source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1254

Last change on this file since 1254 was 1254, checked in by julian.reschke@…, 9 years ago

bump up document dates

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[29]1<?xml version="1.0" encoding="utf-8"?>
[101]2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
[8]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>">
[29]14  <!ENTITY ID-VERSION "latest">
[1254]15  <!ENTITY ID-MONTH "April">
[1099]16  <!ENTITY ID-YEAR "2011">
[1101]17  <!ENTITY mdash "&#8212;">
[424]18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]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'/>">
[994]25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[205]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'/>">
[31]29  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[823]30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[580]31  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]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'/>">
[1065]36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]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'/>">
[688]49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]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'/>">
[835]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'/>">
[31]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'/>">
[190]67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[263]68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[700]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'/>">
[838]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'/>">
[1050]78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[1111]79  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[8]81]>
82<?rfc toc="yes" ?>
[29]83<?rfc symrefs="yes" ?>
84<?rfc sortrefs="yes" ?>
[8]85<?rfc compact="yes"?>
86<?rfc subcompact="no" ?>
87<?rfc linkmailto="no" ?>
88<?rfc editing="no" ?>
[203]89<?rfc comments="yes"?>
90<?rfc inline="yes"?>
[799]91<?rfc rfcedstyle="yes"?>
[8]92<?rfc-ext allow-markup-in-artwork="yes" ?>
93<?rfc-ext include-references-in-index="yes" ?>
[308]94<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
[446]95     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
[286]96     xmlns:x='http://purl.org/net/xml2rfc/ext'
97     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
[8]98<front>
99
[120]100  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
[8]101
[29]102  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]103    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]104    <address>
105      <postal>
[1106]106        <street>345 Park Ave</street>
107        <city>San Jose</city>
[8]108        <region>CA</region>
[1106]109        <code>95110</code>
[29]110        <country>USA</country>
[8]111      </postal>
[29]112      <email>fielding@gbiv.com</email>
113      <uri>http://roy.gbiv.com/</uri>
[8]114    </address>
115  </author>
116
[29]117  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]118    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]119    <address>
120      <postal>
[29]121        <street>21 Oak Knoll Road</street>
122        <city>Carlisle</city>
[8]123        <region>MA</region>
[29]124        <code>01741</code>
125        <country>USA</country>
[8]126      </postal>
[844]127      <email>jg@freedesktop.org</email>
128      <uri>http://gettys.wordpress.com/</uri>
[8]129    </address>
130  </author>
131 
132  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]133    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]134    <address>
135      <postal>
[29]136        <street>HP Labs, Large Scale Systems Group</street>
137        <street>1501 Page Mill Road, MS 1177</street>
[8]138        <city>Palo Alto</city>
139        <region>CA</region>
[29]140        <code>94304</code>
141        <country>USA</country>
[8]142      </postal>
[29]143      <email>JeffMogul@acm.org</email>
[8]144    </address>
145  </author>
146
147  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]148    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]149    <address>
150      <postal>
[29]151        <street>1 Microsoft Way</street>
152        <city>Redmond</city>
153        <region>WA</region>
154        <code>98052</code>
155        <country>USA</country>
[8]156      </postal>
[29]157      <email>henrikn@microsoft.com</email>
[8]158    </address>
159  </author>
160
161  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]162    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]163    <address>
164      <postal>
[29]165        <street>345 Park Ave</street>
166        <city>San Jose</city>
[8]167        <region>CA</region>
[29]168        <code>95110</code>
169        <country>USA</country>
[8]170      </postal>
[29]171      <email>LMM@acm.org</email>
172      <uri>http://larry.masinter.net/</uri>
[8]173    </address>
174  </author>
175 
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email>paulle@microsoft.com</email>
186    </address>
187  </author>
188   
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
[34]193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
[8]196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
[29]199        <country>USA</country>
[8]200      </postal>
201      <email>timbl@w3.org</email>
[34]202      <uri>http://www.w3.org/People/Berners-Lee/</uri>
[8]203    </address>
204  </author>
205
[95]206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email>ylafon@w3.org</email>
218      <uri>http://www.raubacapeu.net/people/yves/</uri>
219    </address>
220  </author>
221
[95]222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
[609]230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email>julian.reschke@greenbytes.de</email>
233      <uri>http://greenbytes.de/tech/webdav/</uri>
[95]234    </address>
235  </author>
236
[31]237  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]238  <workgroup>HTTPbis Working Group</workgroup>
[8]239
240<abstract>
241<t>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
[29]244   systems. HTTP has been in use by the World Wide Web global information
[35]245   initiative since 1990. This document is Part 2 of the seven-part specification
[29]246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
[1163]248   as expressed by request methods, request header fields, response status codes,
249   and response header fields.
[8]250</t>
251</abstract>
[36]252
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
256    mailing list (ietf-http-wg@w3.org). The current issues list is
[848]257    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
[36]258    and related documents (including fancy diffs) can be found at
[324]259    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
[36]260  </t>
[153]261  <t>
[1180]262    The changes in this draft are summarized in <xref target="changes.since.13"/>.
[153]263  </t>
[36]264</note>
[8]265</front>
266<middle>
267<section title="Introduction" anchor="introduction">
268<t>
[162]269   This document defines HTTP/1.1 request and response semantics.  Each HTTP
270   message, as defined in &messaging;, is in the form of either a request or
271   a response.  An HTTP server listens on a connection for HTTP requests and
272   responds to each request, in the order received on that connection, with
273   one or more HTTP response messages.  This document defines the commonly
274   agreed upon semantics of the HTTP uniform interface, the intentions defined
275   by each request method, and the various response messages that might be
[965]276   expected as a result of applying that method to the target resource.
[8]277</t>
278<t>
[162]279   This document is currently disorganized in order to minimize the changes
280   between drafts and enable reviewers to see the smaller errata changes.
[980]281   A future draft will reorganize the sections to better reflect the content.
[162]282   In particular, the sections will be ordered according to the typical
283   processing of an HTTP request message (after message parsing): resource
[1163]284   mapping, methods, request modifying header fields, response status,
285   status modifying header fields, and resource metadata.  The current mess
286   reflects how widely dispersed these topics and associated requirements
287   had become in <xref target="RFC2616"/>.
[8]288</t>
[96]289
290<section title="Requirements" anchor="intro.requirements">
291<t>
292   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
293   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
294   document are to be interpreted as described in <xref target="RFC2119"/>.
295</t>
296<t>
297   An implementation is not compliant if it fails to satisfy one or more
[847]298   of the "MUST" or "REQUIRED" level requirements for the protocols it
299   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
300   level and all the "SHOULD" level requirements for its protocols is said
301   to be "unconditionally compliant"; one that satisfies all the "MUST"
302   level requirements but not all the "SHOULD" level requirements for its
303   protocols is said to be "conditionally compliant".
[96]304</t>
[8]305</section>
306
[424]307<section title="Syntax Notation" anchor="notation">
[425]308  <x:anchor-alias value="CR"/>
309  <x:anchor-alias value="DIGIT"/>
310  <x:anchor-alias value="LF"/>
311  <x:anchor-alias value="VCHAR"/>
312  <x:anchor-alias value="WSP"/>
[424]313<t>
[543]314  This specification uses the ABNF syntax defined in &notation; (which
315  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
316  <xref target="collected.abnf"/> shows the collected ABNF, with the list
317  rule expanded.
318</t>
319<t>
[425]320  The following core rules are included by
321  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
322  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
323  DIGIT (decimal 0-9), DQUOTE (double quote),
324  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
325  OCTET (any 8-bit sequence of data), SP (space),
326  VCHAR (any visible USASCII character),
327  and WSP (whitespace).
[424]328</t>
329
330<section title="Core Rules" anchor="core.rules">
[398]331  <x:anchor-alias value="obs-text"/>
[229]332  <x:anchor-alias value="quoted-string"/>
333  <x:anchor-alias value="token"/>
[356]334  <x:anchor-alias value="OWS"/>
335  <x:anchor-alias value="RWS"/>
[205]336<t>
[424]337  The core rules below are defined in &basic-rules;:
[205]338</t>
339<figure><artwork type="abnf2616">
[229]340  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
341  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
[356]342  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
343  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
[398]344  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
[205]345</artwork></figure>
[424]346</section>
347
348<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]349  <x:anchor-alias value="absolute-URI"/>
[688]350  <x:anchor-alias value="comment"/>
[229]351  <x:anchor-alias value="HTTP-date"/>
[391]352  <x:anchor-alias value="partial-URI"/>
[229]353  <x:anchor-alias value="product"/>
[785]354  <x:anchor-alias value="URI-reference"/>
[424]355<t>
[206]356  The ABNF rules below are defined in other parts:
357</t>
[207]358<figure><!--Part1--><artwork type="abnf2616">
[374]359  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
[688]360  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
[229]361  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
[391]362  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
[229]363  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
[785]364  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
[207]365</artwork></figure>
[205]366</section>
[424]367</section>
368</section>
[205]369
[8]370<section title="Method" anchor="method">
[229]371  <x:anchor-alias value="Method"/>
372  <x:anchor-alias value="extension-method"/>
[8]373<t>
[1161]374   The Method token indicates the request method to be performed on the target
[972]375   resource (&effective-request-uri;). The method is case-sensitive.
[8]376</t>
[1128]377<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
378  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
[8]379</artwork></figure>
380<t>
381   The list of methods allowed by a resource can be specified in an
[965]382   Allow header field (<xref target="header.allow"/>). The status code of the response
[8]383   always notifies the client whether a method is currently allowed on a
384   resource, since the set of allowed methods can change dynamically. An
[965]385   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
[8]386   if the method is known by the origin server but not allowed for the
[965]387   resource, and 501 (Not Implemented) if the method is
[8]388   unrecognized or not implemented by the origin server. The methods GET
389   and HEAD &MUST; be supported by all general-purpose servers. All other
390   methods are &OPTIONAL;; however, if the above methods are implemented,
391   they &MUST; be implemented with the same semantics as those specified
392   in <xref target="method.definitions"/>.
393</t>
[270]394
[1128]395<section title="Overview of Methods" anchor="overview.of.methods">
396<t>
397  The methods listed below are defined in <xref target="method.definitions"/>.
398</t>
399<texttable align="left">
400  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
401 
402  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
403  <c>GET</c> <c><xref target="GET"/></c>
404  <c>HEAD</c> <c><xref target="HEAD"/></c>
405  <c>POST</c> <c><xref target="POST"/></c>
406  <c>PUT</c> <c><xref target="PUT"/></c>
407  <c>DELETE</c> <c><xref target="DELETE"/></c>
408  <c>TRACE</c> <c><xref target="TRACE"/></c>
409  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
410</texttable>
411<t>
[1161]412  Note that this list is not exhaustive &mdash; it does not include request methods defined
[1128]413  in other specifications.
414</t>
415</section>
416
[270]417<section title="Method Registry" anchor="method.registry">
418<t>
419  The HTTP Method Registry defines the name space for the Method token in the
420  Request line of an HTTP request.
421</t>
422<t>
[286]423  Registrations &MUST; include the following fields:
424  <list style="symbols">
425    <t>Method Name (see <xref target="method"/>)</t>
426    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
427    <t>Pointer to specification text</t>
428  </list>
429</t>
430<t>
[270]431  Values to be added to this name space are subject to IETF review
[591]432  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
[270]433</t>
434<t>
[672]435  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
[270]436</t>
[1034]437
[1037]438<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
439<t>
440   When it is necessary to express new semantics for a HTTP request that
441   aren't specific to a single application or media type, and currently defined
442   methods are inadequate, it may be appropriate to register a new method.
443</t>
444<t>
[1042]445   HTTP methods are generic; that is, they are potentially applicable to any
446   resource, not just one particular media type, "type" of resource, or
447   application. As such, it is preferred that new HTTP methods be registered
448   in a document that isn't specific to a single application, so that this is
449   clear.
[1037]450</t>
451<t>
[1040]452   Due to the parsing rules defined in &message-body;, definitions of HTTP
453   methods cannot prohibit the presence of a message-body on either the request
454   or the response message (with responses to HEAD requests being the single
455   exception). Definitions of new methods cannot change this rule, but they can
456   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
[1037]457</t>
458<t>
[1042]459   New method definitions need to indicate whether they are safe (<xref
[1037]460   target="safe.methods"/>) and whether they are idempotent (<xref
[1042]461   target="idempotent.methods"/>). They also need to state whether they can be
[1037]462   cached (&caching;); in particular what conditions a cache may store the
463   response, and under what conditions such a stored response may be used to
464   satisfy a subsequent request.
465</t>
[8]466</section>
[1034]467
[270]468</section>
[1034]469</section>
[8]470
471<section title="Request Header Fields" anchor="request.header.fields">
[229]472  <x:anchor-alias value="request-header"/>
[8]473<t>
[1163]474   The request header fields allow the client to pass additional
[8]475   information about the request, and about the client itself, to the
476   server. These fields act as request modifiers, with semantics
477   equivalent to the parameters on a programming language method
478   invocation.
479</t>
[1138]480<texttable align="left">
481  <ttcol>Header Field Name</ttcol>
482  <ttcol>Defined in...</ttcol>
483
484  <c>Accept</c> <c>&header-accept;</c>
485  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
486  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
487  <c>Accept-Language</c> <c>&header-accept-language;</c>
488  <c>Authorization</c> <c>&header-authorization;</c>
489  <c>Expect</c> <c><xref target="header.expect"/></c>
490  <c>From</c> <c><xref target="header.from"/></c>
491  <c>Host</c> <c>&header-host;</c>
492  <c>If-Match</c> <c>&header-if-match;</c>
493  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
494  <c>If-None-Match</c> <c>&header-if-none-match;</c>
495  <c>If-Range</c> <c>&header-if-range;</c>
496  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
497  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
498  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
499  <c>Range</c> <c>&header-range;</c>
500  <c>Referer</c> <c><xref target="header.referer"/></c>
501  <c>TE</c> <c>&header-te;</c>
502  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
503</texttable>
[8]504</section>
505
506<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
[229]507  <x:anchor-alias value="Reason-Phrase"/>
508  <x:anchor-alias value="Status-Code"/>
[426]509  <x:anchor-alias value="extension-code"/>
[8]510<t>
[1124]511   The Status-Code element is a 3-digit integer result code of the attempt to
512   understand and satisfy the request.
