source: draft-ietf-httpbis/latest/p2-semantics.xml @ 31

Last change on this file since 31 was 31, checked in by julian.reschke@…, 12 years ago

Insert cross-document references.

  • Property svn:eol-style set to native
File size: 117.0 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<!DOCTYPE rfc [
3  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
4  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
5  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
6  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
7  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
8  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
9  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
10  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
11  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
12  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
13  <!ENTITY ID-VERSION "latest">
14  <!ENTITY ID-MONTH "December">
15  <!ENTITY ID-YEAR "2007">
16  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
17  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY diff2045entity             "<xref target='Part3' x:rel='#differences.between.http.entities.and.rfc.2045.entities' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58]>
59<?rfc toc="yes" ?>
60<?rfc symrefs="yes" ?>
61<?rfc sortrefs="yes" ?>
62<?rfc compact="yes"?>
63<?rfc subcompact="no" ?>
64<?rfc linkmailto="no" ?>
65<?rfc editing="no" ?>
66<?rfc-ext allow-markup-in-artwork="yes" ?>
67<?rfc-ext include-references-in-index="yes" ?>
68<rfc obsoletes="2068, 2616, 2617" category="std"
69     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
70     xmlns:x='http://purl.org/net/xml2rfc/ext' xmlns:ed="http://greenbytes.de/2002/rfcedit">
71<front>
72
73  <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
74
75  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
76    <organization abbrev="Day Software">Day Software</organization>
77    <address>
78      <postal>
79        <street>23 Corporate Plaza DR, Suite 280</street>
80        <city>Newport Beach</city>
81        <region>CA</region>
82        <code>92660</code>
83        <country>USA</country>
84      </postal>
85      <phone>+1-949-706-5300</phone>
86      <facsimile>+1-949-706-5305</facsimile>
87      <email>fielding@gbiv.com</email>
88      <uri>http://roy.gbiv.com/</uri>
89    </address>
90  </author>
91
92  <author initials="J." surname="Gettys" fullname="Jim Gettys">
93    <organization>One Laptop per Child</organization>
94    <address>
95      <postal>
96        <street>21 Oak Knoll Road</street>
97        <city>Carlisle</city>
98        <region>MA</region>
99        <code>01741</code>
100        <country>USA</country>
101      </postal>
102      <email>jg@laptop.org</email>
103      <uri>http://www.laptop.org/</uri>
104    </address>
105  </author>
106 
107  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
108    <organization abbrev="HP">Hewlett-Packard Company</organization>
109    <address>
110      <postal>
111        <street>HP Labs, Large Scale Systems Group</street>
112        <street>1501 Page Mill Road, MS 1177</street>
113        <city>Palo Alto</city>
114        <region>CA</region>
115        <code>94304</code>
116        <country>USA</country>
117      </postal>
118      <email>JeffMogul@acm.org</email>
119    </address>
120  </author>
121
122  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
123    <organization abbrev="Microsoft">Microsoft Corporation</organization>
124    <address>
125      <postal>
126        <street>1 Microsoft Way</street>
127        <city>Redmond</city>
128        <region>WA</region>
129        <code>98052</code>
130        <country>USA</country>
131      </postal>
132      <email>henrikn@microsoft.com</email>
133    </address>
134  </author>
135
136  <author initials="L." surname="Masinter" fullname="Larry Masinter">
137    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
138    <address>
139      <postal>
140        <street>345 Park Ave</street>
141        <city>San Jose</city>
142        <region>CA</region>
143        <code>95110</code>
144        <country>USA</country>
145      </postal>
146      <email>LMM@acm.org</email>
147      <uri>http://larry.masinter.net/</uri>
148    </address>
149  </author>
150 
151  <author initials="P." surname="Leach" fullname="Paul J. Leach">
152    <organization abbrev="Microsoft">Microsoft Corporation</organization>
153    <address>
154      <postal>
155        <street>1 Microsoft Way</street>
156        <city>Redmond</city>
157        <region>WA</region>
158        <code>98052</code>
159      </postal>
160      <email>paulle@microsoft.com</email>
161    </address>
162  </author>
163   
164  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
165    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
166    <address>
167      <postal>
168        <street>MIT Laboratory for Computer Science</street>
169        <street>545 Technology Square</street>
170        <city>Cambridge</city>
171        <region>MA</region>
172        <code>02139</code>
173        <country>USA</country>
174      </postal>
175      <facsimile>+1 (617) 258 8682</facsimile>
176      <email>timbl@w3.org</email>
177    </address>
178  </author>
179
180  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
181
182<abstract>
183<t>
184   The Hypertext Transfer Protocol (HTTP) is an application-level
185   protocol for distributed, collaborative, hypermedia information
186   systems. HTTP has been in use by the World Wide Web global information
187   initiative since 1990. This document is Part 2 of the eight-part specification
188   that defines the protocol referred to as "HTTP/1.1" and, taken together,
189   updates RFC 2616 and RFC 2617.  Part 2 defines the semantics of HTTP messages
190   as expressed by request methods, request-header fields, response status codes,
191   and response-header fields.
192</t>
193</abstract>
194</front>
195<middle>
196<section title="Introduction" anchor="introduction">
197<t>
198   This document will define aspects of HTTP related to request and response
199   semantics. Right now it only includes the extracted relevant sections of
200   RFC 2616 with only minor edits.
201</t>
202<t>
203   The HTTP protocol is a request/response protocol. A client sends a
204   request to the server in the form of a request method, URI, and
205   protocol version, followed by a MIME-like message containing request
206   modifiers, client information, and possible body content over a
207   connection with a server. The server responds with a status line,
208   including the message's protocol version and a success or error code,
209   followed by a MIME-like message containing server information, entity
210   metainformation, and possible entity-body content. The relationship
211   between HTTP and MIME is described in &diff2045entity;.
212</t>
213</section>
214
215<section title="Product Tokens" anchor="product.tokens">
216<t>
217   Product tokens are used to allow communicating applications to
218   identify themselves by software name and version. Most fields using
219   product tokens also allow sub-products which form a significant part
220   of the application to be listed, separated by white space. By
221   convention, the products are listed in order of their significance
222   for identifying the application.
223</t>
224<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="product"/><iref primary="true" item="Grammar" subitem="product-version"/>
225    product         = token ["/" product-version]
226    product-version = token
227</artwork></figure>
228<t>
229   Examples:
230</t>
231<figure><artwork type="example">
232    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
233    Server: Apache/0.8.4
234</artwork></figure>
235<t>
236   Product tokens &SHOULD; be short and to the point. They &MUST-NOT; be
237   used for advertising or other non-essential information. Although any
238   token character &MAY; appear in a product-version, this token &SHOULD;
239   only be used for a version identifier (i.e., successive versions of
240   the same product &SHOULD; only differ in the product-version portion of
241   the product value).
242</t>
243</section>
244
245<section title="Method" anchor="method">
246<t>
247   The Method  token indicates the method to be performed on the
248   resource identified by the Request-URI. The method is case-sensitive.
249</t>
250<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
251    Method         = "OPTIONS"                ; <xref target="OPTIONS"/>
252                   | "GET"                    ; <xref target="GET"/>
253                   | "HEAD"                   ; <xref target="HEAD"/>
254                   | "POST"                   ; <xref target="POST"/>
255                   | "PUT"                    ; <xref target="PUT"/>
256                   | "DELETE"                 ; <xref target="DELETE"/>
257                   | "TRACE"                  ; <xref target="TRACE"/>
258                   | "CONNECT"                ; <xref target="CONNECT"/>
259                   | extension-method
260    extension-method = token
261</artwork></figure>
262<t>
263   The list of methods allowed by a resource can be specified in an
264   Allow header field (<xref target="header.allow"/>). The return code of the response
265   always notifies the client whether a method is currently allowed on a
266   resource, since the set of allowed methods can change dynamically. An
267   origin server &SHOULD; return the status code 405 (Method Not Allowed)
268   if the method is known by the origin server but not allowed for the
269   requested resource, and 501 (Not Implemented) if the method is
270   unrecognized or not implemented by the origin server. The methods GET
271   and HEAD &MUST; be supported by all general-purpose servers. All other
272   methods are &OPTIONAL;; however, if the above methods are implemented,
273   they &MUST; be implemented with the same semantics as those specified
274   in <xref target="method.definitions"/>.
275</t>
276</section>
277
278<section title="Request Header Fields" anchor="request.header.fields">
279<t>
280   The request-header fields allow the client to pass additional
281   information about the request, and about the client itself, to the
282   server. These fields act as request modifiers, with semantics
283   equivalent to the parameters on a programming language method
284   invocation.
285</t>
286<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
287    request-header = Accept                   ; &header-accept;
288                   | Accept-Charset           ; &header-accept-charset;
289                   | Accept-Encoding          ; &header-accept-encoding;
290                   | Accept-Language          ; &header-accept-language;
291                   | Authorization            ; &header-authorization;
292                   | Expect                   ; <xref target="header.expect"/>
293                   | From                     ; <xref target="header.from"/>
294                   | Host                     ; &header-host;
295                   | If-Match                 ; &header-if-match;
296                   | If-Modified-Since        ; &header-if-modified-since;
297                   | If-None-Match            ; &header-if-none-match;
298                   | If-Range                 ; &header-if-range;
299                   | If-Unmodified-Since      ; &header-if-unmodified-since;
300                   | Max-Forwards             ; <xref target="header.max-forwards"/>
301                   | Proxy-Authorization      ; &header-proxy-authorization;
302                   | Range                    ; &header-range;
303                   | Referer                  ; <xref target="header.referer"/>
304                   | TE                       ; &header-te;
305                   | User-Agent               ; <xref target="header.user-agent"/>
306</artwork></figure>
307<t>
308   Request-header field names can be extended reliably only in
309   combination with a change in the protocol version. However, new or
310   experimental header fields &MAY; be given the semantics of request-header
311   fields if all parties in the communication recognize them to
312   be request-header fields. Unrecognized header fields are treated as
313   entity-header fields.
314</t>
315</section>
316
317<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
318<t>
319   The Status-Code element is a 3-digit integer result code of the
320   attempt to understand and satisfy the request. These codes are fully
321   defined in <xref target="status.codes"/>. The Reason-Phrase is intended to give a short
322   textual description of the Status-Code. The Status-Code is intended
323   for use by automata and the Reason-Phrase is intended for the human
324   user. The client is not required to examine or display the Reason-Phrase.
325</t>
326<t> 
327   The individual values of the numeric status codes defined for
328   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
329   presented below. The reason phrases listed here are only
330   recommendations -- they &MAY; be replaced by local equivalents without
331   affecting the protocol.
