source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1374

Last change on this file since 1374 was 1374, checked in by fielding@…, 8 years ago

Clarify what should happen when a response is incomplete.
Disentangle the requirements surrounding conditional range
requests, strong validators, and recombining partial content
to remove redundant redundancy. Separate handling of 304
responses into a separate section on cache freshening.

Add definitions for "cache entry" and "cache key".
Improve introductions for caching and cache operation.

These changes should all be editorial, hopefully.
Tangentially related to #101 and #304.

  • Property svn:eol-style set to native
File size: 170.2 KB
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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "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 uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83]>
84<?rfc toc="yes" ?>
85<?rfc symrefs="yes" ?>
86<?rfc sortrefs="yes" ?>
87<?rfc compact="yes"?>
88<?rfc subcompact="no" ?>
89<?rfc linkmailto="no" ?>
90<?rfc editing="no" ?>
91<?rfc comments="yes"?>
92<?rfc inline="yes"?>
93<?rfc rfcedstyle="yes"?>
94<?rfc-ext allow-markup-in-artwork="yes" ?>
95<?rfc-ext include-references-in-index="yes" ?>
96<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
97     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
98     xmlns:x='http://purl.org/net/xml2rfc/ext'
99     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
100<front>
101
102  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
103
104  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
105    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
106    <address>
107      <postal>
108        <street>345 Park Ave</street>
109        <city>San Jose</city>
110        <region>CA</region>
111        <code>95110</code>
112        <country>USA</country>
113      </postal>
114      <email>fielding@gbiv.com</email>
115      <uri>http://roy.gbiv.com/</uri>
116    </address>
117  </author>
118
119  <author initials="J." surname="Gettys" fullname="Jim Gettys">
120    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
121    <address>
122      <postal>
123        <street>21 Oak Knoll Road</street>
124        <city>Carlisle</city>
125        <region>MA</region>
126        <code>01741</code>
127        <country>USA</country>
128      </postal>
129      <email>jg@freedesktop.org</email>
130      <uri>http://gettys.wordpress.com/</uri>
131    </address>
132  </author>
133 
134  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
135    <organization abbrev="HP">Hewlett-Packard Company</organization>
136    <address>
137      <postal>
138        <street>HP Labs, Large Scale Systems Group</street>
139        <street>1501 Page Mill Road, MS 1177</street>
140        <city>Palo Alto</city>
141        <region>CA</region>
142        <code>94304</code>
143        <country>USA</country>
144      </postal>
145      <email>JeffMogul@acm.org</email>
146    </address>
147  </author>
148
149  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
150    <organization abbrev="Microsoft">Microsoft Corporation</organization>
151    <address>
152      <postal>
153        <street>1 Microsoft Way</street>
154        <city>Redmond</city>
155        <region>WA</region>
156        <code>98052</code>
157        <country>USA</country>
158      </postal>
159      <email>henrikn@microsoft.com</email>
160    </address>
161  </author>
162
163  <author initials="L." surname="Masinter" fullname="Larry Masinter">
164    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
165    <address>
166      <postal>
167        <street>345 Park Ave</street>
168        <city>San Jose</city>
169        <region>CA</region>
170        <code>95110</code>
171        <country>USA</country>
172      </postal>
173      <email>LMM@acm.org</email>
174      <uri>http://larry.masinter.net/</uri>
175    </address>
176  </author>
177 
178  <author initials="P." surname="Leach" fullname="Paul J. Leach">
179    <organization abbrev="Microsoft">Microsoft Corporation</organization>
180    <address>
181      <postal>
182        <street>1 Microsoft Way</street>
183        <city>Redmond</city>
184        <region>WA</region>
185        <code>98052</code>
186      </postal>
187      <email>paulle@microsoft.com</email>
188    </address>
189  </author>
190   
191  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
192    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
193    <address>
194      <postal>
195        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
196        <street>The Stata Center, Building 32</street>
197        <street>32 Vassar Street</street>
198        <city>Cambridge</city>
199        <region>MA</region>
200        <code>02139</code>
201        <country>USA</country>
202      </postal>
203      <email>timbl@w3.org</email>
204      <uri>http://www.w3.org/People/Berners-Lee/</uri>
205    </address>
206  </author>
207
208  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
209    <organization abbrev="W3C">World Wide Web Consortium</organization>
210    <address>
211      <postal>
212        <street>W3C / ERCIM</street>
213        <street>2004, rte des Lucioles</street>
214        <city>Sophia-Antipolis</city>
215        <region>AM</region>
216        <code>06902</code>
217        <country>France</country>
218      </postal>
219      <email>ylafon@w3.org</email>
220      <uri>http://www.raubacapeu.net/people/yves/</uri>
221    </address>
222  </author>
223
224  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
225    <organization abbrev="greenbytes">greenbytes GmbH</organization>
226    <address>
227      <postal>
228        <street>Hafenweg 16</street>
229        <city>Muenster</city><region>NW</region><code>48155</code>
230        <country>Germany</country>
231      </postal>
232      <phone>+49 251 2807760</phone>
233      <facsimile>+49 251 2807761</facsimile>
234      <email>julian.reschke@greenbytes.de</email>
235      <uri>http://greenbytes.de/tech/webdav/</uri>
236    </address>
237  </author>
238
239  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
240  <workgroup>HTTPbis Working Group</workgroup>
241
242<abstract>
243<t>
244   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
245   distributed, collaborative, hypertext information systems. HTTP has been in
246   use by the World Wide Web global information initiative since 1990. This
247   document is Part 2 of the seven-part specification that defines the protocol
248   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
249</t>
250<t>
251   Part 2 defines the semantics of HTTP messages as expressed by request
252   methods, request header fields, response status codes, and response header
253   fields.
254</t>
255</abstract>
256
257<note title="Editorial Note (To be removed by RFC Editor)">
258  <t>
259    Discussion of this draft should take place on the HTTPBIS working group
260    mailing list (ietf-http-wg@w3.org), which is archived at
261    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
262  </t>
263  <t>
264    The current issues list is at
265    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
266    documents (including fancy diffs) can be found at
267    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
268  </t>
269  <t>
270    The changes in this draft are summarized in <xref target="changes.since.15"/>.
271  </t>
272</note>
273</front>
274<middle>
275<section title="Introduction" anchor="introduction">
276<t>
277   This document defines HTTP/1.1 request and response semantics.  Each HTTP
278   message, as defined in &messaging;, is in the form of either a request or
279   a response.  An HTTP server listens on a connection for HTTP requests and
280   responds to each request, in the order received on that connection, with
281   one or more HTTP response messages.  This document defines the commonly
282   agreed upon semantics of the HTTP uniform interface, the intentions defined
283   by each request method, and the various response messages that might be
284   expected as a result of applying that method to the target resource.
285</t>
286<t>
287   This document is currently disorganized in order to minimize the changes
288   between drafts and enable reviewers to see the smaller errata changes.
289   A future draft will reorganize the sections to better reflect the content.
290   In particular, the sections will be ordered according to the typical
291   processing of an HTTP request message (after message parsing): resource
292   mapping, methods, request modifying header fields, response status,
293   status modifying header fields, and resource metadata.  The current mess
294   reflects how widely dispersed these topics and associated requirements
295   had become in <xref target="RFC2616"/>.
296</t>
297
298<section title="Requirements" anchor="intro.requirements">
299<t>
300   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
301   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
302   document are to be interpreted as described in <xref target="RFC2119"/>.
303</t>
304<t>
305   An implementation is not compliant if it fails to satisfy one or more
306   of the "MUST" or "REQUIRED" level requirements for the protocols it
307   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
308   level and all the "SHOULD" level requirements for its protocols is said
309   to be "unconditionally compliant"; one that satisfies all the "MUST"
310   level requirements but not all the "SHOULD" level requirements for its
311   protocols is said to be "conditionally compliant".
312</t>
313</section>
314
315<section title="Syntax Notation" anchor="notation">
316  <x:anchor-alias value="CR"/>
317  <x:anchor-alias value="DIGIT"/>
318  <x:anchor-alias value="LF"/>
319  <x:anchor-alias value="VCHAR"/>
320  <x:anchor-alias value="WSP"/>
321<t>
322  This specification uses the ABNF syntax defined in &notation; (which
323  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
324  <xref target="collected.abnf"/> shows the collected ABNF, with the list
325  rule expanded.
326</t>
327<t>
328  The following core rules are included by
329  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
330  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
331  DIGIT (decimal 0-9), DQUOTE (double quote),
332  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
333  OCTET (any 8-bit sequence of data), SP (space),
334  VCHAR (any visible USASCII character),
335  and WSP (whitespace).
336</t>
337
338<section title="Core Rules" anchor="core.rules">
339  <x:anchor-alias value="obs-text"/>
340  <x:anchor-alias value="quoted-string"/>
341  <x:anchor-alias value="token"/>
342  <x:anchor-alias value="OWS"/>
343  <x:anchor-alias value="RWS"/>
344<t>
345  The core rules below are defined in &basic-rules;:
346</t>
347<figure><artwork type="abnf2616">
348  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
349  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
350  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
351  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
352  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
353</artwork></figure>
354</section>
355
356<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
357  <x:anchor-alias value="absolute-URI"/>
358  <x:anchor-alias value="comment"/>
359  <x:anchor-alias value="HTTP-date"/>
360  <x:anchor-alias value="partial-URI"/>
361  <x:anchor-alias value="product"/>
362  <x:anchor-alias value="URI-reference"/>
363<t>
364  The ABNF rules below are defined in other parts:
365</t>
366<figure><!--Part1--><artwork type="abnf2616">
367  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
368  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
369  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
370  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
371  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
372  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
373</artwork></figure>
374</section>
375</section>
376</section>
377
378<section title="Method" anchor="method">
379  <x:anchor-alias value="Method"/>
380  <x:anchor-alias value="extension-method"/>
381<t>
382   The Method token indicates the request method to be performed on the target
383   resource (&effective-request-uri;). The method is case-sensitive.
384</t>
385<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
386  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
387</artwork></figure>
388<t>
389   The list of methods allowed by a resource can be specified in an
390   Allow header field (<xref target="header.allow"/>). The status code of the response
391   always notifies the client whether a method is currently allowed on a
392   resource, since the set of allowed methods can change dynamically. An
393   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
394   if the method is known by the origin server but not allowed for the
395   resource, and 501 (Not Implemented) if the method is
396   unrecognized or not implemented by the origin server. The methods GET
397   and HEAD &MUST; be supported by all general-purpose servers. All other
398   methods are &OPTIONAL;; however, if the above methods are implemented,
399   they &MUST; be implemented with the same semantics as those specified
400   in <xref target="method.definitions"/>.
401</t>
402
403<section title="Overview of Methods" anchor="overview.of.methods">
404<t>
405  The methods listed below are defined in <xref target="method.definitions"/>.
406</t>
407<texttable align="left">
408  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
409 
410  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
411  <c>GET</c> <c><xref target="GET"/></c>
412  <c>HEAD</c> <c><xref target="HEAD"/></c>
413  <c>POST</c> <c><xref target="POST"/></c>
414  <c>PUT</c> <c><xref target="PUT"/></c>
415  <c>DELETE</c> <c><xref target="DELETE"/></c>
416  <c>TRACE</c> <c><xref target="TRACE"/></c>
417  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
418</texttable>
419<t>
420  Note that this list is not exhaustive &mdash; it does not include request methods defined
421  in other specifications.
422</t>
423</section>
424
425<section title="Method Registry" anchor="method.registry">
426<t>
427  The HTTP Method Registry defines the name space for the Method token in the
428  Request line of an HTTP request.
429</t>
430<t>
431  Registrations &MUST; include the following fields:
432  <list style="symbols">
433    <t>Method Name (see <xref target="method"/>)</t>
434    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
435    <t>Pointer to specification text</t>
436  </list>
437</t>
438<t>
439  Values to be added to this name space are subject to IETF review
440  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
441</t>
442<t>
443  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
444</t>
445
446<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
447<t>
448   When it is necessary to express new semantics for a HTTP request that
449   aren't specific to a single application or media type, and currently defined
450   methods are inadequate, it may be appropriate to register a new method.
451</t>
452<t>
453   HTTP methods are generic; that is, they are potentially applicable to any
454   resource, not just one particular media type, "type" of resource, or
455   application. As such, it is preferred that new HTTP methods be registered
456   in a document that isn't specific to a single application, so that this is
457   clear.
458</t>
459<t>
460   Due to the parsing rules defined in &message-body;, definitions of HTTP
461   methods cannot prohibit the presence of a message-body on either the request
462   or the response message (with responses to HEAD requests being the single
463   exception). Definitions of new methods cannot change this rule, but they can
464   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
465</t>
466<t>
467   New method definitions need to indicate whether they are safe (<xref
468   target="safe.methods"/>), what semantics (if any) the request body has,
469   and whether they are idempotent (<xref target="idempotent.methods"/>).
470   They also need to state whether they can be cached (&caching;); in
471   particular what conditions a cache may store the response, and under what
472   conditions such a stored response may be used to satisfy a subsequent
473   request.
474</t>
475</section>
476
477</section>
478</section>
479
480<section title="Request Header Fields" anchor="request.header.fields">
481  <x:anchor-alias value="request-header"/>
482<t>
483   The request header fields allow the client to pass additional
484   information about the request, and about the client itself, to the
485   server. These fields act as request modifiers, with semantics
486   equivalent to the parameters on a programming language method
487   invocation.
488</t>
489<texttable align="left">
490  <ttcol>Header Field Name</ttcol>
491  <ttcol>Defined in...</ttcol>
492
493  <c>Accept</c> <c>&header-accept;</c>
494  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
495  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
496  <c>Accept-Language</c> <c>&header-accept-language;</c>
497  <c>Authorization</c> <c>&header-authorization;</c>
498  <c>Expect</c> <c><xref target="header.expect"/></c>
499  <c>From</c> <c><xref target="header.from"/></c>
500  <c>Host</c> <c>&header-host;</c>
501  <c>If-Match</c> <c>&header-if-match;</c>
502  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
503  <c>If-None-Match</c> <c>&header-if-none-match;</c>
504  <c>If-Range</c> <c>&header-if-range;</c>
505  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
506  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
507  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
508  <c>Range</c> <c>&header-range;</c>
509  <c>Referer</c> <c><xref target="header.referer"/></c>
510  <c>TE</c> <c>&header-te;</c>
511  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
512</texttable>
513</section>
514
515<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
516  <x:anchor-alias value="Reason-Phrase"/>
517  <x:anchor-alias value="Status-Code"/>
518  <x:anchor-alias value="extension-code"/>
519<t>
520   The Status-Code element is a 3-digit integer result code of the attempt to
521   understand and satisfy the request.
522</t>
523<t>
524   The Reason-Phrase is intended to give a short textual description of the
525   Status-Code and is intended for a human user. The client does not need
526   to examine or display the Reason-Phrase.
527</t>
528<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"/>
529  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
530  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
531</artwork></figure>
532<t>
533   HTTP status codes are extensible. HTTP applications are not required
534   to understand the meaning of all registered status codes, though such
535   understanding is obviously desirable. However, applications &MUST;
536   understand the class of any status code, as indicated by the first
537   digit, and treat any unrecognized response as being equivalent to the
538   x00 status code of that class, with the exception that an
539   unrecognized response &MUST-NOT; be cached. For example, if an
540   unrecognized status code of 431 is received by the client, it can
541   safely assume that there was something wrong with its request and
542   treat the response as if it had received a 400 status code. In such
543   cases, user agents &SHOULD; present to the user the representation enclosed
544   with the response, since that representation is likely to include human-readable
545   information which will explain the unusual status.
