source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1037

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Source reformat, update Changes section (see #230 and [1034])

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "October">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness'
77xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime'
79xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80]>
81<?rfc toc="yes" ?>
82<?rfc symrefs="yes" ?>
83<?rfc sortrefs="yes" ?>
84<?rfc compact="yes"?>
85<?rfc subcompact="no" ?>
86<?rfc linkmailto="no" ?>
87<?rfc editing="no" ?>
88<?rfc comments="yes"?>
89<?rfc inline="yes"?>
90<?rfc rfcedstyle="yes"?>
91<?rfc-ext allow-markup-in-artwork="yes" ?>
92<?rfc-ext include-references-in-index="yes" ?>
93<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
94     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
95     xmlns:x='http://purl.org/net/xml2rfc/ext'
96     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
97<front>
98
99  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
100
101  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
102    <organization abbrev="Day Software">Day Software</organization>
103    <address>
104      <postal>
105        <street>23 Corporate Plaza DR, Suite 280</street>
106        <city>Newport Beach</city>
107        <region>CA</region>
108        <code>92660</code>
109        <country>USA</country>
110      </postal>
111      <phone>+1-949-706-5300</phone>
112      <facsimile>+1-949-706-5305</facsimile>
113      <email>fielding@gbiv.com</email>
114      <uri>http://roy.gbiv.com/</uri>
115    </address>
116  </author>
117
118  <author initials="J." surname="Gettys" fullname="Jim Gettys">
119    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
120    <address>
121      <postal>
122        <street>21 Oak Knoll Road</street>
123        <city>Carlisle</city>
124        <region>MA</region>
125        <code>01741</code>
126        <country>USA</country>
127      </postal>
128      <email>jg@freedesktop.org</email>
129      <uri>http://gettys.wordpress.com/</uri>
130    </address>
131  </author>
132 
133  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
134    <organization abbrev="HP">Hewlett-Packard Company</organization>
135    <address>
136      <postal>
137        <street>HP Labs, Large Scale Systems Group</street>
138        <street>1501 Page Mill Road, MS 1177</street>
139        <city>Palo Alto</city>
140        <region>CA</region>
141        <code>94304</code>
142        <country>USA</country>
143      </postal>
144      <email>JeffMogul@acm.org</email>
145    </address>
146  </author>
147
148  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
149    <organization abbrev="Microsoft">Microsoft Corporation</organization>
150    <address>
151      <postal>
152        <street>1 Microsoft Way</street>
153        <city>Redmond</city>
154        <region>WA</region>
155        <code>98052</code>
156        <country>USA</country>
157      </postal>
158      <email>henrikn@microsoft.com</email>
159    </address>
160  </author>
161
162  <author initials="L." surname="Masinter" fullname="Larry Masinter">
163    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
164    <address>
165      <postal>
166        <street>345 Park Ave</street>
167        <city>San Jose</city>
168        <region>CA</region>
169        <code>95110</code>
170        <country>USA</country>
171      </postal>
172      <email>LMM@acm.org</email>
173      <uri>http://larry.masinter.net/</uri>
174    </address>
175  </author>
176 
177  <author initials="P." surname="Leach" fullname="Paul J. Leach">
178    <organization abbrev="Microsoft">Microsoft Corporation</organization>
179    <address>
180      <postal>
181        <street>1 Microsoft Way</street>
182        <city>Redmond</city>
183        <region>WA</region>
184        <code>98052</code>
185      </postal>
186      <email>paulle@microsoft.com</email>
187    </address>
188  </author>
189   
190  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
191    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
195        <street>The Stata Center, Building 32</street>
196        <street>32 Vassar Street</street>
197        <city>Cambridge</city>
198        <region>MA</region>
199        <code>02139</code>
200        <country>USA</country>
201      </postal>
202      <email>timbl@w3.org</email>
203      <uri>http://www.w3.org/People/Berners-Lee/</uri>
204    </address>
205  </author>
206
207  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
208    <organization abbrev="W3C">World Wide Web Consortium</organization>
209    <address>
210      <postal>
211        <street>W3C / ERCIM</street>
212        <street>2004, rte des Lucioles</street>
213        <city>Sophia-Antipolis</city>
214        <region>AM</region>
215        <code>06902</code>
216        <country>France</country>
217      </postal>
218      <email>ylafon@w3.org</email>
219      <uri>http://www.raubacapeu.net/people/yves/</uri>
220    </address>
221  </author>
222
223  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
224    <organization abbrev="greenbytes">greenbytes GmbH</organization>
225    <address>
226      <postal>
227        <street>Hafenweg 16</street>
228        <city>Muenster</city><region>NW</region><code>48155</code>
229        <country>Germany</country>
230      </postal>
231      <phone>+49 251 2807760</phone>
232      <facsimile>+49 251 2807761</facsimile>
233      <email>julian.reschke@greenbytes.de</email>
234      <uri>http://greenbytes.de/tech/webdav/</uri>
235    </address>
236  </author>
237
238  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
239  <workgroup>HTTPbis Working Group</workgroup>
240
241<abstract>
242<t>
243   The Hypertext Transfer Protocol (HTTP) is an application-level
244   protocol for distributed, collaborative, hypermedia information
245   systems. HTTP has been in use by the World Wide Web global information
246   initiative since 1990. This document is Part 2 of the seven-part specification
247   that defines the protocol referred to as "HTTP/1.1" and, taken together,
248   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
249   as expressed by request methods, request-header fields, response status codes,
250   and response-header fields.
251</t>
252</abstract>
253
254<note title="Editorial Note (To be removed by RFC Editor)">
255  <t>
256    Discussion of this draft should take place on the HTTPBIS working group
257    mailing list (ietf-http-wg@w3.org). The current issues list is
258    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
259    and related documents (including fancy diffs) can be found at
260    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
261  </t>
262  <t>
263    The changes in this draft are summarized in <xref target="changes.since.11"/>.
264  </t>
265</note>
266</front>
267<middle>
268<section title="Introduction" anchor="introduction">
269<t>
270   This document defines HTTP/1.1 request and response semantics.  Each HTTP
271   message, as defined in &messaging;, is in the form of either a request or
272   a response.  An HTTP server listens on a connection for HTTP requests and
273   responds to each request, in the order received on that connection, with
274   one or more HTTP response messages.  This document defines the commonly
275   agreed upon semantics of the HTTP uniform interface, the intentions defined
276   by each request method, and the various response messages that might be
277   expected as a result of applying that method to the target resource.
278</t>
279<t>
280   This document is currently disorganized in order to minimize the changes
281   between drafts and enable reviewers to see the smaller errata changes.
282   A future draft will reorganize the sections to better reflect the content.
283   In particular, the sections will be ordered according to the typical
284   processing of an HTTP request message (after message parsing): resource
285   mapping, general header fields, methods, request modifiers, response
286   status, and resource metadata.  The current mess reflects how widely
287   dispersed these topics and associated requirements had become in
288   <xref target="RFC2616"/>.
289</t>
290
291<section title="Requirements" anchor="intro.requirements">
292<t>
293   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
294   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
295   document are to be interpreted as described in <xref target="RFC2119"/>.
296</t>
297<t>
298   An implementation is not compliant if it fails to satisfy one or more
299   of the "MUST" or "REQUIRED" level requirements for the protocols it
300   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
301   level and all the "SHOULD" level requirements for its protocols is said
302   to be "unconditionally compliant"; one that satisfies all the "MUST"
303   level requirements but not all the "SHOULD" level requirements for its
304   protocols is said to be "conditionally compliant".
305</t>
306</section>
307
308<section title="Syntax Notation" anchor="notation">
309  <x:anchor-alias value="CR"/>
310  <x:anchor-alias value="DIGIT"/>
311  <x:anchor-alias value="LF"/>
312  <x:anchor-alias value="VCHAR"/>
313  <x:anchor-alias value="WSP"/>
314<t>
315  This specification uses the ABNF syntax defined in &notation; (which
316  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
317  <xref target="collected.abnf"/> shows the collected ABNF, with the list
318  rule expanded.
319</t>
320<t>
321  The following core rules are included by
322  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
323  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
324  DIGIT (decimal 0-9), DQUOTE (double quote),
325  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
326  OCTET (any 8-bit sequence of data), SP (space),
327  VCHAR (any visible USASCII character),
328  and WSP (whitespace).
329</t>
330
331<section title="Core Rules" anchor="core.rules">
332  <x:anchor-alias value="obs-text"/>
333  <x:anchor-alias value="quoted-string"/>
334  <x:anchor-alias value="token"/>
335  <x:anchor-alias value="OWS"/>
336  <x:anchor-alias value="RWS"/>
337<t>
338  The core rules below are defined in &basic-rules;:
339</t>
340<figure><artwork type="abnf2616">
341  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
342  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
343  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
344  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
345  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
346</artwork></figure>
347</section>
348
349<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
350  <x:anchor-alias value="absolute-URI"/>
351  <x:anchor-alias value="Accept"/>
352  <x:anchor-alias value="Accept-Charset"/>
353  <x:anchor-alias value="Accept-Encoding"/>
354  <x:anchor-alias value="Accept-Language"/>
355  <x:anchor-alias value="Accept-Ranges"/>
356  <x:anchor-alias value="Age"/>
357  <x:anchor-alias value="Authorization"/>
358  <x:anchor-alias value="comment"/>
359  <x:anchor-alias value="ETag"/>
360  <x:anchor-alias value="Host"/>
361  <x:anchor-alias value="HTTP-date"/>
362  <x:anchor-alias value="If-Match"/>
363  <x:anchor-alias value="If-Modified-Since"/>
364  <x:anchor-alias value="If-None-Match"/>
365  <x:anchor-alias value="If-Range"/>
366  <x:anchor-alias value="If-Unmodified-Since"/>
367  <x:anchor-alias value="partial-URI"/>
368  <x:anchor-alias value="product"/>
369  <x:anchor-alias value="Proxy-Authenticate"/>
370  <x:anchor-alias value="Proxy-Authorization"/>
371  <x:anchor-alias value="Range"/>
372  <x:anchor-alias value="TE"/>
373  <x:anchor-alias value="URI-reference"/>
374  <x:anchor-alias value="Vary"/>
375  <x:anchor-alias value="WWW-Authenticate"/>
376<t>
377  The ABNF rules below are defined in other parts:
378</t>
379<figure><!--Part1--><artwork type="abnf2616">
380  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
381  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
382  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
383  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
384  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
385  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
386  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
387  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
388</artwork></figure>
389<figure><!--Part3--><artwork type="abnf2616">
390  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
391  <x:ref>Accept-Charset</x:ref> =
392             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
393  <x:ref>Accept-Encoding</x:ref> =
394             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
395  <x:ref>Accept-Language</x:ref> =
396             &lt;Accept-Language, defined in &header-accept-language;&gt;
397</artwork></figure>
398<figure><!--Part4--><artwork type="abnf2616">
399  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
400  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
401  <x:ref>If-Modified-Since</x:ref> =
402             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
403  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
404  <x:ref>If-Unmodified-Since</x:ref> =
405             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
406</artwork></figure>
407<figure><!--Part5--><artwork type="abnf2616">
408  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
409  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
410  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
411</artwork></figure>
412<figure><!--Part6--><artwork type="abnf2616">
413  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
414  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
415</artwork><!--Part7--></figure>
416<figure><artwork type="abnf2616">
417  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
418  <x:ref>Proxy-Authenticate</x:ref> =
419             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
420  <x:ref>Proxy-Authorization</x:ref> =
421             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
422  <x:ref>WWW-Authenticate</x:ref> =
423             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
424</artwork></figure>
425</section>
426</section>
427</section>
428
429<section title="Method" anchor="method">
430  <x:anchor-alias value="Method"/>
431  <x:anchor-alias value="extension-method"/>
432<t>
433   The Method token indicates the method to be performed on the target
434   resource (&effective-request-uri;). The method is case-sensitive.
435</t>
436<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
437  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
438                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
439                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
440                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
441                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
442                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
443                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
444                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
445                 / <x:ref>extension-method</x:ref>
446  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
447</artwork></figure>
448<t>
449   The list of methods allowed by a resource can be specified in an
450   Allow header field (<xref target="header.allow"/>). The status code of the response
451   always notifies the client whether a method is currently allowed on a
452   resource, since the set of allowed methods can change dynamically. An
453   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
454   if the method is known by the origin server but not allowed for the
455   resource, and 501 (Not Implemented) if the method is
456   unrecognized or not implemented by the origin server. The methods GET
457   and HEAD &MUST; be supported by all general-purpose servers. All other
458   methods are &OPTIONAL;; however, if the above methods are implemented,
459   they &MUST; be implemented with the same semantics as those specified
460   in <xref target="method.definitions"/>.
461</t>
462
463<section title="Method Registry" anchor="method.registry">
464<t>
465  The HTTP Method Registry defines the name space for the Method token in the
466  Request line of an HTTP request.
467</t>
468<t>
469  Registrations &MUST; include the following fields:
470  <list style="symbols">
471    <t>Method Name (see <xref target="method"/>)</t>
472    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
473    <t>Pointer to specification text</t>
474  </list>
475</t>
476<t>
477  Values to be added to this name space are subject to IETF review
478  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
479</t>
480<t>
481  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
482</t>
483
484<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
485<t>
486   When it is necessary to express new semantics for a HTTP request that
487   aren't specific to a single application or media type, and currently defined
488   methods are inadequate, it may be appropriate to register a new method.
489</t>
490<t>
491   New methods &SHOULD; be potentially applicable to any resource. I.e.,
492   they should not be specific to any particular media type, "type" of
493   resource, or application.
494</t>
495<t>
496   New methods &MUST-NOT; prohibit a message-body on either the request or
497   the response message; however they &MAY; specify that only a zero-length
498   body is allowed.
499</t>
500<t>
501   New methods &MUST; define whether they are safe (<xref
502   target="safe.methods"/>) and whether they are idempotent (<xref
503   target="idempotent.methods"/>). They &MUST; also state whether they can be
504   cached (&caching;); in particular what conditions a cache may store the
505   response, and under what conditions such a stored response may be used to
506   satisfy a subsequent request.
507</t>
508<t>
509   New methods &SHOULD; explain how conditional request headers
510   (&conditional;) affect the response (if there is any effect).
511</t>
512<t>
513   HTTP methods &SHOULD; be registered in a document that isn't specific to
514   a single application or other use of HTTP, so that it's clear that they are
515   not specific to that application or extension.
516</t>
517</section>
518
519</section>
520</section>
521
522<section title="Request Header Fields" anchor="request.header.fields">
523  <x:anchor-alias value="request-header"/>
524<t>
525   The request-header fields allow the client to pass additional
526   information about the request, and about the client itself, to the
527   server. These fields act as request modifiers, with semantics
528   equivalent to the parameters on a programming language method
529   invocation.
