source: draft-ietf-httpbis/latest/p2-semantics.xml @ 836

Last change on this file since 836 was 836, checked in by julian.reschke@…, 9 years ago

fix broken section reference

  • Property svn:eol-style set to native
File size: 160.5 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 "July">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching-combining-headers  "<xref target='Part6' x:rel='#combining.headers' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73]>
74<?rfc toc="yes" ?>
75<?rfc symrefs="yes" ?>
76<?rfc sortrefs="yes" ?>
77<?rfc compact="yes"?>
78<?rfc subcompact="no" ?>
79<?rfc linkmailto="no" ?>
80<?rfc editing="no" ?>
81<?rfc comments="yes"?>
82<?rfc inline="yes"?>
83<?rfc rfcedstyle="yes"?>
84<?rfc-ext allow-markup-in-artwork="yes" ?>
85<?rfc-ext include-references-in-index="yes" ?>
86<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
87     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
88     xmlns:x='http://purl.org/net/xml2rfc/ext'
89     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
90<front>
91
92  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
93
94  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
95    <organization abbrev="Day Software">Day Software</organization>
96    <address>
97      <postal>
98        <street>23 Corporate Plaza DR, Suite 280</street>
99        <city>Newport Beach</city>
100        <region>CA</region>
101        <code>92660</code>
102        <country>USA</country>
103      </postal>
104      <phone>+1-949-706-5300</phone>
105      <facsimile>+1-949-706-5305</facsimile>
106      <email>fielding@gbiv.com</email>
107      <uri>http://roy.gbiv.com/</uri>
108    </address>
109  </author>
110
111  <author initials="J." surname="Gettys" fullname="Jim Gettys">
112    <organization>One Laptop per Child</organization>
113    <address>
114      <postal>
115        <street>21 Oak Knoll Road</street>
116        <city>Carlisle</city>
117        <region>MA</region>
118        <code>01741</code>
119        <country>USA</country>
120      </postal>
121      <email>jg@laptop.org</email>
122      <uri>http://www.laptop.org/</uri>
123    </address>
124  </author>
125 
126  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
127    <organization abbrev="HP">Hewlett-Packard Company</organization>
128    <address>
129      <postal>
130        <street>HP Labs, Large Scale Systems Group</street>
131        <street>1501 Page Mill Road, MS 1177</street>
132        <city>Palo Alto</city>
133        <region>CA</region>
134        <code>94304</code>
135        <country>USA</country>
136      </postal>
137      <email>JeffMogul@acm.org</email>
138    </address>
139  </author>
140
141  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
142    <organization abbrev="Microsoft">Microsoft Corporation</organization>
143    <address>
144      <postal>
145        <street>1 Microsoft Way</street>
146        <city>Redmond</city>
147        <region>WA</region>
148        <code>98052</code>
149        <country>USA</country>
150      </postal>
151      <email>henrikn@microsoft.com</email>
152    </address>
153  </author>
154
155  <author initials="L." surname="Masinter" fullname="Larry Masinter">
156    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
157    <address>
158      <postal>
159        <street>345 Park Ave</street>
160        <city>San Jose</city>
161        <region>CA</region>
162        <code>95110</code>
163        <country>USA</country>
164      </postal>
165      <email>LMM@acm.org</email>
166      <uri>http://larry.masinter.net/</uri>
167    </address>
168  </author>
169 
170  <author initials="P." surname="Leach" fullname="Paul J. Leach">
171    <organization abbrev="Microsoft">Microsoft Corporation</organization>
172    <address>
173      <postal>
174        <street>1 Microsoft Way</street>
175        <city>Redmond</city>
176        <region>WA</region>
177        <code>98052</code>
178      </postal>
179      <email>paulle@microsoft.com</email>
180    </address>
181  </author>
182   
183  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
184    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
185    <address>
186      <postal>
187        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
188        <street>The Stata Center, Building 32</street>
189        <street>32 Vassar Street</street>
190        <city>Cambridge</city>
191        <region>MA</region>
192        <code>02139</code>
193        <country>USA</country>
194      </postal>
195      <email>timbl@w3.org</email>
196      <uri>http://www.w3.org/People/Berners-Lee/</uri>
197    </address>
198  </author>
199
200  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
201    <organization abbrev="W3C">World Wide Web Consortium</organization>
202    <address>
203      <postal>
204        <street>W3C / ERCIM</street>
205        <street>2004, rte des Lucioles</street>
206        <city>Sophia-Antipolis</city>
207        <region>AM</region>
208        <code>06902</code>
209        <country>France</country>
210      </postal>
211      <email>ylafon@w3.org</email>
212      <uri>http://www.raubacapeu.net/people/yves/</uri>
213    </address>
214  </author>
215
216  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
217    <organization abbrev="greenbytes">greenbytes GmbH</organization>
218    <address>
219      <postal>
220        <street>Hafenweg 16</street>
221        <city>Muenster</city><region>NW</region><code>48155</code>
222        <country>Germany</country>
223      </postal>
224      <phone>+49 251 2807760</phone>
225      <facsimile>+49 251 2807761</facsimile>
226      <email>julian.reschke@greenbytes.de</email>
227      <uri>http://greenbytes.de/tech/webdav/</uri>
228    </address>
229  </author>
230
231  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
232  <workgroup>HTTPbis Working Group</workgroup>
233
234<abstract>
235<t>
236   The Hypertext Transfer Protocol (HTTP) is an application-level
237   protocol for distributed, collaborative, hypermedia information
238   systems. HTTP has been in use by the World Wide Web global information
239   initiative since 1990. This document is Part 2 of the seven-part specification
240   that defines the protocol referred to as "HTTP/1.1" and, taken together,
241   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
242   as expressed by request methods, request-header fields, response status codes,
243   and response-header fields.
244</t>
245</abstract>
246
247<note title="Editorial Note (To be removed by RFC Editor)">
248  <t>
249    Discussion of this draft should take place on the HTTPBIS working group
250    mailing list (ietf-http-wg@w3.org). The current issues list is
251    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
252    and related documents (including fancy diffs) can be found at
253    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
254  </t>
255  <t>
256    The changes in this draft are summarized in <xref target="changes.since.09"/>.
257  </t>
258</note>
259</front>
260<middle>
261<section title="Introduction" anchor="introduction">
262<t>
263   This document defines HTTP/1.1 request and response semantics.  Each HTTP
264   message, as defined in &messaging;, is in the form of either a request or
265   a response.  An HTTP server listens on a connection for HTTP requests and
266   responds to each request, in the order received on that connection, with
267   one or more HTTP response messages.  This document defines the commonly
268   agreed upon semantics of the HTTP uniform interface, the intentions defined
269   by each request method, and the various response messages that might be
270   expected as a result of applying that method for the requested resource.
271</t>
272<t>
273   This document is currently disorganized in order to minimize the changes
274   between drafts and enable reviewers to see the smaller errata changes.
275   The next draft will reorganize the sections to better reflect the content.
276   In particular, the sections will be ordered according to the typical
277   processing of an HTTP request message (after message parsing): resource
278   mapping, general header fields, methods, request modifiers, response
279   status, and resource metadata.  The current mess reflects how widely
280   dispersed these topics and associated requirements had become in
281   <xref target="RFC2616"/>.
282</t>
283
284<section title="Requirements" anchor="intro.requirements">
285<t>
286   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
287   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
288   document are to be interpreted as described in <xref target="RFC2119"/>.
289</t>
290<t>
291   An implementation is not compliant if it fails to satisfy one or more
292   of the &MUST; or &REQUIRED; level requirements for the protocols it
293   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
294   level and all the &SHOULD; level requirements for its protocols is said
295   to be "unconditionally compliant"; one that satisfies all the &MUST;
296   level requirements but not all the &SHOULD; level requirements for its
297   protocols is said to be "conditionally compliant."
298</t>
299</section>
300
301<section title="Syntax Notation" anchor="notation">
302  <x:anchor-alias value="CR"/>
303  <x:anchor-alias value="DIGIT"/>
304  <x:anchor-alias value="LF"/>
305  <x:anchor-alias value="VCHAR"/>
306  <x:anchor-alias value="WSP"/>
307<t>
308  This specification uses the ABNF syntax defined in &notation; (which
309  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
310  <xref target="collected.abnf"/> shows the collected ABNF, with the list
311  rule expanded.
312</t>
313<t>
314  The following core rules are included by
315  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
316  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
317  DIGIT (decimal 0-9), DQUOTE (double quote),
318  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
319  OCTET (any 8-bit sequence of data), SP (space),
320  VCHAR (any visible USASCII character),
321  and WSP (whitespace).
322</t>
323
324<section title="Core Rules" anchor="core.rules">
325  <x:anchor-alias value="obs-text"/>
326  <x:anchor-alias value="quoted-string"/>
327  <x:anchor-alias value="token"/>
328  <x:anchor-alias value="OWS"/>
329  <x:anchor-alias value="RWS"/>
330<t>
331  The core rules below are defined in &basic-rules;:
332</t>
333<figure><artwork type="abnf2616">
334  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
335  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
336  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
337  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
338  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
339</artwork></figure>
340</section>
341
342<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
343  <x:anchor-alias value="absolute-URI"/>
344  <x:anchor-alias value="Accept"/>
345  <x:anchor-alias value="Accept-Charset"/>
346  <x:anchor-alias value="Accept-Encoding"/>
347  <x:anchor-alias value="Accept-Language"/>
348  <x:anchor-alias value="Accept-Ranges"/>
349  <x:anchor-alias value="Age"/>
350  <x:anchor-alias value="Authorization"/>
351  <x:anchor-alias value="comment"/>
352  <x:anchor-alias value="ETag"/>
353  <x:anchor-alias value="Host"/>
354  <x:anchor-alias value="HTTP-date"/>
355  <x:anchor-alias value="If-Match"/>
356  <x:anchor-alias value="If-Modified-Since"/>
357  <x:anchor-alias value="If-None-Match"/>
358  <x:anchor-alias value="If-Range"/>
359  <x:anchor-alias value="If-Unmodified-Since"/>
360  <x:anchor-alias value="partial-URI"/>
361  <x:anchor-alias value="product"/>
362  <x:anchor-alias value="Proxy-Authenticate"/>
363  <x:anchor-alias value="Proxy-Authorization"/>
364  <x:anchor-alias value="Range"/>
365  <x:anchor-alias value="TE"/>
366  <x:anchor-alias value="URI-reference"/>
367  <x:anchor-alias value="Vary"/>
368  <x:anchor-alias value="WWW-Authenticate"/>
369<t>
370  The ABNF rules below are defined in other parts:
371</t>
372<figure><!--Part1--><artwork type="abnf2616">
373  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
374  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
375  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
376  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
377  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
378  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
379  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
380  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
381</artwork></figure>
382<figure><!--Part3--><artwork type="abnf2616">
383  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
384  <x:ref>Accept-Charset</x:ref> =
385             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
386  <x:ref>Accept-Encoding</x:ref> =
387             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
388  <x:ref>Accept-Language</x:ref> =
389             &lt;Accept-Language, defined in &header-accept-language;&gt;
390</artwork></figure>
391<figure><!--Part4--><artwork type="abnf2616">
392  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
393  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
394  <x:ref>If-Modified-Since</x:ref> =
395             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
396  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
397  <x:ref>If-Unmodified-Since</x:ref> =
398             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
399</artwork></figure>
400<figure><!--Part5--><artwork type="abnf2616">
401  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
402  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
403  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
404</artwork></figure>
405<figure><!--Part6--><artwork type="abnf2616">
406  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
407  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
408</artwork><!--Part7--></figure>
409<figure><artwork type="abnf2616">
410  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
411  <x:ref>Proxy-Authenticate</x:ref> =
412             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
413  <x:ref>Proxy-Authorization</x:ref> =
414             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
415  <x:ref>WWW-Authenticate</x:ref> =
416             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
417</artwork></figure>
418</section>
419</section>
420</section>
421
422<section title="Method" anchor="method">
423  <x:anchor-alias value="Method"/>
424  <x:anchor-alias value="extension-method"/>
425<t>
426   The Method token indicates the method to be performed on the resource
427   identified by the Effective Request URI (&effective-request-uri;). The
428   method is case-sensitive.
429</t>
430<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
431  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
432                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
433                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
434                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
435                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
436                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
437                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
438                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
439                 / <x:ref>extension-method</x:ref>
440  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
441</artwork></figure>
442<t>
443   The list of methods allowed by a resource can be specified in an
444   Allow header field (<xref target="header.allow"/>). The return code of the response
445   always notifies the client whether a method is currently allowed on a
446   resource, since the set of allowed methods can change dynamically. An
447   origin server &SHOULD; return the status code 405 (Method Not Allowed)
448   if the method is known by the origin server but not allowed for the
449   requested resource, and 501 (Not Implemented) if the method is
450   unrecognized or not implemented by the origin server. The methods GET
451   and HEAD &MUST; be supported by all general-purpose servers. All other
452   methods are &OPTIONAL;; however, if the above methods are implemented,
453   they &MUST; be implemented with the same semantics as those specified
454   in <xref target="method.definitions"/>.
455</t>
456
457<section title="Method Registry" anchor="method.registry">
458<t>
459  The HTTP Method Registry defines the name space for the Method token in the
460  Request line of an HTTP request.
461</t>
462<t>
463  Registrations &MUST; include the following fields:
464  <list style="symbols">
465    <t>Method Name (see <xref target="method"/>)</t>
466    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
467    <t>Pointer to specification text</t>
468  </list>
469</t>
470<t>
471  Values to be added to this name space are subject to IETF review
472  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
473</t>
474<t>
475  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
476</t>
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<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
490  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
491                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
492                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
493                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
494                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
495                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
496                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
497                 / <x:ref>Host</x:ref>                     ; &header-host;
498                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
499                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
500                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
501                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
502                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
503                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
504                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
505                 / <x:ref>Range</x:ref>                    ; &header-range;
506                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
507                 / <x:ref>TE</x:ref>                       ; &header-te;
508                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
509</artwork></figure>
510<t>
511   Request-header field names can be extended reliably only in
512   combination with a change in the protocol version. However, new or
513   experimental header fields &MAY; be given the semantics of request-header
514   fields if all parties in the communication recognize them to
515   be request-header fields. Unrecognized header fields are treated as
516   entity-header fields.
517</t>
518</section>
519
520<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
521  <x:anchor-alias value="Reason-Phrase"/>
522  <x:anchor-alias value="Status-Code"/>
523  <x:anchor-alias value="extension-code"/>
524<t>
525   The Status-Code element is a 3-digit integer result code of the
526   attempt to understand and satisfy the request. The status codes listed
527   below are defined in <xref target="status.codes"/>.
