source: draft-ietf-httpbis/latest/p3-payload.xml @ 965

Last change on this file since 965 was 965, checked in by fielding@…, 9 years ago

Addresses #109: Clarify entity / representation / variant terminology

Removed entity-header adjective and ABNF and clarified distinction
between payload and representation.

Uncapitalize the phrase effective request URI so that it doesn't
dominate the prose, and define the term "target resource" to be
used instead of the "resource identified by the effective request URI".

  • Property svn:eol-style set to native
File size: 135.3 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "July">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY notation-abnf            "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY basic-rules              "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY header-fields            "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='#internet.media.type.multipart.byteranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY full-date                "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41]>
42<?rfc toc="yes" ?>
43<?rfc symrefs="yes" ?>
44<?rfc sortrefs="yes" ?>
45<?rfc compact="yes"?>
46<?rfc subcompact="no" ?>
47<?rfc linkmailto="no" ?>
48<?rfc editing="no" ?>
49<?rfc comments="yes"?>
50<?rfc inline="yes"?>
51<?rfc rfcedstyle="yes"?>
52<?rfc-ext allow-markup-in-artwork="yes" ?>
53<?rfc-ext include-references-in-index="yes" ?>
54<rfc obsoletes="2616" category="std" x:maturity-level="draft"
55     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
56     xmlns:x='http://purl.org/net/xml2rfc/ext'>
57<front>
58
59  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
60
61  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
62    <organization abbrev="Day Software">Day Software</organization>
63    <address>
64      <postal>
65        <street>23 Corporate Plaza DR, Suite 280</street>
66        <city>Newport Beach</city>
67        <region>CA</region>
68        <code>92660</code>
69        <country>USA</country>
70      </postal>
71      <phone>+1-949-706-5300</phone>
72      <facsimile>+1-949-706-5305</facsimile>
73      <email>fielding@gbiv.com</email>
74      <uri>http://roy.gbiv.com/</uri>
75    </address>
76  </author>
77
78  <author initials="J." surname="Gettys" fullname="Jim Gettys">
79    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
80    <address>
81      <postal>
82        <street>21 Oak Knoll Road</street>
83        <city>Carlisle</city>
84        <region>MA</region>
85        <code>01741</code>
86        <country>USA</country>
87      </postal>
88      <email>jg@freedesktop.org</email>
89      <uri>http://gettys.wordpress.com/</uri>
90    </address>
91  </author>
92 
93  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
94    <organization abbrev="HP">Hewlett-Packard Company</organization>
95    <address>
96      <postal>
97        <street>HP Labs, Large Scale Systems Group</street>
98        <street>1501 Page Mill Road, MS 1177</street>
99        <city>Palo Alto</city>
100        <region>CA</region>
101        <code>94304</code>
102        <country>USA</country>
103      </postal>
104      <email>JeffMogul@acm.org</email>
105    </address>
106  </author>
107
108  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
109    <organization abbrev="Microsoft">Microsoft Corporation</organization>
110    <address>
111      <postal>
112        <street>1 Microsoft Way</street>
113        <city>Redmond</city>
114        <region>WA</region>
115        <code>98052</code>
116        <country>USA</country>
117      </postal>
118      <email>henrikn@microsoft.com</email>
119    </address>
120  </author>
121
122  <author initials="L." surname="Masinter" fullname="Larry Masinter">
123    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
124    <address>
125      <postal>
126        <street>345 Park Ave</street>
127        <city>San Jose</city>
128        <region>CA</region>
129        <code>95110</code>
130        <country>USA</country>
131      </postal>
132      <email>LMM@acm.org</email>
133      <uri>http://larry.masinter.net/</uri>
134    </address>
135  </author>
136 
137  <author initials="P." surname="Leach" fullname="Paul J. Leach">
138    <organization abbrev="Microsoft">Microsoft Corporation</organization>
139    <address>
140      <postal>
141        <street>1 Microsoft Way</street>
142        <city>Redmond</city>
143        <region>WA</region>
144        <code>98052</code>
145      </postal>
146      <email>paulle@microsoft.com</email>
147    </address>
148  </author>
149   
150  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
151    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
152    <address>
153      <postal>
154        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
155        <street>The Stata Center, Building 32</street>
156        <street>32 Vassar Street</street>
157        <city>Cambridge</city>
158        <region>MA</region>
159        <code>02139</code>
160        <country>USA</country>
161      </postal>
162      <email>timbl@w3.org</email>
163      <uri>http://www.w3.org/People/Berners-Lee/</uri>
164    </address>
165  </author>
166
167  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
168    <organization abbrev="W3C">World Wide Web Consortium</organization>
169    <address>
170      <postal>
171        <street>W3C / ERCIM</street>
172        <street>2004, rte des Lucioles</street>
173        <city>Sophia-Antipolis</city>
174        <region>AM</region>
175        <code>06902</code>
176        <country>France</country>
177      </postal>
178      <email>ylafon@w3.org</email>
179      <uri>http://www.raubacapeu.net/people/yves/</uri>
180    </address>
181  </author>
182
183  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
184    <organization abbrev="greenbytes">greenbytes GmbH</organization>
185    <address>
186      <postal>
187        <street>Hafenweg 16</street>
188        <city>Muenster</city><region>NW</region><code>48155</code>
189        <country>Germany</country>
190      </postal>
191      <phone>+49 251 2807760</phone>
192      <facsimile>+49 251 2807761</facsimile>
193      <email>julian.reschke@greenbytes.de</email>
194      <uri>http://greenbytes.de/tech/webdav/</uri>
195    </address>
196  </author>
197
198  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
199  <workgroup>HTTPbis Working Group</workgroup>
200
201<abstract>
202<t>
203   The Hypertext Transfer Protocol (HTTP) is an application-level
204   protocol for distributed, collaborative, hypermedia information
205   systems. HTTP has been in use by the World Wide Web global information
206   initiative since 1990. This document is Part 3 of the seven-part specification
207   that defines the protocol referred to as "HTTP/1.1" and, taken together,
208   obsoletes RFC 2616.  Part 3 defines HTTP message content,
209   metadata, and content negotiation.
210</t>
211</abstract>
212
213<note title="Editorial Note (To be removed by RFC Editor)">
214  <t>
215    Discussion of this draft should take place on the HTTPBIS working group
216    mailing list (ietf-http-wg@w3.org). The current issues list is
217    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
218    and related documents (including fancy diffs) can be found at
219    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
220  </t>
221  <t>
222    The changes in this draft are summarized in <xref target="changes.since.10"/>.
223  </t>
224</note>
225</front>
226<middle>
227<section title="Introduction" anchor="introduction">
228<t>
229   This document defines HTTP/1.1 message payloads (a.k.a., content), the
230   associated metadata header fields that define how the payload is intended
231   to be interpreted by a recipient, the request header fields that
232   might influence content selection, and the various selection algorithms
233   that are collectively referred to as HTTP content negotiation.
234</t>
235<t>
236   This document is currently disorganized in order to minimize the changes
237   between drafts and enable reviewers to see the smaller errata changes.
238   The next draft will reorganize the sections to better reflect the content.
239   In particular, the sections on entities will be renamed payload and moved
240   to the first half of the document, while the sections on content negotiation
241   and associated request header fields will be moved to the second half.  The
242   current mess reflects how widely dispersed these topics and associated
243   requirements had become in <xref target="RFC2616"/>.
244</t>
245
246<section title="Terminology" anchor="terminology">
247<t>
248   This specification uses a number of terms to refer to the roles
249   played by participants in, and objects of, the HTTP communication.
250</t>
251<t>
252  <iref item="content negotiation"/>
253  <x:dfn>content negotiation</x:dfn>
254  <list>
255    <t>
256      The mechanism for selecting the appropriate representation when
257      servicing a request. The representation in any response
258      can be negotiated (including error responses).
259    </t>
260  </list>
261</t>
262</section>
263
264<section title="Requirements" anchor="intro.requirements">
265<t>
266   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
267   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
268   document are to be interpreted as described in <xref target="RFC2119"/>.
269</t>
270<t>
271   An implementation is not compliant if it fails to satisfy one or more
272   of the "MUST" or "REQUIRED" level requirements for the protocols it
273   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
274   level and all the "SHOULD" level requirements for its protocols is said
275   to be "unconditionally compliant"; one that satisfies all the "MUST"
276   level requirements but not all the "SHOULD" level requirements for its
277   protocols is said to be "conditionally compliant".
278</t>
279</section>
280
281<section title="Syntax Notation" anchor="notation">
282  <x:anchor-alias value="ALPHA"/>
283  <x:anchor-alias value="CR"/>
284  <x:anchor-alias value="DIGIT"/>
285  <x:anchor-alias value="LF"/>
286  <x:anchor-alias value="OCTET"/>
287  <x:anchor-alias value="VCHAR"/>
288  <x:anchor-alias value="WSP"/>
289<t>
290  This specification uses the ABNF syntax defined in &notation; (which
291  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
292  <xref target="collected.abnf"/> shows the collected ABNF, with the list
293  rule expanded.
