source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1416

Last change on this file since 1416 was 1416, checked in by julian.reschke@…, 8 years ago

section reorg (in anticipation of #231)

  • Property svn:eol-style set to native
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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 "August">
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 acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY auth                       "<xref target='Part7' 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 field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84]>
85<?rfc toc="yes" ?>
86<?rfc symrefs="yes" ?>
87<?rfc sortrefs="yes" ?>
88<?rfc compact="yes"?>
89<?rfc subcompact="no" ?>
90<?rfc linkmailto="no" ?>
91<?rfc editing="no" ?>
92<?rfc comments="yes"?>
93<?rfc inline="yes"?>
94<?rfc rfcedstyle="yes"?>
95<?rfc-ext allow-markup-in-artwork="yes" ?>
96<?rfc-ext include-references-in-index="yes" ?>
97<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
98     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
99     xmlns:x='http://purl.org/net/xml2rfc/ext'
100     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
101<front>
102
103  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
104
105  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
106    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
107    <address>
108      <postal>
109        <street>345 Park Ave</street>
110        <city>San Jose</city>
111        <region>CA</region>
112        <code>95110</code>
113        <country>USA</country>
114      </postal>
115      <email>fielding@gbiv.com</email>
116      <uri>http://roy.gbiv.com/</uri>
117    </address>
118  </author>
119
120  <author initials="J." surname="Gettys" fullname="Jim Gettys">
121    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
122    <address>
123      <postal>
124        <street>21 Oak Knoll Road</street>
125        <city>Carlisle</city>
126        <region>MA</region>
127        <code>01741</code>
128        <country>USA</country>
129      </postal>
130      <email>jg@freedesktop.org</email>
131      <uri>http://gettys.wordpress.com/</uri>
132    </address>
133  </author>
134 
135  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
136    <organization abbrev="HP">Hewlett-Packard Company</organization>
137    <address>
138      <postal>
139        <street>HP Labs, Large Scale Systems Group</street>
140        <street>1501 Page Mill Road, MS 1177</street>
141        <city>Palo Alto</city>
142        <region>CA</region>
143        <code>94304</code>
144        <country>USA</country>
145      </postal>
146      <email>JeffMogul@acm.org</email>
147    </address>
148  </author>
149
150  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
151    <organization abbrev="Microsoft">Microsoft Corporation</organization>
152    <address>
153      <postal>
154        <street>1 Microsoft Way</street>
155        <city>Redmond</city>
156        <region>WA</region>
157        <code>98052</code>
158        <country>USA</country>
159      </postal>
160      <email>henrikn@microsoft.com</email>
161    </address>
162  </author>
163
164  <author initials="L." surname="Masinter" fullname="Larry Masinter">
165    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
166    <address>
167      <postal>
168        <street>345 Park Ave</street>
169        <city>San Jose</city>
170        <region>CA</region>
171        <code>95110</code>
172        <country>USA</country>
173      </postal>
174      <email>LMM@acm.org</email>
175      <uri>http://larry.masinter.net/</uri>
176    </address>
177  </author>
178 
179  <author initials="P." surname="Leach" fullname="Paul J. Leach">
180    <organization abbrev="Microsoft">Microsoft Corporation</organization>
181    <address>
182      <postal>
183        <street>1 Microsoft Way</street>
184        <city>Redmond</city>
185        <region>WA</region>
186        <code>98052</code>
187      </postal>
188      <email>paulle@microsoft.com</email>
189    </address>
190  </author>
191   
192  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
193    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
194    <address>
195      <postal>
196        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
197        <street>The Stata Center, Building 32</street>
198        <street>32 Vassar Street</street>
199        <city>Cambridge</city>
200        <region>MA</region>
201        <code>02139</code>
202        <country>USA</country>
203      </postal>
204      <email>timbl@w3.org</email>
205      <uri>http://www.w3.org/People/Berners-Lee/</uri>
206    </address>
207  </author>
208
209  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
210    <organization abbrev="W3C">World Wide Web Consortium</organization>
211    <address>
212      <postal>
213        <street>W3C / ERCIM</street>
214        <street>2004, rte des Lucioles</street>
215        <city>Sophia-Antipolis</city>
216        <region>AM</region>
217        <code>06902</code>
218        <country>France</country>
219      </postal>
220      <email>ylafon@w3.org</email>
221      <uri>http://www.raubacapeu.net/people/yves/</uri>
222    </address>
223  </author>
224
225  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
226    <organization abbrev="greenbytes">greenbytes GmbH</organization>
227    <address>
228      <postal>
229        <street>Hafenweg 16</street>
230        <city>Muenster</city><region>NW</region><code>48155</code>
231        <country>Germany</country>
232      </postal>
233      <phone>+49 251 2807760</phone>
234      <facsimile>+49 251 2807761</facsimile>
235      <email>julian.reschke@greenbytes.de</email>
236      <uri>http://greenbytes.de/tech/webdav/</uri>
237    </address>
238  </author>
239
240  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
241  <workgroup>HTTPbis Working Group</workgroup>
242
243<abstract>
244<t>
245   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
246   distributed, collaborative, hypertext information systems. HTTP has been in
247   use by the World Wide Web global information initiative since 1990. This
248   document is Part 2 of the seven-part specification that defines the protocol
249   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
250</t>
251<t>
252   Part 2 defines the semantics of HTTP messages as expressed by request
253   methods, request header fields, response status codes, and response header
254   fields.
255</t>
256</abstract>
257
258<note title="Editorial Note (To be removed by RFC Editor)">
259  <t>
260    Discussion of this draft should take place on the HTTPBIS working group
261    mailing list (ietf-http-wg@w3.org), which is archived at
262    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
263  </t>
264  <t>
265    The current issues list is at
266    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
267    documents (including fancy diffs) can be found at
268    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
269  </t>
270  <t>
271    The changes in this draft are summarized in <xref target="changes.since.16"/>.
272  </t>
273</note>
274</front>
275<middle>
276<section title="Introduction" anchor="introduction">
277<t>
278   This document defines HTTP/1.1 request and response semantics.  Each HTTP
279   message, as defined in &messaging;, is in the form of either a request or
280   a response.  An HTTP server listens on a connection for HTTP requests and
281   responds to each request, in the order received on that connection, with
282   one or more HTTP response messages.  This document defines the commonly
283   agreed upon semantics of the HTTP uniform interface, the intentions defined
284   by each request method, and the various response messages that might be
285   expected as a result of applying that method to the target resource.
286</t>
287<t>
288   This document is currently disorganized in order to minimize the changes
289   between drafts and enable reviewers to see the smaller errata changes.
290   A future draft will reorganize the sections to better reflect the content.
291   In particular, the sections will be ordered according to the typical
292   processing of an HTTP request message (after message parsing): resource
293   mapping, methods, request modifying header fields, response status,
294   status modifying header fields, and resource metadata.  The current mess
295   reflects how widely dispersed these topics and associated requirements
296   had become in <xref target="RFC2616"/>.
297</t>
298
299<section title="Requirements" anchor="intro.requirements">
300<t>
301   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
302   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
303   document are to be interpreted as described in <xref target="RFC2119"/>.
304</t>
305<t>
306   An implementation is not compliant if it fails to satisfy one or more
307   of the "MUST" or "REQUIRED" level requirements for the protocols it
308   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
309   level and all the "SHOULD" level requirements for its protocols is said
310   to be "unconditionally compliant"; one that satisfies all the "MUST"
311   level requirements but not all the "SHOULD" level requirements for its
312   protocols is said to be "conditionally compliant".
313</t>
314</section>
315
316<section title="Syntax Notation" anchor="notation">
317  <x:anchor-alias value="CR"/>
318  <x:anchor-alias value="DIGIT"/>
319  <x:anchor-alias value="LF"/>
320  <x:anchor-alias value="VCHAR"/>
321  <x:anchor-alias value="WSP"/>
322<t>
323  This specification uses the ABNF syntax defined in &notation; (which
324  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
325  <xref target="collected.abnf"/> shows the collected ABNF, with the list
326  rule expanded.
327</t>
328<t>
329  The following core rules are included by
330  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
331  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
332  DIGIT (decimal 0-9), DQUOTE (double quote),
333  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
334  OCTET (any 8-bit sequence of data), SP (space),
335  VCHAR (any visible USASCII character),
336  and WSP (whitespace).
337</t>
338
339<section title="Core Rules" anchor="core.rules">
340  <x:anchor-alias value="obs-text"/>
341  <x:anchor-alias value="quoted-string"/>
342  <x:anchor-alias value="token"/>
343  <x:anchor-alias value="OWS"/>
344  <x:anchor-alias value="RWS"/>
345<t>
346  The core rules below are defined in <xref target="Part1"/>:
347</t>
348<figure><artwork type="abnf2616">
349  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
350  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
351  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
352  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
353  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
354</artwork></figure>
355</section>
356
357<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
358  <x:anchor-alias value="absolute-URI"/>
359  <x:anchor-alias value="comment"/>
360  <x:anchor-alias value="HTTP-date"/>
361  <x:anchor-alias value="partial-URI"/>
362  <x:anchor-alias value="product"/>
363  <x:anchor-alias value="URI-reference"/>
364<t>
365  The ABNF rules below are defined in other parts:
366</t>
367<figure><!--Part1--><artwork type="abnf2616">
368  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
369  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
370  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
371  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
372  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
373  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
374</artwork></figure>
375</section>
376</section>
377</section>
378
379<section title="Method" anchor="method">
380  <x:anchor-alias value="Method"/>
381  <x:anchor-alias value="extension-method"/>
382<t>
383   The Method token indicates the request method to be performed on the target
384   resource (&effective-request-uri;). The method is case-sensitive.
385</t>
386<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
387  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
388</artwork></figure>
389<t>
390   The list of methods allowed by a resource can be specified in an
391   Allow header field (<xref target="header.allow"/>). The status code of the response
392   always notifies the client whether a method is currently allowed on a
393   resource, since the set of allowed methods can change dynamically. An
394   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
395   if the method is known by the origin server but not allowed for the
396   resource, and 501 (Not Implemented) if the method is
397   unrecognized or not implemented by the origin server. The methods GET
398   and HEAD &MUST; be supported by all general-purpose servers. All other
399   methods are &OPTIONAL;; however, if the above methods are implemented,
400   they &MUST; be implemented with the same semantics as those specified
401   in <xref target="method.definitions"/>.
402</t>
403
404<section title="Overview of Methods" anchor="overview.of.methods">
405<t>
406  The methods listed below are defined in <xref target="method.definitions"/>.
407</t>
408<texttable align="left">
409  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
410 
411  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
412  <c>GET</c> <c><xref target="GET"/></c>
413  <c>HEAD</c> <c><xref target="HEAD"/></c>
414  <c>POST</c> <c><xref target="POST"/></c>
415  <c>PUT</c> <c><xref target="PUT"/></c>
416  <c>DELETE</c> <c><xref target="DELETE"/></c>
417  <c>TRACE</c> <c><xref target="TRACE"/></c>
418  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
419</texttable>
420<t>
421  Note that this list is not exhaustive &mdash; it does not include request methods defined
422  in other specifications.
423</t>
424</section>
425
426<section title="Method Registry" anchor="method.registry">
427<t>
428  The HTTP Method Registry defines the name space for the Method token in the
429  Request line of an HTTP request.
430</t>
431<t>
432  Registrations &MUST; include the following fields:
433  <list style="symbols">
434    <t>Method Name (see <xref target="method"/>)</t>
435    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
436    <t>Pointer to specification text</t>
437  </list>
438</t>
439<t>
440  Values to be added to this name space are subject to IETF review
441  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
442</t>
443<t>
444  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
445</t>
446
447<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
448<t>
449   When it is necessary to express new semantics for a HTTP request that
450   aren't specific to a single application or media type, and currently defined
451   methods are inadequate, it may be appropriate to register a new method.
452</t>
453<t>
454   HTTP methods are generic; that is, they are potentially applicable to any
455   resource, not just one particular media type, "type" of resource, or
456   application. As such, it is preferred that new HTTP methods be registered
457   in a document that isn't specific to a single application, so that this is
458   clear.
459</t>
460<t>
461   Due to the parsing rules defined in &message-body;, definitions of HTTP
462   methods cannot prohibit the presence of a message-body on either the request
463   or the response message (with responses to HEAD requests being the single
464   exception). Definitions of new methods cannot change this rule, but they can
465   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
466</t>
467<t>
468   New method definitions need to indicate whether they are safe (<xref
469   target="safe.methods"/>), what semantics (if any) the request body has,
470   and whether they are idempotent (<xref target="idempotent.methods"/>).
471   They also need to state whether they can be cached (&caching;); in
472   particular what conditions a cache may store the response, and under what
473   conditions such a stored response may be used to satisfy a subsequent
474   request.
475</t>
476</section>
477
478</section>
479</section>
480
481<section title="Header Fields" anchor="header.fields">
482
483<section title="Request Header Fields" anchor="request.header.fields">
484  <x:anchor-alias value="request-header"/>
485<t>
486   The request header fields allow the client to pass additional
487   information about the request, and about the client itself, to the
488   server. These fields act as request modifiers, with semantics
489   equivalent to the parameters on a programming language method
490   invocation.
491</t>
492<texttable align="left">
493  <ttcol>Header Field Name</ttcol>
494  <ttcol>Defined in...</ttcol>
495
496  <c>Accept</c> <c>&header-accept;</c>
497  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
498  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
499  <c>Accept-Language</c> <c>&header-accept-language;</c>
500  <c>Authorization</c> <c>&header-authorization;</c>
501  <c>Expect</c> <c><xref target="header.expect"/></c>
502  <c>From</c> <c><xref target="header.from"/></c>
503  <c>Host</c> <c>&header-host;</c>
504  <c>If-Match</c> <c>&header-if-match;</c>
505  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
506  <c>If-None-Match</c> <c>&header-if-none-match;</c>
507  <c>If-Range</c> <c>&header-if-range;</c>
508  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
509  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
510  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
511  <c>Range</c> <c>&header-range;</c>
512  <c>Referer</c> <c><xref target="header.referer"/></c>
513  <c>TE</c> <c>&header-te;</c>
514  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
515</texttable>
516</section>
517
518<section title="Response Header Fields" anchor="response.header.fields">
519  <x:anchor-alias value="response-header"/>
520<t>
521   The response header fields allow the server to pass additional
522   information about the response which cannot be placed in the Status-Line.
523   These header fields give information about the server and about
524   further access to the target resource (&effective-request-uri;).
525</t>
526<texttable align="left">
527  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
528
529  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
530  <c>Age</c> <c>&header-age;</c>
531  <c>Allow</c> <c><xref target="header.allow"/></c>
532  <c>ETag</c> <c>&header-etag;</c>
533  <c>Location</c> <c><xref target="header.location"/></c>
534  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
535  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
536  <c>Server</c> <c><xref target="header.server"/></c>
537  <c>Vary</c> <c>&header-vary;</c>
538  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
539</texttable>
540</section>
541
542</section>
543
544<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
545  <x:anchor-alias value="Reason-Phrase"/>
546  <x:anchor-alias value="Status-Code"/>
547  <x:anchor-alias value="extension-code"/>
548<t>
549   The Status-Code element is a 3-digit integer result code of the attempt to
550   understand and satisfy the request.
551</t>
552<t>
553   The Reason-Phrase is intended to give a short textual description of the
554   Status-Code and is intended for a human user. The client does not need
555   to examine or display the Reason-Phrase.
