source: draft-ietf-httpbis/12/draft-ietf-httpbis-p3-payload-12.xml @ 1338

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prepare publication of -12 drafts on 2010-10-25

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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-12">
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="Day Software">Day Software</organization>
26    <address>
27      <postal>
28        <street>23 Corporate Plaza DR, Suite 280</street>
29        <city>Newport Beach</city>
30        <region>CA</region>
31        <code>92660</code>
32        <country>USA</country>
33      </postal>
34      <phone>+1-949-706-5300</phone>
35      <facsimile>+1-949-706-5305</facsimile>
36      <email>fielding@gbiv.com</email>
37      <uri>http://roy.gbiv.com/</uri>
38    </address>
39  </author>
40
41  <author initials="J." surname="Gettys" fullname="Jim Gettys">
42    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
43    <address>
44      <postal>
45        <street>21 Oak Knoll Road</street>
46        <city>Carlisle</city>
47        <region>MA</region>
48        <code>01741</code>
49        <country>USA</country>
50      </postal>
51      <email>jg@freedesktop.org</email>
52      <uri>http://gettys.wordpress.com/</uri>
53    </address>
54  </author>
55 
56  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
57    <organization abbrev="HP">Hewlett-Packard Company</organization>
58    <address>
59      <postal>
60        <street>HP Labs, Large Scale Systems Group</street>
61        <street>1501 Page Mill Road, MS 1177</street>
62        <city>Palo Alto</city>
63        <region>CA</region>
64        <code>94304</code>
65        <country>USA</country>
66      </postal>
67      <email>JeffMogul@acm.org</email>
68    </address>
69  </author>
70
71  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
72    <organization abbrev="Microsoft">Microsoft Corporation</organization>
73    <address>
74      <postal>
75        <street>1 Microsoft Way</street>
76        <city>Redmond</city>
77        <region>WA</region>
78        <code>98052</code>
79        <country>USA</country>
80      </postal>
81      <email>henrikn@microsoft.com</email>
82    </address>
83  </author>
84
85  <author initials="L." surname="Masinter" fullname="Larry Masinter">
86    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
87    <address>
88      <postal>
89        <street>345 Park Ave</street>
90        <city>San Jose</city>
91        <region>CA</region>
92        <code>95110</code>
93        <country>USA</country>
94      </postal>
95      <email>LMM@acm.org</email>
96      <uri>http://larry.masinter.net/</uri>
97    </address>
98  </author>
99 
100  <author initials="P." surname="Leach" fullname="Paul J. Leach">
101    <organization abbrev="Microsoft">Microsoft Corporation</organization>
102    <address>
103      <postal>
104        <street>1 Microsoft Way</street>
105        <city>Redmond</city>
106        <region>WA</region>
107        <code>98052</code>
108      </postal>
109      <email>paulle@microsoft.com</email>
110    </address>
111  </author>
112   
113  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
114    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
115    <address>
116      <postal>
117        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
118        <street>The Stata Center, Building 32</street>
119        <street>32 Vassar Street</street>
120        <city>Cambridge</city>
121        <region>MA</region>
122        <code>02139</code>
123        <country>USA</country>
124      </postal>
125      <email>timbl@w3.org</email>
126      <uri>http://www.w3.org/People/Berners-Lee/</uri>
127    </address>
128  </author>
129
130  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
131    <organization abbrev="W3C">World Wide Web Consortium</organization>
132    <address>
133      <postal>
134        <street>W3C / ERCIM</street>
135        <street>2004, rte des Lucioles</street>
136        <city>Sophia-Antipolis</city>
137        <region>AM</region>
138        <code>06902</code>
139        <country>France</country>
140      </postal>
141      <email>ylafon@w3.org</email>
142      <uri>http://www.raubacapeu.net/people/yves/</uri>
143    </address>
144  </author>
145
146  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
147    <organization abbrev="greenbytes">greenbytes GmbH</organization>
148    <address>
149      <postal>
150        <street>Hafenweg 16</street>
151        <city>Muenster</city><region>NW</region><code>48155</code>
152        <country>Germany</country>
153      </postal>
154      <phone>+49 251 2807760</phone>
155      <facsimile>+49 251 2807761</facsimile>
156      <email>julian.reschke@greenbytes.de</email>
157      <uri>http://greenbytes.de/tech/webdav/</uri>
158    </address>
159  </author>
160
161  <date month="October" year="2010" day="25"/>
162  <workgroup>HTTPbis Working Group</workgroup>
163
164<abstract>
165<t>
166   The Hypertext Transfer Protocol (HTTP) is an application-level
167   protocol for distributed, collaborative, hypermedia information
168   systems. HTTP has been in use by the World Wide Web global information
169   initiative since 1990. This document is Part 3 of the seven-part specification
170   that defines the protocol referred to as "HTTP/1.1" and, taken together,
171   obsoletes RFC 2616.  Part 3 defines HTTP message content,
172   metadata, and content negotiation.
173</t>
174</abstract>
175
176<note title="Editorial Note (To be removed by RFC Editor)">
177  <t>
178    Discussion of this draft should take place on the HTTPBIS working group
179    mailing list (ietf-http-wg@w3.org). The current issues list is
180    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
181    and related documents (including fancy diffs) can be found at
182    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
183  </t>
184  <t>
185    The changes in this draft are summarized in <xref target="changes.since.11"/>.
186  </t>
187</note>
188</front>
189<middle>
190<section title="Introduction" anchor="introduction">
191<t>
192   This document defines HTTP/1.1 message payloads (a.k.a., content), the
193   associated metadata header fields that define how the payload is intended
194   to be interpreted by a recipient, the request header fields that
195   might influence content selection, and the various selection algorithms
196   that are collectively referred to as HTTP content negotiation.
197</t>
198<t>
199   This document is currently disorganized in order to minimize the changes
200   between drafts and enable reviewers to see the smaller errata changes.
201   A future draft will reorganize the sections to better reflect the content.
202   In particular, the sections on entities will be renamed payload and moved
203   to the first half of the document, while the sections on content negotiation
204   and associated request header fields will be moved to the second half.  The
205   current mess reflects how widely dispersed these topics and associated
206   requirements had become in <xref target="RFC2616"/>.
207</t>
208
209<section title="Terminology" anchor="terminology">
210<t>
211   This specification uses a number of terms to refer to the roles
212   played by participants in, and objects of, the HTTP communication.
213</t>
214<t>
215  <iref item="content negotiation"/>
216  <?rfc needLines="4"?>content negotiation
217  <list>
218    <t>
219      The mechanism for selecting the appropriate representation when
220      servicing a request. The representation in any response
221      can be negotiated (including error responses).
222    </t>
223  </list>
224</t>
225</section>
226
227<section title="Requirements" anchor="intro.requirements">
228<t>
229   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
230   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
231   document are to be interpreted as described in <xref target="RFC2119"/>.
232</t>
233<t>
234   An implementation is not compliant if it fails to satisfy one or more
235   of the "MUST" or "REQUIRED" level requirements for the protocols it
236   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
237   level and all the "SHOULD" level requirements for its protocols is said
238   to be "unconditionally compliant"; one that satisfies all the "MUST"
239   level requirements but not all the "SHOULD" level requirements for its
240   protocols is said to be "conditionally compliant".
241</t>
242</section>
243
244<section title="Syntax Notation" anchor="notation">
245 
246 
247 
248 
249 
250 
251 
252<t>
253  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
254  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
255  <xref target="collected.abnf"/> shows the collected ABNF, with the list
256  rule expanded.
257</t>
258<t>
259  The following core rules are included by
260  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
261  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
262  DIGIT (decimal 0-9), DQUOTE (double quote),
263  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
264  OCTET (any 8-bit sequence of data), SP (space),
265  VCHAR (any visible USASCII character),
266  and WSP (whitespace).
267</t>
268
269<section title="Core Rules" anchor="core.rules">
270 
271 
272 
273<t>
274  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
275</t>
276<figure><artwork type="abnf2616"><![CDATA[
277  token          = <token, defined in [Part1], Section 1.2.2>
278  word           = <word, defined in [Part1], Section 1.2.2>
279  OWS            = <OWS, defined in [Part1], Section 1.2.2>
280]]></artwork></figure>
281</section>
282
283<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
284 
285 
286 
287 
288 
289 
290 
291 
292<t>
293  The ABNF rules below are defined in other parts:
294</t>
295<figure><artwork type="abnf2616"><![CDATA[
296  absolute-URI   = <absolute-URI, defined in [Part1], Section 2.6>
297  Content-Length = <Content-Length, defined in [Part1], Section 9.2>
298  partial-URI    = <partial-URI, defined in [Part1], Section 2.6>
299  qvalue         = <qvalue, defined in [Part1], Section 6.4>
300]]></artwork></figure>
301<figure><artwork type="abnf2616"><![CDATA[
302  Last-Modified  = <Last-Modified, defined in [Part4], Section 6.6>
303]]></artwork></figure>
304<figure><artwork type="abnf2616"><![CDATA[
305  Content-Range  = <Content-Range, defined in [Part5], Section 5.2>
306]]></artwork></figure>
307<figure><artwork type="abnf2616"><![CDATA[
308  Expires        = <Expires, defined in [Part6], Section 3.3>
309]]></artwork></figure>
310</section>
311
312</section>
313
314</section>
315
316<section title="Protocol Parameters" anchor="protocol.parameters">
317
318<section title="Character Sets" anchor="character.sets">
319<t>
320   HTTP uses the same definition of the term "character set" as that
321   described for MIME:
322</t>
323<t>
324   The term "character set" is used in this document to refer to a
325   method used with one or more tables to convert a sequence of octets
326   into a sequence of characters. Note that unconditional conversion in
327   the other direction is not required, in that not all characters might
328   be available in a given character set and a character set might provide
329   more than one sequence of octets to represent a particular character.
330   This definition is intended to allow various kinds of character
331   encoding, from simple single-table mappings such as US-ASCII to
332   complex table switching methods such as those that use ISO-2022's
333   techniques. However, the definition associated with a MIME character
334   set name MUST fully specify the mapping to be performed from octets
335   to characters. In particular, use of external profiling information
336   to determine the exact mapping is not permitted.
337</t>
338<t><list>
339  <t>
340    Note: This use of the term "character set" is more commonly
341    referred to as a "character encoding". However, since HTTP and
342    MIME share the same registry, it is important that the terminology
343    also be shared.
344  </t>
345</list></t>
346<t anchor="rule.charset">
347 
348   HTTP character sets are identified by case-insensitive tokens. The
349   complete set of tokens is defined by the IANA Character Set registry
350   (<eref target="http://www.iana.org/assignments/character-sets"/>).
351</t>
352<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
353  charset = token
354]]></artwork></figure>
355<t>
356   Although HTTP allows an arbitrary token to be used as a charset
357   value, any token that has a predefined value within the IANA
358   Character Set registry MUST represent the character set defined
359   by that registry. Applications SHOULD limit their use of character
360   sets to those defined by the IANA registry.
361</t>
362<t>
363   HTTP uses charset in two contexts: within an Accept-Charset request
364   header field (in which the charset value is an unquoted token) and as the
365   value of a parameter in a Content-Type header field (within a request or
366   response), in which case the parameter value of the charset parameter
367   can be quoted.
368</t>
369<t>
370   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
371   <xref target="RFC2277"/>.
372</t>
373
374<section title="Missing Charset" anchor="missing.charset">
375<t>
376   Some HTTP/1.0 software has interpreted a Content-Type header field without
377   charset parameter incorrectly to mean "recipient should guess".
378   Senders wishing to defeat this behavior MAY include a charset
379   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and SHOULD do so when
380   it is known that it will not confuse the recipient.
381</t>
382<t>
383   Unfortunately, some older HTTP/1.0 clients did not deal properly with
384   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
385   charset label provided by the sender; and those user agents that have
386   a provision to "guess" a charset MUST use the charset from the
387   content-type field if they support that charset, rather than the
388   recipient's preference, when initially displaying a document. See
389   <xref target="canonicalization.and.text.defaults"/>.
390</t>
391</section>
392</section>
393
394<section title="Content Codings" anchor="content.codings">
395 
396<t>
397   Content coding values indicate an encoding transformation that has
398   been or can be applied to a representation. Content codings are primarily
399   used to allow a representation to be compressed or otherwise usefully
400   transformed without losing the identity of its underlying media type
401   and without loss of information. Frequently, the representation is stored in
402   coded form, transmitted directly, and only decoded by the recipient.
403</t>
404<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
405  content-coding   = token
406]]></artwork></figure>
407<t>
408   All content-coding values are case-insensitive. HTTP/1.1 uses
409   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
410   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
411   describes the content-coding, what is more important is that it
412   indicates what decoding mechanism will be required to remove the
413   encoding.
