source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1158

Last change on this file since 1158 was 1158, checked in by fielding@…, 9 years ago

Replaced the general prohibition on unrecognized Content-* header fields
with a specific prohibition of Content-Range (the only field for which
it is an actual problem) and a general requirement regarding checking
for consistency. Unfortunately, this required rewriting the entire
section on PUT to get rid of the misconceptions about storing resources
and reflect how PUT is actually implemented in practice.

Addresses #79, #102, #103, #104, #112, #180, #231, and #267

  • Property svn:eol-style set to native
File size: 173.3 KB
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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 "March">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81]>
82<?rfc toc="yes" ?>
83<?rfc symrefs="yes" ?>
84<?rfc sortrefs="yes" ?>
85<?rfc compact="yes"?>
86<?rfc subcompact="no" ?>
87<?rfc linkmailto="no" ?>
88<?rfc editing="no" ?>
89<?rfc comments="yes"?>
90<?rfc inline="yes"?>
91<?rfc rfcedstyle="yes"?>
92<?rfc-ext allow-markup-in-artwork="yes" ?>
93<?rfc-ext include-references-in-index="yes" ?>
94<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
95     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
96     xmlns:x='http://purl.org/net/xml2rfc/ext'
97     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
98<front>
99
100  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
101
102  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
103    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
104    <address>
105      <postal>
106        <street>345 Park Ave</street>
107        <city>San Jose</city>
108        <region>CA</region>
109        <code>95110</code>
110        <country>USA</country>
111      </postal>
112      <email>fielding@gbiv.com</email>
113      <uri>http://roy.gbiv.com/</uri>
114    </address>
115  </author>
116
117  <author initials="J." surname="Gettys" fullname="Jim Gettys">
118    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
119    <address>
120      <postal>
121        <street>21 Oak Knoll Road</street>
122        <city>Carlisle</city>
123        <region>MA</region>
124        <code>01741</code>
125        <country>USA</country>
126      </postal>
127      <email>jg@freedesktop.org</email>
128      <uri>http://gettys.wordpress.com/</uri>
129    </address>
130  </author>
131 
132  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
133    <organization abbrev="HP">Hewlett-Packard Company</organization>
134    <address>
135      <postal>
136        <street>HP Labs, Large Scale Systems Group</street>
137        <street>1501 Page Mill Road, MS 1177</street>
138        <city>Palo Alto</city>
139        <region>CA</region>
140        <code>94304</code>
141        <country>USA</country>
142      </postal>
143      <email>JeffMogul@acm.org</email>
144    </address>
145  </author>
146
147  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
148    <organization abbrev="Microsoft">Microsoft Corporation</organization>
149    <address>
150      <postal>
151        <street>1 Microsoft Way</street>
152        <city>Redmond</city>
153        <region>WA</region>
154        <code>98052</code>
155        <country>USA</country>
156      </postal>
157      <email>henrikn@microsoft.com</email>
158    </address>
159  </author>
160
161  <author initials="L." surname="Masinter" fullname="Larry Masinter">
162    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
163    <address>
164      <postal>
165        <street>345 Park Ave</street>
166        <city>San Jose</city>
167        <region>CA</region>
168        <code>95110</code>
169        <country>USA</country>
170      </postal>
171      <email>LMM@acm.org</email>
172      <uri>http://larry.masinter.net/</uri>
173    </address>
174  </author>
175 
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email>paulle@microsoft.com</email>
186    </address>
187  </author>
188   
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
199        <country>USA</country>
200      </postal>
201      <email>timbl@w3.org</email>
202      <uri>http://www.w3.org/People/Berners-Lee/</uri>
203    </address>
204  </author>
205
206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email>ylafon@w3.org</email>
218      <uri>http://www.raubacapeu.net/people/yves/</uri>
219    </address>
220  </author>
221
222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email>julian.reschke@greenbytes.de</email>
233      <uri>http://greenbytes.de/tech/webdav/</uri>
234    </address>
235  </author>
236
237  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
238  <workgroup>HTTPbis Working Group</workgroup>
239
240<abstract>
241<t>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
244   systems. HTTP has been in use by the World Wide Web global information
245   initiative since 1990. This document is Part 2 of the seven-part specification
246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
248   as expressed by request methods, request-header fields, response status codes,
249   and response-header fields.
250</t>
251</abstract>
252
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
256    mailing list (ietf-http-wg@w3.org). The current issues list is
257    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
258    and related documents (including fancy diffs) can be found at
259    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
260  </t>
261  <t>
262    The changes in this draft are summarized in <xref target="changes.since.12"/>.
263  </t>
264</note>
265</front>
266<middle>
267<section title="Introduction" anchor="introduction">
268<t>
269   This document defines HTTP/1.1 request and response semantics.  Each HTTP
270   message, as defined in &messaging;, is in the form of either a request or
271   a response.  An HTTP server listens on a connection for HTTP requests and
272   responds to each request, in the order received on that connection, with
273   one or more HTTP response messages.  This document defines the commonly
274   agreed upon semantics of the HTTP uniform interface, the intentions defined
275   by each request method, and the various response messages that might be
276   expected as a result of applying that method to the target resource.
277</t>
278<t>
279   This document is currently disorganized in order to minimize the changes
280   between drafts and enable reviewers to see the smaller errata changes.
281   A future draft will reorganize the sections to better reflect the content.
282   In particular, the sections will be ordered according to the typical
283   processing of an HTTP request message (after message parsing): resource
284   mapping, general header fields, methods, request modifiers, response
285   status, and resource metadata.  The current mess reflects how widely
286   dispersed these topics and associated requirements had become in
287   <xref target="RFC2616"/>.
288</t>
289
290<section title="Requirements" anchor="intro.requirements">
291<t>
292   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
293   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
294   document are to be interpreted as described in <xref target="RFC2119"/>.
295</t>
296<t>
297   An implementation is not compliant if it fails to satisfy one or more
298   of the "MUST" or "REQUIRED" level requirements for the protocols it
299   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
300   level and all the "SHOULD" level requirements for its protocols is said
301   to be "unconditionally compliant"; one that satisfies all the "MUST"
302   level requirements but not all the "SHOULD" level requirements for its
303   protocols is said to be "conditionally compliant".
304</t>
305</section>
306
307<section title="Syntax Notation" anchor="notation">
308  <x:anchor-alias value="CR"/>
309  <x:anchor-alias value="DIGIT"/>
310  <x:anchor-alias value="LF"/>
311  <x:anchor-alias value="VCHAR"/>
312  <x:anchor-alias value="WSP"/>
313<t>
314  This specification uses the ABNF syntax defined in &notation; (which
315  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
316  <xref target="collected.abnf"/> shows the collected ABNF, with the list
317  rule expanded.
318</t>
319<t>
320  The following core rules are included by
321  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
322  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
323  DIGIT (decimal 0-9), DQUOTE (double quote),
324  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
325  OCTET (any 8-bit sequence of data), SP (space),
326  VCHAR (any visible USASCII character),
327  and WSP (whitespace).
328</t>
329
330<section title="Core Rules" anchor="core.rules">
331  <x:anchor-alias value="obs-text"/>
332  <x:anchor-alias value="quoted-string"/>
333  <x:anchor-alias value="token"/>
334  <x:anchor-alias value="OWS"/>
335  <x:anchor-alias value="RWS"/>
336<t>
337  The core rules below are defined in &basic-rules;:
338</t>
339<figure><artwork type="abnf2616">
340  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
341  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
342  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
343  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
344  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
345</artwork></figure>
346</section>
347
348<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
349  <x:anchor-alias value="absolute-URI"/>
350  <x:anchor-alias value="Accept"/>
351  <x:anchor-alias value="Accept-Charset"/>
352  <x:anchor-alias value="Accept-Encoding"/>
353  <x:anchor-alias value="Accept-Language"/>
354  <x:anchor-alias value="Accept-Ranges"/>
355  <x:anchor-alias value="Age"/>
356  <x:anchor-alias value="Authorization"/>
357  <x:anchor-alias value="comment"/>
358  <x:anchor-alias value="ETag"/>
359  <x:anchor-alias value="Host"/>
360  <x:anchor-alias value="HTTP-date"/>
361  <x:anchor-alias value="If-Match"/>
362  <x:anchor-alias value="If-Modified-Since"/>
363  <x:anchor-alias value="If-None-Match"/>
364  <x:anchor-alias value="If-Range"/>
365  <x:anchor-alias value="If-Unmodified-Since"/>
366  <x:anchor-alias value="partial-URI"/>
367  <x:anchor-alias value="product"/>
368  <x:anchor-alias value="Proxy-Authenticate"/>
369  <x:anchor-alias value="Proxy-Authorization"/>
370  <x:anchor-alias value="Range"/>
371  <x:anchor-alias value="TE"/>
372  <x:anchor-alias value="URI-reference"/>
373  <x:anchor-alias value="Vary"/>
374  <x:anchor-alias value="WWW-Authenticate"/>
375<t>
376  The ABNF rules below are defined in other parts:
377</t>
378<figure><!--Part1--><artwork type="abnf2616">
379  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
380  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
381  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
382  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
383  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
384  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
385  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
386  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
387</artwork></figure>
388<figure><!--Part3--><artwork type="abnf2616">
389  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
390  <x:ref>Accept-Charset</x:ref> =
391             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
392  <x:ref>Accept-Encoding</x:ref> =
393             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
394  <x:ref>Accept-Language</x:ref> =
395             &lt;Accept-Language, defined in &header-accept-language;&gt;
396</artwork></figure>
397<figure><!--Part4--><artwork type="abnf2616">
398  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
399  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
400  <x:ref>If-Modified-Since</x:ref> =
401             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
402  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
403  <x:ref>If-Unmodified-Since</x:ref> =
404             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
405</artwork></figure>
406<figure><!--Part5--><artwork type="abnf2616">
407  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
408  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
409  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
410</artwork></figure>
411<figure><!--Part6--><artwork type="abnf2616">
412  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
413  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
414</artwork><!--Part7--></figure>
415<figure><artwork type="abnf2616">
416  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
417  <x:ref>Proxy-Authenticate</x:ref> =
418             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
419  <x:ref>Proxy-Authorization</x:ref> =
420             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
421  <x:ref>WWW-Authenticate</x:ref> =
422             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
423</artwork></figure>
424</section>
425</section>
426</section>
427
428<section title="Method" anchor="method">
429  <x:anchor-alias value="Method"/>
430  <x:anchor-alias value="extension-method"/>
431<t>
432   The Method token indicates the method to be performed on the target
433   resource (&effective-request-uri;). The method is case-sensitive.
434</t>
435<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
436  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
437</artwork></figure>
438<t>
439   The list of methods allowed by a resource can be specified in an
440   Allow header field (<xref target="header.allow"/>). The status code of the response
441   always notifies the client whether a method is currently allowed on a
442   resource, since the set of allowed methods can change dynamically. An
443   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
444   if the method is known by the origin server but not allowed for the
445   resource, and 501 (Not Implemented) if the method is
446   unrecognized or not implemented by the origin server. The methods GET
447   and HEAD &MUST; be supported by all general-purpose servers. All other
448   methods are &OPTIONAL;; however, if the above methods are implemented,
449   they &MUST; be implemented with the same semantics as those specified
450   in <xref target="method.definitions"/>.
451</t>
452
453<section title="Overview of Methods" anchor="overview.of.methods">
454<t>
455  The methods listed below are defined in <xref target="method.definitions"/>.
456</t>
457<texttable align="left">
458  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
459 
460  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
461  <c>GET</c> <c><xref target="GET"/></c>
462  <c>HEAD</c> <c><xref target="HEAD"/></c>
463  <c>POST</c> <c><xref target="POST"/></c>
464  <c>PUT</c> <c><xref target="PUT"/></c>
465  <c>DELETE</c> <c><xref target="DELETE"/></c>
466  <c>TRACE</c> <c><xref target="TRACE"/></c>
467  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
468</texttable>
469<t>
470  Note that this list is not exhaustive &mdash; it does not include methods defined
471  in other specifications.
472</t>
473</section>
474
475<section title="Method Registry" anchor="method.registry">
476<t>
477  The HTTP Method Registry defines the name space for the Method token in the
478  Request line of an HTTP request.
479</t>
480<t>
481  Registrations &MUST; include the following fields:
482  <list style="symbols">
483    <t>Method Name (see <xref target="method"/>)</t>
484    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
485    <t>Pointer to specification text</t>
486  </list>
487</t>
488<t>
489  Values to be added to this name space are subject to IETF review
490  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
491</t>
492<t>
493  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
494</t>
495
496<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
497<t>
498   When it is necessary to express new semantics for a HTTP request that
499   aren't specific to a single application or media type, and currently defined
500   methods are inadequate, it may be appropriate to register a new method.
501</t>
502<t>
503   HTTP methods are generic; that is, they are potentially applicable to any
504   resource, not just one particular media type, "type" of resource, or
505   application. As such, it is preferred that new HTTP methods be registered
506   in a document that isn't specific to a single application, so that this is
507   clear.
508</t>
509<t>
510   Due to the parsing rules defined in &message-body;, definitions of HTTP
511   methods cannot prohibit the presence of a message-body on either the request
512   or the response message (with responses to HEAD requests being the single
513   exception). Definitions of new methods cannot change this rule, but they can
514   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
515</t>
516<t>
517   New method definitions need to indicate whether they are safe (<xref
518   target="safe.methods"/>) and whether they are idempotent (<xref
519   target="idempotent.methods"/>). They also need to state whether they can be
520   cached (&caching;); in particular what conditions a cache may store the
521   response, and under what conditions such a stored response may be used to
522   satisfy a subsequent request.
523</t>
524</section>
525
526</section>
527</section>
528
529<section title="Request Header Fields" anchor="request.header.fields">
530  <x:anchor-alias value="request-header"/>
531<t>
532   The request-header fields allow the client to pass additional
533   information about the request, and about the client itself, to the
534   server. These fields act as request modifiers, with semantics
535   equivalent to the parameters on a programming language method
536   invocation.
537</t>
538<texttable align="left">
539  <ttcol>Header Field Name</ttcol>
540  <ttcol>Defined in...</ttcol>
541
542  <c>Accept</c> <c>&header-accept;</c>
543  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
544  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
545  <c>Accept-Language</c> <c>&header-accept-language;</c>
546  <c>Authorization</c> <c>&header-authorization;</c>
547  <c>Expect</c> <c><xref target="header.expect"/></c>
548  <c>From</c> <c><xref target="header.from"/></c>
549  <c>Host</c> <c>&header-host;</c>
550  <c>If-Match</c> <c>&header-if-match;</c>
551  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
552  <c>If-None-Match</c> <c>&header-if-none-match;</c>
553  <c>If-Range</c> <c>&header-if-range;</c>
554  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
555  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
556  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
557  <c>Range</c> <c>&header-range;</c>
558  <c>Referer</c> <c><xref target="header.referer"/></c>
559  <c>TE</c> <c>&header-te;</c>
560  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
561</texttable>
562<t>
563   Request-header field names can be extended reliably only in
564   combination with a change in the protocol version. However, new or
565   experimental header fields &MAY; be given the semantics of request-header
566   fields if all parties in the communication recognize them to
567   be request-header fields.
568</t>
569</section>
570
571<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
572  <x:anchor-alias value="Reason-Phrase"/>
573  <x:anchor-alias value="Status-Code"/>
574  <x:anchor-alias value="extension-code"/>
575<t>
576   The Status-Code element is a 3-digit integer result code of the attempt to
577   understand and satisfy the request.