528   The Reason-Phrase is intended to give a short
529   textual description of the Status-Code. The Status-Code is intended
530   for use by automata and the Reason-Phrase is intended for the human
531   user. The client is not required to examine or display the Reason-Phrase.
532</t>
533<t> 
534   The individual values of the numeric status codes defined for
535   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
536   presented below. The reason phrases listed here are only
537   recommendations -- they &MAY; be replaced by local equivalents without
538   affecting the protocol.
539</t>
540<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"/>
541  <x:ref>Status-Code</x:ref>    =
542         "100"  ; <xref target="status.100"/>: Continue
543       / "101"  ; <xref target="status.101"/>: Switching Protocols
544       / "200"  ; <xref target="status.200"/>: OK
545       / "201"  ; <xref target="status.201"/>: Created
546       / "202"  ; <xref target="status.202"/>: Accepted
547       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
548       / "204"  ; <xref target="status.204"/>: No Content
549       / "205"  ; <xref target="status.205"/>: Reset Content
550       / "206"  ; &status-206;: Partial Content
551       / "300"  ; <xref target="status.300"/>: Multiple Choices
552       / "301"  ; <xref target="status.301"/>: Moved Permanently
553       / "302"  ; <xref target="status.302"/>: Found
554       / "303"  ; <xref target="status.303"/>: See Other
555       / "304"  ; &status-304;: Not Modified
556       / "305"  ; <xref target="status.305"/>: Use Proxy
557       / "307"  ; <xref target="status.307"/>: Temporary Redirect
558       / "400"  ; <xref target="status.400"/>: Bad Request
559       / "401"  ; &status-401;: Unauthorized
560       / "402"  ; <xref target="status.402"/>: Payment Required
561       / "403"  ; <xref target="status.403"/>: Forbidden
562       / "404"  ; <xref target="status.404"/>: Not Found
563       / "405"  ; <xref target="status.405"/>: Method Not Allowed
564       / "406"  ; <xref target="status.406"/>: Not Acceptable
565       / "407"  ; &status-407;: Proxy Authentication Required
566       / "408"  ; <xref target="status.408"/>: Request Time-out
567       / "409"  ; <xref target="status.409"/>: Conflict
568       / "410"  ; <xref target="status.410"/>: Gone
569       / "411"  ; <xref target="status.411"/>: Length Required
570       / "412"  ; &status-412;: Precondition Failed
571       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
572       / "414"  ; <xref target="status.414"/>: URI Too Long
573       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
574       / "416"  ; &status-416;: Requested range not satisfiable
575       / "417"  ; <xref target="status.417"/>: Expectation Failed
576       / "500"  ; <xref target="status.500"/>: Internal Server Error
577       / "501"  ; <xref target="status.501"/>: Not Implemented
578       / "502"  ; <xref target="status.502"/>: Bad Gateway
579       / "503"  ; <xref target="status.503"/>: Service Unavailable
580       / "504"  ; <xref target="status.504"/>: Gateway Time-out
581       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
582       / <x:ref>extension-code</x:ref>
583
584  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
585  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
586</artwork></figure>
587<t>
588   HTTP status codes are extensible. HTTP applications are not required
589   to understand the meaning of all registered status codes, though such
590   understanding is obviously desirable. However, applications &MUST;
591   understand the class of any status code, as indicated by the first
592   digit, and treat any unrecognized response as being equivalent to the
593   x00 status code of that class, with the exception that an
594   unrecognized response &MUST-NOT; be cached. For example, if an
595   unrecognized status code of 431 is received by the client, it can
596   safely assume that there was something wrong with its request and
597   treat the response as if it had received a 400 status code. In such
598   cases, user agents &SHOULD; present to the user the entity returned
599   with the response, since that entity is likely to include human-readable
600   information which will explain the unusual status.
601</t>
602
603<section title="Status Code Registry" anchor="status.code.registry">
604<t>
605  The HTTP Status Code Registry defines the name space for the Status-Code
606  token in the Status line of an HTTP response.
607</t>
608<t>
609  Values to be added to this name space are subject to IETF review
610  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
611</t>
612<t>
613  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
614</t>
615</section>
616
617</section>
618
619<section title="Response Header Fields" anchor="response.header.fields">
620  <x:anchor-alias value="response-header"/>
621<t>
622   The response-header fields allow the server to pass additional
623   information about the response which cannot be placed in the Status-Line.
624   These header fields give information about the server and about
625   further access to the resource identified by the Effective Request URI
626   (&effective-request-uri;).
627</t>
628<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
629  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
630                  / <x:ref>Age</x:ref>                     ; &header-age;
631                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
632                  / <x:ref>ETag</x:ref>                    ; &header-etag;
633                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
634                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
635                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
636                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
637                  / <x:ref>Vary</x:ref>                    ; &header-vary;
638                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
639</artwork></figure>
640<t>
641   Response-header field names can be extended reliably only in
642   combination with a change in the protocol version. However, new or
643   experimental header fields &MAY; be given the semantics of response-header
644   fields if all parties in the communication recognize them to
645   be response-header fields. Unrecognized header fields are treated as
646   entity-header fields.
647</t>
648</section>
649
650<section title="Entity" anchor="entity">
651<t>
652   Request and Response messages &MAY; transfer an entity if not otherwise
653   restricted by the request method or response status code. An entity
654   consists of entity-header fields and an entity-body, although some
655   responses will only include the entity-headers. HTTP entity-body and
656   entity-header fields are defined in &payload;.
657</t>
658<t>
659   An entity-body is only present in a message when a message-body is
660   present, as described in &message-body;. The entity-body is obtained
661   from the message-body by decoding any Transfer-Encoding that might
662   have been applied to ensure safe and proper transfer of the message.
663</t>
664
665<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
666<t>
667   It is sometimes necessary to determine the identity of the resource
668   associated with a representation.
669</t>
670<t>
671   An HTTP request representation, when present, is always associated with an
672   anonymous (i.e., unidentified) resource.
673</t>
674<t>
675   In the common case, an HTTP response is a representation of the resource
676   located at the Effective Request URI (see &effective-request-uri;). However,
677   this is not always the case. To determine the URI of the resource a
678   response is associated with, the following rules are used (with the first
679   applicable one being selected):
680</t>
681<t><list style="numbers">
682   <t>If the response status code is 200 or 203 and the request method was GET,
683   the response is a representation of the resource at the Effective Request URI.</t>
684   <t>If the response status is 204, 206, or 304 and the request method was GET
685   or HEAD, the response is a partial representation of the resource at the
686   Effective Request URI (see &caching-combining-headers;).</t>
687   <t>If the response has a Content-Location header, and that URI is the same
688   as the Effective Request URI, the response is a representation of the
689   resource at the Effective Request URI.</t>
690   <t>If the response has a Content-Location header, and that URI is not the
691   same as the Effective Request URI, the response asserts that it is a
692   representation of the resource at the Content-Location URI (but it may not
693   be).</t>
694   <t>Otherwise, the response is a representation of an anonymous (i.e.,
695   unidentified) resource.</t>
696</list></t>
697<t>
698  <cref anchor="TODO-req-uri">
699   The comparison function is going to have to be defined somewhere,
700   because we already need to compare URIs for things like cache invalidation.</cref>
701</t>
702</section>
703
704</section>
705
706
707<section title="Method Definitions" anchor="method.definitions">
708<t>
709   The set of common methods for HTTP/1.1 is defined below. Although
710   this set can be expanded, additional methods cannot be assumed to
711   share the same semantics for separately extended clients and servers.
712</t>
713
714<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
715
716<section title="Safe Methods" anchor="safe.methods">
717<iref item="Safe Methods" primary="true"/>
718<t>
719   Implementors should be aware that the software represents the user in
720   their interactions over the Internet, and should be careful to allow
721   the user to be aware of any actions they might take which may have an
722   unexpected significance to themselves or others.
723</t>
724<t>
725   In particular, the convention has been established that the GET, HEAD,
726   OPTIONS, and TRACE methods &SHOULD-NOT;  have the significance of taking an action
727   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
728   This allows user agents to represent other methods, such as POST, PUT
729   and DELETE, in a special way, so that the user is made aware of the
730   fact that a possibly unsafe action is being requested.
731</t>
732<t>
733   Naturally, it is not possible to ensure that the server does not
734   generate side-effects as a result of performing a GET request; in
735   fact, some dynamic resources consider that a feature. The important
736   distinction here is that the user did not request the side-effects,
737   so therefore cannot be held accountable for them.
738</t>
739</section>
740
741<section title="Idempotent Methods" anchor="idempotent.methods">
742<iref item="Idempotent Methods" primary="true"/>
743<t>
744   Methods can also have the property of "idempotence" in that, aside
745   from error or expiration issues, the intended effect of multiple
746   identical requests is the same as for a single request.
747   The methods PUT, DELETE, and all safe methods are idempotent.
748   It is important to note that idempotence refers only to changes
749   requested by the client: a server is free to change its state due
750   to multiple requests for the purpose of tracking those requests,
751   versioning of results, etc.
752</t>
753</section>
754</section>
755
756<section title="OPTIONS" anchor="OPTIONS">
757  <rdf:Description>
758    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
759  </rdf:Description>
760  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
761  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
762<t>
763   The OPTIONS method represents a request for information about the
764   communication options available on the request/response chain
765   identified by the Effective Request URI. This method allows the client to
766   determine the options and/or requirements associated with a resource,
767   or the capabilities of a server, without implying a resource action
768   or initiating a resource retrieval.
769</t>
770<t>
771   Responses to this method are not cacheable.
772</t>
773<t>
774   If the OPTIONS request includes an entity-body (as indicated by the
775   presence of Content-Length or Transfer-Encoding), then the media type
776   &MUST; be indicated by a Content-Type field. Although this
777   specification does not define any use for such a body, future
778   extensions to HTTP might use the OPTIONS body to make more detailed
779   queries on the server.
780</t>
781<t>
782   If the request-target is an asterisk ("*"), the OPTIONS request is
783   intended to apply to the server in general rather than to a specific
784   resource. Since a server's communication options typically depend on
785   the resource, the "*" request is only useful as a "ping" or "no-op"
786   type of method; it does nothing beyond allowing the client to test
787   the capabilities of the server. For example, this can be used to test
788   a proxy for HTTP/1.1 compliance (or lack thereof).
789</t>
790<t>
791   If the request-target is not an asterisk, the OPTIONS request applies
792   only to the options that are available when communicating with that
793   resource.
794</t>
795<t>
796   A 200 response &SHOULD; include any header fields that indicate
797   optional features implemented by the server and applicable to that
798   resource (e.g., Allow), possibly including extensions not defined by
799   this specification. The response body, if any, &SHOULD; also include
800   information about the communication options. The format for such a
801   body is not defined by this specification, but might be defined by
802   future extensions to HTTP. Content negotiation &MAY; be used to select
803   the appropriate response format. If no response body is included, the
804   response &MUST; include a Content-Length field with a field-value of
805   "0".
806</t>
807<t>
808   The Max-Forwards request-header field &MAY; be used to target a
809   specific proxy in the request chain. When a proxy receives an OPTIONS
810   request on an absolute-URI for which request forwarding is permitted,
811   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
812   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
813   instead, the proxy &SHOULD; respond with its own communication options.
814   If the Max-Forwards field-value is an integer greater than zero, the
815   proxy &MUST; decrement the field-value when it forwards the request. If
816   no Max-Forwards field is present in the request, then the forwarded
817   request &MUST-NOT; include a Max-Forwards field.
818</t>
819</section>
820
821<section title="GET" anchor="GET">
822  <rdf:Description>
823    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
824  </rdf:Description>
825  <iref primary="true" item="GET method" x:for-anchor=""/>
826  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
827<t>
828   The GET method means retrieve whatever information (in the form of an
829   entity) currently corresponds to the resource identified by the
830   Effective Request URI.
831</t>
832<t>   
833   If the Effective Request URI identifies a data-producing process, it is the
834   produced data which shall be returned as the entity in the response and not
835   the source text of the process, unless that text happens to be the output of
836   the process.
837</t>
838<t>
839   The semantics of the GET method change to a "conditional GET" if the
840   request message includes an If-Modified-Since, If-Unmodified-Since,
841   If-Match, If-None-Match, or If-Range header field. A conditional GET
842   method requests that the entity be transferred only under the
843   circumstances described by the conditional header field(s). The
844   conditional GET method is intended to reduce unnecessary network
845   usage by allowing cached entities to be refreshed without requiring
846   multiple requests or transferring data already held by the client.
847</t>
848<t>
849   The semantics of the GET method change to a "partial GET" if the
850   request message includes a Range header field. A partial GET requests
851   that only part of the entity be transferred, as described in &header-range;.
852   The partial GET method is intended to reduce unnecessary
853   network usage by allowing partially-retrieved entities to be
854   completed without transferring data already held by the client.
855</t>
856<t>
857   The response to a GET request is cacheable if and only if it meets
858   the requirements for HTTP caching described in &caching;.
859</t>
860<t>
861   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
862</t>
863</section>
864
865<section title="HEAD" anchor="HEAD">
866  <rdf:Description>
867    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
868  </rdf:Description>
869  <iref primary="true" item="HEAD method" x:for-anchor=""/>
870  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
871<t>
872   The HEAD method is identical to GET except that the server &MUST-NOT;
873   return a message-body in the response. The metainformation contained
874   in the HTTP headers in response to a HEAD request &SHOULD; be identical
875   to the information sent in response to a GET request. This method can
876   be used for obtaining metainformation about the entity implied by the
877   request without transferring the entity-body itself. This method is
878   often used for testing hypertext links for validity, accessibility,
879   and recent modification.
880</t>
881<t>
882   The response to a HEAD request &MAY; be cacheable in the sense that the
883   information contained in the response &MAY; be used to update a
884   previously cached entity from that resource. If the new field values
885   indicate that the cached entity differs from the current entity (as
886   would be indicated by a change in Content-Length, Content-MD5, ETag
887   or Last-Modified), then the cache &MUST; treat the cache entry as
888   stale.
889</t>
890</section>
891
892<section title="POST" anchor="POST">
893  <iref primary="true" item="POST method" x:for-anchor=""/>
894  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
895<t>
896   The POST method is used to request that the origin server accept the
897   entity enclosed in the request as data to be processed by the resource
898   identified by the Effective Request URI. POST is designed
899   to allow a uniform method to cover the following functions:
900  <list style="symbols">
901    <t>
902      Annotation of existing resources;
903    </t>
904    <t>
905        Posting a message to a bulletin board, newsgroup, mailing list,
906        or similar group of articles;
907    </t>
908    <t>
909        Providing a block of data, such as the result of submitting a
910        form, to a data-handling process;
911    </t>
912    <t>
913        Extending a database through an append operation.
914    </t>
915  </list>
916</t>
917<t>
918   The actual function performed by the POST method is determined by the
919   server and is usually dependent on the Effective Request URI.
