source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1103

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Upgrade to latest version of rfc2629.xslt and xml2rfc.tcl; bump up document dates

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "February">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80]>
81<?rfc toc="yes" ?>
82<?rfc symrefs="yes" ?>
83<?rfc sortrefs="yes" ?>
84<?rfc compact="yes"?>
85<?rfc subcompact="no" ?>
86<?rfc linkmailto="no" ?>
87<?rfc editing="no" ?>
88<?rfc comments="yes"?>
89<?rfc inline="yes"?>
90<?rfc rfcedstyle="yes"?>
91<?rfc-ext allow-markup-in-artwork="yes" ?>
92<?rfc-ext include-references-in-index="yes" ?>
93<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
94     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
95     xmlns:x='http://purl.org/net/xml2rfc/ext'
96     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
97<front>
98
99  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
100
101  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
102    <organization abbrev="Day Software">Day Software</organization>
103    <address>
104      <postal>
105        <street>23 Corporate Plaza DR, Suite 280</street>
106        <city>Newport Beach</city>
107        <region>CA</region>
108        <code>92660</code>
109        <country>USA</country>
110      </postal>
111      <phone>+1-949-706-5300</phone>
112      <facsimile>+1-949-706-5305</facsimile>
113      <email>fielding@gbiv.com</email>
114      <uri>http://roy.gbiv.com/</uri>
115    </address>
116  </author>
117
118  <author initials="J." surname="Gettys" fullname="Jim Gettys">
119    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
120    <address>
121      <postal>
122        <street>21 Oak Knoll Road</street>
123        <city>Carlisle</city>
124        <region>MA</region>
125        <code>01741</code>
126        <country>USA</country>
127      </postal>
128      <email>jg@freedesktop.org</email>
129      <uri>http://gettys.wordpress.com/</uri>
130    </address>
131  </author>
132 
133  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
134    <organization abbrev="HP">Hewlett-Packard Company</organization>
135    <address>
136      <postal>
137        <street>HP Labs, Large Scale Systems Group</street>
138        <street>1501 Page Mill Road, MS 1177</street>
139        <city>Palo Alto</city>
140        <region>CA</region>
141        <code>94304</code>
142        <country>USA</country>
143      </postal>
144      <email>JeffMogul@acm.org</email>
145    </address>
146  </author>
147
148  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
149    <organization abbrev="Microsoft">Microsoft Corporation</organization>
150    <address>
151      <postal>
152        <street>1 Microsoft Way</street>
153        <city>Redmond</city>
154        <region>WA</region>
155        <code>98052</code>
156        <country>USA</country>
157      </postal>
158      <email>henrikn@microsoft.com</email>
159    </address>
160  </author>
161
162  <author initials="L." surname="Masinter" fullname="Larry Masinter">
163    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
164    <address>
165      <postal>
166        <street>345 Park Ave</street>
167        <city>San Jose</city>
168        <region>CA</region>
169        <code>95110</code>
170        <country>USA</country>
171      </postal>
172      <email>LMM@acm.org</email>
173      <uri>http://larry.masinter.net/</uri>
174    </address>
175  </author>
176 
177  <author initials="P." surname="Leach" fullname="Paul J. Leach">
178    <organization abbrev="Microsoft">Microsoft Corporation</organization>
179    <address>
180      <postal>
181        <street>1 Microsoft Way</street>
182        <city>Redmond</city>
183        <region>WA</region>
184        <code>98052</code>
185      </postal>
186      <email>paulle@microsoft.com</email>
187    </address>
188  </author>
189   
190  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
191    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
195        <street>The Stata Center, Building 32</street>
196        <street>32 Vassar Street</street>
197        <city>Cambridge</city>
198        <region>MA</region>
199        <code>02139</code>
200        <country>USA</country>
201      </postal>
202      <email>timbl@w3.org</email>
203      <uri>http://www.w3.org/People/Berners-Lee/</uri>
204    </address>
205  </author>
206
207  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
208    <organization abbrev="W3C">World Wide Web Consortium</organization>
209    <address>
210      <postal>
211        <street>W3C / ERCIM</street>
212        <street>2004, rte des Lucioles</street>
213        <city>Sophia-Antipolis</city>
214        <region>AM</region>
215        <code>06902</code>
216        <country>France</country>
217      </postal>
218      <email>ylafon@w3.org</email>
219      <uri>http://www.raubacapeu.net/people/yves/</uri>
220    </address>
221  </author>
222
223  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
224    <organization abbrev="greenbytes">greenbytes GmbH</organization>
225    <address>
226      <postal>
227        <street>Hafenweg 16</street>
228        <city>Muenster</city><region>NW</region><code>48155</code>
229        <country>Germany</country>
230      </postal>
231      <phone>+49 251 2807760</phone>
232      <facsimile>+49 251 2807761</facsimile>
233      <email>julian.reschke@greenbytes.de</email>
234      <uri>http://greenbytes.de/tech/webdav/</uri>
235    </address>
236  </author>
237
238  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
239  <workgroup>HTTPbis Working Group</workgroup>
240
241<abstract>
242<t>
243   The Hypertext Transfer Protocol (HTTP) is an application-level
244   protocol for distributed, collaborative, hypermedia information
245   systems. HTTP has been in use by the World Wide Web global information
246   initiative since 1990. This document is Part 2 of the seven-part specification
247   that defines the protocol referred to as "HTTP/1.1" and, taken together,
248   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
249   as expressed by request methods, request-header fields, response status codes,
250   and response-header fields.
251</t>
252</abstract>
253
254<note title="Editorial Note (To be removed by RFC Editor)">
255  <t>
256    Discussion of this draft should take place on the HTTPBIS working group
257    mailing list (ietf-http-wg@w3.org). The current issues list is
258    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
259    and related documents (including fancy diffs) can be found at
260    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
261  </t>
262  <t>
263    The changes in this draft are summarized in <xref target="changes.since.12"/>.
264  </t>
265</note>
266</front>
267<middle>
268<section title="Introduction" anchor="introduction">
269<t>
270   This document defines HTTP/1.1 request and response semantics.  Each HTTP
271   message, as defined in &messaging;, is in the form of either a request or
272   a response.  An HTTP server listens on a connection for HTTP requests and
273   responds to each request, in the order received on that connection, with
274   one or more HTTP response messages.  This document defines the commonly
275   agreed upon semantics of the HTTP uniform interface, the intentions defined
276   by each request method, and the various response messages that might be
277   expected as a result of applying that method to the target resource.
278</t>
279<t>
280   This document is currently disorganized in order to minimize the changes
281   between drafts and enable reviewers to see the smaller errata changes.
282   A future draft will reorganize the sections to better reflect the content.
283   In particular, the sections will be ordered according to the typical
284   processing of an HTTP request message (after message parsing): resource
285   mapping, general header fields, methods, request modifiers, response
286   status, and resource metadata.  The current mess reflects how widely
287   dispersed these topics and associated requirements had become in
288   <xref target="RFC2616"/>.
289</t>
290
291<section title="Requirements" anchor="intro.requirements">
292<t>
293   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
294   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
295   document are to be interpreted as described in <xref target="RFC2119"/>.
296</t>
297<t>
298   An implementation is not compliant if it fails to satisfy one or more
299   of the "MUST" or "REQUIRED" level requirements for the protocols it
300   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
301   level and all the "SHOULD" level requirements for its protocols is said
302   to be "unconditionally compliant"; one that satisfies all the "MUST"
303   level requirements but not all the "SHOULD" level requirements for its
304   protocols is said to be "conditionally compliant".
305</t>
306</section>
307
308<section title="Syntax Notation" anchor="notation">
309  <x:anchor-alias value="CR"/>
310  <x:anchor-alias value="DIGIT"/>
311  <x:anchor-alias value="LF"/>
312  <x:anchor-alias value="VCHAR"/>
313  <x:anchor-alias value="WSP"/>
314<t>
315  This specification uses the ABNF syntax defined in &notation; (which
316  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
317  <xref target="collected.abnf"/> shows the collected ABNF, with the list
318  rule expanded.
319</t>
320<t>
321  The following core rules are included by
322  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
323  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
324  DIGIT (decimal 0-9), DQUOTE (double quote),
325  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
326  OCTET (any 8-bit sequence of data), SP (space),
327  VCHAR (any visible USASCII character),
328  and WSP (whitespace).
329</t>
330
331<section title="Core Rules" anchor="core.rules">
332  <x:anchor-alias value="obs-text"/>
333  <x:anchor-alias value="quoted-string"/>
334  <x:anchor-alias value="token"/>
335  <x:anchor-alias value="OWS"/>
336  <x:anchor-alias value="RWS"/>
337<t>
338  The core rules below are defined in &basic-rules;:
339</t>
340<figure><artwork type="abnf2616">
341  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
342  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
343  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
344  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
345  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
346</artwork></figure>
347</section>
348
349<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
350  <x:anchor-alias value="absolute-URI"/>
351  <x:anchor-alias value="Accept"/>
352  <x:anchor-alias value="Accept-Charset"/>
353  <x:anchor-alias value="Accept-Encoding"/>
354  <x:anchor-alias value="Accept-Language"/>
355  <x:anchor-alias value="Accept-Ranges"/>
356  <x:anchor-alias value="Age"/>
357  <x:anchor-alias value="Authorization"/>
358  <x:anchor-alias value="comment"/>
359  <x:anchor-alias value="ETag"/>
360  <x:anchor-alias value="Host"/>
361  <x:anchor-alias value="HTTP-date"/>
362  <x:anchor-alias value="If-Match"/>
363  <x:anchor-alias value="If-Modified-Since"/>
364  <x:anchor-alias value="If-None-Match"/>
365  <x:anchor-alias value="If-Range"/>
366  <x:anchor-alias value="If-Unmodified-Since"/>
367  <x:anchor-alias value="partial-URI"/>
368  <x:anchor-alias value="product"/>
369  <x:anchor-alias value="Proxy-Authenticate"/>
370  <x:anchor-alias value="Proxy-Authorization"/>
371  <x:anchor-alias value="Range"/>
372  <x:anchor-alias value="TE"/>
373  <x:anchor-alias value="URI-reference"/>
374  <x:anchor-alias value="Vary"/>
375  <x:anchor-alias value="WWW-Authenticate"/>
376<t>
377  The ABNF rules below are defined in other parts:
378</t>
379<figure><!--Part1--><artwork type="abnf2616">
380  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, 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 &mdash; 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     / "426"  ; <xref target="status.426"/>: Upgrade Required
616     / "500"  ; <xref target="status.500"/>: Internal Server Error
617     / "501"  ; <xref target="status.501"/>: Not Implemented
618     / "502"  ; <xref target="status.502"/>: Bad Gateway
619     / "503"  ; <xref target="status.503"/>: Service Unavailable
620     / "504"  ; <xref target="status.504"/>: Gateway Time-out
621     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
622     / <x:ref>extension-code</x:ref>
623
624  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
625  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
626</artwork></figure>
627<t>
628   HTTP status codes are extensible. HTTP applications are not required
629   to understand the meaning of all registered status codes, though such
630   understanding is obviously desirable. However, applications &MUST;
631   understand the class of any status code, as indicated by the first
632   digit, and treat any unrecognized response as being equivalent to the
633   x00 status code of that class, with the exception that an
634   unrecognized response &MUST-NOT; be cached. For example, if an
635   unrecognized status code of 431 is received by the client, it can
636   safely assume that there was something wrong with its request and
637   treat the response as if it had received a 400 status code. In such
638   cases, user agents &SHOULD; present to the user the representation enclosed
639   with the response, since that representation is likely to include human-readable
640   information which will explain the unusual status.
641</t>
642
643<section title="Status Code Registry" anchor="status.code.registry">
644<t>
645  The HTTP Status Code Registry defines the name space for the Status-Code
646  token in the Status-Line of an HTTP response.
647</t>
648<t>
649  Values to be added to this name space are subject to IETF review
650  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
651</t>
652<t>
653  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
654</t>
655
656<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
657<t>
658   When it is necessary to express new semantics for a HTTP response that
659   aren't specific to a single application or media type, and currently defined
660   status codes are inadequate, a new status code can be registered.
661</t>
662<t>
663   HTTP status codes are generic; that is, they are potentially applicable to
664   any resource, not just one particular media type, "type" of resource, or
665   application. As such, it is preferred that new HTTP status codes be
666   registered in a document that isn't specific to a single application, so
667   that this is clear.
668</t>
669<t>
670   Definitions of new HTTP status codes typically explain the request
671   conditions that produce a response containing the status code (e.g.,
672   combinations of request headers and/or method(s)), along with any
673   interactions with response headers (e.g., those that are required, those
674   that modify the semantics of the response).
675</t>
676<t>
677   New HTTP status codes are required to fall under one of the categories
678   defined in <xref target="status.codes"/>. To allow existing parsers to
679   properly handle them, new status codes cannot disallow a response body,
680   although they can mandate a zero-length response body. They can require the
681   presence of one or more particular HTTP response header(s).
682</t>
683<t>
684   Likewise, their definitions can specify that caches are allowed to use
685   heuristics to determine their freshness (see &caching;; by default, it is
686   not allowed), and can define how to determine the resource which they
687   carry a representation for (see <xref
688   target="identifying.response.associated.with.representation"/>; by default,
689   it is anonymous).
690</t>
691</section>
692
693</section>
694
695</section>
696
697<section title="Response Header Fields" anchor="response.header.fields">
698  <x:anchor-alias value="response-header"/>
699<t>
700   The response-header fields allow the server to pass additional
701   information about the response which cannot be placed in the Status-Line.
702   These header fields give information about the server and about
703   further access to the target resource (&effective-request-uri;).
704</t>
705<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
706  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
707                  / <x:ref>Age</x:ref>                     ; &header-age;
708                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
709                  / <x:ref>ETag</x:ref>                    ; &header-etag;
710                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
711                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
712                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
713                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
714                  / <x:ref>Vary</x:ref>                    ; &header-vary;
715                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
716</artwork></figure>
717<t>
718   Response-header field names can be extended reliably only in
719   combination with a change in the protocol version. However, new or
720   experimental header fields &MAY; be given the semantics of response-header
721   fields if all parties in the communication recognize them to
722   be response-header fields.
