source: draft-ietf-httpbis/latest/p2-semantics.xml @ 866

Last change on this file since 866 was 866, checked in by fielding@…, 9 years ago

Addresses #109: Clarify entity / representation / variant terminology

Replaced entity with representation.

  • Property svn:eol-style set to native
File size: 162.2 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "July">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching-combining-headers  "<xref target='Part6' x:rel='#combining.headers' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76]>
77<?rfc toc="yes" ?>
78<?rfc symrefs="yes" ?>
79<?rfc sortrefs="yes" ?>
80<?rfc compact="yes"?>
81<?rfc subcompact="no" ?>
82<?rfc linkmailto="no" ?>
83<?rfc editing="no" ?>
84<?rfc comments="yes"?>
85<?rfc inline="yes"?>
86<?rfc rfcedstyle="yes"?>
87<?rfc-ext allow-markup-in-artwork="yes" ?>
88<?rfc-ext include-references-in-index="yes" ?>
89<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
90     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
91     xmlns:x='http://purl.org/net/xml2rfc/ext'
92     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
93<front>
94
95  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
96
97  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
98    <organization abbrev="Day Software">Day Software</organization>
99    <address>
100      <postal>
101        <street>23 Corporate Plaza DR, Suite 280</street>
102        <city>Newport Beach</city>
103        <region>CA</region>
104        <code>92660</code>
105        <country>USA</country>
106      </postal>
107      <phone>+1-949-706-5300</phone>
108      <facsimile>+1-949-706-5305</facsimile>
109      <email>fielding@gbiv.com</email>
110      <uri>http://roy.gbiv.com/</uri>
111    </address>
112  </author>
113
114  <author initials="J." surname="Gettys" fullname="Jim Gettys">
115    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
116    <address>
117      <postal>
118        <street>21 Oak Knoll Road</street>
119        <city>Carlisle</city>
120        <region>MA</region>
121        <code>01741</code>
122        <country>USA</country>
123      </postal>
124      <email>jg@freedesktop.org</email>
125      <uri>http://gettys.wordpress.com/</uri>
126    </address>
127  </author>
128 
129  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
130    <organization abbrev="HP">Hewlett-Packard Company</organization>
131    <address>
132      <postal>
133        <street>HP Labs, Large Scale Systems Group</street>
134        <street>1501 Page Mill Road, MS 1177</street>
135        <city>Palo Alto</city>
136        <region>CA</region>
137        <code>94304</code>
138        <country>USA</country>
139      </postal>
140      <email>JeffMogul@acm.org</email>
141    </address>
142  </author>
143
144  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
145    <organization abbrev="Microsoft">Microsoft Corporation</organization>
146    <address>
147      <postal>
148        <street>1 Microsoft Way</street>
149        <city>Redmond</city>
150        <region>WA</region>
151        <code>98052</code>
152        <country>USA</country>
153      </postal>
154      <email>henrikn@microsoft.com</email>
155    </address>
156  </author>
157
158  <author initials="L." surname="Masinter" fullname="Larry Masinter">
159    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
160    <address>
161      <postal>
162        <street>345 Park Ave</street>
163        <city>San Jose</city>
164        <region>CA</region>
165        <code>95110</code>
166        <country>USA</country>
167      </postal>
168      <email>LMM@acm.org</email>
169      <uri>http://larry.masinter.net/</uri>
170    </address>
171  </author>
172 
173  <author initials="P." surname="Leach" fullname="Paul J. Leach">
174    <organization abbrev="Microsoft">Microsoft Corporation</organization>
175    <address>
176      <postal>
177        <street>1 Microsoft Way</street>
178        <city>Redmond</city>
179        <region>WA</region>
180        <code>98052</code>
181      </postal>
182      <email>paulle@microsoft.com</email>
183    </address>
184  </author>
185   
186  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
187    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
188    <address>
189      <postal>
190        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
191        <street>The Stata Center, Building 32</street>
192        <street>32 Vassar Street</street>
193        <city>Cambridge</city>
194        <region>MA</region>
195        <code>02139</code>
196        <country>USA</country>
197      </postal>
198      <email>timbl@w3.org</email>
199      <uri>http://www.w3.org/People/Berners-Lee/</uri>
200    </address>
201  </author>
202
203  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
204    <organization abbrev="W3C">World Wide Web Consortium</organization>
205    <address>
206      <postal>
207        <street>W3C / ERCIM</street>
208        <street>2004, rte des Lucioles</street>
209        <city>Sophia-Antipolis</city>
210        <region>AM</region>
211        <code>06902</code>
212        <country>France</country>
213      </postal>
214      <email>ylafon@w3.org</email>
215      <uri>http://www.raubacapeu.net/people/yves/</uri>
216    </address>
217  </author>
218
219  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
220    <organization abbrev="greenbytes">greenbytes GmbH</organization>
221    <address>
222      <postal>
223        <street>Hafenweg 16</street>
224        <city>Muenster</city><region>NW</region><code>48155</code>
225        <country>Germany</country>
226      </postal>
227      <phone>+49 251 2807760</phone>
228      <facsimile>+49 251 2807761</facsimile>
229      <email>julian.reschke@greenbytes.de</email>
230      <uri>http://greenbytes.de/tech/webdav/</uri>
231    </address>
232  </author>
233
234  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
235  <workgroup>HTTPbis Working Group</workgroup>
236
237<abstract>
238<t>
239   The Hypertext Transfer Protocol (HTTP) is an application-level
240   protocol for distributed, collaborative, hypermedia information
241   systems. HTTP has been in use by the World Wide Web global information
242   initiative since 1990. This document is Part 2 of the seven-part specification
243   that defines the protocol referred to as "HTTP/1.1" and, taken together,
244   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
245   as expressed by request methods, request-header fields, response status codes,
246   and response-header fields.
247</t>
248</abstract>
249
250<note title="Editorial Note (To be removed by RFC Editor)">
251  <t>
252    Discussion of this draft should take place on the HTTPBIS working group
253    mailing list (ietf-http-wg@w3.org). The current issues list is
254    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
255    and related documents (including fancy diffs) can be found at
256    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
257  </t>
258  <t>
259    The changes in this draft are summarized in <xref target="changes.since.10"/>.
260  </t>
261</note>
262</front>
263<middle>
264<section title="Introduction" anchor="introduction">
265<t>
266   This document defines HTTP/1.1 request and response semantics.  Each HTTP
267   message, as defined in &messaging;, is in the form of either a request or
268   a response.  An HTTP server listens on a connection for HTTP requests and
269   responds to each request, in the order received on that connection, with
270   one or more HTTP response messages.  This document defines the commonly
271   agreed upon semantics of the HTTP uniform interface, the intentions defined
272   by each request method, and the various response messages that might be
273   expected as a result of applying that method for the requested resource.
274</t>
275<t>
276   This document is currently disorganized in order to minimize the changes
277   between drafts and enable reviewers to see the smaller errata changes.
278   The next draft will reorganize the sections to better reflect the content.
279   In particular, the sections will be ordered according to the typical
280   processing of an HTTP request message (after message parsing): resource
281   mapping, general header fields, methods, request modifiers, response
282   status, and resource metadata.  The current mess reflects how widely
283   dispersed these topics and associated requirements had become in
284   <xref target="RFC2616"/>.
285</t>
286
287<section title="Requirements" anchor="intro.requirements">
288<t>
289   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
290   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
291   document are to be interpreted as described in <xref target="RFC2119"/>.
292</t>
293<t>
294   An implementation is not compliant if it fails to satisfy one or more
295   of the "MUST" or "REQUIRED" level requirements for the protocols it
296   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
297   level and all the "SHOULD" level requirements for its protocols is said
298   to be "unconditionally compliant"; one that satisfies all the "MUST"
299   level requirements but not all the "SHOULD" level requirements for its
300   protocols is said to be "conditionally compliant".
301</t>
302</section>
303
304<section title="Syntax Notation" anchor="notation">
305  <x:anchor-alias value="CR"/>
306  <x:anchor-alias value="DIGIT"/>
307  <x:anchor-alias value="LF"/>
308  <x:anchor-alias value="VCHAR"/>
309  <x:anchor-alias value="WSP"/>
310<t>
311  This specification uses the ABNF syntax defined in &notation; (which
312  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
313  <xref target="collected.abnf"/> shows the collected ABNF, with the list
314  rule expanded.
315</t>
316<t>
317  The following core rules are included by
318  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
319  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
320  DIGIT (decimal 0-9), DQUOTE (double quote),
321  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
322  OCTET (any 8-bit sequence of data), SP (space),
323  VCHAR (any visible USASCII character),
324  and WSP (whitespace).
325</t>
326
327<section title="Core Rules" anchor="core.rules">
328  <x:anchor-alias value="obs-text"/>
329  <x:anchor-alias value="quoted-string"/>
330  <x:anchor-alias value="token"/>
331  <x:anchor-alias value="OWS"/>
332  <x:anchor-alias value="RWS"/>
333<t>
334  The core rules below are defined in &basic-rules;:
335</t>
336<figure><artwork type="abnf2616">
337  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
338  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
339  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
340  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
341  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
342</artwork></figure>
343</section>
344
345<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
346  <x:anchor-alias value="absolute-URI"/>
347  <x:anchor-alias value="Accept"/>
348  <x:anchor-alias value="Accept-Charset"/>
349  <x:anchor-alias value="Accept-Encoding"/>
350  <x:anchor-alias value="Accept-Language"/>
351  <x:anchor-alias value="Accept-Ranges"/>
352  <x:anchor-alias value="Age"/>
353  <x:anchor-alias value="Authorization"/>
354  <x:anchor-alias value="comment"/>
355  <x:anchor-alias value="ETag"/>
356  <x:anchor-alias value="Host"/>
357  <x:anchor-alias value="HTTP-date"/>
358  <x:anchor-alias value="If-Match"/>
359  <x:anchor-alias value="If-Modified-Since"/>
360  <x:anchor-alias value="If-None-Match"/>
361  <x:anchor-alias value="If-Range"/>
362  <x:anchor-alias value="If-Unmodified-Since"/>
363  <x:anchor-alias value="partial-URI"/>
364  <x:anchor-alias value="product"/>
365  <x:anchor-alias value="Proxy-Authenticate"/>
366  <x:anchor-alias value="Proxy-Authorization"/>
367  <x:anchor-alias value="Range"/>
368  <x:anchor-alias value="TE"/>
369  <x:anchor-alias value="URI-reference"/>
370  <x:anchor-alias value="Vary"/>
371  <x:anchor-alias value="WWW-Authenticate"/>
372<t>
373  The ABNF rules below are defined in other parts:
374</t>
375<figure><!--Part1--><artwork type="abnf2616">
376  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
377  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
378  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
379  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
380  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
381  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
382  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
383  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
384</artwork></figure>
385<figure><!--Part3--><artwork type="abnf2616">
386  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
387  <x:ref>Accept-Charset</x:ref> =
388             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
389  <x:ref>Accept-Encoding</x:ref> =
390             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
391  <x:ref>Accept-Language</x:ref> =
392             &lt;Accept-Language, defined in &header-accept-language;&gt;
393</artwork></figure>
394<figure><!--Part4--><artwork type="abnf2616">
395  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
396  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
397  <x:ref>If-Modified-Since</x:ref> =
398             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
399  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
400  <x:ref>If-Unmodified-Since</x:ref> =
401             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
402</artwork></figure>
403<figure><!--Part5--><artwork type="abnf2616">
404  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
405  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
406  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
407</artwork></figure>
408<figure><!--Part6--><artwork type="abnf2616">
409  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
410  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
411</artwork><!--Part7--></figure>
412<figure><artwork type="abnf2616">
413  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
414  <x:ref>Proxy-Authenticate</x:ref> =
415             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
416  <x:ref>Proxy-Authorization</x:ref> =
417             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
418  <x:ref>WWW-Authenticate</x:ref> =
419             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
420</artwork></figure>
421</section>
422</section>
423</section>
424
425<section title="Method" anchor="method">
426  <x:anchor-alias value="Method"/>
427  <x:anchor-alias value="extension-method"/>
428<t>
429   The Method token indicates the method to be performed on the resource
430   identified by the Effective Request URI (&effective-request-uri;). The
431   method is case-sensitive.
432</t>
433<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
434  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
435                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
436                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
437                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
438                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
439                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
440                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
441                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
442                 / <x:ref>extension-method</x:ref>
443  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
444</artwork></figure>
445<t>
446   The list of methods allowed by a resource can be specified in an
447   Allow header field (<xref target="header.allow"/>). The return code of the response
448   always notifies the client whether a method is currently allowed on a
449   resource, since the set of allowed methods can change dynamically. An
450   origin server &SHOULD; return the status code 405 (Method Not Allowed)
451   if the method is known by the origin server but not allowed for the
452   requested resource, and 501 (Not Implemented) if the method is
453   unrecognized or not implemented by the origin server. The methods GET
454   and HEAD &MUST; be supported by all general-purpose servers. All other
455   methods are &OPTIONAL;; however, if the above methods are implemented,
456   they &MUST; be implemented with the same semantics as those specified
457   in <xref target="method.definitions"/>.
458</t>
459
460<section title="Method Registry" anchor="method.registry">
461<t>
462  The HTTP Method Registry defines the name space for the Method token in the
463  Request line of an HTTP request.
464</t>
465<t>
466  Registrations &MUST; include the following fields:
467  <list style="symbols">
468    <t>Method Name (see <xref target="method"/>)</t>
469    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
470    <t>Pointer to specification text</t>
471  </list>
472</t>
473<t>
474  Values to be added to this name space are subject to IETF review
475  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
476</t>
477<t>
478  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
479</t>
480</section>
481</section>
482
483<section title="Request Header Fields" anchor="request.header.fields">
484  <x:anchor-alias value="request-header"/>
485<t>
486   The request-header fields allow the client to pass additional
487   information about the request, and about the client itself, to the
488   server. These fields act as request modifiers, with semantics
489   equivalent to the parameters on a programming language method
490   invocation.
491</t>
492<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
493  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
494                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
495                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
496                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
497                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
498                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
499                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
500                 / <x:ref>Host</x:ref>                     ; &header-host;
501                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
502                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
503                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
504                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
505                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
506                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
507                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
508                 / <x:ref>Range</x:ref>                    ; &header-range;
509                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
510                 / <x:ref>TE</x:ref>                       ; &header-te;
511                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
512</artwork></figure>
513<t>
514   Request-header field names can be extended reliably only in
515   combination with a change in the protocol version. However, new or
516   experimental header fields &MAY; be given the semantics of request-header
517   fields if all parties in the communication recognize them to
518   be request-header fields. Unrecognized header fields are treated as
519   entity-header fields.