[838]513</t>
514<t>
[1124]515   The Reason-Phrase is intended to give a short textual description of the
[1137]516   Status-Code and is intended for a human user. The client does not need
[1124]517   to examine or display the Reason-Phrase.
[8]518</t>
519<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"/>
[1124]520  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
[398]521  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
[8]522</artwork></figure>
523<t>
524   HTTP status codes are extensible. HTTP applications are not required
525   to understand the meaning of all registered status codes, though such
526   understanding is obviously desirable. However, applications &MUST;
527   understand the class of any status code, as indicated by the first
528   digit, and treat any unrecognized response as being equivalent to the
529   x00 status code of that class, with the exception that an
530   unrecognized response &MUST-NOT; be cached. For example, if an
531   unrecognized status code of 431 is received by the client, it can
532   safely assume that there was something wrong with its request and
533   treat the response as if it had received a 400 status code. In such
[866]534   cases, user agents &SHOULD; present to the user the representation enclosed
535   with the response, since that representation is likely to include human-readable
[8]536   information which will explain the unusual status.
537</t>
[262]538
[1124]539<section title="Overview of Status Codes" anchor="overview.of.status.codes">
540<t> 
[1137]541   The status codes listed below are defined in <xref target="status.codes"/>
542   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
543   The reason phrases listed here are only recommendations &mdash; they can be
544   replaced by local equivalents without affecting the protocol.
[1124]545</t>
546<texttable align="left">
547  <ttcol>Status-Code</ttcol>
548  <ttcol>Reason-Phrase</ttcol>
549  <ttcol>Defined in...</ttcol>
550 
551  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
552  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
553
554  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
555  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
556  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
557  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
558  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
559  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
560  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
561
562  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
563  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
564  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
565  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
566  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
567  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
568  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
569
570  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
571  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
572  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
573  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
574  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
575  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
576  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
577  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
578  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
579  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
580  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
581  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
582  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
583  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
584  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
585  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
586  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
587  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
588  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
589
590  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
591  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
592  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
593  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
594  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
595  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
596</texttable>
597<t>
598   Note that this list is not exhaustive &mdash; it does not include
599   extension status codes defined in other specifications.
600</t>
601</section>
602
[262]603<section title="Status Code Registry" anchor="status.code.registry">
604<t>
605  The HTTP Status Code Registry defines the name space for the Status-Code
[924]606  token in the Status-Line of an HTTP response.
[262]607</t>
608<t>
609  Values to be added to this name space are subject to IETF review
[591]610  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
[262]611</t>
612<t>
613  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
614</t>
[1035]615
[1038]616<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
617<t>
618   When it is necessary to express new semantics for a HTTP response that
619   aren't specific to a single application or media type, and currently defined
620   status codes are inadequate, a new status code can be registered.
621</t>
622<t>
[1043]623   HTTP status codes are generic; that is, they are potentially applicable to
624   any resource, not just one particular media type, "type" of resource, or
625   application. As such, it is preferred that new HTTP status codes be
626   registered in a document that isn't specific to a single application, so
627   that this is clear.
[1038]628</t>
629<t>
[1043]630   Definitions of new HTTP status codes typically explain the request
631   conditions that produce a response containing the status code (e.g.,
632   combinations of request headers and/or method(s)), along with any
633   interactions with response headers (e.g., those that are required, those
634   that modify the semantics of the response).
635</t>
636<t>
637   New HTTP status codes are required to fall under one of the categories
638   defined in <xref target="status.codes"/>. To allow existing parsers to
639   properly handle them, new status codes cannot disallow a response body,
640   although they can mandate a zero-length response body. They can require the
641   presence of one or more particular HTTP response header(s).
642</t>
643<t>
644   Likewise, their definitions can specify that caches are allowed to use
[1035]645   heuristics to determine their freshness (see &caching;; by default, it is
[1043]646   not allowed), and can define how to determine the resource which they
[1035]647   carry a representation for (see <xref
648   target="identifying.response.associated.with.representation"/>; by default,
[1038]649   it is anonymous).
650</t>
[8]651</section>
652
[262]653</section>
654
[1035]655</section>
656
[8]657<section title="Response Header Fields" anchor="response.header.fields">
[229]658  <x:anchor-alias value="response-header"/>
[8]659<t>
[1163]660   The response header fields allow the server to pass additional
[8]661   information about the response which cannot be placed in the Status-Line.
662   These header fields give information about the server and about
[972]663   further access to the target resource (&effective-request-uri;).
[8]664</t>
[1138]665<texttable align="left">
[1163]666  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
[1138]667
668  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
669  <c>Age</c> <c>&header-age;</c>
670  <c>Allow</c> <c><xref target="header.allow"/></c>
671  <c>ETag</c> <c>&header-etag;</c>
672  <c>Location</c> <c><xref target="header.location"/></c>
673  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
674  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
675  <c>Server</c> <c><xref target="header.server"/></c>
676  <c>Vary</c> <c>&header-vary;</c>
677  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
678</texttable>
[8]679</section>
680
[874]681<section title="Representation" anchor="representation">
[8]682<t>
[866]683   Request and Response messages &MAY; transfer a representation if not otherwise
684   restricted by the request method or response status code. A representation
685   consists of metadata (representation header fields) and data (representation
686   body).  When a complete or partial representation is enclosed in an HTTP message,
687   it is referred to as the payload of the message. HTTP representations
688   are defined in &payload;.
[8]689</t>
690<t>
[866]691   A representation body is only present in a message when a message-body is
692   present, as described in &message-body;. The representation body is obtained
[8]693   from the message-body by decoding any Transfer-Encoding that might
694   have been applied to ensure safe and proper transfer of the message.
695</t>
[695]696
697<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
698<t>
[965]699   It is sometimes necessary to determine an identifier for the resource
[695]700   associated with a representation.
701</t>
702<t>
703   An HTTP request representation, when present, is always associated with an
704   anonymous (i.e., unidentified) resource.
705</t>
706<t>
[972]707   In the common case, an HTTP response is a representation of the target
708   resource (see &effective-request-uri;). However, this is not always the
709   case. To determine the URI of the resource a response is associated with,
710   the following rules are used (with the first applicable one being selected):
[695]711</t>
712<t><list style="numbers">
713   <t>If the response status code is 200 or 203 and the request method was GET,
[972]714   the response payload is a representation of the target resource.</t>
[924]715   <t>If the response status code is 204, 206, or 304 and the request method was GET
[972]716   or HEAD, the response payload is a partial representation of the target
[1079]717   resource (see &combining-responses;).</t>
[994]718   <t>If the response has a Content-Location header field, and that URI is the same
[965]719   as the effective request URI, the response payload is a representation of the
[972]720   target resource.</t>
[994]721   <t>If the response has a Content-Location header field, and that URI is not the
[965]722   same as the effective request URI, then the response asserts that its
723   payload is a representation of the resource identified by the
724   Content-Location URI. However, such an assertion cannot be trusted unless
725   it can be verified by other means (not defined by HTTP).</t>
[695]726   <t>Otherwise, the response is a representation of an anonymous (i.e.,
727   unidentified) resource.</t>
728</list></t>
729<t>
730  <cref anchor="TODO-req-uri">
[823]731   The comparison function is going to have to be defined somewhere,
[695]732   because we already need to compare URIs for things like cache invalidation.</cref>
733</t>
[8]734</section>
735
[695]736</section>
[8]737
[695]738
[8]739<section title="Method Definitions" anchor="method.definitions">
740<t>
[1161]741   The set of common request methods for HTTP/1.1 is defined below. Although
[8]742   this set can be expanded, additional methods cannot be assumed to
743   share the same semantics for separately extended clients and servers.
744</t>
745
746<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
747
748<section title="Safe Methods" anchor="safe.methods">
[286]749<iref item="Safe Methods" primary="true"/>
[8]750<t>
[969]751   Implementors need to be aware that the software represents the user in
752   their interactions over the Internet, and need to allow
[901]753   the user to be aware of any actions they take which might have an
[8]754   unexpected significance to themselves or others.
755</t>
756<t>
[708]757   In particular, the convention has been established that the GET, HEAD,
[1161]758   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
759   of taking an action other than retrieval. These request methods ought
760   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
[8]761   This allows user agents to represent other methods, such as POST, PUT
762   and DELETE, in a special way, so that the user is made aware of the
763   fact that a possibly unsafe action is being requested.
764</t>
765<t>
766   Naturally, it is not possible to ensure that the server does not
767   generate side-effects as a result of performing a GET request; in
768   fact, some dynamic resources consider that a feature. The important
769   distinction here is that the user did not request the side-effects,
770   so therefore cannot be held accountable for them.
771</t>
772</section>
773
774<section title="Idempotent Methods" anchor="idempotent.methods">
[286]775<iref item="Idempotent Methods" primary="true"/>
[8]776<t>
[1161]777   Request methods can also have the property of "idempotence" in that,
778   aside from error or expiration issues, the intended effect of multiple
[657]779   identical requests is the same as for a single request.
[1161]780   PUT, DELETE, and all safe request methods are idempotent.
[657]781   It is important to note that idempotence refers only to changes
782   requested by the client: a server is free to change its state due
783   to multiple requests for the purpose of tracking those requests,
784   versioning of results, etc.
[8]785</t>
786</section>
787</section>
788
789<section title="OPTIONS" anchor="OPTIONS">
[286]790  <rdf:Description>
791    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
792  </rdf:Description>
[8]793  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
794  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
795<t>
[1161]796   The OPTIONS method requests information about the
[8]797   communication options available on the request/response chain
[1161]798   identified by the effective request URI. This method allows a client to
[8]799   determine the options and/or requirements associated with a resource,
800   or the capabilities of a server, without implying a resource action
801   or initiating a resource retrieval.
802</t>
803<t>
[1161]804   Responses to the OPTIONS method are not cacheable.
[8]805</t>
806<t>
[874]807   If the OPTIONS request includes a message-body (as indicated by the
[8]808   presence of Content-Length or Transfer-Encoding), then the media type
809   &MUST; be indicated by a Content-Type field. Although this
810   specification does not define any use for such a body, future
811   extensions to HTTP might use the OPTIONS body to make more detailed
[280]812   queries on the server.
[8]813</t>
814<t>
[391]815   If the request-target is an asterisk ("*"), the OPTIONS request is
[8]816   intended to apply to the server in general rather than to a specific
817   resource. Since a server's communication options typically depend on
818   the resource, the "*" request is only useful as a "ping" or "no-op"
819   type of method; it does nothing beyond allowing the client to test
820   the capabilities of the server. For example, this can be used to test
821   a proxy for HTTP/1.1 compliance (or lack thereof).
822</t>
823<t>
[391]824   If the request-target is not an asterisk, the OPTIONS request applies
[8]825   only to the options that are available when communicating with that
826   resource.
827</t>
828<t>
829   A 200 response &SHOULD; include any header fields that indicate
830   optional features implemented by the server and applicable to that
831   resource (e.g., Allow), possibly including extensions not defined by
832   this specification. The response body, if any, &SHOULD; also include
833   information about the communication options. The format for such a
834   body is not defined by this specification, but might be defined by
835   future extensions to HTTP. Content negotiation &MAY; be used to select
836   the appropriate response format. If no response body is included, the
837   response &MUST; include a Content-Length field with a field-value of
838   "0".
839</t>
840<t>
[1163]841   The Max-Forwards header field &MAY; be used to target a
[893]842   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
843   If no Max-Forwards field is present in the request, then the forwarded
[8]844   request &MUST-NOT; include a Max-Forwards field.
845</t>
846</section>
847
848<section title="GET" anchor="GET">
[286]849  <rdf:Description>
850    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
851  </rdf:Description>
[8]852  <iref primary="true" item="GET method" x:for-anchor=""/>
853  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
854<t>
[1161]855   The GET method requests transfer of a current representation of
856   the target resource.
[8]857</t>
[730]858<t>   
[972]859   If the target resource is a data-producing process, it is the
[866]860   produced data which shall be returned as the representation in the response and not
[730]861   the source text of the process, unless that text happens to be the output of
862   the process.
863</t>
[8]864<t>
865   The semantics of the GET method change to a "conditional GET" if the
866   request message includes an If-Modified-Since, If-Unmodified-Since,
867   If-Match, If-None-Match, or If-Range header field. A conditional GET
[1161]868   requests that the representation be transferred only under the
[8]869   circumstances described by the conditional header field(s). The
[1161]870   conditional GET request is intended to reduce unnecessary network
[874]871   usage by allowing cached representations to be refreshed without requiring
[8]872   multiple requests or transferring data already held by the client.
873</t>
874<t>
875   The semantics of the GET method change to a "partial GET" if the
876   request message includes a Range header field. A partial GET requests
[866]877   that only part of the representation be transferred, as described in &header-range;.
[1161]878   The partial GET request is intended to reduce unnecessary
[866]879   network usage by allowing partially-retrieved representations to be
[8]880   completed without transferring data already held by the client.
881</t>
882<t>
[888]883   The response to a GET request is cacheable and &MAY; be used to satisfy
884   subsequent GET and HEAD requests (see &caching;).
[8]885</t>
886<t>
887   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
888</t>
889</section>
890
891<section title="HEAD" anchor="HEAD">
[286]892  <rdf:Description>
893    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
894  </rdf:Description>
[8]895  <iref primary="true" item="HEAD method" x:for-anchor=""/>
896  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
897<t>
898   The HEAD method is identical to GET except that the server &MUST-NOT;
[867]899   return a message-body in the response. The metadata contained
[994]900   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
[8]901   to the information sent in response to a GET request. This method can
[867]902   be used for obtaining metadata about the representation implied by the
[866]903   request without transferring the representation body. This method is
[8]904   often used for testing hypertext links for validity, accessibility,
905   and recent modification.
906</t>
907<t>
[888]908   The response to a HEAD request is cacheable and &MAY; be used to satisfy
909   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
910   representation from that resource; if the new field values
[874]911   indicate that the cached representation differs from the current representation (as
[8]912   would be indicated by a change in Content-Length, Content-MD5, ETag
913   or Last-Modified), then the cache &MUST; treat the cache entry as
914   stale.
