source: draft-ietf-httpbis/13/draft-ietf-httpbis-p3-payload-13.xml @ 1629

Last change on this file since 1629 was 1500, checked in by julian.reschke@…, 9 years ago

fix mime types

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
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1<?xml version="1.0" encoding="UTF-8"?>
2<!--
3    This XML document is the output of clean-for-DTD.xslt; a tool that strips
4    extensions to RFC2629(bis) from documents for processing with xml2rfc.
5-->
6<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
7<?rfc toc="yes" ?>
8<?rfc symrefs="yes" ?>
9<?rfc sortrefs="yes" ?>
10<?rfc compact="yes"?>
11<?rfc subcompact="no" ?>
12<?rfc linkmailto="no" ?>
13<?rfc editing="no" ?>
14<?rfc comments="yes"?>
15<?rfc inline="yes"?>
16<?rfc rfcedstyle="yes"?>
17<!DOCTYPE rfc
18  PUBLIC "" "rfc2629.dtd">
19<rfc obsoletes="2616" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-13">
20<front>
21
22  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
23
24  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
25    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
26    <address>
27      <postal>
28        <street>345 Park Ave</street>
29        <city>San Jose</city>
30        <region>CA</region>
31        <code>95110</code>
32        <country>USA</country>
33      </postal>
34      <email>fielding@gbiv.com</email>
35      <uri>http://roy.gbiv.com/</uri>
36    </address>
37  </author>
38
39  <author initials="J." surname="Gettys" fullname="Jim Gettys">
40    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
41    <address>
42      <postal>
43        <street>21 Oak Knoll Road</street>
44        <city>Carlisle</city>
45        <region>MA</region>
46        <code>01741</code>
47        <country>USA</country>
48      </postal>
49      <email>jg@freedesktop.org</email>
50      <uri>http://gettys.wordpress.com/</uri>
51    </address>
52  </author>
53 
54  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
55    <organization abbrev="HP">Hewlett-Packard Company</organization>
56    <address>
57      <postal>
58        <street>HP Labs, Large Scale Systems Group</street>
59        <street>1501 Page Mill Road, MS 1177</street>
60        <city>Palo Alto</city>
61        <region>CA</region>
62        <code>94304</code>
63        <country>USA</country>
64      </postal>
65      <email>JeffMogul@acm.org</email>
66    </address>
67  </author>
68
69  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
70    <organization abbrev="Microsoft">Microsoft Corporation</organization>
71    <address>
72      <postal>
73        <street>1 Microsoft Way</street>
74        <city>Redmond</city>
75        <region>WA</region>
76        <code>98052</code>
77        <country>USA</country>
78      </postal>
79      <email>henrikn@microsoft.com</email>
80    </address>
81  </author>
82
83  <author initials="L." surname="Masinter" fullname="Larry Masinter">
84    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
85    <address>
86      <postal>
87        <street>345 Park Ave</street>
88        <city>San Jose</city>
89        <region>CA</region>
90        <code>95110</code>
91        <country>USA</country>
92      </postal>
93      <email>LMM@acm.org</email>
94      <uri>http://larry.masinter.net/</uri>
95    </address>
96  </author>
97 
98  <author initials="P." surname="Leach" fullname="Paul J. Leach">
99    <organization abbrev="Microsoft">Microsoft Corporation</organization>
100    <address>
101      <postal>
102        <street>1 Microsoft Way</street>
103        <city>Redmond</city>
104        <region>WA</region>
105        <code>98052</code>
106      </postal>
107      <email>paulle@microsoft.com</email>
108    </address>
109  </author>
110   
111  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
112    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
113    <address>
114      <postal>
115        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
116        <street>The Stata Center, Building 32</street>
117        <street>32 Vassar Street</street>
118        <city>Cambridge</city>
119        <region>MA</region>
120        <code>02139</code>
121        <country>USA</country>
122      </postal>
123      <email>timbl@w3.org</email>
124      <uri>http://www.w3.org/People/Berners-Lee/</uri>
125    </address>
126  </author>
127
128  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
129    <organization abbrev="W3C">World Wide Web Consortium</organization>
130    <address>
131      <postal>
132        <street>W3C / ERCIM</street>
133        <street>2004, rte des Lucioles</street>
134        <city>Sophia-Antipolis</city>
135        <region>AM</region>
136        <code>06902</code>
137        <country>France</country>
138      </postal>
139      <email>ylafon@w3.org</email>
140      <uri>http://www.raubacapeu.net/people/yves/</uri>
141    </address>
142  </author>
143
144  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
145    <organization abbrev="greenbytes">greenbytes GmbH</organization>
146    <address>
147      <postal>
148        <street>Hafenweg 16</street>
149        <city>Muenster</city><region>NW</region><code>48155</code>
150        <country>Germany</country>
151      </postal>
152      <phone>+49 251 2807760</phone>
153      <facsimile>+49 251 2807761</facsimile>
154      <email>julian.reschke@greenbytes.de</email>
155      <uri>http://greenbytes.de/tech/webdav/</uri>
156    </address>
157  </author>
158
159  <date month="March" year="2011" day="14"/>
160  <workgroup>HTTPbis Working Group</workgroup>
161
162<abstract>
163<t>
164   The Hypertext Transfer Protocol (HTTP) is an application-level
165   protocol for distributed, collaborative, hypermedia information
166   systems. HTTP has been in use by the World Wide Web global information
167   initiative since 1990. This document is Part 3 of the seven-part specification
168   that defines the protocol referred to as "HTTP/1.1" and, taken together,
169   obsoletes RFC 2616.  Part 3 defines HTTP message content,
170   metadata, and content negotiation.
171</t>
172</abstract>
173
174<note title="Editorial Note (To be removed by RFC Editor)">
175  <t>
176    Discussion of this draft should take place on the HTTPBIS working group
177    mailing list (ietf-http-wg@w3.org). The current issues list is
178    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
179    and related documents (including fancy diffs) can be found at
180    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
181  </t>
182  <t>
183    The changes in this draft are summarized in <xref target="changes.since.12"/>.
184  </t>
185</note>
186</front>
187<middle>
188<section title="Introduction" anchor="introduction">
189<t>
190   This document defines HTTP/1.1 message payloads (a.k.a., content), the
191   associated metadata header fields that define how the payload is intended
192   to be interpreted by a recipient, the request header fields that
193   might influence content selection, and the various selection algorithms
194   that are collectively referred to as HTTP content negotiation.
195</t>
196<t>
197   This document is currently disorganized in order to minimize the changes
198   between drafts and enable reviewers to see the smaller errata changes.
199   A future draft will reorganize the sections to better reflect the content.
200   In particular, the sections on entities will be renamed payload and moved
201   to the first half of the document, while the sections on content negotiation
202   and associated request header fields will be moved to the second half.  The
203   current mess reflects how widely dispersed these topics and associated
204   requirements had become in <xref target="RFC2616"/>.
205</t>
206
207<section title="Terminology" anchor="terminology">
208<t>
209   This specification uses a number of terms to refer to the roles
210   played by participants in, and objects of, the HTTP communication.
211</t>
212<t>
213  <iref item="content negotiation"/>
214  <?rfc needLines="4"?>content negotiation
215  <list>
216    <t>
217      The mechanism for selecting the appropriate representation when
218      servicing a request. The representation in any response
219      can be negotiated (including error responses).
220    </t>
221  </list>
222</t>
223</section>
224
225<section title="Requirements" anchor="intro.requirements">
226<t>
227   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
228   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
229   document are to be interpreted as described in <xref target="RFC2119"/>.
230</t>
231<t>
232   An implementation is not compliant if it fails to satisfy one or more
233   of the "MUST" or "REQUIRED" level requirements for the protocols it
234   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
235   level and all the "SHOULD" level requirements for its protocols is said
236   to be "unconditionally compliant"; one that satisfies all the "MUST"
237   level requirements but not all the "SHOULD" level requirements for its
238   protocols is said to be "conditionally compliant".
239</t>
240</section>
241
242<section title="Syntax Notation" anchor="notation">
243 
244 
245 
246 
247 
248 
249 
250<t>
251  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
252  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
253  <xref target="collected.abnf"/> shows the collected ABNF, with the list
254  rule expanded.
255</t>
256<t>
257  The following core rules are included by
258  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
259  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
260  DIGIT (decimal 0-9), DQUOTE (double quote),
261  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
262  OCTET (any 8-bit sequence of data), SP (space),
263  VCHAR (any visible USASCII character),
264  and WSP (whitespace).
265</t>
266
267<section title="Core Rules" anchor="core.rules">
268 
269 
270 
271<t>
272  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
273</t>
274<figure><artwork type="abnf2616"><![CDATA[
275  token          = <token, defined in [Part1], Section 1.2.2>
276  word           = <word, defined in [Part1], Section 1.2.2>
277  OWS            = <OWS, defined in [Part1], Section 1.2.2>
278]]></artwork></figure>
279</section>
280
281<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
282 
283 
284 
285<t>
286  The ABNF rules below are defined in other parts:
287</t>
288<figure><artwork type="abnf2616"><![CDATA[
289  absolute-URI   = <absolute-URI, defined in [Part1], Section 2.6>
290  partial-URI    = <partial-URI, defined in [Part1], Section 2.6>
291  qvalue         = <qvalue, defined in [Part1], Section 6.4>
292]]></artwork></figure>
293</section>
294
295</section>
296
297</section>
298
299<section title="Protocol Parameters" anchor="protocol.parameters">
300
301<section title="Character Encodings (charset)" anchor="character.sets">
302<t>
303   HTTP uses charset names to indicate the character encoding of a
304   textual representation.
305</t>
306<t anchor="rule.charset">
307 
308   A character encoding is identified by a case-insensitive token. The
309   complete set of tokens is defined by the IANA Character Set registry
310   (<eref target="http://www.iana.org/assignments/character-sets"/>).
311</t>
312<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
313  charset = token
314]]></artwork></figure>
315<t>
316   Although HTTP allows an arbitrary token to be used as a charset
317   value, any token that has a predefined value within the IANA
318   Character Set registry MUST represent the character encoding defined
319   by that registry. Applications SHOULD limit their use of character
320   encodings to those defined within the IANA registry.
321</t>
322<t>
323   HTTP uses charset in two contexts: within an Accept-Charset request
324   header field (in which the charset value is an unquoted token) and as the
325   value of a parameter in a Content-Type header field (within a request or
326   response), in which case the parameter value of the charset parameter
327   can be quoted.
328</t>
329<t>
330   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
331   <xref target="RFC2277"/>.
332</t>
333
334<section title="Missing Charset" anchor="missing.charset">
335<t>
336   Some HTTP/1.0 software has interpreted a Content-Type header field without
337   charset parameter incorrectly to mean "recipient should guess".
338   Senders wishing to defeat this behavior MAY include a charset
339   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and SHOULD do so when
340   it is known that it will not confuse the recipient.
341</t>
342<t>
343   Unfortunately, some older HTTP/1.0 clients did not deal properly with
344   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
345   charset label provided by the sender; and those user agents that have
346   a provision to "guess" a charset MUST use the charset from the
347   content-type field if they support that charset, rather than the
348   recipient's preference, when initially displaying a document. See
349   <xref target="canonicalization.and.text.defaults"/>.
350</t>
351</section>
352</section>
353
354<section title="Content Codings" anchor="content.codings">
355 
356<t>
357   Content coding values indicate an encoding transformation that has
358   been or can be applied to a representation. Content codings are primarily
359   used to allow a representation to be compressed or otherwise usefully
360   transformed without losing the identity of its underlying media type
361   and without loss of information. Frequently, the representation is stored in
362   coded form, transmitted directly, and only decoded by the recipient.
363</t>
364<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
365  content-coding   = token
366]]></artwork></figure>
367<t>
368   All content-coding values are case-insensitive. HTTP/1.1 uses
369   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
370   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
371   describes the content-coding, what is more important is that it
372   indicates what decoding mechanism will be required to remove the
373   encoding.
374</t>
375<t>
376   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
377  <list>
378    <t>
379      See Section 6.2.2.1 of <xref target="Part1"/>.
380    </t>
381  </list>
382</t>
383<t>
384   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
385  <list>
386    <t>
387      See Section 6.2.2.2 of <xref target="Part1"/>.
388    </t>
389  </list>
390</t>
391<t>
392   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
393  <list>
394    <t>
395      See Section 6.2.2.3 of <xref target="Part1"/>.
396    </t>
397  </list>
398</t>
399<t>
400   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
401  <list><t>
402        The default (identity) encoding; the use of no transformation
403        whatsoever. This content-coding is used only in the Accept-Encoding
404        header field, and SHOULD NOT  be used in the Content-Encoding
405        header field.