546</t>
547
548<section title="Overview of Status Codes" anchor="overview.of.status.codes">
549<t> 
550   The status codes listed below are defined in <xref target="status.codes"/>
551   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
552   The reason phrases listed here are only recommendations &mdash; they can be
553   replaced by local equivalents without affecting the protocol.
554</t>
555<texttable align="left">
556  <ttcol>Status-Code</ttcol>
557  <ttcol>Reason-Phrase</ttcol>
558  <ttcol>Defined in...</ttcol>
559 
560  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
561  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
562
563  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
564  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
565  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
566  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
567  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
568  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
569  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
570
571  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
572  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
573  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
574  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
575  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
576  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
577  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
578
579  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
580  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
581  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
582  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
583  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
584  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
585  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
586  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
587  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
588  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
589  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
590  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
591  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
592  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
593  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
594  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
595  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
596  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
597  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
598
599  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
600  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
601  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
602  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
603  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
604  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
605</texttable>
606<t>
607   Note that this list is not exhaustive &mdash; it does not include
608   extension status codes defined in other specifications.
609</t>
610</section>
611
612<section title="Status Code Registry" anchor="status.code.registry">
613<t>
614  The HTTP Status Code Registry defines the name space for the Status-Code
615  token in the Status-Line of an HTTP response.
616</t>
617<t>
618  Values to be added to this name space are subject to IETF review
619  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
620</t>
621<t>
622  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
623</t>
624
625<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
626<t>
627   When it is necessary to express new semantics for a HTTP response that
628   aren't specific to a single application or media type, and currently defined
629   status codes are inadequate, a new status code can be registered.
630</t>
631<t>
632   HTTP status codes are generic; that is, they are potentially applicable to
633   any resource, not just one particular media type, "type" of resource, or
634   application. As such, it is preferred that new HTTP status codes be
635   registered in a document that isn't specific to a single application, so
636   that this is clear.
637</t>
638<t>
639   Definitions of new HTTP status codes typically explain the request
640   conditions that produce a response containing the status code (e.g.,
641   combinations of request headers and/or method(s)), along with any
642   interactions with response headers (e.g., those that are required, those
643   that modify the semantics of the response).
644</t>
645<t>
646   New HTTP status codes are required to fall under one of the categories
647   defined in <xref target="status.codes"/>. To allow existing parsers to
648   properly handle them, new status codes cannot disallow a response body,
649   although they can mandate a zero-length response body. They can require the
650   presence of one or more particular HTTP response header(s).
651</t>
652<t>
653   Likewise, their definitions can specify that caches are allowed to use
654   heuristics to determine their freshness (see &caching;; by default, it is
655   not allowed), and can define how to determine the resource which they
656   carry a representation for (see <xref
657   target="identifying.response.associated.with.representation"/>; by default,
658   it is anonymous).
659</t>
660</section>
661
662</section>
663
664</section>
665
666<section title="Response Header Fields" anchor="response.header.fields">
667  <x:anchor-alias value="response-header"/>
668<t>
669   The response header fields allow the server to pass additional
670   information about the response which cannot be placed in the Status-Line.
671   These header fields give information about the server and about
672   further access to the target resource (&effective-request-uri;).
673</t>
674<texttable align="left">
675  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
676
677  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
678  <c>Age</c> <c>&header-age;</c>
679  <c>Allow</c> <c><xref target="header.allow"/></c>
680  <c>ETag</c> <c>&header-etag;</c>
681  <c>Location</c> <c><xref target="header.location"/></c>
682  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
683  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
684  <c>Server</c> <c><xref target="header.server"/></c>
685  <c>Vary</c> <c>&header-vary;</c>
686  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
687</texttable>
688</section>
689
690<section title="Representation" anchor="representation">
691<t>
692   Request and Response messages &MAY; transfer a representation if not otherwise
693   restricted by the request method or response status code. A representation
694   consists of metadata (representation header fields) and data (representation
695   body).  When a complete or partial representation is enclosed in an HTTP message,
696   it is referred to as the payload of the message. HTTP representations
697   are defined in &payload;.
698</t>
699<t>
700   A representation body is only present in a message when a message-body is
701   present, as described in &message-body;. The representation body is obtained
702   from the message-body by decoding any Transfer-Encoding that might
703   have been applied to ensure safe and proper transfer of the message.
704</t>
705
706<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
707<t>
708   It is sometimes necessary to determine an identifier for the resource
709   associated with a representation.
710</t>
711<t>
712   An HTTP request representation, when present, is always associated with an
713   anonymous (i.e., unidentified) resource.
714</t>
715<t>
716   In the common case, an HTTP response is a representation of the target
717   resource (see &effective-request-uri;). However, this is not always the
718   case. To determine the URI of the resource a response is associated with,
719   the following rules are used (with the first applicable one being selected):
720</t>
721<t><list style="numbers">
722   <t>If the response status code is 200 or 203 and the request method was GET,
723   the response payload is a representation of the target resource.</t>
724   <t>If the response status code is 204, 206, or 304 and the request method was GET
725   or HEAD, the response payload is a partial representation of the target
726   resource.</t>
727   <t>If the response has a Content-Location header field, and that URI is the same
728   as the effective request URI, the response payload is a representation of the
729   target resource.</t>
730   <t>If the response has a Content-Location header field, and that URI is not the
731   same as the effective request URI, then the response asserts that its
732   payload is a representation of the resource identified by the
733   Content-Location URI. However, such an assertion cannot be trusted unless
734   it can be verified by other means (not defined by HTTP).</t>
735   <t>Otherwise, the response is a representation of an anonymous (i.e.,
736   unidentified) resource.</t>
737</list></t>
738<t>
739  <cref anchor="TODO-req-uri">
740   The comparison function is going to have to be defined somewhere,
741   because we already need to compare URIs for things like cache invalidation.</cref>
742</t>
743</section>
744
745</section>
746
747
748<section title="Method Definitions" anchor="method.definitions">
749<t>
750   The set of common request methods for HTTP/1.1 is defined below. Although
751   this set can be expanded, additional methods cannot be assumed to
752   share the same semantics for separately extended clients and servers.
753</t>
754
755<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
756
757<section title="Safe Methods" anchor="safe.methods">
758<iref item="Safe Methods" primary="true"/>
759<t>
760   Implementors need to be aware that the software represents the user in
761   their interactions over the Internet, and need to allow
762   the user to be aware of any actions they take which might have an
763   unexpected significance to themselves or others.
764</t>
765<t>
766   In particular, the convention has been established that the GET, HEAD,
767   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
768   of taking an action other than retrieval. These request methods ought
769   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
770   This allows user agents to represent other methods, such as POST, PUT
771   and DELETE, in a special way, so that the user is made aware of the
772   fact that a possibly unsafe action is being requested.
773</t>
774<t>
775   Naturally, it is not possible to ensure that the server does not
776   generate side-effects as a result of performing a GET request; in
777   fact, some dynamic resources consider that a feature. The important
778   distinction here is that the user did not request the side-effects,
779   so therefore cannot be held accountable for them.
780</t>
781</section>
782
783<section title="Idempotent Methods" anchor="idempotent.methods">
784<iref item="Idempotent Methods" primary="true"/>
785<t>
786   Request methods can also have the property of "idempotence" in that,
787   aside from error or expiration issues, the intended effect of multiple
788   identical requests is the same as for a single request.
789   PUT, DELETE, and all safe request methods are idempotent.
790   It is important to note that idempotence refers only to changes
791   requested by the client: a server is free to change its state due
792   to multiple requests for the purpose of tracking those requests,
793   versioning of results, etc.
794</t>
795</section>
796</section>
797
798<section title="OPTIONS" anchor="OPTIONS">
799  <rdf:Description>
800    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
801  </rdf:Description>
802  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
803  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
804<t>
805   The OPTIONS method requests information about the
806   communication options available on the request/response chain
807   identified by the effective request URI. This method allows a client to
808   determine the options and/or requirements associated with a resource,
809   or the capabilities of a server, without implying a resource action
810   or initiating a resource retrieval.
811</t>
812<t>
813   Responses to the OPTIONS method are not cacheable.
814</t>
815<t>
816   If the OPTIONS request includes a message-body (as indicated by the
817   presence of Content-Length or Transfer-Encoding), then the media type
818   &MUST; be indicated by a Content-Type field. Although this
819   specification does not define any use for such a body, future
820   extensions to HTTP might use the OPTIONS body to make more detailed
821   queries on the server.
822</t>
823<t>
824   If the request-target is an asterisk ("*"), the OPTIONS request is
825   intended to apply to the server in general rather than to a specific
826   resource. Since a server's communication options typically depend on
827   the resource, the "*" request is only useful as a "ping" or "no-op"
828   type of method; it does nothing beyond allowing the client to test
829   the capabilities of the server. For example, this can be used to test
830   a proxy for HTTP/1.1 compliance (or lack thereof).
831</t>
832<t>
833   If the request-target is not an asterisk, the OPTIONS request applies
834   only to the options that are available when communicating with that
835   resource.
836</t>
837<t>
838   A 200 response &SHOULD; include any header fields that indicate
839   optional features implemented by the server and applicable to that
840   resource (e.g., Allow), possibly including extensions not defined by
841   this specification. The response body, if any, &SHOULD; also include
842   information about the communication options. The format for such a
843   body is not defined by this specification, but might be defined by
844   future extensions to HTTP. Content negotiation &MAY; be used to select
845   the appropriate response format. If no response body is included, the
846   response &MUST; include a Content-Length field with a field-value of
847   "0".
848</t>
849<t>
850   The Max-Forwards header field &MAY; be used to target a
851   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
852   If no Max-Forwards field is present in the request, then the forwarded
853   request &MUST-NOT; include a Max-Forwards field.
854</t>
855</section>
856
857<section title="GET" anchor="GET">
858  <rdf:Description>
859    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
860  </rdf:Description>
861  <iref primary="true" item="GET method" x:for-anchor=""/>
862  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
863<t>
864   The GET method requests transfer of a current representation of
865   the target resource.
866</t>
867<t>   
868   If the target resource is a data-producing process, it is the
869   produced data which shall be returned as the representation in the response and not
870   the source text of the process, unless that text happens to be the output of
871   the process.
872</t>
873<t>
874   The semantics of the GET method change to a "conditional GET" if the
875   request message includes an If-Modified-Since, If-Unmodified-Since,
876   If-Match, If-None-Match, or If-Range header field. A conditional GET
877   requests that the representation be transferred only under the
878   circumstances described by the conditional header field(s). The
879   conditional GET request is intended to reduce unnecessary network
880   usage by allowing cached representations to be refreshed without requiring
881   multiple requests or transferring data already held by the client.
882</t>
883<t>
884   The semantics of the GET method change to a "partial GET" if the
885   request message includes a Range header field. A partial GET requests
886   that only part of the representation be transferred, as described in &header-range;.
887   The partial GET request is intended to reduce unnecessary
888   network usage by allowing partially-retrieved representations to be
889   completed without transferring data already held by the client.
890</t>
891<t>
892   Bodies on GET requests have no defined semantics. Note that sending a body
893   on a GET request might cause some existing implementations to reject the
894   request.
895</t>
896<t>
897   The response to a GET request is cacheable and &MAY; be used to satisfy
898   subsequent GET and HEAD requests (see &caching;).
899</t>
900<t>
901   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
902</t>
903</section>
904
905<section title="HEAD" anchor="HEAD">
906  <rdf:Description>
907    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
908  </rdf:Description>
909  <iref primary="true" item="HEAD method" x:for-anchor=""/>
910  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
911<t>
912   The HEAD method is identical to GET except that the server &MUST-NOT;
913   return a message-body in the response. The metadata contained
914   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
915   to the information sent in response to a GET request. This method can
916   be used for obtaining metadata about the representation implied by the
917   request without transferring the representation body. This method is
918   often used for testing hypertext links for validity, accessibility,
919   and recent modification.
920</t>
921<t>
922   The response to a HEAD request is cacheable and &MAY; be used to satisfy
923   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
924   representation from that resource; if the new field values
925   indicate that the cached representation differs from the current representation (as
926   would be indicated by a change in Content-Length, ETag
927   or Last-Modified), then the cache &MUST; treat the cache entry as
928   stale.
929</t>
930<t>
931   Bodies on HEAD requests have no defined semantics. Note that sending a body
932   on a HEAD request might cause some existing implementations to reject the
933   request.
934</t>
935</section>
936
937<section title="POST" anchor="POST">
938  <iref primary="true" item="POST method" x:for-anchor=""/>
939  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
940<t>
941   The POST method requests that the origin server accept the
942   representation enclosed in the request as data to be processed by the
943   target resource. POST is designed to allow a uniform method to cover the
944   following functions:
945  <list style="symbols">
946    <t>
947      Annotation of existing resources;
948    </t>
949    <t>
950        Posting a message to a bulletin board, newsgroup, mailing list,
951        or similar group of articles;
952    </t>
953    <t>
954        Providing a block of data, such as the result of submitting a
955        form, to a data-handling process;
956    </t>
957    <t>
958        Extending a database through an append operation.
959    </t>
960  </list>
961</t>
962<t>
963   The actual function performed by the POST method is determined by the
964   server and is usually dependent on the effective request URI.
965</t>
966<t>
967   The action performed by the POST method might not result in a
968   resource that can be identified by a URI. In this case, either 200
969   (OK) or 204 (No Content) is the appropriate response status code,
970   depending on whether or not the response includes a representation that
971   describes the result.
972</t>
973<t>
974   If a resource has been created on the origin server, the response
975   &SHOULD; be 201 (Created) and contain a representation which describes the
976   status of the request and refers to the new resource, and a Location
977   header field (see <xref target="header.location"/>).
978</t>
979<t>
980   Responses to POST requests are only cacheable when they
981   include explicit freshness information (see &p6-explicit;). A
982   cached POST response with a Content-Location header field
983   (see &header-content-location;) whose value is the effective
984   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
985</t>
986<t>
987   Note that POST caching is not widely implemented.
988   However, the 303 (See Other) response can be used to direct the
989   user agent to retrieve a cacheable resource.
990</t>
991</section>
992
993<section title="PUT" anchor="PUT">
994  <iref primary="true" item="PUT method" x:for-anchor=""/>
995  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
996<t>
997   The PUT method requests that the state of the target resource
998   be created or replaced with the state defined by the representation
999   enclosed in the request message payload.  A successful PUT of a given
1000   representation would suggest that a subsequent GET on that same target
1001   resource will result in an equivalent representation being returned in
1002   a 200 (OK) response.  However, there is no guarantee that such a state
1003   change will be observable, since the target resource might be acted
1004   upon by other user agents in parallel, or might be subject to dynamic
1005   processing by the origin server, before any subsequent GET is received.
1006   A successful response only implies that the user agent's intent was
1007   achieved at the time of its processing by the origin server.
1008</t>
1009<t>   
1010   If the target resource does not have a current representation and
1011   the PUT successfully creates one, then the origin server &MUST; inform
1012   the user agent by sending a 201 (Created) response.  If the target
1013   resource does have a current representation and that representation is
1014   successfully modified in accordance with the state of the enclosed
1015   representation, then either a 200 (OK) or 204 (No Content) response
1016   &SHOULD; be sent to indicate successful completion of the request.
1017</t>
1018<t>
1019   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1020   as part of the resource state).