414</t>
415<t>
416   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
417  <list>
418    <t>
419      See Section 6.2.2.1 of <xref target="Part1"/>.
420    </t>
421  </list>
422</t>
423<t>
424   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
425  <list>
426    <t>
427      See Section 6.2.2.2 of <xref target="Part1"/>.
428    </t>
429  </list>
430</t>
431<t>
432   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
433  <list>
434    <t>
435      See Section 6.2.2.3 of <xref target="Part1"/>.
436    </t>
437  </list>
438</t>
439<t>
440   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
441  <list><t>
442        The default (identity) encoding; the use of no transformation
443        whatsoever. This content-coding is used only in the Accept-Encoding
444        header field, and SHOULD NOT  be used in the Content-Encoding
445        header field.
446  </t></list>
447</t>
448
449<section title="Content Coding Registry" anchor="content.coding.registry">
450<t>
451   The HTTP Content Coding Registry defines the name space for the content
452   coding names.
453</t>
454<t>
455   Registrations MUST include the following fields:
456   <list style="symbols">
457     <t>Name</t>
458     <t>Description</t>
459     <t>Pointer to specification text</t>
460   </list>
461</t>
462<t>
463   Names of content codings MUST NOT overlap with names of transfer codings
464   (Section 6.2 of <xref target="Part1"/>), unless the encoding transformation is identical (as it
465   is the case for the compression codings defined in
466   Section 6.2.2 of <xref target="Part1"/>).
467</t>
468<t>
469   Values to be added to this name space require a specification
470   (see "Specification Required" in
471   Section 4.1 of <xref target="RFC5226"/>), and MUST
472   conform to the purpose of content coding defined in this section.
473</t>
474<t>
475   The registry itself is maintained at
476   <eref target="http://www.iana.org/assignments/http-parameters"/>.
477</t>
478</section>
479
480</section>
481
482<section title="Media Types" anchor="media.types">
483 
484 
485 
486<t>
487   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
488   and Accept (<xref target="header.accept"/>) header fields in order to provide
489   open and extensible data typing and type negotiation.
490</t>
491<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[
492  media-type = type "/" subtype *( OWS ";" OWS parameter )
493  type       = token
494  subtype    = token
495]]></artwork></figure>
496<t anchor="rule.parameter">
497 
498 
499 
500   Parameters MAY follow the type/subtype in the form of attribute/value
501   pairs.
502</t>
503<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[
504  parameter      = attribute "=" value
505  attribute      = token
506  value          = word
507]]></artwork></figure>
508<t>
509   The type, subtype, and parameter attribute names are case-insensitive.
510   Parameter values might or might not be case-sensitive, depending on the
511   semantics of the parameter name.  The presence or absence of a parameter might
512   be significant to the processing of a media-type, depending on its
513   definition within the media type registry.
514</t>
515<t>
516   A parameter value that matches the <xref target="core.rules" format="none">token</xref> production can be
517   transmitted as either a token or within a quoted-string. The quoted and
518   unquoted values are equivalent.
519</t>
520<t>
521   Note that some older HTTP applications do not recognize media type
522   parameters. When sending data to older HTTP applications,
523   implementations SHOULD only use media type parameters when they are
524   required by that type/subtype definition.
525</t>
526<t>
527   Media-type values are registered with the Internet Assigned Number
528   Authority (IANA). The media type registration process is
529   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
530   discouraged.
531</t>
532
533<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
534<t>
535   Internet media types are registered with a canonical form. A
536   representation transferred via HTTP messages MUST be in the
537   appropriate canonical form prior to its transmission except for
538   "text" types, as defined in the next paragraph.
539</t>
540<t>
541   When in canonical form, media subtypes of the "text" type use CRLF as
542   the text line break. HTTP relaxes this requirement and allows the
543   transport of text media with plain CR or LF alone representing a line
544   break when it is done consistently for an entire representation. HTTP
545   applications MUST accept CRLF, bare CR, and bare LF as indicating
546   a line break in text media received via HTTP. In
547   addition, if the text is in a character encoding that does not
548   use octets 13 and 10 for CR and LF respectively, as is the case for
549   some multi-byte character encodings, HTTP allows the use of whatever octet
550   sequences are defined by that character encoding to represent the
551   equivalent of CR and LF for line breaks. This flexibility regarding
552   line breaks applies only to text media in the payload body; a bare CR
553   or LF MUST NOT be substituted for CRLF within any of the HTTP control
554   structures (such as header fields and multipart boundaries).
555</t>
556<t>
557   If a representation is encoded with a content-coding, the underlying
558   data MUST be in a form defined above prior to being encoded.
559</t>
560<t>
561   The "charset" parameter is used with some media types to define the
562   character encoding (<xref target="character.sets"/>) of the data. When no explicit charset
563   parameter is provided by the sender, media subtypes of the "text"
564   type are defined to have a default charset value of "ISO-8859-1" when
565   received via HTTP. Data in character encodings other than "ISO-8859-1" or
566   its subsets MUST be labeled with an appropriate charset value. See
567   <xref target="missing.charset"/> for compatibility problems.
568</t>
569</section>
570
571<section title="Multipart Types" anchor="multipart.types">
572<t>
573   MIME provides for a number of "multipart" types -- encapsulations of
574   one or more representations within a single message-body. All multipart
575   types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
576   and MUST include a boundary parameter as part of the media type
577   value. The message body is itself a protocol element and MUST
578   therefore use only CRLF to represent line breaks between body-parts.
579</t>
580<t>
581   In general, HTTP treats a multipart message-body no differently than
582   any other media type: strictly as payload.  HTTP does not use the
583   multipart boundary as an indicator of message-body length.
584   <!-- jre: re-insert removed text pointing to caching? -->
585   In all other respects, an HTTP user agent SHOULD follow the same or similar
586   behavior as a MIME user agent would upon receipt of a multipart type.
587   The MIME header fields within each body-part of a multipart message-body
588   do not have any significance to HTTP beyond that defined by
589   their MIME semantics.
590</t>
591<t>
592   If an application receives an unrecognized multipart subtype, the
593   application MUST treat it as being equivalent to "multipart/mixed".
594</t>
595<t><list>
596  <t>
597    Note: The "multipart/form-data" type has been specifically defined
598    for carrying form data suitable for processing via the POST
599    request method, as described in <xref target="RFC2388"/>.
600  </t>
601</list></t>
602</section>
603</section>
604
605<section title="Language Tags" anchor="language.tags">
606 
607<t>
608   A language tag, as defined in <xref target="RFC5646"/>, identifies a
609   natural language spoken, written, or otherwise conveyed by human beings for
610   communication of information to other human beings. Computer languages are
611   explicitly excluded. HTTP uses language tags within the Accept-Language and
612   Content-Language fields.
613</t>
614<t>
615   In summary, a language tag is composed of one or more parts: A primary
616   language subtag followed by a possibly empty series of subtags:
617</t>
618<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
619  language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
620]]></artwork></figure>
621<t>
622   White space is not allowed within the tag and all tags are case-insensitive.
623   The name space of language subtags is administered by the IANA (see
624   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
625</t>
626<figure>
627  <preamble>Example tags include:</preamble>
628<artwork type="example"><![CDATA[
629  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
630]]></artwork>
631</figure>
632<t>
633   See <xref target="RFC5646"/> for further information.
634</t>
635</section>
636</section>
637
638<section title="Payload" anchor="payload">
639<t>
640   HTTP messages MAY transfer a payload if not otherwise restricted by
641   the request method or response status code.  The payload consists of
642   metadata, in the form of header fields, and data, in the form of the
643   sequence of octets in the message-body after any transfer-coding has
644   been decoded.
645</t>
646<iref item="payload"/>
647<t>  
648   A "payload" in HTTP is always a partial or complete
649   representation of some resource.  We use separate terms for payload
650   and representation because some messages contain only the associated
651   representation's header fields (e.g., responses to HEAD) or only some
652   part(s) of the representation (e.g., the 206 status code).
653</t>
654<section title="Payload Header Fields" anchor="payload.header.fields">
655 
656<t>
657   HTTP header fields that specifically define the payload, rather than the
658   associated representation, are referred to as "payload header fields".
659   The following payload header fields are defined by HTTP/1.1:
660</t>
661<figure><artwork><![CDATA[
662   Content-Length           ; [Part1], Section 9.2
663   Content-MD5              ; Section 6.8
664   Content-Range            ; [Part5], Section 5.2
665]]></artwork></figure>
666</section>
667
668<section title="Payload Body" anchor="payload.body">
669 
670<t>
671   A payload body is only present in a message when a message-body is
672   present, as described in Section 3.3 of <xref target="Part1"/>. The payload body is obtained
673   from the message-body by decoding any Transfer-Encoding that might
674   have been applied to ensure safe and proper transfer of the message.
675</t>
676</section>
677</section>
678
679<section title="Representation" anchor="representation">
680<iref item="representation"/>
681<t>
682   A "representation" is information in a format that can be readily
683   communicated from one party to another.  A resource representation
684   is information that reflects the state of that resource, as observed
685   at some point in the past (e.g., in a response to GET) or to be
686   desired at some point in the future (e.g., in a PUT request).
687</t>
688<t>
689   Most, but not all, representations transferred via HTTP are intended
690   to be a representation of the target resource (the resource identified
691   by the effective request URI).  The precise semantics of a representation
692   are determined by the type of message (request or response), the request
693   method, the response status code, and the representation metadata.
694   For example, the above semantic is true for the representation in any
695   200 (OK) response to GET and for the representation in any PUT request.
696   A 200 response to PUT, in contrast, contains either a representation
697   that describes the successful action or a representation of the target
698   resource, with the latter indicated by a Content-Location header field
699   with the same value as the effective request URI.  Likewise, response
700   messages with an error status code usually contain a representation that
701   describes the error and what next steps are suggested for resolving it.
702</t>
703
704<section title="Representation Header Fields" anchor="representation.header.fields">
705 
706<t>
707   Representation header fields define metadata about the representation data
708   enclosed in the message-body or, if no message-body is present, about
709   the representation that would have been transferred in a 200 response
710   to a simultaneous GET request with the same effective request URI.
711</t>
712<t>
713   The following header fields are defined as representation metadata:
714</t>
715<figure><artwork><![CDATA[
716   Content-Encoding         ; Section 6.5
717   Content-Language         ; Section 6.6
718   Content-Location         ; Section 6.7
719   Content-Type             ; Section 6.9
720   Expires                  ; [Part6], Section 3.3
721   Last-Modified            ; [Part4], Section 6.6
722]]></artwork></figure>
723</section>
724
725<section title="Representation Data" anchor="representation.data">
726 
727<t>
728   The representation body associated with an HTTP message is
729   either provided as the payload body of the message or
730   referred to by the message semantics and the effective request
731   URI.  The representation data is in a format and encoding defined by
732   the representation metadata header fields.
733</t>
734<t>
735   The data type of the representation data
736   is determined via the header fields Content-Type and Content-Encoding.
737   These define a two-layer, ordered encoding model:
738</t>
739<figure><artwork type="example"><![CDATA[
740  representation-data := Content-Encoding( Content-Type( bits ) )
741]]></artwork></figure>
742<t>
743   Content-Type specifies the media type of the underlying data, which
744   defines both the data format and how that data SHOULD be processed
745   by the recipient (within the scope of the request method semantics).
746   Any HTTP/1.1 message containing a payload body SHOULD include a
747   Content-Type header field defining the media type of the associated
748   representation unless that metadata is unknown to the sender.
749   If the Content-Type header field is not present, it indicates that
750   the sender does not know the media type of the representation;
751   recipients MAY either assume that the media type is
752   "application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
753   or examine the content to determine its type.
754</t>
755<t>
756   In practice, resource owners do not always properly configure their origin
757   server to provide the correct Content-Type for a given representation,
758   with the result that some clients will examine a response body's content
759   and override the specified type.
760   Clients that do so risk drawing incorrect conclusions, which might expose
761   additional security risks (e.g., "privilege escalation").  Furthermore,
762   it is impossible to determine the sender's intent by examining the data
763   format: many data formats match multiple media types that differ only in
764   processing semantics.  Implementers are encouraged to provide a means of
765   disabling such "content sniffing" when it is used.
766</t>
767<t>
768   Content-Encoding is used to indicate any additional content
769   codings applied to the data, usually for the purpose of data
770   compression, that are a property of the representation.  If
771   Content-Encoding is not present, then there is no additional
772   encoding beyond that defined by the Content-Type.
773</t>
774</section>
775</section>
776
777<section title="Content Negotiation" anchor="content.negotiation">
778<t>
779   HTTP responses include a representation which contains information for
780   interpretation, whether by a human user or for further processing.