915</t>
916</section>
917
918<section title="POST" anchor="POST">
919  <iref primary="true" item="POST method" x:for-anchor=""/>
920  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
921<t>
[1161]922   The POST method requests that the origin server accept the
[972]923   representation enclosed in the request as data to be processed by the
924   target resource. POST is designed to allow a uniform method to cover the
925   following functions:
[8]926  <list style="symbols">
927    <t>
928      Annotation of existing resources;
929    </t>
930    <t>
931        Posting a message to a bulletin board, newsgroup, mailing list,
932        or similar group of articles;
933    </t>
934    <t>
935        Providing a block of data, such as the result of submitting a
936        form, to a data-handling process;
937    </t>
938    <t>
939        Extending a database through an append operation.
940    </t>
941  </list>
942</t>
943<t>
944   The actual function performed by the POST method is determined by the
[965]945   server and is usually dependent on the effective request URI.
[8]946</t>
947<t>
948   The action performed by the POST method might not result in a
949   resource that can be identified by a URI. In this case, either 200
[924]950   (OK) or 204 (No Content) is the appropriate response status code,
[874]951   depending on whether or not the response includes a representation that
[8]952   describes the result.
953</t>
954<t>
955   If a resource has been created on the origin server, the response
[874]956   &SHOULD; be 201 (Created) and contain a representation which describes the
[8]957   status of the request and refers to the new resource, and a Location
[994]958   header field (see <xref target="header.location"/>).
[8]959</t>
960<t>
[910]961   Responses to POST requests are only cacheable when they
962   include explicit freshness information (see &p6-explicit;). A
[994]963   cached POST response with a Content-Location header field
[972]964   (see &header-content-location;) whose value is the effective
[910]965   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
966</t>
967<t>
968   Note that POST caching is not widely implemented.
[888]969   However, the 303 (See Other) response can be used to direct the
970   user agent to retrieve a cacheable resource.
[8]971</t>
972</section>
973
974<section title="PUT" anchor="PUT">
975  <iref primary="true" item="PUT method" x:for-anchor=""/>
976  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
977<t>
[1161]978   The PUT method requests that the state of the target resource
[1158]979   be created or replaced with the state defined by the representation
980   enclosed in the request message payload.  A successful PUT of a given
981   representation would suggest that a subsequent GET on that same target
982   resource will result in an equivalent representation being returned in
983   a 200 (OK) response.  However, there is no guarantee that such a state
984   change will be observable, since the target resource might be acted
985   upon by other user agents in parallel, or might be subject to dynamic
986   processing by the origin server, before any subsequent GET is received.
987   A successful response only implies that the user agent's intent was
988   achieved at the time of its processing by the origin server.
[823]989</t>
990<t>   
[1158]991   If the target resource does not have a current representation and
992   the PUT successfully creates one, then the origin server &MUST; inform
993   the user agent by sending a 201 (Created) response.  If the target
994   resource does have a current representation and that representation is
995   successfully modified in accordance with the state of the enclosed
996   representation, then either a 200 (OK) or 204 (No Content) response
997   &SHOULD; be sent to indicate successful completion of the request.
[823]998</t>
[1158]999<t>
1000   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1001   as part of the resource state).
[8]1002</t>
1003<t>
[1158]1004   An origin server &SHOULD; verify that the PUT representation is
1005   consistent with any constraints which the server has for the target
1006   resource that cannot or will not be changed by the PUT.  This is
1007   particularly important when the origin server uses internal
1008   configuration information related to the URI in order to set the
1009   values for representation metadata on GET responses.  When a PUT
1010   representation is inconsistent with the target resource, the origin
1011   server &SHOULD; either make them consistent, by transforming the
1012   representation or changing the resource configuration, or respond
[1168]1013   with an appropriate error message containing sufficient information
1014   to explain why the representation is unsuitable.  The 409 (Conflict)
1015   or 415 (Unsupported Media Type) status codes are suggested, with the
1016   latter being specific to constraints on Content-Type values.
[8]1017</t>
1018<t>
[1158]1019   For example, if the target resource is configured to always have a
1020   Content-Type of "text/html" and the representation being PUT has a
1021   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1022   (a) reconfigure the target resource to reflect the new media type;
1023   (b) transform the PUT representation to a format consistent with that
1024   of the resource before saving it as the new resource state; or,
[1168]1025   (c) reject the request with a 415 response indicating that the target
[1158]1026   resource is limited to "text/html", perhaps including a link to a
1027   different resource that would be a suitable target for the new
1028   representation.
1029</t>
1030<t>
1031   HTTP does not define exactly how a PUT method affects the state
1032   of an origin server beyond what can be expressed by the intent of
1033   the user agent request and the semantics of the origin server response.
1034   It does not define what a resource might be, in any sense of that
1035   word, beyond the interface provided via HTTP.  It does not define
1036   how resource state is "stored", nor how such storage might change
1037   as a result of a change in resource state, nor how the origin server
1038   translates resource state into representations.  Generally speaking,
1039   all implementation details behind the resource interface are
1040   intentionally hidden by the server.
1041</t>
1042<t>
1043   The fundamental difference between the POST and PUT methods is
1044   highlighted by the different intent for the target resource.
1045   The target resource in a POST request is intended to handle the
1046   enclosed representation as a data-accepting process, such as for
1047   a gateway to some other protocol or a document that accepts annotations.
1048   In contrast, the target resource in a PUT request is intended to
1049   take the enclosed representation as a new or replacement value.
1050   Hence, the intent of PUT is idempotent and visible to intermediaries,
1051   even though the exact effect is only known by the origin server.
1052</t>
1053<t>
1054   Proper interpretation of a PUT request presumes that the user agent
1055   knows what target resource is desired.  A service that is intended
1056   to select a proper URI on behalf of the client, after receiving
1057   a state-changing request, &SHOULD; be implemented using the POST
1058   method rather than PUT.  If the origin server will not make the
1059   requested PUT state change to the target resource and instead
1060   wishes to have it applied to a different resource, such as when the
1061   resource has been moved to a different URI, then the origin server
1062   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
[8]1063   then make its own decision regarding whether or not to redirect the
1064   request.
1065</t>
1066<t>
[1158]1067   A PUT request applied to the target resource &MAY; have side-effects
1068   on other resources.  For example, an article might have a URI for
1069   identifying "the current version" (a resource) which is separate
1070   from the URIs identifying each particular version (different
1071   resources that at one point shared the same state as the current version
1072   resource).  A successful PUT request on "the current version" URI might
1073   therefore create a new version resource in addition to changing the
1074   state of the target resource, and might also cause links to be added
1075   between the related resources.
[8]1076</t>
1077<t>
[1158]1078   An origin server &SHOULD; reject any PUT request that contains a
1079   Content-Range header field, since it might be misinterpreted as
1080   partial content (or might be partial content that is being mistakenly
1081   PUT as a full representation).  Partial content updates are
1082   possible by targeting a separately identified resource with state
1083   that overlaps a portion of the larger resource, or by using a
1084   different method that has been specifically defined for partial
1085   updates (for example, the PATCH method defined in
1086   <xref target="RFC5789"/>).
[8]1087</t>
1088<t>
[1158]1089   Responses to the PUT method are not cacheable. If a PUT request passes
1090   through a cache that has one or more stored responses for the effective
1091   request URI, those stored responses will be invalidated (see
1092   &p6-invalid;).
[8]1093</t>
1094</section>
1095
1096<section title="DELETE" anchor="DELETE">
1097  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1098  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1099<t>
[972]1100   The DELETE method requests that the origin server delete the target
1101   resource. This method &MAY; be overridden by
[823]1102   human intervention (or other means) on the origin server. The client cannot
[8]1103   be guaranteed that the operation has been carried out, even if the
1104   status code returned from the origin server indicates that the action
1105   has been completed successfully. However, the server &SHOULD-NOT; 
1106   indicate success unless, at the time the response is given, it
1107   intends to delete the resource or move it to an inaccessible
1108   location.
1109</t>
1110<t>
1111   A successful response &SHOULD; be 200 (OK) if the response includes an
[874]1112   representation describing the status, 202 (Accepted) if the action has not
[8]1113   yet been enacted, or 204 (No Content) if the action has been enacted
[866]1114   but the response does not include a representation.
[8]1115</t>
1116<t>
[1111]1117   Responses to the DELETE method are not cacheable. If a DELETE request
1118   passes through a cache that has one or more stored responses for the
1119   effective request URI, those stored responses will be invalidated (see
1120   &p6-invalid;).
[8]1121</t>
1122</section>
1123
1124<section title="TRACE" anchor="TRACE">
[286]1125  <rdf:Description>
1126    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1127  </rdf:Description>
[8]1128  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1129  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1130<t>
[1161]1131   The TRACE method requests a remote, application-layer loop-back
[8]1132   of the request message. The final recipient of the request
1133   &SHOULD; reflect the message received back to the client as the
[874]1134   message-body of a 200 (OK) response. The final recipient is either the
[1173]1135   origin server or the first proxy to receive a Max-Forwards
[866]1136   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1137   A TRACE request &MUST-NOT; include a message-body.
[8]1138</t>
1139<t>
1140   TRACE allows the client to see what is being received at the other
1141   end of the request chain and use that data for testing or diagnostic
[29]1142   information. The value of the Via header field (&header-via;) is of
[8]1143   particular interest, since it acts as a trace of the request chain.
1144   Use of the Max-Forwards header field allows the client to limit the
1145   length of the request chain, which is useful for testing a chain of
1146   proxies forwarding messages in an infinite loop.
1147</t>
1148<t>
[874]1149   If the request is valid, the response &SHOULD; have a Content-Type of
1150   "message/http" (see &media-type-message-http;) and contain a message-body
1151   that encloses a copy of the entire request message.
[888]1152   Responses to the TRACE method are not cacheable.
[8]1153</t>
1154</section>
1155
1156<section title="CONNECT" anchor="CONNECT">
1157  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1158  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1159<t>
[1161]1160   The CONNECT method requests that the proxy establish a tunnel
1161   to the request-target and then restrict its behavior to blind
1162   forwarding of packets until the connection is closed.
[8]1163</t>
[1061]1164<t>
[1161]1165   When using CONNECT, the request-target &MUST; use the authority form
1166   (&request-target;); i.e., the request-target consists of only the
1167   host name and port number of the tunnel destination, separated by a colon.
1168   For example,
[1061]1169</t>
[1064]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
[1061]1173
1174</artwork></figure>
1175<t>
[1101]1176   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
[1061]1177   except end-to-end protocol Upgrade requests, since the
1178   tunnel must be established first.
1179</t>
1180<t>
1181   For example, proxy authentication might be used to establish the
1182   authority to create a tunnel:
1183</t>
[1064]1184<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1185CONNECT server.example.com:80 HTTP/1.1
1186Host: server.example.com:80
1187Proxy-Authorization: basic aGVsbG86d29ybGQ=
[1061]1188
1189</artwork></figure>
1190<t>
1191   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1192   sent immediately after the blank line. The usual caveats also apply:
1193   data may be discarded if the eventual response is negative, and the
1194   connection may be reset with no response if more than one TCP segment
1195   is outstanding.
1196</t>
1197
1198<section title="Establishing a Tunnel with CONNECT">
1199<t>
1200   Any successful (2xx) response to a CONNECT request indicates that the
1201   proxy has established a connection to the requested host and port,
1202   and has switched to tunneling the current connection to that server
1203   connection.
1204</t>
1205<t>
1206   It may be the case that the proxy itself can only reach the requested
1207   origin server through another proxy.  In this case, the first proxy
1208   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1209   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1210   unless it has either a direct or tunnel connection established to the
1211   authority.
1212</t>
1213<t>
1214   An origin server which receives a CONNECT request for itself &MAY;
1215   respond with a 2xx status code to indicate that a connection is
1216   established.
1217</t>
1218<t>
1219   If at any point either one of the peers gets disconnected, any
1220   outstanding data that came from that peer will be passed to the other
1221   one, and after that also the other connection will be terminated by
1222   the proxy. If there is outstanding data to that peer undelivered,
1223   that data will be discarded.
1224</t>
1225
[8]1226</section>
1227</section>
[1061]1228</section>
[8]1229
1230
1231<section title="Status Code Definitions" anchor="status.codes">
1232<t>
[867]1233   Each Status-Code is described below, including any metadata required
[579]1234   in the response.
[8]1235</t>
1236
1237<section title="Informational 1xx" anchor="status.1xx">
1238<t>
1239   This class of status code indicates a provisional response,
[994]1240   consisting only of the Status-Line and optional header fields, and is
1241   terminated by an empty line. There are no required header fields for this
[8]1242   class of status code. Since HTTP/1.0 did not define any 1xx status
1243   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1244   except under experimental conditions.
1245</t>
1246<t>
1247   A client &MUST; be prepared to accept one or more 1xx status responses
1248   prior to a regular response, even if the client does not expect a 100
1249   (Continue) status message. Unexpected 1xx status responses &MAY; be
1250   ignored by a user agent.
1251</t>
1252<t>
1253   Proxies &MUST; forward 1xx responses, unless the connection between the
1254   proxy and its client has been closed, or unless the proxy itself
1255   requested the generation of the 1xx response. (For example, if a
1256   proxy adds a "Expect: 100-continue" field when it forwards a request,
1257   then it need not forward the corresponding 100 (Continue)
1258   response(s).)
1259</t>
1260
1261<section title="100 Continue" anchor="status.100">
1262  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1263  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1264<t>
1265   The client &SHOULD; continue with its request. This interim response is
1266   used to inform the client that the initial part of the request has
1267   been received and has not yet been rejected by the server. The client
1268   &SHOULD; continue by sending the remainder of the request or, if the
1269   request has already been completed, ignore this response. The server
1270   &MUST; send a final response after the request has been completed. See
[29]1271   &use100; for detailed discussion of the use and handling of this
[8]1272   status code.
1273</t>
1274</section>
1275
1276<section title="101 Switching Protocols" anchor="status.101">
1277  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1278  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1279<t>
1280   The server understands and is willing to comply with the client's
[29]1281   request, via the Upgrade message header field (&header-upgrade;), for a
[8]1282   change in the application protocol being used on this connection. The
1283   server will switch protocols to those defined by the response's
1284   Upgrade header field immediately after the empty line which
1285   terminates the 101 response.
1286</t>
1287<t>
1288   The protocol &SHOULD; be switched only when it is advantageous to do
1289   so. For example, switching to a newer version of HTTP is advantageous
1290   over older versions, and switching to a real-time, synchronous
1291   protocol might be advantageous when delivering resources that use
1292   such features.
1293</t>
1294</section>
1295</section>
1296
1297<section title="Successful 2xx" anchor="status.2xx">
1298<t>
1299   This class of status code indicates that the client's request was
1300   successfully received, understood, and accepted.