530</t>
531<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
532  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
533                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
534                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
535                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
536                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
537                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
538                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
539                 / <x:ref>Host</x:ref>                     ; &header-host;
540                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
541                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
542                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
543                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
544                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
545                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
546                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
547                 / <x:ref>Range</x:ref>                    ; &header-range;
548                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
549                 / <x:ref>TE</x:ref>                       ; &header-te;
550                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
551</artwork></figure>
552<t>
553   Request-header field names can be extended reliably only in
554   combination with a change in the protocol version. However, new or
555   experimental header fields &MAY; be given the semantics of request-header
556   fields if all parties in the communication recognize them to
557   be request-header fields.
558</t>
559</section>
560
561<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
562  <x:anchor-alias value="Reason-Phrase"/>
563  <x:anchor-alias value="Status-Code"/>
564  <x:anchor-alias value="extension-code"/>
565<t>
566   The Status-Code element is a 3-digit integer result code of the
567   attempt to understand and satisfy the request. The status codes listed
568   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
569   &p5-status-codes;, and &p7-status-codes;.
570</t>
571<t>
572   The Reason-Phrase is intended to give a short
573   textual description of the Status-Code. The Status-Code is intended
574   for use by automata and the Reason-Phrase is intended for the human
575   user. The client is not required to examine or display the Reason-Phrase.
576</t>
577<t> 
578   The individual values of the numeric status codes defined for
579   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
580   presented below. The reason phrases listed here are only
581   recommendations -- they &MAY; be replaced by local equivalents without
582   affecting the protocol.
583</t>
584<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"/>
585  <x:ref>Status-Code</x:ref> =
586       "100"  ; <xref target="status.100"/>: Continue
587     / "101"  ; <xref target="status.101"/>: Switching Protocols
588     / "200"  ; <xref target="status.200"/>: OK
589     / "201"  ; <xref target="status.201"/>: Created
590     / "202"  ; <xref target="status.202"/>: Accepted
591     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
592     / "204"  ; <xref target="status.204"/>: No Content
593     / "205"  ; <xref target="status.205"/>: Reset Content
594     / "206"  ; &status-206;: Partial Content
595     / "300"  ; <xref target="status.300"/>: Multiple Choices
596     / "301"  ; <xref target="status.301"/>: Moved Permanently
597     / "302"  ; <xref target="status.302"/>: Found
598     / "303"  ; <xref target="status.303"/>: See Other
599     / "304"  ; &status-304;: Not Modified
600     / "305"  ; <xref target="status.305"/>: Use Proxy
601     / "307"  ; <xref target="status.307"/>: Temporary Redirect
602     / "400"  ; <xref target="status.400"/>: Bad Request
603     / "401"  ; &status-401;: Unauthorized
604     / "402"  ; <xref target="status.402"/>: Payment Required
605     / "403"  ; <xref target="status.403"/>: Forbidden
606     / "404"  ; <xref target="status.404"/>: Not Found
607     / "405"  ; <xref target="status.405"/>: Method Not Allowed
608     / "406"  ; <xref target="status.406"/>: Not Acceptable
609     / "407"  ; &status-407;: Proxy Authentication Required
610     / "408"  ; <xref target="status.408"/>: Request Time-out
611     / "409"  ; <xref target="status.409"/>: Conflict
612     / "410"  ; <xref target="status.410"/>: Gone
613     / "411"  ; <xref target="status.411"/>: Length Required
614     / "412"  ; &status-412;: Precondition Failed
615     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
616     / "414"  ; <xref target="status.414"/>: URI Too Long
617     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
618     / "416"  ; &status-416;: Requested range not satisfiable
619     / "417"  ; <xref target="status.417"/>: Expectation Failed
620     / "500"  ; <xref target="status.500"/>: Internal Server Error
621     / "501"  ; <xref target="status.501"/>: Not Implemented
622     / "502"  ; <xref target="status.502"/>: Bad Gateway
623     / "503"  ; <xref target="status.503"/>: Service Unavailable
624     / "504"  ; <xref target="status.504"/>: Gateway Time-out
625     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
626     / <x:ref>extension-code</x:ref>
627
628  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
629  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
630</artwork></figure>
631<t>
632   HTTP status codes are extensible. HTTP applications are not required
633   to understand the meaning of all registered status codes, though such
634   understanding is obviously desirable. However, applications &MUST;
635   understand the class of any status code, as indicated by the first
636   digit, and treat any unrecognized response as being equivalent to the
637   x00 status code of that class, with the exception that an
638   unrecognized response &MUST-NOT; be cached. For example, if an
639   unrecognized status code of 431 is received by the client, it can
640   safely assume that there was something wrong with its request and
641   treat the response as if it had received a 400 status code. In such
642   cases, user agents &SHOULD; present to the user the representation enclosed
643   with the response, since that representation is likely to include human-readable
644   information which will explain the unusual status.
645</t>
646
647<section title="Status Code Registry" anchor="status.code.registry">
648<t>
649  The HTTP Status Code Registry defines the name space for the Status-Code
650  token in the Status-Line of an HTTP response.
651</t>
652<t>
653  Values to be added to this name space are subject to IETF review
654  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
655</t>
656<t>
657  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
658</t>
659
660<section title="Considerations for New Status Codes">
661 
662   <t>When it is necessary to express new semantics for a HTTP response that
663  aren't specific to a single application or media type, and currently defined
664  status codes are inadequate, a new status code can be registered.</t>
665 
666   <t>New HTTP status codes &MUST; be defined in one of the categories defined
667   in <xref target="status.codes"/>. They &MUST-NOT; disallow a response body,
668   although they &MAY; mandate a zero-length response body. They &MAY; require
669   the presence of one or more particular HTTP response header(s).</t>
670 
671   <t>Likewise, their definitions &MAY; specify that caches are allowed to use
672   heuristics to determine their freshness (see &caching;; by default, it is
673   not allowed), and &MAY; define how to determine the resource which they
674   carry a representation for (see <xref
675   target="identifying.response.associated.with.representation"/>; by default,
676   it is anonymous).</t>
677 
678   <t>If there are particular request conditions that produce a response
679  containing the status code (e.g., request headers and/or method(s)), they
680  &SHOULD; be described in detail.</t>
681 
682   <t>New HTTP status codes &SHOULD; be registered in a document that isn't
683  specific to a single application or other use of HTTP, so that it's clear that
684  they are not specific to that application or extension.</t>
685 
686</section>
687
688</section>
689
690</section>
691
692<section title="Response Header Fields" anchor="response.header.fields">
693  <x:anchor-alias value="response-header"/>
694<t>
695   The response-header fields allow the server to pass additional
696   information about the response which cannot be placed in the Status-Line.
697   These header fields give information about the server and about
698   further access to the target resource (&effective-request-uri;).
699</t>
700<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
701  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
702                  / <x:ref>Age</x:ref>                     ; &header-age;
703                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
704                  / <x:ref>ETag</x:ref>                    ; &header-etag;
705                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
706                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
707                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
708                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
709                  / <x:ref>Vary</x:ref>                    ; &header-vary;
710                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
711</artwork></figure>
712<t>
713   Response-header field names can be extended reliably only in
714   combination with a change in the protocol version. However, new or
715   experimental header fields &MAY; be given the semantics of response-header
716   fields if all parties in the communication recognize them to
717   be response-header fields.
718</t>
719</section>
720
721<section title="Representation" anchor="representation">
722<t>
723   Request and Response messages &MAY; transfer a representation if not otherwise
724   restricted by the request method or response status code. A representation
725   consists of metadata (representation header fields) and data (representation
726   body).  When a complete or partial representation is enclosed in an HTTP message,
727   it is referred to as the payload of the message. HTTP representations
728   are defined in &payload;.
729</t>
730<t>
731   A representation body is only present in a message when a message-body is
732   present, as described in &message-body;. The representation body is obtained
733   from the message-body by decoding any Transfer-Encoding that might
734   have been applied to ensure safe and proper transfer of the message.
735</t>
736
737<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
738<t>
739   It is sometimes necessary to determine an identifier for the resource
740   associated with a representation.
741</t>
742<t>
743   An HTTP request representation, when present, is always associated with an
744   anonymous (i.e., unidentified) resource.
745</t>
746<t>
747   In the common case, an HTTP response is a representation of the target
748   resource (see &effective-request-uri;). However, this is not always the
749   case. To determine the URI of the resource a response is associated with,
750   the following rules are used (with the first applicable one being selected):
751</t>
752<t><list style="numbers">
753   <t>If the response status code is 200 or 203 and the request method was GET,
754   the response payload is a representation of the target resource.</t>
755   <t>If the response status code is 204, 206, or 304 and the request method was GET
756   or HEAD, the response payload is a partial representation of the target
757   (see &combining-responses;).</t>
758   <t>If the response has a Content-Location header field, and that URI is the same
759   as the effective request URI, the response payload is a representation of the
760   target resource.</t>
761   <t>If the response has a Content-Location header field, and that URI is not the
762   same as the effective request URI, then the response asserts that its
763   payload is a representation of the resource identified by the
764   Content-Location URI. However, such an assertion cannot be trusted unless
765   it can be verified by other means (not defined by HTTP).</t>
766   <t>Otherwise, the response is a representation of an anonymous (i.e.,
767   unidentified) resource.</t>
768</list></t>
769<t>
770  <cref anchor="TODO-req-uri">
771   The comparison function is going to have to be defined somewhere,
772   because we already need to compare URIs for things like cache invalidation.</cref>
773</t>
774</section>
775
776</section>
777
778
779<section title="Method Definitions" anchor="method.definitions">
780<t>
781   The set of common methods for HTTP/1.1 is defined below. Although
782   this set can be expanded, additional methods cannot be assumed to
783   share the same semantics for separately extended clients and servers.
784</t>
785
786<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
787
788<section title="Safe Methods" anchor="safe.methods">
789<iref item="Safe Methods" primary="true"/>
790<t>
791   Implementors need to be aware that the software represents the user in
792   their interactions over the Internet, and need to allow
793   the user to be aware of any actions they take which might have an
794   unexpected significance to themselves or others.
795</t>
796<t>
797   In particular, the convention has been established that the GET, HEAD,
798   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
799   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
800   This allows user agents to represent other methods, such as POST, PUT
801   and DELETE, in a special way, so that the user is made aware of the
802   fact that a possibly unsafe action is being requested.
803</t>
804<t>
805   Naturally, it is not possible to ensure that the server does not
806   generate side-effects as a result of performing a GET request; in
807   fact, some dynamic resources consider that a feature. The important
808   distinction here is that the user did not request the side-effects,
809   so therefore cannot be held accountable for them.
810</t>
811</section>
812
813<section title="Idempotent Methods" anchor="idempotent.methods">
814<iref item="Idempotent Methods" primary="true"/>
815<t>
816   Methods can also have the property of "idempotence" in that, aside
817   from error or expiration issues, the intended effect of multiple
818   identical requests is the same as for a single request.
819   The methods PUT, DELETE, and all safe methods are idempotent.
820   It is important to note that idempotence refers only to changes
821   requested by the client: a server is free to change its state due
822   to multiple requests for the purpose of tracking those requests,
823   versioning of results, etc.
824</t>
825</section>
826</section>
827
828<section title="OPTIONS" anchor="OPTIONS">
829  <rdf:Description>
830    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
831  </rdf:Description>
832  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
833  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
834<t>
835   The OPTIONS method represents a request for information about the
836   communication options available on the request/response chain
837   identified by the effective request URI. This method allows the client to
838   determine the options and/or requirements associated with a resource,
839   or the capabilities of a server, without implying a resource action
840   or initiating a resource retrieval.
841</t>
842<t>
843   Responses to this method are not cacheable.
844</t>
845<t>
846   If the OPTIONS request includes a message-body (as indicated by the
847   presence of Content-Length or Transfer-Encoding), then the media type
848   &MUST; be indicated by a Content-Type field. Although this
849   specification does not define any use for such a body, future
850   extensions to HTTP might use the OPTIONS body to make more detailed
851   queries on the server.
852</t>
853<t>
854   If the request-target is an asterisk ("*"), the OPTIONS request is
855   intended to apply to the server in general rather than to a specific
856   resource. Since a server's communication options typically depend on
857   the resource, the "*" request is only useful as a "ping" or "no-op"
858   type of method; it does nothing beyond allowing the client to test
859   the capabilities of the server. For example, this can be used to test
860   a proxy for HTTP/1.1 compliance (or lack thereof).
861</t>
862<t>
863   If the request-target is not an asterisk, the OPTIONS request applies
864   only to the options that are available when communicating with that
865   resource.
866</t>
867<t>
868   A 200 response &SHOULD; include any header fields that indicate
869   optional features implemented by the server and applicable to that
870   resource (e.g., Allow), possibly including extensions not defined by
871   this specification. The response body, if any, &SHOULD; also include
872   information about the communication options. The format for such a
873   body is not defined by this specification, but might be defined by
874   future extensions to HTTP. Content negotiation &MAY; be used to select
875   the appropriate response format. If no response body is included, the
876   response &MUST; include a Content-Length field with a field-value of
877   "0".
878</t>
879<t>
880   The Max-Forwards request-header field &MAY; be used to target a
881   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
882   If no Max-Forwards field is present in the request, then the forwarded
883   request &MUST-NOT; include a Max-Forwards field.
884</t>
885</section>
886
887<section title="GET" anchor="GET">
888  <rdf:Description>
889    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
890  </rdf:Description>
891  <iref primary="true" item="GET method" x:for-anchor=""/>
892  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
893<t>
894   The GET method means retrieve whatever information (in the form of a
895   representation) currently corresponds to the target resource.
896</t>
897<t>   
898   If the target resource is a data-producing process, it is the
899   produced data which shall be returned as the representation in the response and not
900   the source text of the process, unless that text happens to be the output of
901   the process.
902</t>
903<t>
904   The semantics of the GET method change to a "conditional GET" if the
905   request message includes an If-Modified-Since, If-Unmodified-Since,
906   If-Match, If-None-Match, or If-Range header field. A conditional GET
907   method requests that the representation be transferred only under the
908   circumstances described by the conditional header field(s). The
909   conditional GET method is intended to reduce unnecessary network
910   usage by allowing cached representations to be refreshed without requiring
911   multiple requests or transferring data already held by the client.
912</t>
913<t>
914   The semantics of the GET method change to a "partial GET" if the
915   request message includes a Range header field. A partial GET requests
916   that only part of the representation be transferred, as described in &header-range;.
917   The partial GET method is intended to reduce unnecessary
918   network usage by allowing partially-retrieved representations to be
919   completed without transferring data already held by the client.
920</t>
921<t>
922   The response to a GET request is cacheable and &MAY; be used to satisfy
923   subsequent GET and HEAD requests (see &caching;).