406  </t></list>
407</t>
408
409<section title="Content Coding Registry" anchor="content.coding.registry">
410<t>
411   The HTTP Content Coding Registry defines the name space for the content
412   coding names.
413</t>
414<t>
415   Registrations MUST include the following fields:
416   <list style="symbols">
417     <t>Name</t>
418     <t>Description</t>
419     <t>Pointer to specification text</t>
420   </list>
421</t>
422<t>
423   Names of content codings MUST NOT overlap with names of transfer codings
424   (Section 6.2 of <xref target="Part1"/>), unless the encoding transformation is identical (as it
425   is the case for the compression codings defined in
426   Section 6.2.2 of <xref target="Part1"/>).
427</t>
428<t>
429   Values to be added to this name space require a specification
430   (see "Specification Required" in
431   Section 4.1 of <xref target="RFC5226"/>), and MUST
432   conform to the purpose of content coding defined in this section.
433</t>
434<t>
435   The registry itself is maintained at
436   <eref target="http://www.iana.org/assignments/http-parameters"/>.
437</t>
438</section>
439
440</section>
441
442<section title="Media Types" anchor="media.types">
443 
444 
445 
446<t>
447   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
448   and Accept (<xref target="header.accept"/>) header fields in order to provide
449   open and extensible data typing and type negotiation.
450</t>
451<figure><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/><artwork type="abnf2616"><![CDATA[
452  media-type = type "/" subtype *( OWS ";" OWS parameter )
453  type       = token
454  subtype    = token
455]]></artwork></figure>
456<t anchor="rule.parameter">
457 
458 
459 
460   The type/subtype MAY be followed by parameters in the form of
461   attribute/value pairs.
462</t>
463<figure><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/><artwork type="abnf2616"><![CDATA[
464  parameter      = attribute "=" value
465  attribute      = token
466  value          = word
467]]></artwork></figure>
468<t>
469   The type, subtype, and parameter attribute names are case-insensitive.
470   Parameter values might or might not be case-sensitive, depending on the
471   semantics of the parameter name.  The presence or absence of a parameter might
472   be significant to the processing of a media-type, depending on its
473   definition within the media type registry.
474</t>
475<t>
476   A parameter value that matches the <xref target="core.rules" format="none">token</xref> production can be
477   transmitted as either a token or within a quoted-string. The quoted and
478   unquoted values are equivalent.
479</t>
480<t>
481   Note that some older HTTP applications do not recognize media type
482   parameters. When sending data to older HTTP applications,
483   implementations SHOULD only use media type parameters when they are
484   required by that type/subtype definition.
485</t>
486<t>
487   Media-type values are registered with the Internet Assigned Number
488   Authority (IANA). The media type registration process is
489   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
490   discouraged.
491</t>
492
493<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
494<t>
495   Internet media types are registered with a canonical form. A
496   representation transferred via HTTP messages MUST be in the
497   appropriate canonical form prior to its transmission except for
498   "text" types, as defined in the next paragraph.
499</t>
500<t>
501   When in canonical form, media subtypes of the "text" type use CRLF as
502   the text line break. HTTP relaxes this requirement and allows the
503   transport of text media with plain CR or LF alone representing a line
504   break when it is done consistently for an entire representation. HTTP
505   applications MUST accept CRLF, bare CR, and bare LF as indicating
506   a line break in text media received via HTTP. In
507   addition, if the text is in a character encoding that does not
508   use octets 13 and 10 for CR and LF respectively, as is the case for
509   some multi-byte character encodings, HTTP allows the use of whatever octet
510   sequences are defined by that character encoding to represent the
511   equivalent of CR and LF for line breaks. This flexibility regarding
512   line breaks applies only to text media in the payload body; a bare CR
513   or LF MUST NOT be substituted for CRLF within any of the HTTP control
514   structures (such as header fields and multipart boundaries).
515</t>
516<t>
517   If a representation is encoded with a content-coding, the underlying
518   data MUST be in a form defined above prior to being encoded.
519</t>
520<t>
521   The "charset" parameter is used with some media types to define the
522   character encoding (<xref target="character.sets"/>) of the data. When no explicit charset
523   parameter is provided by the sender, media subtypes of the "text"
524   type are defined to have a default charset value of "ISO-8859-1" when
525   received via HTTP. Data in character encodings other than "ISO-8859-1" or
526   its subsets MUST be labeled with an appropriate charset value. See
527   <xref target="missing.charset"/> for compatibility problems.
528</t>
529</section>
530
531<section title="Multipart Types" anchor="multipart.types">
532<t>
533   MIME provides for a number of "multipart" types — encapsulations of
534   one or more representations within a single message-body. All multipart
535   types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
536   and MUST include a boundary parameter as part of the media type
537   value. The message body is itself a protocol element and MUST
538   therefore use only CRLF to represent line breaks between body-parts.
539</t>
540<t>
541   In general, HTTP treats a multipart message-body no differently than
542   any other media type: strictly as payload.  HTTP does not use the
543   multipart boundary as an indicator of message-body length.
544   <!-- jre: re-insert removed text pointing to caching? -->
545   In all other respects, an HTTP user agent SHOULD follow the same or similar
546   behavior as a MIME user agent would upon receipt of a multipart type.
547   The MIME header fields within each body-part of a multipart message-body
548   do not have any significance to HTTP beyond that defined by
549   their MIME semantics.
550</t>
551<t>
552   If an application receives an unrecognized multipart subtype, the
553   application MUST treat it as being equivalent to "multipart/mixed".
554</t>
555<t><list>
556  <t>
557    Note: The "multipart/form-data" type has been specifically defined
558    for carrying form data suitable for processing via the POST
559    request method, as described in <xref target="RFC2388"/>.
560  </t>
561</list></t>
562</section>
563</section>
564
565<section title="Language Tags" anchor="language.tags">
566 
567<t>
568   A language tag, as defined in <xref target="RFC5646"/>, identifies a
569   natural language spoken, written, or otherwise conveyed by human beings for
570   communication of information to other human beings. Computer languages are
571   explicitly excluded. HTTP uses language tags within the Accept-Language and
572   Content-Language fields.
573</t>
574<t>
575   In summary, a language tag is composed of one or more parts: A primary
576   language subtag followed by a possibly empty series of subtags:
577</t>
578<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
579  language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
580]]></artwork></figure>
581<t>
582   White space is not allowed within the tag and all tags are case-insensitive.
583   The name space of language subtags is administered by the IANA (see
584   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
585</t>
586<figure>
587  <preamble>Example tags include:</preamble>
588<artwork type="example"><![CDATA[
589  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
590]]></artwork>
591</figure>
592<t>
593   See <xref target="RFC5646"/> for further information.
594</t>
595</section>
596</section>
597
598<section title="Payload" anchor="payload">
599<t>
600   HTTP messages MAY transfer a payload if not otherwise restricted by
601   the request method or response status code.  The payload consists of
602   metadata, in the form of header fields, and data, in the form of the
603   sequence of octets in the message-body after any transfer-coding has
604   been decoded.
605</t>
606<iref item="payload"/>
607<t>  
608   A "payload" in HTTP is always a partial or complete
609   representation of some resource.  We use separate terms for payload
610   and representation because some messages contain only the associated
611   representation's header fields (e.g., responses to HEAD) or only some
612   part(s) of the representation (e.g., the 206 status code).
613</t>
614<section title="Payload Header Fields" anchor="payload.header.fields">
615 
616<t>
617   HTTP header fields that specifically define the payload, rather than the
618   associated representation, are referred to as "payload header fields".
619   The following payload header fields are defined by HTTP/1.1:
620</t>
621<texttable align="left">
622  <ttcol>Header Field Name</ttcol>
623  <ttcol>Defined in...</ttcol>
624
625  <c>Content-Length</c> <c>Section 9.2 of <xref target="Part1"/></c>
626  <c>Content-MD5</c> <c><xref target="header.content-md5"/></c>
627  <c>Content-Range</c> <c>Section 5.2 of <xref target="Part5"/></c>
628</texttable>
629</section>
630
631<section title="Payload Body" anchor="payload.body">
632 
633<t>
634   A payload body is only present in a message when a message-body is
635   present, as described in Section 3.3 of <xref target="Part1"/>. The payload body is obtained
636   from the message-body by decoding any Transfer-Encoding that might
637   have been applied to ensure safe and proper transfer of the message.
638</t>
639</section>
640</section>
641
642<section title="Representation" anchor="representation">
643<iref item="representation"/>
644<t>
645   A "representation" is information in a format that can be readily
646   communicated from one party to another.  A resource representation
647   is information that reflects the state of that resource, as observed
648   at some point in the past (e.g., in a response to GET) or to be
649   desired at some point in the future (e.g., in a PUT request).
650</t>
651<t>
652   Most, but not all, representations transferred via HTTP are intended
653   to be a representation of the target resource (the resource identified
654   by the effective request URI).  The precise semantics of a representation
655   are determined by the type of message (request or response), the request
656   method, the response status code, and the representation metadata.
657   For example, the above semantic is true for the representation in any
658   200 (OK) response to GET and for the representation in any PUT request.
659   A 200 response to PUT, in contrast, contains either a representation
660   that describes the successful action or a representation of the target
661   resource, with the latter indicated by a Content-Location header field
662   with the same value as the effective request URI.  Likewise, response
663   messages with an error status code usually contain a representation that
664   describes the error and what next steps are suggested for resolving it.
665</t>
666
667<section title="Representation Header Fields" anchor="representation.header.fields">
668 
669<t>
670   Representation header fields define metadata about the representation data
671   enclosed in the message-body or, if no message-body is present, about
672   the representation that would have been transferred in a 200 response
673   to a simultaneous GET request with the same effective request URI.
674</t>
675<t>
676   The following header fields are defined as representation metadata:
677</t>
678<texttable align="left">
679  <ttcol>Header Field Name</ttcol>
680  <ttcol>Defined in...</ttcol>
681
682  <c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
683  <c>Content-Language</c> <c><xref target="header.content-language"/></c>
684  <c>Content-Location</c> <c><xref target="header.content-location"/></c>
685  <c>Content-Type</c> <c><xref target="header.content-type"/></c>
686  <c>Expires</c> <c>Section 3.3 of <xref target="Part6"/></c>
687  <c>Last-Modified</c> <c>Section 6.6 of <xref target="Part4"/></c>
688</texttable>
689</section>
690
691<section title="Representation Data" anchor="representation.data">
692 
693<t>
694   The representation body associated with an HTTP message is
695   either provided as the payload body of the message or
696   referred to by the message semantics and the effective request
697   URI.  The representation data is in a format and encoding defined by
698   the representation metadata header fields.
699</t>
700<t>
701   The data type of the representation data
702   is determined via the header fields Content-Type and Content-Encoding.
703   These define a two-layer, ordered encoding model:
704</t>
705<figure><artwork type="example"><![CDATA[
706  representation-data := Content-Encoding( Content-Type( bits ) )
707]]></artwork></figure>
708<t>
709   Content-Type specifies the media type of the underlying data, which
710   defines both the data format and how that data SHOULD be processed
711   by the recipient (within the scope of the request method semantics).
712   Any HTTP/1.1 message containing a payload body SHOULD include a
713   Content-Type header field defining the media type of the associated
714   representation unless that metadata is unknown to the sender.
715   If the Content-Type header field is not present, it indicates that
716   the sender does not know the media type of the representation;
717   recipients MAY either assume that the media type is
718   "application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
719   or examine the content to determine its type.
720</t>
721<t>
722   In practice, resource owners do not always properly configure their origin
723   server to provide the correct Content-Type for a given representation,
724   with the result that some clients will examine a response body's content
725   and override the specified type.
726   Clients that do so risk drawing incorrect conclusions, which might expose
727   additional security risks (e.g., "privilege escalation").  Furthermore,
728   it is impossible to determine the sender's intent by examining the data
729   format: many data formats match multiple media types that differ only in
730   processing semantics.  Implementers are encouraged to provide a means of
731   disabling such "content sniffing" when it is used.
732</t>
733<t>
734   Content-Encoding is used to indicate any additional content
735   codings applied to the data, usually for the purpose of data
736   compression, that are a property of the representation.  If
737   Content-Encoding is not present, then there is no additional
738   encoding beyond that defined by the Content-Type.
739</t>
740</section>
741</section>
742
743<section title="Content Negotiation" anchor="content.negotiation">
744<t>
745   HTTP responses include a representation which contains information for
746   interpretation, whether by a human user or for further processing.
747   Often, the server has different ways of representing the
748   same information; for example, in different formats, languages,
749   or using different character encodings.
750</t>
751<t>
752   HTTP clients and their users might have different or variable
753   capabilities, characteristics or preferences which would influence
754   which representation, among those available from the server,
755   would be best for the server to deliver. For this reason, HTTP
756   provides mechanisms for "content negotiation" — a process of
757   allowing selection of a representation of a given resource,
758   when more than one is available.
