source: draft-ietf-httpbis/11/draft-ietf-httpbis-p3-payload-11.xml @ 973

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prepare publication of -11 drafts on 2010-08-04.

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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-11">
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="August" year="2010" day="4"/>
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.10"/>.
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   The next 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 
274<t>
275  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
276</t>
277<figure><artwork type="abnf2616"><![CDATA[
278  quoted-string  = <quoted-string, defined in [Part1], Section 1.2.2>
279  token          = <token, defined in [Part1], Section 1.2.2>
280  word           = <word, defined in [Part1], Section 1.2.2>
281  OWS            = <OWS, defined in [Part1], Section 1.2.2>
282]]></artwork></figure>
283</section>
284
285<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
286 
287 
288 
289 
290 
291 
292 
293 
294 
295<t>
296  The ABNF rules below are defined in other parts:
297</t>
298<figure><artwork type="abnf2616"><![CDATA[
299  absolute-URI   = <absolute-URI, defined in [Part1], Section 2.6>
300  Content-Length = <Content-Length, defined in [Part1], Section 9.2>
301  header-field   = <header-field, defined in [Part1], Section 3.2>
302  partial-URI    = <partial-URI, defined in [Part1], Section 2.6>
303  qvalue         = <qvalue, defined in [Part1], Section 6.4>
304]]></artwork></figure>
305<figure><artwork type="abnf2616"><![CDATA[
306  Last-Modified  = <Last-Modified, defined in [Part4], Section 6.6>
307]]></artwork></figure>
308<figure><artwork type="abnf2616"><![CDATA[
309  Content-Range  = <Content-Range, defined in [Part5], Section 5.2>
310]]></artwork></figure>
311<figure><artwork type="abnf2616"><![CDATA[
312  Expires        = <Expires, defined in [Part6], Section 3.3>
313]]></artwork></figure>
314</section>
315
316</section>
317
318</section>
319
320<section title="Protocol Parameters" anchor="protocol.parameters">
321
322<section title="Character Sets" anchor="character.sets">
323<t>
324   HTTP uses the same definition of the term "character set" as that
325   described for MIME:
326</t>
327<t>
328   The term "character set" is used in this document to refer to a
329   method used with one or more tables to convert a sequence of octets
330   into a sequence of characters. Note that unconditional conversion in
331   the other direction is not required, in that not all characters might
332   be available in a given character set and a character set might provide
333   more than one sequence of octets to represent a particular character.
334   This definition is intended to allow various kinds of character
335   encoding, from simple single-table mappings such as US-ASCII to
336   complex table switching methods such as those that use ISO-2022's
337   techniques. However, the definition associated with a MIME character
338   set name MUST fully specify the mapping to be performed from octets
339   to characters. In particular, use of external profiling information
340   to determine the exact mapping is not permitted.
341</t>
342<t><list>
343  <t>
344    Note: This use of the term "character set" is more commonly
345    referred to as a "character encoding". However, since HTTP and
346    MIME share the same registry, it is important that the terminology
347    also be shared.
348  </t>
349</list></t>
350<t anchor="rule.charset">
351 
352   HTTP character sets are identified by case-insensitive tokens. The
353   complete set of tokens is defined by the IANA Character Set registry
354   (<eref target="http://www.iana.org/assignments/character-sets"/>).
355</t>
356<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
357  charset = token
358]]></artwork></figure>
359<t>
360   Although HTTP allows an arbitrary token to be used as a charset
361   value, any token that has a predefined value within the IANA
362   Character Set registry MUST represent the character set defined
363   by that registry. Applications SHOULD limit their use of character
364   sets to those defined by the IANA registry.
365</t>
366<t>
367   HTTP uses charset in two contexts: within an Accept-Charset request
368   header (in which the charset value is an unquoted token) and as the
369   value of a parameter in a Content-Type header (within a request or
370   response), in which case the parameter value of the charset parameter
371   can be quoted.
372</t>
373<t>
374   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
375   <xref target="RFC2277"/>.
376</t>
377
378<section title="Missing Charset" anchor="missing.charset">
379<t>
380   Some HTTP/1.0 software has interpreted a Content-Type header without
381   charset parameter incorrectly to mean "recipient should guess".
382   Senders wishing to defeat this behavior MAY include a charset
383   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and SHOULD do so when
384   it is known that it will not confuse the recipient.
385</t>
386<t>
387   Unfortunately, some older HTTP/1.0 clients did not deal properly with
388   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
389   charset label provided by the sender; and those user agents that have
390   a provision to "guess" a charset MUST use the charset from the
391   content-type field if they support that charset, rather than the
392   recipient's preference, when initially displaying a document. See
393   <xref target="canonicalization.and.text.defaults"/>.
394</t>
395</section>
396</section>
397
398<section title="Content Codings" anchor="content.codings">
399 
400<t>
401   Content coding values indicate an encoding transformation that has
402   been or can be applied to a representation. Content codings are primarily
403   used to allow a representation to be compressed or otherwise usefully
404   transformed without losing the identity of its underlying media type
405   and without loss of information. Frequently, the representation is stored in
406   coded form, transmitted directly, and only decoded by the recipient.
407</t>
408<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
409  content-coding   = token
410]]></artwork></figure>
411<t>
412   All content-coding values are case-insensitive. HTTP/1.1 uses
413   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
414   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
415   describes the content-coding, what is more important is that it
416   indicates what decoding mechanism will be required to remove the
417   encoding.
418</t>
419<t>
420   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
421  <list>
422    <t>
423      See Section 6.2.2.1 of <xref target="Part1"/>.
424    </t>
425  </list>
426</t>
427<t>
428   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
429  <list>
430    <t>
431      See Section 6.2.2.2 of <xref target="Part1"/>.
432    </t>
433  </list>
434</t>
435<t>
436   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
437  <list>
438    <t>
439      See Section 6.2.2.3 of <xref target="Part1"/>.
440    </t>
441  </list>
442</t>
443<t>
444   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
445  <list><t>
446        The default (identity) encoding; the use of no transformation
447        whatsoever. This content-coding is used only in the Accept-Encoding
448        header, and SHOULD NOT  be used in the Content-Encoding
449        header.
450  </t></list>
451</t>
452
453<section title="Content Coding Registry" anchor="content.coding.registry">
454<t>
455   The HTTP Content Coding Registry defines the name space for the content
456   coding names.
457</t>
458<t>
459   Registrations MUST include the following fields:
460   <list style="symbols">
461     <t>Name</t>
462     <t>Description</t>
463     <t>Pointer to specification text</t>
464   </list>
465</t>
466<t>
467   Names of content codings MUST NOT overlap with names of transfer codings
468   (Section 6.2 of <xref target="Part1"/>), unless the encoding transformation is identical (as it
469   is the case for the compression codings defined in
470   Section 6.2.2 of <xref target="Part1"/>).
471</t>
472<t>
473   Values to be added to this name space require a specification
474   (see "Specification Required" in
475   Section 4.1 of <xref target="RFC5226"/>), and MUST
476   conform to the purpose of content coding defined in this section.
477</t>
478<t>
479   The registry itself is maintained at
480   <eref target="http://www.iana.org/assignments/http-parameters"/>.
481</t>
482</section>
483
484</section>
485
486<section title="Media Types" anchor="media.types">
487 
488 
489 
490<t>
491   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
492   and Accept (<xref target="header.accept"/>) header fields in order to provide
493   open and extensible data typing and type negotiation.
494</t>
495<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[
496  media-type = type "/" subtype *( OWS ";" OWS parameter )
497  type       = token
498  subtype    = token
499]]></artwork></figure>
500<t anchor="rule.parameter">
501 
502 
503 
504   Parameters MAY follow the type/subtype in the form of attribute/value
505   pairs.
506</t>
507<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[
508  parameter      = attribute "=" value
509  attribute      = token
510  value          = word
511]]></artwork></figure>
512<t>
513   The type, subtype, and parameter attribute names are case-insensitive.
514   Parameter values might or might not be case-sensitive, depending on the
515   semantics of the parameter name.  The presence or absence of a parameter might
516   be significant to the processing of a media-type, depending on its
517   definition within the media type registry.
518</t>
519<t>
520   A parameter value that matches the <xref target="core.rules" format="none">token</xref> production can be
521   transmitted as either a token or within a quoted-string. The quoted and
522   unquoted values are equivalent.
523</t>
524<t>
525   Note that some older HTTP applications do not recognize media type
526   parameters. When sending data to older HTTP applications,
527   implementations SHOULD only use media type parameters when they are
528   required by that type/subtype definition.
529</t>
530<t>
531   Media-type values are registered with the Internet Assigned Number
532   Authority (IANA). The media type registration process is
533   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
534   discouraged.
535</t>
536
537<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
538<t>
539   Internet media types are registered with a canonical form. A
540   representation transferred via HTTP messages MUST be in the
541   appropriate canonical form prior to its transmission except for
542   "text" types, as defined in the next paragraph.
543</t>
544<t>
545   When in canonical form, media subtypes of the "text" type use CRLF as
546   the text line break. HTTP relaxes this requirement and allows the
547   transport of text media with plain CR or LF alone representing a line
548   break when it is done consistently for an entire representation. HTTP
549   applications MUST accept CRLF, bare CR, and bare LF as indicating
550   a line break in text media received via HTTP. In
551   addition, if the text is in a character encoding that does not
552   use octets 13 and 10 for CR and LF respectively, as is the case for
553   some multi-byte character encodings, HTTP allows the use of whatever octet
554   sequences are defined by that character encoding to represent the
555   equivalent of CR and LF for line breaks. This flexibility regarding
556   line breaks applies only to text media in the payload body; a bare CR
557   or LF MUST NOT be substituted for CRLF within any of the HTTP control
558   structures (such as header fields and multipart boundaries).
559</t>
560<t>
561   If a representation is encoded with a content-coding, the underlying
562   data MUST be in a form defined above prior to being encoded.
563</t>
564<t>
565   The "charset" parameter is used with some media types to define the
566   character encoding (<xref target="character.sets"/>) of the data. When no explicit charset
567   parameter is provided by the sender, media subtypes of the "text"
568   type are defined to have a default charset value of "ISO-8859-1" when
569   received via HTTP. Data in character encodings other than "ISO-8859-1" or
570   its subsets MUST be labeled with an appropriate charset value. See
571   <xref target="missing.charset"/> for compatibility problems.
572</t>
573</section>
574
575<section title="Multipart Types" anchor="multipart.types">
576<t>
577   MIME provides for a number of "multipart" types -- encapsulations of
578   one or more representations within a single message-body. All multipart
579   types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
580   and MUST include a boundary parameter as part of the media type
581   value. The message body is itself a protocol element and MUST
582   therefore use only CRLF to represent line breaks between body-parts.
583</t>
584<t>
585   In general, HTTP treats a multipart message-body no differently than
586   any other media type: strictly as payload.  HTTP does not use the
587   multipart boundary as an indicator of message-body length.
588   <!-- jre: re-insert removed text pointing to caching? -->
589   In all other respects, an HTTP user agent SHOULD follow the same or similar
590   behavior as a MIME user agent would upon receipt of a multipart type.
591   The MIME header fields within each body-part of a multipart message-body
592   do not have any significance to HTTP beyond that defined by
593   their MIME semantics.
594</t>
595<t>
596   If an application receives an unrecognized multipart subtype, the
597   application MUST treat it as being equivalent to "multipart/mixed".
598</t>
599<t><list>
600  <t>
601    Note: The "multipart/form-data" type has been specifically defined
602    for carrying form data suitable for processing via the POST
603    request method, as described in <xref target="RFC2388"/>.
604  </t>
605</list></t>
606</section>
607</section>
608
609<section title="Language Tags" anchor="language.tags">
610 
611<t>
612   A language tag, as defined in <xref target="RFC5646"/>, identifies a
613   natural language spoken, written, or otherwise conveyed by human beings for
614   communication of information to other human beings. Computer languages are
615   explicitly excluded. HTTP uses language tags within the Accept-Language and
616   Content-Language fields.
617</t>
618<t>
619   In summary, a language tag is composed of one or more parts: A primary
620   language subtag followed by a possibly empty series of subtags:
621</t>
622<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
623  language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
624]]></artwork></figure>
625<t>
626   White space is not allowed within the tag and all tags are case-insensitive.
627   The name space of language subtags is administered by the IANA (see
628   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
629</t>
630<figure>
631  <preamble>Example tags include:</preamble>
632<artwork type="example"><![CDATA[
633  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
634]]></artwork>
635</figure>
636<t>
637   See <xref target="RFC5646"/> for further information.
638</t>
639</section>
640</section>
641
642<section title="Payload" anchor="payload">
643<t>
644   HTTP messages MAY transfer a payload if not otherwise restricted by
645   the request method or response status code.  The payload consists of
646   metadata, in the form of header fields, and data, in the form of the
647   sequence of octets in the message-body after any transfer-coding has
648   been decoded.
