source: draft-ietf-httpbis/latest/p2-semantics.xml @ 730

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