759</t>
760<t>
761   This specification defines two patterns of content negotiation;
762   "server-driven", where the server selects the representation based
763   upon the client's stated preferences, and "agent-driven" negotiation,
764   where the server provides a list of representations for the client to
765   choose from, based upon their metadata. In addition,  there are
766   other patterns: some applications use an "active content" pattern,
767   where the server returns active content which runs on the client
768   and, based on client available parameters, selects additional
769   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
770   has also been proposed.
771</t>
772<t>
773   These patterns are all widely used, and have trade-offs in applicability
774   and practicality. In particular, when the number of preferences or
775   capabilities to be expressed by a client are large (such as when many
776   different formats are supported by a user-agent), server-driven
777   negotiation becomes unwieldy, and might not be appropriate. Conversely,
778   when the number of representations to choose from is very large,
779   agent-driven negotiation might not be appropriate.
780</t>
781<t>
782   Note that in all cases, the supplier of representations has the
783   responsibility for determining which representations might be
784   considered to be the "same information".
785</t>
786
787<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
788<t>
789   If the selection of the best representation for a response is made by
790   an algorithm located at the server, it is called server-driven
791   negotiation. Selection is based on the available representations of
792   the response (the dimensions over which it can vary; e.g., language,
793   content-coding, etc.) and the contents of particular header fields in
794   the request message or on other information pertaining to the request
795   (such as the network address of the client).
796</t>
797<t>
798   Server-driven negotiation is advantageous when the algorithm for
799   selecting from among the available representations is difficult to
800   describe to the user agent, or when the server desires to send its
801   "best guess" to the client along with the first response (hoping to
802   avoid the round-trip delay of a subsequent request if the "best
803   guess" is good enough for the user). In order to improve the server's
804   guess, the user agent MAY include request header fields (Accept,
805   Accept-Language, Accept-Encoding, etc.) which describe its
806   preferences for such a response.
807</t>
808<t>
809   Server-driven negotiation has disadvantages:
810  <list style="numbers">
811    <t>
812         It is impossible for the server to accurately determine what
813         might be "best" for any given user, since that would require
814         complete knowledge of both the capabilities of the user agent
815         and the intended use for the response (e.g., does the user want
816         to view it on screen or print it on paper?).
817    </t>
818    <t>
819         Having the user agent describe its capabilities in every
820         request can be both very inefficient (given that only a small
821         percentage of responses have multiple representations) and a
822         potential violation of the user's privacy.
823    </t>
824    <t>
825         It complicates the implementation of an origin server and the
826         algorithms for generating responses to a request.
827    </t>
828    <t>
829         It might limit a public cache's ability to use the same response
830         for multiple user's requests.
831    </t>
832  </list>
833</t>
834<t>
835   HTTP/1.1 includes the following header fields for enabling
836   server-driven negotiation through description of user agent
837   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
838   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
839   (<xref target="header.accept-language"/>), and User-Agent (Section 9.9 of <xref target="Part2"/>).
840   However, an origin server is not limited to these dimensions and MAY vary
841   the response based on any aspect of the request, including aspects
842   of the connection (e.g., IP address) or information within extension
843   header fields not defined by this specification.
844</t>
845<t><list>
846  <t>
847    Note: In practice, User-Agent based negotiation is fragile,
848    because new clients might not be recognized.
849  </t>
850</list></t>
851<t>
852   The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
853   server uses to select a representation that is subject to server-driven
854   negotiation.
855</t>
856</section>
857
858<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
859<t>
860   With agent-driven negotiation, selection of the best representation
861   for a response is performed by the user agent after receiving an
862   initial response from the origin server. Selection is based on a list
863   of the available representations of the response included within the
864   header fields or body of the initial response, with each
865   representation identified by its own URI. Selection from among the
866   representations can be performed automatically (if the user agent is
867   capable of doing so) or manually by the user selecting from a
868   generated (possibly hypertext) menu.
869</t>
870<t>
871   Agent-driven negotiation is advantageous when the response would vary
872   over commonly-used dimensions (such as type, language, or encoding),
873   when the origin server is unable to determine a user agent's
874   capabilities from examining the request, and generally when public
875   caches are used to distribute server load and reduce network usage.
876</t>
877<t>
878   Agent-driven negotiation suffers from the disadvantage of needing a
879   second request to obtain the best alternate representation. This
880   second request is only efficient when caching is used. In addition,
881   this specification does not define any mechanism for supporting
882   automatic selection, though it also does not prevent any such
883   mechanism from being developed as an extension and used within
884   HTTP/1.1.
885</t>
886<t>
887   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
888   status codes for enabling agent-driven negotiation when the server is
889   unwilling or unable to provide a varying response using server-driven
890   negotiation.
891</t>
892</section>
893</section>
894
895<section title="Header Field Definitions" anchor="header.fields">
896<t>
897   This section defines the syntax and semantics of HTTP/1.1 header fields
898   related to the payload of messages.
899</t>
900
901<section title="Accept" anchor="header.accept">
902  <iref primary="true" item="Accept header field"/>
903  <iref primary="true" item="Header Fields" subitem="Accept"/>
904 
905 
906 
907 
908 
909<t>
910   The "Accept" header field can be used by user agents to specify
911   response media types that are acceptable. Accept header fields can be used to
912   indicate that the request is specifically limited to a small set of desired
913   types, as in the case of a request for an in-line image.
914</t>
915<figure><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="Accept-v"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/><artwork type="abnf2616"><![CDATA[
916  Accept   = "Accept" ":" OWS Accept-v
917  Accept-v = #( media-range [ accept-params ] )
918 
919  media-range    = ( "*/*"
920                   / ( type "/" "*" )
921                   / ( type "/" subtype )
922                   ) *( OWS ";" OWS parameter )
923  accept-params  = OWS ";" OWS "q=" qvalue *( accept-ext )
924  accept-ext     = OWS ";" OWS token [ "=" word ]
925]]></artwork></figure>
926<t>
927   The asterisk "*" character is used to group media types into ranges,
928   with "*/*" indicating all media types and "type/*" indicating all
929   subtypes of that type. The media-range MAY include media type
930   parameters that are applicable to that range.
931</t>
932<t>
933   Each media-range MAY be followed by one or more accept-params,
934   beginning with the "q" parameter for indicating a relative quality
935   factor. The first "q" parameter (if any) separates the media-range
936   parameter(s) from the accept-params. Quality factors allow the user
937   or user agent to indicate the relative degree of preference for that
938   media-range, using the qvalue scale from 0 to 1 (Section 6.4 of <xref target="Part1"/>). The
939   default value is q=1.
940</t>
941<t><list>
942  <t>
943    Note: Use of the "q" parameter name to separate media type
944    parameters from Accept extension parameters is due to historical
945    practice. Although this prevents any media type parameter named
946    "q" from being used with a media range, such an event is believed
947    to be unlikely given the lack of any "q" parameters in the IANA
948    media type registry and the rare usage of any media type
949    parameters in Accept. Future media types are discouraged from
950    registering any parameter named "q".
951  </t>
952</list></t>
953<t>
954   The example
955</t>
956<figure><artwork type="example"><![CDATA[
957  Accept: audio/*; q=0.2, audio/basic
958]]></artwork></figure>
959<t>
960   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
961   type if it is the best available after an 80% mark-down in quality".
962</t>
963<t>
964   If no Accept header field is present, then it is assumed that the
965   client accepts all media types. If an Accept header field is present,
966   and if the server cannot send a response which is acceptable
967   according to the combined Accept field value, then the server SHOULD
968   send a 406 (Not Acceptable) response.
969</t>
970<t>
971   A more elaborate example is
972</t>
973<figure><artwork type="example"><![CDATA[
974  Accept: text/plain; q=0.5, text/html,
975          text/x-dvi; q=0.8, text/x-c
976]]></artwork></figure>
977<t>
978   Verbally, this would be interpreted as "text/html and text/x-c are
979   the preferred media types, but if they do not exist, then send the
980   text/x-dvi representation, and if that does not exist, send the text/plain
981   representation".
982</t>
983<t>
984   Media ranges can be overridden by more specific media ranges or
985   specific media types. If more than one media range applies to a given
986   type, the most specific reference has precedence. For example,
987</t>
988<figure><artwork type="example"><![CDATA[
989  Accept: text/*, text/html, text/html;level=1, */*
990]]></artwork></figure>
991<t>
992   have the following precedence:
993   <list style="numbers">
994    <t>text/html;level=1</t>
995    <t>text/html</t>
996    <t>text/*</t>
997    <t>*/*</t>
998   </list>
999</t>
1000<t>
1001   The media type quality factor associated with a given type is
1002   determined by finding the media range with the highest precedence
1003   which matches that type. For example,
1004</t>
1005<figure><artwork type="example"><![CDATA[
1006  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1007          text/html;level=2;q=0.4, */*;q=0.5
1008]]></artwork></figure>
1009<t>
1010   would cause the following values to be associated:
1011</t>
1012<texttable align="left">
1013  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1014  <c>text/html;level=1</c>    <c>1</c>
1015  <c>text/html</c>            <c>0.7</c>
1016  <c>text/plain</c>           <c>0.3</c>
1017  <c>image/jpeg</c>           <c>0.5</c>
1018  <c>text/html;level=2</c>    <c>0.4</c>
1019  <c>text/html;level=3</c>    <c>0.7</c>
1020</texttable>
1021<t>
1022      Note: A user agent might be provided with a default set of quality
1023      values for certain media ranges. However, unless the user agent is
1024      a closed system which cannot interact with other rendering agents,
1025      this default set ought to be configurable by the user.
1026</t>
1027</section>
1028
1029<section title="Accept-Charset" anchor="header.accept-charset">
1030  <iref primary="true" item="Accept-Charset header field"/>
1031  <iref primary="true" item="Header Fields" subitem="Accept-Charset"/>
1032 
1033 
1034<t>
1035   The "Accept-Charset" header field can be used by user agents to
1036   indicate what character encodings are acceptable in a response
1037   payload. This field allows
1038   clients capable of understanding more comprehensive or special-purpose
1039   character encodings to signal that capability to a server which is capable of
1040   representing documents in those character encodings.
1041</t>
1042<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/><artwork type="abnf2616"><![CDATA[
1043  Accept-Charset   = "Accept-Charset" ":" OWS
1044          Accept-Charset-v
1045  Accept-Charset-v = 1#( ( charset / "*" )
1046                         [ OWS ";" OWS "q=" qvalue ] )
1047]]></artwork></figure>
1048<t>
1049   Character encoding values (a.k.a., charsets) are described in
1050   <xref target="character.sets"/>. Each charset MAY be given an
1051   associated quality value which represents the user's preference
1052   for that charset. The default value is q=1. An example is
1053</t>
1054<figure><artwork type="example"><![CDATA[
1055  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1056]]></artwork></figure>
1057<t>
1058   The special value "*", if present in the Accept-Charset field,
1059   matches every character encoding (including ISO-8859-1) which is not
1060   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1061   in an Accept-Charset field, then all character encodings not explicitly
1062   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1063   a quality value of 1 if not explicitly mentioned.
1064</t>
1065<t>
1066   If no Accept-Charset header field is present, the default is that any
1067   character encoding is acceptable. If an Accept-Charset header field is present,
1068   and if the server cannot send a response which is acceptable
1069   according to the Accept-Charset header field, then the server SHOULD send
1070   an error response with the 406 (Not Acceptable) status code, though
1071   the sending of an unacceptable response is also allowed.
1072</t>
1073</section>
1074
1075<section title="Accept-Encoding" anchor="header.accept-encoding">
1076  <iref primary="true" item="Accept-Encoding header field"/>
1077  <iref primary="true" item="Header Fields" subitem="Accept-Encoding"/>
1078 
1079 
1080 
1081<t>
1082   The "Accept-Encoding" header field can be used by user agents to
1083   indicate what response content-codings (<xref target="content.codings"/>)
1084   are acceptable in the response.
1085</t>
1086<figure><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="Accept-Encoding-v"/><iref primary="true" item="Grammar" subitem="codings"/><artwork type="abnf2616"><![CDATA[
1087  Accept-Encoding    = "Accept-Encoding" ":" OWS
1088                     Accept-Encoding-v
1089  Accept-Encoding-v  =
1090                     #( codings [ OWS ";" OWS "q=" qvalue ] )
1091  codings            = ( content-coding / "*" )
1092]]></artwork></figure>
1093<t>
1094   Each codings value MAY be given an associated quality value which
1095   represents the preference for that encoding. The default value is q=1.