1301</t>
1302
1303<section title="200 OK" anchor="status.200">
1304  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1305  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1306<t>
[965]1307   The request has succeeded. The payload returned with the response
[8]1308   is dependent on the method used in the request, for example:
1309  <list style="hanging">
1310    <t hangText="GET">
[972]1311          a representation of the target resource is sent in the response;
[8]1312    </t>
1313    <t hangText="HEAD">
[965]1314          the same representation as GET, except without the message-body;
[8]1315    </t>
1316    <t hangText="POST">
[874]1317      a representation describing or containing the result of the action;
[8]1318    </t>
1319    <t hangText="TRACE">
[874]1320      a representation containing the request message as received by the
[8]1321      end server.
1322    </t>
1323  </list>
1324</t>
[884]1325<t>
[886]1326   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1327   freshness for 200 responses.
[884]1328</t>
[8]1329</section>
1330
1331<section title="201 Created" anchor="status.201">
1332  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1333  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1334<t>
[758]1335   The request has been fulfilled and has resulted in a new resource being
[8]1336   created. The newly created resource can be referenced by the URI(s)
[856]1337   returned in the payload of the response, with the most specific URI
[8]1338   for the resource given by a Location header field. The response
[856]1339   &SHOULD; include a payload containing a list of resource
[8]1340   characteristics and location(s) from which the user or user agent can
[856]1341   choose the one most appropriate. The payload format is specified by
[8]1342   the media type given in the Content-Type header field. The origin
1343   server &MUST; create the resource before returning the 201 status code.
1344   If the action cannot be carried out immediately, the server &SHOULD;
1345   respond with 202 (Accepted) response instead.
1346</t>
1347<t>
1348   A 201 response &MAY; contain an ETag response header field indicating
[874]1349   the current value of the entity-tag for the representation of the resource
[856]1350   just created (see &header-etag;).
[8]1351</t>
1352</section>
1353
1354<section title="202 Accepted" anchor="status.202">
1355  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1356  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1357<t>
1358   The request has been accepted for processing, but the processing has
1359   not been completed.  The request might or might not eventually be
1360   acted upon, as it might be disallowed when processing actually takes
1361   place. There is no facility for re-sending a status code from an
1362   asynchronous operation such as this.
1363</t>
1364<t>
1365   The 202 response is intentionally non-committal. Its purpose is to
1366   allow a server to accept a request for some other process (perhaps a
1367   batch-oriented process that is only run once per day) without
1368   requiring that the user agent's connection to the server persist
[866]1369   until the process is completed. The representation returned with this
[8]1370   response &SHOULD; include an indication of the request's current status
1371   and either a pointer to a status monitor or some estimate of when the
1372   user can expect the request to be fulfilled.
1373</t>
1374</section>
1375
1376<section title="203 Non-Authoritative Information" anchor="status.203">
1377  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1378  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1379<t>
[965]1380   The returned metadata in the header fields is not the
[8]1381   definitive set as available from the origin server, but is gathered
1382   from a local or a third-party copy. The set presented &MAY; be a subset
1383   or superset of the original version. For example, including local
1384   annotation information about the resource might result in a superset
[867]1385   of the metadata known by the origin server. Use of this
[8]1386   response code is not required and is only appropriate when the
1387   response would otherwise be 200 (OK).
1388</t>
[884]1389<t>
[886]1390   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1391   freshness for 203 responses.
[884]1392</t>
1393
[8]1394</section>
1395
1396<section title="204 No Content" anchor="status.204">
1397  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1398  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1399<t>
[856]1400   The server has successfully fulfilled the request, but there is no
1401   additional content to return in the response payload body.  The
1402   resource metadata and representation metadata in the response message's
[965]1403   header fields refer to the target resource
1404   and its current representation, respectively, after the requested action.
[924]1405   For example, if a 204 status code is received in response to a PUT
[885]1406   and the response contains an ETag header field, then the value of
[856]1407   that field is the current entity-tag for the representation that
[965]1408   was successfully PUT.
[8]1409</t>
1410<t>
[856]1411   If the client is a user agent, it &SHOULD-NOT; change its document view
[8]1412   from that which caused the request to be sent. This response is
1413   primarily intended to allow input for actions to take place without
1414   causing a change to the user agent's active document view, although
[856]1415   any new or updated metadata &SHOULD; be applied to the document
[8]1416   currently in the user agent's active view.
1417</t>
1418<t>
1419   The 204 response &MUST-NOT; include a message-body, and thus is always
1420   terminated by the first empty line after the header fields.
1421</t>
1422</section>
1423
1424<section title="205 Reset Content" anchor="status.205">
1425  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1426  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1427<t>
1428   The server has fulfilled the request and the user agent &SHOULD; reset
1429   the document view which caused the request to be sent. This response
1430   is primarily intended to allow input for actions to take place via
1431   user input, followed by a clearing of the form in which the input is
[1058]1432   given so that the user can easily initiate another input action.
[8]1433</t>
[1058]1434<t>   
1435   The message-body included with the response &MUST; be empty. Note that
1436   receivers still need to parse the response according to the algorithm defined
1437   in &message-body;.
1438</t>
[8]1439</section>
1440
1441<section title="206 Partial Content" anchor="status.206">
1442  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1443  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
[700]1444  <rdf:Description>
1445    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1446  </rdf:Description>
[8]1447<t>
[29]1448   The server has fulfilled the partial GET request for the resource
[874]1449   and the enclosed payload is a partial representation as defined in &status-206;.
[8]1450</t>
[884]1451<t>
[886]1452   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1453   freshness for 206 responses.
[884]1454</t>
[8]1455</section>
1456</section>
1457
1458<section title="Redirection 3xx" anchor="status.3xx">
1459<t>
1460   This class of status code indicates that further action needs to be
1461   taken by the user agent in order to fulfill the request.  The action
1462   required &MAY; be carried out by the user agent without interaction
1463   with the user if and only if the method used in the second request is
[760]1464   known to be "safe", as defined in <xref target="safe.methods"/>.
[759]1465   A client &SHOULD; detect infinite redirection loops, since such loops
1466   generate network traffic for each redirection.
[8]1467</t>
[563]1468<x:note>
1469  <t>
[756]1470    <x:h>Note:</x:h> An earlier version of this specification recommended a
[629]1471    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
[969]1472    Content developers need to be aware that some clients might
[629]1473    implement such a fixed limitation.
[563]1474  </t>
1475</x:note>
[8]1476
1477<section title="300 Multiple Choices" anchor="status.300">
1478  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1479  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1480<t>
[1029]1481   The target resource has more than one
[965]1482   representation, each with its own specific location, and agent-driven
[29]1483   negotiation information (&content-negotiation;) is being provided so that
[965]1484   the user (or user agent) can select a preferred representation by
1485   redirecting its request to that location.
[8]1486</t>
1487<t>
[866]1488   Unless it was a HEAD request, the response &SHOULD; include a representation
[965]1489   containing a list of representation metadata and location(s) from
[8]1490   which the user or user agent can choose the one most appropriate. The
[866]1491   data format is specified by the media type given in the Content-Type
[8]1492   header field. Depending upon the format and the capabilities of
1493   the user agent, selection of the most appropriate choice &MAY; be
1494   performed automatically. However, this specification does not define
1495   any standard for such automatic selection.
1496</t>
1497<t>
1498   If the server has a preferred choice of representation, it &SHOULD;
1499   include the specific URI for that representation in the Location
1500   field; user agents &MAY; use the Location field value for automatic
[884]1501   redirection.
[8]1502</t>
[884]1503<t>
[886]1504   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1505   freshness for 300 responses.
[884]1506</t>
1507
[8]1508</section>
1509
1510<section title="301 Moved Permanently" anchor="status.301">
1511  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1512  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1513<t>
[965]1514   The target resource has been assigned a new permanent URI and any
[8]1515   future references to this resource &SHOULD; use one of the returned
1516   URIs.  Clients with link editing capabilities ought to automatically
[965]1517   re-link references to the effective request URI to one or more of the new
[884]1518   references returned by the server, where possible.
[8]1519</t>
1520<t>
[886]1521   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1522   freshness for 301 responses.
[884]1523</t>
1524<t>
[8]1525   The new permanent URI &SHOULD; be given by the Location field in the
[866]1526   response. Unless the request method was HEAD, the representation of the
[8]1527   response &SHOULD; contain a short hypertext note with a hyperlink to
1528   the new URI(s).
1529</t>
1530<t>
[88]1531   If the 301 status code is received in response to a request method
1532   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1533   then the request &MAY; be automatically redirected by the user agent without
[88]1534   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1535   request unless it can be confirmed by the user, since this might
1536   change the conditions under which the request was issued.
1537</t>
[563]1538<x:note>
1539  <t>
1540    <x:h>Note:</x:h> When automatically redirecting a POST request after
1541    receiving a 301 status code, some existing HTTP/1.0 user agents
1542    will erroneously change it into a GET request.
1543  </t>
1544</x:note>
[8]1545</section>
1546
1547<section title="302 Found" anchor="status.302">
1548  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1549  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1550<t>
[965]1551   The target resource resides temporarily under a different URI.
[8]1552   Since the redirection might be altered on occasion, the client &SHOULD;
[965]1553   continue to use the effective request URI for future requests.
[8]1554</t>
1555<t>
1556   The temporary URI &SHOULD; be given by the Location field in the
[866]1557   response. Unless the request method was HEAD, the representation of the
[8]1558   response &SHOULD; contain a short hypertext note with a hyperlink to
1559   the new URI(s).
1560</t>
1561<t>
[88]1562   If the 302 status code is received in response to a request method
1563   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1564   then the request &MAY; be automatically redirected by the user agent without
[88]1565   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1566   request unless it can be confirmed by the user, since this might
1567   change the conditions under which the request was issued.
1568</t>
[563]1569<x:note>
1570  <t>
[614]1571    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1572    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1573    specify that the client is not allowed to change the method on the
1574    redirected request.  However, most existing user agent implementations
1575    treat 302 as if it were a 303 response, performing a GET on the Location
1576    field-value regardless of the original request method. Therefore, a
1577    previous version of this specification
1578    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1579    status codes
1580    <xref target="status.303" format="none">303</xref> and
1581    <xref target="status.307" format="none">307</xref> for servers that wish
1582    to make unambiguously clear which kind of reaction is expected of the
1583    client.
[563]1584  </t>
1585</x:note>
[8]1586</section>
1587
1588<section title="303 See Other" anchor="status.303">
1589  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1590  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1591<t>
[242]1592   The server directs the user agent to a different resource, indicated
1593   by a URI in the Location header field, that provides an indirect
1594   response to the original request.  The user agent &MAY; perform a GET
1595   request on the URI in the Location field in order to obtain a
1596   representation corresponding to the response, be redirected again,
1597   or end with an error status.  The Location URI is not a substitute
[965]1598   reference for the effective request URI.
[8]1599</t>
1600<t>
[924]1601   The 303 status code is generally applicable to any HTTP method.  It is
[242]1602   primarily used to allow the output of a POST action to redirect
1603   the user agent to a selected resource, since doing so provides the
1604   information corresponding to the POST response in a form that
1605   can be separately identified, bookmarked, and cached independent
1606   of the original request.
[8]1607</t>
[242]1608<t>
1609   A 303 response to a GET request indicates that the requested
1610   resource does not have a representation of its own that can be
1611   transferred by the server over HTTP.  The Location URI indicates a
[965]1612   resource that is descriptive of the target resource, such that the
1613   follow-on representation might be useful to recipients without
1614   implying that it adequately represents the target resource.
[242]1615   Note that answers to the questions of what can be represented, what
1616   representations are adequate, and what might be a useful description
1617   are outside the scope of HTTP and thus entirely determined by the
[602]1618   URI owner(s).
[242]1619</t>
1620<t>
[884]1621   Except for responses to a HEAD request, the representation of a 303
1622   response &SHOULD; contain a short hypertext note with a hyperlink
1623   to the Location URI.
[242]1624</t>
[8]1625</section>
1626
1627<section title="304 Not Modified" anchor="status.304">
1628  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1629  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
[700]1630  <rdf:Description>
1631    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1632  </rdf:Description>
[8]1633<t>
[45]1634   The response to the request has not been modified since the conditions
[700]1635   indicated by the client's conditional GET request, as defined in &status-304;.
[8]1636</t>
1637</section>
1638
1639<section title="305 Use Proxy" anchor="status.305">
1640  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1641  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1642<t>
[924]1643   The 305 status code was defined in a previous version of this specification
[235]1644   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
[8]1645</t>
1646</section>
1647
1648<section title="306 (Unused)" anchor="status.306">
1649  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1650  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1651<t>
1652   The 306 status code was used in a previous version of the
1653   specification, is no longer used, and the code is reserved.
1654</t>
1655</section>
1656
1657<section title="307 Temporary Redirect" anchor="status.307">
1658  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1659  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1660<t>
[965]1661   The target resource resides temporarily under a different URI.
[954]1662   Since the redirection can change over time, the client &SHOULD;
[965]1663   continue to use the effective request URI for future requests.
[8]1664</t>
1665<t>
1666   The temporary URI &SHOULD; be given by the Location field in the
[866]1667   response. Unless the request method was HEAD, the representation of the
[8]1668   response &SHOULD; contain a short hypertext note with a hyperlink to
[1030]1669   the new URI(s), since many pre-HTTP/1.1 user agents do not
[924]1670   understand the 307 status code. Therefore, the note &SHOULD; contain the
[8]1671   information necessary for a user to repeat the original request on
1672   the new URI.
1673</t>
1674<t>
[88]1675   If the 307 status code is received in response to a request method
1676   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1677   then the request &MAY; be automatically redirected by the user agent without
[88]1678   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1679   request unless it can be confirmed by the user, since this might
1680   change the conditions under which the request was issued.
1681</t>
1682</section>
1683</section>
1684
1685<section title="Client Error 4xx" anchor="status.4xx">
1686<t>
1687   The 4xx class of status code is intended for cases in which the
1688   client seems to have erred. Except when responding to a HEAD request,
[874]1689   the server &SHOULD; include a representation containing an explanation of the
[8]1690   error situation, and whether it is a temporary or permanent
1691   condition. These status codes are applicable to any request method.
[874]1692   User agents &SHOULD; display any included representation to the user.