924</t>
925<t>
926   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
927</t>
928</section>
929
930<section title="HEAD" anchor="HEAD">
931  <rdf:Description>
932    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
933  </rdf:Description>
934  <iref primary="true" item="HEAD method" x:for-anchor=""/>
935  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
936<t>
937   The HEAD method is identical to GET except that the server &MUST-NOT;
938   return a message-body in the response. The metadata contained
939   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
940   to the information sent in response to a GET request. This method can
941   be used for obtaining metadata about the representation implied by the
942   request without transferring the representation body. This method is
943   often used for testing hypertext links for validity, accessibility,
944   and recent modification.
945</t>
946<t>
947   The response to a HEAD request is cacheable and &MAY; be used to satisfy
948   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
949   representation from that resource; if the new field values
950   indicate that the cached representation differs from the current representation (as
951   would be indicated by a change in Content-Length, Content-MD5, ETag
952   or Last-Modified), then the cache &MUST; treat the cache entry as
953   stale.
954</t>
955</section>
956
957<section title="POST" anchor="POST">
958  <iref primary="true" item="POST method" x:for-anchor=""/>
959  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
960<t>
961   The POST method is used to request that the origin server accept the
962   representation enclosed in the request as data to be processed by the
963   target resource. POST is designed to allow a uniform method to cover the
964   following functions:
965  <list style="symbols">
966    <t>
967      Annotation of existing resources;
968    </t>
969    <t>
970        Posting a message to a bulletin board, newsgroup, mailing list,
971        or similar group of articles;
972    </t>
973    <t>
974        Providing a block of data, such as the result of submitting a
975        form, to a data-handling process;
976    </t>
977    <t>
978        Extending a database through an append operation.
979    </t>
980  </list>
981</t>
982<t>
983   The actual function performed by the POST method is determined by the
984   server and is usually dependent on the effective request URI.
985</t>
986<t>
987   The action performed by the POST method might not result in a
988   resource that can be identified by a URI. In this case, either 200
989   (OK) or 204 (No Content) is the appropriate response status code,
990   depending on whether or not the response includes a representation that
991   describes the result.
992</t>
993<t>
994   If a resource has been created on the origin server, the response
995   &SHOULD; be 201 (Created) and contain a representation which describes the
996   status of the request and refers to the new resource, and a Location
997   header field (see <xref target="header.location"/>).
998</t>
999<t>
1000   Responses to POST requests are only cacheable when they
1001   include explicit freshness information (see &p6-explicit;). A
1002   cached POST response with a Content-Location header field
1003   (see &header-content-location;) whose value is the effective
1004   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1005</t>
1006<t>
1007   Note that POST caching is not widely implemented.
1008   However, the 303 (See Other) response can be used to direct the
1009   user agent to retrieve a cacheable resource.
1010</t>
1011</section>
1012
1013<section title="PUT" anchor="PUT">
1014  <iref primary="true" item="PUT method" x:for-anchor=""/>
1015  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1016<t>
1017   The PUT method requests that the enclosed representation be stored at the
1018   effective request URI. If the effective request URI refers to an already
1019   existing resource, the enclosed representation &SHOULD; be considered a
1020   modified version of the one residing on the origin server. Otherwise, if the
1021   effective request URI does not point to an existing resource, and that URI is
1022   capable of being defined as a new resource by the requesting user
1023   agent, the origin server can create the resource with that URI.
1024</t>
1025<t>   
1026   If a new resource is created at the effective request URI, the origin
1027   server &MUST; inform the user agent
1028   via the 201 (Created) response. If an existing resource is modified,
1029   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1030   to indicate successful completion of the request.
1031</t>
1032<t>   
1033   If the target resource could not be created or modified, an appropriate
1034   error response &SHOULD; be given that reflects the nature of the problem.
1035   The recipient of the representation &MUST-NOT; ignore any Content-*
1036   header fields (headers starting with the prefix "Content-") that it does
1037   not understand or implement
1038   and &MUST; return a 501 (Not Implemented) response in such cases.
1039</t>
1040<t>
1041   If the request passes through a cache that has one or more stored
1042   responses for the effective request URI, those stored responses
1043   &SHOULD; be marked as stale if the response to the PUT request
1044   has a success status code. Responses to the PUT method are
1045   not cacheable.
1046</t>
1047<t>
1048   The fundamental difference between the POST and PUT requests is
1049   reflected in the different meaning of the effective request URI. The URI in a
1050   POST request identifies the resource that will handle the enclosed
1051   representation. That resource might be a data-accepting process, a gateway to
1052   some other protocol, or a document that accepts annotations.
1053   In contrast, the URI in a PUT request identifies the resource for
1054   which enclosed representation is a new or replacement value; the
1055   user agent knows what URI is intended and the server &MUST-NOT; attempt
1056   to apply the request to some other resource.
1057   If the server desires that the request be applied to a different URI,
1058   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1059   then make its own decision regarding whether or not to redirect the
1060   request.
1061</t>
1062<t>
1063   A single resource &MAY; be identified by many different URIs. For
1064   example, an article might have a URI for identifying "the current
1065   version" which is separate from the URI identifying each particular
1066   version. In this case, a PUT request on a general URI might result in
1067   several other URIs being defined by the origin server.
1068</t>
1069<t>
1070   HTTP/1.1 does not define how a PUT method affects the state of an
1071   origin server.
1072</t>
1073<t>
1074   Header fields in a PUT request that are recognized as representation
1075   metadata &SHOULD; be applied to the resource created or modified by
1076   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1077</t>
1078</section>
1079
1080<section title="DELETE" anchor="DELETE">
1081  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1082  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1083<t>
1084   The DELETE method requests that the origin server delete the target
1085   resource. This method &MAY; be overridden by
1086   human intervention (or other means) on the origin server. The client cannot
1087   be guaranteed that the operation has been carried out, even if the
1088   status code returned from the origin server indicates that the action
1089   has been completed successfully. However, the server &SHOULD-NOT; 
1090   indicate success unless, at the time the response is given, it
1091   intends to delete the resource or move it to an inaccessible
1092   location.
1093</t>
1094<t>
1095   A successful response &SHOULD; be 200 (OK) if the response includes an
1096   representation describing the status, 202 (Accepted) if the action has not
1097   yet been enacted, or 204 (No Content) if the action has been enacted
1098   but the response does not include a representation.
1099</t>
1100<t>
1101   If the request passes through a cache and the effective request URI
1102   identifies one or more currently cached representations, those entries &SHOULD; be
1103   treated as stale. Responses to the DELETE method are not cacheable.
1104</t>
1105</section>
1106
1107<section title="TRACE" anchor="TRACE">
1108  <rdf:Description>
1109    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1110  </rdf:Description>
1111  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1112  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1113<t>
1114   The TRACE method is used to invoke a remote, application-layer loop-back
1115   of the request message. The final recipient of the request
1116   &SHOULD; reflect the message received back to the client as the
1117   message-body of a 200 (OK) response. The final recipient is either the
1118   origin server or the first proxy or gateway to receive a Max-Forwards
1119   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1120   A TRACE request &MUST-NOT; include a message-body.
1121</t>
1122<t>
1123   TRACE allows the client to see what is being received at the other
1124   end of the request chain and use that data for testing or diagnostic
1125   information. The value of the Via header field (&header-via;) is of
1126   particular interest, since it acts as a trace of the request chain.
1127   Use of the Max-Forwards header field allows the client to limit the
1128   length of the request chain, which is useful for testing a chain of
1129   proxies forwarding messages in an infinite loop.
1130</t>
1131<t>
1132   If the request is valid, the response &SHOULD; have a Content-Type of
1133   "message/http" (see &media-type-message-http;) and contain a message-body
1134   that encloses a copy of the entire request message.
1135   Responses to the TRACE method are not cacheable.
1136</t>
1137</section>
1138
1139<section title="CONNECT" anchor="CONNECT">
1140  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1141  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1142<t>
1143   This specification reserves the method name CONNECT for use with a
1144   proxy that can dynamically switch to being a tunnel (e.g., SSL
1145   tunneling <xref target="RFC2817"/>).
1146</t>
1147</section>
1148</section>
1149
1150
1151<section title="Status Code Definitions" anchor="status.codes">
1152<t>
1153   Each Status-Code is described below, including any metadata required
1154   in the response.
1155</t>
1156
1157<section title="Informational 1xx" anchor="status.1xx">
1158<t>
1159   This class of status code indicates a provisional response,
1160   consisting only of the Status-Line and optional header fields, and is
1161   terminated by an empty line. There are no required header fields for this
1162   class of status code. Since HTTP/1.0 did not define any 1xx status
1163   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1164   except under experimental conditions.
1165</t>
1166<t>
1167   A client &MUST; be prepared to accept one or more 1xx status responses
1168   prior to a regular response, even if the client does not expect a 100
1169   (Continue) status message. Unexpected 1xx status responses &MAY; be
1170   ignored by a user agent.
1171</t>
1172<t>
1173   Proxies &MUST; forward 1xx responses, unless the connection between the
1174   proxy and its client has been closed, or unless the proxy itself
1175   requested the generation of the 1xx response. (For example, if a
1176   proxy adds a "Expect: 100-continue" field when it forwards a request,
1177   then it need not forward the corresponding 100 (Continue)
1178   response(s).)
1179</t>
1180
1181<section title="100 Continue" anchor="status.100">
1182  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1183  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1184<t>
1185   The client &SHOULD; continue with its request. This interim response is
1186   used to inform the client that the initial part of the request has
1187   been received and has not yet been rejected by the server. The client
1188   &SHOULD; continue by sending the remainder of the request or, if the
1189   request has already been completed, ignore this response. The server
1190   &MUST; send a final response after the request has been completed. See
1191   &use100; for detailed discussion of the use and handling of this
1192   status code.
1193</t>
1194</section>
1195
1196<section title="101 Switching Protocols" anchor="status.101">
1197  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1198  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1199<t>
1200   The server understands and is willing to comply with the client's
1201   request, via the Upgrade message header field (&header-upgrade;), for a
1202   change in the application protocol being used on this connection. The
1203   server will switch protocols to those defined by the response's
1204   Upgrade header field immediately after the empty line which
1205   terminates the 101 response.
1206</t>
1207<t>
1208   The protocol &SHOULD; be switched only when it is advantageous to do
1209   so. For example, switching to a newer version of HTTP is advantageous
1210   over older versions, and switching to a real-time, synchronous
1211   protocol might be advantageous when delivering resources that use
1212   such features.
1213</t>
1214</section>
1215</section>
1216
1217<section title="Successful 2xx" anchor="status.2xx">
1218<t>
1219   This class of status code indicates that the client's request was
1220   successfully received, understood, and accepted.
1221</t>
1222
1223<section title="200 OK" anchor="status.200">
1224  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1225  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1226<t>
1227   The request has succeeded. The payload returned with the response
1228   is dependent on the method used in the request, for example:
1229  <list style="hanging">
1230    <t hangText="GET">
1231          a representation of the target resource is sent in the response;
1232    </t>
1233    <t hangText="HEAD">
1234          the same representation as GET, except without the message-body;
1235    </t>
1236    <t hangText="POST">
1237      a representation describing or containing the result of the action;
1238    </t>
1239    <t hangText="TRACE">
1240      a representation containing the request message as received by the
1241      end server.
1242    </t>
1243  </list>
1244</t>
1245<t>
1246   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1247   freshness for 200 responses.
1248</t>
1249</section>
1250
1251<section title="201 Created" anchor="status.201">
1252  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1253  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1254<t>
1255   The request has been fulfilled and has resulted in a new resource being
1256   created. The newly created resource can be referenced by the URI(s)
1257   returned in the payload of the response, with the most specific URI
1258   for the resource given by a Location header field. The response
1259   &SHOULD; include a payload containing a list of resource
1260   characteristics and location(s) from which the user or user agent can
1261   choose the one most appropriate. The payload format is specified by
1262   the media type given in the Content-Type header field. The origin
1263   server &MUST; create the resource before returning the 201 status code.
1264   If the action cannot be carried out immediately, the server &SHOULD;
1265   respond with 202 (Accepted) response instead.
1266</t>
1267<t>
1268   A 201 response &MAY; contain an ETag response header field indicating
1269   the current value of the entity-tag for the representation of the resource
1270   just created (see &header-etag;).
1271</t>
1272</section>
1273
1274<section title="202 Accepted" anchor="status.202">
1275  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1276  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1277<t>
1278   The request has been accepted for processing, but the processing has
1279   not been completed.  The request might or might not eventually be
1280   acted upon, as it might be disallowed when processing actually takes
1281   place. There is no facility for re-sending a status code from an
1282   asynchronous operation such as this.
1283</t>
1284<t>
1285   The 202 response is intentionally non-committal. Its purpose is to
1286   allow a server to accept a request for some other process (perhaps a
1287   batch-oriented process that is only run once per day) without
1288   requiring that the user agent's connection to the server persist
1289   until the process is completed. The representation returned with this
1290   response &SHOULD; include an indication of the request's current status
1291   and either a pointer to a status monitor or some estimate of when the
1292   user can expect the request to be fulfilled.
1293</t>
1294</section>
1295
1296<section title="203 Non-Authoritative Information" anchor="status.203">
1297  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1298  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1299<t>
1300   The returned metadata in the header fields is not the
1301   definitive set as available from the origin server, but is gathered
1302   from a local or a third-party copy. The set presented &MAY; be a subset
1303   or superset of the original version. For example, including local
1304   annotation information about the resource might result in a superset
1305   of the metadata known by the origin server. Use of this
1306   response code is not required and is only appropriate when the
1307   response would otherwise be 200 (OK).
1308</t>
1309<t>
1310   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1311   freshness for 203 responses.
1312</t>
1313
1314</section>
1315
1316<section title="204 No Content" anchor="status.204">
1317  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1318  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1319<t>
1320   The server has successfully fulfilled the request, but there is no
1321   additional content to return in the response payload body.  The
1322   resource metadata and representation metadata in the response message's
1323   header fields refer to the target resource
1324   and its current representation, respectively, after the requested action.
1325   For example, if a 204 status code is received in response to a PUT
1326   and the response contains an ETag header field, then the value of
1327   that field is the current entity-tag for the representation that
1328   was successfully PUT.
1329</t>
1330<t>
1331   If the client is a user agent, it &SHOULD-NOT; change its document view
1332   from that which caused the request to be sent. This response is
1333   primarily intended to allow input for actions to take place without
1334   causing a change to the user agent's active document view, although
1335   any new or updated metadata &SHOULD; be applied to the document
1336   currently in the user agent's active view.
1337</t>
1338<t>
1339   The 204 response &MUST-NOT; include a message-body, and thus is always
1340   terminated by the first empty line after the header fields.