1021</t>
1022<t>
1023   An origin server &SHOULD; verify that the PUT representation is
1024   consistent with any constraints which the server has for the target
1025   resource that cannot or will not be changed by the PUT.  This is
1026   particularly important when the origin server uses internal
1027   configuration information related to the URI in order to set the
1028   values for representation metadata on GET responses.  When a PUT
1029   representation is inconsistent with the target resource, the origin
1030   server &SHOULD; either make them consistent, by transforming the
1031   representation or changing the resource configuration, or respond
1032   with an appropriate error message containing sufficient information
1033   to explain why the representation is unsuitable.  The 409 (Conflict)
1034   or 415 (Unsupported Media Type) status codes are suggested, with the
1035   latter being specific to constraints on Content-Type values.
1036</t>
1037<t>
1038   For example, if the target resource is configured to always have a
1039   Content-Type of "text/html" and the representation being PUT has a
1040   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1041   (a) reconfigure the target resource to reflect the new media type;
1042   (b) transform the PUT representation to a format consistent with that
1043   of the resource before saving it as the new resource state; or,
1044   (c) reject the request with a 415 response indicating that the target
1045   resource is limited to "text/html", perhaps including a link to a
1046   different resource that would be a suitable target for the new
1047   representation.
1048</t>
1049<t>
1050   HTTP does not define exactly how a PUT method affects the state
1051   of an origin server beyond what can be expressed by the intent of
1052   the user agent request and the semantics of the origin server response.
1053   It does not define what a resource might be, in any sense of that
1054   word, beyond the interface provided via HTTP.  It does not define
1055   how resource state is "stored", nor how such storage might change
1056   as a result of a change in resource state, nor how the origin server
1057   translates resource state into representations.  Generally speaking,
1058   all implementation details behind the resource interface are
1059   intentionally hidden by the server.
1060</t>
1061<t>
1062   The fundamental difference between the POST and PUT methods is
1063   highlighted by the different intent for the target resource.
1064   The target resource in a POST request is intended to handle the
1065   enclosed representation as a data-accepting process, such as for
1066   a gateway to some other protocol or a document that accepts annotations.
1067   In contrast, the target resource in a PUT request is intended to
1068   take the enclosed representation as a new or replacement value.
1069   Hence, the intent of PUT is idempotent and visible to intermediaries,
1070   even though the exact effect is only known by the origin server.
1071</t>
1072<t>
1073   Proper interpretation of a PUT request presumes that the user agent
1074   knows what target resource is desired.  A service that is intended
1075   to select a proper URI on behalf of the client, after receiving
1076   a state-changing request, &SHOULD; be implemented using the POST
1077   method rather than PUT.  If the origin server will not make the
1078   requested PUT state change to the target resource and instead
1079   wishes to have it applied to a different resource, such as when the
1080   resource has been moved to a different URI, then the origin server
1081   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1082   then make its own decision regarding whether or not to redirect the
1083   request.
1084</t>
1085<t>
1086   A PUT request applied to the target resource &MAY; have side-effects
1087   on other resources.  For example, an article might have a URI for
1088   identifying "the current version" (a resource) which is separate
1089   from the URIs identifying each particular version (different
1090   resources that at one point shared the same state as the current version
1091   resource).  A successful PUT request on "the current version" URI might
1092   therefore create a new version resource in addition to changing the
1093   state of the target resource, and might also cause links to be added
1094   between the related resources.
1095</t>
1096<t>
1097   An origin server &SHOULD; reject any PUT request that contains a
1098   Content-Range header field, since it might be misinterpreted as
1099   partial content (or might be partial content that is being mistakenly
1100   PUT as a full representation).  Partial content updates are
1101   possible by targeting a separately identified resource with state
1102   that overlaps a portion of the larger resource, or by using a
1103   different method that has been specifically defined for partial
1104   updates (for example, the PATCH method defined in
1105   <xref target="RFC5789"/>).
1106</t>
1107<t>
1108   Responses to the PUT method are not cacheable. If a PUT request passes
1109   through a cache that has one or more stored responses for the effective
1110   request URI, those stored responses will be invalidated (see
1111   &p6-invalid;).
1112</t>
1113</section>
1114
1115<section title="DELETE" anchor="DELETE">
1116  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1117  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1118<t>
1119   The DELETE method requests that the origin server delete the target
1120   resource. This method &MAY; be overridden by
1121   human intervention (or other means) on the origin server. The client cannot
1122   be guaranteed that the operation has been carried out, even if the
1123   status code returned from the origin server indicates that the action
1124   has been completed successfully. However, the server &SHOULD-NOT; 
1125   indicate success unless, at the time the response is given, it
1126   intends to delete the resource or move it to an inaccessible
1127   location.
1128</t>
1129<t>
1130   A successful response &SHOULD; be 200 (OK) if the response includes an
1131   representation describing the status, 202 (Accepted) if the action has not
1132   yet been enacted, or 204 (No Content) if the action has been enacted
1133   but the response does not include a representation.
1134</t>
1135<t>
1136   Bodies on DELETE requests have no defined semantics. Note that sending a body
1137   on a DELETE request might cause some existing implementations to reject the
1138   request.
1139</t>
1140<t>
1141   Responses to the DELETE method are not cacheable. If a DELETE request
1142   passes through a cache that has one or more stored responses for the
1143   effective request URI, those stored responses will be invalidated (see
1144   &p6-invalid;).
1145</t>
1146</section>
1147
1148<section title="TRACE" anchor="TRACE">
1149  <rdf:Description>
1150    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1151  </rdf:Description>
1152  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1153  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1154<t>
1155   The TRACE method requests a remote, application-layer loop-back
1156   of the request message. The final recipient of the request
1157   &SHOULD; reflect the message received back to the client as the
1158   message-body of a 200 (OK) response. The final recipient is either the
1159   origin server or the first proxy to receive a Max-Forwards
1160   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1161   A TRACE request &MUST-NOT; include a message-body.
1162</t>
1163<t>
1164   TRACE allows the client to see what is being received at the other
1165   end of the request chain and use that data for testing or diagnostic
1166   information. The value of the Via header field (&header-via;) is of
1167   particular interest, since it acts as a trace of the request chain.
1168   Use of the Max-Forwards header field allows the client to limit the
1169   length of the request chain, which is useful for testing a chain of
1170   proxies forwarding messages in an infinite loop.
1171</t>
1172<t>
1173   If the request is valid, the response &SHOULD; have a Content-Type of
1174   "message/http" (see &media-type-message-http;) and contain a message-body
1175   that encloses a copy of the entire request message.
1176   Responses to the TRACE method are not cacheable.
1177</t>
1178</section>
1179
1180<section title="CONNECT" anchor="CONNECT">
1181  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1182  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1183<t>
1184   The CONNECT method requests that the proxy establish a tunnel
1185   to the request-target and then restrict its behavior to blind
1186   forwarding of packets until the connection is closed.
1187</t>
1188<t>
1189   When using CONNECT, the request-target &MUST; use the authority form
1190   (&request-target;); i.e., the request-target consists of only the
1191   host name and port number of the tunnel destination, separated by a colon.
1192   For example,
1193</t>
1194<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1195CONNECT server.example.com:80 HTTP/1.1
1196Host: server.example.com:80
1197
1198</artwork></figure>
1199<t>
1200   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1201   except end-to-end protocol Upgrade requests, since the
1202   tunnel must be established first.
1203</t>
1204<t>
1205   For example, proxy authentication might be used to establish the
1206   authority to create a tunnel:
1207</t>
1208<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1209CONNECT server.example.com:80 HTTP/1.1
1210Host: server.example.com:80
1211Proxy-Authorization: basic aGVsbG86d29ybGQ=
1212
1213</artwork></figure>
1214<t>
1215   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1216   on a CONNECT request might cause some existing implementations to reject the
1217   request.
1218</t>
1219<t>
1220   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1221   sent immediately after the blank line. The usual caveats also apply:
1222   data may be discarded if the eventual response is negative, and the
1223   connection may be reset with no response if more than one TCP segment
1224   is outstanding.
1225</t>
1226
1227<section title="Establishing a Tunnel with CONNECT">
1228<t>
1229   Any successful (2xx) response to a CONNECT request indicates that the
1230   proxy has established a connection to the requested host and port,
1231   and has switched to tunneling the current connection to that server
1232   connection.
1233</t>
1234<t>
1235   It may be the case that the proxy itself can only reach the requested
1236   origin server through another proxy.  In this case, the first proxy
1237   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1238   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1239   unless it has either a direct or tunnel connection established to the
1240   authority.
1241</t>
1242<t>
1243   An origin server which receives a CONNECT request for itself &MAY;
1244   respond with a 2xx status code to indicate that a connection is
1245   established.
1246</t>
1247<t>
1248   If at any point either one of the peers gets disconnected, any
1249   outstanding data that came from that peer will be passed to the other
1250   one, and after that also the other connection will be terminated by
1251   the proxy. If there is outstanding data to that peer undelivered,
1252   that data will be discarded.
1253</t>
1254
1255</section>
1256</section>
1257</section>
1258
1259
1260<section title="Status Code Definitions" anchor="status.codes">
1261<t>
1262   Each Status-Code is described below, including any metadata required
1263   in the response.
1264</t>
1265
1266<section title="Informational 1xx" anchor="status.1xx">
1267<t>
1268   This class of status code indicates a provisional response,
1269   consisting only of the Status-Line and optional header fields, and is
1270   terminated by an empty line. There are no required header fields for this
1271   class of status code. Since HTTP/1.0 did not define any 1xx status
1272   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1273   except under experimental conditions.
1274</t>
1275<t>
1276   A client &MUST; be prepared to accept one or more 1xx status responses
1277   prior to a regular response, even if the client does not expect a 100
1278   (Continue) status message. Unexpected 1xx status responses &MAY; be
1279   ignored by a user agent.
1280</t>
1281<t>
1282   Proxies &MUST; forward 1xx responses, unless the connection between the
1283   proxy and its client has been closed, or unless the proxy itself
1284   requested the generation of the 1xx response. (For example, if a
1285   proxy adds a "Expect: 100-continue" field when it forwards a request,
1286   then it need not forward the corresponding 100 (Continue)
1287   response(s).)
1288</t>
1289
1290<section title="100 Continue" anchor="status.100">
1291  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1292  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1293<t>
1294   The client &SHOULD; continue with its request. This interim response is
1295   used to inform the client that the initial part of the request has
1296   been received and has not yet been rejected by the server. The client
1297   &SHOULD; continue by sending the remainder of the request or, if the
1298   request has already been completed, ignore this response. The server
1299   &MUST; send a final response after the request has been completed. See
1300   &use100; for detailed discussion of the use and handling of this
1301   status code.
1302</t>
1303</section>
1304
1305<section title="101 Switching Protocols" anchor="status.101">
1306  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1307  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1308<t>
1309   The server understands and is willing to comply with the client's
1310   request, via the Upgrade message header field (&header-upgrade;), for a
1311   change in the application protocol being used on this connection. The
1312   server will switch protocols to those defined by the response's
1313   Upgrade header field immediately after the empty line which
1314   terminates the 101 response.
1315</t>
1316<t>
1317   The protocol &SHOULD; be switched only when it is advantageous to do
1318   so. For example, switching to a newer version of HTTP is advantageous
1319   over older versions, and switching to a real-time, synchronous
1320   protocol might be advantageous when delivering resources that use
1321   such features.
1322</t>
1323</section>
1324</section>
1325
1326<section title="Successful 2xx" anchor="status.2xx">
1327<t>
1328   This class of status code indicates that the client's request was
1329   successfully received, understood, and accepted.
1330</t>
1331
1332<section title="200 OK" anchor="status.200">
1333  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1334  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1335<t>
1336   The request has succeeded. The payload returned with the response
1337   is dependent on the method used in the request, for example:
1338  <list style="hanging">
1339    <t hangText="GET">
1340      a representation of the target resource is sent in the response;
1341    </t>
1342    <t hangText="HEAD">
1343      the same representation as GET, except without the message-body;
1344    </t>
1345    <t hangText="POST">
1346      a representation describing or containing the result of the action;
1347    </t>
1348    <t hangText="TRACE">
1349      a representation containing the request message as received by the
1350      end server.
1351    </t>
1352  </list>
1353</t>
1354<t>
1355   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1356   freshness for 200 responses.
1357</t>
1358</section>
1359
1360<section title="201 Created" anchor="status.201">
1361  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1362  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1363<t>
1364   The request has been fulfilled and has resulted in a new resource being
1365   created. The newly created resource can be referenced by the URI(s)
1366   returned in the payload of the response, with the most specific URI
1367   for the resource given by a Location header field. The response
1368   &SHOULD; include a payload containing a list of resource
1369   characteristics and location(s) from which the user or user agent can
1370   choose the one most appropriate. The payload format is specified by
1371   the media type given in the Content-Type header field. The origin
1372   server &MUST; create the resource before returning the 201 status code.
1373   If the action cannot be carried out immediately, the server &SHOULD;
1374   respond with 202 (Accepted) response instead.
1375</t>
1376<t>
1377   A 201 response &MAY; contain an ETag response header field indicating
1378   the current value of the entity-tag for the representation of the resource
1379   just created (see &header-etag;).
1380</t>
1381</section>
1382
1383<section title="202 Accepted" anchor="status.202">
1384  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1385  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1386<t>
1387   The request has been accepted for processing, but the processing has
1388   not been completed.  The request might or might not eventually be
1389   acted upon, as it might be disallowed when processing actually takes
1390   place. There is no facility for re-sending a status code from an
1391   asynchronous operation such as this.
1392</t>
1393<t>
1394   The 202 response is intentionally non-committal. Its purpose is to
1395   allow a server to accept a request for some other process (perhaps a
1396   batch-oriented process that is only run once per day) without
1397   requiring that the user agent's connection to the server persist
1398   until the process is completed. The representation returned with this
1399   response &SHOULD; include an indication of the request's current status
1400   and either a pointer to a status monitor or some estimate of when the
1401   user can expect the request to be fulfilled.
1402</t>
1403</section>
1404
1405<section title="203 Non-Authoritative Information" anchor="status.203">
1406  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1407  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1408<t>
1409   The representation in the response has been transformed or otherwise
1410   modified by a transforming proxy (&intermediaries;).  Note that the
1411   behaviour of transforming intermediaries is controlled by the no-transform
1412   Cache-Control directive (&header-cache-control;).
1413</t>
1414<t>
1415   This status code is only appropriate when the response status code would
1416   have been 200 (OK) otherwise. When the status code before transformation
1417   would have been different, the 214 Transformation Applied warn-code
1418   (&header-warning;) is appropriate.
1419</t>
1420<t>
1421   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1422   freshness for 203 responses.
1423</t>
1424</section>
1425
1426<section title="204 No Content" anchor="status.204">
1427  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1428  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1429<t>
1430   The 204 (No Content) status code indicates that the server has
1431   successfully fulfilled the request and that there is no additional
1432   content to return in the response payload body.  Metadata in the
1433   response header fields refer to the target resource and its current
1434   representation after the requested action.
1435</t>
1436<t>
1437   For example, if a 204 status code is received in response to a PUT
1438   request and the response contains an ETag header field, then the PUT
1439   was successful and the ETag field-value contains the entity-tag for
1440   the new representation of that target resource.
1441</t>
1442<t>
1443   The 204 response allows a server to indicate that the action has been
1444   successfully applied to the target resource while implying that the
1445   user agent &SHOULD-NOT; traverse away from its current "document view"
1446   (if any).  The server assumes that the user agent will provide some
1447   indication of the success to its user, in accord with its own interface,
1448   and apply any new or updated metadata in the response to the active
1449   representation.
1450</t>
1451<t>
1452   For example, a 204 status code is commonly used with document editing
1453   interfaces corresponding to a "save" action, such that the document
1454   being saved remains available to the user for editing. It is also
1455   frequently used with interfaces that expect automated data transfers
1456   to be prevalent, such as within distributed version control systems.