723</t>
724</section>
725
726<section title="Representation" anchor="representation">
727<t>
728   Request and Response messages &MAY; transfer a representation if not otherwise
729   restricted by the request method or response status code. A representation
730   consists of metadata (representation header fields) and data (representation
731   body).  When a complete or partial representation is enclosed in an HTTP message,
732   it is referred to as the payload of the message. HTTP representations
733   are defined in &payload;.
734</t>
735<t>
736   A representation body is only present in a message when a message-body is
737   present, as described in &message-body;. The representation body is obtained
738   from the message-body by decoding any Transfer-Encoding that might
739   have been applied to ensure safe and proper transfer of the message.
740</t>
741
742<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
743<t>
744   It is sometimes necessary to determine an identifier for the resource
745   associated with a representation.
746</t>
747<t>
748   An HTTP request representation, when present, is always associated with an
749   anonymous (i.e., unidentified) resource.
750</t>
751<t>
752   In the common case, an HTTP response is a representation of the target
753   resource (see &effective-request-uri;). However, this is not always the
754   case. To determine the URI of the resource a response is associated with,
755   the following rules are used (with the first applicable one being selected):
756</t>
757<t><list style="numbers">
758   <t>If the response status code is 200 or 203 and the request method was GET,
759   the response payload is a representation of the target resource.</t>
760   <t>If the response status code is 204, 206, or 304 and the request method was GET
761   or HEAD, the response payload is a partial representation of the target
762   resource (see &combining-responses;).</t>
763   <t>If the response has a Content-Location header field, and that URI is the same
764   as the effective request URI, the response payload is a representation of the
765   target resource.</t>
766   <t>If the response has a Content-Location header field, and that URI is not the
767   same as the effective request URI, then the response asserts that its
768   payload is a representation of the resource identified by the
769   Content-Location URI. However, such an assertion cannot be trusted unless
770   it can be verified by other means (not defined by HTTP).</t>
771   <t>Otherwise, the response is a representation of an anonymous (i.e.,
772   unidentified) resource.</t>
773</list></t>
774<t>
775  <cref anchor="TODO-req-uri">
776   The comparison function is going to have to be defined somewhere,
777   because we already need to compare URIs for things like cache invalidation.</cref>
778</t>
779</section>
780
781</section>
782
783
784<section title="Method Definitions" anchor="method.definitions">
785<t>
786   The set of common methods for HTTP/1.1 is defined below. Although
787   this set can be expanded, additional methods cannot be assumed to
788   share the same semantics for separately extended clients and servers.
789</t>
790
791<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
792
793<section title="Safe Methods" anchor="safe.methods">
794<iref item="Safe Methods" primary="true"/>
795<t>
796   Implementors need to be aware that the software represents the user in
797   their interactions over the Internet, and need to allow
798   the user to be aware of any actions they take which might have an
799   unexpected significance to themselves or others.
800</t>
801<t>
802   In particular, the convention has been established that the GET, HEAD,
803   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
804   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
805   This allows user agents to represent other methods, such as POST, PUT
806   and DELETE, in a special way, so that the user is made aware of the
807   fact that a possibly unsafe action is being requested.
808</t>
809<t>
810   Naturally, it is not possible to ensure that the server does not
811   generate side-effects as a result of performing a GET request; in
812   fact, some dynamic resources consider that a feature. The important
813   distinction here is that the user did not request the side-effects,
814   so therefore cannot be held accountable for them.
815</t>
816</section>
817
818<section title="Idempotent Methods" anchor="idempotent.methods">
819<iref item="Idempotent Methods" primary="true"/>
820<t>
821   Methods can also have the property of "idempotence" in that, aside
822   from error or expiration issues, the intended effect of multiple
823   identical requests is the same as for a single request.
824   The methods PUT, DELETE, and all safe methods are idempotent.
825   It is important to note that idempotence refers only to changes
826   requested by the client: a server is free to change its state due
827   to multiple requests for the purpose of tracking those requests,
828   versioning of results, etc.
829</t>
830</section>
831</section>
832
833<section title="OPTIONS" anchor="OPTIONS">
834  <rdf:Description>
835    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
836  </rdf:Description>
837  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
838  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
839<t>
840   The OPTIONS method represents a request for information about the
841   communication options available on the request/response chain
842   identified by the effective request URI. This method allows the client to
843   determine the options and/or requirements associated with a resource,
844   or the capabilities of a server, without implying a resource action
845   or initiating a resource retrieval.
846</t>
847<t>
848   Responses to this method are not cacheable.
849</t>
850<t>
851   If the OPTIONS request includes a message-body (as indicated by the
852   presence of Content-Length or Transfer-Encoding), then the media type
853   &MUST; be indicated by a Content-Type field. Although this
854   specification does not define any use for such a body, future
855   extensions to HTTP might use the OPTIONS body to make more detailed
856   queries on the server.
857</t>
858<t>
859   If the request-target is an asterisk ("*"), the OPTIONS request is
860   intended to apply to the server in general rather than to a specific
861   resource. Since a server's communication options typically depend on
862   the resource, the "*" request is only useful as a "ping" or "no-op"
863   type of method; it does nothing beyond allowing the client to test
864   the capabilities of the server. For example, this can be used to test
865   a proxy for HTTP/1.1 compliance (or lack thereof).
866</t>
867<t>
868   If the request-target is not an asterisk, the OPTIONS request applies
869   only to the options that are available when communicating with that
870   resource.
871</t>
872<t>
873   A 200 response &SHOULD; include any header fields that indicate
874   optional features implemented by the server and applicable to that
875   resource (e.g., Allow), possibly including extensions not defined by
876   this specification. The response body, if any, &SHOULD; also include
877   information about the communication options. The format for such a
878   body is not defined by this specification, but might be defined by
879   future extensions to HTTP. Content negotiation &MAY; be used to select
880   the appropriate response format. If no response body is included, the
881   response &MUST; include a Content-Length field with a field-value of
882   "0".
883</t>
884<t>
885   The Max-Forwards request-header field &MAY; be used to target a
886   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
887   If no Max-Forwards field is present in the request, then the forwarded
888   request &MUST-NOT; include a Max-Forwards field.
889</t>
890</section>
891
892<section title="GET" anchor="GET">
893  <rdf:Description>
894    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
895  </rdf:Description>
896  <iref primary="true" item="GET method" x:for-anchor=""/>
897  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
898<t>
899   The GET method means retrieve whatever information (in the form of a
900   representation) currently corresponds to the target resource.
901</t>
902<t>   
903   If the target resource is a data-producing process, it is the
904   produced data which shall be returned as the representation in the response and not
905   the source text of the process, unless that text happens to be the output of
906   the process.
907</t>
908<t>
909   The semantics of the GET method change to a "conditional GET" if the
910   request message includes an If-Modified-Since, If-Unmodified-Since,
911   If-Match, If-None-Match, or If-Range header field. A conditional GET
912   method requests that the representation be transferred only under the
913   circumstances described by the conditional header field(s). The
914   conditional GET method is intended to reduce unnecessary network
915   usage by allowing cached representations to be refreshed without requiring
916   multiple requests or transferring data already held by the client.
917</t>
918<t>
919   The semantics of the GET method change to a "partial GET" if the
920   request message includes a Range header field. A partial GET requests
921   that only part of the representation be transferred, as described in &header-range;.
922   The partial GET method is intended to reduce unnecessary
923   network usage by allowing partially-retrieved representations to be
924   completed without transferring data already held by the client.
925</t>
926<t>
927   The response to a GET request is cacheable and &MAY; be used to satisfy
928   subsequent GET and HEAD requests (see &caching;).
929</t>
930<t>
931   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
932</t>
933</section>
934
935<section title="HEAD" anchor="HEAD">
936  <rdf:Description>
937    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
938  </rdf:Description>
939  <iref primary="true" item="HEAD method" x:for-anchor=""/>
940  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
941<t>
942   The HEAD method is identical to GET except that the server &MUST-NOT;
943   return a message-body in the response. The metadata contained
944   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
945   to the information sent in response to a GET request. This method can
946   be used for obtaining metadata about the representation implied by the
947   request without transferring the representation body. This method is
948   often used for testing hypertext links for validity, accessibility,
949   and recent modification.
950</t>
951<t>
952   The response to a HEAD request is cacheable and &MAY; be used to satisfy
953   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
954   representation from that resource; if the new field values
955   indicate that the cached representation differs from the current representation (as
956   would be indicated by a change in Content-Length, Content-MD5, ETag
957   or Last-Modified), then the cache &MUST; treat the cache entry as
958   stale.
959</t>
960</section>
961
962<section title="POST" anchor="POST">
963  <iref primary="true" item="POST method" x:for-anchor=""/>
964  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
965<t>
966   The POST method is used to request that the origin server accept the
967   representation enclosed in the request as data to be processed by the
968   target resource. POST is designed to allow a uniform method to cover the
969   following functions:
970  <list style="symbols">
971    <t>
972      Annotation of existing resources;
973    </t>
974    <t>
975        Posting a message to a bulletin board, newsgroup, mailing list,
976        or similar group of articles;
977    </t>
978    <t>
979        Providing a block of data, such as the result of submitting a
980        form, to a data-handling process;
981    </t>
982    <t>
983        Extending a database through an append operation.
984    </t>
985  </list>
986</t>
987<t>
988   The actual function performed by the POST method is determined by the
989   server and is usually dependent on the effective request URI.
990</t>
991<t>
992   The action performed by the POST method might not result in a
993   resource that can be identified by a URI. In this case, either 200
994   (OK) or 204 (No Content) is the appropriate response status code,
995   depending on whether or not the response includes a representation that
996   describes the result.
997</t>
998<t>
999   If a resource has been created on the origin server, the response
1000   &SHOULD; be 201 (Created) and contain a representation which describes the
1001   status of the request and refers to the new resource, and a Location
1002   header field (see <xref target="header.location"/>).
1003</t>
1004<t>
1005   Responses to POST requests are only cacheable when they
1006   include explicit freshness information (see &p6-explicit;). A
1007   cached POST response with a Content-Location header field
1008   (see &header-content-location;) whose value is the effective
1009   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1010</t>
1011<t>
1012   Note that POST caching is not widely implemented.
1013   However, the 303 (See Other) response can be used to direct the
1014   user agent to retrieve a cacheable resource.
1015</t>
1016</section>
1017
1018<section title="PUT" anchor="PUT">
1019  <iref primary="true" item="PUT method" x:for-anchor=""/>
1020  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1021<t>
1022   The PUT method requests that the enclosed representation be stored at the
1023   effective request URI. If the effective request URI refers to an already
1024   existing resource, the enclosed representation &SHOULD; be considered a
1025   modified version of the one residing on the origin server. Otherwise, if the
1026   effective request URI does not point to an existing resource, and that URI is
1027   capable of being defined as a new resource by the requesting user
1028   agent, the origin server can create the resource with that URI.
1029</t>
1030<t>   
1031   If a new resource is created at the effective request URI, the origin
1032   server &MUST; inform the user agent
1033   via the 201 (Created) response. If an existing resource is modified,
1034   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1035   to indicate successful completion of the request.
1036</t>
1037<t>   
1038   If the target resource could not be created or modified, an appropriate
1039   error response &SHOULD; be given that reflects the nature of the problem.
1040   The recipient of the representation &MUST-NOT; ignore any Content-*
1041   header fields (headers starting with the prefix "Content-") that it does
1042   not understand or implement
1043   and &MUST; return a 501 (Not Implemented) response in such cases.
1044</t>
1045<t>
1046   If the request passes through a cache that has one or more stored
1047   responses for the effective request URI, those stored responses
1048   &SHOULD; be marked as stale if the response to the PUT request
1049   has a success status code. Responses to the PUT method are
1050   not cacheable.
1051</t>
1052<t>
1053   The fundamental difference between the POST and PUT requests is
1054   reflected in the different meaning of the effective request URI. The URI in a
1055   POST request identifies the resource that will handle the enclosed
1056   representation. That resource might be a data-accepting process, a gateway to
1057   some other protocol, or a document that accepts annotations.
1058   In contrast, the URI in a PUT request identifies the resource for
1059   which enclosed representation is a new or replacement value; the
1060   user agent knows what URI is intended and the server &MUST-NOT; attempt
1061   to apply the request to some other resource.
1062   If the server desires that the request be applied to a different URI,
1063   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1064   then make its own decision regarding whether or not to redirect the
1065   request.
1066</t>
1067<t>
1068   A single resource &MAY; be identified by many different URIs. For
1069   example, an article might have a URI for identifying "the current
1070   version" which is separate from the URI identifying each particular
1071   version. In this case, a PUT request on a general URI might result in
1072   several other URIs being defined by the origin server.
1073</t>
1074<t>
1075   HTTP/1.1 does not define how a PUT method affects the state of an
1076   origin server.
1077</t>
1078<t>
1079   Header fields in a PUT request that are recognized as representation
1080   metadata &SHOULD; be applied to the resource created or modified by
1081   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1082</t>
1083</section>
1084
1085<section title="DELETE" anchor="DELETE">
1086  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1087  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1088<t>
1089   The DELETE method requests that the origin server delete the target
1090   resource. This method &MAY; be overridden by
1091   human intervention (or other means) on the origin server. The client cannot
1092   be guaranteed that the operation has been carried out, even if the
1093   status code returned from the origin server indicates that the action
1094   has been completed successfully. However, the server &SHOULD-NOT; 
1095   indicate success unless, at the time the response is given, it
1096   intends to delete the resource or move it to an inaccessible
1097   location.
1098</t>
1099<t>
1100   A successful response &SHOULD; be 200 (OK) if the response includes an
1101   representation describing the status, 202 (Accepted) if the action has not
1102   yet been enacted, or 204 (No Content) if the action has been enacted
1103   but the response does not include a representation.
1104</t>
1105<t>
1106   If the request passes through a cache and the effective request URI
1107   identifies one or more currently cached representations, those entries &SHOULD; be
1108   treated as stale. Responses to the DELETE method are not cacheable.
1109</t>
1110</section>
1111
1112<section title="TRACE" anchor="TRACE">
1113  <rdf:Description>
1114    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1115  </rdf:Description>
1116  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1117  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1118<t>
1119   The TRACE method is used to invoke a remote, application-layer loop-back
1120   of the request message. The final recipient of the request
1121   &SHOULD; reflect the message received back to the client as the
1122   message-body of a 200 (OK) response. The final recipient is either the
1123   origin server or the first proxy or gateway to receive a Max-Forwards
1124   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1125   A TRACE request &MUST-NOT; include a message-body.