1341</t>
1342</section>
1343
1344<section title="205 Reset Content" anchor="status.205">
1345  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1346  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1347<t>
1348   The server has fulfilled the request and the user agent &SHOULD; reset
1349   the document view which caused the request to be sent. This response
1350   is primarily intended to allow input for actions to take place via
1351   user input, followed by a clearing of the form in which the input is
1352   given so that the user can easily initiate another input action. The
1353   response &MUST-NOT; include a message-body.
1354</t>
1355</section>
1356
1357<section title="206 Partial Content" anchor="status.206">
1358  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1359  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1360  <rdf:Description>
1361    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1362  </rdf:Description>
1363<t>
1364   The server has fulfilled the partial GET request for the resource
1365   and the enclosed payload is a partial representation as defined in &status-206;.
1366</t>
1367<t>
1368   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1369   freshness for 206 responses.
1370</t>
1371</section>
1372</section>
1373
1374<section title="Redirection 3xx" anchor="status.3xx">
1375<t>
1376   This class of status code indicates that further action needs to be
1377   taken by the user agent in order to fulfill the request.  The action
1378   required &MAY; be carried out by the user agent without interaction
1379   with the user if and only if the method used in the second request is
1380   known to be "safe", as defined in <xref target="safe.methods"/>.
1381   A client &SHOULD; detect infinite redirection loops, since such loops
1382   generate network traffic for each redirection.
1383</t>
1384<x:note>
1385  <t>
1386    <x:h>Note:</x:h> An earlier version of this specification recommended a
1387    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1388    Content developers need to be aware that some clients might
1389    implement such a fixed limitation.
1390  </t>
1391</x:note>
1392
1393<section title="300 Multiple Choices" anchor="status.300">
1394  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1395  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1396<t>
1397   The target resource has more than one
1398   representation, each with its own specific location, and agent-driven
1399   negotiation information (&content-negotiation;) is being provided so that
1400   the user (or user agent) can select a preferred representation by
1401   redirecting its request to that location.
1402</t>
1403<t>
1404   Unless it was a HEAD request, the response &SHOULD; include a representation
1405   containing a list of representation metadata and location(s) from
1406   which the user or user agent can choose the one most appropriate. The
1407   data format is specified by the media type given in the Content-Type
1408   header field. Depending upon the format and the capabilities of
1409   the user agent, selection of the most appropriate choice &MAY; be
1410   performed automatically. However, this specification does not define
1411   any standard for such automatic selection.
1412</t>
1413<t>
1414   If the server has a preferred choice of representation, it &SHOULD;
1415   include the specific URI for that representation in the Location
1416   field; user agents &MAY; use the Location field value for automatic
1417   redirection.
1418</t>
1419<t>
1420   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1421   freshness for 300 responses.
1422</t>
1423
1424</section>
1425
1426<section title="301 Moved Permanently" anchor="status.301">
1427  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1428  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1429<t>
1430   The target resource has been assigned a new permanent URI and any
1431   future references to this resource &SHOULD; use one of the returned
1432   URIs.  Clients with link editing capabilities ought to automatically
1433   re-link references to the effective request URI to one or more of the new
1434   references returned by the server, where possible.
1435</t>
1436<t>
1437   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1438   freshness for 301 responses.
1439</t>
1440<t>
1441   The new permanent URI &SHOULD; be given by the Location field in the
1442   response. Unless the request method was HEAD, the representation of the
1443   response &SHOULD; contain a short hypertext note with a hyperlink to
1444   the new URI(s).
1445</t>
1446<t>
1447   If the 301 status code is received in response to a request method
1448   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1449   then the request &MAY; be automatically redirected by the user agent without
1450   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1451   request unless it can be confirmed by the user, since this might
1452   change the conditions under which the request was issued.
1453</t>
1454<x:note>
1455  <t>
1456    <x:h>Note:</x:h> When automatically redirecting a POST request after
1457    receiving a 301 status code, some existing HTTP/1.0 user agents
1458    will erroneously change it into a GET request.
1459  </t>
1460</x:note>
1461</section>
1462
1463<section title="302 Found" anchor="status.302">
1464  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1466<t>
1467   The target resource resides temporarily under a different URI.
1468   Since the redirection might be altered on occasion, the client &SHOULD;
1469   continue to use the effective request URI for future requests.
1470</t>
1471<t>
1472   The temporary URI &SHOULD; be given by the Location field in the
1473   response. Unless the request method was HEAD, the representation of the
1474   response &SHOULD; contain a short hypertext note with a hyperlink to
1475   the new URI(s).
1476</t>
1477<t>
1478   If the 302 status code is received in response to a request method
1479   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1480   then the request &MAY; be automatically redirected by the user agent without
1481   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1482   request unless it can be confirmed by the user, since this might
1483   change the conditions under which the request was issued.
1484</t>
1485<x:note>
1486  <t>
1487    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1488    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1489    specify that the client is not allowed to change the method on the
1490    redirected request.  However, most existing user agent implementations
1491    treat 302 as if it were a 303 response, performing a GET on the Location
1492    field-value regardless of the original request method. Therefore, a
1493    previous version of this specification
1494    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1495    status codes
1496    <xref target="status.303" format="none">303</xref> and
1497    <xref target="status.307" format="none">307</xref> for servers that wish
1498    to make unambiguously clear which kind of reaction is expected of the
1499    client.
1500  </t>
1501</x:note>
1502</section>
1503
1504<section title="303 See Other" anchor="status.303">
1505  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1506  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1507<t>
1508   The server directs the user agent to a different resource, indicated
1509   by a URI in the Location header field, that provides an indirect
1510   response to the original request.  The user agent &MAY; perform a GET
1511   request on the URI in the Location field in order to obtain a
1512   representation corresponding to the response, be redirected again,
1513   or end with an error status.  The Location URI is not a substitute
1514   reference for the effective request URI.
1515</t>
1516<t>
1517   The 303 status code is generally applicable to any HTTP method.  It is
1518   primarily used to allow the output of a POST action to redirect
1519   the user agent to a selected resource, since doing so provides the
1520   information corresponding to the POST response in a form that
1521   can be separately identified, bookmarked, and cached independent
1522   of the original request.
1523</t>
1524<t>
1525   A 303 response to a GET request indicates that the requested
1526   resource does not have a representation of its own that can be
1527   transferred by the server over HTTP.  The Location URI indicates a
1528   resource that is descriptive of the target resource, such that the
1529   follow-on representation might be useful to recipients without
1530   implying that it adequately represents the target resource.
1531   Note that answers to the questions of what can be represented, what
1532   representations are adequate, and what might be a useful description
1533   are outside the scope of HTTP and thus entirely determined by the
1534   URI owner(s).
1535</t>
1536<t>
1537   Except for responses to a HEAD request, the representation of a 303
1538   response &SHOULD; contain a short hypertext note with a hyperlink
1539   to the Location URI.
1540</t>
1541</section>
1542
1543<section title="304 Not Modified" anchor="status.304">
1544  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1545  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1546  <rdf:Description>
1547    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1548  </rdf:Description>
1549<t>
1550   The response to the request has not been modified since the conditions
1551   indicated by the client's conditional GET request, as defined in &status-304;.
1552</t>
1553</section>
1554
1555<section title="305 Use Proxy" anchor="status.305">
1556  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1558<t>
1559   The 305 status code was defined in a previous version of this specification
1560   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1561</t>
1562</section>
1563
1564<section title="306 (Unused)" anchor="status.306">
1565  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1566  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1567<t>
1568   The 306 status code was used in a previous version of the
1569   specification, is no longer used, and the code is reserved.
1570</t>
1571</section>
1572
1573<section title="307 Temporary Redirect" anchor="status.307">
1574  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1575  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1576<t>
1577   The target resource resides temporarily under a different URI.
1578   Since the redirection can change over time, the client &SHOULD;
1579   continue to use the effective request URI for future requests.
1580</t>
1581<t>
1582   The temporary URI &SHOULD; be given by the Location field in the
1583   response. Unless the request method was HEAD, the representation of the
1584   response &SHOULD; contain a short hypertext note with a hyperlink to
1585   the new URI(s), since many pre-HTTP/1.1 user agents do not
1586   understand the 307 status code. Therefore, the note &SHOULD; contain the
1587   information necessary for a user to repeat the original request on
1588   the new URI.
1589</t>
1590<t>
1591   If the 307 status code is received in response to a request method
1592   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1593   then the request &MAY; be automatically redirected by the user agent without
1594   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1595   request unless it can be confirmed by the user, since this might
1596   change the conditions under which the request was issued.
1597</t>
1598</section>
1599</section>
1600
1601<section title="Client Error 4xx" anchor="status.4xx">
1602<t>
1603   The 4xx class of status code is intended for cases in which the
1604   client seems to have erred. Except when responding to a HEAD request,
1605   the server &SHOULD; include a representation containing an explanation of the
1606   error situation, and whether it is a temporary or permanent
1607   condition. These status codes are applicable to any request method.
1608   User agents &SHOULD; display any included representation to the user.
1609</t>
1610<t>
1611   If the client is sending data, a server implementation using TCP
1612   &SHOULD; be careful to ensure that the client acknowledges receipt of
1613   the packet(s) containing the response, before the server closes the
1614   input connection. If the client continues sending data to the server
1615   after the close, the server's TCP stack will send a reset packet to
1616   the client, which might erase the client's unacknowledged input buffers
1617   before they can be read and interpreted by the HTTP application.
1618</t>
1619
1620<section title="400 Bad Request" anchor="status.400">
1621  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1622  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1623<t>
1624   The request could not be understood by the server due to malformed
1625   syntax. The client &SHOULD-NOT; repeat the request without
1626   modifications.
1627</t>
1628</section>
1629
1630<section title="401 Unauthorized" anchor="status.401">
1631  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1632  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1633  <rdf:Description>
1634    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1635  </rdf:Description>
1636<t>
1637   The request requires user authentication (see &status-401;).
1638</t>
1639</section>
1640
1641<section title="402 Payment Required" anchor="status.402">
1642  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1643  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1644<t>
1645   This code is reserved for future use.
1646</t>
1647</section>
1648
1649<section title="403 Forbidden" anchor="status.403">
1650  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1651  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1652<t>
1653   The server understood the request, but is refusing to fulfill it.
1654   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1655   If the request method was not HEAD and the server wishes to make
1656   public why the request has not been fulfilled, it &SHOULD; describe the
1657   reason for the refusal in the representation.  If the server does not wish to
1658   make this information available to the client, the status code 404
1659   (Not Found) can be used instead.
1660</t>
1661</section>
1662
1663<section title="404 Not Found" anchor="status.404">
1664  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1665  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1666<t>
1667   The server has not found anything matching the effective request URI. No
1668   indication is given of whether the condition is temporary or
1669   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1670   knows, through some internally configurable mechanism, that an old
1671   resource is permanently unavailable and has no forwarding address.
1672   This status code is commonly used when the server does not wish to
1673   reveal exactly why the request has been refused, or when no other
1674   response is applicable.
1675</t>
1676</section>
1677
1678<section title="405 Method Not Allowed" anchor="status.405">
1679  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1680  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1681<t>
1682   The method specified in the Request-Line is not allowed for the target
1683   resource. The response &MUST; include an
1684   Allow header field containing a list of valid methods for the requested
1685   resource.
1686</t>
1687</section>
1688
1689<section title="406 Not Acceptable" anchor="status.406">
1690  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1691  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1692<t>
1693   The resource identified by the request is only capable of generating
1694   response representations which have content characteristics not acceptable
1695   according to the accept header fields sent in the request.
1696</t>
1697<t>
1698   Unless it was a HEAD request, the response &SHOULD; include a representation
1699   containing a list of available representation characteristics and location(s)
1700   from which the user or user agent can choose the one most
1701   appropriate. The data format is specified by the media type given
1702   in the Content-Type header field. Depending upon the format and the
1703   capabilities of the user agent, selection of the most appropriate
1704   choice &MAY; be performed automatically. However, this specification
1705   does not define any standard for such automatic selection.
1706</t>
1707<x:note>
1708  <t>
1709    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1710    not acceptable according to the accept header fields sent in the
1711    request. In some cases, this might even be preferable to sending a
1712    406 response. User agents are encouraged to inspect the header fields of
1713    an incoming response to determine if it is acceptable.
1714  </t>
1715</x:note>
1716<t>
1717   If the response could be unacceptable, a user agent &SHOULD;
1718   temporarily stop receipt of more data and query the user for a
1719   decision on further actions.
1720</t>
1721</section>
1722
1723<section title="407 Proxy Authentication Required" anchor="status.407">
1724  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1725  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1726<t>
1727   This code is similar to 401 (Unauthorized), but indicates that the
1728   client must first authenticate itself with the proxy (see &status-407;).
1729</t>
1730</section>
1731
1732<section title="408 Request Timeout" anchor="status.408">
1733  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1735<t>
1736   The client did not produce a request within the time that the server
1737   was prepared to wait. The client &MAY; repeat the request without
1738   modifications at any later time.
1739</t>
1740</section>
1741
1742<section title="409 Conflict" anchor="status.409">
1743  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1744  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1745<t>
1746   The request could not be completed due to a conflict with the current
1747   state of the resource. This code is only allowed in situations where
1748   it is expected that the user might be able to resolve the conflict
1749   and resubmit the request. The response body &SHOULD; include enough
1750   information for the user to recognize the source of the conflict.
1751   Ideally, the response representation would include enough information for the
1752   user or user agent to fix the problem; however, that might not be
1753   possible and is not required.
1754</t>
1755<t>
1756   Conflicts are most likely to occur in response to a PUT request. For
1757   example, if versioning were being used and the representation being PUT
1758   included changes to a resource which conflict with those made by an
1759   earlier (third-party) request, the server might use the 409 response
1760   to indicate that it can't complete the request. In this case, the
1761   response representation would likely contain a list of the differences
1762   between the two versions in a format defined by the response
1763   Content-Type.
1764</t>
1765</section>
1766
1767<section title="410 Gone" anchor="status.410">
1768  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1769  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1770<t>
1771   The target resource is no longer available at the server and no
1772   forwarding address is known. This condition is expected to be
1773   considered permanent. Clients with link editing capabilities &SHOULD;
1774   delete references to the effective request URI after user approval. If the
1775   server does not know, or has no facility to determine, whether or not
1776   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1777   used instead.
1778</t>
1779<t>
1780   The 410 response is primarily intended to assist the task of web
1781   maintenance by notifying the recipient that the resource is
1782   intentionally unavailable and that the server owners desire that
1783   remote links to that resource be removed. Such an event is common for
1784   limited-time, promotional services and for resources belonging to
1785   individuals no longer working at the server's site. It is not
1786   necessary to mark all permanently unavailable resources as "gone" or
1787   to keep the mark for any length of time -- that is left to the
1788   discretion of the server owner.
1789</t>
1790<t>
1791   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1792   for 410 responses.