556</t>
557<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"/>
558  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
559  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
560</artwork></figure>
561<t>
562   HTTP status codes are extensible. HTTP applications are not required
563   to understand the meaning of all registered status codes, though such
564   understanding is obviously desirable. However, applications &MUST;
565   understand the class of any status code, as indicated by the first
566   digit, and treat any unrecognized response as being equivalent to the
567   x00 status code of that class, with the exception that an
568   unrecognized response &MUST-NOT; be cached. For example, if an
569   unrecognized status code of 431 is received by the client, it can
570   safely assume that there was something wrong with its request and
571   treat the response as if it had received a 400 status code. In such
572   cases, user agents &SHOULD; present to the user the representation enclosed
573   with the response, since that representation is likely to include human-readable
574   information which will explain the unusual status.
575</t>
576
577<section title="Overview of Status Codes" anchor="overview.of.status.codes">
578<t> 
579   The status codes listed below are defined in <xref target="status.codes"/>
580   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
581   The reason phrases listed here are only recommendations &mdash; they can be
582   replaced by local equivalents without affecting the protocol.
583</t>
584<texttable align="left">
585  <ttcol>Status-Code</ttcol>
586  <ttcol>Reason-Phrase</ttcol>
587  <ttcol>Defined in...</ttcol>
588 
589  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
590  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
591
592  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
593  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
594  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
595  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
596  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
597  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
598  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
599
600  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
601  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
602  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
603  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
604  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
605  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
606  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
607
608  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
609  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
610  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
611  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
612  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
613  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
614  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
615  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
616  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
617  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
618  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
619  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
620  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
621  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
622  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
623  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
624  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
625  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
626  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
627
628  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
629  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
630  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
631  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
632  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
633  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
634</texttable>
635<t>
636   Note that this list is not exhaustive &mdash; it does not include
637   extension status codes defined in other specifications.
638</t>
639</section>
640
641<section title="Status Code Registry" anchor="status.code.registry">
642<t>
643  The HTTP Status Code Registry defines the name space for the Status-Code
644  token in the Status-Line of an HTTP response.
645</t>
646<t>
647  Values to be added to this name space are subject to IETF review
648  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
649</t>
650<t>
651  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
652</t>
653
654<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
655<t>
656   When it is necessary to express new semantics for a HTTP response that
657   aren't specific to a single application or media type, and currently defined
658   status codes are inadequate, a new status code can be registered.
659</t>
660<t>
661   HTTP status codes are generic; that is, they are potentially applicable to
662   any resource, not just one particular media type, "type" of resource, or
663   application. As such, it is preferred that new HTTP status codes be
664   registered in a document that isn't specific to a single application, so
665   that this is clear.
666</t>
667<t>
668   Definitions of new HTTP status codes typically explain the request
669   conditions that produce a response containing the status code (e.g.,
670   combinations of request headers and/or method(s)), along with any
671   interactions with response headers (e.g., those that are required, those
672   that modify the semantics of the response).
673</t>
674<t>
675   New HTTP status codes are required to fall under one of the categories
676   defined in <xref target="status.codes"/>. To allow existing parsers to
677   properly handle them, new status codes cannot disallow a response body,
678   although they can mandate a zero-length response body. They can require the
679   presence of one or more particular HTTP response header(s).
680</t>
681<t>
682   Likewise, their definitions can specify that caches are allowed to use
683   heuristics to determine their freshness (see &caching;; by default, it is
684   not allowed), and can define how to determine the resource which they
685   carry a representation for (see <xref
686   target="identifying.response.associated.with.representation"/>; by default,
687   it is anonymous).
688</t>
689</section>
690
691</section>
692
693</section>
694
695<section title="Representation" anchor="representation">
696<t>
697   Request and Response messages &MAY; transfer a representation if not otherwise
698   restricted by the request method or response status code. A representation
699   consists of metadata (representation header fields) and data (representation
700   body).  When a complete or partial representation is enclosed in an HTTP message,
701   it is referred to as the payload of the message. HTTP representations
702   are defined in &payload;.
703</t>
704<t>
705   A representation body is only present in a message when a message-body is
706   present, as described in &message-body;. The representation body is obtained
707   from the message-body by decoding any Transfer-Encoding that might
708   have been applied to ensure safe and proper transfer of the message.
709</t>
710
711<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
712<t>
713   It is sometimes necessary to determine an identifier for the resource
714   associated with a representation.
715</t>
716<t>
717   An HTTP request representation, when present, is always associated with an
718   anonymous (i.e., unidentified) resource.
719</t>
720<t>
721   In the common case, an HTTP response is a representation of the target
722   resource (see &effective-request-uri;). However, this is not always the
723   case. To determine the URI of the resource a response is associated with,
724   the following rules are used (with the first applicable one being selected):
725</t>
726<t><list style="numbers">
727   <t>If the response status code is 200 or 203 and the request method was GET,
728   the response payload is a representation of the target resource.</t>
729   <t>If the response status code is 204, 206, or 304 and the request method was GET
730   or HEAD, the response payload is a partial representation of the target
731   resource.</t>
732   <t>If the response has a Content-Location header field, and that URI is the same
733   as the effective request URI, the response payload is a representation of the
734   target resource.</t>
735   <t>If the response has a Content-Location header field, and that URI is not the
736   same as the effective request URI, then the response asserts that its
737   payload is a representation of the resource identified by the
738   Content-Location URI. However, such an assertion cannot be trusted unless
739   it can be verified by other means (not defined by HTTP).</t>
740   <t>Otherwise, the response is a representation of an anonymous (i.e.,
741   unidentified) resource.</t>
742</list></t>
743<t>
744  <cref anchor="TODO-req-uri">
745   The comparison function is going to have to be defined somewhere,
746   because we already need to compare URIs for things like cache invalidation.</cref>
747</t>
748</section>
749
750</section>
751
752
753<section title="Method Definitions" anchor="method.definitions">
754<t>
755   The set of common request methods for HTTP/1.1 is defined below. Although
756   this set can be expanded, additional methods cannot be assumed to
757   share the same semantics for separately extended clients and servers.
758</t>
759
760<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
761
762<section title="Safe Methods" anchor="safe.methods">
763<iref item="Safe Methods" primary="true"/>
764<t>
765   Implementors need to be aware that the software represents the user in
766   their interactions over the Internet, and need to allow
767   the user to be aware of any actions they take which might have an
768   unexpected significance to themselves or others.
769</t>
770<t>
771   In particular, the convention has been established that the GET, HEAD,
772   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
773   of taking an action other than retrieval. These request methods ought
774   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
775   This allows user agents to represent other methods, such as POST, PUT
776   and DELETE, in a special way, so that the user is made aware of the
777   fact that a possibly unsafe action is being requested.
778</t>
779<t>
780   Naturally, it is not possible to ensure that the server does not
781   generate side-effects as a result of performing a GET request; in
782   fact, some dynamic resources consider that a feature. The important
783   distinction here is that the user did not request the side-effects,
784   so therefore cannot be held accountable for them.
785</t>
786</section>
787
788<section title="Idempotent Methods" anchor="idempotent.methods">
789<iref item="Idempotent Methods" primary="true"/>
790<t>
791   Request methods can also have the property of "idempotence" in that,
792   aside from error or expiration issues, the intended effect of multiple
793   identical requests is the same as for a single request.
794   PUT, DELETE, and all safe request methods are idempotent.
795   It is important to note that idempotence refers only to changes
796   requested by the client: a server is free to change its state due
797   to multiple requests for the purpose of tracking those requests,
798   versioning of results, etc.
799</t>
800</section>
801</section>
802
803<section title="OPTIONS" anchor="OPTIONS">
804  <rdf:Description>
805    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
806  </rdf:Description>
807  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
808  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
809<t>
810   The OPTIONS method requests information about the
811   communication options available on the request/response chain
812   identified by the effective request URI. This method allows a client to
813   determine the options and/or requirements associated with a resource,
814   or the capabilities of a server, without implying a resource action
815   or initiating a resource retrieval.
816</t>
817<t>
818   Responses to the OPTIONS method are not cacheable.
819</t>
820<t>
821   If the OPTIONS request includes a message-body (as indicated by the
822   presence of Content-Length or Transfer-Encoding), then the media type
823   &MUST; be indicated by a Content-Type field. Although this
824   specification does not define any use for such a body, future
825   extensions to HTTP might use the OPTIONS body to make more detailed
826   queries on the server.
827</t>
828<t>
829   If the request-target is an asterisk ("*"), the OPTIONS request is
830   intended to apply to the server in general rather than to a specific
831   resource. Since a server's communication options typically depend on
832   the resource, the "*" request is only useful as a "ping" or "no-op"
833   type of method; it does nothing beyond allowing the client to test
834   the capabilities of the server. For example, this can be used to test
835   a proxy for HTTP/1.1 compliance (or lack thereof).
836</t>
837<t>
838   If the request-target is not an asterisk, the OPTIONS request applies
839   only to the options that are available when communicating with that
840   resource.
841</t>
842<t>
843   A 200 response &SHOULD; include any header fields that indicate
844   optional features implemented by the server and applicable to that
845   resource (e.g., Allow), possibly including extensions not defined by
846   this specification. The response body, if any, &SHOULD; also include
847   information about the communication options. The format for such a
848   body is not defined by this specification, but might be defined by
849   future extensions to HTTP. Content negotiation &MAY; be used to select
850   the appropriate response format. If no response body is included, the
851   response &MUST; include a Content-Length field with a field-value of
852   "0".
853</t>
854<t>
855   The Max-Forwards header field &MAY; be used to target a
856   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
857   If no Max-Forwards field is present in the request, then the forwarded
858   request &MUST-NOT; include a Max-Forwards field.
859</t>
860</section>
861
862<section title="GET" anchor="GET">
863  <rdf:Description>
864    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
865  </rdf:Description>
866  <iref primary="true" item="GET method" x:for-anchor=""/>
867  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
868<t>
869   The GET method requests transfer of a current representation of
870   the target resource.
871</t>
872<t>   
873   If the target resource is a data-producing process, it is the
874   produced data which shall be returned as the representation in the response and not
875   the source text of the process, unless that text happens to be the output of
876   the process.
877</t>
878<t>
879   The semantics of the GET method change to a "conditional GET" if the
880   request message includes an If-Modified-Since, If-Unmodified-Since,
881   If-Match, If-None-Match, or If-Range header field. A conditional GET
882   requests that the representation be transferred only under the
883   circumstances described by the conditional header field(s). The
884   conditional GET request is intended to reduce unnecessary network
885   usage by allowing cached representations to be refreshed without requiring
886   multiple requests or transferring data already held by the client.
887</t>
888<t>
889   The semantics of the GET method change to a "partial GET" if the
890   request message includes a Range header field. A partial GET requests
891   that only part of the representation be transferred, as described in &header-range;.
892   The partial GET request is intended to reduce unnecessary
893   network usage by allowing partially-retrieved representations to be
894   completed without transferring data already held by the client.
895</t>
896<t>
897   Bodies on GET requests have no defined semantics. Note that sending a body
898   on a GET request might cause some existing implementations to reject the
899   request.
900</t>
901<t>
902   The response to a GET request is cacheable and &MAY; be used to satisfy
903   subsequent GET and HEAD requests (see &caching;).
904</t>
905<t>
906   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
907</t>
908</section>
909
910<section title="HEAD" anchor="HEAD">
911  <rdf:Description>
912    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
913  </rdf:Description>
914  <iref primary="true" item="HEAD method" x:for-anchor=""/>
915  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
916<t>
917   The HEAD method is identical to GET except that the server &MUST-NOT;
918   return a message-body in the response. The metadata contained
919   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
920   to the information sent in response to a GET request. This method can
921   be used for obtaining metadata about the representation implied by the
922   request without transferring the representation body. This method is
923   often used for testing hypertext links for validity, accessibility,
924   and recent modification.
925</t>
926<t>
927   The response to a HEAD request is cacheable and &MAY; be used to satisfy
928   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
929   representation from that resource; if the new field values
930   indicate that the cached representation differs from the current representation (as
931   would be indicated by a change in Content-Length, ETag
932   or Last-Modified), then the cache &MUST; treat the cache entry as
933   stale.
934</t>
935<t>
936   Bodies on HEAD requests have no defined semantics. Note that sending a body
937   on a HEAD request might cause some existing implementations to reject the
938   request.
939</t>
940</section>
941
942<section title="POST" anchor="POST">
943  <iref primary="true" item="POST method" x:for-anchor=""/>
944  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
945<t>
946   The POST method requests that the origin server accept the
947   representation enclosed in the request as data to be processed by the
948   target resource. POST is designed to allow a uniform method to cover the
949   following functions:
950  <list style="symbols">
951    <t>
952      Annotation of existing resources;
953    </t>
954    <t>
955        Posting a message to a bulletin board, newsgroup, mailing list,
956        or similar group of articles;
957    </t>
958    <t>
959        Providing a block of data, such as the result of submitting a
960        form, to a data-handling process;
961    </t>
962    <t>
963        Extending a database through an append operation.
964    </t>
965  </list>
966</t>
967<t>
968   The actual function performed by the POST method is determined by the
969   server and is usually dependent on the effective request URI.
970</t>
971<t>
972   The action performed by the POST method might not result in a
973   resource that can be identified by a URI. In this case, either 200
974   (OK) or 204 (No Content) is the appropriate response status code,
975   depending on whether or not the response includes a representation that
976   describes the result.
977</t>
978<t>
979   If a resource has been created on the origin server, the response
980   &SHOULD; be 201 (Created) and contain a representation which describes the
981   status of the request and refers to the new resource, and a Location
982   header field (see <xref target="header.location"/>).
983</t>
984<t>
985   Responses to POST requests are only cacheable when they
986   include explicit freshness information (see &p6-explicit;). A
987   cached POST response with a Content-Location header field
988   (see &header-content-location;) whose value is the effective
989   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
990</t>
991<t>
992   Note that POST caching is not widely implemented.
993   However, the 303 (See Other) response can be used to direct the
994   user agent to retrieve a cacheable resource.
995</t>
996</section>
997
998<section title="PUT" anchor="PUT">
999  <iref primary="true" item="PUT method" x:for-anchor=""/>
1000  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1001<t>
1002   The PUT method requests that the state of the target resource
1003   be created or replaced with the state defined by the representation
1004   enclosed in the request message payload.  A successful PUT of a given
1005   representation would suggest that a subsequent GET on that same target
1006   resource will result in an equivalent representation being returned in
1007   a 200 (OK) response.  However, there is no guarantee that such a state
1008   change will be observable, since the target resource might be acted
1009   upon by other user agents in parallel, or might be subject to dynamic
1010   processing by the origin server, before any subsequent GET is received.
1011   A successful response only implies that the user agent's intent was
1012   achieved at the time of its processing by the origin server.
1013</t>
1014<t>   
1015   If the target resource does not have a current representation and
1016   the PUT successfully creates one, then the origin server &MUST; inform
1017   the user agent by sending a 201 (Created) response.  If the target
1018   resource does have a current representation and that representation is
1019   successfully modified in accordance with the state of the enclosed
1020   representation, then either a 200 (OK) or 204 (No Content) response
1021   &SHOULD; be sent to indicate successful completion of the request.
1022</t>
1023<t>
1024   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1025   as part of the resource state).
1026</t>
1027<t>
1028   An origin server &SHOULD; verify that the PUT representation is
1029   consistent with any constraints which the server has for the target
1030   resource that cannot or will not be changed by the PUT.  This is
1031   particularly important when the origin server uses internal
1032   configuration information related to the URI in order to set the
1033   values for representation metadata on GET responses.  When a PUT
1034   representation is inconsistent with the target resource, the origin
1035   server &SHOULD; either make them consistent, by transforming the
1036   representation or changing the resource configuration, or respond
1037   with an appropriate error message containing sufficient information
1038   to explain why the representation is unsuitable.  The 409 (Conflict)
1039   or 415 (Unsupported Media Type) status codes are suggested, with the
1040   latter being specific to constraints on Content-Type values.