520</t>
521</section>
522
523<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
524  <x:anchor-alias value="Reason-Phrase"/>
525  <x:anchor-alias value="Status-Code"/>
526  <x:anchor-alias value="extension-code"/>
527<t>
528   The Status-Code element is a 3-digit integer result code of the
529   attempt to understand and satisfy the request. The status codes listed
530   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
531   &p5-status-codes;, and &p7-status-codes;.
532</t>
533<t>
534   The Reason-Phrase is intended to give a short
535   textual description of the Status-Code. The Status-Code is intended
536   for use by automata and the Reason-Phrase is intended for the human
537   user. The client is not required to examine or display the Reason-Phrase.
538</t>
539<t> 
540   The individual values of the numeric status codes defined for
541   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
542   presented below. The reason phrases listed here are only
543   recommendations -- they &MAY; be replaced by local equivalents without
544   affecting the protocol.
545</t>
546<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"/>
547  <x:ref>Status-Code</x:ref> =
548       "100"  ; <xref target="status.100"/>: Continue
549     / "101"  ; <xref target="status.101"/>: Switching Protocols
550     / "200"  ; <xref target="status.200"/>: OK
551     / "201"  ; <xref target="status.201"/>: Created
552     / "202"  ; <xref target="status.202"/>: Accepted
553     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
554     / "204"  ; <xref target="status.204"/>: No Content
555     / "205"  ; <xref target="status.205"/>: Reset Content
556     / "206"  ; &status-206;: Partial Content
557     / "300"  ; <xref target="status.300"/>: Multiple Choices
558     / "301"  ; <xref target="status.301"/>: Moved Permanently
559     / "302"  ; <xref target="status.302"/>: Found
560     / "303"  ; <xref target="status.303"/>: See Other
561     / "304"  ; &status-304;: Not Modified
562     / "305"  ; <xref target="status.305"/>: Use Proxy
563     / "307"  ; <xref target="status.307"/>: Temporary Redirect
564     / "400"  ; <xref target="status.400"/>: Bad Request
565     / "401"  ; &status-401;: Unauthorized
566     / "402"  ; <xref target="status.402"/>: Payment Required
567     / "403"  ; <xref target="status.403"/>: Forbidden
568     / "404"  ; <xref target="status.404"/>: Not Found
569     / "405"  ; <xref target="status.405"/>: Method Not Allowed
570     / "406"  ; <xref target="status.406"/>: Not Acceptable
571     / "407"  ; &status-407;: Proxy Authentication Required
572     / "408"  ; <xref target="status.408"/>: Request Time-out
573     / "409"  ; <xref target="status.409"/>: Conflict
574     / "410"  ; <xref target="status.410"/>: Gone
575     / "411"  ; <xref target="status.411"/>: Length Required
576     / "412"  ; &status-412;: Precondition Failed
577     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
578     / "414"  ; <xref target="status.414"/>: URI Too Long
579     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
580     / "416"  ; &status-416;: Requested range not satisfiable
581     / "417"  ; <xref target="status.417"/>: Expectation Failed
582     / "500"  ; <xref target="status.500"/>: Internal Server Error
583     / "501"  ; <xref target="status.501"/>: Not Implemented
584     / "502"  ; <xref target="status.502"/>: Bad Gateway
585     / "503"  ; <xref target="status.503"/>: Service Unavailable
586     / "504"  ; <xref target="status.504"/>: Gateway Time-out
587     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
588     / <x:ref>extension-code</x:ref>
589
590  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
591  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
592</artwork></figure>
593<t>
594   HTTP status codes are extensible. HTTP applications are not required
595   to understand the meaning of all registered status codes, though such
596   understanding is obviously desirable. However, applications &MUST;
597   understand the class of any status code, as indicated by the first
598   digit, and treat any unrecognized response as being equivalent to the
599   x00 status code of that class, with the exception that an
600   unrecognized response &MUST-NOT; be cached. For example, if an
601   unrecognized status code of 431 is received by the client, it can
602   safely assume that there was something wrong with its request and
603   treat the response as if it had received a 400 status code. In such
604   cases, user agents &SHOULD; present to the user the representation enclosed
605   with the response, since that representation is likely to include human-readable
606   information which will explain the unusual status.
607</t>
608
609<section title="Status Code Registry" anchor="status.code.registry">
610<t>
611  The HTTP Status Code Registry defines the name space for the Status-Code
612  token in the Status line of an HTTP response.
613</t>
614<t>
615  Values to be added to this name space are subject to IETF review
616  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
617</t>
618<t>
619  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
620</t>
621</section>
622
623</section>
624
625<section title="Response Header Fields" anchor="response.header.fields">
626  <x:anchor-alias value="response-header"/>
627<t>
628   The response-header fields allow the server to pass additional
629   information about the response which cannot be placed in the Status-Line.
630   These header fields give information about the server and about
631   further access to the resource identified by the Effective Request URI
632   (&effective-request-uri;).
633</t>
634<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
635  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
636                  / <x:ref>Age</x:ref>                     ; &header-age;
637                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
638                  / <x:ref>ETag</x:ref>                    ; &header-etag;
639                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
640                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
641                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
642                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
643                  / <x:ref>Vary</x:ref>                    ; &header-vary;
644                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
645</artwork></figure>
646<t>
647   Response-header field names can be extended reliably only in
648   combination with a change in the protocol version. However, new or
649   experimental header fields &MAY; be given the semantics of response-header
650   fields if all parties in the communication recognize them to
651   be response-header fields. Unrecognized header fields are treated as
652   entity-header fields.
653</t>
654</section>
655
656<section title="Representation" anchor="entity">
657<t>
658   Request and Response messages &MAY; transfer a representation if not otherwise
659   restricted by the request method or response status code. A representation
660   consists of metadata (representation header fields) and data (representation
661   body).  When a complete or partial representation is enclosed in an HTTP message,
662   it is referred to as the payload of the message. HTTP representations
663   are defined in &payload;.
664</t>
665<t>
666   A representation body is only present in a message when a message-body is
667   present, as described in &message-body;. The representation body is obtained
668   from the message-body by decoding any Transfer-Encoding that might
669   have been applied to ensure safe and proper transfer of the message.
670</t>
671
672<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
673<t>
674   It is sometimes necessary to determine the identity of the resource
675   associated with a representation.
676</t>
677<t>
678   An HTTP request representation, when present, is always associated with an
679   anonymous (i.e., unidentified) resource.
680</t>
681<t>
682   In the common case, an HTTP response is a representation of the resource
683   located at the Effective Request URI (see &effective-request-uri;). However,
684   this is not always the case. To determine the URI of the resource a
685   response is associated with, the following rules are used (with the first
686   applicable one being selected):
687</t>
688<t><list style="numbers">
689   <t>If the response status code is 200 or 203 and the request method was GET,
690   the response is a representation of the resource at the Effective Request URI.</t>
691   <t>If the response status is 204, 206, or 304 and the request method was GET
692   or HEAD, the response is a partial representation of the resource at the
693   Effective Request URI (see &caching-combining-headers;).</t>
694   <t>If the response has a Content-Location header, and that URI is the same
695   as the Effective Request URI, the response is a representation of the
696   resource at the Effective Request URI.</t>
697   <t>If the response has a Content-Location header, and that URI is not the
698   same as the Effective Request URI, the response asserts that it is a
699   representation of the resource at the Content-Location URI (but it may not
700   be).</t>
701   <t>Otherwise, the response is a representation of an anonymous (i.e.,
702   unidentified) resource.</t>
703</list></t>
704<t>
705  <cref anchor="TODO-req-uri">
706   The comparison function is going to have to be defined somewhere,
707   because we already need to compare URIs for things like cache invalidation.</cref>
708</t>
709</section>
710
711</section>
712
713
714<section title="Method Definitions" anchor="method.definitions">
715<t>
716   The set of common methods for HTTP/1.1 is defined below. Although
717   this set can be expanded, additional methods cannot be assumed to
718   share the same semantics for separately extended clients and servers.
719</t>
720
721<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
722
723<section title="Safe Methods" anchor="safe.methods">
724<iref item="Safe Methods" primary="true"/>
725<t>
726   Implementors should be aware that the software represents the user in
727   their interactions over the Internet, and should be careful to allow
728   the user to be aware of any actions they might take which may have an
729   unexpected significance to themselves or others.
730</t>
731<t>
732   In particular, the convention has been established that the GET, HEAD,
733   OPTIONS, and TRACE methods &SHOULD-NOT;  have the significance of taking an action
734   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
735   This allows user agents to represent other methods, such as POST, PUT
736   and DELETE, in a special way, so that the user is made aware of the
737   fact that a possibly unsafe action is being requested.
738</t>
739<t>
740   Naturally, it is not possible to ensure that the server does not
741   generate side-effects as a result of performing a GET request; in
742   fact, some dynamic resources consider that a feature. The important
743   distinction here is that the user did not request the side-effects,
744   so therefore cannot be held accountable for them.
745</t>
746</section>
747
748<section title="Idempotent Methods" anchor="idempotent.methods">
749<iref item="Idempotent Methods" primary="true"/>
750<t>
751   Methods can also have the property of "idempotence" in that, aside
752   from error or expiration issues, the intended effect of multiple
753   identical requests is the same as for a single request.
754   The methods PUT, DELETE, and all safe methods are idempotent.
755   It is important to note that idempotence refers only to changes
756   requested by the client: a server is free to change its state due
757   to multiple requests for the purpose of tracking those requests,
758   versioning of results, etc.
759</t>
760</section>
761</section>
762
763<section title="OPTIONS" anchor="OPTIONS">
764  <rdf:Description>
765    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
766  </rdf:Description>
767  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
768  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
769<t>
770   The OPTIONS method represents a request for information about the
771   communication options available on the request/response chain
772   identified by the Effective Request URI. This method allows the client to
773   determine the options and/or requirements associated with a resource,
774   or the capabilities of a server, without implying a resource action
775   or initiating a resource retrieval.
776</t>
777<t>
778   Responses to this method are not cacheable.
779</t>
780<t>
781   If the OPTIONS request includes an entity-body (as indicated by the
782   presence of Content-Length or Transfer-Encoding), then the media type
783   &MUST; be indicated by a Content-Type field. Although this
784   specification does not define any use for such a body, future
785   extensions to HTTP might use the OPTIONS body to make more detailed
786   queries on the server.
787</t>
788<t>
789   If the request-target is an asterisk ("*"), the OPTIONS request is
790   intended to apply to the server in general rather than to a specific
791   resource. Since a server's communication options typically depend on
792   the resource, the "*" request is only useful as a "ping" or "no-op"
793   type of method; it does nothing beyond allowing the client to test
794   the capabilities of the server. For example, this can be used to test
795   a proxy for HTTP/1.1 compliance (or lack thereof).
796</t>
797<t>
798   If the request-target is not an asterisk, the OPTIONS request applies
799   only to the options that are available when communicating with that
800   resource.
801</t>
802<t>
803   A 200 response &SHOULD; include any header fields that indicate
804   optional features implemented by the server and applicable to that
805   resource (e.g., Allow), possibly including extensions not defined by
806   this specification. The response body, if any, &SHOULD; also include
807   information about the communication options. The format for such a
808   body is not defined by this specification, but might be defined by
809   future extensions to HTTP. Content negotiation &MAY; be used to select
810   the appropriate response format. If no response body is included, the
811   response &MUST; include a Content-Length field with a field-value of
812   "0".
813</t>
814<t>
815   The Max-Forwards request-header field &MAY; be used to target a
816   specific proxy in the request chain. When a proxy receives an OPTIONS
817   request on an absolute-URI for which request forwarding is permitted,
818   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
819   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
820   instead, the proxy &SHOULD; respond with its own communication options.
821   If the Max-Forwards field-value is an integer greater than zero, the
822   proxy &MUST; decrement the field-value when it forwards the request. If
823   no Max-Forwards field is present in the request, then the forwarded
824   request &MUST-NOT; include a Max-Forwards field.
825</t>
826</section>
827
828<section title="GET" anchor="GET">
829  <rdf:Description>
830    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
831  </rdf:Description>
832  <iref primary="true" item="GET method" x:for-anchor=""/>
833  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
834<t>
835   The GET method means retrieve whatever information (in the form of an
836   entity) currently corresponds to the resource identified by the
837   Effective Request URI.
838</t>
839<t>   
840   If the Effective Request URI identifies a data-producing process, it is the
841   produced data which shall be returned as the representation in the response and not
842   the source text of the process, unless that text happens to be the output of
843   the process.
844</t>
845<t>
846   The semantics of the GET method change to a "conditional GET" if the
847   request message includes an If-Modified-Since, If-Unmodified-Since,
848   If-Match, If-None-Match, or If-Range header field. A conditional GET
849   method requests that the representation be transferred only under the
850   circumstances described by the conditional header field(s). The
851   conditional GET method is intended to reduce unnecessary network
852   usage by allowing cached entities to be refreshed without requiring
853   multiple requests or transferring data already held by the client.
854</t>
855<t>
856   The semantics of the GET method change to a "partial GET" if the
857   request message includes a Range header field. A partial GET requests
858   that only part of the representation be transferred, as described in &header-range;.
859   The partial GET method is intended to reduce unnecessary
860   network usage by allowing partially-retrieved representations to be
861   completed without transferring data already held by the client.
862</t>
863<t>
864   The response to a GET request is cacheable if and only if it meets
865   the requirements for HTTP caching described in &caching;.
866</t>
867<t>
868   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
869</t>
870</section>
871
872<section title="HEAD" anchor="HEAD">
873  <rdf:Description>
874    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
875  </rdf:Description>
876  <iref primary="true" item="HEAD method" x:for-anchor=""/>
877  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
878<t>
879   The HEAD method is identical to GET except that the server &MUST-NOT;
880   return a message-body in the response. The metainformation contained
881   in the HTTP headers in response to a HEAD request &SHOULD; be identical
882   to the information sent in response to a GET request. This method can
883   be used for obtaining metainformation about the representation implied by the
884   request without transferring the representation body. This method is
885   often used for testing hypertext links for validity, accessibility,
886   and recent modification.
887</t>
888<t>
889   The response to a HEAD request &MAY; be cacheable in the sense that the
890   information contained in the response &MAY; be used to update a
891   previously cached entity from that resource. If the new field values
892   indicate that the cached entity differs from the current entity (as
893   would be indicated by a change in Content-Length, Content-MD5, ETag
894   or Last-Modified), then the cache &MUST; treat the cache entry as
895   stale.
