source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1062

Last change on this file since 1062 was 1062, checked in by julian.reschke@…, 9 years ago

add internal link for authority (see change [1061])

  • Property svn:eol-style set to native
File size: 167.8 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 "October">
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 combining-responses        "<xref target='Part6' x:rel='#combining.responses' 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  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78]>
79<?rfc toc="yes" ?>
80<?rfc symrefs="yes" ?>
81<?rfc sortrefs="yes" ?>
82<?rfc compact="yes"?>
83<?rfc subcompact="no" ?>
84<?rfc linkmailto="no" ?>
85<?rfc editing="no" ?>
86<?rfc comments="yes"?>
87<?rfc inline="yes"?>
88<?rfc rfcedstyle="yes"?>
89<?rfc-ext allow-markup-in-artwork="yes" ?>
90<?rfc-ext include-references-in-index="yes" ?>
91<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
92     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
93     xmlns:x='http://purl.org/net/xml2rfc/ext'
94     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
95<front>
96
97  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
98
99  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
100    <organization abbrev="Day Software">Day Software</organization>
101    <address>
102      <postal>
103        <street>23 Corporate Plaza DR, Suite 280</street>
104        <city>Newport Beach</city>
105        <region>CA</region>
106        <code>92660</code>
107        <country>USA</country>
108      </postal>
109      <phone>+1-949-706-5300</phone>
110      <facsimile>+1-949-706-5305</facsimile>
111      <email>fielding@gbiv.com</email>
112      <uri>http://roy.gbiv.com/</uri>
113    </address>
114  </author>
115
116  <author initials="J." surname="Gettys" fullname="Jim Gettys">
117    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
118    <address>
119      <postal>
120        <street>21 Oak Knoll Road</street>
121        <city>Carlisle</city>
122        <region>MA</region>
123        <code>01741</code>
124        <country>USA</country>
125      </postal>
126      <email>jg@freedesktop.org</email>
127      <uri>http://gettys.wordpress.com/</uri>
128    </address>
129  </author>
130 
131  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
132    <organization abbrev="HP">Hewlett-Packard Company</organization>
133    <address>
134      <postal>
135        <street>HP Labs, Large Scale Systems Group</street>
136        <street>1501 Page Mill Road, MS 1177</street>
137        <city>Palo Alto</city>
138        <region>CA</region>
139        <code>94304</code>
140        <country>USA</country>
141      </postal>
142      <email>JeffMogul@acm.org</email>
143    </address>
144  </author>
145
146  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
147    <organization abbrev="Microsoft">Microsoft Corporation</organization>
148    <address>
149      <postal>
150        <street>1 Microsoft Way</street>
151        <city>Redmond</city>
152        <region>WA</region>
153        <code>98052</code>
154        <country>USA</country>
155      </postal>
156      <email>henrikn@microsoft.com</email>
157    </address>
158  </author>
159
160  <author initials="L." surname="Masinter" fullname="Larry Masinter">
161    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
162    <address>
163      <postal>
164        <street>345 Park Ave</street>
165        <city>San Jose</city>
166        <region>CA</region>
167        <code>95110</code>
168        <country>USA</country>
169      </postal>
170      <email>LMM@acm.org</email>
171      <uri>http://larry.masinter.net/</uri>
172    </address>
173  </author>
174 
175  <author initials="P." surname="Leach" fullname="Paul J. Leach">
176    <organization abbrev="Microsoft">Microsoft Corporation</organization>
177    <address>
178      <postal>
179        <street>1 Microsoft Way</street>
180        <city>Redmond</city>
181        <region>WA</region>
182        <code>98052</code>
183      </postal>
184      <email>paulle@microsoft.com</email>
185    </address>
186  </author>
187   
188  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
189    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
190    <address>
191      <postal>
192        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
193        <street>The Stata Center, Building 32</street>
194        <street>32 Vassar Street</street>
195        <city>Cambridge</city>
196        <region>MA</region>
197        <code>02139</code>
198        <country>USA</country>
199      </postal>
200      <email>timbl@w3.org</email>
201      <uri>http://www.w3.org/People/Berners-Lee/</uri>
202    </address>
203  </author>
204
205  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
206    <organization abbrev="W3C">World Wide Web Consortium</organization>
207    <address>
208      <postal>
209        <street>W3C / ERCIM</street>
210        <street>2004, rte des Lucioles</street>
211        <city>Sophia-Antipolis</city>
212        <region>AM</region>
213        <code>06902</code>
214        <country>France</country>
215      </postal>
216      <email>ylafon@w3.org</email>
217      <uri>http://www.raubacapeu.net/people/yves/</uri>
218    </address>
219  </author>
220
221  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
222    <organization abbrev="greenbytes">greenbytes GmbH</organization>
223    <address>
224      <postal>
225        <street>Hafenweg 16</street>
226        <city>Muenster</city><region>NW</region><code>48155</code>
227        <country>Germany</country>
228      </postal>
229      <phone>+49 251 2807760</phone>
230      <facsimile>+49 251 2807761</facsimile>
231      <email>julian.reschke@greenbytes.de</email>
232      <uri>http://greenbytes.de/tech/webdav/</uri>
233    </address>
234  </author>
235
236  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
237  <workgroup>HTTPbis Working Group</workgroup>
238
239<abstract>
240<t>
241   The Hypertext Transfer Protocol (HTTP) is an application-level
242   protocol for distributed, collaborative, hypermedia information
243   systems. HTTP has been in use by the World Wide Web global information
244   initiative since 1990. This document is Part 2 of the seven-part specification
245   that defines the protocol referred to as "HTTP/1.1" and, taken together,
246   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
247   as expressed by request methods, request-header fields, response status codes,
248   and response-header fields.
249</t>
250</abstract>
251
252<note title="Editorial Note (To be removed by RFC Editor)">
253  <t>
254    Discussion of this draft should take place on the HTTPBIS working group
255    mailing list (ietf-http-wg@w3.org). The current issues list is
256    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
257    and related documents (including fancy diffs) can be found at
258    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
259  </t>
260  <t>
261    The changes in this draft are summarized in <xref target="changes.since.12"/>.
262  </t>
263</note>
264</front>
265<middle>
266<section title="Introduction" anchor="introduction">
267<t>
268   This document defines HTTP/1.1 request and response semantics.  Each HTTP
269   message, as defined in &messaging;, is in the form of either a request or
270   a response.  An HTTP server listens on a connection for HTTP requests and
271   responds to each request, in the order received on that connection, with
272   one or more HTTP response messages.  This document defines the commonly
273   agreed upon semantics of the HTTP uniform interface, the intentions defined
274   by each request method, and the various response messages that might be
275   expected as a result of applying that method to the target resource.
276</t>
277<t>
278   This document is currently disorganized in order to minimize the changes
279   between drafts and enable reviewers to see the smaller errata changes.
280   A future draft will reorganize the sections to better reflect the content.
281   In particular, the sections will be ordered according to the typical
282   processing of an HTTP request message (after message parsing): resource
283   mapping, general header fields, methods, request modifiers, response
284   status, and resource metadata.  The current mess reflects how widely
285   dispersed these topics and associated requirements had become in
286   <xref target="RFC2616"/>.
287</t>
288
289<section title="Requirements" anchor="intro.requirements">
290<t>
291   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
292   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
293   document are to be interpreted as described in <xref target="RFC2119"/>.
294</t>
295<t>
296   An implementation is not compliant if it fails to satisfy one or more
297   of the "MUST" or "REQUIRED" level requirements for the protocols it
298   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
299   level and all the "SHOULD" level requirements for its protocols is said
300   to be "unconditionally compliant"; one that satisfies all the "MUST"
301   level requirements but not all the "SHOULD" level requirements for its
302   protocols is said to be "conditionally compliant".
303</t>
304</section>
305
306<section title="Syntax Notation" anchor="notation">
307  <x:anchor-alias value="CR"/>
308  <x:anchor-alias value="DIGIT"/>
309  <x:anchor-alias value="LF"/>
310  <x:anchor-alias value="VCHAR"/>
311  <x:anchor-alias value="WSP"/>
312<t>
313  This specification uses the ABNF syntax defined in &notation; (which
314  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
315  <xref target="collected.abnf"/> shows the collected ABNF, with the list
316  rule expanded.
317</t>
318<t>
319  The following core rules are included by
320  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
321  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
322  DIGIT (decimal 0-9), DQUOTE (double quote),
323  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
324  OCTET (any 8-bit sequence of data), SP (space),
325  VCHAR (any visible USASCII character),
326  and WSP (whitespace).
327</t>
328
329<section title="Core Rules" anchor="core.rules">
330  <x:anchor-alias value="obs-text"/>
331  <x:anchor-alias value="quoted-string"/>
332  <x:anchor-alias value="token"/>
333  <x:anchor-alias value="OWS"/>
334  <x:anchor-alias value="RWS"/>
335<t>
336  The core rules below are defined in &basic-rules;:
337</t>
338<figure><artwork type="abnf2616">
339  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
340  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
341  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
342  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
343  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
344</artwork></figure>
345</section>
346
347<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
348  <x:anchor-alias value="absolute-URI"/>
349  <x:anchor-alias value="authority"/>
350  <x:anchor-alias value="Accept"/>
351  <x:anchor-alias value="Accept-Charset"/>
352  <x:anchor-alias value="Accept-Encoding"/>
353  <x:anchor-alias value="Accept-Language"/>
354  <x:anchor-alias value="Accept-Ranges"/>
355  <x:anchor-alias value="Age"/>
356  <x:anchor-alias value="Authorization"/>
357  <x:anchor-alias value="comment"/>
358  <x:anchor-alias value="ETag"/>
359  <x:anchor-alias value="Host"/>
360  <x:anchor-alias value="HTTP-date"/>
361  <x:anchor-alias value="If-Match"/>
362  <x:anchor-alias value="If-Modified-Since"/>
363  <x:anchor-alias value="If-None-Match"/>
364  <x:anchor-alias value="If-Range"/>
365  <x:anchor-alias value="If-Unmodified-Since"/>
366  <x:anchor-alias value="partial-URI"/>
367  <x:anchor-alias value="product"/>
368  <x:anchor-alias value="Proxy-Authenticate"/>
369  <x:anchor-alias value="Proxy-Authorization"/>
370  <x:anchor-alias value="Range"/>
371  <x:anchor-alias value="TE"/>
372  <x:anchor-alias value="URI-reference"/>
373  <x:anchor-alias value="Vary"/>
374  <x:anchor-alias value="WWW-Authenticate"/>
375<t>
376  The ABNF rules below are defined in other parts:
377</t>
378<figure><!--Part1--><artwork type="abnf2616">
379  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
380  <x:ref>authority</x:ref>     = &lt;authority, defined in &uri;&gt;
381  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
382  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
383  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
384  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
385  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
386  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
387  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
388</artwork></figure>
389<figure><!--Part3--><artwork type="abnf2616">
390  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
391  <x:ref>Accept-Charset</x:ref> =
392             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
393  <x:ref>Accept-Encoding</x:ref> =
394             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
395  <x:ref>Accept-Language</x:ref> =
396             &lt;Accept-Language, defined in &header-accept-language;&gt;
397</artwork></figure>
398<figure><!--Part4--><artwork type="abnf2616">
399  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
400  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
401  <x:ref>If-Modified-Since</x:ref> =
402             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
403  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
404  <x:ref>If-Unmodified-Since</x:ref> =
405             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
406</artwork></figure>
407<figure><!--Part5--><artwork type="abnf2616">
408  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
409  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
410  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
411</artwork></figure>
412<figure><!--Part6--><artwork type="abnf2616">
413  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
414  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
415</artwork><!--Part7--></figure>
416<figure><artwork type="abnf2616">
417  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
418  <x:ref>Proxy-Authenticate</x:ref> =
419             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
420  <x:ref>Proxy-Authorization</x:ref> =
421             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
422  <x:ref>WWW-Authenticate</x:ref> =
423             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
424</artwork></figure>
425</section>
426</section>
427</section>
428
429<section title="Method" anchor="method">
430  <x:anchor-alias value="Method"/>
431  <x:anchor-alias value="extension-method"/>
432<t>
433   The Method token indicates the method to be performed on the target
434   resource (&effective-request-uri;). The method is case-sensitive.
435</t>
436<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
437  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
438                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
439                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
440                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
441                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
442                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
443                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
444                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
445                 / <x:ref>extension-method</x:ref>
446  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
447</artwork></figure>
448<t>
449   The list of methods allowed by a resource can be specified in an
450   Allow header field (<xref target="header.allow"/>). The status code of the response
451   always notifies the client whether a method is currently allowed on a
452   resource, since the set of allowed methods can change dynamically. An
453   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
454   if the method is known by the origin server but not allowed for the
455   resource, and 501 (Not Implemented) if the method is
456   unrecognized or not implemented by the origin server. The methods GET
457   and HEAD &MUST; be supported by all general-purpose servers. All other
458   methods are &OPTIONAL;; however, if the above methods are implemented,
459   they &MUST; be implemented with the same semantics as those specified
460   in <xref target="method.definitions"/>.
461</t>
462
463<section title="Method Registry" anchor="method.registry">
464<t>
465  The HTTP Method Registry defines the name space for the Method token in the
466  Request line of an HTTP request.
467</t>
468<t>
469  Registrations &MUST; include the following fields:
470  <list style="symbols">
471    <t>Method Name (see <xref target="method"/>)</t>
472    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
473    <t>Pointer to specification text</t>
474  </list>
475</t>
476<t>
477  Values to be added to this name space are subject to IETF review
478  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
479</t>
480<t>
481  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
482</t>
483
484<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
485<t>
486   When it is necessary to express new semantics for a HTTP request that
487   aren't specific to a single application or media type, and currently defined
488   methods are inadequate, it may be appropriate to register a new method.
489</t>
490<t>
491   HTTP methods are generic; that is, they are potentially applicable to any
492   resource, not just one particular media type, "type" of resource, or
493   application. As such, it is preferred that new HTTP methods be registered
494   in a document that isn't specific to a single application, so that this is
495   clear.
496</t>
497<t>
498   Due to the parsing rules defined in &message-body;, definitions of HTTP
499   methods cannot prohibit the presence of a message-body on either the request
500   or the response message (with responses to HEAD requests being the single
501   exception). Definitions of new methods cannot change this rule, but they can
502   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
503</t>
504<t>
505   New method definitions need to indicate whether they are safe (<xref
506   target="safe.methods"/>) and whether they are idempotent (<xref
507   target="idempotent.methods"/>). They also need to state whether they can be
508   cached (&caching;); in particular what conditions a cache may store the
509   response, and under what conditions such a stored response may be used to
510   satisfy a subsequent request.
511</t>
512</section>
513
514</section>
515</section>
516
517<section title="Request Header Fields" anchor="request.header.fields">
518  <x:anchor-alias value="request-header"/>
519<t>
520   The request-header fields allow the client to pass additional
521   information about the request, and about the client itself, to the
522   server. These fields act as request modifiers, with semantics
523   equivalent to the parameters on a programming language method
524   invocation.