294</t>
295<t>
296  The following core rules are included by
297  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
298  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
299  DIGIT (decimal 0-9), DQUOTE (double quote),
300  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
301  OCTET (any 8-bit sequence of data), SP (space),
302  VCHAR (any visible USASCII character),
303  and WSP (whitespace).
304</t>
305
306<section title="Core Rules" anchor="core.rules">
307  <x:anchor-alias value="quoted-string"/>
308  <x:anchor-alias value="token"/>
309  <x:anchor-alias value="word"/>
310  <x:anchor-alias value="OWS"/>
311<t>
312  The core rules below are defined in &basic-rules;:
313</t>
314<figure><artwork type="abnf2616">
315  <x:ref>quoted-string</x:ref>  = &lt;quoted-string, defined in &basic-rules;&gt;
316  <x:ref>token</x:ref>          = &lt;token, defined in &basic-rules;&gt;
317  <x:ref>word</x:ref>           = &lt;word, defined in &basic-rules;&gt;
318  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
319</artwork></figure>
320</section>
321
322<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
323  <x:anchor-alias value="absolute-URI"/>
324  <x:anchor-alias value="Allow"/>
325  <x:anchor-alias value="Content-Length"/>
326  <x:anchor-alias value="Content-Range"/>
327  <x:anchor-alias value="Expires"/>
328  <x:anchor-alias value="Last-Modified"/>
329  <x:anchor-alias value="header-field"/>
330  <x:anchor-alias value="partial-URI"/>
331  <x:anchor-alias value="qvalue"/>
332<t>
333  The ABNF rules below are defined in other parts:
334</t>
335<figure><!--Part1--><artwork type="abnf2616">
336  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
337  <x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in &header-content-length;&gt;
338  <x:ref>header-field</x:ref>   = &lt;header-field, defined in &header-fields;&gt;
339  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
340  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
341</artwork></figure>
342<figure><!--Part4--><artwork type="abnf2616">
343  <x:ref>Last-Modified</x:ref>  = &lt;Last-Modified, defined in &header-last-modified;&gt;
344</artwork></figure>
345<figure><!--Part5--><artwork type="abnf2616">
346  <x:ref>Content-Range</x:ref>  = &lt;Content-Range, defined in &header-content-range;&gt;
347</artwork></figure>
348<figure><!--Part6--><artwork type="abnf2616">
349  <x:ref>Expires</x:ref>        = &lt;Expires, defined in &header-expires;&gt;
350</artwork></figure>
351</section>
352
353</section>
354
355</section>
356
357<section title="Protocol Parameters" anchor="protocol.parameters">
358
359<section title="Character Sets" anchor="character.sets">
360<t>
361   HTTP uses the same definition of the term "character set" as that
362   described for MIME:
363</t>
364<t>
365   The term "character set" is used in this document to refer to a
366   method used with one or more tables to convert a sequence of octets
367   into a sequence of characters. Note that unconditional conversion in
368   the other direction is not required, in that not all characters might
369   be available in a given character set and a character set might provide
370   more than one sequence of octets to represent a particular character.
371   This definition is intended to allow various kinds of character
372   encoding, from simple single-table mappings such as US-ASCII to
373   complex table switching methods such as those that use ISO-2022's
374   techniques. However, the definition associated with a MIME character
375   set name &MUST; fully specify the mapping to be performed from octets
376   to characters. In particular, use of external profiling information
377   to determine the exact mapping is not permitted.
378</t>
379<x:note>
380  <t>
381    <x:h>Note:</x:h> This use of the term "character set" is more commonly
382    referred to as a "character encoding". However, since HTTP and
383    MIME share the same registry, it is important that the terminology
384    also be shared.
385  </t>
386</x:note>
387<t anchor="rule.charset">
388  <x:anchor-alias value="charset"/>
389   HTTP character sets are identified by case-insensitive tokens. The
390   complete set of tokens is defined by the IANA Character Set registry
391   (<eref target="http://www.iana.org/assignments/character-sets"/>).
392</t>
393<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
394  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
395</artwork></figure>
396<t>
397   Although HTTP allows an arbitrary token to be used as a charset
398   value, any token that has a predefined value within the IANA
399   Character Set registry &MUST; represent the character set defined
400   by that registry. Applications &SHOULD; limit their use of character
401   sets to those defined by the IANA registry.
402</t>
403<t>
404   HTTP uses charset in two contexts: within an Accept-Charset request
405   header (in which the charset value is an unquoted token) and as the
406   value of a parameter in a Content-Type header (within a request or
407   response), in which case the parameter value of the charset parameter
408   can be quoted.
409</t>
410<t>
411   Implementors should be aware of IETF character set requirements <xref target="RFC3629"/>
412   <xref target="RFC2277"/>.
413</t>
414
415<section title="Missing Charset" anchor="missing.charset">
416<t>
417   Some HTTP/1.0 software has interpreted a Content-Type header without
418   charset parameter incorrectly to mean "recipient should guess".
419   Senders wishing to defeat this behavior &MAY; include a charset
420   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and &SHOULD; do so when
421   it is known that it will not confuse the recipient.
422</t>
423<t>
424   Unfortunately, some older HTTP/1.0 clients did not deal properly with
425   an explicit charset parameter. HTTP/1.1 recipients &MUST; respect the
426   charset label provided by the sender; and those user agents that have
427   a provision to "guess" a charset &MUST; use the charset from the
428   content-type field if they support that charset, rather than the
429   recipient's preference, when initially displaying a document. See
430   <xref target="canonicalization.and.text.defaults"/>.
431</t>
432</section>
433</section>
434
435<section title="Content Codings" anchor="content.codings">
436  <x:anchor-alias value="content-coding"/>
437<t>
438   Content coding values indicate an encoding transformation that has
439   been or can be applied to a representation. Content codings are primarily
440   used to allow a representation to be compressed or otherwise usefully
441   transformed without losing the identity of its underlying media type
442   and without loss of information. Frequently, the representation is stored in
443   coded form, transmitted directly, and only decoded by the recipient.
444</t>
445<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
446  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
447</artwork></figure>
448<t>
449   All content-coding values are case-insensitive. HTTP/1.1 uses
450   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
451   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
452   describes the content-coding, what is more important is that it
453   indicates what decoding mechanism will be required to remove the
454   encoding.
455</t>
456<t>
457   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
458  <list>
459    <t>
460      See &compress-coding;.
461    </t>
462  </list>
463</t>
464<t>
465   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
466  <list>
467    <t>
468      See &deflate-coding;.
469    </t>
470  </list>
471</t>
472<t>
473   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
474  <list>
475    <t>
476      See &gzip-coding;.
477    </t>
478  </list>
479</t>
480<t>
481   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
482  <list><t>
483        The default (identity) encoding; the use of no transformation
484        whatsoever. This content-coding is used only in the Accept-Encoding
485        header, and &SHOULD-NOT;  be used in the Content-Encoding
486        header.
487  </t></list>
488</t>
489
490<section title="Content Coding Registry" anchor="content.coding.registry">
491<t>
492   The HTTP Content Coding Registry defines the name space for the content
493   coding names.
494</t>
495<t>
496   Registrations &MUST; include the following fields:
497   <list style="symbols">
498     <t>Name</t>
499     <t>Description</t>
500     <t>Pointer to specification text</t>
501   </list>
502</t>
503<t>
504   Names of content codings &MUST-NOT; overlap with names of transfer codings
505   (&transfer-codings;), unless the encoding transformation is identical (as it
506   is the case for the compression codings defined in
507   &compression-codings;).
508</t>
509<t>
510   Values to be added to this name space require a specification
511   (see "Specification Required" in
512   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
513   conform to the purpose of content coding defined in this section.
514</t>
515<t>
516   The registry itself is maintained at
517   <eref target="http://www.iana.org/assignments/http-parameters"/>.
518</t>
519</section>
520
521</section>
522
523<section title="Media Types" anchor="media.types">
524  <x:anchor-alias value="media-type"/>
525  <x:anchor-alias value="type"/>
526  <x:anchor-alias value="subtype"/>
527<t>
528   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
529   and Accept (<xref target="header.accept"/>) header fields in order to provide
530   open and extensible data typing and type negotiation.
531</t>
532<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/>
533  <x:ref>media-type</x:ref> = <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
534  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
535  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
536</artwork></figure>
537<t anchor="rule.parameter">
538  <x:anchor-alias value="attribute"/>
539  <x:anchor-alias value="parameter"/>
540  <x:anchor-alias value="value"/>
541   Parameters &MAY; follow the type/subtype in the form of attribute/value
542   pairs.
543</t>
544<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/>
545  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
546  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
547  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
548</artwork></figure>
549<t>
550   The type, subtype, and parameter attribute names are case-insensitive.
551   Parameter values might or might not be case-sensitive, depending on the
552   semantics of the parameter name.  The presence or absence of a parameter might
553   be significant to the processing of a media-type, depending on its
554   definition within the media type registry.
555</t>
556<t>
557   A parameter value that matches the <x:ref>token</x:ref> production can be
558   transmitted as either a token or within a quoted-string. The quoted and
559   unquoted values are equivalent.
560</t>
561<t>
562   Note that some older HTTP applications do not recognize media type
563   parameters. When sending data to older HTTP applications,
564   implementations &SHOULD; only use media type parameters when they are
565   required by that type/subtype definition.
