Expect defined but not used
3618; From defined but not used
3619; Location defined but not used
3620; Max-Forwards defined but not used
3621; Reason-Phrase defined but not used
3622; Referer defined but not used
3623; Retry-After defined but not used
3624; Server defined but not used
3625; Status-Code defined but not used
3626; User-Agent defined but not used
3627</artwork></figure></section>
3628<?ENDINC p2-semantics.abnf-appendix ?>
3629
3630<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3631
3632<section title="Since RFC 2616">
3633<t>
3634  Extracted relevant partitions from <xref target="RFC2616"/>.
3635</t>
3636</section>
3637
3638<section title="Since draft-ietf-httpbis-p2-semantics-00">
3639<t>
3640  Closed issues:
3641  <list style="symbols"> 
3642    <t>
3643      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3644      "Via is a MUST"
3645      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3646    </t>
3647    <t>
3648      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3649      "Fragments allowed in Location"
3650      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3651    </t>
3652    <t>
3653      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3654      "Safe Methods vs Redirection"
3655      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3656    </t>
3657    <t>
3658      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3659      "Revise description of the POST method"
3660      (<eref target="http://purl.org/NET/http-errata#post"/>)
3661    </t>
3662    <t>
3663      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3664      "Normative and Informative references"
3665    </t>
3666    <t>
3667      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3668      "RFC2606 Compliance"
3669    </t>
3670    <t>
3671      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3672      "Informative references"
3673    </t>
3674    <t>
3675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3676      "Redundant cross-references"
3677    </t>
3678  </list>
3679</t>
3680<t>
3681  Other changes:
3682  <list style="symbols"> 
3683    <t>
3684      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3685    </t>
3686  </list>
3687</t>
3688</section>
3689
3690<section title="Since draft-ietf-httpbis-p2-semantics-01">
3691<t>
3692  Closed issues:
3693  <list style="symbols"> 
3694    <t>
3695      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3696      "PUT side effects"
3697    </t>
3698    <t>
3699      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3700      "Duplicate Host header requirements"
3701    </t>
3702  </list>
3703</t>
3704<t>
3705  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3706  <list style="symbols"> 
3707    <t>
3708      Move "Product Tokens" section (back) into Part 1, as "token" is used
3709      in the definition of the Upgrade header field.
3710    </t>
3711    <t>
3712      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3713    </t>
3714    <t>
3715      Copy definition of delta-seconds from Part6 instead of referencing it.
3716    </t>
3717  </list>
3718</t>
3719</section>
3720
3721<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3722<t>
3723  Closed issues:
3724  <list style="symbols"> 
3725    <t>
3726      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3727      "Requiring Allow in 405 responses"
3728    </t>
3729    <t>
3730      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3731      "Status Code Registry"
3732    </t>
3733    <t>
3734      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3735      "Redirection vs. Location"
3736    </t>
3737    <t>
3738      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3739      "Cacheability of 303 response"
3740    </t>
3741    <t>
3742      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3743      "305 Use Proxy"
3744    </t>
3745    <t>
3746      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3747      "Classification for Allow header"
3748    </t>
3749    <t>
3750      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3751      "PUT - 'store under' vs 'store at'"
3752    </t>
3753  </list>
3754</t>
3755<t>
3756  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3757  <list style="symbols"> 
3758    <t>
3759      Reference RFC 3984, and update header field registrations for headers defined
3760      in this document.
3761    </t>
3762  </list>
3763</t>
3764<t>
3765  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3766  <list style="symbols"> 
3767    <t>
3768      Replace string literals when the string really is case-sensitive (method).
3769    </t>
3770  </list>
3771</t>
3772</section>
3773
3774<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3775<t>
3776  Closed issues:
3777  <list style="symbols"> 
3778    <t>
3779      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3780      "OPTIONS request bodies"
3781    </t>
3782    <t>
3783      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3784      "Description of CONNECT should refer to RFC2817"
3785    </t>
3786    <t>
3787      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3788      "Location Content-Location reference request/response mixup"
3789    </t>
3790  </list>
3791</t>
3792<t>
3793  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3794  <list style="symbols"> 
3795    <t>
3796      Added initial proposal for registration process, plus initial
3797      content (non-HTTP/1.1 methods to be added by a separate specification).
3798    </t>
3799  </list>
3800</t>
3801</section>
3802
3803<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3804<t>
3805  Closed issues:
3806  <list style="symbols"> 
3807    <t>
3808      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3809      "Content-*"
3810    </t>
3811    <t>
3812      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3813      "RFC 2822 is updated by RFC 5322"
3814    </t>
3815  </list>
3816</t>
3817<t>
3818  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3819  <list style="symbols"> 
3820    <t>
3821      Use "/" instead of "|" for alternatives.
3822    </t>
3823    <t>
3824      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3825      whitespace ("OWS") and required whitespace ("RWS").
3826    </t>
3827    <t>
3828      Rewrite ABNFs to spell out whitespace rules, factor out
3829      header field value format definitions.