649</t>
650<iref item="payload"/>
651<t>   
652   A "payload" in HTTP is always a partial or complete
653   representation of some resource.  We use separate terms for payload
654   and representation because some messages contain only the associated
655   representation's header fields (e.g., responses to HEAD) or only some
656   part(s) of the representation (e.g., the 206 status code).
657</t>
658<section title="Payload Header Fields" anchor="payload.header.fields">
659 
660<t>
661   HTTP header fields that specifically define the payload, rather than the
662   associated representation, are referred to as "payload header fields".
663   The following payload header fields are defined by HTTP/1.1:
664</t>
665<figure><artwork><![CDATA[
666   Content-Length           ; [Part1], Section 9.2
667   Content-MD5              ; Section 6.8
668   Content-Range            ; [Part5], Section 5.2
669]]></artwork></figure>
670</section>
671
672<section title="Payload Body" anchor="payload.body">
673 
674<t>
675   A payload body is only present in a message when a message-body is
676   present, as described in Section 3.3 of <xref target="Part1"/>. The payload body is obtained
677   from the message-body by decoding any Transfer-Encoding that might
678   have been applied to ensure safe and proper transfer of the message.
679</t>
680</section>
681</section>
682
683<section title="Representation" anchor="representation">
684<iref item="representation"/>
685<t>
686   A "representation" is information in a format that can be readily
687   communicated from one party to another.  A resource representation
688   is information that reflects the state of that resource, as observed
689   at some point in the past (e.g., in a response to GET) or to be
690   desired at some point in the future (e.g., in a PUT request).
691</t>
692<t>
693   Most, but not all, representations transferred via HTTP are intended
694   to be a representation of the target resource (the resource identified
695   by the effective request URI).  The precise semantics of a representation
696   are determined by the type of message (request or response), the request
697   method, the response status code, and the representation metadata.
698   For example, the above semantic is true for the representation in any
699   200 (OK) response to GET and for the representation in any PUT request.
700   A 200 response to PUT, in contrast, contains either a representation
701   that describes the successful action or a representation of the target
702   resource, with the latter indicated by a Content-Location header field
703   with the same value as the effective request URI.  Likewise, response
704   messages with an error status code usually contain a representation that
705   describes the error and what next steps are suggested for resolving it.
706</t>
707
708<section title="Representation Header Fields" anchor="representation.header.fields">
709 
710<t>
711   Representation header fields define metadata about the representation data
712   enclosed in the message-body or, if no message-body is present, about
713   the representation that would have been transferred in a 200 response
714   to a simultaneous GET request with the same effective request URI.
715</t>
716<t>
717   The following header fields are defined as representation metadata:
718</t>
719<figure><artwork><![CDATA[
720   Content-Encoding         ; Section 6.5
721   Content-Language         ; Section 6.6
722   Content-Location         ; Section 6.7
723   Content-Type             ; Section 6.9
724   Expires                  ; [Part6], Section 3.3
725   Last-Modified            ; [Part4], Section 6.6
726]]></artwork></figure>
727</section>
728
729<section title="Representation Data" anchor="representation.data">
730 
731<t>
732   The representation body associated with an HTTP message is
733   either provided as the payload body of the message or
734   referred to by the message semantics and the effective request
735   URI.  The representation data is in a format and encoding defined by
736   the representation metadata header fields.
737</t>
738<t>
739   The data type of the representation data
740   is determined via the header fields Content-Type and Content-Encoding.
741   These define a two-layer, ordered encoding model:
742</t>
743<figure><artwork type="example"><![CDATA[
744  representation-data := Content-Encoding( Content-Type( bits ) )
745]]></artwork></figure>
746<t>
747   Content-Type specifies the media type of the underlying data, which
748   defines both the data format and how that data SHOULD be processed
749   by the recipient (within the scope of the request method semantics).
750   Any HTTP/1.1 message containing a payload body SHOULD include a
751   Content-Type header field defining the media type of the associated
752   representation unless that metadata is unknown to the sender.
753   If the Content-Type header field is not present, it indicates that
754   the sender does not know the media type of the representation;
755   recipients MAY either assume that the media type is
756   "application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
757   or examine the content to determine its type.
758</t>
759<t>
760   In practice, resource owners do not always properly configure their origin
761   server to provide the correct Content-Type for a given representation,
762   with the result that some clients will examine a response body's content
763   and override the specified type.
764   Clients that do so risk drawing incorrect conclusions, which might expose
765   additional security risks (e.g., "privilege escalation").  Furthermore,
766   it is impossible to determine the sender's intent by examining the data
767   format: many data formats match multiple media types that differ only in
768   processing semantics.  Implementers are encouraged to provide a means of
769   disabling such "content sniffing" when it is used.
770</t>
771<t>
772   Content-Encoding is used to indicate any additional content
773   codings applied to the data, usually for the purpose of data
774   compression, that are a property of the representation.  If
775   Content-Encoding is not present, then there is no additional
776   encoding beyond that defined by the Content-Type.
777</t>
778</section>
779</section>
780
781<section title="Content Negotiation" anchor="content.negotiation">
782<t>
783   HTTP responses include a representation which contains information for
784   interpretation, whether by a human user or for further processing.
785   Often, the server has different ways of representing the
786   same information; for example, in different formats, languages,
787   or using different character encodings.
788</t>
789<t>
790   HTTP clients and their users might have different or variable
791   capabilities, characteristics or preferences which would influence
792   which representation, among those available from the server,
793   would be best for the server to deliver. For this reason, HTTP
794   provides mechanisms for "content negotiation" -- a process of
795   allowing selection of a representation of a given resource,
796   when more than one is available.
797</t>
798<t>
799   This specification defines two patterns of content negotiation;
800   "server-driven", where the server selects the representation based
801   upon the client's stated preferences, and "agent-driven" negotiation,
802   where the server provides a list of representations for the client to
803   choose from, based upon their metadata. In addition,  there are
804   other patterns: some applications use an "active content" pattern,
805   where the server returns active content which runs on the client
806   and, based on client available parameters, selects additional
807   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
808   has also been proposed.
809</t>
810<t>
811   These patterns are all widely used, and have trade-offs in applicability
812   and practicality. In particular, when the number of preferences or
813   capabilities to be expressed by a client are large (such as when many
814   different formats are supported by a user-agent), server-driven
815   negotiation becomes unwieldy, and might not be appropriate. Conversely,
816   when the number of representations to choose from is very large,
817   agent-driven negotiation might not be appropriate.
818</t>
819<t>
820   Note that in all cases, the supplier of representations has the
821   responsibility for determining which representations might be
822   considered to be the "same information".
823</t>
824
825<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
826<t>
827   If the selection of the best representation for a response is made by
828   an algorithm located at the server, it is called server-driven
829   negotiation. Selection is based on the available representations of
830   the response (the dimensions over which it can vary; e.g., language,
831   content-coding, etc.) and the contents of particular header fields in
832   the request message or on other information pertaining to the request
833   (such as the network address of the client).
834</t>
835<t>
836   Server-driven negotiation is advantageous when the algorithm for
837   selecting from among the available representations is difficult to
838   describe to the user agent, or when the server desires to send its
839   "best guess" to the client along with the first response (hoping to
840   avoid the round-trip delay of a subsequent request if the "best
841   guess" is good enough for the user). In order to improve the server's
842   guess, the user agent MAY include request header fields (Accept,
843   Accept-Language, Accept-Encoding, etc.) which describe its
844   preferences for such a response.
845</t>
846<t>
847   Server-driven negotiation has disadvantages:
848  <list style="numbers">
849    <t>
850         It is impossible for the server to accurately determine what
851         might be "best" for any given user, since that would require
852         complete knowledge of both the capabilities of the user agent
853         and the intended use for the response (e.g., does the user want
854         to view it on screen or print it on paper?).
855    </t>
856    <t>
857         Having the user agent describe its capabilities in every
858         request can be both very inefficient (given that only a small
859         percentage of responses have multiple representations) and a
860         potential violation of the user's privacy.
861    </t>
862    <t>
863         It complicates the implementation of an origin server and the
864         algorithms for generating responses to a request.
865    </t>
866    <t>
867         It might limit a public cache's ability to use the same response
868         for multiple user's requests.
869    </t>
870  </list>
871</t>
872<t>
873   HTTP/1.1 includes the following request-header fields for enabling
874   server-driven negotiation through description of user agent
875   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
876   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
877   (<xref target="header.accept-language"/>), and User-Agent (Section 9.9 of <xref target="Part2"/>).
878   However, an origin server is not limited to these dimensions and MAY vary
879   the response based on any aspect of the request, including information
880   outside the request-header fields or within extension header fields
881   not defined by this specification.
882</t>
883<t><list>
884  <t>
885    Note: In practice, User-Agent based negotiation is fragile,
886    because new clients might not be recognized.
887  </t>
888</list></t>
889<t>
890   The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
891   server uses to select a representation that is subject to server-driven
892   negotiation.
893</t>
894</section>
895
896<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
897<t>
898   With agent-driven negotiation, selection of the best representation
899   for a response is performed by the user agent after receiving an
900   initial response from the origin server. Selection is based on a list
901   of the available representations of the response included within the
902   header fields or body of the initial response, with each
903   representation identified by its own URI. Selection from among the
904   representations can be performed automatically (if the user agent is
905   capable of doing so) or manually by the user selecting from a
906   generated (possibly hypertext) menu.
907</t>
908<t>
909   Agent-driven negotiation is advantageous when the response would vary
910   over commonly-used dimensions (such as type, language, or encoding),
911   when the origin server is unable to determine a user agent's
912   capabilities from examining the request, and generally when public
913   caches are used to distribute server load and reduce network usage.
914</t>
915<t>
916   Agent-driven negotiation suffers from the disadvantage of needing a
917   second request to obtain the best alternate representation. This
918   second request is only efficient when caching is used. In addition,
919   this specification does not define any mechanism for supporting
920   automatic selection, though it also does not prevent any such
921   mechanism from being developed as an extension and used within
922   HTTP/1.1.
923</t>
924<t>
925   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
926   status codes for enabling agent-driven negotiation when the server is
927   unwilling or unable to provide a varying response using server-driven
928   negotiation.
929</t>
930</section>
931</section>
932
933<section title="Header Field Definitions" anchor="header.fields">
934<t>
935   This section defines the syntax and semantics of HTTP/1.1 header fields
936   related to the payload of messages.
937</t>
938
939<section title="Accept" anchor="header.accept">
940  <iref primary="true" item="Accept header"/>
941  <iref primary="true" item="Headers" subitem="Accept"/>
942 
943 
944 
945 
946 
947<t>
948   The "Accept" request-header field can be used by user agents to specify
949   response media types that are acceptable. Accept headers can be used to
950   indicate that the request is specifically limited to a small set of desired
951   types, as in the case of a request for an in-line image.
952</t>
953<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[
954  Accept   = "Accept" ":" OWS Accept-v
955  Accept-v = #( media-range [ accept-params ] )
956 
957  media-range    = ( "*/*"
958                   / ( type "/" "*" )
959                   / ( type "/" subtype )
960                   ) *( OWS ";" OWS parameter )
961  accept-params  = OWS ";" OWS "q=" qvalue *( accept-ext )
962  accept-ext     = OWS ";" OWS token
963                   [ "=" word ]
964]]></artwork></figure>
965<t>
966   The asterisk "*" character is used to group media types into ranges,
967   with "*/*" indicating all media types and "type/*" indicating all
968   subtypes of that type. The media-range MAY include media type
969   parameters that are applicable to that range.