578</t>
579<t>
580   The Reason-Phrase is intended to give a short textual description of the
581   Status-Code and is intended for a human user. The client does not need
582   to examine or display the Reason-Phrase.
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>    = 3<x:ref>DIGIT</x:ref>
586  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
587</artwork></figure>
588<t>
589   HTTP status codes are extensible. HTTP applications are not required
590   to understand the meaning of all registered status codes, though such
591   understanding is obviously desirable. However, applications &MUST;
592   understand the class of any status code, as indicated by the first
593   digit, and treat any unrecognized response as being equivalent to the
594   x00 status code of that class, with the exception that an
595   unrecognized response &MUST-NOT; be cached. For example, if an
596   unrecognized status code of 431 is received by the client, it can
597   safely assume that there was something wrong with its request and
598   treat the response as if it had received a 400 status code. In such
599   cases, user agents &SHOULD; present to the user the representation enclosed
600   with the response, since that representation is likely to include human-readable
601   information which will explain the unusual status.
602</t>
603
604<section title="Overview of Status Codes" anchor="overview.of.status.codes">
605<t> 
606   The status codes listed below are defined in <xref target="status.codes"/>
607   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
608   The reason phrases listed here are only recommendations &mdash; they can be
609   replaced by local equivalents without affecting the protocol.
610</t>
611<texttable align="left">
612  <ttcol>Status-Code</ttcol>
613  <ttcol>Reason-Phrase</ttcol>
614  <ttcol>Defined in...</ttcol>
615 
616  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
617  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
618
619  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
620  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
621  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
622  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
623  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
624  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
625  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
626
627  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
628  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
629  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
630  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
631  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
632  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
633  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
634
635  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
636  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
637  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
638  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
639  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
640  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
641  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
642  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
643  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
644  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
645  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
646  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
647  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
648  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
649  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
650  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
651  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
652  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
653  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
654
655  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
656  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
657  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
658  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
659  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
660  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
661</texttable>
662<t>
663   Note that this list is not exhaustive &mdash; it does not include
664   extension status codes defined in other specifications.
665</t>
666</section>
667
668<section title="Status Code Registry" anchor="status.code.registry">
669<t>
670  The HTTP Status Code Registry defines the name space for the Status-Code
671  token in the Status-Line of an HTTP response.
672</t>
673<t>
674  Values to be added to this name space are subject to IETF review
675  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
676</t>
677<t>
678  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
679</t>
680
681<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
682<t>
683   When it is necessary to express new semantics for a HTTP response that
684   aren't specific to a single application or media type, and currently defined
685   status codes are inadequate, a new status code can be registered.
686</t>
687<t>
688   HTTP status codes are generic; that is, they are potentially applicable to
689   any resource, not just one particular media type, "type" of resource, or
690   application. As such, it is preferred that new HTTP status codes be
691   registered in a document that isn't specific to a single application, so
692   that this is clear.
693</t>
694<t>
695   Definitions of new HTTP status codes typically explain the request
696   conditions that produce a response containing the status code (e.g.,
697   combinations of request headers and/or method(s)), along with any
698   interactions with response headers (e.g., those that are required, those
699   that modify the semantics of the response).
700</t>
701<t>
702   New HTTP status codes are required to fall under one of the categories
703   defined in <xref target="status.codes"/>. To allow existing parsers to
704   properly handle them, new status codes cannot disallow a response body,
705   although they can mandate a zero-length response body. They can require the
706   presence of one or more particular HTTP response header(s).
707</t>
708<t>
709   Likewise, their definitions can specify that caches are allowed to use
710   heuristics to determine their freshness (see &caching;; by default, it is
711   not allowed), and can define how to determine the resource which they
712   carry a representation for (see <xref
713   target="identifying.response.associated.with.representation"/>; by default,
714   it is anonymous).
715</t>
716</section>
717
718</section>
719
720</section>
721
722<section title="Response Header Fields" anchor="response.header.fields">
723  <x:anchor-alias value="response-header"/>
724<t>
725   The response-header fields allow the server to pass additional
726   information about the response which cannot be placed in the Status-Line.
727   These header fields give information about the server and about
728   further access to the target resource (&effective-request-uri;).
729</t>
730<texttable align="left">
731  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
732
733  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
734  <c>Age</c> <c>&header-age;</c>
735  <c>Allow</c> <c><xref target="header.allow"/></c>
736  <c>ETag</c> <c>&header-etag;</c>
737  <c>Location</c> <c><xref target="header.location"/></c>
738  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
739  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
740  <c>Server</c> <c><xref target="header.server"/></c>
741  <c>Vary</c> <c>&header-vary;</c>
742  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
743</texttable>
744<t>
745   Response-header field names can be extended reliably only in
746   combination with a change in the protocol version. However, new or
747   experimental header fields &MAY; be given the semantics of response-header
748   fields if all parties in the communication recognize them to
749   be response-header fields.
750</t>
751</section>
752
753<section title="Representation" anchor="representation">
754<t>
755   Request and Response messages &MAY; transfer a representation if not otherwise
756   restricted by the request method or response status code. A representation
757   consists of metadata (representation header fields) and data (representation
758   body).  When a complete or partial representation is enclosed in an HTTP message,
759   it is referred to as the payload of the message. HTTP representations
760   are defined in &payload;.
761</t>
762<t>
763   A representation body is only present in a message when a message-body is
764   present, as described in &message-body;. The representation body is obtained
765   from the message-body by decoding any Transfer-Encoding that might
766   have been applied to ensure safe and proper transfer of the message.
767</t>
768
769<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
770<t>
771   It is sometimes necessary to determine an identifier for the resource
772   associated with a representation.
773</t>
774<t>
775   An HTTP request representation, when present, is always associated with an
776   anonymous (i.e., unidentified) resource.
777</t>
778<t>
779   In the common case, an HTTP response is a representation of the target
780   resource (see &effective-request-uri;). However, this is not always the
781   case. To determine the URI of the resource a response is associated with,
782   the following rules are used (with the first applicable one being selected):
783</t>
784<t><list style="numbers">
785   <t>If the response status code is 200 or 203 and the request method was GET,
786   the response payload is a representation of the target resource.</t>
787   <t>If the response status code is 204, 206, or 304 and the request method was GET
788   or HEAD, the response payload is a partial representation of the target
789   resource (see &combining-responses;).</t>
790   <t>If the response has a Content-Location header field, and that URI is the same
791   as the effective request URI, the response payload is a representation of the
792   target resource.</t>
793   <t>If the response has a Content-Location header field, and that URI is not the
794   same as the effective request URI, then the response asserts that its
795   payload is a representation of the resource identified by the
796   Content-Location URI. However, such an assertion cannot be trusted unless
797   it can be verified by other means (not defined by HTTP).</t>
798   <t>Otherwise, the response is a representation of an anonymous (i.e.,
799   unidentified) resource.</t>
800</list></t>
801<t>
802  <cref anchor="TODO-req-uri">
803   The comparison function is going to have to be defined somewhere,
804   because we already need to compare URIs for things like cache invalidation.</cref>
805</t>
806</section>
807
808</section>
809
810
811<section title="Method Definitions" anchor="method.definitions">
812<t>
813   The set of common methods for HTTP/1.1 is defined below. Although
814   this set can be expanded, additional methods cannot be assumed to
815   share the same semantics for separately extended clients and servers.
816</t>
817
818<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
819
820<section title="Safe Methods" anchor="safe.methods">
821<iref item="Safe Methods" primary="true"/>
822<t>
823   Implementors need to be aware that the software represents the user in
824   their interactions over the Internet, and need to allow
825   the user to be aware of any actions they take which might have an
826   unexpected significance to themselves or others.
827</t>
828<t>
829   In particular, the convention has been established that the GET, HEAD,
830   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
831   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
832   This allows user agents to represent other methods, such as POST, PUT
833   and DELETE, in a special way, so that the user is made aware of the
834   fact that a possibly unsafe action is being requested.
835</t>
836<t>
837   Naturally, it is not possible to ensure that the server does not
838   generate side-effects as a result of performing a GET request; in
839   fact, some dynamic resources consider that a feature. The important
840   distinction here is that the user did not request the side-effects,
841   so therefore cannot be held accountable for them.
842</t>
843</section>
844
845<section title="Idempotent Methods" anchor="idempotent.methods">
846<iref item="Idempotent Methods" primary="true"/>
847<t>
848   Methods can also have the property of "idempotence" in that, aside
849   from error or expiration issues, the intended effect of multiple
850   identical requests is the same as for a single request.
851   The methods PUT, DELETE, and all safe methods are idempotent.
852   It is important to note that idempotence refers only to changes
853   requested by the client: a server is free to change its state due
854   to multiple requests for the purpose of tracking those requests,
855   versioning of results, etc.
856</t>
857</section>
858</section>
859
860<section title="OPTIONS" anchor="OPTIONS">
861  <rdf:Description>
862    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
863  </rdf:Description>
864  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
865  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
866<t>
867   The OPTIONS method represents a request for information about the
868   communication options available on the request/response chain
869   identified by the effective request URI. This method allows the client to
870   determine the options and/or requirements associated with a resource,
871   or the capabilities of a server, without implying a resource action
872   or initiating a resource retrieval.
873</t>
874<t>
875   Responses to this method are not cacheable.
876</t>
877<t>
878   If the OPTIONS request includes a message-body (as indicated by the
879   presence of Content-Length or Transfer-Encoding), then the media type
880   &MUST; be indicated by a Content-Type field. Although this
881   specification does not define any use for such a body, future
882   extensions to HTTP might use the OPTIONS body to make more detailed
883   queries on the server.
884</t>
885<t>
886   If the request-target is an asterisk ("*"), the OPTIONS request is
887   intended to apply to the server in general rather than to a specific
888   resource. Since a server's communication options typically depend on
889   the resource, the "*" request is only useful as a "ping" or "no-op"
890   type of method; it does nothing beyond allowing the client to test
891   the capabilities of the server. For example, this can be used to test
892   a proxy for HTTP/1.1 compliance (or lack thereof).
893</t>
894<t>
895   If the request-target is not an asterisk, the OPTIONS request applies
896   only to the options that are available when communicating with that
897   resource.
898</t>
899<t>
900   A 200 response &SHOULD; include any header fields that indicate
901   optional features implemented by the server and applicable to that
902   resource (e.g., Allow), possibly including extensions not defined by
903   this specification. The response body, if any, &SHOULD; also include
904   information about the communication options. The format for such a
905   body is not defined by this specification, but might be defined by
906   future extensions to HTTP. Content negotiation &MAY; be used to select
907   the appropriate response format. If no response body is included, the
908   response &MUST; include a Content-Length field with a field-value of
909   "0".
910</t>
911<t>
912   The Max-Forwards request-header field &MAY; be used to target a
913   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
914   If no Max-Forwards field is present in the request, then the forwarded
915   request &MUST-NOT; include a Max-Forwards field.
916</t>
917</section>
918
919<section title="GET" anchor="GET">
920  <rdf:Description>
921    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
922  </rdf:Description>
923  <iref primary="true" item="GET method" x:for-anchor=""/>
924  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
925<t>
926   The GET method means retrieve whatever information (in the form of a
927   representation) currently corresponds to the target resource.
928</t>
929<t>   
930   If the target resource is a data-producing process, it is the
931   produced data which shall be returned as the representation in the response and not
932   the source text of the process, unless that text happens to be the output of
933   the process.
934</t>
935<t>
936   The semantics of the GET method change to a "conditional GET" if the
937   request message includes an If-Modified-Since, If-Unmodified-Since,
938   If-Match, If-None-Match, or If-Range header field. A conditional GET
939   method requests that the representation be transferred only under the
940   circumstances described by the conditional header field(s). The
941   conditional GET method is intended to reduce unnecessary network
942   usage by allowing cached representations to be refreshed without requiring
943   multiple requests or transferring data already held by the client.
944</t>
945<t>
946   The semantics of the GET method change to a "partial GET" if the
947   request message includes a Range header field. A partial GET requests
948   that only part of the representation be transferred, as described in &header-range;.
949   The partial GET method is intended to reduce unnecessary
950   network usage by allowing partially-retrieved representations to be
951   completed without transferring data already held by the client.
952</t>
953<t>
954   The response to a GET request is cacheable and &MAY; be used to satisfy
955   subsequent GET and HEAD requests (see &caching;).
956</t>
957<t>
958   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
959</t>
960</section>
961
962<section title="HEAD" anchor="HEAD">
963  <rdf:Description>
964    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
965  </rdf:Description>
966  <iref primary="true" item="HEAD method" x:for-anchor=""/>
967  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
968<t>
969   The HEAD method is identical to GET except that the server &MUST-NOT;
970   return a message-body in the response. The metadata contained
971   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
972   to the information sent in response to a GET request. This method can
973   be used for obtaining metadata about the representation implied by the
974   request without transferring the representation body. This method is
975   often used for testing hypertext links for validity, accessibility,
976   and recent modification.
977</t>
978<t>
979   The response to a HEAD request is cacheable and &MAY; be used to satisfy
980   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
981   representation from that resource; if the new field values
982   indicate that the cached representation differs from the current representation (as
983   would be indicated by a change in Content-Length, Content-MD5, ETag
984   or Last-Modified), then the cache &MUST; treat the cache entry as
985   stale.
986</t>
987</section>
988
989<section title="POST" anchor="POST">
990  <iref primary="true" item="POST method" x:for-anchor=""/>
991  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
992<t>
993   The POST method is used to request that the origin server accept the
994   representation enclosed in the request as data to be processed by the
995   target resource. POST is designed to allow a uniform method to cover the
996   following functions:
997  <list style="symbols">
998    <t>
999      Annotation of existing resources;
1000    </t>
1001    <t>
1002        Posting a message to a bulletin board, newsgroup, mailing list,
1003        or similar group of articles;
1004    </t>
1005    <t>
1006        Providing a block of data, such as the result of submitting a
1007        form, to a data-handling process;
1008    </t>
1009    <t>
1010        Extending a database through an append operation.
1011    </t>
1012  </list>
1013</t>
1014<t>
1015   The actual function performed by the POST method is determined by the
1016   server and is usually dependent on the effective request URI.
1017</t>
1018<t>
1019   The action performed by the POST method might not result in a
1020   resource that can be identified by a URI. In this case, either 200
1021   (OK) or 204 (No Content) is the appropriate response status code,
1022   depending on whether or not the response includes a representation that
1023   describes the result.
1024</t>
1025<t>
1026   If a resource has been created on the origin server, the response
1027   &SHOULD; be 201 (Created) and contain a representation which describes the
1028   status of the request and refers to the new resource, and a Location
1029   header field (see <xref target="header.location"/>).
1030</t>
1031<t>
1032   Responses to POST requests are only cacheable when they
1033   include explicit freshness information (see &p6-explicit;). A
1034   cached POST response with a Content-Location header field
1035   (see &header-content-location;) whose value is the effective
1036   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1037</t>
1038<t>
1039   Note that POST caching is not widely implemented.
1040   However, the 303 (See Other) response can be used to direct the
1041   user agent to retrieve a cacheable resource.
1042</t>
1043</section>
1044
1045<section title="PUT" anchor="PUT">
1046  <iref primary="true" item="PUT method" x:for-anchor=""/>
1047  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1048<t>
1049   The PUT method is used to request that the state of the target resource
1050   be created or replaced with the state defined by the representation
1051   enclosed in the request message payload.  A successful PUT of a given
1052   representation would suggest that a subsequent GET on that same target
1053   resource will result in an equivalent representation being returned in
1054   a 200 (OK) response.  However, there is no guarantee that such a state
1055   change will be observable, since the target resource might be acted
1056   upon by other user agents in parallel, or might be subject to dynamic
1057   processing by the origin server, before any subsequent GET is received.