[8]1693</t>
1694<t>
1695   If the client is sending data, a server implementation using TCP
1696   &SHOULD; be careful to ensure that the client acknowledges receipt of
1697   the packet(s) containing the response, before the server closes the
1698   input connection. If the client continues sending data to the server
1699   after the close, the server's TCP stack will send a reset packet to
[901]1700   the client, which might erase the client's unacknowledged input buffers
[8]1701   before they can be read and interpreted by the HTTP application.
1702</t>
1703
1704<section title="400 Bad Request" anchor="status.400">
1705  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1706  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1707<t>
1708   The request could not be understood by the server due to malformed
[885]1709   syntax. The client &SHOULD-NOT; repeat the request without
[8]1710   modifications.
1711</t>
1712</section>
1713
1714<section title="401 Unauthorized" anchor="status.401">
1715  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1716  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
[700]1717  <rdf:Description>
1718    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1719  </rdf:Description>
[8]1720<t>
[700]1721   The request requires user authentication (see &status-401;).
[8]1722</t>
1723</section>
1724
1725<section title="402 Payment Required" anchor="status.402">
1726  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1727  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1728<t>
1729   This code is reserved for future use.
1730</t>
1731</section>
1732
1733<section title="403 Forbidden" anchor="status.403">
1734  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1735  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1736<t>
1737   The server understood the request, but is refusing to fulfill it.
1738   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1739   If the request method was not HEAD and the server wishes to make
1740   public why the request has not been fulfilled, it &SHOULD; describe the
[866]1741   reason for the refusal in the representation.  If the server does not wish to
[8]1742   make this information available to the client, the status code 404
1743   (Not Found) can be used instead.
1744</t>
1745</section>
1746
1747<section title="404 Not Found" anchor="status.404">
1748  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1749  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1750<t>
[965]1751   The server has not found anything matching the effective request URI. No
[8]1752   indication is given of whether the condition is temporary or
1753   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1754   knows, through some internally configurable mechanism, that an old
1755   resource is permanently unavailable and has no forwarding address.
1756   This status code is commonly used when the server does not wish to
1757   reveal exactly why the request has been refused, or when no other
1758   response is applicable.
1759</t>
1760</section>
1761
1762<section title="405 Method Not Allowed" anchor="status.405">
1763  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1764  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1765<t>
[965]1766   The method specified in the Request-Line is not allowed for the target
1767   resource. The response &MUST; include an
[994]1768   Allow header field containing a list of valid methods for the requested
[8]1769   resource.
1770</t>
1771</section>
1772
1773<section title="406 Not Acceptable" anchor="status.406">
1774  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1775  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1776<t>
1777   The resource identified by the request is only capable of generating
[874]1778   response representations which have content characteristics not acceptable
[994]1779   according to the accept header fields sent in the request.
[8]1780</t>
1781<t>
[866]1782   Unless it was a HEAD request, the response &SHOULD; include a representation
1783   containing a list of available representation characteristics and location(s)
[8]1784   from which the user or user agent can choose the one most
[866]1785   appropriate. The data format is specified by the media type given
[8]1786   in the Content-Type header field. Depending upon the format and the
1787   capabilities of the user agent, selection of the most appropriate
1788   choice &MAY; be performed automatically. However, this specification
1789   does not define any standard for such automatic selection.
1790</t>
[563]1791<x:note>
1792  <t>
1793    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
[994]1794    not acceptable according to the accept header fields sent in the
[901]1795    request. In some cases, this might even be preferable to sending a
[994]1796    406 response. User agents are encouraged to inspect the header fields of
[563]1797    an incoming response to determine if it is acceptable.
1798  </t>
1799</x:note>
[8]1800<t>
1801   If the response could be unacceptable, a user agent &SHOULD;
1802   temporarily stop receipt of more data and query the user for a
1803   decision on further actions.
1804</t>
1805</section>
1806
1807<section title="407 Proxy Authentication Required" anchor="status.407">
1808  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1809  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1810<t>
1811   This code is similar to 401 (Unauthorized), but indicates that the
[700]1812   client must first authenticate itself with the proxy (see &status-407;).
[8]1813</t>
1814</section>
1815
1816<section title="408 Request Timeout" anchor="status.408">
1817  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1818  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1819<t>
1820   The client did not produce a request within the time that the server
1821   was prepared to wait. The client &MAY; repeat the request without
1822   modifications at any later time.
1823</t>
1824</section>
1825
1826<section title="409 Conflict" anchor="status.409">
1827  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1828  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1829<t>
1830   The request could not be completed due to a conflict with the current
1831   state of the resource. This code is only allowed in situations where
1832   it is expected that the user might be able to resolve the conflict
1833   and resubmit the request. The response body &SHOULD; include enough
1834   information for the user to recognize the source of the conflict.
[874]1835   Ideally, the response representation would include enough information for the
[8]1836   user or user agent to fix the problem; however, that might not be
1837   possible and is not required.
1838</t>
1839<t>
1840   Conflicts are most likely to occur in response to a PUT request. For
[866]1841   example, if versioning were being used and the representation being PUT
[8]1842   included changes to a resource which conflict with those made by an
1843   earlier (third-party) request, the server might use the 409 response
1844   to indicate that it can't complete the request. In this case, the
[866]1845   response representation would likely contain a list of the differences
[8]1846   between the two versions in a format defined by the response
1847   Content-Type.
1848</t>
1849</section>
1850
1851<section title="410 Gone" anchor="status.410">
1852  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1853  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1854<t>
[965]1855   The target resource is no longer available at the server and no
[8]1856   forwarding address is known. This condition is expected to be
1857   considered permanent. Clients with link editing capabilities &SHOULD;
[965]1858   delete references to the effective request URI after user approval. If the
[8]1859   server does not know, or has no facility to determine, whether or not
1860   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
[884]1861   used instead.
[8]1862</t>
1863<t>
1864   The 410 response is primarily intended to assist the task of web
1865   maintenance by notifying the recipient that the resource is
1866   intentionally unavailable and that the server owners desire that
1867   remote links to that resource be removed. Such an event is common for
1868   limited-time, promotional services and for resources belonging to
1869   individuals no longer working at the server's site. It is not
1870   necessary to mark all permanently unavailable resources as "gone" or
[1101]1871   to keep the mark for any length of time &mdash; that is left to the
[8]1872   discretion of the server owner.
1873</t>
[884]1874<t>
[886]1875   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1876   for 410 responses.
[884]1877</t>
1878
[8]1879</section>
1880
1881<section title="411 Length Required" anchor="status.411">
1882  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1883  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1884<t>
1885   The server refuses to accept the request without a defined Content-Length.
1886   The client &MAY; repeat the request if it adds a valid
1887   Content-Length header field containing the length of the message-body
1888   in the request message.
1889</t>
1890</section>
1891
1892<section title="412 Precondition Failed" anchor="status.412">
1893  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1894  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
[700]1895  <rdf:Description>
1896    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1897  </rdf:Description>
[8]1898<t>
[1163]1899   The precondition given in one or more of the header fields
[45]1900   evaluated to false when it was tested on the server, as defined in
[700]1901   &status-412;.
[8]1902</t>
1903</section>
1904
1905<section title="413 Request Entity Too Large" anchor="status.413">
1906  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1907  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1908<t>
1909   The server is refusing to process a request because the request
[874]1910   representation is larger than the server is willing or able to process. The
[8]1911   server &MAY; close the connection to prevent the client from continuing
1912   the request.
1913</t>
1914<t>
1915   If the condition is temporary, the server &SHOULD; include a Retry-After
1916   header field to indicate that it is temporary and after what
1917   time the client &MAY; try again.
1918</t>
1919</section>
1920
[465]1921<section title="414 URI Too Long" anchor="status.414">
1922  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1923  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
[8]1924<t>
[965]1925   The server is refusing to service the request because the effective request URI
[8]1926   is longer than the server is willing to interpret. This rare
1927   condition is only likely to occur when a client has improperly
1928   converted a POST request to a GET request with long query
1929   information, when the client has descended into a URI "black hole" of
1930   redirection (e.g., a redirected URI prefix that points to a suffix of
1931   itself), or when the server is under attack by a client attempting to
1932   exploit security holes present in some servers using fixed-length
[965]1933   buffers for reading or manipulating the effective request URI.
[8]1934</t>
1935</section>
1936
1937<section title="415 Unsupported Media Type" anchor="status.415">
1938  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1939  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1940<t>
[1161]1941   The server is refusing to service the request because the request
1942   payload is in a format not supported by this request method on the
1943   target resource.
[8]1944</t>
1945</section>
1946
1947<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1948  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
[700]1950  <rdf:Description>
1951    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1952  </rdf:Description>
[8]1953<t>
[1163]1954   The request included a Range header field (&header-range;) and none of
[8]1955   the range-specifier values in this field overlap the current extent
[885]1956   of the selected resource. See &status-416;.
[8]1957</t>
1958</section>
1959
1960<section title="417 Expectation Failed" anchor="status.417">
1961  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1962  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1963<t>
[1163]1964   The expectation given in an Expect header field (see <xref target="header.expect"/>)
[8]1965   could not be met by this server, or, if the server is a proxy,
1966   the server has unambiguous evidence that the request could not be met
1967   by the next-hop server.
1968</t>
1969</section>
[1071]1970
1971<section title="426 Upgrade Required" anchor="status.426">
1972  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
1973  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
1974<t>
1975   The request can not be completed without a prior protocol upgrade. This
1976   response &MUST; include an Upgrade header field (&header-upgrade;)
1977   specifying the required protocols.
1978</t>
1979<figure>
1980<preamble>Example:</preamble>
1981<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1982HTTP/1.1 426 Upgrade Required
1983Upgrade: HTTP/2.0
1984Connection: Upgrade
1985
1986</artwork></figure>
1987<t>
1988   The server &SHOULD; include a message body in the 426 response which
1989   indicates in human readable form the reason for the error and describes any
1990   alternative courses which may be available to the user.
1991</t>
[8]1992</section>
[1071]1993</section>
[8]1994
1995<section title="Server Error 5xx" anchor="status.5xx">
1996<t>
1997   Response status codes beginning with the digit "5" indicate cases in
1998   which the server is aware that it has erred or is incapable of
1999   performing the request. Except when responding to a HEAD request, the
[874]2000   server &SHOULD; include a representation containing an explanation of the
[8]2001   error situation, and whether it is a temporary or permanent
[874]2002   condition. User agents &SHOULD; display any included representation to the
[8]2003   user. These response codes are applicable to any request method.
2004</t>
2005
2006<section title="500 Internal Server Error" anchor="status.500">
2007  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2008  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2009<t>
2010   The server encountered an unexpected condition which prevented it
2011   from fulfilling the request.
2012</t>
2013</section>
2014
2015<section title="501 Not Implemented" anchor="status.501">
2016  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2017  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2018<t>
2019   The server does not support the functionality required to fulfill the
2020   request. This is the appropriate response when the server does not
2021   recognize the request method and is not capable of supporting it for
2022   any resource.
2023</t>
2024</section>
2025
2026<section title="502 Bad Gateway" anchor="status.502">
2027  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2028  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2029<t>
2030   The server, while acting as a gateway or proxy, received an invalid
2031   response from the upstream server it accessed in attempting to
2032   fulfill the request.
2033</t>
2034</section>
2035
2036<section title="503 Service Unavailable" anchor="status.503">
2037  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2038  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2039<t>
2040   The server is currently unable to handle the request due to a
2041   temporary overloading or maintenance of the server. The implication
2042   is that this is a temporary condition which will be alleviated after
2043   some delay. If known, the length of the delay &MAY; be indicated in a
[994]2044   Retry-After header field. If no Retry-After is given, the client &SHOULD;
[8]2045   handle the response as it would for a 500 response.
2046</t>
[563]2047<x:note>
2048  <t>
2049    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
[901]2050    server must use it when becoming overloaded. Some servers might wish
[563]2051    to simply refuse the connection.
2052  </t>
2053</x:note>
[8]2054</section>
2055
2056<section title="504 Gateway Timeout" anchor="status.504">
2057  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2058  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2059<t>
2060   The server, while acting as a gateway or proxy, did not receive a
[763]2061   timely response from the upstream server specified by the URI (e.g.,
2062   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
[8]2063   to access in attempting to complete the request.
2064</t>
[563]2065<x:note>
2066  <t>
[757]2067    <x:h>Note</x:h> to implementors: some deployed proxies are known to
[563]2068    return 400 or 500 when DNS lookups time out.
2069  </t>
2070</x:note>
[8]2071</section>
2072
2073<section title="505 HTTP Version Not Supported" anchor="status.505">
2074  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2075  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2076<t>
[172]2077   The server does not support, or refuses to support, the protocol
[8]2078   version that was used in the request message. The server is
2079   indicating that it is unable or unwilling to complete the request
[29]2080   using the same major version as the client, as described in &http-version;,
[8]2081   other than with this error message. The response &SHOULD; contain
[874]2082   a representation describing why that version is not supported and what other
[8]2083   protocols are supported by that server.
2084</t>
2085
2086</section>
2087</section>
2088</section>
2089
2090
2091<section title="Header Field Definitions" anchor="header.fields">
2092<t>
[117]2093   This section defines the syntax and semantics of HTTP/1.1 header fields
2094   related to request and response semantics.
[8]2095</t>
2096
2097<section title="Allow" anchor="header.allow">
[1120]2098  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2099  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
[229]2100  <x:anchor-alias value="Allow"/>
[8]2101<t>
[1163]2102   The "Allow" header field lists the set of methods advertised as
[1067]2103   supported by the target resource. The purpose of this field is strictly to
[1161]2104   inform the recipient of valid request methods associated with the resource.
[8]2105</t>
[1235]2106<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2107  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
[8]2108</artwork></figure>
2109<t>
[1067]2110   Example of use:
[8]2111</t>
2112<figure><artwork type="example">
[356]2113  Allow: GET, HEAD, PUT
[8]2114</artwork></figure>
2115<t>
[1067]2116   The actual set of allowed methods is defined by the origin server at the
2117   time of each request.
[8]2118</t>
2119<t>
[1101]2120   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
[1068]2121   understand all the methods specified in order to handle them according to
2122   the generic message handling rules.
[8]2123</t>
2124</section>
2125
2126<section title="Expect" anchor="header.expect">
[1120]2127  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2128  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
[229]2129  <x:anchor-alias value="Expect"/>
2130  <x:anchor-alias value="expectation"/>
2131  <x:anchor-alias value="expectation-extension"/>
2132  <x:anchor-alias value="expect-params"/>
[8]2133<t>
[1163]2134   The "Expect" header field is used to indicate that particular
[8]2135   server behaviors are required by the client.