896</t>
897</section>
898
899<section title="POST" anchor="POST">
900  <iref primary="true" item="POST method" x:for-anchor=""/>
901  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
902<t>
903   The POST method is used to request that the origin server accept the
904   entity enclosed in the request as data to be processed by the resource
905   identified by the Effective Request URI. POST is designed
906   to allow a uniform method to cover the following functions:
907  <list style="symbols">
908    <t>
909      Annotation of existing resources;
910    </t>
911    <t>
912        Posting a message to a bulletin board, newsgroup, mailing list,
913        or similar group of articles;
914    </t>
915    <t>
916        Providing a block of data, such as the result of submitting a
917        form, to a data-handling process;
918    </t>
919    <t>
920        Extending a database through an append operation.
921    </t>
922  </list>
923</t>
924<t>
925   The actual function performed by the POST method is determined by the
926   server and is usually dependent on the Effective Request URI.
927</t>
928<t>
929   The action performed by the POST method might not result in a
930   resource that can be identified by a URI. In this case, either 200
931   (OK) or 204 (No Content) is the appropriate response status,
932   depending on whether or not the response includes an entity that
933   describes the result.
934</t>
935<t>
936   If a resource has been created on the origin server, the response
937   &SHOULD; be 201 (Created) and contain an entity which describes the
938   status of the request and refers to the new resource, and a Location
939   header (see <xref target="header.location"/>).
940</t>
941<t>
942   Responses to this method are not cacheable, unless the response
943   includes appropriate Cache-Control or Expires header fields. However,
944   the 303 (See Other) response can be used to direct the user agent to
945   retrieve a cacheable resource.
946</t>
947</section>
948
949<section title="PUT" anchor="PUT">
950  <iref primary="true" item="PUT method" x:for-anchor=""/>
951  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
952<t>
953   The PUT method requests that the enclosed representation be stored at the
954   Effective Request URI. If the Effective Request URI refers to an already
955   existing resource, the enclosed representation &SHOULD; be considered a
956   modified version of the one residing on the origin server. Otherwise, if the
957   Effective Request URI does not point to an existing resource, and that URI is
958   capable of being defined as a new resource by the requesting user
959   agent, the origin server can create the resource with that URI.
960</t>
961<t>   
962   If a new resource is created at the Effective Request URI, the origin
963   server &MUST; inform the user agent
964   via the 201 (Created) response. If an existing resource is modified,
965   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
966   to indicate successful completion of the request.
967</t>
968<t>   
969   If the resource identified by the Effective Request URI could not be
970   created or modified, an appropriate error response &SHOULD; be given
971   that reflects the nature of the problem.
972   The recipient of the representation &MUST-NOT; ignore any Content-*
973   headers (headers starting with the prefix "Content-") that it does
974   not understand or implement
975   and &MUST; return a 501 (Not Implemented) response in such cases.
976</t>
977<t>
978   If the request passes through a cache that has one or more stored
979   responses for the Effective Request URI, those stored responses
980   &SHOULD; be marked as stale if the response to the PUT request
981   is a success status. Responses to the PUT method are not cacheable.
982</t>
983<t>
984   The fundamental difference between the POST and PUT requests is
985   reflected in the different meaning of the Effective Request URI. The URI in a
986   POST request identifies the resource that will handle the enclosed
987   representation. That resource might be a data-accepting process, a gateway to
988   some other protocol, or a document that accepts annotations.
989   In contrast, the URI in a PUT request identifies the resource for
990   which enclosed representation is a new or replacement value; the
991   user agent knows what URI is intended and the server &MUST-NOT; attempt
992   to apply the request to some other resource.
993   If the server desires that the request be applied to a different URI,
994   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
995   then make its own decision regarding whether or not to redirect the
996   request.
997</t>
998<t>
999   A single resource &MAY; be identified by many different URIs. For
1000   example, an article might have a URI for identifying "the current
1001   version" which is separate from the URI identifying each particular
1002   version. In this case, a PUT request on a general URI might result in
1003   several other URIs being defined by the origin server.
1004</t>
1005<t>
1006   HTTP/1.1 does not define how a PUT method affects the state of an
1007   origin server.
1008</t>
1009<t>
1010   Unless otherwise specified for a particular entity-header, the
1011   entity-headers in the PUT request &SHOULD; be applied to the resource
1012   created or modified by the PUT.
1013</t>
1014</section>
1015
1016<section title="DELETE" anchor="DELETE">
1017  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1018  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1019<t>
1020   The DELETE method requests that the origin server delete the resource
1021   identified by the Effective Request URI. This method &MAY; be overridden by
1022   human intervention (or other means) on the origin server. The client cannot
1023   be guaranteed that the operation has been carried out, even if the
1024   status code returned from the origin server indicates that the action
1025   has been completed successfully. However, the server &SHOULD-NOT; 
1026   indicate success unless, at the time the response is given, it
1027   intends to delete the resource or move it to an inaccessible
1028   location.
1029</t>
1030<t>
1031   A successful response &SHOULD; be 200 (OK) if the response includes an
1032   entity describing the status, 202 (Accepted) if the action has not
1033   yet been enacted, or 204 (No Content) if the action has been enacted
1034   but the response does not include a representation.
1035</t>
1036<t>
1037   If the request passes through a cache and the Effective Request URI
1038   identifies one or more currently cached entities, those entries &SHOULD; be
1039   treated as stale. Responses to this method are not cacheable.
1040</t>
1041</section>
1042
1043<section title="TRACE" anchor="TRACE">
1044  <rdf:Description>
1045    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1046  </rdf:Description>
1047  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1048  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1049<t>
1050   The TRACE method is used to invoke a remote, application-layer loop-back
1051   of the request message. The final recipient of the request
1052   &SHOULD; reflect the message received back to the client as the
1053   entity-body of a 200 (OK) response. The final recipient is either the
1054   origin server or the first proxy or gateway to receive a Max-Forwards
1055   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1056   A TRACE request &MUST-NOT; include a message-body.
1057</t>
1058<t>
1059   TRACE allows the client to see what is being received at the other
1060   end of the request chain and use that data for testing or diagnostic
1061   information. The value of the Via header field (&header-via;) is of
1062   particular interest, since it acts as a trace of the request chain.
1063   Use of the Max-Forwards header field allows the client to limit the
1064   length of the request chain, which is useful for testing a chain of
1065   proxies forwarding messages in an infinite loop.
1066</t>
1067<t>
1068   If the request is valid, the response &SHOULD; contain the entire
1069   request message in the entity-body, with a Content-Type of
1070   "message/http" (see &media-type-message-http;). Responses to this method
1071   &MUST-NOT; be cached.
1072</t>
1073</section>
1074
1075<section title="CONNECT" anchor="CONNECT">
1076  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1077  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1078<t>
1079   This specification reserves the method name CONNECT for use with a
1080   proxy that can dynamically switch to being a tunnel (e.g., SSL
1081   tunneling <xref target="RFC2817"/>).
1082</t>
1083</section>
1084</section>
1085
1086
1087<section title="Status Code Definitions" anchor="status.codes">
1088<t>
1089   Each Status-Code is described below, including any metainformation required
1090   in the response.
1091</t>
1092
1093<section title="Informational 1xx" anchor="status.1xx">
1094<t>
1095   This class of status code indicates a provisional response,
1096   consisting only of the Status-Line and optional headers, and is
1097   terminated by an empty line. There are no required headers for this
1098   class of status code. Since HTTP/1.0 did not define any 1xx status
1099   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1100   except under experimental conditions.
1101</t>
1102<t>
1103   A client &MUST; be prepared to accept one or more 1xx status responses
1104   prior to a regular response, even if the client does not expect a 100
1105   (Continue) status message. Unexpected 1xx status responses &MAY; be
1106   ignored by a user agent.
1107</t>
1108<t>
1109   Proxies &MUST; forward 1xx responses, unless the connection between the
1110   proxy and its client has been closed, or unless the proxy itself
1111   requested the generation of the 1xx response. (For example, if a
1112   proxy adds a "Expect: 100-continue" field when it forwards a request,
1113   then it need not forward the corresponding 100 (Continue)
1114   response(s).)
1115</t>
1116
1117<section title="100 Continue" anchor="status.100">
1118  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1119  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1120<t>
1121   The client &SHOULD; continue with its request. This interim response is
1122   used to inform the client that the initial part of the request has
1123   been received and has not yet been rejected by the server. The client
1124   &SHOULD; continue by sending the remainder of the request or, if the
1125   request has already been completed, ignore this response. The server
1126   &MUST; send a final response after the request has been completed. See
1127   &use100; for detailed discussion of the use and handling of this
1128   status code.
1129</t>
1130</section>
1131
1132<section title="101 Switching Protocols" anchor="status.101">
1133  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1134  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1135<t>
1136   The server understands and is willing to comply with the client's
1137   request, via the Upgrade message header field (&header-upgrade;), for a
1138   change in the application protocol being used on this connection. The
1139   server will switch protocols to those defined by the response's
1140   Upgrade header field immediately after the empty line which
1141   terminates the 101 response.
1142</t>
1143<t>
1144   The protocol &SHOULD; be switched only when it is advantageous to do
1145   so. For example, switching to a newer version of HTTP is advantageous
1146   over older versions, and switching to a real-time, synchronous
1147   protocol might be advantageous when delivering resources that use
1148   such features.
1149</t>
1150</section>
1151</section>
1152
1153<section title="Successful 2xx" anchor="status.2xx">
1154<t>
1155   This class of status code indicates that the client's request was
1156   successfully received, understood, and accepted.
1157</t>
1158
1159<section title="200 OK" anchor="status.200">
1160  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1161  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1162<t>
1163   The request has succeeded. The information returned with the response
1164   is dependent on the method used in the request, for example:
1165  <list style="hanging">
1166    <t hangText="GET">
1167          an entity corresponding to the requested resource is sent in
1168          the response;
1169    </t>
1170    <t hangText="HEAD">
1171          the entity-header fields corresponding to the requested
1172          resource are sent in the response without any message-body;
1173    </t>
1174    <t hangText="POST">
1175      an entity describing or containing the result of the action;
1176    </t>
1177    <t hangText="TRACE">
1178      an entity containing the request message as received by the
1179      end server.
1180    </t>
1181  </list>
1182</t>
1183</section>
1184
1185<section title="201 Created" anchor="status.201">
1186  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1187  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1188<t>
1189   The request has been fulfilled and has resulted in a new resource being
1190   created. The newly created resource can be referenced by the URI(s)
1191   returned in the payload of the response, with the most specific URI
1192   for the resource given by a Location header field. The response
1193   &SHOULD; include a payload containing a list of resource
1194   characteristics and location(s) from which the user or user agent can
1195   choose the one most appropriate. The payload format is specified by
1196   the media type given in the Content-Type header field. The origin
1197   server &MUST; create the resource before returning the 201 status code.
1198   If the action cannot be carried out immediately, the server &SHOULD;
1199   respond with 202 (Accepted) response instead.
1200</t>
1201<t>
1202   A 201 response &MAY; contain an ETag response header field indicating
1203   the current value of the entity tag for the representation of the resource
1204   just created (see &header-etag;).
1205</t>
1206</section>
1207
1208<section title="202 Accepted" anchor="status.202">
1209  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1210  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1211<t>
1212   The request has been accepted for processing, but the processing has
1213   not been completed.  The request might or might not eventually be
1214   acted upon, as it might be disallowed when processing actually takes
1215   place. There is no facility for re-sending a status code from an
1216   asynchronous operation such as this.
1217</t>
1218<t>
1219   The 202 response is intentionally non-committal. Its purpose is to
1220   allow a server to accept a request for some other process (perhaps a
1221   batch-oriented process that is only run once per day) without
1222   requiring that the user agent's connection to the server persist
1223   until the process is completed. The representation returned with this
1224   response &SHOULD; include an indication of the request's current status
1225   and either a pointer to a status monitor or some estimate of when the
1226   user can expect the request to be fulfilled.
1227</t>
1228</section>
1229
1230<section title="203 Non-Authoritative Information" anchor="status.203">
1231  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1232  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1233<t>
1234   The returned metainformation in the entity-header is not the
1235   definitive set as available from the origin server, but is gathered
1236   from a local or a third-party copy. The set presented &MAY; be a subset
1237   or superset of the original version. For example, including local
1238   annotation information about the resource might result in a superset
1239   of the metainformation known by the origin server. Use of this
1240   response code is not required and is only appropriate when the
1241   response would otherwise be 200 (OK).
1242</t>
1243</section>
1244
1245<section title="204 No Content" anchor="status.204">
1246  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1247  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1248<t>
1249   The server has successfully fulfilled the request, but there is no
1250   additional content to return in the response payload body.  The
1251   resource metadata and representation metadata in the response message's
1252   header fields refer to the requested resource and its current
1253   representation, respectively, after the requested action.
1254   For example, if a 204 status is received in response to a PUT
1255   and the response contains an Etag header field, then the value of
1256   that field is the current entity-tag for the representation that
1257   was successfully PUT to the requested resource.
1258</t>
1259<t>
1260   If the client is a user agent, it &SHOULD-NOT; change its document view
1261   from that which caused the request to be sent. This response is
1262   primarily intended to allow input for actions to take place without
1263   causing a change to the user agent's active document view, although
1264   any new or updated metadata &SHOULD; be applied to the document
1265   currently in the user agent's active view.
1266</t>
1267<t>
1268   The 204 response &MUST-NOT; include a message-body, and thus is always
1269   terminated by the first empty line after the header fields.
1270</t>
1271</section>
1272
1273<section title="205 Reset Content" anchor="status.205">
1274  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1275  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1276<t>
1277   The server has fulfilled the request and the user agent &SHOULD; reset
1278   the document view which caused the request to be sent. This response
1279   is primarily intended to allow input for actions to take place via
1280   user input, followed by a clearing of the form in which the input is
1281   given so that the user can easily initiate another input action. The
1282   response &MUST-NOT; include a message-body.
1283</t>
1284</section>
1285
1286<section title="206 Partial Content" anchor="status.206">
1287  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1288  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1289  <rdf:Description>
1290    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1291  </rdf:Description>
1292<t>
1293   The server has fulfilled the partial GET request for the resource
1294   and the enclosed entity is a partial representation as defined in &status-206;.
1295</t>
1296</section>
1297</section>
1298
1299<section title="Redirection 3xx" anchor="status.3xx">
1300<t>
1301   This class of status code indicates that further action needs to be
1302   taken by the user agent in order to fulfill the request.  The action
1303   required &MAY; be carried out by the user agent without interaction
1304   with the user if and only if the method used in the second request is
1305   known to be "safe", as defined in <xref target="safe.methods"/>.
1306   A client &SHOULD; detect infinite redirection loops, since such loops
1307   generate network traffic for each redirection.
1308</t>
1309<x:note>
1310  <t>
1311    <x:h>Note:</x:h> An earlier version of this specification recommended a
1312    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1313    Content developers should be aware that there might be clients that
1314    implement such a fixed limitation.