1126</t>
1127<t>
1128   TRACE allows the client to see what is being received at the other
1129   end of the request chain and use that data for testing or diagnostic
1130   information. The value of the Via header field (&header-via;) is of
1131   particular interest, since it acts as a trace of the request chain.
1132   Use of the Max-Forwards header field allows the client to limit the
1133   length of the request chain, which is useful for testing a chain of
1134   proxies forwarding messages in an infinite loop.
1135</t>
1136<t>
1137   If the request is valid, the response &SHOULD; have a Content-Type of
1138   "message/http" (see &media-type-message-http;) and contain a message-body
1139   that encloses a copy of the entire request message.
1140   Responses to the TRACE method are not cacheable.
1141</t>
1142</section>
1143
1144<section title="CONNECT" anchor="CONNECT">
1145  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1146  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1147<t>
1148   The CONNECT method is used with a proxy to dynamically switch
1149   the connection to a tunnel.
1150</t>
1151<t>
1152   When using CONNECT, the request-target &MUST; be use the authority form
1153   (&request-target;); i.e., the host name and port number destination of the
1154   requested connection separated by a colon:
1155</t>
1156<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1157CONNECT server.example.com:80 HTTP/1.1
1158Host: server.example.com:80
1159
1160</artwork></figure>
1161<t>
1162   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
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<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1171CONNECT server.example.com:80 HTTP/1.1
1172Host: server.example.com:80
1173Proxy-Authorization: basic aGVsbG86d29ybGQ=
1174
1175</artwork></figure>
1176<t>
1177   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1178   sent immediately after the blank line. The usual caveats also apply:
1179   data may be discarded if the eventual response is negative, and the
1180   connection may be reset with no response if more than one TCP segment
1181   is outstanding.
1182</t>
1183
1184<section title="Establishing a Tunnel with CONNECT">
1185<t>
1186   Any successful (2xx) response to a CONNECT request indicates that the
1187   proxy has established a connection to the requested host and port,
1188   and has switched to tunneling the current connection to that server
1189   connection.
1190</t>
1191<t>
1192   It may be the case that the proxy itself can only reach the requested
1193   origin server through another proxy.  In this case, the first proxy
1194   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1195   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1196   unless it has either a direct or tunnel connection established to the
1197   authority.
1198</t>
1199<t>
1200   An origin server which receives a CONNECT request for itself &MAY;
1201   respond with a 2xx status code to indicate that a connection is
1202   established.
1203</t>
1204<t>
1205   If at any point either one of the peers gets disconnected, any
1206   outstanding data that came from that peer will be passed to the other
1207   one, and after that also the other connection will be terminated by
1208   the proxy. If there is outstanding data to that peer undelivered,
1209   that data will be discarded.
1210</t>
1211
1212</section>
1213</section>
1214</section>
1215
1216
1217<section title="Status Code Definitions" anchor="status.codes">
1218<t>
1219   Each Status-Code is described below, including any metadata required
1220   in the response.
1221</t>
1222
1223<section title="Informational 1xx" anchor="status.1xx">
1224<t>
1225   This class of status code indicates a provisional response,
1226   consisting only of the Status-Line and optional header fields, and is
1227   terminated by an empty line. There are no required header fields for this
1228   class of status code. Since HTTP/1.0 did not define any 1xx status
1229   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1230   except under experimental conditions.
1231</t>
1232<t>
1233   A client &MUST; be prepared to accept one or more 1xx status responses
1234   prior to a regular response, even if the client does not expect a 100
1235   (Continue) status message. Unexpected 1xx status responses &MAY; be
1236   ignored by a user agent.
1237</t>
1238<t>
1239   Proxies &MUST; forward 1xx responses, unless the connection between the
1240   proxy and its client has been closed, or unless the proxy itself
1241   requested the generation of the 1xx response. (For example, if a
1242   proxy adds a "Expect: 100-continue" field when it forwards a request,
1243   then it need not forward the corresponding 100 (Continue)
1244   response(s).)
1245</t>
1246
1247<section title="100 Continue" anchor="status.100">
1248  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1249  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1250<t>
1251   The client &SHOULD; continue with its request. This interim response is
1252   used to inform the client that the initial part of the request has
1253   been received and has not yet been rejected by the server. The client
1254   &SHOULD; continue by sending the remainder of the request or, if the
1255   request has already been completed, ignore this response. The server
1256   &MUST; send a final response after the request has been completed. See
1257   &use100; for detailed discussion of the use and handling of this
1258   status code.
1259</t>
1260</section>
1261
1262<section title="101 Switching Protocols" anchor="status.101">
1263  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1264  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1265<t>
1266   The server understands and is willing to comply with the client's
1267   request, via the Upgrade message header field (&header-upgrade;), for a
1268   change in the application protocol being used on this connection. The
1269   server will switch protocols to those defined by the response's
1270   Upgrade header field immediately after the empty line which
1271   terminates the 101 response.
1272</t>
1273<t>
1274   The protocol &SHOULD; be switched only when it is advantageous to do
1275   so. For example, switching to a newer version of HTTP is advantageous
1276   over older versions, and switching to a real-time, synchronous
1277   protocol might be advantageous when delivering resources that use
1278   such features.
1279</t>
1280</section>
1281</section>
1282
1283<section title="Successful 2xx" anchor="status.2xx">
1284<t>
1285   This class of status code indicates that the client's request was
1286   successfully received, understood, and accepted.
1287</t>
1288
1289<section title="200 OK" anchor="status.200">
1290  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1291  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1292<t>
1293   The request has succeeded. The payload returned with the response
1294   is dependent on the method used in the request, for example:
1295  <list style="hanging">
1296    <t hangText="GET">
1297          a representation of the target resource is sent in the response;
1298    </t>
1299    <t hangText="HEAD">
1300          the same representation as GET, except without the message-body;
1301    </t>
1302    <t hangText="POST">
1303      a representation describing or containing the result of the action;
1304    </t>
1305    <t hangText="TRACE">
1306      a representation containing the request message as received by the
1307      end server.
1308    </t>
1309  </list>
1310</t>
1311<t>
1312   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1313   freshness for 200 responses.
1314</t>
1315</section>
1316
1317<section title="201 Created" anchor="status.201">
1318  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1319  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1320<t>
1321   The request has been fulfilled and has resulted in a new resource being
1322   created. The newly created resource can be referenced by the URI(s)
1323   returned in the payload of the response, with the most specific URI
1324   for the resource given by a Location header field. The response
1325   &SHOULD; include a payload containing a list of resource
1326   characteristics and location(s) from which the user or user agent can
1327   choose the one most appropriate. The payload format is specified by
1328   the media type given in the Content-Type header field. The origin
1329   server &MUST; create the resource before returning the 201 status code.
1330   If the action cannot be carried out immediately, the server &SHOULD;
1331   respond with 202 (Accepted) response instead.
1332</t>
1333<t>
1334   A 201 response &MAY; contain an ETag response header field indicating
1335   the current value of the entity-tag for the representation of the resource
1336   just created (see &header-etag;).
1337</t>
1338</section>
1339
1340<section title="202 Accepted" anchor="status.202">
1341  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1342  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1343<t>
1344   The request has been accepted for processing, but the processing has
1345   not been completed.  The request might or might not eventually be
1346   acted upon, as it might be disallowed when processing actually takes
1347   place. There is no facility for re-sending a status code from an
1348   asynchronous operation such as this.
1349</t>
1350<t>
1351   The 202 response is intentionally non-committal. Its purpose is to
1352   allow a server to accept a request for some other process (perhaps a
1353   batch-oriented process that is only run once per day) without
1354   requiring that the user agent's connection to the server persist
1355   until the process is completed. The representation returned with this
1356   response &SHOULD; include an indication of the request's current status
1357   and either a pointer to a status monitor or some estimate of when the
1358   user can expect the request to be fulfilled.
1359</t>
1360</section>
1361
1362<section title="203 Non-Authoritative Information" anchor="status.203">
1363  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1364  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1365<t>
1366   The returned metadata in the header fields is not the
1367   definitive set as available from the origin server, but is gathered
1368   from a local or a third-party copy. The set presented &MAY; be a subset
1369   or superset of the original version. For example, including local
1370   annotation information about the resource might result in a superset
1371   of the metadata known by the origin server. Use of this
1372   response code is not required and is only appropriate when the
1373   response would otherwise be 200 (OK).
1374</t>
1375<t>
1376   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1377   freshness for 203 responses.
1378</t>
1379
1380</section>
1381
1382<section title="204 No Content" anchor="status.204">
1383  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1384  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1385<t>
1386   The server has successfully fulfilled the request, but there is no
1387   additional content to return in the response payload body.  The
1388   resource metadata and representation metadata in the response message's
1389   header fields refer to the target resource
1390   and its current representation, respectively, after the requested action.
1391   For example, if a 204 status code is received in response to a PUT
1392   and the response contains an ETag header field, then the value of
1393   that field is the current entity-tag for the representation that
1394   was successfully PUT.
1395</t>
1396<t>
1397   If the client is a user agent, it &SHOULD-NOT; change its document view
1398   from that which caused the request to be sent. This response is
1399   primarily intended to allow input for actions to take place without
1400   causing a change to the user agent's active document view, although
1401   any new or updated metadata &SHOULD; be applied to the document
1402   currently in the user agent's active view.
1403</t>
1404<t>
1405   The 204 response &MUST-NOT; include a message-body, and thus is always
1406   terminated by the first empty line after the header fields.
1407</t>
1408</section>
1409
1410<section title="205 Reset Content" anchor="status.205">
1411  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1412  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1413<t>
1414   The server has fulfilled the request and the user agent &SHOULD; reset
1415   the document view which caused the request to be sent. This response
1416   is primarily intended to allow input for actions to take place via
1417   user input, followed by a clearing of the form in which the input is
1418   given so that the user can easily initiate another input action.
1419</t>
1420<t>   
1421   The message-body included with the response &MUST; be empty. Note that
1422   receivers still need to parse the response according to the algorithm defined
1423   in &message-body;.
1424</t>
1425</section>
1426
1427<section title="206 Partial Content" anchor="status.206">
1428  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1429  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1430  <rdf:Description>
1431    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1432  </rdf:Description>
1433<t>
1434   The server has fulfilled the partial GET request for the resource
1435   and the enclosed payload is a partial representation as defined in &status-206;.
1436</t>
1437<t>
1438   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1439   freshness for 206 responses.
1440</t>
1441</section>
1442</section>
1443
1444<section title="Redirection 3xx" anchor="status.3xx">
1445<t>
1446   This class of status code indicates that further action needs to be
1447   taken by the user agent in order to fulfill the request.  The action
1448   required &MAY; be carried out by the user agent without interaction
1449   with the user if and only if the method used in the second request is
1450   known to be "safe", as defined in <xref target="safe.methods"/>.
1451   A client &SHOULD; detect infinite redirection loops, since such loops
1452   generate network traffic for each redirection.
1453</t>
1454<x:note>
1455  <t>
1456    <x:h>Note:</x:h> An earlier version of this specification recommended a
1457    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1458    Content developers need to be aware that some clients might
1459    implement such a fixed limitation.
1460  </t>
1461</x:note>
1462
1463<section title="300 Multiple Choices" anchor="status.300">
1464  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1466<t>
1467   The target resource has more than one
1468   representation, each with its own specific location, and agent-driven
1469   negotiation information (&content-negotiation;) is being provided so that
1470   the user (or user agent) can select a preferred representation by
1471   redirecting its request to that location.
1472</t>
1473<t>
1474   Unless it was a HEAD request, the response &SHOULD; include a representation
1475   containing a list of representation metadata and location(s) from
1476   which the user or user agent can choose the one most appropriate. The
1477   data format is specified by the media type given in the Content-Type
1478   header field. Depending upon the format and the capabilities of
1479   the user agent, selection of the most appropriate choice &MAY; be
1480   performed automatically. However, this specification does not define
1481   any standard for such automatic selection.
1482</t>
1483<t>
1484   If the server has a preferred choice of representation, it &SHOULD;
1485   include the specific URI for that representation in the Location
1486   field; user agents &MAY; use the Location field value for automatic
1487   redirection.
1488</t>
1489<t>
1490   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1491   freshness for 300 responses.
1492</t>
1493
1494</section>
1495
1496<section title="301 Moved Permanently" anchor="status.301">
1497  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1498  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1499<t>
1500   The target resource has been assigned a new permanent URI and any
1501   future references to this resource &SHOULD; use one of the returned
1502   URIs.  Clients with link editing capabilities ought to automatically
1503   re-link references to the effective request URI to one or more of the new
1504   references returned by the server, where possible.
1505</t>
1506<t>
1507   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1508   freshness for 301 responses.
1509</t>
1510<t>
1511   The new permanent URI &SHOULD; be given by the Location field in the
1512   response. Unless the request method was HEAD, the representation of the
1513   response &SHOULD; contain a short hypertext note with a hyperlink to
1514   the new URI(s).
1515</t>
1516<t>
1517   If the 301 status code is received in response to a request method
1518   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1519   then the request &MAY; be automatically redirected by the user agent without
1520   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1521   request unless it can be confirmed by the user, since this might
1522   change the conditions under which the request was issued.
1523</t>
1524<x:note>
1525  <t>
1526    <x:h>Note:</x:h> When automatically redirecting a POST request after
1527    receiving a 301 status code, some existing HTTP/1.0 user agents
1528    will erroneously change it into a GET request.
1529  </t>
1530</x:note>
1531</section>
1532
1533<section title="302 Found" anchor="status.302">
1534  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1535  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1536<t>
1537   The target resource resides temporarily under a different URI.
1538   Since the redirection might be altered on occasion, the client &SHOULD;
1539   continue to use the effective request URI for future requests.
1540</t>
1541<t>
1542   The temporary URI &SHOULD; be given by the Location field in the
1543   response. Unless the request method was HEAD, the representation of the
1544   response &SHOULD; contain a short hypertext note with a hyperlink to
1545   the new URI(s).
1546</t>
1547<t>
1548   If the 302 status code is received in response to a request method
1549   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1550   then the request &MAY; be automatically redirected by the user agent without
1551   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1552   request unless it can be confirmed by the user, since this might
1553   change the conditions under which the request was issued.