2136</t>
[1235]2137<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2138  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
[135]2139 
[356]2140  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2141  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
[229]2142                           *<x:ref>expect-params</x:ref> ]
[356]2143  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
[8]2144</artwork></figure>
2145<t>
2146   A server that does not understand or is unable to comply with any of
2147   the expectation values in the Expect field of a request &MUST; respond
[924]2148   with appropriate error status code. The server &MUST; respond with a 417
2149   (Expectation Failed) status code if any of the expectations cannot be met
[8]2150   or, if there are other problems with the request, some other 4xx
[924]2151   status code.
[8]2152</t>
2153<t>
2154   This header field is defined with extensible syntax to allow for
2155   future extensions. If a server receives a request containing an
2156   Expect field that includes an expectation-extension that it does not
[924]2157   support, it &MUST; respond with a 417 (Expectation Failed) status code.
[8]2158</t>
2159<t>
2160   Comparison of expectation values is case-insensitive for unquoted
2161   tokens (including the 100-continue token), and is case-sensitive for
2162   quoted-string expectation-extensions.
2163</t>
2164<t>
2165   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
[924]2166   return a 417 (Expectation Failed) status code if it receives a request
[8]2167   with an expectation that it cannot meet. However, the Expect
[1163]2168   header field itself is end-to-end; it &MUST; be forwarded if the
[8]2169   request is forwarded.
2170</t>
2171<t>
2172   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
[994]2173   Expect header field.
[8]2174</t>
2175<t>
[924]2176   See &use100; for the use of the 100 (Continue) status code.
[8]2177</t>
2178</section>
2179
2180<section title="From" anchor="header.from">
[1120]2181  <iref primary="true" item="From header field" x:for-anchor=""/>
2182  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
[229]2183  <x:anchor-alias value="From"/>
2184  <x:anchor-alias value="mailbox"/>
[8]2185<t>
[1163]2186   The "From" header field, if given, &SHOULD; contain an Internet
[8]2187   e-mail address for the human user who controls the requesting user
2188   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
[327]2189   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
[8]2190</t>
[1235]2191<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2192  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
[206]2193 
[327]2194  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
[8]2195</artwork></figure>
2196<t>
2197   An example is:
2198</t>
2199<figure><artwork type="example">
[356]2200  From: webmaster@example.org
[8]2201</artwork></figure>
2202<t>
2203   This header field &MAY; be used for logging purposes and as a means for
2204   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2205   be used as an insecure form of access protection. The interpretation
2206   of this field is that the request is being performed on behalf of the
2207   person given, who accepts responsibility for the method performed. In
[994]2208   particular, robot agents &SHOULD; include this header field so that the
[8]2209   person responsible for running the robot can be contacted if problems
2210   occur on the receiving end.
2211</t>
2212<t>
2213   The Internet e-mail address in this field &MAY; be separate from the
2214   Internet host which issued the request. For example, when a request
2215   is passed through a proxy the original issuer's address &SHOULD; be
2216   used.
2217</t>
2218<t>
2219   The client &SHOULD-NOT;  send the From header field without the user's
2220   approval, as it might conflict with the user's privacy interests or
2221   their site's security policy. It is strongly recommended that the
2222   user be able to disable, enable, and modify the value of this field
2223   at any time prior to a request.
2224</t>
2225</section>
2226
2227<section title="Location" anchor="header.location">
[1120]2228  <iref primary="true" item="Location header field" x:for-anchor=""/>
2229  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
[229]2230  <x:anchor-alias value="Location"/>
[8]2231<t>
[1163]2232   The "Location" header field is used to identify a newly created
[698]2233   resource, or to redirect the recipient to a different location for
2234   completion of the request.
[8]2235</t>
[698]2236<t>
2237   For 201 (Created) responses, the Location is the URI of the new resource
2238   which was created by the request. For 3xx responses, the location &SHOULD;
2239   indicate the server's preferred URI for automatic redirection to the
2240   resource.
2241</t>
2242<t>
[785]2243   The field value consists of a single URI-reference. When it has the form
2244   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2245   the final value is computed by resolving it against the effective request
2246   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
[698]2247</t>
[1235]2248<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2249  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
[8]2250</artwork></figure>
[785]2251<figure>
2252<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2253<artwork type="example">
2254  Location: http://www.example.org/pub/WWW/People.html#tim
2255</artwork></figure><figure><artwork type="example">  Location: /index.html
[8]2256</artwork></figure>
[659]2257<t>
[785]2258   There are circumstances in which a fragment identifier in a Location URI
2259   would not be appropriate:
[659]2260   <list style="symbols">
[785]2261      <t>With a 201 Created response, because in this usage the Location header
[994]2262      field specifies the URI for the entire created resource.</t>
[659]2263      <t>With 305 Use Proxy.</t>
2264   </list>
2265</t>
[563]2266<x:note>
2267  <t>
[785]2268    <x:h>Note:</x:h> This specification does not define precedence rules
[791]2269    for the case where the original URI, as navigated to by the user
[785]2270    agent, and the Location header field value both contain fragment
[1097]2271    identifiers. Thus be aware that including fragment identifiers might
2272    inconvenience anyone relying on the semantics of the original URI's
2273    fragment identifier.
[785]2274  </t>
2275</x:note>
2276<x:note>
2277  <t>
[563]2278    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
[866]2279    from Location in that the Content-Location identifies the most specific
2280    resource corresponding to the enclosed representation.
2281    It is therefore possible for a response to contain header fields for
2282    both Location and Content-Location.
[563]2283  </t>
2284</x:note>
[8]2285</section>
2286
2287<section title="Max-Forwards" anchor="header.max-forwards">
[1120]2288  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2289  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
[229]2290  <x:anchor-alias value="Max-Forwards"/>
[8]2291<t>
[1163]2292   The "Max-Forwards" header field provides a mechanism with the
[698]2293   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2294   methods to limit the number of times that the request is forwarded by
[1173]2295   proxies. This can be useful when the client is attempting to
[698]2296   trace a request which appears to be failing or looping in mid-chain.
[8]2297</t>
[1235]2298<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2299  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
[8]2300</artwork></figure>
2301<t>
2302   The Max-Forwards value is a decimal integer indicating the remaining
[901]2303   number of times this request message can be forwarded.
[8]2304</t>
2305<t>
[1173]2306   Each recipient of a TRACE or OPTIONS request
[8]2307   containing a Max-Forwards header field &MUST; check and update its
2308   value prior to forwarding the request. If the received value is zero
2309   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2310   respond as the final recipient. If the received Max-Forwards value is
2311   greater than zero, then the forwarded message &MUST; contain an updated
2312   Max-Forwards field with a value decremented by one (1).
2313</t>
2314<t>
[1161]2315   The Max-Forwards header field &MAY; be ignored for all other request
2316   methods.
[8]2317</t>
2318</section>
2319
2320<section title="Referer" anchor="header.referer">
[1120]2321  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2322  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
[229]2323  <x:anchor-alias value="Referer"/>
[8]2324<t>
[1163]2325   The "Referer" [sic] header field allows the client to specify the
[965]2326   URI of the resource from which the effective request URI was obtained (the
[698]2327   "referrer", although the header field is misspelled.).
[8]2328</t>
[593]2329<t>
[994]2330   The Referer header field allows servers to generate lists of back-links to
[593]2331   resources for interest, logging, optimized caching, etc. It also allows
2332   obsolete or mistyped links to be traced for maintenance. Some servers use
2333   Referer as a means of controlling where they allow links from (so-called
[969]2334   "deep linking"), but legitimate requests do not always
2335   contain a Referer header field.
[593]2336</t>
2337<t>
[965]2338   If the effective request URI was obtained from a source that does not have its own
[812]2339   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
[593]2340   sent with the value "about:blank", or not be sent at all. Note that this
2341   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2342</t>
[1235]2343<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2344  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[8]2345</artwork></figure>
2346<t>
2347   Example:
2348</t>
2349<figure><artwork type="example">
[356]2350  Referer: http://www.example.org/hypertext/Overview.html
[8]2351</artwork></figure>
2352<t>
2353   If the field value is a relative URI, it &SHOULD; be interpreted
[965]2354   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
[8]2355   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2356</t>
2357</section>
2358
2359<section title="Retry-After" anchor="header.retry-after">
[1120]2360  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2361  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
[229]2362  <x:anchor-alias value="Retry-After"/>
[8]2363<t>
[1163]2364   The header "Retry-After" field can be used with a 503 (Service
[8]2365   Unavailable) response to indicate how long the service is expected to
2366   be unavailable to the requesting client. This field &MAY; also be used
2367   with any 3xx (Redirection) response to indicate the minimum time the
[698]2368   user-agent is asked wait before issuing the redirected request.
2369</t>
2370<t>
2371   The value of this field can be either an HTTP-date or an integer number
[8]2372   of seconds (in decimal) after the time of the response.
2373</t>
[1235]2374<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2375  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
[8]2376</artwork></figure>
[229]2377<t anchor="rule.delta-seconds">
2378  <x:anchor-alias value="delta-seconds"/>
[212]2379   Time spans are non-negative decimal integers, representing time in
2380   seconds.
2381</t>
2382<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
[229]2383  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
[212]2384</artwork></figure>
2385<t>
[8]2386   Two examples of its use are
2387</t>
2388<figure><artwork type="example">
[356]2389  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2390  Retry-After: 120
[8]2391</artwork></figure>
2392<t>
2393   In the latter example, the delay is 2 minutes.
2394</t>
2395</section>
2396
2397<section title="Server" anchor="header.server">
[1120]2398  <iref primary="true" item="Server header field" x:for-anchor=""/>
2399  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
[229]2400  <x:anchor-alias value="Server"/>
[8]2401<t>
[1163]2402   The "Server" header field contains information about the
[698]2403   software used by the origin server to handle the request.
[8]2404</t>
[698]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>
[1235]2411<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2412  <x:ref>Server</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
[8]2413</artwork></figure>
2414<t>
2415   Example:
2416</t>
2417<figure><artwork type="example">
[356]2418  Server: CERN/3.0 libwww/2.17
[8]2419</artwork></figure>
2420<t>
2421   If the response is being forwarded through a proxy, the proxy
[1163]2422   application &MUST-NOT; modify the Server header field. Instead, it
[72]2423   &MUST; include a Via field (as described in &header-via;).
[8]2424</t>
[563]2425<x:note>
2426  <t>
2427    <x:h>Note:</x:h> Revealing the specific software version of the server might
2428    allow the server machine to become more vulnerable to attacks
2429    against software that is known to contain security holes. Server
2430    implementors are encouraged to make this field a configurable
2431    option.
2432  </t>
2433</x:note>
[8]2434</section>
2435
2436<section title="User-Agent" anchor="header.user-agent">
[1120]2437  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2438  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
[229]2439  <x:anchor-alias value="User-Agent"/>
[1036]2440<t>
[1163]2441   The "User-Agent" header field contains information about the user
[1036]2442   agent originating the request. User agents &SHOULD; include this field with
2443   requests.
2444</t>
2445<t>
2446   Typically, it is used for statistical purposes, the tracing of protocol
2447   violations, and tailoring responses to avoid particular user agent
2448   limitations.
2449</t>
2450<t>
2451   The field can contain multiple product tokens (&product-tokens;)
2452   and comments (&header-fields;) identifying the agent and its
2453   significant subproducts. By convention, the product tokens are listed in
2454   order of their significance for identifying the application.
2455</t>
2456<t>
2457   Because this field is usually sent on every request a user agent makes,
2458   implementations are encouraged not to include needlessly fine-grained
2459   detail, and to limit (or even prohibit) the addition of subproducts by third
2460   parties. Overly long and detailed User-Agent field values make requests
2461   larger and can also be used to identify ("fingerprint") the user against
2462   their wishes.
2463</t>
2464<t>
2465   Likewise, implementations are encouraged not to use the product tokens of
2466   other implementations in order to declare compatibility with them, as this
2467   circumvents the purpose of the field. Finally, they are encouraged not to
2468   use comments to identify products; doing so makes the field value more
2469   difficult to parse.
2470</t>
[1235]2471<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2472  <x:ref>User-Agent</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
[8]2473</artwork></figure>
2474<t>
2475   Example:
2476</t>
2477<figure><artwork type="example">
[356]2478  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
[8]2479</artwork></figure>
2480</section>
2481
2482</section>
2483
[29]2484<section title="IANA Considerations" anchor="IANA.considerations">
[270]2485
2486<section title="Method Registry" anchor="method.registration">
2487<t>
[1161]2488  The registration procedure for HTTP request methods is defined by
[270]2489  <xref target="method.registry"/> of this document.
2490</t>
[288]2491<t>
[969]2492   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
[818]2493   and be populated with the registrations below:
[288]2494</t>
[682]2495<?BEGININC p2-semantics.iana-methods ?>
[270]2496<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
[288]2497<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
[270]2498   <ttcol>Method</ttcol>
[286]2499   <ttcol>Safe</ttcol>
[270]2500   <ttcol>Reference</ttcol>
2501   <c>CONNECT</c>
[286]2502   <c>no</c>
[270]2503   <c>
2504      <xref target="CONNECT"/>
2505   </c>
2506   <c>DELETE</c>
[286]2507   <c>no</c>
[270]2508   <c>
2509      <xref target="DELETE"/>
2510   </c>
2511   <c>GET</c>
[286]2512   <c>yes</c>
[270]2513   <c>
2514      <xref target="GET"/>
2515   </c>
2516   <c>HEAD</c>
[286]2517   <c>yes</c>
[270]2518   <c>
2519      <xref target="HEAD"/>
2520   </c>
2521   <c>OPTIONS</c>
[286]2522   <c>yes</c>
[270]2523   <c>
2524      <xref target="OPTIONS"/>
2525   </c>
2526   <c>POST</c>
[286]2527   <c>no</c>
[270]2528   <c>
2529      <xref target="POST"/>
2530   </c>
2531   <c>PUT</c>
[286]2532   <c>no</c>
[270]2533   <c>
2534      <xref target="PUT"/>
2535   </c>
2536   <c>TRACE</c>
[286]2537   <c>yes</c>
[270]2538   <c>
2539      <xref target="TRACE"/>
2540   </c>
2541</texttable>
2542<!--(END)-->
[682]2543<?ENDINC p2-semantics.iana-methods ?>
[270]2544</section>
2545
[255]2546<section title="Status Code Registry" anchor="status.code.registration">
[262]2547<t>
[1101]2548   The registration procedure for HTTP Status Codes &mdash; previously defined
2549   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
[288]2550   by <xref target="status.code.registry"/> of this document.