920</t>
921<t>
922   The action performed by the POST method might not result in a
923   resource that can be identified by a URI. In this case, either 200
924   (OK) or 204 (No Content) is the appropriate response status,
925   depending on whether or not the response includes an entity that
926   describes the result.
927</t>
928<t>
929   If a resource has been created on the origin server, the response
930   &SHOULD; be 201 (Created) and contain an entity which describes the
931   status of the request and refers to the new resource, and a Location
932   header (see <xref target="header.location"/>).
933</t>
934<t>
935   Responses to this method are not cacheable, unless the response
936   includes appropriate Cache-Control or Expires header fields. However,
937   the 303 (See Other) response can be used to direct the user agent to
938   retrieve a cacheable resource.
939</t>
940</section>
941
942<section title="PUT" anchor="PUT">
943  <iref primary="true" item="PUT method" x:for-anchor=""/>
944  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
945<t>
946   The PUT method requests that the enclosed entity be stored at the
947   Effective Request URI. If the Effective Request URI refers to an already
948   existing resource, the enclosed entity &SHOULD; be considered as a
949   modified version of the one residing on the origin server. Otherwise, if the
950   Effective Request URI does not point to an existing resource, and that URI is
951   capable of being defined as a new resource by the requesting user
952   agent, the origin server can create the resource with that URI.
953</t>
954<t>   
955   If a new resource is created at the Effective Request URI, the origin
956   server &MUST; inform the user agent
957   via the 201 (Created) response. If an existing resource is modified,
958   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
959   to indicate successful completion of the request.
960</t>
961<t>   
962   If the resource could not be created or modified with the Effective Request
963   URI, an appropriate error response &SHOULD; be given that reflects the nature
964   of the problem. The recipient of the entity &MUST-NOT; ignore any Content-*
965   headers (headers starting with the prefix "Content-") that it does
966   not understand or implement
967   and &MUST; return a 501 (Not Implemented) response in such cases.
968</t>
969<t>
970   If the request passes through a cache and the Effective Request URI
971   identifies one or more currently cached entities, those entries &SHOULD; be
972   treated as stale. Responses to this method are not cacheable.
973</t>
974<t>
975   The fundamental difference between the POST and PUT requests is
976   reflected in the different meaning of the Effective Request URI. The URI in a
977   POST request identifies the resource that will handle the enclosed
978   entity. That resource might be a data-accepting process, a gateway to
979   some other protocol, or a separate entity that accepts annotations.
980   In contrast, the URI in a PUT request identifies the entity enclosed
981   with the request -- the user agent knows what URI is intended and the
982   server &MUST-NOT; attempt to apply the request to some other resource.
983   If the server desires that the request be applied to a different URI,
984   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
985   then make its own decision regarding whether or not to redirect the
986   request.
987</t>
988<t>
989   A single resource &MAY; be identified by many different URIs. For
990   example, an article might have a URI for identifying "the current
991   version" which is separate from the URI identifying each particular
992   version. In this case, a PUT request on a general URI might result in
993   several other URIs being defined by the origin server.
994</t>
995<t>
996   HTTP/1.1 does not define how a PUT method affects the state of an
997   origin server.
998</t>
999<t>
1000   Unless otherwise specified for a particular entity-header, the
1001   entity-headers in the PUT request &SHOULD; be applied to the resource
1002   created or modified by the PUT.
1003</t>
1004</section>
1005
1006<section title="DELETE" anchor="DELETE">
1007  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1008  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1009<t>
1010   The DELETE method requests that the origin server delete the resource
1011   identified by the Effective Request URI. This method &MAY; be overridden by
1012   human intervention (or other means) on the origin server. The client cannot
1013   be guaranteed that the operation has been carried out, even if the
1014   status code returned from the origin server indicates that the action
1015   has been completed successfully. However, the server &SHOULD-NOT; 
1016   indicate success unless, at the time the response is given, it
1017   intends to delete the resource or move it to an inaccessible
1018   location.
1019</t>
1020<t>
1021   A successful response &SHOULD; be 200 (OK) if the response includes an
1022   entity describing the status, 202 (Accepted) if the action has not
1023   yet been enacted, or 204 (No Content) if the action has been enacted
1024   but the response does not include an entity.
1025</t>
1026<t>
1027   If the request passes through a cache and the Effective Request URI
1028   identifies one or more currently cached entities, those entries &SHOULD; be
1029   treated as stale. Responses to this method are not cacheable.
1030</t>
1031</section>
1032
1033<section title="TRACE" anchor="TRACE">
1034  <rdf:Description>
1035    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1036  </rdf:Description>
1037  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1038  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1039<t>
1040   The TRACE method is used to invoke a remote, application-layer loop-back
1041   of the request message. The final recipient of the request
1042   &SHOULD; reflect the message received back to the client as the
1043   entity-body of a 200 (OK) response. The final recipient is either the
1044   origin server or the first proxy or gateway to receive a Max-Forwards
1045   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1046   &MUST-NOT; include an entity.
1047</t>
1048<t>
1049   TRACE allows the client to see what is being received at the other
1050   end of the request chain and use that data for testing or diagnostic
1051   information. The value of the Via header field (&header-via;) is of
1052   particular interest, since it acts as a trace of the request chain.
1053   Use of the Max-Forwards header field allows the client to limit the
1054   length of the request chain, which is useful for testing a chain of
1055   proxies forwarding messages in an infinite loop.
1056</t>
1057<t>
1058   If the request is valid, the response &SHOULD; contain the entire
1059   request message in the entity-body, with a Content-Type of
1060   "message/http" (see &media-type-message-http;). Responses to this method
1061   &MUST-NOT; be cached.
1062</t>
1063</section>
1064
1065<section title="CONNECT" anchor="CONNECT">
1066  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1067  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1068<t>
1069   This specification reserves the method name CONNECT for use with a
1070   proxy that can dynamically switch to being a tunnel (e.g., SSL
1071   tunneling <xref target="RFC2817"/>).
1072</t>
1073</section>
1074</section>
1075
1076
1077<section title="Status Code Definitions" anchor="status.codes">
1078<t>
1079   Each Status-Code is described below, including any metainformation required
1080   in the response.
1081</t>
1082
1083<section title="Informational 1xx" anchor="status.1xx">
1084<t>
1085   This class of status code indicates a provisional response,
1086   consisting only of the Status-Line and optional headers, and is
1087   terminated by an empty line. There are no required headers for this
1088   class of status code. Since HTTP/1.0 did not define any 1xx status
1089   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1090   except under experimental conditions.
1091</t>
1092<t>
1093   A client &MUST; be prepared to accept one or more 1xx status responses
1094   prior to a regular response, even if the client does not expect a 100
1095   (Continue) status message. Unexpected 1xx status responses &MAY; be
1096   ignored by a user agent.
1097</t>
1098<t>
1099   Proxies &MUST; forward 1xx responses, unless the connection between the
1100   proxy and its client has been closed, or unless the proxy itself
1101   requested the generation of the 1xx response. (For example, if a
1102   proxy adds a "Expect: 100-continue" field when it forwards a request,
1103   then it need not forward the corresponding 100 (Continue)
1104   response(s).)
1105</t>
1106
1107<section title="100 Continue" anchor="status.100">
1108  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1109  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1110<t>
1111   The client &SHOULD; continue with its request. This interim response is
1112   used to inform the client that the initial part of the request has
1113   been received and has not yet been rejected by the server. The client
1114   &SHOULD; continue by sending the remainder of the request or, if the
1115   request has already been completed, ignore this response. The server
1116   &MUST; send a final response after the request has been completed. See
1117   &use100; for detailed discussion of the use and handling of this
1118   status code.
1119</t>
1120</section>
1121
1122<section title="101 Switching Protocols" anchor="status.101">
1123  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1124  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1125<t>
1126   The server understands and is willing to comply with the client's
1127   request, via the Upgrade message header field (&header-upgrade;), for a
1128   change in the application protocol being used on this connection. The
1129   server will switch protocols to those defined by the response's
1130   Upgrade header field immediately after the empty line which
1131   terminates the 101 response.
1132</t>
1133<t>
1134   The protocol &SHOULD; be switched only when it is advantageous to do
1135   so. For example, switching to a newer version of HTTP is advantageous
1136   over older versions, and switching to a real-time, synchronous
1137   protocol might be advantageous when delivering resources that use
1138   such features.
1139</t>
1140</section>
1141</section>
1142
1143<section title="Successful 2xx" anchor="status.2xx">
1144<t>
1145   This class of status code indicates that the client's request was
1146   successfully received, understood, and accepted.
1147</t>
1148
1149<section title="200 OK" anchor="status.200">
1150  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1151  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1152<t>
1153   The request has succeeded. The information returned with the response
1154   is dependent on the method used in the request, for example:
1155  <list style="hanging">
1156    <t hangText="GET">
1157          an entity corresponding to the requested resource is sent in
1158          the response;
1159    </t>
1160    <t hangText="HEAD">
1161          the entity-header fields corresponding to the requested
1162          resource are sent in the response without any message-body;
1163    </t>
1164    <t hangText="POST">
1165      an entity describing or containing the result of the action;
1166    </t>
1167    <t hangText="TRACE">
1168      an entity containing the request message as received by the
1169      end server.
1170    </t>
1171  </list>
1172</t>
1173</section>
1174
1175<section title="201 Created" anchor="status.201">
1176  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1177  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1178<t>
1179   The request has been fulfilled and has resulted in a new resource being
1180   created. The newly created resource can be referenced by the URI(s)
1181   returned in the entity of the response, with the most specific URI
1182   for the resource given by a Location header field. The response
1183   &SHOULD; include an entity containing a list of resource
1184   characteristics and location(s) from which the user or user agent can
1185   choose the one most appropriate. The entity format is specified by
1186   the media type given in the Content-Type header field. The origin
1187   server &MUST; create the resource before returning the 201 status code.
1188   If the action cannot be carried out immediately, the server &SHOULD;
1189   respond with 202 (Accepted) response instead.
1190</t>
1191<t>
1192   A 201 response &MAY; contain an ETag response header field indicating
1193   the current value of the entity tag for the requested variant just
1194   created, see &header-etag;.
1195</t>
1196</section>
1197
1198<section title="202 Accepted" anchor="status.202">
1199  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1200  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1201<t>
1202   The request has been accepted for processing, but the processing has
1203   not been completed.  The request might or might not eventually be
1204   acted upon, as it might be disallowed when processing actually takes
1205   place. There is no facility for re-sending a status code from an
1206   asynchronous operation such as this.
1207</t>
1208<t>
1209   The 202 response is intentionally non-committal. Its purpose is to
1210   allow a server to accept a request for some other process (perhaps a
1211   batch-oriented process that is only run once per day) without
1212   requiring that the user agent's connection to the server persist
1213   until the process is completed. The entity returned with this
1214   response &SHOULD; include an indication of the request's current status
1215   and either a pointer to a status monitor or some estimate of when the
1216   user can expect the request to be fulfilled.
1217</t>
1218</section>
1219
1220<section title="203 Non-Authoritative Information" anchor="status.203">
1221  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1222  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1223<t>
1224   The returned metainformation in the entity-header is not the
1225   definitive set as available from the origin server, but is gathered
1226   from a local or a third-party copy. The set presented &MAY; be a subset
1227   or superset of the original version. For example, including local
1228   annotation information about the resource might result in a superset
1229   of the metainformation known by the origin server. Use of this
1230   response code is not required and is only appropriate when the
1231   response would otherwise be 200 (OK).
1232</t>
1233</section>
1234
1235<section title="204 No Content" anchor="status.204">
1236  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1237  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1238<t>
1239   The server has fulfilled the request but does not need to return an
1240   entity-body, and might want to return updated metainformation. The
1241   response &MAY; include new or updated metainformation in the form of
1242   entity-headers, which if present &SHOULD; be associated with the
1243   requested variant.
1244</t>
1245<t>
1246   If the client is a user agent, it &SHOULD-NOT;  change its document view
1247   from that which caused the request to be sent. This response is
1248   primarily intended to allow input for actions to take place without
1249   causing a change to the user agent's active document view, although
1250   any new or updated metainformation &SHOULD; be applied to the document
1251   currently in the user agent's active view.
1252</t>
1253<t>
1254   The 204 response &MUST-NOT; include a message-body, and thus is always
1255   terminated by the first empty line after the header fields.
1256</t>
1257</section>
1258
1259<section title="205 Reset Content" anchor="status.205">
1260  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1261  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1262<t>
1263   The server has fulfilled the request and the user agent &SHOULD; reset
1264   the document view which caused the request to be sent. This response
1265   is primarily intended to allow input for actions to take place via
1266   user input, followed by a clearing of the form in which the input is
1267   given so that the user can easily initiate another input action. The
1268   response &MUST-NOT; include an entity.
1269</t>
1270</section>
1271
1272<section title="206 Partial Content" anchor="status.206">
1273  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1274  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1275  <rdf:Description>
1276    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1277  </rdf:Description>
1278<t>
1279   The server has fulfilled the partial GET request for the resource
1280   and the enclosed entity is a partial representation as defined in &status-206;.
1281</t>
1282</section>
1283</section>
1284
1285<section title="Redirection 3xx" anchor="status.3xx">
1286<t>
1287   This class of status code indicates that further action needs to be
1288   taken by the user agent in order to fulfill the request.  The action
1289   required &MAY; be carried out by the user agent without interaction
1290   with the user if and only if the method used in the second request is
1291   known to be "safe", as defined in <xref target="safe.methods"/>.
1292   A client &SHOULD; detect infinite redirection loops, since such loops
1293   generate network traffic for each redirection.
1294</t>
1295<x:note>
1296  <t>
1297    <x:h>Note:</x:h> An earlier version of this specification recommended a
1298    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1299    Content developers should be aware that there might be clients that
1300    implement such a fixed limitation.
1301  </t>
1302</x:note>
1303
1304<section title="300 Multiple Choices" anchor="status.300">
1305  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1306  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1307<t>
1308   The requested resource corresponds to any one of a set of
1309   representations, each with its own specific location, and agent-driven
1310   negotiation information (&content-negotiation;) is being provided so that
1311   the user (or user agent) can select a preferred representation and
1312   redirect its request to that location.