525</t>
526<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
527  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
528                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
529                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
530                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
531                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
532                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
533                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
534                 / <x:ref>Host</x:ref>                     ; &header-host;
535                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
536                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
537                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
538                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
539                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
540                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
541                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
542                 / <x:ref>Range</x:ref>                    ; &header-range;
543                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
544                 / <x:ref>TE</x:ref>                       ; &header-te;
545                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
546</artwork></figure>
547<t>
548   Request-header field names can be extended reliably only in
549   combination with a change in the protocol version. However, new or
550   experimental header fields &MAY; be given the semantics of request-header
551   fields if all parties in the communication recognize them to
552   be request-header fields.
553</t>
554</section>
555
556<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
557  <x:anchor-alias value="Reason-Phrase"/>
558  <x:anchor-alias value="Status-Code"/>
559  <x:anchor-alias value="extension-code"/>
560<t>
561   The Status-Code element is a 3-digit integer result code of the
562   attempt to understand and satisfy the request. The status codes listed
563   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
564   &p5-status-codes;, and &p7-status-codes;.
565</t>
566<t>
567   The Reason-Phrase is intended to give a short
568   textual description of the Status-Code. The Status-Code is intended
569   for use by automata and the Reason-Phrase is intended for the human
570   user. The client is not required to examine or display the Reason-Phrase.
571</t>
572<t> 
573   The individual values of the numeric status codes defined for
574   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
575   presented below. The reason phrases listed here are only
576   recommendations -- they &MAY; be replaced by local equivalents without
577   affecting the protocol.
578</t>
579<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"/>
580  <x:ref>Status-Code</x:ref> =
581       "100"  ; <xref target="status.100"/>: Continue
582     / "101"  ; <xref target="status.101"/>: Switching Protocols
583     / "200"  ; <xref target="status.200"/>: OK
584     / "201"  ; <xref target="status.201"/>: Created
585     / "202"  ; <xref target="status.202"/>: Accepted
586     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
587     / "204"  ; <xref target="status.204"/>: No Content
588     / "205"  ; <xref target="status.205"/>: Reset Content
589     / "206"  ; &status-206;: Partial Content
590     / "300"  ; <xref target="status.300"/>: Multiple Choices
591     / "301"  ; <xref target="status.301"/>: Moved Permanently
592     / "302"  ; <xref target="status.302"/>: Found
593     / "303"  ; <xref target="status.303"/>: See Other
594     / "304"  ; &status-304;: Not Modified
595     / "305"  ; <xref target="status.305"/>: Use Proxy
596     / "307"  ; <xref target="status.307"/>: Temporary Redirect
597     / "400"  ; <xref target="status.400"/>: Bad Request
598     / "401"  ; &status-401;: Unauthorized
599     / "402"  ; <xref target="status.402"/>: Payment Required
600     / "403"  ; <xref target="status.403"/>: Forbidden
601     / "404"  ; <xref target="status.404"/>: Not Found
602     / "405"  ; <xref target="status.405"/>: Method Not Allowed
603     / "406"  ; <xref target="status.406"/>: Not Acceptable
604     / "407"  ; &status-407;: Proxy Authentication Required
605     / "408"  ; <xref target="status.408"/>: Request Time-out
606     / "409"  ; <xref target="status.409"/>: Conflict
607     / "410"  ; <xref target="status.410"/>: Gone
608     / "411"  ; <xref target="status.411"/>: Length Required
609     / "412"  ; &status-412;: Precondition Failed
610     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
611     / "414"  ; <xref target="status.414"/>: URI Too Long
612     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
613     / "416"  ; &status-416;: Requested range not satisfiable
614     / "417"  ; <xref target="status.417"/>: Expectation Failed
615     / "500"  ; <xref target="status.500"/>: Internal Server Error
616     / "501"  ; <xref target="status.501"/>: Not Implemented
617     / "502"  ; <xref target="status.502"/>: Bad Gateway
618     / "503"  ; <xref target="status.503"/>: Service Unavailable
619     / "504"  ; <xref target="status.504"/>: Gateway Time-out
620     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
621     / <x:ref>extension-code</x:ref>
622
623  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
624  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
625</artwork></figure>
626<t>
627   HTTP status codes are extensible. HTTP applications are not required
628   to understand the meaning of all registered status codes, though such
629   understanding is obviously desirable. However, applications &MUST;
630   understand the class of any status code, as indicated by the first
631   digit, and treat any unrecognized response as being equivalent to the
632   x00 status code of that class, with the exception that an
633   unrecognized response &MUST-NOT; be cached. For example, if an
634   unrecognized status code of 431 is received by the client, it can
635   safely assume that there was something wrong with its request and
636   treat the response as if it had received a 400 status code. In such
637   cases, user agents &SHOULD; present to the user the representation enclosed
638   with the response, since that representation is likely to include human-readable
639   information which will explain the unusual status.
640</t>
641
642<section title="Status Code Registry" anchor="status.code.registry">
643<t>
644  The HTTP Status Code Registry defines the name space for the Status-Code
645  token in the Status-Line of an HTTP response.
646</t>
647<t>
648  Values to be added to this name space are subject to IETF review
649  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
650</t>
651<t>
652  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
653</t>
654
655<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
656<t>
657   When it is necessary to express new semantics for a HTTP response that
658   aren't specific to a single application or media type, and currently defined
659   status codes are inadequate, a new status code can be registered.
660</t>
661<t>
662   HTTP status codes are generic; that is, they are potentially applicable to
663   any resource, not just one particular media type, "type" of resource, or
664   application. As such, it is preferred that new HTTP status codes be
665   registered in a document that isn't specific to a single application, so
666   that this is clear.
667</t>
668<t>
669   Definitions of new HTTP status codes typically explain the request
670   conditions that produce a response containing the status code (e.g.,
671   combinations of request headers and/or method(s)), along with any
672   interactions with response headers (e.g., those that are required, those
673   that modify the semantics of the response).
674</t>
675<t>
676   New HTTP status codes are required to fall under one of the categories
677   defined in <xref target="status.codes"/>. To allow existing parsers to
678   properly handle them, new status codes cannot disallow a response body,
679   although they can mandate a zero-length response body. They can require the
680   presence of one or more particular HTTP response header(s).
681</t>
682<t>
683   Likewise, their definitions can specify that caches are allowed to use
684   heuristics to determine their freshness (see &caching;; by default, it is
685   not allowed), and can define how to determine the resource which they
686   carry a representation for (see <xref
687   target="identifying.response.associated.with.representation"/>; by default,
688   it is anonymous).
689</t>
690</section>
691
692</section>
693
694</section>
695
696<section title="Response Header Fields" anchor="response.header.fields">
697  <x:anchor-alias value="response-header"/>
698<t>
699   The response-header fields allow the server to pass additional
700   information about the response which cannot be placed in the Status-Line.
701   These header fields give information about the server and about
702   further access to the target resource (&effective-request-uri;).
703</t>
704<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
705  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
706                  / <x:ref>Age</x:ref>                     ; &header-age;
707                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
708                  / <x:ref>ETag</x:ref>                    ; &header-etag;
709                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
710                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
711                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
712                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
713                  / <x:ref>Vary</x:ref>                    ; &header-vary;
714                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
715</artwork></figure>
716<t>
717   Response-header field names can be extended reliably only in
718   combination with a change in the protocol version. However, new or
719   experimental header fields &MAY; be given the semantics of response-header
720   fields if all parties in the communication recognize them to
721   be response-header fields.
722</t>
723</section>
724
725<section title="Representation" anchor="representation">
726<t>
727   Request and Response messages &MAY; transfer a representation if not otherwise
728   restricted by the request method or response status code. A representation
729   consists of metadata (representation header fields) and data (representation
730   body).  When a complete or partial representation is enclosed in an HTTP message,
731   it is referred to as the payload of the message. HTTP representations
732   are defined in &payload;.
733</t>
734<t>
735   A representation body is only present in a message when a message-body is
736   present, as described in &message-body;. The representation body is obtained
737   from the message-body by decoding any Transfer-Encoding that might
738   have been applied to ensure safe and proper transfer of the message.
739</t>
740
741<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
742<t>
743   It is sometimes necessary to determine an identifier for the resource
744   associated with a representation.
745</t>
746<t>
747   An HTTP request representation, when present, is always associated with an
748   anonymous (i.e., unidentified) resource.
749</t>
750<t>
751   In the common case, an HTTP response is a representation of the target
752   resource (see &effective-request-uri;). However, this is not always the
753   case. To determine the URI of the resource a response is associated with,
754   the following rules are used (with the first applicable one being selected):
755</t>
756<t><list style="numbers">
757   <t>If the response status code is 200 or 203 and the request method was GET,
758   the response payload is a representation of the target resource.</t>
759   <t>If the response status code is 204, 206, or 304 and the request method was GET
760   or HEAD, the response payload is a partial representation of the target
761   (see &combining-responses;).</t>
762   <t>If the response has a Content-Location header field, and that URI is the same
763   as the effective request URI, the response payload is a representation of the
764   target resource.</t>
765   <t>If the response has a Content-Location header field, and that URI is not the
766   same as the effective request URI, then the response asserts that its
767   payload is a representation of the resource identified by the
768   Content-Location URI. However, such an assertion cannot be trusted unless
769   it can be verified by other means (not defined by HTTP).</t>
770   <t>Otherwise, the response is a representation of an anonymous (i.e.,
771   unidentified) resource.</t>
772</list></t>
773<t>
774  <cref anchor="TODO-req-uri">
775   The comparison function is going to have to be defined somewhere,
776   because we already need to compare URIs for things like cache invalidation.</cref>
777</t>
778</section>
779
780</section>
781
782
783<section title="Method Definitions" anchor="method.definitions">
784<t>
785   The set of common methods for HTTP/1.1 is defined below. Although
786   this set can be expanded, additional methods cannot be assumed to
787   share the same semantics for separately extended clients and servers.
788</t>
789
790<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
791
792<section title="Safe Methods" anchor="safe.methods">
793<iref item="Safe Methods" primary="true"/>
794<t>
795   Implementors need to be aware that the software represents the user in
796   their interactions over the Internet, and need to allow
797   the user to be aware of any actions they take which might have an
798   unexpected significance to themselves or others.
799</t>
800<t>
801   In particular, the convention has been established that the GET, HEAD,
802   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
803   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
804   This allows user agents to represent other methods, such as POST, PUT
805   and DELETE, in a special way, so that the user is made aware of the
806   fact that a possibly unsafe action is being requested.
807</t>
808<t>
809   Naturally, it is not possible to ensure that the server does not
810   generate side-effects as a result of performing a GET request; in
811   fact, some dynamic resources consider that a feature. The important
812   distinction here is that the user did not request the side-effects,
813   so therefore cannot be held accountable for them.
814</t>
815</section>
816
817<section title="Idempotent Methods" anchor="idempotent.methods">
818<iref item="Idempotent Methods" primary="true"/>
819<t>
820   Methods can also have the property of "idempotence" in that, aside
821   from error or expiration issues, the intended effect of multiple
822   identical requests is the same as for a single request.
823   The methods PUT, DELETE, and all safe methods are idempotent.
824   It is important to note that idempotence refers only to changes
825   requested by the client: a server is free to change its state due
826   to multiple requests for the purpose of tracking those requests,
827   versioning of results, etc.
828</t>
829</section>
830</section>
831
832<section title="OPTIONS" anchor="OPTIONS">
833  <rdf:Description>
834    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
835  </rdf:Description>
836  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
837  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
838<t>
839   The OPTIONS method represents a request for information about the
840   communication options available on the request/response chain
841   identified by the effective request URI. This method allows the client to
842   determine the options and/or requirements associated with a resource,
843   or the capabilities of a server, without implying a resource action
844   or initiating a resource retrieval.
845</t>
846<t>
847   Responses to this method are not cacheable.
848</t>
849<t>
850   If the OPTIONS request includes a message-body (as indicated by the
851   presence of Content-Length or Transfer-Encoding), then the media type
852   &MUST; be indicated by a Content-Type field. Although this
853   specification does not define any use for such a body, future
854   extensions to HTTP might use the OPTIONS body to make more detailed
855   queries on the server.
856</t>
857<t>
858   If the request-target is an asterisk ("*"), the OPTIONS request is
859   intended to apply to the server in general rather than to a specific
860   resource. Since a server's communication options typically depend on
861   the resource, the "*" request is only useful as a "ping" or "no-op"
862   type of method; it does nothing beyond allowing the client to test
863   the capabilities of the server. For example, this can be used to test
864   a proxy for HTTP/1.1 compliance (or lack thereof).
865</t>
866<t>
867   If the request-target is not an asterisk, the OPTIONS request applies
868   only to the options that are available when communicating with that
869   resource.
870</t>
871<t>
872   A 200 response &SHOULD; include any header fields that indicate
873   optional features implemented by the server and applicable to that
874   resource (e.g., Allow), possibly including extensions not defined by
875   this specification. The response body, if any, &SHOULD; also include
876   information about the communication options. The format for such a
877   body is not defined by this specification, but might be defined by
878   future extensions to HTTP. Content negotiation &MAY; be used to select
879   the appropriate response format. If no response body is included, the
880   response &MUST; include a Content-Length field with a field-value of
881   "0".
882</t>
883<t>
884   The Max-Forwards request-header field &MAY; be used to target a
885   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
886   If no Max-Forwards field is present in the request, then the forwarded
887   request &MUST-NOT; include a Max-Forwards field.
888</t>
889</section>
890
891<section title="GET" anchor="GET">
892  <rdf:Description>
893    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
894  </rdf:Description>
895  <iref primary="true" item="GET method" x:for-anchor=""/>
896  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
897<t>
898   The GET method means retrieve whatever information (in the form of a
899   representation) currently corresponds to the target resource.
900</t>
901<t>   
902   If the target resource is a data-producing process, it is the
903   produced data which shall be returned as the representation in the response and not
904   the source text of the process, unless that text happens to be the output of
905   the process.
906</t>
907<t>
908   The semantics of the GET method change to a "conditional GET" if the
909   request message includes an If-Modified-Since, If-Unmodified-Since,
910   If-Match, If-None-Match, or If-Range header field. A conditional GET
911   method requests that the representation be transferred only under the
912   circumstances described by the conditional header field(s). The
913   conditional GET method is intended to reduce unnecessary network
914   usage by allowing cached representations to be refreshed without requiring
915   multiple requests or transferring data already held by the client.
916</t>
917<t>
918   The semantics of the GET method change to a "partial GET" if the
919   request message includes a Range header field. A partial GET requests
920   that only part of the representation be transferred, as described in &header-range;.
921   The partial GET method is intended to reduce unnecessary
922   network usage by allowing partially-retrieved representations to be
923   completed without transferring data already held by the client.
924</t>
925<t>
926   The response to a GET request is cacheable and &MAY; be used to satisfy
927   subsequent GET and HEAD requests (see &caching;).
928</t>
929<t>
930   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
931</t>
932</section>
933
934<section title="HEAD" anchor="HEAD">
935  <rdf:Description>
936    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
937  </rdf:Description>
938  <iref primary="true" item="HEAD method" x:for-anchor=""/>
939  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
940<t>
941   The HEAD method is identical to GET except that the server &MUST-NOT;
942   return a message-body in the response. The metadata contained
943   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
944   to the information sent in response to a GET request. This method can
945   be used for obtaining metadata about the representation implied by the
946   request without transferring the representation body. This method is
947   often used for testing hypertext links for validity, accessibility,
948   and recent modification.