781   Often, the server has different ways of representing the
782   same information; for example, in different formats, languages,
783   or using different character encodings.
784</t>
785<t>
786   HTTP clients and their users might have different or variable
787   capabilities, characteristics or preferences which would influence
788   which representation, among those available from the server,
789   would be best for the server to deliver. For this reason, HTTP
790   provides mechanisms for "content negotiation" -- a process of
791   allowing selection of a representation of a given resource,
792   when more than one is available.
793</t>
794<t>
795   This specification defines two patterns of content negotiation;
796   "server-driven", where the server selects the representation based
797   upon the client's stated preferences, and "agent-driven" negotiation,
798   where the server provides a list of representations for the client to
799   choose from, based upon their metadata. In addition,  there are
800   other patterns: some applications use an "active content" pattern,
801   where the server returns active content which runs on the client
802   and, based on client available parameters, selects additional
803   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
804   has also been proposed.
805</t>
806<t>
807   These patterns are all widely used, and have trade-offs in applicability
808   and practicality. In particular, when the number of preferences or
809   capabilities to be expressed by a client are large (such as when many
810   different formats are supported by a user-agent), server-driven
811   negotiation becomes unwieldy, and might not be appropriate. Conversely,
812   when the number of representations to choose from is very large,
813   agent-driven negotiation might not be appropriate.
814</t>
815<t>
816   Note that in all cases, the supplier of representations has the
817   responsibility for determining which representations might be
818   considered to be the "same information".
819</t>
820
821<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
822<t>
823   If the selection of the best representation for a response is made by
824   an algorithm located at the server, it is called server-driven
825   negotiation. Selection is based on the available representations of
826   the response (the dimensions over which it can vary; e.g., language,
827   content-coding, etc.) and the contents of particular header fields in
828   the request message or on other information pertaining to the request
829   (such as the network address of the client).
830</t>
831<t>
832   Server-driven negotiation is advantageous when the algorithm for
833   selecting from among the available representations is difficult to
834   describe to the user agent, or when the server desires to send its
835   "best guess" to the client along with the first response (hoping to
836   avoid the round-trip delay of a subsequent request if the "best
837   guess" is good enough for the user). In order to improve the server's
838   guess, the user agent MAY include request header fields (Accept,
839   Accept-Language, Accept-Encoding, etc.) which describe its
840   preferences for such a response.
841</t>
842<t>
843   Server-driven negotiation has disadvantages:
844  <list style="numbers">
845    <t>
846         It is impossible for the server to accurately determine what
847         might be "best" for any given user, since that would require
848         complete knowledge of both the capabilities of the user agent
849         and the intended use for the response (e.g., does the user want
850         to view it on screen or print it on paper?).
851    </t>
852    <t>
853         Having the user agent describe its capabilities in every
854         request can be both very inefficient (given that only a small
855         percentage of responses have multiple representations) and a
856         potential violation of the user's privacy.
857    </t>
858    <t>
859         It complicates the implementation of an origin server and the
860         algorithms for generating responses to a request.
861    </t>
862    <t>
863         It might limit a public cache's ability to use the same response
864         for multiple user's requests.
865    </t>
866  </list>
867</t>
868<t>
869   HTTP/1.1 includes the following request-header fields for enabling
870   server-driven negotiation through description of user agent
871   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
872   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
873   (<xref target="header.accept-language"/>), and User-Agent (Section 9.9 of <xref target="Part2"/>).
874   However, an origin server is not limited to these dimensions and MAY vary
875   the response based on any aspect of the request, including information
876   outside the request-header fields or within extension header fields
877   not defined by this specification.
878</t>
879<t><list>
880  <t>
881    Note: In practice, User-Agent based negotiation is fragile,
882    because new clients might not be recognized.
883  </t>
884</list></t>
885<t>
886   The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
887   server uses to select a representation that is subject to server-driven
888   negotiation.
889</t>
890</section>
891
892<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
893<t>
894   With agent-driven negotiation, selection of the best representation
895   for a response is performed by the user agent after receiving an
896   initial response from the origin server. Selection is based on a list
897   of the available representations of the response included within the
898   header fields or body of the initial response, with each
899   representation identified by its own URI. Selection from among the
900   representations can be performed automatically (if the user agent is
901   capable of doing so) or manually by the user selecting from a
902   generated (possibly hypertext) menu.
903</t>
904<t>
905   Agent-driven negotiation is advantageous when the response would vary
906   over commonly-used dimensions (such as type, language, or encoding),
907   when the origin server is unable to determine a user agent's
908   capabilities from examining the request, and generally when public
909   caches are used to distribute server load and reduce network usage.
910</t>
911<t>
912   Agent-driven negotiation suffers from the disadvantage of needing a
913   second request to obtain the best alternate representation. This
914   second request is only efficient when caching is used. In addition,
915   this specification does not define any mechanism for supporting
916   automatic selection, though it also does not prevent any such
917   mechanism from being developed as an extension and used within
918   HTTP/1.1.
919</t>
920<t>
921   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
922   status codes for enabling agent-driven negotiation when the server is
923   unwilling or unable to provide a varying response using server-driven
924   negotiation.
925</t>
926</section>
927</section>
928
929<section title="Header Field Definitions" anchor="header.fields">
930<t>
931   This section defines the syntax and semantics of HTTP/1.1 header fields
932   related to the payload of messages.
933</t>
934
935<section title="Accept" anchor="header.accept">
936  <iref primary="true" item="Accept header"/>
937  <iref primary="true" item="Headers" subitem="Accept"/>
938 
939 
940 
941 
942 
943<t>
944   The "Accept" request-header field can be used by user agents to specify
945   response media types that are acceptable. Accept header fields can be used to
946   indicate that the request is specifically limited to a small set of desired
947   types, as in the case of a request for an in-line image.
948</t>
949<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[
950  Accept   = "Accept" ":" OWS Accept-v
951  Accept-v = #( media-range [ accept-params ] )
952 
953  media-range    = ( "*/*"
954                   / ( type "/" "*" )
955                   / ( type "/" subtype )
956                   ) *( OWS ";" OWS parameter )
957  accept-params  = OWS ";" OWS "q=" qvalue *( accept-ext )
958  accept-ext     = OWS ";" OWS token [ "=" word ]
959]]></artwork></figure>
960<t>
961   The asterisk "*" character is used to group media types into ranges,
962   with "*/*" indicating all media types and "type/*" indicating all
963   subtypes of that type. The media-range MAY include media type
964   parameters that are applicable to that range.
965</t>
966<t>
967   Each media-range MAY be followed by one or more accept-params,
968   beginning with the "q" parameter for indicating a relative quality
969   factor. The first "q" parameter (if any) separates the media-range
970   parameter(s) from the accept-params. Quality factors allow the user
971   or user agent to indicate the relative degree of preference for that
972   media-range, using the qvalue scale from 0 to 1 (Section 6.4 of <xref target="Part1"/>). The
973   default value is q=1.
974</t>
975<t><list>
976  <t>
977    Note: Use of the "q" parameter name to separate media type
978    parameters from Accept extension parameters is due to historical
979    practice. Although this prevents any media type parameter named
980    "q" from being used with a media range, such an event is believed
981    to be unlikely given the lack of any "q" parameters in the IANA
982    media type registry and the rare usage of any media type
983    parameters in Accept. Future media types are discouraged from
984    registering any parameter named "q".
985  </t>
986</list></t>
987<t>
988   The example
989</t>
990<figure><artwork type="example"><![CDATA[
991  Accept: audio/*; q=0.2, audio/basic
992]]></artwork></figure>
993<t>
994   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
995   type if it is the best available after an 80% mark-down in quality".
996</t>
997<t>
998   If no Accept header field is present, then it is assumed that the
999   client accepts all media types. If an Accept header field is present,
1000   and if the server cannot send a response which is acceptable
1001   according to the combined Accept field value, then the server SHOULD
1002   send a 406 (Not Acceptable) response.
1003</t>
1004<t>
1005   A more elaborate example is
1006</t>
1007<figure><artwork type="example"><![CDATA[
1008  Accept: text/plain; q=0.5, text/html,
1009          text/x-dvi; q=0.8, text/x-c
1010]]></artwork></figure>
1011<t>
1012   Verbally, this would be interpreted as "text/html and text/x-c are
1013   the preferred media types, but if they do not exist, then send the
1014   text/x-dvi representation, and if that does not exist, send the text/plain
1015   representation".
1016</t>
1017<t>
1018   Media ranges can be overridden by more specific media ranges or
1019   specific media types. If more than one media range applies to a given
1020   type, the most specific reference has precedence. For example,
1021</t>
1022<figure><artwork type="example"><![CDATA[
1023  Accept: text/*, text/html, text/html;level=1, */*
1024]]></artwork></figure>
1025<t>
1026   have the following precedence:
1027   <list style="numbers">
1028    <t>text/html;level=1</t>
1029    <t>text/html</t>
1030    <t>text/*</t>
1031    <t>*/*</t>
1032   </list>
1033</t>
1034<t>
1035   The media type quality factor associated with a given type is
1036   determined by finding the media range with the highest precedence
1037   which matches that type. For example,
1038</t>
1039<figure><artwork type="example"><![CDATA[
1040  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1041          text/html;level=2;q=0.4, */*;q=0.5
1042]]></artwork></figure>
1043<t>
1044   would cause the following values to be associated:
1045</t>
1046<texttable align="left">
1047  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1048  <c>text/html;level=1</c>    <c>1</c>
1049  <c>text/html</c>            <c>0.7</c>
1050  <c>text/plain</c>           <c>0.3</c>
1051  <c>image/jpeg</c>           <c>0.5</c>
1052  <c>text/html;level=2</c>    <c>0.4</c>
1053  <c>text/html;level=3</c>    <c>0.7</c>
1054</texttable>
1055<t>
1056      Note: A user agent might be provided with a default set of quality
1057      values for certain media ranges. However, unless the user agent is
1058      a closed system which cannot interact with other rendering agents,
1059      this default set ought to be configurable by the user.
1060</t>
1061</section>
1062
1063<section title="Accept-Charset" anchor="header.accept-charset">
1064  <iref primary="true" item="Accept-Charset header"/>
1065  <iref primary="true" item="Headers" subitem="Accept-Charset"/>
1066 
1067 
1068<t>
1069   The "Accept-Charset" request-header field can be used by user agents to
1070   indicate what response character sets are acceptable. This field allows
1071   clients capable of understanding more comprehensive or special-purpose
1072   character sets to signal that capability to a server which is capable of
1073   representing documents in those character sets.
1074</t>
1075<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/><artwork type="abnf2616"><![CDATA[
1076  Accept-Charset   = "Accept-Charset" ":" OWS
1077          Accept-Charset-v
1078  Accept-Charset-v = 1#( ( charset / "*" )
1079                         [ OWS ";" OWS "q=" qvalue ] )
1080]]></artwork></figure>
1081<t>
1082   Character set values are described in <xref target="character.sets"/>. Each charset MAY
1083   be given an associated quality value which represents the user's
1084   preference for that charset. The default value is q=1. An example is
1085</t>
1086<figure><artwork type="example"><![CDATA[
1087  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1088]]></artwork></figure>
1089<t>
1090   The special value "*", if present in the Accept-Charset field,
1091   matches every character set (including ISO-8859-1) which is not
1092   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1093   in an Accept-Charset field, then all character sets not explicitly
1094   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1095   a quality value of 1 if not explicitly mentioned.
1096</t>
1097<t>
1098   If no Accept-Charset header field is present, the default is that any
1099   character set is acceptable. If an Accept-Charset header field is present,
1100   and if the server cannot send a response which is acceptable
1101   according to the Accept-Charset header field, then the server SHOULD send
1102   an error response with the 406 (Not Acceptable) status code, though
1103   the sending of an unacceptable response is also allowed.
1104</t>
1105</section>
1106
1107<section title="Accept-Encoding" anchor="header.accept-encoding">
1108  <iref primary="true" item="Accept-Encoding header"/>
1109  <iref primary="true" item="Headers" subitem="Accept-Encoding"/>
1110 
1111 
1112 
1113<t>
1114   The "Accept-Encoding" request-header field can be used by user agents to
1115   indicate what response content-codings (<xref target="content.codings"/>)
1116   are acceptable in the response.
1117</t>
1118<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[
1119  Accept-Encoding    = "Accept-Encoding" ":" OWS
1120                     Accept-Encoding-v
1121  Accept-Encoding-v  =
1122                     #( codings [ OWS ";" OWS "q=" qvalue ] )
1123  codings            = ( content-coding / "*" )
1124]]></artwork></figure>
1125<t>
1126   Each codings value MAY be given an associated quality value which
1127   represents the preference for that encoding. The default value is q=1.