332</t>
333<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"/>
334   Status-Code    =
335         "100"  ; <xref target="status.100"/>: Continue
336       | "101"  ; <xref target="status.101"/>: Switching Protocols
337       | "200"  ; <xref target="status.200"/>: OK
338       | "201"  ; <xref target="status.201"/>: Created
339       | "202"  ; <xref target="status.202"/>: Accepted
340       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
341       | "204"  ; <xref target="status.204"/>: No Content
342       | "205"  ; <xref target="status.205"/>: Reset Content
343       | "206"  ; <xref target="status.206"/>: Partial Content
344       | "300"  ; <xref target="status.300"/>: Multiple Choices
345       | "301"  ; <xref target="status.301"/>: Moved Permanently
346       | "302"  ; <xref target="status.302"/>: Found
347       | "303"  ; <xref target="status.303"/>: See Other
348       | "304"  ; <xref target="status.304"/>: Not Modified
349       | "305"  ; <xref target="status.305"/>: Use Proxy
350       | "307"  ; <xref target="status.307"/>: Temporary Redirect
351       | "400"  ; <xref target="status.400"/>: Bad Request
352       | "401"  ; <xref target="status.401"/>: Unauthorized
353       | "402"  ; <xref target="status.402"/>: Payment Required
354       | "403"  ; <xref target="status.403"/>: Forbidden
355       | "404"  ; <xref target="status.404"/>: Not Found
356       | "405"  ; <xref target="status.405"/>: Method Not Allowed
357       | "406"  ; <xref target="status.406"/>: Not Acceptable
358       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
359       | "408"  ; <xref target="status.408"/>: Request Time-out
360       | "409"  ; <xref target="status.409"/>: Conflict
361       | "410"  ; <xref target="status.410"/>: Gone
362       | "411"  ; <xref target="status.411"/>: Length Required
363       | "412"  ; <xref target="status.412"/>: Precondition Failed
364       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
365       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
366       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
367       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
368       | "417"  ; <xref target="status.417"/>: Expectation Failed
369       | "500"  ; <xref target="status.500"/>: Internal Server Error
370       | "501"  ; <xref target="status.501"/>: Not Implemented
371       | "502"  ; <xref target="status.502"/>: Bad Gateway
372       | "503"  ; <xref target="status.503"/>: Service Unavailable
373       | "504"  ; <xref target="status.504"/>: Gateway Time-out
374       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
375       | extension-code
376
377   extension-code = 3DIGIT
378   Reason-Phrase  = *&lt;TEXT, excluding CR, LF&gt;
379</artwork></figure>
380<t>
381   HTTP status codes are extensible. HTTP applications are not required
382   to understand the meaning of all registered status codes, though such
383   understanding is obviously desirable. However, applications &MUST;
384   understand the class of any status code, as indicated by the first
385   digit, and treat any unrecognized response as being equivalent to the
386   x00 status code of that class, with the exception that an
387   unrecognized response &MUST-NOT; be cached. For example, if an
388   unrecognized status code of 431 is received by the client, it can
389   safely assume that there was something wrong with its request and
390   treat the response as if it had received a 400 status code. In such
391   cases, user agents &SHOULD; present to the user the entity returned
392   with the response, since that entity is likely to include human-readable
393   information which will explain the unusual status.
394</t>
395</section>
396
397<section title="Response Header Fields" anchor="response.header.fields">
398<t>
399   The response-header fields allow the server to pass additional
400   information about the response which cannot be placed in the Status-Line.
401   These header fields give information about the server and about
402   further access to the resource identified by the Request-URI.
403</t>
404<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
405    response-header = Accept-Ranges           ; &header-accept-ranges;
406                    | Age                     ; &header-age;
407                    | ETag                    ; &header-etag;
408                    | Location                ; <xref target="header.location"/>
409                    | Proxy-Authenticate      ; &header-proxy-authenticate;
410                    | Retry-After             ; <xref target="header.retry-after"/>
411                    | Server                  ; <xref target="header.server"/>
412                    | Vary                    ; &header-vary;
413                    | WWW-Authenticate        ; &header-www-authenticate;
414</artwork></figure>
415<t>
416   Response-header field names can be extended reliably only in
417   combination with a change in the protocol version. However, new or
418   experimental header fields &MAY; be given the semantics of response-header
419   fields if all parties in the communication recognize them to
420   be response-header fields. Unrecognized header fields are treated as
421   entity-header fields.
422</t>
423</section>
424
425<section title="Entity" anchor="entity">
426<t>
427   Request and Response messages &MAY; transfer an entity if not otherwise
428   restricted by the request method or response status code. An entity
429   consists of entity-header fields and an entity-body, although some
430   responses will only include the entity-headers. HTTP entity-body and
431   entity-header fields are defined in &payload;.
432</t>
433<t>
434   An entity-body is only present in a message when a message-body is
435   present, as described in &message-body;. The entity-body is obtained
436   from the message-body by decoding any Transfer-Encoding that might
437   have been applied to ensure safe and proper transfer of the message.
438</t>
439</section>
440
441
442<section title="Method Definitions" anchor="method.definitions">
443<t>
444   The set of common methods for HTTP/1.1 is defined below. Although
445   this set can be expanded, additional methods cannot be assumed to
446   share the same semantics for separately extended clients and servers.
447
448   The Host request-header field (&header-host;) &MUST; accompany all
449   HTTP/1.1 requests.
450</t>
451
452<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
453
454<section title="Safe Methods" anchor="safe.methods">
455<t>
456   Implementors should be aware that the software represents the user in
457   their interactions over the Internet, and should be careful to allow
458   the user to be aware of any actions they might take which may have an
459   unexpected significance to themselves or others.
460</t>
461<t>
462   In particular, the convention has been established that the GET and
463   HEAD methods &SHOULD-NOT;  have the significance of taking an action
464   other than retrieval. These methods ought to be considered "safe".
465   This allows user agents to represent other methods, such as POST, PUT
466   and DELETE, in a special way, so that the user is made aware of the
467   fact that a possibly unsafe action is being requested.
468</t>
469<t>
470   Naturally, it is not possible to ensure that the server does not
471   generate side-effects as a result of performing a GET request; in
472   fact, some dynamic resources consider that a feature. The important
473   distinction here is that the user did not request the side-effects,
474   so therefore cannot be held accountable for them.
475</t>
476</section>
477
478<section title="Idempotent Methods" anchor="idempotent.methods">
479<t>
480   Methods can also have the property of "idempotence" in that (aside
481   from error or expiration issues) the side-effects of N &gt; 0 identical
482   requests is the same as for a single request. The methods GET, HEAD,
483   PUT and DELETE share this property. Also, the methods OPTIONS and
484   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
485</t>
486<t>
487   However, it is possible that a sequence of several requests is non-idempotent,
488   even if all of the methods executed in that sequence are
489   idempotent. (A sequence is idempotent if a single execution of the
490   entire sequence always yields a result that is not changed by a
491   reexecution of all, or part, of that sequence.) For example, a
492   sequence is non-idempotent if its result depends on a value that is
493   later modified in the same sequence.
494</t>
495<t>
496   A sequence that never has side effects is idempotent, by definition
497   (provided that no concurrent operations are being executed on the
498   same set of resources).
499</t>
500</section>
501</section>
502
503<section title="OPTIONS" anchor="OPTIONS">
504  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
505  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
506<t>
507   The OPTIONS method represents a request for information about the
508   communication options available on the request/response chain
509   identified by the Request-URI. This method allows the client to
510   determine the options and/or requirements associated with a resource,
511   or the capabilities of a server, without implying a resource action
512   or initiating a resource retrieval.
513</t>
514<t>
515   Responses to this method are not cacheable.
516</t>
517<t>
518   If the OPTIONS request includes an entity-body (as indicated by the
519   presence of Content-Length or Transfer-Encoding), then the media type
520   &MUST; be indicated by a Content-Type field. Although this
521   specification does not define any use for such a body, future
522   extensions to HTTP might use the OPTIONS body to make more detailed
523   queries on the server. A server that does not support such an
524   extension &MAY; discard the request body.
525</t>
526<t>
527   If the Request-URI is an asterisk ("*"), the OPTIONS request is
528   intended to apply to the server in general rather than to a specific
529   resource. Since a server's communication options typically depend on
530   the resource, the "*" request is only useful as a "ping" or "no-op"
531   type of method; it does nothing beyond allowing the client to test
532   the capabilities of the server. For example, this can be used to test
533   a proxy for HTTP/1.1 compliance (or lack thereof).
534</t>
535<t>
536   If the Request-URI is not an asterisk, the OPTIONS request applies
537   only to the options that are available when communicating with that
538   resource.
539</t>
540<t>
541   A 200 response &SHOULD; include any header fields that indicate
542   optional features implemented by the server and applicable to that
543   resource (e.g., Allow), possibly including extensions not defined by
544   this specification. The response body, if any, &SHOULD; also include
545   information about the communication options. The format for such a
546   body is not defined by this specification, but might be defined by
547   future extensions to HTTP. Content negotiation &MAY; be used to select
548   the appropriate response format. If no response body is included, the
549   response &MUST; include a Content-Length field with a field-value of
550   "0".
551</t>
552<t>
553   The Max-Forwards request-header field &MAY; be used to target a
554   specific proxy in the request chain. When a proxy receives an OPTIONS
555   request on an absoluteURI for which request forwarding is permitted,
556   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
557   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
558   instead, the proxy &SHOULD; respond with its own communication options.
559   If the Max-Forwards field-value is an integer greater than zero, the
560   proxy &MUST; decrement the field-value when it forwards the request. If
561   no Max-Forwards field is present in the request, then the forwarded
562   request &MUST-NOT; include a Max-Forwards field.
563</t>
564</section>
565
566<section title="GET" anchor="GET">
567  <iref primary="true" item="GET method" x:for-anchor=""/>
568  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
569<t>
570   The GET method means retrieve whatever information (in the form of an
571   entity) is identified by the Request-URI. If the Request-URI refers
572   to a data-producing process, it is the produced data which shall be
573   returned as the entity in the response and not the source text of the
574   process, unless that text happens to be the output of the process.
575</t>
576<t>
577   The semantics of the GET method change to a "conditional GET" if the
578   request message includes an If-Modified-Since, If-Unmodified-Since,
579   If-Match, If-None-Match, or If-Range header field. A conditional GET
580   method requests that the entity be transferred only under the
581   circumstances described by the conditional header field(s). The
582   conditional GET method is intended to reduce unnecessary network
583   usage by allowing cached entities to be refreshed without requiring
584   multiple requests or transferring data already held by the client.
585</t>
586<t>
587   The semantics of the GET method change to a "partial GET" if the
588   request message includes a Range header field. A partial GET requests
589   that only part of the entity be transferred, as described in &header-range;.
590   The partial GET method is intended to reduce unnecessary
591   network usage by allowing partially-retrieved entities to be
592   completed without transferring data already held by the client.
593</t>
594<t>
595   The response to a GET request is cacheable if and only if it meets
596   the requirements for HTTP caching described in &caching;.
597</t>
598<t>
599   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
600</t>
601</section>
602
603<section title="HEAD" anchor="HEAD">
604  <iref primary="true" item="HEAD method" x:for-anchor=""/>
605  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
606<t>
607   The HEAD method is identical to GET except that the server &MUST-NOT;
608   return a message-body in the response. The metainformation contained
609   in the HTTP headers in response to a HEAD request &SHOULD; be identical
610   to the information sent in response to a GET request. This method can
611   be used for obtaining metainformation about the entity implied by the
612   request without transferring the entity-body itself. This method is
613   often used for testing hypertext links for validity, accessibility,
614   and recent modification.
615</t>
616<t>
617   The response to a HEAD request &MAY; be cacheable in the sense that the
618   information contained in the response &MAY; be used to update a
619   previously cached entity from that resource. If the new field values
620   indicate that the cached entity differs from the current entity (as
621   would be indicated by a change in Content-Length, Content-MD5, ETag
622   or Last-Modified), then the cache &MUST; treat the cache entry as
623   stale.