1096</t>
1097<t>
1098   Examples of its use are:
1099</t>
1100<figure><artwork type="example"><![CDATA[
1101  Accept-Encoding: compress, gzip
1102  Accept-Encoding:
1103  Accept-Encoding: *
1104  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1105  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1106]]></artwork></figure>
1107<t>
1108   A server tests whether a content-coding is acceptable, according to
1109   an Accept-Encoding field, using these rules:
1110  <list style="numbers">
1111      <t>If the content-coding is one of the content-codings listed in
1112         the Accept-Encoding field, then it is acceptable, unless it is
1113         accompanied by a qvalue of 0. (As defined in Section 6.4 of <xref target="Part1"/>, a
1114         qvalue of 0 means "not acceptable".)</t>
1115
1116      <t>The special "*" symbol in an Accept-Encoding field matches any
1117         available content-coding not explicitly listed in the header
1118         field.</t>
1119
1120      <t>If multiple content-codings are acceptable, then the acceptable
1121         content-coding with the highest non-zero qvalue is preferred.</t>
1122
1123      <t>The "identity" content-coding is always acceptable, unless
1124         specifically refused because the Accept-Encoding field includes
1125         "identity;q=0", or because the field includes "*;q=0" and does
1126         not explicitly include the "identity" content-coding. If the
1127         Accept-Encoding field-value is empty, then only the "identity"
1128         encoding is acceptable.</t>
1129  </list>
1130</t>
1131<t>
1132   If an Accept-Encoding field is present in a request, and if the
1133   server cannot send a response which is acceptable according to the
1134   Accept-Encoding header field, then the server SHOULD send an error response
1135   with the 406 (Not Acceptable) status code.
1136</t>
1137<t>
1138   If no Accept-Encoding field is present in a request, the server MAY
1139   assume that the client will accept any content coding. In this case,
1140   if "identity" is one of the available content-codings, then the
1141   server SHOULD use the "identity" content-coding, unless it has
1142   additional information that a different content-coding is meaningful
1143   to the client.
1144</t>
1145<t><list>
1146  <t>
1147    Note: If the request does not include an Accept-Encoding field,
1148    and if the "identity" content-coding is unavailable, then
1149    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1150    "gzip" and "compress") are preferred; some older clients
1151    improperly display messages sent with other content-codings.  The
1152    server might also make this decision based on information about
1153    the particular user-agent or client.
1154  </t>
1155</list></t>
1156<t><list>
1157  <t>
1158    Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1159    associated with content-codings. This means that qvalues will not
1160    work and are not permitted with x-gzip or x-compress.
1161  </t>
1162</list></t>
1163</section>
1164
1165<section title="Accept-Language" anchor="header.accept-language">
1166  <iref primary="true" item="Accept-Language header field"/>
1167  <iref primary="true" item="Header Fields" subitem="Accept-Language"/>
1168 
1169 
1170 
1171<t>
1172   The "Accept-Language" header field can be used by user agents to
1173   indicate the set of natural languages that are preferred in the response.
1174   Language tags are defined in <xref target="language.tags"/>.
1175</t>
1176<figure><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="Accept-Language-v"/><iref primary="true" item="Grammar" subitem="language-range"/><artwork type="abnf2616"><![CDATA[
1177  Accept-Language   = "Accept-Language" ":" OWS
1178                    Accept-Language-v
1179  Accept-Language-v =
1180                    1#( language-range [ OWS ";" OWS "q=" qvalue ] )
1181  language-range    =
1182            <language-range, defined in [RFC4647], Section 2.1>
1183]]></artwork></figure>
1184<t>
1185   Each language-range can be given an associated quality value which
1186   represents an estimate of the user's preference for the languages
1187   specified by that range. The quality value defaults to "q=1". For
1188   example,
1189</t>
1190<figure><artwork type="example"><![CDATA[
1191  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1192]]></artwork></figure>
1193<t>
1194   would mean: "I prefer Danish, but will accept British English and
1195   other types of English".
1196   (see also Section 2.3 of <xref target="RFC4647"/>)
1197</t>
1198<t>
1199   For matching, Section 3 of <xref target="RFC4647"/> defines
1200   several matching schemes. Implementations can offer the most appropriate
1201   matching scheme for their requirements.
1202</t>
1203<t><list>
1204  <t>
1205    Note: The "Basic Filtering" scheme (<xref target="RFC4647"/>, Section 3.3.1) is identical to the matching scheme that was
1206    previously defined in Section 14.4 of <xref target="RFC2616"/>.
1207  </t>
1208</list></t>
1209<t>
1210   It might be contrary to the privacy expectations of the user to send
1211   an Accept-Language header field with the complete linguistic preferences of
1212   the user in every request. For a discussion of this issue, see
1213   <xref target="privacy.issues.connected.to.accept.header.fields"/>.
1214</t>
1215<t>
1216   As intelligibility is highly dependent on the individual user, it is
1217   recommended that client applications make the choice of linguistic
1218   preference available to the user. If the choice is not made
1219   available, then the Accept-Language header field MUST NOT be given in
1220   the request.
1221</t>
1222<t><list>
1223  <t>
1224    Note: When making the choice of linguistic preference available to
1225    the user, we remind implementors of  the fact that users are not
1226    familiar with the details of language matching as described above,
1227    and ought to be provided appropriate guidance. As an example, users
1228    might assume that on selecting "en-gb", they will be served any
1229    kind of English document if British English is not available. A
1230    user agent might suggest in such a case to add "en" to get the
1231    best matching behavior.
1232  </t>
1233</list></t>
1234</section>
1235
1236<section title="Content-Encoding" anchor="header.content-encoding">
1237  <iref primary="true" item="Content-Encoding header field"/>
1238  <iref primary="true" item="Header Fields" subitem="Content-Encoding"/>
1239 
1240 
1241<t>
1242   The "Content-Encoding" header field indicates what content-codings
1243   have been applied to the representation, and thus what decoding mechanisms
1244   must be applied in order to obtain the media-type referenced by the
1245   Content-Type header field. Content-Encoding is primarily used to allow a
1246   representation to be compressed without losing the identity of its underlying
1247   media type.
1248</t>
1249<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/><artwork type="abnf2616"><![CDATA[
1250  Content-Encoding   = "Content-Encoding" ":" OWS Content-Encoding-v
1251  Content-Encoding-v = 1#content-coding
1252]]></artwork></figure>
1253<t>
1254   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1255</t>
1256<figure><artwork type="example"><![CDATA[
1257  Content-Encoding: gzip
1258]]></artwork></figure>
1259<t>
1260   The content-coding is a characteristic of the representation.
1261   Typically, the representation body is stored with this
1262   encoding and is only decoded before rendering or analogous usage.
1263   However, a transforming proxy MAY modify the content-coding if the
1264   new coding is known to be acceptable to the recipient, unless the
1265   "no-transform" cache-control directive is present in the message.
1266</t>
1267<t>
1268   If the content-coding of a representation is not "identity", then the
1269   representation metadata MUST include a Content-Encoding header
1270   field (<xref target="header.content-encoding"/>)
1271   that lists the non-identity content-coding(s) used.
1272</t>
1273<t>
1274   If the content-coding of a representation in a request message is not
1275   acceptable to the origin server, the server SHOULD respond with a
1276   status code of 415 (Unsupported Media Type).
1277</t>
1278<t>
1279   If multiple encodings have been applied to a representation, the content
1280   codings MUST be listed in the order in which they were applied.
1281   Additional information about the encoding parameters MAY be provided
1282   by other header fields not defined by this specification.
1283</t>
1284</section>
1285
1286<section title="Content-Language" anchor="header.content-language">
1287  <iref primary="true" item="Content-Language header field"/>
1288  <iref primary="true" item="Header Fields" subitem="Content-Language"/>
1289 
1290 
1291<t>
1292   The "Content-Language" header field describes the natural
1293   language(s) of the intended audience for the representation. Note that this might
1294   not be equivalent to all the languages used within the representation.
1295</t>
1296<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/><artwork type="abnf2616"><![CDATA[
1297  Content-Language   = "Content-Language" ":" OWS Content-Language-v
1298  Content-Language-v = 1#language-tag
1299]]></artwork></figure>
1300<t>
1301   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1302   Content-Language is to allow a user to identify and differentiate
1303   representations according to the user's own preferred language. Thus, if the
1304   body content is intended only for a Danish-literate audience, the
1305   appropriate field is
1306</t>
1307<figure><artwork type="example"><![CDATA[
1308  Content-Language: da
1309]]></artwork></figure>
1310<t>
1311   If no Content-Language is specified, the default is that the content
1312   is intended for all language audiences. This might mean that the
1313   sender does not consider it to be specific to any natural language,
1314   or that the sender does not know for which language it is intended.
1315</t>
1316<t>
1317   Multiple languages MAY be listed for content that is intended for
1318   multiple audiences. For example, a rendition of the "Treaty of
1319   Waitangi", presented simultaneously in the original Maori and English
1320   versions, would call for
1321</t>
1322<figure><artwork type="example"><![CDATA[
1323  Content-Language: mi, en
1324]]></artwork></figure>
1325<t>
1326   However, just because multiple languages are present within a representation
1327   does not mean that it is intended for multiple linguistic audiences.
1328   An example would be a beginner's language primer, such as "A First
1329   Lesson in Latin", which is clearly intended to be used by an
1330   English-literate audience. In this case, the Content-Language would
1331   properly only include "en".
1332</t>
1333<t>
1334   Content-Language MAY be applied to any media type — it is not
1335   limited to textual documents.
1336</t>
1337</section>
1338
1339<section title="Content-Location" anchor="header.content-location">
1340  <iref primary="true" item="Content-Location header field"/>
1341  <iref primary="true" item="Header Fields" subitem="Content-Location"/>
1342 
1343 
1344<t>
1345   The "Content-Location" header field supplies a URI that can be used
1346   as a specific identifier for the representation in this message.
1347   In other words, if one were to perform a GET on this URI at the time
1348   of this message's generation, then a 200 response would contain the
1349   same representation that is enclosed as payload in this message.
1350</t>
1351<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/><artwork type="abnf2616"><![CDATA[
1352  Content-Location   = "Content-Location" ":" OWS
1353                    Content-Location-v
1354  Content-Location-v =
1355                    absolute-URI / partial-URI
1356]]></artwork></figure>
1357<t>
1358   The Content-Location value is not a replacement for the effective
1359   Request URI (Section 4.3 of <xref target="Part1"/>).  It is representation metadata.
1360   It has the same syntax and semantics as the header field of the same name
1361   defined for MIME body parts in Section 4 of <xref target="RFC2557"/>.
1362   However, its appearance in an HTTP message has some special implications
1363   for HTTP recipients.
1364</t>
1365<t>
1366   If Content-Location is included in a response message and its value
1367   is the same as the effective request URI, then the response payload
1368   SHOULD be considered the current representation of that resource.
1369   For a GET or HEAD request, this is the same as the default semantics
1370   when no Content-Location is provided by the server.  For a state-changing
1371   request like PUT or POST, it implies that the server's response contains
1372   the new representation of that resource, thereby distinguishing it from
1373   representations that might only report about the action (e.g., "It worked!").
1374   This allows authoring applications to update their local copies without
1375   the need for a subsequent GET request.
1376</t>
1377<t>
1378   If Content-Location is included in a response message and its value
1379   differs from the effective request URI, then the origin server is
1380   informing recipients that this representation has its own, presumably
1381   more specific, identifier.  For a GET or HEAD request, this is an
1382   indication that the effective request URI identifies a resource that
1383   is subject to content negotiation and the representation selected for
1384   this response can also be found at the identified URI.  For other
1385   methods, such a Content-Location indicates that this representation
1386   contains a report on the action's status and the same report is
1387   available (for future access with GET) at the given URI.  For
1388   example, a purchase transaction made via a POST request might
1389   include a receipt document as the payload of the 200 response;
1390   the Content-Location value provides an identifier for retrieving
1391   a copy of that same receipt in the future.
1392</t>
1393<t>
1394   If Content-Location is included in a request message, then it MAY
1395   be interpreted by the origin server as an indication of where the
1396   user agent originally obtained the content of the enclosed
1397   representation (prior to any subsequent modification of the content
1398   by that user agent).  In other words, the user agent is providing
1399   the same representation metadata that it received with the original
1400   representation.  However, such interpretation MUST NOT be used to
1401   alter the semantics of the method requested by the client.  For
1402   example, if a client makes a PUT request on a negotiated resource
1403   and the origin server accepts that PUT (without redirection), then the
1404   new set of values for that resource is expected to be consistent with
1405   the one representation supplied in that PUT; the Content-Location
1406   cannot be used as a form of reverse content selection that
1407   identifies only one of the negotiated representations to be updated.
1408   If the user agent had wanted the latter semantics, it would have applied
1409   the PUT directly to the Content-Location URI.