1128</t>
1129<t>
1130   Examples of its use are:
1131</t>
1132<figure><artwork type="example"><![CDATA[
1133  Accept-Encoding: compress, gzip
1134  Accept-Encoding:
1135  Accept-Encoding: *
1136  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1137  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1138]]></artwork></figure>
1139<t>
1140   A server tests whether a content-coding is acceptable, according to
1141   an Accept-Encoding field, using these rules:
1142  <list style="numbers">
1143      <t>If the content-coding is one of the content-codings listed in
1144         the Accept-Encoding field, then it is acceptable, unless it is
1145         accompanied by a qvalue of 0. (As defined in Section 6.4 of <xref target="Part1"/>, a
1146         qvalue of 0 means "not acceptable".)</t>
1147
1148      <t>The special "*" symbol in an Accept-Encoding field matches any
1149         available content-coding not explicitly listed in the header
1150         field.</t>
1151
1152      <t>If multiple content-codings are acceptable, then the acceptable
1153         content-coding with the highest non-zero qvalue is preferred.</t>
1154
1155      <t>The "identity" content-coding is always acceptable, unless
1156         specifically refused because the Accept-Encoding field includes
1157         "identity;q=0", or because the field includes "*;q=0" and does
1158         not explicitly include the "identity" content-coding. If the
1159         Accept-Encoding field-value is empty, then only the "identity"
1160         encoding is acceptable.</t>
1161  </list>
1162</t>
1163<t>
1164   If an Accept-Encoding field is present in a request, and if the
1165   server cannot send a response which is acceptable according to the
1166   Accept-Encoding header field, then the server SHOULD send an error response
1167   with the 406 (Not Acceptable) status code.
1168</t>
1169<t>
1170   If no Accept-Encoding field is present in a request, the server MAY
1171   assume that the client will accept any content coding. In this case,
1172   if "identity" is one of the available content-codings, then the
1173   server SHOULD use the "identity" content-coding, unless it has
1174   additional information that a different content-coding is meaningful
1175   to the client.
1176</t>
1177<t><list>
1178  <t>
1179    Note: If the request does not include an Accept-Encoding field,
1180    and if the "identity" content-coding is unavailable, then
1181    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1182    "gzip" and "compress") are preferred; some older clients
1183    improperly display messages sent with other content-codings.  The
1184    server might also make this decision based on information about
1185    the particular user-agent or client.
1186  </t>
1187</list></t>
1188<t><list>
1189  <t>
1190    Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1191    associated with content-codings. This means that qvalues will not
1192    work and are not permitted with x-gzip or x-compress.
1193  </t>
1194</list></t>
1195</section>
1196
1197<section title="Accept-Language" anchor="header.accept-language">
1198  <iref primary="true" item="Accept-Language header"/>
1199  <iref primary="true" item="Headers" subitem="Accept-Language"/>
1200 
1201 
1202 
1203<t>
1204   The "Accept-Language" request-header field can be used by user agents to
1205   indicate the set of natural languages that are preferred in the response.
1206   Language tags are defined in <xref target="language.tags"/>.
1207</t>
1208<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[
1209  Accept-Language   = "Accept-Language" ":" OWS
1210                    Accept-Language-v
1211  Accept-Language-v =
1212                    1#( language-range [ OWS ";" OWS "q=" qvalue ] )
1213  language-range    =
1214            <language-range, defined in [RFC4647], Section 2.1>
1215]]></artwork></figure>
1216<t>
1217   Each language-range can be given an associated quality value which
1218   represents an estimate of the user's preference for the languages
1219   specified by that range. The quality value defaults to "q=1". For
1220   example,
1221</t>
1222<figure><artwork type="example"><![CDATA[
1223  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1224]]></artwork></figure>
1225<t>
1226   would mean: "I prefer Danish, but will accept British English and
1227   other types of English".
1228   (see also Section 2.3 of <xref target="RFC4647"/>)
1229</t>
1230<t>
1231   For matching, Section 3 of <xref target="RFC4647"/> defines
1232   several matching schemes. Implementations can offer the most appropriate
1233   matching scheme for their requirements.
1234</t>
1235<t><list>
1236  <t>
1237    Note: The "Basic Filtering" scheme (<xref target="RFC4647"/>, Section 3.3.1) is identical to the matching scheme that was
1238    previously defined in Section 14.4 of <xref target="RFC2616"/>.
1239  </t>
1240</list></t>
1241<t>
1242   It might be contrary to the privacy expectations of the user to send
1243   an Accept-Language header field with the complete linguistic preferences of
1244   the user in every request. For a discussion of this issue, see
1245   <xref target="privacy.issues.connected.to.accept.header.fields"/>.
1246</t>
1247<t>
1248   As intelligibility is highly dependent on the individual user, it is
1249   recommended that client applications make the choice of linguistic
1250   preference available to the user. If the choice is not made
1251   available, then the Accept-Language header field MUST NOT be given in
1252   the request.
1253</t>
1254<t><list>
1255  <t>
1256    Note: When making the choice of linguistic preference available to
1257    the user, we remind implementors of  the fact that users are not
1258    familiar with the details of language matching as described above,
1259    and ought to be provided appropriate guidance. As an example, users
1260    might assume that on selecting "en-gb", they will be served any
1261    kind of English document if British English is not available. A
1262    user agent might suggest in such a case to add "en" to get the
1263    best matching behavior.
1264  </t>
1265</list></t>
1266</section>
1267
1268<section title="Content-Encoding" anchor="header.content-encoding">
1269  <iref primary="true" item="Content-Encoding header"/>
1270  <iref primary="true" item="Headers" subitem="Content-Encoding"/>
1271 
1272 
1273<t>
1274   The "Content-Encoding" header field indicates what content-codings
1275   have been applied to the representation, and thus what decoding mechanisms
1276   must be applied in order to obtain the media-type referenced by the
1277   Content-Type header field. Content-Encoding is primarily used to allow a
1278   representation to be compressed without losing the identity of its underlying
1279   media type.
1280</t>
1281<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/><artwork type="abnf2616"><![CDATA[
1282  Content-Encoding   = "Content-Encoding" ":" OWS Content-Encoding-v
1283  Content-Encoding-v = 1#content-coding
1284]]></artwork></figure>
1285<t>
1286   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1287</t>
1288<figure><artwork type="example"><![CDATA[
1289  Content-Encoding: gzip
1290]]></artwork></figure>
1291<t>
1292   The content-coding is a characteristic of the representation.
1293   Typically, the representation body is stored with this
1294   encoding and is only decoded before rendering or analogous usage.
1295   However, a non-transparent proxy MAY modify the content-coding if the
1296   new coding is known to be acceptable to the recipient, unless the
1297   "no-transform" cache-control directive is present in the message.
1298</t>
1299<t>
1300   If the content-coding of a representation is not "identity", then the
1301   representation metadata MUST include a Content-Encoding header
1302   field (<xref target="header.content-encoding"/>)
1303   that lists the non-identity content-coding(s) used.
1304</t>
1305<t>
1306   If the content-coding of a representation in a request message is not
1307   acceptable to the origin server, the server SHOULD respond with a
1308   status code of 415 (Unsupported Media Type).
1309</t>
1310<t>
1311   If multiple encodings have been applied to a representation, the content
1312   codings MUST be listed in the order in which they were applied.
1313   Additional information about the encoding parameters MAY be provided
1314   by other header fields not defined by this specification.
1315</t>
1316</section>
1317
1318<section title="Content-Language" anchor="header.content-language">
1319  <iref primary="true" item="Content-Language header"/>
1320  <iref primary="true" item="Headers" subitem="Content-Language"/>
1321 
1322 
1323<t>
1324   The "Content-Language" header field describes the natural
1325   language(s) of the intended audience for the representation. Note that this might
1326   not be equivalent to all the languages used within the representation.
1327</t>
1328<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/><artwork type="abnf2616"><![CDATA[
1329  Content-Language   = "Content-Language" ":" OWS Content-Language-v
1330  Content-Language-v = 1#language-tag
1331]]></artwork></figure>
1332<t>
1333   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1334   Content-Language is to allow a user to identify and differentiate
1335   representations according to the user's own preferred language. Thus, if the
1336   body content is intended only for a Danish-literate audience, the
1337   appropriate field is
1338</t>
1339<figure><artwork type="example"><![CDATA[
1340  Content-Language: da
1341]]></artwork></figure>
1342<t>
1343   If no Content-Language is specified, the default is that the content
1344   is intended for all language audiences. This might mean that the
1345   sender does not consider it to be specific to any natural language,
1346   or that the sender does not know for which language it is intended.
1347</t>
1348<t>
1349   Multiple languages MAY be listed for content that is intended for
1350   multiple audiences. For example, a rendition of the "Treaty of
1351   Waitangi", presented simultaneously in the original Maori and English
1352   versions, would call for
1353</t>
1354<figure><artwork type="example"><![CDATA[
1355  Content-Language: mi, en
1356]]></artwork></figure>
1357<t>
1358   However, just because multiple languages are present within a representation
1359   does not mean that it is intended for multiple linguistic audiences.
1360   An example would be a beginner's language primer, such as "A First
1361   Lesson in Latin", which is clearly intended to be used by an
1362   English-literate audience. In this case, the Content-Language would
1363   properly only include "en".
1364</t>
1365<t>
1366   Content-Language MAY be applied to any media type -- it is not
1367   limited to textual documents.
1368</t>
1369</section>
1370
1371<section title="Content-Location" anchor="header.content-location">
1372  <iref primary="true" item="Content-Location header"/>
1373  <iref primary="true" item="Headers" subitem="Content-Location"/>
1374 
1375 
1376<t>
1377   The "Content-Location" header field supplies a URI that can be used
1378   as a specific identifier for the representation in this message.
1379   In other words, if one were to perform a GET on this URI at the time
1380   of this message's generation, then a 200 response would contain the
1381   same representation that is enclosed as payload in this message.
1382</t>
1383<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/><artwork type="abnf2616"><![CDATA[
1384  Content-Location   = "Content-Location" ":" OWS
1385                    Content-Location-v
1386  Content-Location-v =
1387                    absolute-URI / partial-URI
1388]]></artwork></figure>
1389<t>
1390   The Content-Location value is not a replacement for the effective
1391   Request URI (Section 4.3 of <xref target="Part1"/>).  It is representation metadata.
1392   It has the same syntax and semantics as the header field of the same name
1393   defined for MIME body parts in Section 4 of <xref target="RFC2557"/>.
1394   However, its appearance in an HTTP message has some special implications
1395   for HTTP recipients.
1396</t>
1397<t>
1398   If Content-Location is included in a response message and its value
1399   is the same as the effective request URI, then the response payload
1400   SHOULD be considered the current representation of that resource.
1401   For a GET or HEAD request, this is the same as the default semantics
1402   when no Content-Location is provided by the server.  For a state-changing
1403   method like PUT or POST, it implies that the server's response contains
1404   the new representation of that resource, thereby distinguishing it from
1405   representations that might only report about the action (e.g., "It worked!").
1406   This allows authoring applications to update their local copies without
1407   the need for a subsequent GET request.
1408</t>
1409<t>
1410   If Content-Location is included in a response message and its value
1411   differs from the effective request URI, then the origin server is
1412   informing recipients that this representation has its own, presumably
1413   more specific, identifier.  For a GET or HEAD request, this is an
1414   indication that the effective request URI identifies a resource that
1415   is subject to content negotiation and the representation selected for
1416   this response can also be found at the identified URI.  For other
1417   methods, such a Content-Location indicates that this representation
1418   contains a report on the action's status and the same report is
1419   available (for future access with GET) at the given URI.  For
1420   example, a purchase transaction made via the POST method might
1421   include a receipt document as the payload of the 200 response;
1422   the Content-Location value provides an identifier for retrieving
1423   a copy of that same receipt in the future.
1424</t>
1425<t>
1426   If Content-Location is included in a request message, then it MAY
1427   be interpreted by the origin server as an indication of where the
1428   user agent originally obtained the content of the enclosed
1429   representation (prior to any subsequent modification of the content
1430   by that user agent).  In other words, the user agent is providing
1431   the same representation metadata that it received with the original
1432   representation.  However, such interpretation MUST NOT be used to
1433   alter the semantics of the method requested by the client.  For
1434   example, if a client makes a PUT request on a negotiated resource
1435   and the origin server accepts that PUT (without redirection), then the
1436   new set of values for that resource is expected to be consistent with
1437   the one representation supplied in that PUT; the Content-Location
1438   cannot be used as a form of reverse content selection that
1439   identifies only one of the negotiated representations to be updated.
1440   If the user agent had wanted the latter semantics, it would have applied
1441   the PUT directly to the Content-Location URI.