949</t>
950<t>
951   The response to a HEAD request is cacheable and &MAY; be used to satisfy
952   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
953   representation from that resource; if the new field values
954   indicate that the cached representation differs from the current representation (as
955   would be indicated by a change in Content-Length, Content-MD5, ETag
956   or Last-Modified), then the cache &MUST; treat the cache entry as
957   stale.
958</t>
959</section>
960
961<section title="POST" anchor="POST">
962  <iref primary="true" item="POST method" x:for-anchor=""/>
963  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
964<t>
965   The POST method is used to request that the origin server accept the
966   representation enclosed in the request as data to be processed by the
967   target resource. POST is designed to allow a uniform method to cover the
968   following functions:
969  <list style="symbols">
970    <t>
971      Annotation of existing resources;
972    </t>
973    <t>
974        Posting a message to a bulletin board, newsgroup, mailing list,
975        or similar group of articles;
976    </t>
977    <t>
978        Providing a block of data, such as the result of submitting a
979        form, to a data-handling process;
980    </t>
981    <t>
982        Extending a database through an append operation.
983    </t>
984  </list>
985</t>
986<t>
987   The actual function performed by the POST method is determined by the
988   server and is usually dependent on the effective request URI.
989</t>
990<t>
991   The action performed by the POST method might not result in a
992   resource that can be identified by a URI. In this case, either 200
993   (OK) or 204 (No Content) is the appropriate response status code,
994   depending on whether or not the response includes a representation that
995   describes the result.
996</t>
997<t>
998   If a resource has been created on the origin server, the response
999   &SHOULD; be 201 (Created) and contain a representation which describes the
1000   status of the request and refers to the new resource, and a Location
1001   header field (see <xref target="header.location"/>).
1002</t>
1003<t>
1004   Responses to POST requests are only cacheable when they
1005   include explicit freshness information (see &p6-explicit;). A
1006   cached POST response with a Content-Location header field
1007   (see &header-content-location;) whose value is the effective
1008   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1009</t>
1010<t>
1011   Note that POST caching is not widely implemented.
1012   However, the 303 (See Other) response can be used to direct the
1013   user agent to retrieve a cacheable resource.
1014</t>
1015</section>
1016
1017<section title="PUT" anchor="PUT">
1018  <iref primary="true" item="PUT method" x:for-anchor=""/>
1019  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1020<t>
1021   The PUT method requests that the enclosed representation be stored at the
1022   effective request URI. If the effective request URI refers to an already
1023   existing resource, the enclosed representation &SHOULD; be considered a
1024   modified version of the one residing on the origin server. Otherwise, if the
1025   effective request URI does not point to an existing resource, and that URI is
1026   capable of being defined as a new resource by the requesting user
1027   agent, the origin server can create the resource with that URI.
1028</t>
1029<t>   
1030   If a new resource is created at the effective request URI, the origin
1031   server &MUST; inform the user agent
1032   via the 201 (Created) response. If an existing resource is modified,
1033   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1034   to indicate successful completion of the request.
1035</t>
1036<t>   
1037   If the target resource could not be created or modified, an appropriate
1038   error response &SHOULD; be given that reflects the nature of the problem.
1039   The recipient of the representation &MUST-NOT; ignore any Content-*
1040   header fields (headers starting with the prefix "Content-") that it does
1041   not understand or implement
1042   and &MUST; return a 501 (Not Implemented) response in such cases.
1043</t>
1044<t>
1045   If the request passes through a cache that has one or more stored
1046   responses for the effective request URI, those stored responses
1047   &SHOULD; be marked as stale if the response to the PUT request
1048   has a success status code. Responses to the PUT method are
1049   not cacheable.
1050</t>
1051<t>
1052   The fundamental difference between the POST and PUT requests is
1053   reflected in the different meaning of the effective request URI. The URI in a
1054   POST request identifies the resource that will handle the enclosed
1055   representation. That resource might be a data-accepting process, a gateway to
1056   some other protocol, or a document that accepts annotations.
1057   In contrast, the URI in a PUT request identifies the resource for
1058   which enclosed representation is a new or replacement value; the
1059   user agent knows what URI is intended and the server &MUST-NOT; attempt
1060   to apply the request to some other resource.
1061   If the server desires that the request be applied to a different URI,
1062   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1063   then make its own decision regarding whether or not to redirect the
1064   request.
1065</t>
1066<t>
1067   A single resource &MAY; be identified by many different URIs. For
1068   example, an article might have a URI for identifying "the current
1069   version" which is separate from the URI identifying each particular
1070   version. In this case, a PUT request on a general URI might result in
1071   several other URIs being defined by the origin server.
1072</t>
1073<t>
1074   HTTP/1.1 does not define how a PUT method affects the state of an
1075   origin server.
1076</t>
1077<t>
1078   Header fields in a PUT request that are recognized as representation
1079   metadata &SHOULD; be applied to the resource created or modified by
1080   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1081</t>
1082</section>
1083
1084<section title="DELETE" anchor="DELETE">
1085  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1086  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1087<t>
1088   The DELETE method requests that the origin server delete the target
1089   resource. This method &MAY; be overridden by
1090   human intervention (or other means) on the origin server. The client cannot
1091   be guaranteed that the operation has been carried out, even if the
1092   status code returned from the origin server indicates that the action
1093   has been completed successfully. However, the server &SHOULD-NOT; 
1094   indicate success unless, at the time the response is given, it
1095   intends to delete the resource or move it to an inaccessible
1096   location.
1097</t>
1098<t>
1099   A successful response &SHOULD; be 200 (OK) if the response includes an
1100   representation describing the status, 202 (Accepted) if the action has not
1101   yet been enacted, or 204 (No Content) if the action has been enacted
1102   but the response does not include a representation.
1103</t>
1104<t>
1105   If the request passes through a cache and the effective request URI
1106   identifies one or more currently cached representations, those entries &SHOULD; be
1107   treated as stale. Responses to the DELETE method are not cacheable.
1108</t>
1109</section>
1110
1111<section title="TRACE" anchor="TRACE">
1112  <rdf:Description>
1113    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1114  </rdf:Description>
1115  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1116  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1117<t>
1118   The TRACE method is used to invoke a remote, application-layer loop-back
1119   of the request message. The final recipient of the request
1120   &SHOULD; reflect the message received back to the client as the
1121   message-body of a 200 (OK) response. The final recipient is either the
1122   origin server or the first proxy or gateway to receive a Max-Forwards
1123   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1124   A TRACE request &MUST-NOT; include a message-body.
1125</t>
1126<t>
1127   TRACE allows the client to see what is being received at the other
1128   end of the request chain and use that data for testing or diagnostic
1129   information. The value of the Via header field (&header-via;) is of
1130   particular interest, since it acts as a trace of the request chain.
1131   Use of the Max-Forwards header field allows the client to limit the
1132   length of the request chain, which is useful for testing a chain of
1133   proxies forwarding messages in an infinite loop.
1134</t>
1135<t>
1136   If the request is valid, the response &SHOULD; have a Content-Type of
1137   "message/http" (see &media-type-message-http;) and contain a message-body
1138   that encloses a copy of the entire request message.
1139   Responses to the TRACE method are not cacheable.
1140</t>
1141</section>
1142
1143<section title="CONNECT" anchor="CONNECT">
1144  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1145  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1146<t>
1147   The CONNECT method is used with a proxy to dynamically switch
1148   the connection to a tunnel.
1149</t>
1150<t>
1151   When using CONNECT, the request-target &MUST; be an authority; i.e.,
1152   the host name and port number destination of the requested connection
1153   separated by a colon:
1154</t>
1155
1156<figure><artwork type="example">
1157    CONNECT server.example.com:80 HTTP/1.1
1158    Host: server.example.com:80
1159</artwork></figure>
1160
1161<t>
1162   Other HTTP mechanisms can be used normally with the CONNECT method --
1163   except end-to-end protocol Upgrade requests, since the
1164   tunnel must be established first.
1165</t>
1166<t>
1167   For example, proxy authentication might be used to establish the
1168   authority to create a tunnel:
1169</t>
1170
1171<figure><artwork type="example">
1172    CONNECT server.example.com:80 HTTP/1.1
1173    Host: server.example.com:80
1174    Proxy-Authorization: basic aGVsbG86d29ybGQ=
1175</artwork></figure>
1176
1177<t>
1178   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1179   sent immediately after the blank line. The usual caveats also apply:
1180   data may be discarded if the eventual response is negative, and the
1181   connection may be reset with no response if more than one TCP segment
1182   is outstanding.
1183</t>
1184
1185<section title="Establishing a Tunnel with CONNECT">
1186<t>
1187   Any successful (2xx) response to a CONNECT request indicates that the
1188   proxy has established a connection to the requested host and port,
1189   and has switched to tunneling the current connection to that server
1190   connection.
1191</t>
1192<t>
1193   It may be the case that the proxy itself can only reach the requested
1194   origin server through another proxy.  In this case, the first proxy
1195   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1196   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1197   unless it has either a direct or tunnel connection established to the
1198   authority.
1199</t>
1200<t>
1201   An origin server which receives a CONNECT request for itself &MAY;
1202   respond with a 2xx status code to indicate that a connection is
1203   established.
1204</t>
1205<t>
1206   If at any point either one of the peers gets disconnected, any
1207   outstanding data that came from that peer will be passed to the other
1208   one, and after that also the other connection will be terminated by
1209   the proxy. If there is outstanding data to that peer undelivered,
1210   that data will be discarded.
1211</t>
1212
1213</section>
1214</section>
1215</section>
1216
1217
1218<section title="Status Code Definitions" anchor="status.codes">
1219<t>
1220   Each Status-Code is described below, including any metadata required
1221   in the response.
1222</t>
1223
1224<section title="Informational 1xx" anchor="status.1xx">
1225<t>
1226   This class of status code indicates a provisional response,
1227   consisting only of the Status-Line and optional header fields, and is
1228   terminated by an empty line. There are no required header fields for this
1229   class of status code. Since HTTP/1.0 did not define any 1xx status
1230   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1231   except under experimental conditions.
1232</t>
1233<t>
1234   A client &MUST; be prepared to accept one or more 1xx status responses
1235   prior to a regular response, even if the client does not expect a 100
1236   (Continue) status message. Unexpected 1xx status responses &MAY; be
1237   ignored by a user agent.
1238</t>
1239<t>
1240   Proxies &MUST; forward 1xx responses, unless the connection between the
1241   proxy and its client has been closed, or unless the proxy itself
1242   requested the generation of the 1xx response. (For example, if a
1243   proxy adds a "Expect: 100-continue" field when it forwards a request,
1244   then it need not forward the corresponding 100 (Continue)
1245   response(s).)
1246</t>
1247
1248<section title="100 Continue" anchor="status.100">
1249  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1250  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1251<t>
1252   The client &SHOULD; continue with its request. This interim response is
1253   used to inform the client that the initial part of the request has
1254   been received and has not yet been rejected by the server. The client
1255   &SHOULD; continue by sending the remainder of the request or, if the
1256   request has already been completed, ignore this response. The server
1257   &MUST; send a final response after the request has been completed. See
1258   &use100; for detailed discussion of the use and handling of this
1259   status code.
1260</t>
1261</section>
1262
1263<section title="101 Switching Protocols" anchor="status.101">
1264  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1265  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1266<t>
1267   The server understands and is willing to comply with the client's
1268   request, via the Upgrade message header field (&header-upgrade;), for a
1269   change in the application protocol being used on this connection. The
1270   server will switch protocols to those defined by the response's
1271   Upgrade header field immediately after the empty line which
1272   terminates the 101 response.
1273</t>
1274<t>
1275   The protocol &SHOULD; be switched only when it is advantageous to do
1276   so. For example, switching to a newer version of HTTP is advantageous
1277   over older versions, and switching to a real-time, synchronous
1278   protocol might be advantageous when delivering resources that use
1279   such features.
1280</t>
1281</section>
1282</section>
1283
1284<section title="Successful 2xx" anchor="status.2xx">
1285<t>
1286   This class of status code indicates that the client's request was
1287   successfully received, understood, and accepted.
1288</t>
1289
1290<section title="200 OK" anchor="status.200">
1291  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1292  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1293<t>
1294   The request has succeeded. The payload returned with the response
1295   is dependent on the method used in the request, for example:
1296  <list style="hanging">
1297    <t hangText="GET">
1298          a representation of the target resource is sent in the response;
1299    </t>
1300    <t hangText="HEAD">
1301          the same representation as GET, except without the message-body;
1302    </t>
1303    <t hangText="POST">
1304      a representation describing or containing the result of the action;
1305    </t>
1306    <t hangText="TRACE">
1307      a representation containing the request message as received by the
1308      end server.
1309    </t>
1310  </list>
1311</t>
1312<t>
1313   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1314   freshness for 200 responses.
1315</t>
1316</section>
1317
1318<section title="201 Created" anchor="status.201">
1319  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1320  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1321<t>
1322   The request has been fulfilled and has resulted in a new resource being
1323   created. The newly created resource can be referenced by the URI(s)
1324   returned in the payload of the response, with the most specific URI
1325   for the resource given by a Location header field. The response
1326   &SHOULD; include a payload containing a list of resource
1327   characteristics and location(s) from which the user or user agent can
1328   choose the one most appropriate. The payload format is specified by
1329   the media type given in the Content-Type header field. The origin
1330   server &MUST; create the resource before returning the 201 status code.
1331   If the action cannot be carried out immediately, the server &SHOULD;
1332   respond with 202 (Accepted) response instead.
1333</t>
1334<t>
1335   A 201 response &MAY; contain an ETag response header field indicating
1336   the current value of the entity-tag for the representation of the resource
1337   just created (see &header-etag;).
1338</t>
1339</section>
1340
1341<section title="202 Accepted" anchor="status.202">
1342  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1343  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1344<t>
1345   The request has been accepted for processing, but the processing has
1346   not been completed.  The request might or might not eventually be
1347   acted upon, as it might be disallowed when processing actually takes
1348   place. There is no facility for re-sending a status code from an
1349   asynchronous operation such as this.
1350</t>
1351<t>
1352   The 202 response is intentionally non-committal. Its purpose is to
1353   allow a server to accept a request for some other process (perhaps a
1354   batch-oriented process that is only run once per day) without
1355   requiring that the user agent's connection to the server persist
1356   until the process is completed. The representation returned with this
1357   response &SHOULD; include an indication of the request's current status
1358   and either a pointer to a status monitor or some estimate of when the
1359   user can expect the request to be fulfilled.
1360</t>
1361</section>
1362
1363<section title="203 Non-Authoritative Information" anchor="status.203">
1364  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1365  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1366<t>
1367   The returned metadata in the header fields is not the
1368   definitive set as available from the origin server, but is gathered
1369   from a local or a third-party copy. The set presented &MAY; be a subset
1370   or superset of the original version. For example, including local
1371   annotation information about the resource might result in a superset
1372   of the metadata known by the origin server. Use of this
1373   response code is not required and is only appropriate when the
1374   response would otherwise be 200 (OK).
1375</t>
1376<t>
1377   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1378   freshness for 203 responses.