1457</t>
1458<t>
1459   The 204 response &MUST-NOT; include a message-body, and thus is always
1460   terminated by the first empty line after the header fields.
1461</t>
1462</section>
1463
1464<section title="205 Reset Content" anchor="status.205">
1465  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1466  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1467<t>
1468   The server has fulfilled the request and the user agent &SHOULD; reset
1469   the document view which caused the request to be sent. This response
1470   is primarily intended to allow input for actions to take place via
1471   user input, followed by a clearing of the form in which the input is
1472   given so that the user can easily initiate another input action.
1473</t>
1474<t>   
1475   The message-body included with the response &MUST; be empty. Note that
1476   receivers still need to parse the response according to the algorithm defined
1477   in &message-body;.
1478</t>
1479</section>
1480
1481<section title="206 Partial Content" anchor="status.206">
1482  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1483  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1484  <rdf:Description>
1485    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1486  </rdf:Description>
1487<t>
1488   The server has fulfilled the partial GET request for the resource
1489   and the enclosed payload is a partial representation as defined in &status-206;.
1490</t>
1491<t>
1492   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1493   freshness for 206 responses.
1494</t>
1495</section>
1496</section>
1497
1498<section title="Redirection 3xx" anchor="status.3xx">
1499<t>
1500   This class of status code indicates that further action needs to be
1501   taken by the user agent in order to fulfill the request.  The action
1502   required &MAY; be carried out by the user agent without interaction
1503   with the user if and only if the method used in the second request is
1504   known to be "safe", as defined in <xref target="safe.methods"/>.
1505   A client &SHOULD; detect infinite redirection loops, since such loops
1506   generate network traffic for each redirection.
1507</t>
1508<x:note>
1509  <t>
1510    <x:h>Note:</x:h> An earlier version of this specification recommended a
1511    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1512    Content developers need to be aware that some clients might
1513    implement such a fixed limitation.
1514  </t>
1515</x:note>
1516
1517<section title="300 Multiple Choices" anchor="status.300">
1518  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1519  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1520<t>
1521   The target resource has more than one
1522   representation, each with its own specific location, and agent-driven
1523   negotiation information (&content-negotiation;) is being provided so that
1524   the user (or user agent) can select a preferred representation by
1525   redirecting its request to that location.
1526</t>
1527<t>
1528   Unless it was a HEAD request, the response &SHOULD; include a representation
1529   containing a list of representation metadata and location(s) from
1530   which the user or user agent can choose the one most appropriate. The
1531   data format is specified by the media type given in the Content-Type
1532   header field. Depending upon the format and the capabilities of
1533   the user agent, selection of the most appropriate choice &MAY; be
1534   performed automatically. However, this specification does not define
1535   any standard for such automatic selection.
1536</t>
1537<t>
1538   If the server has a preferred choice of representation, it &SHOULD;
1539   include the specific URI for that representation in the Location
1540   field; user agents &MAY; use the Location field value for automatic
1541   redirection.
1542</t>
1543<t>
1544   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1545   freshness for 300 responses.
1546</t>
1547
1548</section>
1549
1550<section title="301 Moved Permanently" anchor="status.301">
1551  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1552  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1553<t>
1554   The target resource has been assigned a new permanent URI and any
1555   future references to this resource &SHOULD; use one of the returned
1556   URIs.  Clients with link editing capabilities ought to automatically
1557   re-link references to the effective request URI to one or more of the new
1558   references returned by the server, where possible.
1559</t>
1560<t>
1561   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1562   freshness for 301 responses.
1563</t>
1564<t>
1565   The new permanent URI &SHOULD; be given by the Location field in the
1566   response. Unless the request method was HEAD, the representation of the
1567   response &SHOULD; contain a short hypertext note with a hyperlink to
1568   the new URI(s).
1569</t>
1570<t>
1571   If the 301 status code is received in response to a request method
1572   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1573   then the request &MAY; be automatically redirected by the user agent without
1574   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1575   request unless it can be confirmed by the user, since this might
1576   change the conditions under which the request was issued.
1577</t>
1578<x:note>
1579  <t>
1580    <x:h>Note:</x:h> When automatically redirecting a POST request after
1581    receiving a 301 status code, some existing HTTP/1.0 user agents
1582    will erroneously change it into a GET request.
1583  </t>
1584</x:note>
1585</section>
1586
1587<section title="302 Found" anchor="status.302">
1588  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1589  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1590<t>
1591   The target resource resides temporarily under a different URI.
1592   Since the redirection might be altered on occasion, the client &SHOULD;
1593   continue to use the effective request URI for future requests.
1594</t>
1595<t>
1596   The temporary URI &SHOULD; be given by the Location field in the
1597   response. Unless the request method was HEAD, the representation of the
1598   response &SHOULD; contain a short hypertext note with a hyperlink to
1599   the new URI(s).
1600</t>
1601<t>
1602   If the 302 status code is received in response to a request method
1603   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1604   then the request &MAY; be automatically redirected by the user agent without
1605   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1606   request unless it can be confirmed by the user, since this might
1607   change the conditions under which the request was issued.
1608</t>
1609<x:note>
1610  <t>
1611    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1612    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1613    specify that the client is not allowed to change the method on the
1614    redirected request.  However, most existing user agent implementations
1615    treat 302 as if it were a 303 response, performing a GET on the Location
1616    field-value regardless of the original request method. Therefore, a
1617    previous version of this specification
1618    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1619    status codes
1620    <xref target="status.303" format="none">303</xref> and
1621    <xref target="status.307" format="none">307</xref> for servers that wish
1622    to make unambiguously clear which kind of reaction is expected of the
1623    client.
1624  </t>
1625</x:note>
1626</section>
1627
1628<section title="303 See Other" anchor="status.303">
1629  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1630  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1631<t>
1632   The server directs the user agent to a different resource, indicated
1633   by a URI in the Location header field, that provides an indirect
1634   response to the original request.  The user agent &MAY; perform a GET
1635   request on the URI in the Location field in order to obtain a
1636   representation corresponding to the response, be redirected again,
1637   or end with an error status.  The Location URI is not a substitute
1638   reference for the effective request URI.
1639</t>
1640<t>
1641   The 303 status code is generally applicable to any HTTP method.  It is
1642   primarily used to allow the output of a POST action to redirect
1643   the user agent to a selected resource, since doing so provides the
1644   information corresponding to the POST response in a form that
1645   can be separately identified, bookmarked, and cached independent
1646   of the original request.
1647</t>
1648<t>
1649   A 303 response to a GET request indicates that the requested
1650   resource does not have a representation of its own that can be
1651   transferred by the server over HTTP.  The Location URI indicates a
1652   resource that is descriptive of the target resource, such that the
1653   follow-on representation might be useful to recipients without
1654   implying that it adequately represents the target resource.
1655   Note that answers to the questions of what can be represented, what
1656   representations are adequate, and what might be a useful description
1657   are outside the scope of HTTP and thus entirely determined by the
1658   URI owner(s).
1659</t>
1660<t>
1661   Except for responses to a HEAD request, the representation of a 303
1662   response &SHOULD; contain a short hypertext note with a hyperlink
1663   to the Location URI.
1664</t>
1665</section>
1666
1667<section title="304 Not Modified" anchor="status.304">
1668  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1669  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1670  <rdf:Description>
1671    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1672  </rdf:Description>
1673<t>
1674   The response to the request has not been modified since the conditions
1675   indicated by the client's conditional GET request, as defined in &status-304;.
1676</t>
1677</section>
1678
1679<section title="305 Use Proxy" anchor="status.305">
1680  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1682<t>
1683   The 305 status code was defined in a previous version of this specification
1684   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1685</t>
1686</section>
1687
1688<section title="306 (Unused)" anchor="status.306">
1689  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1690  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1691<t>
1692   The 306 status code was used in a previous version of the
1693   specification, is no longer used, and the code is reserved.
1694</t>
1695</section>
1696
1697<section title="307 Temporary Redirect" anchor="status.307">
1698  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1699  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1700<t>
1701   The target resource resides temporarily under a different URI.
1702   Since the redirection can change over time, the client &SHOULD;
1703   continue to use the effective request URI for future requests.
1704</t>
1705<t>
1706   The temporary URI &SHOULD; be given by the Location field in the
1707   response. Unless the request method was HEAD, the representation of the
1708   response &SHOULD; contain a short hypertext note with a hyperlink to
1709   the new URI(s), since many pre-HTTP/1.1 user agents do not
1710   understand the 307 status code. Therefore, the note &SHOULD; contain the
1711   information necessary for a user to repeat the original request on
1712   the new URI.
1713</t>
1714<t>
1715   If the 307 status code is received in response to a request method
1716   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1717   then the request &MAY; be automatically redirected by the user agent without
1718   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1719   request unless it can be confirmed by the user, since this might
1720   change the conditions under which the request was issued.
1721</t>
1722</section>
1723</section>
1724
1725<section title="Client Error 4xx" anchor="status.4xx">
1726<t>
1727   The 4xx class of status code is intended for cases in which the
1728   client seems to have erred. Except when responding to a HEAD request,
1729   the server &SHOULD; include a representation containing an explanation of the
1730   error situation, and whether it is a temporary or permanent
1731   condition. These status codes are applicable to any request method.
1732   User agents &SHOULD; display any included representation to the user.
1733</t>
1734<t>
1735   If the client is sending data, a server implementation using TCP
1736   &SHOULD; be careful to ensure that the client acknowledges receipt of
1737   the packet(s) containing the response, before the server closes the
1738   input connection. If the client continues sending data to the server
1739   after the close, the server's TCP stack will send a reset packet to
1740   the client, which might erase the client's unacknowledged input buffers
1741   before they can be read and interpreted by the HTTP application.
1742</t>
1743
1744<section title="400 Bad Request" anchor="status.400">
1745  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1746  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1747<t>
1748   The server cannot or will not process the request, due to a client error (e.g.,
1749   malformed syntax).</t>
1750</section>
1751
1752<section title="401 Unauthorized" anchor="status.401">
1753  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1754  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1755  <rdf:Description>
1756    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1757  </rdf:Description>
1758<t>
1759   The request requires user authentication (see &status-401;).
1760</t>
1761</section>
1762
1763<section title="402 Payment Required" anchor="status.402">
1764  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1765  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1766<t>
1767   This code is reserved for future use.
1768</t>
1769</section>
1770
1771<section title="403 Forbidden" anchor="status.403">
1772  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1773  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1774<t>
1775   The server understood the request, but refuses to authorize it. Providing
1776   different user authentication credentials might be successful, but any
1777   credentials that were provided in the request are insufficient. The request
1778   &SHOULD-NOT; be repeated with the same credentials.
1779</t>
1780<t>
1781   If the request method was not HEAD and the server wishes to make
1782   public why the request has not been fulfilled, it &SHOULD; describe the
1783   reason for the refusal in the representation.  If the server does not wish to
1784   make this information available to the client, the status code 404
1785   (Not Found) &MAY; be used instead.
1786</t>
1787</section>
1788
1789<section title="404 Not Found" anchor="status.404">
1790  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1791  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1792<t>
1793   The server has not found anything matching the effective request URI. No
1794   indication is given of whether the condition is temporary or
1795   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1796   knows, through some internally configurable mechanism, that an old
1797   resource is permanently unavailable and has no forwarding address.
1798   This status code is commonly used when the server does not wish to
1799   reveal exactly why the request has been refused, or when no other
1800   response is applicable.
1801</t>
1802</section>
1803
1804<section title="405 Method Not Allowed" anchor="status.405">
1805  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1806  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1807<t>
1808   The method specified in the Request-Line is not allowed for the target
1809   resource. The response &MUST; include an Allow header field containing a
1810   list of valid methods for the requested resource.
1811</t>
1812</section>
1813
1814<section title="406 Not Acceptable" anchor="status.406">
1815  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1816  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1817<t>
1818   The resource identified by the request is only capable of generating
1819   response representations which have content characteristics not acceptable
1820   according to the Accept and Accept-* header fields sent in the request
1821   (see &p3-header-fields;).
1822</t>
1823<t>
1824   Unless it was a HEAD request, the response &SHOULD; include a representation
1825   containing a list of available representation characteristics and location(s)
1826   from which the user or user agent can choose the one most
1827   appropriate. The data format is specified by the media type given
1828   in the Content-Type header field. Depending upon the format and the
1829   capabilities of the user agent, selection of the most appropriate
1830   choice &MAY; be performed automatically. However, this specification
1831   does not define any standard for such automatic selection.
1832</t>
1833<x:note>
1834  <t>
1835    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1836    not acceptable according to the accept header fields sent in the
1837    request. In some cases, this might even be preferable to sending a
1838    406 response. User agents are encouraged to inspect the header fields of
1839    an incoming response to determine if it is acceptable.
1840  </t>
1841</x:note>
1842<t>
1843   If the response could be unacceptable, a user agent &SHOULD;
1844   temporarily stop receipt of more data and query the user for a
1845   decision on further actions.
1846</t>
1847</section>
1848
1849<section title="407 Proxy Authentication Required" anchor="status.407">
1850  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1851  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1852<t>
1853   This code is similar to 401 (Unauthorized), but indicates that the
1854   client must first authenticate itself with the proxy (see &status-407;).
1855</t>
1856</section>
1857
1858<section title="408 Request Timeout" anchor="status.408">
1859  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1860  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1861<t>
1862   The client did not produce a request within the time that the server
1863   was prepared to wait. The client &MAY; repeat the request without
1864   modifications at any later time.
1865</t>
1866</section>
1867
1868<section title="409 Conflict" anchor="status.409">
1869  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1870  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1871<t>
1872   The request could not be completed due to a conflict with the current
1873   state of the resource. This code is only allowed in situations where
1874   it is expected that the user might be able to resolve the conflict
1875   and resubmit the request. The response body &SHOULD; include enough
1876   information for the user to recognize the source of the conflict.
1877   Ideally, the response representation would include enough information for the
1878   user or user agent to fix the problem; however, that might not be
1879   possible and is not required.
1880</t>
1881<t>
1882   Conflicts are most likely to occur in response to a PUT request. For
1883   example, if versioning were being used and the representation being PUT
1884   included changes to a resource which conflict with those made by an
1885   earlier (third-party) request, the server might use the 409 response
1886   to indicate that it can't complete the request. In this case, the
1887   response representation would likely contain a list of the differences
1888   between the two versions in a format defined by the response
1889   Content-Type.
1890</t>
1891</section>
1892
1893<section title="410 Gone" anchor="status.410">
1894  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1895  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1896<t>
1897   The target resource is no longer available at the server and no
1898   forwarding address is known. This condition is expected to be
1899   considered permanent. Clients with link editing capabilities &SHOULD;
1900   delete references to the effective request URI after user approval. If the
1901   server does not know, or has no facility to determine, whether or not
1902   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1903   used instead.
1904</t>
1905<t>
1906   The 410 response is primarily intended to assist the task of web
1907   maintenance by notifying the recipient that the resource is
1908   intentionally unavailable and that the server owners desire that
1909   remote links to that resource be removed. Such an event is common for
1910   limited-time, promotional services and for resources belonging to
1911   individuals no longer working at the server's site. It is not
1912   necessary to mark all permanently unavailable resources as "gone" or
1913   to keep the mark for any length of time &mdash; that is left to the
1914   discretion of the server owner.
1915</t>
1916<t>
1917   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1918   for 410 responses.
1919</t>
1920
1921</section>
1922
1923<section title="411 Length Required" anchor="status.411">
1924  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1925  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1926<t>
1927   The server refuses to accept the request without a defined Content-Length.
1928   The client &MAY; repeat the request if it adds a valid
1929   Content-Length header field containing the length of the message-body
1930   in the request message.