[262]2551</t>
[288]2552<t>
2553   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
[969]2554   shall be updated with the registrations below:
[288]2555</t>
[682]2556<?BEGININC p2-semantics.iana-status-codes ?>
[255]2557<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
[288]2558<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
[255]2559   <ttcol>Value</ttcol>
2560   <ttcol>Description</ttcol>
2561   <ttcol>Reference</ttcol>
2562   <c>100</c>
2563   <c>Continue</c>
2564   <c>
2565      <xref target="status.100"/>
2566   </c>
2567   <c>101</c>
2568   <c>Switching Protocols</c>
2569   <c>
2570      <xref target="status.101"/>
2571   </c>
2572   <c>200</c>
2573   <c>OK</c>
2574   <c>
2575      <xref target="status.200"/>
2576   </c>
2577   <c>201</c>
2578   <c>Created</c>
2579   <c>
2580      <xref target="status.201"/>
2581   </c>
2582   <c>202</c>
2583   <c>Accepted</c>
2584   <c>
2585      <xref target="status.202"/>
2586   </c>
2587   <c>203</c>
2588   <c>Non-Authoritative Information</c>
2589   <c>
2590      <xref target="status.203"/>
2591   </c>
2592   <c>204</c>
2593   <c>No Content</c>
2594   <c>
2595      <xref target="status.204"/>
2596   </c>
2597   <c>205</c>
2598   <c>Reset Content</c>
2599   <c>
2600      <xref target="status.205"/>
2601   </c>
2602   <c>300</c>
2603   <c>Multiple Choices</c>
2604   <c>
2605      <xref target="status.300"/>
2606   </c>
2607   <c>301</c>
2608   <c>Moved Permanently</c>
2609   <c>
2610      <xref target="status.301"/>
2611   </c>
2612   <c>302</c>
2613   <c>Found</c>
2614   <c>
2615      <xref target="status.302"/>
2616   </c>
2617   <c>303</c>
2618   <c>See Other</c>
2619   <c>
2620      <xref target="status.303"/>
2621   </c>
2622   <c>305</c>
2623   <c>Use Proxy</c>
2624   <c>
2625      <xref target="status.305"/>
2626   </c>
2627   <c>306</c>
2628   <c>(Unused)</c>
2629   <c>
2630      <xref target="status.306"/>
2631   </c>
2632   <c>307</c>
2633   <c>Temporary Redirect</c>
2634   <c>
2635      <xref target="status.307"/>
2636   </c>
2637   <c>400</c>
2638   <c>Bad Request</c>
2639   <c>
2640      <xref target="status.400"/>
2641   </c>
2642   <c>402</c>
2643   <c>Payment Required</c>
2644   <c>
2645      <xref target="status.402"/>
2646   </c>
2647   <c>403</c>
2648   <c>Forbidden</c>
2649   <c>
2650      <xref target="status.403"/>
2651   </c>
2652   <c>404</c>
2653   <c>Not Found</c>
2654   <c>
2655      <xref target="status.404"/>
2656   </c>
2657   <c>405</c>
2658   <c>Method Not Allowed</c>
2659   <c>
2660      <xref target="status.405"/>
2661   </c>
2662   <c>406</c>
2663   <c>Not Acceptable</c>
2664   <c>
2665      <xref target="status.406"/>
2666   </c>
2667   <c>407</c>
2668   <c>Proxy Authentication Required</c>
2669   <c>
2670      <xref target="status.407"/>
2671   </c>
2672   <c>408</c>
2673   <c>Request Timeout</c>
2674   <c>
2675      <xref target="status.408"/>
2676   </c>
2677   <c>409</c>
2678   <c>Conflict</c>
2679   <c>
2680      <xref target="status.409"/>
2681   </c>
2682   <c>410</c>
2683   <c>Gone</c>
2684   <c>
2685      <xref target="status.410"/>
2686   </c>
2687   <c>411</c>
2688   <c>Length Required</c>
2689   <c>
2690      <xref target="status.411"/>
2691   </c>
2692   <c>413</c>
2693   <c>Request Entity Too Large</c>
2694   <c>
2695      <xref target="status.413"/>
2696   </c>
2697   <c>414</c>
[465]2698   <c>URI Too Long</c>
[255]2699   <c>
2700      <xref target="status.414"/>
2701   </c>
2702   <c>415</c>
2703   <c>Unsupported Media Type</c>
2704   <c>
2705      <xref target="status.415"/>
2706   </c>
2707   <c>417</c>
2708   <c>Expectation Failed</c>
2709   <c>
2710      <xref target="status.417"/>
2711   </c>
[1071]2712   <c>426</c>
2713   <c>Upgrade Required</c>
2714   <c>
2715      <xref target="status.426"/>
2716   </c>
[255]2717   <c>500</c>
2718   <c>Internal Server Error</c>
2719   <c>
2720      <xref target="status.500"/>
2721   </c>
2722   <c>501</c>
2723   <c>Not Implemented</c>
2724   <c>
2725      <xref target="status.501"/>
2726   </c>
2727   <c>502</c>
2728   <c>Bad Gateway</c>
2729   <c>
2730      <xref target="status.502"/>
2731   </c>
2732   <c>503</c>
2733   <c>Service Unavailable</c>
2734   <c>
2735      <xref target="status.503"/>
2736   </c>
2737   <c>504</c>
2738   <c>Gateway Timeout</c>
2739   <c>
2740      <xref target="status.504"/>
2741   </c>
2742   <c>505</c>
2743   <c>HTTP Version Not Supported</c>
2744   <c>
2745      <xref target="status.505"/>
2746   </c>
2747</texttable>
2748<!--(END)-->
[682]2749<?ENDINC p2-semantics.iana-status-codes ?>
[8]2750</section>
[921]2751<section title="Header Field Registration" anchor="header.field.registration">
[290]2752<t>
[969]2753   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
[290]2754   with the permanent registrations below (see <xref target="RFC3864"/>):
2755</t>
[680]2756<?BEGININC p2-semantics.iana-headers ?>
[253]2757<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]2758<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]2759   <ttcol>Header Field Name</ttcol>
2760   <ttcol>Protocol</ttcol>
2761   <ttcol>Status</ttcol>
2762   <ttcol>Reference</ttcol>
[680]2763
[253]2764   <c>Allow</c>
2765   <c>http</c>
2766   <c>standard</c>
2767   <c>
2768      <xref target="header.allow"/>
2769   </c>
2770   <c>Expect</c>
2771   <c>http</c>
2772   <c>standard</c>
2773   <c>
2774      <xref target="header.expect"/>
2775   </c>
2776   <c>From</c>
2777   <c>http</c>
2778   <c>standard</c>
2779   <c>
2780      <xref target="header.from"/>
2781   </c>
2782   <c>Location</c>
2783   <c>http</c>
2784   <c>standard</c>
2785   <c>
2786      <xref target="header.location"/>
2787   </c>
2788   <c>Max-Forwards</c>
2789   <c>http</c>
2790   <c>standard</c>
2791   <c>
2792      <xref target="header.max-forwards"/>
2793   </c>
2794   <c>Referer</c>
2795   <c>http</c>
2796   <c>standard</c>
2797   <c>
2798      <xref target="header.referer"/>
2799   </c>
2800   <c>Retry-After</c>
2801   <c>http</c>
2802   <c>standard</c>
2803   <c>
2804      <xref target="header.retry-after"/>
2805   </c>
2806   <c>Server</c>
2807   <c>http</c>
2808   <c>standard</c>
2809   <c>
2810      <xref target="header.server"/>
2811   </c>
2812   <c>User-Agent</c>
2813   <c>http</c>
2814   <c>standard</c>
2815   <c>
2816      <xref target="header.user-agent"/>
2817   </c>
2818</texttable>
[290]2819<!--(END)-->
[680]2820<?ENDINC p2-semantics.iana-headers ?>
[253]2821<t>
[290]2822   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
[253]2823</t>
2824</section>
2825</section>
2826
[8]2827<section title="Security Considerations" anchor="security.considerations">
2828<t>
2829   This section is meant to inform application developers, information
2830   providers, and users of the security limitations in HTTP/1.1 as
2831   described by this document. The discussion does not include
2832   definitive solutions to the problems revealed, though it does make
2833   some suggestions for reducing security risks.
2834</t>
2835
2836<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2837<t>
2838   Like any generic data transfer protocol, HTTP cannot regulate the
2839   content of the data that is transferred, nor is there any a priori
2840   method of determining the sensitivity of any particular piece of
2841   information within the context of any given request. Therefore,
2842   applications &SHOULD; supply as much control over this information as
2843   possible to the provider of that information. Four header fields are
2844   worth special mention in this context: Server, Via, Referer and From.
2845</t>
2846<t>
2847   Revealing the specific software version of the server might allow the
2848   server machine to become more vulnerable to attacks against software
2849   that is known to contain security holes. Implementors &SHOULD; make the
2850   Server header field a configurable option.
2851</t>
2852<t>
2853   Proxies which serve as a portal through a network firewall &SHOULD;
2854   take special precautions regarding the transfer of header information
2855   that identifies the hosts behind the firewall. In particular, they
2856   &SHOULD; remove, or replace with sanitized versions, any Via fields
2857   generated behind the firewall.
2858</t>
2859<t>
[994]2860   The Referer header field allows reading patterns to be studied and reverse
[8]2861   links drawn. Although it can be very useful, its power can be abused
2862   if user details are not separated from the information contained in
2863   the Referer. Even when the personal information has been removed, the
[994]2864   Referer header field might indicate a private document's URI whose
[8]2865   publication would be inappropriate.
2866</t>
2867<t>
2868   The information sent in the From field might conflict with the user's
2869   privacy interests or their site's security policy, and hence it
2870   &SHOULD-NOT;  be transmitted without the user being able to disable,
2871   enable, and modify the contents of the field. The user &MUST; be able
2872   to set the contents of this field within a user preference or
2873   application defaults configuration.
2874</t>
2875<t>
2876   We suggest, though do not require, that a convenient toggle interface
2877   be provided for the user to enable or disable the sending of From and
2878   Referer information.
2879</t>
2880<t>
[1036]2881   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2882   target="header.server"/>) header fields can sometimes be used to determine
2883   that a specific client or server have a particular security hole which might
2884   be exploited. Unfortunately, this same information is often used for other
2885   valuable purposes for which HTTP currently has no better mechanism.
2886</t>
2887<t>
2888   Furthermore, the User-Agent header field may contain enough entropy to be
2889   used, possibly in conjunction with other material, to uniquely identify the
2890   user.
2891</t>
2892<t>
[1161]2893   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
[994]2894   that was sent in request header fields within the body of their response.
[666]2895   Clients &SHOULD; be careful with sensitive information, like Cookies,
[1161]2896   Authorization credentials, and other header fields that might be used to
[666]2897   collect data from the client.
[654]2898</t> 
[8]2899</section>
2900
[184]2901<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
[8]2902<t>
2903   Because the source of a link might be private information or might
2904   reveal an otherwise private information source, it is strongly
2905   recommended that the user be able to select whether or not the
2906   Referer field is sent. For example, a browser client could have a
2907   toggle switch for browsing openly/anonymously, which would
2908   respectively enable/disable the sending of Referer and From
2909   information.
2910</t>
2911<t>
[172]2912   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
[8]2913   HTTP request if the referring page was transferred with a secure
2914   protocol.
2915</t>
2916<t>
[969]2917   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2918   sensitive data because that data will be placed in the request-target. Many
[823]2919   existing servers, proxies, and user agents log or display the request-target
2920   in places where it might be visible to third parties. Such services can
[172]2921   use POST-based form submission instead.
[8]2922</t>
2923</section>
2924
2925<section title="Location Headers and Spoofing" anchor="location.spoofing">
2926<t>
2927   If a single server supports multiple organizations that do not trust
2928   one another, then it &MUST; check the values of Location and Content-Location
[994]2929   header fields in responses that are generated under control of
[8]2930   said organizations to make sure that they do not attempt to
2931   invalidate resources over which they have no authority.
2932</t>
2933</section>
2934
[1061]2935<section title="Security Considerations for CONNECT">
2936<t>
2937   Since tunneled data is opaque to the proxy, there are additional
2938   risks to tunneling to other well-known or reserved ports.
2939   A HTTP client CONNECTing to port 25 could relay spam
2940   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2941   access to a small number of known ports.