1041</t>
1042<t>
1043   For example, if the target resource is configured to always have a
1044   Content-Type of "text/html" and the representation being PUT has a
1045   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1046   (a) reconfigure the target resource to reflect the new media type;
1047   (b) transform the PUT representation to a format consistent with that
1048   of the resource before saving it as the new resource state; or,
1049   (c) reject the request with a 415 response indicating that the target
1050   resource is limited to "text/html", perhaps including a link to a
1051   different resource that would be a suitable target for the new
1052   representation.
1053</t>
1054<t>
1055   HTTP does not define exactly how a PUT method affects the state
1056   of an origin server beyond what can be expressed by the intent of
1057   the user agent request and the semantics of the origin server response.
1058   It does not define what a resource might be, in any sense of that
1059   word, beyond the interface provided via HTTP.  It does not define
1060   how resource state is "stored", nor how such storage might change
1061   as a result of a change in resource state, nor how the origin server
1062   translates resource state into representations.  Generally speaking,
1063   all implementation details behind the resource interface are
1064   intentionally hidden by the server.
1065</t>
1066<t>
1067   The fundamental difference between the POST and PUT methods is
1068   highlighted by the different intent for the target resource.
1069   The target resource in a POST request is intended to handle the
1070   enclosed representation as a data-accepting process, such as for
1071   a gateway to some other protocol or a document that accepts annotations.
1072   In contrast, the target resource in a PUT request is intended to
1073   take the enclosed representation as a new or replacement value.
1074   Hence, the intent of PUT is idempotent and visible to intermediaries,
1075   even though the exact effect is only known by the origin server.
1076</t>
1077<t>
1078   Proper interpretation of a PUT request presumes that the user agent
1079   knows what target resource is desired.  A service that is intended
1080   to select a proper URI on behalf of the client, after receiving
1081   a state-changing request, &SHOULD; be implemented using the POST
1082   method rather than PUT.  If the origin server will not make the
1083   requested PUT state change to the target resource and instead
1084   wishes to have it applied to a different resource, such as when the
1085   resource has been moved to a different URI, then the origin server
1086   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1087   then make its own decision regarding whether or not to redirect the
1088   request.
1089</t>
1090<t>
1091   A PUT request applied to the target resource &MAY; have side-effects
1092   on other resources.  For example, an article might have a URI for
1093   identifying "the current version" (a resource) which is separate
1094   from the URIs identifying each particular version (different
1095   resources that at one point shared the same state as the current version
1096   resource).  A successful PUT request on "the current version" URI might
1097   therefore create a new version resource in addition to changing the
1098   state of the target resource, and might also cause links to be added
1099   between the related resources.
1100</t>
1101<t>
1102   An origin server &SHOULD; reject any PUT request that contains a
1103   Content-Range header field, since it might be misinterpreted as
1104   partial content (or might be partial content that is being mistakenly
1105   PUT as a full representation).  Partial content updates are
1106   possible by targeting a separately identified resource with state
1107   that overlaps a portion of the larger resource, or by using a
1108   different method that has been specifically defined for partial
1109   updates (for example, the PATCH method defined in
1110   <xref target="RFC5789"/>).
1111</t>
1112<t>
1113   Responses to the PUT method are not cacheable. If a PUT request passes
1114   through a cache that has one or more stored responses for the effective
1115   request URI, those stored responses will be invalidated (see
1116   &p6-invalid;).
1117</t>
1118</section>
1119
1120<section title="DELETE" anchor="DELETE">
1121  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1122  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1123<t>
1124   The DELETE method requests that the origin server delete the target
1125   resource. This method &MAY; be overridden by
1126   human intervention (or other means) on the origin server. The client cannot
1127   be guaranteed that the operation has been carried out, even if the
1128   status code returned from the origin server indicates that the action
1129   has been completed successfully. However, the server &SHOULD-NOT; 
1130   indicate success unless, at the time the response is given, it
1131   intends to delete the resource or move it to an inaccessible
1132   location.
1133</t>
1134<t>
1135   A successful response &SHOULD; be 200 (OK) if the response includes an
1136   representation describing the status, 202 (Accepted) if the action has not
1137   yet been enacted, or 204 (No Content) if the action has been enacted
1138   but the response does not include a representation.
1139</t>
1140<t>
1141   Bodies on DELETE requests have no defined semantics. Note that sending a body
1142   on a DELETE request might cause some existing implementations to reject the
1143   request.
1144</t>
1145<t>
1146   Responses to the DELETE method are not cacheable. If a DELETE request
1147   passes through a cache that has one or more stored responses for the
1148   effective request URI, those stored responses will be invalidated (see
1149   &p6-invalid;).
1150</t>
1151</section>
1152
1153<section title="TRACE" anchor="TRACE">
1154  <rdf:Description>
1155    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1156  </rdf:Description>
1157  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1158  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1159<t>
1160   The TRACE method requests a remote, application-layer loop-back
1161   of the request message. The final recipient of the request
1162   &SHOULD; reflect the message received back to the client as the
1163   message-body of a 200 (OK) response. The final recipient is either the
1164   origin server or the first proxy to receive a Max-Forwards
1165   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1166   A TRACE request &MUST-NOT; include a message-body.
1167</t>
1168<t>
1169   TRACE allows the client to see what is being received at the other
1170   end of the request chain and use that data for testing or diagnostic
1171   information. The value of the Via header field (&header-via;) is of
1172   particular interest, since it acts as a trace of the request chain.
1173   Use of the Max-Forwards header field allows the client to limit the
1174   length of the request chain, which is useful for testing a chain of
1175   proxies forwarding messages in an infinite loop.
1176</t>
1177<t>
1178   If the request is valid, the response &SHOULD; have a Content-Type of
1179   "message/http" (see &media-type-message-http;) and contain a message-body
1180   that encloses a copy of the entire request message.
1181   Responses to the TRACE method are not cacheable.
1182</t>
1183</section>
1184
1185<section title="CONNECT" anchor="CONNECT">
1186  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1187  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1188<t>
1189   The CONNECT method requests that the proxy establish a tunnel
1190   to the request-target and then restrict its behavior to blind
1191   forwarding of packets until the connection is closed.
1192</t>
1193<t>
1194   When using CONNECT, the request-target &MUST; use the authority form
1195   (&request-target;); i.e., the request-target consists of only the
1196   host name and port number of the tunnel destination, separated by a colon.
1197   For example,
1198</t>
1199<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1200CONNECT server.example.com:80 HTTP/1.1
1201Host: server.example.com:80
1202
1203</artwork></figure>
1204<t>
1205   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1206   except end-to-end protocol Upgrade requests, since the
1207   tunnel must be established first.
1208</t>
1209<t>
1210   For example, proxy authentication might be used to establish the
1211   authority to create a tunnel:
1212</t>
1213<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1214CONNECT server.example.com:80 HTTP/1.1
1215Host: server.example.com:80
1216Proxy-Authorization: basic aGVsbG86d29ybGQ=
1217
1218</artwork></figure>
1219<t>
1220   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1221   on a CONNECT request might cause some existing implementations to reject the
1222   request.
1223</t>
1224<t>
1225   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1226   sent immediately after the blank line. The usual caveats also apply:
1227   data may be discarded if the eventual response is negative, and the
1228   connection may be reset with no response if more than one TCP segment
1229   is outstanding.
1230</t>
1231
1232<section title="Establishing a Tunnel with CONNECT">
1233<t>
1234   Any successful (2xx) response to a CONNECT request indicates that the
1235   proxy has established a connection to the requested host and port,
1236   and has switched to tunneling the current connection to that server
1237   connection.
1238</t>
1239<t>
1240   It may be the case that the proxy itself can only reach the requested
1241   origin server through another proxy.  In this case, the first proxy
1242   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1243   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1244   unless it has either a direct or tunnel connection established to the
1245   authority.
1246</t>
1247<t>
1248   An origin server which receives a CONNECT request for itself &MAY;
1249   respond with a 2xx status code to indicate that a connection is
1250   established.
1251</t>
1252<t>
1253   If at any point either one of the peers gets disconnected, any
1254   outstanding data that came from that peer will be passed to the other
1255   one, and after that also the other connection will be terminated by
1256   the proxy. If there is outstanding data to that peer undelivered,
1257   that data will be discarded.
1258</t>
1259
1260</section>
1261</section>
1262</section>
1263
1264
1265<section title="Status Code Definitions" anchor="status.codes">
1266<t>
1267   Each Status-Code is described below, including any metadata required
1268   in the response.
1269</t>
1270
1271<section title="Informational 1xx" anchor="status.1xx">
1272<t>
1273   This class of status code indicates a provisional response,
1274   consisting only of the Status-Line and optional header fields, and is
1275   terminated by an empty line. There are no required header fields for this
1276   class of status code. Since HTTP/1.0 did not define any 1xx status
1277   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1278   except under experimental conditions.
1279</t>
1280<t>
1281   A client &MUST; be prepared to accept one or more 1xx status responses
1282   prior to a regular response, even if the client does not expect a 100
1283   (Continue) status message. Unexpected 1xx status responses &MAY; be
1284   ignored by a user agent.
1285</t>
1286<t>
1287   Proxies &MUST; forward 1xx responses, unless the connection between the
1288   proxy and its client has been closed, or unless the proxy itself
1289   requested the generation of the 1xx response. (For example, if a
1290   proxy adds a "Expect: 100-continue" field when it forwards a request,
1291   then it need not forward the corresponding 100 (Continue)
1292   response(s).)
1293</t>
1294
1295<section title="100 Continue" anchor="status.100">
1296  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1297  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1298<t>
1299   The client &SHOULD; continue with its request. This interim response is
1300   used to inform the client that the initial part of the request has
1301   been received and has not yet been rejected by the server. The client
1302   &SHOULD; continue by sending the remainder of the request or, if the
1303   request has already been completed, ignore this response. The server
1304   &MUST; send a final response after the request has been completed. See
1305   &use100; for detailed discussion of the use and handling of this
1306   status code.
1307</t>
1308</section>
1309
1310<section title="101 Switching Protocols" anchor="status.101">
1311  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1312  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1313<t>
1314   The server understands and is willing to comply with the client's
1315   request, via the Upgrade message header field (&header-upgrade;), for a
1316   change in the application protocol being used on this connection. The
1317   server will switch protocols to those defined by the response's
1318   Upgrade header field immediately after the empty line which
1319   terminates the 101 response.
1320</t>
1321<t>
1322   The protocol &SHOULD; be switched only when it is advantageous to do
1323   so. For example, switching to a newer version of HTTP is advantageous
1324   over older versions, and switching to a real-time, synchronous
1325   protocol might be advantageous when delivering resources that use
1326   such features.
1327</t>
1328</section>
1329</section>
1330
1331<section title="Successful 2xx" anchor="status.2xx">
1332<t>
1333   This class of status code indicates that the client's request was
1334   successfully received, understood, and accepted.
1335</t>
1336
1337<section title="200 OK" anchor="status.200">
1338  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1339  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1340<t>
1341   The request has succeeded. The payload returned with the response
1342   is dependent on the method used in the request, for example:
1343  <list style="hanging">
1344    <t hangText="GET">
1345      a representation of the target resource is sent in the response;
1346    </t>
1347    <t hangText="HEAD">
1348      the same representation as GET, except without the message-body;
1349    </t>
1350    <t hangText="POST">
1351      a representation describing or containing the result of the action;
1352    </t>
1353    <t hangText="TRACE">
1354      a representation containing the request message as received by the
1355      end server.
1356    </t>
1357  </list>
1358</t>
1359<t>
1360   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1361   freshness for 200 responses.
1362</t>
1363</section>
1364
1365<section title="201 Created" anchor="status.201">
1366  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1367  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1368<t>
1369   The request has been fulfilled and has resulted in a new resource being
1370   created. The newly created resource can be referenced by the URI(s)
1371   returned in the payload of the response, with the most specific URI
1372   for the resource given by a Location header field. The response
1373   &SHOULD; include a payload containing a list of resource
1374   characteristics and location(s) from which the user or user agent can
1375   choose the one most appropriate. The payload format is specified by
1376   the media type given in the Content-Type header field. The origin
1377   server &MUST; create the resource before returning the 201 status code.
1378   If the action cannot be carried out immediately, the server &SHOULD;
1379   respond with 202 (Accepted) response instead.
1380</t>
1381<t>
1382   A 201 response &MAY; contain an ETag response header field indicating
1383   the current value of the entity-tag for the representation of the resource
1384   just created (see &header-etag;).
1385</t>
1386</section>
1387
1388<section title="202 Accepted" anchor="status.202">
1389  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1390  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1391<t>
1392   The request has been accepted for processing, but the processing has
1393   not been completed.  The request might or might not eventually be
1394   acted upon, as it might be disallowed when processing actually takes
1395   place. There is no facility for re-sending a status code from an
1396   asynchronous operation such as this.
1397</t>
1398<t>
1399   The 202 response is intentionally non-committal. Its purpose is to
1400   allow a server to accept a request for some other process (perhaps a
1401   batch-oriented process that is only run once per day) without
1402   requiring that the user agent's connection to the server persist
1403   until the process is completed. The representation returned with this
1404   response &SHOULD; include an indication of the request's current status
1405   and either a pointer to a status monitor or some estimate of when the
1406   user can expect the request to be fulfilled.
1407</t>
1408</section>
1409
1410<section title="203 Non-Authoritative Information" anchor="status.203">
1411  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1412  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1413<t>
1414   The representation in the response has been transformed or otherwise
1415   modified by a transforming proxy (&intermediaries;).  Note that the
1416   behaviour of transforming intermediaries is controlled by the no-transform
1417   Cache-Control directive (&header-cache-control;).
1418</t>
1419<t>
1420   This status code is only appropriate when the response status code would
1421   have been 200 (OK) otherwise. When the status code before transformation
1422   would have been different, the 214 Transformation Applied warn-code
1423   (&header-warning;) is appropriate.
1424</t>
1425<t>
1426   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1427   freshness for 203 responses.
1428</t>
1429</section>
1430
1431<section title="204 No Content" anchor="status.204">
1432  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1433  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1434<t>
1435   The 204 (No Content) status code indicates that the server has
1436   successfully fulfilled the request and that there is no additional
1437   content to return in the response payload body.  Metadata in the
1438   response header fields refer to the target resource and its current
1439   representation after the requested action.
1440</t>
1441<t>
1442   For example, if a 204 status code is received in response to a PUT
1443   request and the response contains an ETag header field, then the PUT
1444   was successful and the ETag field-value contains the entity-tag for
1445   the new representation of that target resource.
1446</t>
1447<t>
1448   The 204 response allows a server to indicate that the action has been
1449   successfully applied to the target resource while implying that the
1450   user agent &SHOULD-NOT; traverse away from its current "document view"
1451   (if any).  The server assumes that the user agent will provide some
1452   indication of the success to its user, in accord with its own interface,
1453   and apply any new or updated metadata in the response to the active
1454   representation.
1455</t>
1456<t>
1457   For example, a 204 status code is commonly used with document editing
1458   interfaces corresponding to a "save" action, such that the document
1459   being saved remains available to the user for editing. It is also
1460   frequently used with interfaces that expect automated data transfers
1461   to be prevalent, such as within distributed version control systems.
1462</t>
1463<t>
1464   The 204 response &MUST-NOT; include a message-body, and thus is always
1465   terminated by the first empty line after the header fields.