566</t>
567<t>
568   Media-type values are registered with the Internet Assigned Number
569   Authority (IANA). The media type registration process is
570   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
571   discouraged.
572</t>
573
574<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
575<t>
576   Internet media types are registered with a canonical form. A
577   representation transferred via HTTP messages &MUST; be in the
578   appropriate canonical form prior to its transmission except for
579   "text" types, as defined in the next paragraph.
580</t>
581<t>
582   When in canonical form, media subtypes of the "text" type use CRLF as
583   the text line break. HTTP relaxes this requirement and allows the
584   transport of text media with plain CR or LF alone representing a line
585   break when it is done consistently for an entire representation. HTTP
586   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
587   a line break in text media received via HTTP. In
588   addition, if the text is in a character encoding that does not
589   use octets 13 and 10 for CR and LF respectively, as is the case for
590   some multi-byte character encodings, HTTP allows the use of whatever octet
591   sequences are defined by that character encoding to represent the
592   equivalent of CR and LF for line breaks. This flexibility regarding
593   line breaks applies only to text media in the payload body; a bare CR
594   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
595   structures (such as header fields and multipart boundaries).
596</t>
597<t>
598   If a representation is encoded with a content-coding, the underlying
599   data &MUST; be in a form defined above prior to being encoded.
600</t>
601<t>
602   The "charset" parameter is used with some media types to define the
603   character encoding (<xref target="character.sets"/>) of the data. When no explicit charset
604   parameter is provided by the sender, media subtypes of the "text"
605   type are defined to have a default charset value of "ISO-8859-1" when
606   received via HTTP. Data in character encodings other than "ISO-8859-1" or
607   its subsets &MUST; be labeled with an appropriate charset value. See
608   <xref target="missing.charset"/> for compatibility problems.
609</t>
610</section>
611
612<section title="Multipart Types" anchor="multipart.types">
613<t>
614   MIME provides for a number of "multipart" types -- encapsulations of
615   one or more representations within a single message-body. All multipart
616   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
617   and &MUST; include a boundary parameter as part of the media type
618   value. The message body is itself a protocol element and &MUST;
619   therefore use only CRLF to represent line breaks between body-parts.
620</t>
621<t>
622   In general, HTTP treats a multipart message-body no differently than
623   any other media type: strictly as payload.  HTTP does not use the
624   multipart boundary as an indicator of message-body length.
625   <!-- jre: re-insert removed text pointing to caching? -->
626   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
627   behavior as a MIME user agent would upon receipt of a multipart type.
628   The MIME header fields within each body-part of a multipart message-body
629   do not have any significance to HTTP beyond that defined by
630   their MIME semantics.
631</t>
632<t>
633   If an application receives an unrecognized multipart subtype, the
634   application &MUST; treat it as being equivalent to "multipart/mixed".
635</t>
636<x:note>
637  <t>
638    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
639    for carrying form data suitable for processing via the POST
640    request method, as described in <xref target="RFC2388"/>.
641  </t>
642</x:note>
643</section>
644</section>
645
646<section title="Language Tags" anchor="language.tags">
647  <x:anchor-alias value="language-tag"/>
648<t>
649   A language tag, as defined in <xref target="RFC5646"/>, identifies a
650   natural language spoken, written, or otherwise conveyed by human beings for
651   communication of information to other human beings. Computer languages are
652   explicitly excluded. HTTP uses language tags within the Accept-Language and
653   Content-Language fields.
654</t>
655<t>
656   In summary, a language tag is composed of one or more parts: A primary
657   language subtag followed by a possibly empty series of subtags:
658</t>
659<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
660  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
661</artwork></figure>
662<t>
663   White space is not allowed within the tag and all tags are case-insensitive.
664   The name space of language subtags is administered by the IANA (see
665   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
666</t>
667<figure>
668  <preamble>Example tags include:</preamble>
669<artwork type="example">
670  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
671</artwork>
672</figure>
673<t>
674   See <xref target="RFC5646"/> for further information.
675</t>
676</section>
677</section>
678
679<section title="Payload" anchor="payload">
680<t>
681   HTTP messages &MAY; transfer a payload if not otherwise restricted by
682   the request method or response status code.  The payload consists of
683   metadata, in the form of header fields, and data, in the form of the
684   sequence of octets in the message-body after any transfer-coding has
685   been decoded.
686</t>
687<iref item="payload"/>
688<t>   
689   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
690   representation of some resource.  We use separate terms for payload
691   and representation because some messages contain only the associated
692   representation's header fields (e.g., responses to HEAD) or only some
693   part(s) of the representation (e.g., the 206 status code).
694</t>
695<t>
696    define metadata for the whole representation, which we refer
697   to as "representation header fields", while others define only metadata
698   about what is included in the message, which we
699</t>
700<section title="Payload Header Fields" anchor="payload.header.fields">
701  <x:anchor-alias value="payload-header"/>
702<t>
703   HTTP header fields that specifically define the payload, rather than the
704   associated representation, are referred to as "payload header fields".
705   The following payload header fields are defined by HTTP/1.1:
706</t>
707<figure><artwork>
708   <x:ref>Content-Length</x:ref>           ; &header-content-length;
709   <x:ref>Content-MD5</x:ref>              ; <xref target="header.content-md5"/>
710   <x:ref>Content-Range</x:ref>            ; &header-content-range;
711</artwork></figure>
712</section>
713
714<section title="Payload Body" anchor="payload.body">
715  <x:anchor-alias value="payload-body"/>
716<t>
717   A payload body is only present in a message when a message-body is
718   present, as described in &message-body;. The payload body is obtained
719   from the message-body by decoding any Transfer-Encoding that might
720   have been applied to ensure safe and proper transfer of the message.
721</t>
722</section>
723</section>
724
725<section title="Representation" anchor="representation">
726<iref item="representation"/>
727<t>
728   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
729   communicated from one party to another.  A resource representation
730   is information that reflects the state of that resource, as observed
731   at some point in the past (e.g., in a response to GET) or to be
732   desired at some point in the future (e.g., in a PUT request).
733</t>
734<t>
735   Most, but not all, representations transferred via HTTP are intended
736   to be a representation of the target resource (the resource identified
737   by the effective request URI).  The precise semantics of a representation
738   are determined by the type of message (request or response), the request
739   method, the response status code, and the representation metadata.
740   For example, the above semantic is true for the representation in any
741   200 (OK) response to GET and for the representation in any PUT request.
742   A 200 response to PUT, in contrast, contains either a representation
743   that describes the successful action or a representation of the target
744   resource, with the latter indicated by a Content-Location header field
745   with the same value as the effective request URI.  Likewise, response
746   messages with an error status code usually contain a representation that
747   describes the error and what next steps are suggested for resolving it.
748</t>
749
750<section title="Representation Header Fields" anchor="representation.header.fields">
751  <x:anchor-alias value="representation-header"/>
752<t>
753   Representation header fields define metadata about the representation data
754   enclosed in the message-body or, if no message-body is present, about
755   the representation that would have been transferred in a 200 response
756   to a simultaneous GET request with the same effective request URI.
757</t>
758<t>
759   The following header fields are defined as representation metadata:
760</t>
761<figure><artwork>
762   <x:ref>Content-Encoding</x:ref>         ; <xref target="header.content-encoding"/>
763   <x:ref>Content-Language</x:ref>         ; <xref target="header.content-language"/>
764   <x:ref>Content-Location</x:ref>         ; <xref target="header.content-location"/>
765   <x:ref>Content-Type</x:ref>             ; <xref target="header.content-type"/>
766   <x:ref>Expires</x:ref>                  ; &header-expires;
767   <x:ref>Last-Modified</x:ref>            ; &header-last-modified;
768</artwork></figure>
769</section>
770
771<section title="Representation Data" anchor="representation.data">
772  <x:anchor-alias value="representation-data"/>
773<t>
774   The representation body associated with an HTTP message is
775   either provided as the payload body of the message or
776   referred to by the message semantics and the effective request
777   URI.  The representation data is in a format and encoding defined by
778   the representation metadata header fields.
779</t>
780<t>
781   The data type of the representation data
782   is determined via the header fields Content-Type and Content-Encoding.
783   These define a two-layer, ordered encoding model:
784</t>
785<figure><artwork type="example">
786  representation-data := Content-Encoding( Content-Type( bits ) )
787</artwork></figure>
788<t>
789   Content-Type specifies the media type of the underlying data, which
790   defines both the data format and how that data &SHOULD; be processed
791   by the recipient (within the scope of the request method semantics).
792   Any HTTP/1.1 message containing a payload body &SHOULD; include a
793   Content-Type header field defining the media type of the associated
794   representation unless that metadata is unknown to the sender.
795   If the Content-Type header field is not present, it indicates that
796   the sender does not know the media type of the representation;
797   recipients &MAY; either assume that the media type is
798   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
799   or examine the content to determine its type.
800</t>
801<t>
802   In practice, resource owners do not always properly configure their origin
803   server to provide the correct Content-Type for a given representation,
804   with the result that some clients will examine a response body's content
805   and override the specified type.