970</t>
971<t>
972   Each media-range MAY be followed by one or more accept-params,
973   beginning with the "q" parameter for indicating a relative quality
974   factor. The first "q" parameter (if any) separates the media-range
975   parameter(s) from the accept-params. Quality factors allow the user
976   or user agent to indicate the relative degree of preference for that
977   media-range, using the qvalue scale from 0 to 1 (Section 6.4 of <xref target="Part1"/>). The
978   default value is q=1.
979</t>
980<t><list>
981  <t>
982    Note: Use of the "q" parameter name to separate media type
983    parameters from Accept extension parameters is due to historical
984    practice. Although this prevents any media type parameter named
985    "q" from being used with a media range, such an event is believed
986    to be unlikely given the lack of any "q" parameters in the IANA
987    media type registry and the rare usage of any media type
988    parameters in Accept. Future media types are discouraged from
989    registering any parameter named "q".
990  </t>
991</list></t>
992<t>
993   The example
994</t>
995<figure><artwork type="example"><![CDATA[
996  Accept: audio/*; q=0.2, audio/basic
997]]></artwork></figure>
998<t>
999   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
1000   type if it is the best available after an 80% mark-down in quality".
1001</t>
1002<t>
1003   If no Accept header field is present, then it is assumed that the
1004   client accepts all media types. If an Accept header field is present,
1005   and if the server cannot send a response which is acceptable
1006   according to the combined Accept field value, then the server SHOULD
1007   send a 406 (Not Acceptable) response.
1008</t>
1009<t>
1010   A more elaborate example is
1011</t>
1012<figure><artwork type="example"><![CDATA[
1013  Accept: text/plain; q=0.5, text/html,
1014          text/x-dvi; q=0.8, text/x-c
1015]]></artwork></figure>
1016<t>
1017   Verbally, this would be interpreted as "text/html and text/x-c are
1018   the preferred media types, but if they do not exist, then send the
1019   text/x-dvi representation, and if that does not exist, send the text/plain
1020   representation".
1021</t>
1022<t>
1023   Media ranges can be overridden by more specific media ranges or
1024   specific media types. If more than one media range applies to a given
1025   type, the most specific reference has precedence. For example,
1026</t>
1027<figure><artwork type="example"><![CDATA[
1028  Accept: text/*, text/html, text/html;level=1, */*
1029]]></artwork></figure>
1030<t>
1031   have the following precedence:
1032   <list style="numbers">
1033    <t>text/html;level=1</t>
1034    <t>text/html</t>
1035    <t>text/*</t>
1036    <t>*/*</t>
1037   </list>
1038</t>
1039<t>
1040   The media type quality factor associated with a given type is
1041   determined by finding the media range with the highest precedence
1042   which matches that type. For example,
1043</t>
1044<figure><artwork type="example"><![CDATA[
1045  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1046          text/html;level=2;q=0.4, */*;q=0.5
1047]]></artwork></figure>
1048<t>
1049   would cause the following values to be associated:
1050</t>
1051<texttable align="left">
1052  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1053  <c>text/html;level=1</c>    <c>1</c>
1054  <c>text/html</c>            <c>0.7</c>
1055  <c>text/plain</c>           <c>0.3</c>
1056  <c>image/jpeg</c>           <c>0.5</c>
1057  <c>text/html;level=2</c>    <c>0.4</c>
1058  <c>text/html;level=3</c>    <c>0.7</c>
1059</texttable>
1060<t>
1061      Note: A user agent might be provided with a default set of quality
1062      values for certain media ranges. However, unless the user agent is
1063      a closed system which cannot interact with other rendering agents,
1064      this default set ought to be configurable by the user.
1065</t>
1066</section>
1067
1068<section title="Accept-Charset" anchor="header.accept-charset">
1069  <iref primary="true" item="Accept-Charset header"/>
1070  <iref primary="true" item="Headers" subitem="Accept-Charset"/>
1071 
1072 
1073<t>
1074   The "Accept-Charset" request-header field can be used by user agents to
1075   indicate what response character sets are acceptable. This field allows
1076   clients capable of understanding more comprehensive or special-purpose
1077   character sets to signal that capability to a server which is capable of
1078   representing documents in those character sets.
1079</t>
1080<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/><artwork type="abnf2616"><![CDATA[
1081  Accept-Charset   = "Accept-Charset" ":" OWS
1082          Accept-Charset-v
1083  Accept-Charset-v = 1#( ( charset / "*" )
1084                         [ OWS ";" OWS "q=" qvalue ] )
1085]]></artwork></figure>
1086<t>
1087   Character set values are described in <xref target="character.sets"/>. Each charset MAY
1088   be given an associated quality value which represents the user's
1089   preference for that charset. The default value is q=1. An example is
1090</t>
1091<figure><artwork type="example"><![CDATA[
1092  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1093]]></artwork></figure>
1094<t>
1095   The special value "*", if present in the Accept-Charset field,
1096   matches every character set (including ISO-8859-1) which is not
1097   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1098   in an Accept-Charset field, then all character sets not explicitly
1099   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1100   a quality value of 1 if not explicitly mentioned.
1101</t>
1102<t>
1103   If no Accept-Charset header is present, the default is that any
1104   character set is acceptable. If an Accept-Charset header is present,
1105   and if the server cannot send a response which is acceptable
1106   according to the Accept-Charset header, then the server SHOULD send
1107   an error response with the 406 (Not Acceptable) status code, though
1108   the sending of an unacceptable response is also allowed.
1109</t>
1110</section>
1111
1112<section title="Accept-Encoding" anchor="header.accept-encoding">
1113  <iref primary="true" item="Accept-Encoding header"/>
1114  <iref primary="true" item="Headers" subitem="Accept-Encoding"/>
1115 
1116 
1117 
1118<t>
1119   The "Accept-Encoding" request-header field can be used by user agents to
1120   indicate what response content-codings (<xref target="content.codings"/>)
1121   are acceptable in the response.
1122</t>
1123<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[
1124  Accept-Encoding    = "Accept-Encoding" ":" OWS
1125                     Accept-Encoding-v
1126  Accept-Encoding-v  =
1127                     #( codings [ OWS ";" OWS "q=" qvalue ] )
1128  codings            = ( content-coding / "*" )
1129]]></artwork></figure>
1130<t>
1131   Each codings value MAY be given an associated quality value which
1132   represents the preference for that encoding. The default value is q=1.
1133</t>
1134<t>
1135   Examples of its use are:
1136</t>
1137<figure><artwork type="example"><![CDATA[
1138  Accept-Encoding: compress, gzip
1139  Accept-Encoding:
1140  Accept-Encoding: *
1141  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1142  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1143]]></artwork></figure>
1144<t>
1145   A server tests whether a content-coding is acceptable, according to
1146   an Accept-Encoding field, using these rules:
1147  <list style="numbers">
1148      <t>If the content-coding is one of the content-codings listed in
1149         the Accept-Encoding field, then it is acceptable, unless it is
1150         accompanied by a qvalue of 0. (As defined in Section 6.4 of <xref target="Part1"/>, a
1151         qvalue of 0 means "not acceptable".)</t>
1152
1153      <t>The special "*" symbol in an Accept-Encoding field matches any
1154         available content-coding not explicitly listed in the header
1155         field.</t>
1156
1157      <t>If multiple content-codings are acceptable, then the acceptable
1158         content-coding with the highest non-zero qvalue is preferred.</t>
1159
1160      <t>The "identity" content-coding is always acceptable, unless
1161         specifically refused because the Accept-Encoding field includes
1162         "identity;q=0", or because the field includes "*;q=0" and does
1163         not explicitly include the "identity" content-coding. If the
1164         Accept-Encoding field-value is empty, then only the "identity"
1165         encoding is acceptable.</t>
1166  </list>
1167</t>
1168<t>
1169   If an Accept-Encoding field is present in a request, and if the
1170   server cannot send a response which is acceptable according to the
1171   Accept-Encoding header, then the server SHOULD send an error response
1172   with the 406 (Not Acceptable) status code.
1173</t>
1174<t>
1175   If no Accept-Encoding field is present in a request, the server MAY
1176   assume that the client will accept any content coding. In this case,
1177   if "identity" is one of the available content-codings, then the
1178   server SHOULD use the "identity" content-coding, unless it has
1179   additional information that a different content-coding is meaningful
1180   to the client.
1181</t>
1182<t><list>
1183  <t>
1184    Note: If the request does not include an Accept-Encoding field,
1185    and if the "identity" content-coding is unavailable, then
1186    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1187    "gzip" and "compress") are preferred; some older clients
1188    improperly display messages sent with other content-codings.  The
1189    server might also make this decision based on information about
1190    the particular user-agent or client.
1191  </t>
1192</list></t>
1193<t><list>
1194  <t>
1195    Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1196    associated with content-codings. This means that qvalues will not
1197    work and are not permitted with x-gzip or x-compress.
1198  </t>
1199</list></t>
1200</section>
1201
1202<section title="Accept-Language" anchor="header.accept-language">
1203  <iref primary="true" item="Accept-Language header"/>
1204  <iref primary="true" item="Headers" subitem="Accept-Language"/>
1205 
1206 
1207 
1208<t>
1209   The "Accept-Language" request-header field can be used by user agents to
1210   indicate the set of natural languages that are preferred in the response.
1211   Language tags are defined in <xref target="language.tags"/>.
1212</t>
1213<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[
1214  Accept-Language   = "Accept-Language" ":" OWS
1215                    Accept-Language-v
1216  Accept-Language-v =
1217                    1#( language-range [ OWS ";" OWS "q=" qvalue ] )
1218  language-range    =
1219            <language-range, defined in [RFC4647], Section 2.1>
1220]]></artwork></figure>
1221<t>
1222   Each language-range can be given an associated quality value which
1223   represents an estimate of the user's preference for the languages
1224   specified by that range. The quality value defaults to "q=1". For
1225   example,
1226</t>
1227<figure><artwork type="example"><![CDATA[
1228  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1229]]></artwork></figure>
1230<t>
1231   would mean: "I prefer Danish, but will accept British English and
1232   other types of English".
1233   (see also Section 2.3 of <xref target="RFC4647"/>)
1234</t>
1235<t>
1236   For matching, Section 3 of <xref target="RFC4647"/> defines
1237   several matching schemes. Implementations can offer the most appropriate
1238   matching scheme for their requirements.
1239</t>
1240<t><list>
1241  <t>
1242    Note: The "Basic Filtering" scheme (<xref target="RFC4647"/>, Section 3.3.1) is identical to the matching scheme that was
1243    previously defined in Section 14.4 of <xref target="RFC2616"/>.
1244  </t>
1245</list></t>
1246<t>
1247   It might be contrary to the privacy expectations of the user to send
1248   an Accept-Language header with the complete linguistic preferences of
1249   the user in every request. For a discussion of this issue, see
1250   <xref target="privacy.issues.connected.to.accept.headers"/>.
1251</t>
1252<t>
1253   As intelligibility is highly dependent on the individual user, it is
1254   recommended that client applications make the choice of linguistic
1255   preference available to the user. If the choice is not made
1256   available, then the Accept-Language header field MUST NOT be given in
1257   the request.
1258</t>
1259<t><list>
1260  <t>
1261    Note: When making the choice of linguistic preference available to
1262    the user, we remind implementors of  the fact that users are not
1263    familiar with the details of language matching as described above,
1264    and ought to be provided appropriate guidance. As an example, users
1265    might assume that on selecting "en-gb", they will be served any
1266    kind of English document if British English is not available. A
1267    user agent might suggest in such a case to add "en" to get the
1268    best matching behavior.
1269  </t>
1270</list></t>
1271</section>
1272
1273<section title="Content-Encoding" anchor="header.content-encoding">
1274  <iref primary="true" item="Content-Encoding header"/>
1275  <iref primary="true" item="Headers" subitem="Content-Encoding"/>
1276 
1277 
1278<t>
1279   The "Content-Encoding" header field indicates what content-codings
1280   have been applied to the representation, and thus what decoding mechanisms
1281   must be applied in order to obtain the media-type referenced by the
1282   Content-Type header field. Content-Encoding is primarily used to allow a
1283   representation to be compressed without losing the identity of its underlying
1284   media type.