1793</t>
1794
1795</section>
1796
1797<section title="411 Length Required" anchor="status.411">
1798  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1799  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1800<t>
1801   The server refuses to accept the request without a defined Content-Length.
1802   The client &MAY; repeat the request if it adds a valid
1803   Content-Length header field containing the length of the message-body
1804   in the request message.
1805</t>
1806</section>
1807
1808<section title="412 Precondition Failed" anchor="status.412">
1809  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1810  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1811  <rdf:Description>
1812    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1813  </rdf:Description>
1814<t>
1815   The precondition given in one or more of the request-header fields
1816   evaluated to false when it was tested on the server, as defined in
1817   &status-412;.
1818</t>
1819</section>
1820
1821<section title="413 Request Entity Too Large" anchor="status.413">
1822  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1823  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1824<t>
1825   The server is refusing to process a request because the request
1826   representation is larger than the server is willing or able to process. The
1827   server &MAY; close the connection to prevent the client from continuing
1828   the request.
1829</t>
1830<t>
1831   If the condition is temporary, the server &SHOULD; include a Retry-After
1832   header field to indicate that it is temporary and after what
1833   time the client &MAY; try again.
1834</t>
1835</section>
1836
1837<section title="414 URI Too Long" anchor="status.414">
1838  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1839  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1840<t>
1841   The server is refusing to service the request because the effective request URI
1842   is longer than the server is willing to interpret. This rare
1843   condition is only likely to occur when a client has improperly
1844   converted a POST request to a GET request with long query
1845   information, when the client has descended into a URI "black hole" of
1846   redirection (e.g., a redirected URI prefix that points to a suffix of
1847   itself), or when the server is under attack by a client attempting to
1848   exploit security holes present in some servers using fixed-length
1849   buffers for reading or manipulating the effective request URI.
1850</t>
1851</section>
1852
1853<section title="415 Unsupported Media Type" anchor="status.415">
1854  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1855  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1856<t>
1857   The server is refusing to service the request because the representation of
1858   the request is in a format not supported by the target resource
1859   for the requested method.
1860</t>
1861</section>
1862
1863<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1864  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1865  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1866  <rdf:Description>
1867    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1868  </rdf:Description>
1869<t>
1870   The request included a Range request-header field (&header-range;) and none of
1871   the range-specifier values in this field overlap the current extent
1872   of the selected resource. See &status-416;.
1873</t>
1874</section>
1875
1876<section title="417 Expectation Failed" anchor="status.417">
1877  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1878  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1879<t>
1880   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1881   could not be met by this server, or, if the server is a proxy,
1882   the server has unambiguous evidence that the request could not be met
1883   by the next-hop server.
1884</t>
1885</section>
1886</section>
1887
1888<section title="Server Error 5xx" anchor="status.5xx">
1889<t>
1890   Response status codes beginning with the digit "5" indicate cases in
1891   which the server is aware that it has erred or is incapable of
1892   performing the request. Except when responding to a HEAD request, the
1893   server &SHOULD; include a representation containing an explanation of the
1894   error situation, and whether it is a temporary or permanent
1895   condition. User agents &SHOULD; display any included representation to the
1896   user. These response codes are applicable to any request method.
1897</t>
1898
1899<section title="500 Internal Server Error" anchor="status.500">
1900  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1901  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1902<t>
1903   The server encountered an unexpected condition which prevented it
1904   from fulfilling the request.
1905</t>
1906</section>
1907
1908<section title="501 Not Implemented" anchor="status.501">
1909  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1910  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1911<t>
1912   The server does not support the functionality required to fulfill the
1913   request. This is the appropriate response when the server does not
1914   recognize the request method and is not capable of supporting it for
1915   any resource.
1916</t>
1917</section>
1918
1919<section title="502 Bad Gateway" anchor="status.502">
1920  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1921  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1922<t>
1923   The server, while acting as a gateway or proxy, received an invalid
1924   response from the upstream server it accessed in attempting to
1925   fulfill the request.
1926</t>
1927</section>
1928
1929<section title="503 Service Unavailable" anchor="status.503">
1930  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1931  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1932<t>
1933   The server is currently unable to handle the request due to a
1934   temporary overloading or maintenance of the server. The implication
1935   is that this is a temporary condition which will be alleviated after
1936   some delay. If known, the length of the delay &MAY; be indicated in a
1937   Retry-After header field. If no Retry-After is given, the client &SHOULD;
1938   handle the response as it would for a 500 response.
1939</t>
1940<x:note>
1941  <t>
1942    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1943    server must use it when becoming overloaded. Some servers might wish
1944    to simply refuse the connection.
1945  </t>
1946</x:note>
1947</section>
1948
1949<section title="504 Gateway Timeout" anchor="status.504">
1950  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1951  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1952<t>
1953   The server, while acting as a gateway or proxy, did not receive a
1954   timely response from the upstream server specified by the URI (e.g.,
1955   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1956   to access in attempting to complete the request.
1957</t>
1958<x:note>
1959  <t>
1960    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1961    return 400 or 500 when DNS lookups time out.
1962  </t>
1963</x:note>
1964</section>
1965
1966<section title="505 HTTP Version Not Supported" anchor="status.505">
1967  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1968  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1969<t>
1970   The server does not support, or refuses to support, the protocol
1971   version that was used in the request message. The server is
1972   indicating that it is unable or unwilling to complete the request
1973   using the same major version as the client, as described in &http-version;,
1974   other than with this error message. The response &SHOULD; contain
1975   a representation describing why that version is not supported and what other
1976   protocols are supported by that server.
1977</t>
1978
1979</section>
1980</section>
1981</section>
1982
1983
1984<section title="Header Field Definitions" anchor="header.fields">
1985<t>
1986   This section defines the syntax and semantics of HTTP/1.1 header fields
1987   related to request and response semantics.
1988</t>
1989
1990<section title="Allow" anchor="header.allow">
1991  <iref primary="true" item="Allow header" x:for-anchor=""/>
1992  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1993  <x:anchor-alias value="Allow"/>
1994  <x:anchor-alias value="Allow-v"/>
1995<t>
1996   The "Allow" response-header field lists the set of methods advertised as
1997   supported by the target resource. The purpose of
1998   this field is strictly to inform the recipient of valid methods
1999   associated with the resource.
2000</t>
2001<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2002  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2003  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2004</artwork></figure>
2005<t>
2006      Example of use:
2007</t>
2008<figure><artwork type="example">
2009  Allow: GET, HEAD, PUT
2010</artwork></figure>
2011<t>
2012      The actual set of allowed methods is defined
2013      by the origin server at the time of each request.
2014</t>
2015<t>
2016      A proxy &MUST-NOT; modify the Allow header field even if it does not
2017      understand all the methods specified, since the user agent might
2018      have other means of communicating with the origin server.
2019</t>
2020</section>
2021
2022<section title="Expect" anchor="header.expect">
2023  <iref primary="true" item="Expect header" x:for-anchor=""/>
2024  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
2025  <x:anchor-alias value="Expect"/>
2026  <x:anchor-alias value="Expect-v"/>
2027  <x:anchor-alias value="expectation"/>
2028  <x:anchor-alias value="expectation-extension"/>
2029  <x:anchor-alias value="expect-params"/>
2030<t>
2031   The "Expect" request-header field is used to indicate that particular
2032   server behaviors are required by the client.
2033</t>
2034<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"/>
2035  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2036  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2037 
2038  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2039  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2040                           *<x:ref>expect-params</x:ref> ]
2041  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2042</artwork></figure>
2043<t>
2044   A server that does not understand or is unable to comply with any of
2045   the expectation values in the Expect field of a request &MUST; respond
2046   with appropriate error status code. The server &MUST; respond with a 417
2047   (Expectation Failed) status code if any of the expectations cannot be met
2048   or, if there are other problems with the request, some other 4xx
2049   status code.
2050</t>
2051<t>
2052   This header field is defined with extensible syntax to allow for
2053   future extensions. If a server receives a request containing an
2054   Expect field that includes an expectation-extension that it does not
2055   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2056</t>
2057<t>
2058   Comparison of expectation values is case-insensitive for unquoted
2059   tokens (including the 100-continue token), and is case-sensitive for
2060   quoted-string expectation-extensions.
2061</t>
2062<t>
2063   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2064   return a 417 (Expectation Failed) status code if it receives a request
2065   with an expectation that it cannot meet. However, the Expect
2066   request-header field itself is end-to-end; it &MUST; be forwarded if the
2067   request is forwarded.
2068</t>
2069<t>
2070   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2071   Expect header field.
2072</t>
2073<t>
2074   See &use100; for the use of the 100 (Continue) status code.
2075</t>
2076</section>
2077
2078<section title="From" anchor="header.from">
2079  <iref primary="true" item="From header" x:for-anchor=""/>
2080  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2081  <x:anchor-alias value="From"/>
2082  <x:anchor-alias value="From-v"/>
2083  <x:anchor-alias value="mailbox"/>
2084<t>
2085   The "From" request-header field, if given, &SHOULD; contain an Internet
2086   e-mail address for the human user who controls the requesting user
2087   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2088   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2089</t>
2090<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2091  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2092  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2093 
2094  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2095</artwork></figure>
2096<t>
2097   An example is:
2098</t>
2099<figure><artwork type="example">
2100  From: webmaster@example.org
2101</artwork></figure>
2102<t>
2103   This header field &MAY; be used for logging purposes and as a means for
2104   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2105   be used as an insecure form of access protection. The interpretation
2106   of this field is that the request is being performed on behalf of the
2107   person given, who accepts responsibility for the method performed. In
2108   particular, robot agents &SHOULD; include this header field so that the
2109   person responsible for running the robot can be contacted if problems
2110   occur on the receiving end.
2111</t>
2112<t>
2113   The Internet e-mail address in this field &MAY; be separate from the
2114   Internet host which issued the request. For example, when a request
2115   is passed through a proxy the original issuer's address &SHOULD; be
2116   used.
2117</t>
2118<t>
2119   The client &SHOULD-NOT;  send the From header field without the user's
2120   approval, as it might conflict with the user's privacy interests or
2121   their site's security policy. It is strongly recommended that the
2122   user be able to disable, enable, and modify the value of this field
2123   at any time prior to a request.
2124</t>
2125</section>
2126
2127<section title="Location" anchor="header.location">
2128  <iref primary="true" item="Location header" x:for-anchor=""/>
2129  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2130  <x:anchor-alias value="Location"/>
2131  <x:anchor-alias value="Location-v"/>
2132<t>
2133   The "Location" response-header field is used to identify a newly created
2134   resource, or to redirect the recipient to a different location for
2135   completion of the request.
2136</t>
2137<t>
2138   For 201 (Created) responses, the Location is the URI of the new resource
2139   which was created by the request. For 3xx responses, the location &SHOULD;
2140   indicate the server's preferred URI for automatic redirection to the
2141   resource.
2142</t>
2143<t>
2144   The field value consists of a single URI-reference. When it has the form
2145   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2146   the final value is computed by resolving it against the effective request
2147   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2148</t>
2149<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2150  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2151  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2152</artwork></figure>
2153<figure>
2154<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2155<artwork type="example">
2156  Location: http://www.example.org/pub/WWW/People.html#tim
2157</artwork></figure><figure><artwork type="example">  Location: /index.html
2158</artwork></figure>
2159<t>
2160   There are circumstances in which a fragment identifier in a Location URI
2161   would not be appropriate:
2162   <list style="symbols">
2163      <t>With a 201 Created response, because in this usage the Location header
2164      field specifies the URI for the entire created resource.</t>
2165      <t>With 305 Use Proxy.</t>
2166   </list>
2167</t>
2168<x:note>
2169  <t>
2170    <x:h>Note:</x:h> This specification does not define precedence rules
2171    for the case where the original URI, as navigated to by the user
2172    agent, and the Location header field value both contain fragment
2173    identifiers.
2174  </t>
2175</x:note>
2176<x:note>
2177  <t>
2178    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2179    from Location in that the Content-Location identifies the most specific
2180    resource corresponding to the enclosed representation.
2181    It is therefore possible for a response to contain header fields for
2182    both Location and Content-Location.
2183  </t>
2184</x:note>
2185</section>
2186
2187<section title="Max-Forwards" anchor="header.max-forwards">
2188  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2189  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2190  <x:anchor-alias value="Max-Forwards"/>
2191  <x:anchor-alias value="Max-Forwards-v"/>
2192<t>
2193   The "Max-Forwards" request-header field provides a mechanism with the
2194   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2195   methods to limit the number of times that the request is forwarded by
2196   proxies or gateways. This can be useful when the client is attempting to
2197   trace a request which appears to be failing or looping in mid-chain.
2198</t>
2199<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2200  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2201  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2202</artwork></figure>
2203<t>
2204   The Max-Forwards value is a decimal integer indicating the remaining
2205   number of times this request message can be forwarded.
2206</t>
2207<t>
2208   Each proxy or gateway recipient of a TRACE or OPTIONS request
2209   containing a Max-Forwards header field &MUST; check and update its
2210   value prior to forwarding the request. If the received value is zero
2211   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2212   respond as the final recipient. If the received Max-Forwards value is
2213   greater than zero, then the forwarded message &MUST; contain an updated
2214   Max-Forwards field with a value decremented by one (1).
2215</t>
2216<t>
2217   The Max-Forwards header field &MAY; be ignored for all other methods
2218   defined by this specification and for any extension methods for which
2219   it is not explicitly referred to as part of that method definition.
2220</t>
2221</section>
2222
2223<section title="Referer" anchor="header.referer">
2224  <iref primary="true" item="Referer header" x:for-anchor=""/>
2225  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2226  <x:anchor-alias value="Referer"/>
2227  <x:anchor-alias value="Referer-v"/>
2228<t>
2229   The "Referer" [sic] request-header field allows the client to specify the
2230   URI of the resource from which the effective request URI was obtained (the
2231   "referrer", although the header field is misspelled.).
2232</t>
2233<t>
2234   The Referer header field allows servers to generate lists of back-links to
2235   resources for interest, logging, optimized caching, etc. It also allows
2236   obsolete or mistyped links to be traced for maintenance. Some servers use
2237   Referer as a means of controlling where they allow links from (so-called
2238   "deep linking"), but legitimate requests do not always
2239   contain a Referer header field.
2240</t>
2241<t>
2242   If the effective request URI was obtained from a source that does not have its own
2243   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2244   sent with the value "about:blank", or not be sent at all. Note that this
2245   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2246</t>
2247<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2248  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2249  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2250</artwork></figure>
2251<t>
2252   Example:
2253</t>
2254<figure><artwork type="example">
2255  Referer: http://www.example.org/hypertext/Overview.html
2256</artwork></figure>
2257<t>
2258   If the field value is a relative URI, it &SHOULD; be interpreted
2259   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2260   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2261</t>
2262</section>
2263
2264<section title="Retry-After" anchor="header.retry-after">
2265  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2266  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2267  <x:anchor-alias value="Retry-After"/>
2268  <x:anchor-alias value="Retry-After-v"/>
2269<t>
2270   The response-header "Retry-After" field can be used with a 503 (Service
2271   Unavailable) response to indicate how long the service is expected to
2272   be unavailable to the requesting client. This field &MAY; also be used
2273   with any 3xx (Redirection) response to indicate the minimum time the
2274   user-agent is asked wait before issuing the redirected request.