1554</t>
1555<x:note>
1556  <t>
1557    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1558    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1559    specify that the client is not allowed to change the method on the
1560    redirected request.  However, most existing user agent implementations
1561    treat 302 as if it were a 303 response, performing a GET on the Location
1562    field-value regardless of the original request method. Therefore, a
1563    previous version of this specification
1564    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1565    status codes
1566    <xref target="status.303" format="none">303</xref> and
1567    <xref target="status.307" format="none">307</xref> for servers that wish
1568    to make unambiguously clear which kind of reaction is expected of the
1569    client.
1570  </t>
1571</x:note>
1572</section>
1573
1574<section title="303 See Other" anchor="status.303">
1575  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1576  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1577<t>
1578   The server directs the user agent to a different resource, indicated
1579   by a URI in the Location header field, that provides an indirect
1580   response to the original request.  The user agent &MAY; perform a GET
1581   request on the URI in the Location field in order to obtain a
1582   representation corresponding to the response, be redirected again,
1583   or end with an error status.  The Location URI is not a substitute
1584   reference for the effective request URI.
1585</t>
1586<t>
1587   The 303 status code is generally applicable to any HTTP method.  It is
1588   primarily used to allow the output of a POST action to redirect
1589   the user agent to a selected resource, since doing so provides the
1590   information corresponding to the POST response in a form that
1591   can be separately identified, bookmarked, and cached independent
1592   of the original request.
1593</t>
1594<t>
1595   A 303 response to a GET request indicates that the requested
1596   resource does not have a representation of its own that can be
1597   transferred by the server over HTTP.  The Location URI indicates a
1598   resource that is descriptive of the target resource, such that the
1599   follow-on representation might be useful to recipients without
1600   implying that it adequately represents the target resource.
1601   Note that answers to the questions of what can be represented, what
1602   representations are adequate, and what might be a useful description
1603   are outside the scope of HTTP and thus entirely determined by the
1604   URI owner(s).
1605</t>
1606<t>
1607   Except for responses to a HEAD request, the representation of a 303
1608   response &SHOULD; contain a short hypertext note with a hyperlink
1609   to the Location URI.
1610</t>
1611</section>
1612
1613<section title="304 Not Modified" anchor="status.304">
1614  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1615  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1616  <rdf:Description>
1617    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1618  </rdf:Description>
1619<t>
1620   The response to the request has not been modified since the conditions
1621   indicated by the client's conditional GET request, as defined in &status-304;.
1622</t>
1623</section>
1624
1625<section title="305 Use Proxy" anchor="status.305">
1626  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1627  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1628<t>
1629   The 305 status code was defined in a previous version of this specification
1630   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1631</t>
1632</section>
1633
1634<section title="306 (Unused)" anchor="status.306">
1635  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1636  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1637<t>
1638   The 306 status code was used in a previous version of the
1639   specification, is no longer used, and the code is reserved.
1640</t>
1641</section>
1642
1643<section title="307 Temporary Redirect" anchor="status.307">
1644  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1645  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1646<t>
1647   The target resource resides temporarily under a different URI.
1648   Since the redirection can change over time, the client &SHOULD;
1649   continue to use the effective request URI for future requests.
1650</t>
1651<t>
1652   The temporary URI &SHOULD; be given by the Location field in the
1653   response. Unless the request method was HEAD, the representation of the
1654   response &SHOULD; contain a short hypertext note with a hyperlink to
1655   the new URI(s), since many pre-HTTP/1.1 user agents do not
1656   understand the 307 status code. Therefore, the note &SHOULD; contain the
1657   information necessary for a user to repeat the original request on
1658   the new URI.
1659</t>
1660<t>
1661   If the 307 status code is received in response to a request method
1662   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1663   then the request &MAY; be automatically redirected by the user agent without
1664   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1665   request unless it can be confirmed by the user, since this might
1666   change the conditions under which the request was issued.
1667</t>
1668</section>
1669</section>
1670
1671<section title="Client Error 4xx" anchor="status.4xx">
1672<t>
1673   The 4xx class of status code is intended for cases in which the
1674   client seems to have erred. Except when responding to a HEAD request,
1675   the server &SHOULD; include a representation containing an explanation of the
1676   error situation, and whether it is a temporary or permanent
1677   condition. These status codes are applicable to any request method.
1678   User agents &SHOULD; display any included representation to the user.
1679</t>
1680<t>
1681   If the client is sending data, a server implementation using TCP
1682   &SHOULD; be careful to ensure that the client acknowledges receipt of
1683   the packet(s) containing the response, before the server closes the
1684   input connection. If the client continues sending data to the server
1685   after the close, the server's TCP stack will send a reset packet to
1686   the client, which might erase the client's unacknowledged input buffers
1687   before they can be read and interpreted by the HTTP application.
1688</t>
1689
1690<section title="400 Bad Request" anchor="status.400">
1691  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1692  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1693<t>
1694   The request could not be understood by the server due to malformed
1695   syntax. The client &SHOULD-NOT; repeat the request without
1696   modifications.
1697</t>
1698</section>
1699
1700<section title="401 Unauthorized" anchor="status.401">
1701  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1702  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1703  <rdf:Description>
1704    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1705  </rdf:Description>
1706<t>
1707   The request requires user authentication (see &status-401;).
1708</t>
1709</section>
1710
1711<section title="402 Payment Required" anchor="status.402">
1712  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1713  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1714<t>
1715   This code is reserved for future use.
1716</t>
1717</section>
1718
1719<section title="403 Forbidden" anchor="status.403">
1720  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1721  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1722<t>
1723   The server understood the request, but is refusing to fulfill it.
1724   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1725   If the request method was not HEAD and the server wishes to make
1726   public why the request has not been fulfilled, it &SHOULD; describe the
1727   reason for the refusal in the representation.  If the server does not wish to
1728   make this information available to the client, the status code 404
1729   (Not Found) can be used instead.
1730</t>
1731</section>
1732
1733<section title="404 Not Found" anchor="status.404">
1734  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1735  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1736<t>
1737   The server has not found anything matching the effective request URI. No
1738   indication is given of whether the condition is temporary or
1739   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1740   knows, through some internally configurable mechanism, that an old
1741   resource is permanently unavailable and has no forwarding address.
1742   This status code is commonly used when the server does not wish to
1743   reveal exactly why the request has been refused, or when no other
1744   response is applicable.
1745</t>
1746</section>
1747
1748<section title="405 Method Not Allowed" anchor="status.405">
1749  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1750  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1751<t>
1752   The method specified in the Request-Line is not allowed for the target
1753   resource. The response &MUST; include an
1754   Allow header field containing a list of valid methods for the requested
1755   resource.
1756</t>
1757</section>
1758
1759<section title="406 Not Acceptable" anchor="status.406">
1760  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1761  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1762<t>
1763   The resource identified by the request is only capable of generating
1764   response representations which have content characteristics not acceptable
1765   according to the accept header fields sent in the request.
1766</t>
1767<t>
1768   Unless it was a HEAD request, the response &SHOULD; include a representation
1769   containing a list of available representation characteristics and location(s)
1770   from which the user or user agent can choose the one most
1771   appropriate. The data format is specified by the media type given
1772   in the Content-Type header field. Depending upon the format and the
1773   capabilities of the user agent, selection of the most appropriate
1774   choice &MAY; be performed automatically. However, this specification
1775   does not define any standard for such automatic selection.
1776</t>
1777<x:note>
1778  <t>
1779    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1780    not acceptable according to the accept header fields sent in the
1781    request. In some cases, this might even be preferable to sending a
1782    406 response. User agents are encouraged to inspect the header fields of
1783    an incoming response to determine if it is acceptable.
1784  </t>
1785</x:note>
1786<t>
1787   If the response could be unacceptable, a user agent &SHOULD;
1788   temporarily stop receipt of more data and query the user for a
1789   decision on further actions.
1790</t>
1791</section>
1792
1793<section title="407 Proxy Authentication Required" anchor="status.407">
1794  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1795  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1796<t>
1797   This code is similar to 401 (Unauthorized), but indicates that the
1798   client must first authenticate itself with the proxy (see &status-407;).
1799</t>
1800</section>
1801
1802<section title="408 Request Timeout" anchor="status.408">
1803  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1804  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1805<t>
1806   The client did not produce a request within the time that the server
1807   was prepared to wait. The client &MAY; repeat the request without
1808   modifications at any later time.
1809</t>
1810</section>
1811
1812<section title="409 Conflict" anchor="status.409">
1813  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1814  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1815<t>
1816   The request could not be completed due to a conflict with the current
1817   state of the resource. This code is only allowed in situations where
1818   it is expected that the user might be able to resolve the conflict
1819   and resubmit the request. The response body &SHOULD; include enough
1820   information for the user to recognize the source of the conflict.
1821   Ideally, the response representation would include enough information for the
1822   user or user agent to fix the problem; however, that might not be
1823   possible and is not required.
1824</t>
1825<t>
1826   Conflicts are most likely to occur in response to a PUT request. For
1827   example, if versioning were being used and the representation being PUT
1828   included changes to a resource which conflict with those made by an
1829   earlier (third-party) request, the server might use the 409 response
1830   to indicate that it can't complete the request. In this case, the
1831   response representation would likely contain a list of the differences
1832   between the two versions in a format defined by the response
1833   Content-Type.
1834</t>
1835</section>
1836
1837<section title="410 Gone" anchor="status.410">
1838  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1839  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1840<t>
1841   The target resource is no longer available at the server and no
1842   forwarding address is known. This condition is expected to be
1843   considered permanent. Clients with link editing capabilities &SHOULD;
1844   delete references to the effective request URI after user approval. If the
1845   server does not know, or has no facility to determine, whether or not
1846   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1847   used instead.
1848</t>
1849<t>
1850   The 410 response is primarily intended to assist the task of web
1851   maintenance by notifying the recipient that the resource is
1852   intentionally unavailable and that the server owners desire that
1853   remote links to that resource be removed. Such an event is common for
1854   limited-time, promotional services and for resources belonging to
1855   individuals no longer working at the server's site. It is not
1856   necessary to mark all permanently unavailable resources as "gone" or
1857   to keep the mark for any length of time &mdash; that is left to the
1858   discretion of the server owner.
1859</t>
1860<t>
1861   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1862   for 410 responses.
1863</t>
1864
1865</section>
1866
1867<section title="411 Length Required" anchor="status.411">
1868  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1869  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1870<t>
1871   The server refuses to accept the request without a defined Content-Length.
1872   The client &MAY; repeat the request if it adds a valid
1873   Content-Length header field containing the length of the message-body
1874   in the request message.
1875</t>
1876</section>
1877
1878<section title="412 Precondition Failed" anchor="status.412">
1879  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1880  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1881  <rdf:Description>
1882    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1883  </rdf:Description>
1884<t>
1885   The precondition given in one or more of the request-header fields
1886   evaluated to false when it was tested on the server, as defined in
1887   &status-412;.
1888</t>
1889</section>
1890
1891<section title="413 Request Entity Too Large" anchor="status.413">
1892  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1893  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1894<t>
1895   The server is refusing to process a request because the request
1896   representation is larger than the server is willing or able to process. The
1897   server &MAY; close the connection to prevent the client from continuing
1898   the request.
1899</t>
1900<t>
1901   If the condition is temporary, the server &SHOULD; include a Retry-After
1902   header field to indicate that it is temporary and after what
1903   time the client &MAY; try again.
1904</t>
1905</section>
1906
1907<section title="414 URI Too Long" anchor="status.414">
1908  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1909  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1910<t>
1911   The server is refusing to service the request because the effective request URI
1912   is longer than the server is willing to interpret. This rare
1913   condition is only likely to occur when a client has improperly
1914   converted a POST request to a GET request with long query
1915   information, when the client has descended into a URI "black hole" of
1916   redirection (e.g., a redirected URI prefix that points to a suffix of
1917   itself), or when the server is under attack by a client attempting to
1918   exploit security holes present in some servers using fixed-length
1919   buffers for reading or manipulating the effective request URI.
1920</t>
1921</section>
1922
1923<section title="415 Unsupported Media Type" anchor="status.415">
1924  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1925  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1926<t>
1927   The server is refusing to service the request because the representation of
1928   the request is in a format not supported by the target resource
1929   for the requested method.
1930</t>
1931</section>
1932
1933<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1934  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1935  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1936  <rdf:Description>
1937    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1938  </rdf:Description>
1939<t>
1940   The request included a Range request-header field (&header-range;) and none of
1941   the range-specifier values in this field overlap the current extent
1942   of the selected resource. See &status-416;.
1943</t>
1944</section>
1945
1946<section title="417 Expectation Failed" anchor="status.417">
1947  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1948  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1949<t>
1950   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1951   could not be met by this server, or, if the server is a proxy,
1952   the server has unambiguous evidence that the request could not be met
1953   by the next-hop server.
1954</t>
1955</section>
1956
1957<section title="426 Upgrade Required" anchor="status.426">
1958  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
1959  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
1960<t>
1961   The request can not be completed without a prior protocol upgrade. This
1962   response &MUST; include an Upgrade header field (&header-upgrade;)
1963   specifying the required protocols.
1964</t>
1965<figure>
1966<preamble>Example:</preamble>
1967<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1968HTTP/1.1 426 Upgrade Required
1969Upgrade: HTTP/2.0
1970Connection: Upgrade
1971
1972</artwork></figure>
1973<t>
1974   The server &SHOULD; include a message body in the 426 response which
1975   indicates in human readable form the reason for the error and describes any
1976   alternative courses which may be available to the user.
1977</t>
1978</section>
1979</section>
1980
1981<section title="Server Error 5xx" anchor="status.5xx">
1982<t>
1983   Response status codes beginning with the digit "5" indicate cases in
1984   which the server is aware that it has erred or is incapable of
1985   performing the request. Except when responding to a HEAD request, the
1986   server &SHOULD; include a representation containing an explanation of the
1987   error situation, and whether it is a temporary or permanent
1988   condition. User agents &SHOULD; display any included representation to the
1989   user. These response codes are applicable to any request method.
1990</t>
1991
1992<section title="500 Internal Server Error" anchor="status.500">
1993  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1994  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1995<t>
1996   The server encountered an unexpected condition which prevented it
1997   from fulfilling the request.
1998</t>
1999</section>
2000
2001<section title="501 Not Implemented" anchor="status.501">
2002  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2003  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2004<t>
2005   The server does not support the functionality required to fulfill the
2006   request. This is the appropriate response when the server does not
2007   recognize the request method and is not capable of supporting it for
2008   any resource.