1315  </t>
1316</x:note>
1317
1318<section title="300 Multiple Choices" anchor="status.300">
1319  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1320  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1321<t>
1322   The requested resource corresponds to any one of a set of
1323   representations, each with its own specific location, and agent-driven
1324   negotiation information (&content-negotiation;) is being provided so that
1325   the user (or user agent) can select a preferred representation and
1326   redirect its request to that location.
1327</t>
1328<t>
1329   Unless it was a HEAD request, the response &SHOULD; include a representation
1330   containing a list of resource characteristics and location(s) from
1331   which the user or user agent can choose the one most appropriate. The
1332   data format is specified by the media type given in the Content-Type
1333   header field. Depending upon the format and the capabilities of
1334   the user agent, selection of the most appropriate choice &MAY; be
1335   performed automatically. However, this specification does not define
1336   any standard for such automatic selection.
1337</t>
1338<t>
1339   If the server has a preferred choice of representation, it &SHOULD;
1340   include the specific URI for that representation in the Location
1341   field; user agents &MAY; use the Location field value for automatic
1342   redirection. This response is cacheable unless indicated otherwise.
1343</t>
1344</section>
1345
1346<section title="301 Moved Permanently" anchor="status.301">
1347  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1348  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1349<t>
1350   The requested resource has been assigned a new permanent URI and any
1351   future references to this resource &SHOULD; use one of the returned
1352   URIs.  Clients with link editing capabilities ought to automatically
1353   re-link references to the Effective Request URI to one or more of the new
1354   references returned by the server, where possible. This response is
1355   cacheable unless indicated otherwise.
1356</t>
1357<t>
1358   The new permanent URI &SHOULD; be given by the Location field in the
1359   response. Unless the request method was HEAD, the representation of the
1360   response &SHOULD; contain a short hypertext note with a hyperlink to
1361   the new URI(s).
1362</t>
1363<t>
1364   If the 301 status code is received in response to a request method
1365   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1366   then the request &MAY; be automatically redirected by the user agent without
1367   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1368   request unless it can be confirmed by the user, since this might
1369   change the conditions under which the request was issued.
1370</t>
1371<x:note>
1372  <t>
1373    <x:h>Note:</x:h> When automatically redirecting a POST request after
1374    receiving a 301 status code, some existing HTTP/1.0 user agents
1375    will erroneously change it into a GET request.
1376  </t>
1377</x:note>
1378</section>
1379
1380<section title="302 Found" anchor="status.302">
1381  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1382  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1383<t>
1384   The requested resource resides temporarily under a different URI.
1385   Since the redirection might be altered on occasion, the client &SHOULD;
1386   continue to use the Effectice Request URI for future requests.  This response
1387   is only cacheable if indicated by a Cache-Control or Expires header
1388   field.
1389</t>
1390<t>
1391   The temporary URI &SHOULD; be given by the Location field in the
1392   response. Unless the request method was HEAD, the representation of the
1393   response &SHOULD; contain a short hypertext note with a hyperlink to
1394   the new URI(s).
1395</t>
1396<t>
1397   If the 302 status code is received in response to a request method
1398   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1399   then the request &MAY; be automatically redirected by the user agent without
1400   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1401   request unless it can be confirmed by the user, since this might
1402   change the conditions under which the request was issued.
1403</t>
1404<x:note>
1405  <t>
1406    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1407    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1408    specify that the client is not allowed to change the method on the
1409    redirected request.  However, most existing user agent implementations
1410    treat 302 as if it were a 303 response, performing a GET on the Location
1411    field-value regardless of the original request method. Therefore, a
1412    previous version of this specification
1413    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1414    status codes
1415    <xref target="status.303" format="none">303</xref> and
1416    <xref target="status.307" format="none">307</xref> for servers that wish
1417    to make unambiguously clear which kind of reaction is expected of the
1418    client.
1419  </t>
1420</x:note>
1421</section>
1422
1423<section title="303 See Other" anchor="status.303">
1424  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1425  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1426<t>
1427   The server directs the user agent to a different resource, indicated
1428   by a URI in the Location header field, that provides an indirect
1429   response to the original request.  The user agent &MAY; perform a GET
1430   request on the URI in the Location field in order to obtain a
1431   representation corresponding to the response, be redirected again,
1432   or end with an error status.  The Location URI is not a substitute
1433   reference for the originally requested resource.
1434</t>
1435<t>
1436   The 303 status is generally applicable to any HTTP method.  It is
1437   primarily used to allow the output of a POST action to redirect
1438   the user agent to a selected resource, since doing so provides the
1439   information corresponding to the POST response in a form that
1440   can be separately identified, bookmarked, and cached independent
1441   of the original request.
1442</t>
1443<t>
1444   A 303 response to a GET request indicates that the requested
1445   resource does not have a representation of its own that can be
1446   transferred by the server over HTTP.  The Location URI indicates a
1447   resource that is descriptive of the requested resource such that
1448   the follow-on representation may be useful without implying that
1449   it adequately represents the previously requested resource.
1450   Note that answers to the questions of what can be represented, what
1451   representations are adequate, and what might be a useful description
1452   are outside the scope of HTTP and thus entirely determined by the
1453   URI owner(s).
1454</t>
1455<t>
1456   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1457   cacheable by Cache-Control or Expires header fields.  Except for
1458   responses to a HEAD request, the representation of a 303 response &SHOULD;
1459   contain a short hypertext note with a hyperlink to the Location URI.
1460</t>
1461</section>
1462
1463<section title="304 Not Modified" anchor="status.304">
1464  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1466  <rdf:Description>
1467    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1468  </rdf:Description>
1469<t>
1470   The response to the request has not been modified since the conditions
1471   indicated by the client's conditional GET request, as defined in &status-304;.
1472</t>
1473</section>
1474
1475<section title="305 Use Proxy" anchor="status.305">
1476  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1477  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1478<t>
1479   The 305 status was defined in a previous version of this specification
1480   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1481</t>
1482</section>
1483
1484<section title="306 (Unused)" anchor="status.306">
1485  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1486  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1487<t>
1488   The 306 status code was used in a previous version of the
1489   specification, is no longer used, and the code is reserved.
1490</t>
1491</section>
1492
1493<section title="307 Temporary Redirect" anchor="status.307">
1494  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1495  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1496<t>
1497   The requested resource resides temporarily under a different URI.
1498   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1499   continue to use the Effective Request URI for future requests.  This response
1500   is only cacheable if indicated by a Cache-Control or Expires header
1501   field.
1502</t>
1503<t>
1504   The temporary URI &SHOULD; be given by the Location field in the
1505   response. Unless the request method was HEAD, the representation of the
1506   response &SHOULD; contain a short hypertext note with a hyperlink to
1507   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1508   understand the 307 status. Therefore, the note &SHOULD; contain the
1509   information necessary for a user to repeat the original request on
1510   the new URI.
1511</t>
1512<t>
1513   If the 307 status code is received in response to a request method
1514   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1515   then the request &MAY; be automatically redirected by the user agent without
1516   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1517   request unless it can be confirmed by the user, since this might
1518   change the conditions under which the request was issued.
1519</t>
1520</section>
1521</section>
1522
1523<section title="Client Error 4xx" anchor="status.4xx">
1524<t>
1525   The 4xx class of status code is intended for cases in which the
1526   client seems to have erred. Except when responding to a HEAD request,
1527   the server &SHOULD; include an entity containing an explanation of the
1528   error situation, and whether it is a temporary or permanent
1529   condition. These status codes are applicable to any request method.
1530   User agents &SHOULD; display any included entity to the user.
1531</t>
1532<t>
1533   If the client is sending data, a server implementation using TCP
1534   &SHOULD; be careful to ensure that the client acknowledges receipt of
1535   the packet(s) containing the response, before the server closes the
1536   input connection. If the client continues sending data to the server
1537   after the close, the server's TCP stack will send a reset packet to
1538   the client, which may erase the client's unacknowledged input buffers
1539   before they can be read and interpreted by the HTTP application.
1540</t>
1541
1542<section title="400 Bad Request" anchor="status.400">
1543  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1544  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1545<t>
1546   The request could not be understood by the server due to malformed
1547   syntax. The client &SHOULD-NOT;  repeat the request without
1548   modifications.
1549</t>
1550</section>
1551
1552<section title="401 Unauthorized" anchor="status.401">
1553  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1554  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1555  <rdf:Description>
1556    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1557  </rdf:Description>
1558<t>
1559   The request requires user authentication (see &status-401;).
1560</t>
1561</section>
1562
1563<section title="402 Payment Required" anchor="status.402">
1564  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1565  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1566<t>
1567   This code is reserved for future use.
1568</t>
1569</section>
1570
1571<section title="403 Forbidden" anchor="status.403">
1572  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1573  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1574<t>
1575   The server understood the request, but is refusing to fulfill it.
1576   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1577   If the request method was not HEAD and the server wishes to make
1578   public why the request has not been fulfilled, it &SHOULD; describe the
1579   reason for the refusal in the representation.  If the server does not wish to
1580   make this information available to the client, the status code 404
1581   (Not Found) can be used instead.
1582</t>
1583</section>
1584
1585<section title="404 Not Found" anchor="status.404">
1586  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1587  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1588<t>
1589   The server has not found anything matching the Effective Request URI. No
1590   indication is given of whether the condition is temporary or
1591   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1592   knows, through some internally configurable mechanism, that an old
1593   resource is permanently unavailable and has no forwarding address.
1594   This status code is commonly used when the server does not wish to
1595   reveal exactly why the request has been refused, or when no other
1596   response is applicable.
1597</t>
1598</section>
1599
1600<section title="405 Method Not Allowed" anchor="status.405">
1601  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1602  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1603<t>
1604   The method specified in the Request-Line is not allowed for the
1605   resource identified by the Effective Request URI. The response &MUST; include an
1606   Allow header containing a list of valid methods for the requested
1607   resource.
1608</t>
1609</section>
1610
1611<section title="406 Not Acceptable" anchor="status.406">
1612  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1613  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1614<t>
1615   The resource identified by the request is only capable of generating
1616   response entities which have content characteristics not acceptable
1617   according to the accept headers sent in the request.
1618</t>
1619<t>
1620   Unless it was a HEAD request, the response &SHOULD; include a representation
1621   containing a list of available representation characteristics and location(s)
1622   from which the user or user agent can choose the one most
1623   appropriate. The data format is specified by the media type given
1624   in the Content-Type header field. Depending upon the format and the
1625   capabilities of the user agent, selection of the most appropriate
1626   choice &MAY; be performed automatically. However, this specification
1627   does not define any standard for such automatic selection.
1628</t>
1629<x:note>
1630  <t>
1631    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1632    not acceptable according to the accept headers sent in the
1633    request. In some cases, this may even be preferable to sending a
1634    406 response. User agents are encouraged to inspect the headers of
1635    an incoming response to determine if it is acceptable.
1636  </t>
1637</x:note>
1638<t>
1639   If the response could be unacceptable, a user agent &SHOULD;
1640   temporarily stop receipt of more data and query the user for a
1641   decision on further actions.
1642</t>
1643</section>
1644
1645<section title="407 Proxy Authentication Required" anchor="status.407">
1646  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1647  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1648<t>
1649   This code is similar to 401 (Unauthorized), but indicates that the
1650   client must first authenticate itself with the proxy (see &status-407;).
1651</t>
1652</section>
1653
1654<section title="408 Request Timeout" anchor="status.408">
1655  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1656  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1657<t>
1658   The client did not produce a request within the time that the server
1659   was prepared to wait. The client &MAY; repeat the request without
1660   modifications at any later time.
1661</t>
1662</section>
1663
1664<section title="409 Conflict" anchor="status.409">
1665  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1666  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1667<t>
1668   The request could not be completed due to a conflict with the current
1669   state of the resource. This code is only allowed in situations where
1670   it is expected that the user might be able to resolve the conflict
1671   and resubmit the request. The response body &SHOULD; include enough
1672   information for the user to recognize the source of the conflict.
1673   Ideally, the response entity would include enough information for the
1674   user or user agent to fix the problem; however, that might not be
1675   possible and is not required.
1676</t>
1677<t>
1678   Conflicts are most likely to occur in response to a PUT request. For
1679   example, if versioning were being used and the representation being PUT
1680   included changes to a resource which conflict with those made by an
1681   earlier (third-party) request, the server might use the 409 response
1682   to indicate that it can't complete the request. In this case, the
1683   response representation would likely contain a list of the differences
1684   between the two versions in a format defined by the response
1685   Content-Type.
1686</t>
1687</section>
1688
1689<section title="410 Gone" anchor="status.410">
1690  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1691  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1692<t>
1693   The requested resource is no longer available at the server and no
1694   forwarding address is known. This condition is expected to be
1695   considered permanent. Clients with link editing capabilities &SHOULD;
1696   delete references to the Effective Request URI after user approval. If the
1697   server does not know, or has no facility to determine, whether or not
1698   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1699   used instead. This response is cacheable unless indicated otherwise.
1700</t>
1701<t>
1702   The 410 response is primarily intended to assist the task of web
1703   maintenance by notifying the recipient that the resource is
1704   intentionally unavailable and that the server owners desire that
1705   remote links to that resource be removed. Such an event is common for
1706   limited-time, promotional services and for resources belonging to
1707   individuals no longer working at the server's site. It is not
1708   necessary to mark all permanently unavailable resources as "gone" or
1709   to keep the mark for any length of time -- that is left to the
1710   discretion of the server owner.
1711</t>
1712</section>
1713
1714<section title="411 Length Required" anchor="status.411">
1715  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1716  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1717<t>
1718   The server refuses to accept the request without a defined Content-Length.
1719   The client &MAY; repeat the request if it adds a valid
1720   Content-Length header field containing the length of the message-body
1721   in the request message.
1722</t>
1723</section>
1724
1725<section title="412 Precondition Failed" anchor="status.412">
1726  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1727  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1728  <rdf:Description>
1729    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1730  </rdf:Description>
1731<t>
1732   The precondition given in one or more of the request-header fields
1733   evaluated to false when it was tested on the server, as defined in
1734   &status-412;.
1735</t>
1736</section>
1737
1738<section title="413 Request Entity Too Large" anchor="status.413">
1739  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1740  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1741<t>
1742   The server is refusing to process a request because the request
1743   entity is larger than the server is willing or able to process. The
1744   server &MAY; close the connection to prevent the client from continuing
1745   the request.
1746</t>
1747<t>
1748   If the condition is temporary, the server &SHOULD; include a Retry-After
1749   header field to indicate that it is temporary and after what
1750   time the client &MAY; try again.