2275</t>
2276<t>
2277   The value of this field can be either an HTTP-date or an integer number
2278   of seconds (in decimal) after the time of the response.
2279</t>
2280<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2281  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2282  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2283</artwork></figure>
2284<t anchor="rule.delta-seconds">
2285  <x:anchor-alias value="delta-seconds"/>
2286   Time spans are non-negative decimal integers, representing time in
2287   seconds.
2288</t>
2289<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2290  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2291</artwork></figure>
2292<t>
2293   Two examples of its use are
2294</t>
2295<figure><artwork type="example">
2296  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2297  Retry-After: 120
2298</artwork></figure>
2299<t>
2300   In the latter example, the delay is 2 minutes.
2301</t>
2302</section>
2303
2304<section title="Server" anchor="header.server">
2305  <iref primary="true" item="Server header" x:for-anchor=""/>
2306  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2307  <x:anchor-alias value="Server"/>
2308  <x:anchor-alias value="Server-v"/>
2309<t>
2310   The "Server" response-header field contains information about the
2311   software used by the origin server to handle the request.
2312</t>
2313<t>
2314   The field can contain multiple product tokens (&product-tokens;) and
2315   comments (&header-fields;) identifying the server and any significant
2316   subproducts. The product tokens are listed in order of their significance
2317   for identifying the application.
2318</t>
2319<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2320  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2321  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2322                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2323</artwork></figure>
2324<t>
2325   Example:
2326</t>
2327<figure><artwork type="example">
2328  Server: CERN/3.0 libwww/2.17
2329</artwork></figure>
2330<t>
2331   If the response is being forwarded through a proxy, the proxy
2332   application &MUST-NOT; modify the Server response-header field. Instead, it
2333   &MUST; include a Via field (as described in &header-via;).
2334</t>
2335<x:note>
2336  <t>
2337    <x:h>Note:</x:h> Revealing the specific software version of the server might
2338    allow the server machine to become more vulnerable to attacks
2339    against software that is known to contain security holes. Server
2340    implementors are encouraged to make this field a configurable
2341    option.
2342  </t>
2343</x:note>
2344</section>
2345
2346<section title="User-Agent" anchor="header.user-agent">
2347  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2348  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2349  <x:anchor-alias value="User-Agent"/>
2350  <x:anchor-alias value="User-Agent-v"/>
2351<t>
2352   The "User-Agent" request-header field contains information about the user
2353   agent originating the request. User agents &SHOULD; include this field with
2354   requests.
2355</t>
2356<t>
2357   Typically, it is used for statistical purposes, the tracing of protocol
2358   violations, and tailoring responses to avoid particular user agent
2359   limitations.
2360</t>
2361<t>
2362   The field can contain multiple product tokens (&product-tokens;)
2363   and comments (&header-fields;) identifying the agent and its
2364   significant subproducts. By convention, the product tokens are listed in
2365   order of their significance for identifying the application.
2366</t>
2367<t>
2368   Because this field is usually sent on every request a user agent makes,
2369   implementations are encouraged not to include needlessly fine-grained
2370   detail, and to limit (or even prohibit) the addition of subproducts by third
2371   parties. Overly long and detailed User-Agent field values make requests
2372   larger and can also be used to identify ("fingerprint") the user against
2373   their wishes.
2374</t>
2375<t>
2376   Likewise, implementations are encouraged not to use the product tokens of
2377   other implementations in order to declare compatibility with them, as this
2378   circumvents the purpose of the field. Finally, they are encouraged not to
2379   use comments to identify products; doing so makes the field value more
2380   difficult to parse.
2381</t>
2382<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2383  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2384  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2385                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2386</artwork></figure>
2387<t>
2388   Example:
2389</t>
2390<figure><artwork type="example">
2391  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2392</artwork></figure>
2393</section>
2394
2395</section>
2396
2397<section title="IANA Considerations" anchor="IANA.considerations">
2398
2399<section title="Method Registry" anchor="method.registration">
2400<t>
2401  The registration procedure for HTTP Methods is defined by
2402  <xref target="method.registry"/> of this document.
2403</t>
2404<t>
2405   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2406   and be populated with the registrations below:
2407</t>
2408<?BEGININC p2-semantics.iana-methods ?>
2409<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2410<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2411   <ttcol>Method</ttcol>
2412   <ttcol>Safe</ttcol>
2413   <ttcol>Reference</ttcol>
2414   <c>CONNECT</c>
2415   <c>no</c>
2416   <c>
2417      <xref target="CONNECT"/>
2418   </c>
2419   <c>DELETE</c>
2420   <c>no</c>
2421   <c>
2422      <xref target="DELETE"/>
2423   </c>
2424   <c>GET</c>
2425   <c>yes</c>
2426   <c>
2427      <xref target="GET"/>
2428   </c>
2429   <c>HEAD</c>
2430   <c>yes</c>
2431   <c>
2432      <xref target="HEAD"/>
2433   </c>
2434   <c>OPTIONS</c>
2435   <c>yes</c>
2436   <c>
2437      <xref target="OPTIONS"/>
2438   </c>
2439   <c>POST</c>
2440   <c>no</c>
2441   <c>
2442      <xref target="POST"/>
2443   </c>
2444   <c>PUT</c>
2445   <c>no</c>
2446   <c>
2447      <xref target="PUT"/>
2448   </c>
2449   <c>TRACE</c>
2450   <c>yes</c>
2451   <c>
2452      <xref target="TRACE"/>
2453   </c>
2454</texttable>
2455<!--(END)-->
2456<?ENDINC p2-semantics.iana-methods ?>
2457</section>
2458
2459<section title="Status Code Registry" anchor="status.code.registration">
2460<t>
2461   The registration procedure for HTTP Status Codes -- previously defined
2462   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2463   by <xref target="status.code.registry"/> of this document.
2464</t>
2465<t>
2466   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2467   shall be updated with the registrations below:
2468</t>
2469<?BEGININC p2-semantics.iana-status-codes ?>
2470<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2471<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2472   <ttcol>Value</ttcol>
2473   <ttcol>Description</ttcol>
2474   <ttcol>Reference</ttcol>
2475   <c>100</c>
2476   <c>Continue</c>
2477   <c>
2478      <xref target="status.100"/>
2479   </c>
2480   <c>101</c>
2481   <c>Switching Protocols</c>
2482   <c>
2483      <xref target="status.101"/>
2484   </c>
2485   <c>200</c>
2486   <c>OK</c>
2487   <c>
2488      <xref target="status.200"/>
2489   </c>
2490   <c>201</c>
2491   <c>Created</c>
2492   <c>
2493      <xref target="status.201"/>
2494   </c>
2495   <c>202</c>
2496   <c>Accepted</c>
2497   <c>
2498      <xref target="status.202"/>
2499   </c>
2500   <c>203</c>
2501   <c>Non-Authoritative Information</c>
2502   <c>
2503      <xref target="status.203"/>
2504   </c>
2505   <c>204</c>
2506   <c>No Content</c>
2507   <c>
2508      <xref target="status.204"/>
2509   </c>
2510   <c>205</c>
2511   <c>Reset Content</c>
2512   <c>
2513      <xref target="status.205"/>
2514   </c>
2515   <c>300</c>
2516   <c>Multiple Choices</c>
2517   <c>
2518      <xref target="status.300"/>
2519   </c>
2520   <c>301</c>
2521   <c>Moved Permanently</c>
2522   <c>
2523      <xref target="status.301"/>
2524   </c>
2525   <c>302</c>
2526   <c>Found</c>
2527   <c>
2528      <xref target="status.302"/>
2529   </c>
2530   <c>303</c>
2531   <c>See Other</c>
2532   <c>
2533      <xref target="status.303"/>
2534   </c>
2535   <c>305</c>
2536   <c>Use Proxy</c>
2537   <c>
2538      <xref target="status.305"/>
2539   </c>
2540   <c>306</c>
2541   <c>(Unused)</c>
2542   <c>
2543      <xref target="status.306"/>
2544   </c>
2545   <c>307</c>
2546   <c>Temporary Redirect</c>
2547   <c>
2548      <xref target="status.307"/>
2549   </c>
2550   <c>400</c>
2551   <c>Bad Request</c>
2552   <c>
2553      <xref target="status.400"/>
2554   </c>
2555   <c>402</c>
2556   <c>Payment Required</c>
2557   <c>
2558      <xref target="status.402"/>
2559   </c>
2560   <c>403</c>
2561   <c>Forbidden</c>
2562   <c>
2563      <xref target="status.403"/>
2564   </c>
2565   <c>404</c>
2566   <c>Not Found</c>
2567   <c>
2568      <xref target="status.404"/>
2569   </c>
2570   <c>405</c>
2571   <c>Method Not Allowed</c>
2572   <c>
2573      <xref target="status.405"/>
2574   </c>
2575   <c>406</c>
2576   <c>Not Acceptable</c>
2577   <c>
2578      <xref target="status.406"/>
2579   </c>
2580   <c>407</c>
2581   <c>Proxy Authentication Required</c>
2582   <c>
2583      <xref target="status.407"/>
2584   </c>
2585   <c>408</c>
2586   <c>Request Timeout</c>
2587   <c>
2588      <xref target="status.408"/>
2589   </c>
2590   <c>409</c>
2591   <c>Conflict</c>
2592   <c>
2593      <xref target="status.409"/>
2594   </c>
2595   <c>410</c>
2596   <c>Gone</c>
2597   <c>
2598      <xref target="status.410"/>
2599   </c>
2600   <c>411</c>
2601   <c>Length Required</c>
2602   <c>
2603      <xref target="status.411"/>
2604   </c>
2605   <c>413</c>
2606   <c>Request Entity Too Large</c>
2607   <c>
2608      <xref target="status.413"/>
2609   </c>
2610   <c>414</c>
2611   <c>URI Too Long</c>
2612   <c>
2613      <xref target="status.414"/>
2614   </c>
2615   <c>415</c>
2616   <c>Unsupported Media Type</c>
2617   <c>
2618      <xref target="status.415"/>
2619   </c>
2620   <c>417</c>
2621   <c>Expectation Failed</c>
2622   <c>
2623      <xref target="status.417"/>
2624   </c>
2625   <c>500</c>
2626   <c>Internal Server Error</c>
2627   <c>
2628      <xref target="status.500"/>
2629   </c>
2630   <c>501</c>
2631   <c>Not Implemented</c>
2632   <c>
2633      <xref target="status.501"/>
2634   </c>
2635   <c>502</c>
2636   <c>Bad Gateway</c>
2637   <c>
2638      <xref target="status.502"/>
2639   </c>
2640   <c>503</c>
2641   <c>Service Unavailable</c>
2642   <c>
2643      <xref target="status.503"/>
2644   </c>
2645   <c>504</c>
2646   <c>Gateway Timeout</c>
2647   <c>
2648      <xref target="status.504"/>
2649   </c>
2650   <c>505</c>
2651   <c>HTTP Version Not Supported</c>
2652   <c>
2653      <xref target="status.505"/>
2654   </c>
2655</texttable>
2656<!--(END)-->
2657<?ENDINC p2-semantics.iana-status-codes ?>
2658</section>
2659<section title="Header Field Registration" anchor="header.field.registration">
2660<t>
2661   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2662   with the permanent registrations below (see <xref target="RFC3864"/>):
2663</t>
2664<?BEGININC p2-semantics.iana-headers ?>
2665<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2666<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2667   <ttcol>Header Field Name</ttcol>
2668   <ttcol>Protocol</ttcol>
2669   <ttcol>Status</ttcol>
2670   <ttcol>Reference</ttcol>
2671
2672   <c>Allow</c>
2673   <c>http</c>
2674   <c>standard</c>
2675   <c>
2676      <xref target="header.allow"/>
2677   </c>
2678   <c>Expect</c>
2679   <c>http</c>
2680   <c>standard</c>
2681   <c>
2682      <xref target="header.expect"/>
2683   </c>
2684   <c>From</c>
2685   <c>http</c>
2686   <c>standard</c>
2687   <c>
2688      <xref target="header.from"/>
2689   </c>
2690   <c>Location</c>
2691   <c>http</c>
2692   <c>standard</c>
2693   <c>
2694      <xref target="header.location"/>
2695   </c>
2696   <c>Max-Forwards</c>
2697   <c>http</c>
2698   <c>standard</c>
2699   <c>
2700      <xref target="header.max-forwards"/>
2701   </c>
2702   <c>Referer</c>
2703   <c>http</c>
2704   <c>standard</c>
2705   <c>
2706      <xref target="header.referer"/>
2707   </c>
2708   <c>Retry-After</c>
2709   <c>http</c>
2710   <c>standard</c>
2711   <c>
2712      <xref target="header.retry-after"/>
2713   </c>
2714   <c>Server</c>
2715   <c>http</c>
2716   <c>standard</c>
2717   <c>
2718      <xref target="header.server"/>
2719   </c>
2720   <c>User-Agent</c>
2721   <c>http</c>
2722   <c>standard</c>
2723   <c>
2724      <xref target="header.user-agent"/>
2725   </c>
2726</texttable>
2727<!--(END)-->
2728<?ENDINC p2-semantics.iana-headers ?>
2729<t>
2730   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2731</t>
2732</section>
2733</section>
2734
2735<section title="Security Considerations" anchor="security.considerations">
2736<t>
2737   This section is meant to inform application developers, information
2738   providers, and users of the security limitations in HTTP/1.1 as
2739   described by this document. The discussion does not include
2740   definitive solutions to the problems revealed, though it does make
2741   some suggestions for reducing security risks.
2742</t>
2743
2744<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2745<t>
2746   Like any generic data transfer protocol, HTTP cannot regulate the
2747   content of the data that is transferred, nor is there any a priori
2748   method of determining the sensitivity of any particular piece of
2749   information within the context of any given request. Therefore,
2750   applications &SHOULD; supply as much control over this information as
2751   possible to the provider of that information. Four header fields are
2752   worth special mention in this context: Server, Via, Referer and From.
2753</t>
2754<t>
2755   Revealing the specific software version of the server might allow the
2756   server machine to become more vulnerable to attacks against software
2757   that is known to contain security holes. Implementors &SHOULD; make the
2758   Server header field a configurable option.
2759</t>
2760<t>
2761   Proxies which serve as a portal through a network firewall &SHOULD;
2762   take special precautions regarding the transfer of header information
2763   that identifies the hosts behind the firewall. In particular, they
2764   &SHOULD; remove, or replace with sanitized versions, any Via fields
2765   generated behind the firewall.