1058   A successful response only implies that the user agent's intent was
1059   achieved at the time of its processing by the origin server.
1060</t>
1061<t>   
1062   If the target resource does not have a current representation and
1063   the PUT successfully creates one, then the origin server &MUST; inform
1064   the user agent by sending a 201 (Created) response.  If the target
1065   resource does have a current representation and that representation is
1066   successfully modified in accordance with the state of the enclosed
1067   representation, then either a 200 (OK) or 204 (No Content) response
1068   &SHOULD; be sent to indicate successful completion of the request.
1069</t>
1070<t>
1071   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1072   as part of the resource state).
1073</t>
1074<t>
1075   An origin server &SHOULD; verify that the PUT representation is
1076   consistent with any constraints which the server has for the target
1077   resource that cannot or will not be changed by the PUT.  This is
1078   particularly important when the origin server uses internal
1079   configuration information related to the URI in order to set the
1080   values for representation metadata on GET responses.  When a PUT
1081   representation is inconsistent with the target resource, the origin
1082   server &SHOULD; either make them consistent, by transforming the
1083   representation or changing the resource configuration, or respond
1084   with a 409 (Conflict) status code and sufficient information
1085   to explain why the representation is unsuitable.
1086</t>
1087<t>
1088   For example, if the target resource is configured to always have a
1089   Content-Type of "text/html" and the representation being PUT has a
1090   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1091   (a) reconfigure the target resource to reflect the new media type;
1092   (b) transform the PUT representation to a format consistent with that
1093   of the resource before saving it as the new resource state; or,
1094   (c) reject the request with a 409 response indicating that the target
1095   resource is limited to "text/html", perhaps including a link to a
1096   different resource that would be a suitable target for the new
1097   representation.
1098</t>
1099<t>
1100   HTTP does not define exactly how a PUT method affects the state
1101   of an origin server beyond what can be expressed by the intent of
1102   the user agent request and the semantics of the origin server response.
1103   It does not define what a resource might be, in any sense of that
1104   word, beyond the interface provided via HTTP.  It does not define
1105   how resource state is "stored", nor how such storage might change
1106   as a result of a change in resource state, nor how the origin server
1107   translates resource state into representations.  Generally speaking,
1108   all implementation details behind the resource interface are
1109   intentionally hidden by the server.
1110</t>
1111<t>
1112   The fundamental difference between the POST and PUT methods is
1113   highlighted by the different intent for the target resource.
1114   The target resource in a POST request is intended to handle the
1115   enclosed representation as a data-accepting process, such as for
1116   a gateway to some other protocol or a document that accepts annotations.
1117   In contrast, the target resource in a PUT request is intended to
1118   take the enclosed representation as a new or replacement value.
1119   Hence, the intent of PUT is idempotent and visible to intermediaries,
1120   even though the exact effect is only known by the origin server.
1121</t>
1122<t>
1123   Proper interpretation of a PUT request presumes that the user agent
1124   knows what target resource is desired.  A service that is intended
1125   to select a proper URI on behalf of the client, after receiving
1126   a state-changing request, &SHOULD; be implemented using the POST
1127   method rather than PUT.  If the origin server will not make the
1128   requested PUT state change to the target resource and instead
1129   wishes to have it applied to a different resource, such as when the
1130   resource has been moved to a different URI, then the origin server
1131   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1132   then make its own decision regarding whether or not to redirect the
1133   request.
1134</t>
1135<t>
1136   A PUT request applied to the target resource &MAY; have side-effects
1137   on other resources.  For example, an article might have a URI for
1138   identifying "the current version" (a resource) which is separate
1139   from the URIs identifying each particular version (different
1140   resources that at one point shared the same state as the current version
1141   resource).  A successful PUT request on "the current version" URI might
1142   therefore create a new version resource in addition to changing the
1143   state of the target resource, and might also cause links to be added
1144   between the related resources.
1145</t>
1146<t>
1147   An origin server &SHOULD; reject any PUT request that contains a
1148   Content-Range header field, since it might be misinterpreted as
1149   partial content (or might be partial content that is being mistakenly
1150   PUT as a full representation).  Partial content updates are
1151   possible by targeting a separately identified resource with state
1152   that overlaps a portion of the larger resource, or by using a
1153   different method that has been specifically defined for partial
1154   updates (for example, the PATCH method defined in
1155   <xref target="RFC5789"/>).
1156</t>
1157<t>
1158   Responses to the PUT method are not cacheable. If a PUT request passes
1159   through a cache that has one or more stored responses for the effective
1160   request URI, those stored responses will be invalidated (see
1161   &p6-invalid;).
1162</t>
1163</section>
1164
1165<section title="DELETE" anchor="DELETE">
1166  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1167  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1168<t>
1169   The DELETE method requests that the origin server delete the target
1170   resource. This method &MAY; be overridden by
1171   human intervention (or other means) on the origin server. The client cannot
1172   be guaranteed that the operation has been carried out, even if the
1173   status code returned from the origin server indicates that the action
1174   has been completed successfully. However, the server &SHOULD-NOT; 
1175   indicate success unless, at the time the response is given, it
1176   intends to delete the resource or move it to an inaccessible
1177   location.
1178</t>
1179<t>
1180   A successful response &SHOULD; be 200 (OK) if the response includes an
1181   representation describing the status, 202 (Accepted) if the action has not
1182   yet been enacted, or 204 (No Content) if the action has been enacted
1183   but the response does not include a representation.
1184</t>
1185<t>
1186   Responses to the DELETE method are not cacheable. If a DELETE request
1187   passes through a cache that has one or more stored responses for the
1188   effective request URI, those stored responses will be invalidated (see
1189   &p6-invalid;).
1190</t>
1191</section>
1192
1193<section title="TRACE" anchor="TRACE">
1194  <rdf:Description>
1195    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1196  </rdf:Description>
1197  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1198  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1199<t>
1200   The TRACE method is used to invoke a remote, application-layer loop-back
1201   of the request message. The final recipient of the request
1202   &SHOULD; reflect the message received back to the client as the
1203   message-body of a 200 (OK) response. The final recipient is either the
1204   origin server or the first proxy or gateway to receive a Max-Forwards
1205   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1206   A TRACE request &MUST-NOT; include a message-body.
1207</t>
1208<t>
1209   TRACE allows the client to see what is being received at the other
1210   end of the request chain and use that data for testing or diagnostic
1211   information. The value of the Via header field (&header-via;) is of
1212   particular interest, since it acts as a trace of the request chain.
1213   Use of the Max-Forwards header field allows the client to limit the
1214   length of the request chain, which is useful for testing a chain of
1215   proxies forwarding messages in an infinite loop.
1216</t>
1217<t>
1218   If the request is valid, the response &SHOULD; have a Content-Type of
1219   "message/http" (see &media-type-message-http;) and contain a message-body
1220   that encloses a copy of the entire request message.
1221   Responses to the TRACE method are not cacheable.
1222</t>
1223</section>
1224
1225<section title="CONNECT" anchor="CONNECT">
1226  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1227  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1228<t>
1229   The CONNECT method is used with a proxy to dynamically switch
1230   the connection to a tunnel.
1231</t>
1232<t>
1233   When using CONNECT, the request-target &MUST; be use the authority form
1234   (&request-target;); i.e., the host name and port number destination of the
1235   requested connection separated by a colon:
1236</t>
1237<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1238CONNECT server.example.com:80 HTTP/1.1
1239Host: server.example.com:80
1240
1241</artwork></figure>
1242<t>
1243   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1244   except end-to-end protocol Upgrade requests, since the
1245   tunnel must be established first.
1246</t>
1247<t>
1248   For example, proxy authentication might be used to establish the
1249   authority to create a tunnel:
1250</t>
1251<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1252CONNECT server.example.com:80 HTTP/1.1
1253Host: server.example.com:80
1254Proxy-Authorization: basic aGVsbG86d29ybGQ=
1255
1256</artwork></figure>
1257<t>
1258   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1259   sent immediately after the blank line. The usual caveats also apply:
1260   data may be discarded if the eventual response is negative, and the
1261   connection may be reset with no response if more than one TCP segment
1262   is outstanding.
1263</t>
1264
1265<section title="Establishing a Tunnel with CONNECT">
1266<t>
1267   Any successful (2xx) response to a CONNECT request indicates that the
1268   proxy has established a connection to the requested host and port,
1269   and has switched to tunneling the current connection to that server
1270   connection.
1271</t>
1272<t>
1273   It may be the case that the proxy itself can only reach the requested
1274   origin server through another proxy.  In this case, the first proxy
1275   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1276   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1277   unless it has either a direct or tunnel connection established to the
1278   authority.
1279</t>
1280<t>
1281   An origin server which receives a CONNECT request for itself &MAY;
1282   respond with a 2xx status code to indicate that a connection is
1283   established.
1284</t>
1285<t>
1286   If at any point either one of the peers gets disconnected, any
1287   outstanding data that came from that peer will be passed to the other
1288   one, and after that also the other connection will be terminated by
1289   the proxy. If there is outstanding data to that peer undelivered,
1290   that data will be discarded.
1291</t>
1292
1293</section>
1294</section>
1295</section>
1296
1297
1298<section title="Status Code Definitions" anchor="status.codes">
1299<t>
1300   Each Status-Code is described below, including any metadata required
1301   in the response.
1302</t>
1303
1304<section title="Informational 1xx" anchor="status.1xx">
1305<t>
1306   This class of status code indicates a provisional response,
1307   consisting only of the Status-Line and optional header fields, and is
1308   terminated by an empty line. There are no required header fields for this
1309   class of status code. Since HTTP/1.0 did not define any 1xx status
1310   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1311   except under experimental conditions.
1312</t>
1313<t>
1314   A client &MUST; be prepared to accept one or more 1xx status responses
1315   prior to a regular response, even if the client does not expect a 100
1316   (Continue) status message. Unexpected 1xx status responses &MAY; be
1317   ignored by a user agent.
1318</t>
1319<t>
1320   Proxies &MUST; forward 1xx responses, unless the connection between the
1321   proxy and its client has been closed, or unless the proxy itself
1322   requested the generation of the 1xx response. (For example, if a
1323   proxy adds a "Expect: 100-continue" field when it forwards a request,
1324   then it need not forward the corresponding 100 (Continue)
1325   response(s).)
1326</t>
1327
1328<section title="100 Continue" anchor="status.100">
1329  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1330  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1331<t>
1332   The client &SHOULD; continue with its request. This interim response is
1333   used to inform the client that the initial part of the request has
1334   been received and has not yet been rejected by the server. The client
1335   &SHOULD; continue by sending the remainder of the request or, if the
1336   request has already been completed, ignore this response. The server
1337   &MUST; send a final response after the request has been completed. See
1338   &use100; for detailed discussion of the use and handling of this
1339   status code.
1340</t>
1341</section>
1342
1343<section title="101 Switching Protocols" anchor="status.101">
1344  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1345  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1346<t>
1347   The server understands and is willing to comply with the client's
1348   request, via the Upgrade message header field (&header-upgrade;), for a
1349   change in the application protocol being used on this connection. The
1350   server will switch protocols to those defined by the response's
1351   Upgrade header field immediately after the empty line which
1352   terminates the 101 response.
1353</t>
1354<t>
1355   The protocol &SHOULD; be switched only when it is advantageous to do
1356   so. For example, switching to a newer version of HTTP is advantageous
1357   over older versions, and switching to a real-time, synchronous
1358   protocol might be advantageous when delivering resources that use
1359   such features.
1360</t>
1361</section>
1362</section>
1363
1364<section title="Successful 2xx" anchor="status.2xx">
1365<t>
1366   This class of status code indicates that the client's request was
1367   successfully received, understood, and accepted.
1368</t>
1369
1370<section title="200 OK" anchor="status.200">
1371  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1372  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1373<t>
1374   The request has succeeded. The payload returned with the response
1375   is dependent on the method used in the request, for example:
1376  <list style="hanging">
1377    <t hangText="GET">
1378          a representation of the target resource is sent in the response;
1379    </t>
1380    <t hangText="HEAD">
1381          the same representation as GET, except without the message-body;
1382    </t>
1383    <t hangText="POST">
1384      a representation describing or containing the result of the action;
1385    </t>
1386    <t hangText="TRACE">
1387      a representation containing the request message as received by the
1388      end server.
1389    </t>
1390  </list>
1391</t>
1392<t>
1393   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1394   freshness for 200 responses.
1395</t>
1396</section>
1397
1398<section title="201 Created" anchor="status.201">
1399  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1400  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1401<t>
1402   The request has been fulfilled and has resulted in a new resource being
1403   created. The newly created resource can be referenced by the URI(s)
1404   returned in the payload of the response, with the most specific URI
1405   for the resource given by a Location header field. The response
1406   &SHOULD; include a payload containing a list of resource
1407   characteristics and location(s) from which the user or user agent can
1408   choose the one most appropriate. The payload format is specified by
1409   the media type given in the Content-Type header field. The origin
1410   server &MUST; create the resource before returning the 201 status code.
1411   If the action cannot be carried out immediately, the server &SHOULD;
1412   respond with 202 (Accepted) response instead.
1413</t>
1414<t>
1415   A 201 response &MAY; contain an ETag response header field indicating
1416   the current value of the entity-tag for the representation of the resource
1417   just created (see &header-etag;).
1418</t>
1419</section>
1420
1421<section title="202 Accepted" anchor="status.202">
1422  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1423  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1424<t>
1425   The request has been accepted for processing, but the processing has
1426   not been completed.  The request might or might not eventually be
1427   acted upon, as it might be disallowed when processing actually takes
1428   place. There is no facility for re-sending a status code from an
1429   asynchronous operation such as this.
1430</t>
1431<t>
1432   The 202 response is intentionally non-committal. Its purpose is to
1433   allow a server to accept a request for some other process (perhaps a
1434   batch-oriented process that is only run once per day) without
1435   requiring that the user agent's connection to the server persist
1436   until the process is completed. The representation returned with this
1437   response &SHOULD; include an indication of the request's current status
1438   and either a pointer to a status monitor or some estimate of when the
1439   user can expect the request to be fulfilled.
1440</t>
1441</section>
1442
1443<section title="203 Non-Authoritative Information" anchor="status.203">
1444  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1445  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1446<t>
1447   The returned metadata in the header fields is not the
1448   definitive set as available from the origin server, but is gathered
1449   from a local or a third-party copy. The set presented &MAY; be a subset
1450   or superset of the original version. For example, including local
1451   annotation information about the resource might result in a superset
1452   of the metadata known by the origin server. Use of this
1453   response code is not required and is only appropriate when the
1454   response would otherwise be 200 (OK).
1455</t>
1456<t>
1457   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1458   freshness for 203 responses.
1459</t>
1460
1461</section>
1462
1463<section title="204 No Content" anchor="status.204">
1464  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1466<t>
1467   The server has successfully fulfilled the request, but there is no
1468   additional content to return in the response payload body.  The
1469   resource metadata and representation metadata in the response message's
1470   header fields refer to the target resource
1471   and its current representation, respectively, after the requested action.
1472   For example, if a 204 status code is received in response to a PUT
1473   and the response contains an ETag header field, then the value of
1474   that field is the current entity-tag for the representation that
1475   was successfully PUT.
1476</t>
1477<t>
1478   If the client is a user agent, it &SHOULD-NOT; change its document view
1479   from that which caused the request to be sent. This response is
1480   primarily intended to allow input for actions to take place without
1481   causing a change to the user agent's active document view, although
1482   any new or updated metadata &SHOULD; be applied to the document
1483   currently in the user agent's active view.