1466</t>
1467</section>
1468
1469<section title="205 Reset Content" anchor="status.205">
1470  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1471  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1472<t>
1473   The server has fulfilled the request and the user agent &SHOULD; reset
1474   the document view which caused the request to be sent. This response
1475   is primarily intended to allow input for actions to take place via
1476   user input, followed by a clearing of the form in which the input is
1477   given so that the user can easily initiate another input action.
1478</t>
1479<t>   
1480   The message-body included with the response &MUST; be empty. Note that
1481   receivers still need to parse the response according to the algorithm defined
1482   in &message-body;.
1483</t>
1484</section>
1485
1486<section title="206 Partial Content" anchor="status.206">
1487  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1488  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1489  <rdf:Description>
1490    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1491  </rdf:Description>
1492<t>
1493   The server has fulfilled the partial GET request for the resource
1494   and the enclosed payload is a partial representation as defined in &status-206;.
1495</t>
1496<t>
1497   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1498   freshness for 206 responses.
1499</t>
1500</section>
1501</section>
1502
1503<section title="Redirection 3xx" anchor="status.3xx">
1504<t>
1505   This class of status code indicates that further action needs to be
1506   taken by the user agent in order to fulfill the request.  The action
1507   required &MAY; be carried out by the user agent without interaction
1508   with the user if and only if the method used in the second request is
1509   known to be "safe", as defined in <xref target="safe.methods"/>.
1510   A client &SHOULD; detect infinite redirection loops, since such loops
1511   generate network traffic for each redirection.
1512</t>
1513<x:note>
1514  <t>
1515    <x:h>Note:</x:h> An earlier version of this specification recommended a
1516    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1517    Content developers need to be aware that some clients might
1518    implement such a fixed limitation.
1519  </t>
1520</x:note>
1521
1522<section title="300 Multiple Choices" anchor="status.300">
1523  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1524  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1525<t>
1526   The target resource has more than one
1527   representation, each with its own specific location, and agent-driven
1528   negotiation information (&content-negotiation;) is being provided so that
1529   the user (or user agent) can select a preferred representation by
1530   redirecting its request to that location.
1531</t>
1532<t>
1533   Unless it was a HEAD request, the response &SHOULD; include a representation
1534   containing a list of representation metadata and location(s) from
1535   which the user or user agent can choose the one most appropriate. The
1536   data format is specified by the media type given in the Content-Type
1537   header field. Depending upon the format and the capabilities of
1538   the user agent, selection of the most appropriate choice &MAY; be
1539   performed automatically. However, this specification does not define
1540   any standard for such automatic selection.
1541</t>
1542<t>
1543   If the server has a preferred choice of representation, it &SHOULD;
1544   include the specific URI for that representation in the Location
1545   field; user agents &MAY; use the Location field value for automatic
1546   redirection.
1547</t>
1548<t>
1549   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1550   freshness for 300 responses.
1551</t>
1552
1553</section>
1554
1555<section title="301 Moved Permanently" anchor="status.301">
1556  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1558<t>
1559   The target resource has been assigned a new permanent URI and any
1560   future references to this resource &SHOULD; use one of the returned
1561   URIs.  Clients with link editing capabilities ought to automatically
1562   re-link references to the effective request URI to one or more of the new
1563   references returned by the server, where possible.
1564</t>
1565<t>
1566   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1567   freshness for 301 responses.
1568</t>
1569<t>
1570   The new permanent URI &SHOULD; be given by the Location field in the
1571   response. Unless the request method was HEAD, the representation of the
1572   response &SHOULD; contain a short hypertext note with a hyperlink to
1573   the new URI(s).
1574</t>
1575<t>
1576   If the 301 status code is received in response to a request method
1577   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1578   then the request &MAY; be automatically redirected by the user agent without
1579   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1580   request unless it can be confirmed by the user, since this might
1581   change the conditions under which the request was issued.
1582</t>
1583<x:note>
1584  <t>
1585    <x:h>Note:</x:h> When automatically redirecting a POST request after
1586    receiving a 301 status code, some existing HTTP/1.0 user agents
1587    will erroneously change it into a GET request.
1588  </t>
1589</x:note>
1590</section>
1591
1592<section title="302 Found" anchor="status.302">
1593  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1594  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1595<t>
1596   The target resource resides temporarily under a different URI.
1597   Since the redirection might be altered on occasion, the client &SHOULD;
1598   continue to use the effective request URI for future requests.
1599</t>
1600<t>
1601   The temporary URI &SHOULD; be given by the Location field in the
1602   response. Unless the request method was HEAD, the representation of the
1603   response &SHOULD; contain a short hypertext note with a hyperlink to
1604   the new URI(s).
1605</t>
1606<t>
1607   If the 302 status code is received in response to a request method
1608   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1609   then the request &MAY; be automatically redirected by the user agent without
1610   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1611   request unless it can be confirmed by the user, since this might
1612   change the conditions under which the request was issued.
1613</t>
1614<x:note>
1615  <t>
1616    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1617    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1618    specify that the client is not allowed to change the method on the
1619    redirected request.  However, most existing user agent implementations
1620    treat 302 as if it were a 303 response, performing a GET on the Location
1621    field-value regardless of the original request method. Therefore, a
1622    previous version of this specification
1623    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1624    status codes
1625    <xref target="status.303" format="none">303</xref> and
1626    <xref target="status.307" format="none">307</xref> for servers that wish
1627    to make unambiguously clear which kind of reaction is expected of the
1628    client.
1629  </t>
1630</x:note>
1631</section>
1632
1633<section title="303 See Other" anchor="status.303">
1634  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1635  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1636<t>
1637   The server directs the user agent to a different resource, indicated
1638   by a URI in the Location header field, that provides an indirect
1639   response to the original request.  The user agent &MAY; perform a GET
1640   request on the URI in the Location field in order to obtain a
1641   representation corresponding to the response, be redirected again,
1642   or end with an error status.  The Location URI is not a substitute
1643   reference for the effective request URI.
1644</t>
1645<t>
1646   The 303 status code is generally applicable to any HTTP method.  It is
1647   primarily used to allow the output of a POST action to redirect
1648   the user agent to a selected resource, since doing so provides the
1649   information corresponding to the POST response in a form that
1650   can be separately identified, bookmarked, and cached independent
1651   of the original request.
1652</t>
1653<t>
1654   A 303 response to a GET request indicates that the requested
1655   resource does not have a representation of its own that can be
1656   transferred by the server over HTTP.  The Location URI indicates a
1657   resource that is descriptive of the target resource, such that the
1658   follow-on representation might be useful to recipients without
1659   implying that it adequately represents the target resource.
1660   Note that answers to the questions of what can be represented, what
1661   representations are adequate, and what might be a useful description
1662   are outside the scope of HTTP and thus entirely determined by the
1663   URI owner(s).
1664</t>
1665<t>
1666   Except for responses to a HEAD request, the representation of a 303
1667   response &SHOULD; contain a short hypertext note with a hyperlink
1668   to the Location URI.
1669</t>
1670</section>
1671
1672<section title="304 Not Modified" anchor="status.304">
1673  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1674  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1675  <rdf:Description>
1676    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1677  </rdf:Description>
1678<t>
1679   The response to the request has not been modified since the conditions
1680   indicated by the client's conditional GET request, as defined in &status-304;.
1681</t>
1682</section>
1683
1684<section title="305 Use Proxy" anchor="status.305">
1685  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1686  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1687<t>
1688   The 305 status code was defined in a previous version of this specification
1689   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1690</t>
1691</section>
1692
1693<section title="306 (Unused)" anchor="status.306">
1694  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1695  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1696<t>
1697   The 306 status code was used in a previous version of the
1698   specification, is no longer used, and the code is reserved.
1699</t>
1700</section>
1701
1702<section title="307 Temporary Redirect" anchor="status.307">
1703  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1704  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1705<t>
1706   The target resource resides temporarily under a different URI.
1707   Since the redirection can change over time, the client &SHOULD;
1708   continue to use the effective request URI for future requests.
1709</t>
1710<t>
1711   The temporary URI &SHOULD; be given by the Location field in the
1712   response. Unless the request method was HEAD, the representation of the
1713   response &SHOULD; contain a short hypertext note with a hyperlink to
1714   the new URI(s), since many pre-HTTP/1.1 user agents do not
1715   understand the 307 status code. Therefore, the note &SHOULD; contain the
1716   information necessary for a user to repeat the original request on
1717   the new URI.
1718</t>
1719<t>
1720   If the 307 status code is received in response to a request method
1721   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1722   then the request &MAY; be automatically redirected by the user agent without
1723   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1724   request unless it can be confirmed by the user, since this might
1725   change the conditions under which the request was issued.
1726</t>
1727</section>
1728</section>
1729
1730<section title="Client Error 4xx" anchor="status.4xx">
1731<t>
1732   The 4xx class of status code is intended for cases in which the
1733   client seems to have erred. Except when responding to a HEAD request,
1734   the server &SHOULD; include a representation containing an explanation of the
1735   error situation, and whether it is a temporary or permanent
1736   condition. These status codes are applicable to any request method.
1737   User agents &SHOULD; display any included representation to the user.
1738</t>
1739<t>
1740   If the client is sending data, a server implementation using TCP
1741   &SHOULD; be careful to ensure that the client acknowledges receipt of
1742   the packet(s) containing the response, before the server closes the
1743   input connection. If the client continues sending data to the server
1744   after the close, the server's TCP stack will send a reset packet to
1745   the client, which might erase the client's unacknowledged input buffers
1746   before they can be read and interpreted by the HTTP application.
1747</t>
1748
1749<section title="400 Bad Request" anchor="status.400">
1750  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1751  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1752<t>
1753   The server cannot or will not process the request, due to a client error (e.g.,
1754   malformed syntax).</t>
1755</section>
1756
1757<section title="401 Unauthorized" anchor="status.401">
1758  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1759  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1760  <rdf:Description>
1761    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1762  </rdf:Description>
1763<t>
1764   The request requires user authentication (see &status-401;).
1765</t>
1766</section>
1767
1768<section title="402 Payment Required" anchor="status.402">
1769  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1770  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1771<t>
1772   This code is reserved for future use.
1773</t>
1774</section>
1775
1776<section title="403 Forbidden" anchor="status.403">
1777  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1778  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1779<t>
1780   The server understood the request, but refuses to authorize it. Providing
1781   different user authentication credentials might be successful, but any
1782   credentials that were provided in the request are insufficient. The request
1783   &SHOULD-NOT; be repeated with the same credentials.
1784</t>
1785<t>
1786   If the request method was not HEAD and the server wishes to make
1787   public why the request has not been fulfilled, it &SHOULD; describe the
1788   reason for the refusal in the representation.  If the server does not wish to
1789   make this information available to the client, the status code 404
1790   (Not Found) &MAY; be used instead.
1791</t>
1792</section>
1793
1794<section title="404 Not Found" anchor="status.404">
1795  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1796  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1797<t>
1798   The server has not found anything matching the effective request URI. No
1799   indication is given of whether the condition is temporary or
1800   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1801   knows, through some internally configurable mechanism, that an old
1802   resource is permanently unavailable and has no forwarding address.
1803   This status code is commonly used when the server does not wish to
1804   reveal exactly why the request has been refused, or when no other
1805   response is applicable.
1806</t>
1807</section>
1808
1809<section title="405 Method Not Allowed" anchor="status.405">
1810  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1811  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1812<t>
1813   The method specified in the Request-Line is not allowed for the target
1814   resource. The response &MUST; include an Allow header field containing a
1815   list of valid methods for the requested resource.
1816</t>
1817</section>
1818
1819<section title="406 Not Acceptable" anchor="status.406">
1820  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1821  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1822<t>
1823   The resource identified by the request is only capable of generating
1824   response representations which have content characteristics not acceptable
1825   according to the Accept and Accept-* header fields sent in the request
1826   (see &p3-header-fields;).
1827</t>
1828<t>
1829   Unless it was a HEAD request, the response &SHOULD; include a representation
1830   containing a list of available representation characteristics and location(s)
1831   from which the user or user agent can choose the one most
1832   appropriate. The data format is specified by the media type given
1833   in the Content-Type header field. Depending upon the format and the
1834   capabilities of the user agent, selection of the most appropriate
1835   choice &MAY; be performed automatically. However, this specification
1836   does not define any standard for such automatic selection.
1837</t>
1838<x:note>
1839  <t>
1840    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1841    not acceptable according to the accept header fields sent in the
1842    request. In some cases, this might even be preferable to sending a
1843    406 response. User agents are encouraged to inspect the header fields of
1844    an incoming response to determine if it is acceptable.
1845  </t>
1846</x:note>
1847<t>
1848   If the response could be unacceptable, a user agent &SHOULD;
1849   temporarily stop receipt of more data and query the user for a
1850   decision on further actions.
1851</t>
1852</section>
1853
1854<section title="407 Proxy Authentication Required" anchor="status.407">
1855  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1856  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1857<t>
1858   This code is similar to 401 (Unauthorized), but indicates that the
1859   client must first authenticate itself with the proxy (see &status-407;).
1860</t>
1861</section>
1862
1863<section title="408 Request Timeout" anchor="status.408">
1864  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1865  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1866<t>
1867   The client did not produce a request within the time that the server
1868   was prepared to wait. The client &MAY; repeat the request without
1869   modifications at any later time.
1870</t>
1871</section>
1872
1873<section title="409 Conflict" anchor="status.409">
1874  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1875  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1876<t>
1877   The request could not be completed due to a conflict with the current
1878   state of the resource. This code is only allowed in situations where
1879   it is expected that the user might be able to resolve the conflict
1880   and resubmit the request. The response body &SHOULD; include enough
1881   information for the user to recognize the source of the conflict.
1882   Ideally, the response representation would include enough information for the
1883   user or user agent to fix the problem; however, that might not be
1884   possible and is not required.
1885</t>
1886<t>
1887   Conflicts are most likely to occur in response to a PUT request. For
1888   example, if versioning were being used and the representation being PUT
1889   included changes to a resource which conflict with those made by an
1890   earlier (third-party) request, the server might use the 409 response
1891   to indicate that it can't complete the request. In this case, the
1892   response representation would likely contain a list of the differences
1893   between the two versions in a format defined by the response
1894   Content-Type.
1895</t>
1896</section>
1897
1898<section title="410 Gone" anchor="status.410">
1899  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1900  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1901<t>
1902   The target resource is no longer available at the server and no
1903   forwarding address is known. This condition is expected to be
1904   considered permanent. Clients with link editing capabilities &SHOULD;
1905   delete references to the effective request URI after user approval. If the
1906   server does not know, or has no facility to determine, whether or not
1907   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1908   used instead.
1909</t>
1910<t>
1911   The 410 response is primarily intended to assist the task of web
1912   maintenance by notifying the recipient that the resource is
1913   intentionally unavailable and that the server owners desire that
1914   remote links to that resource be removed. Such an event is common for
1915   limited-time, promotional services and for resources belonging to
1916   individuals no longer working at the server's site. It is not
1917   necessary to mark all permanently unavailable resources as "gone" or
1918   to keep the mark for any length of time &mdash; that is left to the
1919   discretion of the server owner.
1920</t>
1921<t>
1922   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1923   for 410 responses.
1924</t>
1925
1926</section>
1927
1928<section title="411 Length Required" anchor="status.411">
1929  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1930  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1931<t>
1932   The server refuses to accept the request without a defined Content-Length.
1933   The client &MAY; repeat the request if it adds a valid
1934   Content-Length header field containing the length of the message-body
1935   in the request message.