2942</t>
[8]2943</section>
2944
[1061]2945</section>
2946
[8]2947<section title="Acknowledgments" anchor="ack">
2948</section>
2949</middle>
2950<back>
2951
[119]2952<references title="Normative References">
2953
[31]2954<reference anchor="Part1">
[119]2955  <front>
2956    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2957    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]2958      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]2959      <address><email>fielding@gbiv.com</email></address>
2960    </author>
2961    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2962      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2963      <address><email>jg@freedesktop.org</email></address>
[119]2964    </author>
2965    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2966      <organization abbrev="HP">Hewlett-Packard Company</organization>
2967      <address><email>JeffMogul@acm.org</email></address>
2968    </author>
2969    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2970      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2971      <address><email>henrikn@microsoft.com</email></address>
2972    </author>
2973    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]2974      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]2975      <address><email>LMM@acm.org</email></address>
2976    </author>
2977    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2978      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2979      <address><email>paulle@microsoft.com</email></address>
2980    </author>
2981    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2982      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2983      <address><email>timbl@w3.org</email></address>
2984    </author>
2985    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2986      <organization abbrev="W3C">World Wide Web Consortium</organization>
2987      <address><email>ylafon@w3.org</email></address>
2988    </author>
2989    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2990      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2991      <address><email>julian.reschke@greenbytes.de</email></address>
2992    </author>
2993    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2994  </front>
2995  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2996  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
[31]2997</reference>
2998
2999<reference anchor="Part3">
[119]3000  <front>
3001    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3002    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3003      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3004      <address><email>fielding@gbiv.com</email></address>
3005    </author>
3006    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3007      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3008      <address><email>jg@freedesktop.org</email></address>
[119]3009    </author>
3010    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3011      <organization abbrev="HP">Hewlett-Packard Company</organization>
3012      <address><email>JeffMogul@acm.org</email></address>
3013    </author>
3014    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3015      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3016      <address><email>henrikn@microsoft.com</email></address>
3017    </author>
3018    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3019      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3020      <address><email>LMM@acm.org</email></address>
3021    </author>
3022    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3023      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3024      <address><email>paulle@microsoft.com</email></address>
3025    </author>
3026    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3027      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3028      <address><email>timbl@w3.org</email></address>
3029    </author>
3030    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3031      <organization abbrev="W3C">World Wide Web Consortium</organization>
3032      <address><email>ylafon@w3.org</email></address>
3033    </author>
3034    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3035      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3036      <address><email>julian.reschke@greenbytes.de</email></address>
3037    </author>
3038    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3039  </front>
3040  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3041  <x:source href="p3-payload.xml" basename="p3-payload"/>
[31]3042</reference>
3043
3044<reference anchor="Part4">
[119]3045  <front>
3046    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3047    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3048      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3049      <address><email>fielding@gbiv.com</email></address>
3050    </author>
3051    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3052      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3053      <address><email>jg@freedesktop.org</email></address>
[119]3054    </author>
3055    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3056      <organization abbrev="HP">Hewlett-Packard Company</organization>
3057      <address><email>JeffMogul@acm.org</email></address>
3058    </author>
3059    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3060      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3061      <address><email>henrikn@microsoft.com</email></address>
3062    </author>
3063    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3064      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3065      <address><email>LMM@acm.org</email></address>
3066    </author>
3067    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3068      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3069      <address><email>paulle@microsoft.com</email></address>
3070    </author>
3071    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3072      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3073      <address><email>timbl@w3.org</email></address>
3074    </author>
3075    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3076      <organization abbrev="W3C">World Wide Web Consortium</organization>
3077      <address><email>ylafon@w3.org</email></address>
3078    </author>
3079    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3080      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3081      <address><email>julian.reschke@greenbytes.de</email></address>
3082    </author>
3083    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3084  </front>
3085  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3086  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
[31]3087</reference>
3088
3089<reference anchor="Part5">
[119]3090  <front>
3091    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3092    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3093      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3094      <address><email>fielding@gbiv.com</email></address>
3095    </author>
3096    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3097      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3098      <address><email>jg@freedesktop.org</email></address>
[119]3099    </author>
3100    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3101      <organization abbrev="HP">Hewlett-Packard Company</organization>
3102      <address><email>JeffMogul@acm.org</email></address>
3103    </author>
3104    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3105      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3106      <address><email>henrikn@microsoft.com</email></address>
3107    </author>
3108    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3109      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3110      <address><email>LMM@acm.org</email></address>
3111    </author>
3112    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3113      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3114      <address><email>paulle@microsoft.com</email></address>
3115    </author>
3116    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3117      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3118      <address><email>timbl@w3.org</email></address>
3119    </author>
3120    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3121      <organization abbrev="W3C">World Wide Web Consortium</organization>
3122      <address><email>ylafon@w3.org</email></address>
3123    </author>
3124    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3125      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3126      <address><email>julian.reschke@greenbytes.de</email></address>
3127    </author>
3128    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3129  </front>
3130  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3131  <x:source href="p5-range.xml" basename="p5-range"/>
[31]3132</reference>
3133
3134<reference anchor="Part6">
[119]3135  <front>
3136    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3137    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3138      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3139      <address><email>fielding@gbiv.com</email></address>
3140    </author>
3141    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3142      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3143      <address><email>jg@freedesktop.org</email></address>
[119]3144    </author>
3145    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3146      <organization abbrev="HP">Hewlett-Packard Company</organization>
3147      <address><email>JeffMogul@acm.org</email></address>
3148    </author>
3149    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3150      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3151      <address><email>henrikn@microsoft.com</email></address>
3152    </author>
3153    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3154      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3155      <address><email>LMM@acm.org</email></address>
3156    </author>
3157    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3158      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3159      <address><email>paulle@microsoft.com</email></address>
3160    </author>
3161    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3162      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3163      <address><email>timbl@w3.org</email></address>
3164    </author>
3165    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3166      <organization abbrev="W3C">World Wide Web Consortium</organization>
3167      <address><email>ylafon@w3.org</email></address>
3168    </author>
[601]3169    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3170      <address><email>mnot@mnot.net</email></address>
3171    </author>
[119]3172    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3173      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3174      <address><email>julian.reschke@greenbytes.de</email></address>
3175    </author>
3176    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3177  </front>
3178  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3179  <x:source href="p6-cache.xml" basename="p6-cache"/>
[31]3180</reference>
3181
3182<reference anchor="Part7">
[119]3183  <front>
3184    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3185    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3186      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3187      <address><email>fielding@gbiv.com</email></address>
3188    </author>
3189    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3190      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3191      <address><email>jg@freedesktop.org</email></address>
[119]3192    </author>
3193    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3194      <organization abbrev="HP">Hewlett-Packard Company</organization>
3195      <address><email>JeffMogul@acm.org</email></address>
3196    </author>
3197    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3198      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3199      <address><email>henrikn@microsoft.com</email></address>
3200    </author>
3201    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3202      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3203      <address><email>LMM@acm.org</email></address>
3204    </author>
3205    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3206      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3207      <address><email>paulle@microsoft.com</email></address>
3208    </author>
3209    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3210      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3211      <address><email>timbl@w3.org</email></address>
3212    </author>
3213    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3214      <organization abbrev="W3C">World Wide Web Consortium</organization>
3215      <address><email>ylafon@w3.org</email></address>
3216    </author>
3217    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3218      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3219      <address><email>julian.reschke@greenbytes.de</email></address>
3220    </author>
3221    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3222  </front>
3223  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3224  <x:source href="p7-auth.xml" basename="p7-auth"/>
[31]3225</reference>
3226
[119]3227<reference anchor="RFC2119">
3228  <front>
3229    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3230    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3231      <organization>Harvard University</organization>
3232      <address><email>sob@harvard.edu</email></address>
3233    </author>
3234    <date month="March" year="1997"/>
3235  </front>
3236  <seriesInfo name="BCP" value="14"/>
3237  <seriesInfo name="RFC" value="2119"/>
3238</reference>
3239
[785]3240<reference anchor="RFC3986">
3241 <front>
3242  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3243  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3244    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3245    <address>
3246       <email>timbl@w3.org</email>
3247       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3248    </address>
3249  </author>
3250  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3251    <organization abbrev="Day Software">Day Software</organization>
3252    <address>
3253      <email>fielding@gbiv.com</email>
3254      <uri>http://roy.gbiv.com/</uri>
3255    </address>
3256  </author>
3257  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3258    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3259    <address>
3260      <email>LMM@acm.org</email>
3261      <uri>http://larry.masinter.net/</uri>
3262    </address>
3263  </author>
3264  <date month='January' year='2005'></date>
3265 </front>
[1003]3266 <seriesInfo name="STD" value="66"/>
[785]3267 <seriesInfo name="RFC" value="3986"/>
3268</reference>
3269
[425]3270<reference anchor="RFC5234">
3271  <front>
3272    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3273    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3274      <organization>Brandenburg InternetWorking</organization>
3275      <address>
[728]3276        <email>dcrocker@bbiw.net</email>
3277      </address> 
[425]3278    </author>
3279    <author initials="P." surname="Overell" fullname="Paul Overell">
3280      <organization>THUS plc.</organization>
3281      <address>
[728]3282        <email>paul.overell@thus.net</email>
3283      </address>
[425]3284    </author>
3285    <date month="January" year="2008"/>
3286  </front>
3287  <seriesInfo name="STD" value="68"/>
3288  <seriesInfo name="RFC" value="5234"/>
3289</reference>
3290
[119]3291</references>
3292
3293<references title="Informative References">
3294
[129]3295<reference anchor="RFC1945">
3296  <front>
3297    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3298    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3299      <organization>MIT, Laboratory for Computer Science</organization>
3300      <address><email>timbl@w3.org</email></address>
3301    </author>
3302    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3303      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3304      <address><email>fielding@ics.uci.edu</email></address>
3305    </author>
3306    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3307      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3308      <address><email>frystyk@w3.org</email></address>
3309    </author>
3310    <date month="May" year="1996"/>
3311  </front>
3312  <seriesInfo name="RFC" value="1945"/>
3313</reference>
3314
[119]3315<reference anchor="RFC2068">
3316  <front>
3317    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3318    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3319      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3320      <address><email>fielding@ics.uci.edu</email></address>
3321    </author>
3322    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3323      <organization>MIT Laboratory for Computer Science</organization>
3324      <address><email>jg@w3.org</email></address>
3325    </author>
3326    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3327      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3328      <address><email>mogul@wrl.dec.com</email></address>
3329    </author>
3330    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3331      <organization>MIT Laboratory for Computer Science</organization>
3332      <address><email>frystyk@w3.org</email></address>
3333    </author>
3334    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3335      <organization>MIT Laboratory for Computer Science</organization>
3336      <address><email>timbl@w3.org</email></address>
3337    </author>
3338    <date month="January" year="1997"/>
3339  </front>
3340  <seriesInfo name="RFC" value="2068"/>
3341</reference>
3342
[36]3343<reference anchor="RFC2616">
[119]3344  <front>
3345    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3346    <author initials="R." surname="Fielding" fullname="R. Fielding">
3347      <organization>University of California, Irvine</organization>
3348      <address><email>fielding@ics.uci.edu</email></address>
3349    </author>
3350    <author initials="J." surname="Gettys" fullname="J. Gettys">
3351      <organization>W3C</organization>
3352      <address><email>jg@w3.org</email></address>
3353    </author>
3354    <author initials="J." surname="Mogul" fullname="J. Mogul">
3355      <organization>Compaq Computer Corporation</organization>
3356      <address><email>mogul@wrl.dec.com</email></address>
3357    </author>
3358    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3359      <organization>MIT Laboratory for Computer Science</organization>
3360      <address><email>frystyk@w3.org</email></address>
3361    </author>
3362    <author initials="L." surname="Masinter" fullname="L. Masinter">
3363      <organization>Xerox Corporation</organization>
3364      <address><email>masinter@parc.xerox.com</email></address>
3365    </author>
3366    <author initials="P." surname="Leach" fullname="P. Leach">
3367      <organization>Microsoft Corporation</organization>
3368      <address><email>paulle@microsoft.com</email></address>
3369    </author>
3370    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3371      <organization>W3C</organization>
3372      <address><email>timbl@w3.org</email></address>
3373    </author>
3374    <date month="June" year="1999"/>
3375  </front>
3376  <seriesInfo name="RFC" value="2616"/>
[36]3377</reference>
3378
[255]3379<reference anchor='RFC2817'>
3380  <front>
3381    <title>Upgrading to TLS Within HTTP/1.1</title>
3382    <author initials='R.' surname='Khare' fullname='R. Khare'>
3383      <organization>4K Associates / UC Irvine</organization>
3384      <address><email>rohit@4K-associates.com</email></address>
3385    </author>
3386    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3387      <organization>Agranat Systems, Inc.</organization>
3388      <address><email>lawrence@agranat.com</email></address>
3389    </author>
3390    <date year='2000' month='May' />
3391  </front>
3392  <seriesInfo name='RFC' value='2817' />
3393</reference>
3394
[253]3395<reference anchor='RFC3864'>
3396  <front>
3397    <title>Registration Procedures for Message Header Fields</title>
3398    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3399      <organization>Nine by Nine</organization>
3400      <address><email>GK-IETF@ninebynine.org</email></address>
3401    </author>
3402    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3403      <organization>BEA Systems</organization>
3404      <address><email>mnot@pobox.com</email></address>
3405    </author>
3406    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3407      <organization>HP Labs</organization>
3408      <address><email>JeffMogul@acm.org</email></address>
3409    </author>
3410    <date year='2004' month='September' />
3411  </front>
3412  <seriesInfo name='BCP' value='90' />
3413  <seriesInfo name='RFC' value='3864' />
3414</reference>
3415
[262]3416<reference anchor='RFC5226'>
3417  <front>
3418    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3419    <author initials='T.' surname='Narten' fullname='T. Narten'>
3420      <organization>IBM</organization>
3421      <address><email>narten@us.ibm.com</email></address>
3422    </author>
3423    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3424      <organization>Google</organization>
3425      <address><email>Harald@Alvestrand.no</email></address>
3426    </author>
3427    <date year='2008' month='May' />
3428  </front>
3429  <seriesInfo name='BCP' value='26' />
3430  <seriesInfo name='RFC' value='5226' />
3431</reference>
3432
[327]3433<reference anchor="RFC5322">
3434  <front>
3435    <title>Internet Message Format</title>
3436    <author initials="P." surname="Resnick" fullname="P. Resnick">
3437      <organization>Qualcomm Incorporated</organization>
3438    </author>
3439    <date year="2008" month="October"/>
3440  </front> 
3441  <seriesInfo name="RFC" value="5322"/>
3442</reference>
3443
[1158]3444<reference anchor='RFC5789'>
3445  <front>
3446    <title>PATCH Method for HTTP</title>
3447    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3448      <organization>Linden Lab</organization>
3449    </author>
[1160]3450    <author initials='J.' surname='Snell' fullname='J. Snell' />
[1158]3451    <date year='2010' month='March' />
3452  </front>
3453  <seriesInfo name='RFC' value='5789' />
3454</reference>
3455
[119]3456</references>
3457
[99]3458<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
[108]3459<t>
[262]3460  This document takes over the Status Code Registry, previously defined
3461  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3462  (<xref target="status.code.registry"/>)
3463</t>
3464<t>
[108]3465  Clarify definition of POST.
3466  (<xref target="POST"/>)
3467</t>
[109]3468<t>
[1160]3469  Remove requirement to handle all Content-* header fields; ban use of
3470  Content-Range with PUT.
3471  (<xref target="PUT"/>)
3472</t>
3473<t>
[1066]3474  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3475  (<xref target="CONNECT"/>)
3476</t>
3477<t>
[109]3478  Failed to consider that there are
3479  many other request methods that are safe to automatically redirect,
3480  and further that the user agent is able to make that determination
3481  based on the request method semantics.
3482  (Sections <xref format="counter" target="status.301"/>,
3483  <xref format="counter" target="status.302"/> and
[233]3484  <xref format="counter" target="status.307"/>)
[109]3485</t>
[112]3486<t>
[235]3487  Deprecate 305 Use Proxy status code, because user agents did not implement it.
[965]3488  It used to indicate that the target resource must be accessed through the