806   Clients that do so risk drawing incorrect conclusions, which might expose
807   additional security risks (e.g., "privilege escalation").  Furthermore,
808   it is impossible to determine the sender's intent by examining the data
809   format: many data formats match multiple media types that differ only in
810   processing semantics.  Implementers are encouraged to provide a means of
811   disabling such "content sniffing" when it is used.
812</t>
813<t>
814   Content-Encoding is used to indicate any additional content
815   codings applied to the data, usually for the purpose of data
816   compression, that are a property of the representation.  If
817   Content-Encoding is not present, then there is no additional
818   encoding beyond that defined by the Content-Type.
819</t>
820</section>
821</section>
822
823<section title="Content Negotiation" anchor="content.negotiation">
824<t>
825   HTTP responses include a representation which contains information for
826   interpretation, whether by a human user or for further processing.
827   Often, the server has different ways of representing the
828   same information; for example, in different formats, languages,
829   or using different character encodings.
830</t>
831<t>
832   HTTP clients and their users might have different or variable
833   capabilities, characteristics or preferences which would influence
834   which representation, among those available from the server,
835   would be best for the server to deliver. For this reason, HTTP
836   provides mechanisms for "content negotiation" -- a process of
837   allowing selection of a representation of a given resource,
838   when more than one is available.
839</t>
840<t>
841   This specification defines two patterns of content negotiation;
842   "server-driven", where the server selects the representation based
843   upon the client's stated preferences, and "agent-driven" negotiation,
844   where the server provides a list of representations for the client to
845   choose from, based upon their metadata. In addition,  there are
846   other patterns: some applications use an "active content" pattern,
847   where the server returns active content which runs on the client
848   and, based on client available parameters, selects additional
849   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
850   has also been proposed.
851</t>
852<t>
853   These patterns are all widely used, and have trade-offs in applicability
854   and practicality. In particular, when the number of preferences or
855   capabilities to be expressed by a client are large (such as when many
856   different formats are supported by a user-agent), server-driven
857   negotiation becomes unwieldy, and might not be appropriate. Conversely,
858   when the number of representations to choose from is very large,
859   agent-driven negotiation might not be appropriate.
860</t>
861<t>
862   Note that in all cases, the supplier of representations has the
863   responsibility for determining which representations might be
864   considered to be the "same information".
865</t>
866
867<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
868<t>
869   If the selection of the best representation for a response is made by
870   an algorithm located at the server, it is called server-driven
871   negotiation. Selection is based on the available representations of
872   the response (the dimensions over which it can vary; e.g., language,
873   content-coding, etc.) and the contents of particular header fields in
874   the request message or on other information pertaining to the request
875   (such as the network address of the client).
876</t>
877<t>
878   Server-driven negotiation is advantageous when the algorithm for
879   selecting from among the available representations is difficult to
880   describe to the user agent, or when the server desires to send its
881   "best guess" to the client along with the first response (hoping to
882   avoid the round-trip delay of a subsequent request if the "best
883   guess" is good enough for the user). In order to improve the server's
884   guess, the user agent &MAY; include request header fields (Accept,
885   Accept-Language, Accept-Encoding, etc.) which describe its
886   preferences for such a response.
887</t>
888<t>
889   Server-driven negotiation has disadvantages:
890  <list style="numbers">
891    <t>
892         It is impossible for the server to accurately determine what
893         might be "best" for any given user, since that would require
894         complete knowledge of both the capabilities of the user agent
895         and the intended use for the response (e.g., does the user want
896         to view it on screen or print it on paper?).
897    </t>
898    <t>
899         Having the user agent describe its capabilities in every
900         request can be both very inefficient (given that only a small
901         percentage of responses have multiple representations) and a
902         potential violation of the user's privacy.
903    </t>
904    <t>
905         It complicates the implementation of an origin server and the
906         algorithms for generating responses to a request.
907    </t>
908    <t>
909         It might limit a public cache's ability to use the same response
910         for multiple user's requests.
911    </t>
912  </list>
913</t>
914<t>
915   HTTP/1.1 includes the following request-header fields for enabling
916   server-driven negotiation through description of user agent
917   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
918   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
919   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
920   However, an origin server is not limited to these dimensions and &MAY; vary
921   the response based on any aspect of the request, including information
922   outside the request-header fields or within extension header fields
923   not defined by this specification.
924</t>
925<x:note>
926  <t>
927    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
928    because new clients might not be recognized.
929  </t>
930</x:note>
931<t>
932   The Vary header field (&header-vary;) can be used to express the parameters the
933   server uses to select a representation that is subject to server-driven
934   negotiation.
935</t>
936</section>
937
938<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
939<t>
940   With agent-driven negotiation, selection of the best representation
941   for a response is performed by the user agent after receiving an
942   initial response from the origin server. Selection is based on a list
943   of the available representations of the response included within the
944   header fields or body of the initial response, with each
945   representation identified by its own URI. Selection from among the
946   representations can be performed automatically (if the user agent is
947   capable of doing so) or manually by the user selecting from a
948   generated (possibly hypertext) menu.
949</t>
950<t>
951   Agent-driven negotiation is advantageous when the response would vary
952   over commonly-used dimensions (such as type, language, or encoding),
953   when the origin server is unable to determine a user agent's
954   capabilities from examining the request, and generally when public
955   caches are used to distribute server load and reduce network usage.
956</t>
957<t>
958   Agent-driven negotiation suffers from the disadvantage of needing a
959   second request to obtain the best alternate representation. This
960   second request is only efficient when caching is used. In addition,
961   this specification does not define any mechanism for supporting
962   automatic selection, though it also does not prevent any such
963   mechanism from being developed as an extension and used within
964   HTTP/1.1.
965</t>
966<t>
967   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
968   status codes for enabling agent-driven negotiation when the server is
969   unwilling or unable to provide a varying response using server-driven
970   negotiation.
971</t>
972</section>
973</section>
974
975<section title="Header Field Definitions" anchor="header.fields">
976<t>
977   This section defines the syntax and semantics of HTTP/1.1 header fields
978   related to the payload of messages.
979</t>
980
981<section title="Accept" anchor="header.accept">
982  <iref primary="true" item="Accept header" x:for-anchor=""/>
983  <iref primary="true" item="Headers" subitem="Accept" x:for-anchor=""/>
984  <x:anchor-alias value="Accept"/>
985  <x:anchor-alias value="Accept-v"/>
986  <x:anchor-alias value="accept-ext"/>
987  <x:anchor-alias value="accept-params"/>
988  <x:anchor-alias value="media-range"/>
989<t>
990   The "Accept" request-header field can be used by user agents to specify
991   response media types that are acceptable. Accept headers can be used to
992   indicate that the request is specifically limited to a small set of desired
993   types, as in the case of a request for an in-line image.
994</t>
995<figure><artwork type="abnf2616"><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"/>
996  <x:ref>Accept</x:ref>   = "Accept" ":" <x:ref>OWS</x:ref> <x:ref>Accept-v</x:ref>
997  <x:ref>Accept-v</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
998 
999  <x:ref>media-range</x:ref>    = ( "*/*"
1000                   / ( <x:ref>type</x:ref> "/" "*" )
1001                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
1002                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
1003  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
1004  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref>
1005                   [ "=" <x:ref>word</x:ref> ]
1006</artwork></figure>
1007<t>
1008   The asterisk "*" character is used to group media types into ranges,
1009   with "*/*" indicating all media types and "type/*" indicating all
1010   subtypes of that type. The media-range &MAY; include media type
1011   parameters that are applicable to that range.
1012</t>
1013<t>
1014   Each media-range &MAY; be followed by one or more accept-params,
1015   beginning with the "q" parameter for indicating a relative quality
1016   factor. The first "q" parameter (if any) separates the media-range
1017   parameter(s) from the accept-params. Quality factors allow the user
1018   or user agent to indicate the relative degree of preference for that
1019   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
1020   default value is q=1.
1021</t>
1022<x:note>
1023  <t>
1024    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
1025    parameters from Accept extension parameters is due to historical
1026    practice. Although this prevents any media type parameter named
1027    "q" from being used with a media range, such an event is believed
1028    to be unlikely given the lack of any "q" parameters in the IANA
1029    media type registry and the rare usage of any media type
1030    parameters in Accept. Future media types are discouraged from
1031    registering any parameter named "q".
1032  </t>
1033</x:note>
1034<t>
1035   The example
1036</t>
1037<figure><artwork type="example">
1038  Accept: audio/*; q=0.2, audio/basic
1039</artwork></figure>
1040<t>
1041   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
1042   type if it is the best available after an 80% mark-down in quality".
1043</t>
1044<t>
1045   If no Accept header field is present, then it is assumed that the
1046   client accepts all media types. If an Accept header field is present,
1047   and if the server cannot send a response which is acceptable
1048   according to the combined Accept field value, then the server &SHOULD;
1049   send a 406 (Not Acceptable) response.
1050</t>
1051<t>
1052   A more elaborate example is
1053</t>
1054<figure><artwork type="example">
1055  Accept: text/plain; q=0.5, text/html,
1056          text/x-dvi; q=0.8, text/x-c
1057</artwork></figure>
1058<t>
1059   Verbally, this would be interpreted as "text/html and text/x-c are
1060   the preferred media types, but if they do not exist, then send the
1061   text/x-dvi representation, and if that does not exist, send the text/plain
1062   representation".