1442</t>
1443<t>
1444   A Content-Location field received in a request message is transitory
1445   information that SHOULD NOT be saved with other representation
1446   metadata for use in later responses.  The Content-Location's value
1447   might be saved for use in other contexts, such as within source links
1448   or other metadata.
1449</t>
1450<t>
1451   A cache cannot assume that a representation with a Content-Location
1452   different from the URI used to retrieve it can be used to respond to
1453   later requests on that Content-Location URI.
1454</t>
1455<t>
1456   If the Content-Location value is a partial URI, the partial URI is
1457   interpreted relative to the effective request URI.
1458</t>
1459</section>
1460
1461<section title="Content-MD5" anchor="header.content-md5">
1462  <iref primary="true" item="Content-MD5 header"/>
1463  <iref primary="true" item="Headers" subitem="Content-MD5"/>
1464 
1465 
1466<t>
1467   The "Content-MD5" header field, as defined in <xref target="RFC1864"/>, is
1468   an MD5 digest of the payload body that provides an end-to-end message
1469   integrity check (MIC) of the payload body (the message-body after any
1470   transfer-coding is decoded). Note that a MIC is good for
1471   detecting accidental modification of the payload body in transit, but is not
1472   proof against malicious attacks.
1473</t>
1474<figure><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/><artwork type="abnf2616"><![CDATA[
1475  Content-MD5   = "Content-MD5" ":" OWS Content-MD5-v
1476  Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
1477]]></artwork></figure>
1478<t>
1479   The Content-MD5 header field MAY be generated by an origin server or
1480   client to function as an integrity check of the payload body. Only
1481   origin servers or user agents MAY generate the Content-MD5 header field;
1482   proxies and gateways MUST NOT generate it, as this would defeat its
1483   value as an end-to-end integrity check. Any recipient MAY check that
1484   the digest value in this header field matches a corresponding digest
1485   calculated on payload body as received.
1486</t>
1487<t>
1488   The MD5 digest is computed based on the content of the payload body,
1489   including any content-coding, but not including any transfer-coding
1490   applied to the message-body because such transfer-codings might be
1491   applied or removed anywhere along the request/response chain.
1492   If the message is received with a transfer-coding, that encoding MUST
1493   be decoded prior to checking the Content-MD5 value against the received
1494   payload.
1495</t>
1496<t>
1497   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1498   composite media-types (e.g., multipart/* and message/rfc822), but
1499   this does not change how the digest is computed as defined in the
1500   preceding paragraph.
1501</t>
1502<t>
1503   There are several consequences of this. The payload for composite
1504   types MAY contain many body-parts, each with its own MIME and HTTP
1505   header fields (including Content-MD5, Content-Transfer-Encoding, and
1506   Content-Encoding header fields). If a body-part has a Content-Transfer-Encoding
1507   or Content-Encoding header field, it is assumed that the content
1508   of the body-part has had the encoding applied, and the body-part is
1509   included in the Content-MD5 digest as is -- i.e., after the
1510   application. The Transfer-Encoding header field is not allowed within
1511   body-parts.
1512</t>
1513<t>
1514   Conversion of all line breaks to CRLF MUST NOT be done before
1515   computing or checking the digest: the line break convention used in
1516   the text actually transmitted MUST be left unaltered when computing
1517   the digest.
1518</t>
1519<t><list>
1520  <t>
1521    Note: While the definition of Content-MD5 is exactly the same for
1522    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1523    in which the application of Content-MD5 to HTTP entity-bodies
1524    differs from its application to MIME entity-bodies. One is that
1525    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1526    does use Transfer-Encoding and Content-Encoding. Another is that
1527    HTTP more frequently uses binary content types than MIME, so it is
1528    worth noting that, in such cases, the byte order used to compute
1529    the digest is the transmission byte order defined for the type.
1530    Lastly, HTTP allows transmission of text types with any of several
1531    line break conventions and not just the canonical form using CRLF.
1532  </t>
1533</list></t>
1534</section>
1535
1536<section title="Content-Type" anchor="header.content-type">
1537  <iref primary="true" item="Content-Type header"/>
1538  <iref primary="true" item="Headers" subitem="Content-Type"/>
1539 
1540 
1541<t>
1542   The "Content-Type" header field indicates the media type of the
1543   representation. In the case of responses to the HEAD method, the media type is
1544   that which would have been sent had the request been a GET.
1545</t>
1546<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/><artwork type="abnf2616"><![CDATA[
1547  Content-Type   = "Content-Type" ":" OWS Content-Type-v
1548  Content-Type-v = media-type
1549]]></artwork></figure>
1550<t>
1551   Media types are defined in <xref target="media.types"/>. An example of the field is
1552</t>
1553<figure><artwork type="example"><![CDATA[
1554  Content-Type: text/html; charset=ISO-8859-4
1555]]></artwork></figure>
1556<t>
1557   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1558</t>
1559</section>
1560
1561</section>
1562
1563<section title="IANA Considerations" anchor="IANA.considerations">
1564<section title="Header Field Registration" anchor="header.field.registration">
1565<t>
1566   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
1567   with the permanent registrations below (see <xref target="RFC3864"/>):
1568</t>
1569
1570<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1571<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1572   <ttcol>Header Field Name</ttcol>
1573   <ttcol>Protocol</ttcol>
1574   <ttcol>Status</ttcol>
1575   <ttcol>Reference</ttcol>
1576
1577   <c>Accept</c>
1578   <c>http</c>
1579   <c>standard</c>
1580   <c>
1581      <xref target="header.accept"/>
1582   </c>
1583   <c>Accept-Charset</c>
1584   <c>http</c>
1585   <c>standard</c>
1586   <c>
1587      <xref target="header.accept-charset"/>
1588   </c>
1589   <c>Accept-Encoding</c>
1590   <c>http</c>
1591   <c>standard</c>
1592   <c>
1593      <xref target="header.accept-encoding"/>
1594   </c>
1595   <c>Accept-Language</c>
1596   <c>http</c>
1597   <c>standard</c>
1598   <c>
1599      <xref target="header.accept-language"/>
1600   </c>
1601   <c>Content-Encoding</c>
1602   <c>http</c>
1603   <c>standard</c>
1604   <c>
1605      <xref target="header.content-encoding"/>
1606   </c>
1607   <c>Content-Language</c>
1608   <c>http</c>
1609   <c>standard</c>
1610   <c>
1611      <xref target="header.content-language"/>
1612   </c>
1613   <c>Content-Location</c>
1614   <c>http</c>
1615   <c>standard</c>
1616   <c>
1617      <xref target="header.content-location"/>
1618   </c>
1619   <c>Content-MD5</c>
1620   <c>http</c>
1621   <c>standard</c>
1622   <c>
1623      <xref target="header.content-md5"/>
1624   </c>
1625   <c>Content-Type</c>
1626   <c>http</c>
1627   <c>standard</c>
1628   <c>
1629      <xref target="header.content-type"/>
1630   </c>
1631   <c>MIME-Version</c>
1632   <c>http</c>
1633   <c>standard</c>
1634   <c>
1635      <xref target="mime-version"/>
1636   </c>
1637</texttable>
1638<!--(END)-->
1639
1640<t>
1641   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1642</t>
1643</section>
1644
1645<section title="Content Coding Registry" anchor="content.coding.registration">
1646<t>
1647   The registration procedure for HTTP Content Codings is now defined
1648   by <xref target="content.coding.registry"/> of this document.
1649</t>
1650<t>
1651   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1652   shall be updated with the registration below:
1653</t>
1654<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1655   <ttcol>Name</ttcol>
1656   <ttcol>Description</ttcol>
1657   <ttcol>Reference</ttcol>
1658   <c>compress</c>
1659   <c>UNIX "compress" program method</c>
1660   <c>
1661      Section 6.2.2.1 of <xref target="Part1"/>
1662   </c>
1663   <c>deflate</c>
1664   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1665   the "zlib" data format (<xref target="RFC1950"/>)
1666   </c>
1667   <c>
1668      Section 6.2.2.2 of <xref target="Part1"/>
1669   </c>
1670   <c>gzip</c>
1671   <c>Same as GNU zip <xref target="RFC1952"/></c>
1672   <c>
1673      Section 6.2.2.3 of <xref target="Part1"/>
1674   </c>
1675   <c>identity</c>
1676   <c>No transformation</c>
1677   <c>
1678      <xref target="content.codings"/>
1679   </c>
1680</texttable>
1681</section>
1682
1683</section>
1684
1685<section title="Security Considerations" anchor="security.considerations">
1686<t>
1687   This section is meant to inform application developers, information
1688   providers, and users of the security limitations in HTTP/1.1 as
1689   described by this document. The discussion does not include
1690   definitive solutions to the problems revealed, though it does make
1691   some suggestions for reducing security risks.
1692</t>
1693
1694<section title="Privacy Issues Connected to Accept Header Fields" anchor="privacy.issues.connected.to.accept.header.fields">
1695<t>
1696   Accept request-headers fields can reveal information about the user to all
1697   servers which are accessed. The Accept-Language header field in particular
1698   can reveal information the user would consider to be of a private
1699   nature, because the understanding of particular languages is often
1700   strongly correlated to the membership of a particular ethnic group.
1701   User agents which offer the option to configure the contents of an
1702   Accept-Language header field to be sent in every request are strongly
1703   encouraged to let the configuration process include a message which
1704   makes the user aware of the loss of privacy involved.
1705</t>
1706<t>
1707   An approach that limits the loss of privacy would be for a user agent
1708   to omit the sending of Accept-Language header fields by default, and to ask
1709   the user whether or not to start sending Accept-Language header fields to a
1710   server if it detects, by looking for any Vary response-header fields
1711   generated by the server, that such sending could improve the quality
1712   of service.
1713</t>
1714<t>
1715   Elaborate user-customized accept header fields sent in every request,
1716   in particular if these include quality values, can be used by servers
1717   as relatively reliable and long-lived user identifiers. Such user
1718   identifiers would allow content providers to do click-trail tracking,
1719   and would allow collaborating content providers to match cross-server
1720   click-trails or form submissions of individual users. Note that for
1721   many users not behind a proxy, the network address of the host
1722   running the user agent will also serve as a long-lived user
1723   identifier. In environments where proxies are used to enhance
1724   privacy, user agents ought to be conservative in offering accept
1725   header configuration options to end users. As an extreme privacy
1726   measure, proxies could filter the accept header fields in relayed requests.
1727   General purpose user agents which provide a high degree of header
1728   configurability SHOULD warn users about the loss of privacy which can
1729   be involved.