1379</t>
1380
1381</section>
1382
1383<section title="204 No Content" anchor="status.204">
1384  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1385  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1386<t>
1387   The server has successfully fulfilled the request, but there is no
1388   additional content to return in the response payload body.  The
1389   resource metadata and representation metadata in the response message's
1390   header fields refer to the target resource
1391   and its current representation, respectively, after the requested action.
1392   For example, if a 204 status code is received in response to a PUT
1393   and the response contains an ETag header field, then the value of
1394   that field is the current entity-tag for the representation that
1395   was successfully PUT.
1396</t>
1397<t>
1398   If the client is a user agent, it &SHOULD-NOT; change its document view
1399   from that which caused the request to be sent. This response is
1400   primarily intended to allow input for actions to take place without
1401   causing a change to the user agent's active document view, although
1402   any new or updated metadata &SHOULD; be applied to the document
1403   currently in the user agent's active view.
1404</t>
1405<t>
1406   The 204 response &MUST-NOT; include a message-body, and thus is always
1407   terminated by the first empty line after the header fields.
1408</t>
1409</section>
1410
1411<section title="205 Reset Content" anchor="status.205">
1412  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1413  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1414<t>
1415   The server has fulfilled the request and the user agent &SHOULD; reset
1416   the document view which caused the request to be sent. This response
1417   is primarily intended to allow input for actions to take place via
1418   user input, followed by a clearing of the form in which the input is
1419   given so that the user can easily initiate another input action.
1420</t>
1421<t>   
1422   The message-body included with the response &MUST; be empty. Note that
1423   receivers still need to parse the response according to the algorithm defined
1424   in &message-body;.
1425</t>
1426</section>
1427
1428<section title="206 Partial Content" anchor="status.206">
1429  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1430  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1431  <rdf:Description>
1432    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1433  </rdf:Description>
1434<t>
1435   The server has fulfilled the partial GET request for the resource
1436   and the enclosed payload is a partial representation as defined in &status-206;.
1437</t>
1438<t>
1439   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1440   freshness for 206 responses.
1441</t>
1442</section>
1443</section>
1444
1445<section title="Redirection 3xx" anchor="status.3xx">
1446<t>
1447   This class of status code indicates that further action needs to be
1448   taken by the user agent in order to fulfill the request.  The action
1449   required &MAY; be carried out by the user agent without interaction
1450   with the user if and only if the method used in the second request is
1451   known to be "safe", as defined in <xref target="safe.methods"/>.
1452   A client &SHOULD; detect infinite redirection loops, since such loops
1453   generate network traffic for each redirection.
1454</t>
1455<x:note>
1456  <t>
1457    <x:h>Note:</x:h> An earlier version of this specification recommended a
1458    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1459    Content developers need to be aware that some clients might
1460    implement such a fixed limitation.
1461  </t>
1462</x:note>
1463
1464<section title="300 Multiple Choices" anchor="status.300">
1465  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1466  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1467<t>
1468   The target resource has more than one
1469   representation, each with its own specific location, and agent-driven
1470   negotiation information (&content-negotiation;) is being provided so that
1471   the user (or user agent) can select a preferred representation by
1472   redirecting its request to that location.
1473</t>
1474<t>
1475   Unless it was a HEAD request, the response &SHOULD; include a representation
1476   containing a list of representation metadata and location(s) from
1477   which the user or user agent can choose the one most appropriate. The
1478   data format is specified by the media type given in the Content-Type
1479   header field. Depending upon the format and the capabilities of
1480   the user agent, selection of the most appropriate choice &MAY; be
1481   performed automatically. However, this specification does not define
1482   any standard for such automatic selection.
1483</t>
1484<t>
1485   If the server has a preferred choice of representation, it &SHOULD;
1486   include the specific URI for that representation in the Location
1487   field; user agents &MAY; use the Location field value for automatic
1488   redirection.
1489</t>
1490<t>
1491   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1492   freshness for 300 responses.
1493</t>
1494
1495</section>
1496
1497<section title="301 Moved Permanently" anchor="status.301">
1498  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1499  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1500<t>
1501   The target resource has been assigned a new permanent URI and any
1502   future references to this resource &SHOULD; use one of the returned
1503   URIs.  Clients with link editing capabilities ought to automatically
1504   re-link references to the effective request URI to one or more of the new
1505   references returned by the server, where possible.
1506</t>
1507<t>
1508   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1509   freshness for 301 responses.
1510</t>
1511<t>
1512   The new permanent URI &SHOULD; be given by the Location field in the
1513   response. Unless the request method was HEAD, the representation of the
1514   response &SHOULD; contain a short hypertext note with a hyperlink to
1515   the new URI(s).
1516</t>
1517<t>
1518   If the 301 status code is received in response to a request method
1519   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1520   then the request &MAY; be automatically redirected by the user agent without
1521   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1522   request unless it can be confirmed by the user, since this might
1523   change the conditions under which the request was issued.
1524</t>
1525<x:note>
1526  <t>
1527    <x:h>Note:</x:h> When automatically redirecting a POST request after
1528    receiving a 301 status code, some existing HTTP/1.0 user agents
1529    will erroneously change it into a GET request.
1530  </t>
1531</x:note>
1532</section>
1533
1534<section title="302 Found" anchor="status.302">
1535  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1536  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1537<t>
1538   The target resource resides temporarily under a different URI.
1539   Since the redirection might be altered on occasion, the client &SHOULD;
1540   continue to use the effective request URI for future requests.
1541</t>
1542<t>
1543   The temporary URI &SHOULD; be given by the Location field in the
1544   response. Unless the request method was HEAD, the representation of the
1545   response &SHOULD; contain a short hypertext note with a hyperlink to
1546   the new URI(s).
1547</t>
1548<t>
1549   If the 302 status code is received in response to a request method
1550   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1551   then the request &MAY; be automatically redirected by the user agent without
1552   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1553   request unless it can be confirmed by the user, since this might
1554   change the conditions under which the request was issued.
1555</t>
1556<x:note>
1557  <t>
1558    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1559    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1560    specify that the client is not allowed to change the method on the
1561    redirected request.  However, most existing user agent implementations
1562    treat 302 as if it were a 303 response, performing a GET on the Location
1563    field-value regardless of the original request method. Therefore, a
1564    previous version of this specification
1565    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1566    status codes
1567    <xref target="status.303" format="none">303</xref> and
1568    <xref target="status.307" format="none">307</xref> for servers that wish
1569    to make unambiguously clear which kind of reaction is expected of the
1570    client.
1571  </t>
1572</x:note>
1573</section>
1574
1575<section title="303 See Other" anchor="status.303">
1576  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1577  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1578<t>
1579   The server directs the user agent to a different resource, indicated
1580   by a URI in the Location header field, that provides an indirect
1581   response to the original request.  The user agent &MAY; perform a GET
1582   request on the URI in the Location field in order to obtain a
1583   representation corresponding to the response, be redirected again,
1584   or end with an error status.  The Location URI is not a substitute
1585   reference for the effective request URI.
1586</t>
1587<t>
1588   The 303 status code is generally applicable to any HTTP method.  It is
1589   primarily used to allow the output of a POST action to redirect
1590   the user agent to a selected resource, since doing so provides the
1591   information corresponding to the POST response in a form that
1592   can be separately identified, bookmarked, and cached independent
1593   of the original request.
1594</t>
1595<t>
1596   A 303 response to a GET request indicates that the requested
1597   resource does not have a representation of its own that can be
1598   transferred by the server over HTTP.  The Location URI indicates a
1599   resource that is descriptive of the target resource, such that the
1600   follow-on representation might be useful to recipients without
1601   implying that it adequately represents the target resource.
1602   Note that answers to the questions of what can be represented, what
1603   representations are adequate, and what might be a useful description
1604   are outside the scope of HTTP and thus entirely determined by the
1605   URI owner(s).
1606</t>
1607<t>
1608   Except for responses to a HEAD request, the representation of a 303
1609   response &SHOULD; contain a short hypertext note with a hyperlink
1610   to the Location URI.
1611</t>
1612</section>
1613
1614<section title="304 Not Modified" anchor="status.304">
1615  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1616  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1617  <rdf:Description>
1618    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1619  </rdf:Description>
1620<t>
1621   The response to the request has not been modified since the conditions
1622   indicated by the client's conditional GET request, as defined in &status-304;.
1623</t>
1624</section>
1625
1626<section title="305 Use Proxy" anchor="status.305">
1627  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1628  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1629<t>
1630   The 305 status code was defined in a previous version of this specification
1631   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1632</t>
1633</section>
1634
1635<section title="306 (Unused)" anchor="status.306">
1636  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1637  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1638<t>
1639   The 306 status code was used in a previous version of the
1640   specification, is no longer used, and the code is reserved.
1641</t>
1642</section>
1643
1644<section title="307 Temporary Redirect" anchor="status.307">
1645  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1646  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1647<t>
1648   The target resource resides temporarily under a different URI.
1649   Since the redirection can change over time, the client &SHOULD;
1650   continue to use the effective request URI for future requests.
1651</t>
1652<t>
1653   The temporary URI &SHOULD; be given by the Location field in the
1654   response. Unless the request method was HEAD, the representation of the
1655   response &SHOULD; contain a short hypertext note with a hyperlink to
1656   the new URI(s), since many pre-HTTP/1.1 user agents do not
1657   understand the 307 status code. Therefore, the note &SHOULD; contain the
1658   information necessary for a user to repeat the original request on
1659   the new URI.
1660</t>
1661<t>
1662   If the 307 status code is received in response to a request method
1663   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1664   then the request &MAY; be automatically redirected by the user agent without
1665   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1666   request unless it can be confirmed by the user, since this might
1667   change the conditions under which the request was issued.
1668</t>
1669</section>
1670</section>
1671
1672<section title="Client Error 4xx" anchor="status.4xx">
1673<t>
1674   The 4xx class of status code is intended for cases in which the
1675   client seems to have erred. Except when responding to a HEAD request,
1676   the server &SHOULD; include a representation containing an explanation of the
1677   error situation, and whether it is a temporary or permanent
1678   condition. These status codes are applicable to any request method.
1679   User agents &SHOULD; display any included representation to the user.
1680</t>
1681<t>
1682   If the client is sending data, a server implementation using TCP
1683   &SHOULD; be careful to ensure that the client acknowledges receipt of
1684   the packet(s) containing the response, before the server closes the
1685   input connection. If the client continues sending data to the server
1686   after the close, the server's TCP stack will send a reset packet to
1687   the client, which might erase the client's unacknowledged input buffers
1688   before they can be read and interpreted by the HTTP application.
1689</t>
1690
1691<section title="400 Bad Request" anchor="status.400">
1692  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1693  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1694<t>
1695   The request could not be understood by the server due to malformed
1696   syntax. The client &SHOULD-NOT; repeat the request without
1697   modifications.
1698</t>
1699</section>
1700
1701<section title="401 Unauthorized" anchor="status.401">
1702  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1703  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1704  <rdf:Description>
1705    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1706  </rdf:Description>
1707<t>
1708   The request requires user authentication (see &status-401;).
1709</t>
1710</section>
1711
1712<section title="402 Payment Required" anchor="status.402">
1713  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1715<t>
1716   This code is reserved for future use.
1717</t>
1718</section>
1719
1720<section title="403 Forbidden" anchor="status.403">
1721  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1722  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1723<t>
1724   The server understood the request, but is refusing to fulfill it.
1725   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1726   If the request method was not HEAD and the server wishes to make
1727   public why the request has not been fulfilled, it &SHOULD; describe the
1728   reason for the refusal in the representation.  If the server does not wish to
1729   make this information available to the client, the status code 404
1730   (Not Found) can be used instead.
1731</t>
1732</section>
1733
1734<section title="404 Not Found" anchor="status.404">
1735  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1736  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1737<t>
1738   The server has not found anything matching the effective request URI. No
1739   indication is given of whether the condition is temporary or
1740   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1741   knows, through some internally configurable mechanism, that an old
1742   resource is permanently unavailable and has no forwarding address.
1743   This status code is commonly used when the server does not wish to
1744   reveal exactly why the request has been refused, or when no other
1745   response is applicable.
1746</t>
1747</section>
1748
1749<section title="405 Method Not Allowed" anchor="status.405">
1750  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1751  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1752<t>
1753   The method specified in the Request-Line is not allowed for the target
1754   resource. The response &MUST; include an
1755   Allow header field containing a list of valid methods for the requested
1756   resource.
1757</t>
1758</section>
1759
1760<section title="406 Not Acceptable" anchor="status.406">
1761  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1762  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1763<t>
1764   The resource identified by the request is only capable of generating
1765   response representations which have content characteristics not acceptable
1766   according to the accept header fields sent in the request.
1767</t>
1768<t>
1769   Unless it was a HEAD request, the response &SHOULD; include a representation
1770   containing a list of available representation characteristics and location(s)
1771   from which the user or user agent can choose the one most
1772   appropriate. The data format is specified by the media type given
1773   in the Content-Type header field. Depending upon the format and the
1774   capabilities of the user agent, selection of the most appropriate
1775   choice &MAY; be performed automatically. However, this specification
1776   does not define any standard for such automatic selection.
1777</t>
1778<x:note>
1779  <t>
1780    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1781    not acceptable according to the accept header fields sent in the
1782    request. In some cases, this might even be preferable to sending a
1783    406 response. User agents are encouraged to inspect the header fields of
1784    an incoming response to determine if it is acceptable.
1785  </t>
1786</x:note>
1787<t>
1788   If the response could be unacceptable, a user agent &SHOULD;
1789   temporarily stop receipt of more data and query the user for a
1790   decision on further actions.
1791</t>
1792</section>
1793
1794<section title="407 Proxy Authentication Required" anchor="status.407">
1795  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1796  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1797<t>
1798   This code is similar to 401 (Unauthorized), but indicates that the
1799   client must first authenticate itself with the proxy (see &status-407;).
1800</t>
1801</section>
1802
1803<section title="408 Request Timeout" anchor="status.408">
1804  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1805  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1806<t>
1807   The client did not produce a request within the time that the server
1808   was prepared to wait. The client &MAY; repeat the request without
1809   modifications at any later time.
1810</t>
1811</section>
1812
1813<section title="409 Conflict" anchor="status.409">
1814  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1815  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1816<t>
1817   The request could not be completed due to a conflict with the current
1818   state of the resource. This code is only allowed in situations where
1819   it is expected that the user might be able to resolve the conflict
1820   and resubmit the request. The response body &SHOULD; include enough
1821   information for the user to recognize the source of the conflict.
1822   Ideally, the response representation would include enough information for the
1823   user or user agent to fix the problem; however, that might not be
1824   possible and is not required.
1825</t>
1826<t>
1827   Conflicts are most likely to occur in response to a PUT request. For
1828   example, if versioning were being used and the representation being PUT
1829   included changes to a resource which conflict with those made by an
1830   earlier (third-party) request, the server might use the 409 response
1831   to indicate that it can't complete the request. In this case, the
1832   response representation would likely contain a list of the differences
1833   between the two versions in a format defined by the response
1834   Content-Type.
1835</t>
1836</section>
1837
1838<section title="410 Gone" anchor="status.410">
1839  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1840  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1841<t>
1842   The target resource is no longer available at the server and no
1843   forwarding address is known. This condition is expected to be
1844   considered permanent. Clients with link editing capabilities &SHOULD;
1845   delete references to the effective request URI after user approval. If the
1846   server does not know, or has no facility to determine, whether or not
1847   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1848   used instead.