1751</t>
1752</section>
1753
1754<section title="414 URI Too Long" anchor="status.414">
1755  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1756  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1757<t>
1758   The server is refusing to service the request because the Effective Request URI
1759   is longer than the server is willing to interpret. This rare
1760   condition is only likely to occur when a client has improperly
1761   converted a POST request to a GET request with long query
1762   information, when the client has descended into a URI "black hole" of
1763   redirection (e.g., a redirected URI prefix that points to a suffix of
1764   itself), or when the server is under attack by a client attempting to
1765   exploit security holes present in some servers using fixed-length
1766   buffers for reading or manipulating the Effective Request URI.
1767</t>
1768</section>
1769
1770<section title="415 Unsupported Media Type" anchor="status.415">
1771  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1773<t>
1774   The server is refusing to service the request because the representation of
1775   the request is in a format not supported by the requested resource
1776   for the requested method.
1777</t>
1778</section>
1779
1780<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1781  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1782  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1783  <rdf:Description>
1784    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1785  </rdf:Description>
1786<t>
1787   The request included a Range request-header field (&header-range;) and none of
1788   the range-specifier values in this field overlap the current extent
1789   of the selected resource. See &status-416;
1790</t>
1791</section>
1792
1793<section title="417 Expectation Failed" anchor="status.417">
1794  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1795  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1796<t>
1797   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1798   could not be met by this server, or, if the server is a proxy,
1799   the server has unambiguous evidence that the request could not be met
1800   by the next-hop server.
1801</t>
1802</section>
1803</section>
1804
1805<section title="Server Error 5xx" anchor="status.5xx">
1806<t>
1807   Response status codes beginning with the digit "5" indicate cases in
1808   which the server is aware that it has erred or is incapable of
1809   performing the request. Except when responding to a HEAD request, the
1810   server &SHOULD; include an entity containing an explanation of the
1811   error situation, and whether it is a temporary or permanent
1812   condition. User agents &SHOULD; display any included entity to the
1813   user. These response codes are applicable to any request method.
1814</t>
1815
1816<section title="500 Internal Server Error" anchor="status.500">
1817  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1818  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1819<t>
1820   The server encountered an unexpected condition which prevented it
1821   from fulfilling the request.
1822</t>
1823</section>
1824
1825<section title="501 Not Implemented" anchor="status.501">
1826  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1827  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1828<t>
1829   The server does not support the functionality required to fulfill the
1830   request. This is the appropriate response when the server does not
1831   recognize the request method and is not capable of supporting it for
1832   any resource.
1833</t>
1834</section>
1835
1836<section title="502 Bad Gateway" anchor="status.502">
1837  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1838  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1839<t>
1840   The server, while acting as a gateway or proxy, received an invalid
1841   response from the upstream server it accessed in attempting to
1842   fulfill the request.
1843</t>
1844</section>
1845
1846<section title="503 Service Unavailable" anchor="status.503">
1847  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1848  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1849<t>
1850   The server is currently unable to handle the request due to a
1851   temporary overloading or maintenance of the server. The implication
1852   is that this is a temporary condition which will be alleviated after
1853   some delay. If known, the length of the delay &MAY; be indicated in a
1854   Retry-After header. If no Retry-After is given, the client &SHOULD;
1855   handle the response as it would for a 500 response.
1856</t>
1857<x:note>
1858  <t>
1859    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1860    server must use it when becoming overloaded. Some servers may wish
1861    to simply refuse the connection.
1862  </t>
1863</x:note>
1864</section>
1865
1866<section title="504 Gateway Timeout" anchor="status.504">
1867  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1868  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1869<t>
1870   The server, while acting as a gateway or proxy, did not receive a
1871   timely response from the upstream server specified by the URI (e.g.,
1872   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1873   to access in attempting to complete the request.
1874</t>
1875<x:note>
1876  <t>
1877    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1878    return 400 or 500 when DNS lookups time out.
1879  </t>
1880</x:note>
1881</section>
1882
1883<section title="505 HTTP Version Not Supported" anchor="status.505">
1884  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1885  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1886<t>
1887   The server does not support, or refuses to support, the protocol
1888   version that was used in the request message. The server is
1889   indicating that it is unable or unwilling to complete the request
1890   using the same major version as the client, as described in &http-version;,
1891   other than with this error message. The response &SHOULD; contain
1892   an entity describing why that version is not supported and what other
1893   protocols are supported by that server.
1894</t>
1895
1896</section>
1897</section>
1898</section>
1899
1900
1901<section title="Header Field Definitions" anchor="header.fields">
1902<t>
1903   This section defines the syntax and semantics of HTTP/1.1 header fields
1904   related to request and response semantics.
1905</t>
1906<t>
1907   For entity-header fields, both sender and recipient refer to either the
1908   client or the server, depending on who sends and who receives the message.
1909</t>
1910
1911<section title="Allow" anchor="header.allow">
1912  <iref primary="true" item="Allow header" x:for-anchor=""/>
1913  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1914  <x:anchor-alias value="Allow"/>
1915  <x:anchor-alias value="Allow-v"/>
1916<t>
1917   The "Allow" response-header field lists the set of methods advertised as
1918   supported by the resource identified by the Effective Request URI. The purpose of
1919   this field is strictly to inform the recipient of valid methods
1920   associated with the resource.
1921</t>
1922<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1923  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1924  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1925</artwork></figure>
1926<t>
1927      Example of use:
1928</t>
1929<figure><artwork type="example">
1930  Allow: GET, HEAD, PUT
1931</artwork></figure>
1932<t>
1933      The actual set of allowed methods is defined
1934      by the origin server at the time of each request.
1935</t>
1936<t>
1937      A proxy &MUST-NOT; modify the Allow header field even if it does not
1938      understand all the methods specified, since the user agent might
1939      have other means of communicating with the origin server.
1940</t>
1941</section>
1942
1943<section title="Expect" anchor="header.expect">
1944  <iref primary="true" item="Expect header" x:for-anchor=""/>
1945  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1946  <x:anchor-alias value="Expect"/>
1947  <x:anchor-alias value="Expect-v"/>
1948  <x:anchor-alias value="expectation"/>
1949  <x:anchor-alias value="expectation-extension"/>
1950  <x:anchor-alias value="expect-params"/>
1951<t>
1952   The "Expect" request-header field is used to indicate that particular
1953   server behaviors are required by the client.
1954</t>
1955<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"/>
1956  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1957  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1958 
1959  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1960  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1961                           *<x:ref>expect-params</x:ref> ]
1962  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1963</artwork></figure>
1964<t>
1965   A server that does not understand or is unable to comply with any of
1966   the expectation values in the Expect field of a request &MUST; respond
1967   with appropriate error status. The server &MUST; respond with a 417
1968   (Expectation Failed) status if any of the expectations cannot be met
1969   or, if there are other problems with the request, some other 4xx
1970   status.
1971</t>
1972<t>
1973   This header field is defined with extensible syntax to allow for
1974   future extensions. If a server receives a request containing an
1975   Expect field that includes an expectation-extension that it does not
1976   support, it &MUST; respond with a 417 (Expectation Failed) status.
1977</t>
1978<t>
1979   Comparison of expectation values is case-insensitive for unquoted
1980   tokens (including the 100-continue token), and is case-sensitive for
1981   quoted-string expectation-extensions.
1982</t>
1983<t>
1984   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1985   return a 417 (Expectation Failed) status if it receives a request
1986   with an expectation that it cannot meet. However, the Expect
1987   request-header itself is end-to-end; it &MUST; be forwarded if the
1988   request is forwarded.
1989</t>
1990<t>
1991   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1992   Expect header.
1993</t>
1994<t>
1995   See &use100; for the use of the 100 (Continue) status.
1996</t>
1997</section>
1998
1999<section title="From" anchor="header.from">
2000  <iref primary="true" item="From header" x:for-anchor=""/>
2001  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2002  <x:anchor-alias value="From"/>
2003  <x:anchor-alias value="From-v"/>
2004  <x:anchor-alias value="mailbox"/>
2005<t>
2006   The "From" request-header field, if given, &SHOULD; contain an Internet
2007   e-mail address for the human user who controls the requesting user
2008   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2009   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2010</t>
2011<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2012  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2013  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2014 
2015  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2016</artwork></figure>
2017<t>
2018   An example is:
2019</t>
2020<figure><artwork type="example">
2021  From: webmaster@example.org
2022</artwork></figure>
2023<t>
2024   This header field &MAY; be used for logging purposes and as a means for
2025   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2026   be used as an insecure form of access protection. The interpretation
2027   of this field is that the request is being performed on behalf of the
2028   person given, who accepts responsibility for the method performed. In
2029   particular, robot agents &SHOULD; include this header so that the
2030   person responsible for running the robot can be contacted if problems
2031   occur on the receiving end.
2032</t>
2033<t>
2034   The Internet e-mail address in this field &MAY; be separate from the
2035   Internet host which issued the request. For example, when a request
2036   is passed through a proxy the original issuer's address &SHOULD; be
2037   used.
2038</t>
2039<t>
2040   The client &SHOULD-NOT;  send the From header field without the user's
2041   approval, as it might conflict with the user's privacy interests or
2042   their site's security policy. It is strongly recommended that the
2043   user be able to disable, enable, and modify the value of this field
2044   at any time prior to a request.
2045</t>
2046</section>
2047
2048<section title="Location" anchor="header.location">
2049  <iref primary="true" item="Location header" x:for-anchor=""/>
2050  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2051  <x:anchor-alias value="Location"/>
2052  <x:anchor-alias value="Location-v"/>
2053<t>
2054   The "Location" response-header field is used to identify a newly created
2055   resource, or to redirect the recipient to a different location for
2056   completion of the request.
2057</t>
2058<t>
2059   For 201 (Created) responses, the Location is the URI of the new resource
2060   which was created by the request. For 3xx responses, the location &SHOULD;
2061   indicate the server's preferred URI for automatic redirection to the
2062   resource.
2063</t>
2064<t>
2065   The field value consists of a single URI-reference. When it has the form
2066   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2067   the final value is computed by resolving it against the effective request
2068   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2069</t>
2070<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2071  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2072  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2073</artwork></figure>
2074<figure>
2075<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2076<artwork type="example">
2077  Location: http://www.example.org/pub/WWW/People.html#tim
2078</artwork></figure><figure><artwork type="example">  Location: /index.html
2079</artwork></figure>
2080<t>
2081   There are circumstances in which a fragment identifier in a Location URI
2082   would not be appropriate:
2083   <list style="symbols">
2084      <t>With a 201 Created response, because in this usage the Location header
2085      specifies the URI for the entire created resource.</t>
2086      <t>With 305 Use Proxy.</t>
2087   </list>
2088</t>
2089<x:note>
2090  <t>
2091    <x:h>Note:</x:h> This specification does not define precedence rules
2092    for the case where the original URI, as navigated to by the user
2093    agent, and the Location header field value both contain fragment
2094    identifiers.
2095  </t>
2096</x:note>
2097<x:note>
2098  <t>
2099    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2100    from Location in that the Content-Location identifies the most specific
2101    resource corresponding to the enclosed representation.
2102    It is therefore possible for a response to contain header fields for
2103    both Location and Content-Location.
2104  </t>
2105</x:note>
2106</section>
2107
2108<section title="Max-Forwards" anchor="header.max-forwards">
2109  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2110  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2111  <x:anchor-alias value="Max-Forwards"/>
2112  <x:anchor-alias value="Max-Forwards-v"/>
2113<t>
2114   The "Max-Forwards" request-header field provides a mechanism with the
2115   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2116   methods to limit the number of times that the request is forwarded by
2117   proxies or gateways. This can be useful when the client is attempting to
2118   trace a request which appears to be failing or looping in mid-chain.
2119</t>
2120<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2121  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2122  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2123</artwork></figure>
2124<t>
2125   The Max-Forwards value is a decimal integer indicating the remaining
2126   number of times this request message may be forwarded.
2127</t>
2128<t>
2129   Each proxy or gateway recipient of a TRACE or OPTIONS request
2130   containing a Max-Forwards header field &MUST; check and update its
2131   value prior to forwarding the request. If the received value is zero
2132   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2133   respond as the final recipient. If the received Max-Forwards value is
2134   greater than zero, then the forwarded message &MUST; contain an updated
2135   Max-Forwards field with a value decremented by one (1).
2136</t>
2137<t>
2138   The Max-Forwards header field &MAY; be ignored for all other methods
2139   defined by this specification and for any extension methods for which
2140   it is not explicitly referred to as part of that method definition.
2141</t>
2142</section>
2143
2144<section title="Referer" anchor="header.referer">
2145  <iref primary="true" item="Referer header" x:for-anchor=""/>
2146  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2147  <x:anchor-alias value="Referer"/>
2148  <x:anchor-alias value="Referer-v"/>
2149<t>
2150   The "Referer" [sic] request-header field allows the client to specify the
2151   URI of the resource from which the Effective Request URI was obtained (the
2152   "referrer", although the header field is misspelled.).
2153</t>
2154<t>
2155   The Referer header allows servers to generate lists of back-links to
2156   resources for interest, logging, optimized caching, etc. It also allows
2157   obsolete or mistyped links to be traced for maintenance. Some servers use
2158   Referer as a means of controlling where they allow links from (so-called
2159   "deep linking"), but it should be noted that legitimate requests are not
2160   required to contain a Referer header field.
2161</t>
2162<t>
2163   If the Effective Request URI was obtained from a source that does not have its own
2164   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2165   sent with the value "about:blank", or not be sent at all. Note that this
2166   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2167</t>
2168<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2169  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2170  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2171</artwork></figure>
2172<t>
2173   Example:
2174</t>
2175<figure><artwork type="example">
2176  Referer: http://www.example.org/hypertext/Overview.html
2177</artwork></figure>
2178<t>
2179   If the field value is a relative URI, it &SHOULD; be interpreted
2180   relative to the Effective Request URI. The URI &MUST-NOT; include a fragment. See
2181   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2182</t>
2183</section>
2184
2185<section title="Retry-After" anchor="header.retry-after">
2186  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2187  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2188  <x:anchor-alias value="Retry-After"/>
2189  <x:anchor-alias value="Retry-After-v"/>
2190<t>
2191   The response-header "Retry-After" field can be used with a 503 (Service
2192   Unavailable) response to indicate how long the service is expected to
2193   be unavailable to the requesting client. This field &MAY; also be used
2194   with any 3xx (Redirection) response to indicate the minimum time the
2195   user-agent is asked wait before issuing the redirected request.
2196</t>
2197<t>
2198   The value of this field can be either an HTTP-date or an integer number
2199   of seconds (in decimal) after the time of the response.
2200</t>
2201<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2202  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2203  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2204</artwork></figure>
2205<t anchor="rule.delta-seconds">
2206  <x:anchor-alias value="delta-seconds"/>
2207   Time spans are non-negative decimal integers, representing time in
2208   seconds.
