source: draft-ietf-httpbis/latest/p2-semantics.xml @ 579

Last change on this file since 579 was 579, checked in by julian.reschke@…, 11 years ago

Resolve #164: remove claim that we're listing applicable methods for each status code (closes #164)

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File size: 151.9 KB
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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">
[573]15  <!ENTITY ID-MONTH "May">
[439]16  <!ENTITY ID-YEAR "2009">
[424]17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[205]25  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[206]28  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[31]29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[190]62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[263]63  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
[8]64]>
65<?rfc toc="yes" ?>
[29]66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
[8]68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
[203]72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
[8]74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
[308]76<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
[446]77     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
[286]78     xmlns:x='http://purl.org/net/xml2rfc/ext'
79     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
[8]80<front>
81
[120]82  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
[8]83
[29]84  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
85    <organization abbrev="Day Software">Day Software</organization>
[8]86    <address>
87      <postal>
[29]88        <street>23 Corporate Plaza DR, Suite 280</street>
89        <city>Newport Beach</city>
[8]90        <region>CA</region>
[29]91        <code>92660</code>
92        <country>USA</country>
[8]93      </postal>
[29]94      <phone>+1-949-706-5300</phone>
95      <facsimile>+1-949-706-5305</facsimile>
96      <email>fielding@gbiv.com</email>
97      <uri>http://roy.gbiv.com/</uri>
[8]98    </address>
99  </author>
100
[29]101  <author initials="J." surname="Gettys" fullname="Jim Gettys">
102    <organization>One Laptop per Child</organization>
[8]103    <address>
104      <postal>
[29]105        <street>21 Oak Knoll Road</street>
106        <city>Carlisle</city>
[8]107        <region>MA</region>
[29]108        <code>01741</code>
109        <country>USA</country>
[8]110      </postal>
[29]111      <email>jg@laptop.org</email>
112      <uri>http://www.laptop.org/</uri>
[8]113    </address>
114  </author>
115 
116  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]117    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]118    <address>
119      <postal>
[29]120        <street>HP Labs, Large Scale Systems Group</street>
121        <street>1501 Page Mill Road, MS 1177</street>
[8]122        <city>Palo Alto</city>
123        <region>CA</region>
[29]124        <code>94304</code>
125        <country>USA</country>
[8]126      </postal>
[29]127      <email>JeffMogul@acm.org</email>
[8]128    </address>
129  </author>
130
131  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]132    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]133    <address>
134      <postal>
[29]135        <street>1 Microsoft Way</street>
136        <city>Redmond</city>
137        <region>WA</region>
138        <code>98052</code>
139        <country>USA</country>
[8]140      </postal>
[29]141      <email>henrikn@microsoft.com</email>
[8]142    </address>
143  </author>
144
145  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[29]146    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
[8]147    <address>
148      <postal>
[29]149        <street>345 Park Ave</street>
150        <city>San Jose</city>
[8]151        <region>CA</region>
[29]152        <code>95110</code>
153        <country>USA</country>
[8]154      </postal>
[29]155      <email>LMM@acm.org</email>
156      <uri>http://larry.masinter.net/</uri>
[8]157    </address>
158  </author>
159 
160  <author initials="P." surname="Leach" fullname="Paul J. Leach">
161    <organization abbrev="Microsoft">Microsoft Corporation</organization>
162    <address>
163      <postal>
164        <street>1 Microsoft Way</street>
165        <city>Redmond</city>
166        <region>WA</region>
167        <code>98052</code>
168      </postal>
169      <email>paulle@microsoft.com</email>
170    </address>
171  </author>
172   
173  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
174    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
175    <address>
176      <postal>
[34]177        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
178        <street>The Stata Center, Building 32</street>
179        <street>32 Vassar Street</street>
[8]180        <city>Cambridge</city>
181        <region>MA</region>
182        <code>02139</code>
[29]183        <country>USA</country>
[8]184      </postal>
185      <email>timbl@w3.org</email>
[34]186      <uri>http://www.w3.org/People/Berners-Lee/</uri>
[8]187    </address>
188  </author>
189
[95]190  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]191    <organization abbrev="W3C">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>W3C / ERCIM</street>
195        <street>2004, rte des Lucioles</street>
196        <city>Sophia-Antipolis</city>
197        <region>AM</region>
198        <code>06902</code>
199        <country>France</country>
200      </postal>
201      <email>ylafon@w3.org</email>
202      <uri>http://www.raubacapeu.net/people/yves/</uri>
203    </address>
204  </author>
205
[95]206  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
207    <organization abbrev="greenbytes">greenbytes GmbH</organization>
208    <address>
209      <postal>
210        <street>Hafenweg 16</street>
211        <city>Muenster</city><region>NW</region><code>48155</code>
212        <country>Germany</country>
213      </postal>
214      <phone>+49 251 2807760</phone>   
215      <facsimile>+49 251 2807761</facsimile>   
216      <email>julian.reschke@greenbytes.de</email>       
217      <uri>http://greenbytes.de/tech/webdav/</uri>     
218    </address>
219  </author>
220
[31]221  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]222  <workgroup>HTTPbis Working Group</workgroup>
[8]223
224<abstract>
225<t>
226   The Hypertext Transfer Protocol (HTTP) is an application-level
227   protocol for distributed, collaborative, hypermedia information
[29]228   systems. HTTP has been in use by the World Wide Web global information
[35]229   initiative since 1990. This document is Part 2 of the seven-part specification
[29]230   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]231   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
[29]232   as expressed by request methods, request-header fields, response status codes,
233   and response-header fields.
[8]234</t>
235</abstract>
[36]236
237<note title="Editorial Note (To be removed by RFC Editor)">
238  <t>
239    Discussion of this draft should take place on the HTTPBIS working group
240    mailing list (ietf-http-wg@w3.org). The current issues list is
[324]241    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
[36]242    and related documents (including fancy diffs) can be found at
[324]243    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
[36]244  </t>
[153]245  <t>
[547]246    The changes in this draft are summarized in <xref target="changes.since.06"/>.
[153]247  </t>
[36]248</note>
[8]249</front>
250<middle>
251<section title="Introduction" anchor="introduction">
252<t>
[162]253   This document defines HTTP/1.1 request and response semantics.  Each HTTP
254   message, as defined in &messaging;, is in the form of either a request or
255   a response.  An HTTP server listens on a connection for HTTP requests and
256   responds to each request, in the order received on that connection, with
257   one or more HTTP response messages.  This document defines the commonly
258   agreed upon semantics of the HTTP uniform interface, the intentions defined
259   by each request method, and the various response messages that might be
260   expected as a result of applying that method for the requested resource.
[8]261</t>
262<t>
[162]263   This document is currently disorganized in order to minimize the changes
264   between drafts and enable reviewers to see the smaller errata changes.
265   The next draft will reorganize the sections to better reflect the content.
266   In particular, the sections will be ordered according to the typical
267   processing of an HTTP request message (after message parsing): resource
268   mapping, general header fields, methods, request modifiers, response
269   status, and resource metadata.  The current mess reflects how widely
270   dispersed these topics and associated requirements had become in
271   <xref target="RFC2616"/>.
[8]272</t>
[96]273
274<section title="Requirements" anchor="intro.requirements">
275<t>
276   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
277   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
278   document are to be interpreted as described in <xref target="RFC2119"/>.
279</t>
280<t>
281   An implementation is not compliant if it fails to satisfy one or more
282   of the &MUST; or &REQUIRED; level requirements for the protocols it
283   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
284   level and all the &SHOULD; level requirements for its protocols is said
285   to be "unconditionally compliant"; one that satisfies all the &MUST;
286   level requirements but not all the &SHOULD; level requirements for its
287   protocols is said to be "conditionally compliant."
288</t>
[8]289</section>
290
[424]291<section title="Syntax Notation" anchor="notation">
[425]292  <x:anchor-alias value="CR"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="LF"/>
295  <x:anchor-alias value="VCHAR"/>
296  <x:anchor-alias value="WSP"/>
[424]297<t>
[543]298  This specification uses the ABNF syntax defined in &notation; (which
299  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
300  <xref target="collected.abnf"/> shows the collected ABNF, with the list
301  rule expanded.
302</t>
303<t>
[425]304  The following core rules are included by
305  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
306  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
307  DIGIT (decimal 0-9), DQUOTE (double quote),
308  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
309  OCTET (any 8-bit sequence of data), SP (space),
310  VCHAR (any visible USASCII character),
311  and WSP (whitespace).
[424]312</t>
313
314<section title="Core Rules" anchor="core.rules">
[229]315  <x:anchor-alias value="comment"/>
[398]316  <x:anchor-alias value="obs-text"/>
[229]317  <x:anchor-alias value="quoted-string"/>
318  <x:anchor-alias value="token"/>
[356]319  <x:anchor-alias value="OWS"/>
320  <x:anchor-alias value="RWS"/>
[205]321<t>
[424]322  The core rules below are defined in &basic-rules;:
[205]323</t>
324<figure><artwork type="abnf2616">
[229]325  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
326  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
327  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
[356]328  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
329  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
[398]330  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
[205]331</artwork></figure>
[424]332</section>
333
334<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]335  <x:anchor-alias value="absolute-URI"/>
[229]336  <x:anchor-alias value="Accept"/>
337  <x:anchor-alias value="Accept-Charset"/>
338  <x:anchor-alias value="Accept-Encoding"/>
339  <x:anchor-alias value="Accept-Language"/>
340  <x:anchor-alias value="Accept-Ranges"/>
341  <x:anchor-alias value="Age"/>
342  <x:anchor-alias value="Authorization"/>
343  <x:anchor-alias value="ETag"/>
344  <x:anchor-alias value="fragment"/>
345  <x:anchor-alias value="Host"/>
346  <x:anchor-alias value="HTTP-date"/>
347  <x:anchor-alias value="If-Match"/>
348  <x:anchor-alias value="If-Modified-Since"/>
349  <x:anchor-alias value="If-None-Match"/>
350  <x:anchor-alias value="If-Range"/>
351  <x:anchor-alias value="If-Unmodified-Since"/>
[391]352  <x:anchor-alias value="partial-URI"/>
[229]353  <x:anchor-alias value="product"/>
354  <x:anchor-alias value="Proxy-Authenticate"/>
355  <x:anchor-alias value="Proxy-Authorization"/>
356  <x:anchor-alias value="Range"/>
357  <x:anchor-alias value="TE"/>
358  <x:anchor-alias value="Vary"/>
359  <x:anchor-alias value="WWW-Authenticate"/>
[424]360<t>
[206]361  The ABNF rules below are defined in other parts:
362</t>
[207]363<figure><!--Part1--><artwork type="abnf2616">
[374]364  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
365  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
366  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
[229]367  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
[391]368  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
[229]369  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
370  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
[207]371</artwork></figure>
372<figure><!--Part3--><artwork type="abnf2616">
[229]373  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
374  <x:ref>Accept-Charset</x:ref> =
[206]375             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
[229]376  <x:ref>Accept-Encoding</x:ref> =
[206]377             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
[229]378  <x:ref>Accept-Language</x:ref> =
[206]379             &lt;Accept-Language, defined in &header-accept-language;&gt;
[207]380</artwork></figure>
381<figure><!--Part4--><artwork type="abnf2616">
[229]382  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
383  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
384  <x:ref>If-Modified-Since</x:ref> =
[206]385             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
[229]386  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
387  <x:ref>If-Unmodified-Since</x:ref> =
[206]388             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
[207]389</artwork></figure>
390<figure><!--Part5--><artwork type="abnf2616">
[229]391  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
392  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
393  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
[207]394</artwork></figure>
395<figure><!--Part6--><artwork type="abnf2616">
[229]396  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
397  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
[207]398</artwork><!--Part7--></figure>
399<figure><artwork type="abnf2616">
[229]400  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
401  <x:ref>Proxy-Authenticate</x:ref> =
[206]402             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
[229]403  <x:ref>Proxy-Authorization</x:ref> =
[206]404             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
[229]405  <x:ref>WWW-Authenticate</x:ref> =
[206]406             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
407</artwork></figure>
[205]408</section>
[424]409</section>
410</section>
[205]411
[8]412<section title="Method" anchor="method">
[229]413  <x:anchor-alias value="Method"/>
414  <x:anchor-alias value="extension-method"/>
[8]415<t>
416   The Method  token indicates the method to be performed on the
[391]417   resource identified by the request-target. The method is case-sensitive.
[8]418</t>
419<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
[272]420  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
[334]421                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
422                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
423                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
424                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
425                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
426                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
427                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
428                 / <x:ref>extension-method</x:ref>
[229]429  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
[8]430</artwork></figure>
431<t>
432   The list of methods allowed by a resource can be specified in an
433   Allow header field (<xref target="header.allow"/>). The return code of the response
434   always notifies the client whether a method is currently allowed on a
435   resource, since the set of allowed methods can change dynamically. An
436   origin server &SHOULD; return the status code 405 (Method Not Allowed)
437   if the method is known by the origin server but not allowed for the
438   requested resource, and 501 (Not Implemented) if the method is
439   unrecognized or not implemented by the origin server. The methods GET
440   and HEAD &MUST; be supported by all general-purpose servers. All other
441   methods are &OPTIONAL;; however, if the above methods are implemented,
442   they &MUST; be implemented with the same semantics as those specified
443   in <xref target="method.definitions"/>.
444</t>
[270]445
446<section title="Method Registry" anchor="method.registry">
447<t>
448  The HTTP Method Registry defines the name space for the Method token in the
449  Request line of an HTTP request.
450</t>
451<t>
[286]452  Registrations &MUST; include the following fields:
453  <list style="symbols">
454    <t>Method Name (see <xref target="method"/>)</t>
455    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
456    <t>Pointer to specification text</t>
457  </list>
458</t>
459<t>
[270]460  Values to be added to this name space are subject to IETF review
461  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
462  new method names should be traceable through statuses of either 'Obsoletes'
463  or 'Updates' to this document.
464</t>
465<t>
466  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
467</t>
[8]468</section>
[270]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>
474   The request-header fields allow the client to pass additional
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>
480<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
[229]481  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
[334]482                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
483                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
484                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
485                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
486                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
487                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
488                 / <x:ref>Host</x:ref>                     ; &header-host;
489                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
490                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
491                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
492                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
493                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
494                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
495                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
496                 / <x:ref>Range</x:ref>                    ; &header-range;
497                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
498                 / <x:ref>TE</x:ref>                       ; &header-te;
499                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
[8]500</artwork></figure>
501<t>
502   Request-header field names can be extended reliably only in
503   combination with a change in the protocol version. However, new or
504   experimental header fields &MAY; be given the semantics of request-header
505   fields if all parties in the communication recognize them to
506   be request-header fields. Unrecognized header fields are treated as
507   entity-header fields.