1849</t>
1850<t>
1851   The 410 response is primarily intended to assist the task of web
1852   maintenance by notifying the recipient that the resource is
1853   intentionally unavailable and that the server owners desire that
1854   remote links to that resource be removed. Such an event is common for
1855   limited-time, promotional services and for resources belonging to
1856   individuals no longer working at the server's site. It is not
1857   necessary to mark all permanently unavailable resources as "gone" or
1858   to keep the mark for any length of time -- that is left to the
1859   discretion of the server owner.
1860</t>
1861<t>
1862   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1863   for 410 responses.
1864</t>
1865
1866</section>
1867
1868<section title="411 Length Required" anchor="status.411">
1869  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1870  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1871<t>
1872   The server refuses to accept the request without a defined Content-Length.
1873   The client &MAY; repeat the request if it adds a valid
1874   Content-Length header field containing the length of the message-body
1875   in the request message.
1876</t>
1877</section>
1878
1879<section title="412 Precondition Failed" anchor="status.412">
1880  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1881  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1882  <rdf:Description>
1883    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1884  </rdf:Description>
1885<t>
1886   The precondition given in one or more of the request-header fields
1887   evaluated to false when it was tested on the server, as defined in
1888   &status-412;.
1889</t>
1890</section>
1891
1892<section title="413 Request Entity Too Large" anchor="status.413">
1893  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1894  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1895<t>
1896   The server is refusing to process a request because the request
1897   representation is larger than the server is willing or able to process. The
1898   server &MAY; close the connection to prevent the client from continuing
1899   the request.
1900</t>
1901<t>
1902   If the condition is temporary, the server &SHOULD; include a Retry-After
1903   header field to indicate that it is temporary and after what
1904   time the client &MAY; try again.
1905</t>
1906</section>
1907
1908<section title="414 URI Too Long" anchor="status.414">
1909  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1910  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1911<t>
1912   The server is refusing to service the request because the effective request URI
1913   is longer than the server is willing to interpret. This rare
1914   condition is only likely to occur when a client has improperly
1915   converted a POST request to a GET request with long query
1916   information, when the client has descended into a URI "black hole" of
1917   redirection (e.g., a redirected URI prefix that points to a suffix of
1918   itself), or when the server is under attack by a client attempting to
1919   exploit security holes present in some servers using fixed-length
1920   buffers for reading or manipulating the effective request URI.
1921</t>
1922</section>
1923
1924<section title="415 Unsupported Media Type" anchor="status.415">
1925  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1926  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1927<t>
1928   The server is refusing to service the request because the representation of
1929   the request is in a format not supported by the target resource
1930   for the requested method.
1931</t>
1932</section>
1933
1934<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1935  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1936  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1937  <rdf:Description>
1938    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1939  </rdf:Description>
1940<t>
1941   The request included a Range request-header field (&header-range;) and none of
1942   the range-specifier values in this field overlap the current extent
1943   of the selected resource. See &status-416;.
1944</t>
1945</section>
1946
1947<section title="417 Expectation Failed" anchor="status.417">
1948  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1950<t>
1951   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1952   could not be met by this server, or, if the server is a proxy,
1953   the server has unambiguous evidence that the request could not be met
1954   by the next-hop server.
1955</t>
1956</section>
1957</section>
1958
1959<section title="Server Error 5xx" anchor="status.5xx">
1960<t>
1961   Response status codes beginning with the digit "5" indicate cases in
1962   which the server is aware that it has erred or is incapable of
1963   performing the request. Except when responding to a HEAD request, the
1964   server &SHOULD; include a representation containing an explanation of the
1965   error situation, and whether it is a temporary or permanent
1966   condition. User agents &SHOULD; display any included representation to the
1967   user. These response codes are applicable to any request method.
1968</t>
1969
1970<section title="500 Internal Server Error" anchor="status.500">
1971  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1972  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1973<t>
1974   The server encountered an unexpected condition which prevented it
1975   from fulfilling the request.
1976</t>
1977</section>
1978
1979<section title="501 Not Implemented" anchor="status.501">
1980  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1981  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1982<t>
1983   The server does not support the functionality required to fulfill the
1984   request. This is the appropriate response when the server does not
1985   recognize the request method and is not capable of supporting it for
1986   any resource.
1987</t>
1988</section>
1989
1990<section title="502 Bad Gateway" anchor="status.502">
1991  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1992  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1993<t>
1994   The server, while acting as a gateway or proxy, received an invalid
1995   response from the upstream server it accessed in attempting to
1996   fulfill the request.
1997</t>
1998</section>
1999
2000<section title="503 Service Unavailable" anchor="status.503">
2001  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2002  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2003<t>
2004   The server is currently unable to handle the request due to a
2005   temporary overloading or maintenance of the server. The implication
2006   is that this is a temporary condition which will be alleviated after
2007   some delay. If known, the length of the delay &MAY; be indicated in a
2008   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2009   handle the response as it would for a 500 response.
2010</t>
2011<x:note>
2012  <t>
2013    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2014    server must use it when becoming overloaded. Some servers might wish
2015    to simply refuse the connection.
2016  </t>
2017</x:note>
2018</section>
2019
2020<section title="504 Gateway Timeout" anchor="status.504">
2021  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2022  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2023<t>
2024   The server, while acting as a gateway or proxy, did not receive a
2025   timely response from the upstream server specified by the URI (e.g.,
2026   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2027   to access in attempting to complete the request.
2028</t>
2029<x:note>
2030  <t>
2031    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2032    return 400 or 500 when DNS lookups time out.
2033  </t>
2034</x:note>
2035</section>
2036
2037<section title="505 HTTP Version Not Supported" anchor="status.505">
2038  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2039  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2040<t>
2041   The server does not support, or refuses to support, the protocol
2042   version that was used in the request message. The server is
2043   indicating that it is unable or unwilling to complete the request
2044   using the same major version as the client, as described in &http-version;,
2045   other than with this error message. The response &SHOULD; contain
2046   a representation describing why that version is not supported and what other
2047   protocols are supported by that server.
2048</t>
2049
2050</section>
2051</section>
2052</section>
2053
2054
2055<section title="Header Field Definitions" anchor="header.fields">
2056<t>
2057   This section defines the syntax and semantics of HTTP/1.1 header fields
2058   related to request and response semantics.
2059</t>
2060
2061<section title="Allow" anchor="header.allow">
2062  <iref primary="true" item="Allow header" x:for-anchor=""/>
2063  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
2064  <x:anchor-alias value="Allow"/>
2065  <x:anchor-alias value="Allow-v"/>
2066<t>
2067   The "Allow" response-header field lists the set of methods advertised as
2068   supported by the target resource. The purpose of
2069   this field is strictly to inform the recipient of valid methods
2070   associated with the resource.
2071</t>
2072<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2073  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2074  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2075</artwork></figure>
2076<t>
2077      Example of use:
2078</t>
2079<figure><artwork type="example">
2080  Allow: GET, HEAD, PUT
2081</artwork></figure>
2082<t>
2083      The actual set of allowed methods is defined
2084      by the origin server at the time of each request.
2085</t>
2086<t>
2087      A proxy &MUST-NOT; modify the Allow header field even if it does not
2088      understand all the methods specified, since the user agent might
2089      have other means of communicating with the origin server.
2090</t>
2091</section>
2092
2093<section title="Expect" anchor="header.expect">
2094  <iref primary="true" item="Expect header" x:for-anchor=""/>
2095  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
2096  <x:anchor-alias value="Expect"/>
2097  <x:anchor-alias value="Expect-v"/>
2098  <x:anchor-alias value="expectation"/>
2099  <x:anchor-alias value="expectation-extension"/>
2100  <x:anchor-alias value="expect-params"/>
2101<t>
2102   The "Expect" request-header field is used to indicate that particular
2103   server behaviors are required by the client.
2104</t>
2105<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"/>
2106  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2107  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2108 
2109  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2110  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2111                           *<x:ref>expect-params</x:ref> ]
2112  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2113</artwork></figure>
2114<t>
2115   A server that does not understand or is unable to comply with any of
2116   the expectation values in the Expect field of a request &MUST; respond
2117   with appropriate error status code. The server &MUST; respond with a 417
2118   (Expectation Failed) status code if any of the expectations cannot be met
2119   or, if there are other problems with the request, some other 4xx
2120   status code.
2121</t>
2122<t>
2123   This header field is defined with extensible syntax to allow for
2124   future extensions. If a server receives a request containing an
2125   Expect field that includes an expectation-extension that it does not
2126   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2127</t>
2128<t>
2129   Comparison of expectation values is case-insensitive for unquoted
2130   tokens (including the 100-continue token), and is case-sensitive for
2131   quoted-string expectation-extensions.
2132</t>
2133<t>
2134   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2135   return a 417 (Expectation Failed) status code if it receives a request
2136   with an expectation that it cannot meet. However, the Expect
2137   request-header field itself is end-to-end; it &MUST; be forwarded if the
2138   request is forwarded.
2139</t>
2140<t>
2141   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2142   Expect header field.
2143</t>
2144<t>
2145   See &use100; for the use of the 100 (Continue) status code.
2146</t>
2147</section>
2148
2149<section title="From" anchor="header.from">
2150  <iref primary="true" item="From header" x:for-anchor=""/>
2151  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2152  <x:anchor-alias value="From"/>
2153  <x:anchor-alias value="From-v"/>
2154  <x:anchor-alias value="mailbox"/>
2155<t>
2156   The "From" request-header field, if given, &SHOULD; contain an Internet
2157   e-mail address for the human user who controls the requesting user
2158   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2159   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2160</t>
2161<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2162  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2163  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2164 
2165  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2166</artwork></figure>
2167<t>
2168   An example is:
2169</t>
2170<figure><artwork type="example">
2171  From: webmaster@example.org
2172</artwork></figure>
2173<t>
2174   This header field &MAY; be used for logging purposes and as a means for
2175   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2176   be used as an insecure form of access protection. The interpretation
2177   of this field is that the request is being performed on behalf of the
2178   person given, who accepts responsibility for the method performed. In
2179   particular, robot agents &SHOULD; include this header field so that the
2180   person responsible for running the robot can be contacted if problems
2181   occur on the receiving end.
2182</t>
2183<t>
2184   The Internet e-mail address in this field &MAY; be separate from the
2185   Internet host which issued the request. For example, when a request
2186   is passed through a proxy the original issuer's address &SHOULD; be
2187   used.
2188</t>
2189<t>
2190   The client &SHOULD-NOT;  send the From header field without the user's
2191   approval, as it might conflict with the user's privacy interests or
2192   their site's security policy. It is strongly recommended that the
2193   user be able to disable, enable, and modify the value of this field
2194   at any time prior to a request.
2195</t>
2196</section>
2197
2198<section title="Location" anchor="header.location">
2199  <iref primary="true" item="Location header" x:for-anchor=""/>
2200  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2201  <x:anchor-alias value="Location"/>
2202  <x:anchor-alias value="Location-v"/>
2203<t>
2204   The "Location" response-header field is used to identify a newly created
2205   resource, or to redirect the recipient to a different location for
2206   completion of the request.
2207</t>
2208<t>
2209   For 201 (Created) responses, the Location is the URI of the new resource
2210   which was created by the request. For 3xx responses, the location &SHOULD;
2211   indicate the server's preferred URI for automatic redirection to the
2212   resource.
2213</t>
2214<t>
2215   The field value consists of a single URI-reference. When it has the form
2216   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2217   the final value is computed by resolving it against the effective request
2218   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2219</t>
2220<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2221  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2222  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2223</artwork></figure>
2224<figure>
2225<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2226<artwork type="example">
2227  Location: http://www.example.org/pub/WWW/People.html#tim
2228</artwork></figure><figure><artwork type="example">  Location: /index.html
2229</artwork></figure>
2230<t>
2231   There are circumstances in which a fragment identifier in a Location URI
2232   would not be appropriate:
2233   <list style="symbols">
2234      <t>With a 201 Created response, because in this usage the Location header
2235      field specifies the URI for the entire created resource.</t>
2236      <t>With 305 Use Proxy.</t>
2237   </list>
2238</t>
2239<x:note>
2240  <t>
2241    <x:h>Note:</x:h> This specification does not define precedence rules
2242    for the case where the original URI, as navigated to by the user
2243    agent, and the Location header field value both contain fragment
2244    identifiers.
2245  </t>
2246</x:note>
2247<x:note>
2248  <t>
2249    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2250    from Location in that the Content-Location identifies the most specific
2251    resource corresponding to the enclosed representation.
2252    It is therefore possible for a response to contain header fields for
2253    both Location and Content-Location.
2254  </t>
2255</x:note>
2256</section>
2257
2258<section title="Max-Forwards" anchor="header.max-forwards">
2259  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2260  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2261  <x:anchor-alias value="Max-Forwards"/>
2262  <x:anchor-alias value="Max-Forwards-v"/>
2263<t>
2264   The "Max-Forwards" request-header field provides a mechanism with the
2265   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2266   methods to limit the number of times that the request is forwarded by
2267   proxies or gateways. This can be useful when the client is attempting to
2268   trace a request which appears to be failing or looping in mid-chain.
2269</t>
2270<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2271  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2272  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2273</artwork></figure>
2274<t>
2275   The Max-Forwards value is a decimal integer indicating the remaining
2276   number of times this request message can be forwarded.
2277</t>
2278<t>
2279   Each proxy or gateway recipient of a TRACE or OPTIONS request
2280   containing a Max-Forwards header field &MUST; check and update its
2281   value prior to forwarding the request. If the received value is zero
2282   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2283   respond as the final recipient. If the received Max-Forwards value is
2284   greater than zero, then the forwarded message &MUST; contain an updated
2285   Max-Forwards field with a value decremented by one (1).
2286</t>
2287<t>
2288   The Max-Forwards header field &MAY; be ignored for all other methods
2289   defined by this specification and for any extension methods for which
2290   it is not explicitly referred to as part of that method definition.
2291</t>
2292</section>
2293
2294<section title="Referer" anchor="header.referer">
2295  <iref primary="true" item="Referer header" x:for-anchor=""/>
2296  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2297  <x:anchor-alias value="Referer"/>
2298  <x:anchor-alias value="Referer-v"/>
2299<t>
2300   The "Referer" [sic] request-header field allows the client to specify the
2301   URI of the resource from which the effective request URI was obtained (the
2302   "referrer", although the header field is misspelled.).
2303</t>
2304<t>
2305   The Referer header field allows servers to generate lists of back-links to
2306   resources for interest, logging, optimized caching, etc. It also allows
2307   obsolete or mistyped links to be traced for maintenance. Some servers use
2308   Referer as a means of controlling where they allow links from (so-called
2309   "deep linking"), but legitimate requests do not always
2310   contain a Referer header field.