1313</t>
1314<t>
1315   Unless it was a HEAD request, the response &SHOULD; include an entity
1316   containing a list of resource characteristics and location(s) from
1317   which the user or user agent can choose the one most appropriate. The
1318   entity format is specified by the media type given in the Content-Type
1319   header field. Depending upon the format and the capabilities of
1320   the user agent, selection of the most appropriate choice &MAY; be
1321   performed automatically. However, this specification does not define
1322   any standard for such automatic selection.
1323</t>
1324<t>
1325   If the server has a preferred choice of representation, it &SHOULD;
1326   include the specific URI for that representation in the Location
1327   field; user agents &MAY; use the Location field value for automatic
1328   redirection. This response is cacheable unless indicated otherwise.
1329</t>
1330</section>
1331
1332<section title="301 Moved Permanently" anchor="status.301">
1333  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1334  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1335<t>
1336   The requested resource has been assigned a new permanent URI and any
1337   future references to this resource &SHOULD; use one of the returned
1338   URIs.  Clients with link editing capabilities ought to automatically
1339   re-link references to the Effective Request URI to one or more of the new
1340   references returned by the server, where possible. This response is
1341   cacheable unless indicated otherwise.
1342</t>
1343<t>
1344   The new permanent URI &SHOULD; be given by the Location field in the
1345   response. Unless the request method was HEAD, the entity of the
1346   response &SHOULD; contain a short hypertext note with a hyperlink to
1347   the new URI(s).
1348</t>
1349<t>
1350   If the 301 status code is received in response to a request method
1351   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1352   then the request &MAY; be automatically redirected by the user agent without
1353   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1354   request unless it can be confirmed by the user, since this might
1355   change the conditions under which the request was issued.
1356</t>
1357<x:note>
1358  <t>
1359    <x:h>Note:</x:h> When automatically redirecting a POST request after
1360    receiving a 301 status code, some existing HTTP/1.0 user agents
1361    will erroneously change it into a GET request.
1362  </t>
1363</x:note>
1364</section>
1365
1366<section title="302 Found" anchor="status.302">
1367  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1368  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1369<t>
1370   The requested resource resides temporarily under a different URI.
1371   Since the redirection might be altered on occasion, the client &SHOULD;
1372   continue to use the Effectice Request URI for future requests.  This response
1373   is only cacheable if indicated by a Cache-Control or Expires header
1374   field.
1375</t>
1376<t>
1377   The temporary URI &SHOULD; be given by the Location field in the
1378   response. Unless the request method was HEAD, the entity of the
1379   response &SHOULD; contain a short hypertext note with a hyperlink to
1380   the new URI(s).
1381</t>
1382<t>
1383   If the 302 status code is received in response to a request method
1384   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1385   then the request &MAY; be automatically redirected by the user agent without
1386   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1387   request unless it can be confirmed by the user, since this might
1388   change the conditions under which the request was issued.
1389</t>
1390<x:note>
1391  <t>
1392    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1393    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1394    specify that the client is not allowed to change the method on the
1395    redirected request.  However, most existing user agent implementations
1396    treat 302 as if it were a 303 response, performing a GET on the Location
1397    field-value regardless of the original request method. Therefore, a
1398    previous version of this specification
1399    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1400    status codes
1401    <xref target="status.303" format="none">303</xref> and
1402    <xref target="status.307" format="none">307</xref> for servers that wish
1403    to make unambiguously clear which kind of reaction is expected of the
1404    client.
1405  </t>
1406</x:note>
1407</section>
1408
1409<section title="303 See Other" anchor="status.303">
1410  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1411  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1412<t>
1413   The server directs the user agent to a different resource, indicated
1414   by a URI in the Location header field, that provides an indirect
1415   response to the original request.  The user agent &MAY; perform a GET
1416   request on the URI in the Location field in order to obtain a
1417   representation corresponding to the response, be redirected again,
1418   or end with an error status.  The Location URI is not a substitute
1419   reference for the originally requested resource.
1420</t>
1421<t>
1422   The 303 status is generally applicable to any HTTP method.  It is
1423   primarily used to allow the output of a POST action to redirect
1424   the user agent to a selected resource, since doing so provides the
1425   information corresponding to the POST response in a form that
1426   can be separately identified, bookmarked, and cached independent
1427   of the original request.
1428</t>
1429<t>
1430   A 303 response to a GET request indicates that the requested
1431   resource does not have a representation of its own that can be
1432   transferred by the server over HTTP.  The Location URI indicates a
1433   resource that is descriptive of the requested resource such that
1434   the follow-on representation may be useful without implying that
1435   it adequately represents the previously requested resource.
1436   Note that answers to the questions of what can be represented, what
1437   representations are adequate, and what might be a useful description
1438   are outside the scope of HTTP and thus entirely determined by the
1439   URI owner(s).
1440</t>
1441<t>
1442   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1443   cacheable by Cache-Control or Expires header fields.  Except for
1444   responses to a HEAD request, the entity of a 303 response &SHOULD;
1445   contain a short hypertext note with a hyperlink to the Location URI.
1446</t>
1447</section>
1448
1449<section title="304 Not Modified" anchor="status.304">
1450  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1451  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1452  <rdf:Description>
1453    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1454  </rdf:Description>
1455<t>
1456   The response to the request has not been modified since the conditions
1457   indicated by the client's conditional GET request, as defined in &status-304;.
1458</t>
1459</section>
1460
1461<section title="305 Use Proxy" anchor="status.305">
1462  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1463  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1464<t>
1465   The 305 status was defined in a previous version of this specification
1466   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1467</t>
1468</section>
1469
1470<section title="306 (Unused)" anchor="status.306">
1471  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1472  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1473<t>
1474   The 306 status code was used in a previous version of the
1475   specification, is no longer used, and the code is reserved.
1476</t>
1477</section>
1478
1479<section title="307 Temporary Redirect" anchor="status.307">
1480  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1481  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1482<t>
1483   The requested resource resides temporarily under a different URI.
1484   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1485   continue to use the Effective Request URI for future requests.  This response
1486   is only cacheable if indicated by a Cache-Control or Expires header
1487   field.
1488</t>
1489<t>
1490   The temporary URI &SHOULD; be given by the Location field in the
1491   response. Unless the request method was HEAD, the entity of the
1492   response &SHOULD; contain a short hypertext note with a hyperlink to
1493   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1494   understand the 307 status. Therefore, the note &SHOULD; contain the
1495   information necessary for a user to repeat the original request on
1496   the new URI.
1497</t>
1498<t>
1499   If the 307 status code is received in response to a request method
1500   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1501   then the request &MAY; be automatically redirected by the user agent without
1502   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1503   request unless it can be confirmed by the user, since this might
1504   change the conditions under which the request was issued.
1505</t>
1506</section>
1507</section>
1508
1509<section title="Client Error 4xx" anchor="status.4xx">
1510<t>
1511   The 4xx class of status code is intended for cases in which the
1512   client seems to have erred. Except when responding to a HEAD request,
1513   the server &SHOULD; include an entity containing an explanation of the
1514   error situation, and whether it is a temporary or permanent
1515   condition. These status codes are applicable to any request method.
1516   User agents &SHOULD; display any included entity to the user.
1517</t>
1518<t>
1519   If the client is sending data, a server implementation using TCP
1520   &SHOULD; be careful to ensure that the client acknowledges receipt of
1521   the packet(s) containing the response, before the server closes the
1522   input connection. If the client continues sending data to the server
1523   after the close, the server's TCP stack will send a reset packet to
1524   the client, which may erase the client's unacknowledged input buffers
1525   before they can be read and interpreted by the HTTP application.
1526</t>
1527
1528<section title="400 Bad Request" anchor="status.400">
1529  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1530  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1531<t>
1532   The request could not be understood by the server due to malformed
1533   syntax. The client &SHOULD-NOT;  repeat the request without
1534   modifications.
1535</t>
1536</section>
1537
1538<section title="401 Unauthorized" anchor="status.401">
1539  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1540  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1541  <rdf:Description>
1542    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1543  </rdf:Description>
1544<t>
1545   The request requires user authentication (see &status-401;).
1546</t>
1547</section>
1548
1549<section title="402 Payment Required" anchor="status.402">
1550  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1551  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1552<t>
1553   This code is reserved for future use.
1554</t>
1555</section>
1556
1557<section title="403 Forbidden" anchor="status.403">
1558  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1559  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1560<t>
1561   The server understood the request, but is refusing to fulfill it.
1562   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1563   If the request method was not HEAD and the server wishes to make
1564   public why the request has not been fulfilled, it &SHOULD; describe the
1565   reason for the refusal in the entity.  If the server does not wish to
1566   make this information available to the client, the status code 404
1567   (Not Found) can be used instead.
1568</t>
1569</section>
1570
1571<section title="404 Not Found" anchor="status.404">
1572  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1573  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1574<t>
1575   The server has not found anything matching the Effective Request URI. No
1576   indication is given of whether the condition is temporary or
1577   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1578   knows, through some internally configurable mechanism, that an old
1579   resource is permanently unavailable and has no forwarding address.
1580   This status code is commonly used when the server does not wish to
1581   reveal exactly why the request has been refused, or when no other
1582   response is applicable.
1583</t>
1584</section>
1585
1586<section title="405 Method Not Allowed" anchor="status.405">
1587  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1588  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1589<t>
1590   The method specified in the Request-Line is not allowed for the
1591   resource identified by the Effective Request URI. The response &MUST; include an
1592   Allow header containing a list of valid methods for the requested
1593   resource.
1594</t>
1595</section>
1596
1597<section title="406 Not Acceptable" anchor="status.406">
1598  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1599  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1600<t>
1601   The resource identified by the request is only capable of generating
1602   response entities which have content characteristics not acceptable
1603   according to the accept headers sent in the request.
1604</t>
1605<t>
1606   Unless it was a HEAD request, the response &SHOULD; include an entity
1607   containing a list of available entity characteristics and location(s)
1608   from which the user or user agent can choose the one most
1609   appropriate. The entity format is specified by the media type given
1610   in the Content-Type header field. Depending upon the format and the
1611   capabilities of the user agent, selection of the most appropriate
1612   choice &MAY; be performed automatically. However, this specification
1613   does not define any standard for such automatic selection.
1614</t>
1615<x:note>
1616  <t>
1617    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1618    not acceptable according to the accept headers sent in the
1619    request. In some cases, this may even be preferable to sending a
1620    406 response. User agents are encouraged to inspect the headers of
1621    an incoming response to determine if it is acceptable.
1622  </t>
1623</x:note>
1624<t>
1625   If the response could be unacceptable, a user agent &SHOULD;
1626   temporarily stop receipt of more data and query the user for a
1627   decision on further actions.
1628</t>
1629</section>
1630
1631<section title="407 Proxy Authentication Required" anchor="status.407">
1632  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1633  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1634<t>
1635   This code is similar to 401 (Unauthorized), but indicates that the
1636   client must first authenticate itself with the proxy (see &status-407;).
1637</t>
1638</section>
1639
1640<section title="408 Request Timeout" anchor="status.408">
1641  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1642  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1643<t>
1644   The client did not produce a request within the time that the server
1645   was prepared to wait. The client &MAY; repeat the request without
1646   modifications at any later time.
1647</t>
1648</section>
1649
1650<section title="409 Conflict" anchor="status.409">
1651  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1652  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1653<t>
1654   The request could not be completed due to a conflict with the current
1655   state of the resource. This code is only allowed in situations where
1656   it is expected that the user might be able to resolve the conflict
1657   and resubmit the request. The response body &SHOULD; include enough
1658   information for the user to recognize the source of the conflict.
1659   Ideally, the response entity would include enough information for the
1660   user or user agent to fix the problem; however, that might not be
1661   possible and is not required.
1662</t>
1663<t>
1664   Conflicts are most likely to occur in response to a PUT request. For
1665   example, if versioning were being used and the entity being PUT
1666   included changes to a resource which conflict with those made by an
1667   earlier (third-party) request, the server might use the 409 response
1668   to indicate that it can't complete the request. In this case, the
1669   response entity would likely contain a list of the differences
1670   between the two versions in a format defined by the response
1671   Content-Type.
1672</t>
1673</section>
1674
1675<section title="410 Gone" anchor="status.410">
1676  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1677  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1678<t>
1679   The requested resource is no longer available at the server and no
1680   forwarding address is known. This condition is expected to be
1681   considered permanent. Clients with link editing capabilities &SHOULD;
1682   delete references to the Effective Request URI after user approval. If the
1683   server does not know, or has no facility to determine, whether or not
1684   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1685   used instead. This response is cacheable unless indicated otherwise.
1686</t>
1687<t>
1688   The 410 response is primarily intended to assist the task of web
1689   maintenance by notifying the recipient that the resource is
1690   intentionally unavailable and that the server owners desire that
1691   remote links to that resource be removed. Such an event is common for
1692   limited-time, promotional services and for resources belonging to
1693   individuals no longer working at the server's site. It is not
1694   necessary to mark all permanently unavailable resources as "gone" or
1695   to keep the mark for any length of time -- that is left to the
1696   discretion of the server owner.
1697</t>
1698</section>
1699
1700<section title="411 Length Required" anchor="status.411">
1701  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1702  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1703<t>
1704   The server refuses to accept the request without a defined Content-Length.
1705   The client &MAY; repeat the request if it adds a valid
1706   Content-Length header field containing the length of the message-body
1707   in the request message.
1708</t>
1709</section>
1710
1711<section title="412 Precondition Failed" anchor="status.412">
1712  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1713  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1714  <rdf:Description>
1715    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1716  </rdf:Description>
1717<t>
1718   The precondition given in one or more of the request-header fields
1719   evaluated to false when it was tested on the server, as defined in
1720   &status-412;.
1721</t>
1722</section>
1723
1724<section title="413 Request Entity Too Large" anchor="status.413">
1725  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1726  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1727<t>
1728   The server is refusing to process a request because the request
1729   entity is larger than the server is willing or able to process. The
1730   server &MAY; close the connection to prevent the client from continuing
1731   the request.
1732</t>
1733<t>
1734   If the condition is temporary, the server &SHOULD; include a Retry-After
1735   header field to indicate that it is temporary and after what
1736   time the client &MAY; try again.
1737</t>
1738</section>
1739
1740<section title="414 URI Too Long" anchor="status.414">
1741  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1742  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1743<t>
1744   The server is refusing to service the request because the Effective Request URI
1745   is longer than the server is willing to interpret. This rare
1746   condition is only likely to occur when a client has improperly
1747   converted a POST request to a GET request with long query
1748   information, when the client has descended into a URI "black hole" of
1749   redirection (e.g., a redirected URI prefix that points to a suffix of
1750   itself), or when the server is under attack by a client attempting to
1751   exploit security holes present in some servers using fixed-length
1752   buffers for reading or manipulating the Effective Request URI.