624</t>
625</section>
626
627<section title="POST" anchor="POST">
628  <iref primary="true" item="POST method" x:for-anchor=""/>
629  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
630<t>
631   The POST method is used to request that the origin server accept the
632   entity enclosed in the request as a new subordinate of the resource
633   identified by the Request-URI in the Request-Line. POST is designed
634   to allow a uniform method to cover the following functions:
635  <list style="symbols">
636    <t>
637      Annotation of existing resources;
638    </t>
639    <t>
640        Posting a message to a bulletin board, newsgroup, mailing list,
641        or similar group of articles;
642    </t>
643    <t>
644        Providing a block of data, such as the result of submitting a
645        form, to a data-handling process;
646    </t>
647    <t>
648        Extending a database through an append operation.
649    </t>
650  </list>
651</t>
652<t>
653   The actual function performed by the POST method is determined by the
654   server and is usually dependent on the Request-URI. The posted entity
655   is subordinate to that URI in the same way that a file is subordinate
656   to a directory containing it, a news article is subordinate to a
657   newsgroup to which it is posted, or a record is subordinate to a
658   database.
659</t>
660<t>
661   The action performed by the POST method might not result in a
662   resource that can be identified by a URI. In this case, either 200
663   (OK) or 204 (No Content) is the appropriate response status,
664   depending on whether or not the response includes an entity that
665   describes the result.
666</t>
667<t>
668   If a resource has been created on the origin server, the response
669   &SHOULD; be 201 (Created) and contain an entity which describes the
670   status of the request and refers to the new resource, and a Location
671   header (see <xref target="header.location"/>).
672</t>
673<t>
674   Responses to this method are not cacheable, unless the response
675   includes appropriate Cache-Control or Expires header fields. However,
676   the 303 (See Other) response can be used to direct the user agent to
677   retrieve a cacheable resource.
678</t>
679<t>
680   POST requests &MUST; obey the message transmission requirements set out
681   in [message.transmission.requirements].
682</t>
683<t>
684   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
685</t>
686</section>
687
688<section title="PUT" anchor="PUT">
689  <iref primary="true" item="PUT method" x:for-anchor=""/>
690  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
691<t>
692   The PUT method requests that the enclosed entity be stored under the
693   supplied Request-URI. If the Request-URI refers to an already
694   existing resource, the enclosed entity &SHOULD; be considered as a
695   modified version of the one residing on the origin server. If the
696   Request-URI does not point to an existing resource, and that URI is
697   capable of being defined as a new resource by the requesting user
698   agent, the origin server can create the resource with that URI. If a
699   new resource is created, the origin server &MUST; inform the user agent
700   via the 201 (Created) response. If an existing resource is modified,
701   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
702   to indicate successful completion of the request. If the resource
703   could not be created or modified with the Request-URI, an appropriate
704   error response &SHOULD; be given that reflects the nature of the
705   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
706   (e.g. Content-Range) headers that it does not understand or implement
707   and &MUST; return a 501 (Not Implemented) response in such cases.
708</t>
709<t>
710   If the request passes through a cache and the Request-URI identifies
711   one or more currently cached entities, those entries &SHOULD; be
712   treated as stale. Responses to this method are not cacheable.
713</t>
714<t>
715   The fundamental difference between the POST and PUT requests is
716   reflected in the different meaning of the Request-URI. The URI in a
717   POST request identifies the resource that will handle the enclosed
718   entity. That resource might be a data-accepting process, a gateway to
719   some other protocol, or a separate entity that accepts annotations.
720   In contrast, the URI in a PUT request identifies the entity enclosed
721   with the request -- the user agent knows what URI is intended and the
722   server &MUST-NOT; attempt to apply the request to some other resource.
723   If the server desires that the request be applied to a different URI,
724   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
725   then make its own decision regarding whether or not to redirect the
726   request.
727</t>
728<t>
729   A single resource &MAY; be identified by many different URIs. For
730   example, an article might have a URI for identifying "the current
731   version" which is separate from the URI identifying each particular
732   version. In this case, a PUT request on a general URI might result in
733   several other URIs being defined by the origin server.
734</t>
735<t>
736   HTTP/1.1 does not define how a PUT method affects the state of an
737   origin server.
738</t>
739<t>
740   PUT requests &MUST; obey the message transmission requirements set out
741   in [message.transmission.requirements].
742</t>
743<t>
744   Unless otherwise specified for a particular entity-header, the
745   entity-headers in the PUT request &SHOULD; be applied to the resource
746   created or modified by the PUT.
747</t>
748</section>
749
750<section title="DELETE" anchor="DELETE">
751  <iref primary="true" item="DELETE method" x:for-anchor=""/>
752  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
753<t>
754   The DELETE method requests that the origin server delete the resource
755   identified by the Request-URI. This method &MAY; be overridden by human
756   intervention (or other means) on the origin server. The client cannot
757   be guaranteed that the operation has been carried out, even if the
758   status code returned from the origin server indicates that the action
759   has been completed successfully. However, the server &SHOULD-NOT; 
760   indicate success unless, at the time the response is given, it
761   intends to delete the resource or move it to an inaccessible
762   location.
763</t>
764<t>
765   A successful response &SHOULD; be 200 (OK) if the response includes an
766   entity describing the status, 202 (Accepted) if the action has not
767   yet been enacted, or 204 (No Content) if the action has been enacted
768   but the response does not include an entity.
769</t>
770<t>
771   If the request passes through a cache and the Request-URI identifies
772   one or more currently cached entities, those entries &SHOULD; be
773   treated as stale. Responses to this method are not cacheable.
774</t>
775</section>
776
777<section title="TRACE" anchor="TRACE">
778  <iref primary="true" item="TRACE method" x:for-anchor=""/>
779  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
780<t>
781   The TRACE method is used to invoke a remote, application-layer loop-back
782   of the request message. The final recipient of the request
783   &SHOULD; reflect the message received back to the client as the
784   entity-body of a 200 (OK) response. The final recipient is either the
785   origin server or the first proxy or gateway to receive a Max-Forwards
786   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
787   &MUST-NOT; include an entity.
788</t>
789<t>
790   TRACE allows the client to see what is being received at the other
791   end of the request chain and use that data for testing or diagnostic
792   information. The value of the Via header field (&header-via;) is of
793   particular interest, since it acts as a trace of the request chain.
794   Use of the Max-Forwards header field allows the client to limit the
795   length of the request chain, which is useful for testing a chain of
796   proxies forwarding messages in an infinite loop.
797</t>
798<t>
799   If the request is valid, the response &SHOULD; contain the entire
800   request message in the entity-body, with a Content-Type of
801   "message/http". Responses to this method &MUST-NOT; be cached.
802</t>
803</section>
804
805<section title="CONNECT" anchor="CONNECT">
806  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
807  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
808<t>
809   This specification reserves the method name CONNECT for use with a
810   proxy that can dynamically switch to being a tunnel (e.g. SSL
811   tunneling <xref target="Luo1998"/>).
812</t>
813</section>
814</section>
815
816
817<section title="Status Code Definitions" anchor="status.codes">
818<t>
819   Each Status-Code is described below, including a description of which
820   method(s) it can follow and any metainformation required in the
821   response.
822</t>
823
824<section title="Informational 1xx" anchor="status.1xx">
825<t>
826   This class of status code indicates a provisional response,
827   consisting only of the Status-Line and optional headers, and is
828   terminated by an empty line. There are no required headers for this
829   class of status code. Since HTTP/1.0 did not define any 1xx status
830   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
831   except under experimental conditions.
832</t>
833<t>
834   A client &MUST; be prepared to accept one or more 1xx status responses
835   prior to a regular response, even if the client does not expect a 100
836   (Continue) status message. Unexpected 1xx status responses &MAY; be
837   ignored by a user agent.
838</t>
839<t>
840   Proxies &MUST; forward 1xx responses, unless the connection between the
841   proxy and its client has been closed, or unless the proxy itself
842   requested the generation of the 1xx response. (For example, if a
843   proxy adds a "Expect: 100-continue" field when it forwards a request,
844   then it need not forward the corresponding 100 (Continue)
845   response(s).)
846</t>
847
848<section title="100 Continue" anchor="status.100">
849  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
850  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
851<t>
852   The client &SHOULD; continue with its request. This interim response is
853   used to inform the client that the initial part of the request has
854   been received and has not yet been rejected by the server. The client
855   &SHOULD; continue by sending the remainder of the request or, if the
856   request has already been completed, ignore this response. The server
857   &MUST; send a final response after the request has been completed. See
858   &use100; for detailed discussion of the use and handling of this
859   status code.
860</t>
861</section>
862
863<section title="101 Switching Protocols" anchor="status.101">
864  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
865  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
866<t>
867   The server understands and is willing to comply with the client's
868   request, via the Upgrade message header field (&header-upgrade;), for a
869   change in the application protocol being used on this connection. The
870   server will switch protocols to those defined by the response's
871   Upgrade header field immediately after the empty line which
872   terminates the 101 response.
873</t>
874<t>
875   The protocol &SHOULD; be switched only when it is advantageous to do
876   so. For example, switching to a newer version of HTTP is advantageous
877   over older versions, and switching to a real-time, synchronous
878   protocol might be advantageous when delivering resources that use
879   such features.
880</t>
881</section>
882</section>
883
884<section title="Successful 2xx" anchor="status.2xx">
885<t>
886   This class of status code indicates that the client's request was
887   successfully received, understood, and accepted.
888</t>
889
890<section title="200 OK" anchor="status.200">
891  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
892  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
893<t>
894   The request has succeeded. The information returned with the response
895   is dependent on the method used in the request, for example:
896  <list style="hanging">
897    <t hangText="GET">
898          an entity corresponding to the requested resource is sent in
899          the response;
900    </t>
901    <t hangText="HEAD">
902          the entity-header fields corresponding to the requested
903          resource are sent in the response without any message-body;
904    </t>
905    <t hangText="POST">
906      an entity describing or containing the result of the action;
907    </t>
908    <t hangText="TRACE">
909      an entity containing the request message as received by the
910      end server.
911    </t>
912  </list>
913</t>
914</section>
915
916<section title="201 Created" anchor="status.201">
917  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
918  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
919<t>
920   The request has been fulfilled and resulted in a new resource being
921   created. The newly created resource can be referenced by the URI(s)
922   returned in the entity of the response, with the most specific URI
923   for the resource given by a Location header field. The response
924   &SHOULD; include an entity containing a list of resource
925   characteristics and location(s) from which the user or user agent can
926   choose the one most appropriate. The entity format is specified by
927   the media type given in the Content-Type header field. The origin
928   server &MUST; create the resource before returning the 201 status code.
929   If the action cannot be carried out immediately, the server &SHOULD;
930   respond with 202 (Accepted) response instead.
931</t>
932<t>
933   A 201 response &MAY; contain an ETag response header field indicating
934   the current value of the entity tag for the requested variant just
935   created, see &header-etag;.
936</t>
937</section>
938
939<section title="202 Accepted" anchor="status.202">
940  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
941  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
942<t>
943   The request has been accepted for processing, but the processing has
944   not been completed.  The request might or might not eventually be
945   acted upon, as it might be disallowed when processing actually takes
946   place. There is no facility for re-sending a status code from an
947   asynchronous operation such as this.
948</t>
949<t>
950   The 202 response is intentionally non-committal. Its purpose is to
951   allow a server to accept a request for some other process (perhaps a
952   batch-oriented process that is only run once per day) without
953   requiring that the user agent's connection to the server persist
954   until the process is completed. The entity returned with this
955   response &SHOULD; include an indication of the request's current status
956   and either a pointer to a status monitor or some estimate of when the
957   user can expect the request to be fulfilled.