1410</t>
1411<t>
1412   A Content-Location field received in a request message is transitory
1413   information that SHOULD NOT be saved with other representation
1414   metadata for use in later responses.  The Content-Location's value
1415   might be saved for use in other contexts, such as within source links
1416   or other metadata.
1417</t>
1418<t>
1419   A cache cannot assume that a representation with a Content-Location
1420   different from the URI used to retrieve it can be used to respond to
1421   later requests on that Content-Location URI.
1422</t>
1423<t>
1424   If the Content-Location value is a partial URI, the partial URI is
1425   interpreted relative to the effective request URI.
1426</t>
1427</section>
1428
1429<section title="Content-MD5" anchor="header.content-md5">
1430  <iref primary="true" item="Content-MD5 header field"/>
1431  <iref primary="true" item="Header Fields" subitem="Content-MD5"/>
1432 
1433 
1434<t>
1435   The "Content-MD5" header field, as defined in <xref target="RFC1864"/>, is
1436   an MD5 digest of the payload body that provides an end-to-end message
1437   integrity check (MIC) of the payload body (the message-body after any
1438   transfer-coding is decoded). Note that a MIC is good for
1439   detecting accidental modification of the payload body in transit, but is not
1440   proof against malicious attacks.
1441</t>
1442<figure><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/><artwork type="abnf2616"><![CDATA[
1443  Content-MD5   = "Content-MD5" ":" OWS Content-MD5-v
1444  Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
1445]]></artwork></figure>
1446<t>
1447   The Content-MD5 header field MAY be generated by an origin server or
1448   client to function as an integrity check of the payload body. Only
1449   origin servers or user agents MAY generate the Content-MD5 header field;
1450   proxies MUST NOT generate it, as this would defeat its
1451   value as an end-to-end integrity check. Any recipient MAY check that
1452   the digest value in this header field matches a corresponding digest
1453   calculated on payload body as received.
1454</t>
1455<t>
1456   The MD5 digest is computed based on the content of the payload body,
1457   including any content-coding, but not including any transfer-coding
1458   applied to the message-body because such transfer-codings might be
1459   applied or removed anywhere along the request/response chain.
1460   If the message is received with a transfer-coding, that encoding MUST
1461   be decoded prior to checking the Content-MD5 value against the received
1462   payload.
1463</t>
1464<t>
1465   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1466   composite media-types (e.g., multipart/* and message/rfc822), but
1467   this does not change how the digest is computed as defined in the
1468   preceding paragraph.
1469</t>
1470<t>
1471   There are several consequences of this. The payload for composite
1472   types MAY contain many body-parts, each with its own MIME and HTTP
1473   header fields (including Content-MD5, Content-Transfer-Encoding, and
1474   Content-Encoding header fields). If a body-part has a Content-Transfer-Encoding
1475   or Content-Encoding header field, it is assumed that the content
1476   of the body-part has had the encoding applied, and the body-part is
1477   included in the Content-MD5 digest as is — i.e., after the
1478   application. The Transfer-Encoding header field is not allowed within
1479   body-parts.
1480</t>
1481<t>
1482   Conversion of all line breaks to CRLF MUST NOT be done before
1483   computing or checking the digest: the line break convention used in
1484   the text actually transmitted MUST be left unaltered when computing
1485   the digest.
1486</t>
1487<t><list>
1488  <t>
1489    Note: While the definition of Content-MD5 is exactly the same for
1490    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1491    in which the application of Content-MD5 to HTTP entity-bodies
1492    differs from its application to MIME entity-bodies. One is that
1493    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1494    does use Transfer-Encoding and Content-Encoding. Another is that
1495    HTTP more frequently uses binary content types than MIME, so it is
1496    worth noting that, in such cases, the byte order used to compute
1497    the digest is the transmission byte order defined for the type.
1498    Lastly, HTTP allows transmission of text types with any of several
1499    line break conventions and not just the canonical form using CRLF.
1500  </t>
1501</list></t>
1502</section>
1503
1504<section title="Content-Type" anchor="header.content-type">
1505  <iref primary="true" item="Content-Type header field"/>
1506  <iref primary="true" item="Header Fields" subitem="Content-Type"/>
1507 
1508 
1509<t>
1510   The "Content-Type" header field indicates the media type of the
1511   representation. In the case of responses to the HEAD method, the media type is
1512   that which would have been sent had the request been a GET.
1513</t>
1514<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/><artwork type="abnf2616"><![CDATA[
1515  Content-Type   = "Content-Type" ":" OWS Content-Type-v
1516  Content-Type-v = media-type
1517]]></artwork></figure>
1518<t>
1519   Media types are defined in <xref target="media.types"/>. An example of the field is
1520</t>
1521<figure><artwork type="example"><![CDATA[
1522  Content-Type: text/html; charset=ISO-8859-4
1523]]></artwork></figure>
1524<t>
1525   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1526</t>
1527</section>
1528
1529</section>
1530
1531<section title="IANA Considerations" anchor="IANA.considerations">
1532<section title="Header Field Registration" anchor="header.field.registration">
1533<t>
1534   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
1535   with the permanent registrations below (see <xref target="RFC3864"/>):
1536</t>
1537
1538<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1539<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1540   <ttcol>Header Field Name</ttcol>
1541   <ttcol>Protocol</ttcol>
1542   <ttcol>Status</ttcol>
1543   <ttcol>Reference</ttcol>
1544
1545   <c>Accept</c>
1546   <c>http</c>
1547   <c>standard</c>
1548   <c>
1549      <xref target="header.accept"/>
1550   </c>
1551   <c>Accept-Charset</c>
1552   <c>http</c>
1553   <c>standard</c>
1554   <c>
1555      <xref target="header.accept-charset"/>
1556   </c>
1557   <c>Accept-Encoding</c>
1558   <c>http</c>
1559   <c>standard</c>
1560   <c>
1561      <xref target="header.accept-encoding"/>
1562   </c>
1563   <c>Accept-Language</c>
1564   <c>http</c>
1565   <c>standard</c>
1566   <c>
1567      <xref target="header.accept-language"/>
1568   </c>
1569   <c>Content-Encoding</c>
1570   <c>http</c>
1571   <c>standard</c>
1572   <c>
1573      <xref target="header.content-encoding"/>
1574   </c>
1575   <c>Content-Language</c>
1576   <c>http</c>
1577   <c>standard</c>
1578   <c>
1579      <xref target="header.content-language"/>
1580   </c>
1581   <c>Content-Location</c>
1582   <c>http</c>
1583   <c>standard</c>
1584   <c>
1585      <xref target="header.content-location"/>
1586   </c>
1587   <c>Content-MD5</c>
1588   <c>http</c>
1589   <c>standard</c>
1590   <c>
1591      <xref target="header.content-md5"/>
1592   </c>
1593   <c>Content-Type</c>
1594   <c>http</c>
1595   <c>standard</c>
1596   <c>
1597      <xref target="header.content-type"/>
1598   </c>
1599   <c>MIME-Version</c>
1600   <c>http</c>
1601   <c>standard</c>
1602   <c>
1603      <xref target="mime-version"/>
1604   </c>
1605</texttable>
1606<!--(END)-->
1607
1608<t>
1609   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1610</t>
1611</section>
1612
1613<section title="Content Coding Registry" anchor="content.coding.registration">
1614<t>
1615   The registration procedure for HTTP Content Codings is now defined
1616   by <xref target="content.coding.registry"/> of this document.
1617</t>
1618<t>
1619   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1620   shall be updated with the registration below:
1621</t>
1622<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1623   <ttcol>Name</ttcol>
1624   <ttcol>Description</ttcol>
1625   <ttcol>Reference</ttcol>
1626   <c>compress</c>
1627   <c>UNIX "compress" program method</c>
1628   <c>
1629      Section 6.2.2.1 of <xref target="Part1"/>
1630   </c>
1631   <c>deflate</c>
1632   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1633   the "zlib" data format (<xref target="RFC1950"/>)
1634   </c>
1635   <c>
1636      Section 6.2.2.2 of <xref target="Part1"/>
1637   </c>
1638   <c>gzip</c>
1639   <c>Same as GNU zip <xref target="RFC1952"/></c>
1640   <c>
1641      Section 6.2.2.3 of <xref target="Part1"/>
1642   </c>
1643   <c>identity</c>
1644   <c>No transformation</c>
1645   <c>
1646      <xref target="content.codings"/>
1647   </c>
1648</texttable>
1649</section>
1650
1651</section>
1652
1653<section title="Security Considerations" anchor="security.considerations">
1654<t>
1655   This section is meant to inform application developers, information
1656   providers, and users of the security limitations in HTTP/1.1 as
1657   described by this document. The discussion does not include
1658   definitive solutions to the problems revealed, though it does make
1659   some suggestions for reducing security risks.
1660</t>
1661
1662<section title="Privacy Issues Connected to Accept Header Fields" anchor="privacy.issues.connected.to.accept.header.fields">
1663<t>
1664   Accept headers fields can reveal information about the user to all
1665   servers which are accessed. The Accept-Language header field in particular
1666   can reveal information the user would consider to be of a private
1667   nature, because the understanding of particular languages is often
1668   strongly correlated to the membership of a particular ethnic group.
1669   User agents which offer the option to configure the contents of an
1670   Accept-Language header field to be sent in every request are strongly
1671   encouraged to let the configuration process include a message which
1672   makes the user aware of the loss of privacy involved.
1673</t>
1674<t>
1675   An approach that limits the loss of privacy would be for a user agent
1676   to omit the sending of Accept-Language header fields by default, and to ask
1677   the user whether or not to start sending Accept-Language header fields to a
1678   server if it detects, by looking for any Vary header fields
1679   generated by the server, that such sending could improve the quality
1680   of service.
1681</t>
1682<t>
1683   Elaborate user-customized accept header fields sent in every request,
1684   in particular if these include quality values, can be used by servers
1685   as relatively reliable and long-lived user identifiers. Such user
1686   identifiers would allow content providers to do click-trail tracking,
1687   and would allow collaborating content providers to match cross-server
1688   click-trails or form submissions of individual users. Note that for
1689   many users not behind a proxy, the network address of the host
1690   running the user agent will also serve as a long-lived user
1691   identifier. In environments where proxies are used to enhance
1692   privacy, user agents ought to be conservative in offering accept
1693   header configuration options to end users. As an extreme privacy
1694   measure, proxies could filter the accept header fields in relayed requests.
1695   General purpose user agents which provide a high degree of header
1696   configurability SHOULD warn users about the loss of privacy which can
1697   be involved.