1484</t>
1485<t>
1486   The 204 response &MUST-NOT; include a message-body, and thus is always
1487   terminated by the first empty line after the header fields.
1488</t>
1489</section>
1490
1491<section title="205 Reset Content" anchor="status.205">
1492  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1493  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1494<t>
1495   The server has fulfilled the request and the user agent &SHOULD; reset
1496   the document view which caused the request to be sent. This response
1497   is primarily intended to allow input for actions to take place via
1498   user input, followed by a clearing of the form in which the input is
1499   given so that the user can easily initiate another input action.
1500</t>
1501<t>   
1502   The message-body included with the response &MUST; be empty. Note that
1503   receivers still need to parse the response according to the algorithm defined
1504   in &message-body;.
1505</t>
1506</section>
1507
1508<section title="206 Partial Content" anchor="status.206">
1509  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1511  <rdf:Description>
1512    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1513  </rdf:Description>
1514<t>
1515   The server has fulfilled the partial GET request for the resource
1516   and the enclosed payload is a partial representation as defined in &status-206;.
1517</t>
1518<t>
1519   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1520   freshness for 206 responses.
1521</t>
1522</section>
1523</section>
1524
1525<section title="Redirection 3xx" anchor="status.3xx">
1526<t>
1527   This class of status code indicates that further action needs to be
1528   taken by the user agent in order to fulfill the request.  The action
1529   required &MAY; be carried out by the user agent without interaction
1530   with the user if and only if the method used in the second request is
1531   known to be "safe", as defined in <xref target="safe.methods"/>.
1532   A client &SHOULD; detect infinite redirection loops, since such loops
1533   generate network traffic for each redirection.
1534</t>
1535<x:note>
1536  <t>
1537    <x:h>Note:</x:h> An earlier version of this specification recommended a
1538    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1539    Content developers need to be aware that some clients might
1540    implement such a fixed limitation.
1541  </t>
1542</x:note>
1543
1544<section title="300 Multiple Choices" anchor="status.300">
1545  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1546  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1547<t>
1548   The target resource has more than one
1549   representation, each with its own specific location, and agent-driven
1550   negotiation information (&content-negotiation;) is being provided so that
1551   the user (or user agent) can select a preferred representation by
1552   redirecting its request to that location.
1553</t>
1554<t>
1555   Unless it was a HEAD request, the response &SHOULD; include a representation
1556   containing a list of representation metadata and location(s) from
1557   which the user or user agent can choose the one most appropriate. The
1558   data format is specified by the media type given in the Content-Type
1559   header field. Depending upon the format and the capabilities of
1560   the user agent, selection of the most appropriate choice &MAY; be
1561   performed automatically. However, this specification does not define
1562   any standard for such automatic selection.
1563</t>
1564<t>
1565   If the server has a preferred choice of representation, it &SHOULD;
1566   include the specific URI for that representation in the Location
1567   field; user agents &MAY; use the Location field value for automatic
1568   redirection.
1569</t>
1570<t>
1571   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1572   freshness for 300 responses.
1573</t>
1574
1575</section>
1576
1577<section title="301 Moved Permanently" anchor="status.301">
1578  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1579  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1580<t>
1581   The target resource has been assigned a new permanent URI and any
1582   future references to this resource &SHOULD; use one of the returned
1583   URIs.  Clients with link editing capabilities ought to automatically
1584   re-link references to the effective request URI to one or more of the new
1585   references returned by the server, where possible.
1586</t>
1587<t>
1588   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1589   freshness for 301 responses.
1590</t>
1591<t>
1592   The new permanent URI &SHOULD; be given by the Location field in the
1593   response. Unless the request method was HEAD, the representation of the
1594   response &SHOULD; contain a short hypertext note with a hyperlink to
1595   the new URI(s).
1596</t>
1597<t>
1598   If the 301 status code is received in response to a request method
1599   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1600   then the request &MAY; be automatically redirected by the user agent without
1601   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1602   request unless it can be confirmed by the user, since this might
1603   change the conditions under which the request was issued.
1604</t>
1605<x:note>
1606  <t>
1607    <x:h>Note:</x:h> When automatically redirecting a POST request after
1608    receiving a 301 status code, some existing HTTP/1.0 user agents
1609    will erroneously change it into a GET request.
1610  </t>
1611</x:note>
1612</section>
1613
1614<section title="302 Found" anchor="status.302">
1615  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1616  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1617<t>
1618   The target resource resides temporarily under a different URI.
1619   Since the redirection might be altered on occasion, the client &SHOULD;
1620   continue to use the effective request URI for future requests.
1621</t>
1622<t>
1623   The temporary URI &SHOULD; be given by the Location field in the
1624   response. Unless the request method was HEAD, the representation of the
1625   response &SHOULD; contain a short hypertext note with a hyperlink to
1626   the new URI(s).
1627</t>
1628<t>
1629   If the 302 status code is received in response to a request method
1630   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1631   then the request &MAY; be automatically redirected by the user agent without
1632   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1633   request unless it can be confirmed by the user, since this might
1634   change the conditions under which the request was issued.
1635</t>
1636<x:note>
1637  <t>
1638    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1639    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1640    specify that the client is not allowed to change the method on the
1641    redirected request.  However, most existing user agent implementations
1642    treat 302 as if it were a 303 response, performing a GET on the Location
1643    field-value regardless of the original request method. Therefore, a
1644    previous version of this specification
1645    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1646    status codes
1647    <xref target="status.303" format="none">303</xref> and
1648    <xref target="status.307" format="none">307</xref> for servers that wish
1649    to make unambiguously clear which kind of reaction is expected of the
1650    client.
1651  </t>
1652</x:note>
1653</section>
1654
1655<section title="303 See Other" anchor="status.303">
1656  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1657  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1658<t>
1659   The server directs the user agent to a different resource, indicated
1660   by a URI in the Location header field, that provides an indirect
1661   response to the original request.  The user agent &MAY; perform a GET
1662   request on the URI in the Location field in order to obtain a
1663   representation corresponding to the response, be redirected again,
1664   or end with an error status.  The Location URI is not a substitute
1665   reference for the effective request URI.
1666</t>
1667<t>
1668   The 303 status code is generally applicable to any HTTP method.  It is
1669   primarily used to allow the output of a POST action to redirect
1670   the user agent to a selected resource, since doing so provides the
1671   information corresponding to the POST response in a form that
1672   can be separately identified, bookmarked, and cached independent
1673   of the original request.
1674</t>
1675<t>
1676   A 303 response to a GET request indicates that the requested
1677   resource does not have a representation of its own that can be
1678   transferred by the server over HTTP.  The Location URI indicates a
1679   resource that is descriptive of the target resource, such that the
1680   follow-on representation might be useful to recipients without
1681   implying that it adequately represents the target resource.
1682   Note that answers to the questions of what can be represented, what
1683   representations are adequate, and what might be a useful description
1684   are outside the scope of HTTP and thus entirely determined by the
1685   URI owner(s).
1686</t>
1687<t>
1688   Except for responses to a HEAD request, the representation of a 303
1689   response &SHOULD; contain a short hypertext note with a hyperlink
1690   to the Location URI.
1691</t>
1692</section>
1693
1694<section title="304 Not Modified" anchor="status.304">
1695  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1696  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1697  <rdf:Description>
1698    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1699  </rdf:Description>
1700<t>
1701   The response to the request has not been modified since the conditions
1702   indicated by the client's conditional GET request, as defined in &status-304;.
1703</t>
1704</section>
1705
1706<section title="305 Use Proxy" anchor="status.305">
1707  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1708  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1709<t>
1710   The 305 status code was defined in a previous version of this specification
1711   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1712</t>
1713</section>
1714
1715<section title="306 (Unused)" anchor="status.306">
1716  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1717  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1718<t>
1719   The 306 status code was used in a previous version of the
1720   specification, is no longer used, and the code is reserved.
1721</t>
1722</section>
1723
1724<section title="307 Temporary Redirect" anchor="status.307">
1725  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1726  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1727<t>
1728   The target resource resides temporarily under a different URI.
1729   Since the redirection can change over time, the client &SHOULD;
1730   continue to use the effective request URI for future requests.
1731</t>
1732<t>
1733   The temporary URI &SHOULD; be given by the Location field in the
1734   response. Unless the request method was HEAD, the representation of the
1735   response &SHOULD; contain a short hypertext note with a hyperlink to
1736   the new URI(s), since many pre-HTTP/1.1 user agents do not
1737   understand the 307 status code. Therefore, the note &SHOULD; contain the
1738   information necessary for a user to repeat the original request on
1739   the new URI.
1740</t>
1741<t>
1742   If the 307 status code is received in response to a request method
1743   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1744   then the request &MAY; be automatically redirected by the user agent without
1745   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1746   request unless it can be confirmed by the user, since this might
1747   change the conditions under which the request was issued.
1748</t>
1749</section>
1750</section>
1751
1752<section title="Client Error 4xx" anchor="status.4xx">
1753<t>
1754   The 4xx class of status code is intended for cases in which the
1755   client seems to have erred. Except when responding to a HEAD request,
1756   the server &SHOULD; include a representation containing an explanation of the
1757   error situation, and whether it is a temporary or permanent
1758   condition. These status codes are applicable to any request method.
1759   User agents &SHOULD; display any included representation to the user.
1760</t>
1761<t>
1762   If the client is sending data, a server implementation using TCP
1763   &SHOULD; be careful to ensure that the client acknowledges receipt of
1764   the packet(s) containing the response, before the server closes the
1765   input connection. If the client continues sending data to the server
1766   after the close, the server's TCP stack will send a reset packet to
1767   the client, which might erase the client's unacknowledged input buffers
1768   before they can be read and interpreted by the HTTP application.
1769</t>
1770
1771<section title="400 Bad Request" anchor="status.400">
1772  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1773  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1774<t>
1775   The request could not be understood by the server due to malformed
1776   syntax. The client &SHOULD-NOT; repeat the request without
1777   modifications.
1778</t>
1779</section>
1780
1781<section title="401 Unauthorized" anchor="status.401">
1782  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1783  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1784  <rdf:Description>
1785    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1786  </rdf:Description>
1787<t>
1788   The request requires user authentication (see &status-401;).
1789</t>
1790</section>
1791
1792<section title="402 Payment Required" anchor="status.402">
1793  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1794  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1795<t>
1796   This code is reserved for future use.
1797</t>
1798</section>
1799
1800<section title="403 Forbidden" anchor="status.403">
1801  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1802  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1803<t>
1804   The server understood the request, but is refusing to fulfill it.
1805   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1806   If the request method was not HEAD and the server wishes to make
1807   public why the request has not been fulfilled, it &SHOULD; describe the
1808   reason for the refusal in the representation.  If the server does not wish to
1809   make this information available to the client, the status code 404
1810   (Not Found) can be used instead.
1811</t>
1812</section>
1813
1814<section title="404 Not Found" anchor="status.404">
1815  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1816  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1817<t>
1818   The server has not found anything matching the effective request URI. No
1819   indication is given of whether the condition is temporary or
1820   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1821   knows, through some internally configurable mechanism, that an old
1822   resource is permanently unavailable and has no forwarding address.
1823   This status code is commonly used when the server does not wish to
1824   reveal exactly why the request has been refused, or when no other
1825   response is applicable.
1826</t>
1827</section>
1828
1829<section title="405 Method Not Allowed" anchor="status.405">
1830  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1831  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1832<t>
1833   The method specified in the Request-Line is not allowed for the target
1834   resource. The response &MUST; include an
1835   Allow header field containing a list of valid methods for the requested
1836   resource.
1837</t>
1838</section>
1839
1840<section title="406 Not Acceptable" anchor="status.406">
1841  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1842  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1843<t>
1844   The resource identified by the request is only capable of generating
1845   response representations which have content characteristics not acceptable
1846   according to the accept header fields sent in the request.
1847</t>
1848<t>
1849   Unless it was a HEAD request, the response &SHOULD; include a representation
1850   containing a list of available representation characteristics and location(s)
1851   from which the user or user agent can choose the one most
1852   appropriate. The data format is specified by the media type given
1853   in the Content-Type header field. Depending upon the format and the
1854   capabilities of the user agent, selection of the most appropriate
1855   choice &MAY; be performed automatically. However, this specification
1856   does not define any standard for such automatic selection.
1857</t>
1858<x:note>
1859  <t>
1860    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1861    not acceptable according to the accept header fields sent in the
1862    request. In some cases, this might even be preferable to sending a
1863    406 response. User agents are encouraged to inspect the header fields of
1864    an incoming response to determine if it is acceptable.
1865  </t>
1866</x:note>
1867<t>
1868   If the response could be unacceptable, a user agent &SHOULD;
1869   temporarily stop receipt of more data and query the user for a
1870   decision on further actions.
1871</t>
1872</section>
1873
1874<section title="407 Proxy Authentication Required" anchor="status.407">
1875  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1876  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1877<t>
1878   This code is similar to 401 (Unauthorized), but indicates that the
1879   client must first authenticate itself with the proxy (see &status-407;).
1880</t>
1881</section>
1882
1883<section title="408 Request Timeout" anchor="status.408">
1884  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1885  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1886<t>
1887   The client did not produce a request within the time that the server
1888   was prepared to wait. The client &MAY; repeat the request without
1889   modifications at any later time.
1890</t>
1891</section>
1892
1893<section title="409 Conflict" anchor="status.409">
1894  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1895  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1896<t>
1897   The request could not be completed due to a conflict with the current
1898   state of the resource. This code is only allowed in situations where
1899   it is expected that the user might be able to resolve the conflict
1900   and resubmit the request. The response body &SHOULD; include enough
1901   information for the user to recognize the source of the conflict.
1902   Ideally, the response representation would include enough information for the
1903   user or user agent to fix the problem; however, that might not be
1904   possible and is not required.
1905</t>
1906<t>
1907   Conflicts are most likely to occur in response to a PUT request. For
1908   example, if versioning were being used and the representation being PUT
1909   included changes to a resource which conflict with those made by an
1910   earlier (third-party) request, the server might use the 409 response
1911   to indicate that it can't complete the request. In this case, the
1912   response representation would likely contain a list of the differences
1913   between the two versions in a format defined by the response
1914   Content-Type.
1915</t>
1916</section>
1917
1918<section title="410 Gone" anchor="status.410">
1919  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1920  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1921<t>
1922   The target resource is no longer available at the server and no
1923   forwarding address is known. This condition is expected to be
1924   considered permanent. Clients with link editing capabilities &SHOULD;
1925   delete references to the effective request URI after user approval. If the
1926   server does not know, or has no facility to determine, whether or not
1927   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1928   used instead.
1929</t>
1930<t>
1931   The 410 response is primarily intended to assist the task of web
1932   maintenance by notifying the recipient that the resource is
1933   intentionally unavailable and that the server owners desire that
1934   remote links to that resource be removed. Such an event is common for
1935   limited-time, promotional services and for resources belonging to
1936   individuals no longer working at the server's site. It is not
1937   necessary to mark all permanently unavailable resources as "gone" or
1938   to keep the mark for any length of time &mdash; that is left to the
1939   discretion of the server owner.
1940</t>
1941<t>
1942   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1943   for 410 responses.
1944</t>
1945
1946</section>
1947
1948<section title="411 Length Required" anchor="status.411">
1949  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1950  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1951<t>
1952   The server refuses to accept the request without a defined Content-Length.
1953   The client &MAY; repeat the request if it adds a valid
1954   Content-Length header field containing the length of the message-body
1955   in the request message.