1753</t>
1754</section>
1755
1756<section title="415 Unsupported Media Type" anchor="status.415">
1757  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1759<t>
1760   The server is refusing to service the request because the entity of
1761   the request is in a format not supported by the requested resource
1762   for the requested method.
1763</t>
1764</section>
1765
1766<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1767  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1768  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1769  <rdf:Description>
1770    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1771  </rdf:Description>
1772<t>
1773   The request included a Range request-header field (&header-range;) and none of
1774   the range-specifier values in this field overlap the current extent
1775   of the selected resource. See &status-416;
1776</t>
1777</section>
1778
1779<section title="417 Expectation Failed" anchor="status.417">
1780  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1781  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1782<t>
1783   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1784   could not be met by this server, or, if the server is a proxy,
1785   the server has unambiguous evidence that the request could not be met
1786   by the next-hop server.
1787</t>
1788</section>
1789</section>
1790
1791<section title="Server Error 5xx" anchor="status.5xx">
1792<t>
1793   Response status codes beginning with the digit "5" indicate cases in
1794   which the server is aware that it has erred or is incapable of
1795   performing the request. Except when responding to a HEAD request, the
1796   server &SHOULD; include an entity containing an explanation of the
1797   error situation, and whether it is a temporary or permanent
1798   condition. User agents &SHOULD; display any included entity to the
1799   user. These response codes are applicable to any request method.
1800</t>
1801
1802<section title="500 Internal Server Error" anchor="status.500">
1803  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1804  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1805<t>
1806   The server encountered an unexpected condition which prevented it
1807   from fulfilling the request.
1808</t>
1809</section>
1810
1811<section title="501 Not Implemented" anchor="status.501">
1812  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1813  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1814<t>
1815   The server does not support the functionality required to fulfill the
1816   request. This is the appropriate response when the server does not
1817   recognize the request method and is not capable of supporting it for
1818   any resource.
1819</t>
1820</section>
1821
1822<section title="502 Bad Gateway" anchor="status.502">
1823  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1824  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1825<t>
1826   The server, while acting as a gateway or proxy, received an invalid
1827   response from the upstream server it accessed in attempting to
1828   fulfill the request.
1829</t>
1830</section>
1831
1832<section title="503 Service Unavailable" anchor="status.503">
1833  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1834  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1835<t>
1836   The server is currently unable to handle the request due to a
1837   temporary overloading or maintenance of the server. The implication
1838   is that this is a temporary condition which will be alleviated after
1839   some delay. If known, the length of the delay &MAY; be indicated in a
1840   Retry-After header. If no Retry-After is given, the client &SHOULD;
1841   handle the response as it would for a 500 response.
1842</t>
1843<x:note>
1844  <t>
1845    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1846    server must use it when becoming overloaded. Some servers may wish
1847    to simply refuse the connection.
1848  </t>
1849</x:note>
1850</section>
1851
1852<section title="504 Gateway Timeout" anchor="status.504">
1853  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1854  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1855<t>
1856   The server, while acting as a gateway or proxy, did not receive a
1857   timely response from the upstream server specified by the URI (e.g.,
1858   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1859   to access in attempting to complete the request.
1860</t>
1861<x:note>
1862  <t>
1863    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1864    return 400 or 500 when DNS lookups time out.
1865  </t>
1866</x:note>
1867</section>
1868
1869<section title="505 HTTP Version Not Supported" anchor="status.505">
1870  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1871  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1872<t>
1873   The server does not support, or refuses to support, the protocol
1874   version that was used in the request message. The server is
1875   indicating that it is unable or unwilling to complete the request
1876   using the same major version as the client, as described in &http-version;,
1877   other than with this error message. The response &SHOULD; contain
1878   an entity describing why that version is not supported and what other
1879   protocols are supported by that server.
1880</t>
1881
1882</section>
1883</section>
1884</section>
1885
1886
1887<section title="Header Field Definitions" anchor="header.fields">
1888<t>
1889   This section defines the syntax and semantics of HTTP/1.1 header fields
1890   related to request and response semantics.
1891</t>
1892<t>
1893   For entity-header fields, both sender and recipient refer to either the
1894   client or the server, depending on who sends and who receives the entity.
1895</t>
1896
1897<section title="Allow" anchor="header.allow">
1898  <iref primary="true" item="Allow header" x:for-anchor=""/>
1899  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1900  <x:anchor-alias value="Allow"/>
1901  <x:anchor-alias value="Allow-v"/>
1902<t>
1903   The "Allow" response-header field lists the set of methods advertised as
1904   supported by the resource identified by the Effective Request URI. The purpose of
1905   this field is strictly to inform the recipient of valid methods
1906   associated with the resource.
1907</t>
1908<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1909  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1910  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1911</artwork></figure>
1912<t>
1913      Example of use:
1914</t>
1915<figure><artwork type="example">
1916  Allow: GET, HEAD, PUT
1917</artwork></figure>
1918<t>
1919      The actual set of allowed methods is defined
1920      by the origin server at the time of each request.
1921</t>
1922<t>
1923      A proxy &MUST-NOT; modify the Allow header field even if it does not
1924      understand all the methods specified, since the user agent might
1925      have other means of communicating with the origin server.
1926</t>
1927</section>
1928
1929<section title="Expect" anchor="header.expect">
1930  <iref primary="true" item="Expect header" x:for-anchor=""/>
1931  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1932  <x:anchor-alias value="Expect"/>
1933  <x:anchor-alias value="Expect-v"/>
1934  <x:anchor-alias value="expectation"/>
1935  <x:anchor-alias value="expectation-extension"/>
1936  <x:anchor-alias value="expect-params"/>
1937<t>
1938   The "Expect" request-header field is used to indicate that particular
1939   server behaviors are required by the client.
1940</t>
1941<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1942  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1943  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1944 
1945  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1946  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1947                           *<x:ref>expect-params</x:ref> ]
1948  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1949</artwork></figure>
1950<t>
1951   A server that does not understand or is unable to comply with any of
1952   the expectation values in the Expect field of a request &MUST; respond
1953   with appropriate error status. The server &MUST; respond with a 417
1954   (Expectation Failed) status if any of the expectations cannot be met
1955   or, if there are other problems with the request, some other 4xx
1956   status.
1957</t>
1958<t>
1959   This header field is defined with extensible syntax to allow for
1960   future extensions. If a server receives a request containing an
1961   Expect field that includes an expectation-extension that it does not
1962   support, it &MUST; respond with a 417 (Expectation Failed) status.
1963</t>
1964<t>
1965   Comparison of expectation values is case-insensitive for unquoted
1966   tokens (including the 100-continue token), and is case-sensitive for
1967   quoted-string expectation-extensions.
1968</t>
1969<t>
1970   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1971   return a 417 (Expectation Failed) status if it receives a request
1972   with an expectation that it cannot meet. However, the Expect
1973   request-header itself is end-to-end; it &MUST; be forwarded if the
1974   request is forwarded.
1975</t>
1976<t>
1977   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1978   Expect header.
1979</t>
1980<t>
1981   See &use100; for the use of the 100 (Continue) status.
1982</t>
1983</section>
1984
1985<section title="From" anchor="header.from">
1986  <iref primary="true" item="From header" x:for-anchor=""/>
1987  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1988  <x:anchor-alias value="From"/>
1989  <x:anchor-alias value="From-v"/>
1990  <x:anchor-alias value="mailbox"/>
1991<t>
1992   The "From" request-header field, if given, &SHOULD; contain an Internet
1993   e-mail address for the human user who controls the requesting user
1994   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1995   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1996</t>
1997<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1998  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1999  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2000 
2001  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2002</artwork></figure>
2003<t>
2004   An example is:
2005</t>
2006<figure><artwork type="example">
2007  From: webmaster@example.org
2008</artwork></figure>
2009<t>
2010   This header field &MAY; be used for logging purposes and as a means for
2011   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2012   be used as an insecure form of access protection. The interpretation
2013   of this field is that the request is being performed on behalf of the
2014   person given, who accepts responsibility for the method performed. In
2015   particular, robot agents &SHOULD; include this header so that the
2016   person responsible for running the robot can be contacted if problems
2017   occur on the receiving end.
2018</t>
2019<t>
2020   The Internet e-mail address in this field &MAY; be separate from the
2021   Internet host which issued the request. For example, when a request
2022   is passed through a proxy the original issuer's address &SHOULD; be
2023   used.
2024</t>
2025<t>
2026   The client &SHOULD-NOT;  send the From header field without the user's
2027   approval, as it might conflict with the user's privacy interests or
2028   their site's security policy. It is strongly recommended that the
2029   user be able to disable, enable, and modify the value of this field
2030   at any time prior to a request.
2031</t>
2032</section>
2033
2034<section title="Location" anchor="header.location">
2035  <iref primary="true" item="Location header" x:for-anchor=""/>
2036  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2037  <x:anchor-alias value="Location"/>
2038  <x:anchor-alias value="Location-v"/>
2039<t>
2040   The "Location" response-header field is used to identify a newly created
2041   resource, or to redirect the recipient to a different location for
2042   completion of the request.
2043</t>
2044<t>
2045   For 201 (Created) responses, the Location is the URI of the new resource
2046   which was created by the request. For 3xx responses, the location &SHOULD;
2047   indicate the server's preferred URI for automatic redirection to the
2048   resource.
2049</t>
2050<t>
2051   The field value consists of a single URI-reference. When it has the form
2052   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2053   the final value is computed by resolving it against the effective request
2054   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2055</t>
2056<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2057  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2058  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2059</artwork></figure>
2060<figure>
2061<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2062<artwork type="example">
2063  Location: http://www.example.org/pub/WWW/People.html#tim
2064</artwork></figure><figure><artwork type="example">  Location: /index.html
2065</artwork></figure>
2066<t>
2067   There are circumstances in which a fragment identifier in a Location URI
2068   would not be appropriate:
2069   <list style="symbols">
2070      <t>With a 201 Created response, because in this usage the Location header
2071      specifies the URI for the entire created resource.</t>
2072      <t>With 305 Use Proxy.</t>
2073   </list>
2074</t>
2075<x:note>
2076  <t>
2077    <x:h>Note:</x:h> This specification does not define precedence rules
2078    for the case where the original URI, as navigated to by the user
2079    agent, and the Location header field value both contain fragment
2080    identifiers.
2081  </t>
2082</x:note>
2083<x:note>
2084  <t>
2085    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2086    from Location in that the Content-Location identifies the original
2087    location of the entity enclosed in the response. It is therefore
2088    possible for a response to contain header fields for both Location
2089    and Content-Location.
2090  </t>
2091</x:note>
2092</section>
2093
2094<section title="Max-Forwards" anchor="header.max-forwards">
2095  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2096  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2097  <x:anchor-alias value="Max-Forwards"/>
2098  <x:anchor-alias value="Max-Forwards-v"/>
2099<t>
2100   The "Max-Forwards" request-header field provides a mechanism with the
2101   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2102   methods to limit the number of times that the request is forwarded by
2103   proxies or gateways. This can be useful when the client is attempting to
2104   trace a request which appears to be failing or looping in mid-chain.
2105</t>
2106<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2107  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2108  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2109</artwork></figure>
2110<t>
2111   The Max-Forwards value is a decimal integer indicating the remaining
2112   number of times this request message may be forwarded.
2113</t>
2114<t>
2115   Each proxy or gateway recipient of a TRACE or OPTIONS request
2116   containing a Max-Forwards header field &MUST; check and update its
2117   value prior to forwarding the request. If the received value is zero
2118   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2119   respond as the final recipient. If the received Max-Forwards value is
2120   greater than zero, then the forwarded message &MUST; contain an updated
2121   Max-Forwards field with a value decremented by one (1).
2122</t>
2123<t>
2124   The Max-Forwards header field &MAY; be ignored for all other methods
2125   defined by this specification and for any extension methods for which
2126   it is not explicitly referred to as part of that method definition.
2127</t>
2128</section>
2129
2130<section title="Referer" anchor="header.referer">
2131  <iref primary="true" item="Referer header" x:for-anchor=""/>
2132  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2133  <x:anchor-alias value="Referer"/>
2134  <x:anchor-alias value="Referer-v"/>
2135<t>
2136   The "Referer" [sic] request-header field allows the client to specify the
2137   URI of the resource from which the Effective Request URI was obtained (the
2138   "referrer", although the header field is misspelled.).
2139</t>
2140<t>
2141   The Referer header allows servers to generate lists of back-links to
2142   resources for interest, logging, optimized caching, etc. It also allows
2143   obsolete or mistyped links to be traced for maintenance. Some servers use
2144   Referer as a means of controlling where they allow links from (so-called
2145   "deep linking"), but it should be noted that legitimate requests are not
2146   required to contain a Referer header field.
2147</t>
2148<t>
2149   If the Effective Request URI was obtained from a source that does not have its own
2150   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2151   sent with the value "about:blank", or not be sent at all. Note that this
2152   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2153</t>
2154<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2155  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2156  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2157</artwork></figure>
2158<t>
2159   Example:
2160</t>
2161<figure><artwork type="example">
2162  Referer: http://www.example.org/hypertext/Overview.html
2163</artwork></figure>
2164<t>
2165   If the field value is a relative URI, it &SHOULD; be interpreted
2166   relative to the Effective Request URI. The URI &MUST-NOT; include a fragment. See
2167   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2168</t>
2169</section>
2170
2171<section title="Retry-After" anchor="header.retry-after">
2172  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2173  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2174  <x:anchor-alias value="Retry-After"/>
2175  <x:anchor-alias value="Retry-After-v"/>
2176<t>
2177   The response-header "Retry-After" field can be used with a 503 (Service
2178   Unavailable) response to indicate how long the service is expected to
2179   be unavailable to the requesting client. This field &MAY; also be used
2180   with any 3xx (Redirection) response to indicate the minimum time the
2181   user-agent is asked wait before issuing the redirected request.
2182</t>
2183<t>
2184   The value of this field can be either an HTTP-date or an integer number
2185   of seconds (in decimal) after the time of the response.
2186</t>
2187<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2188  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2189  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2190</artwork></figure>
2191<t anchor="rule.delta-seconds">
2192  <x:anchor-alias value="delta-seconds"/>
2193   Time spans are non-negative decimal integers, representing time in
2194   seconds.