1698</t>
1699</section>
1700
1701</section>
1702
1703<section title="Acknowledgments" anchor="ack">
1704</section>
1705</middle>
1706<back>
1707
1708<references title="Normative References">
1709
1710<reference anchor="ISO-8859-1">
1711  <front>
1712    <title>
1713     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1714    </title>
1715    <author>
1716      <organization>International Organization for Standardization</organization>
1717    </author>
1718    <date year="1998"/>
1719  </front>
1720  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1721</reference>
1722
1723<reference anchor="Part1">
1724  <front>
1725    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1726    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1727      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1728      <address><email>fielding@gbiv.com</email></address>
1729    </author>
1730    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1731      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1732      <address><email>jg@freedesktop.org</email></address>
1733    </author>
1734    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1735      <organization abbrev="HP">Hewlett-Packard Company</organization>
1736      <address><email>JeffMogul@acm.org</email></address>
1737    </author>
1738    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1739      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1740      <address><email>henrikn@microsoft.com</email></address>
1741    </author>
1742    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1743      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1744      <address><email>LMM@acm.org</email></address>
1745    </author>
1746    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1747      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1748      <address><email>paulle@microsoft.com</email></address>
1749    </author>
1750    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1751      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1752      <address><email>timbl@w3.org</email></address>
1753    </author>
1754    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1755      <organization abbrev="W3C">World Wide Web Consortium</organization>
1756      <address><email>ylafon@w3.org</email></address>
1757    </author>
1758    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1759      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1760      <address><email>julian.reschke@greenbytes.de</email></address>
1761    </author>
1762    <date month="March" year="2011"/>
1763  </front>
1764  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-13"/>
1765 
1766</reference>
1767
1768<reference anchor="Part2">
1769  <front>
1770    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1771    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1772      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1773      <address><email>fielding@gbiv.com</email></address>
1774    </author>
1775    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1776      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1777      <address><email>jg@freedesktop.org</email></address>
1778    </author>
1779    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1780      <organization abbrev="HP">Hewlett-Packard Company</organization>
1781      <address><email>JeffMogul@acm.org</email></address>
1782    </author>
1783    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1784      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1785      <address><email>henrikn@microsoft.com</email></address>
1786    </author>
1787    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1788      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1789      <address><email>LMM@acm.org</email></address>
1790    </author>
1791    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1792      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1793      <address><email>paulle@microsoft.com</email></address>
1794    </author>
1795    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1796      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1797      <address><email>timbl@w3.org</email></address>
1798    </author>
1799    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1800      <organization abbrev="W3C">World Wide Web Consortium</organization>
1801      <address><email>ylafon@w3.org</email></address>
1802    </author>
1803    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1804      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1805      <address><email>julian.reschke@greenbytes.de</email></address>
1806    </author>
1807    <date month="March" year="2011"/>
1808  </front>
1809  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-13"/>
1810 
1811</reference>
1812
1813<reference anchor="Part4">
1814  <front>
1815    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1816    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1817      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1818      <address><email>fielding@gbiv.com</email></address>
1819    </author>
1820    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1821      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1822      <address><email>jg@freedesktop.org</email></address>
1823    </author>
1824    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1825      <organization abbrev="HP">Hewlett-Packard Company</organization>
1826      <address><email>JeffMogul@acm.org</email></address>
1827    </author>
1828    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1829      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1830      <address><email>henrikn@microsoft.com</email></address>
1831    </author>
1832    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1833      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1834      <address><email>LMM@acm.org</email></address>
1835    </author>
1836    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1837      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1838      <address><email>paulle@microsoft.com</email></address>
1839    </author>
1840    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1841      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1842      <address><email>timbl@w3.org</email></address>
1843    </author>
1844    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1845      <organization abbrev="W3C">World Wide Web Consortium</organization>
1846      <address><email>ylafon@w3.org</email></address>
1847    </author>
1848    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1849      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1850      <address><email>julian.reschke@greenbytes.de</email></address>
1851    </author>
1852    <date month="March" year="2011"/>
1853  </front>
1854  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-13"/>
1855 
1856</reference>
1857
1858<reference anchor="Part5">
1859  <front>
1860    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1861    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1862      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1863      <address><email>fielding@gbiv.com</email></address>
1864    </author>
1865    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1866      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1867      <address><email>jg@freedesktop.org</email></address>
1868    </author>
1869    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1870      <organization abbrev="HP">Hewlett-Packard Company</organization>
1871      <address><email>JeffMogul@acm.org</email></address>
1872    </author>
1873    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1874      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1875      <address><email>henrikn@microsoft.com</email></address>
1876    </author>
1877    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1878      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1879      <address><email>LMM@acm.org</email></address>
1880    </author>
1881    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1882      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1883      <address><email>paulle@microsoft.com</email></address>
1884    </author>
1885    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1886      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1887      <address><email>timbl@w3.org</email></address>
1888    </author>
1889    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1890      <organization abbrev="W3C">World Wide Web Consortium</organization>
1891      <address><email>ylafon@w3.org</email></address>
1892    </author>
1893    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1894      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1895      <address><email>julian.reschke@greenbytes.de</email></address>
1896    </author>
1897    <date month="March" year="2011"/>
1898  </front>
1899  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-13"/>
1900 
1901</reference>
1902
1903<reference anchor="Part6">
1904  <front>
1905    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1906    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1907      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1908      <address><email>fielding@gbiv.com</email></address>
1909    </author>
1910    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1911      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1912      <address><email>jg@freedesktop.org</email></address>
1913    </author>
1914    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1915      <organization abbrev="HP">Hewlett-Packard Company</organization>
1916      <address><email>JeffMogul@acm.org</email></address>
1917    </author>
1918    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1919      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1920      <address><email>henrikn@microsoft.com</email></address>
1921    </author>
1922    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1923      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1924      <address><email>LMM@acm.org</email></address>
1925    </author>
1926    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1927      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1928      <address><email>paulle@microsoft.com</email></address>
1929    </author>
1930    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1931      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1932      <address><email>timbl@w3.org</email></address>
1933    </author>
1934    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1935      <organization abbrev="W3C">World Wide Web Consortium</organization>
1936      <address><email>ylafon@w3.org</email></address>
1937    </author>
1938    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1939      <address><email>mnot@mnot.net</email></address>
1940    </author>
1941    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1942      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1943      <address><email>julian.reschke@greenbytes.de</email></address>
1944    </author>
1945    <date month="March" year="2011"/>
1946  </front>
1947  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-13"/>
1948 
1949</reference>
1950
1951<reference anchor="RFC1864">
1952  <front>
1953    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
1954    <author initials="J." surname="Myers" fullname="John G. Myers">
1955      <organization>Carnegie Mellon University</organization>
1956      <address><email>jgm+@cmu.edu</email></address>
1957    </author>
1958    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
1959      <organization>Dover Beach Consulting, Inc.</organization>
1960      <address><email>mrose@dbc.mtview.ca.us</email></address>
1961    </author>
1962    <date month="October" year="1995"/>
1963  </front>
1964  <seriesInfo name="RFC" value="1864"/>
1965</reference>
1966
1967<reference anchor="RFC1950">
1968  <front>
1969    <title>ZLIB Compressed Data Format Specification version 3.3</title>
1970    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1971      <organization>Aladdin Enterprises</organization>
1972      <address><email>ghost@aladdin.com</email></address>
1973    </author>
1974    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
1975    <date month="May" year="1996"/>
1976  </front>
1977  <seriesInfo name="RFC" value="1950"/>
1978  <annotation>
1979    RFC 1950 is an Informational RFC, thus it might be less stable than
1980    this specification. On the other hand, this downward reference was
1981    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
1982    therefore it is unlikely to cause problems in practice. See also
1983    <xref target="BCP97"/>.
1984  </annotation>
1985</reference>
1986
1987<reference anchor="RFC1951">
1988  <front>
1989    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
1990    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1991      <organization>Aladdin Enterprises</organization>
1992      <address><email>ghost@aladdin.com</email></address>
1993    </author>
1994    <date month="May" year="1996"/>
1995  </front>
1996  <seriesInfo name="RFC" value="1951"/>
1997  <annotation>
1998    RFC 1951 is an Informational RFC, thus it might be less stable than
1999    this specification. On the other hand, this downward reference was
2000    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2001    therefore it is unlikely to cause problems in practice. See also
2002    <xref target="BCP97"/>.
2003  </annotation>
2004</reference>
2005
2006<reference anchor="RFC1952">
2007  <front>
2008    <title>GZIP file format specification version 4.3</title>
2009    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2010      <organization>Aladdin Enterprises</organization>
2011      <address><email>ghost@aladdin.com</email></address>
2012    </author>
2013    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2014      <address><email>gzip@prep.ai.mit.edu</email></address>
2015    </author>
2016    <author initials="M." surname="Adler" fullname="Mark Adler">
2017      <address><email>madler@alumni.caltech.edu</email></address>
2018    </author>
2019    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2020      <address><email>ghost@aladdin.com</email></address>
2021    </author>
2022    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2023      <address><email>randeg@alumni.rpi.edu</email></address>
2024    </author>
2025    <date month="May" year="1996"/>
2026  </front>
2027  <seriesInfo name="RFC" value="1952"/>
2028  <annotation>
2029    RFC 1952 is an Informational RFC, thus it might be less stable than
2030    this specification. On the other hand, this downward reference was
2031    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2032    therefore it is unlikely to cause problems in practice. See also
2033    <xref target="BCP97"/>.
2034  </annotation>
2035</reference>
2036
2037<reference anchor="RFC2045">
2038  <front>
2039    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2040    <author initials="N." surname="Freed" fullname="Ned Freed">
2041      <organization>Innosoft International, Inc.</organization>
2042      <address><email>ned@innosoft.com</email></address>
2043    </author>
2044    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2045      <organization>First Virtual Holdings</organization>
2046      <address><email>nsb@nsb.fv.com</email></address>
2047    </author>
2048    <date month="November" year="1996"/>
2049  </front>
2050  <seriesInfo name="RFC" value="2045"/>
2051</reference>
2052
2053<reference anchor="RFC2046">
2054  <front>
2055    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2056    <author initials="N." surname="Freed" fullname="Ned Freed">
2057      <organization>Innosoft International, Inc.</organization>
2058      <address><email>ned@innosoft.com</email></address>
2059    </author>
2060    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2061      <organization>First Virtual Holdings</organization>
2062      <address><email>nsb@nsb.fv.com</email></address>
2063    </author>
2064    <date month="November" year="1996"/>
2065  </front>
2066  <seriesInfo name="RFC" value="2046"/>
2067</reference>
2068
2069<reference anchor="RFC2119">
2070  <front>
2071    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2072    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2073      <organization>Harvard University</organization>
2074      <address><email>sob@harvard.edu</email></address>
2075    </author>
2076    <date month="March" year="1997"/>
2077  </front>
2078  <seriesInfo name="BCP" value="14"/>
2079  <seriesInfo name="RFC" value="2119"/>
2080</reference>
2081
2082<reference anchor="RFC4647">
2083  <front>
2084    <title>Matching of Language Tags</title>
2085    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2086      <organization>Yahoo! Inc.</organization>
2087      <address><email>addison@inter-locale.com</email></address>
2088    </author>
2089    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2090      <organization>Google</organization>
2091      <address><email>mark.davis@macchiato.com</email></address>
2092    </author>
2093    <date year="2006" month="September"/>
2094  </front>
2095  <seriesInfo name="BCP" value="47"/>
2096  <seriesInfo name="RFC" value="4647"/>
2097</reference>
2098
2099<reference anchor="RFC5234">
2100  <front>
2101    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2102    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2103      <organization>Brandenburg InternetWorking</organization>
2104      <address>
2105        <email>dcrocker@bbiw.net</email>
2106      </address> 
2107    </author>
2108    <author initials="P." surname="Overell" fullname="Paul Overell">
2109      <organization>THUS plc.</organization>
2110      <address>
2111        <email>paul.overell@thus.net</email>
2112      </address>
2113    </author>
2114    <date month="January" year="2008"/>
2115  </front>
2116  <seriesInfo name="STD" value="68"/>
2117  <seriesInfo name="RFC" value="5234"/>
2118</reference>
2119
2120<reference anchor="RFC5646">
2121  <front>