1956</t>
1957</section>
1958
1959<section title="412 Precondition Failed" anchor="status.412">
1960  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1961  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1962  <rdf:Description>
1963    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1964  </rdf:Description>
1965<t>
1966   The precondition given in one or more of the request-header fields
1967   evaluated to false when it was tested on the server, as defined in
1968   &status-412;.
1969</t>
1970</section>
1971
1972<section title="413 Request Entity Too Large" anchor="status.413">
1973  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1974  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1975<t>
1976   The server is refusing to process a request because the request
1977   representation is larger than the server is willing or able to process. The
1978   server &MAY; close the connection to prevent the client from continuing
1979   the request.
1980</t>
1981<t>
1982   If the condition is temporary, the server &SHOULD; include a Retry-After
1983   header field to indicate that it is temporary and after what
1984   time the client &MAY; try again.
1985</t>
1986</section>
1987
1988<section title="414 URI Too Long" anchor="status.414">
1989  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1990  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1991<t>
1992   The server is refusing to service the request because the effective request URI
1993   is longer than the server is willing to interpret. This rare
1994   condition is only likely to occur when a client has improperly
1995   converted a POST request to a GET request with long query
1996   information, when the client has descended into a URI "black hole" of
1997   redirection (e.g., a redirected URI prefix that points to a suffix of
1998   itself), or when the server is under attack by a client attempting to
1999   exploit security holes present in some servers using fixed-length
2000   buffers for reading or manipulating the effective request URI.
2001</t>
2002</section>
2003
2004<section title="415 Unsupported Media Type" anchor="status.415">
2005  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2006  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2007<t>
2008   The server is refusing to service the request because the representation of
2009   the request is in a format not supported by the target resource
2010   for the requested method.
2011</t>
2012</section>
2013
2014<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2015  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2016  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2017  <rdf:Description>
2018    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2019  </rdf:Description>
2020<t>
2021   The request included a Range request-header field (&header-range;) and none of
2022   the range-specifier values in this field overlap the current extent
2023   of the selected resource. See &status-416;.
2024</t>
2025</section>
2026
2027<section title="417 Expectation Failed" anchor="status.417">
2028  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2029  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2030<t>
2031   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
2032   could not be met by this server, or, if the server is a proxy,
2033   the server has unambiguous evidence that the request could not be met
2034   by the next-hop server.
2035</t>
2036</section>
2037
2038<section title="426 Upgrade Required" anchor="status.426">
2039  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2040  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2041<t>
2042   The request can not be completed without a prior protocol upgrade. This
2043   response &MUST; include an Upgrade header field (&header-upgrade;)
2044   specifying the required protocols.
2045</t>
2046<figure>
2047<preamble>Example:</preamble>
2048<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2049HTTP/1.1 426 Upgrade Required
2050Upgrade: HTTP/2.0
2051Connection: Upgrade
2052
2053</artwork></figure>
2054<t>
2055   The server &SHOULD; include a message body in the 426 response which
2056   indicates in human readable form the reason for the error and describes any
2057   alternative courses which may be available to the user.
2058</t>
2059</section>
2060</section>
2061
2062<section title="Server Error 5xx" anchor="status.5xx">
2063<t>
2064   Response status codes beginning with the digit "5" indicate cases in
2065   which the server is aware that it has erred or is incapable of
2066   performing the request. Except when responding to a HEAD request, the
2067   server &SHOULD; include a representation containing an explanation of the
2068   error situation, and whether it is a temporary or permanent
2069   condition. User agents &SHOULD; display any included representation to the
2070   user. These response codes are applicable to any request method.
2071</t>
2072
2073<section title="500 Internal Server Error" anchor="status.500">
2074  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2075  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2076<t>
2077   The server encountered an unexpected condition which prevented it
2078   from fulfilling the request.
2079</t>
2080</section>
2081
2082<section title="501 Not Implemented" anchor="status.501">
2083  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2084  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2085<t>
2086   The server does not support the functionality required to fulfill the
2087   request. This is the appropriate response when the server does not
2088   recognize the request method and is not capable of supporting it for
2089   any resource.
2090</t>
2091</section>
2092
2093<section title="502 Bad Gateway" anchor="status.502">
2094  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2095  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2096<t>
2097   The server, while acting as a gateway or proxy, received an invalid
2098   response from the upstream server it accessed in attempting to
2099   fulfill the request.
2100</t>
2101</section>
2102
2103<section title="503 Service Unavailable" anchor="status.503">
2104  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2105  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2106<t>
2107   The server is currently unable to handle the request due to a
2108   temporary overloading or maintenance of the server. The implication
2109   is that this is a temporary condition which will be alleviated after
2110   some delay. If known, the length of the delay &MAY; be indicated in a
2111   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2112   handle the response as it would for a 500 response.
2113</t>
2114<x:note>
2115  <t>
2116    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2117    server must use it when becoming overloaded. Some servers might wish
2118    to simply refuse the connection.
2119  </t>
2120</x:note>
2121</section>
2122
2123<section title="504 Gateway Timeout" anchor="status.504">
2124  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2125  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2126<t>
2127   The server, while acting as a gateway or proxy, did not receive a
2128   timely response from the upstream server specified by the URI (e.g.,
2129   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2130   to access in attempting to complete the request.
2131</t>
2132<x:note>
2133  <t>
2134    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2135    return 400 or 500 when DNS lookups time out.
2136  </t>
2137</x:note>
2138</section>
2139
2140<section title="505 HTTP Version Not Supported" anchor="status.505">
2141  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2142  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2143<t>
2144   The server does not support, or refuses to support, the protocol
2145   version that was used in the request message. The server is
2146   indicating that it is unable or unwilling to complete the request
2147   using the same major version as the client, as described in &http-version;,
2148   other than with this error message. The response &SHOULD; contain
2149   a representation describing why that version is not supported and what other
2150   protocols are supported by that server.
2151</t>
2152
2153</section>
2154</section>
2155</section>
2156
2157
2158<section title="Header Field Definitions" anchor="header.fields">
2159<t>
2160   This section defines the syntax and semantics of HTTP/1.1 header fields
2161   related to request and response semantics.
2162</t>
2163
2164<section title="Allow" anchor="header.allow">
2165  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2166  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2167  <x:anchor-alias value="Allow"/>
2168  <x:anchor-alias value="Allow-v"/>
2169<t>
2170   The "Allow" response-header field lists the set of methods advertised as
2171   supported by the target resource. The purpose of this field is strictly to
2172   inform the recipient of valid methods associated with the resource.
2173</t>
2174<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2175  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2176  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2177</artwork></figure>
2178<t>
2179   Example of use:
2180</t>
2181<figure><artwork type="example">
2182  Allow: GET, HEAD, PUT
2183</artwork></figure>
2184<t>
2185   The actual set of allowed methods is defined by the origin server at the
2186   time of each request.
2187</t>
2188<t>
2189   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2190   understand all the methods specified in order to handle them according to
2191   the generic message handling rules.
2192</t>
2193</section>
2194
2195<section title="Expect" anchor="header.expect">
2196  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2197  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2198  <x:anchor-alias value="Expect"/>
2199  <x:anchor-alias value="Expect-v"/>
2200  <x:anchor-alias value="expectation"/>
2201  <x:anchor-alias value="expectation-extension"/>
2202  <x:anchor-alias value="expect-params"/>
2203<t>
2204   The "Expect" request-header field is used to indicate that particular
2205   server behaviors are required by the client.
2206</t>
2207<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"/>
2208  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2209  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2210 
2211  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2212  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2213                           *<x:ref>expect-params</x:ref> ]
2214  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2215</artwork></figure>
2216<t>
2217   A server that does not understand or is unable to comply with any of
2218   the expectation values in the Expect field of a request &MUST; respond
2219   with appropriate error status code. The server &MUST; respond with a 417
2220   (Expectation Failed) status code if any of the expectations cannot be met
2221   or, if there are other problems with the request, some other 4xx
2222   status code.
2223</t>
2224<t>
2225   This header field is defined with extensible syntax to allow for
2226   future extensions. If a server receives a request containing an
2227   Expect field that includes an expectation-extension that it does not
2228   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2229</t>
2230<t>
2231   Comparison of expectation values is case-insensitive for unquoted
2232   tokens (including the 100-continue token), and is case-sensitive for
2233   quoted-string expectation-extensions.
2234</t>
2235<t>
2236   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2237   return a 417 (Expectation Failed) status code if it receives a request
2238   with an expectation that it cannot meet. However, the Expect
2239   request-header field itself is end-to-end; it &MUST; be forwarded if the
2240   request is forwarded.
2241</t>
2242<t>
2243   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2244   Expect header field.
2245</t>
2246<t>
2247   See &use100; for the use of the 100 (Continue) status code.
2248</t>
2249</section>
2250
2251<section title="From" anchor="header.from">
2252  <iref primary="true" item="From header field" x:for-anchor=""/>
2253  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2254  <x:anchor-alias value="From"/>
2255  <x:anchor-alias value="From-v"/>
2256  <x:anchor-alias value="mailbox"/>
2257<t>
2258   The "From" request-header field, if given, &SHOULD; contain an Internet
2259   e-mail address for the human user who controls the requesting user
2260   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2261   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2262</t>
2263<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2264  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2265  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2266 
2267  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2268</artwork></figure>
2269<t>
2270   An example is:
2271</t>
2272<figure><artwork type="example">
2273  From: webmaster@example.org
2274</artwork></figure>
2275<t>
2276   This header field &MAY; be used for logging purposes and as a means for
2277   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2278   be used as an insecure form of access protection. The interpretation
2279   of this field is that the request is being performed on behalf of the
2280   person given, who accepts responsibility for the method performed. In
2281   particular, robot agents &SHOULD; include this header field so that the
2282   person responsible for running the robot can be contacted if problems
2283   occur on the receiving end.
2284</t>
2285<t>
2286   The Internet e-mail address in this field &MAY; be separate from the
2287   Internet host which issued the request. For example, when a request
2288   is passed through a proxy the original issuer's address &SHOULD; be
2289   used.
2290</t>
2291<t>
2292   The client &SHOULD-NOT;  send the From header field without the user's
2293   approval, as it might conflict with the user's privacy interests or
2294   their site's security policy. It is strongly recommended that the
2295   user be able to disable, enable, and modify the value of this field
2296   at any time prior to a request.
2297</t>
2298</section>
2299
2300<section title="Location" anchor="header.location">
2301  <iref primary="true" item="Location header field" x:for-anchor=""/>
2302  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2303  <x:anchor-alias value="Location"/>
2304  <x:anchor-alias value="Location-v"/>
2305<t>
2306   The "Location" response-header field is used to identify a newly created
2307   resource, or to redirect the recipient to a different location for
2308   completion of the request.
2309</t>
2310<t>
2311   For 201 (Created) responses, the Location is the URI of the new resource
2312   which was created by the request. For 3xx responses, the location &SHOULD;
2313   indicate the server's preferred URI for automatic redirection to the
2314   resource.
2315</t>
2316<t>
2317   The field value consists of a single URI-reference. When it has the form
2318   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2319   the final value is computed by resolving it against the effective request
2320   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2321</t>
2322<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2323  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2324  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2325</artwork></figure>
2326<figure>
2327<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2328<artwork type="example">
2329  Location: http://www.example.org/pub/WWW/People.html#tim
2330</artwork></figure><figure><artwork type="example">  Location: /index.html
2331</artwork></figure>
2332<t>
2333   There are circumstances in which a fragment identifier in a Location URI
2334   would not be appropriate:
2335   <list style="symbols">
2336      <t>With a 201 Created response, because in this usage the Location header
2337      field specifies the URI for the entire created resource.</t>
2338      <t>With 305 Use Proxy.</t>
2339   </list>
2340</t>
2341<x:note>
2342  <t>
2343    <x:h>Note:</x:h> This specification does not define precedence rules
2344    for the case where the original URI, as navigated to by the user
2345    agent, and the Location header field value both contain fragment
2346    identifiers. Thus be aware that including fragment identifiers might
2347    inconvenience anyone relying on the semantics of the original URI's
2348    fragment identifier.
2349  </t>
2350</x:note>
2351<x:note>
2352  <t>
2353    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2354    from Location in that the Content-Location identifies the most specific
2355    resource corresponding to the enclosed representation.
2356    It is therefore possible for a response to contain header fields for
2357    both Location and Content-Location.
2358  </t>
2359</x:note>
2360</section>
2361
2362<section title="Max-Forwards" anchor="header.max-forwards">
2363  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2364  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2365  <x:anchor-alias value="Max-Forwards"/>
2366  <x:anchor-alias value="Max-Forwards-v"/>
2367<t>
2368   The "Max-Forwards" request-header field provides a mechanism with the
2369   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2370   methods to limit the number of times that the request is forwarded by
2371   proxies or gateways. This can be useful when the client is attempting to
2372   trace a request which appears to be failing or looping in mid-chain.
2373</t>
2374<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2375  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2376  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2377</artwork></figure>
2378<t>
2379   The Max-Forwards value is a decimal integer indicating the remaining
2380   number of times this request message can be forwarded.
2381</t>
2382<t>
2383   Each proxy or gateway recipient of a TRACE or OPTIONS request
2384   containing a Max-Forwards header field &MUST; check and update its
2385   value prior to forwarding the request. If the received value is zero
2386   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2387   respond as the final recipient. If the received Max-Forwards value is
2388   greater than zero, then the forwarded message &MUST; contain an updated
2389   Max-Forwards field with a value decremented by one (1).
2390</t>
2391<t>
2392   The Max-Forwards header field &MAY; be ignored for all other methods.
2393</t>
2394</section>
2395
2396<section title="Referer" anchor="header.referer">
2397  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2398  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2399  <x:anchor-alias value="Referer"/>
2400  <x:anchor-alias value="Referer-v"/>
2401<t>
2402   The "Referer" [sic] request-header field allows the client to specify the
2403   URI of the resource from which the effective request URI was obtained (the
2404   "referrer", although the header field is misspelled.).
2405</t>
2406<t>
2407   The Referer header field allows servers to generate lists of back-links to
2408   resources for interest, logging, optimized caching, etc. It also allows
2409   obsolete or mistyped links to be traced for maintenance. Some servers use
2410   Referer as a means of controlling where they allow links from (so-called
2411   "deep linking"), but legitimate requests do not always
2412   contain a Referer header field.
2413</t>
2414<t>
2415   If the effective request URI was obtained from a source that does not have its own
2416   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2417   sent with the value "about:blank", or not be sent at all. Note that this
2418   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2419</t>
2420<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2421  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2422  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2423</artwork></figure>
2424<t>
2425   Example:
2426</t>
2427<figure><artwork type="example">
2428  Referer: http://www.example.org/hypertext/Overview.html
2429</artwork></figure>
2430<t>
2431   If the field value is a relative URI, it &SHOULD; be interpreted
2432   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2433   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2434</t>
2435</section>
2436
2437<section title="Retry-After" anchor="header.retry-after">
2438  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2439  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2440  <x:anchor-alias value="Retry-After"/>
2441  <x:anchor-alias value="Retry-After-v"/>
2442<t>
2443   The response-header "Retry-After" field can be used with a 503 (Service
2444   Unavailable) response to indicate how long the service is expected to
2445   be unavailable to the requesting client. This field &MAY; also be used
2446   with any 3xx (Redirection) response to indicate the minimum time the
2447   user-agent is asked wait before issuing the redirected request.
2448</t>
2449<t>
2450   The value of this field can be either an HTTP-date or an integer number
2451   of seconds (in decimal) after the time of the response.