2195</t>
2196<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2197  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2198</artwork></figure>
2199<t>
2200   Two examples of its use are
2201</t>
2202<figure><artwork type="example">
2203  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2204  Retry-After: 120
2205</artwork></figure>
2206<t>
2207   In the latter example, the delay is 2 minutes.
2208</t>
2209</section>
2210
2211<section title="Server" anchor="header.server">
2212  <iref primary="true" item="Server header" x:for-anchor=""/>
2213  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2214  <x:anchor-alias value="Server"/>
2215  <x:anchor-alias value="Server-v"/>
2216<t>
2217   The "Server" response-header field contains information about the
2218   software used by the origin server to handle the request.
2219</t>
2220<t>
2221   The field can contain multiple product tokens (&product-tokens;) and
2222   comments (&header-fields;) identifying the server and any significant
2223   subproducts. The product tokens are listed in order of their significance
2224   for identifying the application.
2225</t>
2226<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2227  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2228  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2229                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2230</artwork></figure>
2231<t>
2232   Example:
2233</t>
2234<figure><artwork type="example">
2235  Server: CERN/3.0 libwww/2.17
2236</artwork></figure>
2237<t>
2238   If the response is being forwarded through a proxy, the proxy
2239   application &MUST-NOT; modify the Server response-header. Instead, it
2240   &MUST; include a Via field (as described in &header-via;).
2241</t>
2242<x:note>
2243  <t>
2244    <x:h>Note:</x:h> Revealing the specific software version of the server might
2245    allow the server machine to become more vulnerable to attacks
2246    against software that is known to contain security holes. Server
2247    implementors are encouraged to make this field a configurable
2248    option.
2249  </t>
2250</x:note>
2251</section>
2252
2253<section title="User-Agent" anchor="header.user-agent">
2254  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2255  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2256  <x:anchor-alias value="User-Agent"/>
2257  <x:anchor-alias value="User-Agent-v"/>
2258<t>
2259   The "User-Agent" request-header field contains information about the
2260   user agent originating the request. This is for statistical purposes,
2261   the tracing of protocol violations, and automated recognition of user
2262   agents for the sake of tailoring responses to avoid particular user
2263   agent limitations.
2264</t>
2265<t>
2266   User agents &SHOULD; include this field with requests. The field can contain
2267   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2268   identifying the agent and any subproducts which form a significant part of
2269   the user agent. By convention, the product tokens are listed in order of
2270   their significance for identifying the application.
2271</t>
2272<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2273  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2274  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2275                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2276</artwork></figure>
2277<t>
2278   Example:
2279</t>
2280<figure><artwork type="example">
2281  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2282</artwork></figure>
2283</section>
2284
2285</section>
2286
2287<section title="IANA Considerations" anchor="IANA.considerations">
2288
2289<section title="Method Registry" anchor="method.registration">
2290<t>
2291  The registration procedure for HTTP Methods is defined by
2292  <xref target="method.registry"/> of this document.
2293</t>
2294<t>
2295   The HTTP Method Registry should be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2296   and be populated with the registrations below:
2297</t>
2298<?BEGININC p2-semantics.iana-methods ?>
2299<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2300<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2301   <ttcol>Method</ttcol>
2302   <ttcol>Safe</ttcol>
2303   <ttcol>Reference</ttcol>
2304   <c>CONNECT</c>
2305   <c>no</c>
2306   <c>
2307      <xref target="CONNECT"/>
2308   </c>
2309   <c>DELETE</c>
2310   <c>no</c>
2311   <c>
2312      <xref target="DELETE"/>
2313   </c>
2314   <c>GET</c>
2315   <c>yes</c>
2316   <c>
2317      <xref target="GET"/>
2318   </c>
2319   <c>HEAD</c>
2320   <c>yes</c>
2321   <c>
2322      <xref target="HEAD"/>
2323   </c>
2324   <c>OPTIONS</c>
2325   <c>yes</c>
2326   <c>
2327      <xref target="OPTIONS"/>
2328   </c>
2329   <c>POST</c>
2330   <c>no</c>
2331   <c>
2332      <xref target="POST"/>
2333   </c>
2334   <c>PUT</c>
2335   <c>no</c>
2336   <c>
2337      <xref target="PUT"/>
2338   </c>
2339   <c>TRACE</c>
2340   <c>yes</c>
2341   <c>
2342      <xref target="TRACE"/>
2343   </c>
2344</texttable>
2345<!--(END)-->
2346<?ENDINC p2-semantics.iana-methods ?>
2347</section>
2348
2349<section title="Status Code Registry" anchor="status.code.registration">
2350<t>
2351   The registration procedure for HTTP Status Codes -- previously defined
2352   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2353   by <xref target="status.code.registry"/> of this document.
2354</t>
2355<t>
2356   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2357   should be updated with the registrations below:
2358</t>
2359<?BEGININC p2-semantics.iana-status-codes ?>
2360<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2361<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2362   <ttcol>Value</ttcol>
2363   <ttcol>Description</ttcol>
2364   <ttcol>Reference</ttcol>
2365   <c>100</c>
2366   <c>Continue</c>
2367   <c>
2368      <xref target="status.100"/>
2369   </c>
2370   <c>101</c>
2371   <c>Switching Protocols</c>
2372   <c>
2373      <xref target="status.101"/>
2374   </c>
2375   <c>200</c>
2376   <c>OK</c>
2377   <c>
2378      <xref target="status.200"/>
2379   </c>
2380   <c>201</c>
2381   <c>Created</c>
2382   <c>
2383      <xref target="status.201"/>
2384   </c>
2385   <c>202</c>
2386   <c>Accepted</c>
2387   <c>
2388      <xref target="status.202"/>
2389   </c>
2390   <c>203</c>
2391   <c>Non-Authoritative Information</c>
2392   <c>
2393      <xref target="status.203"/>
2394   </c>
2395   <c>204</c>
2396   <c>No Content</c>
2397   <c>
2398      <xref target="status.204"/>
2399   </c>
2400   <c>205</c>
2401   <c>Reset Content</c>
2402   <c>
2403      <xref target="status.205"/>
2404   </c>
2405   <c>300</c>
2406   <c>Multiple Choices</c>
2407   <c>
2408      <xref target="status.300"/>
2409   </c>
2410   <c>301</c>
2411   <c>Moved Permanently</c>
2412   <c>
2413      <xref target="status.301"/>
2414   </c>
2415   <c>302</c>
2416   <c>Found</c>
2417   <c>
2418      <xref target="status.302"/>
2419   </c>
2420   <c>303</c>
2421   <c>See Other</c>
2422   <c>
2423      <xref target="status.303"/>
2424   </c>
2425   <c>305</c>
2426   <c>Use Proxy</c>
2427   <c>
2428      <xref target="status.305"/>
2429   </c>
2430   <c>306</c>
2431   <c>(Unused)</c>
2432   <c>
2433      <xref target="status.306"/>
2434   </c>
2435   <c>307</c>
2436   <c>Temporary Redirect</c>
2437   <c>
2438      <xref target="status.307"/>
2439   </c>
2440   <c>400</c>
2441   <c>Bad Request</c>
2442   <c>
2443      <xref target="status.400"/>
2444   </c>
2445   <c>402</c>
2446   <c>Payment Required</c>
2447   <c>
2448      <xref target="status.402"/>
2449   </c>
2450   <c>403</c>
2451   <c>Forbidden</c>
2452   <c>
2453      <xref target="status.403"/>
2454   </c>
2455   <c>404</c>
2456   <c>Not Found</c>
2457   <c>
2458      <xref target="status.404"/>
2459   </c>
2460   <c>405</c>
2461   <c>Method Not Allowed</c>
2462   <c>
2463      <xref target="status.405"/>
2464   </c>
2465   <c>406</c>
2466   <c>Not Acceptable</c>
2467   <c>
2468      <xref target="status.406"/>
2469   </c>
2470   <c>407</c>
2471   <c>Proxy Authentication Required</c>
2472   <c>
2473      <xref target="status.407"/>
2474   </c>
2475   <c>408</c>
2476   <c>Request Timeout</c>
2477   <c>
2478      <xref target="status.408"/>
2479   </c>
2480   <c>409</c>
2481   <c>Conflict</c>
2482   <c>
2483      <xref target="status.409"/>
2484   </c>
2485   <c>410</c>
2486   <c>Gone</c>
2487   <c>
2488      <xref target="status.410"/>
2489   </c>
2490   <c>411</c>
2491   <c>Length Required</c>
2492   <c>
2493      <xref target="status.411"/>
2494   </c>
2495   <c>413</c>
2496   <c>Request Entity Too Large</c>
2497   <c>
2498      <xref target="status.413"/>
2499   </c>
2500   <c>414</c>
2501   <c>URI Too Long</c>
2502   <c>
2503      <xref target="status.414"/>
2504   </c>
2505   <c>415</c>
2506   <c>Unsupported Media Type</c>
2507   <c>
2508      <xref target="status.415"/>
2509   </c>
2510   <c>417</c>
2511   <c>Expectation Failed</c>
2512   <c>
2513      <xref target="status.417"/>
2514   </c>
2515   <c>500</c>
2516   <c>Internal Server Error</c>
2517   <c>
2518      <xref target="status.500"/>
2519   </c>
2520   <c>501</c>
2521   <c>Not Implemented</c>
2522   <c>
2523      <xref target="status.501"/>
2524   </c>
2525   <c>502</c>
2526   <c>Bad Gateway</c>
2527   <c>
2528      <xref target="status.502"/>
2529   </c>
2530   <c>503</c>
2531   <c>Service Unavailable</c>
2532   <c>
2533      <xref target="status.503"/>
2534   </c>
2535   <c>504</c>
2536   <c>Gateway Timeout</c>
2537   <c>
2538      <xref target="status.504"/>
2539   </c>
2540   <c>505</c>
2541   <c>HTTP Version Not Supported</c>
2542   <c>
2543      <xref target="status.505"/>
2544   </c>
2545</texttable>
2546<!--(END)-->
2547<?ENDINC p2-semantics.iana-status-codes ?>
2548</section>
2549<section title="Message Header Registration" anchor="message.header.registration">
2550<t>
2551   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2552   with the permanent registrations below (see <xref target="RFC3864"/>):
2553</t>
2554<?BEGININC p2-semantics.iana-headers ?>
2555<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2556<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2557   <ttcol>Header Field Name</ttcol>
2558   <ttcol>Protocol</ttcol>
2559   <ttcol>Status</ttcol>
2560   <ttcol>Reference</ttcol>
2561
2562   <c>Allow</c>
2563   <c>http</c>
2564   <c>standard</c>
2565   <c>
2566      <xref target="header.allow"/>
2567   </c>
2568   <c>Expect</c>
2569   <c>http</c>
2570   <c>standard</c>
2571   <c>
2572      <xref target="header.expect"/>
2573   </c>
2574   <c>From</c>
2575   <c>http</c>
2576   <c>standard</c>
2577   <c>
2578      <xref target="header.from"/>
2579   </c>
2580   <c>Location</c>
2581   <c>http</c>
2582   <c>standard</c>
2583   <c>
2584      <xref target="header.location"/>
2585   </c>
2586   <c>Max-Forwards</c>
2587   <c>http</c>
2588   <c>standard</c>
2589   <c>
2590      <xref target="header.max-forwards"/>
2591   </c>
2592   <c>Referer</c>
2593   <c>http</c>
2594   <c>standard</c>
2595   <c>
2596      <xref target="header.referer"/>
2597   </c>
2598   <c>Retry-After</c>
2599   <c>http</c>
2600   <c>standard</c>
2601   <c>
2602      <xref target="header.retry-after"/>
2603   </c>
2604   <c>Server</c>
2605   <c>http</c>
2606   <c>standard</c>
2607   <c>
2608      <xref target="header.server"/>
2609   </c>
2610   <c>User-Agent</c>
2611   <c>http</c>
2612   <c>standard</c>
2613   <c>
2614      <xref target="header.user-agent"/>
2615   </c>
2616</texttable>
2617<!--(END)-->
2618<?ENDINC p2-semantics.iana-headers ?>
2619<t>
2620   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2621</t>
2622</section>
2623</section>
2624
2625<section title="Security Considerations" anchor="security.considerations">
2626<t>
2627   This section is meant to inform application developers, information
2628   providers, and users of the security limitations in HTTP/1.1 as
2629   described by this document. The discussion does not include
2630   definitive solutions to the problems revealed, though it does make
2631   some suggestions for reducing security risks.
2632</t>
2633
2634<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2635<t>
2636   Like any generic data transfer protocol, HTTP cannot regulate the
2637   content of the data that is transferred, nor is there any a priori
2638   method of determining the sensitivity of any particular piece of
2639   information within the context of any given request. Therefore,
2640   applications &SHOULD; supply as much control over this information as
2641   possible to the provider of that information. Four header fields are
2642   worth special mention in this context: Server, Via, Referer and From.
2643</t>
2644<t>
2645   Revealing the specific software version of the server might allow the
2646   server machine to become more vulnerable to attacks against software
2647   that is known to contain security holes. Implementors &SHOULD; make the
2648   Server header field a configurable option.
2649</t>
2650<t>
2651   Proxies which serve as a portal through a network firewall &SHOULD;
2652   take special precautions regarding the transfer of header information
2653   that identifies the hosts behind the firewall. In particular, they
2654   &SHOULD; remove, or replace with sanitized versions, any Via fields
2655   generated behind the firewall.
2656</t>
2657<t>
2658   The Referer header allows reading patterns to be studied and reverse
2659   links drawn. Although it can be very useful, its power can be abused
2660   if user details are not separated from the information contained in
2661   the Referer. Even when the personal information has been removed, the
2662   Referer header might indicate a private document's URI whose
2663   publication would be inappropriate.
2664</t>
2665<t>
2666   The information sent in the From field might conflict with the user's
2667   privacy interests or their site's security policy, and hence it
2668   &SHOULD-NOT;  be transmitted without the user being able to disable,
2669   enable, and modify the contents of the field. The user &MUST; be able
2670   to set the contents of this field within a user preference or
2671   application defaults configuration.
2672</t>
2673<t>
2674   We suggest, though do not require, that a convenient toggle interface
2675   be provided for the user to enable or disable the sending of From and
2676   Referer information.
2677</t>
2678<t>
2679   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2680   fields can sometimes be used to determine that a specific client or
2681   server have a particular security hole which might be exploited.
2682   Unfortunately, this same information is often used for other valuable
2683   purposes for which HTTP currently has no better mechanism.
2684</t>
2685<t>
2686   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2687   information sent in request headers in the response entity.
2688   Clients &SHOULD; be careful with sensitive information, like Cookies,
2689   Authorization credentials and other headers that might be used to
2690   collect data from the client.