958</t>
959</section>
960
961<section title="203 Non-Authoritative Information" anchor="status.203">
962  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
963  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
964<t>
965   The returned metainformation in the entity-header is not the
966   definitive set as available from the origin server, but is gathered
967   from a local or a third-party copy. The set presented &MAY; be a subset
968   or superset of the original version. For example, including local
969   annotation information about the resource might result in a superset
970   of the metainformation known by the origin server. Use of this
971   response code is not required and is only appropriate when the
972   response would otherwise be 200 (OK).
973</t>
974</section>
975
976<section title="204 No Content" anchor="status.204">
977  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
978  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
979<t>
980   The server has fulfilled the request but does not need to return an
981   entity-body, and might want to return updated metainformation. The
982   response &MAY; include new or updated metainformation in the form of
983   entity-headers, which if present &SHOULD; be associated with the
984   requested variant.
985</t>
986<t>
987   If the client is a user agent, it &SHOULD-NOT;  change its document view
988   from that which caused the request to be sent. This response is
989   primarily intended to allow input for actions to take place without
990   causing a change to the user agent's active document view, although
991   any new or updated metainformation &SHOULD; be applied to the document
992   currently in the user agent's active view.
993</t>
994<t>
995   The 204 response &MUST-NOT; include a message-body, and thus is always
996   terminated by the first empty line after the header fields.
997</t>
998</section>
999
1000<section title="205 Reset Content" anchor="status.205">
1001  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1002  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1003<t>
1004   The server has fulfilled the request and the user agent &SHOULD; reset
1005   the document view which caused the request to be sent. This response
1006   is primarily intended to allow input for actions to take place via
1007   user input, followed by a clearing of the form in which the input is
1008   given so that the user can easily initiate another input action. The
1009   response &MUST-NOT; include an entity.
1010</t>
1011</section>
1012
1013<section title="206 Partial Content" anchor="status.206">
1014  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1015  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1016<t>
1017   The server has fulfilled the partial GET request for the resource
1018   and the enclosed entity is a partial representation as defined in &range;.
1019</t>
1020</section>
1021</section>
1022
1023<section title="Redirection 3xx" anchor="status.3xx">
1024<t>
1025   This class of status code indicates that further action needs to be
1026   taken by the user agent in order to fulfill the request.  The action
1027   required &MAY; be carried out by the user agent without interaction
1028   with the user if and only if the method used in the second request is
1029   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1030   such loops generate network traffic for each redirection.
1031  <list><t>
1032      <x:h>Note:</x:h> previous versions of this specification recommended a
1033      maximum of five redirections. Content developers should be aware
1034      that there might be clients that implement such a fixed
1035      limitation.
1036  </t></list>
1037</t>
1038
1039<section title="300 Multiple Choices" anchor="status.300">
1040  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1041  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1042<t>
1043   The requested resource corresponds to any one of a set of
1044   representations, each with its own specific location, and agent-driven
1045   negotiation information (&content-negotiation;) is being provided so that
1046   the user (or user agent) can select a preferred representation and
1047   redirect its request to that location.
1048</t>
1049<t>
1050   Unless it was a HEAD request, the response &SHOULD; include an entity
1051   containing a list of resource characteristics and location(s) from
1052   which the user or user agent can choose the one most appropriate. The
1053   entity format is specified by the media type given in the Content-Type
1054   header field. Depending upon the format and the capabilities of
1055   the user agent, selection of the most appropriate choice &MAY; be
1056   performed automatically. However, this specification does not define
1057   any standard for such automatic selection.
1058</t>
1059<t>
1060   If the server has a preferred choice of representation, it &SHOULD;
1061   include the specific URI for that representation in the Location
1062   field; user agents &MAY; use the Location field value for automatic
1063   redirection. This response is cacheable unless indicated otherwise.
1064</t>
1065</section>
1066
1067<section title="301 Moved Permanently" anchor="status.301">
1068  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1069  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1070<t>
1071   The requested resource has been assigned a new permanent URI and any
1072   future references to this resource &SHOULD; use one of the returned
1073   URIs.  Clients with link editing capabilities ought to automatically
1074   re-link references to the Request-URI to one or more of the new
1075   references returned by the server, where possible. This response is
1076   cacheable unless indicated otherwise.
1077</t>
1078<t>
1079   The new permanent URI &SHOULD; be given by the Location field in the
1080   response. Unless the request method was HEAD, the entity of the
1081   response &SHOULD; contain a short hypertext note with a hyperlink to
1082   the new URI(s).
1083</t>
1084<t>
1085   If the 301 status code is received in response to a request other
1086   than GET or HEAD, the user agent &MUST-NOT; automatically redirect the
1087   request unless it can be confirmed by the user, since this might
1088   change the conditions under which the request was issued.
1089  <list><t>
1090      <x:h>Note:</x:h> When automatically redirecting a POST request after
1091      receiving a 301 status code, some existing HTTP/1.0 user agents
1092      will erroneously change it into a GET request.
1093  </t></list>
1094</t>
1095</section>
1096
1097<section title="302 Found" anchor="status.302">
1098  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1099  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1100<t>
1101   The requested resource resides temporarily under a different URI.
1102   Since the redirection might be altered on occasion, the client &SHOULD;
1103   continue to use the Request-URI for future requests.  This response
1104   is only cacheable if indicated by a Cache-Control or Expires header
1105   field.
1106</t>
1107<t>
1108   The temporary URI &SHOULD; be given by the Location field in the
1109   response. Unless the request method was HEAD, the entity of the
1110   response &SHOULD; contain a short hypertext note with a hyperlink to
1111   the new URI(s).
1112</t>
1113<t>
1114   If the 302 status code is received in response to a request other
1115   than GET or HEAD, the user agent &MUST-NOT; automatically redirect the
1116   request unless it can be confirmed by the user, since this might
1117   change the conditions under which the request was issued.
1118  <list><t>
1119      <x:h>Note:</x:h> RFC 1945 and RFC 2068 specify that the client is not allowed
1120      to change the method on the redirected request.  However, most
1121      existing user agent implementations treat 302 as if it were a 303
1122      response, performing a GET on the Location field-value regardless
1123      of the original request method. The status codes 303 and 307 have
1124      been added for servers that wish to make unambiguously clear which
1125      kind of reaction is expected of the client.
1126  </t></list>
1127</t>
1128</section>
1129
1130<section title="303 See Other" anchor="status.303">
1131  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1132  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1133<t>
1134   The response to the request can be found under a different URI and
1135   &SHOULD; be retrieved using a GET method on that resource. This method
1136   exists primarily to allow the output of a POST-activated script to
1137   redirect the user agent to a selected resource. The new URI is not a
1138   substitute reference for the originally requested resource. The 303
1139   response &MUST-NOT; be cached, but the response to the second
1140   (redirected) request might be cacheable.
1141</t>
1142<t>
1143   The different URI &SHOULD; be given by the Location field in the
1144   response. Unless the request method was HEAD, the entity of the
1145   response &SHOULD; contain a short hypertext note with a hyperlink to
1146   the new URI(s).
1147  <list><t>
1148      <x:h>Note:</x:h> Many pre-HTTP/1.1 user agents do not understand the 303
1149      status. When interoperability with such clients is a concern, the
1150      302 status code may be used instead, since most user agents react
1151      to a 302 response as described here for 303.
1152  </t></list>
1153</t>
1154</section>
1155
1156<section title="304 Not Modified" anchor="status.304">
1157  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1158  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1159<t>
1160   If the client has performed a conditional GET request and access is
1161   allowed, but the document has not been modified, the server &SHOULD;
1162   respond with this status code. The 304 response &MUST-NOT; contain a
1163   message-body, and thus is always terminated by the first empty line
1164   after the header fields.
1165</t>
1166<t>
1167   The response &MUST; include the following header fields:
1168  <list style="symbols">
1169    <t>Date, unless its omission is required by [clockless.origin.server.operation]</t>
1170  </list>
1171</t>
1172<t>
1173   If a clockless origin server obeys these rules, and proxies and
1174   clients add their own Date to any response received without one (as
1175   already specified by [RFC 2068], section <xref target="RFC2068" x:sec="14.19" x:fmt="number"/>), caches will operate
1176   correctly.
1177  <list style="symbols">
1178    <t>ETag and/or Content-Location, if the header would have been sent
1179        in a 200 response to the same request</t>
1180    <t>Expires, Cache-Control, and/or Vary, if the field-value might
1181        differ from that sent in any previous response for the same
1182        variant</t>
1183  </list>
1184</t>
1185<t>
1186   If the conditional GET used a strong cache validator (see &caching;),
1187   the response &SHOULD-NOT;  include other entity-headers.
1188   Otherwise (i.e., the conditional GET used a weak validator), the
1189   response &MUST-NOT; include other entity-headers; this prevents
1190   inconsistencies between cached entity-bodies and updated headers.
1191</t>
1192<t>
1193   If a 304 response indicates an entity not currently cached, then the
1194   cache &MUST; disregard the response and repeat the request without the
1195   conditional.
1196</t>
1197<t>
1198   If a cache uses a received 304 response to update a cache entry, the
1199   cache &MUST; update the entry to reflect any new field values given in
1200   the response.
1201</t>
1202</section>
1203
1204<section title="305 Use Proxy" anchor="status.305">
1205  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1206  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1207<t>
1208   The requested resource &MUST; be accessed through the proxy given by
1209   the Location field. The Location field gives the URI of the proxy.
1210   The recipient is expected to repeat this single request via the
1211   proxy. 305 responses &MUST; only be generated by origin servers.
1212  <list><t>
1213      <x:h>Note:</x:h> RFC 2068 was not clear that 305 was intended to redirect a
1214      single request, and to be generated by origin servers only.  Not
1215      observing these limitations has significant security consequences.
1216  </t></list>
1217</t>
1218</section>
1219
1220<section title="306 (Unused)" anchor="status.306">
1221  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1222  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1223<t>
1224   The 306 status code was used in a previous version of the
1225   specification, is no longer used, and the code is reserved.
1226</t>
1227</section>
1228
1229<section title="307 Temporary Redirect" anchor="status.307">
1230  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1231  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1232<t>
1233   The requested resource resides temporarily under a different URI.
1234   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1235   continue to use the Request-URI for future requests.  This response
1236   is only cacheable if indicated by a Cache-Control or Expires header
1237   field.
1238</t>
1239<t>
1240   The temporary URI &SHOULD; be given by the Location field in the
1241   response. Unless the request method was HEAD, the entity of the
1242   response &SHOULD; contain a short hypertext note with a hyperlink to
1243   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1244   understand the 307 status. Therefore, the note &SHOULD; contain the
1245   information necessary for a user to repeat the original request on
1246   the new URI.
1247</t>
1248<t>
1249   If the 307 status code is received in response to a request other
1250   than GET or HEAD, the user agent &MUST-NOT; automatically redirect the
1251   request unless it can be confirmed by the user, since this might
1252   change the conditions under which the request was issued.
1253</t>
1254</section>
1255</section>
1256
1257<section title="Client Error 4xx" anchor="status.4xx">
1258<t>
1259   The 4xx class of status code is intended for cases in which the
1260   client seems to have erred. Except when responding to a HEAD request,
1261   the server &SHOULD; include an entity containing an explanation of the
1262   error situation, and whether it is a temporary or permanent
1263   condition. These status codes are applicable to any request method.