2452</t>
2453<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2454  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2455  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2456</artwork></figure>
2457<t anchor="rule.delta-seconds">
2458  <x:anchor-alias value="delta-seconds"/>
2459   Time spans are non-negative decimal integers, representing time in
2460   seconds.
2461</t>
2462<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2463  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2464</artwork></figure>
2465<t>
2466   Two examples of its use are
2467</t>
2468<figure><artwork type="example">
2469  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2470  Retry-After: 120
2471</artwork></figure>
2472<t>
2473   In the latter example, the delay is 2 minutes.
2474</t>
2475</section>
2476
2477<section title="Server" anchor="header.server">
2478  <iref primary="true" item="Server header field" x:for-anchor=""/>
2479  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2480  <x:anchor-alias value="Server"/>
2481  <x:anchor-alias value="Server-v"/>
2482<t>
2483   The "Server" response-header field contains information about the
2484   software used by the origin server to handle the request.
2485</t>
2486<t>
2487   The field can contain multiple product tokens (&product-tokens;) and
2488   comments (&header-fields;) identifying the server and any significant
2489   subproducts. The product tokens are listed in order of their significance
2490   for identifying the application.
2491</t>
2492<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2493  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2494  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2495                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2496</artwork></figure>
2497<t>
2498   Example:
2499</t>
2500<figure><artwork type="example">
2501  Server: CERN/3.0 libwww/2.17
2502</artwork></figure>
2503<t>
2504   If the response is being forwarded through a proxy, the proxy
2505   application &MUST-NOT; modify the Server response-header field. Instead, it
2506   &MUST; include a Via field (as described in &header-via;).
2507</t>
2508<x:note>
2509  <t>
2510    <x:h>Note:</x:h> Revealing the specific software version of the server might
2511    allow the server machine to become more vulnerable to attacks
2512    against software that is known to contain security holes. Server
2513    implementors are encouraged to make this field a configurable
2514    option.
2515  </t>
2516</x:note>
2517</section>
2518
2519<section title="User-Agent" anchor="header.user-agent">
2520  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2521  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2522  <x:anchor-alias value="User-Agent"/>
2523  <x:anchor-alias value="User-Agent-v"/>
2524<t>
2525   The "User-Agent" request-header field contains information about the user
2526   agent originating the request. User agents &SHOULD; include this field with
2527   requests.
2528</t>
2529<t>
2530   Typically, it is used for statistical purposes, the tracing of protocol
2531   violations, and tailoring responses to avoid particular user agent
2532   limitations.
2533</t>
2534<t>
2535   The field can contain multiple product tokens (&product-tokens;)
2536   and comments (&header-fields;) identifying the agent and its
2537   significant subproducts. By convention, the product tokens are listed in
2538   order of their significance for identifying the application.
2539</t>
2540<t>
2541   Because this field is usually sent on every request a user agent makes,
2542   implementations are encouraged not to include needlessly fine-grained
2543   detail, and to limit (or even prohibit) the addition of subproducts by third
2544   parties. Overly long and detailed User-Agent field values make requests
2545   larger and can also be used to identify ("fingerprint") the user against
2546   their wishes.
2547</t>
2548<t>
2549   Likewise, implementations are encouraged not to use the product tokens of
2550   other implementations in order to declare compatibility with them, as this
2551   circumvents the purpose of the field. Finally, they are encouraged not to
2552   use comments to identify products; doing so makes the field value more
2553   difficult to parse.
2554</t>
2555<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2556  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2557  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2558</artwork></figure>
2559<t>
2560   Example:
2561</t>
2562<figure><artwork type="example">
2563  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2564</artwork></figure>
2565</section>
2566
2567</section>
2568
2569<section title="IANA Considerations" anchor="IANA.considerations">
2570
2571<section title="Method Registry" anchor="method.registration">
2572<t>
2573  The registration procedure for HTTP Methods is defined by
2574  <xref target="method.registry"/> of this document.
2575</t>
2576<t>
2577   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2578   and be populated with the registrations below:
2579</t>
2580<?BEGININC p2-semantics.iana-methods ?>
2581<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2582<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2583   <ttcol>Method</ttcol>
2584   <ttcol>Safe</ttcol>
2585   <ttcol>Reference</ttcol>
2586   <c>CONNECT</c>
2587   <c>no</c>
2588   <c>
2589      <xref target="CONNECT"/>
2590   </c>
2591   <c>DELETE</c>
2592   <c>no</c>
2593   <c>
2594      <xref target="DELETE"/>
2595   </c>
2596   <c>GET</c>
2597   <c>yes</c>
2598   <c>
2599      <xref target="GET"/>
2600   </c>
2601   <c>HEAD</c>
2602   <c>yes</c>
2603   <c>
2604      <xref target="HEAD"/>
2605   </c>
2606   <c>OPTIONS</c>
2607   <c>yes</c>
2608   <c>
2609      <xref target="OPTIONS"/>
2610   </c>
2611   <c>POST</c>
2612   <c>no</c>
2613   <c>
2614      <xref target="POST"/>
2615   </c>
2616   <c>PUT</c>
2617   <c>no</c>
2618   <c>
2619      <xref target="PUT"/>
2620   </c>
2621   <c>TRACE</c>
2622   <c>yes</c>
2623   <c>
2624      <xref target="TRACE"/>
2625   </c>
2626</texttable>
2627<!--(END)-->
2628<?ENDINC p2-semantics.iana-methods ?>
2629</section>
2630
2631<section title="Status Code Registry" anchor="status.code.registration">
2632<t>
2633   The registration procedure for HTTP Status Codes &mdash; previously defined
2634   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2635   by <xref target="status.code.registry"/> of this document.
2636</t>
2637<t>
2638   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2639   shall be updated with the registrations below:
2640</t>
2641<?BEGININC p2-semantics.iana-status-codes ?>
2642<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2643<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2644   <ttcol>Value</ttcol>
2645   <ttcol>Description</ttcol>
2646   <ttcol>Reference</ttcol>
2647   <c>100</c>
2648   <c>Continue</c>
2649   <c>
2650      <xref target="status.100"/>
2651   </c>
2652   <c>101</c>
2653   <c>Switching Protocols</c>
2654   <c>
2655      <xref target="status.101"/>
2656   </c>
2657   <c>200</c>
2658   <c>OK</c>
2659   <c>
2660      <xref target="status.200"/>
2661   </c>
2662   <c>201</c>
2663   <c>Created</c>
2664   <c>
2665      <xref target="status.201"/>
2666   </c>
2667   <c>202</c>
2668   <c>Accepted</c>
2669   <c>
2670      <xref target="status.202"/>
2671   </c>
2672   <c>203</c>
2673   <c>Non-Authoritative Information</c>
2674   <c>
2675      <xref target="status.203"/>
2676   </c>
2677   <c>204</c>
2678   <c>No Content</c>
2679   <c>
2680      <xref target="status.204"/>
2681   </c>
2682   <c>205</c>
2683   <c>Reset Content</c>
2684   <c>
2685      <xref target="status.205"/>
2686   </c>
2687   <c>300</c>
2688   <c>Multiple Choices</c>
2689   <c>
2690      <xref target="status.300"/>
2691   </c>
2692   <c>301</c>
2693   <c>Moved Permanently</c>
2694   <c>
2695      <xref target="status.301"/>
2696   </c>
2697   <c>302</c>
2698   <c>Found</c>
2699   <c>
2700      <xref target="status.302"/>
2701   </c>
2702   <c>303</c>
2703   <c>See Other</c>
2704   <c>
2705      <xref target="status.303"/>
2706   </c>
2707   <c>305</c>
2708   <c>Use Proxy</c>
2709   <c>
2710      <xref target="status.305"/>
2711   </c>
2712   <c>306</c>
2713   <c>(Unused)</c>
2714   <c>
2715      <xref target="status.306"/>
2716   </c>
2717   <c>307</c>
2718   <c>Temporary Redirect</c>
2719   <c>
2720      <xref target="status.307"/>
2721   </c>
2722   <c>400</c>
2723   <c>Bad Request</c>
2724   <c>
2725      <xref target="status.400"/>
2726   </c>
2727   <c>402</c>
2728   <c>Payment Required</c>
2729   <c>
2730      <xref target="status.402"/>
2731   </c>
2732   <c>403</c>
2733   <c>Forbidden</c>
2734   <c>
2735      <xref target="status.403"/>
2736   </c>
2737   <c>404</c>
2738   <c>Not Found</c>
2739   <c>
2740      <xref target="status.404"/>
2741   </c>
2742   <c>405</c>
2743   <c>Method Not Allowed</c>
2744   <c>
2745      <xref target="status.405"/>
2746   </c>
2747   <c>406</c>
2748   <c>Not Acceptable</c>
2749   <c>
2750      <xref target="status.406"/>
2751   </c>
2752   <c>407</c>
2753   <c>Proxy Authentication Required</c>
2754   <c>
2755      <xref target="status.407"/>
2756   </c>
2757   <c>408</c>
2758   <c>Request Timeout</c>
2759   <c>
2760      <xref target="status.408"/>
2761   </c>
2762   <c>409</c>
2763   <c>Conflict</c>
2764   <c>
2765      <xref target="status.409"/>
2766   </c>
2767   <c>410</c>
2768   <c>Gone</c>
2769   <c>
2770      <xref target="status.410"/>
2771   </c>
2772   <c>411</c>
2773   <c>Length Required</c>
2774   <c>
2775      <xref target="status.411"/>
2776   </c>
2777   <c>413</c>
2778   <c>Request Entity Too Large</c>
2779   <c>
2780      <xref target="status.413"/>
2781   </c>
2782   <c>414</c>
2783   <c>URI Too Long</c>
2784   <c>
2785      <xref target="status.414"/>
2786   </c>
2787   <c>415</c>
2788   <c>Unsupported Media Type</c>
2789   <c>
2790      <xref target="status.415"/>
2791   </c>
2792   <c>417</c>
2793   <c>Expectation Failed</c>
2794   <c>
2795      <xref target="status.417"/>
2796   </c>
2797   <c>426</c>
2798   <c>Upgrade Required</c>
2799   <c>
2800      <xref target="status.426"/>
2801   </c>
2802   <c>500</c>
2803   <c>Internal Server Error</c>
2804   <c>
2805      <xref target="status.500"/>
2806   </c>
2807   <c>501</c>
2808   <c>Not Implemented</c>
2809   <c>
2810      <xref target="status.501"/>
2811   </c>
2812   <c>502</c>
2813   <c>Bad Gateway</c>
2814   <c>
2815      <xref target="status.502"/>
2816   </c>
2817   <c>503</c>
2818   <c>Service Unavailable</c>
2819   <c>
2820      <xref target="status.503"/>
2821   </c>
2822   <c>504</c>
2823   <c>Gateway Timeout</c>
2824   <c>
2825      <xref target="status.504"/>
2826   </c>
2827   <c>505</c>
2828   <c>HTTP Version Not Supported</c>
2829   <c>
2830      <xref target="status.505"/>
2831   </c>
2832</texttable>
2833<!--(END)-->
2834<?ENDINC p2-semantics.iana-status-codes ?>
2835</section>
2836<section title="Header Field Registration" anchor="header.field.registration">
2837<t>
2838   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2839   with the permanent registrations below (see <xref target="RFC3864"/>):
2840</t>
2841<?BEGININC p2-semantics.iana-headers ?>
2842<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2843<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2844   <ttcol>Header Field Name</ttcol>
2845   <ttcol>Protocol</ttcol>
2846   <ttcol>Status</ttcol>
2847   <ttcol>Reference</ttcol>
2848
2849   <c>Allow</c>
2850   <c>http</c>
2851   <c>standard</c>
2852   <c>
2853      <xref target="header.allow"/>
2854   </c>
2855   <c>Expect</c>
2856   <c>http</c>
2857   <c>standard</c>
2858   <c>
2859      <xref target="header.expect"/>
2860   </c>
2861   <c>From</c>
2862   <c>http</c>
2863   <c>standard</c>
2864   <c>
2865      <xref target="header.from"/>
2866   </c>
2867   <c>Location</c>
2868   <c>http</c>
2869   <c>standard</c>
2870   <c>
2871      <xref target="header.location"/>
2872   </c>
2873   <c>Max-Forwards</c>
2874   <c>http</c>
2875   <c>standard</c>
2876   <c>
2877      <xref target="header.max-forwards"/>
2878   </c>
2879   <c>Referer</c>
2880   <c>http</c>
2881   <c>standard</c>
2882   <c>
2883      <xref target="header.referer"/>
2884   </c>
2885   <c>Retry-After</c>
2886   <c>http</c>
2887   <c>standard</c>
2888   <c>
2889      <xref target="header.retry-after"/>
2890   </c>
2891   <c>Server</c>
2892   <c>http</c>
2893   <c>standard</c>
2894   <c>
2895      <xref target="header.server"/>
2896   </c>
2897   <c>User-Agent</c>
2898   <c>http</c>
2899   <c>standard</c>
2900   <c>
2901      <xref target="header.user-agent"/>
2902   </c>
2903</texttable>
2904<!--(END)-->
2905<?ENDINC p2-semantics.iana-headers ?>
2906<t>
2907   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2908</t>
2909</section>
2910</section>
2911
2912<section title="Security Considerations" anchor="security.considerations">
2913<t>
2914   This section is meant to inform application developers, information
2915   providers, and users of the security limitations in HTTP/1.1 as
2916   described by this document. The discussion does not include
2917   definitive solutions to the problems revealed, though it does make
2918   some suggestions for reducing security risks.
2919</t>
2920
2921<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2922<t>
2923   Like any generic data transfer protocol, HTTP cannot regulate the
2924   content of the data that is transferred, nor is there any a priori
2925   method of determining the sensitivity of any particular piece of
2926   information within the context of any given request. Therefore,
2927   applications &SHOULD; supply as much control over this information as
2928   possible to the provider of that information. Four header fields are
2929   worth special mention in this context: Server, Via, Referer and From.
2930</t>
2931<t>
2932   Revealing the specific software version of the server might allow the
2933   server machine to become more vulnerable to attacks against software
2934   that is known to contain security holes. Implementors &SHOULD; make the
2935   Server header field a configurable option.
2936</t>
2937<t>
2938   Proxies which serve as a portal through a network firewall &SHOULD;
2939   take special precautions regarding the transfer of header information
2940   that identifies the hosts behind the firewall. In particular, they
2941   &SHOULD; remove, or replace with sanitized versions, any Via fields
2942   generated behind the firewall.
2943</t>
2944<t>
2945   The Referer header field allows reading patterns to be studied and reverse
2946   links drawn. Although it can be very useful, its power can be abused
2947   if user details are not separated from the information contained in
2948   the Referer. Even when the personal information has been removed, the
2949   Referer header field might indicate a private document's URI whose
2950   publication would be inappropriate.
2951</t>
2952<t>
2953   The information sent in the From field might conflict with the user's
2954   privacy interests or their site's security policy, and hence it
2955   &SHOULD-NOT;  be transmitted without the user being able to disable,
2956   enable, and modify the contents of the field. The user &MUST; be able
2957   to set the contents of this field within a user preference or
2958   application defaults configuration.
2959</t>
2960<t>
2961   We suggest, though do not require, that a convenient toggle interface
2962   be provided for the user to enable or disable the sending of From and
2963   Referer information.
2964</t>
2965<t>
2966   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2967   target="header.server"/>) header fields can sometimes be used to determine
2968   that a specific client or server have a particular security hole which might
2969   be exploited. Unfortunately, this same information is often used for other
2970   valuable purposes for which HTTP currently has no better mechanism.