2691</t> 
2692</section>
2693
2694<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2695<t>
2696   Because the source of a link might be private information or might
2697   reveal an otherwise private information source, it is strongly
2698   recommended that the user be able to select whether or not the
2699   Referer field is sent. For example, a browser client could have a
2700   toggle switch for browsing openly/anonymously, which would
2701   respectively enable/disable the sending of Referer and From
2702   information.
2703</t>
2704<t>
2705   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2706   HTTP request if the referring page was transferred with a secure
2707   protocol.
2708</t>
2709<t>
2710   Authors of services should not use GET-based forms for the submission of
2711   sensitive data because that data will be encoded in the request-target. Many
2712   existing servers, proxies, and user agents log or display the request-target
2713   in places where it might be visible to third parties. Such services can
2714   use POST-based form submission instead.
2715</t>
2716</section>
2717
2718<section title="Location Headers and Spoofing" anchor="location.spoofing">
2719<t>
2720   If a single server supports multiple organizations that do not trust
2721   one another, then it &MUST; check the values of Location and Content-Location
2722   headers in responses that are generated under control of
2723   said organizations to make sure that they do not attempt to
2724   invalidate resources over which they have no authority.
2725</t>
2726</section>
2727
2728</section>
2729
2730<section title="Acknowledgments" anchor="ack">
2731</section>
2732</middle>
2733<back>
2734
2735<references title="Normative References">
2736
2737<reference anchor="Part1">
2738  <front>
2739    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2740    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2741      <organization abbrev="Day Software">Day Software</organization>
2742      <address><email>fielding@gbiv.com</email></address>
2743    </author>
2744    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2745      <organization>One Laptop per Child</organization>
2746      <address><email>jg@laptop.org</email></address>
2747    </author>
2748    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2749      <organization abbrev="HP">Hewlett-Packard Company</organization>
2750      <address><email>JeffMogul@acm.org</email></address>
2751    </author>
2752    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2753      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2754      <address><email>henrikn@microsoft.com</email></address>
2755    </author>
2756    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2757      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2758      <address><email>LMM@acm.org</email></address>
2759    </author>
2760    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2761      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2762      <address><email>paulle@microsoft.com</email></address>
2763    </author>
2764    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2765      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2766      <address><email>timbl@w3.org</email></address>
2767    </author>
2768    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2769      <organization abbrev="W3C">World Wide Web Consortium</organization>
2770      <address><email>ylafon@w3.org</email></address>
2771    </author>
2772    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2773      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2774      <address><email>julian.reschke@greenbytes.de</email></address>
2775    </author>
2776    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2777  </front>
2778  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2779  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2780</reference>
2781
2782<reference anchor="Part3">
2783  <front>
2784    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2785    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2786      <organization abbrev="Day Software">Day Software</organization>
2787      <address><email>fielding@gbiv.com</email></address>
2788    </author>
2789    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2790      <organization>One Laptop per Child</organization>
2791      <address><email>jg@laptop.org</email></address>
2792    </author>
2793    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2794      <organization abbrev="HP">Hewlett-Packard Company</organization>
2795      <address><email>JeffMogul@acm.org</email></address>
2796    </author>
2797    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2798      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2799      <address><email>henrikn@microsoft.com</email></address>
2800    </author>
2801    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2802      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2803      <address><email>LMM@acm.org</email></address>
2804    </author>
2805    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2806      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2807      <address><email>paulle@microsoft.com</email></address>
2808    </author>
2809    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2810      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2811      <address><email>timbl@w3.org</email></address>
2812    </author>
2813    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2814      <organization abbrev="W3C">World Wide Web Consortium</organization>
2815      <address><email>ylafon@w3.org</email></address>
2816    </author>
2817    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2818      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2819      <address><email>julian.reschke@greenbytes.de</email></address>
2820    </author>
2821    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2822  </front>
2823  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2824  <x:source href="p3-payload.xml" basename="p3-payload"/>
2825</reference>
2826
2827<reference anchor="Part4">
2828  <front>
2829    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2830    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2831      <organization abbrev="Day Software">Day Software</organization>
2832      <address><email>fielding@gbiv.com</email></address>
2833    </author>
2834    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2835      <organization>One Laptop per Child</organization>
2836      <address><email>jg@laptop.org</email></address>
2837    </author>
2838    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2839      <organization abbrev="HP">Hewlett-Packard Company</organization>
2840      <address><email>JeffMogul@acm.org</email></address>
2841    </author>
2842    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2843      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2844      <address><email>henrikn@microsoft.com</email></address>
2845    </author>
2846    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2847      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2848      <address><email>LMM@acm.org</email></address>
2849    </author>
2850    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2851      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2852      <address><email>paulle@microsoft.com</email></address>
2853    </author>
2854    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2855      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2856      <address><email>timbl@w3.org</email></address>
2857    </author>
2858    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2859      <organization abbrev="W3C">World Wide Web Consortium</organization>
2860      <address><email>ylafon@w3.org</email></address>
2861    </author>
2862    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2863      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2864      <address><email>julian.reschke@greenbytes.de</email></address>
2865    </author>
2866    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2867  </front>
2868  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2869  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2870</reference>
2871
2872<reference anchor="Part5">
2873  <front>
2874    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2875    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2876      <organization abbrev="Day Software">Day Software</organization>
2877      <address><email>fielding@gbiv.com</email></address>
2878    </author>
2879    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2880      <organization>One Laptop per Child</organization>
2881      <address><email>jg@laptop.org</email></address>
2882    </author>
2883    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2884      <organization abbrev="HP">Hewlett-Packard Company</organization>
2885      <address><email>JeffMogul@acm.org</email></address>
2886    </author>
2887    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2888      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2889      <address><email>henrikn@microsoft.com</email></address>
2890    </author>
2891    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2892      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2893      <address><email>LMM@acm.org</email></address>
2894    </author>
2895    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2896      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2897      <address><email>paulle@microsoft.com</email></address>
2898    </author>
2899    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2900      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2901      <address><email>timbl@w3.org</email></address>
2902    </author>
2903    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2904      <organization abbrev="W3C">World Wide Web Consortium</organization>
2905      <address><email>ylafon@w3.org</email></address>
2906    </author>
2907    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2908      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2909      <address><email>julian.reschke@greenbytes.de</email></address>
2910    </author>
2911    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2912  </front>
2913  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2914  <x:source href="p5-range.xml" basename="p5-range"/>
2915</reference>
2916
2917<reference anchor="Part6">
2918  <front>
2919    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2920    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2921      <organization abbrev="Day Software">Day Software</organization>
2922      <address><email>fielding@gbiv.com</email></address>
2923    </author>
2924    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2925      <organization>One Laptop per Child</organization>
2926      <address><email>jg@laptop.org</email></address>
2927    </author>
2928    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2929      <organization abbrev="HP">Hewlett-Packard Company</organization>
2930      <address><email>JeffMogul@acm.org</email></address>
2931    </author>
2932    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2933      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2934      <address><email>henrikn@microsoft.com</email></address>
2935    </author>
2936    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2937      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2938      <address><email>LMM@acm.org</email></address>
2939    </author>
2940    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2941      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2942      <address><email>paulle@microsoft.com</email></address>
2943    </author>
2944    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2945      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2946      <address><email>timbl@w3.org</email></address>
2947    </author>
2948    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2949      <organization abbrev="W3C">World Wide Web Consortium</organization>
2950      <address><email>ylafon@w3.org</email></address>
2951    </author>
2952    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2953      <address><email>mnot@mnot.net</email></address>
2954    </author>
2955    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2956      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2957      <address><email>julian.reschke@greenbytes.de</email></address>
2958    </author>
2959    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2960  </front>
2961  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2962  <x:source href="p6-cache.xml" basename="p6-cache"/>
2963</reference>
2964
2965<reference anchor="Part7">
2966  <front>
2967    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2968    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2969      <organization abbrev="Day Software">Day Software</organization>
2970      <address><email>fielding@gbiv.com</email></address>
2971    </author>
2972    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2973      <organization>One Laptop per Child</organization>
2974      <address><email>jg@laptop.org</email></address>
2975    </author>
2976    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2977      <organization abbrev="HP">Hewlett-Packard Company</organization>
2978      <address><email>JeffMogul@acm.org</email></address>
2979    </author>
2980    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2981      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2982      <address><email>henrikn@microsoft.com</email></address>
2983    </author>
2984    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2985      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2986      <address><email>LMM@acm.org</email></address>
2987    </author>
2988    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2989      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2990      <address><email>paulle@microsoft.com</email></address>
2991    </author>
2992    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2993      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2994      <address><email>timbl@w3.org</email></address>
2995    </author>
2996    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2997      <organization abbrev="W3C">World Wide Web Consortium</organization>
2998      <address><email>ylafon@w3.org</email></address>
2999    </author>
3000    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3001      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3002      <address><email>julian.reschke@greenbytes.de</email></address>
3003    </author>
3004    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3005  </front>
3006  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3007  <x:source href="p7-auth.xml" basename="p7-auth"/>
3008</reference>
3009
3010<reference anchor="RFC2119">
3011  <front>
3012    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3013    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3014      <organization>Harvard University</organization>
3015      <address><email>sob@harvard.edu</email></address>
3016    </author>
3017    <date month="March" year="1997"/>
3018  </front>
3019  <seriesInfo name="BCP" value="14"/>
3020  <seriesInfo name="RFC" value="2119"/>
3021</reference>
3022
3023<reference anchor="RFC3986">
3024 <front>
3025  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3026  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3027    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3028    <address>
3029       <email>timbl@w3.org</email>
3030       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3031    </address>
3032  </author>
3033  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3034    <organization abbrev="Day Software">Day Software</organization>
3035    <address>
3036      <email>fielding@gbiv.com</email>
3037      <uri>http://roy.gbiv.com/</uri>
3038    </address>
3039  </author>
3040  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3041    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3042    <address>
3043      <email>LMM@acm.org</email>
3044      <uri>http://larry.masinter.net/</uri>
3045    </address>
3046  </author>
3047  <date month='January' year='2005'></date>
3048 </front>
3049 <seriesInfo name="RFC" value="3986"/>
3050 <seriesInfo name="STD" value="66"/>
3051</reference>
3052
3053<reference anchor="RFC5234">
3054  <front>
3055    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3056    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3057      <organization>Brandenburg InternetWorking</organization>
3058      <address>
3059        <email>dcrocker@bbiw.net</email>
3060      </address> 
3061    </author>
3062    <author initials="P." surname="Overell" fullname="Paul Overell">
3063      <organization>THUS plc.</organization>
3064      <address>
3065        <email>paul.overell@thus.net</email>
3066      </address>
3067    </author>
3068    <date month="January" year="2008"/>
3069  </front>
3070  <seriesInfo name="STD" value="68"/>
3071  <seriesInfo name="RFC" value="5234"/>
3072</reference>
3073
3074</references>
3075
3076<references title="Informative References">
3077
3078<reference anchor="RFC1945">
3079  <front>
3080    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3081    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3082      <organization>MIT, Laboratory for Computer Science</organization>
3083      <address><email>timbl@w3.org</email></address>
3084    </author>
3085    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3086      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3087      <address><email>fielding@ics.uci.edu</email></address>
3088    </author>
3089    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3090      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3091      <address><email>frystyk@w3.org</email></address>
3092    </author>
3093    <date month="May" year="1996"/>
3094  </front>
3095  <seriesInfo name="RFC" value="1945"/>
3096</reference>
3097
3098<reference anchor="RFC2068">
3099  <front>
3100    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3101    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3102      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3103      <address><email>fielding@ics.uci.edu</email></address>
3104    </author>
3105    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3106      <organization>MIT Laboratory for Computer Science</organization>
3107      <address><email>jg@w3.org</email></address>
3108    </author>
3109    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3110      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3111      <address><email>mogul@wrl.dec.com</email></address>
3112    </author>
3113    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3114      <organization>MIT Laboratory for Computer Science</organization>
3115      <address><email>frystyk@w3.org</email></address>
3116    </author>
3117    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3118      <organization>MIT Laboratory for Computer Science</organization>
3119      <address><email>timbl@w3.org</email></address>
3120    </author>
3121    <date month="January" year="1997"/>
3122  </front>
3123  <seriesInfo name="RFC" value="2068"/>
3124</reference>
3125
3126<reference anchor="RFC2616">
3127  <front>
3128    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3129    <author initials="R." surname="Fielding" fullname="R. Fielding">
3130      <organization>University of California, Irvine</organization>
3131      <address><email>fielding@ics.uci.edu</email></address>
3132    </author>
3133    <author initials="J." surname="Gettys" fullname="J. Gettys">
3134      <organization>W3C</organization>
3135      <address><email>jg@w3.org</email></address>
3136    </author>
3137    <author initials="J." surname="Mogul" fullname="J. Mogul">
3138      <organization>Compaq Computer Corporation</organization>
3139      <address><email>mogul@wrl.dec.com</email></address>
3140    </author>
3141    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3142      <organization>MIT Laboratory for Computer Science</organization>
3143      <address><email>frystyk@w3.org</email></address>
3144    </author>
3145    <author initials="L." surname="Masinter" fullname="L. Masinter">
3146      <organization>Xerox Corporation</organization>
3147      <address><email>masinter@parc.xerox.com</email></address>
3148    </author>
3149    <author initials="P." surname="Leach" fullname="P. Leach">
3150      <organization>Microsoft Corporation</organization>
3151      <address><email>paulle@microsoft.com</email></address>
3152    </author>
3153    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3154      <organization>W3C</organization>
3155      <address><email>timbl@w3.org</email></address>
3156    </author>
3157    <date month="June" year="1999"/>
3158  </front>
3159  <seriesInfo name="RFC" value="2616"/>
3160</reference>
3161
3162<reference anchor='RFC2817'>
3163  <front>
3164    <title>Upgrading to TLS Within HTTP/1.1</title>
3165    <author initials='R.' surname='Khare' fullname='R. Khare'>
3166      <organization>4K Associates / UC Irvine</organization>
3167      <address><email>rohit@4K-associates.com</email></address>
3168    </author>
3169    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3170      <organization>Agranat Systems, Inc.</organization>
3171      <address><email>lawrence@agranat.com</email></address>
3172    </author>
3173    <date year='2000' month='May' />
3174  </front>
3175  <seriesInfo name='RFC' value='2817' />
3176</reference>
3177
3178<reference anchor='RFC3864'>
3179  <front>
3180    <title>Registration Procedures for Message Header Fields</title>
3181    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3182      <organization>Nine by Nine</organization>
3183      <address><email>GK-IETF@ninebynine.org</email></address>
3184    </author>
3185    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3186      <organization>BEA Systems</organization>
3187      <address><email>mnot@pobox.com</email></address>
3188    </author>
3189    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3190      <organization>HP Labs</organization>
3191      <address><email>JeffMogul@acm.org</email></address>
3192    </author>
3193    <date year='2004' month='September' />
3194  </front>
3195  <seriesInfo name='BCP' value='90' />
3196  <seriesInfo name='RFC' value='3864' />
3197</reference>
3198
3199<reference anchor='RFC5226'>
3200  <front>
3201    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3202    <author initials='T.' surname='Narten' fullname='T. Narten'>
3203      <organization>IBM</organization>
3204      <address><email>narten@us.ibm.com</email></address>
3205    </author>
3206    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3207      <organization>Google</organization>
3208      <address><email>Harald@Alvestrand.no</email></address>
3209    </author>
3210    <date year='2008' month='May' />
3211  </front>
3212  <seriesInfo name='BCP' value='26' />
3213  <seriesInfo name='RFC' value='5226' />
3214</reference>
3215
3216<reference anchor="RFC5322">
3217  <front>
3218    <title>Internet Message Format</title>
3219    <author initials="P." surname="Resnick" fullname="P. Resnick">
3220      <organization>Qualcomm Incorporated</organization>
3221    </author>
3222    <date year="2008" month="October"/>
3223  </front> 
3224  <seriesInfo name="RFC" value="5322"/>
3225</reference>
3226
3227</references>
3228
3229<section title="Compatibility with Previous Versions" anchor="compatibility">
3230<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3231<t>
3232   Clarified which error code should be used for inbound server failures
3233   (e.g., DNS failures). (<xref target="status.504"/>).