2766</t>
2767<t>
2768   The Referer header field allows reading patterns to be studied and reverse
2769   links drawn. Although it can be very useful, its power can be abused
2770   if user details are not separated from the information contained in
2771   the Referer. Even when the personal information has been removed, the
2772   Referer header field might indicate a private document's URI whose
2773   publication would be inappropriate.
2774</t>
2775<t>
2776   The information sent in the From field might conflict with the user's
2777   privacy interests or their site's security policy, and hence it
2778   &SHOULD-NOT;  be transmitted without the user being able to disable,
2779   enable, and modify the contents of the field. The user &MUST; be able
2780   to set the contents of this field within a user preference or
2781   application defaults configuration.
2782</t>
2783<t>
2784   We suggest, though do not require, that a convenient toggle interface
2785   be provided for the user to enable or disable the sending of From and
2786   Referer information.
2787</t>
2788<t>
2789   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2790   target="header.server"/>) header fields can sometimes be used to determine
2791   that a specific client or server have a particular security hole which might
2792   be exploited. Unfortunately, this same information is often used for other
2793   valuable purposes for which HTTP currently has no better mechanism.
2794</t>
2795<t>
2796   Furthermore, the User-Agent header field may contain enough entropy to be
2797   used, possibly in conjunction with other material, to uniquely identify the
2798   user.
2799</t>
2800<t>
2801   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2802   that was sent in request header fields within the body of their response.
2803   Clients &SHOULD; be careful with sensitive information, like Cookies,
2804   Authorization credentials and other header fields that might be used to
2805   collect data from the client.
2806</t> 
2807</section>
2808
2809<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2810<t>
2811   Because the source of a link might be private information or might
2812   reveal an otherwise private information source, it is strongly
2813   recommended that the user be able to select whether or not the
2814   Referer field is sent. For example, a browser client could have a
2815   toggle switch for browsing openly/anonymously, which would
2816   respectively enable/disable the sending of Referer and From
2817   information.
2818</t>
2819<t>
2820   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2821   HTTP request if the referring page was transferred with a secure
2822   protocol.
2823</t>
2824<t>
2825   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2826   sensitive data because that data will be placed in the request-target. Many
2827   existing servers, proxies, and user agents log or display the request-target
2828   in places where it might be visible to third parties. Such services can
2829   use POST-based form submission instead.
2830</t>
2831</section>
2832
2833<section title="Location Headers and Spoofing" anchor="location.spoofing">
2834<t>
2835   If a single server supports multiple organizations that do not trust
2836   one another, then it &MUST; check the values of Location and Content-Location
2837   header fields in responses that are generated under control of
2838   said organizations to make sure that they do not attempt to
2839   invalidate resources over which they have no authority.
2840</t>
2841</section>
2842
2843</section>
2844
2845<section title="Acknowledgments" anchor="ack">
2846</section>
2847</middle>
2848<back>
2849
2850<references title="Normative References">
2851
2852<reference anchor="Part1">
2853  <front>
2854    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2855    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2856      <organization abbrev="Day Software">Day Software</organization>
2857      <address><email>fielding@gbiv.com</email></address>
2858    </author>
2859    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2860      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2861      <address><email>jg@freedesktop.org</email></address>
2862    </author>
2863    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2864      <organization abbrev="HP">Hewlett-Packard Company</organization>
2865      <address><email>JeffMogul@acm.org</email></address>
2866    </author>
2867    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2868      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2869      <address><email>henrikn@microsoft.com</email></address>
2870    </author>
2871    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2872      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2873      <address><email>LMM@acm.org</email></address>
2874    </author>
2875    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2876      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2877      <address><email>paulle@microsoft.com</email></address>
2878    </author>
2879    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2880      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2881      <address><email>timbl@w3.org</email></address>
2882    </author>
2883    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2884      <organization abbrev="W3C">World Wide Web Consortium</organization>
2885      <address><email>ylafon@w3.org</email></address>
2886    </author>
2887    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2888      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2889      <address><email>julian.reschke@greenbytes.de</email></address>
2890    </author>
2891    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2892  </front>
2893  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2894  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2895</reference>
2896
2897<reference anchor="Part3">
2898  <front>
2899    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2900    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2901      <organization abbrev="Day Software">Day Software</organization>
2902      <address><email>fielding@gbiv.com</email></address>
2903    </author>
2904    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2905      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2906      <address><email>jg@freedesktop.org</email></address>
2907    </author>
2908    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2909      <organization abbrev="HP">Hewlett-Packard Company</organization>
2910      <address><email>JeffMogul@acm.org</email></address>
2911    </author>
2912    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2913      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2914      <address><email>henrikn@microsoft.com</email></address>
2915    </author>
2916    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2917      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2918      <address><email>LMM@acm.org</email></address>
2919    </author>
2920    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2921      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2922      <address><email>paulle@microsoft.com</email></address>
2923    </author>
2924    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2925      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2926      <address><email>timbl@w3.org</email></address>
2927    </author>
2928    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2929      <organization abbrev="W3C">World Wide Web Consortium</organization>
2930      <address><email>ylafon@w3.org</email></address>
2931    </author>
2932    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2933      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2934      <address><email>julian.reschke@greenbytes.de</email></address>
2935    </author>
2936    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2937  </front>
2938  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2939  <x:source href="p3-payload.xml" basename="p3-payload"/>
2940</reference>
2941
2942<reference anchor="Part4">
2943  <front>
2944    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2945    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2946      <organization abbrev="Day Software">Day Software</organization>
2947      <address><email>fielding@gbiv.com</email></address>
2948    </author>
2949    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2950      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2951      <address><email>jg@freedesktop.org</email></address>
2952    </author>
2953    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2954      <organization abbrev="HP">Hewlett-Packard Company</organization>
2955      <address><email>JeffMogul@acm.org</email></address>
2956    </author>
2957    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2958      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2959      <address><email>henrikn@microsoft.com</email></address>
2960    </author>
2961    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2962      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2963      <address><email>LMM@acm.org</email></address>
2964    </author>
2965    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2966      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2967      <address><email>paulle@microsoft.com</email></address>
2968    </author>
2969    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2970      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2971      <address><email>timbl@w3.org</email></address>
2972    </author>
2973    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2974      <organization abbrev="W3C">World Wide Web Consortium</organization>
2975      <address><email>ylafon@w3.org</email></address>
2976    </author>
2977    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2978      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2979      <address><email>julian.reschke@greenbytes.de</email></address>
2980    </author>
2981    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2982  </front>
2983  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2984  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2985</reference>
2986
2987<reference anchor="Part5">
2988  <front>
2989    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2990    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2991      <organization abbrev="Day Software">Day Software</organization>
2992      <address><email>fielding@gbiv.com</email></address>
2993    </author>
2994    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2995      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2996      <address><email>jg@freedesktop.org</email></address>
2997    </author>
2998    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2999      <organization abbrev="HP">Hewlett-Packard Company</organization>
3000      <address><email>JeffMogul@acm.org</email></address>
3001    </author>
3002    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3003      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3004      <address><email>henrikn@microsoft.com</email></address>
3005    </author>
3006    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3007      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3008      <address><email>LMM@acm.org</email></address>
3009    </author>
3010    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3011      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3012      <address><email>paulle@microsoft.com</email></address>
3013    </author>
3014    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3015      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3016      <address><email>timbl@w3.org</email></address>
3017    </author>
3018    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3019      <organization abbrev="W3C">World Wide Web Consortium</organization>
3020      <address><email>ylafon@w3.org</email></address>
3021    </author>
3022    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3023      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3024      <address><email>julian.reschke@greenbytes.de</email></address>
3025    </author>
3026    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3027  </front>
3028  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3029  <x:source href="p5-range.xml" basename="p5-range"/>
3030</reference>
3031
3032<reference anchor="Part6">
3033  <front>
3034    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3035    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3036      <organization abbrev="Day Software">Day Software</organization>
3037      <address><email>fielding@gbiv.com</email></address>
3038    </author>
3039    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3040      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3041      <address><email>jg@freedesktop.org</email></address>
3042    </author>
3043    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3044      <organization abbrev="HP">Hewlett-Packard Company</organization>
3045      <address><email>JeffMogul@acm.org</email></address>
3046    </author>
3047    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3048      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3049      <address><email>henrikn@microsoft.com</email></address>
3050    </author>
3051    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3052      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3053      <address><email>LMM@acm.org</email></address>
3054    </author>
3055    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3056      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3057      <address><email>paulle@microsoft.com</email></address>
3058    </author>
3059    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3060      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3061      <address><email>timbl@w3.org</email></address>
3062    </author>
3063    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3064      <organization abbrev="W3C">World Wide Web Consortium</organization>
3065      <address><email>ylafon@w3.org</email></address>
3066    </author>
3067    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3068      <address><email>mnot@mnot.net</email></address>
3069    </author>
3070    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3071      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3072      <address><email>julian.reschke@greenbytes.de</email></address>
3073    </author>
3074    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3075  </front>
3076  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3077  <x:source href="p6-cache.xml" basename="p6-cache"/>
3078</reference>
3079
3080<reference anchor="Part7">
3081  <front>
3082    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3083    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3084      <organization abbrev="Day Software">Day Software</organization>
3085      <address><email>fielding@gbiv.com</email></address>
3086    </author>
3087    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3088      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3089      <address><email>jg@freedesktop.org</email></address>
3090    </author>
3091    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3092      <organization abbrev="HP">Hewlett-Packard Company</organization>
3093      <address><email>JeffMogul@acm.org</email></address>
3094    </author>
3095    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3096      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3097      <address><email>henrikn@microsoft.com</email></address>
3098    </author>
3099    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3100      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3101      <address><email>LMM@acm.org</email></address>
3102    </author>
3103    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3104      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3105      <address><email>paulle@microsoft.com</email></address>
3106    </author>
3107    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3108      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3109      <address><email>timbl@w3.org</email></address>
3110    </author>
3111    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3112      <organization abbrev="W3C">World Wide Web Consortium</organization>
3113      <address><email>ylafon@w3.org</email></address>
3114    </author>
3115    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3116      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3117      <address><email>julian.reschke@greenbytes.de</email></address>
3118    </author>
3119    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3120  </front>
3121  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3122  <x:source href="p7-auth.xml" basename="p7-auth"/>
3123</reference>
3124
3125<reference anchor="RFC2119">
3126  <front>
3127    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3128    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3129      <organization>Harvard University</organization>
3130      <address><email>sob@harvard.edu</email></address>
3131    </author>
3132    <date month="March" year="1997"/>
3133  </front>
3134  <seriesInfo name="BCP" value="14"/>
3135  <seriesInfo name="RFC" value="2119"/>
3136</reference>
3137
3138<reference anchor="RFC3986">
3139 <front>
3140  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3141  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3142    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3143    <address>
3144       <email>timbl@w3.org</email>
3145       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3146    </address>
3147  </author>
3148  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3149    <organization abbrev="Day Software">Day Software</organization>
3150    <address>
3151      <email>fielding@gbiv.com</email>
3152      <uri>http://roy.gbiv.com/</uri>
3153    </address>
3154  </author>
3155  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3156    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3157    <address>
3158      <email>LMM@acm.org</email>
3159      <uri>http://larry.masinter.net/</uri>
3160    </address>
3161  </author>
3162  <date month='January' year='2005'></date>
3163 </front>
3164 <seriesInfo name="STD" value="66"/>
3165 <seriesInfo name="RFC" value="3986"/>
3166</reference>
3167
3168<reference anchor="RFC5234">
3169  <front>
3170    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3171    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3172      <organization>Brandenburg InternetWorking</organization>
3173      <address>
3174        <email>dcrocker@bbiw.net</email>
3175      </address> 
3176    </author>
3177    <author initials="P." surname="Overell" fullname="Paul Overell">
3178      <organization>THUS plc.</organization>
3179      <address>
3180        <email>paul.overell@thus.net</email>
3181      </address>
3182    </author>
3183    <date month="January" year="2008"/>
3184  </front>
3185  <seriesInfo name="STD" value="68"/>
3186  <seriesInfo name="RFC" value="5234"/>
3187</reference>
3188
3189</references>
3190
3191<references title="Informative References">
3192
3193<reference anchor="RFC1945">
3194  <front>
3195    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3196    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3197      <organization>MIT, Laboratory for Computer Science</organization>
3198      <address><email>timbl@w3.org</email></address>
3199    </author>
3200    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3201      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3202      <address><email>fielding@ics.uci.edu</email></address>
3203    </author>
3204    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3205      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3206      <address><email>frystyk@w3.org</email></address>
3207    </author>
3208    <date month="May" year="1996"/>
3209  </front>
3210  <seriesInfo name="RFC" value="1945"/>
3211</reference>
3212
3213<reference anchor="RFC2068">
3214  <front>
3215    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3216    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3217      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3218      <address><email>fielding@ics.uci.edu</email></address>
3219    </author>
3220    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3221      <organization>MIT Laboratory for Computer Science</organization>
3222      <address><email>jg@w3.org</email></address>
3223    </author>
3224    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3225      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3226      <address><email>mogul@wrl.dec.com</email></address>
3227    </author>
3228    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3229      <organization>MIT Laboratory for Computer Science</organization>
3230      <address><email>frystyk@w3.org</email></address>
3231    </author>
3232    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3233      <organization>MIT Laboratory for Computer Science</organization>
3234      <address><email>timbl@w3.org</email></address>
3235    </author>
3236    <date month="January" year="1997"/>
3237  </front>
3238  <seriesInfo name="RFC" value="2068"/>
3239</reference>
3240
3241<reference anchor="RFC2616">
3242  <front>
3243    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3244    <author initials="R." surname="Fielding" fullname="R. Fielding">
3245      <organization>University of California, Irvine</organization>
3246      <address><email>fielding@ics.uci.edu</email></address>
3247    </author>
3248    <author initials="J." surname="Gettys" fullname="J. Gettys">
3249      <organization>W3C</organization>
3250      <address><email>jg@w3.org</email></address>
3251    </author>
3252    <author initials="J." surname="Mogul" fullname="J. Mogul">
3253      <organization>Compaq Computer Corporation</organization>
3254      <address><email>mogul@wrl.dec.com</email></address>
3255    </author>
3256    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3257      <organization>MIT Laboratory for Computer Science</organization>
3258      <address><email>frystyk@w3.org</email></address>
3259    </author>
3260    <author initials="L." surname="Masinter" fullname="L. Masinter">
3261      <organization>Xerox Corporation</organization>
3262      <address><email>masinter@parc.xerox.com</email></address>
3263    </author>
3264    <author initials="P." surname="Leach" fullname="P. Leach">
3265      <organization>Microsoft Corporation</organization>
3266      <address><email>paulle@microsoft.com</email></address>
3267    </author>
3268    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3269      <organization>W3C</organization>
3270      <address><email>timbl@w3.org</email></address>
3271    </author>
3272    <date month="June" year="1999"/>
3273  </front>
3274  <seriesInfo name="RFC" value="2616"/>
3275</reference>
3276
3277<reference anchor='RFC2817'>
3278  <front>
3279    <title>Upgrading to TLS Within HTTP/1.1</title>
3280    <author initials='R.' surname='Khare' fullname='R. Khare'>
3281      <organization>4K Associates / UC Irvine</organization>
3282      <address><email>rohit@4K-associates.com</email></address>
3283    </author>
3284    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3285      <organization>Agranat Systems, Inc.</organization>
3286      <address><email>lawrence@agranat.com</email></address>
3287    </author>
3288    <date year='2000' month='May' />
3289  </front>
3290  <seriesInfo name='RFC' value='2817' />
3291</reference>
3292
3293<reference anchor='RFC3864'>
3294  <front>
3295    <title>Registration Procedures for Message Header Fields</title>
3296    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3297      <organization>Nine by Nine</organization>
3298      <address><email>GK-IETF@ninebynine.org</email></address>
3299    </author>
3300    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3301      <organization>BEA Systems</organization>
3302      <address><email>mnot@pobox.com</email></address>
3303    </author>
3304    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3305      <organization>HP Labs</organization>
3306      <address><email>JeffMogul@acm.org</email></address>
3307    </author>
3308    <date year='2004' month='September' />
3309  </front>
3310  <seriesInfo name='BCP' value='90' />
3311  <seriesInfo name='RFC' value='3864' />
3312</reference>
3313
3314<reference anchor='RFC5226'>
3315  <front>
3316    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3317    <author initials='T.' surname='Narten' fullname='T. Narten'>
3318      <organization>IBM</organization>
3319      <address><email>narten@us.ibm.com</email></address>
3320    </author>
3321    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3322      <organization>Google</organization>
3323      <address><email>Harald@Alvestrand.no</email></address>
3324    </author>
3325    <date year='2008' month='May' />
3326  </front>
3327  <seriesInfo name='BCP' value='26' />
3328  <seriesInfo name='RFC' value='5226' />
3329</reference>
3330
3331<reference anchor="RFC5322">
3332  <front>
3333    <title>Internet Message Format</title>
3334    <author initials="P." surname="Resnick" fullname="P. Resnick">
3335      <organization>Qualcomm Incorporated</organization>
3336    </author>
3337    <date year="2008" month="October"/>
3338  </front> 
3339  <seriesInfo name="RFC" value="5322"/>
3340</reference>
3341
3342</references>
3343
3344<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3345<t>
3346  This document takes over the Status Code Registry, previously defined
3347  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3348  (<xref target="status.code.registry"/>)