2971</t>
2972<t>
2973   Furthermore, the User-Agent header field may contain enough entropy to be
2974   used, possibly in conjunction with other material, to uniquely identify the
2975   user.
2976</t>
2977<t>
2978   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2979   that was sent in request header fields within the body of their response.
2980   Clients &SHOULD; be careful with sensitive information, like Cookies,
2981   Authorization credentials and other header fields that might be used to
2982   collect data from the client.
2983</t> 
2984</section>
2985
2986<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2987<t>
2988   Because the source of a link might be private information or might
2989   reveal an otherwise private information source, it is strongly
2990   recommended that the user be able to select whether or not the
2991   Referer field is sent. For example, a browser client could have a
2992   toggle switch for browsing openly/anonymously, which would
2993   respectively enable/disable the sending of Referer and From
2994   information.
2995</t>
2996<t>
2997   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2998   HTTP request if the referring page was transferred with a secure
2999   protocol.
3000</t>
3001<t>
3002   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3003   sensitive data because that data will be placed in the request-target. Many
3004   existing servers, proxies, and user agents log or display the request-target
3005   in places where it might be visible to third parties. Such services can
3006   use POST-based form submission instead.
3007</t>
3008</section>
3009
3010<section title="Location Headers and Spoofing" anchor="location.spoofing">
3011<t>
3012   If a single server supports multiple organizations that do not trust
3013   one another, then it &MUST; check the values of Location and Content-Location
3014   header fields in responses that are generated under control of
3015   said organizations to make sure that they do not attempt to
3016   invalidate resources over which they have no authority.
3017</t>
3018</section>
3019
3020<section title="Security Considerations for CONNECT">
3021<t>
3022   Since tunneled data is opaque to the proxy, there are additional
3023   risks to tunneling to other well-known or reserved ports.
3024   A HTTP client CONNECTing to port 25 could relay spam
3025   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3026   access to a small number of known ports.
3027</t>
3028</section>
3029
3030</section>
3031
3032<section title="Acknowledgments" anchor="ack">
3033</section>
3034</middle>
3035<back>
3036
3037<references title="Normative References">
3038
3039<reference anchor="Part1">
3040  <front>
3041    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3042    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3043      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3044      <address><email>fielding@gbiv.com</email></address>
3045    </author>
3046    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3047      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3048      <address><email>jg@freedesktop.org</email></address>
3049    </author>
3050    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3051      <organization abbrev="HP">Hewlett-Packard Company</organization>
3052      <address><email>JeffMogul@acm.org</email></address>
3053    </author>
3054    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3055      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3056      <address><email>henrikn@microsoft.com</email></address>
3057    </author>
3058    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3059      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3060      <address><email>LMM@acm.org</email></address>
3061    </author>
3062    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3063      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3064      <address><email>paulle@microsoft.com</email></address>
3065    </author>
3066    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3067      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3068      <address><email>timbl@w3.org</email></address>
3069    </author>
3070    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3071      <organization abbrev="W3C">World Wide Web Consortium</organization>
3072      <address><email>ylafon@w3.org</email></address>
3073    </author>
3074    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3075      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3076      <address><email>julian.reschke@greenbytes.de</email></address>
3077    </author>
3078    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3079  </front>
3080  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3081  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3082</reference>
3083
3084<reference anchor="Part3">
3085  <front>
3086    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3087    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3088      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3089      <address><email>fielding@gbiv.com</email></address>
3090    </author>
3091    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3092      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3093      <address><email>jg@freedesktop.org</email></address>
3094    </author>
3095    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3096      <organization abbrev="HP">Hewlett-Packard Company</organization>
3097      <address><email>JeffMogul@acm.org</email></address>
3098    </author>
3099    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3100      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3101      <address><email>henrikn@microsoft.com</email></address>
3102    </author>
3103    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3104      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3105      <address><email>LMM@acm.org</email></address>
3106    </author>
3107    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3108      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3109      <address><email>paulle@microsoft.com</email></address>
3110    </author>
3111    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3112      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3113      <address><email>timbl@w3.org</email></address>
3114    </author>
3115    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3116      <organization abbrev="W3C">World Wide Web Consortium</organization>
3117      <address><email>ylafon@w3.org</email></address>
3118    </author>
3119    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3120      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3121      <address><email>julian.reschke@greenbytes.de</email></address>
3122    </author>
3123    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3124  </front>
3125  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3126  <x:source href="p3-payload.xml" basename="p3-payload"/>
3127</reference>
3128
3129<reference anchor="Part4">
3130  <front>
3131    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3132    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3133      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3134      <address><email>fielding@gbiv.com</email></address>
3135    </author>
3136    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3137      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3138      <address><email>jg@freedesktop.org</email></address>
3139    </author>
3140    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3141      <organization abbrev="HP">Hewlett-Packard Company</organization>
3142      <address><email>JeffMogul@acm.org</email></address>
3143    </author>
3144    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3145      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3146      <address><email>henrikn@microsoft.com</email></address>
3147    </author>
3148    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3149      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3150      <address><email>LMM@acm.org</email></address>
3151    </author>
3152    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3153      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3154      <address><email>paulle@microsoft.com</email></address>
3155    </author>
3156    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3157      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3158      <address><email>timbl@w3.org</email></address>
3159    </author>
3160    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3161      <organization abbrev="W3C">World Wide Web Consortium</organization>
3162      <address><email>ylafon@w3.org</email></address>
3163    </author>
3164    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3165      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3166      <address><email>julian.reschke@greenbytes.de</email></address>
3167    </author>
3168    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3169  </front>
3170  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3171  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3172</reference>
3173
3174<reference anchor="Part5">
3175  <front>
3176    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3177    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3178      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3179      <address><email>fielding@gbiv.com</email></address>
3180    </author>
3181    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3182      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3183      <address><email>jg@freedesktop.org</email></address>
3184    </author>
3185    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3186      <organization abbrev="HP">Hewlett-Packard Company</organization>
3187      <address><email>JeffMogul@acm.org</email></address>
3188    </author>
3189    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3190      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3191      <address><email>henrikn@microsoft.com</email></address>
3192    </author>
3193    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3194      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3195      <address><email>LMM@acm.org</email></address>
3196    </author>
3197    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3198      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3199      <address><email>paulle@microsoft.com</email></address>
3200    </author>
3201    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3202      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3203      <address><email>timbl@w3.org</email></address>
3204    </author>
3205    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3206      <organization abbrev="W3C">World Wide Web Consortium</organization>
3207      <address><email>ylafon@w3.org</email></address>
3208    </author>
3209    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3210      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3211      <address><email>julian.reschke@greenbytes.de</email></address>
3212    </author>
3213    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3214  </front>
3215  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3216  <x:source href="p5-range.xml" basename="p5-range"/>
3217</reference>
3218
3219<reference anchor="Part6">
3220  <front>
3221    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3222    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3223      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3224      <address><email>fielding@gbiv.com</email></address>
3225    </author>
3226    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3227      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3228      <address><email>jg@freedesktop.org</email></address>
3229    </author>
3230    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3231      <organization abbrev="HP">Hewlett-Packard Company</organization>
3232      <address><email>JeffMogul@acm.org</email></address>
3233    </author>
3234    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3235      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3236      <address><email>henrikn@microsoft.com</email></address>
3237    </author>
3238    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3239      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3240      <address><email>LMM@acm.org</email></address>
3241    </author>
3242    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3243      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3244      <address><email>paulle@microsoft.com</email></address>
3245    </author>
3246    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3247      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3248      <address><email>timbl@w3.org</email></address>
3249    </author>
3250    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3251      <organization abbrev="W3C">World Wide Web Consortium</organization>
3252      <address><email>ylafon@w3.org</email></address>
3253    </author>
3254    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3255      <address><email>mnot@mnot.net</email></address>
3256    </author>
3257    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3258      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3259      <address><email>julian.reschke@greenbytes.de</email></address>
3260    </author>
3261    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3262  </front>
3263  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3264  <x:source href="p6-cache.xml" basename="p6-cache"/>
3265</reference>
3266
3267<reference anchor="Part7">
3268  <front>
3269    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3270    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3271      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3272      <address><email>fielding@gbiv.com</email></address>
3273    </author>
3274    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3275      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3276      <address><email>jg@freedesktop.org</email></address>
3277    </author>
3278    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3279      <organization abbrev="HP">Hewlett-Packard Company</organization>
3280      <address><email>JeffMogul@acm.org</email></address>
3281    </author>
3282    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3283      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3284      <address><email>henrikn@microsoft.com</email></address>
3285    </author>
3286    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3287      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3288      <address><email>LMM@acm.org</email></address>
3289    </author>
3290    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3291      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3292      <address><email>paulle@microsoft.com</email></address>
3293    </author>
3294    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3295      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3296      <address><email>timbl@w3.org</email></address>
3297    </author>
3298    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3299      <organization abbrev="W3C">World Wide Web Consortium</organization>
3300      <address><email>ylafon@w3.org</email></address>
3301    </author>
3302    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3303      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3304      <address><email>julian.reschke@greenbytes.de</email></address>
3305    </author>
3306    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3307  </front>
3308  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3309  <x:source href="p7-auth.xml" basename="p7-auth"/>
3310</reference>
3311
3312<reference anchor="RFC2119">
3313  <front>
3314    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3315    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3316      <organization>Harvard University</organization>
3317      <address><email>sob@harvard.edu</email></address>
3318    </author>
3319    <date month="March" year="1997"/>
3320  </front>
3321  <seriesInfo name="BCP" value="14"/>
3322  <seriesInfo name="RFC" value="2119"/>
3323</reference>
3324
3325<reference anchor="RFC3986">
3326 <front>
3327  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3328  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3329    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3330    <address>
3331       <email>timbl@w3.org</email>
3332       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3333    </address>
3334  </author>
3335  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3336    <organization abbrev="Day Software">Day Software</organization>
3337    <address>
3338      <email>fielding@gbiv.com</email>
3339      <uri>http://roy.gbiv.com/</uri>
3340    </address>
3341  </author>
3342  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3343    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3344    <address>
3345      <email>LMM@acm.org</email>
3346      <uri>http://larry.masinter.net/</uri>
3347    </address>
3348  </author>
3349  <date month='January' year='2005'></date>
3350 </front>
3351 <seriesInfo name="STD" value="66"/>
3352 <seriesInfo name="RFC" value="3986"/>
3353</reference>
3354
3355<reference anchor="RFC5234">
3356  <front>
3357    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3358    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3359      <organization>Brandenburg InternetWorking</organization>
3360      <address>
3361        <email>dcrocker@bbiw.net</email>
3362      </address> 
3363    </author>
3364    <author initials="P." surname="Overell" fullname="Paul Overell">
3365      <organization>THUS plc.</organization>
3366      <address>
3367        <email>paul.overell@thus.net</email>
3368      </address>
3369    </author>
3370    <date month="January" year="2008"/>
3371  </front>
3372  <seriesInfo name="STD" value="68"/>
3373  <seriesInfo name="RFC" value="5234"/>
3374</reference>
3375
3376</references>
3377
3378<references title="Informative References">
3379
3380<reference anchor="RFC1945">
3381  <front>
3382    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3383    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3384      <organization>MIT, Laboratory for Computer Science</organization>
3385      <address><email>timbl@w3.org</email></address>
3386    </author>
3387    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3388      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3389      <address><email>fielding@ics.uci.edu</email></address>
3390    </author>
3391    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3392      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3393      <address><email>frystyk@w3.org</email></address>
3394    </author>
3395    <date month="May" year="1996"/>
3396  </front>
3397  <seriesInfo name="RFC" value="1945"/>
3398</reference>
3399
3400<reference anchor="RFC2068">
3401  <front>
3402    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3403    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3404      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3405      <address><email>fielding@ics.uci.edu</email></address>
3406    </author>
3407    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3408      <organization>MIT Laboratory for Computer Science</organization>
3409      <address><email>jg@w3.org</email></address>
3410    </author>
3411    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3412      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3413      <address><email>mogul@wrl.dec.com</email></address>
3414    </author>
3415    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3416      <organization>MIT Laboratory for Computer Science</organization>
3417      <address><email>frystyk@w3.org</email></address>
3418    </author>
3419    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3420      <organization>MIT Laboratory for Computer Science</organization>
3421      <address><email>timbl@w3.org</email></address>
3422    </author>
3423    <date month="January" year="1997"/>
3424  </front>
3425  <seriesInfo name="RFC" value="2068"/>
3426</reference>
3427
3428<reference anchor="RFC2616">
3429  <front>
3430    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3431    <author initials="R." surname="Fielding" fullname="R. Fielding">
3432      <organization>University of California, Irvine</organization>
3433      <address><email>fielding@ics.uci.edu</email></address>
3434    </author>
3435    <author initials="J." surname="Gettys" fullname="J. Gettys">
3436      <organization>W3C</organization>
3437      <address><email>jg@w3.org</email></address>
3438    </author>
3439    <author initials="J." surname="Mogul" fullname="J. Mogul">
3440      <organization>Compaq Computer Corporation</organization>
3441      <address><email>mogul@wrl.dec.com</email></address>
3442    </author>
3443    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3444      <organization>MIT Laboratory for Computer Science</organization>
3445      <address><email>frystyk@w3.org</email></address>
3446    </author>
3447    <author initials="L." surname="Masinter" fullname="L. Masinter">
3448      <organization>Xerox Corporation</organization>
3449      <address><email>masinter@parc.xerox.com</email></address>
3450    </author>
3451    <author initials="P." surname="Leach" fullname="P. Leach">
3452      <organization>Microsoft Corporation</organization>
3453      <address><email>paulle@microsoft.com</email></address>
3454    </author>
3455    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3456      <organization>W3C</organization>
3457      <address><email>timbl@w3.org</email></address>
3458    </author>
3459    <date month="June" year="1999"/>
3460  </front>
3461  <seriesInfo name="RFC" value="2616"/>
3462</reference>
3463
3464<reference anchor='RFC2817'>
3465  <front>
3466    <title>Upgrading to TLS Within HTTP/1.1</title>
3467    <author initials='R.' surname='Khare' fullname='R. Khare'>
3468      <organization>4K Associates / UC Irvine</organization>
3469      <address><email>rohit@4K-associates.com</email></address>
3470    </author>
3471    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3472      <organization>Agranat Systems, Inc.</organization>
3473      <address><email>lawrence@agranat.com</email></address>
3474    </author>
3475    <date year='2000' month='May' />
3476  </front>
3477  <seriesInfo name='RFC' value='2817' />
3478</reference>
3479
3480<reference anchor='RFC3864'>
3481  <front>
3482    <title>Registration Procedures for Message Header Fields</title>
3483    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3484      <organization>Nine by Nine</organization>
3485      <address><email>GK-IETF@ninebynine.org</email></address>
3486    </author>
3487    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3488      <organization>BEA Systems</organization>
3489      <address><email>mnot@pobox.com</email></address>
3490    </author>
3491    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3492      <organization>HP Labs</organization>
3493      <address><email>JeffMogul@acm.org</email></address>
3494    </author>
3495    <date year='2004' month='September' />
3496  </front>
3497  <seriesInfo name='BCP' value='90' />
3498  <seriesInfo name='RFC' value='3864' />
3499</reference>
3500
3501<reference anchor='RFC5226'>
3502  <front>
3503    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3504    <author initials='T.' surname='Narten' fullname='T. Narten'>
3505      <organization>IBM</organization>
3506      <address><email>narten@us.ibm.com</email></address>
3507    </author>
3508    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3509      <organization>Google</organization>
3510      <address><email>Harald@Alvestrand.no</email></address>
3511    </author>
3512    <date year='2008' month='May' />
3513  </front>
3514  <seriesInfo name='BCP' value='26' />
3515  <seriesInfo name='RFC' value='5226' />
3516</reference>
3517
3518<reference anchor="RFC5322">
3519  <front>
3520    <title>Internet Message Format</title>
3521    <author initials="P." surname="Resnick" fullname="P. Resnick">
3522      <organization>Qualcomm Incorporated</organization>
3523    </author>
3524    <date year="2008" month="October"/>
3525  </front> 
3526  <seriesInfo name="RFC" value="5322"/>
3527</reference>
3528
3529<reference anchor='RFC5789'>
3530  <front>
3531    <title>PATCH Method for HTTP</title>
3532    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3533      <organization>Linden Lab</organization>
3534    </author>
3535    <author initials='J.' surname='Snell' fullname='J. Snell'>
3536      <organization />
3537    </author>
3538    <date year='2010' month='March' />
3539  </front>
3540  <seriesInfo name='RFC' value='5789' />
3541</reference>
3542
3543</references>
3544
3545<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3546<t>
3547  This document takes over the Status Code Registry, previously defined
3548  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3549  (<xref target="status.code.registry"/>)
3550</t>
3551<t>
3552  Clarify definition of POST.
3553  (<xref target="POST"/>)
3554</t>
3555<t>
3556  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3557  (<xref target="CONNECT"/>)
3558</t>
3559<t>
3560  Failed to consider that there are
3561  many other request methods that are safe to automatically redirect,
3562  and further that the user agent is able to make that determination
3563  based on the request method semantics.