1285</t>
1286<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/><artwork type="abnf2616"><![CDATA[
1287  Content-Encoding   = "Content-Encoding" ":" OWS Content-Encoding-v
1288  Content-Encoding-v = 1#content-coding
1289]]></artwork></figure>
1290<t>
1291   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1292</t>
1293<figure><artwork type="example"><![CDATA[
1294  Content-Encoding: gzip
1295]]></artwork></figure>
1296<t>
1297   The content-coding is a characteristic of the representation.
1298   Typically, the representation body is stored with this
1299   encoding and is only decoded before rendering or analogous usage.
1300   However, a non-transparent proxy MAY modify the content-coding if the
1301   new coding is known to be acceptable to the recipient, unless the
1302   "no-transform" cache-control directive is present in the message.
1303</t>
1304<t>
1305   If the content-coding of a representation is not "identity", then the
1306   representation metadata MUST include a Content-Encoding header
1307   field (<xref target="header.content-encoding"/>)
1308   that lists the non-identity content-coding(s) used.
1309</t>
1310<t>
1311   If the content-coding of a representation in a request message is not
1312   acceptable to the origin server, the server SHOULD respond with a
1313   status code of 415 (Unsupported Media Type).
1314</t>
1315<t>
1316   If multiple encodings have been applied to a representation, the content
1317   codings MUST be listed in the order in which they were applied.
1318   Additional information about the encoding parameters MAY be provided
1319   by other header fields not defined by this specification.
1320</t>
1321</section>
1322
1323<section title="Content-Language" anchor="header.content-language">
1324  <iref primary="true" item="Content-Language header"/>
1325  <iref primary="true" item="Headers" subitem="Content-Language"/>
1326 
1327 
1328<t>
1329   The "Content-Language" header field describes the natural
1330   language(s) of the intended audience for the representation. Note that this might
1331   not be equivalent to all the languages used within the representation.
1332</t>
1333<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/><artwork type="abnf2616"><![CDATA[
1334  Content-Language   = "Content-Language" ":" OWS Content-Language-v
1335  Content-Language-v = 1#language-tag
1336]]></artwork></figure>
1337<t>
1338   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1339   Content-Language is to allow a user to identify and differentiate
1340   representations according to the user's own preferred language. Thus, if the
1341   body content is intended only for a Danish-literate audience, the
1342   appropriate field is
1343</t>
1344<figure><artwork type="example"><![CDATA[
1345  Content-Language: da
1346]]></artwork></figure>
1347<t>
1348   If no Content-Language is specified, the default is that the content
1349   is intended for all language audiences. This might mean that the
1350   sender does not consider it to be specific to any natural language,
1351   or that the sender does not know for which language it is intended.
1352</t>
1353<t>
1354   Multiple languages MAY be listed for content that is intended for
1355   multiple audiences. For example, a rendition of the "Treaty of
1356   Waitangi", presented simultaneously in the original Maori and English
1357   versions, would call for
1358</t>
1359<figure><artwork type="example"><![CDATA[
1360  Content-Language: mi, en
1361]]></artwork></figure>
1362<t>
1363   However, just because multiple languages are present within a representation
1364   does not mean that it is intended for multiple linguistic audiences.
1365   An example would be a beginner's language primer, such as "A First
1366   Lesson in Latin", which is clearly intended to be used by an
1367   English-literate audience. In this case, the Content-Language would
1368   properly only include "en".
1369</t>
1370<t>
1371   Content-Language MAY be applied to any media type -- it is not
1372   limited to textual documents.
1373</t>
1374</section>
1375
1376<section title="Content-Location" anchor="header.content-location">
1377  <iref primary="true" item="Content-Location header"/>
1378  <iref primary="true" item="Headers" subitem="Content-Location"/>
1379 
1380 
1381<t>
1382   The "Content-Location" header field supplies a URI that can be used
1383   as a specific identifier for the representation in this message.
1384   In other words, if one were to perform a GET on this URI at the time
1385   of this message's generation, then a 200 response would contain the
1386   same representation that is enclosed as payload in this message.
1387</t>
1388<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/><artwork type="abnf2616"><![CDATA[
1389  Content-Location   = "Content-Location" ":" OWS
1390                    Content-Location-v
1391  Content-Location-v =
1392                    absolute-URI / partial-URI
1393]]></artwork></figure>
1394<t>
1395   The Content-Location value is not a replacement for the effective
1396   Request URI (Section 4.3 of <xref target="Part1"/>).  It is representation metadata.
1397   It has the same syntax and semantics as the header field of the same name
1398   defined for MIME body parts in Section 4 of <xref target="RFC2557"/>.
1399   However, its appearance in an HTTP message has some special implications
1400   for HTTP recipients.
1401</t>
1402<t>
1403   If Content-Location is included in a response message and its value
1404   is the same as the effective request URI, then the response payload
1405   SHOULD be considered the current representation of that resource.
1406   For a GET or HEAD request, this is the same as the default semantics
1407   when no Content-Location is provided by the server.  For a state-changing
1408   method like PUT or POST, it implies that the server's response contains
1409   the new representation of that resource, thereby distinguishing it from
1410   representations that might only report about the action (e.g., "It worked!").
1411   This allows authoring applications to update their local copies without
1412   the need for a subsequent GET request.
1413</t>
1414<t>
1415   If Content-Location is included in a response message and its value
1416   differs from the effective request URI, then the origin server is
1417   informing recipients that this representation has its own, presumably
1418   more specific, identifier.  For a GET or HEAD request, this is an
1419   indication that the effective request URI identifies a resource that
1420   is subject to content negotiation and the representation selected for
1421   this response can also be found at the identified URI.  For other
1422   methods, such a Content-Location indicates that this representation
1423   contains a report on the action's status and the same report is
1424   available (for future access with GET) at the given URI.  For
1425   example, a purchase transaction made via the POST method might
1426   include a receipt document as the payload of the 200 response;
1427   the Content-Location value provides an identifier for retrieving
1428   a copy of that same receipt in the future.
1429</t>
1430<t>
1431   If Content-Location is included in a request message, then it MAY
1432   be interpreted by the origin server as an indication of where the
1433   user agent originally obtained the content of the enclosed
1434   representation (prior to any subsequent modification of the content
1435   by that user agent).  In other words, the user agent is providing
1436   the same representation metadata that it received with the original
1437   representation.  However, such interpretation MUST NOT be used to
1438   alter the semantics of the method requested by the client.  For
1439   example, if a client makes a PUT request on a negotiated resource
1440   and the origin server accepts that PUT (without redirection), then the
1441   new set of values for that resource is expected to be consistent with
1442   the one representation supplied in that PUT; the Content-Location
1443   cannot be used as a form of reverse content selection that
1444   identifies only one of the negotiated representations to be updated.
1445   If the user agent had wanted the latter semantics, it would have applied
1446   the PUT directly to the Content-Location URI.
1447</t>
1448<t>
1449   A Content-Location field received in a request message is transitory
1450   information that SHOULD NOT be saved with other representation
1451   metadata for use in later responses.  The Content-Location's value
1452   might be saved for use in other contexts, such as within source links
1453   or other metadata.
1454</t>
1455<t>
1456   A cache cannot assume that a representation with a Content-Location
1457   different from the URI used to retrieve it can be used to respond to
1458   later requests on that Content-Location URI.
1459</t>
1460<t>
1461   If the Content-Location value is a partial URI, the partial URI is
1462   interpreted relative to the effective request URI.
1463</t>
1464</section>
1465
1466<section title="Content-MD5" anchor="header.content-md5">
1467  <iref primary="true" item="Content-MD5 header"/>
1468  <iref primary="true" item="Headers" subitem="Content-MD5"/>
1469 
1470 
1471<t>
1472   The "Content-MD5" header field, as defined in <xref target="RFC1864"/>, is
1473   an MD5 digest of the payload body that provides an end-to-end message
1474   integrity check (MIC) of the payload body (the message-body after any
1475   transfer-coding is decoded). Note that a MIC is good for
1476   detecting accidental modification of the payload body in transit, but is not
1477   proof against malicious attacks.
1478</t>
1479<figure><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/><artwork type="abnf2616"><![CDATA[
1480  Content-MD5   = "Content-MD5" ":" OWS Content-MD5-v
1481  Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
1482]]></artwork></figure>
1483<t>
1484   The Content-MD5 header field MAY be generated by an origin server or
1485   client to function as an integrity check of the payload body. Only
1486   origin servers or user agents MAY generate the Content-MD5 header field;
1487   proxies and gateways MUST NOT generate it, as this would defeat its
1488   value as an end-to-end integrity check. Any recipient MAY check that
1489   the digest value in this header field matches a corresponding digest
1490   calculated on payload body as received.
1491</t>
1492<t>
1493   The MD5 digest is computed based on the content of the payload body,
1494   including any content-coding, but not including any transfer-coding
1495   applied to the message-body because such transfer-codings might be
1496   applied or removed anywhere along the request/response chain.
1497   If the message is received with a transfer-coding, that encoding MUST
1498   be decoded prior to checking the Content-MD5 value against the received
1499   payload.
1500</t>
1501<t>
1502   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1503   composite media-types (e.g., multipart/* and message/rfc822), but
1504   this does not change how the digest is computed as defined in the
1505   preceding paragraph.
1506</t>
1507<t>
1508   There are several consequences of this. The payload for composite
1509   types MAY contain many body-parts, each with its own MIME and HTTP
1510   headers (including Content-MD5, Content-Transfer-Encoding, and
1511   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1512   or Content-Encoding header, it is assumed that the content
1513   of the body-part has had the encoding applied, and the body-part is
1514   included in the Content-MD5 digest as is -- i.e., after the
1515   application. The Transfer-Encoding header field is not allowed within
1516   body-parts.
1517</t>
1518<t>
1519   Conversion of all line breaks to CRLF MUST NOT be done before
1520   computing or checking the digest: the line break convention used in
1521   the text actually transmitted MUST be left unaltered when computing
1522   the digest.
1523</t>
1524<t><list>
1525  <t>
1526    Note: While the definition of Content-MD5 is exactly the same for
1527    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1528    in which the application of Content-MD5 to HTTP entity-bodies
1529    differs from its application to MIME entity-bodies. One is that
1530    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1531    does use Transfer-Encoding and Content-Encoding. Another is that
1532    HTTP more frequently uses binary content types than MIME, so it is
1533    worth noting that, in such cases, the byte order used to compute
1534    the digest is the transmission byte order defined for the type.
1535    Lastly, HTTP allows transmission of text types with any of several
1536    line break conventions and not just the canonical form using CRLF.
1537  </t>
1538</list></t>
1539</section>
1540
1541<section title="Content-Type" anchor="header.content-type">
1542  <iref primary="true" item="Content-Type header"/>
1543  <iref primary="true" item="Headers" subitem="Content-Type"/>
1544 
1545 
1546<t>
1547   The "Content-Type" header field indicates the media type of the
1548   representation. In the case of responses to the HEAD method, the media type is
1549   that which would have been sent had the request been a GET.