1264   User agents &SHOULD; display any included entity to the user.
1265</t>
1266<t>
1267   If the client is sending data, a server implementation using TCP
1268   &SHOULD; be careful to ensure that the client acknowledges receipt of
1269   the packet(s) containing the response, before the server closes the
1270   input connection. If the client continues sending data to the server
1271   after the close, the server's TCP stack will send a reset packet to
1272   the client, which may erase the client's unacknowledged input buffers
1273   before they can be read and interpreted by the HTTP application.
1274</t>
1275
1276<section title="400 Bad Request" anchor="status.400">
1277  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1278  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1279<t>
1280   The request could not be understood by the server due to malformed
1281   syntax. The client &SHOULD-NOT;  repeat the request without
1282   modifications.
1283</t>
1284</section>
1285
1286<section title="401 Unauthorized" anchor="status.401">
1287  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1288  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1289<t>
1290   The request requires user authentication. The response &MUST; include a
1291   WWW-Authenticate header field (&header-www-authenticate;) containing a challenge
1292   applicable to the requested resource. The client &MAY; repeat the
1293   request with a suitable Authorization header field (&header-authorization;). If
1294   the request already included Authorization credentials, then the 401
1295   response indicates that authorization has been refused for those
1296   credentials. If the 401 response contains the same challenge as the
1297   prior response, and the user agent has already attempted
1298   authentication at least once, then the user &SHOULD; be presented the
1299   entity that was given in the response, since that entity might
1300   include relevant diagnostic information. HTTP access authentication
1301   is explained in "HTTP Authentication: Basic and Digest Access
1302   Authentication" <xref target="RFC2617"/>.
1303</t>
1304</section>
1305
1306<section title="402 Payment Required" anchor="status.402">
1307  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1308  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1309<t>
1310   This code is reserved for future use.
1311</t>
1312</section>
1313
1314<section title="403 Forbidden" anchor="status.403">
1315  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1316  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1317<t>
1318   The server understood the request, but is refusing to fulfill it.
1319   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1320   If the request method was not HEAD and the server wishes to make
1321   public why the request has not been fulfilled, it &SHOULD; describe the
1322   reason for the refusal in the entity.  If the server does not wish to
1323   make this information available to the client, the status code 404
1324   (Not Found) can be used instead.
1325</t>
1326</section>
1327
1328<section title="404 Not Found" anchor="status.404">
1329  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1330  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1331<t>
1332   The server has not found anything matching the Request-URI. No
1333   indication is given of whether the condition is temporary or
1334   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1335   knows, through some internally configurable mechanism, that an old
1336   resource is permanently unavailable and has no forwarding address.
1337   This status code is commonly used when the server does not wish to
1338   reveal exactly why the request has been refused, or when no other
1339   response is applicable.
1340</t>
1341</section>
1342
1343<section title="405 Method Not Allowed" anchor="status.405">
1344  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1345  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1346<t>
1347   The method specified in the Request-Line is not allowed for the
1348   resource identified by the Request-URI. The response &MUST; include an
1349   Allow header containing a list of valid methods for the requested
1350   resource.
1351</t>
1352</section>
1353
1354<section title="406 Not Acceptable" anchor="status.406">
1355  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1356  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1357<t>
1358   The resource identified by the request is only capable of generating
1359   response entities which have content characteristics not acceptable
1360   according to the accept headers sent in the request.
1361</t>
1362<t>
1363   Unless it was a HEAD request, the response &SHOULD; include an entity
1364   containing a list of available entity characteristics and location(s)
1365   from which the user or user agent can choose the one most
1366   appropriate. The entity format is specified by the media type given
1367   in the Content-Type header field. Depending upon the format and the
1368   capabilities of the user agent, selection of the most appropriate
1369   choice &MAY; be performed automatically. However, this specification
1370   does not define any standard for such automatic selection.
1371  <list><t>
1372      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1373      not acceptable according to the accept headers sent in the
1374      request. In some cases, this may even be preferable to sending a
1375      406 response. User agents are encouraged to inspect the headers of
1376      an incoming response to determine if it is acceptable.
1377  </t></list>
1378</t>
1379<t>
1380   If the response could be unacceptable, a user agent &SHOULD;
1381   temporarily stop receipt of more data and query the user for a
1382   decision on further actions.
1383</t>
1384</section>
1385
1386<section title="407 Proxy Authentication Required" anchor="status.407">
1387  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1388  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1389<t>
1390   This code is similar to 401 (Unauthorized), but indicates that the
1391   client must first authenticate itself with the proxy. The proxy &MUST;
1392   return a Proxy-Authenticate header field (&header-proxy-authenticate;) containing a
1393   challenge applicable to the proxy for the requested resource. The
1394   client &MAY; repeat the request with a suitable Proxy-Authorization
1395   header field (&header-proxy-authorization;). HTTP access authentication is explained
1396   in "HTTP Authentication: Basic and Digest Access Authentication"
1397   <xref target="RFC2617"/>.
1398</t>
1399</section>
1400
1401<section title="408 Request Timeout" anchor="status.408">
1402  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1403  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1404<t>
1405   The client did not produce a request within the time that the server
1406   was prepared to wait. The client &MAY; repeat the request without
1407   modifications at any later time.
1408</t>
1409</section>
1410
1411<section title="409 Conflict" anchor="status.409">
1412  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1413  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1414<t>
1415   The request could not be completed due to a conflict with the current
1416   state of the resource. This code is only allowed in situations where
1417   it is expected that the user might be able to resolve the conflict
1418   and resubmit the request. The response body &SHOULD; include enough
1419   information for the user to recognize the source of the conflict.
1420   Ideally, the response entity would include enough information for the
1421   user or user agent to fix the problem; however, that might not be
1422   possible and is not required.
1423</t>
1424<t>
1425   Conflicts are most likely to occur in response to a PUT request. For
1426   example, if versioning were being used and the entity being PUT
1427   included changes to a resource which conflict with those made by an
1428   earlier (third-party) request, the server might use the 409 response
1429   to indicate that it can't complete the request. In this case, the
1430   response entity would likely contain a list of the differences
1431   between the two versions in a format defined by the response
1432   Content-Type.
1433</t>
1434</section>
1435
1436<section title="410 Gone" anchor="status.410">
1437  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1438  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1439<t>
1440   The requested resource is no longer available at the server and no
1441   forwarding address is known. This condition is expected to be
1442   considered permanent. Clients with link editing capabilities &SHOULD;
1443   delete references to the Request-URI after user approval. If the
1444   server does not know, or has no facility to determine, whether or not
1445   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1446   used instead. This response is cacheable unless indicated otherwise.
1447</t>
1448<t>
1449   The 410 response is primarily intended to assist the task of web
1450   maintenance by notifying the recipient that the resource is
1451   intentionally unavailable and that the server owners desire that
1452   remote links to that resource be removed. Such an event is common for
1453   limited-time, promotional services and for resources belonging to
1454   individuals no longer working at the server's site. It is not
1455   necessary to mark all permanently unavailable resources as "gone" or
1456   to keep the mark for any length of time -- that is left to the
1457   discretion of the server owner.
1458</t>
1459</section>
1460
1461<section title="411 Length Required" anchor="status.411">
1462  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1463  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1464<t>
1465   The server refuses to accept the request without a defined Content-Length.
1466   The client &MAY; repeat the request if it adds a valid
1467   Content-Length header field containing the length of the message-body
1468   in the request message.
1469</t>
1470</section>
1471
1472<section title="412 Precondition Failed" anchor="status.412">
1473  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1474  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1475<t>
1476   The precondition given in one or more of the request-header fields
1477   evaluated to false when it was tested on the server. This response
1478   code allows the client to place preconditions on the current resource
1479   metainformation (header field data) and thus prevent the requested
1480   method from being applied to a resource other than the one intended.
1481</t>
1482</section>
1483
1484<section title="413 Request Entity Too Large" anchor="status.413">
1485  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1486  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1487<t>
1488   The server is refusing to process a request because the request
1489   entity is larger than the server is willing or able to process. The
1490   server &MAY; close the connection to prevent the client from continuing
1491   the request.
1492</t>
1493<t>
1494   If the condition is temporary, the server &SHOULD; include a Retry-After
1495   header field to indicate that it is temporary and after what
1496   time the client &MAY; try again.
1497</t>
1498</section>
1499
1500<section title="414 Request-URI Too Long" anchor="status.414">
1501  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1502  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1503<t>
1504   The server is refusing to service the request because the Request-URI
1505   is longer than the server is willing to interpret. This rare
1506   condition is only likely to occur when a client has improperly
1507   converted a POST request to a GET request with long query
1508   information, when the client has descended into a URI "black hole" of
1509   redirection (e.g., a redirected URI prefix that points to a suffix of
1510   itself), or when the server is under attack by a client attempting to
1511   exploit security holes present in some servers using fixed-length
1512   buffers for reading or manipulating the Request-URI.
1513</t>
1514</section>
1515
1516<section title="415 Unsupported Media Type" anchor="status.415">
1517  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1518  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1519<t>
1520   The server is refusing to service the request because the entity of
1521   the request is in a format not supported by the requested resource
1522   for the requested method.
1523</t>
1524</section>
1525
1526<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1527  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1528  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1529<t>
1530   The request included a Range request-header field (&header-range;) and none of
1531   the range-specifier values in this field overlap the current extent
1532   of the selected resource.
1533</t>
1534</section>
1535
1536<section title="417 Expectation Failed" anchor="status.417">
1537  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1538  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1539<t>
1540   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1541   could not be met by this server, or, if the server is a proxy,
1542   the server has unambiguous evidence that the request could not be met
1543   by the next-hop server.
1544</t>
1545</section>
1546</section>
1547
1548<section title="Server Error 5xx" anchor="status.5xx">
1549<t>
1550   Response status codes beginning with the digit "5" indicate cases in
1551   which the server is aware that it has erred or is incapable of
1552   performing the request. Except when responding to a HEAD request, the
1553   server &SHOULD; include an entity containing an explanation of the
1554   error situation, and whether it is a temporary or permanent
1555   condition. User agents &SHOULD; display any included entity to the
1556   user. These response codes are applicable to any request method.
1557</t>
1558
1559<section title="500 Internal Server Error" anchor="status.500">
1560  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1561  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1562<t>
1563   The server encountered an unexpected condition which prevented it
1564   from fulfilling the request.
1565</t>
1566</section>
1567
1568<section title="501 Not Implemented" anchor="status.501">
1569  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1570  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1571<t>
1572   The server does not support the functionality required to fulfill the
1573   request. This is the appropriate response when the server does not
1574   recognize the request method and is not capable of supporting it for
1575   any resource.
1576</t>
1577</section>
1578
1579<section title="502 Bad Gateway" anchor="status.502">
1580  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1581  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1582<t>
1583   The server, while acting as a gateway or proxy, received an invalid
1584   response from the upstream server it accessed in attempting to
1585   fulfill the request.
1586</t>
1587</section>
1588
1589<section title="503 Service Unavailable" anchor="status.503">
1590  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1591  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1592<t>
1593   The server is currently unable to handle the request due to a
1594   temporary overloading or maintenance of the server. The implication
1595   is that this is a temporary condition which will be alleviated after
1596   some delay. If known, the length of the delay &MAY; be indicated in a
1597   Retry-After header. If no Retry-After is given, the client &SHOULD;
1598   handle the response as it would for a 500 response.