2209</t>
2210<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2211  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2212</artwork></figure>
2213<t>
2214   Two examples of its use are
2215</t>
2216<figure><artwork type="example">
2217  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2218  Retry-After: 120
2219</artwork></figure>
2220<t>
2221   In the latter example, the delay is 2 minutes.
2222</t>
2223</section>
2224
2225<section title="Server" anchor="header.server">
2226  <iref primary="true" item="Server header" x:for-anchor=""/>
2227  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2228  <x:anchor-alias value="Server"/>
2229  <x:anchor-alias value="Server-v"/>
2230<t>
2231   The "Server" response-header field contains information about the
2232   software used by the origin server to handle the request.
2233</t>
2234<t>
2235   The field can contain multiple product tokens (&product-tokens;) and
2236   comments (&header-fields;) identifying the server and any significant
2237   subproducts. The product tokens are listed in order of their significance
2238   for identifying the application.
2239</t>
2240<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2241  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2242  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2243                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2244</artwork></figure>
2245<t>
2246   Example:
2247</t>
2248<figure><artwork type="example">
2249  Server: CERN/3.0 libwww/2.17
2250</artwork></figure>
2251<t>
2252   If the response is being forwarded through a proxy, the proxy
2253   application &MUST-NOT; modify the Server response-header. Instead, it
2254   &MUST; include a Via field (as described in &header-via;).
2255</t>
2256<x:note>
2257  <t>
2258    <x:h>Note:</x:h> Revealing the specific software version of the server might
2259    allow the server machine to become more vulnerable to attacks
2260    against software that is known to contain security holes. Server
2261    implementors are encouraged to make this field a configurable
2262    option.
2263  </t>
2264</x:note>
2265</section>
2266
2267<section title="User-Agent" anchor="header.user-agent">
2268  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2269  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2270  <x:anchor-alias value="User-Agent"/>
2271  <x:anchor-alias value="User-Agent-v"/>
2272<t>
2273   The "User-Agent" request-header field contains information about the
2274   user agent originating the request. This is for statistical purposes,
2275   the tracing of protocol violations, and automated recognition of user
2276   agents for the sake of tailoring responses to avoid particular user
2277   agent limitations.
2278</t>
2279<t>
2280   User agents &SHOULD; include this field with requests. The field can contain
2281   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2282   identifying the agent and any subproducts which form a significant part of
2283   the user agent. By convention, the product tokens are listed in order of
2284   their significance for identifying the application.
2285</t>
2286<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2287  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2288  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2289                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2290</artwork></figure>
2291<t>
2292   Example:
2293</t>
2294<figure><artwork type="example">
2295  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2296</artwork></figure>
2297</section>
2298
2299</section>
2300
2301<section title="IANA Considerations" anchor="IANA.considerations">
2302
2303<section title="Method Registry" anchor="method.registration">
2304<t>
2305  The registration procedure for HTTP Methods is defined by
2306  <xref target="method.registry"/> of this document.
2307</t>
2308<t>
2309   The HTTP Method Registry should be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2310   and be populated with the registrations below:
2311</t>
2312<?BEGININC p2-semantics.iana-methods ?>
2313<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2314<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2315   <ttcol>Method</ttcol>
2316   <ttcol>Safe</ttcol>
2317   <ttcol>Reference</ttcol>
2318   <c>CONNECT</c>
2319   <c>no</c>
2320   <c>
2321      <xref target="CONNECT"/>
2322   </c>
2323   <c>DELETE</c>
2324   <c>no</c>
2325   <c>
2326      <xref target="DELETE"/>
2327   </c>
2328   <c>GET</c>
2329   <c>yes</c>
2330   <c>
2331      <xref target="GET"/>
2332   </c>
2333   <c>HEAD</c>
2334   <c>yes</c>
2335   <c>
2336      <xref target="HEAD"/>
2337   </c>
2338   <c>OPTIONS</c>
2339   <c>yes</c>
2340   <c>
2341      <xref target="OPTIONS"/>
2342   </c>
2343   <c>POST</c>
2344   <c>no</c>
2345   <c>
2346      <xref target="POST"/>
2347   </c>
2348   <c>PUT</c>
2349   <c>no</c>
2350   <c>
2351      <xref target="PUT"/>
2352   </c>
2353   <c>TRACE</c>
2354   <c>yes</c>
2355   <c>
2356      <xref target="TRACE"/>
2357   </c>
2358</texttable>
2359<!--(END)-->
2360<?ENDINC p2-semantics.iana-methods ?>
2361</section>
2362
2363<section title="Status Code Registry" anchor="status.code.registration">
2364<t>
2365   The registration procedure for HTTP Status Codes -- previously defined
2366   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2367   by <xref target="status.code.registry"/> of this document.
2368</t>
2369<t>
2370   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2371   should be updated with the registrations below:
2372</t>
2373<?BEGININC p2-semantics.iana-status-codes ?>
2374<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2375<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2376   <ttcol>Value</ttcol>
2377   <ttcol>Description</ttcol>
2378   <ttcol>Reference</ttcol>
2379   <c>100</c>
2380   <c>Continue</c>
2381   <c>
2382      <xref target="status.100"/>
2383   </c>
2384   <c>101</c>
2385   <c>Switching Protocols</c>
2386   <c>
2387      <xref target="status.101"/>
2388   </c>
2389   <c>200</c>
2390   <c>OK</c>
2391   <c>
2392      <xref target="status.200"/>
2393   </c>
2394   <c>201</c>
2395   <c>Created</c>
2396   <c>
2397      <xref target="status.201"/>
2398   </c>
2399   <c>202</c>
2400   <c>Accepted</c>
2401   <c>
2402      <xref target="status.202"/>
2403   </c>
2404   <c>203</c>
2405   <c>Non-Authoritative Information</c>
2406   <c>
2407      <xref target="status.203"/>
2408   </c>
2409   <c>204</c>
2410   <c>No Content</c>
2411   <c>
2412      <xref target="status.204"/>
2413   </c>
2414   <c>205</c>
2415   <c>Reset Content</c>
2416   <c>
2417      <xref target="status.205"/>
2418   </c>
2419   <c>300</c>
2420   <c>Multiple Choices</c>
2421   <c>
2422      <xref target="status.300"/>
2423   </c>
2424   <c>301</c>
2425   <c>Moved Permanently</c>
2426   <c>
2427      <xref target="status.301"/>
2428   </c>
2429   <c>302</c>
2430   <c>Found</c>
2431   <c>
2432      <xref target="status.302"/>
2433   </c>
2434   <c>303</c>
2435   <c>See Other</c>
2436   <c>
2437      <xref target="status.303"/>
2438   </c>
2439   <c>305</c>
2440   <c>Use Proxy</c>
2441   <c>
2442      <xref target="status.305"/>
2443   </c>
2444   <c>306</c>
2445   <c>(Unused)</c>
2446   <c>
2447      <xref target="status.306"/>
2448   </c>
2449   <c>307</c>
2450   <c>Temporary Redirect</c>
2451   <c>
2452      <xref target="status.307"/>
2453   </c>
2454   <c>400</c>
2455   <c>Bad Request</c>
2456   <c>
2457      <xref target="status.400"/>
2458   </c>
2459   <c>402</c>
2460   <c>Payment Required</c>
2461   <c>
2462      <xref target="status.402"/>
2463   </c>
2464   <c>403</c>
2465   <c>Forbidden</c>
2466   <c>
2467      <xref target="status.403"/>
2468   </c>
2469   <c>404</c>
2470   <c>Not Found</c>
2471   <c>
2472      <xref target="status.404"/>
2473   </c>
2474   <c>405</c>
2475   <c>Method Not Allowed</c>
2476   <c>
2477      <xref target="status.405"/>
2478   </c>
2479   <c>406</c>
2480   <c>Not Acceptable</c>
2481   <c>
2482      <xref target="status.406"/>
2483   </c>
2484   <c>407</c>
2485   <c>Proxy Authentication Required</c>
2486   <c>
2487      <xref target="status.407"/>
2488   </c>
2489   <c>408</c>
2490   <c>Request Timeout</c>
2491   <c>
2492      <xref target="status.408"/>
2493   </c>
2494   <c>409</c>
2495   <c>Conflict</c>
2496   <c>
2497      <xref target="status.409"/>
2498   </c>
2499   <c>410</c>
2500   <c>Gone</c>
2501   <c>
2502      <xref target="status.410"/>
2503   </c>
2504   <c>411</c>
2505   <c>Length Required</c>
2506   <c>
2507      <xref target="status.411"/>
2508   </c>
2509   <c>413</c>
2510   <c>Request Entity Too Large</c>
2511   <c>
2512      <xref target="status.413"/>
2513   </c>
2514   <c>414</c>
2515   <c>URI Too Long</c>
2516   <c>
2517      <xref target="status.414"/>
2518   </c>
2519   <c>415</c>
2520   <c>Unsupported Media Type</c>
2521   <c>
2522      <xref target="status.415"/>
2523   </c>
2524   <c>417</c>
2525   <c>Expectation Failed</c>
2526   <c>
2527      <xref target="status.417"/>
2528   </c>
2529   <c>500</c>
2530   <c>Internal Server Error</c>
2531   <c>
2532      <xref target="status.500"/>
2533   </c>
2534   <c>501</c>
2535   <c>Not Implemented</c>
2536   <c>
2537      <xref target="status.501"/>
2538   </c>
2539   <c>502</c>
2540   <c>Bad Gateway</c>
2541   <c>
2542      <xref target="status.502"/>
2543   </c>
2544   <c>503</c>
2545   <c>Service Unavailable</c>
2546   <c>
2547      <xref target="status.503"/>
2548   </c>
2549   <c>504</c>
2550   <c>Gateway Timeout</c>
2551   <c>
2552      <xref target="status.504"/>
2553   </c>
2554   <c>505</c>
2555   <c>HTTP Version Not Supported</c>
2556   <c>
2557      <xref target="status.505"/>
2558   </c>
2559</texttable>
2560<!--(END)-->
2561<?ENDINC p2-semantics.iana-status-codes ?>
2562</section>
2563<section title="Message Header Registration" anchor="message.header.registration">
2564<t>
2565   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2566   with the permanent registrations below (see <xref target="RFC3864"/>):
2567</t>
2568<?BEGININC p2-semantics.iana-headers ?>
2569<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2570<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2571   <ttcol>Header Field Name</ttcol>
2572   <ttcol>Protocol</ttcol>
2573   <ttcol>Status</ttcol>
2574   <ttcol>Reference</ttcol>
2575
2576   <c>Allow</c>
2577   <c>http</c>
2578   <c>standard</c>
2579   <c>
2580      <xref target="header.allow"/>
2581   </c>
2582   <c>Expect</c>
2583   <c>http</c>
2584   <c>standard</c>
2585   <c>
2586      <xref target="header.expect"/>
2587   </c>
2588   <c>From</c>
2589   <c>http</c>
2590   <c>standard</c>
2591   <c>
2592      <xref target="header.from"/>
2593   </c>
2594   <c>Location</c>
2595   <c>http</c>
2596   <c>standard</c>
2597   <c>
2598      <xref target="header.location"/>
2599   </c>
2600   <c>Max-Forwards</c>
2601   <c>http</c>
2602   <c>standard</c>
2603   <c>
2604      <xref target="header.max-forwards"/>
2605   </c>
2606   <c>Referer</c>
2607   <c>http</c>
2608   <c>standard</c>
2609   <c>
2610      <xref target="header.referer"/>
2611   </c>
2612   <c>Retry-After</c>
2613   <c>http</c>
2614   <c>standard</c>
2615   <c>
2616      <xref target="header.retry-after"/>
2617   </c>
2618   <c>Server</c>
2619   <c>http</c>
2620   <c>standard</c>
2621   <c>
2622      <xref target="header.server"/>
2623   </c>
2624   <c>User-Agent</c>
2625   <c>http</c>
2626   <c>standard</c>
2627   <c>
2628      <xref target="header.user-agent"/>
2629   </c>
2630</texttable>
2631<!--(END)-->
2632<?ENDINC p2-semantics.iana-headers ?>
2633<t>
2634   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2635</t>
2636</section>
2637</section>
2638
2639<section title="Security Considerations" anchor="security.considerations">
2640<t>
2641   This section is meant to inform application developers, information
2642   providers, and users of the security limitations in HTTP/1.1 as
2643   described by this document. The discussion does not include
2644   definitive solutions to the problems revealed, though it does make
2645   some suggestions for reducing security risks.
2646</t>
2647
2648<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2649<t>
2650   Like any generic data transfer protocol, HTTP cannot regulate the
2651   content of the data that is transferred, nor is there any a priori
2652   method of determining the sensitivity of any particular piece of
2653   information within the context of any given request. Therefore,
2654   applications &SHOULD; supply as much control over this information as
2655   possible to the provider of that information. Four header fields are
2656   worth special mention in this context: Server, Via, Referer and From.
2657</t>
2658<t>
2659   Revealing the specific software version of the server might allow the
2660   server machine to become more vulnerable to attacks against software
2661   that is known to contain security holes. Implementors &SHOULD; make the
2662   Server header field a configurable option.
2663</t>
2664<t>
2665   Proxies which serve as a portal through a network firewall &SHOULD;
2666   take special precautions regarding the transfer of header information
2667   that identifies the hosts behind the firewall. In particular, they
2668   &SHOULD; remove, or replace with sanitized versions, any Via fields
2669   generated behind the firewall.
2670</t>
2671<t>
2672   The Referer header allows reading patterns to be studied and reverse
2673   links drawn. Although it can be very useful, its power can be abused
2674   if user details are not separated from the information contained in
2675   the Referer. Even when the personal information has been removed, the
2676   Referer header might indicate a private document's URI whose
2677   publication would be inappropriate.
2678</t>
2679<t>
2680   The information sent in the From field might conflict with the user's
2681   privacy interests or their site's security policy, and hence it
2682   &SHOULD-NOT;  be transmitted without the user being able to disable,
2683   enable, and modify the contents of the field. The user &MUST; be able
2684   to set the contents of this field within a user preference or
2685   application defaults configuration.
2686</t>
2687<t>
2688   We suggest, though do not require, that a convenient toggle interface
2689   be provided for the user to enable or disable the sending of From and
2690   Referer information.
2691</t>
2692<t>
2693   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2694   fields can sometimes be used to determine that a specific client or
2695   server have a particular security hole which might be exploited.
2696   Unfortunately, this same information is often used for other valuable
2697   purposes for which HTTP currently has no better mechanism.
2698</t>
2699<t>
2700   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2701   information sent in request headers in the response.