1931</t>
1932</section>
1933
1934<section title="412 Precondition Failed" anchor="status.412">
1935  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1936  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1937  <rdf:Description>
1938    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1939  </rdf:Description>
1940<t>
1941   The precondition given in one or more of the header fields
1942   evaluated to false when it was tested on the server, as defined in
1943   &status-412;.
1944</t>
1945</section>
1946
1947<section title="413 Request Representation Too Large" anchor="status.413">
1948  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
1950<t>
1951   The server is refusing to process a request because the request
1952   representation is larger than the server is willing or able to process. The
1953   server &MAY; close the connection to prevent the client from continuing
1954   the request.
1955</t>
1956<t>
1957   If the condition is temporary, the server &SHOULD; include a Retry-After
1958   header field to indicate that it is temporary and after what
1959   time the client &MAY; try again.
1960</t>
1961</section>
1962
1963<section title="414 URI Too Long" anchor="status.414">
1964  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1965  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1966<t>
1967   The server is refusing to service the request because the effective request URI
1968   is longer than the server is willing to interpret. This rare
1969   condition is only likely to occur when a client has improperly
1970   converted a POST request to a GET request with long query
1971   information, when the client has descended into a URI "black hole" of
1972   redirection (e.g., a redirected URI prefix that points to a suffix of
1973   itself), or when the server is under attack by a client attempting to
1974   exploit security holes present in some servers using fixed-length
1975   buffers for reading or manipulating the effective request URI.
1976</t>
1977</section>
1978
1979<section title="415 Unsupported Media Type" anchor="status.415">
1980  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1981  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1982<t>
1983   The server is refusing to service the request because the request
1984   payload is in a format not supported by this request method on the
1985   target resource.
1986</t>
1987</section>
1988
1989<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1990  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1991  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1992  <rdf:Description>
1993    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1994  </rdf:Description>
1995<t>
1996   The request included a Range header field (&header-range;) and none of
1997   the range-specifier values in this field overlap the current extent
1998   of the selected resource. See &status-416;.
1999</t>
2000</section>
2001
2002<section title="417 Expectation Failed" anchor="status.417">
2003  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2004  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2005<t>
2006   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2007   could not be met by this server, or, if the server is a proxy,
2008   the server has unambiguous evidence that the request could not be met
2009   by the next-hop server.
2010</t>
2011</section>
2012
2013<section title="426 Upgrade Required" anchor="status.426">
2014  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2015  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2016<t>
2017   The request can not be completed without a prior protocol upgrade. This
2018   response &MUST; include an Upgrade header field (&header-upgrade;)
2019   specifying the required protocols.
2020</t>
2021<figure>
2022<preamble>Example:</preamble>
2023<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2024HTTP/1.1 426 Upgrade Required
2025Upgrade: HTTP/2.0
2026Connection: Upgrade
2027
2028</artwork></figure>
2029<t>
2030   The server &SHOULD; include a message body in the 426 response which
2031   indicates in human readable form the reason for the error and describes any
2032   alternative courses which may be available to the user.
2033</t>
2034</section>
2035</section>
2036
2037<section title="Server Error 5xx" anchor="status.5xx">
2038<t>
2039   Response status codes beginning with the digit "5" indicate cases in
2040   which the server is aware that it has erred or is incapable of
2041   performing the request. Except when responding to a HEAD request, the
2042   server &SHOULD; include a representation containing an explanation of the
2043   error situation, and whether it is a temporary or permanent
2044   condition. User agents &SHOULD; display any included representation to the
2045   user. These response codes are applicable to any request method.
2046</t>
2047
2048<section title="500 Internal Server Error" anchor="status.500">
2049  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2050  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2051<t>
2052   The server encountered an unexpected condition which prevented it
2053   from fulfilling the request.
2054</t>
2055</section>
2056
2057<section title="501 Not Implemented" anchor="status.501">
2058  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2059  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2060<t>
2061   The server does not support the functionality required to fulfill the
2062   request. This is the appropriate response when the server does not
2063   recognize the request method and is not capable of supporting it for
2064   any resource.
2065</t>
2066</section>
2067
2068<section title="502 Bad Gateway" anchor="status.502">
2069  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2070  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2071<t>
2072   The server, while acting as a gateway or proxy, received an invalid
2073   response from the upstream server it accessed in attempting to
2074   fulfill the request.
2075</t>
2076</section>
2077
2078<section title="503 Service Unavailable" anchor="status.503">
2079  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2080  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2081<t>
2082   The server is currently unable or unwilling to handle the request due to
2083   reasons such as temporary overloading, maintenance of the server, or rate
2084   limiting of the client.
2085</t>
2086<t>
2087   The implication is that this is a temporary condition which will be
2088   alleviated after some delay. If known, the length of the delay &MAY; be
2089   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2090   If no Retry-After is given, the client &SHOULD; handle the response as it
2091   would for a 500 response.
2092</t>
2093<x:note>
2094  <t>
2095    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2096    server must use it when becoming overloaded. Some servers might wish
2097    to simply refuse the connection.
2098  </t>
2099</x:note>
2100</section>
2101
2102<section title="504 Gateway Timeout" anchor="status.504">
2103  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2104  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2105<t>
2106   The server, while acting as a gateway or proxy, did not receive a
2107   timely response from the upstream server specified by the URI (e.g.,
2108   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2109   to access in attempting to complete the request.
2110</t>
2111<x:note>
2112  <t>
2113    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2114    return 400 or 500 when DNS lookups time out.
2115  </t>
2116</x:note>
2117</section>
2118
2119<section title="505 HTTP Version Not Supported" anchor="status.505">
2120  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2121  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2122<t>
2123   The server does not support, or refuses to support, the protocol
2124   version that was used in the request message. The server is
2125   indicating that it is unable or unwilling to complete the request
2126   using the same major version as the client, as described in &http-version;,
2127   other than with this error message. The response &SHOULD; contain
2128   a representation describing why that version is not supported and what other
2129   protocols are supported by that server.
2130</t>
2131
2132</section>
2133</section>
2134</section>
2135
2136
2137<section title="Header Field Definitions" anchor="header.fields">
2138<t>
2139   This section defines the syntax and semantics of HTTP/1.1 header fields
2140   related to request and response semantics.
2141</t>
2142
2143<section title="Allow" anchor="header.allow">
2144  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2145  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2146  <x:anchor-alias value="Allow"/>
2147<t>
2148   The "Allow" header field lists the set of methods advertised as
2149   supported by the target resource. The purpose of this field is strictly to
2150   inform the recipient of valid request methods associated with the resource.
2151</t>
2152<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2153  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2154</artwork></figure>
2155<t>
2156   Example of use:
2157</t>
2158<figure><artwork type="example">
2159  Allow: GET, HEAD, PUT
2160</artwork></figure>
2161<t>
2162   The actual set of allowed methods is defined by the origin server at the
2163   time of each request.
2164</t>
2165<t>
2166   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2167   understand all the methods specified in order to handle them according to
2168   the generic message handling rules.
2169</t>
2170</section>
2171
2172<section title="Expect" anchor="header.expect">
2173  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2174  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2175  <x:anchor-alias value="Expect"/>
2176  <x:anchor-alias value="expectation"/>
2177  <x:anchor-alias value="expectation-extension"/>
2178  <x:anchor-alias value="expect-params"/>
2179<t>
2180   The "Expect" header field is used to indicate that particular
2181   server behaviors are required by the client.
2182</t>
2183<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"/>
2184  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2185 
2186  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2187  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2188                           *<x:ref>expect-params</x:ref> ]
2189  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2190</artwork></figure>
2191<t>
2192   A server that does not understand or is unable to comply with any of
2193   the expectation values in the Expect field of a request &MUST; respond
2194   with appropriate error status code. The server &MUST; respond with a 417
2195   (Expectation Failed) status code if any of the expectations cannot be met
2196   or, if there are other problems with the request, some other 4xx
2197   status code.
2198</t>
2199<t>
2200   This header field is defined with extensible syntax to allow for
2201   future extensions. If a server receives a request containing an
2202   Expect field that includes an expectation-extension that it does not
2203   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2204</t>
2205<t>
2206   Comparison of expectation values is case-insensitive for unquoted
2207   tokens (including the 100-continue token), and is case-sensitive for
2208   quoted-string expectation-extensions.
2209</t>
2210<t>
2211   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2212   return a 417 (Expectation Failed) status code if it receives a request
2213   with an expectation that it cannot meet. However, the Expect
2214   header field itself is end-to-end; it &MUST; be forwarded if the
2215   request is forwarded.
2216</t>
2217<t>
2218   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2219   Expect header field.
2220</t>
2221<t>
2222   See &use100; for the use of the 100 (Continue) status code.
2223</t>
2224</section>
2225
2226<section title="From" anchor="header.from">
2227  <iref primary="true" item="From header field" x:for-anchor=""/>
2228  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2229  <x:anchor-alias value="From"/>
2230  <x:anchor-alias value="mailbox"/>
2231<t>
2232   The "From" header field, if given, &SHOULD; contain an Internet
2233   e-mail address for the human user who controls the requesting user
2234   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2235   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2236</t>
2237<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2238  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2239 
2240  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2241</artwork></figure>
2242<t>
2243   An example is:
2244</t>
2245<figure><artwork type="example">
2246  From: webmaster@example.org
2247</artwork></figure>
2248<t>
2249   This header field &MAY; be used for logging purposes and as a means for
2250   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2251   be used as an insecure form of access protection. The interpretation
2252   of this field is that the request is being performed on behalf of the
2253   person given, who accepts responsibility for the method performed. In
2254   particular, robot agents &SHOULD; include this header field so that the
2255   person responsible for running the robot can be contacted if problems
2256   occur on the receiving end.
2257</t>
2258<t>
2259   The Internet e-mail address in this field &MAY; be separate from the
2260   Internet host which issued the request. For example, when a request
2261   is passed through a proxy the original issuer's address &SHOULD; be
2262   used.
2263</t>
2264<t>
2265   The client &SHOULD-NOT;  send the From header field without the user's
2266   approval, as it might conflict with the user's privacy interests or
2267   their site's security policy. It is strongly recommended that the
2268   user be able to disable, enable, and modify the value of this field
2269   at any time prior to a request.
2270</t>
2271</section>
2272
2273<section title="Location" anchor="header.location">
2274  <iref primary="true" item="Location header field" x:for-anchor=""/>
2275  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2276  <x:anchor-alias value="Location"/>
2277<t>
2278   The "Location" header field is used to identify a newly created
2279   resource, or to redirect the recipient to a different location for
2280   completion of the request.
2281</t>
2282<t>
2283   For 201 (Created) responses, the Location is the URI of the new resource
2284   which was created by the request. For 3xx responses, the location &SHOULD;
2285   indicate the server's preferred URI for automatic redirection to the
2286   resource.
2287</t>
2288<t>
2289   The field value consists of a single URI-reference. When it has the form
2290   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2291   the final value is computed by resolving it against the effective request
2292   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2293</t>
2294<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2295  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2296</artwork></figure>
2297<figure>
2298<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2299<artwork type="example">
2300  Location: http://www.example.org/pub/WWW/People.html#tim
2301</artwork></figure><figure><artwork type="example">  Location: /index.html
2302</artwork></figure>
2303<t>
2304   There are circumstances in which a fragment identifier in a Location URI
2305   would not be appropriate. For instance, when it appears in a 201 Created
2306   response, where the Location header field specifies the URI for the entire
2307   created resource.
2308</t>
2309<x:note>
2310  <t>
2311    <x:h>Note:</x:h> This specification does not define precedence rules
2312    for the case where the original URI, as navigated to by the user
2313    agent, and the Location header field value both contain fragment
2314    identifiers. Thus be aware that including fragment identifiers might
2315    inconvenience anyone relying on the semantics of the original URI's
2316    fragment identifier.
2317  </t>
2318</x:note>
2319<x:note>
2320  <t>
2321    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2322    from Location in that the Content-Location identifies the most specific
2323    resource corresponding to the enclosed representation.
2324    It is therefore possible for a response to contain header fields for
2325    both Location and Content-Location.
2326  </t>
2327</x:note>
2328</section>
2329
2330<section title="Max-Forwards" anchor="header.max-forwards">
2331  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2332  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2333  <x:anchor-alias value="Max-Forwards"/>
2334<t>
2335   The "Max-Forwards" header field provides a mechanism with the
2336   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2337   methods to limit the number of times that the request is forwarded by
2338   proxies. This can be useful when the client is attempting to
2339   trace a request which appears to be failing or looping in mid-chain.
2340</t>
2341<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2342  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2343</artwork></figure>
2344<t>
2345   The Max-Forwards value is a decimal integer indicating the remaining
2346   number of times this request message can be forwarded.
2347</t>
2348<t>
2349   Each recipient of a TRACE or OPTIONS request
2350   containing a Max-Forwards header field &MUST; check and update its
2351   value prior to forwarding the request. If the received value is zero
2352   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2353   respond as the final recipient. If the received Max-Forwards value is
2354   greater than zero, then the forwarded message &MUST; contain an updated
2355   Max-Forwards field with a value decremented by one (1).
2356</t>
2357<t>
2358   The Max-Forwards header field &MAY; be ignored for all other request
2359   methods.
2360</t>
2361</section>
2362
2363<section title="Referer" anchor="header.referer">
2364  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2365  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2366  <x:anchor-alias value="Referer"/>
2367<t>
2368   The "Referer" [sic] header field allows the client to specify the
2369   URI of the resource from which the effective request URI was obtained (the
2370   "referrer", although the header field is misspelled.).
2371</t>
2372<t>
2373   The Referer header field allows servers to generate lists of back-links to
2374   resources for interest, logging, optimized caching, etc. It also allows
2375   obsolete or mistyped links to be traced for maintenance. Some servers use
2376   Referer as a means of controlling where they allow links from (so-called
2377   "deep linking"), but legitimate requests do not always
2378   contain a Referer header field.
2379</t>
2380<t>
2381   If the effective request URI was obtained from a source that does not have its own
2382   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2383   sent with the value "about:blank", or not be sent at all. Note that this
2384   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2385</t>
2386<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2387  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2388</artwork></figure>
2389<t>
2390   Example:
2391</t>
2392<figure><artwork type="example">
2393  Referer: http://www.example.org/hypertext/Overview.html
2394</artwork></figure>
2395<t>
2396   If the field value is a relative URI, it &SHOULD; be interpreted
2397   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2398   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2399</t>
2400</section>
2401
2402<section title="Retry-After" anchor="header.retry-after">
2403  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2404  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2405  <x:anchor-alias value="Retry-After"/>
2406<t>
2407   The header "Retry-After" field can be used with a 503 (Service
2408   Unavailable) response to indicate how long the service is expected to
2409   be unavailable to the requesting client. This field &MAY; also be used
2410   with any 3xx (Redirection) response to indicate the minimum time the
2411   user-agent is asked wait before issuing the redirected request.
2412</t>
2413<t>
2414   The value of this field can be either an HTTP-date or an integer number
2415   of seconds (in decimal) after the time of the response.
2416</t>
2417<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2418  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2419</artwork></figure>
2420<t anchor="rule.delta-seconds">
2421  <x:anchor-alias value="delta-seconds"/>
2422   Time spans are non-negative decimal integers, representing time in
2423   seconds.