2009</t>
2010</section>
2011
2012<section title="502 Bad Gateway" anchor="status.502">
2013  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2014  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2015<t>
2016   The server, while acting as a gateway or proxy, received an invalid
2017   response from the upstream server it accessed in attempting to
2018   fulfill the request.
2019</t>
2020</section>
2021
2022<section title="503 Service Unavailable" anchor="status.503">
2023  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2024  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2025<t>
2026   The server is currently unable to handle the request due to a
2027   temporary overloading or maintenance of the server. The implication
2028   is that this is a temporary condition which will be alleviated after
2029   some delay. If known, the length of the delay &MAY; be indicated in a
2030   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2031   handle the response as it would for a 500 response.
2032</t>
2033<x:note>
2034  <t>
2035    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2036    server must use it when becoming overloaded. Some servers might wish
2037    to simply refuse the connection.
2038  </t>
2039</x:note>
2040</section>
2041
2042<section title="504 Gateway Timeout" anchor="status.504">
2043  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2044  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2045<t>
2046   The server, while acting as a gateway or proxy, did not receive a
2047   timely response from the upstream server specified by the URI (e.g.,
2048   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2049   to access in attempting to complete the request.
2050</t>
2051<x:note>
2052  <t>
2053    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2054    return 400 or 500 when DNS lookups time out.
2055  </t>
2056</x:note>
2057</section>
2058
2059<section title="505 HTTP Version Not Supported" anchor="status.505">
2060  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2061  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2062<t>
2063   The server does not support, or refuses to support, the protocol
2064   version that was used in the request message. The server is
2065   indicating that it is unable or unwilling to complete the request
2066   using the same major version as the client, as described in &http-version;,
2067   other than with this error message. The response &SHOULD; contain
2068   a representation describing why that version is not supported and what other
2069   protocols are supported by that server.
2070</t>
2071
2072</section>
2073</section>
2074</section>
2075
2076
2077<section title="Header Field Definitions" anchor="header.fields">
2078<t>
2079   This section defines the syntax and semantics of HTTP/1.1 header fields
2080   related to request and response semantics.
2081</t>
2082
2083<section title="Allow" anchor="header.allow">
2084  <iref primary="true" item="Allow header" x:for-anchor=""/>
2085  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
2086  <x:anchor-alias value="Allow"/>
2087  <x:anchor-alias value="Allow-v"/>
2088<t>
2089   The "Allow" response-header field lists the set of methods advertised as
2090   supported by the target resource. The purpose of this field is strictly to
2091   inform the recipient of valid methods associated with the resource.
2092</t>
2093<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2094  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2095  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2096</artwork></figure>
2097<t>
2098   Example of use:
2099</t>
2100<figure><artwork type="example">
2101  Allow: GET, HEAD, PUT
2102</artwork></figure>
2103<t>
2104   The actual set of allowed methods is defined by the origin server at the
2105   time of each request.
2106</t>
2107<t>
2108   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2109   understand all the methods specified in order to handle them according to
2110   the generic message handling rules.
2111</t>
2112</section>
2113
2114<section title="Expect" anchor="header.expect">
2115  <iref primary="true" item="Expect header" x:for-anchor=""/>
2116  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
2117  <x:anchor-alias value="Expect"/>
2118  <x:anchor-alias value="Expect-v"/>
2119  <x:anchor-alias value="expectation"/>
2120  <x:anchor-alias value="expectation-extension"/>
2121  <x:anchor-alias value="expect-params"/>
2122<t>
2123   The "Expect" request-header field is used to indicate that particular
2124   server behaviors are required by the client.
2125</t>
2126<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"/>
2127  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2128  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2129 
2130  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2131  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2132                           *<x:ref>expect-params</x:ref> ]
2133  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2134</artwork></figure>
2135<t>
2136   A server that does not understand or is unable to comply with any of
2137   the expectation values in the Expect field of a request &MUST; respond
2138   with appropriate error status code. The server &MUST; respond with a 417
2139   (Expectation Failed) status code if any of the expectations cannot be met
2140   or, if there are other problems with the request, some other 4xx
2141   status code.
2142</t>
2143<t>
2144   This header field is defined with extensible syntax to allow for
2145   future extensions. If a server receives a request containing an
2146   Expect field that includes an expectation-extension that it does not
2147   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2148</t>
2149<t>
2150   Comparison of expectation values is case-insensitive for unquoted
2151   tokens (including the 100-continue token), and is case-sensitive for
2152   quoted-string expectation-extensions.
2153</t>
2154<t>
2155   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2156   return a 417 (Expectation Failed) status code if it receives a request
2157   with an expectation that it cannot meet. However, the Expect
2158   request-header field itself is end-to-end; it &MUST; be forwarded if the
2159   request is forwarded.
2160</t>
2161<t>
2162   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2163   Expect header field.
2164</t>
2165<t>
2166   See &use100; for the use of the 100 (Continue) status code.
2167</t>
2168</section>
2169
2170<section title="From" anchor="header.from">
2171  <iref primary="true" item="From header" x:for-anchor=""/>
2172  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2173  <x:anchor-alias value="From"/>
2174  <x:anchor-alias value="From-v"/>
2175  <x:anchor-alias value="mailbox"/>
2176<t>
2177   The "From" request-header field, if given, &SHOULD; contain an Internet
2178   e-mail address for the human user who controls the requesting user
2179   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2180   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2181</t>
2182<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2183  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2184  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2185 
2186  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2187</artwork></figure>
2188<t>
2189   An example is:
2190</t>
2191<figure><artwork type="example">
2192  From: webmaster@example.org
2193</artwork></figure>
2194<t>
2195   This header field &MAY; be used for logging purposes and as a means for
2196   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2197   be used as an insecure form of access protection. The interpretation
2198   of this field is that the request is being performed on behalf of the
2199   person given, who accepts responsibility for the method performed. In
2200   particular, robot agents &SHOULD; include this header field so that the
2201   person responsible for running the robot can be contacted if problems
2202   occur on the receiving end.
2203</t>
2204<t>
2205   The Internet e-mail address in this field &MAY; be separate from the
2206   Internet host which issued the request. For example, when a request
2207   is passed through a proxy the original issuer's address &SHOULD; be
2208   used.
2209</t>
2210<t>
2211   The client &SHOULD-NOT;  send the From header field without the user's
2212   approval, as it might conflict with the user's privacy interests or
2213   their site's security policy. It is strongly recommended that the
2214   user be able to disable, enable, and modify the value of this field
2215   at any time prior to a request.
2216</t>
2217</section>
2218
2219<section title="Location" anchor="header.location">
2220  <iref primary="true" item="Location header" x:for-anchor=""/>
2221  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2222  <x:anchor-alias value="Location"/>
2223  <x:anchor-alias value="Location-v"/>
2224<t>
2225   The "Location" response-header field is used to identify a newly created
2226   resource, or to redirect the recipient to a different location for
2227   completion of the request.
2228</t>
2229<t>
2230   For 201 (Created) responses, the Location is the URI of the new resource
2231   which was created by the request. For 3xx responses, the location &SHOULD;
2232   indicate the server's preferred URI for automatic redirection to the
2233   resource.
2234</t>
2235<t>
2236   The field value consists of a single URI-reference. When it has the form
2237   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2238   the final value is computed by resolving it against the effective request
2239   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2240</t>
2241<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2242  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2243  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2244</artwork></figure>
2245<figure>
2246<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2247<artwork type="example">
2248  Location: http://www.example.org/pub/WWW/People.html#tim
2249</artwork></figure><figure><artwork type="example">  Location: /index.html
2250</artwork></figure>
2251<t>
2252   There are circumstances in which a fragment identifier in a Location URI
2253   would not be appropriate:
2254   <list style="symbols">
2255      <t>With a 201 Created response, because in this usage the Location header
2256      field specifies the URI for the entire created resource.</t>
2257      <t>With 305 Use Proxy.</t>
2258   </list>
2259</t>
2260<x:note>
2261  <t>
2262    <x:h>Note:</x:h> This specification does not define precedence rules
2263    for the case where the original URI, as navigated to by the user
2264    agent, and the Location header field value both contain fragment
2265    identifiers. Thus be aware that including fragment identifiers might
2266    inconvenience anyone relying on the semantics of the original URI's
2267    fragment identifier.
2268  </t>
2269</x:note>
2270<x:note>
2271  <t>
2272    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2273    from Location in that the Content-Location identifies the most specific
2274    resource corresponding to the enclosed representation.
2275    It is therefore possible for a response to contain header fields for
2276    both Location and Content-Location.
2277  </t>
2278</x:note>
2279</section>
2280
2281<section title="Max-Forwards" anchor="header.max-forwards">
2282  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2283  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2284  <x:anchor-alias value="Max-Forwards"/>
2285  <x:anchor-alias value="Max-Forwards-v"/>
2286<t>
2287   The "Max-Forwards" request-header field provides a mechanism with the
2288   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2289   methods to limit the number of times that the request is forwarded by
2290   proxies or gateways. This can be useful when the client is attempting to
2291   trace a request which appears to be failing or looping in mid-chain.
2292</t>
2293<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2294  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2295  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2296</artwork></figure>
2297<t>
2298   The Max-Forwards value is a decimal integer indicating the remaining
2299   number of times this request message can be forwarded.
2300</t>
2301<t>
2302   Each proxy or gateway recipient of a TRACE or OPTIONS request
2303   containing a Max-Forwards header field &MUST; check and update its
2304   value prior to forwarding the request. If the received value is zero
2305   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2306   respond as the final recipient. If the received Max-Forwards value is
2307   greater than zero, then the forwarded message &MUST; contain an updated
2308   Max-Forwards field with a value decremented by one (1).
2309</t>
2310<t>
2311   The Max-Forwards header field &MAY; be ignored for all other methods.
2312</t>
2313</section>
2314
2315<section title="Referer" anchor="header.referer">
2316  <iref primary="true" item="Referer header" x:for-anchor=""/>
2317  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2318  <x:anchor-alias value="Referer"/>
2319  <x:anchor-alias value="Referer-v"/>
2320<t>
2321   The "Referer" [sic] request-header field allows the client to specify the
2322   URI of the resource from which the effective request URI was obtained (the
2323   "referrer", although the header field is misspelled.).
2324</t>
2325<t>
2326   The Referer header field allows servers to generate lists of back-links to
2327   resources for interest, logging, optimized caching, etc. It also allows
2328   obsolete or mistyped links to be traced for maintenance. Some servers use
2329   Referer as a means of controlling where they allow links from (so-called
2330   "deep linking"), but legitimate requests do not always
2331   contain a Referer header field.
2332</t>
2333<t>
2334   If the effective request URI was obtained from a source that does not have its own
2335   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2336   sent with the value "about:blank", or not be sent at all. Note that this
2337   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2338</t>
2339<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2340  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2341  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2342</artwork></figure>
2343<t>
2344   Example:
2345</t>
2346<figure><artwork type="example">
2347  Referer: http://www.example.org/hypertext/Overview.html
2348</artwork></figure>
2349<t>
2350   If the field value is a relative URI, it &SHOULD; be interpreted
2351   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2352   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2353</t>
2354</section>
2355
2356<section title="Retry-After" anchor="header.retry-after">
2357  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2358  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2359  <x:anchor-alias value="Retry-After"/>
2360  <x:anchor-alias value="Retry-After-v"/>
2361<t>
2362   The response-header "Retry-After" field can be used with a 503 (Service
2363   Unavailable) response to indicate how long the service is expected to
2364   be unavailable to the requesting client. This field &MAY; also be used
2365   with any 3xx (Redirection) response to indicate the minimum time the
2366   user-agent is asked wait before issuing the redirected request.
2367</t>
2368<t>
2369   The value of this field can be either an HTTP-date or an integer number
2370   of seconds (in decimal) after the time of the response.
2371</t>
2372<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2373  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2374  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2375</artwork></figure>
2376<t anchor="rule.delta-seconds">
2377  <x:anchor-alias value="delta-seconds"/>
2378   Time spans are non-negative decimal integers, representing time in
2379   seconds.
2380</t>
2381<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2382  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2383</artwork></figure>
2384<t>
2385   Two examples of its use are
2386</t>
2387<figure><artwork type="example">
2388  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2389  Retry-After: 120
2390</artwork></figure>
2391<t>
2392   In the latter example, the delay is 2 minutes.
2393</t>
2394</section>
2395
2396<section title="Server" anchor="header.server">
2397  <iref primary="true" item="Server header" x:for-anchor=""/>
2398  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2399  <x:anchor-alias value="Server"/>
2400  <x:anchor-alias value="Server-v"/>
2401<t>
2402   The "Server" response-header field contains information about the
2403   software used by the origin server to handle the request.
2404</t>
2405<t>
2406   The field can contain multiple product tokens (&product-tokens;) and
2407   comments (&header-fields;) identifying the server and any significant
2408   subproducts. The product tokens are listed in order of their significance
2409   for identifying the application.
2410</t>
2411<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2412  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2413  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2414                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2415</artwork></figure>
2416<t>
2417   Example:
2418</t>
2419<figure><artwork type="example">
2420  Server: CERN/3.0 libwww/2.17
2421</artwork></figure>
2422<t>
2423   If the response is being forwarded through a proxy, the proxy
2424   application &MUST-NOT; modify the Server response-header field. Instead, it
2425   &MUST; include a Via field (as described in &header-via;).
2426</t>
2427<x:note>
2428  <t>
2429    <x:h>Note:</x:h> Revealing the specific software version of the server might
2430    allow the server machine to become more vulnerable to attacks
2431    against software that is known to contain security holes. Server
2432    implementors are encouraged to make this field a configurable
2433    option.
2434  </t>
2435</x:note>
2436</section>
2437
2438<section title="User-Agent" anchor="header.user-agent">
2439  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2440  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2441  <x:anchor-alias value="User-Agent"/>
2442  <x:anchor-alias value="User-Agent-v"/>
2443<t>
2444   The "User-Agent" request-header field contains information about the user
2445   agent originating the request. User agents &SHOULD; include this field with
2446   requests.
2447</t>
2448<t>
2449   Typically, it is used for statistical purposes, the tracing of protocol
2450   violations, and tailoring responses to avoid particular user agent
2451   limitations.
2452</t>
2453<t>
2454   The field can contain multiple product tokens (&product-tokens;)
2455   and comments (&header-fields;) identifying the agent and its
2456   significant subproducts. By convention, the product tokens are listed in
2457   order of their significance for identifying the application.