508</t>
509</section>
510
511<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
[229]512  <x:anchor-alias value="Reason-Phrase"/>
513  <x:anchor-alias value="Status-Code"/>
[426]514  <x:anchor-alias value="extension-code"/>
[8]515<t>
516   The Status-Code element is a 3-digit integer result code of the
[149]517   attempt to understand and satisfy the request. The status codes listed
518   below are defined in <xref target="status.codes"/>.
519   The Reason-Phrase is intended to give a short
[8]520   textual description of the Status-Code. The Status-Code is intended
521   for use by automata and the Reason-Phrase is intended for the human
522   user. The client is not required to examine or display the Reason-Phrase.
523</t>
524<t> 
525   The individual values of the numeric status codes defined for
526   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
527   presented below. The reason phrases listed here are only
528   recommendations -- they &MAY; be replaced by local equivalents without
529   affecting the protocol.
530</t>
531<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"/>
[229]532  <x:ref>Status-Code</x:ref>    =
[8]533         "100"  ; <xref target="status.100"/>: Continue
[334]534       / "101"  ; <xref target="status.101"/>: Switching Protocols
535       / "200"  ; <xref target="status.200"/>: OK
536       / "201"  ; <xref target="status.201"/>: Created
537       / "202"  ; <xref target="status.202"/>: Accepted
538       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
539       / "204"  ; <xref target="status.204"/>: No Content
540       / "205"  ; <xref target="status.205"/>: Reset Content
541       / "206"  ; <xref target="status.206"/>: Partial Content
542       / "300"  ; <xref target="status.300"/>: Multiple Choices
543       / "301"  ; <xref target="status.301"/>: Moved Permanently
544       / "302"  ; <xref target="status.302"/>: Found
545       / "303"  ; <xref target="status.303"/>: See Other
546       / "304"  ; <xref target="status.304"/>: Not Modified
547       / "305"  ; <xref target="status.305"/>: Use Proxy
548       / "307"  ; <xref target="status.307"/>: Temporary Redirect
549       / "400"  ; <xref target="status.400"/>: Bad Request
550       / "401"  ; <xref target="status.401"/>: Unauthorized
551       / "402"  ; <xref target="status.402"/>: Payment Required
552       / "403"  ; <xref target="status.403"/>: Forbidden
553       / "404"  ; <xref target="status.404"/>: Not Found
554       / "405"  ; <xref target="status.405"/>: Method Not Allowed
555       / "406"  ; <xref target="status.406"/>: Not Acceptable
556       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
557       / "408"  ; <xref target="status.408"/>: Request Time-out
558       / "409"  ; <xref target="status.409"/>: Conflict
559       / "410"  ; <xref target="status.410"/>: Gone
560       / "411"  ; <xref target="status.411"/>: Length Required
561       / "412"  ; <xref target="status.412"/>: Precondition Failed
562       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
[465]563       / "414"  ; <xref target="status.414"/>: URI Too Long
[334]564       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
565       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
566       / "417"  ; <xref target="status.417"/>: Expectation Failed
567       / "500"  ; <xref target="status.500"/>: Internal Server Error
568       / "501"  ; <xref target="status.501"/>: Not Implemented
569       / "502"  ; <xref target="status.502"/>: Bad Gateway
570       / "503"  ; <xref target="status.503"/>: Service Unavailable
571       / "504"  ; <xref target="status.504"/>: Gateway Time-out
572       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
573       / <x:ref>extension-code</x:ref>
[8]574
[229]575  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
[398]576  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
[8]577</artwork></figure>
578<t>
579   HTTP status codes are extensible. HTTP applications are not required
580   to understand the meaning of all registered status codes, though such
581   understanding is obviously desirable. However, applications &MUST;
582   understand the class of any status code, as indicated by the first
583   digit, and treat any unrecognized response as being equivalent to the
584   x00 status code of that class, with the exception that an
585   unrecognized response &MUST-NOT; be cached. For example, if an
586   unrecognized status code of 431 is received by the client, it can
587   safely assume that there was something wrong with its request and
588   treat the response as if it had received a 400 status code. In such
589   cases, user agents &SHOULD; present to the user the entity returned
590   with the response, since that entity is likely to include human-readable
591   information which will explain the unusual status.
592</t>
[262]593
594<section title="Status Code Registry" anchor="status.code.registry">
595<t>
596  The HTTP Status Code Registry defines the name space for the Status-Code
597  token in the Status line of an HTTP response.
598</t>
599<t>
600  Values to be added to this name space are subject to IETF review
601  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
602  new status codes should be traceable through statuses of either 'Obsoletes'
603  or 'Updates' to this document.
604</t>
605<t>
606  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
607</t>
[8]608</section>
609
[262]610</section>
611
[8]612<section title="Response Header Fields" anchor="response.header.fields">
[229]613  <x:anchor-alias value="response-header"/>
[8]614<t>
615   The response-header fields allow the server to pass additional
616   information about the response which cannot be placed in the Status-Line.
617   These header fields give information about the server and about
[391]618   further access to the resource identified by the request-target.
[8]619</t>
620<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
[229]621  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
[334]622                  / <x:ref>Age</x:ref>                     ; &header-age;
623                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
624                  / <x:ref>ETag</x:ref>                    ; &header-etag;
625                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
626                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
627                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
628                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
629                  / <x:ref>Vary</x:ref>                    ; &header-vary;
630                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
[8]631</artwork></figure>
632<t>
633   Response-header field names can be extended reliably only in
634   combination with a change in the protocol version. However, new or
635   experimental header fields &MAY; be given the semantics of response-header
636   fields if all parties in the communication recognize them to
637   be response-header fields. Unrecognized header fields are treated as
638   entity-header fields.
639</t>
640</section>
641
642<section title="Entity" anchor="entity">
643<t>
644   Request and Response messages &MAY; transfer an entity if not otherwise
645   restricted by the request method or response status code. An entity
646   consists of entity-header fields and an entity-body, although some
[29]647   responses will only include the entity-headers. HTTP entity-body and
648   entity-header fields are defined in &payload;.
[8]649</t>
650<t>
651   An entity-body is only present in a message when a message-body is
[29]652   present, as described in &message-body;. The entity-body is obtained
[8]653   from the message-body by decoding any Transfer-Encoding that might
654   have been applied to ensure safe and proper transfer of the message.
655</t>
656</section>
657
658
659<section title="Method Definitions" anchor="method.definitions">
660<t>
661   The set of common methods for HTTP/1.1 is defined below. Although
662   this set can be expanded, additional methods cannot be assumed to
663   share the same semantics for separately extended clients and servers.
664</t>
665
666<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
667
668<section title="Safe Methods" anchor="safe.methods">
[286]669<iref item="Safe Methods" primary="true"/>
[8]670<t>
671   Implementors should be aware that the software represents the user in
672   their interactions over the Internet, and should be careful to allow
673   the user to be aware of any actions they might take which may have an
674   unexpected significance to themselves or others.
675</t>
676<t>
677   In particular, the convention has been established that the GET and
678   HEAD methods &SHOULD-NOT;  have the significance of taking an action
[286]679   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
[8]680   This allows user agents to represent other methods, such as POST, PUT
681   and DELETE, in a special way, so that the user is made aware of the
682   fact that a possibly unsafe action is being requested.
683</t>
684<t>
685   Naturally, it is not possible to ensure that the server does not
686   generate side-effects as a result of performing a GET request; in
687   fact, some dynamic resources consider that a feature. The important
688   distinction here is that the user did not request the side-effects,
689   so therefore cannot be held accountable for them.
690</t>
691</section>
692
693<section title="Idempotent Methods" anchor="idempotent.methods">
[286]694<iref item="Idempotent Methods" primary="true"/>
[8]695<t>
696   Methods can also have the property of "idempotence" in that (aside
697   from error or expiration issues) the side-effects of N &gt; 0 identical
698   requests is the same as for a single request. The methods GET, HEAD,
699   PUT and DELETE share this property. Also, the methods OPTIONS and
700   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
701</t>
702<t>
703   However, it is possible that a sequence of several requests is non-idempotent,
704   even if all of the methods executed in that sequence are
705   idempotent. (A sequence is idempotent if a single execution of the
706   entire sequence always yields a result that is not changed by a
707   reexecution of all, or part, of that sequence.) For example, a
708   sequence is non-idempotent if its result depends on a value that is
709   later modified in the same sequence.
710</t>
711<t>
712   A sequence that never has side effects is idempotent, by definition
713   (provided that no concurrent operations are being executed on the
714   same set of resources).
715</t>
716</section>
717</section>
718
719<section title="OPTIONS" anchor="OPTIONS">
[286]720  <rdf:Description>
721    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
722  </rdf:Description>
[8]723  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
724  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
725<t>
726   The OPTIONS method represents a request for information about the
727   communication options available on the request/response chain
[391]728   identified by the request-target. This method allows the client to
[8]729   determine the options and/or requirements associated with a resource,
730   or the capabilities of a server, without implying a resource action
731   or initiating a resource retrieval.
732</t>
733<t>
734   Responses to this method are not cacheable.
735</t>
736<t>
737   If the OPTIONS request includes an entity-body (as indicated by the
738   presence of Content-Length or Transfer-Encoding), then the media type
739   &MUST; be indicated by a Content-Type field. Although this
740   specification does not define any use for such a body, future
741   extensions to HTTP might use the OPTIONS body to make more detailed
[280]742   queries on the server.
[8]743</t>
744<t>
[391]745   If the request-target is an asterisk ("*"), the OPTIONS request is
[8]746   intended to apply to the server in general rather than to a specific
747   resource. Since a server's communication options typically depend on
748   the resource, the "*" request is only useful as a "ping" or "no-op"
749   type of method; it does nothing beyond allowing the client to test
750   the capabilities of the server. For example, this can be used to test
751   a proxy for HTTP/1.1 compliance (or lack thereof).
752</t>
753<t>
[391]754   If the request-target is not an asterisk, the OPTIONS request applies
[8]755   only to the options that are available when communicating with that
756   resource.
757</t>
758<t>
759   A 200 response &SHOULD; include any header fields that indicate
760   optional features implemented by the server and applicable to that
761   resource (e.g., Allow), possibly including extensions not defined by
762   this specification. The response body, if any, &SHOULD; also include
763   information about the communication options. The format for such a
764   body is not defined by this specification, but might be defined by
765   future extensions to HTTP. Content negotiation &MAY; be used to select
766   the appropriate response format. If no response body is included, the
767   response &MUST; include a Content-Length field with a field-value of
768   "0".
769</t>
770<t>
771   The Max-Forwards request-header field &MAY; be used to target a
772   specific proxy in the request chain. When a proxy receives an OPTIONS
[374]773   request on an absolute-URI for which request forwarding is permitted,
[8]774   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
775   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
776   instead, the proxy &SHOULD; respond with its own communication options.
777   If the Max-Forwards field-value is an integer greater than zero, the
778   proxy &MUST; decrement the field-value when it forwards the request. If
779   no Max-Forwards field is present in the request, then the forwarded
780   request &MUST-NOT; include a Max-Forwards field.
781</t>
782</section>
783
784<section title="GET" anchor="GET">
[286]785  <rdf:Description>
786    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
787  </rdf:Description>
[8]788  <iref primary="true" item="GET method" x:for-anchor=""/>
789  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
790<t>
791   The GET method means retrieve whatever information (in the form of an
[391]792   entity) is identified by the request-target. If the request-target refers
[8]793   to a data-producing process, it is the produced data which shall be
794   returned as the entity in the response and not the source text of the
795   process, unless that text happens to be the output of the process.
796</t>
797<t>
798   The semantics of the GET method change to a "conditional GET" if the
799   request message includes an If-Modified-Since, If-Unmodified-Since,
800   If-Match, If-None-Match, or If-Range header field. A conditional GET
801   method requests that the entity be transferred only under the
802   circumstances described by the conditional header field(s). The
803   conditional GET method is intended to reduce unnecessary network
804   usage by allowing cached entities to be refreshed without requiring
805   multiple requests or transferring data already held by the client.
806</t>
807<t>
808   The semantics of the GET method change to a "partial GET" if the
809   request message includes a Range header field. A partial GET requests
[29]810   that only part of the entity be transferred, as described in &header-range;.
[8]811   The partial GET method is intended to reduce unnecessary
812   network usage by allowing partially-retrieved entities to be
813   completed without transferring data already held by the client.
814</t>
815<t>
816   The response to a GET request is cacheable if and only if it meets
[29]817   the requirements for HTTP caching described in &caching;.
[8]818</t>
819<t>
820   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
821</t>
822</section>
823
824<section title="HEAD" anchor="HEAD">
[286]825  <rdf:Description>
826    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
827  </rdf:Description>
[8]828  <iref primary="true" item="HEAD method" x:for-anchor=""/>
829  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
830<t>
831   The HEAD method is identical to GET except that the server &MUST-NOT;
832   return a message-body in the response. The metainformation contained
833   in the HTTP headers in response to a HEAD request &SHOULD; be identical
834   to the information sent in response to a GET request. This method can
835   be used for obtaining metainformation about the entity implied by the
836   request without transferring the entity-body itself. This method is
837   often used for testing hypertext links for validity, accessibility,
838   and recent modification.
839</t>
840<t>
841   The response to a HEAD request &MAY; be cacheable in the sense that the
842   information contained in the response &MAY; be used to update a
843   previously cached entity from that resource. If the new field values
844   indicate that the cached entity differs from the current entity (as
845   would be indicated by a change in Content-Length, Content-MD5, ETag
846   or Last-Modified), then the cache &MUST; treat the cache entry as
847   stale.
848</t>
849</section>
850
851<section title="POST" anchor="POST">
852  <iref primary="true" item="POST method" x:for-anchor=""/>
853  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
854<t>
855   The POST method is used to request that the origin server accept the
[78]856   entity enclosed in the request as data to be processed by the resource
[391]857   identified by the request-target in the Request-Line. POST is designed
[8]858   to allow a uniform method to cover the following functions:
859  <list style="symbols">
860    <t>
861      Annotation of existing resources;
862    </t>
863    <t>
864        Posting a message to a bulletin board, newsgroup, mailing list,
865        or similar group of articles;
866    </t>
867    <t>
868        Providing a block of data, such as the result of submitting a
869        form, to a data-handling process;
870    </t>
871    <t>
872        Extending a database through an append operation.
873    </t>
874  </list>
875</t>
876<t>
877   The actual function performed by the POST method is determined by the
[391]878   server and is usually dependent on the request-target.