1599  <list><t>
1600      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1601      server must use it when becoming overloaded. Some servers may wish
1602      to simply refuse the connection.
1603  </t></list>
1604</t>
1605</section>
1606
1607<section title="504 Gateway Timeout" anchor="status.504">
1608  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1609  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1610<t>
1611   The server, while acting as a gateway or proxy, did not receive a
1612   timely response from the upstream server specified by the URI (e.g.
1613   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1614   to access in attempting to complete the request.
1615  <list><t>
1616      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1617      return 400 or 500 when DNS lookups time out.
1618  </t></list>
1619</t>
1620</section>
1621
1622<section title="505 HTTP Version Not Supported" anchor="status.505">
1623  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1624  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1625<t>
1626   The server does not support, or refuses to support, the HTTP protocol
1627   version that was used in the request message. The server is
1628   indicating that it is unable or unwilling to complete the request
1629   using the same major version as the client, as described in &http-version;,
1630   other than with this error message. The response &SHOULD; contain
1631   an entity describing why that version is not supported and what other
1632   protocols are supported by that server.
1633</t>
1634
1635</section>
1636</section>
1637</section>
1638
1639
1640<section title="Header Field Definitions" anchor="header.fields">
1641<t>
1642   This section defines the syntax and semantics of all standard
1643   HTTP/1.1 header fields. For entity-header fields, both sender and
1644   recipient refer to either the client or the server, depending on who
1645   sends and who receives the entity.
1646</t>
1647
1648<section title="Allow" anchor="header.allow">
1649  <iref primary="true" item="Allow header" x:for-anchor=""/>
1650  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1651<t>
1652      The Allow entity-header field lists the set of methods supported
1653      by the resource identified by the Request-URI. The purpose of this
1654      field is strictly to inform the recipient of valid methods
1655      associated with the resource. An Allow header field &MUST; be
1656      present in a 405 (Method Not Allowed) response.
1657</t>
1658<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1659       Allow   = "Allow" ":" #Method
1660</artwork></figure>
1661<t>
1662      Example of use:
1663</t>
1664<figure><artwork type="example">
1665       Allow: GET, HEAD, PUT
1666</artwork></figure>
1667<t>
1668      This field cannot prevent a client from trying other methods.
1669      However, the indications given by the Allow header field value
1670      &SHOULD; be followed. The actual set of allowed methods is defined
1671      by the origin server at the time of each request.
1672</t>
1673<t>
1674      The Allow header field &MAY; be provided with a PUT request to
1675      recommend the methods to be supported by the new or modified
1676      resource. The server is not required to support these methods and
1677      &SHOULD; include an Allow header in the response giving the actual
1678      supported methods.
1679</t>
1680<t>
1681      A proxy &MUST-NOT; modify the Allow header field even if it does not
1682      understand all the methods specified, since the user agent might
1683      have other means of communicating with the origin server.
1684</t>
1685</section>
1686
1687<section title="Expect" anchor="header.expect">
1688  <iref primary="true" item="Expect header" x:for-anchor=""/>
1689  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1690<t>
1691   The Expect request-header field is used to indicate that particular
1692   server behaviors are required by the client.
1693</t>
1694<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1695   Expect       =  "Expect" ":" 1#expectation
1696
1697   expectation  =  "100-continue" | expectation-extension
1698   expectation-extension =  token [ "=" ( token | quoted-string )
1699                            *expect-params ]
1700   expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1701</artwork></figure>
1702<t>
1703   A server that does not understand or is unable to comply with any of
1704   the expectation values in the Expect field of a request &MUST; respond
1705   with appropriate error status. The server &MUST; respond with a 417
1706   (Expectation Failed) status if any of the expectations cannot be met
1707   or, if there are other problems with the request, some other 4xx
1708   status.
1709</t>
1710<t>
1711   This header field is defined with extensible syntax to allow for
1712   future extensions. If a server receives a request containing an
1713   Expect field that includes an expectation-extension that it does not
1714   support, it &MUST; respond with a 417 (Expectation Failed) status.
1715</t>
1716<t>
1717   Comparison of expectation values is case-insensitive for unquoted
1718   tokens (including the 100-continue token), and is case-sensitive for
1719   quoted-string expectation-extensions.
1720</t>
1721<t>
1722   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1723   return a 417 (Expectation Failed) status if it receives a request
1724   with an expectation that it cannot meet. However, the Expect
1725   request-header itself is end-to-end; it &MUST; be forwarded if the
1726   request is forwarded.
1727</t>
1728<t>
1729   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1730   Expect header.
1731</t>
1732<t>
1733   See &use100; for the use of the 100 (continue) status.
1734</t>
1735</section>
1736
1737<section title="From" anchor="header.from">
1738  <iref primary="true" item="From header" x:for-anchor=""/>
1739  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1740<t>
1741   The From request-header field, if given, &SHOULD; contain an Internet
1742   e-mail address for the human user who controls the requesting user
1743   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1744   in RFC 822 <xref target="RFC822"/> as updated by RFC 1123 <xref target="RFC1123"/>:
1745</t>
1746<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1747    From   = "From" ":" mailbox
1748</artwork></figure>
1749<t>
1750   An example is:
1751</t>
1752<figure><artwork type="example">
1753    From: webmaster@w3.org
1754</artwork></figure>
1755<t>
1756   This header field &MAY; be used for logging purposes and as a means for
1757   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1758   be used as an insecure form of access protection. The interpretation
1759   of this field is that the request is being performed on behalf of the
1760   person given, who accepts responsibility for the method performed. In
1761   particular, robot agents &SHOULD; include this header so that the
1762   person responsible for running the robot can be contacted if problems
1763   occur on the receiving end.
1764</t>
1765<t>
1766   The Internet e-mail address in this field &MAY; be separate from the
1767   Internet host which issued the request. For example, when a request
1768   is passed through a proxy the original issuer's address &SHOULD; be
1769   used.
1770</t>
1771<t>
1772   The client &SHOULD-NOT;  send the From header field without the user's
1773   approval, as it might conflict with the user's privacy interests or
1774   their site's security policy. It is strongly recommended that the
1775   user be able to disable, enable, and modify the value of this field
1776   at any time prior to a request.
1777</t>
1778</section>
1779
1780<section title="Location" anchor="header.location">
1781  <iref primary="true" item="Location header" x:for-anchor=""/>
1782  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1783<t>
1784   The Location response-header field is used to redirect the recipient
1785   to a location other than the Request-URI for completion of the
1786   request or identification of a new resource. For 201 (Created)
1787   responses, the Location is that of the new resource which was created
1788   by the request. For 3xx responses, the location &SHOULD; indicate the
1789   server's preferred URI for automatic redirection to the resource. The
1790   field value consists of a single absolute URI.
1791</t>
1792<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1793    Location       = "Location" ":" absoluteURI
1794</artwork></figure>
1795<t>
1796   An example is:
1797</t>
1798<figure><artwork type="example">
1799    Location: http://www.w3.org/pub/WWW/People.html
1800</artwork></figure>
1801<t>
1802  <list><t>
1803      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1804      from Location in that the Content-Location identifies the original
1805      location of the entity enclosed in the request. It is therefore
1806      possible for a response to contain header fields for both Location
1807      and Content-Location.
1808  </t></list>
1809</t>
1810</section>
1811
1812<section title="Max-Forwards" anchor="header.max-forwards">
1813  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1814  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1815<t>
1816   The Max-Forwards request-header field provides a mechanism with the
1817   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1818   number of proxies or gateways that can forward the request to the
1819   next inbound server. This can be useful when the client is attempting
1820   to trace a request chain which appears to be failing or looping in
1821   mid-chain.
1822</t>
1823<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1824    Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1825</artwork></figure>
1826<t>
1827   The Max-Forwards value is a decimal integer indicating the remaining
1828   number of times this request message may be forwarded.
1829</t>
1830<t>
1831   Each proxy or gateway recipient of a TRACE or OPTIONS request
1832   containing a Max-Forwards header field &MUST; check and update its
1833   value prior to forwarding the request. If the received value is zero
1834   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1835   respond as the final recipient. If the received Max-Forwards value is
1836   greater than zero, then the forwarded message &MUST; contain an updated
1837   Max-Forwards field with a value decremented by one (1).
1838</t>
1839<t>
1840   The Max-Forwards header field &MAY; be ignored for all other methods
1841   defined by this specification and for any extension methods for which
1842   it is not explicitly referred to as part of that method definition.
1843</t>
1844</section>
1845
1846<section title="Referer" anchor="header.referer">
1847  <iref primary="true" item="Referer header" x:for-anchor=""/>
1848  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
1849<t>
1850   The Referer[sic] request-header field allows the client to specify,
1851   for the server's benefit, the address (URI) of the resource from
1852   which the Request-URI was obtained (the "referrer", although the
1853   header field is misspelled.) The Referer request-header allows a
1854   server to generate lists of back-links to resources for interest,
1855   logging, optimized caching, etc. It also allows obsolete or mistyped
1856   links to be traced for maintenance. The Referer field &MUST-NOT; be
1857   sent if the Request-URI was obtained from a source that does not have
1858   its own URI, such as input from the user keyboard.
1859</t>
1860<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1861    Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1862</artwork></figure>
1863<t>
1864   Example:
1865</t>
1866<figure><artwork type="example">
1867    Referer: http://www.w3.org/hypertext/DataSources/Overview.html
1868</artwork></figure>
1869<t>
1870   If the field value is a relative URI, it &SHOULD; be interpreted
1871   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
1872   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
1873</t>
1874</section>
1875
1876<section title="Retry-After" anchor="header.retry-after">
1877  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
1878  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
1879<t>
1880   The Retry-After response-header field can be used with a 503 (Service
1881   Unavailable) response to indicate how long the service is expected to
1882   be unavailable to the requesting client. This field &MAY; also be used
1883   with any 3xx (Redirection) response to indicate the minimum time the
1884   user-agent is asked wait before issuing the redirected request. The
1885   value of this field can be either an HTTP-date or an integer number
1886   of seconds (in decimal) after the time of the response.
1887</t>
1888<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
1889    Retry-After  = "Retry-After" ":" ( HTTP-date | delta-seconds )
1890</artwork></figure>
1891<t>
1892   Two examples of its use are
1893</t>
1894<figure><artwork type="example">
1895    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1896    Retry-After: 120
1897</artwork></figure>
1898<t>
1899   In the latter example, the delay is 2 minutes.
1900</t>
1901</section>
1902
1903<section title="Server" anchor="header.server">
1904  <iref primary="true" item="Server header" x:for-anchor=""/>
1905  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
1906<t>
1907   The Server response-header field contains information about the
1908   software used by the origin server to handle the request. The field
1909   can contain multiple product tokens (<xref target="product.tokens"/>) and comments
1910   identifying the server and any significant subproducts. The product
1911   tokens are listed in order of their significance for identifying the
1912   application.
1913</t>
1914<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
1915    Server         = "Server" ":" 1*( product | comment )
1916</artwork></figure>
1917<t>
1918   Example:
1919</t>
1920<figure><artwork type="example">
1921    Server: CERN/3.0 libwww/2.17
1922</artwork></figure>
1923<t>
1924   If the response is being forwarded through a proxy, the proxy
1925   application &MUST-NOT; modify the Server response-header. Instead, it
1926   &SHOULD; include a Via field (as described in &header-via;).