2458</t>
2459<t>
2460   Because this field is usually sent on every request a user agent makes,
2461   implementations are encouraged not to include needlessly fine-grained
2462   detail, and to limit (or even prohibit) the addition of subproducts by third
2463   parties. Overly long and detailed User-Agent field values make requests
2464   larger and can also be used to identify ("fingerprint") the user against
2465   their wishes.
2466</t>
2467<t>
2468   Likewise, implementations are encouraged not to use the product tokens of
2469   other implementations in order to declare compatibility with them, as this
2470   circumvents the purpose of the field. Finally, they are encouraged not to
2471   use comments to identify products; doing so makes the field value more
2472   difficult to parse.
2473</t>
2474<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2475  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2476  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2477                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2478</artwork></figure>
2479<t>
2480   Example:
2481</t>
2482<figure><artwork type="example">
2483  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2484</artwork></figure>
2485</section>
2486
2487</section>
2488
2489<section title="IANA Considerations" anchor="IANA.considerations">
2490
2491<section title="Method Registry" anchor="method.registration">
2492<t>
2493  The registration procedure for HTTP Methods is defined by
2494  <xref target="method.registry"/> of this document.
2495</t>
2496<t>
2497   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2498   and be populated with the registrations below:
2499</t>
2500<?BEGININC p2-semantics.iana-methods ?>
2501<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2502<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2503   <ttcol>Method</ttcol>
2504   <ttcol>Safe</ttcol>
2505   <ttcol>Reference</ttcol>
2506   <c>CONNECT</c>
2507   <c>no</c>
2508   <c>
2509      <xref target="CONNECT"/>
2510   </c>
2511   <c>DELETE</c>
2512   <c>no</c>
2513   <c>
2514      <xref target="DELETE"/>
2515   </c>
2516   <c>GET</c>
2517   <c>yes</c>
2518   <c>
2519      <xref target="GET"/>
2520   </c>
2521   <c>HEAD</c>
2522   <c>yes</c>
2523   <c>
2524      <xref target="HEAD"/>
2525   </c>
2526   <c>OPTIONS</c>
2527   <c>yes</c>
2528   <c>
2529      <xref target="OPTIONS"/>
2530   </c>
2531   <c>POST</c>
2532   <c>no</c>
2533   <c>
2534      <xref target="POST"/>
2535   </c>
2536   <c>PUT</c>
2537   <c>no</c>
2538   <c>
2539      <xref target="PUT"/>
2540   </c>
2541   <c>TRACE</c>
2542   <c>yes</c>
2543   <c>
2544      <xref target="TRACE"/>
2545   </c>
2546</texttable>
2547<!--(END)-->
2548<?ENDINC p2-semantics.iana-methods ?>
2549</section>
2550
2551<section title="Status Code Registry" anchor="status.code.registration">
2552<t>
2553   The registration procedure for HTTP Status Codes &mdash; previously defined
2554   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2555   by <xref target="status.code.registry"/> of this document.
2556</t>
2557<t>
2558   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2559   shall be updated with the registrations below:
2560</t>
2561<?BEGININC p2-semantics.iana-status-codes ?>
2562<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2563<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2564   <ttcol>Value</ttcol>
2565   <ttcol>Description</ttcol>
2566   <ttcol>Reference</ttcol>
2567   <c>100</c>
2568   <c>Continue</c>
2569   <c>
2570      <xref target="status.100"/>
2571   </c>
2572   <c>101</c>
2573   <c>Switching Protocols</c>
2574   <c>
2575      <xref target="status.101"/>
2576   </c>
2577   <c>200</c>
2578   <c>OK</c>
2579   <c>
2580      <xref target="status.200"/>
2581   </c>
2582   <c>201</c>
2583   <c>Created</c>
2584   <c>
2585      <xref target="status.201"/>
2586   </c>
2587   <c>202</c>
2588   <c>Accepted</c>
2589   <c>
2590      <xref target="status.202"/>
2591   </c>
2592   <c>203</c>
2593   <c>Non-Authoritative Information</c>
2594   <c>
2595      <xref target="status.203"/>
2596   </c>
2597   <c>204</c>
2598   <c>No Content</c>
2599   <c>
2600      <xref target="status.204"/>
2601   </c>
2602   <c>205</c>
2603   <c>Reset Content</c>
2604   <c>
2605      <xref target="status.205"/>
2606   </c>
2607   <c>300</c>
2608   <c>Multiple Choices</c>
2609   <c>
2610      <xref target="status.300"/>
2611   </c>
2612   <c>301</c>
2613   <c>Moved Permanently</c>
2614   <c>
2615      <xref target="status.301"/>
2616   </c>
2617   <c>302</c>
2618   <c>Found</c>
2619   <c>
2620      <xref target="status.302"/>
2621   </c>
2622   <c>303</c>
2623   <c>See Other</c>
2624   <c>
2625      <xref target="status.303"/>
2626   </c>
2627   <c>305</c>
2628   <c>Use Proxy</c>
2629   <c>
2630      <xref target="status.305"/>
2631   </c>
2632   <c>306</c>
2633   <c>(Unused)</c>
2634   <c>
2635      <xref target="status.306"/>
2636   </c>
2637   <c>307</c>
2638   <c>Temporary Redirect</c>
2639   <c>
2640      <xref target="status.307"/>
2641   </c>
2642   <c>400</c>
2643   <c>Bad Request</c>
2644   <c>
2645      <xref target="status.400"/>
2646   </c>
2647   <c>402</c>
2648   <c>Payment Required</c>
2649   <c>
2650      <xref target="status.402"/>
2651   </c>
2652   <c>403</c>
2653   <c>Forbidden</c>
2654   <c>
2655      <xref target="status.403"/>
2656   </c>
2657   <c>404</c>
2658   <c>Not Found</c>
2659   <c>
2660      <xref target="status.404"/>
2661   </c>
2662   <c>405</c>
2663   <c>Method Not Allowed</c>
2664   <c>
2665      <xref target="status.405"/>
2666   </c>
2667   <c>406</c>
2668   <c>Not Acceptable</c>
2669   <c>
2670      <xref target="status.406"/>
2671   </c>
2672   <c>407</c>
2673   <c>Proxy Authentication Required</c>
2674   <c>
2675      <xref target="status.407"/>
2676   </c>
2677   <c>408</c>
2678   <c>Request Timeout</c>
2679   <c>
2680      <xref target="status.408"/>
2681   </c>
2682   <c>409</c>
2683   <c>Conflict</c>
2684   <c>
2685      <xref target="status.409"/>
2686   </c>
2687   <c>410</c>
2688   <c>Gone</c>
2689   <c>
2690      <xref target="status.410"/>
2691   </c>
2692   <c>411</c>
2693   <c>Length Required</c>
2694   <c>
2695      <xref target="status.411"/>
2696   </c>
2697   <c>413</c>
2698   <c>Request Entity Too Large</c>
2699   <c>
2700      <xref target="status.413"/>
2701   </c>
2702   <c>414</c>
2703   <c>URI Too Long</c>
2704   <c>
2705      <xref target="status.414"/>
2706   </c>
2707   <c>415</c>
2708   <c>Unsupported Media Type</c>
2709   <c>
2710      <xref target="status.415"/>
2711   </c>
2712   <c>417</c>
2713   <c>Expectation Failed</c>
2714   <c>
2715      <xref target="status.417"/>
2716   </c>
2717   <c>426</c>
2718   <c>Upgrade Required</c>
2719   <c>
2720      <xref target="status.426"/>
2721   </c>
2722   <c>500</c>
2723   <c>Internal Server Error</c>
2724   <c>
2725      <xref target="status.500"/>
2726   </c>
2727   <c>501</c>
2728   <c>Not Implemented</c>
2729   <c>
2730      <xref target="status.501"/>
2731   </c>
2732   <c>502</c>
2733   <c>Bad Gateway</c>
2734   <c>
2735      <xref target="status.502"/>
2736   </c>
2737   <c>503</c>
2738   <c>Service Unavailable</c>
2739   <c>
2740      <xref target="status.503"/>
2741   </c>
2742   <c>504</c>
2743   <c>Gateway Timeout</c>
2744   <c>
2745      <xref target="status.504"/>
2746   </c>
2747   <c>505</c>
2748   <c>HTTP Version Not Supported</c>
2749   <c>
2750      <xref target="status.505"/>
2751   </c>
2752</texttable>
2753<!--(END)-->
2754<?ENDINC p2-semantics.iana-status-codes ?>
2755</section>
2756<section title="Header Field Registration" anchor="header.field.registration">
2757<t>
2758   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2759   with the permanent registrations below (see <xref target="RFC3864"/>):
2760</t>
2761<?BEGININC p2-semantics.iana-headers ?>
2762<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2763<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2764   <ttcol>Header Field Name</ttcol>
2765   <ttcol>Protocol</ttcol>
2766   <ttcol>Status</ttcol>
2767   <ttcol>Reference</ttcol>
2768
2769   <c>Allow</c>
2770   <c>http</c>
2771   <c>standard</c>
2772   <c>
2773      <xref target="header.allow"/>
2774   </c>
2775   <c>Expect</c>
2776   <c>http</c>
2777   <c>standard</c>
2778   <c>
2779      <xref target="header.expect"/>
2780   </c>
2781   <c>From</c>
2782   <c>http</c>
2783   <c>standard</c>
2784   <c>
2785      <xref target="header.from"/>
2786   </c>
2787   <c>Location</c>
2788   <c>http</c>
2789   <c>standard</c>
2790   <c>
2791      <xref target="header.location"/>
2792   </c>
2793   <c>Max-Forwards</c>
2794   <c>http</c>
2795   <c>standard</c>
2796   <c>
2797      <xref target="header.max-forwards"/>
2798   </c>
2799   <c>Referer</c>
2800   <c>http</c>
2801   <c>standard</c>
2802   <c>
2803      <xref target="header.referer"/>
2804   </c>
2805   <c>Retry-After</c>
2806   <c>http</c>
2807   <c>standard</c>
2808   <c>
2809      <xref target="header.retry-after"/>
2810   </c>
2811   <c>Server</c>
2812   <c>http</c>
2813   <c>standard</c>
2814   <c>
2815      <xref target="header.server"/>
2816   </c>
2817   <c>User-Agent</c>
2818   <c>http</c>
2819   <c>standard</c>
2820   <c>
2821      <xref target="header.user-agent"/>
2822   </c>
2823</texttable>
2824<!--(END)-->
2825<?ENDINC p2-semantics.iana-headers ?>
2826<t>
2827   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2828</t>
2829</section>
2830</section>
2831
2832<section title="Security Considerations" anchor="security.considerations">
2833<t>
2834   This section is meant to inform application developers, information
2835   providers, and users of the security limitations in HTTP/1.1 as
2836   described by this document. The discussion does not include
2837   definitive solutions to the problems revealed, though it does make
2838   some suggestions for reducing security risks.
2839</t>
2840
2841<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2842<t>
2843   Like any generic data transfer protocol, HTTP cannot regulate the
2844   content of the data that is transferred, nor is there any a priori
2845   method of determining the sensitivity of any particular piece of
2846   information within the context of any given request. Therefore,
2847   applications &SHOULD; supply as much control over this information as
2848   possible to the provider of that information. Four header fields are
2849   worth special mention in this context: Server, Via, Referer and From.
2850</t>
2851<t>
2852   Revealing the specific software version of the server might allow the
2853   server machine to become more vulnerable to attacks against software
2854   that is known to contain security holes. Implementors &SHOULD; make the
2855   Server header field a configurable option.
2856</t>
2857<t>
2858   Proxies which serve as a portal through a network firewall &SHOULD;
2859   take special precautions regarding the transfer of header information
2860   that identifies the hosts behind the firewall. In particular, they
2861   &SHOULD; remove, or replace with sanitized versions, any Via fields
2862   generated behind the firewall.
2863</t>
2864<t>
2865   The Referer header field allows reading patterns to be studied and reverse
2866   links drawn. Although it can be very useful, its power can be abused
2867   if user details are not separated from the information contained in
2868   the Referer. Even when the personal information has been removed, the
2869   Referer header field might indicate a private document's URI whose
2870   publication would be inappropriate.
2871</t>
2872<t>
2873   The information sent in the From field might conflict with the user's
2874   privacy interests or their site's security policy, and hence it
2875   &SHOULD-NOT;  be transmitted without the user being able to disable,
2876   enable, and modify the contents of the field. The user &MUST; be able
2877   to set the contents of this field within a user preference or
2878   application defaults configuration.
2879</t>
2880<t>
2881   We suggest, though do not require, that a convenient toggle interface
2882   be provided for the user to enable or disable the sending of From and
2883   Referer information.
2884</t>
2885<t>
2886   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2887   target="header.server"/>) header fields can sometimes be used to determine
2888   that a specific client or server have a particular security hole which might
2889   be exploited. Unfortunately, this same information is often used for other
2890   valuable purposes for which HTTP currently has no better mechanism.
2891</t>
2892<t>
2893   Furthermore, the User-Agent header field may contain enough entropy to be
2894   used, possibly in conjunction with other material, to uniquely identify the
2895   user.
2896</t>
2897<t>
2898   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2899   that was sent in request header fields within the body of their response.
2900   Clients &SHOULD; be careful with sensitive information, like Cookies,
2901   Authorization credentials and other header fields that might be used to
2902   collect data from the client.
2903</t> 
2904</section>
2905
2906<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2907<t>
2908   Because the source of a link might be private information or might
2909   reveal an otherwise private information source, it is strongly
2910   recommended that the user be able to select whether or not the
2911   Referer field is sent. For example, a browser client could have a
2912   toggle switch for browsing openly/anonymously, which would
2913   respectively enable/disable the sending of Referer and From
2914   information.
2915</t>
2916<t>
2917   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2918   HTTP request if the referring page was transferred with a secure
2919   protocol.
2920</t>
2921<t>
2922   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2923   sensitive data because that data will be placed in the request-target. Many
2924   existing servers, proxies, and user agents log or display the request-target
2925   in places where it might be visible to third parties. Such services can
2926   use POST-based form submission instead.
2927</t>
2928</section>
2929
2930<section title="Location Headers and Spoofing" anchor="location.spoofing">
2931<t>
2932   If a single server supports multiple organizations that do not trust
2933   one another, then it &MUST; check the values of Location and Content-Location
2934   header fields in responses that are generated under control of
2935   said organizations to make sure that they do not attempt to
2936   invalidate resources over which they have no authority.