1550</t>
1551<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/><artwork type="abnf2616"><![CDATA[
1552  Content-Type   = "Content-Type" ":" OWS Content-Type-v
1553  Content-Type-v = media-type
1554]]></artwork></figure>
1555<t>
1556   Media types are defined in <xref target="media.types"/>. An example of the field is
1557</t>
1558<figure><artwork type="example"><![CDATA[
1559  Content-Type: text/html; charset=ISO-8859-4
1560]]></artwork></figure>
1561<t>
1562   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1563</t>
1564</section>
1565
1566</section>
1567
1568<section title="IANA Considerations" anchor="IANA.considerations">
1569<section title="Header Field Registration" anchor="header.field.registration">
1570<t>
1571   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
1572   with the permanent registrations below (see <xref target="RFC3864"/>):
1573</t>
1574
1575<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1576<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1577   <ttcol>Header Field Name</ttcol>
1578   <ttcol>Protocol</ttcol>
1579   <ttcol>Status</ttcol>
1580   <ttcol>Reference</ttcol>
1581
1582   <c>Accept</c>
1583   <c>http</c>
1584   <c>standard</c>
1585   <c>
1586      <xref target="header.accept"/>
1587   </c>
1588   <c>Accept-Charset</c>
1589   <c>http</c>
1590   <c>standard</c>
1591   <c>
1592      <xref target="header.accept-charset"/>
1593   </c>
1594   <c>Accept-Encoding</c>
1595   <c>http</c>
1596   <c>standard</c>
1597   <c>
1598      <xref target="header.accept-encoding"/>
1599   </c>
1600   <c>Accept-Language</c>
1601   <c>http</c>
1602   <c>standard</c>
1603   <c>
1604      <xref target="header.accept-language"/>
1605   </c>
1606   <c>Content-Disposition</c>
1607   <c>http</c>
1608   <c>standard</c>
1609   <c>
1610      <xref target="content-disposition"/>
1611   </c>
1612   <c>Content-Encoding</c>
1613   <c>http</c>
1614   <c>standard</c>
1615   <c>
1616      <xref target="header.content-encoding"/>
1617   </c>
1618   <c>Content-Language</c>
1619   <c>http</c>
1620   <c>standard</c>
1621   <c>
1622      <xref target="header.content-language"/>
1623   </c>
1624   <c>Content-Location</c>
1625   <c>http</c>
1626   <c>standard</c>
1627   <c>
1628      <xref target="header.content-location"/>
1629   </c>
1630   <c>Content-MD5</c>
1631   <c>http</c>
1632   <c>standard</c>
1633   <c>
1634      <xref target="header.content-md5"/>
1635   </c>
1636   <c>Content-Type</c>
1637   <c>http</c>
1638   <c>standard</c>
1639   <c>
1640      <xref target="header.content-type"/>
1641   </c>
1642   <c>MIME-Version</c>
1643   <c>http</c>
1644   <c>standard</c>
1645   <c>
1646      <xref target="mime-version"/>
1647   </c>
1648</texttable>
1649<!--(END)-->
1650
1651<t>
1652   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1653</t>
1654</section>
1655
1656<section title="Content Coding Registry" anchor="content.coding.registration">
1657<t>
1658   The registration procedure for HTTP Content Codings is now defined
1659   by <xref target="content.coding.registry"/> of this document.
1660</t>
1661<t>
1662   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1663   shall be updated with the registration below:
1664</t>
1665<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1666   <ttcol>Name</ttcol>
1667   <ttcol>Description</ttcol>
1668   <ttcol>Reference</ttcol>
1669   <c>compress</c>
1670   <c>UNIX "compress" program method</c>
1671   <c>
1672      Section 6.2.2.1 of <xref target="Part1"/>
1673   </c>
1674   <c>deflate</c>
1675   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1676   the "zlib" data format (<xref target="RFC1950"/>)
1677   </c>
1678   <c>
1679      Section 6.2.2.2 of <xref target="Part1"/>
1680   </c>
1681   <c>gzip</c>
1682   <c>Same as GNU zip <xref target="RFC1952"/></c>
1683   <c>
1684      Section 6.2.2.3 of <xref target="Part1"/>
1685   </c>
1686   <c>identity</c>
1687   <c>No transformation</c>
1688   <c>
1689      <xref target="content.codings"/>
1690   </c>
1691</texttable>
1692</section>
1693
1694</section>
1695
1696<section title="Security Considerations" anchor="security.considerations">
1697<t>
1698   This section is meant to inform application developers, information
1699   providers, and users of the security limitations in HTTP/1.1 as
1700   described by this document. The discussion does not include
1701   definitive solutions to the problems revealed, though it does make
1702   some suggestions for reducing security risks.
1703</t>
1704
1705<section title="Privacy Issues Connected to Accept Headers" anchor="privacy.issues.connected.to.accept.headers">
1706<t>
1707   Accept request-headers can reveal information about the user to all
1708   servers which are accessed. The Accept-Language header in particular
1709   can reveal information the user would consider to be of a private
1710   nature, because the understanding of particular languages is often
1711   strongly correlated to the membership of a particular ethnic group.
1712   User agents which offer the option to configure the contents of an
1713   Accept-Language header to be sent in every request are strongly
1714   encouraged to let the configuration process include a message which
1715   makes the user aware of the loss of privacy involved.
1716</t>
1717<t>
1718   An approach that limits the loss of privacy would be for a user agent
1719   to omit the sending of Accept-Language headers by default, and to ask
1720   the user whether or not to start sending Accept-Language headers to a
1721   server if it detects, by looking for any Vary response-header fields
1722   generated by the server, that such sending could improve the quality
1723   of service.
1724</t>
1725<t>
1726   Elaborate user-customized accept header fields sent in every request,
1727   in particular if these include quality values, can be used by servers
1728   as relatively reliable and long-lived user identifiers. Such user
1729   identifiers would allow content providers to do click-trail tracking,
1730   and would allow collaborating content providers to match cross-server
1731   click-trails or form submissions of individual users. Note that for
1732   many users not behind a proxy, the network address of the host
1733   running the user agent will also serve as a long-lived user
1734   identifier. In environments where proxies are used to enhance
1735   privacy, user agents ought to be conservative in offering accept
1736   header configuration options to end users. As an extreme privacy
1737   measure, proxies could filter the accept headers in relayed requests.
1738   General purpose user agents which provide a high degree of header
1739   configurability SHOULD warn users about the loss of privacy which can
1740   be involved.
1741</t>
1742</section>
1743
1744<section title="Content-Disposition Issues" anchor="content-disposition.issues">
1745<t>
1746   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
1747   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1748   serious security considerations. Content-Disposition is not part of
1749   the HTTP standard, but since it is widely implemented, we are
1750   documenting its use and risks for implementors. See Section 5 of <xref target="RFC2183"/>
1751   for details.
1752</t>
1753</section>
1754
1755</section>
1756
1757<section title="Acknowledgments" anchor="ack">
1758</section>
1759</middle>
1760<back>
1761
1762<references title="Normative References">
1763
1764<reference anchor="ISO-8859-1">
1765  <front>
1766    <title>
1767     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1768    </title>
1769    <author>
1770      <organization>International Organization for Standardization</organization>
1771    </author>
1772    <date year="1998"/>
1773  </front>
1774  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1775</reference>
1776
1777<reference anchor="Part1">
1778  <front>
1779    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1780    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1781      <organization abbrev="Day Software">Day Software</organization>
1782      <address><email>fielding@gbiv.com</email></address>
1783    </author>
1784    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1785      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1786      <address><email>jg@freedesktop.org</email></address>
1787    </author>
1788    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1789      <organization abbrev="HP">Hewlett-Packard Company</organization>
1790      <address><email>JeffMogul@acm.org</email></address>
1791    </author>
1792    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1793      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1794      <address><email>henrikn@microsoft.com</email></address>
1795    </author>
1796    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1797      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1798      <address><email>LMM@acm.org</email></address>
1799    </author>
1800    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1801      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1802      <address><email>paulle@microsoft.com</email></address>
1803    </author>
1804    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1805      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1806      <address><email>timbl@w3.org</email></address>
1807    </author>
1808    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1809      <organization abbrev="W3C">World Wide Web Consortium</organization>
1810      <address><email>ylafon@w3.org</email></address>
1811    </author>
1812    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1813      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1814      <address><email>julian.reschke@greenbytes.de</email></address>
1815    </author>
1816    <date month="August" year="2010"/>
1817  </front>
1818  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-11"/>
1819 
1820</reference>
1821
1822<reference anchor="Part2">
1823  <front>
1824    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1825    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1826      <organization abbrev="Day Software">Day Software</organization>
1827      <address><email>fielding@gbiv.com</email></address>
1828    </author>
1829    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1830      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1831      <address><email>jg@freedesktop.org</email></address>
1832    </author>
1833    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1834      <organization abbrev="HP">Hewlett-Packard Company</organization>
1835      <address><email>JeffMogul@acm.org</email></address>
1836    </author>
1837    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1838      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1839      <address><email>henrikn@microsoft.com</email></address>
1840    </author>
1841    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1842      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1843      <address><email>LMM@acm.org</email></address>
1844    </author>
1845    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1846      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1847      <address><email>paulle@microsoft.com</email></address>
1848    </author>
1849    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1850      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1851      <address><email>timbl@w3.org</email></address>
1852    </author>
1853    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1854      <organization abbrev="W3C">World Wide Web Consortium</organization>
1855      <address><email>ylafon@w3.org</email></address>
1856    </author>
1857    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1858      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1859      <address><email>julian.reschke@greenbytes.de</email></address>
1860    </author>
1861    <date month="August" year="2010"/>
1862  </front>
1863  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-11"/>
1864 
1865</reference>
1866
1867<reference anchor="Part4">
1868  <front>
1869    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1870    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1871      <organization abbrev="Day Software">Day Software</organization>
1872      <address><email>fielding@gbiv.com</email></address>
1873    </author>
1874    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1875      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1876      <address><email>jg@freedesktop.org</email></address>
1877    </author>
1878    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1879      <organization abbrev="HP">Hewlett-Packard Company</organization>
1880      <address><email>JeffMogul@acm.org</email></address>
1881    </author>
1882    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1883      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1884      <address><email>henrikn@microsoft.com</email></address>
1885    </author>
1886    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1887      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1888      <address><email>LMM@acm.org</email></address>
1889    </author>
1890    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1891      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1892      <address><email>paulle@microsoft.com</email></address>
1893    </author>
1894    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1895      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1896      <address><email>timbl@w3.org</email></address>
1897    </author>
1898    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1899      <organization abbrev="W3C">World Wide Web Consortium</organization>
1900      <address><email>ylafon@w3.org</email></address>
1901    </author>
1902    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1903      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1904      <address><email>julian.reschke@greenbytes.de</email></address>
1905    </author>
1906    <date month="August" year="2010"/>
1907  </front>
1908  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-11"/>
1909 
1910</reference>
1911
1912<reference anchor="Part5">
1913  <front>
1914    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1915    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1916      <organization abbrev="Day Software">Day Software</organization>
1917      <address><email>fielding@gbiv.com</email></address>
1918    </author>
1919    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1920      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1921      <address><email>jg@freedesktop.org</email></address>
1922    </author>
1923    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1924      <organization abbrev="HP">Hewlett-Packard Company</organization>
1925      <address><email>JeffMogul@acm.org</email></address>
1926    </author>
1927    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1928      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1929      <address><email>henrikn@microsoft.com</email></address>
1930    </author>
1931    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1932      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1933      <address><email>LMM@acm.org</email></address>
1934    </author>
1935    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1936      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1937      <address><email>paulle@microsoft.com</email></address>
1938    </author>
1939    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1940      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1941      <address><email>timbl@w3.org</email></address>
1942    </author>
1943    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1944      <organization abbrev="W3C">World Wide Web Consortium</organization>
1945      <address><email>ylafon@w3.org</email></address>
1946    </author>
1947    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1948      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1949      <address><email>julian.reschke@greenbytes.de</email></address>
1950    </author>
1951    <date month="August" year="2010"/>
1952  </front>
1953  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-11"/>
1954 
1955</reference>
1956
1957<reference anchor="Part6">
1958  <front>
1959    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1960    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1961      <organization abbrev="Day Software">Day Software</organization>
1962      <address><email>fielding@gbiv.com</email></address>
1963    </author>
1964    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1965      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1966      <address><email>jg@freedesktop.org</email></address>
1967    </author>
1968    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1969      <organization abbrev="HP">Hewlett-Packard Company</organization>
1970      <address><email>JeffMogul@acm.org</email></address>
1971    </author>
1972    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1973      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1974      <address><email>henrikn@microsoft.com</email></address>
1975    </author>
1976    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1977      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1978      <address><email>LMM@acm.org</email></address>
1979    </author>
1980    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1981      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1982      <address><email>paulle@microsoft.com</email></address>
1983    </author>
1984    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1985      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1986      <address><email>timbl@w3.org</email></address>
1987    </author>
1988    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1989      <organization abbrev="W3C">World Wide Web Consortium</organization>
1990      <address><email>ylafon@w3.org</email></address>
1991    </author>
1992    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1993      <address><email>mnot@mnot.net</email></address>
1994    </author>
1995    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1996      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1997      <address><email>julian.reschke@greenbytes.de</email></address>
1998    </author>
1999    <date month="August" year="2010"/>
2000  </front>
2001  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-11"/>
2002 
2003</reference>
2004
2005<reference anchor="RFC1864">
2006  <front>
2007    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
2008    <author initials="J." surname="Myers" fullname="John G. Myers">
2009      <organization>Carnegie Mellon University</organization>
2010      <address><email>jgm+@cmu.edu</email></address>
2011    </author>
2012    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2013      <organization>Dover Beach Consulting, Inc.</organization>
2014      <address><email>mrose@dbc.mtview.ca.us</email></address>
2015    </author>
2016    <date month="October" year="1995"/>
2017  </front>
2018  <seriesInfo name="RFC" value="1864"/>
2019</reference>
2020
2021<reference anchor="RFC1950">
2022  <front>
2023    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2024    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2025      <organization>Aladdin Enterprises</organization>
2026      <address><email>ghost@aladdin.com</email></address>
2027    </author>
2028    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2029    <date month="May" year="1996"/>
2030  </front>
2031  <seriesInfo name="RFC" value="1950"/>
2032  <annotation>
2033    RFC 1950 is an Informational RFC, thus it might be less stable than
2034    this specification. On the other hand, this downward reference was
2035    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2036    therefore it is unlikely to cause problems in practice. See also
2037    <xref target="BCP97"/>.