[8]879</t>
880<t>
881   The action performed by the POST method might not result in a
882   resource that can be identified by a URI. In this case, either 200
883   (OK) or 204 (No Content) is the appropriate response status,
884   depending on whether or not the response includes an entity that
885   describes the result.
886</t>
887<t>
888   If a resource has been created on the origin server, the response
889   &SHOULD; be 201 (Created) and contain an entity which describes the
890   status of the request and refers to the new resource, and a Location
891   header (see <xref target="header.location"/>).
892</t>
893<t>
894   Responses to this method are not cacheable, unless the response
895   includes appropriate Cache-Control or Expires header fields. However,
896   the 303 (See Other) response can be used to direct the user agent to
897   retrieve a cacheable resource.
898</t>
899</section>
900
901<section title="PUT" anchor="PUT">
902  <iref primary="true" item="PUT method" x:for-anchor=""/>
903  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
904<t>
[241]905   The PUT method requests that the enclosed entity be stored at the
[391]906   supplied request-target. If the request-target refers to an already
[8]907   existing resource, the enclosed entity &SHOULD; be considered as a
908   modified version of the one residing on the origin server. If the
[391]909   request-target does not point to an existing resource, and that URI is
[8]910   capable of being defined as a new resource by the requesting user
911   agent, the origin server can create the resource with that URI. If a
[391]912   new resource is created at the request-target, the origin server &MUST;
[180]913         inform the user agent
[8]914   via the 201 (Created) response. If an existing resource is modified,
915   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
916   to indicate successful completion of the request. If the resource
[391]917   could not be created or modified with the request-target, an appropriate
[8]918   error response &SHOULD; be given that reflects the nature of the
919   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
[333]920   headers (headers starting with the prefix 'Content-') that it does
921   not understand or implement
[8]922   and &MUST; return a 501 (Not Implemented) response in such cases.
923</t>
924<t>
[391]925   If the request passes through a cache and the request-target identifies
[8]926   one or more currently cached entities, those entries &SHOULD; be
927   treated as stale. Responses to this method are not cacheable.
928</t>
929<t>
930   The fundamental difference between the POST and PUT requests is
[391]931   reflected in the different meaning of the request-target. The URI in a
[8]932   POST request identifies the resource that will handle the enclosed
933   entity. That resource might be a data-accepting process, a gateway to
934   some other protocol, or a separate entity that accepts annotations.
935   In contrast, the URI in a PUT request identifies the entity enclosed
936   with the request -- the user agent knows what URI is intended and the
937   server &MUST-NOT; attempt to apply the request to some other resource.
938   If the server desires that the request be applied to a different URI,
939   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
940   then make its own decision regarding whether or not to redirect the
941   request.
942</t>
943<t>
944   A single resource &MAY; be identified by many different URIs. For
945   example, an article might have a URI for identifying "the current
946   version" which is separate from the URI identifying each particular
947   version. In this case, a PUT request on a general URI might result in
948   several other URIs being defined by the origin server.
949</t>
950<t>
951   HTTP/1.1 does not define how a PUT method affects the state of an
952   origin server.
953</t>
954<t>
955   Unless otherwise specified for a particular entity-header, the
956   entity-headers in the PUT request &SHOULD; be applied to the resource
957   created or modified by the PUT.
958</t>
959</section>
960
961<section title="DELETE" anchor="DELETE">
962  <iref primary="true" item="DELETE method" x:for-anchor=""/>
963  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
964<t>
965   The DELETE method requests that the origin server delete the resource
[391]966   identified by the request-target. This method &MAY; be overridden by human
[8]967   intervention (or other means) on the origin server. The client cannot
968   be guaranteed that the operation has been carried out, even if the
969   status code returned from the origin server indicates that the action
970   has been completed successfully. However, the server &SHOULD-NOT; 
971   indicate success unless, at the time the response is given, it
972   intends to delete the resource or move it to an inaccessible
973   location.
974</t>
975<t>
976   A successful response &SHOULD; be 200 (OK) if the response includes an
977   entity describing the status, 202 (Accepted) if the action has not
978   yet been enacted, or 204 (No Content) if the action has been enacted
979   but the response does not include an entity.
980</t>
981<t>
[391]982   If the request passes through a cache and the request-target identifies
[8]983   one or more currently cached entities, those entries &SHOULD; be
984   treated as stale. Responses to this method are not cacheable.
985</t>
986</section>
987
988<section title="TRACE" anchor="TRACE">
[286]989  <rdf:Description>
990    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
991  </rdf:Description>
[8]992  <iref primary="true" item="TRACE method" x:for-anchor=""/>
993  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
994<t>
995   The TRACE method is used to invoke a remote, application-layer loop-back
996   of the request message. The final recipient of the request
997   &SHOULD; reflect the message received back to the client as the
998   entity-body of a 200 (OK) response. The final recipient is either the
999   origin server or the first proxy or gateway to receive a Max-Forwards
1000   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1001   &MUST-NOT; include an entity.
1002</t>
1003<t>
1004   TRACE allows the client to see what is being received at the other
1005   end of the request chain and use that data for testing or diagnostic
[29]1006   information. The value of the Via header field (&header-via;) is of
[8]1007   particular interest, since it acts as a trace of the request chain.
1008   Use of the Max-Forwards header field allows the client to limit the
1009   length of the request chain, which is useful for testing a chain of
1010   proxies forwarding messages in an infinite loop.
1011</t>
1012<t>
1013   If the request is valid, the response &SHOULD; contain the entire
1014   request message in the entity-body, with a Content-Type of
[263]1015   "message/http" (see &media-type-message-http;). Responses to this method
1016   &MUST-NOT; be cached.
[8]1017</t>
1018</section>
1019
1020<section title="CONNECT" anchor="CONNECT">
1021  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1022  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1023<t>
1024   This specification reserves the method name CONNECT for use with a
1025   proxy that can dynamically switch to being a tunnel (e.g. SSL
[274]1026   tunneling <xref target="RFC2817"/>).
[8]1027</t>
1028</section>
1029</section>
1030
1031
1032<section title="Status Code Definitions" anchor="status.codes">
1033<t>
[579]1034   Each Status-Code is described below, including any metainformation required
1035   in the response.
[8]1036</t>
1037
1038<section title="Informational 1xx" anchor="status.1xx">
1039<t>
1040   This class of status code indicates a provisional response,
1041   consisting only of the Status-Line and optional headers, and is
1042   terminated by an empty line. There are no required headers for this
1043   class of status code. Since HTTP/1.0 did not define any 1xx status
1044   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1045   except under experimental conditions.
1046</t>
1047<t>
1048   A client &MUST; be prepared to accept one or more 1xx status responses
1049   prior to a regular response, even if the client does not expect a 100
1050   (Continue) status message. Unexpected 1xx status responses &MAY; be
1051   ignored by a user agent.
1052</t>
1053<t>
1054   Proxies &MUST; forward 1xx responses, unless the connection between the
1055   proxy and its client has been closed, or unless the proxy itself
1056   requested the generation of the 1xx response. (For example, if a
1057   proxy adds a "Expect: 100-continue" field when it forwards a request,
1058   then it need not forward the corresponding 100 (Continue)
1059   response(s).)
1060</t>
1061
1062<section title="100 Continue" anchor="status.100">
1063  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1064  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1065<t>
1066   The client &SHOULD; continue with its request. This interim response is
1067   used to inform the client that the initial part of the request has
1068   been received and has not yet been rejected by the server. The client
1069   &SHOULD; continue by sending the remainder of the request or, if the
1070   request has already been completed, ignore this response. The server
1071   &MUST; send a final response after the request has been completed. See
[29]1072   &use100; for detailed discussion of the use and handling of this
[8]1073   status code.
1074</t>
1075</section>
1076
1077<section title="101 Switching Protocols" anchor="status.101">
1078  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1079  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1080<t>
1081   The server understands and is willing to comply with the client's
[29]1082   request, via the Upgrade message header field (&header-upgrade;), for a
[8]1083   change in the application protocol being used on this connection. The
1084   server will switch protocols to those defined by the response's
1085   Upgrade header field immediately after the empty line which
1086   terminates the 101 response.
1087</t>
1088<t>
1089   The protocol &SHOULD; be switched only when it is advantageous to do
1090   so. For example, switching to a newer version of HTTP is advantageous
1091   over older versions, and switching to a real-time, synchronous
1092   protocol might be advantageous when delivering resources that use
1093   such features.
1094</t>
1095</section>
1096</section>
1097
1098<section title="Successful 2xx" anchor="status.2xx">
1099<t>
1100   This class of status code indicates that the client's request was
1101   successfully received, understood, and accepted.
1102</t>
1103
1104<section title="200 OK" anchor="status.200">
1105  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1106  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1107<t>
1108   The request has succeeded. The information returned with the response
1109   is dependent on the method used in the request, for example:
1110  <list style="hanging">
1111    <t hangText="GET">
1112          an entity corresponding to the requested resource is sent in
1113          the response;
1114    </t>
1115    <t hangText="HEAD">
1116          the entity-header fields corresponding to the requested
1117          resource are sent in the response without any message-body;
1118    </t>
1119    <t hangText="POST">
1120      an entity describing or containing the result of the action;
1121    </t>
1122    <t hangText="TRACE">
1123      an entity containing the request message as received by the
1124      end server.
1125    </t>
1126  </list>
1127</t>
1128</section>
1129
1130<section title="201 Created" anchor="status.201">
1131  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1132  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1133<t>
1134   The request has been fulfilled and resulted in a new resource being
1135   created. The newly created resource can be referenced by the URI(s)
1136   returned in the entity of the response, with the most specific URI
1137   for the resource given by a Location header field. The response
1138   &SHOULD; include an entity containing a list of resource
1139   characteristics and location(s) from which the user or user agent can
1140   choose the one most appropriate. The entity format is specified by
1141   the media type given in the Content-Type header field. The origin
1142   server &MUST; create the resource before returning the 201 status code.
1143   If the action cannot be carried out immediately, the server &SHOULD;
1144   respond with 202 (Accepted) response instead.
1145</t>
1146<t>
1147   A 201 response &MAY; contain an ETag response header field indicating
1148   the current value of the entity tag for the requested variant just
[29]1149   created, see &header-etag;.
[8]1150</t>
1151</section>
1152
1153<section title="202 Accepted" anchor="status.202">
1154  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1155  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1156<t>
1157   The request has been accepted for processing, but the processing has
1158   not been completed.  The request might or might not eventually be
1159   acted upon, as it might be disallowed when processing actually takes
1160   place. There is no facility for re-sending a status code from an
1161   asynchronous operation such as this.
1162</t>
1163<t>
1164   The 202 response is intentionally non-committal. Its purpose is to
1165   allow a server to accept a request for some other process (perhaps a
1166   batch-oriented process that is only run once per day) without
1167   requiring that the user agent's connection to the server persist
1168   until the process is completed. The entity returned with this
1169   response &SHOULD; include an indication of the request's current status
1170   and either a pointer to a status monitor or some estimate of when the
1171   user can expect the request to be fulfilled.
1172</t>
1173</section>
1174
1175<section title="203 Non-Authoritative Information" anchor="status.203">
1176  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1177  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1178<t>
1179   The returned metainformation in the entity-header is not the
1180   definitive set as available from the origin server, but is gathered
1181   from a local or a third-party copy. The set presented &MAY; be a subset
1182   or superset of the original version. For example, including local
1183   annotation information about the resource might result in a superset
1184   of the metainformation known by the origin server. Use of this
1185   response code is not required and is only appropriate when the
1186   response would otherwise be 200 (OK).
1187</t>
1188</section>
1189
1190<section title="204 No Content" anchor="status.204">
1191  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1192  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1193<t>
1194   The server has fulfilled the request but does not need to return an
1195   entity-body, and might want to return updated metainformation. The
1196   response &MAY; include new or updated metainformation in the form of
1197   entity-headers, which if present &SHOULD; be associated with the
1198   requested variant.
1199</t>
1200<t>
1201   If the client is a user agent, it &SHOULD-NOT;  change its document view
1202   from that which caused the request to be sent. This response is
1203   primarily intended to allow input for actions to take place without
1204   causing a change to the user agent's active document view, although
1205   any new or updated metainformation &SHOULD; be applied to the document
1206   currently in the user agent's active view.
1207</t>
1208<t>
1209   The 204 response &MUST-NOT; include a message-body, and thus is always
1210   terminated by the first empty line after the header fields.
1211</t>
1212</section>
1213
1214<section title="205 Reset Content" anchor="status.205">
1215  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1216  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1217<t>
1218   The server has fulfilled the request and the user agent &SHOULD; reset
1219   the document view which caused the request to be sent. This response
1220   is primarily intended to allow input for actions to take place via
1221   user input, followed by a clearing of the form in which the input is
1222   given so that the user can easily initiate another input action. The
1223   response &MUST-NOT; include an entity.
1224</t>
1225</section>
1226
1227<section title="206 Partial Content" anchor="status.206">
1228  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1229  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1230<t>
[29]1231   The server has fulfilled the partial GET request for the resource
1232   and the enclosed entity is a partial representation as defined in &range;.
[8]1233</t>
1234</section>
1235</section>
1236
1237<section title="Redirection 3xx" anchor="status.3xx">
1238<t>
1239   This class of status code indicates that further action needs to be
1240   taken by the user agent in order to fulfill the request.  The action
1241   required &MAY; be carried out by the user agent without interaction
1242   with the user if and only if the method used in the second request is
1243   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1244   such loops generate network traffic for each redirection.
1245</t>
[563]1246<x:note>
1247  <t>
1248    <x:h>Note:</x:h> previous versions of this specification recommended a
1249    maximum of five redirections. Content developers should be aware
1250    that there might be clients that implement such a fixed
1251    limitation.
1252  </t>
1253</x:note>
[8]1254
1255<section title="300 Multiple Choices" anchor="status.300">
1256  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1257  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1258<t>
1259   The requested resource corresponds to any one of a set of
1260   representations, each with its own specific location, and agent-driven
[29]1261   negotiation information (&content-negotiation;) is being provided so that
[8]1262   the user (or user agent) can select a preferred representation and
1263   redirect its request to that location.