2702   Clients &SHOULD; be careful with sensitive information, like Cookies,
2703   Authorization credentials and other headers that might be used to
2704   collect data from the client.
2705</t> 
2706</section>
2707
2708<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2709<t>
2710   Because the source of a link might be private information or might
2711   reveal an otherwise private information source, it is strongly
2712   recommended that the user be able to select whether or not the
2713   Referer field is sent. For example, a browser client could have a
2714   toggle switch for browsing openly/anonymously, which would
2715   respectively enable/disable the sending of Referer and From
2716   information.
2717</t>
2718<t>
2719   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2720   HTTP request if the referring page was transferred with a secure
2721   protocol.
2722</t>
2723<t>
2724   Authors of services should not use GET-based forms for the submission of
2725   sensitive data because that data will be encoded in the request-target. Many
2726   existing servers, proxies, and user agents log or display the request-target
2727   in places where it might be visible to third parties. Such services can
2728   use POST-based form submission instead.
2729</t>
2730</section>
2731
2732<section title="Location Headers and Spoofing" anchor="location.spoofing">
2733<t>
2734   If a single server supports multiple organizations that do not trust
2735   one another, then it &MUST; check the values of Location and Content-Location
2736   headers in responses that are generated under control of
2737   said organizations to make sure that they do not attempt to
2738   invalidate resources over which they have no authority.
2739</t>
2740</section>
2741
2742</section>
2743
2744<section title="Acknowledgments" anchor="ack">
2745</section>
2746</middle>
2747<back>
2748
2749<references title="Normative References">
2750
2751<reference anchor="Part1">
2752  <front>
2753    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2754    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2755      <organization abbrev="Day Software">Day Software</organization>
2756      <address><email>fielding@gbiv.com</email></address>
2757    </author>
2758    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2759      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2760      <address><email>jg@freedesktop.org</email></address>
2761    </author>
2762    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2763      <organization abbrev="HP">Hewlett-Packard Company</organization>
2764      <address><email>JeffMogul@acm.org</email></address>
2765    </author>
2766    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2767      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2768      <address><email>henrikn@microsoft.com</email></address>
2769    </author>
2770    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2771      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2772      <address><email>LMM@acm.org</email></address>
2773    </author>
2774    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2775      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2776      <address><email>paulle@microsoft.com</email></address>
2777    </author>
2778    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2779      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2780      <address><email>timbl@w3.org</email></address>
2781    </author>
2782    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2783      <organization abbrev="W3C">World Wide Web Consortium</organization>
2784      <address><email>ylafon@w3.org</email></address>
2785    </author>
2786    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2787      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2788      <address><email>julian.reschke@greenbytes.de</email></address>
2789    </author>
2790    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2791  </front>
2792  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2793  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2794</reference>
2795
2796<reference anchor="Part3">
2797  <front>
2798    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2799    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2800      <organization abbrev="Day Software">Day Software</organization>
2801      <address><email>fielding@gbiv.com</email></address>
2802    </author>
2803    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2804      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2805      <address><email>jg@freedesktop.org</email></address>
2806    </author>
2807    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2808      <organization abbrev="HP">Hewlett-Packard Company</organization>
2809      <address><email>JeffMogul@acm.org</email></address>
2810    </author>
2811    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2812      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2813      <address><email>henrikn@microsoft.com</email></address>
2814    </author>
2815    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2816      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2817      <address><email>LMM@acm.org</email></address>
2818    </author>
2819    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2820      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2821      <address><email>paulle@microsoft.com</email></address>
2822    </author>
2823    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2824      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2825      <address><email>timbl@w3.org</email></address>
2826    </author>
2827    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2828      <organization abbrev="W3C">World Wide Web Consortium</organization>
2829      <address><email>ylafon@w3.org</email></address>
2830    </author>
2831    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2832      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2833      <address><email>julian.reschke@greenbytes.de</email></address>
2834    </author>
2835    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2836  </front>
2837  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2838  <x:source href="p3-payload.xml" basename="p3-payload"/>
2839</reference>
2840
2841<reference anchor="Part4">
2842  <front>
2843    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2844    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2845      <organization abbrev="Day Software">Day Software</organization>
2846      <address><email>fielding@gbiv.com</email></address>
2847    </author>
2848    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2849      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2850      <address><email>jg@freedesktop.org</email></address>
2851    </author>
2852    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2853      <organization abbrev="HP">Hewlett-Packard Company</organization>
2854      <address><email>JeffMogul@acm.org</email></address>
2855    </author>
2856    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2857      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2858      <address><email>henrikn@microsoft.com</email></address>
2859    </author>
2860    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2861      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2862      <address><email>LMM@acm.org</email></address>
2863    </author>
2864    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2865      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2866      <address><email>paulle@microsoft.com</email></address>
2867    </author>
2868    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2869      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2870      <address><email>timbl@w3.org</email></address>
2871    </author>
2872    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2873      <organization abbrev="W3C">World Wide Web Consortium</organization>
2874      <address><email>ylafon@w3.org</email></address>
2875    </author>
2876    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2877      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2878      <address><email>julian.reschke@greenbytes.de</email></address>
2879    </author>
2880    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2881  </front>
2882  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2883  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2884</reference>
2885
2886<reference anchor="Part5">
2887  <front>
2888    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2889    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2890      <organization abbrev="Day Software">Day Software</organization>
2891      <address><email>fielding@gbiv.com</email></address>
2892    </author>
2893    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2894      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2895      <address><email>jg@freedesktop.org</email></address>
2896    </author>
2897    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2898      <organization abbrev="HP">Hewlett-Packard Company</organization>
2899      <address><email>JeffMogul@acm.org</email></address>
2900    </author>
2901    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2902      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2903      <address><email>henrikn@microsoft.com</email></address>
2904    </author>
2905    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2906      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2907      <address><email>LMM@acm.org</email></address>
2908    </author>
2909    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2910      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2911      <address><email>paulle@microsoft.com</email></address>
2912    </author>
2913    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2914      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2915      <address><email>timbl@w3.org</email></address>
2916    </author>
2917    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2918      <organization abbrev="W3C">World Wide Web Consortium</organization>
2919      <address><email>ylafon@w3.org</email></address>
2920    </author>
2921    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2922      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2923      <address><email>julian.reschke@greenbytes.de</email></address>
2924    </author>
2925    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2926  </front>
2927  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2928  <x:source href="p5-range.xml" basename="p5-range"/>
2929</reference>
2930
2931<reference anchor="Part6">
2932  <front>
2933    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2934    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2935      <organization abbrev="Day Software">Day Software</organization>
2936      <address><email>fielding@gbiv.com</email></address>
2937    </author>
2938    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2939      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2940      <address><email>jg@freedesktop.org</email></address>
2941    </author>
2942    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2943      <organization abbrev="HP">Hewlett-Packard Company</organization>
2944      <address><email>JeffMogul@acm.org</email></address>
2945    </author>
2946    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2947      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2948      <address><email>henrikn@microsoft.com</email></address>
2949    </author>
2950    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2951      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2952      <address><email>LMM@acm.org</email></address>
2953    </author>
2954    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2955      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2956      <address><email>paulle@microsoft.com</email></address>
2957    </author>
2958    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2959      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2960      <address><email>timbl@w3.org</email></address>
2961    </author>
2962    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2963      <organization abbrev="W3C">World Wide Web Consortium</organization>
2964      <address><email>ylafon@w3.org</email></address>
2965    </author>
2966    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2967      <address><email>mnot@mnot.net</email></address>
2968    </author>
2969    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2970      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2971      <address><email>julian.reschke@greenbytes.de</email></address>
2972    </author>
2973    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2974  </front>
2975  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2976  <x:source href="p6-cache.xml" basename="p6-cache"/>
2977</reference>
2978
2979<reference anchor="Part7">
2980  <front>
2981    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2982    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2983      <organization abbrev="Day Software">Day Software</organization>
2984      <address><email>fielding@gbiv.com</email></address>
2985    </author>
2986    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2987      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2988      <address><email>jg@freedesktop.org</email></address>
2989    </author>
2990    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2991      <organization abbrev="HP">Hewlett-Packard Company</organization>
2992      <address><email>JeffMogul@acm.org</email></address>
2993    </author>
2994    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2995      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2996      <address><email>henrikn@microsoft.com</email></address>
2997    </author>
2998    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2999      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3000      <address><email>LMM@acm.org</email></address>
3001    </author>
3002    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3003      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3004      <address><email>paulle@microsoft.com</email></address>
3005    </author>
3006    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3007      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3008      <address><email>timbl@w3.org</email></address>
3009    </author>
3010    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3011      <organization abbrev="W3C">World Wide Web Consortium</organization>
3012      <address><email>ylafon@w3.org</email></address>
3013    </author>
3014    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3015      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3016      <address><email>julian.reschke@greenbytes.de</email></address>
3017    </author>
3018    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3019  </front>
3020  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3021  <x:source href="p7-auth.xml" basename="p7-auth"/>
3022</reference>
3023
3024<reference anchor="RFC2119">
3025  <front>
3026    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3027    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3028      <organization>Harvard University</organization>
3029      <address><email>sob@harvard.edu</email></address>
3030    </author>
3031    <date month="March" year="1997"/>
3032  </front>
3033  <seriesInfo name="BCP" value="14"/>
3034  <seriesInfo name="RFC" value="2119"/>
3035</reference>
3036
3037<reference anchor="RFC3986">
3038 <front>
3039  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3040  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3041    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3042    <address>
3043       <email>timbl@w3.org</email>
3044       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3045    </address>
3046  </author>
3047  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3048    <organization abbrev="Day Software">Day Software</organization>
3049    <address>
3050      <email>fielding@gbiv.com</email>
3051      <uri>http://roy.gbiv.com/</uri>
3052    </address>
3053  </author>
3054  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3055    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3056    <address>
3057      <email>LMM@acm.org</email>
3058      <uri>http://larry.masinter.net/</uri>
3059    </address>
3060  </author>
3061  <date month='January' year='2005'></date>
3062 </front>
3063 <seriesInfo name="RFC" value="3986"/>
3064 <seriesInfo name="STD" value="66"/>
3065</reference>
3066
3067<reference anchor="RFC5234">
3068  <front>
3069    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3070    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3071      <organization>Brandenburg InternetWorking</organization>
3072      <address>
3073        <email>dcrocker@bbiw.net</email>
3074      </address> 
3075    </author>
3076    <author initials="P." surname="Overell" fullname="Paul Overell">
3077      <organization>THUS plc.</organization>
3078      <address>
3079        <email>paul.overell@thus.net</email>
3080      </address>
3081    </author>
3082    <date month="January" year="2008"/>
3083  </front>
3084  <seriesInfo name="STD" value="68"/>
3085  <seriesInfo name="RFC" value="5234"/>
3086</reference>
3087
3088</references>
3089
3090<references title="Informative References">
3091
3092<reference anchor="RFC1945">
3093  <front>
3094    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3095    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3096      <organization>MIT, Laboratory for Computer Science</organization>
3097      <address><email>timbl@w3.org</email></address>
3098    </author>
3099    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3100      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3101      <address><email>fielding@ics.uci.edu</email></address>
3102    </author>
3103    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3104      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3105      <address><email>frystyk@w3.org</email></address>
3106    </author>
3107    <date month="May" year="1996"/>
3108  </front>
3109  <seriesInfo name="RFC" value="1945"/>
3110</reference>
3111
3112<reference anchor="RFC2068">
3113  <front>
3114    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3115    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3116      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3117      <address><email>fielding@ics.uci.edu</email></address>
3118    </author>
3119    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3120      <organization>MIT Laboratory for Computer Science</organization>
3121      <address><email>jg@w3.org</email></address>
3122    </author>
3123    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3124      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3125      <address><email>mogul@wrl.dec.com</email></address>
3126    </author>
3127    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3128      <organization>MIT Laboratory for Computer Science</organization>
3129      <address><email>frystyk@w3.org</email></address>
3130    </author>
3131    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3132      <organization>MIT Laboratory for Computer Science</organization>
3133      <address><email>timbl@w3.org</email></address>
3134    </author>
3135    <date month="January" year="1997"/>
3136  </front>
3137  <seriesInfo name="RFC" value="2068"/>
3138</reference>
3139
3140<reference anchor="RFC2616">
3141  <front>
3142    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3143    <author initials="R." surname="Fielding" fullname="R. Fielding">
3144      <organization>University of California, Irvine</organization>
3145      <address><email>fielding@ics.uci.edu</email></address>
3146    </author>
3147    <author initials="J." surname="Gettys" fullname="J. Gettys">
3148      <organization>W3C</organization>
3149      <address><email>jg@w3.org</email></address>
3150    </author>
3151    <author initials="J." surname="Mogul" fullname="J. Mogul">
3152      <organization>Compaq Computer Corporation</organization>
3153      <address><email>mogul@wrl.dec.com</email></address>
3154    </author>
3155    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3156      <organization>MIT Laboratory for Computer Science</organization>
3157      <address><email>frystyk@w3.org</email></address>
3158    </author>
3159    <author initials="L." surname="Masinter" fullname="L. Masinter">
3160      <organization>Xerox Corporation</organization>
3161      <address><email>masinter@parc.xerox.com</email></address>
3162    </author>
3163    <author initials="P." surname="Leach" fullname="P. Leach">
3164      <organization>Microsoft Corporation</organization>
3165      <address><email>paulle@microsoft.com</email></address>
3166    </author>
3167    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3168      <organization>W3C</organization>
3169      <address><email>timbl@w3.org</email></address>
3170    </author>
3171    <date month="June" year="1999"/>
3172  </front>
3173  <seriesInfo name="RFC" value="2616"/>
3174</reference>
3175
3176<reference anchor='RFC2817'>
3177  <front>
3178    <title>Upgrading to TLS Within HTTP/1.1</title>
3179    <author initials='R.' surname='Khare' fullname='R. Khare'>
3180      <organization>4K Associates / UC Irvine</organization>
3181      <address><email>rohit@4K-associates.com</email></address>
3182    </author>
3183    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3184      <organization>Agranat Systems, Inc.</organization>
3185      <address><email>lawrence@agranat.com</email></address>
3186    </author>
3187    <date year='2000' month='May' />
3188  </front>
3189  <seriesInfo name='RFC' value='2817' />
3190</reference>
3191
3192<reference anchor='RFC3864'>
3193  <front>
3194    <title>Registration Procedures for Message Header Fields</title>
3195    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3196      <organization>Nine by Nine</organization>
3197      <address><email>GK-IETF@ninebynine.org</email></address>
3198    </author>
3199    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3200      <organization>BEA Systems</organization>
3201      <address><email>mnot@pobox.com</email></address>
3202    </author>
3203    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3204      <organization>HP Labs</organization>
3205      <address><email>JeffMogul@acm.org</email></address>
3206    </author>
3207    <date year='2004' month='September' />
3208  </front>
3209  <seriesInfo name='BCP' value='90' />
3210  <seriesInfo name='RFC' value='3864' />
3211</reference>
3212
3213<reference anchor='RFC5226'>
3214  <front>
3215    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3216    <author initials='T.' surname='Narten' fullname='T. Narten'>
3217      <organization>IBM</organization>
3218      <address><email>narten@us.ibm.com</email></address>
3219    </author>
3220    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3221      <organization>Google</organization>
3222      <address><email>Harald@Alvestrand.no</email></address>
3223    </author>
3224    <date year='2008' month='May' />
3225  </front>
3226  <seriesInfo name='BCP' value='26' />
3227  <seriesInfo name='RFC' value='5226' />
3228</reference>
3229
3230<reference anchor="RFC5322">
3231  <front>
3232    <title>Internet Message Format</title>
3233    <author initials="P." surname="Resnick" fullname="P. Resnick">
3234      <organization>Qualcomm Incorporated</organization>
3235    </author>
3236    <date year="2008" month="October"/>
3237  </front> 
3238  <seriesInfo name="RFC" value="5322"/>
3239</reference>
3240
3241</references>
3242
3243<section title="Compatibility with Previous Versions" anchor="compatibility">
3244<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3245<t>
3246   Clarified which error code should be used for inbound server failures
3247   (e.g., DNS failures). (<xref target="status.504"/>).