1063</t>
1064<t>
1065   Media ranges can be overridden by more specific media ranges or
1066   specific media types. If more than one media range applies to a given
1067   type, the most specific reference has precedence. For example,
1068</t>
1069<figure><artwork type="example">
1070  Accept: text/*, text/html, text/html;level=1, */*
1071</artwork></figure>
1072<t>
1073   have the following precedence:
1074   <list style="numbers">
1075    <t>text/html;level=1</t>
1076    <t>text/html</t>
1077    <t>text/*</t>
1078    <t>*/*</t>
1079   </list>
1080</t>
1081<t>
1082   The media type quality factor associated with a given type is
1083   determined by finding the media range with the highest precedence
1084   which matches that type. For example,
1085</t>
1086<figure><artwork type="example">
1087  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1088          text/html;level=2;q=0.4, */*;q=0.5
1089</artwork></figure>
1090<t>
1091   would cause the following values to be associated:
1092</t>
1093<texttable align="left">
1094  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1095  <c>text/html;level=1</c>    <c>1</c>
1096  <c>text/html</c>            <c>0.7</c>
1097  <c>text/plain</c>           <c>0.3</c>
1098  <c>image/jpeg</c>           <c>0.5</c>
1099  <c>text/html;level=2</c>    <c>0.4</c>
1100  <c>text/html;level=3</c>    <c>0.7</c>
1101</texttable>
1102<t>
1103      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1104      values for certain media ranges. However, unless the user agent is
1105      a closed system which cannot interact with other rendering agents,
1106      this default set ought to be configurable by the user.
1107</t>
1108</section>
1109
1110<section title="Accept-Charset" anchor="header.accept-charset">
1111  <iref primary="true" item="Accept-Charset header" x:for-anchor=""/>
1112  <iref primary="true" item="Headers" subitem="Accept-Charset" x:for-anchor=""/>
1113  <x:anchor-alias value="Accept-Charset"/>
1114  <x:anchor-alias value="Accept-Charset-v"/>
1115<t>
1116   The "Accept-Charset" request-header field can be used by user agents to
1117   indicate what response character sets are acceptable. This field allows
1118   clients capable of understanding more comprehensive or special-purpose
1119   character sets to signal that capability to a server which is capable of
1120   representing documents in those character sets.
1121</t>
1122<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/>
1123  <x:ref>Accept-Charset</x:ref>   = "Accept-Charset" ":" <x:ref>OWS</x:ref>
1124          <x:ref>Accept-Charset-v</x:ref>
1125  <x:ref>Accept-Charset-v</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1126                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1127</artwork></figure>
1128<t>
1129   Character set values are described in <xref target="character.sets"/>. Each charset &MAY;
1130   be given an associated quality value which represents the user's
1131   preference for that charset. The default value is q=1. An example is
1132</t>
1133<figure><artwork type="example">
1134  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1135</artwork></figure>
1136<t>
1137   The special value "*", if present in the Accept-Charset field,
1138   matches every character set (including ISO-8859-1) which is not
1139   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1140   in an Accept-Charset field, then all character sets not explicitly
1141   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1142   a quality value of 1 if not explicitly mentioned.
1143</t>
1144<t>
1145   If no Accept-Charset header is present, the default is that any
1146   character set is acceptable. If an Accept-Charset header is present,
1147   and if the server cannot send a response which is acceptable
1148   according to the Accept-Charset header, then the server &SHOULD; send
1149   an error response with the 406 (Not Acceptable) status code, though
1150   the sending of an unacceptable response is also allowed.
1151</t>
1152</section>
1153
1154<section title="Accept-Encoding" anchor="header.accept-encoding">
1155  <iref primary="true" item="Accept-Encoding header" x:for-anchor=""/>
1156  <iref primary="true" item="Headers" subitem="Accept-Encoding" x:for-anchor=""/>
1157  <x:anchor-alias value="Accept-Encoding"/>
1158  <x:anchor-alias value="Accept-Encoding-v"/>
1159  <x:anchor-alias value="codings"/>
1160<t>
1161   The "Accept-Encoding" request-header field can be used by user agents to
1162   indicate what response content-codings (<xref target="content.codings"/>)
1163   are acceptable in the response.
1164</t>
1165<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="Accept-Encoding-v"/><iref primary="true" item="Grammar" subitem="codings"/>
1166  <x:ref>Accept-Encoding</x:ref>    = "Accept-Encoding" ":" <x:ref>OWS</x:ref>
1167                     <x:ref>Accept-Encoding-v</x:ref>
1168  <x:ref>Accept-Encoding-v</x:ref>  =
1169                     #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1170  <x:ref>codings</x:ref>            = ( <x:ref>content-coding</x:ref> / "*" )
1171</artwork></figure>
1172<t>
1173   Each codings value &MAY; be given an associated quality value which
1174   represents the preference for that encoding. The default value is q=1.
1175</t>
1176<t>
1177   Examples of its use are:
1178</t>
1179<figure><artwork type="example">
1180  Accept-Encoding: compress, gzip
1181  Accept-Encoding:
1182  Accept-Encoding: *
1183  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1184  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1185</artwork></figure>
1186<t>
1187   A server tests whether a content-coding is acceptable, according to
1188   an Accept-Encoding field, using these rules:
1189  <list style="numbers">
1190      <t>If the content-coding is one of the content-codings listed in
1191         the Accept-Encoding field, then it is acceptable, unless it is
1192         accompanied by a qvalue of 0. (As defined in &qvalue;, a
1193         qvalue of 0 means "not acceptable".)</t>
1194
1195      <t>The special "*" symbol in an Accept-Encoding field matches any
1196         available content-coding not explicitly listed in the header
1197         field.</t>
1198
1199      <t>If multiple content-codings are acceptable, then the acceptable
1200         content-coding with the highest non-zero qvalue is preferred.</t>
1201
1202      <t>The "identity" content-coding is always acceptable, unless
1203         specifically refused because the Accept-Encoding field includes
1204         "identity;q=0", or because the field includes "*;q=0" and does
1205         not explicitly include the "identity" content-coding. If the
1206         Accept-Encoding field-value is empty, then only the "identity"
1207         encoding is acceptable.</t>
1208  </list>
1209</t>
1210<t>
1211   If an Accept-Encoding field is present in a request, and if the
1212   server cannot send a response which is acceptable according to the
1213   Accept-Encoding header, then the server &SHOULD; send an error response
1214   with the 406 (Not Acceptable) status code.
1215</t>
1216<t>
1217   If no Accept-Encoding field is present in a request, the server &MAY;
1218   assume that the client will accept any content coding. In this case,
1219   if "identity" is one of the available content-codings, then the
1220   server &SHOULD; use the "identity" content-coding, unless it has
1221   additional information that a different content-coding is meaningful
1222   to the client.
1223</t>
1224<x:note>
1225  <t>
1226    <x:h>Note:</x:h> If the request does not include an Accept-Encoding field,
1227    and if the "identity" content-coding is unavailable, then
1228    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1229    "gzip" and "compress") are preferred; some older clients
1230    improperly display messages sent with other content-codings.  The
1231    server might also make this decision based on information about
1232    the particular user-agent or client.
1233  </t>
1234</x:note>
1235<x:note>
1236  <t>
1237    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1238    associated with content-codings. This means that qvalues will not
1239    work and are not permitted with x-gzip or x-compress.
1240  </t>
1241</x:note>
1242</section>
1243
1244<section title="Accept-Language" anchor="header.accept-language">
1245  <iref primary="true" item="Accept-Language header" x:for-anchor=""/>
1246  <iref primary="true" item="Headers" subitem="Accept-Language" x:for-anchor=""/>
1247  <x:anchor-alias value="Accept-Language"/>
1248  <x:anchor-alias value="Accept-Language-v"/>
1249  <x:anchor-alias value="language-range"/>
1250<t>
1251   The "Accept-Language" request-header field can be used by user agents to
1252   indicate the set of natural languages that are preferred in the response.
1253   Language tags are defined in <xref target="language.tags"/>.
1254</t>
1255<figure><artwork type="abnf2616"><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"/>
1256  <x:ref>Accept-Language</x:ref>   = "Accept-Language" ":" <x:ref>OWS</x:ref>
1257                    <x:ref>Accept-Language-v</x:ref>
1258  <x:ref>Accept-Language-v</x:ref> =
1259                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1260  <x:ref>language-range</x:ref>    =
1261            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
1262</artwork></figure>
1263<t>
1264   Each language-range can be given an associated quality value which
1265   represents an estimate of the user's preference for the languages
1266   specified by that range. The quality value defaults to "q=1". For
1267   example,
1268</t>
1269<figure><artwork type="example">
1270  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1271</artwork></figure>
1272<t>
1273   would mean: "I prefer Danish, but will accept British English and
1274   other types of English".
1275   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
1276</t>
1277<t>
1278   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1279   several matching schemes. Implementations can offer the most appropriate
1280   matching scheme for their requirements.