1264</t>
1265<t>
1266   Unless it was a HEAD request, the response &SHOULD; include an entity
1267   containing a list of resource characteristics and location(s) from
1268   which the user or user agent can choose the one most appropriate. The
1269   entity format is specified by the media type given in the Content-Type
1270   header field. Depending upon the format and the capabilities of
1271   the user agent, selection of the most appropriate choice &MAY; be
1272   performed automatically. However, this specification does not define
1273   any standard for such automatic selection.
1274</t>
1275<t>
1276   If the server has a preferred choice of representation, it &SHOULD;
1277   include the specific URI for that representation in the Location
1278   field; user agents &MAY; use the Location field value for automatic
1279   redirection. This response is cacheable unless indicated otherwise.
1280</t>
1281</section>
1282
1283<section title="301 Moved Permanently" anchor="status.301">
1284  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1285  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1286<t>
1287   The requested resource has been assigned a new permanent URI and any
1288   future references to this resource &SHOULD; use one of the returned
1289   URIs.  Clients with link editing capabilities ought to automatically
[391]1290   re-link references to the request-target to one or more of the new
[8]1291   references returned by the server, where possible. This response is
1292   cacheable unless indicated otherwise.
1293</t>
1294<t>
1295   The new permanent URI &SHOULD; be given by the Location field in the
1296   response. Unless the request method was HEAD, the entity of the
1297   response &SHOULD; contain a short hypertext note with a hyperlink to
1298   the new URI(s).
1299</t>
1300<t>
[88]1301   If the 301 status code is received in response to a request method
1302   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1303   then the request &MAY; be automatically redirected by the user agent without
[88]1304   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1305   request unless it can be confirmed by the user, since this might
1306   change the conditions under which the request was issued.
1307</t>
[563]1308<x:note>
1309  <t>
1310    <x:h>Note:</x:h> When automatically redirecting a POST request after
1311    receiving a 301 status code, some existing HTTP/1.0 user agents
1312    will erroneously change it into a GET request.
1313  </t>
1314</x:note>
[8]1315</section>
1316
1317<section title="302 Found" anchor="status.302">
1318  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1319  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1320<t>
1321   The requested resource resides temporarily under a different URI.
1322   Since the redirection might be altered on occasion, the client &SHOULD;
[391]1323   continue to use the request-target for future requests.  This response
[8]1324   is only cacheable if indicated by a Cache-Control or Expires header
1325   field.
1326</t>
1327<t>
1328   The temporary URI &SHOULD; be given by the Location field in the
1329   response. Unless the request method was HEAD, the entity of the
1330   response &SHOULD; contain a short hypertext note with a hyperlink to
1331   the new URI(s).
1332</t>
1333<t>
[88]1334   If the 302 status code is received in response to a request method
1335   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1336   then the request &MAY; be automatically redirected by the user agent without
[88]1337   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1338   request unless it can be confirmed by the user, since this might
1339   change the conditions under which the request was issued.
1340</t>
[563]1341<x:note>
1342  <t>
1343    <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1344    to change the method on the redirected request.  However, most
1345    existing user agent implementations treat 302 as if it were a 303
1346    response, performing a GET on the Location field-value regardless
1347    of the original request method. The status codes 303 and 307 have
1348    been added for servers that wish to make unambiguously clear which
1349    kind of reaction is expected of the client.
1350  </t>
1351</x:note>
[8]1352</section>
1353
1354<section title="303 See Other" anchor="status.303">
1355  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1356  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1357<t>
[242]1358   The server directs the user agent to a different resource, indicated
1359   by a URI in the Location header field, that provides an indirect
1360   response to the original request.  The user agent &MAY; perform a GET
1361   request on the URI in the Location field in order to obtain a
1362   representation corresponding to the response, be redirected again,
1363   or end with an error status.  The Location URI is not a substitute
1364   reference for the originally requested resource.
[8]1365</t>
1366<t>
[242]1367   The 303 status is generally applicable to any HTTP method.  It is
1368   primarily used to allow the output of a POST action to redirect
1369   the user agent to a selected resource, since doing so provides the
1370   information corresponding to the POST response in a form that
1371   can be separately identified, bookmarked, and cached independent
1372   of the original request.
[8]1373</t>
[242]1374<t>
1375   A 303 response to a GET request indicates that the requested
1376   resource does not have a representation of its own that can be
1377   transferred by the server over HTTP.  The Location URI indicates a
1378   resource that is descriptive of the requested resource such that
1379   the follow-on representation may be useful without implying that
[243]1380   it adequately represents the previously requested resource.
[242]1381   Note that answers to the questions of what can be represented, what
1382   representations are adequate, and what might be a useful description
1383   are outside the scope of HTTP and thus entirely determined by the
1384   resource owner(s).
1385</t>
1386<t>
1387   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1388   cacheable by Cache-Control or Expires header fields.  Except for
1389   responses to a HEAD request, the entity of a 303 response &SHOULD;
1390   contain a short hypertext note with a hyperlink to the Location URI.
1391</t>
[8]1392</section>
1393
1394<section title="304 Not Modified" anchor="status.304">
1395  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1396  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1397<t>
[45]1398   The response to the request has not been modified since the conditions
1399   indicated by the client's conditional GET request, as defined in &conditional;.
[8]1400</t>
1401</section>
1402
1403<section title="305 Use Proxy" anchor="status.305">
1404  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1405  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1406<t>
[235]1407   The 305 status was defined in a previous version of this specification
1408   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
[8]1409</t>
1410</section>
1411
1412<section title="306 (Unused)" anchor="status.306">
1413  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1414  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1415<t>
1416   The 306 status code was used in a previous version of the
1417   specification, is no longer used, and the code is reserved.
1418</t>
1419</section>
1420
1421<section title="307 Temporary Redirect" anchor="status.307">
1422  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1423  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1424<t>
1425   The requested resource resides temporarily under a different URI.
1426   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
[391]1427   continue to use the request-target for future requests.  This response
[8]1428   is only cacheable if indicated by a Cache-Control or Expires header
1429   field.
1430</t>
1431<t>
1432   The temporary URI &SHOULD; be given by the Location field in the
1433   response. Unless the request method was HEAD, the entity of the
1434   response &SHOULD; contain a short hypertext note with a hyperlink to
1435   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1436   understand the 307 status. Therefore, the note &SHOULD; contain the
1437   information necessary for a user to repeat the original request on
1438   the new URI.
1439</t>
1440<t>
[88]1441   If the 307 status code is received in response to a request method
1442   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1443   then the request &MAY; be automatically redirected by the user agent without
[88]1444   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1445   request unless it can be confirmed by the user, since this might
1446   change the conditions under which the request was issued.
1447</t>
1448</section>
1449</section>
1450
1451<section title="Client Error 4xx" anchor="status.4xx">
1452<t>
1453   The 4xx class of status code is intended for cases in which the
1454   client seems to have erred. Except when responding to a HEAD request,
1455   the server &SHOULD; include an entity containing an explanation of the
1456   error situation, and whether it is a temporary or permanent
1457   condition. These status codes are applicable to any request method.
1458   User agents &SHOULD; display any included entity to the user.
1459</t>
1460<t>
1461   If the client is sending data, a server implementation using TCP
1462   &SHOULD; be careful to ensure that the client acknowledges receipt of
1463   the packet(s) containing the response, before the server closes the
1464   input connection. If the client continues sending data to the server
1465   after the close, the server's TCP stack will send a reset packet to
1466   the client, which may erase the client's unacknowledged input buffers
1467   before they can be read and interpreted by the HTTP application.
1468</t>
1469
1470<section title="400 Bad Request" anchor="status.400">
1471  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1472  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1473<t>
1474   The request could not be understood by the server due to malformed
1475   syntax. The client &SHOULD-NOT;  repeat the request without
1476   modifications.
1477</t>
1478</section>
1479
1480<section title="401 Unauthorized" anchor="status.401">
1481  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1483<t>
[41]1484   The request requires user authentication (see &auth;).
[8]1485</t>
1486</section>
1487
1488<section title="402 Payment Required" anchor="status.402">
1489  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1490  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1491<t>
1492   This code is reserved for future use.
1493</t>
1494</section>
1495
1496<section title="403 Forbidden" anchor="status.403">
1497  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1498  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1499<t>
1500   The server understood the request, but is refusing to fulfill it.
1501   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1502   If the request method was not HEAD and the server wishes to make
1503   public why the request has not been fulfilled, it &SHOULD; describe the
1504   reason for the refusal in the entity.  If the server does not wish to
1505   make this information available to the client, the status code 404
1506   (Not Found) can be used instead.
1507</t>
1508</section>
1509
1510<section title="404 Not Found" anchor="status.404">
1511  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1512  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1513<t>
[391]1514   The server has not found anything matching the request-target. No
[8]1515   indication is given of whether the condition is temporary or
1516   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1517   knows, through some internally configurable mechanism, that an old
1518   resource is permanently unavailable and has no forwarding address.
1519   This status code is commonly used when the server does not wish to
1520   reveal exactly why the request has been refused, or when no other
1521   response is applicable.
1522</t>
1523</section>
1524
1525<section title="405 Method Not Allowed" anchor="status.405">
1526  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1527  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1528<t>
1529   The method specified in the Request-Line is not allowed for the
[391]1530   resource identified by the request-target. The response &MUST; include an
[8]1531   Allow header containing a list of valid methods for the requested
1532   resource.
1533</t>
1534</section>
1535
1536<section title="406 Not Acceptable" anchor="status.406">
1537  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1538  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1539<t>
1540   The resource identified by the request is only capable of generating
1541   response entities which have content characteristics not acceptable
1542   according to the accept headers sent in the request.
1543</t>
1544<t>
1545   Unless it was a HEAD request, the response &SHOULD; include an entity
1546   containing a list of available entity characteristics and location(s)
1547   from which the user or user agent can choose the one most
1548   appropriate. The entity format is specified by the media type given
1549   in the Content-Type header field. Depending upon the format and the
1550   capabilities of the user agent, selection of the most appropriate
1551   choice &MAY; be performed automatically. However, this specification
1552   does not define any standard for such automatic selection.
1553</t>
[563]1554<x:note>
1555  <t>
1556    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1557    not acceptable according to the accept headers sent in the
1558    request. In some cases, this may even be preferable to sending a
1559    406 response. User agents are encouraged to inspect the headers of
1560    an incoming response to determine if it is acceptable.
1561  </t>
1562</x:note>
[8]1563<t>
1564   If the response could be unacceptable, a user agent &SHOULD;
1565   temporarily stop receipt of more data and query the user for a
1566   decision on further actions.
1567</t>
1568</section>
1569
1570<section title="407 Proxy Authentication Required" anchor="status.407">
1571  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1572  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1573<t>
1574   This code is similar to 401 (Unauthorized), but indicates that the
[39]1575   client must first authenticate itself with the proxy (see &auth;).
[8]1576</t>
1577</section>
1578
1579<section title="408 Request Timeout" anchor="status.408">
1580  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1581  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1582<t>
1583   The client did not produce a request within the time that the server
1584   was prepared to wait. The client &MAY; repeat the request without
1585   modifications at any later time.
1586</t>
1587</section>
1588
1589<section title="409 Conflict" anchor="status.409">
1590  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1591  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1592<t>
1593   The request could not be completed due to a conflict with the current
1594   state of the resource. This code is only allowed in situations where
1595   it is expected that the user might be able to resolve the conflict
1596   and resubmit the request. The response body &SHOULD; include enough
1597   information for the user to recognize the source of the conflict.
1598   Ideally, the response entity would include enough information for the
1599   user or user agent to fix the problem; however, that might not be
1600   possible and is not required.
1601</t>
1602<t>
1603   Conflicts are most likely to occur in response to a PUT request. For
1604   example, if versioning were being used and the entity being PUT
1605   included changes to a resource which conflict with those made by an
1606   earlier (third-party) request, the server might use the 409 response
1607   to indicate that it can't complete the request. In this case, the
1608   response entity would likely contain a list of the differences
1609   between the two versions in a format defined by the response
1610   Content-Type.
1611</t>
1612</section>
1613
1614<section title="410 Gone" anchor="status.410">
1615  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1616  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1617<t>
1618   The requested resource is no longer available at the server and no
1619   forwarding address is known. This condition is expected to be
1620   considered permanent. Clients with link editing capabilities &SHOULD;
[391]1621   delete references to the request-target after user approval. If the
[8]1622   server does not know, or has no facility to determine, whether or not
1623   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1624   used instead. This response is cacheable unless indicated otherwise.
1625</t>
1626<t>
1627   The 410 response is primarily intended to assist the task of web
1628   maintenance by notifying the recipient that the resource is
1629   intentionally unavailable and that the server owners desire that
1630   remote links to that resource be removed. Such an event is common for
1631   limited-time, promotional services and for resources belonging to
1632   individuals no longer working at the server's site. It is not
1633   necessary to mark all permanently unavailable resources as "gone" or
1634   to keep the mark for any length of time -- that is left to the
1635   discretion of the server owner.
1636</t>
1637</section>
1638
1639<section title="411 Length Required" anchor="status.411">
1640  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1641  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1642<t>
1643   The server refuses to accept the request without a defined Content-Length.
1644   The client &MAY; repeat the request if it adds a valid
1645   Content-Length header field containing the length of the message-body
1646   in the request message.
1647</t>
1648</section>
1649
1650<section title="412 Precondition Failed" anchor="status.412">
1651  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1652  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1653<t>
1654   The precondition given in one or more of the request-header fields
[45]1655   evaluated to false when it was tested on the server, as defined in
1656   &conditional;.
[8]1657</t>
1658</section>
1659
1660<section title="413 Request Entity Too Large" anchor="status.413">
1661  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1662  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1663<t>
1664   The server is refusing to process a request because the request
1665   entity is larger than the server is willing or able to process. The
1666   server &MAY; close the connection to prevent the client from continuing
1667   the request.
1668</t>
1669<t>
1670   If the condition is temporary, the server &SHOULD; include a Retry-After
1671   header field to indicate that it is temporary and after what
1672   time the client &MAY; try again.
1673</t>
1674</section>
1675
[465]1676<section title="414 URI Too Long" anchor="status.414">
1677  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1678  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
[8]1679<t>
[391]1680   The server is refusing to service the request because the request-target
[8]1681   is longer than the server is willing to interpret. This rare
1682   condition is only likely to occur when a client has improperly
1683   converted a POST request to a GET request with long query
1684   information, when the client has descended into a URI "black hole" of
1685   redirection (e.g., a redirected URI prefix that points to a suffix of
1686   itself), or when the server is under attack by a client attempting to
1687   exploit security holes present in some servers using fixed-length
[391]1688   buffers for reading or manipulating the request-target.