2038  </annotation>
2039</reference>
2040
2041<reference anchor="RFC1951">
2042  <front>
2043    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2044    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2045      <organization>Aladdin Enterprises</organization>
2046      <address><email>ghost@aladdin.com</email></address>
2047    </author>
2048    <date month="May" year="1996"/>
2049  </front>
2050  <seriesInfo name="RFC" value="1951"/>
2051  <annotation>
2052    RFC 1951 is an Informational RFC, thus it might be less stable than
2053    this specification. On the other hand, this downward reference was
2054    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2055    therefore it is unlikely to cause problems in practice. See also
2056    <xref target="BCP97"/>.
2057  </annotation>
2058</reference>
2059
2060<reference anchor="RFC1952">
2061  <front>
2062    <title>GZIP file format specification version 4.3</title>
2063    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2064      <organization>Aladdin Enterprises</organization>
2065      <address><email>ghost@aladdin.com</email></address>
2066    </author>
2067    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2068      <address><email>gzip@prep.ai.mit.edu</email></address>
2069    </author>
2070    <author initials="M." surname="Adler" fullname="Mark Adler">
2071      <address><email>madler@alumni.caltech.edu</email></address>
2072    </author>
2073    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2074      <address><email>ghost@aladdin.com</email></address>
2075    </author>
2076    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2077      <address><email>randeg@alumni.rpi.edu</email></address>
2078    </author>
2079    <date month="May" year="1996"/>
2080  </front>
2081  <seriesInfo name="RFC" value="1952"/>
2082  <annotation>
2083    RFC 1952 is an Informational RFC, thus it might be less stable than
2084    this specification. On the other hand, this downward reference was
2085    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2086    therefore it is unlikely to cause problems in practice. See also
2087    <xref target="BCP97"/>.
2088  </annotation>
2089</reference>
2090
2091<reference anchor="RFC2045">
2092  <front>
2093    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2094    <author initials="N." surname="Freed" fullname="Ned Freed">
2095      <organization>Innosoft International, Inc.</organization>
2096      <address><email>ned@innosoft.com</email></address>
2097    </author>
2098    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2099      <organization>First Virtual Holdings</organization>
2100      <address><email>nsb@nsb.fv.com</email></address>
2101    </author>
2102    <date month="November" year="1996"/>
2103  </front>
2104  <seriesInfo name="RFC" value="2045"/>
2105</reference>
2106
2107<reference anchor="RFC2046">
2108  <front>
2109    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2110    <author initials="N." surname="Freed" fullname="Ned Freed">
2111      <organization>Innosoft International, Inc.</organization>
2112      <address><email>ned@innosoft.com</email></address>
2113    </author>
2114    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2115      <organization>First Virtual Holdings</organization>
2116      <address><email>nsb@nsb.fv.com</email></address>
2117    </author>
2118    <date month="November" year="1996"/>
2119  </front>
2120  <seriesInfo name="RFC" value="2046"/>
2121</reference>
2122
2123<reference anchor="RFC2119">
2124  <front>
2125    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2126    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2127      <organization>Harvard University</organization>
2128      <address><email>sob@harvard.edu</email></address>
2129    </author>
2130    <date month="March" year="1997"/>
2131  </front>
2132  <seriesInfo name="BCP" value="14"/>
2133  <seriesInfo name="RFC" value="2119"/>
2134</reference>
2135
2136<reference anchor="RFC4647">
2137  <front>
2138    <title>Matching of Language Tags</title>
2139    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2140      <organization>Yahoo! Inc.</organization>
2141      <address><email>addison@inter-locale.com</email></address>
2142    </author>
2143    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2144      <organization>Google</organization>
2145      <address><email>mark.davis@macchiato.com</email></address>
2146    </author>
2147    <date year="2006" month="September"/>
2148  </front>
2149  <seriesInfo name="BCP" value="47"/>
2150  <seriesInfo name="RFC" value="4647"/>
2151</reference>
2152
2153<reference anchor="RFC5234">
2154  <front>
2155    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2156    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2157      <organization>Brandenburg InternetWorking</organization>
2158      <address>
2159        <email>dcrocker@bbiw.net</email>
2160      </address> 
2161    </author>
2162    <author initials="P." surname="Overell" fullname="Paul Overell">
2163      <organization>THUS plc.</organization>
2164      <address>
2165        <email>paul.overell@thus.net</email>
2166      </address>
2167    </author>
2168    <date month="January" year="2008"/>
2169  </front>
2170  <seriesInfo name="STD" value="68"/>
2171  <seriesInfo name="RFC" value="5234"/>
2172</reference>
2173
2174<reference anchor="RFC5646">
2175  <front>
2176    <title>Tags for Identifying Languages</title>
2177    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2178      <organization>Lab126</organization>
2179      <address><email>addison@inter-locale.com</email></address>
2180    </author>
2181    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2182      <organization>Google</organization>
2183      <address><email>mark.davis@google.com</email></address>
2184    </author>
2185    <date month="September" year="2009"/>
2186  </front>
2187  <seriesInfo name="BCP" value="47"/>
2188  <seriesInfo name="RFC" value="5646"/>
2189</reference>
2190
2191</references>
2192
2193<references title="Informative References">
2194
2195<reference anchor="RFC1945">
2196  <front>
2197    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2198    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2199      <organization>MIT, Laboratory for Computer Science</organization>
2200      <address><email>timbl@w3.org</email></address>
2201    </author>
2202    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2203      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2204      <address><email>fielding@ics.uci.edu</email></address>
2205    </author>
2206    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2207      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2208      <address><email>frystyk@w3.org</email></address>
2209    </author>
2210    <date month="May" year="1996"/>
2211  </front>
2212  <seriesInfo name="RFC" value="1945"/>
2213</reference>
2214
2215<reference anchor="RFC2049">
2216  <front>
2217    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2218    <author initials="N." surname="Freed" fullname="Ned Freed">
2219      <organization>Innosoft International, Inc.</organization>
2220      <address><email>ned@innosoft.com</email></address>
2221    </author>
2222    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2223      <organization>First Virtual Holdings</organization>
2224      <address><email>nsb@nsb.fv.com</email></address>
2225    </author>
2226    <date month="November" year="1996"/>
2227  </front>
2228  <seriesInfo name="RFC" value="2049"/>
2229</reference>
2230
2231<reference anchor="RFC2068">
2232  <front>
2233    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2234    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2235      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2236      <address><email>fielding@ics.uci.edu</email></address>
2237    </author>
2238    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2239      <organization>MIT Laboratory for Computer Science</organization>
2240      <address><email>jg@w3.org</email></address>
2241    </author>
2242    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2243      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2244      <address><email>mogul@wrl.dec.com</email></address>
2245    </author>
2246    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2247      <organization>MIT Laboratory for Computer Science</organization>
2248      <address><email>frystyk@w3.org</email></address>
2249    </author>
2250    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2251      <organization>MIT Laboratory for Computer Science</organization>
2252      <address><email>timbl@w3.org</email></address>
2253    </author>
2254    <date month="January" year="1997"/>
2255  </front>
2256  <seriesInfo name="RFC" value="2068"/>
2257</reference>
2258
2259<reference anchor="RFC2076">
2260  <front>
2261    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2262    <author initials="J." surname="Palme" fullname="Jacob Palme">
2263      <organization>Stockholm University/KTH</organization>
2264      <address><email>jpalme@dsv.su.se</email></address>
2265    </author>
2266    <date month="February" year="1997"/>
2267  </front>
2268  <seriesInfo name="RFC" value="2076"/>
2269</reference>
2270
2271<reference anchor="RFC2183">
2272  <front>
2273    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2274    <author initials="R." surname="Troost" fullname="Rens Troost">
2275      <organization>New Century Systems</organization>
2276      <address><email>rens@century.com</email></address>
2277    </author>
2278    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2279      <organization>QUALCOMM Incorporated</organization>
2280      <address><email>sdorner@qualcomm.com</email></address>
2281    </author>
2282    <author initials="K." surname="Moore" fullname="Keith Moore">
2283      <organization>Department of Computer Science</organization>
2284      <address><email>moore@cs.utk.edu</email></address>
2285    </author>
2286    <date month="August" year="1997"/>
2287  </front>
2288  <seriesInfo name="RFC" value="2183"/>
2289</reference>
2290
2291<reference anchor="RFC2277">
2292  <front>
2293    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2294    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2295      <organization>UNINETT</organization>
2296      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2297    </author>
2298    <date month="January" year="1998"/>
2299  </front>
2300  <seriesInfo name="BCP" value="18"/>
2301  <seriesInfo name="RFC" value="2277"/>
2302</reference>
2303
2304<reference anchor="RFC2295">
2305  <front>
2306    <title abbrev="HTTP Content Negotiation">Transparent Content Negotiation in HTTP</title>
2307    <author initials="K." surname="Holtman" fullname="Koen Holtman">
2308      <organization>Technische Universiteit Eindhoven</organization>
2309      <address>
2310        <email>koen@win.tue.nl</email>
2311      </address>
2312    </author>
2313    <author initials="A.H." surname="Mutz" fullname="Andrew H. Mutz">
2314      <organization>Hewlett-Packard Company</organization>
2315      <address>
2316        <email>mutz@hpl.hp.com</email>
2317      </address>
2318    </author>
2319    <date year="1998" month="March"/>
2320  </front>
2321  <seriesInfo name="RFC" value="2295"/>
2322</reference>
2323
2324<reference anchor="RFC2388">
2325  <front>
2326    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2327    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2328      <organization>Xerox Palo Alto Research Center</organization>
2329      <address><email>masinter@parc.xerox.com</email></address>
2330    </author>
2331    <date year="1998" month="August"/>
2332  </front>
2333  <seriesInfo name="RFC" value="2388"/>
2334</reference>
2335
2336<reference anchor="RFC2557">
2337  <front>
2338    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2339    <author initials="F." surname="Palme" fullname="Jacob Palme">
2340      <organization>Stockholm University and KTH</organization>
2341      <address><email>jpalme@dsv.su.se</email></address>
2342    </author>
2343    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2344      <organization>Microsoft Corporation</organization>
2345      <address><email>alexhop@microsoft.com</email></address>
2346    </author>
2347    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2348      <organization>Lotus Development Corporation</organization>
2349      <address><email>Shelness@lotus.com</email></address>
2350    </author>
2351    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2352      <address><email>stef@nma.com</email></address>
2353    </author>
2354    <date year="1999" month="March"/>
2355  </front>
2356  <seriesInfo name="RFC" value="2557"/>
2357</reference>
2358
2359<reference anchor="RFC2616">
2360  <front>
2361    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2362    <author initials="R." surname="Fielding" fullname="R. Fielding">
2363      <organization>University of California, Irvine</organization>
2364      <address><email>fielding@ics.uci.edu</email></address>
2365    </author>
2366    <author initials="J." surname="Gettys" fullname="J. Gettys">
2367      <organization>W3C</organization>
2368      <address><email>jg@w3.org</email></address>
2369    </author>
2370    <author initials="J." surname="Mogul" fullname="J. Mogul">
2371      <organization>Compaq Computer Corporation</organization>
2372      <address><email>mogul@wrl.dec.com</email></address>
2373    </author>
2374    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2375      <organization>MIT Laboratory for Computer Science</organization>
2376      <address><email>frystyk@w3.org</email></address>
2377    </author>
2378    <author initials="L." surname="Masinter" fullname="L. Masinter">
2379      <organization>Xerox Corporation</organization>
2380      <address><email>masinter@parc.xerox.com</email></address>
2381    </author>