2122    <title>Tags for Identifying Languages</title>
2123    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2124      <organization>Lab126</organization>
2125      <address><email>addison@inter-locale.com</email></address>
2126    </author>
2127    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2128      <organization>Google</organization>
2129      <address><email>mark.davis@google.com</email></address>
2130    </author>
2131    <date month="September" year="2009"/>
2132  </front>
2133  <seriesInfo name="BCP" value="47"/>
2134  <seriesInfo name="RFC" value="5646"/>
2135</reference>
2136
2137</references>
2138
2139<references title="Informative References">
2140
2141<reference anchor="RFC1945">
2142  <front>
2143    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2144    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2145      <organization>MIT, Laboratory for Computer Science</organization>
2146      <address><email>timbl@w3.org</email></address>
2147    </author>
2148    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2149      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2150      <address><email>fielding@ics.uci.edu</email></address>
2151    </author>
2152    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2153      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2154      <address><email>frystyk@w3.org</email></address>
2155    </author>
2156    <date month="May" year="1996"/>
2157  </front>
2158  <seriesInfo name="RFC" value="1945"/>
2159</reference>
2160
2161<reference anchor="RFC2049">
2162  <front>
2163    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2164    <author initials="N." surname="Freed" fullname="Ned Freed">
2165      <organization>Innosoft International, Inc.</organization>
2166      <address><email>ned@innosoft.com</email></address>
2167    </author>
2168    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2169      <organization>First Virtual Holdings</organization>
2170      <address><email>nsb@nsb.fv.com</email></address>
2171    </author>
2172    <date month="November" year="1996"/>
2173  </front>
2174  <seriesInfo name="RFC" value="2049"/>
2175</reference>
2176
2177<reference anchor="RFC2068">
2178  <front>
2179    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2180    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2181      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2182      <address><email>fielding@ics.uci.edu</email></address>
2183    </author>
2184    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2185      <organization>MIT Laboratory for Computer Science</organization>
2186      <address><email>jg@w3.org</email></address>
2187    </author>
2188    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2189      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2190      <address><email>mogul@wrl.dec.com</email></address>
2191    </author>
2192    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2193      <organization>MIT Laboratory for Computer Science</organization>
2194      <address><email>frystyk@w3.org</email></address>
2195    </author>
2196    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2197      <organization>MIT Laboratory for Computer Science</organization>
2198      <address><email>timbl@w3.org</email></address>
2199    </author>
2200    <date month="January" year="1997"/>
2201  </front>
2202  <seriesInfo name="RFC" value="2068"/>
2203</reference>
2204
2205<reference anchor="RFC2076">
2206  <front>
2207    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2208    <author initials="J." surname="Palme" fullname="Jacob Palme">
2209      <organization>Stockholm University/KTH</organization>
2210      <address><email>jpalme@dsv.su.se</email></address>
2211    </author>
2212    <date month="February" year="1997"/>
2213  </front>
2214  <seriesInfo name="RFC" value="2076"/>
2215</reference>
2216
2217<reference anchor="RFC2277">
2218  <front>
2219    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2220    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2221      <organization>UNINETT</organization>
2222      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2223    </author>
2224    <date month="January" year="1998"/>
2225  </front>
2226  <seriesInfo name="BCP" value="18"/>
2227  <seriesInfo name="RFC" value="2277"/>
2228</reference>
2229
2230<reference anchor="RFC2295">
2231  <front>
2232    <title abbrev="HTTP Content Negotiation">Transparent Content Negotiation in HTTP</title>
2233    <author initials="K." surname="Holtman" fullname="Koen Holtman">
2234      <organization>Technische Universiteit Eindhoven</organization>
2235      <address>
2236        <email>koen@win.tue.nl</email>
2237      </address>
2238    </author>
2239    <author initials="A.H." surname="Mutz" fullname="Andrew H. Mutz">
2240      <organization>Hewlett-Packard Company</organization>
2241      <address>
2242        <email>mutz@hpl.hp.com</email>
2243      </address>
2244    </author>
2245    <date year="1998" month="March"/>
2246  </front>
2247  <seriesInfo name="RFC" value="2295"/>
2248</reference>
2249
2250<reference anchor="RFC2388">
2251  <front>
2252    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2253    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2254      <organization>Xerox Palo Alto Research Center</organization>
2255      <address><email>masinter@parc.xerox.com</email></address>
2256    </author>
2257    <date year="1998" month="August"/>
2258  </front>
2259  <seriesInfo name="RFC" value="2388"/>
2260</reference>
2261
2262<reference anchor="RFC2557">
2263  <front>
2264    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2265    <author initials="F." surname="Palme" fullname="Jacob Palme">
2266      <organization>Stockholm University and KTH</organization>
2267      <address><email>jpalme@dsv.su.se</email></address>
2268    </author>
2269    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2270      <organization>Microsoft Corporation</organization>
2271      <address><email>alexhop@microsoft.com</email></address>
2272    </author>
2273    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2274      <organization>Lotus Development Corporation</organization>
2275      <address><email>Shelness@lotus.com</email></address>
2276    </author>
2277    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2278      <address><email>stef@nma.com</email></address>
2279    </author>
2280    <date year="1999" month="March"/>
2281  </front>
2282  <seriesInfo name="RFC" value="2557"/>
2283</reference>
2284
2285<reference anchor="RFC2616">
2286  <front>
2287    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2288    <author initials="R." surname="Fielding" fullname="R. Fielding">
2289      <organization>University of California, Irvine</organization>
2290      <address><email>fielding@ics.uci.edu</email></address>
2291    </author>
2292    <author initials="J." surname="Gettys" fullname="J. Gettys">
2293      <organization>W3C</organization>
2294      <address><email>jg@w3.org</email></address>
2295    </author>
2296    <author initials="J." surname="Mogul" fullname="J. Mogul">
2297      <organization>Compaq Computer Corporation</organization>
2298      <address><email>mogul@wrl.dec.com</email></address>
2299    </author>
2300    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2301      <organization>MIT Laboratory for Computer Science</organization>
2302      <address><email>frystyk@w3.org</email></address>
2303    </author>
2304    <author initials="L." surname="Masinter" fullname="L. Masinter">
2305      <organization>Xerox Corporation</organization>
2306      <address><email>masinter@parc.xerox.com</email></address>
2307    </author>
2308    <author initials="P." surname="Leach" fullname="P. Leach">
2309      <organization>Microsoft Corporation</organization>
2310      <address><email>paulle@microsoft.com</email></address>
2311    </author>
2312    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2313      <organization>W3C</organization>
2314      <address><email>timbl@w3.org</email></address>
2315    </author>
2316    <date month="June" year="1999"/>
2317  </front>
2318  <seriesInfo name="RFC" value="2616"/>
2319</reference>
2320
2321<reference anchor="RFC3629">
2322  <front>
2323    <title>UTF-8, a transformation format of ISO 10646</title>
2324    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2325      <organization>Alis Technologies</organization>
2326      <address><email>fyergeau@alis.com</email></address>
2327    </author>
2328    <date month="November" year="2003"/>
2329  </front>
2330  <seriesInfo name="STD" value="63"/>
2331  <seriesInfo name="RFC" value="3629"/>
2332</reference>
2333
2334<reference anchor="RFC3864">
2335  <front>
2336    <title>Registration Procedures for Message Header Fields</title>
2337    <author initials="G." surname="Klyne" fullname="G. Klyne">
2338      <organization>Nine by Nine</organization>
2339      <address><email>GK-IETF@ninebynine.org</email></address>
2340    </author>
2341    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2342      <organization>BEA Systems</organization>
2343      <address><email>mnot@pobox.com</email></address>
2344    </author>
2345    <author initials="J." surname="Mogul" fullname="J. Mogul">
2346      <organization>HP Labs</organization>
2347      <address><email>JeffMogul@acm.org</email></address>
2348    </author>
2349    <date year="2004" month="September"/>
2350  </front>
2351  <seriesInfo name="BCP" value="90"/>
2352  <seriesInfo name="RFC" value="3864"/>
2353</reference>
2354
2355<reference anchor="RFC4288">
2356  <front>
2357    <title>Media Type Specifications and Registration Procedures</title>
2358    <author initials="N." surname="Freed" fullname="N. Freed">
2359      <organization>Sun Microsystems</organization>
2360      <address>
2361        <email>ned.freed@mrochek.com</email>
2362      </address>
2363    </author>
2364    <author initials="J." surname="Klensin" fullname="J. Klensin">
2365      <address>
2366        <email>klensin+ietf@jck.com</email>
2367      </address>
2368    </author>
2369    <date year="2005" month="December"/>
2370  </front>
2371  <seriesInfo name="BCP" value="13"/>
2372  <seriesInfo name="RFC" value="4288"/>
2373</reference>
2374
2375<reference anchor="RFC5226">
2376  <front>
2377    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2378    <author initials="T." surname="Narten" fullname="T. Narten">
2379      <organization>IBM</organization>
2380      <address><email>narten@us.ibm.com</email></address>
2381    </author>
2382    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2383      <organization>Google</organization>
2384      <address><email>Harald@Alvestrand.no</email></address>
2385    </author>
2386    <date year="2008" month="May"/>
2387  </front>
2388  <seriesInfo name="BCP" value="26"/>
2389  <seriesInfo name="RFC" value="5226"/>
2390</reference>
2391
2392<reference anchor="RFC5322">
2393  <front>
2394    <title>Internet Message Format</title>
2395    <author initials="P." surname="Resnick" fullname="P. Resnick">
2396      <organization>Qualcomm Incorporated</organization>
2397    </author>
2398    <date year="2008" month="October"/>
2399  </front>
2400  <seriesInfo name="RFC" value="5322"/>
2401</reference>
2402
2403<reference anchor="BCP97">
2404  <front>
2405    <title>Handling Normative References to Standards-Track Documents</title>
2406    <author initials="J." surname="Klensin" fullname="J. Klensin">
2407      <address>
2408        <email>klensin+ietf@jck.com</email>
2409      </address>
2410    </author>
2411    <author initials="S." surname="Hartman" fullname="S. Hartman">
2412      <organization>MIT</organization>
2413      <address>
2414        <email>hartmans-ietf@mit.edu</email>
2415      </address>
2416    </author>
2417    <date year="2007" month="June"/>
2418  </front>
2419  <seriesInfo name="BCP" value="97"/>
2420  <seriesInfo name="RFC" value="4897"/>
2421</reference>
2422
2423
2424</references>
2425
2426<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2427<t>
2428   HTTP/1.1 uses many of the constructs defined for Internet Mail (<xref target="RFC5322"/>) and the Multipurpose Internet Mail Extensions (MIME <xref target="RFC2045"/>) to
2429   allow a message-body to be transmitted in an open variety of
2430   representations and with extensible mechanisms. However, RFC 2045
2431   discusses mail, and HTTP has a few features that are different from
2432   those described in MIME. These differences were carefully chosen
2433   to optimize performance over binary connections, to allow greater
2434   freedom in the use of new media types, to make date comparisons
2435   easier, and to acknowledge the practice of some early HTTP servers
2436   and clients.
2437</t>
2438<t>
2439   This appendix describes specific areas where HTTP differs from MIME.
2440   Proxies and gateways to strict MIME environments SHOULD be
2441   aware of these differences and provide the appropriate conversions
2442   where necessary. Proxies and gateways from MIME environments to HTTP
2443   also need to be aware of the differences because some conversions
2444   might be required.
2445</t>
2446
2447<section title="MIME-Version" anchor="mime-version">
2448  <iref primary="true" item="MIME-Version header field"/>
2449  <iref primary="true" item="Header Fields" subitem="MIME-Version"/>
2450 
2451 
2452<t>
2453   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
2454   include a single MIME-Version header field to indicate what
2455   version of the MIME protocol was used to construct the message. Use
2456   of the MIME-Version header field indicates that the message is in
2457   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2458   Proxies/gateways are responsible for ensuring full compliance (where
2459   possible) when exporting HTTP messages to strict MIME environments.
2460</t>
2461<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/><artwork type="abnf2616"><![CDATA[
2462  MIME-Version   = "MIME-Version" ":" OWS MIME-Version-v
2463  MIME-Version-v = 1*DIGIT "." 1*DIGIT
2464]]></artwork></figure>
2465<t>
2466   MIME version "1.0" is the default for use in HTTP/1.1. However,
2467   HTTP/1.1 message parsing and semantics are defined by this document
2468   and not the MIME specification.
2469</t>
2470</section>
2471
2472<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2473<t>
2474   MIME requires that an Internet mail body-part be converted to
2475   canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
2476   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2477   allowed for subtypes of the "text" media type when transmitted over
2478   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2479   line breaks as CRLF and forbids the use of CR or LF outside of line
2480   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2481   line break within text content when a message is transmitted over
2482   HTTP.
2483</t>
2484<t>
2485   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2486   environment SHOULD translate all line breaks within the text media
2487   types described in <xref target="canonicalization.and.text.defaults"/>
2488   of this document to the RFC 2049
2489   canonical form of CRLF. Note, however, that this might be complicated
2490   by the presence of a Content-Encoding and by the fact that HTTP
2491   allows the use of some character encodings which do not use octets 13 and
2492   10 to represent CR and LF, respectively, as is the case for some multi-byte
2493   character encodings.
2494</t>
2495<t>
2496   Conversion will break any cryptographic
2497   checksums applied to the original content unless the original content
2498   is already in canonical form. Therefore, the canonical form is
2499   recommended for any content that uses such checksums in HTTP.
2500</t>
2501</section>
2502
2503
2504<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2505<t>
2506   HTTP/1.1 uses a restricted set of date formats (Section 6.1 of <xref target="Part1"/>) to
2507   simplify the process of date comparison. Proxies and gateways from
2508   other protocols SHOULD ensure that any Date header field present in a
2509   message conforms to one of the HTTP/1.1 formats and rewrite the date
2510   if necessary.
2511</t>
2512</section>
2513
2514<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2515<t>
2516   MIME does not include any concept equivalent to HTTP/1.1's
2517   Content-Encoding header field. Since this acts as a modifier on the
2518   media type, proxies and gateways from HTTP to MIME-compliant
2519   protocols MUST either change the value of the Content-Type header
2520   field or decode the representation before forwarding the message. (Some
2521   experimental applications of Content-Type for Internet mail have used
2522   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2523   a function equivalent to Content-Encoding. However, this parameter is
2524   not part of the MIME standards).
2525</t>
2526</section>
2527
2528<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2529<t>
2530   HTTP does not use the Content-Transfer-Encoding field of MIME.
2531   Proxies and gateways from MIME-compliant protocols to HTTP MUST
2532   remove any Content-Transfer-Encoding
2533   prior to delivering the response message to an HTTP client.
2534</t>
2535<t>
2536   Proxies and gateways from HTTP to MIME-compliant protocols are
2537   responsible for ensuring that the message is in the correct format
2538   and encoding for safe transport on that protocol, where "safe
2539   transport" is defined by the limitations of the protocol being used.
2540   Such a proxy or gateway SHOULD label the data with an appropriate
2541   Content-Transfer-Encoding if doing so will improve the likelihood of
2542   safe transport over the destination protocol.
2543</t>
2544</section>
2545
2546<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2547<t>
2548   HTTP/1.1 introduces the Transfer-Encoding header field (Section 9.7 of <xref target="Part1"/>).
2549   Proxies/gateways MUST remove any transfer-coding prior to
2550   forwarding a message via a MIME-compliant protocol.