2937</t>
2938</section>
2939
2940<section title="Security Considerations for CONNECT">
2941<t>
2942   Since tunneled data is opaque to the proxy, there are additional
2943   risks to tunneling to other well-known or reserved ports.
2944   A HTTP client CONNECTing to port 25 could relay spam
2945   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2946   access to a small number of known ports.
2947</t>
2948</section>
2949
2950</section>
2951
2952<section title="Acknowledgments" anchor="ack">
2953</section>
2954</middle>
2955<back>
2956
2957<references title="Normative References">
2958
2959<reference anchor="Part1">
2960  <front>
2961    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2962    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2963      <organization abbrev="Day Software">Day Software</organization>
2964      <address><email>fielding@gbiv.com</email></address>
2965    </author>
2966    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2967      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2968      <address><email>jg@freedesktop.org</email></address>
2969    </author>
2970    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2971      <organization abbrev="HP">Hewlett-Packard Company</organization>
2972      <address><email>JeffMogul@acm.org</email></address>
2973    </author>
2974    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2975      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2976      <address><email>henrikn@microsoft.com</email></address>
2977    </author>
2978    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2979      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2980      <address><email>LMM@acm.org</email></address>
2981    </author>
2982    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2983      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2984      <address><email>paulle@microsoft.com</email></address>
2985    </author>
2986    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2987      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2988      <address><email>timbl@w3.org</email></address>
2989    </author>
2990    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2991      <organization abbrev="W3C">World Wide Web Consortium</organization>
2992      <address><email>ylafon@w3.org</email></address>
2993    </author>
2994    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2995      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2996      <address><email>julian.reschke@greenbytes.de</email></address>
2997    </author>
2998    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2999  </front>
3000  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3001  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3002</reference>
3003
3004<reference anchor="Part3">
3005  <front>
3006    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3007    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3008      <organization abbrev="Day Software">Day Software</organization>
3009      <address><email>fielding@gbiv.com</email></address>
3010    </author>
3011    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3012      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3013      <address><email>jg@freedesktop.org</email></address>
3014    </author>
3015    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3016      <organization abbrev="HP">Hewlett-Packard Company</organization>
3017      <address><email>JeffMogul@acm.org</email></address>
3018    </author>
3019    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3020      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3021      <address><email>henrikn@microsoft.com</email></address>
3022    </author>
3023    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3024      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3025      <address><email>LMM@acm.org</email></address>
3026    </author>
3027    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3028      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3029      <address><email>paulle@microsoft.com</email></address>
3030    </author>
3031    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3032      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3033      <address><email>timbl@w3.org</email></address>
3034    </author>
3035    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3036      <organization abbrev="W3C">World Wide Web Consortium</organization>
3037      <address><email>ylafon@w3.org</email></address>
3038    </author>
3039    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3040      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3041      <address><email>julian.reschke@greenbytes.de</email></address>
3042    </author>
3043    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3044  </front>
3045  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3046  <x:source href="p3-payload.xml" basename="p3-payload"/>
3047</reference>
3048
3049<reference anchor="Part4">
3050  <front>
3051    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3052    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3053      <organization abbrev="Day Software">Day Software</organization>
3054      <address><email>fielding@gbiv.com</email></address>
3055    </author>
3056    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3057      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3058      <address><email>jg@freedesktop.org</email></address>
3059    </author>
3060    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3061      <organization abbrev="HP">Hewlett-Packard Company</organization>
3062      <address><email>JeffMogul@acm.org</email></address>
3063    </author>
3064    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3065      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3066      <address><email>henrikn@microsoft.com</email></address>
3067    </author>
3068    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3069      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3070      <address><email>LMM@acm.org</email></address>
3071    </author>
3072    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3073      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3074      <address><email>paulle@microsoft.com</email></address>
3075    </author>
3076    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3077      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3078      <address><email>timbl@w3.org</email></address>
3079    </author>
3080    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3081      <organization abbrev="W3C">World Wide Web Consortium</organization>
3082      <address><email>ylafon@w3.org</email></address>
3083    </author>
3084    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3085      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3086      <address><email>julian.reschke@greenbytes.de</email></address>
3087    </author>
3088    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3089  </front>
3090  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3091  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3092</reference>
3093
3094<reference anchor="Part5">
3095  <front>
3096    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3097    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3098      <organization abbrev="Day Software">Day Software</organization>
3099      <address><email>fielding@gbiv.com</email></address>
3100    </author>
3101    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3102      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3103      <address><email>jg@freedesktop.org</email></address>
3104    </author>
3105    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3106      <organization abbrev="HP">Hewlett-Packard Company</organization>
3107      <address><email>JeffMogul@acm.org</email></address>
3108    </author>
3109    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3110      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3111      <address><email>henrikn@microsoft.com</email></address>
3112    </author>
3113    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3114      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3115      <address><email>LMM@acm.org</email></address>
3116    </author>
3117    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3118      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3119      <address><email>paulle@microsoft.com</email></address>
3120    </author>
3121    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3122      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3123      <address><email>timbl@w3.org</email></address>
3124    </author>
3125    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3126      <organization abbrev="W3C">World Wide Web Consortium</organization>
3127      <address><email>ylafon@w3.org</email></address>
3128    </author>
3129    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3130      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3131      <address><email>julian.reschke@greenbytes.de</email></address>
3132    </author>
3133    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3134  </front>
3135  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3136  <x:source href="p5-range.xml" basename="p5-range"/>
3137</reference>
3138
3139<reference anchor="Part6">
3140  <front>
3141    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3142    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3143      <organization abbrev="Day Software">Day Software</organization>
3144      <address><email>fielding@gbiv.com</email></address>
3145    </author>
3146    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3147      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3148      <address><email>jg@freedesktop.org</email></address>
3149    </author>
3150    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3151      <organization abbrev="HP">Hewlett-Packard Company</organization>
3152      <address><email>JeffMogul@acm.org</email></address>
3153    </author>
3154    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3155      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3156      <address><email>henrikn@microsoft.com</email></address>
3157    </author>
3158    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3159      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3160      <address><email>LMM@acm.org</email></address>
3161    </author>
3162    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3163      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3164      <address><email>paulle@microsoft.com</email></address>
3165    </author>
3166    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3167      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3168      <address><email>timbl@w3.org</email></address>
3169    </author>
3170    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3171      <organization abbrev="W3C">World Wide Web Consortium</organization>
3172      <address><email>ylafon@w3.org</email></address>
3173    </author>
3174    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3175      <address><email>mnot@mnot.net</email></address>
3176    </author>
3177    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3178      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3179      <address><email>julian.reschke@greenbytes.de</email></address>
3180    </author>
3181    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3182  </front>
3183  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3184  <x:source href="p6-cache.xml" basename="p6-cache"/>
3185</reference>
3186
3187<reference anchor="Part7">
3188  <front>
3189    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3190    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3191      <organization abbrev="Day Software">Day Software</organization>
3192      <address><email>fielding@gbiv.com</email></address>
3193    </author>
3194    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3195      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3196      <address><email>jg@freedesktop.org</email></address>
3197    </author>
3198    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3199      <organization abbrev="HP">Hewlett-Packard Company</organization>
3200      <address><email>JeffMogul@acm.org</email></address>
3201    </author>
3202    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3203      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3204      <address><email>henrikn@microsoft.com</email></address>
3205    </author>
3206    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3207      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3208      <address><email>LMM@acm.org</email></address>
3209    </author>
3210    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3211      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3212      <address><email>paulle@microsoft.com</email></address>
3213    </author>
3214    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3215      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3216      <address><email>timbl@w3.org</email></address>
3217    </author>
3218    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3219      <organization abbrev="W3C">World Wide Web Consortium</organization>
3220      <address><email>ylafon@w3.org</email></address>
3221    </author>
3222    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3223      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3224      <address><email>julian.reschke@greenbytes.de</email></address>
3225    </author>
3226    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3227  </front>
3228  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3229  <x:source href="p7-auth.xml" basename="p7-auth"/>
3230</reference>
3231
3232<reference anchor="RFC2119">
3233  <front>
3234    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3235    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3236      <organization>Harvard University</organization>
3237      <address><email>sob@harvard.edu</email></address>
3238    </author>
3239    <date month="March" year="1997"/>
3240  </front>
3241  <seriesInfo name="BCP" value="14"/>
3242  <seriesInfo name="RFC" value="2119"/>
3243</reference>
3244
3245<reference anchor="RFC3986">
3246 <front>
3247  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3248  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3249    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3250    <address>
3251       <email>timbl@w3.org</email>
3252       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3253    </address>
3254  </author>
3255  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3256    <organization abbrev="Day Software">Day Software</organization>
3257    <address>
3258      <email>fielding@gbiv.com</email>
3259      <uri>http://roy.gbiv.com/</uri>
3260    </address>
3261  </author>
3262  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3263    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3264    <address>
3265      <email>LMM@acm.org</email>
3266      <uri>http://larry.masinter.net/</uri>
3267    </address>
3268  </author>
3269  <date month='January' year='2005'></date>
3270 </front>
3271 <seriesInfo name="STD" value="66"/>
3272 <seriesInfo name="RFC" value="3986"/>
3273</reference>
3274
3275<reference anchor="RFC5234">
3276  <front>
3277    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3278    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3279      <organization>Brandenburg InternetWorking</organization>
3280      <address>
3281        <email>dcrocker@bbiw.net</email>
3282      </address> 
3283    </author>
3284    <author initials="P." surname="Overell" fullname="Paul Overell">
3285      <organization>THUS plc.</organization>
3286      <address>
3287        <email>paul.overell@thus.net</email>
3288      </address>
3289    </author>
3290    <date month="January" year="2008"/>
3291  </front>
3292  <seriesInfo name="STD" value="68"/>
3293  <seriesInfo name="RFC" value="5234"/>
3294</reference>
3295
3296</references>
3297
3298<references title="Informative References">
3299
3300<reference anchor="RFC1945">
3301  <front>
3302    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3303    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3304      <organization>MIT, Laboratory for Computer Science</organization>
3305      <address><email>timbl@w3.org</email></address>
3306    </author>
3307    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3308      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3309      <address><email>fielding@ics.uci.edu</email></address>
3310    </author>
3311    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3312      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3313      <address><email>frystyk@w3.org</email></address>
3314    </author>
3315    <date month="May" year="1996"/>
3316  </front>
3317  <seriesInfo name="RFC" value="1945"/>
3318</reference>
3319
3320<reference anchor="RFC2068">
3321  <front>
3322    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3323    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3324      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3325      <address><email>fielding@ics.uci.edu</email></address>
3326    </author>
3327    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3328      <organization>MIT Laboratory for Computer Science</organization>
3329      <address><email>jg@w3.org</email></address>
3330    </author>
3331    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3332      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3333      <address><email>mogul@wrl.dec.com</email></address>
3334    </author>
3335    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3336      <organization>MIT Laboratory for Computer Science</organization>
3337      <address><email>frystyk@w3.org</email></address>
3338    </author>
3339    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3340      <organization>MIT Laboratory for Computer Science</organization>
3341      <address><email>timbl@w3.org</email></address>
3342    </author>
3343    <date month="January" year="1997"/>
3344  </front>
3345  <seriesInfo name="RFC" value="2068"/>
3346</reference>
3347
3348<reference anchor="RFC2616">
3349  <front>
3350    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3351    <author initials="R." surname="Fielding" fullname="R. Fielding">
3352      <organization>University of California, Irvine</organization>
3353      <address><email>fielding@ics.uci.edu</email></address>
3354    </author>
3355    <author initials="J." surname="Gettys" fullname="J. Gettys">
3356      <organization>W3C</organization>
3357      <address><email>jg@w3.org</email></address>
3358    </author>
3359    <author initials="J." surname="Mogul" fullname="J. Mogul">
3360      <organization>Compaq Computer Corporation</organization>
3361      <address><email>mogul@wrl.dec.com</email></address>
3362    </author>
3363    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3364      <organization>MIT Laboratory for Computer Science</organization>
3365      <address><email>frystyk@w3.org</email></address>
3366    </author>
3367    <author initials="L." surname="Masinter" fullname="L. Masinter">
3368      <organization>Xerox Corporation</organization>
3369      <address><email>masinter@parc.xerox.com</email></address>
3370    </author>
3371    <author initials="P." surname="Leach" fullname="P. Leach">
3372      <organization>Microsoft Corporation</organization>
3373      <address><email>paulle@microsoft.com</email></address>
3374    </author>
3375    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3376      <organization>W3C</organization>
3377      <address><email>timbl@w3.org</email></address>
3378    </author>
3379    <date month="June" year="1999"/>
3380  </front>
3381  <seriesInfo name="RFC" value="2616"/>
3382</reference>
3383
3384<reference anchor='RFC2817'>
3385  <front>
3386    <title>Upgrading to TLS Within HTTP/1.1</title>
3387    <author initials='R.' surname='Khare' fullname='R. Khare'>
3388      <organization>4K Associates / UC Irvine</organization>
3389      <address><email>rohit@4K-associates.com</email></address>
3390    </author>
3391    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3392      <organization>Agranat Systems, Inc.</organization>
3393      <address><email>lawrence@agranat.com</email></address>
3394    </author>
3395    <date year='2000' month='May' />
3396  </front>
3397  <seriesInfo name='RFC' value='2817' />
3398</reference>
3399
3400<reference anchor='RFC3864'>
3401  <front>
3402    <title>Registration Procedures for Message Header Fields</title>
3403    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3404      <organization>Nine by Nine</organization>
3405      <address><email>GK-IETF@ninebynine.org</email></address>
3406    </author>
3407    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3408      <organization>BEA Systems</organization>
3409      <address><email>mnot@pobox.com</email></address>
3410    </author>
3411    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3412      <organization>HP Labs</organization>
3413      <address><email>JeffMogul@acm.org</email></address>
3414    </author>
3415    <date year='2004' month='September' />
3416  </front>
3417  <seriesInfo name='BCP' value='90' />
3418  <seriesInfo name='RFC' value='3864' />
3419</reference>
3420
3421<reference anchor='RFC5226'>
3422  <front>
3423    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3424    <author initials='T.' surname='Narten' fullname='T. Narten'>
3425      <organization>IBM</organization>
3426      <address><email>narten@us.ibm.com</email></address>
3427    </author>
3428    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3429      <organization>Google</organization>
3430      <address><email>Harald@Alvestrand.no</email></address>
3431    </author>
3432    <date year='2008' month='May' />
3433  </front>
3434  <seriesInfo name='BCP' value='26' />
3435  <seriesInfo name='RFC' value='5226' />
3436</reference>
3437
3438<reference anchor="RFC5322">
3439  <front>
3440    <title>Internet Message Format</title>
3441    <author initials="P." surname="Resnick" fullname="P. Resnick">
3442      <organization>Qualcomm Incorporated</organization>
3443    </author>
3444    <date year="2008" month="October"/>
3445  </front> 
3446  <seriesInfo name="RFC" value="5322"/>
3447</reference>
3448
3449</references>
3450
3451<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3452<t>
3453  This document takes over the Status Code Registry, previously defined
3454  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3455  (<xref target="status.code.registry"/>)
3456</t>
3457<t>
3458  Clarify definition of POST.
3459  (<xref target="POST"/>)
3460</t>
3461<t>
3462  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3463  (<xref target="CONNECT"/>)
3464</t>
3465<t>
3466  Failed to consider that there are
3467  many other request methods that are safe to automatically redirect,
3468  and further that the user agent is able to make that determination
3469  based on the request method semantics.