2382    <author initials="P." surname="Leach" fullname="P. Leach">
2383      <organization>Microsoft Corporation</organization>
2384      <address><email>paulle@microsoft.com</email></address>
2385    </author>
2386    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2387      <organization>W3C</organization>
2388      <address><email>timbl@w3.org</email></address>
2389    </author>
2390    <date month="June" year="1999"/>
2391  </front>
2392  <seriesInfo name="RFC" value="2616"/>
2393</reference>
2394
2395<reference anchor="RFC3629">
2396  <front>
2397    <title>UTF-8, a transformation format of ISO 10646</title>
2398    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2399      <organization>Alis Technologies</organization>
2400      <address><email>fyergeau@alis.com</email></address>
2401    </author>
2402    <date month="November" year="2003"/>
2403  </front>
2404  <seriesInfo name="RFC" value="3629"/>
2405  <seriesInfo name="STD" value="63"/>
2406</reference>
2407
2408<reference anchor="RFC3864">
2409  <front>
2410    <title>Registration Procedures for Message Header Fields</title>
2411    <author initials="G." surname="Klyne" fullname="G. Klyne">
2412      <organization>Nine by Nine</organization>
2413      <address><email>GK-IETF@ninebynine.org</email></address>
2414    </author>
2415    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2416      <organization>BEA Systems</organization>
2417      <address><email>mnot@pobox.com</email></address>
2418    </author>
2419    <author initials="J." surname="Mogul" fullname="J. Mogul">
2420      <organization>HP Labs</organization>
2421      <address><email>JeffMogul@acm.org</email></address>
2422    </author>
2423    <date year="2004" month="September"/>
2424  </front>
2425  <seriesInfo name="BCP" value="90"/>
2426  <seriesInfo name="RFC" value="3864"/>
2427</reference>
2428
2429<reference anchor="RFC4288">
2430  <front>
2431    <title>Media Type Specifications and Registration Procedures</title>
2432    <author initials="N." surname="Freed" fullname="N. Freed">
2433      <organization>Sun Microsystems</organization>
2434      <address>
2435        <email>ned.freed@mrochek.com</email>
2436      </address>
2437    </author>
2438    <author initials="J." surname="Klensin" fullname="J. Klensin">
2439      <address>
2440        <email>klensin+ietf@jck.com</email>
2441      </address>
2442    </author>
2443    <date year="2005" month="December"/>
2444  </front>
2445  <seriesInfo name="BCP" value="13"/>
2446  <seriesInfo name="RFC" value="4288"/>
2447</reference>
2448
2449<reference anchor="RFC5226">
2450  <front>
2451    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2452    <author initials="T." surname="Narten" fullname="T. Narten">
2453      <organization>IBM</organization>
2454      <address><email>narten@us.ibm.com</email></address>
2455    </author>
2456    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2457      <organization>Google</organization>
2458      <address><email>Harald@Alvestrand.no</email></address>
2459    </author>
2460    <date year="2008" month="May"/>
2461  </front>
2462  <seriesInfo name="BCP" value="26"/>
2463  <seriesInfo name="RFC" value="5226"/>
2464</reference>
2465
2466<reference anchor="RFC5322">
2467  <front>
2468    <title>Internet Message Format</title>
2469    <author initials="P." surname="Resnick" fullname="P. Resnick">
2470      <organization>Qualcomm Incorporated</organization>
2471    </author>
2472    <date year="2008" month="October"/>
2473  </front> 
2474  <seriesInfo name="RFC" value="5322"/>
2475</reference>
2476
2477<reference anchor="BCP97">
2478  <front>
2479    <title>Handling Normative References to Standards-Track Documents</title>
2480    <author initials="J." surname="Klensin" fullname="J. Klensin">
2481      <address>
2482        <email>klensin+ietf@jck.com</email>
2483      </address>
2484    </author>
2485    <author initials="S." surname="Hartman" fullname="S. Hartman">
2486      <organization>MIT</organization>
2487      <address>
2488        <email>hartmans-ietf@mit.edu</email>
2489      </address>
2490    </author>
2491    <date year="2007" month="June"/>
2492  </front>
2493  <seriesInfo name="BCP" value="97"/>
2494  <seriesInfo name="RFC" value="4897"/>
2495</reference>
2496
2497
2498</references>
2499
2500<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2501<t>
2502   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
2503   allow a message-body to be transmitted in an open variety of
2504   representations and with extensible mechanisms. However, RFC 2045
2505   discusses mail, and HTTP has a few features that are different from
2506   those described in MIME. These differences were carefully chosen
2507   to optimize performance over binary connections, to allow greater
2508   freedom in the use of new media types, to make date comparisons
2509   easier, and to acknowledge the practice of some early HTTP servers
2510   and clients.
2511</t>
2512<t>
2513   This appendix describes specific areas where HTTP differs from MIME.
2514   Proxies and gateways to strict MIME environments SHOULD be
2515   aware of these differences and provide the appropriate conversions
2516   where necessary. Proxies and gateways from MIME environments to HTTP
2517   also need to be aware of the differences because some conversions
2518   might be required.
2519</t>
2520
2521<section title="MIME-Version" anchor="mime-version">
2522  <iref primary="true" item="MIME-Version header"/>
2523  <iref primary="true" item="Headers" subitem="MIME-Version"/>
2524 
2525 
2526<t>
2527   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
2528   include a single MIME-Version general-header field to indicate what
2529   version of the MIME protocol was used to construct the message. Use
2530   of the MIME-Version header field indicates that the message is in
2531   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2532   Proxies/gateways are responsible for ensuring full compliance (where
2533   possible) when exporting HTTP messages to strict MIME environments.
2534</t>
2535<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/><artwork type="abnf2616"><![CDATA[
2536  MIME-Version   = "MIME-Version" ":" OWS MIME-Version-v
2537  MIME-Version-v = 1*DIGIT "." 1*DIGIT
2538]]></artwork></figure>
2539<t>
2540   MIME version "1.0" is the default for use in HTTP/1.1. However,
2541   HTTP/1.1 message parsing and semantics are defined by this document
2542   and not the MIME specification.
2543</t>
2544</section>
2545
2546<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2547<t>
2548   MIME requires that an Internet mail body-part be converted to
2549   canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
2550   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2551   allowed for subtypes of the "text" media type when transmitted over
2552   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2553   line breaks as CRLF and forbids the use of CR or LF outside of line
2554   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2555   line break within text content when a message is transmitted over
2556   HTTP.
2557</t>
2558<t>
2559   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2560   environment SHOULD translate all line breaks within the text media
2561   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2562   canonical form of CRLF. Note, however, that this might be complicated
2563   by the presence of a Content-Encoding and by the fact that HTTP
2564   allows the use of some character sets which do not use octets 13 and
2565   10 to represent CR and LF, as is the case for some multi-byte
2566   character sets.
2567</t>
2568<t>
2569   Conversion will break any cryptographic
2570   checksums applied to the original content unless the original content
2571   is already in canonical form. Therefore, the canonical form is
2572   recommended for any content that uses such checksums in HTTP.
2573</t>
2574</section>
2575
2576
2577<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2578<t>
2579   HTTP/1.1 uses a restricted set of date formats (Section 6.1 of <xref target="Part1"/>) to
2580   simplify the process of date comparison. Proxies and gateways from
2581   other protocols SHOULD ensure that any Date header field present in a
2582   message conforms to one of the HTTP/1.1 formats and rewrite the date
2583   if necessary.
2584</t>
2585</section>
2586
2587<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2588<t>
2589   MIME does not include any concept equivalent to HTTP/1.1's
2590   Content-Encoding header field. Since this acts as a modifier on the
2591   media type, proxies and gateways from HTTP to MIME-compliant
2592   protocols MUST either change the value of the Content-Type header
2593   field or decode the representation before forwarding the message. (Some
2594   experimental applications of Content-Type for Internet mail have used
2595   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2596   a function equivalent to Content-Encoding. However, this parameter is
2597   not part of the MIME standards).
2598</t>
2599</section>
2600
2601<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2602<t>
2603   HTTP does not use the Content-Transfer-Encoding field of MIME.
2604   Proxies and gateways from MIME-compliant protocols to HTTP MUST
2605   remove any Content-Transfer-Encoding
2606   prior to delivering the response message to an HTTP client.
2607</t>
2608<t>
2609   Proxies and gateways from HTTP to MIME-compliant protocols are
2610   responsible for ensuring that the message is in the correct format
2611   and encoding for safe transport on that protocol, where "safe
2612   transport" is defined by the limitations of the protocol being used.
2613   Such a proxy or gateway SHOULD label the data with an appropriate
2614   Content-Transfer-Encoding if doing so will improve the likelihood of
2615   safe transport over the destination protocol.
2616</t>
2617</section>
2618
2619<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2620<t>
2621   HTTP/1.1 introduces the Transfer-Encoding header field (Section 9.7 of <xref target="Part1"/>).
2622   Proxies/gateways MUST remove any transfer-coding prior to
2623   forwarding a message via a MIME-compliant protocol.
2624</t>
2625</section>
2626
2627<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2628<t>
2629   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2630   need to be aware of MIME line length limitations. Since HTTP does not
2631   have this limitation, HTTP does not fold long lines. MHTML messages
2632   being transported by HTTP follow all conventions of MHTML, including
2633   line length limitations and folding, canonicalization, etc., since
2634   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2635   does not interpret the content or any MIME header lines that might be
2636   contained therein.
2637</t>
2638</section>
2639</section>
2640
2641<section title="Additional Features" anchor="additional.features">
2642<t>
2643   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2644   existing HTTP implementations, but not consistently and correctly
2645   across most HTTP/1.1 applications. Implementors are advised to be
2646   aware of these features, but cannot rely upon their presence in, or
2647   interoperability with, other HTTP/1.1 applications. Some of these
2648   describe proposed experimental features, and some describe features
2649   that experimental deployment found lacking that are now addressed in
2650   the base HTTP/1.1 specification.
2651</t>
2652<t>
2653   A number of other headers, such as Content-Disposition and Title,
2654   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2655</t>
2656
2657<section title="Content-Disposition" anchor="content-disposition">
2658<iref item="Headers" subitem="Content-Disposition" primary="true"/>
2659<iref item="Content-Disposition header" primary="true"/>
2660 
2661 
2662 
2663 
2664 
2665 
2666 
2667<t>
2668   The "Content-Disposition" response-header field has been proposed as a
2669   means for the origin server to suggest a default filename if the user
2670   requests that the content is saved to a file. This usage is derived
2671   from the definition of Content-Disposition in <xref target="RFC2183"/>.
2672</t>
2673<figure><iref primary="true" item="Grammar" subitem="content-disposition"/><iref primary="true" item="Grammar" subitem="content-disposition-v"/><iref primary="true" item="Grammar" subitem="disposition-type"/><iref primary="true" item="Grammar" subitem="disposition-parm"/><iref primary="true" item="Grammar" subitem="filename-parm"/><iref primary="true" item="Grammar" subitem="disp-extension-token"/><iref primary="true" item="Grammar" subitem="disp-extension-parm"/><artwork type="abnf2616"><![CDATA[
2674  content-disposition = "Content-Disposition" ":" OWS
2675                        content-disposition-v
2676  content-disposition-v = disposition-type
2677                          *( OWS ";" OWS disposition-parm )
2678  disposition-type = "attachment" / disp-extension-token
2679  disposition-parm = filename-parm / disp-extension-parm
2680  filename-parm = "filename" "=" quoted-string
2681  disp-extension-token = token
2682  disp-extension-parm = token "=" word
2683]]></artwork></figure>
2684<t>
2685   An example is
2686</t>
2687<figure><artwork type="example"><![CDATA[
2688  Content-Disposition: attachment; filename="fname.ext"
2689]]></artwork></figure>
2690<t>
2691   The receiving user agent SHOULD NOT  respect any directory path
2692   information present in the filename-parm parameter, which is the only
2693   parameter believed to apply to HTTP implementations at this time. The
2694   filename SHOULD be treated as a terminal component only.
2695</t>
2696<t>
2697   If this header is used in a response with the application/octet-stream
2698   content-type, the implied suggestion is that the user agent
2699   should not display the response, but directly enter a "save response
2700   as..." dialog.