3234</t>
3235<t>
3236   201 (Created) had a race that required an Etag be sent when a resource is
3237   first created. (<xref target="status.201"/>).
3238</t>
3239<t>
3240   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3241   failure to implement status code 302 properly.
3242   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
3243</t>
3244<t>
3245   Rewrite of message transmission requirements to make it much harder
3246   for implementors to get it wrong, as the consequences of errors here
3247   can have significant impact on the Internet, and to deal with the
3248   following problems:
3249  <list style="numbers">
3250      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3251         this was incorrectly placing a requirement on the behavior of
3252         an implementation of a future version of HTTP/1.x</t>
3253
3254      <t>Made it clear that user-agents should retry requests, not
3255         "clients" in general.</t>
3256
3257      <t>Converted requirements for clients to ignore unexpected 100
3258         (Continue) responses, and for proxies to forward 100 responses,
3259         into a general requirement for 1xx responses.</t>
3260
3261      <t>Modified some TCP-specific language, to make it clearer that
3262         non-TCP transports are possible for HTTP.</t>
3263
3264      <t>Require that the origin server &MUST-NOT; wait for the request
3265         body before it sends a required 100 (Continue) response.</t>
3266
3267      <t>Allow, rather than require, a server to omit 100 (Continue) if
3268         it has already seen some of the request body.</t>
3269
3270      <t>Allow servers to defend against denial-of-service attacks and
3271         broken clients.</t>
3272  </list>
3273</t>
3274<t>
3275   This change adds the Expect header and 417 status code.
3276</t>
3277<t>
3278   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3279   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3280</t>
3281<t>
3282   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
3283   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3284</t>
3285</section>
3286
3287<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3288<t>
3289  This document takes over the Status Code Registry, previously defined
3290  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3291  (<xref target="status.code.registry"/>)
3292</t>
3293<t>
3294  Clarify definition of POST.
3295  (<xref target="POST"/>)
3296</t>
3297<t>
3298  Failed to consider that there are
3299  many other request methods that are safe to automatically redirect,
3300  and further that the user agent is able to make that determination
3301  based on the request method semantics.
3302  (Sections <xref format="counter" target="status.301"/>,
3303  <xref format="counter" target="status.302"/> and
3304  <xref format="counter" target="status.307"/>)
3305</t>
3306<t>
3307  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3308  It used to indicate that the requested resource must be accessed through the
3309  proxy given by the Location field. The Location field gave the URI of the
3310  proxy. The recipient was expected to repeat this single request via the proxy.
3311  (<xref target="status.305"/>)
3312</t>
3313<t>
3314  Reclassify Allow header as response header, removing the option to
3315  specify it in a PUT request.
3316  Relax the server requirement on the contents of the Allow header and
3317  remove requirement on clients to always trust the header value.
3318  (<xref target="header.allow"/>)
3319</t>
3320<t>
3321  Correct syntax of Location header to allow URI references (including
3322  relative references and fragments), as referred symbol "absoluteURI" wasn't
3323  what was expected, and add some clarifications as to when use of fragments
3324  would not be appropriate.
3325  (<xref target="header.location"/>)
3326</t>
3327<t>
3328  Allow Referer value of "about:blank" as alternative to not specifying it.
3329  (<xref target="header.referer"/>)
3330</t>
3331<t>
3332  In the description of the Server header, the Via field
3333  was described as a SHOULD. The requirement was and is stated
3334  correctly in the description of the Via header in &header-via;.
3335  (<xref target="header.server"/>)
3336</t>
3337</section>
3338
3339</section>
3340
3341<?BEGININC p2-semantics.abnf-appendix ?>
3342<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3343<figure>
3344<artwork type="abnf" name="p2-semantics.parsed-abnf">
3345<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3346<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3347<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3348<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3349<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3350<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3351<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3352<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3353<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3354
3355<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3356<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3357<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3358
3359<x:ref>From</x:ref> = "From:" OWS From-v
3360<x:ref>From-v</x:ref> = mailbox
3361
3362<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3363<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3364
3365<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3366If-Modified-Since =
3367 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3368<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3369<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3370If-Unmodified-Since =
3371 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3372
3373<x:ref>Location</x:ref> = "Location:" OWS Location-v
3374<x:ref>Location-v</x:ref> = URI-reference
3375
3376<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3377<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3378<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3379 / %x47.45.54 ; GET
3380 / %x48.45.41.44 ; HEAD
3381 / %x50.4F.53.54 ; POST
3382 / %x50.55.54 ; PUT
3383 / %x44.45.4C.45.54.45 ; DELETE
3384 / %x54.52.41.43.45 ; TRACE
3385 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3386 / extension-method
3387
3388<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3389
3390Proxy-Authenticate =
3391 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3392Proxy-Authorization =
3393 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3394
3395<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3396<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3397<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3398<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3399<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3400<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3401<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3402
3403<x:ref>Server</x:ref> = "Server:" OWS Server-v
3404<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3405<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3406 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3407 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3408 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3409 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3410 "505" / extension-code
3411
3412<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.8&gt;
3413
3414<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3415<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3416<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3417
3418<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3419
3420WWW-Authenticate =
3421 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3422
3423<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3424
3425<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3426
3427<x:ref>delta-seconds</x:ref> = 1*DIGIT
3428
3429<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3430<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3431<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3432 *expect-params ]
3433<x:ref>extension-code</x:ref> = 3DIGIT
3434<x:ref>extension-method</x:ref> = token
3435
3436<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3437
3438<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3439
3440<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3441<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3442
3443<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3444
3445<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3446 Accept-Language / Authorization / Expect / From / Host / If-Match /
3447 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3448 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3449 User-Agent
3450<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3451 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3452
3453<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3454</artwork>
3455</figure>
3456<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3457; Reason-Phrase defined but not used
3458; Status-Code defined but not used
3459; request-header defined but not used
3460; response-header defined but not used
3461</artwork></figure></section>
3462<?ENDINC p2-semantics.abnf-appendix ?>
3463
3464<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3465
3466<section title="Since RFC2616">
3467<t>
3468  Extracted relevant partitions from <xref target="RFC2616"/>.
3469</t>
3470</section>
3471
3472<section title="Since draft-ietf-httpbis-p2-semantics-00">
3473<t>
3474  Closed issues:
3475  <list style="symbols"> 
3476    <t>
3477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3478      "Via is a MUST"
3479      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3480    </t>
3481    <t>
3482      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3483      "Fragments allowed in Location"
3484      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3485    </t>
3486    <t>
3487      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3488      "Safe Methods vs Redirection"
3489      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3490    </t>
3491    <t>
3492      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3493      "Revise description of the POST method"
3494      (<eref target="http://purl.org/NET/http-errata#post"/>)
3495    </t>
3496    <t>
3497      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3498      "Normative and Informative references"
3499    </t>
3500    <t>
3501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3502      "RFC2606 Compliance"
3503    </t>
3504    <t>
3505      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3506      "Informative references"
3507    </t>
3508    <t>
3509      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3510      "Redundant cross-references"
3511    </t>
3512  </list>
3513</t>
3514<t>
3515  Other changes:
3516  <list style="symbols"> 
3517    <t>
3518      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3519    </t>
3520  </list>
3521</t>
3522</section>
3523
3524<section title="Since draft-ietf-httpbis-p2-semantics-01">
3525<t>
3526  Closed issues:
3527  <list style="symbols"> 
3528    <t>
3529      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3530      "PUT side effects"
3531    </t>
3532    <t>
3533      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3534      "Duplicate Host header requirements"
3535    </t>
3536  </list>
3537</t>
3538<t>
3539  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3540  <list style="symbols"> 
3541    <t>
3542      Move "Product Tokens" section (back) into Part 1, as "token" is used
3543      in the definition of the Upgrade header.
3544    </t>
3545    <t>
3546      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3547    </t>
3548    <t>
3549      Copy definition of delta-seconds from Part6 instead of referencing it.
3550    </t>
3551  </list>
3552</t>
3553</section>
3554
3555<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3556<t>
3557  Closed issues:
3558  <list style="symbols"> 
3559    <t>
3560      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3561      "Requiring Allow in 405 responses"
3562    </t>
3563    <t>
3564      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3565      "Status Code Registry"
3566    </t>
3567    <t>
3568      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3569      "Redirection vs. Location"
3570    </t>
3571    <t>
3572      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3573      "Cacheability of 303 response"
3574    </t>
3575    <t>
3576      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3577      "305 Use Proxy"
3578    </t>
3579    <t>
3580      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3581      "Classification for Allow header"
3582    </t>
3583    <t>
3584      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3585      "PUT - 'store under' vs 'store at'"
3586    </t>
3587  </list>
3588</t>
3589<t>
3590  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3591  <list style="symbols"> 
3592    <t>
3593      Reference RFC 3984, and update header registrations for headers defined
3594      in this document.
3595    </t>
3596  </list>
3597</t>
3598<t>
3599  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3600  <list style="symbols"> 
3601    <t>
3602      Replace string literals when the string really is case-sensitive (method).
3603    </t>
3604  </list>
3605</t>
3606</section>
3607
3608<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3609<t>
3610  Closed issues:
3611  <list style="symbols"> 
3612    <t>
3613      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3614      "OPTIONS request bodies"
3615    </t>
3616    <t>
3617      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3618      "Description of CONNECT should refer to RFC2817"
3619    </t>
3620    <t>
3621      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3622      "Location Content-Location reference request/response mixup"
3623    </t>
3624  </list>
3625</t>
3626<t>
3627  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3628  <list style="symbols"> 
3629    <t>
3630      Added initial proposal for registration process, plus initial
3631      content (non-HTTP/1.1 methods to be added by a separate specification).
3632    </t>
3633  </list>
3634</t>
3635</section>
3636
3637<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3638<t>
3639  Closed issues:
3640  <list style="symbols"> 
3641    <t>
3642      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3643      "Content-*"
3644    </t>
3645    <t>
3646      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3647      "RFC 2822 is updated by RFC 5322"
3648    </t>
3649  </list>
3650</t>
3651<t>
3652  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3653  <list style="symbols"> 
3654    <t>
3655      Use "/" instead of "|" for alternatives.
3656    </t>
3657    <t>
3658      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3659      whitespace ("OWS") and required whitespace ("RWS").
3660    </t>
3661    <t>
3662      Rewrite ABNFs to spell out whitespace rules, factor out
3663      header value format definitions.
3664    </t>
3665  </list>
3666</t>
3667</section>
3668
3669<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3670<t>
3671  Closed issues:
3672  <list style="symbols"> 
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3675      "Reason-Phrase BNF"
3676    </t>
3677  </list>
3678</t>
3679<t>
3680  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3681  <list style="symbols"> 
3682    <t>
3683      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3684    </t>
3685  </list>
3686</t>
3687</section>
3688
3689<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3690<t>
3691  Closed issues:
3692  <list style="symbols"> 
3693    <t>
3694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3695      "Clarify when Referer is sent"
3696    </t>
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3699      "status codes vs methods"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3703      "Do not require "updates" relation for specs that register status codes or method names"
3704    </t>
3705  </list>
3706</t>
3707</section>
3708
3709<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3710<t>
3711  Closed issues:
3712  <list style="symbols"> 
3713    <t>
3714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3715      "Idempotency"
3716    </t>
3717    <t>
3718      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3719      "TRACE security considerations"
3720    </t>
3721    <t>
3722      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3723      "Clarify rules for determining what entities a response carries"
3724    </t>
3725    <t>
3726      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3727      "update note citing RFC 1945 and 2068"
3728    </t>
3729    <t>
3730      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3731      "update note about redirect limit"
3732    </t>
3733    <t>
3734      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3735      "Location header ABNF should use 'URI'"
3736    </t>
3737    <t>
3738      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3739      "fragments in Location vs status 303"
3740    </t>
3741    <t>
3742      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3743      "move IANA registrations for optional status codes"
3744    </t>
3745  </list>
3746</t>
3747<t>
3748  Partly resolved issues:
3749  <list style="symbols"> 
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3752      "Are OPTIONS and TRACE safe?"
3753    </t>
3754  </list>
3755</t>
3756</section>
3757
3758<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3759<t>
3760  Closed issues:
3761  <list style="symbols"> 
3762    <t>
3763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3764      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3765      status codes when fixing this previously)
3766    </t>
3767  </list>
3768</t>
3769</section>
3770
3771<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3772<t>
3773  Closed issues:
3774  <list style="symbols"> 
3775    <t>
3776      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3777      "Fragment combination / precedence during redirects"
3778    </t>
3779  </list>
3780</t>
3781<t>
3782  Partly resolved issues:
3783  <list style="symbols"> 
3784    <t>
3785      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3786      "Location header payload handling"
3787    </t>
3788    <t>
3789      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3790      "Term for the requested resource's URI"
3791    </t>
3792  </list>
3793</t>
3794</section>
3795
3796</section>
3797
3798</back>
3799</rfc>
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