2311</t>
2312<t>
2313   If the effective request URI was obtained from a source that does not have its own
2314   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2315   sent with the value "about:blank", or not be sent at all. Note that this
2316   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2317</t>
2318<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2319  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2320  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2321</artwork></figure>
2322<t>
2323   Example:
2324</t>
2325<figure><artwork type="example">
2326  Referer: http://www.example.org/hypertext/Overview.html
2327</artwork></figure>
2328<t>
2329   If the field value is a relative URI, it &SHOULD; be interpreted
2330   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2331   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2332</t>
2333</section>
2334
2335<section title="Retry-After" anchor="header.retry-after">
2336  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2337  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2338  <x:anchor-alias value="Retry-After"/>
2339  <x:anchor-alias value="Retry-After-v"/>
2340<t>
2341   The response-header "Retry-After" field can be used with a 503 (Service
2342   Unavailable) response to indicate how long the service is expected to
2343   be unavailable to the requesting client. This field &MAY; also be used
2344   with any 3xx (Redirection) response to indicate the minimum time the
2345   user-agent is asked wait before issuing the redirected request.
2346</t>
2347<t>
2348   The value of this field can be either an HTTP-date or an integer number
2349   of seconds (in decimal) after the time of the response.
2350</t>
2351<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2352  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2353  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2354</artwork></figure>
2355<t anchor="rule.delta-seconds">
2356  <x:anchor-alias value="delta-seconds"/>
2357   Time spans are non-negative decimal integers, representing time in
2358   seconds.
2359</t>
2360<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2361  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2362</artwork></figure>
2363<t>
2364   Two examples of its use are
2365</t>
2366<figure><artwork type="example">
2367  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2368  Retry-After: 120
2369</artwork></figure>
2370<t>
2371   In the latter example, the delay is 2 minutes.
2372</t>
2373</section>
2374
2375<section title="Server" anchor="header.server">
2376  <iref primary="true" item="Server header" x:for-anchor=""/>
2377  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2378  <x:anchor-alias value="Server"/>
2379  <x:anchor-alias value="Server-v"/>
2380<t>
2381   The "Server" response-header field contains information about the
2382   software used by the origin server to handle the request.
2383</t>
2384<t>
2385   The field can contain multiple product tokens (&product-tokens;) and
2386   comments (&header-fields;) identifying the server and any significant
2387   subproducts. The product tokens are listed in order of their significance
2388   for identifying the application.
2389</t>
2390<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2391  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2392  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2393                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2394</artwork></figure>
2395<t>
2396   Example:
2397</t>
2398<figure><artwork type="example">
2399  Server: CERN/3.0 libwww/2.17
2400</artwork></figure>
2401<t>
2402   If the response is being forwarded through a proxy, the proxy
2403   application &MUST-NOT; modify the Server response-header field. Instead, it
2404   &MUST; include a Via field (as described in &header-via;).
2405</t>
2406<x:note>
2407  <t>
2408    <x:h>Note:</x:h> Revealing the specific software version of the server might
2409    allow the server machine to become more vulnerable to attacks
2410    against software that is known to contain security holes. Server
2411    implementors are encouraged to make this field a configurable
2412    option.
2413  </t>
2414</x:note>
2415</section>
2416
2417<section title="User-Agent" anchor="header.user-agent">
2418  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2419  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2420  <x:anchor-alias value="User-Agent"/>
2421  <x:anchor-alias value="User-Agent-v"/>
2422<t>
2423   The "User-Agent" request-header field contains information about the user
2424   agent originating the request. User agents &SHOULD; include this field with
2425   requests.
2426</t>
2427<t>
2428   Typically, it is used for statistical purposes, the tracing of protocol
2429   violations, and tailoring responses to avoid particular user agent
2430   limitations.
2431</t>
2432<t>
2433   The field can contain multiple product tokens (&product-tokens;)
2434   and comments (&header-fields;) identifying the agent and its
2435   significant subproducts. By convention, the product tokens are listed in
2436   order of their significance for identifying the application.
2437</t>
2438<t>
2439   Because this field is usually sent on every request a user agent makes,
2440   implementations are encouraged not to include needlessly fine-grained
2441   detail, and to limit (or even prohibit) the addition of subproducts by third
2442   parties. Overly long and detailed User-Agent field values make requests
2443   larger and can also be used to identify ("fingerprint") the user against
2444   their wishes.
2445</t>
2446<t>
2447   Likewise, implementations are encouraged not to use the product tokens of
2448   other implementations in order to declare compatibility with them, as this
2449   circumvents the purpose of the field. Finally, they are encouraged not to
2450   use comments to identify products; doing so makes the field value more
2451   difficult to parse.
2452</t>
2453<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2454  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2455  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2456                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2457</artwork></figure>
2458<t>
2459   Example:
2460</t>
2461<figure><artwork type="example">
2462  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2463</artwork></figure>
2464</section>
2465
2466</section>
2467
2468<section title="IANA Considerations" anchor="IANA.considerations">
2469
2470<section title="Method Registry" anchor="method.registration">
2471<t>
2472  The registration procedure for HTTP Methods is defined by
2473  <xref target="method.registry"/> of this document.
2474</t>
2475<t>
2476   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2477   and be populated with the registrations below:
2478</t>
2479<?BEGININC p2-semantics.iana-methods ?>
2480<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2481<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2482   <ttcol>Method</ttcol>
2483   <ttcol>Safe</ttcol>
2484   <ttcol>Reference</ttcol>
2485   <c>CONNECT</c>
2486   <c>no</c>
2487   <c>
2488      <xref target="CONNECT"/>
2489   </c>
2490   <c>DELETE</c>
2491   <c>no</c>
2492   <c>
2493      <xref target="DELETE"/>
2494   </c>
2495   <c>GET</c>
2496   <c>yes</c>
2497   <c>
2498      <xref target="GET"/>
2499   </c>
2500   <c>HEAD</c>
2501   <c>yes</c>
2502   <c>
2503      <xref target="HEAD"/>
2504   </c>
2505   <c>OPTIONS</c>
2506   <c>yes</c>
2507   <c>
2508      <xref target="OPTIONS"/>
2509   </c>
2510   <c>POST</c>
2511   <c>no</c>
2512   <c>
2513      <xref target="POST"/>
2514   </c>
2515   <c>PUT</c>
2516   <c>no</c>
2517   <c>
2518      <xref target="PUT"/>
2519   </c>
2520   <c>TRACE</c>
2521   <c>yes</c>
2522   <c>
2523      <xref target="TRACE"/>
2524   </c>
2525</texttable>
2526<!--(END)-->
2527<?ENDINC p2-semantics.iana-methods ?>
2528</section>
2529
2530<section title="Status Code Registry" anchor="status.code.registration">
2531<t>
2532   The registration procedure for HTTP Status Codes -- previously defined
2533   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2534   by <xref target="status.code.registry"/> of this document.
2535</t>
2536<t>
2537   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2538   shall be updated with the registrations below:
2539</t>
2540<?BEGININC p2-semantics.iana-status-codes ?>
2541<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2542<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2543   <ttcol>Value</ttcol>
2544   <ttcol>Description</ttcol>
2545   <ttcol>Reference</ttcol>
2546   <c>100</c>
2547   <c>Continue</c>
2548   <c>
2549      <xref target="status.100"/>
2550   </c>
2551   <c>101</c>
2552   <c>Switching Protocols</c>
2553   <c>
2554      <xref target="status.101"/>
2555   </c>
2556   <c>200</c>
2557   <c>OK</c>
2558   <c>
2559      <xref target="status.200"/>
2560   </c>
2561   <c>201</c>
2562   <c>Created</c>
2563   <c>
2564      <xref target="status.201"/>
2565   </c>
2566   <c>202</c>
2567   <c>Accepted</c>
2568   <c>
2569      <xref target="status.202"/>
2570   </c>
2571   <c>203</c>
2572   <c>Non-Authoritative Information</c>
2573   <c>
2574      <xref target="status.203"/>
2575   </c>
2576   <c>204</c>
2577   <c>No Content</c>
2578   <c>
2579      <xref target="status.204"/>
2580   </c>
2581   <c>205</c>
2582   <c>Reset Content</c>
2583   <c>
2584      <xref target="status.205"/>
2585   </c>
2586   <c>300</c>
2587   <c>Multiple Choices</c>
2588   <c>
2589      <xref target="status.300"/>
2590   </c>
2591   <c>301</c>
2592   <c>Moved Permanently</c>
2593   <c>
2594      <xref target="status.301"/>
2595   </c>
2596   <c>302</c>
2597   <c>Found</c>
2598   <c>
2599      <xref target="status.302"/>
2600   </c>
2601   <c>303</c>
2602   <c>See Other</c>
2603   <c>
2604      <xref target="status.303"/>
2605   </c>
2606   <c>305</c>
2607   <c>Use Proxy</c>
2608   <c>
2609      <xref target="status.305"/>
2610   </c>
2611   <c>306</c>
2612   <c>(Unused)</c>
2613   <c>
2614      <xref target="status.306"/>
2615   </c>
2616   <c>307</c>
2617   <c>Temporary Redirect</c>
2618   <c>
2619      <xref target="status.307"/>
2620   </c>
2621   <c>400</c>
2622   <c>Bad Request</c>
2623   <c>
2624      <xref target="status.400"/>
2625   </c>
2626   <c>402</c>
2627   <c>Payment Required</c>
2628   <c>
2629      <xref target="status.402"/>
2630   </c>
2631   <c>403</c>
2632   <c>Forbidden</c>
2633   <c>
2634      <xref target="status.403"/>
2635   </c>
2636   <c>404</c>
2637   <c>Not Found</c>
2638   <c>
2639      <xref target="status.404"/>
2640   </c>
2641   <c>405</c>
2642   <c>Method Not Allowed</c>
2643   <c>
2644      <xref target="status.405"/>
2645   </c>
2646   <c>406</c>
2647   <c>Not Acceptable</c>
2648   <c>
2649      <xref target="status.406"/>
2650   </c>
2651   <c>407</c>
2652   <c>Proxy Authentication Required</c>
2653   <c>
2654      <xref target="status.407"/>
2655   </c>
2656   <c>408</c>
2657   <c>Request Timeout</c>
2658   <c>
2659      <xref target="status.408"/>
2660   </c>
2661   <c>409</c>
2662   <c>Conflict</c>
2663   <c>
2664      <xref target="status.409"/>
2665   </c>
2666   <c>410</c>
2667   <c>Gone</c>
2668   <c>
2669      <xref target="status.410"/>
2670   </c>
2671   <c>411</c>
2672   <c>Length Required</c>
2673   <c>
2674      <xref target="status.411"/>
2675   </c>
2676   <c>413</c>
2677   <c>Request Entity Too Large</c>
2678   <c>
2679      <xref target="status.413"/>
2680   </c>
2681   <c>414</c>
2682   <c>URI Too Long</c>
2683   <c>
2684      <xref target="status.414"/>
2685   </c>
2686   <c>415</c>
2687   <c>Unsupported Media Type</c>
2688   <c>
2689      <xref target="status.415"/>
2690   </c>
2691   <c>417</c>
2692   <c>Expectation Failed</c>
2693   <c>
2694      <xref target="status.417"/>
2695   </c>
2696   <c>500</c>
2697   <c>Internal Server Error</c>
2698   <c>
2699      <xref target="status.500"/>
2700   </c>
2701   <c>501</c>
2702   <c>Not Implemented</c>
2703   <c>
2704      <xref target="status.501"/>
2705   </c>
2706   <c>502</c>
2707   <c>Bad Gateway</c>
2708   <c>
2709      <xref target="status.502"/>
2710   </c>
2711   <c>503</c>
2712   <c>Service Unavailable</c>
2713   <c>
2714      <xref target="status.503"/>
2715   </c>
2716   <c>504</c>
2717   <c>Gateway Timeout</c>
2718   <c>
2719      <xref target="status.504"/>
2720   </c>
2721   <c>505</c>
2722   <c>HTTP Version Not Supported</c>
2723   <c>
2724      <xref target="status.505"/>
2725   </c>
2726</texttable>
2727<!--(END)-->
2728<?ENDINC p2-semantics.iana-status-codes ?>
2729</section>
2730<section title="Header Field Registration" anchor="header.field.registration">
2731<t>
2732   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2733   with the permanent registrations below (see <xref target="RFC3864"/>):
2734</t>
2735<?BEGININC p2-semantics.iana-headers ?>
2736<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2737<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2738   <ttcol>Header Field Name</ttcol>
2739   <ttcol>Protocol</ttcol>
2740   <ttcol>Status</ttcol>
2741   <ttcol>Reference</ttcol>
2742
2743   <c>Allow</c>
2744   <c>http</c>
2745   <c>standard</c>
2746   <c>
2747      <xref target="header.allow"/>
2748   </c>
2749   <c>Expect</c>
2750   <c>http</c>
2751   <c>standard</c>
2752   <c>
2753      <xref target="header.expect"/>
2754   </c>
2755   <c>From</c>
2756   <c>http</c>
2757   <c>standard</c>
2758   <c>
2759      <xref target="header.from"/>
2760   </c>
2761   <c>Location</c>
2762   <c>http</c>
2763   <c>standard</c>
2764   <c>
2765      <xref target="header.location"/>
2766   </c>
2767   <c>Max-Forwards</c>
2768   <c>http</c>
2769   <c>standard</c>
2770   <c>
2771      <xref target="header.max-forwards"/>
2772   </c>
2773   <c>Referer</c>
2774   <c>http</c>
2775   <c>standard</c>
2776   <c>
2777      <xref target="header.referer"/>
2778   </c>
2779   <c>Retry-After</c>
2780   <c>http</c>
2781   <c>standard</c>
2782   <c>
2783      <xref target="header.retry-after"/>
2784   </c>
2785   <c>Server</c>
2786   <c>http</c>
2787   <c>standard</c>
2788   <c>
2789      <xref target="header.server"/>
2790   </c>
2791   <c>User-Agent</c>
2792   <c>http</c>
2793   <c>standard</c>
2794   <c>
2795      <xref target="header.user-agent"/>
2796   </c>
2797</texttable>
2798<!--(END)-->
2799<?ENDINC p2-semantics.iana-headers ?>
2800<t>
2801   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2802</t>
2803</section>
2804</section>
2805
2806<section title="Security Considerations" anchor="security.considerations">
2807<t>
2808   This section is meant to inform application developers, information
2809   providers, and users of the security limitations in HTTP/1.1 as
2810   described by this document. The discussion does not include
2811   definitive solutions to the problems revealed, though it does make
2812   some suggestions for reducing security risks.
2813</t>
2814
2815<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2816<t>
2817   Like any generic data transfer protocol, HTTP cannot regulate the
2818   content of the data that is transferred, nor is there any a priori
2819   method of determining the sensitivity of any particular piece of
2820   information within the context of any given request. Therefore,
2821   applications &SHOULD; supply as much control over this information as
2822   possible to the provider of that information. Four header fields are
2823   worth special mention in this context: Server, Via, Referer and From.
2824</t>
2825<t>
2826   Revealing the specific software version of the server might allow the
2827   server machine to become more vulnerable to attacks against software
2828   that is known to contain security holes. Implementors &SHOULD; make the
2829   Server header field a configurable option.
2830</t>
2831<t>
2832   Proxies which serve as a portal through a network firewall &SHOULD;
2833   take special precautions regarding the transfer of header information
2834   that identifies the hosts behind the firewall. In particular, they
2835   &SHOULD; remove, or replace with sanitized versions, any Via fields
2836   generated behind the firewall.