1281</t>
1282<x:note>
1283  <t>
1284    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
1285    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1286    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
1287  </t>
1288</x:note>
1289<t>
1290   It might be contrary to the privacy expectations of the user to send
1291   an Accept-Language header with the complete linguistic preferences of
1292   the user in every request. For a discussion of this issue, see
1293   <xref target="privacy.issues.connected.to.accept.headers"/>.
1294</t>
1295<t>
1296   As intelligibility is highly dependent on the individual user, it is
1297   recommended that client applications make the choice of linguistic
1298   preference available to the user. If the choice is not made
1299   available, then the Accept-Language header field &MUST-NOT; be given in
1300   the request.
1301</t>
1302<x:note>
1303  <t>
1304    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1305    the user, we remind implementors of  the fact that users are not
1306    familiar with the details of language matching as described above,
1307    and should provide appropriate guidance. As an example, users
1308    might assume that on selecting "en-gb", they will be served any
1309    kind of English document if British English is not available. A
1310    user agent might suggest in such a case to add "en" to get the
1311    best matching behavior.
1312  </t>
1313</x:note>
1314</section>
1315
1316<section title="Content-Encoding" anchor="header.content-encoding">
1317  <iref primary="true" item="Content-Encoding header" x:for-anchor=""/>
1318  <iref primary="true" item="Headers" subitem="Content-Encoding" x:for-anchor=""/>
1319  <x:anchor-alias value="Content-Encoding"/>
1320  <x:anchor-alias value="Content-Encoding-v"/>
1321<t>
1322   The "Content-Encoding" header field indicates what content-codings
1323   have been applied to the representation, and thus what decoding mechanisms
1324   must be applied in order to obtain the media-type referenced by the
1325   Content-Type header field. Content-Encoding is primarily used to allow a
1326   representation to be compressed without losing the identity of its underlying
1327   media type.
1328</t>
1329<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/>
1330  <x:ref>Content-Encoding</x:ref>   = "Content-Encoding" ":" <x:ref>OWS</x:ref> <x:ref>Content-Encoding-v</x:ref>
1331  <x:ref>Content-Encoding-v</x:ref> = 1#<x:ref>content-coding</x:ref>
1332</artwork></figure>
1333<t>
1334   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1335</t>
1336<figure><artwork type="example">
1337  Content-Encoding: gzip
1338</artwork></figure>
1339<t>
1340   The content-coding is a characteristic of the representation.
1341   Typically, the representation body is stored with this
1342   encoding and is only decoded before rendering or analogous usage.
1343   However, a non-transparent proxy &MAY; modify the content-coding if the
1344   new coding is known to be acceptable to the recipient, unless the
1345   "no-transform" cache-control directive is present in the message.
1346</t>
1347<t>
1348   If the content-coding of a representation is not "identity", then the
1349   representation metadata &MUST; include a Content-Encoding header
1350   field (<xref target="header.content-encoding"/>)
1351   that lists the non-identity content-coding(s) used.
1352</t>
1353<t>
1354   If the content-coding of a representation in a request message is not
1355   acceptable to the origin server, the server &SHOULD; respond with a
1356   status code of 415 (Unsupported Media Type).
1357</t>
1358<t>
1359   If multiple encodings have been applied to a representation, the content
1360   codings &MUST; be listed in the order in which they were applied.
1361   Additional information about the encoding parameters &MAY; be provided
1362   by other header fields not defined by this specification.
1363</t>
1364</section>
1365
1366<section title="Content-Language" anchor="header.content-language">
1367  <iref primary="true" item="Content-Language header" x:for-anchor=""/>
1368  <iref primary="true" item="Headers" subitem="Content-Language" x:for-anchor=""/>
1369  <x:anchor-alias value="Content-Language"/>
1370  <x:anchor-alias value="Content-Language-v"/>
1371<t>
1372   The "Content-Language" header field describes the natural
1373   language(s) of the intended audience for the representation. Note that this might
1374   not be equivalent to all the languages used within the representation.
1375</t>
1376<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/>
1377  <x:ref>Content-Language</x:ref>   = "Content-Language" ":" <x:ref>OWS</x:ref> <x:ref>Content-Language-v</x:ref>
1378  <x:ref>Content-Language-v</x:ref> = 1#<x:ref>language-tag</x:ref>
1379</artwork></figure>
1380<t>
1381   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1382   Content-Language is to allow a user to identify and differentiate
1383   representations according to the user's own preferred language. Thus, if the
1384   body content is intended only for a Danish-literate audience, the
1385   appropriate field is
1386</t>
1387<figure><artwork type="example">
1388  Content-Language: da
1389</artwork></figure>
1390<t>
1391   If no Content-Language is specified, the default is that the content
1392   is intended for all language audiences. This might mean that the
1393   sender does not consider it to be specific to any natural language,
1394   or that the sender does not know for which language it is intended.
1395</t>
1396<t>
1397   Multiple languages &MAY; be listed for content that is intended for
1398   multiple audiences. For example, a rendition of the "Treaty of
1399   Waitangi", presented simultaneously in the original Maori and English
1400   versions, would call for
1401</t>
1402<figure><artwork type="example">
1403  Content-Language: mi, en
1404</artwork></figure>
1405<t>
1406   However, just because multiple languages are present within a representation
1407   does not mean that it is intended for multiple linguistic audiences.
1408   An example would be a beginner's language primer, such as "A First
1409   Lesson in Latin", which is clearly intended to be used by an
1410   English-literate audience. In this case, the Content-Language would
1411   properly only include "en".
1412</t>
1413<t>
1414   Content-Language &MAY; be applied to any media type -- it is not
1415   limited to textual documents.
1416</t>
1417</section>
1418
1419<section title="Content-Location" anchor="header.content-location">
1420  <iref primary="true" item="Content-Location header" x:for-anchor=""/>
1421  <iref primary="true" item="Headers" subitem="Content-Location" x:for-anchor=""/>
1422  <x:anchor-alias value="Content-Location"/>
1423  <x:anchor-alias value="Content-Location-v"/>
1424<t>
1425   The "Content-Location" header field supplies a URI that can be used
1426   as a specific identifier for the representation in this message.
1427   In other words, if one were to perform a GET on this URI at the time
1428   of this message's generation, then a 200 response would contain the
1429   same representation that is enclosed as payload in this message.
1430</t>
1431<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/>
1432  <x:ref>Content-Location</x:ref>   = "Content-Location" ":" <x:ref>OWS</x:ref>
1433                    <x:ref>Content-Location-v</x:ref>
1434  <x:ref>Content-Location-v</x:ref> =
1435                    <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
1436</artwork></figure>
1437<t>
1438   The Content-Location value is not a replacement for the Effective
1439   Request URI (&effective-request-uri;).  It is representation metadata.
1440   It has the same syntax and semantics as the header field of the same name
1441   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
1442   However, its appearance in an HTTP message has some special implications
1443   for HTTP recipients.
1444</t>
1445<t>
1446   If Content-Location is included in a response message and its value
1447   is the same as the effective request URI, then the response payload
1448   &SHOULD; be considered the current representation of that resource.
1449   For a GET or HEAD request, this is the same as the default semantics
1450   when no Content-Location is provided by the server.  For a state-changing
1451   method like PUT or POST, it implies that the server's response contains
1452   the new representation of that resource, thereby distinguishing it from
1453   representations that might only report about the action (e.g., "It worked!").
1454   This allows authoring applications to update their local copies without
1455   the need for a subsequent GET request.
1456</t>
1457<t>
1458   If Content-Location is included in a response message and its value
1459   differs from the effective request URI, then the origin server is
1460   informing recipients that this representation has its own, presumably
1461   more specific, identifier.  For a GET or HEAD request, this is an
1462   indication that the effective request URI identifies a resource that
1463   is subject to content negotiation and the representation selected for
1464   this response can also be found at the identified URI.  For other
1465   methods, such a Content-Location indicates that this representation
1466   contains a report on the action's status and the same report is
1467   available (for future access with GET) at the given URI.  For
1468   example, a purchase transaction made via the POST method might
1469   include a receipt document as the payload of the 200 response;
1470   the Content-Location value provides an identifier for retrieving
1471   a copy of that same receipt in the future.
1472</t>
1473<t>
1474   If Content-Location is included in a request message, then it &MAY;
1475   be interpreted by the origin server as an indication of where the
1476   user agent originally obtained the content of the enclosed
1477   representation (prior to any subsequent modification of the content
1478   by that user agent).  In other words, the user agent is providing
1479   the same representation metadata that it received with the original
1480   representation.  However, such interpretation &MUST-NOT; be used to
1481   alter the semantics of the method requested by the client.  For
1482   example, if a client makes a PUT request on a negotiated resource
1483   and the origin server accepts that PUT (without redirection), then the
1484   new set of values for that resource is expected to be consistent with
1485   the one representation supplied in that PUT; the Content-Location
1486   cannot be used as a form of reverse content selection that
1487   identifies only one of the negotiated representations to be updated.
1488   If the user agent had wanted the latter semantics, it would have applied
1489   the PUT directly to the Content-Location URI.