1730</t>
1731</section>
1732
1733</section>
1734
1735<section title="Acknowledgments" anchor="ack">
1736</section>
1737</middle>
1738<back>
1739
1740<references title="Normative References">
1741
1742<reference anchor="ISO-8859-1">
1743  <front>
1744    <title>
1745     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1746    </title>
1747    <author>
1748      <organization>International Organization for Standardization</organization>
1749    </author>
1750    <date year="1998"/>
1751  </front>
1752  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1753</reference>
1754
1755<reference anchor="Part1">
1756  <front>
1757    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1758    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1759      <organization abbrev="Day Software">Day Software</organization>
1760      <address><email>fielding@gbiv.com</email></address>
1761    </author>
1762    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1763      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1764      <address><email>jg@freedesktop.org</email></address>
1765    </author>
1766    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1767      <organization abbrev="HP">Hewlett-Packard Company</organization>
1768      <address><email>JeffMogul@acm.org</email></address>
1769    </author>
1770    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1771      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1772      <address><email>henrikn@microsoft.com</email></address>
1773    </author>
1774    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1775      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1776      <address><email>LMM@acm.org</email></address>
1777    </author>
1778    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1779      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1780      <address><email>paulle@microsoft.com</email></address>
1781    </author>
1782    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1783      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1784      <address><email>timbl@w3.org</email></address>
1785    </author>
1786    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1787      <organization abbrev="W3C">World Wide Web Consortium</organization>
1788      <address><email>ylafon@w3.org</email></address>
1789    </author>
1790    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1791      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1792      <address><email>julian.reschke@greenbytes.de</email></address>
1793    </author>
1794    <date month="October" year="2010"/>
1795  </front>
1796  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-12"/>
1797 
1798</reference>
1799
1800<reference anchor="Part2">
1801  <front>
1802    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1803    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1804      <organization abbrev="Day Software">Day Software</organization>
1805      <address><email>fielding@gbiv.com</email></address>
1806    </author>
1807    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1808      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1809      <address><email>jg@freedesktop.org</email></address>
1810    </author>
1811    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1812      <organization abbrev="HP">Hewlett-Packard Company</organization>
1813      <address><email>JeffMogul@acm.org</email></address>
1814    </author>
1815    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1816      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1817      <address><email>henrikn@microsoft.com</email></address>
1818    </author>
1819    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1820      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1821      <address><email>LMM@acm.org</email></address>
1822    </author>
1823    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1824      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1825      <address><email>paulle@microsoft.com</email></address>
1826    </author>
1827    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1828      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1829      <address><email>timbl@w3.org</email></address>
1830    </author>
1831    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1832      <organization abbrev="W3C">World Wide Web Consortium</organization>
1833      <address><email>ylafon@w3.org</email></address>
1834    </author>
1835    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1836      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1837      <address><email>julian.reschke@greenbytes.de</email></address>
1838    </author>
1839    <date month="October" year="2010"/>
1840  </front>
1841  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-12"/>
1842 
1843</reference>
1844
1845<reference anchor="Part4">
1846  <front>
1847    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1848    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1849      <organization abbrev="Day Software">Day Software</organization>
1850      <address><email>fielding@gbiv.com</email></address>
1851    </author>
1852    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1853      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1854      <address><email>jg@freedesktop.org</email></address>
1855    </author>
1856    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1857      <organization abbrev="HP">Hewlett-Packard Company</organization>
1858      <address><email>JeffMogul@acm.org</email></address>
1859    </author>
1860    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1861      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1862      <address><email>henrikn@microsoft.com</email></address>
1863    </author>
1864    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1865      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1866      <address><email>LMM@acm.org</email></address>
1867    </author>
1868    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1869      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1870      <address><email>paulle@microsoft.com</email></address>
1871    </author>
1872    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1873      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1874      <address><email>timbl@w3.org</email></address>
1875    </author>
1876    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1877      <organization abbrev="W3C">World Wide Web Consortium</organization>
1878      <address><email>ylafon@w3.org</email></address>
1879    </author>
1880    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1881      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1882      <address><email>julian.reschke@greenbytes.de</email></address>
1883    </author>
1884    <date month="October" year="2010"/>
1885  </front>
1886  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-12"/>
1887 
1888</reference>
1889
1890<reference anchor="Part5">
1891  <front>
1892    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1893    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1894      <organization abbrev="Day Software">Day Software</organization>
1895      <address><email>fielding@gbiv.com</email></address>
1896    </author>
1897    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1898      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1899      <address><email>jg@freedesktop.org</email></address>
1900    </author>
1901    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1902      <organization abbrev="HP">Hewlett-Packard Company</organization>
1903      <address><email>JeffMogul@acm.org</email></address>
1904    </author>
1905    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1906      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1907      <address><email>henrikn@microsoft.com</email></address>
1908    </author>
1909    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1910      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1911      <address><email>LMM@acm.org</email></address>
1912    </author>
1913    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1914      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1915      <address><email>paulle@microsoft.com</email></address>
1916    </author>
1917    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1918      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1919      <address><email>timbl@w3.org</email></address>
1920    </author>
1921    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1922      <organization abbrev="W3C">World Wide Web Consortium</organization>
1923      <address><email>ylafon@w3.org</email></address>
1924    </author>
1925    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1926      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1927      <address><email>julian.reschke@greenbytes.de</email></address>
1928    </author>
1929    <date month="October" year="2010"/>
1930  </front>
1931  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-12"/>
1932 
1933</reference>
1934
1935<reference anchor="Part6">
1936  <front>
1937    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1938    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1939      <organization abbrev="Day Software">Day Software</organization>
1940      <address><email>fielding@gbiv.com</email></address>
1941    </author>
1942    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1943      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1944      <address><email>jg@freedesktop.org</email></address>
1945    </author>
1946    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1947      <organization abbrev="HP">Hewlett-Packard Company</organization>
1948      <address><email>JeffMogul@acm.org</email></address>
1949    </author>
1950    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1951      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1952      <address><email>henrikn@microsoft.com</email></address>
1953    </author>
1954    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1955      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1956      <address><email>LMM@acm.org</email></address>
1957    </author>
1958    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1959      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1960      <address><email>paulle@microsoft.com</email></address>
1961    </author>
1962    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1963      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1964      <address><email>timbl@w3.org</email></address>
1965    </author>
1966    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1967      <organization abbrev="W3C">World Wide Web Consortium</organization>
1968      <address><email>ylafon@w3.org</email></address>
1969    </author>
1970    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1971      <address><email>mnot@mnot.net</email></address>
1972    </author>
1973    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1974      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1975      <address><email>julian.reschke@greenbytes.de</email></address>
1976    </author>
1977    <date month="October" year="2010"/>
1978  </front>
1979  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-12"/>
1980 
1981</reference>
1982
1983<reference anchor="RFC1864">
1984  <front>
1985    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
1986    <author initials="J." surname="Myers" fullname="John G. Myers">
1987      <organization>Carnegie Mellon University</organization>
1988      <address><email>jgm+@cmu.edu</email></address>
1989    </author>
1990    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
1991      <organization>Dover Beach Consulting, Inc.</organization>
1992      <address><email>mrose@dbc.mtview.ca.us</email></address>
1993    </author>
1994    <date month="October" year="1995"/>
1995  </front>
1996  <seriesInfo name="RFC" value="1864"/>
1997</reference>
1998
1999<reference anchor="RFC1950">
2000  <front>
2001    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2002    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2003      <organization>Aladdin Enterprises</organization>
2004      <address><email>ghost@aladdin.com</email></address>
2005    </author>
2006    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2007    <date month="May" year="1996"/>
2008  </front>
2009  <seriesInfo name="RFC" value="1950"/>
2010  <annotation>
2011    RFC 1950 is an Informational RFC, thus it might be less stable than
2012    this specification. On the other hand, this downward reference was
2013    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2014    therefore it is unlikely to cause problems in practice. See also
2015    <xref target="BCP97"/>.
2016  </annotation>
2017</reference>
2018
2019<reference anchor="RFC1951">
2020  <front>
2021    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2022    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2023      <organization>Aladdin Enterprises</organization>
2024      <address><email>ghost@aladdin.com</email></address>
2025    </author>
2026    <date month="May" year="1996"/>
2027  </front>
2028  <seriesInfo name="RFC" value="1951"/>
2029  <annotation>
2030    RFC 1951 is an Informational RFC, thus it might be less stable than
2031    this specification. On the other hand, this downward reference was
2032    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2033    therefore it is unlikely to cause problems in practice. See also
2034    <xref target="BCP97"/>.
2035  </annotation>
2036</reference>
2037
2038<reference anchor="RFC1952">
2039  <front>
2040    <title>GZIP file format specification version 4.3</title>
2041    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2042      <organization>Aladdin Enterprises</organization>
2043      <address><email>ghost@aladdin.com</email></address>
2044    </author>
2045    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2046      <address><email>gzip@prep.ai.mit.edu</email></address>
2047    </author>
2048    <author initials="M." surname="Adler" fullname="Mark Adler">
2049      <address><email>madler@alumni.caltech.edu</email></address>
2050    </author>
2051    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2052      <address><email>ghost@aladdin.com</email></address>
2053    </author>
2054    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2055      <address><email>randeg@alumni.rpi.edu</email></address>
2056    </author>
2057    <date month="May" year="1996"/>
2058  </front>
2059  <seriesInfo name="RFC" value="1952"/>
2060  <annotation>
2061    RFC 1952 is an Informational RFC, thus it might be less stable than
2062    this specification. On the other hand, this downward reference was
2063    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2064    therefore it is unlikely to cause problems in practice. See also
2065    <xref target="BCP97"/>.
2066  </annotation>
2067</reference>
2068
2069<reference anchor="RFC2045">
2070  <front>
2071    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2072    <author initials="N." surname="Freed" fullname="Ned Freed">
2073      <organization>Innosoft International, Inc.</organization>
2074      <address><email>ned@innosoft.com</email></address>
2075    </author>
2076    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2077      <organization>First Virtual Holdings</organization>
2078      <address><email>nsb@nsb.fv.com</email></address>
2079    </author>
2080    <date month="November" year="1996"/>
2081  </front>
2082  <seriesInfo name="RFC" value="2045"/>
2083</reference>
2084
2085<reference anchor="RFC2046">
2086  <front>
2087    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2088    <author initials="N." surname="Freed" fullname="Ned Freed">
2089      <organization>Innosoft International, Inc.</organization>
2090      <address><email>ned@innosoft.com</email></address>
2091    </author>
2092    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2093      <organization>First Virtual Holdings</organization>
2094      <address><email>nsb@nsb.fv.com</email></address>
2095    </author>
2096    <date month="November" year="1996"/>
2097  </front>
2098  <seriesInfo name="RFC" value="2046"/>
2099</reference>
2100
2101<reference anchor="RFC2119">
2102  <front>
2103    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2104    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2105      <organization>Harvard University</organization>
2106      <address><email>sob@harvard.edu</email></address>
2107    </author>
2108    <date month="March" year="1997"/>
2109  </front>
2110  <seriesInfo name="BCP" value="14"/>
2111  <seriesInfo name="RFC" value="2119"/>
2112</reference>
2113
2114<reference anchor="RFC4647">
2115  <front>
2116    <title>Matching of Language Tags</title>
2117    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2118      <organization>Yahoo! Inc.</organization>
2119      <address><email>addison@inter-locale.com</email></address>
2120    </author>
2121    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2122      <organization>Google</organization>
2123      <address><email>mark.davis@macchiato.com</email></address>
2124    </author>
2125    <date year="2006" month="September"/>
2126  </front>
2127  <seriesInfo name="BCP" value="47"/>
2128  <seriesInfo name="RFC" value="4647"/>
2129</reference>
2130
2131<reference anchor="RFC5234">
2132  <front>
2133    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2134    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2135      <organization>Brandenburg InternetWorking</organization>
2136      <address>
2137        <email>dcrocker@bbiw.net</email>
2138      </address> 
2139    </author>
2140    <author initials="P." surname="Overell" fullname="Paul Overell">
2141      <organization>THUS plc.</organization>
2142      <address>
2143        <email>paul.overell@thus.net</email>
2144      </address>
2145    </author>