3248</t>
3249<t>
3250   201 (Created) had a race that required an Etag be sent when a resource is
3251   first created. (<xref target="status.201"/>).
3252</t>
3253<t>
3254   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3255   failure to implement status code 302 properly.
3256   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
3257</t>
3258<t>
3259   Rewrite of message transmission requirements to make it much harder
3260   for implementors to get it wrong, as the consequences of errors here
3261   can have significant impact on the Internet, and to deal with the
3262   following problems:
3263  <list style="numbers">
3264      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3265         this was incorrectly placing a requirement on the behavior of
3266         an implementation of a future version of HTTP/1.x</t>
3267
3268      <t>Made it clear that user-agents should retry requests, not
3269         "clients" in general.</t>
3270
3271      <t>Converted requirements for clients to ignore unexpected 100
3272         (Continue) responses, and for proxies to forward 100 responses,
3273         into a general requirement for 1xx responses.</t>
3274
3275      <t>Modified some TCP-specific language, to make it clearer that
3276         non-TCP transports are possible for HTTP.</t>
3277
3278      <t>Require that the origin server &MUST-NOT; wait for the request
3279         body before it sends a required 100 (Continue) response.</t>
3280
3281      <t>Allow, rather than require, a server to omit 100 (Continue) if
3282         it has already seen some of the request body.</t>
3283
3284      <t>Allow servers to defend against denial-of-service attacks and
3285         broken clients.</t>
3286  </list>
3287</t>
3288<t>
3289   This change adds the Expect header and 417 status code.
3290</t>
3291<t>
3292   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3293   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3294</t>
3295<t>
3296   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
3297   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3298</t>
3299</section>
3300
3301<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3302<t>
3303  This document takes over the Status Code Registry, previously defined
3304  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3305  (<xref target="status.code.registry"/>)
3306</t>
3307<t>
3308  Clarify definition of POST.
3309  (<xref target="POST"/>)
3310</t>
3311<t>
3312  Failed to consider that there are
3313  many other request methods that are safe to automatically redirect,
3314  and further that the user agent is able to make that determination
3315  based on the request method semantics.
3316  (Sections <xref format="counter" target="status.301"/>,
3317  <xref format="counter" target="status.302"/> and
3318  <xref format="counter" target="status.307"/>)
3319</t>
3320<t>
3321  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3322  It used to indicate that the requested resource must be accessed through the
3323  proxy given by the Location field. The Location field gave the URI of the
3324  proxy. The recipient was expected to repeat this single request via the proxy.
3325  (<xref target="status.305"/>)
3326</t>
3327<t>
3328  Reclassify Allow header as response header, removing the option to
3329  specify it in a PUT request.
3330  Relax the server requirement on the contents of the Allow header and
3331  remove requirement on clients to always trust the header value.
3332  (<xref target="header.allow"/>)
3333</t>
3334<t>
3335  Correct syntax of Location header to allow URI references (including
3336  relative references and fragments), as referred symbol "absoluteURI" wasn't
3337  what was expected, and add some clarifications as to when use of fragments
3338  would not be appropriate.
3339  (<xref target="header.location"/>)
3340</t>
3341<t>
3342  Allow Referer value of "about:blank" as alternative to not specifying it.
3343  (<xref target="header.referer"/>)
3344</t>
3345<t>
3346  In the description of the Server header, the Via field
3347  was described as a SHOULD. The requirement was and is stated
3348  correctly in the description of the Via header in &header-via;.
3349  (<xref target="header.server"/>)
3350</t>
3351</section>
3352
3353</section>
3354
3355<?BEGININC p2-semantics.abnf-appendix ?>
3356<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3357<figure>
3358<artwork type="abnf" name="p2-semantics.parsed-abnf">
3359<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3360<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3361<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3362<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3363<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3364<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3365<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3366<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3367<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3368
3369<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3370<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3371<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3372
3373<x:ref>From</x:ref> = "From:" OWS From-v
3374<x:ref>From-v</x:ref> = mailbox
3375
3376<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3377<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3378
3379<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3380If-Modified-Since =
3381 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3382<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3383<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3384If-Unmodified-Since =
3385 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3386
3387<x:ref>Location</x:ref> = "Location:" OWS Location-v
3388<x:ref>Location-v</x:ref> = URI-reference
3389
3390<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3391<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3392<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3393 / %x47.45.54 ; GET
3394 / %x48.45.41.44 ; HEAD
3395 / %x50.4F.53.54 ; POST
3396 / %x50.55.54 ; PUT
3397 / %x44.45.4C.45.54.45 ; DELETE
3398 / %x54.52.41.43.45 ; TRACE
3399 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3400 / extension-method
3401
3402<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3403
3404Proxy-Authenticate =
3405 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3406Proxy-Authorization =
3407 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3408
3409<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3410<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3411<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3412<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3413<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3414<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3415<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3416
3417<x:ref>Server</x:ref> = "Server:" OWS Server-v
3418<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3419<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3420 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3421 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3422 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3423 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3424 "505" / extension-code
3425
3426<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3427
3428<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3429<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3430<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3431
3432<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3433
3434WWW-Authenticate =
3435 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3436
3437<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3438
3439<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3440
3441<x:ref>delta-seconds</x:ref> = 1*DIGIT
3442
3443<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3444<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3445<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3446 *expect-params ]
3447<x:ref>extension-code</x:ref> = 3DIGIT
3448<x:ref>extension-method</x:ref> = token
3449
3450<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3451
3452<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3453
3454<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3455<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3456
3457<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3458
3459<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3460 Accept-Language / Authorization / Expect / From / Host / If-Match /
3461 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3462 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3463 User-Agent
3464<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3465 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3466
3467<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3468</artwork>
3469</figure>
3470<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3471; Reason-Phrase defined but not used
3472; Status-Code defined but not used
3473; request-header defined but not used
3474; response-header defined but not used
3475</artwork></figure></section>
3476<?ENDINC p2-semantics.abnf-appendix ?>
3477
3478<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3479
3480<section title="Since RFC2616">
3481<t>
3482  Extracted relevant partitions from <xref target="RFC2616"/>.
3483</t>
3484</section>
3485
3486<section title="Since draft-ietf-httpbis-p2-semantics-00">
3487<t>
3488  Closed issues:
3489  <list style="symbols"> 
3490    <t>
3491      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3492      "Via is a MUST"
3493      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3494    </t>
3495    <t>
3496      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3497      "Fragments allowed in Location"
3498      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3499    </t>
3500    <t>
3501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3502      "Safe Methods vs Redirection"
3503      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3504    </t>
3505    <t>
3506      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3507      "Revise description of the POST method"
3508      (<eref target="http://purl.org/NET/http-errata#post"/>)
3509    </t>
3510    <t>
3511      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3512      "Normative and Informative references"
3513    </t>
3514    <t>
3515      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3516      "RFC2606 Compliance"
3517    </t>
3518    <t>
3519      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3520      "Informative references"
3521    </t>
3522    <t>
3523      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3524      "Redundant cross-references"
3525    </t>
3526  </list>
3527</t>
3528<t>
3529  Other changes:
3530  <list style="symbols"> 
3531    <t>
3532      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3533    </t>
3534  </list>
3535</t>
3536</section>
3537
3538<section title="Since draft-ietf-httpbis-p2-semantics-01">
3539<t>
3540  Closed issues:
3541  <list style="symbols"> 
3542    <t>
3543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3544      "PUT side effects"
3545    </t>
3546    <t>
3547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3548      "Duplicate Host header requirements"
3549    </t>
3550  </list>
3551</t>
3552<t>
3553  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3554  <list style="symbols"> 
3555    <t>
3556      Move "Product Tokens" section (back) into Part 1, as "token" is used
3557      in the definition of the Upgrade header.
3558    </t>
3559    <t>
3560      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3561    </t>
3562    <t>
3563      Copy definition of delta-seconds from Part6 instead of referencing it.
3564    </t>
3565  </list>
3566</t>
3567</section>
3568
3569<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3570<t>
3571  Closed issues:
3572  <list style="symbols"> 
3573    <t>
3574      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3575      "Requiring Allow in 405 responses"
3576    </t>
3577    <t>
3578      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3579      "Status Code Registry"
3580    </t>
3581    <t>
3582      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3583      "Redirection vs. Location"
3584    </t>
3585    <t>
3586      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3587      "Cacheability of 303 response"
3588    </t>
3589    <t>
3590      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3591      "305 Use Proxy"
3592    </t>
3593    <t>
3594      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3595      "Classification for Allow header"
3596    </t>
3597    <t>
3598      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3599      "PUT - 'store under' vs 'store at'"
3600    </t>
3601  </list>
3602</t>
3603<t>
3604  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3605  <list style="symbols"> 
3606    <t>
3607      Reference RFC 3984, and update header registrations for headers defined
3608      in this document.
3609    </t>
3610  </list>
3611</t>
3612<t>
3613  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3614  <list style="symbols"> 
3615    <t>
3616      Replace string literals when the string really is case-sensitive (method).
3617    </t>
3618  </list>
3619</t>
3620</section>
3621
3622<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3623<t>
3624  Closed issues:
3625  <list style="symbols"> 
3626    <t>
3627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3628      "OPTIONS request bodies"
3629    </t>
3630    <t>
3631      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3632      "Description of CONNECT should refer to RFC2817"
3633    </t>
3634    <t>
3635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3636      "Location Content-Location reference request/response mixup"
3637    </t>
3638  </list>
3639</t>
3640<t>
3641  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3642  <list style="symbols"> 
3643    <t>
3644      Added initial proposal for registration process, plus initial
3645      content (non-HTTP/1.1 methods to be added by a separate specification).
3646    </t>
3647  </list>
3648</t>
3649</section>
3650
3651<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3652<t>
3653  Closed issues:
3654  <list style="symbols"> 
3655    <t>
3656      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3657      "Content-*"
3658    </t>
3659    <t>
3660      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3661      "RFC 2822 is updated by RFC 5322"
3662    </t>
3663  </list>
3664</t>
3665<t>
3666  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3667  <list style="symbols"> 
3668    <t>
3669      Use "/" instead of "|" for alternatives.
3670    </t>
3671    <t>
3672      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3673      whitespace ("OWS") and required whitespace ("RWS").
3674    </t>
3675    <t>
3676      Rewrite ABNFs to spell out whitespace rules, factor out
3677      header value format definitions.
3678    </t>
3679  </list>
3680</t>
3681</section>
3682
3683<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3684<t>
3685  Closed issues:
3686  <list style="symbols"> 
3687    <t>
3688      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3689      "Reason-Phrase BNF"
3690    </t>
3691  </list>
3692</t>
3693<t>
3694  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3695  <list style="symbols"> 
3696    <t>
3697      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3698    </t>
3699  </list>
3700</t>
3701</section>
3702
3703<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3704<t>
3705  Closed issues:
3706  <list style="symbols"> 
3707    <t>
3708      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3709      "Clarify when Referer is sent"
3710    </t>
3711    <t>
3712      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3713      "status codes vs methods"
3714    </t>
3715    <t>
3716      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3717      "Do not require "updates" relation for specs that register status codes or method names"
3718    </t>
3719  </list>
3720</t>
3721</section>
3722
3723<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3724<t>
3725  Closed issues:
3726  <list style="symbols"> 
3727    <t>
3728      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3729      "Idempotency"
3730    </t>
3731    <t>
3732      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3733      "TRACE security considerations"
3734    </t>
3735    <t>
3736      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3737      "Clarify rules for determining what entities a response carries"
3738    </t>
3739    <t>
3740      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3741      "update note citing RFC 1945 and 2068"
3742    </t>
3743    <t>
3744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3745      "update note about redirect limit"
3746    </t>
3747    <t>
3748      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3749      "Location header ABNF should use 'URI'"
3750    </t>
3751    <t>
3752      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3753      "fragments in Location vs status 303"
3754    </t>
3755    <t>
3756      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3757      "move IANA registrations for optional status codes"
3758    </t>
3759  </list>
3760</t>
3761<t>
3762  Partly resolved issues:
3763  <list style="symbols"> 
3764    <t>
3765      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3766      "Are OPTIONS and TRACE safe?"
3767    </t>
3768  </list>
3769</t>
3770</section>
3771
3772<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3773<t>
3774  Closed issues:
3775  <list style="symbols"> 
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3778      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3779      status codes when fixing this previously)
3780    </t>
3781  </list>
3782</t>
3783</section>
3784
3785<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3786<t>
3787  Closed issues:
3788  <list style="symbols"> 
3789    <t>
3790      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3791      "Fragment combination / precedence during redirects"
3792    </t>
3793  </list>
3794</t>
3795<t>
3796  Partly resolved issues:
3797  <list style="symbols"> 
3798    <t>
3799      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3800      "Location header payload handling"
3801    </t>
3802    <t>
3803      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3804      "Term for the requested resource's URI"
3805    </t>
3806  </list>
3807</t>
3808</section>
3809
3810<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3811<t>
3812  Closed issues:
3813  <list style="symbols"> 
3814    <t>
3815      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3816      "Clarify 'Requested Variant'"
3817    </t>
3818    <t>
3819      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3820      "Clarify entity / representation / variant terminology"
3821    </t>
3822  </list>
3823</t>
3824</section>
3825
3826</section>
3827
3828</back>
3829</rfc>
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