1490</t>
1491<t>
1492   A Content-Location field received in a request message is transitory
1493   information that &SHOULD-NOT; be saved with other representation
1494   metadata for use in later responses.  The Content-Location's value
1495   might be saved for use in other contexts, such as within source links
1496   or other metadata.
1497</t>
1498<t>
1499   A cache cannot assume that a representation with a Content-Location
1500   different from the URI used to retrieve it can be used to respond to
1501   later requests on that Content-Location URI.
1502</t>
1503<t>
1504   If the Content-Location value is a partial URI, the partial URI is
1505   interpreted relative to the effective request URI.
1506</t>
1507</section>
1508
1509<section title="Content-MD5" anchor="header.content-md5">
1510  <iref primary="true" item="Content-MD5 header" x:for-anchor=""/>
1511  <iref primary="true" item="Headers" subitem="Content-MD5" x:for-anchor=""/>
1512  <x:anchor-alias value="Content-MD5"/>
1513  <x:anchor-alias value="Content-MD5-v"/>
1514<t>
1515   The "Content-MD5" header field, as defined in <xref target="RFC1864"/>, is
1516   an MD5 digest of the payload body that provides an end-to-end message
1517   integrity check (MIC) of the payload body (the message-body after any
1518   transfer-coding is decoded). Note that a MIC is good for
1519   detecting accidental modification of the payload body in transit, but is not
1520   proof against malicious attacks.
1521</t>
1522<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/>
1523  <x:ref>Content-MD5</x:ref>   = "Content-MD5" ":" <x:ref>OWS</x:ref> <x:ref>Content-MD5-v</x:ref>
1524  <x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per <xref target="RFC1864"/>&gt;
1525</artwork></figure>
1526<t>
1527   The Content-MD5 header field &MAY; be generated by an origin server or
1528   client to function as an integrity check of the payload body. Only
1529   origin servers or user agents &MAY; generate the Content-MD5 header field;
1530   proxies and gateways &MUST-NOT; generate it, as this would defeat its
1531   value as an end-to-end integrity check. Any recipient &MAY; check that
1532   the digest value in this header field matches a corresponding digest
1533   calculated on payload body as received.
1534</t>
1535<t>
1536   The MD5 digest is computed based on the content of the payload body,
1537   including any content-coding, but not including any transfer-coding
1538   applied to the message-body because such transfer-codings might be
1539   applied or removed anywhere along the request/response chain.
1540   If the message is received with a transfer-coding, that encoding &MUST;
1541   be decoded prior to checking the Content-MD5 value against the received
1542   payload.
1543</t>
1544<t>
1545   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1546   composite media-types (e.g., multipart/* and message/rfc822), but
1547   this does not change how the digest is computed as defined in the
1548   preceding paragraph.
1549</t>
1550<t>
1551   There are several consequences of this. The payload for composite
1552   types &MAY; contain many body-parts, each with its own MIME and HTTP
1553   headers (including Content-MD5, Content-Transfer-Encoding, and
1554   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1555   or Content-Encoding header, it is assumed that the content
1556   of the body-part has had the encoding applied, and the body-part is
1557   included in the Content-MD5 digest as is -- i.e., after the
1558   application. The Transfer-Encoding header field is not allowed within
1559   body-parts.
1560</t>
1561<t>
1562   Conversion of all line breaks to CRLF &MUST-NOT; be done before
1563   computing or checking the digest: the line break convention used in
1564   the text actually transmitted &MUST; be left unaltered when computing
1565   the digest.
1566</t>
1567<x:note>
1568  <t>
1569    <x:h>Note:</x:h> While the definition of Content-MD5 is exactly the same for
1570    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1571    in which the application of Content-MD5 to HTTP entity-bodies
1572    differs from its application to MIME entity-bodies. One is that
1573    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1574    does use Transfer-Encoding and Content-Encoding. Another is that
1575    HTTP more frequently uses binary content types than MIME, so it is
1576    worth noting that, in such cases, the byte order used to compute
1577    the digest is the transmission byte order defined for the type.
1578    Lastly, HTTP allows transmission of text types with any of several
1579    line break conventions and not just the canonical form using CRLF.
1580  </t>
1581</x:note>
1582</section>
1583
1584<section title="Content-Type" anchor="header.content-type">
1585  <iref primary="true" item="Content-Type header" x:for-anchor=""/>
1586  <iref primary="true" item="Headers" subitem="Content-Type" x:for-anchor=""/>
1587  <x:anchor-alias value="Content-Type"/>
1588  <x:anchor-alias value="Content-Type-v"/>
1589<t>
1590   The "Content-Type" header field indicates the media type of the
1591   representation. In the case of responses to the HEAD method, the media type is
1592   that which would have been sent had the request been a GET.
1593</t>
1594<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/>
1595  <x:ref>Content-Type</x:ref>   = "Content-Type" ":" <x:ref>OWS</x:ref> <x:ref>Content-Type-v</x:ref>
1596  <x:ref>Content-Type-v</x:ref> = <x:ref>media-type</x:ref>
1597</artwork></figure>
1598<t>
1599   Media types are defined in <xref target="media.types"/>. An example of the field is
1600</t>
1601<figure><artwork type="example">
1602  Content-Type: text/html; charset=ISO-8859-4
1603</artwork></figure>
1604<t>
1605   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1606</t>
1607</section>
1608
1609</section>
1610
1611<section title="IANA Considerations" anchor="IANA.considerations">
1612<section title="Header Field Registration" anchor="header.field.registration">
1613<t>
1614   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
1615   with the permanent registrations below (see <xref target="RFC3864"/>):
1616</t>
1617<?BEGININC p3-payload.iana-headers ?>
1618<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1619<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1620   <ttcol>Header Field Name</ttcol>
1621   <ttcol>Protocol</ttcol>
1622   <ttcol>Status</ttcol>
1623   <ttcol>Reference</ttcol>
1624
1625   <c>Accept</c>
1626   <c>http</c>
1627   <c>standard</c>
1628   <c>
1629      <xref target="header.accept"/>
1630   </c>
1631   <c>Accept-Charset</c>
1632   <c>http</c>
1633   <c>standard</c>
1634   <c>
1635      <xref target="header.accept-charset"/>
1636   </c>
1637   <c>Accept-Encoding</c>
1638   <c>http</c>
1639   <c>standard</c>
1640   <c>
1641      <xref target="header.accept-encoding"/>
1642   </c>
1643   <c>Accept-Language</c>
1644   <c>http</c>
1645   <c>standard</c>
1646   <c>
1647      <xref target="header.accept-language"/>
1648   </c>
1649   <c>Content-Disposition</c>
1650   <c>http</c>
1651   <c>standard</c>
1652   <c>
1653      <xref target="content-disposition"/>
1654   </c>
1655   <c>Content-Encoding</c>
1656   <c>http</c>
1657   <c>standard</c>
1658   <c>
1659      <xref target="header.content-encoding"/>
1660   </c>
1661   <c>Content-Language</c>
1662   <c>http</c>
1663   <c>standard</c>
1664   <c>
1665      <xref target="header.content-language"/>
1666   </c>
1667   <c>Content-Location</c>
1668   <c>http</c>
1669   <c>standard</c>
1670   <c>
1671      <xref target="header.content-location"/>
1672   </c>
1673   <c>Content-MD5</c>
1674   <c>http</c>
1675   <c>standard</c>
1676   <c>
1677      <xref target="header.content-md5"/>
1678   </c>
1679   <c>Content-Type</c>
1680   <c>http</c>
1681   <c>standard</c>
1682   <c>
1683      <xref target="header.content-type"/>
1684   </c>
1685   <c>MIME-Version</c>
1686   <c>http</c>
1687   <c>standard</c>
1688   <c>
1689      <xref target="mime-version"/>
1690   </c>
1691</texttable>
1692<!--(END)-->
1693<?ENDINC p3-payload.iana-headers ?>
1694<t>
1695   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1696</t>
1697</section>
1698
1699<section title="Content Coding Registry" anchor="content.coding.registration">
1700<t>
1701   The registration procedure for HTTP Content Codings is now defined
1702   by <xref target="content.coding.registry"/> of this document.
1703</t>
1704<t>
1705   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1706   should be updated with the registration below:
1707</t>
1708<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1709   <ttcol>Name</ttcol>
1710   <ttcol>Description</ttcol>
1711   <ttcol>Reference</ttcol>
1712   <c>compress</c>
1713   <c>UNIX "compress" program method</c>
1714   <c>
1715      &compress-coding;
1716   </c>
1717   <c>deflate</c>
1718   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1719   the "zlib" data format (<xref target="RFC1950"/>)
1720   </c>
1721   <c>
1722      &deflate-coding;
1723   </c>
1724   <c>gzip</c>
1725   <c>Same as GNU zip <xref target="RFC1952"/></c>
1726   <c>
1727      &gzip-coding;
1728   </c>
1729   <c>identity</c>
1730   <c>No transformation</c>
1731   <c>
1732      <xref target="content.codings"/>
1733   </c>
1734</texttable>
1735</section>
1736
1737</section>
1738
1739<section title="Security Considerations" anchor="security.considerations">
1740<t>
1741   This section is meant to inform application developers, information
1742   providers, and users of the security limitations in HTTP/1.1 as
1743   described by this document. The discussion does not include
1744   definitive solutions to the problems revealed, though it does make
1745   some suggestions for reducing security risks.