2146    <date month="January" year="2008"/>
2147  </front>
2148  <seriesInfo name="STD" value="68"/>
2149  <seriesInfo name="RFC" value="5234"/>
2150</reference>
2151
2152<reference anchor="RFC5646">
2153  <front>
2154    <title>Tags for Identifying Languages</title>
2155    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2156      <organization>Lab126</organization>
2157      <address><email>addison@inter-locale.com</email></address>
2158    </author>
2159    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2160      <organization>Google</organization>
2161      <address><email>mark.davis@google.com</email></address>
2162    </author>
2163    <date month="September" year="2009"/>
2164  </front>
2165  <seriesInfo name="BCP" value="47"/>
2166  <seriesInfo name="RFC" value="5646"/>
2167</reference>
2168
2169</references>
2170
2171<references title="Informative References">
2172
2173<reference anchor="RFC1945">
2174  <front>
2175    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2176    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2177      <organization>MIT, Laboratory for Computer Science</organization>
2178      <address><email>timbl@w3.org</email></address>
2179    </author>
2180    <author initials="R.T." 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="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2185      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2186      <address><email>frystyk@w3.org</email></address>
2187    </author>
2188    <date month="May" year="1996"/>
2189  </front>
2190  <seriesInfo name="RFC" value="1945"/>
2191</reference>
2192
2193<reference anchor="RFC2049">
2194  <front>
2195    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2196    <author initials="N." surname="Freed" fullname="Ned Freed">
2197      <organization>Innosoft International, Inc.</organization>
2198      <address><email>ned@innosoft.com</email></address>
2199    </author>
2200    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2201      <organization>First Virtual Holdings</organization>
2202      <address><email>nsb@nsb.fv.com</email></address>
2203    </author>
2204    <date month="November" year="1996"/>
2205  </front>
2206  <seriesInfo name="RFC" value="2049"/>
2207</reference>
2208
2209<reference anchor="RFC2068">
2210  <front>
2211    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2212    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2213      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2214      <address><email>fielding@ics.uci.edu</email></address>
2215    </author>
2216    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2217      <organization>MIT Laboratory for Computer Science</organization>
2218      <address><email>jg@w3.org</email></address>
2219    </author>
2220    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2221      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2222      <address><email>mogul@wrl.dec.com</email></address>
2223    </author>
2224    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2225      <organization>MIT Laboratory for Computer Science</organization>
2226      <address><email>frystyk@w3.org</email></address>
2227    </author>
2228    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2229      <organization>MIT Laboratory for Computer Science</organization>
2230      <address><email>timbl@w3.org</email></address>
2231    </author>
2232    <date month="January" year="1997"/>
2233  </front>
2234  <seriesInfo name="RFC" value="2068"/>
2235</reference>
2236
2237<reference anchor="RFC2076">
2238  <front>
2239    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2240    <author initials="J." surname="Palme" fullname="Jacob Palme">
2241      <organization>Stockholm University/KTH</organization>
2242      <address><email>jpalme@dsv.su.se</email></address>
2243    </author>
2244    <date month="February" year="1997"/>
2245  </front>
2246  <seriesInfo name="RFC" value="2076"/>
2247</reference>
2248
2249<reference anchor="RFC2277">
2250  <front>
2251    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2252    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2253      <organization>UNINETT</organization>
2254      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2255    </author>
2256    <date month="January" year="1998"/>
2257  </front>
2258  <seriesInfo name="BCP" value="18"/>
2259  <seriesInfo name="RFC" value="2277"/>
2260</reference>
2261
2262<reference anchor="RFC2295">
2263  <front>
2264    <title abbrev="HTTP Content Negotiation">Transparent Content Negotiation in HTTP</title>
2265    <author initials="K." surname="Holtman" fullname="Koen Holtman">
2266      <organization>Technische Universiteit Eindhoven</organization>
2267      <address>
2268        <email>koen@win.tue.nl</email>
2269      </address>
2270    </author>
2271    <author initials="A.H." surname="Mutz" fullname="Andrew H. Mutz">
2272      <organization>Hewlett-Packard Company</organization>
2273      <address>
2274        <email>mutz@hpl.hp.com</email>
2275      </address>
2276    </author>
2277    <date year="1998" month="March"/>
2278  </front>
2279  <seriesInfo name="RFC" value="2295"/>
2280</reference>
2281
2282<reference anchor="RFC2388">
2283  <front>
2284    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2285    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2286      <organization>Xerox Palo Alto Research Center</organization>
2287      <address><email>masinter@parc.xerox.com</email></address>
2288    </author>
2289    <date year="1998" month="August"/>
2290  </front>
2291  <seriesInfo name="RFC" value="2388"/>
2292</reference>
2293
2294<reference anchor="RFC2557">
2295  <front>
2296    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2297    <author initials="F." surname="Palme" fullname="Jacob Palme">
2298      <organization>Stockholm University and KTH</organization>
2299      <address><email>jpalme@dsv.su.se</email></address>
2300    </author>
2301    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2302      <organization>Microsoft Corporation</organization>
2303      <address><email>alexhop@microsoft.com</email></address>
2304    </author>
2305    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2306      <organization>Lotus Development Corporation</organization>
2307      <address><email>Shelness@lotus.com</email></address>
2308    </author>
2309    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2310      <address><email>stef@nma.com</email></address>
2311    </author>
2312    <date year="1999" month="March"/>
2313  </front>
2314  <seriesInfo name="RFC" value="2557"/>
2315</reference>
2316
2317<reference anchor="RFC2616">
2318  <front>
2319    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2320    <author initials="R." surname="Fielding" fullname="R. Fielding">
2321      <organization>University of California, Irvine</organization>
2322      <address><email>fielding@ics.uci.edu</email></address>
2323    </author>
2324    <author initials="J." surname="Gettys" fullname="J. Gettys">
2325      <organization>W3C</organization>
2326      <address><email>jg@w3.org</email></address>
2327    </author>
2328    <author initials="J." surname="Mogul" fullname="J. Mogul">
2329      <organization>Compaq Computer Corporation</organization>
2330      <address><email>mogul@wrl.dec.com</email></address>
2331    </author>
2332    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2333      <organization>MIT Laboratory for Computer Science</organization>
2334      <address><email>frystyk@w3.org</email></address>
2335    </author>
2336    <author initials="L." surname="Masinter" fullname="L. Masinter">
2337      <organization>Xerox Corporation</organization>
2338      <address><email>masinter@parc.xerox.com</email></address>
2339    </author>
2340    <author initials="P." surname="Leach" fullname="P. Leach">
2341      <organization>Microsoft Corporation</organization>
2342      <address><email>paulle@microsoft.com</email></address>
2343    </author>
2344    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2345      <organization>W3C</organization>
2346      <address><email>timbl@w3.org</email></address>
2347    </author>
2348    <date month="June" year="1999"/>
2349  </front>
2350  <seriesInfo name="RFC" value="2616"/>
2351</reference>
2352
2353<reference anchor="RFC3629">
2354  <front>
2355    <title>UTF-8, a transformation format of ISO 10646</title>
2356    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2357      <organization>Alis Technologies</organization>
2358      <address><email>fyergeau@alis.com</email></address>
2359    </author>
2360    <date month="November" year="2003"/>
2361  </front>
2362  <seriesInfo name="STD" value="63"/>
2363  <seriesInfo name="RFC" value="3629"/>
2364</reference>
2365
2366<reference anchor="RFC3864">
2367  <front>
2368    <title>Registration Procedures for Message Header Fields</title>
2369    <author initials="G." surname="Klyne" fullname="G. Klyne">
2370      <organization>Nine by Nine</organization>
2371      <address><email>GK-IETF@ninebynine.org</email></address>
2372    </author>
2373    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2374      <organization>BEA Systems</organization>
2375      <address><email>mnot@pobox.com</email></address>
2376    </author>
2377    <author initials="J." surname="Mogul" fullname="J. Mogul">
2378      <organization>HP Labs</organization>
2379      <address><email>JeffMogul@acm.org</email></address>
2380    </author>
2381    <date year="2004" month="September"/>
2382  </front>
2383  <seriesInfo name="BCP" value="90"/>
2384  <seriesInfo name="RFC" value="3864"/>
2385</reference>
2386
2387<reference anchor="RFC4288">
2388  <front>
2389    <title>Media Type Specifications and Registration Procedures</title>
2390    <author initials="N." surname="Freed" fullname="N. Freed">
2391      <organization>Sun Microsystems</organization>
2392      <address>
2393        <email>ned.freed@mrochek.com</email>
2394      </address>
2395    </author>
2396    <author initials="J." surname="Klensin" fullname="J. Klensin">
2397      <address>
2398        <email>klensin+ietf@jck.com</email>
2399      </address>
2400    </author>
2401    <date year="2005" month="December"/>
2402  </front>
2403  <seriesInfo name="BCP" value="13"/>
2404  <seriesInfo name="RFC" value="4288"/>
2405</reference>
2406
2407<reference anchor="RFC5226">
2408  <front>
2409    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2410    <author initials="T." surname="Narten" fullname="T. Narten">
2411      <organization>IBM</organization>
2412      <address><email>narten@us.ibm.com</email></address>
2413    </author>
2414    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2415      <organization>Google</organization>
2416      <address><email>Harald@Alvestrand.no</email></address>
2417    </author>
2418    <date year="2008" month="May"/>
2419  </front>
2420  <seriesInfo name="BCP" value="26"/>
2421  <seriesInfo name="RFC" value="5226"/>
2422</reference>
2423
2424<reference anchor="RFC5322">
2425  <front>
2426    <title>Internet Message Format</title>
2427    <author initials="P." surname="Resnick" fullname="P. Resnick">
2428      <organization>Qualcomm Incorporated</organization>
2429    </author>
2430    <date year="2008" month="October"/>
2431  </front>
2432  <seriesInfo name="RFC" value="5322"/>
2433</reference>
2434
2435<reference anchor="BCP97">
2436  <front>
2437    <title>Handling Normative References to Standards-Track Documents</title>
2438    <author initials="J." surname="Klensin" fullname="J. Klensin">
2439      <address>
2440        <email>klensin+ietf@jck.com</email>
2441      </address>
2442    </author>
2443    <author initials="S." surname="Hartman" fullname="S. Hartman">
2444      <organization>MIT</organization>
2445      <address>
2446        <email>hartmans-ietf@mit.edu</email>
2447      </address>
2448    </author>
2449    <date year="2007" month="June"/>
2450  </front>
2451  <seriesInfo name="BCP" value="97"/>
2452  <seriesInfo name="RFC" value="4897"/>
2453</reference>
2454
2455
2456</references>
2457
2458<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2459<t>
2460   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
2461   allow a message-body to be transmitted in an open variety of
2462   representations and with extensible mechanisms. However, RFC 2045
2463   discusses mail, and HTTP has a few features that are different from
2464   those described in MIME. These differences were carefully chosen
2465   to optimize performance over binary connections, to allow greater
2466   freedom in the use of new media types, to make date comparisons
2467   easier, and to acknowledge the practice of some early HTTP servers
2468   and clients.
2469</t>
2470<t>
2471   This appendix describes specific areas where HTTP differs from MIME.
2472   Proxies and gateways to strict MIME environments SHOULD be
2473   aware of these differences and provide the appropriate conversions
2474   where necessary. Proxies and gateways from MIME environments to HTTP
2475   also need to be aware of the differences because some conversions
2476   might be required.
2477</t>
2478
2479<section title="MIME-Version" anchor="mime-version">
2480  <iref primary="true" item="MIME-Version header"/>
2481  <iref primary="true" item="Headers" subitem="MIME-Version"/>
2482 
2483 
2484<t>
2485   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
2486   include a single MIME-Version general-header field to indicate what
2487   version of the MIME protocol was used to construct the message. Use
2488   of the MIME-Version header field indicates that the message is in
2489   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2490   Proxies/gateways are responsible for ensuring full compliance (where
2491   possible) when exporting HTTP messages to strict MIME environments.
2492</t>
2493<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/><artwork type="abnf2616"><![CDATA[
2494  MIME-Version   = "MIME-Version" ":" OWS MIME-Version-v
2495  MIME-Version-v = 1*DIGIT "." 1*DIGIT
2496]]></artwork></figure>
2497<t>
2498   MIME version "1.0" is the default for use in HTTP/1.1. However,
2499   HTTP/1.1 message parsing and semantics are defined by this document
2500   and not the MIME specification.
2501</t>
2502</section>
2503
2504<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2505<t>
2506   MIME requires that an Internet mail body-part be converted to
2507   canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
2508   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2509   allowed for subtypes of the "text" media type when transmitted over
2510   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2511   line breaks as CRLF and forbids the use of CR or LF outside of line
2512   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2513   line break within text content when a message is transmitted over
2514   HTTP.
2515</t>
2516<t>
2517   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2518   environment SHOULD translate all line breaks within the text media
2519   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2520   canonical form of CRLF. Note, however, that this might be complicated
2521   by the presence of a Content-Encoding and by the fact that HTTP
2522   allows the use of some character sets which do not use octets 13 and
2523   10 to represent CR and LF, as is the case for some multi-byte
2524   character sets.
2525</t>
2526<t>
2527   Conversion will break any cryptographic
2528   checksums applied to the original content unless the original content
2529   is already in canonical form. Therefore, the canonical form is
2530   recommended for any content that uses such checksums in HTTP.
2531</t>
2532</section>
2533
2534
2535<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2536<t>
2537   HTTP/1.1 uses a restricted set of date formats (Section 6.1 of <xref target="Part1"/>) to
2538   simplify the process of date comparison. Proxies and gateways from
2539   other protocols SHOULD ensure that any Date header field present in a
2540   message conforms to one of the HTTP/1.1 formats and rewrite the date
2541   if necessary.
2542</t>
2543</section>
2544
2545<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2546<t>
2547   MIME does not include any concept equivalent to HTTP/1.1's
2548   Content-Encoding header field. Since this acts as a modifier on the
2549   media type, proxies and gateways from HTTP to MIME-compliant
2550   protocols MUST either change the value of the Content-Type header
2551   field or decode the representation before forwarding the message. (Some
2552   experimental applications of Content-Type for Internet mail have used
2553   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2554   a function equivalent to Content-Encoding. However, this parameter is
2555   not part of the MIME standards).
2556</t>
2557</section>
2558
2559<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2560<t>
2561   HTTP does not use the Content-Transfer-Encoding field of MIME.
2562   Proxies and gateways from MIME-compliant protocols to HTTP MUST
2563   remove any Content-Transfer-Encoding
2564   prior to delivering the response message to an HTTP client.
2565</t>
2566<t>
2567   Proxies and gateways from HTTP to MIME-compliant protocols are
2568   responsible for ensuring that the message is in the correct format
2569   and encoding for safe transport on that protocol, where "safe
2570   transport" is defined by the limitations of the protocol being used.
2571   Such a proxy or gateway SHOULD label the data with an appropriate
2572   Content-Transfer-Encoding if doing so will improve the likelihood of
2573   safe transport over the destination protocol.
2574</t>
2575</section>
2576
2577<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2578<t>
2579   HTTP/1.1 introduces the Transfer-Encoding header field (Section 9.7 of <xref target="Part1"/>).
2580   Proxies/gateways MUST remove any transfer-coding prior to
2581   forwarding a message via a MIME-compliant protocol.