2424</t>
2425<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2426  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2427</artwork></figure>
2428<t>
2429   Two examples of its use are
2430</t>
2431<figure><artwork type="example">
2432  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2433  Retry-After: 120
2434</artwork></figure>
2435<t>
2436   In the latter example, the delay is 2 minutes.
2437</t>
2438</section>
2439
2440<section title="Server" anchor="header.server">
2441  <iref primary="true" item="Server header field" x:for-anchor=""/>
2442  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2443  <x:anchor-alias value="Server"/>
2444<t>
2445   The "Server" header field contains information about the
2446   software used by the origin server to handle the request.
2447</t>
2448<t>
2449   The field can contain multiple product tokens (&product-tokens;) and
2450   comments (&header-fields;) identifying the server and any significant
2451   subproducts. The product tokens are listed in order of their significance
2452   for identifying the application.
2453</t>
2454<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2455  <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> ) )
2456</artwork></figure>
2457<t>
2458   Example:
2459</t>
2460<figure><artwork type="example">
2461  Server: CERN/3.0 libwww/2.17
2462</artwork></figure>
2463<t>
2464   If the response is being forwarded through a proxy, the proxy
2465   application &MUST-NOT; modify the Server header field. Instead, it
2466   &MUST; include a Via field (as described in &header-via;).
2467</t>
2468<x:note>
2469  <t>
2470    <x:h>Note:</x:h> Revealing the specific software version of the server might
2471    allow the server machine to become more vulnerable to attacks
2472    against software that is known to contain security holes. Server
2473    implementors are encouraged to make this field a configurable
2474    option.
2475  </t>
2476</x:note>
2477</section>
2478
2479<section title="User-Agent" anchor="header.user-agent">
2480  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2481  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2482  <x:anchor-alias value="User-Agent"/>
2483<t>
2484   The "User-Agent" header field contains information about the user
2485   agent originating the request. User agents &SHOULD; include this field with
2486   requests.
2487</t>
2488<t>
2489   Typically, it is used for statistical purposes, the tracing of protocol
2490   violations, and tailoring responses to avoid particular user agent
2491   limitations.
2492</t>
2493<t>
2494   The field can contain multiple product tokens (&product-tokens;)
2495   and comments (&header-fields;) identifying the agent and its
2496   significant subproducts. By convention, the product tokens are listed in
2497   order of their significance for identifying the application.
2498</t>
2499<t>
2500   Because this field is usually sent on every request a user agent makes,
2501   implementations are encouraged not to include needlessly fine-grained
2502   detail, and to limit (or even prohibit) the addition of subproducts by third
2503   parties. Overly long and detailed User-Agent field values make requests
2504   larger and can also be used to identify ("fingerprint") the user against
2505   their wishes.
2506</t>
2507<t>
2508   Likewise, implementations are encouraged not to use the product tokens of
2509   other implementations in order to declare compatibility with them, as this
2510   circumvents the purpose of the field. Finally, they are encouraged not to
2511   use comments to identify products; doing so makes the field value more
2512   difficult to parse.
2513</t>
2514<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2515  <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> ) )
2516</artwork></figure>
2517<t>
2518   Example:
2519</t>
2520<figure><artwork type="example">
2521  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2522</artwork></figure>
2523</section>
2524
2525</section>
2526
2527<section title="IANA Considerations" anchor="IANA.considerations">
2528
2529<section title="Method Registry" anchor="method.registration">
2530<t>
2531  The registration procedure for HTTP request methods is defined by
2532  <xref target="method.registry"/> of this document.
2533</t>
2534<t>
2535   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2536   and be populated with the registrations below:
2537</t>
2538<?BEGININC p2-semantics.iana-methods ?>
2539<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2540<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2541   <ttcol>Method</ttcol>
2542   <ttcol>Safe</ttcol>
2543   <ttcol>Reference</ttcol>
2544   <c>CONNECT</c>
2545   <c>no</c>
2546   <c>
2547      <xref target="CONNECT"/>
2548   </c>
2549   <c>DELETE</c>
2550   <c>no</c>
2551   <c>
2552      <xref target="DELETE"/>
2553   </c>
2554   <c>GET</c>
2555   <c>yes</c>
2556   <c>
2557      <xref target="GET"/>
2558   </c>
2559   <c>HEAD</c>
2560   <c>yes</c>
2561   <c>
2562      <xref target="HEAD"/>
2563   </c>
2564   <c>OPTIONS</c>
2565   <c>yes</c>
2566   <c>
2567      <xref target="OPTIONS"/>
2568   </c>
2569   <c>POST</c>
2570   <c>no</c>
2571   <c>
2572      <xref target="POST"/>
2573   </c>
2574   <c>PUT</c>
2575   <c>no</c>
2576   <c>
2577      <xref target="PUT"/>
2578   </c>
2579   <c>TRACE</c>
2580   <c>yes</c>
2581   <c>
2582      <xref target="TRACE"/>
2583   </c>
2584</texttable>
2585<!--(END)-->
2586<?ENDINC p2-semantics.iana-methods ?>
2587</section>
2588
2589<section title="Status Code Registry" anchor="status.code.registration">
2590<t>
2591   The registration procedure for HTTP Status Codes &mdash; previously defined
2592   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2593   by <xref target="status.code.registry"/> of this document.
2594</t>
2595<t>
2596   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2597   shall be updated with the registrations below:
2598</t>
2599<?BEGININC p2-semantics.iana-status-codes ?>
2600<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2601<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2602   <ttcol>Value</ttcol>
2603   <ttcol>Description</ttcol>
2604   <ttcol>Reference</ttcol>
2605   <c>100</c>
2606   <c>Continue</c>
2607   <c>
2608      <xref target="status.100"/>
2609   </c>
2610   <c>101</c>
2611   <c>Switching Protocols</c>
2612   <c>
2613      <xref target="status.101"/>
2614   </c>
2615   <c>200</c>
2616   <c>OK</c>
2617   <c>
2618      <xref target="status.200"/>
2619   </c>
2620   <c>201</c>
2621   <c>Created</c>
2622   <c>
2623      <xref target="status.201"/>
2624   </c>
2625   <c>202</c>
2626   <c>Accepted</c>
2627   <c>
2628      <xref target="status.202"/>
2629   </c>
2630   <c>203</c>
2631   <c>Non-Authoritative Information</c>
2632   <c>
2633      <xref target="status.203"/>
2634   </c>
2635   <c>204</c>
2636   <c>No Content</c>
2637   <c>
2638      <xref target="status.204"/>
2639   </c>
2640   <c>205</c>
2641   <c>Reset Content</c>
2642   <c>
2643      <xref target="status.205"/>
2644   </c>
2645   <c>300</c>
2646   <c>Multiple Choices</c>
2647   <c>
2648      <xref target="status.300"/>
2649   </c>
2650   <c>301</c>
2651   <c>Moved Permanently</c>
2652   <c>
2653      <xref target="status.301"/>
2654   </c>
2655   <c>302</c>
2656   <c>Found</c>
2657   <c>
2658      <xref target="status.302"/>
2659   </c>
2660   <c>303</c>
2661   <c>See Other</c>
2662   <c>
2663      <xref target="status.303"/>
2664   </c>
2665   <c>305</c>
2666   <c>Use Proxy</c>
2667   <c>
2668      <xref target="status.305"/>
2669   </c>
2670   <c>306</c>
2671   <c>(Unused)</c>
2672   <c>
2673      <xref target="status.306"/>
2674   </c>
2675   <c>307</c>
2676   <c>Temporary Redirect</c>
2677   <c>
2678      <xref target="status.307"/>
2679   </c>
2680   <c>400</c>
2681   <c>Bad Request</c>
2682   <c>
2683      <xref target="status.400"/>
2684   </c>
2685   <c>402</c>
2686   <c>Payment Required</c>
2687   <c>
2688      <xref target="status.402"/>
2689   </c>
2690   <c>403</c>
2691   <c>Forbidden</c>
2692   <c>
2693      <xref target="status.403"/>
2694   </c>
2695   <c>404</c>
2696   <c>Not Found</c>
2697   <c>
2698      <xref target="status.404"/>
2699   </c>
2700   <c>405</c>
2701   <c>Method Not Allowed</c>
2702   <c>
2703      <xref target="status.405"/>
2704   </c>
2705   <c>406</c>
2706   <c>Not Acceptable</c>
2707   <c>
2708      <xref target="status.406"/>
2709   </c>
2710   <c>407</c>
2711   <c>Proxy Authentication Required</c>
2712   <c>
2713      <xref target="status.407"/>
2714   </c>
2715   <c>408</c>
2716   <c>Request Timeout</c>
2717   <c>
2718      <xref target="status.408"/>
2719   </c>
2720   <c>409</c>
2721   <c>Conflict</c>
2722   <c>
2723      <xref target="status.409"/>
2724   </c>
2725   <c>410</c>
2726   <c>Gone</c>
2727   <c>
2728      <xref target="status.410"/>
2729   </c>
2730   <c>411</c>
2731   <c>Length Required</c>
2732   <c>
2733      <xref target="status.411"/>
2734   </c>
2735   <c>413</c>
2736   <c>Request Representation Too Large</c>
2737   <c>
2738      <xref target="status.413"/>
2739   </c>
2740   <c>414</c>
2741   <c>URI Too Long</c>
2742   <c>
2743      <xref target="status.414"/>
2744   </c>
2745   <c>415</c>
2746   <c>Unsupported Media Type</c>
2747   <c>
2748      <xref target="status.415"/>
2749   </c>
2750   <c>417</c>
2751   <c>Expectation Failed</c>
2752   <c>
2753      <xref target="status.417"/>
2754   </c>
2755   <c>426</c>
2756   <c>Upgrade Required</c>
2757   <c>
2758      <xref target="status.426"/>
2759   </c>
2760   <c>500</c>
2761   <c>Internal Server Error</c>
2762   <c>
2763      <xref target="status.500"/>
2764   </c>
2765   <c>501</c>
2766   <c>Not Implemented</c>
2767   <c>
2768      <xref target="status.501"/>
2769   </c>
2770   <c>502</c>
2771   <c>Bad Gateway</c>
2772   <c>
2773      <xref target="status.502"/>
2774   </c>
2775   <c>503</c>
2776   <c>Service Unavailable</c>
2777   <c>
2778      <xref target="status.503"/>
2779   </c>
2780   <c>504</c>
2781   <c>Gateway Timeout</c>
2782   <c>
2783      <xref target="status.504"/>
2784   </c>
2785   <c>505</c>
2786   <c>HTTP Version Not Supported</c>
2787   <c>
2788      <xref target="status.505"/>
2789   </c>
2790</texttable>
2791<!--(END)-->
2792<?ENDINC p2-semantics.iana-status-codes ?>
2793</section>
2794<section title="Header Field Registration" anchor="header.field.registration">
2795<t>
2796   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2797   with the permanent registrations below (see <xref target="RFC3864"/>):
2798</t>
2799<?BEGININC p2-semantics.iana-headers ?>
2800<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2801<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2802   <ttcol>Header Field Name</ttcol>
2803   <ttcol>Protocol</ttcol>
2804   <ttcol>Status</ttcol>
2805   <ttcol>Reference</ttcol>
2806
2807   <c>Allow</c>
2808   <c>http</c>
2809   <c>standard</c>
2810   <c>
2811      <xref target="header.allow"/>
2812   </c>
2813   <c>Expect</c>
2814   <c>http</c>
2815   <c>standard</c>
2816   <c>
2817      <xref target="header.expect"/>
2818   </c>
2819   <c>From</c>
2820   <c>http</c>
2821   <c>standard</c>
2822   <c>
2823      <xref target="header.from"/>
2824   </c>
2825   <c>Location</c>
2826   <c>http</c>
2827   <c>standard</c>
2828   <c>
2829      <xref target="header.location"/>
2830   </c>
2831   <c>Max-Forwards</c>
2832   <c>http</c>
2833   <c>standard</c>
2834   <c>
2835      <xref target="header.max-forwards"/>
2836   </c>
2837   <c>Referer</c>
2838   <c>http</c>
2839   <c>standard</c>
2840   <c>
2841      <xref target="header.referer"/>
2842   </c>
2843   <c>Retry-After</c>
2844   <c>http</c>
2845   <c>standard</c>
2846   <c>
2847      <xref target="header.retry-after"/>
2848   </c>
2849   <c>Server</c>
2850   <c>http</c>
2851   <c>standard</c>
2852   <c>
2853      <xref target="header.server"/>
2854   </c>
2855   <c>User-Agent</c>
2856   <c>http</c>
2857   <c>standard</c>
2858   <c>
2859      <xref target="header.user-agent"/>
2860   </c>
2861</texttable>
2862<!--(END)-->
2863<?ENDINC p2-semantics.iana-headers ?>
2864<t>
2865   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2866</t>
2867</section>
2868</section>
2869
2870<section title="Security Considerations" anchor="security.considerations">
2871<t>
2872   This section is meant to inform application developers, information
2873   providers, and users of the security limitations in HTTP/1.1 as
2874   described by this document. The discussion does not include
2875   definitive solutions to the problems revealed, though it does make
2876   some suggestions for reducing security risks.
2877</t>
2878
2879<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2880<t>
2881   Like any generic data transfer protocol, HTTP cannot regulate the
2882   content of the data that is transferred, nor is there any a priori
2883   method of determining the sensitivity of any particular piece of
2884   information within the context of any given request. Therefore,
2885   applications &SHOULD; supply as much control over this information as
2886   possible to the provider of that information. Four header fields are
2887   worth special mention in this context: Server, Via, Referer and From.
2888</t>
2889<t>
2890   Revealing the specific software version of the server might allow the
2891   server machine to become more vulnerable to attacks against software
2892   that is known to contain security holes. Implementors &SHOULD; make the
2893   Server header field a configurable option.
2894</t>
2895<t>
2896   Proxies which serve as a portal through a network firewall &SHOULD;
2897   take special precautions regarding the transfer of header information
2898   that identifies the hosts behind the firewall. In particular, they
2899   &SHOULD; remove, or replace with sanitized versions, any Via fields
2900   generated behind the firewall.
2901</t>
2902<t>
2903   The Referer header field allows reading patterns to be studied and reverse
2904   links drawn. Although it can be very useful, its power can be abused
2905   if user details are not separated from the information contained in
2906   the Referer. Even when the personal information has been removed, the
2907   Referer header field might indicate a private document's URI whose
2908   publication would be inappropriate.
2909</t>
2910<t>
2911   The information sent in the From field might conflict with the user's
2912   privacy interests or their site's security policy, and hence it
2913   &SHOULD-NOT;  be transmitted without the user being able to disable,
2914   enable, and modify the contents of the field. The user &MUST; be able
2915   to set the contents of this field within a user preference or
2916   application defaults configuration.
2917</t>
2918<t>
2919   We suggest, though do not require, that a convenient toggle interface
2920   be provided for the user to enable or disable the sending of From and
2921   Referer information.
2922</t>
2923<t>
2924   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2925   target="header.server"/>) header fields can sometimes be used to determine
2926   that a specific client or server have a particular security hole which might
2927   be exploited. Unfortunately, this same information is often used for other
2928   valuable purposes for which HTTP currently has no better mechanism.
2929</t>
2930<t>
2931   Furthermore, the User-Agent header field may contain enough entropy to be
2932   used, possibly in conjunction with other material, to uniquely identify the
2933   user.
2934</t>
2935<t>
2936   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2937   that was sent in request header fields within the body of their response.
2938   Clients &SHOULD; be careful with sensitive information, like Cookies,
2939   Authorization credentials, and other header fields that might be used to
2940   collect data from the client.
2941</t> 
2942</section>
2943
2944<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2945<t>
2946   Because the source of a link might be private information or might
2947   reveal an otherwise private information source, it is strongly
2948   recommended that the user be able to select whether or not the
2949   Referer field is sent. For example, a browser client could have a
2950   toggle switch for browsing openly/anonymously, which would
2951   respectively enable/disable the sending of Referer and From
2952   information.