3830    </t>
3831  </list>
3832</t>
3833</section>
3834
3835<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3836<t>
3837  Closed issues:
3838  <list style="symbols"> 
3839    <t>
3840      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3841      "Reason-Phrase BNF"
3842    </t>
3843  </list>
3844</t>
3845<t>
3846  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3847  <list style="symbols"> 
3848    <t>
3849      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3850    </t>
3851  </list>
3852</t>
3853</section>
3854
3855<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3856<t>
3857  Closed issues:
3858  <list style="symbols"> 
3859    <t>
3860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3861      "Clarify when Referer is sent"
3862    </t>
3863    <t>
3864      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3865      "status codes vs methods"
3866    </t>
3867    <t>
3868      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3869      "Do not require "updates" relation for specs that register status codes or method names"
3870    </t>
3871  </list>
3872</t>
3873</section>
3874
3875<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3876<t>
3877  Closed issues:
3878  <list style="symbols"> 
3879    <t>
3880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3881      "Idempotency"
3882    </t>
3883    <t>
3884      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3885      "TRACE security considerations"
3886    </t>
3887    <t>
3888      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3889      "Clarify rules for determining what entities a response carries"
3890    </t>
3891    <t>
3892      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3893      "update note citing RFC 1945 and 2068"
3894    </t>
3895    <t>
3896      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3897      "update note about redirect limit"
3898    </t>
3899    <t>
3900      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3901      "Location header ABNF should use 'URI'"
3902    </t>
3903    <t>
3904      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3905      "fragments in Location vs status 303"
3906    </t>
3907    <t>
3908      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3909      "move IANA registrations for optional status codes"
3910    </t>
3911  </list>
3912</t>
3913<t>
3914  Partly resolved issues:
3915  <list style="symbols"> 
3916    <t>
3917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3918      "Are OPTIONS and TRACE safe?"
3919    </t>
3920  </list>
3921</t>
3922</section>
3923
3924<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3925<t>
3926  Closed issues:
3927  <list style="symbols"> 
3928    <t>
3929      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3930      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3931      status codes when fixing this previously)
3932    </t>
3933  </list>
3934</t>
3935</section>
3936
3937<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3938<t>
3939  Closed issues:
3940  <list style="symbols"> 
3941    <t>
3942      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3943      "Fragment combination / precedence during redirects"
3944    </t>
3945  </list>
3946</t>
3947<t>
3948  Partly resolved issues:
3949  <list style="symbols"> 
3950    <t>
3951      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3952      "Location header payload handling"
3953    </t>
3954    <t>
3955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3956      "Term for the requested resource's URI"
3957    </t>
3958  </list>
3959</t>
3960</section>
3961
3962<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3963<t>
3964  Closed issues:
3965  <list style="symbols"> 
3966    <t>
3967      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3968      "Clarify 'Requested Variant'"
3969    </t>
3970    <t>
3971      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3972      "Clarify entity / representation / variant terminology"
3973    </t>
3974    <t>
3975      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3976      "Methods and Caching"
3977    </t>
3978    <t>
3979      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3980      "OPTIONS vs Max-Forwards"
3981    </t>
3982    <t>
3983      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3984      "Status codes and caching"
3985    </t>
3986    <t>
3987      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3988      "consider removing the 'changes from 2068' sections"
3989    </t>
3990  </list>
3991</t>
3992</section>
3993
3994<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3995<t>
3996  Closed issues:
3997  <list style="symbols"> 
3998    <t>
3999      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4000      "Considerations for new status codes"
4001    </t>
4002    <t>
4003      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4004      "Considerations for new methods"
4005    </t>
4006    <t>
4007      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4008      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4009    </t>
4010  </list>
4011</t>
4012</section>
4013
4014<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4015<t>
4016  Closed issues:
4017  <list style="symbols"> 
4018    <t>
4019      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4020      "Fragment combination / precedence during redirects" (added warning
4021      about having a fragid on the redirect may cause inconvenience in
4022      some cases)
4023    </t>
4024    <t>
4025      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4026      "Content-* vs. PUT"
4027    </t>
4028    <t>
4029      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4030      "205 Bodies"
4031    </t>
4032    <t>
4033      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4034      "Understanding Content-* on non-PUT requests"
4035    </t>
4036    <t>
4037      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4038      "Content-*"
4039    </t>
4040    <t>
4041      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4042      "Header type defaulting"
4043    </t>
4044    <t>
4045      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4046      "PUT - 'store under' vs 'store at'"
4047    </t>
4048    <t>
4049      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4050      "duplicate ABNF for Reason-Phrase"
4051    </t>
4052    <t>
4053      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4054      "Note special status of Content-* prefix in header registration procedures"
4055    </t>
4056    <t>
4057      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4058      "Max-Forwards vs extension methods"
4059    </t>
4060    <t>
4061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4062      "What is the value space of HTTP status codes?" (actually fixed in
4063      draft-ietf-httpbis-p2-semantics-11)
4064    </t>
4065    <t>
4066      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4067      "Header Classification"
4068    </t>
4069    <t>
4070      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4071      "PUT side effect: invalidation or just stale?"
4072    </t>
4073    <t>
4074      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4075      "proxies not supporting certain methods"
4076    </t>
4077    <t>
4078      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4079      "Migrate CONNECT from RFC2817 to p2"
4080    </t>
4081    <t>
4082      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4083      "Migrate Upgrade details from RFC2817"
4084    </t>
4085    <t>
4086      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4087      "clarify PUT semantics'"
4088    </t>
4089    <t>
4090      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4091      "duplicate ABNF for 'Method'"
4092    </t>
4093    <t>
4094      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4095      "untangle ABNFs for header fields"
4096    </t>
4097  </list>
4098</t>
4099</section>
4100
4101<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4102<t>
4103  Closed issues:
4104  <list style="symbols"> 
4105    <t>
4106      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4107      "untangle ABNFs for header fields"
4108    </t>
4109    <t>
4110      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4111      "message-body in CONNECT request"
4112    </t>
4113  </list>
4114</t>
4115</section>
4116
4117</section>
4118
4119</back>
4120</rfc>
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