1936</t>
1937</section>
1938
1939<section title="412 Precondition Failed" anchor="status.412">
1940  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1941  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1942  <rdf:Description>
1943    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1944  </rdf:Description>
1945<t>
1946   The precondition given in one or more of the header fields
1947   evaluated to false when it was tested on the server, as defined in
1948   &status-412;.
1949</t>
1950</section>
1951
1952<section title="413 Request Representation Too Large" anchor="status.413">
1953  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
1954  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
1955<t>
1956   The server is refusing to process a request because the request
1957   representation is larger than the server is willing or able to process. The
1958   server &MAY; close the connection to prevent the client from continuing
1959   the request.
1960</t>
1961<t>
1962   If the condition is temporary, the server &SHOULD; include a Retry-After
1963   header field to indicate that it is temporary and after what
1964   time the client &MAY; try again.
1965</t>
1966</section>
1967
1968<section title="414 URI Too Long" anchor="status.414">
1969  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1970  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1971<t>
1972   The server is refusing to service the request because the effective request URI
1973   is longer than the server is willing to interpret. This rare
1974   condition is only likely to occur when a client has improperly
1975   converted a POST request to a GET request with long query
1976   information, when the client has descended into a URI "black hole" of
1977   redirection (e.g., a redirected URI prefix that points to a suffix of
1978   itself), or when the server is under attack by a client attempting to
1979   exploit security holes present in some servers using fixed-length
1980   buffers for reading or manipulating the effective request URI.
1981</t>
1982</section>
1983
1984<section title="415 Unsupported Media Type" anchor="status.415">
1985  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1986  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1987<t>
1988   The server is refusing to service the request because the request
1989   payload is in a format not supported by this request method on the
1990   target resource.
1991</t>
1992</section>
1993
1994<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1995  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1996  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1997  <rdf:Description>
1998    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1999  </rdf:Description>
2000<t>
2001   The request included a Range header field (&header-range;) and none of
2002   the range-specifier values in this field overlap the current extent
2003   of the selected resource. See &status-416;.
2004</t>
2005</section>
2006
2007<section title="417 Expectation Failed" anchor="status.417">
2008  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2009  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2010<t>
2011   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2012   could not be met by this server, or, if the server is a proxy,
2013   the server has unambiguous evidence that the request could not be met
2014   by the next-hop server.
2015</t>
2016</section>
2017
2018<section title="426 Upgrade Required" anchor="status.426">
2019  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2020  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2021<t>
2022   The request can not be completed without a prior protocol upgrade. This
2023   response &MUST; include an Upgrade header field (&header-upgrade;)
2024   specifying the required protocols.
2025</t>
2026<figure>
2027<preamble>Example:</preamble>
2028<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2029HTTP/1.1 426 Upgrade Required
2030Upgrade: HTTP/2.0
2031Connection: Upgrade
2032
2033</artwork></figure>
2034<t>
2035   The server &SHOULD; include a message body in the 426 response which
2036   indicates in human readable form the reason for the error and describes any
2037   alternative courses which may be available to the user.
2038</t>
2039</section>
2040</section>
2041
2042<section title="Server Error 5xx" anchor="status.5xx">
2043<t>
2044   Response status codes beginning with the digit "5" indicate cases in
2045   which the server is aware that it has erred or is incapable of
2046   performing the request. Except when responding to a HEAD request, the
2047   server &SHOULD; include a representation containing an explanation of the
2048   error situation, and whether it is a temporary or permanent
2049   condition. User agents &SHOULD; display any included representation to the
2050   user. These response codes are applicable to any request method.
2051</t>
2052
2053<section title="500 Internal Server Error" anchor="status.500">
2054  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2055  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2056<t>
2057   The server encountered an unexpected condition which prevented it
2058   from fulfilling the request.
2059</t>
2060</section>
2061
2062<section title="501 Not Implemented" anchor="status.501">
2063  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2064  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2065<t>
2066   The server does not support the functionality required to fulfill the
2067   request. This is the appropriate response when the server does not
2068   recognize the request method and is not capable of supporting it for
2069   any resource.
2070</t>
2071</section>
2072
2073<section title="502 Bad Gateway" anchor="status.502">
2074  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2075  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2076<t>
2077   The server, while acting as a gateway or proxy, received an invalid
2078   response from the upstream server it accessed in attempting to
2079   fulfill the request.
2080</t>
2081</section>
2082
2083<section title="503 Service Unavailable" anchor="status.503">
2084  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2085  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2086<t>
2087   The server is currently unable or unwilling to handle the request due to
2088   reasons such as temporary overloading, maintenance of the server, or rate
2089   limiting of the client.
2090</t>
2091<t>
2092   The implication is that this is a temporary condition which will be
2093   alleviated after some delay. If known, the length of the delay &MAY; be
2094   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2095   If no Retry-After is given, the client &SHOULD; handle the response as it
2096   would for a 500 response.
2097</t>
2098<x:note>
2099  <t>
2100    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2101    server must use it when becoming overloaded. Some servers might wish
2102    to simply refuse the connection.
2103  </t>
2104</x:note>
2105</section>
2106
2107<section title="504 Gateway Timeout" anchor="status.504">
2108  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2109  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2110<t>
2111   The server, while acting as a gateway or proxy, did not receive a
2112   timely response from the upstream server specified by the URI (e.g.,
2113   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2114   to access in attempting to complete the request.
2115</t>
2116<x:note>
2117  <t>
2118    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2119    return 400 or 500 when DNS lookups time out.
2120  </t>
2121</x:note>
2122</section>
2123
2124<section title="505 HTTP Version Not Supported" anchor="status.505">
2125  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2126  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2127<t>
2128   The server does not support, or refuses to support, the protocol
2129   version that was used in the request message. The server is
2130   indicating that it is unable or unwilling to complete the request
2131   using the same major version as the client, as described in &http-version;,
2132   other than with this error message. The response &SHOULD; contain
2133   a representation describing why that version is not supported and what other
2134   protocols are supported by that server.
2135</t>
2136
2137</section>
2138</section>
2139</section>
2140
2141
2142<section title="Header Field Definitions" anchor="header.field.definitions">
2143<t>
2144   This section defines the syntax and semantics of HTTP/1.1 header fields
2145   related to request and response semantics.
2146</t>
2147
2148<section title="Allow" anchor="header.allow">
2149  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2150  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2151  <x:anchor-alias value="Allow"/>
2152<t>
2153   The "Allow" header field lists the set of methods advertised as
2154   supported by the target resource. The purpose of this field is strictly to
2155   inform the recipient of valid request methods associated with the resource.
2156</t>
2157<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2158  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2159</artwork></figure>
2160<t>
2161   Example of use:
2162</t>
2163<figure><artwork type="example">
2164  Allow: GET, HEAD, PUT
2165</artwork></figure>
2166<t>
2167   The actual set of allowed methods is defined by the origin server at the
2168   time of each request.
2169</t>
2170<t>
2171   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2172   understand all the methods specified in order to handle them according to
2173   the generic message handling rules.
2174</t>
2175</section>
2176
2177<section title="Expect" anchor="header.expect">
2178  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2179  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2180  <x:anchor-alias value="Expect"/>
2181  <x:anchor-alias value="expectation"/>
2182  <x:anchor-alias value="expectation-extension"/>
2183  <x:anchor-alias value="expect-params"/>
2184<t>
2185   The "Expect" header field is used to indicate that particular
2186   server behaviors are required by the client.
2187</t>
2188<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"/>
2189  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2190 
2191  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2192  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2193                           *<x:ref>expect-params</x:ref> ]
2194  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2195</artwork></figure>
2196<t>
2197   A server that does not understand or is unable to comply with any of
2198   the expectation values in the Expect field of a request &MUST; respond
2199   with appropriate error status code. The server &MUST; respond with a 417
2200   (Expectation Failed) status code if any of the expectations cannot be met
2201   or, if there are other problems with the request, some other 4xx
2202   status code.
2203</t>
2204<t>
2205   This header field is defined with extensible syntax to allow for
2206   future extensions. If a server receives a request containing an
2207   Expect field that includes an expectation-extension that it does not
2208   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2209</t>
2210<t>
2211   Comparison of expectation values is case-insensitive for unquoted
2212   tokens (including the 100-continue token), and is case-sensitive for
2213   quoted-string expectation-extensions.
2214</t>
2215<t>
2216   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2217   return a 417 (Expectation Failed) status code if it receives a request
2218   with an expectation that it cannot meet. However, the Expect
2219   header field itself is end-to-end; it &MUST; be forwarded if the
2220   request is forwarded.
2221</t>
2222<t>
2223   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2224   Expect header field.
2225</t>
2226<t>
2227   See &use100; for the use of the 100 (Continue) status code.
2228</t>
2229</section>
2230
2231<section title="From" anchor="header.from">
2232  <iref primary="true" item="From header field" x:for-anchor=""/>
2233  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2234  <x:anchor-alias value="From"/>
2235  <x:anchor-alias value="mailbox"/>
2236<t>
2237   The "From" header field, if given, &SHOULD; contain an Internet
2238   e-mail address for the human user who controls the requesting user
2239   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2240   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2241</t>
2242<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2243  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2244 
2245  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2246</artwork></figure>
2247<t>
2248   An example is:
2249</t>
2250<figure><artwork type="example">
2251  From: webmaster@example.org
2252</artwork></figure>
2253<t>
2254   This header field &MAY; be used for logging purposes and as a means for
2255   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2256   be used as an insecure form of access protection. The interpretation
2257   of this field is that the request is being performed on behalf of the
2258   person given, who accepts responsibility for the method performed. In
2259   particular, robot agents &SHOULD; include this header field so that the
2260   person responsible for running the robot can be contacted if problems
2261   occur on the receiving end.
2262</t>
2263<t>
2264   The Internet e-mail address in this field &MAY; be separate from the
2265   Internet host which issued the request. For example, when a request
2266   is passed through a proxy the original issuer's address &SHOULD; be
2267   used.
2268</t>
2269<t>
2270   The client &SHOULD-NOT;  send the From header field without the user's
2271   approval, as it might conflict with the user's privacy interests or
2272   their site's security policy. It is strongly recommended that the
2273   user be able to disable, enable, and modify the value of this field
2274   at any time prior to a request.
2275</t>
2276</section>
2277
2278<section title="Location" anchor="header.location">
2279  <iref primary="true" item="Location header field" x:for-anchor=""/>
2280  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2281  <x:anchor-alias value="Location"/>
2282<t>
2283   The "Location" header field is used to identify a newly created
2284   resource, or to redirect the recipient to a different location for
2285   completion of the request.
2286</t>
2287<t>
2288   For 201 (Created) responses, the Location is the URI of the new resource
2289   which was created by the request. For 3xx responses, the location &SHOULD;
2290   indicate the server's preferred URI for automatic redirection to the
2291   resource.
2292</t>
2293<t>
2294   The field value consists of a single URI-reference. When it has the form
2295   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2296   the final value is computed by resolving it against the effective request
2297   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2298</t>
2299<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2300  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2301</artwork></figure>
2302<figure>
2303<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2304<artwork type="example">
2305  Location: http://www.example.org/pub/WWW/People.html#tim
2306</artwork></figure><figure><artwork type="example">  Location: /index.html
2307</artwork></figure>
2308<t>
2309   There are circumstances in which a fragment identifier in a Location URI
2310   would not be appropriate. For instance, when it appears in a 201 Created
2311   response, where the Location header field specifies the URI for the entire
2312   created resource.
2313</t>
2314<x:note>
2315  <t>
2316    <x:h>Note:</x:h> This specification does not define precedence rules
2317    for the case where the original URI, as navigated to by the user
2318    agent, and the Location header field value both contain fragment
2319    identifiers. Thus be aware that including fragment identifiers might
2320    inconvenience anyone relying on the semantics of the original URI's
2321    fragment identifier.
2322  </t>
2323</x:note>
2324<x:note>
2325  <t>
2326    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2327    from Location in that the Content-Location identifies the most specific
2328    resource corresponding to the enclosed representation.
2329    It is therefore possible for a response to contain header fields for
2330    both Location and Content-Location.
2331  </t>
2332</x:note>
2333</section>
2334
2335<section title="Max-Forwards" anchor="header.max-forwards">
2336  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2337  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2338  <x:anchor-alias value="Max-Forwards"/>
2339<t>
2340   The "Max-Forwards" header field provides a mechanism with the
2341   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2342   methods to limit the number of times that the request is forwarded by
2343   proxies. This can be useful when the client is attempting to
2344   trace a request which appears to be failing or looping in mid-chain.
2345</t>
2346<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2347  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2348</artwork></figure>
2349<t>
2350   The Max-Forwards value is a decimal integer indicating the remaining
2351   number of times this request message can be forwarded.
2352</t>
2353<t>
2354   Each recipient of a TRACE or OPTIONS request
2355   containing a Max-Forwards header field &MUST; check and update its
2356   value prior to forwarding the request. If the received value is zero
2357   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2358   respond as the final recipient. If the received Max-Forwards value is
2359   greater than zero, then the forwarded message &MUST; contain an updated
2360   Max-Forwards field with a value decremented by one (1).
2361</t>
2362<t>
2363   The Max-Forwards header field &MAY; be ignored for all other request
2364   methods.
2365</t>
2366</section>
2367
2368<section title="Referer" anchor="header.referer">
2369  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2370  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2371  <x:anchor-alias value="Referer"/>
2372<t>
2373   The "Referer" [sic] header field allows the client to specify the
2374   URI of the resource from which the effective request URI was obtained (the
2375   "referrer", although the header field is misspelled.).
2376</t>
2377<t>
2378   The Referer header field allows servers to generate lists of back-links to
2379   resources for interest, logging, optimized caching, etc. It also allows
2380   obsolete or mistyped links to be traced for maintenance. Some servers use
2381   Referer as a means of controlling where they allow links from (so-called
2382   "deep linking"), but legitimate requests do not always
2383   contain a Referer header field.
2384</t>
2385<t>
2386   If the effective request URI was obtained from a source that does not have its own
2387   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2388   sent with the value "about:blank", or not be sent at all. Note that this
2389   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2390</t>
2391<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2392  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2393</artwork></figure>
2394<t>
2395   Example:
2396</t>
2397<figure><artwork type="example">
2398  Referer: http://www.example.org/hypertext/Overview.html
2399</artwork></figure>
2400<t>
2401   If the field value is a relative URI, it &SHOULD; be interpreted
2402   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2403   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2404</t>
2405</section>
2406
2407<section title="Retry-After" anchor="header.retry-after">
2408  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2409  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2410  <x:anchor-alias value="Retry-After"/>
2411<t>
2412   The header "Retry-After" field can be used with a 503 (Service
2413   Unavailable) response to indicate how long the service is expected to
2414   be unavailable to the requesting client. This field &MAY; also be used
2415   with any 3xx (Redirection) response to indicate the minimum time the
2416   user-agent is asked wait before issuing the redirected request.
2417</t>
2418<t>
2419   The value of this field can be either an HTTP-date or an integer number
2420   of seconds (in decimal) after the time of the response.
2421</t>
2422<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2423  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2424</artwork></figure>
2425<t anchor="rule.delta-seconds">
2426  <x:anchor-alias value="delta-seconds"/>
2427   Time spans are non-negative decimal integers, representing time in
2428   seconds.
2429</t>
2430<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2431  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2432</artwork></figure>
2433<t>
2434   Two examples of its use are
2435</t>
2436<figure><artwork type="example">
2437  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2438  Retry-After: 120
2439</artwork></figure>
2440<t>
2441   In the latter example, the delay is 2 minutes.
2442</t>
2443</section>
2444
2445<section title="Server" anchor="header.server">
2446  <iref primary="true" item="Server header field" x:for-anchor=""/>
2447  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2448  <x:anchor-alias value="Server"/>
2449<t>
2450   The "Server" header field contains information about the
2451   software used by the origin server to handle the request.