2953</t>
2954<t>
2955   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2956   HTTP request if the referring page was transferred with a secure
2957   protocol.
2958</t>
2959<t>
2960   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2961   sensitive data because that data will be placed in the request-target. Many
2962   existing servers, proxies, and user agents log or display the request-target
2963   in places where it might be visible to third parties. Such services can
2964   use POST-based form submission instead.
2965</t>
2966</section>
2967
2968<section title="Location Headers and Spoofing" anchor="location.spoofing">
2969<t>
2970   If a single server supports multiple organizations that do not trust
2971   one another, then it &MUST; check the values of Location and Content-Location
2972   header fields in responses that are generated under control of
2973   said organizations to make sure that they do not attempt to
2974   invalidate resources over which they have no authority.
2975</t>
2976</section>
2977
2978<section title="Security Considerations for CONNECT">
2979<t>
2980   Since tunneled data is opaque to the proxy, there are additional
2981   risks to tunneling to other well-known or reserved ports.
2982   A HTTP client CONNECTing to port 25 could relay spam
2983   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2984   access to a small number of known ports.
2985</t>
2986</section>
2987
2988</section>
2989
2990<section title="Acknowledgments" anchor="acks">
2991<t>
2992  See &acks;.
2993</t>
2994</section>
2995</middle>
2996<back>
2997
2998<references title="Normative References">
2999
3000<reference anchor="Part1">
3001  <front>
3002    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3003    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3004      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3005      <address><email>fielding@gbiv.com</email></address>
3006    </author>
3007    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3008      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3009      <address><email>jg@freedesktop.org</email></address>
3010    </author>
3011    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3012      <organization abbrev="HP">Hewlett-Packard Company</organization>
3013      <address><email>JeffMogul@acm.org</email></address>
3014    </author>
3015    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3016      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3017      <address><email>henrikn@microsoft.com</email></address>
3018    </author>
3019    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3020      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3021      <address><email>LMM@acm.org</email></address>
3022    </author>
3023    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3024      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3025      <address><email>paulle@microsoft.com</email></address>
3026    </author>
3027    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3028      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3029      <address><email>timbl@w3.org</email></address>
3030    </author>
3031    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3032      <organization abbrev="W3C">World Wide Web Consortium</organization>
3033      <address><email>ylafon@w3.org</email></address>
3034    </author>
3035    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3036      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3037      <address><email>julian.reschke@greenbytes.de</email></address>
3038    </author>
3039    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3040  </front>
3041  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3042  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3043</reference>
3044
3045<reference anchor="Part3">
3046  <front>
3047    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3048    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3049      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3050      <address><email>fielding@gbiv.com</email></address>
3051    </author>
3052    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3053      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3054      <address><email>jg@freedesktop.org</email></address>
3055    </author>
3056    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3057      <organization abbrev="HP">Hewlett-Packard Company</organization>
3058      <address><email>JeffMogul@acm.org</email></address>
3059    </author>
3060    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3061      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3062      <address><email>henrikn@microsoft.com</email></address>
3063    </author>
3064    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3065      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3066      <address><email>LMM@acm.org</email></address>
3067    </author>
3068    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3069      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3070      <address><email>paulle@microsoft.com</email></address>
3071    </author>
3072    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3073      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3074      <address><email>timbl@w3.org</email></address>
3075    </author>
3076    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3077      <organization abbrev="W3C">World Wide Web Consortium</organization>
3078      <address><email>ylafon@w3.org</email></address>
3079    </author>
3080    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3081      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3082      <address><email>julian.reschke@greenbytes.de</email></address>
3083    </author>
3084    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3085  </front>
3086  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3087  <x:source href="p3-payload.xml" basename="p3-payload"/>
3088</reference>
3089
3090<reference anchor="Part4">
3091  <front>
3092    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3093    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3094      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3095      <address><email>fielding@gbiv.com</email></address>
3096    </author>
3097    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3098      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3099      <address><email>jg@freedesktop.org</email></address>
3100    </author>
3101    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3102      <organization abbrev="HP">Hewlett-Packard Company</organization>
3103      <address><email>JeffMogul@acm.org</email></address>
3104    </author>
3105    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3106      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3107      <address><email>henrikn@microsoft.com</email></address>
3108    </author>
3109    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3110      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3111      <address><email>LMM@acm.org</email></address>
3112    </author>
3113    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3114      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3115      <address><email>paulle@microsoft.com</email></address>
3116    </author>
3117    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3118      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3119      <address><email>timbl@w3.org</email></address>
3120    </author>
3121    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3122      <organization abbrev="W3C">World Wide Web Consortium</organization>
3123      <address><email>ylafon@w3.org</email></address>
3124    </author>
3125    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3126      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3127      <address><email>julian.reschke@greenbytes.de</email></address>
3128    </author>
3129    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3130  </front>
3131  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3132  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3133</reference>
3134
3135<reference anchor="Part5">
3136  <front>
3137    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3138    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3139      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3140      <address><email>fielding@gbiv.com</email></address>
3141    </author>
3142    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3143      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3144      <address><email>jg@freedesktop.org</email></address>
3145    </author>
3146    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3147      <organization abbrev="HP">Hewlett-Packard Company</organization>
3148      <address><email>JeffMogul@acm.org</email></address>
3149    </author>
3150    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3151      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3152      <address><email>henrikn@microsoft.com</email></address>
3153    </author>
3154    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3155      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3156      <address><email>LMM@acm.org</email></address>
3157    </author>
3158    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3159      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3160      <address><email>paulle@microsoft.com</email></address>
3161    </author>
3162    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3163      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3164      <address><email>timbl@w3.org</email></address>
3165    </author>
3166    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3167      <organization abbrev="W3C">World Wide Web Consortium</organization>
3168      <address><email>ylafon@w3.org</email></address>
3169    </author>
3170    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3171      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3172      <address><email>julian.reschke@greenbytes.de</email></address>
3173    </author>
3174    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3175  </front>
3176  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3177  <x:source href="p5-range.xml" basename="p5-range"/>
3178</reference>
3179
3180<reference anchor="Part6">
3181  <front>
3182    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3183    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3184      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3185      <address><email>fielding@gbiv.com</email></address>
3186    </author>
3187    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3188      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3189      <address><email>jg@freedesktop.org</email></address>
3190    </author>
3191    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3192      <organization abbrev="HP">Hewlett-Packard Company</organization>
3193      <address><email>JeffMogul@acm.org</email></address>
3194    </author>
3195    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3196      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3197      <address><email>henrikn@microsoft.com</email></address>
3198    </author>
3199    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3200      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3201      <address><email>LMM@acm.org</email></address>
3202    </author>
3203    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3204      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3205      <address><email>paulle@microsoft.com</email></address>
3206    </author>
3207    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3208      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3209      <address><email>timbl@w3.org</email></address>
3210    </author>
3211    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3212      <organization abbrev="W3C">World Wide Web Consortium</organization>
3213      <address><email>ylafon@w3.org</email></address>
3214    </author>
3215    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3216      <address><email>mnot@mnot.net</email></address>
3217    </author>
3218    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3219      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3220      <address><email>julian.reschke@greenbytes.de</email></address>
3221    </author>
3222    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3223  </front>
3224  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3225  <x:source href="p6-cache.xml" basename="p6-cache"/>
3226</reference>
3227
3228<reference anchor="Part7">
3229  <front>
3230    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3231    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3232      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3233      <address><email>fielding@gbiv.com</email></address>
3234    </author>
3235    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3236      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3237      <address><email>jg@freedesktop.org</email></address>
3238    </author>
3239    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3240      <organization abbrev="HP">Hewlett-Packard Company</organization>
3241      <address><email>JeffMogul@acm.org</email></address>
3242    </author>
3243    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3244      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3245      <address><email>henrikn@microsoft.com</email></address>
3246    </author>
3247    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3248      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3249      <address><email>LMM@acm.org</email></address>
3250    </author>
3251    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3252      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3253      <address><email>paulle@microsoft.com</email></address>
3254    </author>
3255    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3256      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3257      <address><email>timbl@w3.org</email></address>
3258    </author>
3259    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3260      <organization abbrev="W3C">World Wide Web Consortium</organization>
3261      <address><email>ylafon@w3.org</email></address>
3262    </author>
3263    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3264      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3265      <address><email>julian.reschke@greenbytes.de</email></address>
3266    </author>
3267    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3268  </front>
3269  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3270  <x:source href="p7-auth.xml" basename="p7-auth"/>
3271</reference>
3272
3273<reference anchor="RFC2119">
3274  <front>
3275    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3276    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3277      <organization>Harvard University</organization>
3278      <address><email>sob@harvard.edu</email></address>
3279    </author>
3280    <date month="March" year="1997"/>
3281  </front>
3282  <seriesInfo name="BCP" value="14"/>
3283  <seriesInfo name="RFC" value="2119"/>
3284</reference>
3285
3286<reference anchor="RFC3986">
3287 <front>
3288  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3289  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3290    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3291    <address>
3292       <email>timbl@w3.org</email>
3293       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3294    </address>
3295  </author>
3296  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3297    <organization abbrev="Day Software">Day Software</organization>
3298    <address>
3299      <email>fielding@gbiv.com</email>
3300      <uri>http://roy.gbiv.com/</uri>
3301    </address>
3302  </author>
3303  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3304    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3305    <address>
3306      <email>LMM@acm.org</email>
3307      <uri>http://larry.masinter.net/</uri>
3308    </address>
3309  </author>
3310  <date month='January' year='2005'></date>
3311 </front>
3312 <seriesInfo name="STD" value="66"/>
3313 <seriesInfo name="RFC" value="3986"/>
3314</reference>
3315
3316<reference anchor="RFC5234">
3317  <front>
3318    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3319    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3320      <organization>Brandenburg InternetWorking</organization>
3321      <address>
3322        <email>dcrocker@bbiw.net</email>
3323      </address> 
3324    </author>
3325    <author initials="P." surname="Overell" fullname="Paul Overell">
3326      <organization>THUS plc.</organization>
3327      <address>
3328        <email>paul.overell@thus.net</email>
3329      </address>
3330    </author>
3331    <date month="January" year="2008"/>
3332  </front>
3333  <seriesInfo name="STD" value="68"/>
3334  <seriesInfo name="RFC" value="5234"/>
3335</reference>
3336
3337</references>
3338
3339<references title="Informative References">
3340
3341<reference anchor="RFC1945">
3342  <front>
3343    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3344    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3345      <organization>MIT, Laboratory for Computer Science</organization>
3346      <address><email>timbl@w3.org</email></address>
3347    </author>
3348    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3349      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3350      <address><email>fielding@ics.uci.edu</email></address>
3351    </author>
3352    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3353      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3354      <address><email>frystyk@w3.org</email></address>
3355    </author>
3356    <date month="May" year="1996"/>
3357  </front>
3358  <seriesInfo name="RFC" value="1945"/>
3359</reference>
3360
3361<reference anchor="RFC2068">
3362  <front>
3363    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3364    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3365      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3366      <address><email>fielding@ics.uci.edu</email></address>
3367    </author>
3368    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3369      <organization>MIT Laboratory for Computer Science</organization>
3370      <address><email>jg@w3.org</email></address>
3371    </author>
3372    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3373      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3374      <address><email>mogul@wrl.dec.com</email></address>
3375    </author>
3376    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3377      <organization>MIT Laboratory for Computer Science</organization>
3378      <address><email>frystyk@w3.org</email></address>
3379    </author>
3380    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3381      <organization>MIT Laboratory for Computer Science</organization>
3382      <address><email>timbl@w3.org</email></address>
3383    </author>
3384    <date month="January" year="1997"/>
3385  </front>
3386  <seriesInfo name="RFC" value="2068"/>
3387</reference>
3388
3389<reference anchor="RFC2616">
3390  <front>
3391    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3392    <author initials="R." surname="Fielding" fullname="R. Fielding">
3393      <organization>University of California, Irvine</organization>
3394      <address><email>fielding@ics.uci.edu</email></address>
3395    </author>
3396    <author initials="J." surname="Gettys" fullname="J. Gettys">
3397      <organization>W3C</organization>
3398      <address><email>jg@w3.org</email></address>
3399    </author>
3400    <author initials="J." surname="Mogul" fullname="J. Mogul">
3401      <organization>Compaq Computer Corporation</organization>
3402      <address><email>mogul@wrl.dec.com</email></address>
3403    </author>
3404    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3405      <organization>MIT Laboratory for Computer Science</organization>
3406      <address><email>frystyk@w3.org</email></address>
3407    </author>
3408    <author initials="L." surname="Masinter" fullname="L. Masinter">
3409      <organization>Xerox Corporation</organization>
3410      <address><email>masinter@parc.xerox.com</email></address>
3411    </author>
3412    <author initials="P." surname="Leach" fullname="P. Leach">
3413      <organization>Microsoft Corporation</organization>
3414      <address><email>paulle@microsoft.com</email></address>
3415    </author>
3416    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3417      <organization>W3C</organization>
3418      <address><email>timbl@w3.org</email></address>
3419    </author>
3420    <date month="June" year="1999"/>
3421  </front>
3422  <seriesInfo name="RFC" value="2616"/>
3423</reference>
3424
3425<reference anchor='RFC2817'>
3426  <front>
3427    <title>Upgrading to TLS Within HTTP/1.1</title>
3428    <author initials='R.' surname='Khare' fullname='R. Khare'>
3429      <organization>4K Associates / UC Irvine</organization>
3430      <address><email>rohit@4K-associates.com</email></address>
3431    </author>
3432    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3433      <organization>Agranat Systems, Inc.</organization>
3434      <address><email>lawrence@agranat.com</email></address>
3435    </author>
3436    <date year='2000' month='May' />
3437  </front>
3438  <seriesInfo name='RFC' value='2817' />
3439</reference>
3440
3441<reference anchor='RFC3864'>
3442  <front>
3443    <title>Registration Procedures for Message Header Fields</title>
3444    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3445      <organization>Nine by Nine</organization>
3446      <address><email>GK-IETF@ninebynine.org</email></address>
3447    </author>
3448    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3449      <organization>BEA Systems</organization>
3450      <address><email>mnot@pobox.com</email></address>
3451    </author>
3452    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3453      <organization>HP Labs</organization>
3454      <address><email>JeffMogul@acm.org</email></address>
3455    </author>
3456    <date year='2004' month='September' />
3457  </front>
3458  <seriesInfo name='BCP' value='90' />
3459  <seriesInfo name='RFC' value='3864' />
3460</reference>
3461
3462<reference anchor='RFC5226'>
3463  <front>
3464    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3465    <author initials='T.' surname='Narten' fullname='T. Narten'>
3466      <organization>IBM</organization>
3467      <address><email>narten@us.ibm.com</email></address>
3468    </author>
3469    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3470      <organization>Google</organization>
3471      <address><email>Harald@Alvestrand.no</email></address>
3472    </author>
3473    <date year='2008' month='May' />
3474  </front>
3475  <seriesInfo name='BCP' value='26' />
3476  <seriesInfo name='RFC' value='5226' />
3477</reference>
3478
3479<reference anchor="RFC5322">
3480  <front>
3481    <title>Internet Message Format</title>
3482    <author initials="P." surname="Resnick" fullname="P. Resnick">
3483      <organization>Qualcomm Incorporated</organization>
3484    </author>
3485    <date year="2008" month="October"/>
3486  </front> 
3487  <seriesInfo name="RFC" value="5322"/>
3488</reference>
3489
3490<reference anchor='RFC5789'>
3491  <front>
3492    <title>PATCH Method for HTTP</title>
3493    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3494      <organization>Linden Lab</organization>
3495    </author>
3496    <author initials='J.' surname='Snell' fullname='J. Snell' />
3497    <date year='2010' month='March' />
3498  </front>
3499  <seriesInfo name='RFC' value='5789' />
3500</reference>
3501
3502</references>
3503
3504<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3505<t>
3506  This document takes over the Status Code Registry, previously defined
3507  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3508  (<xref target="status.code.registry"/>)
3509</t>
3510<t>
3511  Clarify definition of POST.
3512  (<xref target="POST"/>)
3513</t>
3514<t>
3515  Remove requirement to handle all Content-* header fields; ban use of
3516  Content-Range with PUT.
3517  (<xref target="PUT"/>)
3518</t>
3519<t>
3520  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3521  (<xref target="CONNECT"/>)
3522</t>
3523<t>
3524  Broadened the definition of 203 (Non-Authoritative Information) to include
3525  cases of payload transformations as well.