[8]1689</t>
1690</section>
1691
1692<section title="415 Unsupported Media Type" anchor="status.415">
1693  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1694  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1695<t>
1696   The server is refusing to service the request because the entity of
1697   the request is in a format not supported by the requested resource
1698   for the requested method.
1699</t>
1700</section>
1701
1702<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1703  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1704  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1705<t>
[29]1706   The request included a Range request-header field (&header-range;) and none of
[8]1707   the range-specifier values in this field overlap the current extent
[29]1708   of the selected resource.
[8]1709</t>
1710</section>
1711
1712<section title="417 Expectation Failed" anchor="status.417">
1713  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1715<t>
1716   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1717   could not be met by this server, or, if the server is a proxy,
1718   the server has unambiguous evidence that the request could not be met
1719   by the next-hop server.
1720</t>
1721</section>
1722</section>
1723
1724<section title="Server Error 5xx" anchor="status.5xx">
1725<t>
1726   Response status codes beginning with the digit "5" indicate cases in
1727   which the server is aware that it has erred or is incapable of
1728   performing the request. Except when responding to a HEAD request, the
1729   server &SHOULD; include an entity containing an explanation of the
1730   error situation, and whether it is a temporary or permanent
1731   condition. User agents &SHOULD; display any included entity to the
1732   user. These response codes are applicable to any request method.
1733</t>
1734
1735<section title="500 Internal Server Error" anchor="status.500">
1736  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1737  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1738<t>
1739   The server encountered an unexpected condition which prevented it
1740   from fulfilling the request.
1741</t>
1742</section>
1743
1744<section title="501 Not Implemented" anchor="status.501">
1745  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1746  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1747<t>
1748   The server does not support the functionality required to fulfill the
1749   request. This is the appropriate response when the server does not
1750   recognize the request method and is not capable of supporting it for
1751   any resource.
1752</t>
1753</section>
1754
1755<section title="502 Bad Gateway" anchor="status.502">
1756  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1757  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1758<t>
1759   The server, while acting as a gateway or proxy, received an invalid
1760   response from the upstream server it accessed in attempting to
1761   fulfill the request.
1762</t>
1763</section>
1764
1765<section title="503 Service Unavailable" anchor="status.503">
1766  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1767  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1768<t>
1769   The server is currently unable to handle the request due to a
1770   temporary overloading or maintenance of the server. The implication
1771   is that this is a temporary condition which will be alleviated after
1772   some delay. If known, the length of the delay &MAY; be indicated in a
1773   Retry-After header. If no Retry-After is given, the client &SHOULD;
1774   handle the response as it would for a 500 response.
1775</t>
[563]1776<x:note>
1777  <t>
1778    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1779    server must use it when becoming overloaded. Some servers may wish
1780    to simply refuse the connection.
1781  </t>
1782</x:note>
[8]1783</section>
1784
1785<section title="504 Gateway Timeout" anchor="status.504">
1786  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1787  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1788<t>
1789   The server, while acting as a gateway or proxy, did not receive a
1790   timely response from the upstream server specified by the URI (e.g.
1791   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1792   to access in attempting to complete the request.
1793</t>
[563]1794<x:note>
1795  <t>
1796    <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1797    return 400 or 500 when DNS lookups time out.
1798  </t>
1799</x:note>
[8]1800</section>
1801
1802<section title="505 HTTP Version Not Supported" anchor="status.505">
1803  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1804  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1805<t>
[172]1806   The server does not support, or refuses to support, the protocol
[8]1807   version that was used in the request message. The server is
1808   indicating that it is unable or unwilling to complete the request
[29]1809   using the same major version as the client, as described in &http-version;,
[8]1810   other than with this error message. The response &SHOULD; contain
1811   an entity describing why that version is not supported and what other
1812   protocols are supported by that server.
1813</t>
1814
1815</section>
1816</section>
1817</section>
1818
1819
1820<section title="Header Field Definitions" anchor="header.fields">
1821<t>
[117]1822   This section defines the syntax and semantics of HTTP/1.1 header fields
1823   related to request and response semantics.
[8]1824</t>
[117]1825<t>
1826   For entity-header fields, both sender and recipient refer to either the
1827   client or the server, depending on who sends and who receives the entity.
1828</t>
[8]1829
1830<section title="Allow" anchor="header.allow">
1831  <iref primary="true" item="Allow header" x:for-anchor=""/>
1832  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
[229]1833  <x:anchor-alias value="Allow"/>
[356]1834  <x:anchor-alias value="Allow-v"/>
[8]1835<t>
[356]1836      The response-header field "Allow" lists the set of methods advertised as
[391]1837      supported by the resource identified by the request-target. The purpose of
[240]1838      this field is strictly to inform the recipient of valid methods
[8]1839      associated with the resource. An Allow header field &MUST; be
1840      present in a 405 (Method Not Allowed) response.
1841</t>
[356]1842<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
[366]1843  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
[356]1844  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
[8]1845</artwork></figure>
1846<t>
1847      Example of use:
1848</t>
1849<figure><artwork type="example">
[356]1850  Allow: GET, HEAD, PUT
[8]1851</artwork></figure>
1852<t>
[240]1853      The actual set of allowed methods is defined
[8]1854      by the origin server at the time of each request.
1855</t>
1856<t>
1857      A proxy &MUST-NOT; modify the Allow header field even if it does not
1858      understand all the methods specified, since the user agent might
1859      have other means of communicating with the origin server.
1860</t>
1861</section>
1862
1863<section title="Expect" anchor="header.expect">
1864  <iref primary="true" item="Expect header" x:for-anchor=""/>
1865  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
[229]1866  <x:anchor-alias value="Expect"/>
[356]1867  <x:anchor-alias value="Expect-v"/>
[229]1868  <x:anchor-alias value="expectation"/>
1869  <x:anchor-alias value="expectation-extension"/>
1870  <x:anchor-alias value="expect-params"/>
[8]1871<t>
[356]1872   The request-header field "Expect" is used to indicate that particular
[8]1873   server behaviors are required by the client.
1874</t>
[356]1875<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
[366]1876  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
[356]1877  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
[135]1878 
[356]1879  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1880  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
[229]1881                           *<x:ref>expect-params</x:ref> ]
[356]1882  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
[8]1883</artwork></figure>
1884<t>
1885   A server that does not understand or is unable to comply with any of
1886   the expectation values in the Expect field of a request &MUST; respond
1887   with appropriate error status. The server &MUST; respond with a 417
1888   (Expectation Failed) status if any of the expectations cannot be met
1889   or, if there are other problems with the request, some other 4xx
1890   status.
1891</t>
1892<t>
1893   This header field is defined with extensible syntax to allow for
1894   future extensions. If a server receives a request containing an
1895   Expect field that includes an expectation-extension that it does not
1896   support, it &MUST; respond with a 417 (Expectation Failed) status.
1897</t>
1898<t>
1899   Comparison of expectation values is case-insensitive for unquoted
1900   tokens (including the 100-continue token), and is case-sensitive for
1901   quoted-string expectation-extensions.
1902</t>
1903<t>
1904   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1905   return a 417 (Expectation Failed) status if it receives a request
1906   with an expectation that it cannot meet. However, the Expect
1907   request-header itself is end-to-end; it &MUST; be forwarded if the
1908   request is forwarded.
1909</t>
1910<t>
1911   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1912   Expect header.
1913</t>
1914<t>
[137]1915   See &use100; for the use of the 100 (Continue) status.
[8]1916</t>
1917</section>
1918
1919<section title="From" anchor="header.from">
1920  <iref primary="true" item="From header" x:for-anchor=""/>
1921  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
[229]1922  <x:anchor-alias value="From"/>
[356]1923  <x:anchor-alias value="From-v"/>
[229]1924  <x:anchor-alias value="mailbox"/>
[8]1925<t>
[356]1926   The request-header field "From", if given, &SHOULD; contain an Internet
[8]1927   e-mail address for the human user who controls the requesting user
1928   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
[327]1929   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
[8]1930</t>
[356]1931<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
[366]1932  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
[356]1933  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
[206]1934 
[327]1935  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
[8]1936</artwork></figure>
1937<t>
1938   An example is:
1939</t>
1940<figure><artwork type="example">
[356]1941  From: webmaster@example.org
[8]1942</artwork></figure>
1943<t>
1944   This header field &MAY; be used for logging purposes and as a means for
1945   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1946   be used as an insecure form of access protection. The interpretation
1947   of this field is that the request is being performed on behalf of the
1948   person given, who accepts responsibility for the method performed. In
1949   particular, robot agents &SHOULD; include this header so that the
1950   person responsible for running the robot can be contacted if problems
1951   occur on the receiving end.
1952</t>
1953<t>
1954   The Internet e-mail address in this field &MAY; be separate from the
1955   Internet host which issued the request. For example, when a request
1956   is passed through a proxy the original issuer's address &SHOULD; be
1957   used.
1958</t>
1959<t>
1960   The client &SHOULD-NOT;  send the From header field without the user's
1961   approval, as it might conflict with the user's privacy interests or
1962   their site's security policy. It is strongly recommended that the
1963   user be able to disable, enable, and modify the value of this field
1964   at any time prior to a request.
1965</t>
1966</section>
1967
1968<section title="Location" anchor="header.location">
1969  <iref primary="true" item="Location header" x:for-anchor=""/>
1970  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
[229]1971  <x:anchor-alias value="Location"/>
[356]1972  <x:anchor-alias value="Location-v"/>
[8]1973<t>
[356]1974   The response-header field "Location" is used for the identification of a
[237]1975   new resource or to redirect the recipient to a location other than the
[391]1976   request-target for completion of the request.  For 201 (Created)
[8]1977   responses, the Location is that of the new resource which was created
1978   by the request. For 3xx responses, the location &SHOULD; indicate the
1979   server's preferred URI for automatic redirection to the resource. The
1980   field value consists of a single absolute URI.
1981</t>
[356]1982<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
[366]1983  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
[374]1984  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
[8]1985</artwork></figure>
1986<t>
1987   An example is:
1988</t>
1989<figure><artwork type="example">
[356]1990  Location: http://www.example.org/pub/WWW/People.html
[8]1991</artwork></figure>
[563]1992<x:note>
1993  <t>
1994    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1995    from Location in that the Content-Location identifies the original
1996    location of the entity enclosed in the response. It is therefore
1997    possible for a response to contain header fields for both Location
1998    and Content-Location.
1999  </t>
2000</x:note>
[8]2001<t>
[114]2002   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
2003   <list style="symbols">
2004      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
2005      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
2006      <t>With 305 Use Proxy.</t>
2007   </list>
2008</t>
[8]2009</section>
2010
2011<section title="Max-Forwards" anchor="header.max-forwards">
2012  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2013  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
[229]2014  <x:anchor-alias value="Max-Forwards"/>
[356]2015  <x:anchor-alias value="Max-Forwards-v"/>
[8]2016<t>
[356]2017   The request-header "Max-Forwards" field provides a mechanism with the
[8]2018   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2019   number of proxies or gateways that can forward the request to the
2020   next inbound server. This can be useful when the client is attempting
2021   to trace a request chain which appears to be failing or looping in
2022   mid-chain.
2023</t>
[356]2024<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
[366]2025  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
[356]2026  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
[8]2027</artwork></figure>
2028<t>
2029   The Max-Forwards value is a decimal integer indicating the remaining
2030   number of times this request message may be forwarded.
2031</t>
2032<t>
2033   Each proxy or gateway recipient of a TRACE or OPTIONS request
2034   containing a Max-Forwards header field &MUST; check and update its
2035   value prior to forwarding the request. If the received value is zero
2036   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2037   respond as the final recipient. If the received Max-Forwards value is
2038   greater than zero, then the forwarded message &MUST; contain an updated
2039   Max-Forwards field with a value decremented by one (1).
2040</t>
2041<t>
2042   The Max-Forwards header field &MAY; be ignored for all other methods
2043   defined by this specification and for any extension methods for which
2044   it is not explicitly referred to as part of that method definition.
2045</t>
2046</section>
2047
2048<section title="Referer" anchor="header.referer">
2049  <iref primary="true" item="Referer header" x:for-anchor=""/>
2050  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
[229]2051  <x:anchor-alias value="Referer"/>
[356]2052  <x:anchor-alias value="Referer-v"/>
[8]2053<t>
[356]2054   The request-header field "Referer" [sic] allows the client to specify,
[8]2055   for the server's benefit, the address (URI) of the resource from
[391]2056   which the request-target was obtained (the "referrer", although the
[8]2057   header field is misspelled.) The Referer request-header allows a
2058   server to generate lists of back-links to resources for interest,
2059   logging, optimized caching, etc. It also allows obsolete or mistyped
2060   links to be traced for maintenance. The Referer field &MUST-NOT; be
[391]2061   sent if the request-target was obtained from a source that does not have
[8]2062   its own URI, such as input from the user keyboard.
2063</t>
[356]2064<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
[366]2065  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
[391]2066  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[8]2067</artwork></figure>
2068<t>
2069   Example:
2070</t>
2071<figure><artwork type="example">
[356]2072  Referer: http://www.example.org/hypertext/Overview.html
[8]2073</artwork></figure>
2074<t>
2075   If the field value is a relative URI, it &SHOULD; be interpreted
[391]2076   relative to the request-target. The URI &MUST-NOT; include a fragment. See
[8]2077   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2078</t>
2079</section>
2080
2081<section title="Retry-After" anchor="header.retry-after">
2082  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2083  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
[229]2084  <x:anchor-alias value="Retry-After"/>
[356]2085  <x:anchor-alias value="Retry-After-v"/>
[8]2086<t>
[356]2087   The response-header "Retry-After" field can be used with a 503 (Service
[8]2088   Unavailable) response to indicate how long the service is expected to
2089   be unavailable to the requesting client. This field &MAY; also be used
2090   with any 3xx (Redirection) response to indicate the minimum time the
2091   user-agent is asked wait before issuing the redirected request. The
2092   value of this field can be either an HTTP-date or an integer number
2093   of seconds (in decimal) after the time of the response.
2094</t>
[356]2095<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
[366]2096  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
[356]2097  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
[8]2098</artwork></figure>
[229]2099<t anchor="rule.delta-seconds">
2100  <x:anchor-alias value="delta-seconds"/>
[212]2101   Time spans are non-negative decimal integers, representing time in
2102   seconds.