2452</t>
2453<t>
2454   The field can contain multiple product tokens (&product-tokens;) and
2455   comments (&header-fields;) identifying the server and any significant
2456   subproducts. The product tokens are listed in order of their significance
2457   for identifying the application.
2458</t>
2459<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2460  <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> ) )
2461</artwork></figure>
2462<t>
2463   Example:
2464</t>
2465<figure><artwork type="example">
2466  Server: CERN/3.0 libwww/2.17
2467</artwork></figure>
2468<t>
2469   If the response is being forwarded through a proxy, the proxy
2470   application &MUST-NOT; modify the Server header field. Instead, it
2471   &MUST; include a Via field (as described in &header-via;).
2472</t>
2473<x:note>
2474  <t>
2475    <x:h>Note:</x:h> Revealing the specific software version of the server might
2476    allow the server machine to become more vulnerable to attacks
2477    against software that is known to contain security holes. Server
2478    implementors are encouraged to make this field a configurable
2479    option.
2480  </t>
2481</x:note>
2482</section>
2483
2484<section title="User-Agent" anchor="header.user-agent">
2485  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2486  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2487  <x:anchor-alias value="User-Agent"/>
2488<t>
2489   The "User-Agent" header field contains information about the user
2490   agent originating the request. User agents &SHOULD; include this field with
2491   requests.
2492</t>
2493<t>
2494   Typically, it is used for statistical purposes, the tracing of protocol
2495   violations, and tailoring responses to avoid particular user agent
2496   limitations.
2497</t>
2498<t>
2499   The field can contain multiple product tokens (&product-tokens;)
2500   and comments (&header-fields;) identifying the agent and its
2501   significant subproducts. By convention, the product tokens are listed in
2502   order of their significance for identifying the application.
2503</t>
2504<t>
2505   Because this field is usually sent on every request a user agent makes,
2506   implementations are encouraged not to include needlessly fine-grained
2507   detail, and to limit (or even prohibit) the addition of subproducts by third
2508   parties. Overly long and detailed User-Agent field values make requests
2509   larger and can also be used to identify ("fingerprint") the user against
2510   their wishes.
2511</t>
2512<t>
2513   Likewise, implementations are encouraged not to use the product tokens of
2514   other implementations in order to declare compatibility with them, as this
2515   circumvents the purpose of the field. Finally, they are encouraged not to
2516   use comments to identify products; doing so makes the field value more
2517   difficult to parse.
2518</t>
2519<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2520  <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> ) )
2521</artwork></figure>
2522<t>
2523   Example:
2524</t>
2525<figure><artwork type="example">
2526  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2527</artwork></figure>
2528</section>
2529
2530</section>
2531
2532<section title="IANA Considerations" anchor="IANA.considerations">
2533
2534<section title="Method Registry" anchor="method.registration">
2535<t>
2536  The registration procedure for HTTP request methods is defined by
2537  <xref target="method.registry"/> of this document.
2538</t>
2539<t>
2540   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2541   and be populated with the registrations below:
2542</t>
2543<?BEGININC p2-semantics.iana-methods ?>
2544<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2545<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2546   <ttcol>Method</ttcol>
2547   <ttcol>Safe</ttcol>
2548   <ttcol>Reference</ttcol>
2549   <c>CONNECT</c>
2550   <c>no</c>
2551   <c>
2552      <xref target="CONNECT"/>
2553   </c>
2554   <c>DELETE</c>
2555   <c>no</c>
2556   <c>
2557      <xref target="DELETE"/>
2558   </c>
2559   <c>GET</c>
2560   <c>yes</c>
2561   <c>
2562      <xref target="GET"/>
2563   </c>
2564   <c>HEAD</c>
2565   <c>yes</c>
2566   <c>
2567      <xref target="HEAD"/>
2568   </c>
2569   <c>OPTIONS</c>
2570   <c>yes</c>
2571   <c>
2572      <xref target="OPTIONS"/>
2573   </c>
2574   <c>POST</c>
2575   <c>no</c>
2576   <c>
2577      <xref target="POST"/>
2578   </c>
2579   <c>PUT</c>
2580   <c>no</c>
2581   <c>
2582      <xref target="PUT"/>
2583   </c>
2584   <c>TRACE</c>
2585   <c>yes</c>
2586   <c>
2587      <xref target="TRACE"/>
2588   </c>
2589</texttable>
2590<!--(END)-->
2591<?ENDINC p2-semantics.iana-methods ?>
2592</section>
2593
2594<section title="Status Code Registry" anchor="status.code.registration">
2595<t>
2596   The registration procedure for HTTP Status Codes &mdash; previously defined
2597   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2598   by <xref target="status.code.registry"/> of this document.
2599</t>
2600<t>
2601   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2602   shall be updated with the registrations below:
2603</t>
2604<?BEGININC p2-semantics.iana-status-codes ?>
2605<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2606<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2607   <ttcol>Value</ttcol>
2608   <ttcol>Description</ttcol>
2609   <ttcol>Reference</ttcol>
2610   <c>100</c>
2611   <c>Continue</c>
2612   <c>
2613      <xref target="status.100"/>
2614   </c>
2615   <c>101</c>
2616   <c>Switching Protocols</c>
2617   <c>
2618      <xref target="status.101"/>
2619   </c>
2620   <c>200</c>
2621   <c>OK</c>
2622   <c>
2623      <xref target="status.200"/>
2624   </c>
2625   <c>201</c>
2626   <c>Created</c>
2627   <c>
2628      <xref target="status.201"/>
2629   </c>
2630   <c>202</c>
2631   <c>Accepted</c>
2632   <c>
2633      <xref target="status.202"/>
2634   </c>
2635   <c>203</c>
2636   <c>Non-Authoritative Information</c>
2637   <c>
2638      <xref target="status.203"/>
2639   </c>
2640   <c>204</c>
2641   <c>No Content</c>
2642   <c>
2643      <xref target="status.204"/>
2644   </c>
2645   <c>205</c>
2646   <c>Reset Content</c>
2647   <c>
2648      <xref target="status.205"/>
2649   </c>
2650   <c>300</c>
2651   <c>Multiple Choices</c>
2652   <c>
2653      <xref target="status.300"/>
2654   </c>
2655   <c>301</c>
2656   <c>Moved Permanently</c>
2657   <c>
2658      <xref target="status.301"/>
2659   </c>
2660   <c>302</c>
2661   <c>Found</c>
2662   <c>
2663      <xref target="status.302"/>
2664   </c>
2665   <c>303</c>
2666   <c>See Other</c>
2667   <c>
2668      <xref target="status.303"/>
2669   </c>
2670   <c>305</c>
2671   <c>Use Proxy</c>
2672   <c>
2673      <xref target="status.305"/>
2674   </c>
2675   <c>306</c>
2676   <c>(Unused)</c>
2677   <c>
2678      <xref target="status.306"/>
2679   </c>
2680   <c>307</c>
2681   <c>Temporary Redirect</c>
2682   <c>
2683      <xref target="status.307"/>
2684   </c>
2685   <c>400</c>
2686   <c>Bad Request</c>
2687   <c>
2688      <xref target="status.400"/>
2689   </c>
2690   <c>402</c>
2691   <c>Payment Required</c>
2692   <c>
2693      <xref target="status.402"/>
2694   </c>
2695   <c>403</c>
2696   <c>Forbidden</c>
2697   <c>
2698      <xref target="status.403"/>
2699   </c>
2700   <c>404</c>
2701   <c>Not Found</c>
2702   <c>
2703      <xref target="status.404"/>
2704   </c>
2705   <c>405</c>
2706   <c>Method Not Allowed</c>
2707   <c>
2708      <xref target="status.405"/>
2709   </c>
2710   <c>406</c>
2711   <c>Not Acceptable</c>
2712   <c>
2713      <xref target="status.406"/>
2714   </c>
2715   <c>407</c>
2716   <c>Proxy Authentication Required</c>
2717   <c>
2718      <xref target="status.407"/>
2719   </c>
2720   <c>408</c>
2721   <c>Request Timeout</c>
2722   <c>
2723      <xref target="status.408"/>
2724   </c>
2725   <c>409</c>
2726   <c>Conflict</c>
2727   <c>
2728      <xref target="status.409"/>
2729   </c>
2730   <c>410</c>
2731   <c>Gone</c>
2732   <c>
2733      <xref target="status.410"/>
2734   </c>
2735   <c>411</c>
2736   <c>Length Required</c>
2737   <c>
2738      <xref target="status.411"/>
2739   </c>
2740   <c>413</c>
2741   <c>Request Representation Too Large</c>
2742   <c>
2743      <xref target="status.413"/>
2744   </c>
2745   <c>414</c>
2746   <c>URI Too Long</c>
2747   <c>
2748      <xref target="status.414"/>
2749   </c>
2750   <c>415</c>
2751   <c>Unsupported Media Type</c>
2752   <c>
2753      <xref target="status.415"/>
2754   </c>
2755   <c>417</c>
2756   <c>Expectation Failed</c>
2757   <c>
2758      <xref target="status.417"/>
2759   </c>
2760   <c>426</c>
2761   <c>Upgrade Required</c>
2762   <c>
2763      <xref target="status.426"/>
2764   </c>
2765   <c>500</c>
2766   <c>Internal Server Error</c>
2767   <c>
2768      <xref target="status.500"/>
2769   </c>
2770   <c>501</c>
2771   <c>Not Implemented</c>
2772   <c>
2773      <xref target="status.501"/>
2774   </c>
2775   <c>502</c>
2776   <c>Bad Gateway</c>
2777   <c>
2778      <xref target="status.502"/>
2779   </c>
2780   <c>503</c>
2781   <c>Service Unavailable</c>
2782   <c>
2783      <xref target="status.503"/>
2784   </c>
2785   <c>504</c>
2786   <c>Gateway Timeout</c>
2787   <c>
2788      <xref target="status.504"/>
2789   </c>
2790   <c>505</c>
2791   <c>HTTP Version Not Supported</c>
2792   <c>
2793      <xref target="status.505"/>
2794   </c>
2795</texttable>
2796<!--(END)-->
2797<?ENDINC p2-semantics.iana-status-codes ?>
2798</section>
2799<section title="Header Field Registration" anchor="header.field.registration">
2800<t>
2801   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2802   with the permanent registrations below (see <xref target="RFC3864"/>):
2803</t>
2804<?BEGININC p2-semantics.iana-headers ?>
2805<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2806<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2807   <ttcol>Header Field Name</ttcol>
2808   <ttcol>Protocol</ttcol>
2809   <ttcol>Status</ttcol>
2810   <ttcol>Reference</ttcol>
2811
2812   <c>Allow</c>
2813   <c>http</c>
2814   <c>standard</c>
2815   <c>
2816      <xref target="header.allow"/>
2817   </c>
2818   <c>Expect</c>
2819   <c>http</c>
2820   <c>standard</c>
2821   <c>
2822      <xref target="header.expect"/>
2823   </c>
2824   <c>From</c>
2825   <c>http</c>
2826   <c>standard</c>
2827   <c>
2828      <xref target="header.from"/>
2829   </c>
2830   <c>Location</c>
2831   <c>http</c>
2832   <c>standard</c>
2833   <c>
2834      <xref target="header.location"/>
2835   </c>
2836   <c>Max-Forwards</c>
2837   <c>http</c>
2838   <c>standard</c>
2839   <c>
2840      <xref target="header.max-forwards"/>
2841   </c>
2842   <c>Referer</c>
2843   <c>http</c>
2844   <c>standard</c>
2845   <c>
2846      <xref target="header.referer"/>
2847   </c>
2848   <c>Retry-After</c>
2849   <c>http</c>
2850   <c>standard</c>
2851   <c>
2852      <xref target="header.retry-after"/>
2853   </c>
2854   <c>Server</c>
2855   <c>http</c>
2856   <c>standard</c>
2857   <c>
2858      <xref target="header.server"/>
2859   </c>
2860   <c>User-Agent</c>
2861   <c>http</c>
2862   <c>standard</c>
2863   <c>
2864      <xref target="header.user-agent"/>
2865   </c>
2866</texttable>
2867<!--(END)-->
2868<?ENDINC p2-semantics.iana-headers ?>
2869<t>
2870   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2871</t>
2872</section>
2873</section>
2874
2875<section title="Security Considerations" anchor="security.considerations">
2876<t>
2877   This section is meant to inform application developers, information
2878   providers, and users of the security limitations in HTTP/1.1 as
2879   described by this document. The discussion does not include
2880   definitive solutions to the problems revealed, though it does make
2881   some suggestions for reducing security risks.
2882</t>
2883
2884<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2885<t>
2886   Like any generic data transfer protocol, HTTP cannot regulate the
2887   content of the data that is transferred, nor is there any a priori
2888   method of determining the sensitivity of any particular piece of
2889   information within the context of any given request. Therefore,
2890   applications &SHOULD; supply as much control over this information as
2891   possible to the provider of that information. Four header fields are
2892   worth special mention in this context: Server, Via, Referer and From.
2893</t>
2894<t>
2895   Revealing the specific software version of the server might allow the
2896   server machine to become more vulnerable to attacks against software
2897   that is known to contain security holes. Implementors &SHOULD; make the
2898   Server header field a configurable option.
2899</t>
2900<t>
2901   Proxies which serve as a portal through a network firewall &SHOULD;
2902   take special precautions regarding the transfer of header information
2903   that identifies the hosts behind the firewall. In particular, they
2904   &SHOULD; remove, or replace with sanitized versions, any Via fields
2905   generated behind the firewall.
2906</t>
2907<t>
2908   The Referer header field allows reading patterns to be studied and reverse
2909   links drawn. Although it can be very useful, its power can be abused
2910   if user details are not separated from the information contained in
2911   the Referer. Even when the personal information has been removed, the
2912   Referer header field might indicate a private document's URI whose
2913   publication would be inappropriate.
2914</t>
2915<t>
2916   The information sent in the From field might conflict with the user's
2917   privacy interests or their site's security policy, and hence it
2918   &SHOULD-NOT;  be transmitted without the user being able to disable,
2919   enable, and modify the contents of the field. The user &MUST; be able
2920   to set the contents of this field within a user preference or
2921   application defaults configuration.
2922</t>
2923<t>
2924   We suggest, though do not require, that a convenient toggle interface
2925   be provided for the user to enable or disable the sending of From and
2926   Referer information.
2927</t>
2928<t>
2929   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2930   target="header.server"/>) header fields can sometimes be used to determine
2931   that a specific client or server have a particular security hole which might
2932   be exploited. Unfortunately, this same information is often used for other
2933   valuable purposes for which HTTP currently has no better mechanism.
2934</t>
2935<t>
2936   Furthermore, the User-Agent header field may contain enough entropy to be
2937   used, possibly in conjunction with other material, to uniquely identify the
2938   user.
2939</t>
2940<t>
2941   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2942   that was sent in request header fields within the body of their response.
2943   Clients &SHOULD; be careful with sensitive information, like Cookies,
2944   Authorization credentials, and other header fields that might be used to
2945   collect data from the client.
2946</t> 
2947</section>
2948
2949<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2950<t>
2951   Because the source of a link might be private information or might
2952   reveal an otherwise private information source, it is strongly
2953   recommended that the user be able to select whether or not the
2954   Referer field is sent. For example, a browser client could have a
2955   toggle switch for browsing openly/anonymously, which would
2956   respectively enable/disable the sending of Referer and From
2957   information.