2701</t>
2702<t>
2703   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
2704</t>
2705</section>
2706</section>
2707
2708<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2709<t>
2710  Clarify contexts that charset is used in.
2711  (<xref target="character.sets"/>)
2712</t>
2713<t>
2714  Remove base URI setting semantics for Content-Location due to poor
2715  implementation support, which was caused by too many broken servers emitting
2716  bogus Content-Location headers, and also the potentially undesirable effect
2717  of potentially breaking relative links in content-negotiated resources.
2718  (<xref target="header.content-location"/>)
2719</t>
2720<t>
2721  Remove reference to non-existant identity transfer-coding value tokens.
2722  (<xref target="no.content-transfer-encoding"/>)
2723</t>
2724</section>
2725
2726
2727<section title="Collected ABNF" anchor="collected.abnf">
2728<figure>
2729<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
2730Accept = "Accept:" OWS Accept-v
2731Accept-Charset = "Accept-Charset:" OWS Accept-Charset-v
2732Accept-Charset-v = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2733 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2734 qvalue ] ] )
2735Accept-Encoding = "Accept-Encoding:" OWS Accept-Encoding-v
2736Accept-Encoding-v = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2737 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2738Accept-Language = "Accept-Language:" OWS Accept-Language-v
2739Accept-Language-v = *( "," OWS ) language-range [ OWS ";" OWS "q="
2740 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2741 ] )
2742Accept-v = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2743 OWS media-range [ accept-params ] ] ) ]
2744
2745Content-Encoding = "Content-Encoding:" OWS Content-Encoding-v
2746Content-Encoding-v = *( "," OWS ) content-coding *( OWS "," [ OWS
2747 content-coding ] )
2748Content-Language = "Content-Language:" OWS Content-Language-v
2749Content-Language-v = *( "," OWS ) language-tag *( OWS "," [ OWS
2750 language-tag ] )
2751Content-Length = <Content-Length, defined in [Part1], Section 9.2>
2752Content-Location = "Content-Location:" OWS Content-Location-v
2753Content-Location-v = absolute-URI / partial-URI
2754Content-MD5 = "Content-MD5:" OWS Content-MD5-v
2755Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
2756Content-Range = <Content-Range, defined in [Part5], Section 5.2>
2757Content-Type = "Content-Type:" OWS Content-Type-v
2758Content-Type-v = media-type
2759
2760Expires = <Expires, defined in [Part6], Section 3.3>
2761
2762Last-Modified = <Last-Modified, defined in [Part4], Section 6.6>
2763
2764MIME-Version = "MIME-Version:" OWS MIME-Version-v
2765MIME-Version-v = 1*DIGIT "." 1*DIGIT
2766
2767OWS = <OWS, defined in [Part1], Section 1.2.2>
2768
2769absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
2770accept-ext = OWS ";" OWS token [ "=" word ]
2771accept-params = OWS ";" OWS "q=" qvalue *accept-ext
2772attribute = token
2773
2774charset = token
2775codings = ( content-coding / "*" )
2776content-coding = token
2777content-disposition = "Content-Disposition:" OWS
2778 content-disposition-v
2779content-disposition-v = disposition-type *( OWS ";" OWS
2780 disposition-parm )
2781
2782disp-extension-parm = token "=" word
2783disp-extension-token = token
2784disposition-parm = filename-parm / disp-extension-parm
2785disposition-type = "attachment" / disp-extension-token
2786
2787filename-parm = "filename=" quoted-string
2788
2789header-field = <header-field, defined in [Part1], Section 3.2>
2790
2791language-range = <language-range, defined in [RFC4647], Section 2.1>
2792language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
2793
2794media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2795 ";" OWS parameter )
2796media-type = type "/" subtype *( OWS ";" OWS parameter )
2797
2798parameter = attribute "=" value
2799partial-URI = <partial-URI, defined in [Part1], Section 2.6>
2800
2801quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
2802qvalue = <qvalue, defined in [Part1], Section 6.4>
2803
2804subtype = token
2805
2806token = <token, defined in [Part1], Section 1.2.2>
2807type = token
2808
2809value = word
2810
2811word = <word, defined in [Part1], Section 1.2.2>
2812]]></artwork>
2813</figure>
2814<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
2815; Accept defined but not used
2816; Accept-Charset defined but not used
2817; Accept-Encoding defined but not used
2818; Accept-Language defined but not used
2819; Content-Encoding defined but not used
2820; Content-Language defined but not used
2821; Content-Length defined but not used
2822; Content-Location defined but not used
2823; Content-MD5 defined but not used
2824; Content-Range defined but not used
2825; Content-Type defined but not used
2826; Expires defined but not used
2827; Last-Modified defined but not used
2828; MIME-Version defined but not used
2829; content-disposition defined but not used
2830; header-field defined but not used
2831]]></artwork></figure></section>
2832
2833
2834<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2835
2836<section title="Since RFC2616">
2837<t>
2838  Extracted relevant partitions from <xref target="RFC2616"/>.
2839</t>
2840</section>
2841
2842<section title="Since draft-ietf-httpbis-p3-payload-00">
2843<t>
2844  Closed issues:
2845  <list style="symbols"> 
2846    <t>
2847      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2848      "Media Type Registrations"
2849      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2850    </t>
2851    <t>
2852      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2853      "Clarification regarding quoting of charset values"
2854      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2855    </t>
2856    <t>
2857      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2858      "Remove 'identity' token references"
2859      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2860    </t>
2861    <t>
2862      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2863      "Accept-Encoding BNF"
2864    </t>
2865    <t>
2866      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2867      "Normative and Informative references"
2868    </t>
2869    <t>
2870      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2871      "RFC1700 references"
2872    </t>
2873    <t>
2874      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2875      "Updating to RFC4288"
2876    </t>
2877    <t>
2878      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2879      "Informative references"
2880    </t>
2881    <t>
2882      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2883      "ISO-8859-1 Reference"
2884    </t>
2885    <t>
2886      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2887      "Encoding References Normative"
2888    </t>
2889    <t>
2890      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2891      "Normative up-to-date references"
2892    </t>
2893  </list>
2894</t>
2895</section>
2896
2897<section title="Since draft-ietf-httpbis-p3-payload-01">
2898<t>
2899  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2900  <list style="symbols"> 
2901    <t>
2902      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2903    </t>
2904  </list>
2905</t>
2906</section>
2907
2908<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2909<t>
2910  Closed issues:
2911  <list style="symbols"> 
2912    <t>
2913      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2914      "Quoting Charsets"
2915    </t>
2916    <t>
2917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2918      "Classification for Allow header"
2919    </t>
2920    <t>
2921      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2922      "missing default for qvalue in description of Accept-Encoding"
2923    </t>
2924  </list>
2925</t>
2926<t>
2927  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2928  <list style="symbols"> 
2929    <t>
2930      Reference RFC 3984, and update header registrations for headers defined
2931      in this document.
2932    </t>
2933  </list>
2934</t>
2935</section>
2936
2937<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2938<t>
2939  Closed issues:
2940  <list style="symbols"> 
2941    <t>
2942      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2943      "Quoting Charsets"
2944    </t>
2945    <t>
2946      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2947      "language tag matching (Accept-Language) vs RFC4647"
2948    </t>
2949    <t>
2950      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2951      "RFC 1806 has been replaced by RFC2183"
2952    </t>
2953  </list>
2954</t>
2955<t>
2956  Other changes:
2957  <list style="symbols"> 
2958    <t>
2959      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2960      "Encoding References Normative" -- rephrase the annotation and reference
2961      <xref target="BCP97"/>.
2962    </t>
2963  </list>
2964</t>
2965 </section>
2966
2967<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2968<t>
2969  Closed issues:
2970  <list style="symbols"> 
2971    <t>
2972      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2973      "RFC 2822 is updated by RFC 5322"
2974    </t>
2975  </list>
2976</t>
2977<t>
2978  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2979  <list style="symbols"> 
2980    <t>
2981      Use "/" instead of "|" for alternatives.
2982    </t>
2983    <t>
2984      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2985      whitespace ("OWS") and required whitespace ("RWS").
2986    </t>
2987    <t>
2988      Rewrite ABNFs to spell out whitespace rules, factor out
2989      header value format definitions.
2990    </t>
2991  </list>
2992</t>
2993</section>
2994
2995<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2996<t>
2997  Closed issues:
2998  <list style="symbols"> 
2999    <t>
3000      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
3001      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3002    </t>
3003  </list>
3004</t>
3005<t>
3006  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3007  <list style="symbols"> 
3008    <t>
3009      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3010    </t>
3011  </list>
3012</t>
3013<t>
3014  Other changes:
3015  <list style="symbols"> 
3016    <t>
3017      Move definition of quality values into Part 1.
3018    </t>
3019  </list>
3020</t>
3021</section>
3022
3023<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
3024<t>
3025  Closed issues:
3026  <list style="symbols"> 
3027    <t>
3028      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3029      "Content-Location isn't special"
3030    </t>
3031    <t>
3032      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3033      "Content Sniffing"
3034    </t>
3035  </list>
3036</t>
3037</section>
3038
3039<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
3040<t>
3041  Closed issues:
3042  <list style="symbols"> 
3043    <t>
3044      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
3045      "Updated reference for language tags"
3046    </t>
3047    <t>
3048      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3049      "Clarify rules for determining what entities a response carries"
3050    </t>
3051    <t>
3052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
3053      "Content-Location base-setting problems"
3054    </t>
3055    <t>
3056      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3057      "Content Sniffing"
3058    </t>
3059    <t>
3060      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
3061      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3062    </t>
3063    <t>
3064      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
3065      "move definitions of gzip/deflate/compress to part 1"
3066    </t>
3067  </list>
3068</t>
3069<t>
3070  Partly resolved issues:
3071  <list style="symbols"> 
3072    <t>
3073      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
3074      "update IANA requirements wrt Transfer-Coding values" (add the
3075      IANA Considerations subsection)
3076    </t>
3077    <t>
3078      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
3079      "update IANA requirements wrt Content-Coding values" (add the
3080      IANA Considerations subsection)
3081    </t>
3082  </list>
3083</t>
3084</section>
3085
3086<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
3087<t>
3088  Closed issues:
3089  <list style="symbols"> 
3090    <t>
3091      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
3092      "Content Negotiation for media types"
3093    </t>
3094    <t>
3095      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
3096      "Accept-Language: which RFC4647 filtering?"
3097    </t>
3098  </list>
3099</t>
3100</section>
3101
3102<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
3103<t>
3104  Closed issues:
3105  <list style="symbols"> 
3106    <t>
3107      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
3108      "MIME-Version not listed in P1, general header fields"
3109    </t>
3110    <t>
3111      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
3112      "IANA registry for content/transfer encodings"
3113    </t>
3114    <t>
3115      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3116      "Content Sniffing"
3117    </t>
3118    <t>
3119      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
3120      "use of term "word" when talking about header structure"
3121    </t>
3122  </list>
3123</t>
3124<t>
3125  Partly resolved issues:
3126  <list style="symbols"> 
3127    <t>
3128      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3129      "Term for the requested resource's URI"
3130    </t>
3131  </list>
3132</t>
3133</section>
3134
3135<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
3136<t>
3137  Closed issues:
3138  <list style="symbols"> 
3139    <t>
3140      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3141      "Clarify 'Requested Variant'"
3142    </t>
3143    <t>
3144      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3145      "Content-Location isn't special"
3146    </t>
3147    <t>
3148      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
3149      "Delimiting messages with multipart/byteranges"
3150    </t>
3151    <t>
3152      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3153      "Clarify entity / representation / variant terminology"
3154    </t>
3155    <t>
3156      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
3157      "confusing req. language for Content-Location"
3158    </t>
3159    <t>
3160      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
3161      "Content-Location on 304 responses"
3162    </t>
3163    <t>
3164      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
3165      "'requested resource' in content-encoding definition"
3166    </t>
3167    <t>
3168      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3169      "consider removing the 'changes from 2068' sections"
3170    </t>
3171  </list>
3172</t>
3173<t>
3174  Partly resolved issues:
3175  <list style="symbols"> 
3176    <t>
3177      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3178      "Content-MD5 and partial responses"
3179    </t>
3180  </list>
3181</t>
3182</section>
3183
3184</section>
3185
3186</back>
3187</rfc>
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