3526  (<xref target="status.203"/>)
3527</t>
3528<t>
3529  Failed to consider that there are
3530  many other request methods that are safe to automatically redirect,
3531  and further that the user agent is able to make that determination
3532  based on the request method semantics.
3533  (Sections <xref format="counter" target="status.301"/>,
3534  <xref format="counter" target="status.302"/> and
3535  <xref format="counter" target="status.307"/>)
3536</t>
3537<t>
3538  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3539  It used to indicate that the target resource must be accessed through the
3540  proxy given by the Location field. The Location field gave the URI of the
3541  proxy. The recipient was expected to repeat this single request via the proxy.
3542  (<xref target="status.305"/>)
3543</t>
3544<t>
3545  Define status 426 (Upgrade Required) (this was incorporated from
3546  <xref target="RFC2817"/>).
3547  (<xref target="status.426"/>)
3548</t>
3549<t>
3550  Change ABNF productions for header fields to only define the field value.
3551  (<xref target="header.fields"/>)
3552</t>
3553<t>
3554  Reclassify "Allow" as response header field, removing the option to
3555  specify it in a PUT request.
3556  Relax the server requirement on the contents of the Allow header field and
3557  remove requirement on clients to always trust the header field value.
3558  (<xref target="header.allow"/>)
3559</t>
3560<t>
3561  Correct syntax of Location header field to allow URI references (including
3562  relative references and fragments), as referred symbol "absoluteURI" wasn't
3563  what was expected, and add some clarifications as to when use of fragments
3564  would not be appropriate.
3565  (<xref target="header.location"/>)
3566</t>
3567<t>
3568  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3569  extension methods could have used it as well).
3570  (<xref target="header.max-forwards"/>)
3571</t>
3572<t>
3573  Allow Referer field value of "about:blank" as alternative to not specifying it.
3574  (<xref target="header.referer"/>)
3575</t>
3576<t>
3577  In the description of the Server header field, the Via field
3578  was described as a SHOULD. The requirement was and is stated
3579  correctly in the description of the Via header field in &header-via;.
3580  (<xref target="header.server"/>)
3581</t>
3582</section>
3583
3584<?BEGININC p2-semantics.abnf-appendix ?>
3585<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3586<figure>
3587<artwork type="abnf" name="p2-semantics.parsed-abnf">
3588<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3589
3590<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3591
3592<x:ref>From</x:ref> = mailbox
3593
3594<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3595
3596<x:ref>Location</x:ref> = URI-reference
3597
3598<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3599<x:ref>Method</x:ref> = token
3600
3601<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3602
3603<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3604<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3605<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3606<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3607
3608<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3609<x:ref>Status-Code</x:ref> = 3DIGIT
3610
3611<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
3612<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3613
3614<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
3615
3616<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3617
3618<x:ref>delta-seconds</x:ref> = 1*DIGIT
3619
3620<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3621<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3622<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3623 *expect-params ]
3624
3625<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3626
3627<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3628
3629<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
3630<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3631
3632<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3633
3634<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3635</artwork>
3636</figure>
3637<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3638; Allow defined but not used
3639; Expect defined but not used
3640; From defined but not used
3641; Location defined but not used
3642; Max-Forwards defined but not used
3643; Reason-Phrase defined but not used
3644; Referer defined but not used
3645; Retry-After defined but not used
3646; Server defined but not used
3647; Status-Code defined but not used
3648; User-Agent defined but not used
3649</artwork></figure></section>
3650<?ENDINC p2-semantics.abnf-appendix ?>
3651
3652<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3653
3654<section title="Since RFC 2616">
3655<t>
3656  Extracted relevant partitions from <xref target="RFC2616"/>.
3657</t>
3658</section>
3659
3660<section title="Since draft-ietf-httpbis-p2-semantics-00">
3661<t>
3662  Closed issues:
3663  <list style="symbols"> 
3664    <t>
3665      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3666      "Via is a MUST"
3667      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3668    </t>
3669    <t>
3670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3671      "Fragments allowed in Location"
3672      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3673    </t>
3674    <t>
3675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3676      "Safe Methods vs Redirection"
3677      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3678    </t>
3679    <t>
3680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3681      "Revise description of the POST method"
3682      (<eref target="http://purl.org/NET/http-errata#post"/>)
3683    </t>
3684    <t>
3685      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3686      "Normative and Informative references"
3687    </t>
3688    <t>
3689      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3690      "RFC2606 Compliance"
3691    </t>
3692    <t>
3693      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3694      "Informative references"
3695    </t>
3696    <t>
3697      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3698      "Redundant cross-references"
3699    </t>
3700  </list>
3701</t>
3702<t>
3703  Other changes:
3704  <list style="symbols"> 
3705    <t>
3706      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3707    </t>
3708  </list>
3709</t>
3710</section>
3711
3712<section title="Since draft-ietf-httpbis-p2-semantics-01">
3713<t>
3714  Closed issues:
3715  <list style="symbols"> 
3716    <t>
3717      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3718      "PUT side effects"
3719    </t>
3720    <t>
3721      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3722      "Duplicate Host header requirements"
3723    </t>
3724  </list>
3725</t>
3726<t>
3727  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3728  <list style="symbols"> 
3729    <t>
3730      Move "Product Tokens" section (back) into Part 1, as "token" is used
3731      in the definition of the Upgrade header field.
3732    </t>
3733    <t>
3734      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3735    </t>
3736    <t>
3737      Copy definition of delta-seconds from Part6 instead of referencing it.
3738    </t>
3739  </list>
3740</t>
3741</section>
3742
3743<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3744<t>
3745  Closed issues:
3746  <list style="symbols"> 
3747    <t>
3748      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3749      "Requiring Allow in 405 responses"
3750    </t>
3751    <t>
3752      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3753      "Status Code Registry"
3754    </t>
3755    <t>
3756      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3757      "Redirection vs. Location"
3758    </t>
3759    <t>
3760      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3761      "Cacheability of 303 response"
3762    </t>
3763    <t>
3764      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3765      "305 Use Proxy"
3766    </t>
3767    <t>
3768      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3769      "Classification for Allow header"
3770    </t>
3771    <t>
3772      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3773      "PUT - 'store under' vs 'store at'"
3774    </t>
3775  </list>
3776</t>
3777<t>
3778  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3779  <list style="symbols"> 
3780    <t>
3781      Reference RFC 3984, and update header field registrations for headers defined
3782      in this document.
3783    </t>
3784  </list>
3785</t>
3786<t>
3787  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3788  <list style="symbols"> 
3789    <t>
3790      Replace string literals when the string really is case-sensitive (method).
3791    </t>
3792  </list>
3793</t>
3794</section>
3795
3796<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3797<t>
3798  Closed issues:
3799  <list style="symbols"> 
3800    <t>
3801      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3802      "OPTIONS request bodies"
3803    </t>
3804    <t>
3805      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3806      "Description of CONNECT should refer to RFC2817"
3807    </t>
3808    <t>
3809      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3810      "Location Content-Location reference request/response mixup"
3811    </t>
3812  </list>
3813</t>
3814<t>
3815  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3816  <list style="symbols"> 
3817    <t>
3818      Added initial proposal for registration process, plus initial
3819      content (non-HTTP/1.1 methods to be added by a separate specification).
3820    </t>
3821  </list>
3822</t>
3823</section>
3824
3825<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3826<t>
3827  Closed issues:
3828  <list style="symbols"> 
3829    <t>
3830      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3831      "Content-*"
3832    </t>
3833    <t>
3834      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3835      "RFC 2822 is updated by RFC 5322"
3836    </t>
3837  </list>
3838</t>
3839<t>
3840  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3841  <list style="symbols"> 
3842    <t>
3843      Use "/" instead of "|" for alternatives.
3844    </t>
3845    <t>
3846      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3847      whitespace ("OWS") and required whitespace ("RWS").
3848    </t>
3849    <t>
3850      Rewrite ABNFs to spell out whitespace rules, factor out
3851      header field value format definitions.
3852    </t>
3853  </list>
3854</t>
3855</section>
3856
3857<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3858<t>
3859  Closed issues:
3860  <list style="symbols"> 
3861    <t>
3862      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3863      "Reason-Phrase BNF"
3864    </t>
3865  </list>
3866</t>
3867<t>
3868  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3869  <list style="symbols"> 
3870    <t>
3871      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3872    </t>
3873  </list>
3874</t>
3875</section>
3876
3877<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3878<t>
3879  Closed issues:
3880  <list style="symbols"> 
3881    <t>
3882      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3883      "Clarify when Referer is sent"
3884    </t>
3885    <t>
3886      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3887      "status codes vs methods"
3888    </t>
3889    <t>
3890      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3891      "Do not require "updates" relation for specs that register status codes or method names"
3892    </t>
3893  </list>
3894</t>
3895</section>
3896
3897<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3898<t>
3899  Closed issues:
3900  <list style="symbols"> 
3901    <t>
3902      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3903      "Idempotency"
3904    </t>
3905    <t>
3906      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3907      "TRACE security considerations"
3908    </t>
3909    <t>
3910      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3911      "Clarify rules for determining what entities a response carries"
3912    </t>
3913    <t>
3914      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3915      "update note citing RFC 1945 and 2068"
3916    </t>
3917    <t>
3918      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3919      "update note about redirect limit"
3920    </t>
3921    <t>
3922      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3923      "Location header ABNF should use 'URI'"
3924    </t>
3925    <t>
3926      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3927      "fragments in Location vs status 303"
3928    </t>
3929    <t>
3930      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3931      "move IANA registrations for optional status codes"
3932    </t>
3933  </list>
3934</t>
3935<t>
3936  Partly resolved issues:
3937  <list style="symbols"> 
3938    <t>
3939      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3940      "Are OPTIONS and TRACE safe?"
3941    </t>
3942  </list>
3943</t>
3944</section>
3945
3946<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3947<t>
3948  Closed issues:
3949  <list style="symbols"> 
3950    <t>
3951      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3952      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3953      status codes when fixing this previously)
3954    </t>
3955  </list>
3956</t>
3957</section>
3958
3959<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3960<t>
3961  Closed issues:
3962  <list style="symbols"> 
3963    <t>
3964      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3965      "Fragment combination / precedence during redirects"
3966    </t>
3967  </list>
3968</t>
3969<t>
3970  Partly resolved issues:
3971  <list style="symbols"> 
3972    <t>
3973      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3974      "Location header payload handling"
3975    </t>
3976    <t>
3977      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3978      "Term for the requested resource's URI"
3979    </t>
3980  </list>
3981</t>
3982</section>
3983
3984<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3985<t>
3986  Closed issues:
3987  <list style="symbols"> 
3988    <t>
3989      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3990      "Clarify 'Requested Variant'"
3991    </t>
3992    <t>
3993      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3994      "Clarify entity / representation / variant terminology"
3995    </t>
3996    <t>
3997      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3998      "Methods and Caching"
3999    </t>
4000    <t>
4001      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4002      "OPTIONS vs Max-Forwards"
4003    </t>
4004    <t>
4005      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4006      "Status codes and caching"
4007    </t>
4008    <t>
4009      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4010      "consider removing the 'changes from 2068' sections"
4011    </t>
4012  </list>
4013</t>
4014</section>
4015
4016<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4017<t>
4018  Closed issues:
4019  <list style="symbols"> 
4020    <t>
4021      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4022      "Considerations for new status codes"
4023    </t>
4024    <t>
4025      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4026      "Considerations for new methods"
4027    </t>
4028    <t>
4029      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4030      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4031    </t>
4032  </list>
4033</t>
4034</section>
4035
4036<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4037<t>
4038  Closed issues:
4039  <list style="symbols"> 
4040    <t>
4041      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4042      "Fragment combination / precedence during redirects" (added warning
4043      about having a fragid on the redirect may cause inconvenience in
4044      some cases)
4045    </t>
4046    <t>
4047      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4048      "Content-* vs. PUT"
4049    </t>
4050    <t>
4051      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4052      "205 Bodies"
4053    </t>
4054    <t>
4055      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4056      "Understanding Content-* on non-PUT requests"
4057    </t>
4058    <t>
4059      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4060      "Content-*"
4061    </t>
4062    <t>
4063      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4064      "Header type defaulting"
4065    </t>
4066    <t>
4067      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4068      "PUT - 'store under' vs 'store at'"
4069    </t>
4070    <t>
4071      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4072      "duplicate ABNF for Reason-Phrase"
4073    </t>
4074    <t>
4075      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4076      "Note special status of Content-* prefix in header registration procedures"
4077    </t>
4078    <t>
4079      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4080      "Max-Forwards vs extension methods"
4081    </t>
4082    <t>
4083      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4084      "What is the value space of HTTP status codes?" (actually fixed in
4085      draft-ietf-httpbis-p2-semantics-11)
4086    </t>
4087    <t>
4088      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4089      "Header Classification"
4090    </t>
4091    <t>
4092      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4093      "PUT side effect: invalidation or just stale?"
4094    </t>
4095    <t>
4096      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4097      "proxies not supporting certain methods"
4098    </t>
4099    <t>
4100      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4101      "Migrate CONNECT from RFC2817 to p2"
4102    </t>
4103    <t>
4104      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4105      "Migrate Upgrade details from RFC2817"
4106    </t>
4107    <t>
4108      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4109      "clarify PUT semantics'"
4110    </t>
4111    <t>
4112      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4113      "duplicate ABNF for 'Method'"
4114    </t>
4115    <t>
4116      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4117      "untangle ABNFs for header fields"
4118    </t>
4119  </list>
4120</t>
4121</section>
4122
4123<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4124<t>
4125  Closed issues:
4126  <list style="symbols"> 
4127    <t>
4128      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4129      "untangle ABNFs for header fields"
4130    </t>
4131    <t>
4132      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4133      "message-body in CONNECT request"
4134    </t>
4135  </list>
4136</t>
4137</section>
4138
4139<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4140<t>
4141  Closed issues:
4142  <list style="symbols"> 
4143    <t>
4144      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4145      "Clarify status code for rate limiting"
4146    </t>
4147    <t>
4148      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4149      "clarify 403 forbidden"
4150    </t>
4151    <t>
4152      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4153      "Clarify 203 Non-Authoritative Information"
4154    </t>
4155    <t>
4156      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4157      "update default reason phrase for 413"
4158    </t>
4159  </list>
4160</t>
4161</section>
4162
4163<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4164<t>
4165  Closed issues:
4166  <list style="symbols"> 
4167    <t>
4168      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4169      "Strength of requirements on Accept re: 406"
4170    </t>
4171    <t>
4172      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4173      "400 response isn't generic"
4174    </t>
4175  </list>
4176</t>
4177</section>
4178</section>
4179
4180</back>
4181</rfc>
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