2103</t>
2104<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
[229]2105  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
[212]2106</artwork></figure>
2107<t>
[8]2108   Two examples of its use are
2109</t>
2110<figure><artwork type="example">
[356]2111  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2112  Retry-After: 120
[8]2113</artwork></figure>
2114<t>
2115   In the latter example, the delay is 2 minutes.
2116</t>
2117</section>
2118
2119<section title="Server" anchor="header.server">
2120  <iref primary="true" item="Server header" x:for-anchor=""/>
2121  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
[229]2122  <x:anchor-alias value="Server"/>
[356]2123  <x:anchor-alias value="Server-v"/>
[8]2124<t>
[356]2125   The response-header field "Server" contains information about the
[8]2126   software used by the origin server to handle the request. The field
[190]2127   can contain multiple product tokens (&product-tokens;) and comments
[8]2128   identifying the server and any significant subproducts. The product
2129   tokens are listed in order of their significance for identifying the
2130   application.
2131</t>
[356]2132<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
[366]2133  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
[370]2134  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2135                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
[8]2136</artwork></figure>
2137<t>
2138   Example:
2139</t>
2140<figure><artwork type="example">
[356]2141  Server: CERN/3.0 libwww/2.17
[8]2142</artwork></figure>
2143<t>
2144   If the response is being forwarded through a proxy, the proxy
2145   application &MUST-NOT; modify the Server response-header. Instead, it
[72]2146   &MUST; include a Via field (as described in &header-via;).
[8]2147</t>
[563]2148<x:note>
2149  <t>
2150    <x:h>Note:</x:h> Revealing the specific software version of the server might
2151    allow the server machine to become more vulnerable to attacks
2152    against software that is known to contain security holes. Server
2153    implementors are encouraged to make this field a configurable
2154    option.
2155  </t>
2156</x:note>
[8]2157</section>
2158
2159<section title="User-Agent" anchor="header.user-agent">
2160  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2161  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
[229]2162  <x:anchor-alias value="User-Agent"/>
[356]2163  <x:anchor-alias value="User-Agent-v"/>
[8]2164<t>
[356]2165   The request-header field "User-Agent" contains information about the
[8]2166   user agent originating the request. This is for statistical purposes,
2167   the tracing of protocol violations, and automated recognition of user
2168   agents for the sake of tailoring responses to avoid particular user
2169   agent limitations. User agents &SHOULD; include this field with
[190]2170   requests. The field can contain multiple product tokens (&product-tokens;)
[8]2171   and comments identifying the agent and any subproducts which form a
2172   significant part of the user agent. By convention, the product tokens
2173   are listed in order of their significance for identifying the
2174   application.
2175</t>
[356]2176<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
[366]2177  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
[370]2178  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2179                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
[8]2180</artwork></figure>
2181<t>
2182   Example:
2183</t>
2184<figure><artwork type="example">
[356]2185  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
[8]2186</artwork></figure>
2187</section>
2188
2189</section>
2190
[29]2191<section title="IANA Considerations" anchor="IANA.considerations">
[270]2192
2193<section title="Method Registry" anchor="method.registration">
2194<t>
2195  The registration procedure for HTTP Methods is defined by
2196  <xref target="method.registry"/> of this document.
2197</t>
[288]2198<t>
2199   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2200   should be populated with the registrations below:
2201</t>
[270]2202<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
[288]2203<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
[270]2204   <ttcol>Method</ttcol>
[286]2205   <ttcol>Safe</ttcol>
[270]2206   <ttcol>Reference</ttcol>
2207   <c>CONNECT</c>
[286]2208   <c>no</c>
[270]2209   <c>
2210      <xref target="CONNECT"/>
2211   </c>
2212   <c>DELETE</c>
[286]2213   <c>no</c>
[270]2214   <c>
2215      <xref target="DELETE"/>
2216   </c>
2217   <c>GET</c>
[286]2218   <c>yes</c>
[270]2219   <c>
2220      <xref target="GET"/>
2221   </c>
2222   <c>HEAD</c>
[286]2223   <c>yes</c>
[270]2224   <c>
2225      <xref target="HEAD"/>
2226   </c>
2227   <c>OPTIONS</c>
[286]2228   <c>yes</c>
[270]2229   <c>
2230      <xref target="OPTIONS"/>
2231   </c>
2232   <c>POST</c>
[286]2233   <c>no</c>
[270]2234   <c>
2235      <xref target="POST"/>
2236   </c>
2237   <c>PUT</c>
[286]2238   <c>no</c>
[270]2239   <c>
2240      <xref target="PUT"/>
2241   </c>
2242   <c>TRACE</c>
[286]2243   <c>yes</c>
[270]2244   <c>
2245      <xref target="TRACE"/>
2246   </c>
2247</texttable>
2248<!--(END)-->
2249</section>
2250
[255]2251<section title="Status Code Registry" anchor="status.code.registration">
[262]2252<t>
[288]2253   The registration procedure for HTTP Status Codes -- previously defined
2254   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2255   by <xref target="status.code.registry"/> of this document.
[262]2256</t>
[288]2257<t>
2258   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2259   should be updated with the registrations below:
2260</t>
[255]2261<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
[288]2262<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
[255]2263   <ttcol>Value</ttcol>
2264   <ttcol>Description</ttcol>
2265   <ttcol>Reference</ttcol>
2266   <c>100</c>
2267   <c>Continue</c>
2268   <c>
2269      <xref target="status.100"/>
2270   </c>
2271   <c>101</c>
2272   <c>Switching Protocols</c>
2273   <c>
2274      <xref target="status.101"/>
2275   </c>
2276   <c>200</c>
2277   <c>OK</c>
2278   <c>
2279      <xref target="status.200"/>
2280   </c>
2281   <c>201</c>
2282   <c>Created</c>
2283   <c>
2284      <xref target="status.201"/>
2285   </c>
2286   <c>202</c>
2287   <c>Accepted</c>
2288   <c>
2289      <xref target="status.202"/>
2290   </c>
2291   <c>203</c>
2292   <c>Non-Authoritative Information</c>
2293   <c>
2294      <xref target="status.203"/>
2295   </c>
2296   <c>204</c>
2297   <c>No Content</c>
2298   <c>
2299      <xref target="status.204"/>
2300   </c>
2301   <c>205</c>
2302   <c>Reset Content</c>
2303   <c>
2304      <xref target="status.205"/>
2305   </c>
2306   <c>206</c>
2307   <c>Partial Content</c>
2308   <c>
2309      <xref target="status.206"/>
2310   </c>
2311   <c>300</c>
2312   <c>Multiple Choices</c>
2313   <c>
2314      <xref target="status.300"/>
2315   </c>
2316   <c>301</c>
2317   <c>Moved Permanently</c>
2318   <c>
2319      <xref target="status.301"/>
2320   </c>
2321   <c>302</c>
2322   <c>Found</c>
2323   <c>
2324      <xref target="status.302"/>
2325   </c>
2326   <c>303</c>
2327   <c>See Other</c>
2328   <c>
2329      <xref target="status.303"/>
2330   </c>
2331   <c>304</c>
2332   <c>Not Modified</c>
2333   <c>
2334      <xref target="status.304"/>
2335   </c>
2336   <c>305</c>
2337   <c>Use Proxy</c>
2338   <c>
2339      <xref target="status.305"/>
2340   </c>
2341   <c>306</c>
2342   <c>(Unused)</c>
2343   <c>
2344      <xref target="status.306"/>
2345   </c>
2346   <c>307</c>
2347   <c>Temporary Redirect</c>
2348   <c>
2349      <xref target="status.307"/>
2350   </c>
2351   <c>400</c>
2352   <c>Bad Request</c>
2353   <c>
2354      <xref target="status.400"/>
2355   </c>
2356   <c>401</c>
2357   <c>Unauthorized</c>
2358   <c>
2359      <xref target="status.401"/>
2360   </c>
2361   <c>402</c>
2362   <c>Payment Required</c>
2363   <c>
2364      <xref target="status.402"/>
2365   </c>
2366   <c>403</c>
2367   <c>Forbidden</c>
2368   <c>
2369      <xref target="status.403"/>
2370   </c>
2371   <c>404</c>
2372   <c>Not Found</c>
2373   <c>
2374      <xref target="status.404"/>
2375   </c>
2376   <c>405</c>
2377   <c>Method Not Allowed</c>
2378   <c>
2379      <xref target="status.405"/>
2380   </c>
2381   <c>406</c>
2382   <c>Not Acceptable</c>
2383   <c>
2384      <xref target="status.406"/>
2385   </c>
2386   <c>407</c>
2387   <c>Proxy Authentication Required</c>
2388   <c>
2389      <xref target="status.407"/>
2390   </c>
2391   <c>408</c>
2392   <c>Request Timeout</c>
2393   <c>
2394      <xref target="status.408"/>
2395   </c>
2396   <c>409</c>
2397   <c>Conflict</c>
2398   <c>
2399      <xref target="status.409"/>
2400   </c>
2401   <c>410</c>
2402   <c>Gone</c>
2403   <c>
2404      <xref target="status.410"/>
2405   </c>
2406   <c>411</c>
2407   <c>Length Required</c>
2408   <c>
2409      <xref target="status.411"/>
2410   </c>
2411   <c>412</c>
2412   <c>Precondition Failed</c>
2413   <c>
2414      <xref target="status.412"/>
2415   </c>
2416   <c>413</c>
2417   <c>Request Entity Too Large</c>
2418   <c>
2419      <xref target="status.413"/>
2420   </c>
2421   <c>414</c>
[465]2422   <c>URI Too Long</c>
[255]2423   <c>
2424      <xref target="status.414"/>
2425   </c>
2426   <c>415</c>
2427   <c>Unsupported Media Type</c>
2428   <c>
2429      <xref target="status.415"/>
2430   </c>
2431   <c>416</c>
2432   <c>Requested Range Not Satisfiable</c>
2433   <c>
2434      <xref target="status.416"/>
2435   </c>
2436   <c>417</c>
2437   <c>Expectation Failed</c>
2438   <c>
2439      <xref target="status.417"/>
2440   </c>
2441   <c>500</c>
2442   <c>Internal Server Error</c>
2443   <c>
2444      <xref target="status.500"/>
2445   </c>
2446   <c>501</c>
2447   <c>Not Implemented</c>
2448   <c>
2449      <xref target="status.501"/>
2450   </c>
2451   <c>502</c>
2452   <c>Bad Gateway</c>
2453   <c>
2454      <xref target="status.502"/>
2455   </c>
2456   <c>503</c>
2457   <c>Service Unavailable</c>
2458   <c>
2459      <xref target="status.503"/>
2460   </c>
2461   <c>504</c>
2462   <c>Gateway Timeout</c>
2463   <c>
2464      <xref target="status.504"/>
2465   </c>
2466   <c>505</c>
2467   <c>HTTP Version Not Supported</c>
2468   <c>
2469      <xref target="status.505"/>
2470   </c>
2471</texttable>
2472<!--(END)-->
[8]2473</section>
[253]2474<section title="Message Header Registration" anchor="message.header.registration">
[290]2475<t>
2476   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2477   with the permanent registrations below (see <xref target="RFC3864"/>):
2478</t>
[253]2479<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]2480<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]2481   <ttcol>Header Field Name</ttcol>
2482   <ttcol>Protocol</ttcol>
2483   <ttcol>Status</ttcol>
2484   <ttcol>Reference</ttcol>
2485   <c>Allow</c>
2486   <c>http</c>
2487   <c>standard</c>
2488   <c>
2489      <xref target="header.allow"/>
2490   </c>
2491   <c>Expect</c>
2492   <c>http</c>
2493   <c>standard</c>
2494   <c>
2495      <xref target="header.expect"/>
2496   </c>
2497   <c>From</c>
2498   <c>http</c>
2499   <c>standard</c>
2500   <c>
2501      <xref target="header.from"/>
2502   </c>
2503   <c>Location</c>
2504   <c>http</c>
2505   <c>standard</c>
2506   <c>
2507      <xref target="header.location"/>
2508   </c>
2509   <c>Max-Forwards</c>
2510   <c>http</c>
2511   <c>standard</c>
2512   <c>
2513      <xref target="header.max-forwards"/>
2514   </c>
2515   <c>Referer</c>
2516   <c>http</c>
2517   <c>standard</c>
2518   <c>
2519      <xref target="header.referer"/>
2520   </c>
2521   <c>Retry-After</c>
2522   <c>http</c>
2523   <c>standard</c>
2524   <c>
2525      <xref target="header.retry-after"/>
2526   </c>
2527   <c>Server</c>
2528   <c>http</c>
2529   <c>standard</c>
2530   <c>
2531      <xref target="header.server"/>
2532   </c>
2533   <c>User-Agent</c>
2534   <c>http</c>
2535   <c>standard</c>
2536   <c>
2537      <xref target="header.user-agent"/>
2538   </c>
2539</texttable>
[290]2540<!--(END)-->
[253]2541<t>
[290]2542   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
[253]2543</t>
2544</section>
2545</section>
2546
[8]2547<section title="Security Considerations" anchor="security.considerations">
2548<t>
2549   This section is meant to inform application developers, information
2550   providers, and users of the security limitations in HTTP/1.1 as
2551   described by this document. The discussion does not include
2552   definitive solutions to the problems revealed, though it does make
2553   some suggestions for reducing security risks.
2554</t>
2555
2556<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2557<t>
2558   Like any generic data transfer protocol, HTTP cannot regulate the
2559   content of the data that is transferred, nor is there any a priori
2560   method of determining the sensitivity of any particular piece of
2561   information within the context of any given request. Therefore,
2562   applications &SHOULD; supply as much control over this information as
2563   possible to the provider of that information. Four header fields are
2564   worth special mention in this context: Server, Via, Referer and From.
2565</t>
2566<t>
2567   Revealing the specific software version of the server might allow the
2568   server machine to become more vulnerable to attacks against software
2569   that is known to contain security holes. Implementors &SHOULD; make the
2570   Server header field a configurable option.
2571</t>
2572<t>
2573   Proxies which serve as a portal through a network firewall &SHOULD;
2574   take special precautions regarding the transfer of header information
2575   that identifies the hosts behind the firewall. In particular, they
2576   &SHOULD; remove, or replace with sanitized versions, any Via fields
2577   generated behind the firewall.
2578</t>
2579<t>
2580   The Referer header allows reading patterns to be studied and reverse
2581   links drawn. Although it can be very useful, its power can be abused
2582   if user details are not separated from the information contained in
2583   the Referer. Even when the personal information has been removed, the
2584   Referer header might indicate a private document's URI whose
2585   publication would be inappropriate.