1927  <list><t>
1928      <x:h>Note:</x:h> Revealing the specific software version of the server might
1929      allow the server machine to become more vulnerable to attacks
1930      against software that is known to contain security holes. Server
1931      implementors are encouraged to make this field a configurable
1932      option.
1933  </t></list>
1934</t>
1935</section>
1936
1937<section title="User-Agent" anchor="header.user-agent">
1938  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
1939  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
1940<t>
1941   The User-Agent request-header field contains information about the
1942   user agent originating the request. This is for statistical purposes,
1943   the tracing of protocol violations, and automated recognition of user
1944   agents for the sake of tailoring responses to avoid particular user
1945   agent limitations. User agents &SHOULD; include this field with
1946   requests. The field can contain multiple product tokens (<xref target="product.tokens"/>)
1947   and comments identifying the agent and any subproducts which form a
1948   significant part of the user agent. By convention, the product tokens
1949   are listed in order of their significance for identifying the
1950   application.
1951</t>
1952<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
1953    User-Agent     = "User-Agent" ":" 1*( product | comment )
1954</artwork></figure>
1955<t>
1956   Example:
1957</t>
1958<figure><artwork type="example">
1959    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
1960</artwork></figure>
1961</section>
1962
1963</section>
1964
1965<section title="IANA Considerations" anchor="IANA.considerations">
1966<t>
1967   TBD.
1968</t>
1969</section>
1970
1971<section title="Security Considerations" anchor="security.considerations">
1972<t>
1973   This section is meant to inform application developers, information
1974   providers, and users of the security limitations in HTTP/1.1 as
1975   described by this document. The discussion does not include
1976   definitive solutions to the problems revealed, though it does make
1977   some suggestions for reducing security risks.
1978</t>
1979
1980<section title="Transfer of Sensitive Information" anchor="security.sensitive">
1981<t>
1982   Like any generic data transfer protocol, HTTP cannot regulate the
1983   content of the data that is transferred, nor is there any a priori
1984   method of determining the sensitivity of any particular piece of
1985   information within the context of any given request. Therefore,
1986   applications &SHOULD; supply as much control over this information as
1987   possible to the provider of that information. Four header fields are
1988   worth special mention in this context: Server, Via, Referer and From.
1989</t>
1990<t>
1991   Revealing the specific software version of the server might allow the
1992   server machine to become more vulnerable to attacks against software
1993   that is known to contain security holes. Implementors &SHOULD; make the
1994   Server header field a configurable option.
1995</t>
1996<t>
1997   Proxies which serve as a portal through a network firewall &SHOULD;
1998   take special precautions regarding the transfer of header information
1999   that identifies the hosts behind the firewall. In particular, they
2000   &SHOULD; remove, or replace with sanitized versions, any Via fields
2001   generated behind the firewall.
2002</t>
2003<t>
2004   The Referer header allows reading patterns to be studied and reverse
2005   links drawn. Although it can be very useful, its power can be abused
2006   if user details are not separated from the information contained in
2007   the Referer. Even when the personal information has been removed, the
2008   Referer header might indicate a private document's URI whose
2009   publication would be inappropriate.
2010</t>
2011<t>
2012   The information sent in the From field might conflict with the user's
2013   privacy interests or their site's security policy, and hence it
2014   &SHOULD-NOT;  be transmitted without the user being able to disable,
2015   enable, and modify the contents of the field. The user &MUST; be able
2016   to set the contents of this field within a user preference or
2017   application defaults configuration.
2018</t>
2019<t>
2020   We suggest, though do not require, that a convenient toggle interface
2021   be provided for the user to enable or disable the sending of From and
2022   Referer information.
2023</t>
2024<t>
2025   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2026   fields can sometimes be used to determine that a specific client or
2027   server have a particular security hole which might be exploited.
2028   Unfortunately, this same information is often used for other valuable
2029   purposes for which HTTP currently has no better mechanism.
2030</t>
2031</section>
2032
2033<section title="Encoding Sensitive Information in URI's" anchor="encoding.sensitive.information.in.uris">
2034<t>
2035   Because the source of a link might be private information or might
2036   reveal an otherwise private information source, it is strongly
2037   recommended that the user be able to select whether or not the
2038   Referer field is sent. For example, a browser client could have a
2039   toggle switch for browsing openly/anonymously, which would
2040   respectively enable/disable the sending of Referer and From
2041   information.
2042</t>
2043<t>
2044   Clients &SHOULD-NOT;  include a Referer header field in a (non-secure)
2045   HTTP request if the referring page was transferred with a secure
2046   protocol.
2047</t>
2048<t>
2049   Authors of services which use the HTTP protocol &SHOULD-NOT;  use GET
2050   based forms for the submission of sensitive data, because this will
2051   cause this data to be encoded in the Request-URI. Many existing
2052   servers, proxies, and user agents will log the request URI in some
2053   place where it might be visible to third parties. Servers can use
2054   POST-based form submission instead
2055</t>
2056</section>
2057
2058<section title="Location Headers and Spoofing" anchor="location.spoofing">
2059<t>
2060   If a single server supports multiple organizations that do not trust
2061   one another, then it &MUST; check the values of Location and Content-Location
2062   headers in responses that are generated under control of
2063   said organizations to make sure that they do not attempt to
2064   invalidate resources over which they have no authority.
2065</t>
2066</section>
2067
2068</section>
2069
2070<section title="Acknowledgments" anchor="ack">
2071<t>
2072   Based on an XML translation of RFC 2616 by Julian Reschke.
2073</t>
2074</section>
2075</middle>
2076<back>
2077<references>
2078
2079<reference anchor="Part1">
2080  <front>
2081    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2082 
2083    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2084      <organization abbrev="Day Software">Day Software</organization>
2085      <address>
2086        <email>fielding@gbiv.com</email>
2087      </address>
2088    </author>
2089 
2090    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2091      <organization>One Laptop per Child</organization>
2092      <address>
2093        <email>jg@laptop.org</email>
2094      </address>
2095    </author>
2096   
2097    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2098      <organization abbrev="HP">Hewlett-Packard Company</organization>
2099      <address>
2100        <email>JeffMogul@acm.org</email>
2101      </address>
2102    </author>
2103 
2104    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2105      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2106      <address>
2107        <email>henrikn@microsoft.com</email>
2108      </address>
2109    </author>
2110 
2111    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2112      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2113      <address>
2114        <email>LMM@acm.org</email>
2115      </address>
2116    </author>
2117   
2118    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2119      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2120      <address>
2121        <email>paulle@microsoft.com</email>
2122      </address>
2123    </author>
2124     
2125    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2126      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2127      <address>
2128        <email>timbl@w3.org</email>
2129      </address>
2130    </author>
2131 
2132    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2133  </front>
2134  <seriesInfo name="Internet-Draft" value="draft-fielding-p1-messaging-&ID-VERSION;"/>
2135  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2136</reference>
2137
2138<reference anchor="Part3">
2139  <front>
2140    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2141 
2142    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2143      <organization abbrev="Day Software">Day Software</organization>
2144      <address>
2145        <email>fielding@gbiv.com</email>
2146      </address>
2147    </author>
2148 
2149    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2150      <organization>One Laptop per Child</organization>
2151      <address>
2152        <email>jg@laptop.org</email>
2153      </address>
2154    </author>
2155   
2156    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2157      <organization abbrev="HP">Hewlett-Packard Company</organization>
2158      <address>
2159        <email>JeffMogul@acm.org</email>
2160      </address>
2161    </author>
2162 
2163    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2164      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2165      <address>
2166        <email>henrikn@microsoft.com</email>
2167      </address>
2168    </author>
2169 
2170    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2171      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2172      <address>
2173        <email>LMM@acm.org</email>
2174      </address>
2175    </author>
2176   
2177    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2178      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2179      <address>
2180        <email>paulle@microsoft.com</email>
2181      </address>
2182    </author>
2183     
2184    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2185      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2186      <address>
2187        <email>timbl@w3.org</email>
2188      </address>
2189    </author>
2190 
2191    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2192  </front>
2193  <seriesInfo name="Internet-Draft" value="draft-fielding-p3-payload-&ID-VERSION;"/>
2194  <x:source href="p3-payload.xml" basename="p3-payload"/>
2195</reference>
2196
2197<reference anchor="Part4">
2198  <front>
2199    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2200 
2201    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2202      <organization abbrev="Day Software">Day Software</organization>
2203      <address>
2204        <email>fielding@gbiv.com</email>
2205      </address>
2206    </author>
2207 
2208    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2209      <organization>One Laptop per Child</organization>
2210      <address>
2211        <email>jg@laptop.org</email>
2212      </address>
2213    </author>
2214   
2215    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2216      <organization abbrev="HP">Hewlett-Packard Company</organization>
2217      <address>
2218        <email>JeffMogul@acm.org</email>
2219      </address>
2220    </author>
2221 
2222    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2223      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2224      <address>
2225        <email>henrikn@microsoft.com</email>
2226      </address>
2227    </author>
2228 
2229    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2230      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2231      <address>
2232        <email>LMM@acm.org</email>
2233      </address>
2234    </author>
2235   
2236    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2237      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2238      <address>
2239        <email>paulle@microsoft.com</email>
2240      </address>
2241    </author>
2242     
2243    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2244      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2245      <address>
2246        <email>timbl@w3.org</email>
2247      </address>
2248    </author>
2249 
2250    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2251  </front>
2252  <seriesInfo name="Internet-Draft" value="draft-fielding-p4-conditional-&ID-VERSION;"/>
2253  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2254</reference>
2255
2256<reference anchor="Part5">
2257  <front>
2258    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2259 
2260    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2261      <organization abbrev="Day Software">Day Software</organization>
2262      <address>
2263        <email>fielding@gbiv.com</email>
2264      </address>
2265    </author>
2266 
2267    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2268      <organization>One Laptop per Child</organization>
2269      <address>
2270        <email>jg@laptop.org</email>
2271      </address>
2272    </author>
2273   
2274    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2275      <organization abbrev="HP">Hewlett-Packard Company</organization>
2276      <address>
2277        <email>JeffMogul@acm.org</email>
2278      </address>
2279    </author>
2280 
2281    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2282      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2283      <address>
2284        <email>henrikn@microsoft.com</email>
2285      </address>
2286    </author>
2287 
2288    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2289      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2290      <address>
2291        <email>LMM@acm.org</email>
2292      </address>
2293    </author>
2294   