2837</t>
2838<t>
2839   The Referer header field allows reading patterns to be studied and reverse
2840   links drawn. Although it can be very useful, its power can be abused
2841   if user details are not separated from the information contained in
2842   the Referer. Even when the personal information has been removed, the
2843   Referer header field might indicate a private document's URI whose
2844   publication would be inappropriate.
2845</t>
2846<t>
2847   The information sent in the From field might conflict with the user's
2848   privacy interests or their site's security policy, and hence it
2849   &SHOULD-NOT;  be transmitted without the user being able to disable,
2850   enable, and modify the contents of the field. The user &MUST; be able
2851   to set the contents of this field within a user preference or
2852   application defaults configuration.
2853</t>
2854<t>
2855   We suggest, though do not require, that a convenient toggle interface
2856   be provided for the user to enable or disable the sending of From and
2857   Referer information.
2858</t>
2859<t>
2860   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2861   target="header.server"/>) header fields can sometimes be used to determine
2862   that a specific client or server have a particular security hole which might
2863   be exploited. Unfortunately, this same information is often used for other
2864   valuable purposes for which HTTP currently has no better mechanism.
2865</t>
2866<t>
2867   Furthermore, the User-Agent header field may contain enough entropy to be
2868   used, possibly in conjunction with other material, to uniquely identify the
2869   user.
2870</t>
2871<t>
2872   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2873   that was sent in request header fields within the body of their response.
2874   Clients &SHOULD; be careful with sensitive information, like Cookies,
2875   Authorization credentials and other header fields that might be used to
2876   collect data from the client.
2877</t> 
2878</section>
2879
2880<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2881<t>
2882   Because the source of a link might be private information or might
2883   reveal an otherwise private information source, it is strongly
2884   recommended that the user be able to select whether or not the
2885   Referer field is sent. For example, a browser client could have a
2886   toggle switch for browsing openly/anonymously, which would
2887   respectively enable/disable the sending of Referer and From
2888   information.
2889</t>
2890<t>
2891   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2892   HTTP request if the referring page was transferred with a secure
2893   protocol.
2894</t>
2895<t>
2896   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2897   sensitive data because that data will be placed in the request-target. Many
2898   existing servers, proxies, and user agents log or display the request-target
2899   in places where it might be visible to third parties. Such services can
2900   use POST-based form submission instead.
2901</t>
2902</section>
2903
2904<section title="Location Headers and Spoofing" anchor="location.spoofing">
2905<t>
2906   If a single server supports multiple organizations that do not trust
2907   one another, then it &MUST; check the values of Location and Content-Location
2908   header fields in responses that are generated under control of
2909   said organizations to make sure that they do not attempt to
2910   invalidate resources over which they have no authority.
2911</t>
2912</section>
2913
2914<section title="Security Considerations for CONNECT">
2915<t>
2916   Since tunneled data is opaque to the proxy, there are additional
2917   risks to tunneling to other well-known or reserved ports.
2918   A HTTP client CONNECTing to port 25 could relay spam
2919   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2920   access to a small number of known ports.
2921</t>
2922</section>
2923
2924</section>
2925
2926<section title="Acknowledgments" anchor="ack">
2927</section>
2928</middle>
2929<back>
2930
2931<references title="Normative References">
2932
2933<reference anchor="Part1">
2934  <front>
2935    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2936    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2937      <organization abbrev="Day Software">Day Software</organization>
2938      <address><email>fielding@gbiv.com</email></address>
2939    </author>
2940    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2941      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2942      <address><email>jg@freedesktop.org</email></address>
2943    </author>
2944    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2945      <organization abbrev="HP">Hewlett-Packard Company</organization>
2946      <address><email>JeffMogul@acm.org</email></address>
2947    </author>
2948    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2949      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2950      <address><email>henrikn@microsoft.com</email></address>
2951    </author>
2952    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2953      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2954      <address><email>LMM@acm.org</email></address>
2955    </author>
2956    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2957      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2958      <address><email>paulle@microsoft.com</email></address>
2959    </author>
2960    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2961      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2962      <address><email>timbl@w3.org</email></address>
2963    </author>
2964    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2965      <organization abbrev="W3C">World Wide Web Consortium</organization>
2966      <address><email>ylafon@w3.org</email></address>
2967    </author>
2968    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2969      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2970      <address><email>julian.reschke@greenbytes.de</email></address>
2971    </author>
2972    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2973  </front>
2974  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2975  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2976</reference>
2977
2978<reference anchor="Part3">
2979  <front>
2980    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2981    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2982      <organization abbrev="Day Software">Day Software</organization>
2983      <address><email>fielding@gbiv.com</email></address>
2984    </author>
2985    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2986      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2987      <address><email>jg@freedesktop.org</email></address>
2988    </author>
2989    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2990      <organization abbrev="HP">Hewlett-Packard Company</organization>
2991      <address><email>JeffMogul@acm.org</email></address>
2992    </author>
2993    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2994      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2995      <address><email>henrikn@microsoft.com</email></address>
2996    </author>
2997    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2998      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2999      <address><email>LMM@acm.org</email></address>
3000    </author>
3001    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3002      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3003      <address><email>paulle@microsoft.com</email></address>
3004    </author>
3005    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3006      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3007      <address><email>timbl@w3.org</email></address>
3008    </author>
3009    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3010      <organization abbrev="W3C">World Wide Web Consortium</organization>
3011      <address><email>ylafon@w3.org</email></address>
3012    </author>
3013    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3014      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3015      <address><email>julian.reschke@greenbytes.de</email></address>
3016    </author>
3017    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3018  </front>
3019  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3020  <x:source href="p3-payload.xml" basename="p3-payload"/>
3021</reference>
3022
3023<reference anchor="Part4">
3024  <front>
3025    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3026    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3027      <organization abbrev="Day Software">Day Software</organization>
3028      <address><email>fielding@gbiv.com</email></address>
3029    </author>
3030    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3031      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3032      <address><email>jg@freedesktop.org</email></address>
3033    </author>
3034    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3035      <organization abbrev="HP">Hewlett-Packard Company</organization>
3036      <address><email>JeffMogul@acm.org</email></address>
3037    </author>
3038    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3039      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3040      <address><email>henrikn@microsoft.com</email></address>
3041    </author>
3042    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3043      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3044      <address><email>LMM@acm.org</email></address>
3045    </author>
3046    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3047      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3048      <address><email>paulle@microsoft.com</email></address>
3049    </author>
3050    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3051      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3052      <address><email>timbl@w3.org</email></address>
3053    </author>
3054    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3055      <organization abbrev="W3C">World Wide Web Consortium</organization>
3056      <address><email>ylafon@w3.org</email></address>
3057    </author>
3058    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3059      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3060      <address><email>julian.reschke@greenbytes.de</email></address>
3061    </author>
3062    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3063  </front>
3064  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3065  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3066</reference>
3067
3068<reference anchor="Part5">
3069  <front>
3070    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3071    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3072      <organization abbrev="Day Software">Day Software</organization>
3073      <address><email>fielding@gbiv.com</email></address>
3074    </author>
3075    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3076      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3077      <address><email>jg@freedesktop.org</email></address>
3078    </author>
3079    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3080      <organization abbrev="HP">Hewlett-Packard Company</organization>
3081      <address><email>JeffMogul@acm.org</email></address>
3082    </author>
3083    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3084      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3085      <address><email>henrikn@microsoft.com</email></address>
3086    </author>
3087    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3088      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3089      <address><email>LMM@acm.org</email></address>
3090    </author>
3091    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3092      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3093      <address><email>paulle@microsoft.com</email></address>
3094    </author>
3095    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3096      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3097      <address><email>timbl@w3.org</email></address>
3098    </author>
3099    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3100      <organization abbrev="W3C">World Wide Web Consortium</organization>
3101      <address><email>ylafon@w3.org</email></address>
3102    </author>
3103    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3104      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3105      <address><email>julian.reschke@greenbytes.de</email></address>
3106    </author>
3107    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3108  </front>
3109  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3110  <x:source href="p5-range.xml" basename="p5-range"/>
3111</reference>
3112
3113<reference anchor="Part6">
3114  <front>
3115    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3116    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3117      <organization abbrev="Day Software">Day Software</organization>
3118      <address><email>fielding@gbiv.com</email></address>
3119    </author>
3120    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3121      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3122      <address><email>jg@freedesktop.org</email></address>
3123    </author>
3124    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3125      <organization abbrev="HP">Hewlett-Packard Company</organization>
3126      <address><email>JeffMogul@acm.org</email></address>
3127    </author>
3128    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3129      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3130      <address><email>henrikn@microsoft.com</email></address>
3131    </author>
3132    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3133      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3134      <address><email>LMM@acm.org</email></address>
3135    </author>
3136    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3137      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3138      <address><email>paulle@microsoft.com</email></address>
3139    </author>
3140    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3141      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3142      <address><email>timbl@w3.org</email></address>
3143    </author>
3144    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3145      <organization abbrev="W3C">World Wide Web Consortium</organization>
3146      <address><email>ylafon@w3.org</email></address>
3147    </author>
3148    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3149      <address><email>mnot@mnot.net</email></address>
3150    </author>
3151    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3152      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3153      <address><email>julian.reschke@greenbytes.de</email></address>
3154    </author>
3155    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3156  </front>
3157  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3158  <x:source href="p6-cache.xml" basename="p6-cache"/>
3159</reference>
3160
3161<reference anchor="Part7">
3162  <front>
3163    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3164    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3165      <organization abbrev="Day Software">Day Software</organization>
3166      <address><email>fielding@gbiv.com</email></address>
3167    </author>
3168    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3169      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3170      <address><email>jg@freedesktop.org</email></address>
3171    </author>
3172    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3173      <organization abbrev="HP">Hewlett-Packard Company</organization>
3174      <address><email>JeffMogul@acm.org</email></address>
3175    </author>
3176    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3177      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3178      <address><email>henrikn@microsoft.com</email></address>
3179    </author>
3180    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3181      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3182      <address><email>LMM@acm.org</email></address>
3183    </author>
3184    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3185      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3186      <address><email>paulle@microsoft.com</email></address>
3187    </author>
3188    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3189      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3190      <address><email>timbl@w3.org</email></address>
3191    </author>
3192    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3193      <organization abbrev="W3C">World Wide Web Consortium</organization>
3194      <address><email>ylafon@w3.org</email></address>
3195    </author>
3196    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3197      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3198      <address><email>julian.reschke@greenbytes.de</email></address>
3199    </author>
3200    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3201  </front>
3202  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3203  <x:source href="p7-auth.xml" basename="p7-auth"/>
3204</reference>
3205
3206<reference anchor="RFC2119">
3207  <front>
3208    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3209    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3210      <organization>Harvard University</organization>
3211      <address><email>sob@harvard.edu</email></address>
3212    </author>
3213    <date month="March" year="1997"/>
3214  </front>
3215  <seriesInfo name="BCP" value="14"/>
3216  <seriesInfo name="RFC" value="2119"/>
3217</reference>
3218
3219<reference anchor="RFC3986">
3220 <front>
3221  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3222  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3223    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3224    <address>
3225       <email>timbl@w3.org</email>
3226       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3227    </address>
3228  </author>
3229  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3230    <organization abbrev="Day Software">Day Software</organization>
3231    <address>
3232      <email>fielding@gbiv.com</email>
3233      <uri>http://roy.gbiv.com/</uri>
3234    </address>
3235  </author>
3236  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3237    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3238    <address>
3239      <email>LMM@acm.org</email>
3240      <uri>http://larry.masinter.net/</uri>
3241    </address>
3242  </author>
3243  <date month='January' year='2005'></date>
3244 </front>
3245 <seriesInfo name="STD" value="66"/>
3246 <seriesInfo name="RFC" value="3986"/>
3247</reference>
3248
3249<reference anchor="RFC5234">
3250  <front>
3251    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3252    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3253      <organization>Brandenburg InternetWorking</organization>
3254      <address>
3255        <email>dcrocker@bbiw.net</email>
3256      </address> 
3257    </author>
3258    <author initials="P." surname="Overell" fullname="Paul Overell">
3259      <organization>THUS plc.</organization>
3260      <address>
3261        <email>paul.overell@thus.net</email>
3262      </address>
3263    </author>
3264    <date month="January" year="2008"/>
3265  </front>
3266  <seriesInfo name="STD" value="68"/>
3267  <seriesInfo name="RFC" value="5234"/>
3268</reference>
3269
3270</references>
3271
3272<references title="Informative References">
3273
3274<reference anchor="RFC1945">
3275  <front>
3276    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3277    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3278      <organization>MIT, Laboratory for Computer Science</organization>
3279      <address><email>timbl@w3.org</email></address>
3280    </author>
3281    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3282      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3283      <address><email>fielding@ics.uci.edu</email></address>
3284    </author>
3285    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3286      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3287      <address><email>frystyk@w3.org</email></address>
3288    </author>
3289    <date month="May" year="1996"/>
3290  </front>
3291  <seriesInfo name="RFC" value="1945"/>
3292</reference>
3293
3294<reference anchor="RFC2068">
3295  <front>
3296    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3297    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3298      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3299      <address><email>fielding@ics.uci.edu</email></address>
3300    </author>
3301    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3302      <organization>MIT Laboratory for Computer Science</organization>
3303      <address><email>jg@w3.org</email></address>
3304    </author>
3305    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3306      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3307      <address><email>mogul@wrl.dec.com</email></address>
3308    </author>
3309    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3310      <organization>MIT Laboratory for Computer Science</organization>
3311      <address><email>frystyk@w3.org</email></address>
3312    </author>
3313    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3314      <organization>MIT Laboratory for Computer Science</organization>
3315      <address><email>timbl@w3.org</email></address>
3316    </author>
3317    <date month="January" year="1997"/>
3318  </front>
3319  <seriesInfo name="RFC" value="2068"/>
3320</reference>
3321
3322<reference anchor="RFC2616">
3323  <front>
3324    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3325    <author initials="R." surname="Fielding" fullname="R. Fielding">
3326      <organization>University of California, Irvine</organization>
3327      <address><email>fielding@ics.uci.edu</email></address>
3328    </author>
3329    <author initials="J." surname="Gettys" fullname="J. Gettys">
3330      <organization>W3C</organization>
3331      <address><email>jg@w3.org</email></address>
3332    </author>
3333    <author initials="J." surname="Mogul" fullname="J. Mogul">
3334      <organization>Compaq Computer Corporation</organization>
3335      <address><email>mogul@wrl.dec.com</email></address>
3336    </author>
3337    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3338      <organization>MIT Laboratory for Computer Science</organization>
3339      <address><email>frystyk@w3.org</email></address>
3340    </author>
3341    <author initials="L." surname="Masinter" fullname="L. Masinter">
3342      <organization>Xerox Corporation</organization>
3343      <address><email>masinter@parc.xerox.com</email></address>
3344    </author>
3345    <author initials="P." surname="Leach" fullname="P. Leach">
3346      <organization>Microsoft Corporation</organization>
3347      <address><email>paulle@microsoft.com</email></address>
3348    </author>
3349    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3350      <organization>W3C</organization>
3351      <address><email>timbl@w3.org</email></address>
3352    </author>
3353    <date month="June" year="1999"/>
3354  </front>
3355  <seriesInfo name="RFC" value="2616"/>
3356</reference>
3357
3358<reference anchor='RFC2817'>
3359  <front>
3360    <title>Upgrading to TLS Within HTTP/1.1</title>
3361    <author initials='R.' surname='Khare' fullname='R. Khare'>
3362      <organization>4K Associates / UC Irvine</organization>
3363      <address><email>rohit@4K-associates.com</email></address>
3364    </author>
3365    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3366      <organization>Agranat Systems, Inc.</organization>
3367      <address><email>lawrence@agranat.com</email></address>
3368    </author>
3369    <date year='2000' month='May' />
3370  </front>
3371  <seriesInfo name='RFC' value='2817' />
3372</reference>
3373
3374<reference anchor='RFC3864'>
3375  <front>
3376    <title>Registration Procedures for Message Header Fields</title>
3377    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3378      <organization>Nine by Nine</organization>
3379      <address><email>GK-IETF@ninebynine.org</email></address>
3380    </author>
3381    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3382      <organization>BEA Systems</organization>
3383      <address><email>mnot@pobox.com</email></address>
3384    </author>
3385    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3386      <organization>HP Labs</organization>
3387      <address><email>JeffMogul@acm.org</email></address>
3388    </author>
3389    <date year='2004' month='September' />
3390  </front>
3391  <seriesInfo name='BCP' value='90' />
3392  <seriesInfo name='RFC' value='3864' />
3393</reference>
3394
3395<reference anchor='RFC5226'>
3396  <front>
3397    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3398    <author initials='T.' surname='Narten' fullname='T. Narten'>
3399      <organization>IBM</organization>
3400      <address><email>narten@us.ibm.com</email></address>
3401    </author>
3402    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3403      <organization>Google</organization>
3404      <address><email>Harald@Alvestrand.no</email></address>
3405    </author>
3406    <date year='2008' month='May' />
3407  </front>
3408  <seriesInfo name='BCP' value='26' />
3409  <seriesInfo name='RFC' value='5226' />
3410</reference>
3411
3412<reference anchor="RFC5322">
3413  <front>
3414    <title>Internet Message Format</title>
3415    <author initials="P." surname="Resnick" fullname="P. Resnick">
3416      <organization>Qualcomm Incorporated</organization>
3417    </author>
3418    <date year="2008" month="October"/>
3419  </front> 
3420  <seriesInfo name="RFC" value="5322"/>
3421</reference>
3422
3423</references>
3424
3425<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3426<t>
3427  This document takes over the Status Code Registry, previously defined
3428  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3429  (<xref target="status.code.registry"/>)