2958</t>
2959<t>
2960   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2961   HTTP request if the referring page was transferred with a secure
2962   protocol.
2963</t>
2964<t>
2965   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2966   sensitive data because that data will be placed in the request-target. Many
2967   existing servers, proxies, and user agents log or display the request-target
2968   in places where it might be visible to third parties. Such services can
2969   use POST-based form submission instead.
2970</t>
2971</section>
2972
2973<section title="Location Headers and Spoofing" anchor="location.spoofing">
2974<t>
2975   If a single server supports multiple organizations that do not trust
2976   one another, then it &MUST; check the values of Location and Content-Location
2977   header fields in responses that are generated under control of
2978   said organizations to make sure that they do not attempt to
2979   invalidate resources over which they have no authority.
2980</t>
2981</section>
2982
2983<section title="Security Considerations for CONNECT">
2984<t>
2985   Since tunneled data is opaque to the proxy, there are additional
2986   risks to tunneling to other well-known or reserved ports.
2987   A HTTP client CONNECTing to port 25 could relay spam
2988   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2989   access to a small number of known ports.
2990</t>
2991</section>
2992
2993</section>
2994
2995<section title="Acknowledgments" anchor="acks">
2996<t>
2997  See &acks;.
2998</t>
2999</section>
3000</middle>
3001<back>
3002
3003<references title="Normative References">
3004
3005<reference anchor="Part1">
3006  <front>
3007    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3008    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3009      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3010      <address><email>fielding@gbiv.com</email></address>
3011    </author>
3012    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3013      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3014      <address><email>jg@freedesktop.org</email></address>
3015    </author>
3016    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3017      <organization abbrev="HP">Hewlett-Packard Company</organization>
3018      <address><email>JeffMogul@acm.org</email></address>
3019    </author>
3020    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3021      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3022      <address><email>henrikn@microsoft.com</email></address>
3023    </author>
3024    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3025      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3026      <address><email>LMM@acm.org</email></address>
3027    </author>
3028    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3029      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3030      <address><email>paulle@microsoft.com</email></address>
3031    </author>
3032    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3033      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3034      <address><email>timbl@w3.org</email></address>
3035    </author>
3036    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3037      <organization abbrev="W3C">World Wide Web Consortium</organization>
3038      <address><email>ylafon@w3.org</email></address>
3039    </author>
3040    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3041      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3042      <address><email>julian.reschke@greenbytes.de</email></address>
3043    </author>
3044    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3045  </front>
3046  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3047  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3048</reference>
3049
3050<reference anchor="Part3">
3051  <front>
3052    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3053    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3054      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3055      <address><email>fielding@gbiv.com</email></address>
3056    </author>
3057    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3058      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3059      <address><email>jg@freedesktop.org</email></address>
3060    </author>
3061    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3062      <organization abbrev="HP">Hewlett-Packard Company</organization>
3063      <address><email>JeffMogul@acm.org</email></address>
3064    </author>
3065    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3066      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3067      <address><email>henrikn@microsoft.com</email></address>
3068    </author>
3069    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3070      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3071      <address><email>LMM@acm.org</email></address>
3072    </author>
3073    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3074      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3075      <address><email>paulle@microsoft.com</email></address>
3076    </author>
3077    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3078      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3079      <address><email>timbl@w3.org</email></address>
3080    </author>
3081    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3082      <organization abbrev="W3C">World Wide Web Consortium</organization>
3083      <address><email>ylafon@w3.org</email></address>
3084    </author>
3085    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3086      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3087      <address><email>julian.reschke@greenbytes.de</email></address>
3088    </author>
3089    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3090  </front>
3091  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3092  <x:source href="p3-payload.xml" basename="p3-payload"/>
3093</reference>
3094
3095<reference anchor="Part4">
3096  <front>
3097    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3098    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3099      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3100      <address><email>fielding@gbiv.com</email></address>
3101    </author>
3102    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3103      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3104      <address><email>jg@freedesktop.org</email></address>
3105    </author>
3106    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3107      <organization abbrev="HP">Hewlett-Packard Company</organization>
3108      <address><email>JeffMogul@acm.org</email></address>
3109    </author>
3110    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3111      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3112      <address><email>henrikn@microsoft.com</email></address>
3113    </author>
3114    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3115      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3116      <address><email>LMM@acm.org</email></address>
3117    </author>
3118    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3119      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3120      <address><email>paulle@microsoft.com</email></address>
3121    </author>
3122    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3123      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3124      <address><email>timbl@w3.org</email></address>
3125    </author>
3126    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3127      <organization abbrev="W3C">World Wide Web Consortium</organization>
3128      <address><email>ylafon@w3.org</email></address>
3129    </author>
3130    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3131      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3132      <address><email>julian.reschke@greenbytes.de</email></address>
3133    </author>
3134    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3135  </front>
3136  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3137  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3138</reference>
3139
3140<reference anchor="Part5">
3141  <front>
3142    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3143    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3144      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3145      <address><email>fielding@gbiv.com</email></address>
3146    </author>
3147    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3148      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3149      <address><email>jg@freedesktop.org</email></address>
3150    </author>
3151    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3152      <organization abbrev="HP">Hewlett-Packard Company</organization>
3153      <address><email>JeffMogul@acm.org</email></address>
3154    </author>
3155    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3156      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3157      <address><email>henrikn@microsoft.com</email></address>
3158    </author>
3159    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3160      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3161      <address><email>LMM@acm.org</email></address>
3162    </author>
3163    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3164      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3165      <address><email>paulle@microsoft.com</email></address>
3166    </author>
3167    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3168      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3169      <address><email>timbl@w3.org</email></address>
3170    </author>
3171    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3172      <organization abbrev="W3C">World Wide Web Consortium</organization>
3173      <address><email>ylafon@w3.org</email></address>
3174    </author>
3175    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3176      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3177      <address><email>julian.reschke@greenbytes.de</email></address>
3178    </author>
3179    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3180  </front>
3181  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3182  <x:source href="p5-range.xml" basename="p5-range"/>
3183</reference>
3184
3185<reference anchor="Part6">
3186  <front>
3187    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3188    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3189      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3190      <address><email>fielding@gbiv.com</email></address>
3191    </author>
3192    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3193      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3194      <address><email>jg@freedesktop.org</email></address>
3195    </author>
3196    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3197      <organization abbrev="HP">Hewlett-Packard Company</organization>
3198      <address><email>JeffMogul@acm.org</email></address>
3199    </author>
3200    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3201      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3202      <address><email>henrikn@microsoft.com</email></address>
3203    </author>
3204    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3205      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3206      <address><email>LMM@acm.org</email></address>
3207    </author>
3208    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3209      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3210      <address><email>paulle@microsoft.com</email></address>
3211    </author>
3212    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3213      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3214      <address><email>timbl@w3.org</email></address>
3215    </author>
3216    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3217      <organization abbrev="W3C">World Wide Web Consortium</organization>
3218      <address><email>ylafon@w3.org</email></address>
3219    </author>
3220    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3221      <address><email>mnot@mnot.net</email></address>
3222    </author>
3223    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3224      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3225      <address><email>julian.reschke@greenbytes.de</email></address>
3226    </author>
3227    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3228  </front>
3229  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3230  <x:source href="p6-cache.xml" basename="p6-cache"/>
3231</reference>
3232
3233<reference anchor="Part7">
3234  <front>
3235    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3236    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3237      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3238      <address><email>fielding@gbiv.com</email></address>
3239    </author>
3240    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3241      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3242      <address><email>jg@freedesktop.org</email></address>
3243    </author>
3244    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3245      <organization abbrev="HP">Hewlett-Packard Company</organization>
3246      <address><email>JeffMogul@acm.org</email></address>
3247    </author>
3248    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3249      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3250      <address><email>henrikn@microsoft.com</email></address>
3251    </author>
3252    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3253      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3254      <address><email>LMM@acm.org</email></address>
3255    </author>
3256    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3257      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3258      <address><email>paulle@microsoft.com</email></address>
3259    </author>
3260    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3261      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3262      <address><email>timbl@w3.org</email></address>
3263    </author>
3264    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3265      <organization abbrev="W3C">World Wide Web Consortium</organization>
3266      <address><email>ylafon@w3.org</email></address>
3267    </author>
3268    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3269      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3270      <address><email>julian.reschke@greenbytes.de</email></address>
3271    </author>
3272    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3273  </front>
3274  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3275  <x:source href="p7-auth.xml" basename="p7-auth"/>
3276</reference>
3277
3278<reference anchor="RFC2119">
3279  <front>
3280    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3281    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3282      <organization>Harvard University</organization>
3283      <address><email>sob@harvard.edu</email></address>
3284    </author>
3285    <date month="March" year="1997"/>
3286  </front>
3287  <seriesInfo name="BCP" value="14"/>
3288  <seriesInfo name="RFC" value="2119"/>
3289</reference>
3290
3291<reference anchor="RFC3986">
3292 <front>
3293  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3294  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3295    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3296    <address>
3297       <email>timbl@w3.org</email>
3298       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3299    </address>
3300  </author>
3301  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3302    <organization abbrev="Day Software">Day Software</organization>
3303    <address>
3304      <email>fielding@gbiv.com</email>
3305      <uri>http://roy.gbiv.com/</uri>
3306    </address>
3307  </author>
3308  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3309    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3310    <address>
3311      <email>LMM@acm.org</email>
3312      <uri>http://larry.masinter.net/</uri>
3313    </address>
3314  </author>
3315  <date month='January' year='2005'></date>
3316 </front>
3317 <seriesInfo name="STD" value="66"/>
3318 <seriesInfo name="RFC" value="3986"/>
3319</reference>
3320
3321<reference anchor="RFC5234">
3322  <front>
3323    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3324    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3325      <organization>Brandenburg InternetWorking</organization>
3326      <address>
3327        <email>dcrocker@bbiw.net</email>
3328      </address> 
3329    </author>
3330    <author initials="P." surname="Overell" fullname="Paul Overell">
3331      <organization>THUS plc.</organization>
3332      <address>
3333        <email>paul.overell@thus.net</email>
3334      </address>
3335    </author>
3336    <date month="January" year="2008"/>
3337  </front>
3338  <seriesInfo name="STD" value="68"/>
3339  <seriesInfo name="RFC" value="5234"/>
3340</reference>
3341
3342</references>
3343
3344<references title="Informative References">
3345
3346<reference anchor="RFC1945">
3347  <front>
3348    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3349    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3350      <organization>MIT, Laboratory for Computer Science</organization>
3351      <address><email>timbl@w3.org</email></address>
3352    </author>
3353    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3354      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3355      <address><email>fielding@ics.uci.edu</email></address>
3356    </author>
3357    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3358      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3359      <address><email>frystyk@w3.org</email></address>
3360    </author>
3361    <date month="May" year="1996"/>
3362  </front>
3363  <seriesInfo name="RFC" value="1945"/>
3364</reference>
3365
3366<reference anchor="RFC2068">
3367  <front>
3368    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3369    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3370      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3371      <address><email>fielding@ics.uci.edu</email></address>
3372    </author>
3373    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3374      <organization>MIT Laboratory for Computer Science</organization>
3375      <address><email>jg@w3.org</email></address>
3376    </author>
3377    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3378      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3379      <address><email>mogul@wrl.dec.com</email></address>
3380    </author>
3381    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3382      <organization>MIT Laboratory for Computer Science</organization>
3383      <address><email>frystyk@w3.org</email></address>
3384    </author>
3385    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3386      <organization>MIT Laboratory for Computer Science</organization>
3387      <address><email>timbl@w3.org</email></address>
3388    </author>
3389    <date month="January" year="1997"/>
3390  </front>
3391  <seriesInfo name="RFC" value="2068"/>
3392</reference>
3393
3394<reference anchor="RFC2616">
3395  <front>
3396    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3397    <author initials="R." surname="Fielding" fullname="R. Fielding">
3398      <organization>University of California, Irvine</organization>
3399      <address><email>fielding@ics.uci.edu</email></address>
3400    </author>
3401    <author initials="J." surname="Gettys" fullname="J. Gettys">
3402      <organization>W3C</organization>
3403      <address><email>jg@w3.org</email></address>
3404    </author>
3405    <author initials="J." surname="Mogul" fullname="J. Mogul">
3406      <organization>Compaq Computer Corporation</organization>
3407      <address><email>mogul@wrl.dec.com</email></address>
3408    </author>
3409    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3410      <organization>MIT Laboratory for Computer Science</organization>
3411      <address><email>frystyk@w3.org</email></address>
3412    </author>
3413    <author initials="L." surname="Masinter" fullname="L. Masinter">
3414      <organization>Xerox Corporation</organization>
3415      <address><email>masinter@parc.xerox.com</email></address>
3416    </author>
3417    <author initials="P." surname="Leach" fullname="P. Leach">
3418      <organization>Microsoft Corporation</organization>
3419      <address><email>paulle@microsoft.com</email></address>
3420    </author>
3421    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3422      <organization>W3C</organization>
3423      <address><email>timbl@w3.org</email></address>
3424    </author>
3425    <date month="June" year="1999"/>
3426  </front>
3427  <seriesInfo name="RFC" value="2616"/>
3428</reference>
3429
3430<reference anchor='RFC2817'>
3431  <front>
3432    <title>Upgrading to TLS Within HTTP/1.1</title>
3433    <author initials='R.' surname='Khare' fullname='R. Khare'>
3434      <organization>4K Associates / UC Irvine</organization>
3435      <address><email>rohit@4K-associates.com</email></address>
3436    </author>
3437    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3438      <organization>Agranat Systems, Inc.</organization>
3439      <address><email>lawrence@agranat.com</email></address>
3440    </author>
3441    <date year='2000' month='May' />
3442  </front>
3443  <seriesInfo name='RFC' value='2817' />
3444</reference>
3445
3446<reference anchor='RFC3864'>
3447  <front>
3448    <title>Registration Procedures for Message Header Fields</title>
3449    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3450      <organization>Nine by Nine</organization>
3451      <address><email>GK-IETF@ninebynine.org</email></address>
3452    </author>
3453    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3454      <organization>BEA Systems</organization>
3455      <address><email>mnot@pobox.com</email></address>
3456    </author>
3457    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3458      <organization>HP Labs</organization>
3459      <address><email>JeffMogul@acm.org</email></address>
3460    </author>
3461    <date year='2004' month='September' />
3462  </front>
3463  <seriesInfo name='BCP' value='90' />
3464  <seriesInfo name='RFC' value='3864' />
3465</reference>
3466
3467<reference anchor='RFC5226'>
3468  <front>
3469    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3470    <author initials='T.' surname='Narten' fullname='T. Narten'>
3471      <organization>IBM</organization>
3472      <address><email>narten@us.ibm.com</email></address>
3473    </author>
3474    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3475      <organization>Google</organization>
3476      <address><email>Harald@Alvestrand.no</email></address>
3477    </author>
3478    <date year='2008' month='May' />
3479  </front>
3480  <seriesInfo name='BCP' value='26' />
3481  <seriesInfo name='RFC' value='5226' />
3482</reference>
3483
3484<reference anchor="RFC5322">
3485  <front>
3486    <title>Internet Message Format</title>
3487    <author initials="P." surname="Resnick" fullname="P. Resnick">
3488      <organization>Qualcomm Incorporated</organization>
3489    </author>
3490    <date year="2008" month="October"/>
3491  </front> 
3492  <seriesInfo name="RFC" value="5322"/>
3493</reference>
3494
3495<reference anchor='RFC5789'>
3496  <front>
3497    <title>PATCH Method for HTTP</title>
3498    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3499      <organization>Linden Lab</organization>
3500    </author>
3501    <author initials='J.' surname='Snell' fullname='J. Snell' />
3502    <date year='2010' month='March' />
3503  </front>
3504  <seriesInfo name='RFC' value='5789' />
3505</reference>
3506
3507</references>
3508
3509<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3510<t>
3511  This document takes over the Status Code Registry, previously defined
3512  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3513  (<xref target="status.code.registry"/>)
3514</t>
3515<t>
3516  Clarify definition of POST.
3517  (<xref target="POST"/>)
3518</t>
3519<t>
3520  Remove requirement to handle all Content-* header fields; ban use of
3521  Content-Range with PUT.
3522  (<xref target="PUT"/>)
3523</t>
3524<t>
3525  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3526  (<xref target="CONNECT"/>)
3527</t>
3528<t>
3529  Broadened the definition of 203 (Non-Authoritative Information) to include
3530  cases of payload transformations as well.
