source: draft-ietf-httpbis/latest/p2-semantics.xml @ 758

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