3349</t>
3350<t>
3351  Clarify definition of POST.
3352  (<xref target="POST"/>)
3353</t>
3354<t>
3355  Failed to consider that there are
3356  many other request methods that are safe to automatically redirect,
3357  and further that the user agent is able to make that determination
3358  based on the request method semantics.
3359  (Sections <xref format="counter" target="status.301"/>,
3360  <xref format="counter" target="status.302"/> and
3361  <xref format="counter" target="status.307"/>)
3362</t>
3363<t>
3364  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3365  It used to indicate that the target resource must be accessed through the
3366  proxy given by the Location field. The Location field gave the URI of the
3367  proxy. The recipient was expected to repeat this single request via the proxy.
3368  (<xref target="status.305"/>)
3369</t>
3370<t>
3371  Reclassify "Allow" as response header field, removing the option to
3372  specify it in a PUT request.
3373  Relax the server requirement on the contents of the Allow header field and
3374  remove requirement on clients to always trust the header field value.
3375  (<xref target="header.allow"/>)
3376</t>
3377<t>
3378  Correct syntax of Location header field to allow URI references (including
3379  relative references and fragments), as referred symbol "absoluteURI" wasn't
3380  what was expected, and add some clarifications as to when use of fragments
3381  would not be appropriate.
3382  (<xref target="header.location"/>)
3383</t>
3384<t>
3385  Allow Referer field value of "about:blank" as alternative to not specifying it.
3386  (<xref target="header.referer"/>)
3387</t>
3388<t>
3389  In the description of the Server header field, the Via field
3390  was described as a SHOULD. The requirement was and is stated
3391  correctly in the description of the Via header field in &header-via;.
3392  (<xref target="header.server"/>)
3393</t>
3394</section>
3395
3396<?BEGININC p2-semantics.abnf-appendix ?>
3397<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3398<figure>
3399<artwork type="abnf" name="p2-semantics.parsed-abnf">
3400<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3401<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3402<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3403<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3404<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3405<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3406<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3407<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3408<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3409
3410<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3411<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3412<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3413
3414<x:ref>From</x:ref> = "From:" OWS From-v
3415<x:ref>From-v</x:ref> = mailbox
3416
3417<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3418<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3419
3420<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3421If-Modified-Since =
3422 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3423<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3424<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3425If-Unmodified-Since =
3426 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3427
3428<x:ref>Location</x:ref> = "Location:" OWS Location-v
3429<x:ref>Location-v</x:ref> = URI-reference
3430
3431<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3432<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3433<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3434 / %x47.45.54 ; GET
3435 / %x48.45.41.44 ; HEAD
3436 / %x50.4F.53.54 ; POST
3437 / %x50.55.54 ; PUT
3438 / %x44.45.4C.45.54.45 ; DELETE
3439 / %x54.52.41.43.45 ; TRACE
3440 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3441 / extension-method
3442
3443<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3444
3445Proxy-Authenticate =
3446 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3447Proxy-Authorization =
3448 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3449
3450<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3451<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3452<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3453<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3454<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3455<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3456<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3457
3458<x:ref>Server</x:ref> = "Server:" OWS Server-v
3459<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3460<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3461 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3462 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3463 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3464 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3465 "505" / extension-code
3466
3467<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3468
3469<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3470<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3471<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3472
3473<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3474
3475WWW-Authenticate =
3476 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3477
3478<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3479
3480<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3481
3482<x:ref>delta-seconds</x:ref> = 1*DIGIT
3483
3484<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3485<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3486<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3487 *expect-params ]
3488<x:ref>extension-code</x:ref> = 3DIGIT
3489<x:ref>extension-method</x:ref> = token
3490
3491<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3492
3493<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3494
3495<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3496<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3497
3498<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3499
3500<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3501 Accept-Language / Authorization / Expect / From / Host / If-Match /
3502 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3503 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3504 User-Agent
3505<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3506 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3507
3508<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3509</artwork>
3510</figure>
3511<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3512; Reason-Phrase defined but not used
3513; Status-Code defined but not used
3514; request-header defined but not used
3515; response-header defined but not used
3516</artwork></figure></section>
3517<?ENDINC p2-semantics.abnf-appendix ?>
3518
3519<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3520
3521<section title="Since RFC 2616">
3522<t>
3523  Extracted relevant partitions from <xref target="RFC2616"/>.
3524</t>
3525</section>
3526
3527<section title="Since draft-ietf-httpbis-p2-semantics-00">
3528<t>
3529  Closed issues:
3530  <list style="symbols"> 
3531    <t>
3532      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3533      "Via is a MUST"
3534      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3535    </t>
3536    <t>
3537      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3538      "Fragments allowed in Location"
3539      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3540    </t>
3541    <t>
3542      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3543      "Safe Methods vs Redirection"
3544      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3545    </t>
3546    <t>
3547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3548      "Revise description of the POST method"
3549      (<eref target="http://purl.org/NET/http-errata#post"/>)
3550    </t>
3551    <t>
3552      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3553      "Normative and Informative references"
3554    </t>
3555    <t>
3556      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3557      "RFC2606 Compliance"
3558    </t>
3559    <t>
3560      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3561      "Informative references"
3562    </t>
3563    <t>
3564      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3565      "Redundant cross-references"
3566    </t>
3567  </list>
3568</t>
3569<t>
3570  Other changes:
3571  <list style="symbols"> 
3572    <t>
3573      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3574    </t>
3575  </list>
3576</t>
3577</section>
3578
3579<section title="Since draft-ietf-httpbis-p2-semantics-01">
3580<t>
3581  Closed issues:
3582  <list style="symbols"> 
3583    <t>
3584      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3585      "PUT side effects"
3586    </t>
3587    <t>
3588      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3589      "Duplicate Host header requirements"
3590    </t>
3591  </list>
3592</t>
3593<t>
3594  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3595  <list style="symbols"> 
3596    <t>
3597      Move "Product Tokens" section (back) into Part 1, as "token" is used
3598      in the definition of the Upgrade header field.
3599    </t>
3600    <t>
3601      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3602    </t>
3603    <t>
3604      Copy definition of delta-seconds from Part6 instead of referencing it.
3605    </t>
3606  </list>
3607</t>
3608</section>
3609
3610<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3611<t>
3612  Closed issues:
3613  <list style="symbols"> 
3614    <t>
3615      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3616      "Requiring Allow in 405 responses"
3617    </t>
3618    <t>
3619      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3620      "Status Code Registry"
3621    </t>
3622    <t>
3623      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3624      "Redirection vs. Location"
3625    </t>
3626    <t>
3627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3628      "Cacheability of 303 response"
3629    </t>
3630    <t>
3631      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3632      "305 Use Proxy"
3633    </t>
3634    <t>
3635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3636      "Classification for Allow header"
3637    </t>
3638    <t>
3639      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3640      "PUT - 'store under' vs 'store at'"
3641    </t>
3642  </list>
3643</t>
3644<t>
3645  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3646  <list style="symbols"> 
3647    <t>
3648      Reference RFC 3984, and update header field registrations for headers defined
3649      in this document.
3650    </t>
3651  </list>
3652</t>
3653<t>
3654  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3655  <list style="symbols"> 
3656    <t>
3657      Replace string literals when the string really is case-sensitive (method).
3658    </t>
3659  </list>
3660</t>
3661</section>
3662
3663<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3664<t>
3665  Closed issues:
3666  <list style="symbols"> 
3667    <t>
3668      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3669      "OPTIONS request bodies"
3670    </t>
3671    <t>
3672      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3673      "Description of CONNECT should refer to RFC2817"
3674    </t>
3675    <t>
3676      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3677      "Location Content-Location reference request/response mixup"
3678    </t>
3679  </list>
3680</t>
3681<t>
3682  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3683  <list style="symbols"> 
3684    <t>
3685      Added initial proposal for registration process, plus initial
3686      content (non-HTTP/1.1 methods to be added by a separate specification).
3687    </t>
3688  </list>
3689</t>
3690</section>
3691
3692<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3693<t>
3694  Closed issues:
3695  <list style="symbols"> 
3696    <t>
3697      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3698      "Content-*"
3699    </t>
3700    <t>
3701      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3702      "RFC 2822 is updated by RFC 5322"
3703    </t>
3704  </list>
3705</t>
3706<t>
3707  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3708  <list style="symbols"> 
3709    <t>
3710      Use "/" instead of "|" for alternatives.
3711    </t>
3712    <t>
3713      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3714      whitespace ("OWS") and required whitespace ("RWS").
3715    </t>
3716    <t>
3717      Rewrite ABNFs to spell out whitespace rules, factor out
3718      header field value format definitions.
3719    </t>
3720  </list>
3721</t>
3722</section>
3723
3724<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3725<t>
3726  Closed issues:
3727  <list style="symbols"> 
3728    <t>
3729      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3730      "Reason-Phrase BNF"
3731    </t>
3732  </list>
3733</t>
3734<t>
3735  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3736  <list style="symbols"> 
3737    <t>
3738      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3739    </t>
3740  </list>
3741</t>
3742</section>
3743
3744<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3745<t>
3746  Closed issues:
3747  <list style="symbols"> 
3748    <t>
3749      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3750      "Clarify when Referer is sent"
3751    </t>
3752    <t>
3753      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3754      "status codes vs methods"
3755    </t>
3756    <t>
3757      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3758      "Do not require "updates" relation for specs that register status codes or method names"
3759    </t>
3760  </list>
3761</t>
3762</section>
3763
3764<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3765<t>
3766  Closed issues:
3767  <list style="symbols"> 
3768    <t>
3769      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3770      "Idempotency"
3771    </t>
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3774      "TRACE security considerations"
3775    </t>
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3778      "Clarify rules for determining what entities a response carries"
3779    </t>
3780    <t>
3781      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3782      "update note citing RFC 1945 and 2068"
3783    </t>
3784    <t>
3785      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3786      "update note about redirect limit"
3787    </t>
3788    <t>
3789      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3790      "Location header ABNF should use 'URI'"
3791    </t>
3792    <t>
3793      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3794      "fragments in Location vs status 303"
3795    </t>
3796    <t>
3797      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3798      "move IANA registrations for optional status codes"
3799    </t>
3800  </list>
3801</t>
3802<t>
3803  Partly resolved issues:
3804  <list style="symbols"> 
3805    <t>
3806      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3807      "Are OPTIONS and TRACE safe?"
3808    </t>
3809  </list>
3810</t>
3811</section>
3812
3813<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3814<t>
3815  Closed issues:
3816  <list style="symbols"> 
3817    <t>
3818      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3819      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3820      status codes when fixing this previously)
3821    </t>
3822  </list>
3823</t>
3824</section>
3825
3826<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3827<t>
3828  Closed issues:
3829  <list style="symbols"> 
3830    <t>
3831      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3832      "Fragment combination / precedence during redirects"
3833    </t>
3834  </list>
3835</t>
3836<t>
3837  Partly resolved issues:
3838  <list style="symbols"> 
3839    <t>
3840      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3841      "Location header payload handling"
3842    </t>
3843    <t>
3844      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3845      "Term for the requested resource's URI"
3846    </t>
3847  </list>
3848</t>
3849</section>
3850
3851<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3852<t>
3853  Closed issues:
3854  <list style="symbols"> 
3855    <t>
3856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3857      "Clarify 'Requested Variant'"
3858    </t>
3859    <t>
3860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3861      "Clarify entity / representation / variant terminology"
3862    </t>
3863    <t>
3864      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3865      "Methods and Caching"
3866    </t>
3867    <t>
3868      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3869      "OPTIONS vs Max-Forwards"
3870    </t>
3871    <t>
3872      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3873      "Status codes and caching"
3874    </t>
3875    <t>
3876      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3877      "consider removing the 'changes from 2068' sections"
3878    </t>
3879  </list>
3880</t>
3881</section>
3882
3883<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3884<t>
3885  Closed issues:
3886  <list style="symbols"> 
3887    <t>
3888      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
3889      "Considerations for new methods"
3890    </t>
3891    <t>
3892      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
3893      "User-Agent guidelines" (relating to the 'User-Agent' header field)
3894    </t>
3895  </list>
3896</t>
3897</section>
3898
3899</section>
3900
3901</back>
3902</rfc>
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