2295    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2296      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2297      <address>
2298        <email>paulle@microsoft.com</email>
2299      </address>
2300    </author>
2301     
2302    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2303      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2304      <address>
2305        <email>timbl@w3.org</email>
2306      </address>
2307    </author>
2308 
2309    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2310  </front>
2311  <seriesInfo name="Internet-Draft" value="draft-fielding-p5-range-&ID-VERSION;"/>
2312  <x:source href="p5-range.xml" basename="p5-range"/>
2313</reference>
2314
2315<reference anchor="Part6">
2316  <front>
2317    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2318 
2319    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2320      <organization abbrev="Day Software">Day Software</organization>
2321      <address>
2322        <email>fielding@gbiv.com</email>
2323      </address>
2324    </author>
2325 
2326    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2327      <organization>One Laptop per Child</organization>
2328      <address>
2329        <email>jg@laptop.org</email>
2330      </address>
2331    </author>
2332   
2333    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2334      <organization abbrev="HP">Hewlett-Packard Company</organization>
2335      <address>
2336        <email>JeffMogul@acm.org</email>
2337      </address>
2338    </author>
2339 
2340    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2341      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2342      <address>
2343        <email>henrikn@microsoft.com</email>
2344      </address>
2345    </author>
2346 
2347    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2348      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2349      <address>
2350        <email>LMM@acm.org</email>
2351      </address>
2352    </author>
2353   
2354    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2355      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2356      <address>
2357        <email>paulle@microsoft.com</email>
2358      </address>
2359    </author>
2360     
2361    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2362      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2363      <address>
2364        <email>timbl@w3.org</email>
2365      </address>
2366    </author>
2367 
2368    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2369  </front>
2370  <seriesInfo name="Internet-Draft" value="draft-fielding-p6-cache-&ID-VERSION;"/>
2371  <x:source href="p6-cache.xml" basename="p6-cache"/>
2372</reference>
2373
2374<reference anchor="Part7">
2375  <front>
2376    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2377 
2378    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2379      <organization abbrev="Day Software">Day Software</organization>
2380      <address>
2381        <email>fielding@gbiv.com</email>
2382      </address>
2383    </author>
2384 
2385    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2386      <organization>One Laptop per Child</organization>
2387      <address>
2388        <email>jg@laptop.org</email>
2389      </address>
2390    </author>
2391   
2392    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2393      <organization abbrev="HP">Hewlett-Packard Company</organization>
2394      <address>
2395        <email>JeffMogul@acm.org</email>
2396      </address>
2397    </author>
2398 
2399    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2400      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2401      <address>
2402        <email>henrikn@microsoft.com</email>
2403      </address>
2404    </author>
2405 
2406    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2407      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2408      <address>
2409        <email>LMM@acm.org</email>
2410      </address>
2411    </author>
2412   
2413    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2414      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2415      <address>
2416        <email>paulle@microsoft.com</email>
2417      </address>
2418    </author>
2419     
2420    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2421      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2422      <address>
2423        <email>timbl@w3.org</email>
2424      </address>
2425    </author>
2426 
2427    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2428  </front>
2429  <seriesInfo name="Internet-Draft" value="draft-fielding-p7-auth-&ID-VERSION;"/>
2430  <x:source href="p7-auth.xml" basename="p7-auth"/>
2431</reference>
2432
2433<reference anchor="RFC1123">
2434<front>
2435<title>Requirements for Internet Hosts - Application and Support</title>
2436<author initials="R." surname="Braden" fullname="Robert Braden">
2437<organization>University of Southern California (USC), Information Sciences Institute</organization>
2438<address>
2439<postal>
2440<street>4676 Admiralty Way</street>
2441<city>Marina del Rey</city>
2442<region>CA</region>
2443<code>90292-6695</code>
2444<country>US</country></postal>
2445<phone>+1 213 822 1511</phone>
2446<email>Braden@ISI.EDU</email></address></author>
2447<date month="October" year="1989"/></front>
2448<seriesInfo name="STD" value="3"/>
2449<seriesInfo name="RFC" value="1123"/>
2450</reference>
2451
2452<reference anchor="RFC822">
2453<front>
2454<title abbrev="Standard for ARPA Internet Text Messages">Standard for the format of ARPA Internet text messages</title>
2455<author initials="D.H." surname="Crocker" fullname="David H. Crocker">
2456<organization>University of Delaware, Dept. of Electrical Engineering</organization>
2457<address>
2458<postal>
2459<street/>
2460<city>Newark</city>
2461<region>DE</region>
2462<code>19711</code>
2463<country>US</country></postal>
2464<email>DCrocker@UDel-Relay</email></address></author>
2465<date month="August" day="13" year="1982"/></front>
2466<seriesInfo name="STD" value="11"/>
2467<seriesInfo name="RFC" value="822"/>
2468</reference>
2469
2470<reference anchor="RFC2068">
2471<front>
2472<title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2473<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2474<organization>University of California, Irvine, Department of Information and Computer Science</organization>
2475<address>
2476<postal>
2477<street/>
2478<city>Irvine</city>
2479<region>CA</region>
2480<code>92717-3425</code>
2481<country>US</country></postal>
2482<facsimile>+1 714 824 4056</facsimile>
2483<email>fielding@ics.uci.edu</email></address></author>
2484<author initials="J." surname="Gettys" fullname="Jim Gettys">
2485<organization>MIT Laboratory for Computer Science</organization>
2486<address>
2487<postal>
2488<street>545 Technology Square</street>
2489<city>Cambridge</city>
2490<region>MA</region>
2491<code>02139</code>
2492<country>US</country></postal>
2493<facsimile>+1 617 258 8682</facsimile>
2494<email>jg@w3.org</email></address></author>
2495<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2496<organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2497<address>
2498<postal>
2499<street>250 University Avenue</street>
2500<city>Palo Alto</city>
2501<region>CA</region>
2502<code>94301</code>
2503<country>US</country></postal>
2504<email>mogul@wrl.dec.com</email></address></author>
2505<author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2506<organization>MIT Laboratory for Computer Science</organization>
2507<address>
2508<postal>
2509<street>545 Technology Square</street>
2510<city>Cambridge</city>
2511<region>MA</region>
2512<code>02139</code>
2513<country>US</country></postal>
2514<facsimile>+1 617 258 8682</facsimile>
2515<email>frystyk@w3.org</email></address></author>
2516<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2517<organization>MIT Laboratory for Computer Science</organization>
2518<address>
2519<postal>
2520<street>545 Technology Square</street>
2521<city>Cambridge</city>
2522<region>MA</region>
2523<code>02139</code>
2524<country>US</country></postal>
2525<facsimile>+1 617 258 8682</facsimile>
2526<email>timbl@w3.org</email></address></author>
2527<date month="January" year="1997"/>
2528<abstract>
2529<t>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, object-oriented protocol which can be used for many tasks, such as name servers and distributed object management systems, through extension of its request methods. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred.</t>
2530<t>HTTP has been in use by the World-Wide Web global information initiative since 1990. This specification defines the protocol referred to as "HTTP/1.1".</t></abstract></front>
2531<seriesInfo name="RFC" value="2068"/>
2532</reference>
2533
2534<reference anchor="RFC2617">
2535<front>
2536<title abbrev="HTTP Authentication">HTTP Authentication: Basic and Digest Access Authentication</title>
2537<author initials="J." surname="Franks" fullname="John Franks">
2538<organization>Northwestern University, Department of Mathematics</organization>
2539<address>
2540<postal>
2541<street/>
2542<city>Evanston</city>
2543<region>IL</region>
2544<code>60208-2730</code>
2545<country>US</country></postal>
2546<email>john@math.nwu.edu</email></address></author>
2547<author initials="P.M." surname="Hallam-Baker" fullname="Phillip M. Hallam-Baker">
2548<organization>Verisign Inc.</organization>
2549<address>
2550<postal>
2551<street>301 Edgewater Place</street>
2552<street>Suite 210</street>
2553<city>Wakefield</city>
2554<region>MA</region>
2555<code>01880</code>
2556<country>US</country></postal>
2557<email>pbaker@verisign.com</email></address></author>
2558<author initials="J.L." surname="Hostetler" fullname="Jeffery L. Hostetler">
2559<organization>AbiSource, Inc.</organization>
2560<address>
2561<postal>
2562<street>6 Dunlap Court</street>
2563<city>Savoy</city>
2564<region>IL</region>
2565<code>61874</code>
2566<country>US</country></postal>
2567<email>jeff@AbiSource.com</email></address></author>
2568<author initials="S.D." surname="Lawrence" fullname="Scott D. Lawrence">
2569<organization>Agranat Systems, Inc.</organization>
2570<address>
2571<postal>
2572<street>5 Clocktower Place</street>
2573<street>Suite 400</street>
2574<city>Maynard</city>
2575<region>MA</region>
2576<code>01754</code>
2577<country>US</country></postal>
2578<email>lawrence@agranat.com</email></address></author>
2579<author initials="P.J." surname="Leach" fullname="Paul J. Leach">
2580<organization>Microsoft Corporation</organization>
2581<address>
2582<postal>
2583<street>1 Microsoft Way</street>
2584<city>Redmond</city>
2585<region>WA</region>
2586<code>98052</code>
2587<country>US</country></postal>
2588<email>paulle@microsoft.com</email></address></author>
2589<author initials="A." surname="Luotonen" fullname="Ari Luotonen">
2590<organization>Netscape Communications Corporation</organization>
2591<address>
2592<postal>
2593<street>501 East Middlefield Road</street>
2594<city>Mountain View</city>
2595<region>CA</region>
2596<code>94043</code>
2597<country>US</country></postal></address></author>
2598<author initials="L." surname="Stewart" fullname="Lawrence C. Stewart">
2599<organization>Open Market, Inc.</organization>
2600<address>
2601<postal>
2602<street>215 First Street</street>
2603<city>Cambridge</city>
2604<region>MA</region>
2605<code>02142</code>
2606<country>US</country></postal>
2607<email>stewart@OpenMarket.com</email></address></author>
2608<date month="June" year="1999"/>
2609</front>
2610<seriesInfo name="RFC" value="2617"/>
2611</reference>
2612
2613<reference anchor="Luo1998">
2614<front>
2615<title>Tunneling TCP based protocols through Web proxy servers</title>
2616<author initials="A." surname="Luotonen" fullname="A. Luotonen">
2617  <organization/>
2618</author>
2619<date/>
2620</front>
2621<seriesInfo name="" value="Work in Progress"/>
2622</reference>
2623
2624</references>
2625
2626<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2627<t>
2628   Clarified which error code should be used for inbound server failures
2629   (e.g. DNS failures). (<xref target="status.504"/>).
2630</t>
2631<t>
2632   CREATE had a race that required an Etag be sent when a resource is
2633   first created. (<xref target="status.201"/>).
2634</t>
2635<t>
2636   Rewrite of message transmission requirements to make it much harder
2637   for implementors to get it wrong, as the consequences of errors here
2638   can have significant impact on the Internet, and to deal with the
2639   following problems:
2640  <list style="numbers">
2641      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2642         this was incorrectly placing a requirement on the behavior of
2643         an implementation of a future version of HTTP/1.x</t>
2644
2645      <t>Made it clear that user-agents should retry requests, not
2646         "clients" in general.</t>
2647
2648      <t>Converted requirements for clients to ignore unexpected 100
2649         (Continue) responses, and for proxies to forward 100 responses,
2650         into a general requirement for 1xx responses.</t>
2651
2652      <t>Modified some TCP-specific language, to make it clearer that
2653         non-TCP transports are possible for HTTP.</t>
2654
2655      <t>Require that the origin server &MUST-NOT; wait for the request
2656         body before it sends a required 100 (Continue) response.</t>
2657
2658      <t>Allow, rather than require, a server to omit 100 (Continue) if
2659         it has already seen some of the request body.</t>
2660
2661      <t>Allow servers to defend against denial-of-service attacks and
2662         broken clients.</t>
2663  </list>
2664</t>
2665<t>
2666   This change adds the Expect header and 417 status code.
2667</t>
2668<t>
2669   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
2670   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
2671</t>
2672<t>
2673   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
2674   implemented in previous versions of this specification. See RFC 2068
2675   <xref target="RFC2068"/>.
2676</t>
2677</section>
2678</back>
2679</rfc>
Note: See TracBrowser for help on using the repository browser.