3564  (Sections <xref format="counter" target="status.301"/>,
3565  <xref format="counter" target="status.302"/> and
3566  <xref format="counter" target="status.307"/>)
3567</t>
3568<t>
3569  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3570  It used to indicate that the target resource must be accessed through the
3571  proxy given by the Location field. The Location field gave the URI of the
3572  proxy. The recipient was expected to repeat this single request via the proxy.
3573  (<xref target="status.305"/>)
3574</t>
3575<t>
3576  Define status 426 (Upgrade Required) (this was incorporated from
3577  <xref target="RFC2817"/>).
3578  (<xref target="status.426"/>)
3579</t>
3580<t>
3581  Reclassify "Allow" as response header field, removing the option to
3582  specify it in a PUT request.
3583  Relax the server requirement on the contents of the Allow header field and
3584  remove requirement on clients to always trust the header field value.
3585  (<xref target="header.allow"/>)
3586</t>
3587<t>
3588  Correct syntax of Location header field to allow URI references (including
3589  relative references and fragments), as referred symbol "absoluteURI" wasn't
3590  what was expected, and add some clarifications as to when use of fragments
3591  would not be appropriate.
3592  (<xref target="header.location"/>)
3593</t>
3594<t>
3595  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3596  extension methods could have used it as well).
3597  (<xref target="header.max-forwards"/>)
3598</t>
3599<t>
3600  Allow Referer field value of "about:blank" as alternative to not specifying it.
3601  (<xref target="header.referer"/>)
3602</t>
3603<t>
3604  In the description of the Server header field, the Via field
3605  was described as a SHOULD. The requirement was and is stated
3606  correctly in the description of the Via header field in &header-via;.
3607  (<xref target="header.server"/>)
3608</t>
3609</section>
3610
3611<?BEGININC p2-semantics.abnf-appendix ?>
3612<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3613<figure>
3614<artwork type="abnf" name="p2-semantics.parsed-abnf">
3615<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3616<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3617<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3618<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3619<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3620<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3621<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3622<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3623<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3624
3625<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3626<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3627<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3628
3629<x:ref>From</x:ref> = "From:" OWS From-v
3630<x:ref>From-v</x:ref> = mailbox
3631
3632<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3633<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3634
3635<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3636If-Modified-Since =
3637 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3638<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3639<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3640If-Unmodified-Since =
3641 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3642
3643<x:ref>Location</x:ref> = "Location:" OWS Location-v
3644<x:ref>Location-v</x:ref> = URI-reference
3645
3646<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3647<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3648<x:ref>Method</x:ref> = token
3649
3650<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3651
3652Proxy-Authenticate =
3653 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3654Proxy-Authorization =
3655 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3656
3657<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3658<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3659<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3660<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3661<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3662<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3663<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3664
3665<x:ref>Server</x:ref> = "Server:" OWS Server-v
3666<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3667<x:ref>Status-Code</x:ref> = 3DIGIT
3668
3669<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3670
3671<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3672<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3673<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3674
3675<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3676
3677WWW-Authenticate =
3678 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3679
3680<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3681
3682<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3683
3684<x:ref>delta-seconds</x:ref> = 1*DIGIT
3685
3686<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3687<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3688<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3689 *expect-params ]
3690
3691<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3692
3693<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3694
3695<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3696<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3697
3698<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3699
3700<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3701</artwork>
3702</figure>
3703<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3704; Accept defined but not used
3705; Accept-Charset defined but not used
3706; Accept-Encoding defined but not used
3707; Accept-Language defined but not used
3708; Accept-Ranges defined but not used
3709; Age defined but not used
3710; Allow defined but not used
3711; Authorization defined but not used
3712; ETag defined but not used
3713; Expect defined but not used
3714; From defined but not used
3715; Host defined but not used
3716; If-Match defined but not used
3717; If-Modified-Since defined but not used
3718; If-None-Match defined but not used
3719; If-Range defined but not used
3720; If-Unmodified-Since defined but not used
3721; Location defined but not used
3722; Max-Forwards defined but not used
3723; Proxy-Authenticate defined but not used
3724; Proxy-Authorization defined but not used
3725; Range defined but not used
3726; Reason-Phrase defined but not used
3727; Referer defined but not used
3728; Retry-After defined but not used
3729; Server defined but not used
3730; Status-Code defined but not used
3731; TE defined but not used
3732; User-Agent defined but not used
3733; Vary defined but not used
3734; WWW-Authenticate defined but not used
3735</artwork></figure></section>
3736<?ENDINC p2-semantics.abnf-appendix ?>
3737
3738<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3739
3740<section title="Since RFC 2616">
3741<t>
3742  Extracted relevant partitions from <xref target="RFC2616"/>.
3743</t>
3744</section>
3745
3746<section title="Since draft-ietf-httpbis-p2-semantics-00">
3747<t>
3748  Closed issues:
3749  <list style="symbols"> 
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3752      "Via is a MUST"
3753      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3754    </t>
3755    <t>
3756      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3757      "Fragments allowed in Location"
3758      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3759    </t>
3760    <t>
3761      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3762      "Safe Methods vs Redirection"
3763      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3764    </t>
3765    <t>
3766      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3767      "Revise description of the POST method"
3768      (<eref target="http://purl.org/NET/http-errata#post"/>)
3769    </t>
3770    <t>
3771      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3772      "Normative and Informative references"
3773    </t>
3774    <t>
3775      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3776      "RFC2606 Compliance"
3777    </t>
3778    <t>
3779      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3780      "Informative references"
3781    </t>
3782    <t>
3783      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3784      "Redundant cross-references"
3785    </t>
3786  </list>
3787</t>
3788<t>
3789  Other changes:
3790  <list style="symbols"> 
3791    <t>
3792      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3793    </t>
3794  </list>
3795</t>
3796</section>
3797
3798<section title="Since draft-ietf-httpbis-p2-semantics-01">
3799<t>
3800  Closed issues:
3801  <list style="symbols"> 
3802    <t>
3803      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3804      "PUT side effects"
3805    </t>
3806    <t>
3807      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3808      "Duplicate Host header requirements"
3809    </t>
3810  </list>
3811</t>
3812<t>
3813  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3814  <list style="symbols"> 
3815    <t>
3816      Move "Product Tokens" section (back) into Part 1, as "token" is used
3817      in the definition of the Upgrade header field.
3818    </t>
3819    <t>
3820      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3821    </t>
3822    <t>
3823      Copy definition of delta-seconds from Part6 instead of referencing it.
3824    </t>
3825  </list>
3826</t>
3827</section>
3828
3829<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3830<t>
3831  Closed issues:
3832  <list style="symbols"> 
3833    <t>
3834      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3835      "Requiring Allow in 405 responses"
3836    </t>
3837    <t>
3838      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3839      "Status Code Registry"
3840    </t>
3841    <t>
3842      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3843      "Redirection vs. Location"
3844    </t>
3845    <t>
3846      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3847      "Cacheability of 303 response"
3848    </t>
3849    <t>
3850      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3851      "305 Use Proxy"
3852    </t>
3853    <t>
3854      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3855      "Classification for Allow header"
3856    </t>
3857    <t>
3858      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3859      "PUT - 'store under' vs 'store at'"
3860    </t>
3861  </list>
3862</t>
3863<t>
3864  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3865  <list style="symbols"> 
3866    <t>
3867      Reference RFC 3984, and update header field registrations for headers defined
3868      in this document.
3869    </t>
3870  </list>
3871</t>
3872<t>
3873  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3874  <list style="symbols"> 
3875    <t>
3876      Replace string literals when the string really is case-sensitive (method).
3877    </t>
3878  </list>
3879</t>
3880</section>
3881
3882<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3883<t>
3884  Closed issues:
3885  <list style="symbols"> 
3886    <t>
3887      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3888      "OPTIONS request bodies"
3889    </t>
3890    <t>
3891      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3892      "Description of CONNECT should refer to RFC2817"
3893    </t>
3894    <t>
3895      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3896      "Location Content-Location reference request/response mixup"
3897    </t>
3898  </list>
3899</t>
3900<t>
3901  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3902  <list style="symbols"> 
3903    <t>
3904      Added initial proposal for registration process, plus initial
3905      content (non-HTTP/1.1 methods to be added by a separate specification).
3906    </t>
3907  </list>
3908</t>
3909</section>
3910
3911<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3912<t>
3913  Closed issues:
3914  <list style="symbols"> 
3915    <t>
3916      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3917      "Content-*"
3918    </t>
3919    <t>
3920      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3921      "RFC 2822 is updated by RFC 5322"
3922    </t>
3923  </list>
3924</t>
3925<t>
3926  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3927  <list style="symbols"> 
3928    <t>
3929      Use "/" instead of "|" for alternatives.
3930    </t>
3931    <t>
3932      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3933      whitespace ("OWS") and required whitespace ("RWS").
3934    </t>
3935    <t>
3936      Rewrite ABNFs to spell out whitespace rules, factor out
3937      header field value format definitions.
3938    </t>
3939  </list>
3940</t>
3941</section>
3942
3943<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3944<t>
3945  Closed issues:
3946  <list style="symbols"> 
3947    <t>
3948      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3949      "Reason-Phrase BNF"
3950    </t>
3951  </list>
3952</t>
3953<t>
3954  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3955  <list style="symbols"> 
3956    <t>
3957      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3958    </t>
3959  </list>
3960</t>
3961</section>
3962
3963<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3964<t>
3965  Closed issues:
3966  <list style="symbols"> 
3967    <t>
3968      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3969      "Clarify when Referer is sent"
3970    </t>
3971    <t>
3972      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3973      "status codes vs methods"
3974    </t>
3975    <t>
3976      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3977      "Do not require "updates" relation for specs that register status codes or method names"
3978    </t>
3979  </list>
3980</t>
3981</section>
3982
3983<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3984<t>
3985  Closed issues:
3986  <list style="symbols"> 
3987    <t>
3988      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3989      "Idempotency"
3990    </t>
3991    <t>
3992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3993      "TRACE security considerations"
3994    </t>
3995    <t>
3996      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3997      "Clarify rules for determining what entities a response carries"
3998    </t>
3999    <t>
4000      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4001      "update note citing RFC 1945 and 2068"
4002    </t>
4003    <t>
4004      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4005      "update note about redirect limit"
4006    </t>
4007    <t>
4008      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4009      "Location header ABNF should use 'URI'"
4010    </t>
4011    <t>
4012      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4013      "fragments in Location vs status 303"
4014    </t>
4015    <t>
4016      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4017      "move IANA registrations for optional status codes"
4018    </t>
4019  </list>
4020</t>
4021<t>
4022  Partly resolved issues:
4023  <list style="symbols"> 
4024    <t>
4025      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4026      "Are OPTIONS and TRACE safe?"
4027    </t>
4028  </list>
4029</t>
4030</section>
4031
4032<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4033<t>
4034  Closed issues:
4035  <list style="symbols"> 
4036    <t>
4037      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4038      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4039      status codes when fixing this previously)
4040    </t>
4041  </list>
4042</t>
4043</section>
4044
4045<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4046<t>
4047  Closed issues:
4048  <list style="symbols"> 
4049    <t>
4050      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4051      "Fragment combination / precedence during redirects"
4052    </t>
4053  </list>
4054</t>
4055<t>
4056  Partly resolved issues:
4057  <list style="symbols"> 
4058    <t>
4059      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4060      "Location header payload handling"
4061    </t>
4062    <t>
4063      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4064      "Term for the requested resource's URI"
4065    </t>
4066  </list>
4067</t>
4068</section>
4069
4070<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4071<t>
4072  Closed issues:
4073  <list style="symbols"> 
4074    <t>
4075      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4076      "Clarify 'Requested Variant'"
4077    </t>
4078    <t>
4079      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4080      "Clarify entity / representation / variant terminology"
4081    </t>
4082    <t>
4083      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4084      "Methods and Caching"
4085    </t>
4086    <t>
4087      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4088      "OPTIONS vs Max-Forwards"
4089    </t>
4090    <t>
4091      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4092      "Status codes and caching"
4093    </t>
4094    <t>
4095      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4096      "consider removing the 'changes from 2068' sections"
4097    </t>
4098  </list>
4099</t>
4100</section>
4101
4102<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4103<t>
4104  Closed issues:
4105  <list style="symbols"> 
4106    <t>
4107      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4108      "Considerations for new status codes"
4109    </t>
4110    <t>
4111      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4112      "Considerations for new methods"
4113    </t>
4114    <t>
4115      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4116      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4117    </t>
4118  </list>
4119</t>
4120</section>
4121
4122<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4123<t>
4124  Closed issues:
4125  <list style="symbols"> 
4126    <t>
4127      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4128      "Fragment combination / precedence during redirects" (added warning
4129      about having a fragid on the redirect may cause inconvenience in
4130      some cases)
4131    </t>
4132    <t>
4133      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4134      "205 Bodies"
4135    </t>
4136    <t>
4137      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4138      "duplicate ABNF for Reason-Phrase"
4139    </t>
4140    <t>
4141      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4142      "Max-Forwards vs extension methods"
4143    </t>
4144    <t>
4145      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4146      "What is the value space of HTTP status codes?" (actually fixed in
4147      draft-ietf-httpbis-p2-semantics-11)
4148    </t>
4149    <t>
4150      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4151      "proxies not supporting certain methods"
4152    </t>
4153    <t>
4154      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4155      "Migrate CONNECT from RFC2817 to p2"
4156    </t>
4157    <t>
4158      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4159      "Migrate Upgrade details from RFC2817"
4160    </t>
4161    <t>
4162      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4163      "PUT side effect: invalidation or just stale?"
4164    </t>
4165    <t>
4166      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4167      "duplicate ABNF for 'Method'"
4168    </t>
4169    <t>
4170      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4171      "untangle ABNFs for header fields"
4172    </t>
4173  </list>
4174</t>
4175</section>
4176
4177</section>
4178
4179</back>
4180</rfc>
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