2586</t>
2587<t>
2588   The information sent in the From field might conflict with the user's
2589   privacy interests or their site's security policy, and hence it
2590   &SHOULD-NOT;  be transmitted without the user being able to disable,
2591   enable, and modify the contents of the field. The user &MUST; be able
2592   to set the contents of this field within a user preference or
2593   application defaults configuration.
2594</t>
2595<t>
2596   We suggest, though do not require, that a convenient toggle interface
2597   be provided for the user to enable or disable the sending of From and
2598   Referer information.
2599</t>
2600<t>
2601   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2602   fields can sometimes be used to determine that a specific client or
2603   server have a particular security hole which might be exploited.
2604   Unfortunately, this same information is often used for other valuable
2605   purposes for which HTTP currently has no better mechanism.
2606</t>
2607</section>
2608
[184]2609<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
[8]2610<t>
2611   Because the source of a link might be private information or might
2612   reveal an otherwise private information source, it is strongly
2613   recommended that the user be able to select whether or not the
2614   Referer field is sent. For example, a browser client could have a
2615   toggle switch for browsing openly/anonymously, which would
2616   respectively enable/disable the sending of Referer and From
2617   information.
2618</t>
2619<t>
[172]2620   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
[8]2621   HTTP request if the referring page was transferred with a secure
2622   protocol.
2623</t>
2624<t>
[172]2625   Authors of services should not use
2626   GET-based forms for the submission of sensitive data because that
[391]2627   data will be encoded in the Request-target. Many existing
2628   servers, proxies, and user agents log or display the Request-target in
[172]2629   places where it might be visible to third parties. Such services can
2630   use POST-based form submission instead.
[8]2631</t>
2632</section>
2633
2634<section title="Location Headers and Spoofing" anchor="location.spoofing">
2635<t>
2636   If a single server supports multiple organizations that do not trust
2637   one another, then it &MUST; check the values of Location and Content-Location
2638   headers in responses that are generated under control of
2639   said organizations to make sure that they do not attempt to
2640   invalidate resources over which they have no authority.
2641</t>
2642</section>
2643
2644</section>
2645
2646<section title="Acknowledgments" anchor="ack">
2647</section>
2648</middle>
2649<back>
2650
[119]2651<references title="Normative References">
2652
[31]2653<reference anchor="Part1">
[119]2654  <front>
2655    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2656    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2657      <organization abbrev="Day Software">Day Software</organization>
2658      <address><email>fielding@gbiv.com</email></address>
2659    </author>
2660    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2661      <organization>One Laptop per Child</organization>
2662      <address><email>jg@laptop.org</email></address>
2663    </author>
2664    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2665      <organization abbrev="HP">Hewlett-Packard Company</organization>
2666      <address><email>JeffMogul@acm.org</email></address>
2667    </author>
2668    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2669      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2670      <address><email>henrikn@microsoft.com</email></address>
2671    </author>
2672    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2673      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2674      <address><email>LMM@acm.org</email></address>
2675    </author>
2676    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2677      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2678      <address><email>paulle@microsoft.com</email></address>
2679    </author>
2680    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2681      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2682      <address><email>timbl@w3.org</email></address>
2683    </author>
2684    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2685      <organization abbrev="W3C">World Wide Web Consortium</organization>
2686      <address><email>ylafon@w3.org</email></address>
2687    </author>
2688    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2689      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2690      <address><email>julian.reschke@greenbytes.de</email></address>
2691    </author>
2692    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2693  </front>
2694  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2695  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
[31]2696</reference>
2697
2698<reference anchor="Part3">
[119]2699  <front>
2700    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2701    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2702      <organization abbrev="Day Software">Day Software</organization>
2703      <address><email>fielding@gbiv.com</email></address>
2704    </author>
2705    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2706      <organization>One Laptop per Child</organization>
2707      <address><email>jg@laptop.org</email></address>
2708    </author>
2709    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2710      <organization abbrev="HP">Hewlett-Packard Company</organization>
2711      <address><email>JeffMogul@acm.org</email></address>
2712    </author>
2713    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2714      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2715      <address><email>henrikn@microsoft.com</email></address>
2716    </author>
2717    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2718      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2719      <address><email>LMM@acm.org</email></address>
2720    </author>
2721    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2722      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2723      <address><email>paulle@microsoft.com</email></address>
2724    </author>
2725    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2726      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2727      <address><email>timbl@w3.org</email></address>
2728    </author>
2729    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2730      <organization abbrev="W3C">World Wide Web Consortium</organization>
2731      <address><email>ylafon@w3.org</email></address>
2732    </author>
2733    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2734      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2735      <address><email>julian.reschke@greenbytes.de</email></address>
2736    </author>
2737    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2738  </front>
2739  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2740  <x:source href="p3-payload.xml" basename="p3-payload"/>
[31]2741</reference>
2742
2743<reference anchor="Part4">
[119]2744  <front>
2745    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2746    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2747      <organization abbrev="Day Software">Day Software</organization>
2748      <address><email>fielding@gbiv.com</email></address>
2749    </author>
2750    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2751      <organization>One Laptop per Child</organization>
2752      <address><email>jg@laptop.org</email></address>
2753    </author>
2754    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2755      <organization abbrev="HP">Hewlett-Packard Company</organization>
2756      <address><email>JeffMogul@acm.org</email></address>
2757    </author>
2758    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2759      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2760      <address><email>henrikn@microsoft.com</email></address>
2761    </author>
2762    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2763      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2764      <address><email>LMM@acm.org</email></address>
2765    </author>
2766    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2767      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2768      <address><email>paulle@microsoft.com</email></address>
2769    </author>
2770    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2771      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2772      <address><email>timbl@w3.org</email></address>
2773    </author>
2774    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2775      <organization abbrev="W3C">World Wide Web Consortium</organization>
2776      <address><email>ylafon@w3.org</email></address>
2777    </author>
2778    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2779      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2780      <address><email>julian.reschke@greenbytes.de</email></address>
2781    </author>
2782    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2783  </front>
2784  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2785  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
[31]2786</reference>
2787
2788<reference anchor="Part5">
[119]2789  <front>
2790    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2791    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2792      <organization abbrev="Day Software">Day Software</organization>
2793      <address><email>fielding@gbiv.com</email></address>
2794    </author>
2795    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2796      <organization>One Laptop per Child</organization>
2797      <address><email>jg@laptop.org</email></address>
2798    </author>
2799    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2800      <organization abbrev="HP">Hewlett-Packard Company</organization>
2801      <address><email>JeffMogul@acm.org</email></address>
2802    </author>
2803    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2804      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2805      <address><email>henrikn@microsoft.com</email></address>
2806    </author>
2807    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2808      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2809      <address><email>LMM@acm.org</email></address>
2810    </author>
2811    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2812      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2813      <address><email>paulle@microsoft.com</email></address>
2814    </author>
2815    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2816      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2817      <address><email>timbl@w3.org</email></address>
2818    </author>
2819    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2820      <organization abbrev="W3C">World Wide Web Consortium</organization>
2821      <address><email>ylafon@w3.org</email></address>
2822    </author>
2823    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2824      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2825      <address><email>julian.reschke@greenbytes.de</email></address>
2826    </author>
2827    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2828  </front>
2829  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2830  <x:source href="p5-range.xml" basename="p5-range"/>
[31]2831</reference>
2832
2833<reference anchor="Part6">
[119]2834  <front>
2835    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2836    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2837      <organization abbrev="Day Software">Day Software</organization>
2838      <address><email>fielding@gbiv.com</email></address>
2839    </author>
2840    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2841      <organization>One Laptop per Child</organization>
2842      <address><email>jg@laptop.org</email></address>
2843    </author>
2844    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2845      <organization abbrev="HP">Hewlett-Packard Company</organization>
2846      <address><email>JeffMogul@acm.org</email></address>
2847    </author>
2848    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2849      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2850      <address><email>henrikn@microsoft.com</email></address>
2851    </author>
2852    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2853      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2854      <address><email>LMM@acm.org</email></address>
2855    </author>
2856    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2857      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2858      <address><email>paulle@microsoft.com</email></address>
2859    </author>
2860    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2861      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2862      <address><email>timbl@w3.org</email></address>
2863    </author>
2864    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2865      <organization abbrev="W3C">World Wide Web Consortium</organization>
2866      <address><email>ylafon@w3.org</email></address>
2867    </author>
2868    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2869      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2870      <address><email>julian.reschke@greenbytes.de</email></address>
2871    </author>
2872    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2873  </front>
2874  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2875  <x:source href="p6-cache.xml" basename="p6-cache"/>
[31]2876</reference>
2877
2878<reference anchor="Part7">
[119]2879  <front>
2880    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2881    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2882      <organization abbrev="Day Software">Day Software</organization>
2883      <address><email>fielding@gbiv.com</email></address>
2884    </author>
2885    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2886      <organization>One Laptop per Child</organization>
2887      <address><email>jg@laptop.org</email></address>
2888    </author>
2889    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2890      <organization abbrev="HP">Hewlett-Packard Company</organization>
2891      <address><email>JeffMogul@acm.org</email></address>
2892    </author>
2893    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2894      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2895      <address><email>henrikn@microsoft.com</email></address>
2896    </author>
2897    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2898      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2899      <address><email>LMM@acm.org</email></address>
2900    </author>
2901    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2902      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2903      <address><email>paulle@microsoft.com</email></address>
2904    </author>
2905    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2906      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2907      <address><email>timbl@w3.org</email></address>
2908    </author>
2909    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2910      <organization abbrev="W3C">World Wide Web Consortium</organization>
2911      <address><email>ylafon@w3.org</email></address>
2912    </author>
2913    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2914      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2915      <address><email>julian.reschke@greenbytes.de</email></address>
2916    </author>
2917    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2918  </front>
2919  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2920  <x:source href="p7-auth.xml" basename="p7-auth"/>
[31]2921</reference>
2922
[119]2923<reference anchor="RFC2119">
2924  <front>
2925    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2926    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2927      <organization>Harvard University</organization>
2928      <address><email>sob@harvard.edu</email></address>
2929    </author>
2930    <date month="March" year="1997"/>
2931  </front>
2932  <seriesInfo name="BCP" value="14"/>
2933  <seriesInfo name="RFC" value="2119"/>
2934</reference>
2935
[425]2936<reference anchor="RFC5234">
2937  <front>
2938    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2939    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2940      <organization>Brandenburg InternetWorking</organization>
2941      <address>
2942      <postal>
2943      <street>675 Spruce Dr.</street>
2944      <city>Sunnyvale</city>
2945      <region>CA</region>
2946      <code>94086</code>
2947      <country>US</country></postal>
2948      <phone>+1.408.246.8253</phone>
2949      <email>dcrocker@bbiw.net</email></address> 
2950    </author>
2951    <author initials="P." surname="Overell" fullname="Paul Overell">
2952      <organization>THUS plc.</organization>
2953      <address>
2954      <postal>
2955      <street>1/2 Berkeley Square</street>
2956      <street>99 Berkely Street</street>
2957      <city>Glasgow</city>
2958      <code>G3 7HR</code>
2959      <country>UK</country></postal>
2960      <email>paul.overell@thus.net</email></address>
2961    </author>
2962    <date month="January" year="2008"/>
2963  </front>
2964  <seriesInfo name="STD" value="68"/>
2965  <seriesInfo name="RFC" value="5234"/>
2966</reference>
2967
[119]2968</references>
2969
2970<references title="Informative References">
2971
[129]2972<reference anchor="RFC1945">
2973  <front>
2974    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2975    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2976      <organization>MIT, Laboratory for Computer Science</organization>
2977      <address><email>timbl@w3.org</email></address>
2978    </author>
2979    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2980      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2981      <address><email>fielding@ics.uci.edu</email></address>
2982    </author>
2983    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2984      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2985      <address><email>frystyk@w3.org</email></address>
2986    </author>
2987    <date month="May" year="1996"/>
2988  </front>
2989  <seriesInfo name="RFC" value="1945"/>
2990</reference>
2991
[119]2992<reference anchor="RFC2068">
2993  <front>
2994    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2995    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2996      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2997      <address><email>fielding@ics.uci.edu</email></address>
2998    </author>
2999    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3000      <organization>MIT Laboratory for Computer Science</organization>
3001      <address><email>jg@w3.org</email></address>
3002    </author>
3003    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3004      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3005      <address><email>mogul@wrl.dec.com</email></address>
3006    </author>
3007    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3008      <organization>MIT Laboratory for Computer Science</organization>
3009      <address><email>frystyk@w3.org</email></address>
3010    </author>
3011    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3012      <organization>MIT Laboratory for Computer Science</organization>
3013      <address><email>timbl@w3.org</email></address>
3014    </author>
3015    <date month="January" year="1997"/>
3016  </front>
3017  <seriesInfo name="RFC" value="2068"/>
3018</reference>
3019
[36]3020<reference anchor="RFC2616">
[119]3021  <front>
3022    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3023    <author initials="R." surname="Fielding" fullname="R. Fielding">
3024      <organization>University of California, Irvine</organization>
3025      <address><email>fielding@ics.uci.edu</email></address>
3026    </author>
3027    <author initials="J." surname="Gettys" fullname="J. Gettys">
3028      <organization>W3C</organization>
3029      <address><email>jg@w3.org</email></address>
3030    </author>
3031    <author initials="J." surname="Mogul" fullname="J. Mogul">
3032      <organization>Compaq Computer Corporation</organization>
3033      <address><email>mogul@wrl.dec.com</email></address>
3034    </author>
3035    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3036      <organization>MIT Laboratory for Computer Science</organization>
3037      <address><email>frystyk@w3.org</email></address>
3038    </author>
3039    <author initials="L." surname="Masinter" fullname="L. Masinter">
3040      <organization>Xerox Corporation</organization>
3041      <address><email>masinter@parc.xerox.com</email></address>
3042    </author>
3043    <author initials="P." surname="Leach" fullname="P. Leach">
3044      <organization>Microsoft Corporation</organization>
3045      <address><email>paulle@microsoft.com</email></address>
3046    </author>
3047    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3048      <organization>W3C</organization>
3049      <address><email>timbl@w3.org</email></address>
3050    </author>
3051    <date month="June" year="1999"/>
3052  </front>
3053  <seriesInfo name="RFC" value="2616"/>
[36]3054</reference>
3055
[255]3056<reference anchor='RFC2817'>
3057  <front>
3058    <title>Upgrading to TLS Within HTTP/1.1</title>
3059    <author initials='R.' surname='Khare' fullname='R. Khare'>
3060      <organization>4K Associates / UC Irvine</organization>
3061      <address><email>rohit@4K-associates.com</email></address>
3062    </author>
3063    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3064      <organization>Agranat Systems, Inc.</organization>
3065      <address><email>lawrence@agranat.com</email></address>
3066    </author>
3067    <date year='2000' month='May' />
3068  </front>
3069  <seriesInfo name='RFC' value='2817' />
3070</reference>
3071
[253]3072<reference anchor='RFC3864'>
3073  <front>
3074    <title>Registration Procedures for Message Header Fields</title>
3075    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3076      <organization>Nine by Nine</organization>
3077      <address><email>GK-IETF@ninebynine.org</email></address>
3078    </author>
3079    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3080      <organization>BEA Systems</organization>
3081      <address><email>mnot@pobox.com</email></address>
3082    </author>
3083    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3084      <organization>HP Labs</organization>
3085      <address><email>JeffMogul@acm.org</email></address>
3086    </author>
3087    <date year='2004' month='September' />
3088  </front>
3089  <seriesInfo name='BCP' value='90' />
3090  <seriesInfo name='RFC' value='3864' />
3091</reference>
3092
[262]3093<reference anchor='RFC5226'>
3094  <front>
3095    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3096    <author initials='T.' surname='Narten' fullname='T. Narten'>
3097      <organization>IBM</organization>
3098      <address><email>narten@us.ibm.com</email></address>
3099    </author>
3100    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3101      <organization>Google</organization>
3102      <address><email>Harald@Alvestrand.no</email></address>
3103    </author>
3104    <date year='2008' month='May' />
3105  </front>
3106  <seriesInfo name='BCP' value='26' />
3107  <seriesInfo name='RFC' value='5226' />
3108</reference>
3109
[327]3110<reference anchor="RFC5322">
3111  <front>
3112    <title>Internet Message Format</title>
3113    <author initials="P." surname="Resnick" fullname="P. Resnick">
3114      <organization>Qualcomm Incorporated</organization>
3115    </author>
3116    <date year="2008" month="October"/>
3117  </front> 
3118  <seriesInfo name="RFC" value="5322"/>
3119</reference>
3120
[119]3121</references>
3122
[99]3123<section title="Compatibility with Previous Versions" anchor="compatibility">
[8]3124<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3125<t>
3126   Clarified which error code should be used for inbound server failures
3127   (e.g. DNS failures). (<xref target="status.504"/>).