3470  (Sections <xref format="counter" target="status.301"/>,
3471  <xref format="counter" target="status.302"/> and
3472  <xref format="counter" target="status.307"/>)
3473</t>
3474<t>
3475  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3476  It used to indicate that the target resource must be accessed through the
3477  proxy given by the Location field. The Location field gave the URI of the
3478  proxy. The recipient was expected to repeat this single request via the proxy.
3479  (<xref target="status.305"/>)
3480</t>
3481<t>
3482  Define status 426 (Upgrade Required) (this was incorporated from
3483  <xref target="RFC2817"/>).
3484  (<xref target="status.426"/>)
3485</t>
3486<t>
3487  Reclassify "Allow" as response header field, removing the option to
3488  specify it in a PUT request.
3489  Relax the server requirement on the contents of the Allow header field and
3490  remove requirement on clients to always trust the header field value.
3491  (<xref target="header.allow"/>)
3492</t>
3493<t>
3494  Correct syntax of Location header field to allow URI references (including
3495  relative references and fragments), as referred symbol "absoluteURI" wasn't
3496  what was expected, and add some clarifications as to when use of fragments
3497  would not be appropriate.
3498  (<xref target="header.location"/>)
3499</t>
3500<t>
3501  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3502  extension methods could have used it as well).
3503  (<xref target="header.max-forwards"/>)
3504</t>
3505<t>
3506  Allow Referer field value of "about:blank" as alternative to not specifying it.
3507  (<xref target="header.referer"/>)
3508</t>
3509<t>
3510  In the description of the Server header field, the Via field
3511  was described as a SHOULD. The requirement was and is stated
3512  correctly in the description of the Via header field in &header-via;.
3513  (<xref target="header.server"/>)
3514</t>
3515</section>
3516
3517<?BEGININC p2-semantics.abnf-appendix ?>
3518<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3519<figure>
3520<artwork type="abnf" name="p2-semantics.parsed-abnf">
3521<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3522<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3523<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3524<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3525<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3526<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3527<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3528<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3529<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3530
3531<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3532<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3533<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3534
3535<x:ref>From</x:ref> = "From:" OWS From-v
3536<x:ref>From-v</x:ref> = mailbox
3537
3538<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3539<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3540
3541<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3542If-Modified-Since =
3543 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3544<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3545<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3546If-Unmodified-Since =
3547 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3548
3549<x:ref>Location</x:ref> = "Location:" OWS Location-v
3550<x:ref>Location-v</x:ref> = URI-reference
3551
3552<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3553<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3554<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3555 / %x47.45.54 ; GET
3556 / %x48.45.41.44 ; HEAD
3557 / %x50.4F.53.54 ; POST
3558 / %x50.55.54 ; PUT
3559 / %x44.45.4C.45.54.45 ; DELETE
3560 / %x54.52.41.43.45 ; TRACE
3561 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3562 / extension-method
3563
3564<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3565
3566Proxy-Authenticate =
3567 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3568Proxy-Authorization =
3569 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3570
3571<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3572<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3573<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3574<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3575<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3576<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3577<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3578
3579<x:ref>Server</x:ref> = "Server:" OWS Server-v
3580<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3581<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3582 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3583 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3584 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3585 "415" / "416" / "417" / "426" / "500" / "501" / "502" / "503" /
3586 "504" / "505" / extension-code
3587
3588<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3589
3590<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3591<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3592<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3593
3594<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3595
3596WWW-Authenticate =
3597 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3598
3599<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3600
3601<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3602
3603<x:ref>delta-seconds</x:ref> = 1*DIGIT
3604
3605<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3606<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3607<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3608 *expect-params ]
3609<x:ref>extension-code</x:ref> = 3DIGIT
3610<x:ref>extension-method</x:ref> = token
3611
3612<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3613
3614<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3615
3616<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3617<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3618
3619<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3620
3621<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3622 Accept-Language / Authorization / Expect / From / Host / If-Match /
3623 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3624 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3625 User-Agent
3626<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3627 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3628
3629<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3630</artwork>
3631</figure>
3632<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3633; Reason-Phrase defined but not used
3634; Status-Code defined but not used
3635; request-header defined but not used
3636; response-header defined but not used
3637</artwork></figure></section>
3638<?ENDINC p2-semantics.abnf-appendix ?>
3639
3640<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3641
3642<section title="Since RFC 2616">
3643<t>
3644  Extracted relevant partitions from <xref target="RFC2616"/>.
3645</t>
3646</section>
3647
3648<section title="Since draft-ietf-httpbis-p2-semantics-00">
3649<t>
3650  Closed issues:
3651  <list style="symbols"> 
3652    <t>
3653      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3654      "Via is a MUST"
3655      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3656    </t>
3657    <t>
3658      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3659      "Fragments allowed in Location"
3660      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3661    </t>
3662    <t>
3663      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3664      "Safe Methods vs Redirection"
3665      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3666    </t>
3667    <t>
3668      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3669      "Revise description of the POST method"
3670      (<eref target="http://purl.org/NET/http-errata#post"/>)
3671    </t>
3672    <t>
3673      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3674      "Normative and Informative references"
3675    </t>
3676    <t>
3677      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3678      "RFC2606 Compliance"
3679    </t>
3680    <t>
3681      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3682      "Informative references"
3683    </t>
3684    <t>
3685      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3686      "Redundant cross-references"
3687    </t>
3688  </list>
3689</t>
3690<t>
3691  Other changes:
3692  <list style="symbols"> 
3693    <t>
3694      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3695    </t>
3696  </list>
3697</t>
3698</section>
3699
3700<section title="Since draft-ietf-httpbis-p2-semantics-01">
3701<t>
3702  Closed issues:
3703  <list style="symbols"> 
3704    <t>
3705      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3706      "PUT side effects"
3707    </t>
3708    <t>
3709      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3710      "Duplicate Host header requirements"
3711    </t>
3712  </list>
3713</t>
3714<t>
3715  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3716  <list style="symbols"> 
3717    <t>
3718      Move "Product Tokens" section (back) into Part 1, as "token" is used
3719      in the definition of the Upgrade header field.
3720    </t>
3721    <t>
3722      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3723    </t>
3724    <t>
3725      Copy definition of delta-seconds from Part6 instead of referencing it.
3726    </t>
3727  </list>
3728</t>
3729</section>
3730
3731<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3732<t>
3733  Closed issues:
3734  <list style="symbols"> 
3735    <t>
3736      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3737      "Requiring Allow in 405 responses"
3738    </t>
3739    <t>
3740      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3741      "Status Code Registry"
3742    </t>
3743    <t>
3744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3745      "Redirection vs. Location"
3746    </t>
3747    <t>
3748      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3749      "Cacheability of 303 response"
3750    </t>
3751    <t>
3752      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3753      "305 Use Proxy"
3754    </t>
3755    <t>
3756      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3757      "Classification for Allow header"
3758    </t>
3759    <t>
3760      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3761      "PUT - 'store under' vs 'store at'"
3762    </t>
3763  </list>
3764</t>
3765<t>
3766  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3767  <list style="symbols"> 
3768    <t>
3769      Reference RFC 3984, and update header field registrations for headers defined
3770      in this document.
3771    </t>
3772  </list>
3773</t>
3774<t>
3775  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3776  <list style="symbols"> 
3777    <t>
3778      Replace string literals when the string really is case-sensitive (method).
3779    </t>
3780  </list>
3781</t>
3782</section>
3783
3784<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3785<t>
3786  Closed issues:
3787  <list style="symbols"> 
3788    <t>
3789      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3790      "OPTIONS request bodies"
3791    </t>
3792    <t>
3793      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3794      "Description of CONNECT should refer to RFC2817"
3795    </t>
3796    <t>
3797      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3798      "Location Content-Location reference request/response mixup"
3799    </t>
3800  </list>
3801</t>
3802<t>
3803  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3804  <list style="symbols"> 
3805    <t>
3806      Added initial proposal for registration process, plus initial
3807      content (non-HTTP/1.1 methods to be added by a separate specification).
3808    </t>
3809  </list>
3810</t>
3811</section>
3812
3813<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3814<t>
3815  Closed issues:
3816  <list style="symbols"> 
3817    <t>
3818      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3819      "Content-*"
3820    </t>
3821    <t>
3822      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3823      "RFC 2822 is updated by RFC 5322"
3824    </t>
3825  </list>
3826</t>
3827<t>
3828  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3829  <list style="symbols"> 
3830    <t>
3831      Use "/" instead of "|" for alternatives.
3832    </t>
3833    <t>
3834      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3835      whitespace ("OWS") and required whitespace ("RWS").
3836    </t>
3837    <t>
3838      Rewrite ABNFs to spell out whitespace rules, factor out
3839      header field value format definitions.
3840    </t>
3841  </list>
3842</t>
3843</section>
3844
3845<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3846<t>
3847  Closed issues:
3848  <list style="symbols"> 
3849    <t>
3850      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3851      "Reason-Phrase BNF"
3852    </t>
3853  </list>
3854</t>
3855<t>
3856  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3857  <list style="symbols"> 
3858    <t>
3859      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3860    </t>
3861  </list>
3862</t>
3863</section>
3864
3865<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3866<t>
3867  Closed issues:
3868  <list style="symbols"> 
3869    <t>
3870      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3871      "Clarify when Referer is sent"
3872    </t>
3873    <t>
3874      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3875      "status codes vs methods"
3876    </t>
3877    <t>
3878      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3879      "Do not require "updates" relation for specs that register status codes or method names"
3880    </t>
3881  </list>
3882</t>
3883</section>
3884
3885<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3886<t>
3887  Closed issues:
3888  <list style="symbols"> 
3889    <t>
3890      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3891      "Idempotency"
3892    </t>
3893    <t>
3894      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3895      "TRACE security considerations"
3896    </t>
3897    <t>
3898      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3899      "Clarify rules for determining what entities a response carries"
3900    </t>
3901    <t>
3902      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3903      "update note citing RFC 1945 and 2068"
3904    </t>
3905    <t>
3906      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3907      "update note about redirect limit"
3908    </t>
3909    <t>
3910      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3911      "Location header ABNF should use 'URI'"
3912    </t>
3913    <t>
3914      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3915      "fragments in Location vs status 303"
3916    </t>
3917    <t>
3918      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3919      "move IANA registrations for optional status codes"
3920    </t>
3921  </list>
3922</t>
3923<t>
3924  Partly resolved issues:
3925  <list style="symbols"> 
3926    <t>
3927      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3928      "Are OPTIONS and TRACE safe?"
3929    </t>
3930  </list>
3931</t>
3932</section>
3933
3934<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3935<t>
3936  Closed issues:
3937  <list style="symbols"> 
3938    <t>
3939      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3940      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3941      status codes when fixing this previously)
3942    </t>
3943  </list>
3944</t>
3945</section>
3946
3947<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3948<t>
3949  Closed issues:
3950  <list style="symbols"> 
3951    <t>
3952      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3953      "Fragment combination / precedence during redirects"
3954    </t>
3955  </list>
3956</t>
3957<t>
3958  Partly resolved issues:
3959  <list style="symbols"> 
3960    <t>
3961      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3962      "Location header payload handling"
3963    </t>
3964    <t>
3965      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3966      "Term for the requested resource's URI"
3967    </t>
3968  </list>
3969</t>
3970</section>
3971
3972<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3973<t>
3974  Closed issues:
3975  <list style="symbols"> 
3976    <t>
3977      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3978      "Clarify 'Requested Variant'"
3979    </t>
3980    <t>
3981      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3982      "Clarify entity / representation / variant terminology"
3983    </t>
3984    <t>
3985      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3986      "Methods and Caching"
3987    </t>
3988    <t>
3989      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3990      "OPTIONS vs Max-Forwards"
3991    </t>
3992    <t>
3993      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3994      "Status codes and caching"
3995    </t>
3996    <t>
3997      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3998      "consider removing the 'changes from 2068' sections"
3999    </t>
4000  </list>
4001</t>
4002</section>
4003
4004<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4005<t>
4006  Closed issues:
4007  <list style="symbols"> 
4008    <t>
4009      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4010      "Considerations for new status codes"
4011    </t>
4012    <t>
4013      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4014      "Considerations for new methods"
4015    </t>
4016    <t>
4017      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4018      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4019    </t>
4020  </list>
4021</t>
4022</section>
4023
4024<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4025<t>
4026  Closed issues:
4027  <list style="symbols"> 
4028    <t>
4029      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4030      "Fragment combination / precedence during redirects" (added warning
4031      about having a fragid on the redirect may cause inconvenience in
4032      some cases)
4033    </t>
4034    <t>
4035      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4036      "205 Bodies"
4037    </t>
4038    <t>
4039      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4040      "Max-Forwards vs extension methods"
4041    </t>
4042    <t>
4043      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4044      "proxies not supporting certain methods"
4045    </t>
4046    <t>
4047      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4048      "Migrate CONNECT from RFC2817 to p2"
4049    </t>
4050    <t>
4051      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4052      "Migrate Upgrade details from RFC2817"
4053    </t>
4054  </list>
4055</t>
4056</section>
4057
4058</section>
4059
4060</back>
4061</rfc>
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