3531  (<xref target="status.203"/>)
3532</t>
3533<t>
3534  Failed to consider that there are
3535  many other request methods that are safe to automatically redirect,
3536  and further that the user agent is able to make that determination
3537  based on the request method semantics.
3538  (Sections <xref format="counter" target="status.301"/>,
3539  <xref format="counter" target="status.302"/> and
3540  <xref format="counter" target="status.307"/>)
3541</t>
3542<t>
3543  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3544  It used to indicate that the target resource must be accessed through the
3545  proxy given by the Location field. The Location field gave the URI of the
3546  proxy. The recipient was expected to repeat this single request via the proxy.
3547  (<xref target="status.305"/>)
3548</t>
3549<t>
3550  Define status 426 (Upgrade Required) (this was incorporated from
3551  <xref target="RFC2817"/>).
3552  (<xref target="status.426"/>)
3553</t>
3554<t>
3555  Change ABNF productions for header fields to only define the field value.
3556  (<xref target="header.field.definitions"/>)
3557</t>
3558<t>
3559  Reclassify "Allow" as response header field, removing the option to
3560  specify it in a PUT request.
3561  Relax the server requirement on the contents of the Allow header field and
3562  remove requirement on clients to always trust the header field value.
3563  (<xref target="header.allow"/>)
3564</t>
3565<t>
3566  Correct syntax of Location header field to allow URI references (including
3567  relative references and fragments), as referred symbol "absoluteURI" wasn't
3568  what was expected, and add some clarifications as to when use of fragments
3569  would not be appropriate.
3570  (<xref target="header.location"/>)
3571</t>
3572<t>
3573  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3574  extension methods could have used it as well).
3575  (<xref target="header.max-forwards"/>)
3576</t>
3577<t>
3578  Allow Referer field value of "about:blank" as alternative to not specifying it.
3579  (<xref target="header.referer"/>)
3580</t>
3581<t>
3582  In the description of the Server header field, the Via field
3583  was described as a SHOULD. The requirement was and is stated
3584  correctly in the description of the Via header field in &header-via;.
3585  (<xref target="header.server"/>)
3586</t>
3587</section>
3588
3589<?BEGININC p2-semantics.abnf-appendix ?>
3590<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3591<figure>
3592<artwork type="abnf" name="p2-semantics.parsed-abnf">
3593<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3594
3595<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3596
3597<x:ref>From</x:ref> = mailbox
3598
3599<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3600
3601<x:ref>Location</x:ref> = URI-reference
3602
3603<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3604<x:ref>Method</x:ref> = token
3605
3606<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3607
3608<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3609<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3610<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3611<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3612
3613<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3614<x:ref>Status-Code</x:ref> = 3DIGIT
3615
3616<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
3617<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3618
3619<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
3620
3621<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3622
3623<x:ref>delta-seconds</x:ref> = 1*DIGIT
3624
3625<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3626<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3627<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3628 *expect-params ]
3629
3630<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3631
3632<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3633
3634<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
3635<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3636
3637<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
3638
3639<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
3640</artwork>
3641</figure>
3642<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3643; Allow defined but not used
3644; Expect defined but not used
3645; From defined but not used
3646; Location defined but not used
3647; Max-Forwards defined but not used
3648; Reason-Phrase defined but not used
3649; Referer defined but not used
3650; Retry-After defined but not used
3651; Server defined but not used
3652; Status-Code defined but not used
3653; User-Agent defined but not used
3654</artwork></figure></section>
3655<?ENDINC p2-semantics.abnf-appendix ?>
3656
3657<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3658
3659<section title="Since RFC 2616">
3660<t>
3661  Extracted relevant partitions from <xref target="RFC2616"/>.
3662</t>
3663</section>
3664
3665<section title="Since draft-ietf-httpbis-p2-semantics-00">
3666<t>
3667  Closed issues:
3668  <list style="symbols"> 
3669    <t>
3670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3671      "Via is a MUST"
3672      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3673    </t>
3674    <t>
3675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3676      "Fragments allowed in Location"
3677      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3678    </t>
3679    <t>
3680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3681      "Safe Methods vs Redirection"
3682      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3683    </t>
3684    <t>
3685      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3686      "Revise description of the POST method"
3687      (<eref target="http://purl.org/NET/http-errata#post"/>)
3688    </t>
3689    <t>
3690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3691      "Normative and Informative references"
3692    </t>
3693    <t>
3694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3695      "RFC2606 Compliance"
3696    </t>
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3699      "Informative references"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3703      "Redundant cross-references"
3704    </t>
3705  </list>
3706</t>
3707<t>
3708  Other changes:
3709  <list style="symbols"> 
3710    <t>
3711      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3712    </t>
3713  </list>
3714</t>
3715</section>
3716
3717<section title="Since draft-ietf-httpbis-p2-semantics-01">
3718<t>
3719  Closed issues:
3720  <list style="symbols"> 
3721    <t>
3722      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3723      "PUT side effects"
3724    </t>
3725    <t>
3726      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3727      "Duplicate Host header requirements"
3728    </t>
3729  </list>
3730</t>
3731<t>
3732  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3733  <list style="symbols"> 
3734    <t>
3735      Move "Product Tokens" section (back) into Part 1, as "token" is used
3736      in the definition of the Upgrade header field.
3737    </t>
3738    <t>
3739      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3740    </t>
3741    <t>
3742      Copy definition of delta-seconds from Part6 instead of referencing it.
3743    </t>
3744  </list>
3745</t>
3746</section>
3747
3748<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3749<t>
3750  Closed issues:
3751  <list style="symbols"> 
3752    <t>
3753      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3754      "Requiring Allow in 405 responses"
3755    </t>
3756    <t>
3757      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3758      "Status Code Registry"
3759    </t>
3760    <t>
3761      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3762      "Redirection vs. Location"
3763    </t>
3764    <t>
3765      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3766      "Cacheability of 303 response"
3767    </t>
3768    <t>
3769      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3770      "305 Use Proxy"
3771    </t>
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3774      "Classification for Allow header"
3775    </t>
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3778      "PUT - 'store under' vs 'store at'"
3779    </t>
3780  </list>
3781</t>
3782<t>
3783  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3784  <list style="symbols"> 
3785    <t>
3786      Reference RFC 3984, and update header field registrations for headers defined
3787      in this document.
3788    </t>
3789  </list>
3790</t>
3791<t>
3792  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3793  <list style="symbols"> 
3794    <t>
3795      Replace string literals when the string really is case-sensitive (method).
3796    </t>
3797  </list>
3798</t>
3799</section>
3800
3801<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3802<t>
3803  Closed issues:
3804  <list style="symbols"> 
3805    <t>
3806      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3807      "OPTIONS request bodies"
3808    </t>
3809    <t>
3810      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3811      "Description of CONNECT should refer to RFC2817"
3812    </t>
3813    <t>
3814      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3815      "Location Content-Location reference request/response mixup"
3816    </t>
3817  </list>
3818</t>
3819<t>
3820  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3821  <list style="symbols"> 
3822    <t>
3823      Added initial proposal for registration process, plus initial
3824      content (non-HTTP/1.1 methods to be added by a separate specification).
3825    </t>
3826  </list>
3827</t>
3828</section>
3829
3830<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3831<t>
3832  Closed issues:
3833  <list style="symbols"> 
3834    <t>
3835      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3836      "Content-*"
3837    </t>
3838    <t>
3839      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3840      "RFC 2822 is updated by RFC 5322"
3841    </t>
3842  </list>
3843</t>
3844<t>
3845  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3846  <list style="symbols"> 
3847    <t>
3848      Use "/" instead of "|" for alternatives.
3849    </t>
3850    <t>
3851      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3852      whitespace ("OWS") and required whitespace ("RWS").
3853    </t>
3854    <t>
3855      Rewrite ABNFs to spell out whitespace rules, factor out
3856      header field value format definitions.
3857    </t>
3858  </list>
3859</t>
3860</section>
3861
3862<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3863<t>
3864  Closed issues:
3865  <list style="symbols"> 
3866    <t>
3867      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3868      "Reason-Phrase BNF"
3869    </t>
3870  </list>
3871</t>
3872<t>
3873  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3874  <list style="symbols"> 
3875    <t>
3876      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3877    </t>
3878  </list>
3879</t>
3880</section>
3881
3882<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3883<t>
3884  Closed issues:
3885  <list style="symbols"> 
3886    <t>
3887      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3888      "Clarify when Referer is sent"
3889    </t>
3890    <t>
3891      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3892      "status codes vs methods"
3893    </t>
3894    <t>
3895      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3896      "Do not require "updates" relation for specs that register status codes or method names"
3897    </t>
3898  </list>
3899</t>
3900</section>
3901
3902<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3903<t>
3904  Closed issues:
3905  <list style="symbols"> 
3906    <t>
3907      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3908      "Idempotency"
3909    </t>
3910    <t>
3911      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3912      "TRACE security considerations"
3913    </t>
3914    <t>
3915      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3916      "Clarify rules for determining what entities a response carries"
3917    </t>
3918    <t>
3919      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3920      "update note citing RFC 1945 and 2068"
3921    </t>
3922    <t>
3923      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3924      "update note about redirect limit"
3925    </t>
3926    <t>
3927      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3928      "Location header ABNF should use 'URI'"
3929    </t>
3930    <t>
3931      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3932      "fragments in Location vs status 303"
3933    </t>
3934    <t>
3935      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3936      "move IANA registrations for optional status codes"
3937    </t>
3938  </list>
3939</t>
3940<t>
3941  Partly resolved issues:
3942  <list style="symbols"> 
3943    <t>
3944      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3945      "Are OPTIONS and TRACE safe?"
3946    </t>
3947  </list>
3948</t>
3949</section>
3950
3951<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3952<t>
3953  Closed issues:
3954  <list style="symbols"> 
3955    <t>
3956      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3957      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3958      status codes when fixing this previously)
3959    </t>
3960  </list>
3961</t>
3962</section>
3963
3964<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3965<t>
3966  Closed issues:
3967  <list style="symbols"> 
3968    <t>
3969      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3970      "Fragment combination / precedence during redirects"
3971    </t>
3972  </list>
3973</t>
3974<t>
3975  Partly resolved issues:
3976  <list style="symbols"> 
3977    <t>
3978      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3979      "Location header payload handling"
3980    </t>
3981    <t>
3982      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3983      "Term for the requested resource's URI"
3984    </t>
3985  </list>
3986</t>
3987</section>
3988
3989<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3990<t>
3991  Closed issues:
3992  <list style="symbols"> 
3993    <t>
3994      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3995      "Clarify 'Requested Variant'"
3996    </t>
3997    <t>
3998      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3999      "Clarify entity / representation / variant terminology"
4000    </t>
4001    <t>
4002      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4003      "Methods and Caching"
4004    </t>
4005    <t>
4006      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4007      "OPTIONS vs Max-Forwards"
4008    </t>
4009    <t>
4010      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4011      "Status codes and caching"
4012    </t>
4013    <t>
4014      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4015      "consider removing the 'changes from 2068' sections"
4016    </t>
4017  </list>
4018</t>
4019</section>
4020
4021<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4022<t>
4023  Closed issues:
4024  <list style="symbols"> 
4025    <t>
4026      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4027      "Considerations for new status codes"
4028    </t>
4029    <t>
4030      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4031      "Considerations for new methods"
4032    </t>
4033    <t>
4034      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4035      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4036    </t>
4037  </list>
4038</t>
4039</section>
4040
4041<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4042<t>
4043  Closed issues:
4044  <list style="symbols"> 
4045    <t>
4046      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4047      "Fragment combination / precedence during redirects" (added warning
4048      about having a fragid on the redirect may cause inconvenience in
4049      some cases)
4050    </t>
4051    <t>
4052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4053      "Content-* vs. PUT"
4054    </t>
4055    <t>
4056      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4057      "205 Bodies"
4058    </t>
4059    <t>
4060      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4061      "Understanding Content-* on non-PUT requests"
4062    </t>
4063    <t>
4064      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4065      "Content-*"
4066    </t>
4067    <t>
4068      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4069      "Header type defaulting"
4070    </t>
4071    <t>
4072      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4073      "PUT - 'store under' vs 'store at'"
4074    </t>
4075    <t>
4076      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4077      "duplicate ABNF for Reason-Phrase"
4078    </t>
4079    <t>
4080      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4081      "Note special status of Content-* prefix in header registration procedures"
4082    </t>
4083    <t>
4084      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4085      "Max-Forwards vs extension methods"
4086    </t>
4087    <t>
4088      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4089      "What is the value space of HTTP status codes?" (actually fixed in
4090      draft-ietf-httpbis-p2-semantics-11)
4091    </t>
4092    <t>
4093      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4094      "Header Classification"
4095    </t>
4096    <t>
4097      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4098      "PUT side effect: invalidation or just stale?"
4099    </t>
4100    <t>
4101      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4102      "proxies not supporting certain methods"
4103    </t>
4104    <t>
4105      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4106      "Migrate CONNECT from RFC2817 to p2"
4107    </t>
4108    <t>
4109      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4110      "Migrate Upgrade details from RFC2817"
4111    </t>
4112    <t>
4113      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4114      "clarify PUT semantics'"
4115    </t>
4116    <t>
4117      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4118      "duplicate ABNF for 'Method'"
4119    </t>
4120    <t>
4121      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4122      "untangle ABNFs for header fields"
4123    </t>
4124  </list>
4125</t>
4126</section>
4127
4128<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4129<t>
4130  Closed issues:
4131  <list style="symbols"> 
4132    <t>
4133      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4134      "untangle ABNFs for header fields"
4135    </t>
4136    <t>
4137      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4138      "message-body in CONNECT request"
4139    </t>
4140  </list>
4141</t>
4142</section>
4143
4144<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4145<t>
4146  Closed issues:
4147  <list style="symbols"> 
4148    <t>
4149      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4150      "Clarify status code for rate limiting"
4151    </t>
4152    <t>
4153      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4154      "clarify 403 forbidden"
4155    </t>
4156    <t>
4157      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4158      "Clarify 203 Non-Authoritative Information"
4159    </t>
4160    <t>
4161      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4162      "update default reason phrase for 413"
4163    </t>
4164  </list>
4165</t>
4166</section>
4167
4168<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4169<t>
4170  Closed issues:
4171  <list style="symbols"> 
4172    <t>
4173      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4174      "Strength of requirements on Accept re: 406"
4175    </t>
4176    <t>
4177      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4178      "400 response isn't generic"
4179    </t>
4180  </list>
4181</t>
4182</section>
4183
4184<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4185<t>
4186  None yet.
4187</t>
4188</section>
4189
4190</section>
4191
4192</back>
4193</rfc>
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