2582</t>
2583</section>
2584
2585<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2586<t>
2587   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2588   need to be aware of MIME line length limitations. Since HTTP does not
2589   have this limitation, HTTP does not fold long lines. MHTML messages
2590   being transported by HTTP follow all conventions of MHTML, including
2591   line length limitations and folding, canonicalization, etc., since
2592   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2593   does not interpret the content or any MIME header lines that might be
2594   contained therein.
2595</t>
2596</section>
2597</section>
2598
2599<section title="Additional Features" anchor="additional.features">
2600<t>
2601   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2602   existing HTTP implementations, but not consistently and correctly
2603   across most HTTP/1.1 applications. Implementors are advised to be
2604   aware of these features, but cannot rely upon their presence in, or
2605   interoperability with, other HTTP/1.1 applications. Some of these
2606   describe proposed experimental features, and some describe features
2607   that experimental deployment found lacking that are now addressed in
2608   the base HTTP/1.1 specification.
2609</t>
2610<t>
2611   A number of other header fields, such as Content-Disposition and Title,
2612   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2613</t>
2614</section>
2615
2616<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2617<t>
2618  Clarify contexts that charset is used in.
2619  (<xref target="character.sets"/>)
2620</t>
2621<t>
2622  Remove base URI setting semantics for Content-Location due to poor
2623  implementation support, which was caused by too many broken servers emitting
2624  bogus Content-Location header fields, and also the potentially undesirable effect
2625  of potentially breaking relative links in content-negotiated resources.
2626  (<xref target="header.content-location"/>)
2627</t>
2628<t>
2629  Remove reference to non-existant identity transfer-coding value tokens.
2630  (<xref target="no.content-transfer-encoding"/>)
2631</t>
2632</section>
2633
2634
2635<section title="Collected ABNF" anchor="collected.abnf">
2636<figure>
2637<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
2638Accept = "Accept:" OWS Accept-v
2639Accept-Charset = "Accept-Charset:" OWS Accept-Charset-v
2640Accept-Charset-v = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2641 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2642 qvalue ] ] )
2643Accept-Encoding = "Accept-Encoding:" OWS Accept-Encoding-v
2644Accept-Encoding-v = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2645 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2646Accept-Language = "Accept-Language:" OWS Accept-Language-v
2647Accept-Language-v = *( "," OWS ) language-range [ OWS ";" OWS "q="
2648 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2649 ] )
2650Accept-v = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2651 OWS media-range [ accept-params ] ] ) ]
2652
2653Content-Encoding = "Content-Encoding:" OWS Content-Encoding-v
2654Content-Encoding-v = *( "," OWS ) content-coding *( OWS "," [ OWS
2655 content-coding ] )
2656Content-Language = "Content-Language:" OWS Content-Language-v
2657Content-Language-v = *( "," OWS ) language-tag *( OWS "," [ OWS
2658 language-tag ] )
2659Content-Length = <Content-Length, defined in [Part1], Section 9.2>
2660Content-Location = "Content-Location:" OWS Content-Location-v
2661Content-Location-v = absolute-URI / partial-URI
2662Content-MD5 = "Content-MD5:" OWS Content-MD5-v
2663Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
2664Content-Range = <Content-Range, defined in [Part5], Section 5.2>
2665Content-Type = "Content-Type:" OWS Content-Type-v
2666Content-Type-v = media-type
2667
2668Expires = <Expires, defined in [Part6], Section 3.3>
2669
2670Last-Modified = <Last-Modified, defined in [Part4], Section 6.6>
2671
2672MIME-Version = "MIME-Version:" OWS MIME-Version-v
2673MIME-Version-v = 1*DIGIT "." 1*DIGIT
2674
2675OWS = <OWS, defined in [Part1], Section 1.2.2>
2676
2677absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
2678accept-ext = OWS ";" OWS token [ "=" word ]
2679accept-params = OWS ";" OWS "q=" qvalue *accept-ext
2680attribute = token
2681
2682charset = token
2683codings = ( content-coding / "*" )
2684content-coding = token
2685
2686language-range = <language-range, defined in [RFC4647], Section 2.1>
2687language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
2688
2689media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2690 ";" OWS parameter )
2691media-type = type "/" subtype *( OWS ";" OWS parameter )
2692
2693parameter = attribute "=" value
2694partial-URI = <partial-URI, defined in [Part1], Section 2.6>
2695
2696qvalue = <qvalue, defined in [Part1], Section 6.4>
2697
2698subtype = token
2699
2700token = <token, defined in [Part1], Section 1.2.2>
2701type = token
2702
2703value = word
2704
2705word = <word, defined in [Part1], Section 1.2.2>
2706]]></artwork>
2707</figure>
2708<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
2709; Accept defined but not used
2710; Accept-Charset defined but not used
2711; Accept-Encoding defined but not used
2712; Accept-Language defined but not used
2713; Content-Encoding defined but not used
2714; Content-Language defined but not used
2715; Content-Length defined but not used
2716; Content-Location defined but not used
2717; Content-MD5 defined but not used
2718; Content-Range defined but not used
2719; Content-Type defined but not used
2720; Expires defined but not used
2721; Last-Modified defined but not used
2722; MIME-Version defined but not used
2723]]></artwork></figure></section>
2724
2725
2726<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2727
2728<section title="Since RFC 2616">
2729<t>
2730  Extracted relevant partitions from <xref target="RFC2616"/>.
2731</t>
2732</section>
2733
2734<section title="Since draft-ietf-httpbis-p3-payload-00">
2735<t>
2736  Closed issues:
2737  <list style="symbols">
2738    <t>
2739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2740      "Media Type Registrations"
2741      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2742    </t>
2743    <t>
2744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2745      "Clarification regarding quoting of charset values"
2746      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2747    </t>
2748    <t>
2749      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2750      "Remove 'identity' token references"
2751      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2752    </t>
2753    <t>
2754      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2755      "Accept-Encoding BNF"
2756    </t>
2757    <t>
2758      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2759      "Normative and Informative references"
2760    </t>
2761    <t>
2762      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2763      "RFC1700 references"
2764    </t>
2765    <t>
2766      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2767      "Updating to RFC4288"
2768    </t>
2769    <t>
2770      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2771      "Informative references"
2772    </t>
2773    <t>
2774      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2775      "ISO-8859-1 Reference"
2776    </t>
2777    <t>
2778      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2779      "Encoding References Normative"
2780    </t>
2781    <t>
2782      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2783      "Normative up-to-date references"
2784    </t>
2785  </list>
2786</t>
2787</section>
2788
2789<section title="Since draft-ietf-httpbis-p3-payload-01">
2790<t>
2791  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2792  <list style="symbols">
2793    <t>
2794      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2795    </t>
2796  </list>
2797</t>
2798</section>
2799
2800<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2801<t>
2802  Closed issues:
2803  <list style="symbols">
2804    <t>
2805      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2806      "Quoting Charsets"
2807    </t>
2808    <t>
2809      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2810      "Classification for Allow header"
2811    </t>
2812    <t>
2813      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2814      "missing default for qvalue in description of Accept-Encoding"
2815    </t>
2816  </list>
2817</t>
2818<t>
2819  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2820  <list style="symbols">
2821    <t>
2822      Reference RFC 3984, and update header field registrations for headers defined
2823      in this document.
2824    </t>
2825  </list>
2826</t>
2827</section>
2828
2829<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2830<t>
2831  Closed issues:
2832  <list style="symbols">
2833    <t>
2834      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2835      "Quoting Charsets"
2836    </t>
2837    <t>
2838      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2839      "language tag matching (Accept-Language) vs RFC4647"
2840    </t>
2841    <t>
2842      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2843      "RFC 1806 has been replaced by RFC2183"
2844    </t>
2845  </list>
2846</t>
2847<t>
2848  Other changes:
2849  <list style="symbols">
2850    <t>
2851      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2852      "Encoding References Normative" -- rephrase the annotation and reference
2853      <xref target="BCP97"/>.
2854    </t>
2855  </list>
2856</t>
2857 </section>
2858
2859<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2860<t>
2861  Closed issues:
2862  <list style="symbols">
2863    <t>
2864      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2865      "RFC 2822 is updated by RFC 5322"
2866    </t>
2867  </list>
2868</t>
2869<t>
2870  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2871  <list style="symbols">
2872    <t>
2873      Use "/" instead of "|" for alternatives.
2874    </t>
2875    <t>
2876      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2877      whitespace ("OWS") and required whitespace ("RWS").
2878    </t>
2879    <t>
2880      Rewrite ABNFs to spell out whitespace rules, factor out
2881      header field value format definitions.
2882    </t>
2883  </list>
2884</t>
2885</section>
2886
2887<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2888<t>
2889  Closed issues:
2890  <list style="symbols">
2891    <t>
2892      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
2893      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2894    </t>
2895  </list>
2896</t>
2897<t>
2898  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2899  <list style="symbols">
2900    <t>
2901      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
2902    </t>
2903  </list>
2904</t>
2905<t>
2906  Other changes:
2907  <list style="symbols">
2908    <t>
2909      Move definition of quality values into Part 1.
2910    </t>
2911  </list>
2912</t>
2913</section>
2914
2915<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
2916<t>
2917  Closed issues:
2918  <list style="symbols">
2919    <t>
2920      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2921      "Content-Location isn't special"
2922    </t>
2923    <t>
2924      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2925      "Content Sniffing"
2926    </t>
2927  </list>
2928</t>
2929</section>
2930
2931<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
2932<t>
2933  Closed issues:
2934  <list style="symbols">
2935    <t>
2936      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
2937      "Updated reference for language tags"
2938    </t>
2939    <t>
2940      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
2941      "Clarify rules for determining what entities a response carries"
2942    </t>
2943    <t>
2944      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
2945      "Content-Location base-setting problems"
2946    </t>
2947    <t>
2948      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2949      "Content Sniffing"
2950    </t>
2951    <t>
2952      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
2953      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2954    </t>
2955    <t>
2956      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
2957      "move definitions of gzip/deflate/compress to part 1"
2958    </t>
2959  </list>
2960</t>
2961<t>
2962  Partly resolved issues:
2963  <list style="symbols">
2964    <t>
2965      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
2966      "update IANA requirements wrt Transfer-Coding values" (add the
2967      IANA Considerations subsection)
2968    </t>
2969    <t>
2970      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
2971      "update IANA requirements wrt Content-Coding values" (add the
2972      IANA Considerations subsection)
2973    </t>
2974  </list>
2975</t>
2976</section>
2977
2978<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
2979<t>
2980  Closed issues:
2981  <list style="symbols">
2982    <t>
2983      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
2984      "Content Negotiation for media types"
2985    </t>
2986    <t>
2987      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
2988      "Accept-Language: which RFC4647 filtering?"
2989    </t>
2990  </list>
2991</t>
2992</section>
2993
2994<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
2995<t>
2996  Closed issues:
2997  <list style="symbols">
2998    <t>
2999      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
3000      "MIME-Version not listed in P1, general header fields"
3001    </t>
3002    <t>
3003      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
3004      "IANA registry for content/transfer encodings"
3005    </t>
3006    <t>
3007      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3008      "Content Sniffing"
3009    </t>
3010    <t>
3011      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
3012      "use of term "word" when talking about header structure"
3013    </t>
3014  </list>
3015</t>
3016<t>
3017  Partly resolved issues:
3018  <list style="symbols">
3019    <t>
3020      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3021      "Term for the requested resource's URI"
3022    </t>
3023  </list>
3024</t>
3025</section>
3026
3027<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
3028<t>
3029  Closed issues:
3030  <list style="symbols">
3031    <t>
3032      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3033      "Clarify 'Requested Variant'"
3034    </t>
3035    <t>
3036      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3037      "Content-Location isn't special"
3038    </t>
3039    <t>
3040      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
3041      "Delimiting messages with multipart/byteranges"
3042    </t>
3043    <t>
3044      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3045      "Clarify entity / representation / variant terminology"
3046    </t>
3047    <t>
3048      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
3049      "confusing req. language for Content-Location"
3050    </t>
3051    <t>
3052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
3053      "Content-Location on 304 responses"
3054    </t>
3055    <t>
3056      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
3057      "'requested resource' in content-encoding definition"
3058    </t>
3059    <t>
3060      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3061      "consider removing the 'changes from 2068' sections"
3062    </t>
3063  </list>
3064</t>
3065<t>
3066  Partly resolved issues:
3067  <list style="symbols">
3068    <t>
3069      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3070      "Content-MD5 and partial responses"
3071    </t>
3072  </list>
3073</t>
3074</section>
3075
3076<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
3077<t>
3078  Closed issues:
3079  <list style="symbols">
3080    <t>
3081      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/123"/>:
3082      "Factor out Content-Disposition"
3083    </t>
3084  </list>
3085</t>
3086</section>
3087
3088</section>
3089
3090</back>
3091</rfc>
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