3430</t>
3431<t>
3432  Clarify definition of POST.
3433  (<xref target="POST"/>)
3434</t>
3435<t>
3436  Failed to consider that there are
3437  many other request methods that are safe to automatically redirect,
3438  and further that the user agent is able to make that determination
3439  based on the request method semantics.
3440  (Sections <xref format="counter" target="status.301"/>,
3441  <xref format="counter" target="status.302"/> and
3442  <xref format="counter" target="status.307"/>)
3443</t>
3444<t>
3445  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3446  It used to indicate that the target resource must be accessed through the
3447  proxy given by the Location field. The Location field gave the URI of the
3448  proxy. The recipient was expected to repeat this single request via the proxy.
3449  (<xref target="status.305"/>)
3450</t>
3451<t>
3452  Reclassify "Allow" as response header field, removing the option to
3453  specify it in a PUT request.
3454  Relax the server requirement on the contents of the Allow header field and
3455  remove requirement on clients to always trust the header field value.
3456  (<xref target="header.allow"/>)
3457</t>
3458<t>
3459  Correct syntax of Location header field to allow URI references (including
3460  relative references and fragments), as referred symbol "absoluteURI" wasn't
3461  what was expected, and add some clarifications as to when use of fragments
3462  would not be appropriate.
3463  (<xref target="header.location"/>)
3464</t>
3465<t>
3466  Allow Referer field value of "about:blank" as alternative to not specifying it.
3467  (<xref target="header.referer"/>)
3468</t>
3469<t>
3470  In the description of the Server header field, the Via field
3471  was described as a SHOULD. The requirement was and is stated
3472  correctly in the description of the Via header field in &header-via;.
3473  (<xref target="header.server"/>)
3474</t>
3475</section>
3476
3477<?BEGININC p2-semantics.abnf-appendix ?>
3478<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3479<figure>
3480<artwork type="abnf" name="p2-semantics.parsed-abnf">
3481<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3482<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3483<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3484<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3485<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3486<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3487<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3488<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3489<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3490
3491<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3492<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3493<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3494
3495<x:ref>From</x:ref> = "From:" OWS From-v
3496<x:ref>From-v</x:ref> = mailbox
3497
3498<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3499<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3500
3501<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3502If-Modified-Since =
3503 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3504<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3505<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3506If-Unmodified-Since =
3507 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3508
3509<x:ref>Location</x:ref> = "Location:" OWS Location-v
3510<x:ref>Location-v</x:ref> = URI-reference
3511
3512<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3513<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3514<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3515 / %x47.45.54 ; GET
3516 / %x48.45.41.44 ; HEAD
3517 / %x50.4F.53.54 ; POST
3518 / %x50.55.54 ; PUT
3519 / %x44.45.4C.45.54.45 ; DELETE
3520 / %x54.52.41.43.45 ; TRACE
3521 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3522 / extension-method
3523
3524<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3525
3526Proxy-Authenticate =
3527 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3528Proxy-Authorization =
3529 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3530
3531<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3532<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3533<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3534<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3535<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3536<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3537<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3538
3539<x:ref>Server</x:ref> = "Server:" OWS Server-v
3540<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3541<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3542 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3543 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3544 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3545 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3546 "505" / extension-code
3547
3548<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3549
3550<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3551<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3552<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3553
3554<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3555
3556WWW-Authenticate =
3557 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3558
3559<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3560authority = &lt;authority, defined in [Part1], Section 2.6&gt;
3561
3562<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3563
3564<x:ref>delta-seconds</x:ref> = 1*DIGIT
3565
3566<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3567<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3568<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3569 *expect-params ]
3570<x:ref>extension-code</x:ref> = 3DIGIT
3571<x:ref>extension-method</x:ref> = token
3572
3573<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3574
3575<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3576
3577<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3578<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3579
3580<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3581
3582<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3583 Accept-Language / Authorization / Expect / From / Host / If-Match /
3584 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3585 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3586 User-Agent
3587<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3588 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3589
3590<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3591</artwork>
3592</figure>
3593<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3594; Reason-Phrase defined but not used
3595; Status-Code defined but not used
3596; authority defined but not used
3597; request-header defined but not used
3598; response-header defined but not used
3599</artwork></figure></section>
3600<?ENDINC p2-semantics.abnf-appendix ?>
3601
3602<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3603
3604<section title="Since RFC 2616">
3605<t>
3606  Extracted relevant partitions from <xref target="RFC2616"/>.
3607</t>
3608</section>
3609
3610<section title="Since draft-ietf-httpbis-p2-semantics-00">
3611<t>
3612  Closed issues:
3613  <list style="symbols"> 
3614    <t>
3615      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3616      "Via is a MUST"
3617      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3618    </t>
3619    <t>
3620      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3621      "Fragments allowed in Location"
3622      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3623    </t>
3624    <t>
3625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3626      "Safe Methods vs Redirection"
3627      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3628    </t>
3629    <t>
3630      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3631      "Revise description of the POST method"
3632      (<eref target="http://purl.org/NET/http-errata#post"/>)
3633    </t>
3634    <t>
3635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3636      "Normative and Informative references"
3637    </t>
3638    <t>
3639      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3640      "RFC2606 Compliance"
3641    </t>
3642    <t>
3643      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3644      "Informative references"
3645    </t>
3646    <t>
3647      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3648      "Redundant cross-references"
3649    </t>
3650  </list>
3651</t>
3652<t>
3653  Other changes:
3654  <list style="symbols"> 
3655    <t>
3656      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3657    </t>
3658  </list>
3659</t>
3660</section>
3661
3662<section title="Since draft-ietf-httpbis-p2-semantics-01">
3663<t>
3664  Closed issues:
3665  <list style="symbols"> 
3666    <t>
3667      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3668      "PUT side effects"
3669    </t>
3670    <t>
3671      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3672      "Duplicate Host header requirements"
3673    </t>
3674  </list>
3675</t>
3676<t>
3677  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3678  <list style="symbols"> 
3679    <t>
3680      Move "Product Tokens" section (back) into Part 1, as "token" is used
3681      in the definition of the Upgrade header field.
3682    </t>
3683    <t>
3684      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3685    </t>
3686    <t>
3687      Copy definition of delta-seconds from Part6 instead of referencing it.
3688    </t>
3689  </list>
3690</t>
3691</section>
3692
3693<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3694<t>
3695  Closed issues:
3696  <list style="symbols"> 
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3699      "Requiring Allow in 405 responses"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3703      "Status Code Registry"
3704    </t>
3705    <t>
3706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3707      "Redirection vs. Location"
3708    </t>
3709    <t>
3710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3711      "Cacheability of 303 response"
3712    </t>
3713    <t>
3714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3715      "305 Use Proxy"
3716    </t>
3717    <t>
3718      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3719      "Classification for Allow header"
3720    </t>
3721    <t>
3722      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3723      "PUT - 'store under' vs 'store at'"
3724    </t>
3725  </list>
3726</t>
3727<t>
3728  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3729  <list style="symbols"> 
3730    <t>
3731      Reference RFC 3984, and update header field registrations for headers defined
3732      in this document.
3733    </t>
3734  </list>
3735</t>
3736<t>
3737  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3738  <list style="symbols"> 
3739    <t>
3740      Replace string literals when the string really is case-sensitive (method).
3741    </t>
3742  </list>
3743</t>
3744</section>
3745
3746<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3747<t>
3748  Closed issues:
3749  <list style="symbols"> 
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3752      "OPTIONS request bodies"
3753    </t>
3754    <t>
3755      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3756      "Description of CONNECT should refer to RFC2817"
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3760      "Location Content-Location reference request/response mixup"
3761    </t>
3762  </list>
3763</t>
3764<t>
3765  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3766  <list style="symbols"> 
3767    <t>
3768      Added initial proposal for registration process, plus initial
3769      content (non-HTTP/1.1 methods to be added by a separate specification).
3770    </t>
3771  </list>
3772</t>
3773</section>
3774
3775<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3776<t>
3777  Closed issues:
3778  <list style="symbols"> 
3779    <t>
3780      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3781      "Content-*"
3782    </t>
3783    <t>
3784      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3785      "RFC 2822 is updated by RFC 5322"
3786    </t>
3787  </list>
3788</t>
3789<t>
3790  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3791  <list style="symbols"> 
3792    <t>
3793      Use "/" instead of "|" for alternatives.
3794    </t>
3795    <t>
3796      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3797      whitespace ("OWS") and required whitespace ("RWS").
3798    </t>
3799    <t>
3800      Rewrite ABNFs to spell out whitespace rules, factor out
3801      header field value format definitions.
3802    </t>
3803  </list>
3804</t>
3805</section>
3806
3807<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3808<t>
3809  Closed issues:
3810  <list style="symbols"> 
3811    <t>
3812      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3813      "Reason-Phrase BNF"
3814    </t>
3815  </list>
3816</t>
3817<t>
3818  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3819  <list style="symbols"> 
3820    <t>
3821      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3822    </t>
3823  </list>
3824</t>
3825</section>
3826
3827<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3828<t>
3829  Closed issues:
3830  <list style="symbols"> 
3831    <t>
3832      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3833      "Clarify when Referer is sent"
3834    </t>
3835    <t>
3836      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3837      "status codes vs methods"
3838    </t>
3839    <t>
3840      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3841      "Do not require "updates" relation for specs that register status codes or method names"
3842    </t>
3843  </list>
3844</t>
3845</section>
3846
3847<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3848<t>
3849  Closed issues:
3850  <list style="symbols"> 
3851    <t>
3852      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3853      "Idempotency"
3854    </t>
3855    <t>
3856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3857      "TRACE security considerations"
3858    </t>
3859    <t>
3860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3861      "Clarify rules for determining what entities a response carries"
3862    </t>
3863    <t>
3864      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3865      "update note citing RFC 1945 and 2068"
3866    </t>
3867    <t>
3868      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3869      "update note about redirect limit"
3870    </t>
3871    <t>
3872      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3873      "Location header ABNF should use 'URI'"
3874    </t>
3875    <t>
3876      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3877      "fragments in Location vs status 303"
3878    </t>
3879    <t>
3880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3881      "move IANA registrations for optional status codes"
3882    </t>
3883  </list>
3884</t>
3885<t>
3886  Partly resolved issues:
3887  <list style="symbols"> 
3888    <t>
3889      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3890      "Are OPTIONS and TRACE safe?"
3891    </t>
3892  </list>
3893</t>
3894</section>
3895
3896<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3897<t>
3898  Closed issues:
3899  <list style="symbols"> 
3900    <t>
3901      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3902      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3903      status codes when fixing this previously)
3904    </t>
3905  </list>
3906</t>
3907</section>
3908
3909<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3910<t>
3911  Closed issues:
3912  <list style="symbols"> 
3913    <t>
3914      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3915      "Fragment combination / precedence during redirects"
3916    </t>
3917  </list>
3918</t>
3919<t>
3920  Partly resolved issues:
3921  <list style="symbols"> 
3922    <t>
3923      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3924      "Location header payload handling"
3925    </t>
3926    <t>
3927      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3928      "Term for the requested resource's URI"
3929    </t>
3930  </list>
3931</t>
3932</section>
3933
3934<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3935<t>
3936  Closed issues:
3937  <list style="symbols"> 
3938    <t>
3939      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3940      "Clarify 'Requested Variant'"
3941    </t>
3942    <t>
3943      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3944      "Clarify entity / representation / variant terminology"
3945    </t>
3946    <t>
3947      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3948      "Methods and Caching"
3949    </t>
3950    <t>
3951      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3952      "OPTIONS vs Max-Forwards"
3953    </t>
3954    <t>
3955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3956      "Status codes and caching"
3957    </t>
3958    <t>
3959      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3960      "consider removing the 'changes from 2068' sections"
3961    </t>
3962  </list>
3963</t>
3964</section>
3965
3966<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3967<t>
3968  Closed issues:
3969  <list style="symbols"> 
3970    <t>
3971      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
3972      "Considerations for new status codes"
3973    </t>
3974    <t>
3975      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
3976      "Considerations for new methods"
3977    </t>
3978    <t>
3979      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
3980      "User-Agent guidelines" (relating to the 'User-Agent' header field)
3981    </t>
3982  </list>
3983</t>
3984</section>
3985
3986<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
3987<t>
3988  Closed issues:
3989  <list style="symbols"> 
3990    <t>
3991      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
3992      "205 Bodies"
3993    </t>
3994    <t>
3995      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
3996      "Migrate CONNECT from RFC2817 to p2"
3997    </t>
3998  </list>
3999</t>
4000</section>
4001
4002</section>
4003
4004</back>
4005</rfc>
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