2551</t>
2552</section>
2553
2554<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2555<t>
2556   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2557   need to be aware of MIME line length limitations. Since HTTP does not
2558   have this limitation, HTTP does not fold long lines. MHTML messages
2559   being transported by HTTP follow all conventions of MHTML, including
2560   line length limitations and folding, canonicalization, etc., since
2561   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2562   does not interpret the content or any MIME header lines that might be
2563   contained therein.
2564</t>
2565</section>
2566</section>
2567
2568<section title="Additional Features" anchor="additional.features">
2569<t>
2570   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2571   existing HTTP implementations, but not consistently and correctly
2572   across most HTTP/1.1 applications. Implementors are advised to be
2573   aware of these features, but cannot rely upon their presence in, or
2574   interoperability with, other HTTP/1.1 applications. Some of these
2575   describe proposed experimental features, and some describe features
2576   that experimental deployment found lacking that are now addressed in
2577   the base HTTP/1.1 specification.
2578</t>
2579<t>
2580   A number of other header fields, such as Content-Disposition and Title,
2581   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2582</t>
2583</section>
2584
2585<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2586<t>
2587  Clarify contexts that charset is used in.
2588  (<xref target="character.sets"/>)
2589</t>
2590<t>
2591  Remove base URI setting semantics for Content-Location due to poor
2592  implementation support, which was caused by too many broken servers emitting
2593  bogus Content-Location header fields, and also the potentially undesirable effect
2594  of potentially breaking relative links in content-negotiated resources.
2595  (<xref target="header.content-location"/>)
2596</t>
2597<t>
2598  Remove reference to non-existant identity transfer-coding value tokens.
2599  (<xref target="no.content-transfer-encoding"/>)
2600</t>
2601</section>
2602
2603
2604<section title="Collected ABNF" anchor="collected.abnf">
2605<figure>
2606<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
2607Accept = "Accept:" OWS Accept-v
2608Accept-Charset = "Accept-Charset:" OWS Accept-Charset-v
2609Accept-Charset-v = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2610 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2611 qvalue ] ] )
2612Accept-Encoding = "Accept-Encoding:" OWS Accept-Encoding-v
2613Accept-Encoding-v = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2614 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2615Accept-Language = "Accept-Language:" OWS Accept-Language-v
2616Accept-Language-v = *( "," OWS ) language-range [ OWS ";" OWS "q="
2617 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2618 ] )
2619Accept-v = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2620 OWS media-range [ accept-params ] ] ) ]
2621
2622Content-Encoding = "Content-Encoding:" OWS Content-Encoding-v
2623Content-Encoding-v = *( "," OWS ) content-coding *( OWS "," [ OWS
2624 content-coding ] )
2625Content-Language = "Content-Language:" OWS Content-Language-v
2626Content-Language-v = *( "," OWS ) language-tag *( OWS "," [ OWS
2627 language-tag ] )
2628Content-Location = "Content-Location:" OWS Content-Location-v
2629Content-Location-v = absolute-URI / partial-URI
2630Content-MD5 = "Content-MD5:" OWS Content-MD5-v
2631Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
2632Content-Type = "Content-Type:" OWS Content-Type-v
2633Content-Type-v = media-type
2634
2635MIME-Version = "MIME-Version:" OWS MIME-Version-v
2636MIME-Version-v = 1*DIGIT "." 1*DIGIT
2637
2638OWS = <OWS, defined in [Part1], Section 1.2.2>
2639
2640absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
2641accept-ext = OWS ";" OWS token [ "=" word ]
2642accept-params = OWS ";" OWS "q=" qvalue *accept-ext
2643attribute = token
2644
2645charset = token
2646codings = ( content-coding / "*" )
2647content-coding = token
2648
2649language-range = <language-range, defined in [RFC4647], Section 2.1>
2650language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
2651
2652media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2653 ";" OWS parameter )
2654media-type = type "/" subtype *( OWS ";" OWS parameter )
2655
2656parameter = attribute "=" value
2657partial-URI = <partial-URI, defined in [Part1], Section 2.6>
2658
2659qvalue = <qvalue, defined in [Part1], Section 6.4>
2660
2661subtype = token
2662
2663token = <token, defined in [Part1], Section 1.2.2>
2664type = token
2665
2666value = word
2667
2668word = <word, defined in [Part1], Section 1.2.2>
2669]]></artwork>
2670</figure>
2671<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
2672; Accept defined but not used
2673; Accept-Charset defined but not used
2674; Accept-Encoding defined but not used
2675; Accept-Language defined but not used
2676; Content-Encoding defined but not used
2677; Content-Language defined but not used
2678; Content-Location defined but not used
2679; Content-MD5 defined but not used
2680; Content-Type defined but not used
2681; MIME-Version defined but not used
2682]]></artwork></figure></section>
2683
2684
2685<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2686
2687<section title="Since RFC 2616">
2688<t>
2689  Extracted relevant partitions from <xref target="RFC2616"/>.
2690</t>
2691</section>
2692
2693<section title="Since draft-ietf-httpbis-p3-payload-00">
2694<t>
2695  Closed issues:
2696  <list style="symbols">
2697    <t>
2698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2699      "Media Type Registrations"
2700      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2701    </t>
2702    <t>
2703      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2704      "Clarification regarding quoting of charset values"
2705      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2706    </t>
2707    <t>
2708      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2709      "Remove 'identity' token references"
2710      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2711    </t>
2712    <t>
2713      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2714      "Accept-Encoding BNF"
2715    </t>
2716    <t>
2717      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2718      "Normative and Informative references"
2719    </t>
2720    <t>
2721      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2722      "RFC1700 references"
2723    </t>
2724    <t>
2725      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2726      "Updating to RFC4288"
2727    </t>
2728    <t>
2729      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2730      "Informative references"
2731    </t>
2732    <t>
2733      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2734      "ISO-8859-1 Reference"
2735    </t>
2736    <t>
2737      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2738      "Encoding References Normative"
2739    </t>
2740    <t>
2741      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2742      "Normative up-to-date references"
2743    </t>
2744  </list>
2745</t>
2746</section>
2747
2748<section title="Since draft-ietf-httpbis-p3-payload-01">
2749<t>
2750  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2751  <list style="symbols">
2752    <t>
2753      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2754    </t>
2755  </list>
2756</t>
2757</section>
2758
2759<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2760<t>
2761  Closed issues:
2762  <list style="symbols">
2763    <t>
2764      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2765      "Quoting Charsets"
2766    </t>
2767    <t>
2768      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2769      "Classification for Allow header"
2770    </t>
2771    <t>
2772      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2773      "missing default for qvalue in description of Accept-Encoding"
2774    </t>
2775  </list>
2776</t>
2777<t>
2778  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2779  <list style="symbols">
2780    <t>
2781      Reference RFC 3984, and update header field registrations for headers defined
2782      in this document.
2783    </t>
2784  </list>
2785</t>
2786</section>
2787
2788<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2789<t>
2790  Closed issues:
2791  <list style="symbols">
2792    <t>
2793      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2794      "Quoting Charsets"
2795    </t>
2796    <t>
2797      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2798      "language tag matching (Accept-Language) vs RFC4647"
2799    </t>
2800    <t>
2801      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2802      "RFC 1806 has been replaced by RFC2183"
2803    </t>
2804  </list>
2805</t>
2806<t>
2807  Other changes:
2808  <list style="symbols">
2809    <t>
2810      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2811      "Encoding References Normative" — rephrase the annotation and reference
2812      <xref target="BCP97"/>.
2813    </t>
2814  </list>
2815</t>
2816 </section>
2817
2818<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2819<t>
2820  Closed issues:
2821  <list style="symbols">
2822    <t>
2823      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2824      "RFC 2822 is updated by RFC 5322"
2825    </t>
2826  </list>
2827</t>
2828<t>
2829  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2830  <list style="symbols">
2831    <t>
2832      Use "/" instead of "|" for alternatives.
2833    </t>
2834    <t>
2835      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2836      whitespace ("OWS") and required whitespace ("RWS").
2837    </t>
2838    <t>
2839      Rewrite ABNFs to spell out whitespace rules, factor out
2840      header field value format definitions.
2841    </t>
2842  </list>
2843</t>
2844</section>
2845
2846<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2847<t>
2848  Closed issues:
2849  <list style="symbols">
2850    <t>
2851      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
2852      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2853    </t>
2854  </list>
2855</t>
2856<t>
2857  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2858  <list style="symbols">
2859    <t>
2860      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
2861    </t>
2862  </list>
2863</t>
2864<t>
2865  Other changes:
2866  <list style="symbols">
2867    <t>
2868      Move definition of quality values into Part 1.
2869    </t>
2870  </list>
2871</t>
2872</section>
2873
2874<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
2875<t>
2876  Closed issues:
2877  <list style="symbols">
2878    <t>
2879      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2880      "Content-Location isn't special"
2881    </t>
2882    <t>
2883      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2884      "Content Sniffing"
2885    </t>
2886  </list>
2887</t>
2888</section>
2889
2890<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
2891<t>
2892  Closed issues:
2893  <list style="symbols">
2894    <t>
2895      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
2896      "Updated reference for language tags"
2897    </t>
2898    <t>
2899      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
2900      "Clarify rules for determining what entities a response carries"
2901    </t>
2902    <t>
2903      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
2904      "Content-Location base-setting problems"
2905    </t>
2906    <t>
2907      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2908      "Content Sniffing"
2909    </t>
2910    <t>
2911      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
2912      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2913    </t>
2914    <t>
2915      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
2916      "move definitions of gzip/deflate/compress to part 1"
2917    </t>
2918  </list>
2919</t>
2920<t>
2921  Partly resolved issues:
2922  <list style="symbols">
2923    <t>
2924      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
2925      "update IANA requirements wrt Transfer-Coding values" (add the
2926      IANA Considerations subsection)
2927    </t>
2928    <t>
2929      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
2930      "update IANA requirements wrt Content-Coding values" (add the
2931      IANA Considerations subsection)
2932    </t>
2933  </list>
2934</t>
2935</section>
2936
2937<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
2938<t>
2939  Closed issues:
2940  <list style="symbols">
2941    <t>
2942      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
2943      "Content Negotiation for media types"
2944    </t>
2945    <t>
2946      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
2947      "Accept-Language: which RFC4647 filtering?"
2948    </t>
2949  </list>
2950</t>
2951</section>
2952
2953<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
2954<t>
2955  Closed issues:
2956  <list style="symbols">
2957    <t>
2958      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
2959      "MIME-Version not listed in P1, general header fields"
2960    </t>
2961    <t>
2962      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
2963      "IANA registry for content/transfer encodings"
2964    </t>
2965    <t>
2966      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2967      "Content Sniffing"
2968    </t>
2969    <t>
2970      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
2971      "use of term "word" when talking about header structure"
2972    </t>
2973  </list>
2974</t>
2975<t>
2976  Partly resolved issues:
2977  <list style="symbols">
2978    <t>
2979      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
2980      "Term for the requested resource's URI"
2981    </t>
2982  </list>
2983</t>
2984</section>
2985
2986<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
2987<t>
2988  Closed issues:
2989  <list style="symbols">
2990    <t>
2991      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
2992      "Clarify 'Requested Variant'"
2993    </t>
2994    <t>
2995      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2996      "Content-Location isn't special"
2997    </t>
2998    <t>
2999      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
3000      "Delimiting messages with multipart/byteranges"
3001    </t>
3002    <t>
3003      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3004      "Clarify entity / representation / variant terminology"
3005    </t>
3006    <t>
3007      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
3008      "confusing req. language for Content-Location"
3009    </t>
3010    <t>
3011      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
3012      "Content-Location on 304 responses"
3013    </t>
3014    <t>
3015      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
3016      "'requested resource' in content-encoding definition"
3017    </t>
3018    <t>
3019      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3020      "consider removing the 'changes from 2068' sections"
3021    </t>
3022  </list>
3023</t>
3024<t>
3025  Partly resolved issues:
3026  <list style="symbols">
3027    <t>
3028      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3029      "Content-MD5 and partial responses"
3030    </t>
3031  </list>
3032</t>
3033</section>
3034
3035<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
3036<t>
3037  Closed issues:
3038  <list style="symbols">
3039    <t>
3040      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/123"/>:
3041      "Factor out Content-Disposition"
3042    </t>
3043  </list>
3044</t>
3045</section>
3046
3047<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
3048<t>
3049  Closed issues:
3050  <list style="symbols">
3051    <t>
3052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
3053      "Header Classification"
3054    </t>
3055    <t>
3056      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
3057      "untangle ABNFs for header fields"
3058    </t>
3059    <t>
3060      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/277"/>:
3061      "potentially misleading MAY in media-type def"
3062    </t>
3063  </list>
3064</t>
3065</section>
3066
3067</section>
3068
3069</back>
3070</rfc>
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