3128</t>
3129<t>
[140]3130   201 (Created) had a race that required an Etag be sent when a resource is
[8]3131   first created. (<xref target="status.201"/>).
3132</t>
3133<t>
3134   Rewrite of message transmission requirements to make it much harder
3135   for implementors to get it wrong, as the consequences of errors here
3136   can have significant impact on the Internet, and to deal with the
3137   following problems:
3138  <list style="numbers">
3139      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3140         this was incorrectly placing a requirement on the behavior of
3141         an implementation of a future version of HTTP/1.x</t>
3142
3143      <t>Made it clear that user-agents should retry requests, not
3144         "clients" in general.</t>
3145
3146      <t>Converted requirements for clients to ignore unexpected 100
3147         (Continue) responses, and for proxies to forward 100 responses,
3148         into a general requirement for 1xx responses.</t>
3149
3150      <t>Modified some TCP-specific language, to make it clearer that
3151         non-TCP transports are possible for HTTP.</t>
3152
3153      <t>Require that the origin server &MUST-NOT; wait for the request
3154         body before it sends a required 100 (Continue) response.</t>
3155
3156      <t>Allow, rather than require, a server to omit 100 (Continue) if
3157         it has already seen some of the request body.</t>
3158
3159      <t>Allow servers to defend against denial-of-service attacks and
3160         broken clients.</t>
3161  </list>
3162</t>
3163<t>
[29]3164   This change adds the Expect header and 417 status code.
[8]3165</t>
3166<t>
3167   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3168   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3169</t>
3170<t>
3171   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
[266]3172   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
[8]3173</t>
3174</section>
[99]3175
3176<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
[108]3177<t>
[262]3178  This document takes over the Status Code Registry, previously defined
3179  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3180  (<xref target="status.code.registry"/>)
3181</t>
3182<t>
[108]3183  Clarify definition of POST.
3184  (<xref target="POST"/>)
3185</t>
[109]3186<t>
3187  Failed to consider that there are
3188  many other request methods that are safe to automatically redirect,
3189  and further that the user agent is able to make that determination
3190  based on the request method semantics.
3191  (Sections <xref format="counter" target="status.301"/>,
3192  <xref format="counter" target="status.302"/> and
[233]3193  <xref format="counter" target="status.307"/>)
[109]3194</t>
[112]3195<t>
[235]3196  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3197  It used to indicate that the requested resource must be accessed through the
3198  proxy given by the Location field. The Location field gave the URI of the
3199  proxy. The recipient was expected to repeat this single request via the proxy.
3200  (<xref target="status.305"/>)
3201</t>
3202<t>
[232]3203  Reclassify Allow header as response header, removing the option to
3204  specify it in a PUT request.
[240]3205  Relax the server requirement on the contents of the Allow header and
3206  remove requirement on clients to always trust the header value.
[232]3207  (<xref target="header.allow"/>)
3208</t>
3209<t>
[114]3210  Correct syntax of Location header to allow fragment,
3211  as referred symbol wasn't what was expected, and add some
3212  clarifications as to when it would not be appropriate.
3213  (<xref target="header.location"/>)
3214</t>
3215<t>
[112]3216  In the description of the Server header, the Via field
3217  was described as a SHOULD. The requirement was and is stated
3218  correctly in the description of the Via header in &header-via;.
3219  (<xref target="header.server"/>)
3220</t>
[99]3221</section>
3222
3223</section>
3224
[427]3225<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3226<figure>
3227<artwork type="abnf" name="p2-semantics.parsed-abnf">
3228<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3229<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3230<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3231<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3232<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
[538]3233<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
[427]3234<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3235<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3236<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3237
3238<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3239<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3240<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3241
3242<x:ref>From</x:ref> = "From:" OWS From-v
3243<x:ref>From-v</x:ref> = mailbox
3244
3245<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;
3246<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.1&gt;
3247
3248<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
[454]3249If-Modified-Since =
3250 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
[427]3251<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3252<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
[454]3253If-Unmodified-Since =
3254 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
[428]3255
[427]3256<x:ref>Location</x:ref> = "Location:" OWS Location-v
3257<x:ref>Location-v</x:ref> = absolute-URI [ "#" fragment ]
3258
3259<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3260<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3261<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 /
[454]3262 %x50.4F.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45 /
3263 %x43.4E.4E.45.43.54 / extension-method
[428]3264
[427]3265<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3266
[454]3267Proxy-Authenticate =
3268 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3269Proxy-Authorization =
3270 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
[428]3271
[427]3272<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3273<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3274<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3275<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3276<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3277<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3278<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3279
3280<x:ref>Server</x:ref> = "Server:" OWS Server-v
3281<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3282<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
[425]3283 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3284 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3285 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3286 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3287 "505" / extension-code
[428]3288
[427]3289<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 8.8&gt;
3290
3291<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3292<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3293
[538]3294<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
[427]3295
[454]3296WWW-Authenticate =
3297 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
[428]3298
[427]3299<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;
3300
3301<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 1.2.2&gt;
3302
3303<x:ref>delta-seconds</x:ref> = 1*DIGIT
3304
3305<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3306<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3307<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
[425]3308 *expect-params ]
[427]3309<x:ref>extension-code</x:ref> = 3DIGIT
3310<x:ref>extension-method</x:ref> = token
3311
3312<x:ref>fragment</x:ref> = &lt;fragment, defined in [Part1], Section 2.1&gt;
3313
3314<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3315
3316<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3317
3318<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.1&gt;
3319<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 3.4&gt;
3320
3321<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3322
3323<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
[425]3324 Accept-Language / Authorization / Expect / From / Host / If-Match /
3325 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3326 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3327 User-Agent
[427]3328<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
[425]3329 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
[428]3330
[427]3331<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3332
[454]3333
3334</artwork>
3335</figure>
[532]3336<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3337; Reason-Phrase defined but not used
[425]3338; Status-Code defined but not used
3339; request-header defined but not used
3340; response-header defined but not used
[454]3341</artwork></figure></section>
[427]3342
[252]3343<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
[115]3344
3345<section title="Since RFC2616">
3346<t>
3347  Extracted relevant partitions from <xref target="RFC2616"/>.
3348</t>
3349</section>
3350
3351<section title="Since draft-ietf-httpbis-p2-semantics-00">
3352<t>
[116]3353  Closed issues:
3354  <list style="symbols"> 
3355    <t>
[324]3356      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
[116]3357      "Via is a MUST"
3358      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3359    </t>
3360    <t>
[324]3361      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
[116]3362      "Fragments allowed in Location"
3363      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3364    </t>
3365    <t>
[324]3366      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
[116]3367      "Safe Methods vs Redirection"
3368      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3369    </t>
3370    <t>
[324]3371      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
[116]3372      "Revise description of the POST method"
3373      (<eref target="http://purl.org/NET/http-errata#post"/>)
3374    </t>
3375    <t>
[324]3376      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
[152]3377      "Normative and Informative references"
3378    </t>
3379    <t>
[324]3380      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
[116]3381      "RFC2606 Compliance"
3382    </t>
[129]3383    <t>
[324]3384      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
[129]3385      "Informative references"
3386    </t>
[130]3387    <t>
[324]3388      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
[130]3389      "Redundant cross-references"
3390    </t>
[116]3391  </list>
[115]3392</t>
[116]3393<t>
3394  Other changes:
3395  <list style="symbols"> 
3396    <t>
3397      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3398    </t>
3399  </list>
3400</t>
[115]3401</section>
3402
[170]3403<section title="Since draft-ietf-httpbis-p2-semantics-01">
3404<t>
[180]3405  Closed issues:
3406  <list style="symbols"> 
3407    <t>
[324]3408      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
[180]3409      "PUT side effects"
3410    </t>
[201]3411    <t>
[324]3412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
[201]3413      "Duplicate Host header requirements"
3414    </t>
[180]3415  </list>
[170]3416</t>
[190]3417<t>
[324]3418  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
[190]3419  <list style="symbols"> 
3420    <t>
3421      Move "Product Tokens" section (back) into Part 1, as "token" is used
3422      in the definition of the Upgrade header.
3423    </t>
[205]3424    <t>
3425      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3426    </t>
[210]3427    <t>
[212]3428      Copy definition of delta-seconds from Part6 instead of referencing it.
[210]3429    </t>
[190]3430  </list>
3431</t>
[115]3432</section>
3433
[252]3434<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
[228]3435<t>
[232]3436  Closed issues:
3437  <list style="symbols"> 
3438    <t>
[324]3439      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
[240]3440      "Requiring Allow in 405 responses"
3441    </t>
3442    <t>
[324]3443      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
[262]3444      "Status Code Registry"
3445    </t>
3446    <t>
[324]3447      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
[237]3448      "Redirection vs. Location"
3449    </t>
3450    <t>
[324]3451      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
[242]3452      "Cacheability of 303 response"
3453    </t>
3454    <t>
[324]3455      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
[236]3456      "305 Use Proxy"
3457    </t>
3458    <t>
[324]3459      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
[232]3460      "Classification for Allow header"
3461    </t>
[241]3462    <t>
[324]3463      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
[241]3464      "PUT - 'store under' vs 'store at'"
3465    </t>
[232]3466  </list>
[228]3467</t>
[253]3468<t>
[324]3469  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
[253]3470  <list style="symbols"> 
3471    <t>
3472      Reference RFC 3984, and update header registrations for headers defined
3473      in this document.
3474    </t>
3475  </list>
3476</t>
[256]3477<t>
[324]3478  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
[260]3479  <list style="symbols"> 
3480    <t>
3481      Replace string literals when the string really is case-sensitive (method).
3482    </t>
3483  </list>
3484</t>
[170]3485</section>
3486
[267]3487<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3488<t>
[274]3489  Closed issues:
3490  <list style="symbols"> 
3491    <t>
[324]3492      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
[280]3493      "OPTIONS request bodies"
3494    </t>
3495    <t>
[324]3496      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
[274]3497      "Description of CONNECT should refer to RFC2817"
3498    </t>
[300]3499    <t>
[324]3500      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
[300]3501      "Location Content-Location reference request/response mixup"
3502    </t>
[274]3503  </list>
3504</t>
3505<t>
[324]3506  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
[270]3507  <list style="symbols"> 
3508    <t>
3509      Added initial proposal for registration process, plus initial
3510      content (non-HTTP/1.1 methods to be added by a separate specification).
3511    </t>
3512  </list>
[267]3513</t>
[228]3514</section>
3515
[323]3516<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3517<t>
[327]3518  Closed issues:
3519  <list style="symbols"> 
3520    <t>
[333]3521      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3522      "Content-*"
3523    </t>
3524    <t>
[327]3525      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3526      "RFC 2822 is updated by RFC 5322"
3527    </t>
3528  </list>
[323]3529</t>
[334]3530<t>
3531  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3532  <list style="symbols"> 
3533    <t>
3534      Use "/" instead of "|" for alternatives.
3535    </t>
[356]3536    <t>
3537      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
[357]3538      whitespace ("OWS") and required whitespace ("RWS").
[356]3539    </t>
3540    <t>
[357]3541      Rewrite ABNFs to spell out whitespace rules, factor out
3542      header value format definitions.
[356]3543    </t>
[334]3544  </list>
3545</t>
[267]3546</section>
3547
[382]3548<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3549<t>
[398]3550  Closed issues:
3551  <list style="symbols"> 
3552    <t>
3553      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3554      "Reason-Phrase BNF"
3555    </t>
3556  </list>
[382]3557</t>
[421]3558<t>
[543]3559  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
[421]3560  <list style="symbols"> 
3561    <t>
[424]3562      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]3563    </t>
3564  </list>
3565</t>
[323]3566</section>
3567
[547]3568<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3569<t>
[579]3570  Closed issues:
3571  <list style="symbols"> 
3572    <t>
3573      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3574      "status codes vs methods"
3575    </t>
3576  </list>
[547]3577</t>
[382]3578</section>
3579
[547]3580</section>
3581
[8]3582</back>
3583</rfc>
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