1746</t>
1747
1748<section title="Privacy Issues Connected to Accept Headers" anchor="privacy.issues.connected.to.accept.headers">
1749<t>
1750   Accept request-headers can reveal information about the user to all
1751   servers which are accessed. The Accept-Language header in particular
1752   can reveal information the user would consider to be of a private
1753   nature, because the understanding of particular languages is often
1754   strongly correlated to the membership of a particular ethnic group.
1755   User agents which offer the option to configure the contents of an
1756   Accept-Language header to be sent in every request are strongly
1757   encouraged to let the configuration process include a message which
1758   makes the user aware of the loss of privacy involved.
1759</t>
1760<t>
1761   An approach that limits the loss of privacy would be for a user agent
1762   to omit the sending of Accept-Language headers by default, and to ask
1763   the user whether or not to start sending Accept-Language headers to a
1764   server if it detects, by looking for any Vary response-header fields
1765   generated by the server, that such sending could improve the quality
1766   of service.
1767</t>
1768<t>
1769   Elaborate user-customized accept header fields sent in every request,
1770   in particular if these include quality values, can be used by servers
1771   as relatively reliable and long-lived user identifiers. Such user
1772   identifiers would allow content providers to do click-trail tracking,
1773   and would allow collaborating content providers to match cross-server
1774   click-trails or form submissions of individual users. Note that for
1775   many users not behind a proxy, the network address of the host
1776   running the user agent will also serve as a long-lived user
1777   identifier. In environments where proxies are used to enhance
1778   privacy, user agents ought to be conservative in offering accept
1779   header configuration options to end users. As an extreme privacy
1780   measure, proxies could filter the accept headers in relayed requests.
1781   General purpose user agents which provide a high degree of header
1782   configurability &SHOULD; warn users about the loss of privacy which can
1783   be involved.
1784</t>
1785</section>
1786
1787<section title="Content-Disposition Issues" anchor="content-disposition.issues">
1788<t>
1789   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
1790   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1791   serious security considerations. Content-Disposition is not part of
1792   the HTTP standard, but since it is widely implemented, we are
1793   documenting its use and risks for implementors. See <xref target="RFC2183" x:fmt="of" x:sec="5"/>
1794   for details.
1795</t>
1796</section>
1797
1798</section>
1799
1800<section title="Acknowledgments" anchor="ack">
1801</section>
1802</middle>
1803<back>
1804
1805<references title="Normative References">
1806
1807<reference anchor="ISO-8859-1">
1808  <front>
1809    <title>
1810     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1811    </title>
1812    <author>
1813      <organization>International Organization for Standardization</organization>
1814    </author>
1815    <date year="1998"/>
1816  </front>
1817  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1818</reference>
1819
1820<reference anchor="Part1">
1821  <front>
1822    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1823    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1824      <organization abbrev="Day Software">Day Software</organization>
1825      <address><email>fielding@gbiv.com</email></address>
1826    </author>
1827    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1828      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1829      <address><email>jg@freedesktop.org</email></address>
1830    </author>
1831    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1832      <organization abbrev="HP">Hewlett-Packard Company</organization>
1833      <address><email>JeffMogul@acm.org</email></address>
1834    </author>
1835    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1836      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1837      <address><email>henrikn@microsoft.com</email></address>
1838    </author>
1839    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1840      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1841      <address><email>LMM@acm.org</email></address>
1842    </author>
1843    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1844      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1845      <address><email>paulle@microsoft.com</email></address>
1846    </author>
1847    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1848      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1849      <address><email>timbl@w3.org</email></address>
1850    </author>
1851    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1852      <organization abbrev="W3C">World Wide Web Consortium</organization>
1853      <address><email>ylafon@w3.org</email></address>
1854    </author>
1855    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1856      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1857      <address><email>julian.reschke@greenbytes.de</email></address>
1858    </author>
1859    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1860  </front>
1861  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1862  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1863</reference>
1864
1865<reference anchor="Part2">
1866  <front>
1867    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1868    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1869      <organization abbrev="Day Software">Day Software</organization>
1870      <address><email>fielding@gbiv.com</email></address>
1871    </author>
1872    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1873      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1874      <address><email>jg@freedesktop.org</email></address>
1875    </author>
1876    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1877      <organization abbrev="HP">Hewlett-Packard Company</organization>
1878      <address><email>JeffMogul@acm.org</email></address>
1879    </author>
1880    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1881      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1882      <address><email>henrikn@microsoft.com</email></address>
1883    </author>
1884    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1885      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1886      <address><email>LMM@acm.org</email></address>
1887    </author>
1888    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1889      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1890      <address><email>paulle@microsoft.com</email></address>
1891    </author>
1892    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1893      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1894      <address><email>timbl@w3.org</email></address>
1895    </author>
1896    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1897      <organization abbrev="W3C">World Wide Web Consortium</organization>
1898      <address><email>ylafon@w3.org</email></address>
1899    </author>
1900    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1901      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1902      <address><email>julian.reschke@greenbytes.de</email></address>
1903    </author>
1904    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1905  </front>
1906  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1907  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1908</reference>
1909
1910<reference anchor="Part4">
1911  <front>
1912    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1913    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1914      <organization abbrev="Day Software">Day Software</organization>
1915      <address><email>fielding@gbiv.com</email></address>
1916    </author>
1917    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1918      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1919      <address><email>jg@freedesktop.org</email></address>
1920    </author>
1921    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1922      <organization abbrev="HP">Hewlett-Packard Company</organization>
1923      <address><email>JeffMogul@acm.org</email></address>
1924    </author>
1925    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1926      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1927      <address><email>henrikn@microsoft.com</email></address>
1928    </author>
1929    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1930      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1931      <address><email>LMM@acm.org</email></address>
1932    </author>
1933    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1934      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1935      <address><email>paulle@microsoft.com</email></address>
1936    </author>
1937    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1938      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1939      <address><email>timbl@w3.org</email></address>
1940    </author>
1941    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1942      <organization abbrev="W3C">World Wide Web Consortium</organization>
1943      <address><email>ylafon@w3.org</email></address>
1944    </author>
1945    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1946      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1947      <address><email>julian.reschke@greenbytes.de</email></address>
1948    </author>
1949    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1950  </front>
1951  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1952  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1953</reference>
1954
1955<reference anchor="Part5">
1956  <front>
1957    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1958    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1959      <organization abbrev="Day Software">Day Software</organization>
1960      <address><email>fielding@gbiv.com</email></address>
1961    </author>
1962    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1963      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1964      <address><email>jg@freedesktop.org</email></address>
1965    </author>
1966    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1967      <organization abbrev="HP">Hewlett-Packard Company</organization>
1968      <address><email>JeffMogul@acm.org</email></address>
1969    </author>
1970    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1971      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1972      <address><email>henrikn@microsoft.com</email></address>
1973    </author>
1974    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1975      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1976      <address><email>LMM@acm.org</email></address>
1977    </author>
1978    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1979      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1980      <address><email>paulle@microsoft.com</email></address>
1981    </author>
1982    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1983      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1984      <address><email>timbl@w3.org</email></address>
1985    </author>
1986    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1987      <organization abbrev="W3C">World Wide Web Consortium</organization>
1988      <address><email>ylafon@w3.org</email></address>
1989    </author>
1990    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1991      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1992      <address><email>julian.reschke@greenbytes.de</email></address>
1993    </author>
1994    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1995  </front>
1996  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1997  <x:source href="p5-range.xml" basename="p5-range"/>
1998</reference>
1999
2000<reference anchor="Part6">
2001  <front>
2002    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2003    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2004      <organization abbrev="Day Software">Day Software</organization>
2005      <address><email>fielding@gbiv.com</email></address>
2006    </author>
2007    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2008      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2009      <address><email>jg@freedesktop.org</email></address>
2010    </author>
2011    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2012      <organization abbrev="HP">Hewlett-Packard Company</organization>
2013      <address><email>JeffMogul@acm.org</email></address>
2014    </author>
2015    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2016      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2017      <address><email>henrikn@microsoft.com</email></address>
2018    </author>
2019    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2020      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2021      <address><email>LMM@acm.org</email></address>
2022    </author>
2023    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2024      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2025      <address><email>paulle@microsoft.com</email></address>
2026    </author>
2027    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2028      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2029      <address><email>timbl@w3.org</email></address>
2030    </author>
2031    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2032      <organization abbrev="W3C">World Wide Web Consortium</organization>
2033      <address><email>ylafon@w3.org</email></address>
2034    </author>
2035    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2036      <address><email>mnot@mnot.net</email></address>
2037    </author>
2038    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2039      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2040      <address><email>julian.reschke@greenbytes.de</email></address>
2041    </author>
2042    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2043  </front>
2044  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2045  <x:source href="p6-cache.xml" basename="p6-cache"/>
2046</reference>
2047
2048<reference anchor="RFC1864">
2049  <front>
2050    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
2051    <author initials="J." surname="Myers" fullname="John G. Myers">
2052      <organization>Carnegie Mellon University</organization>
2053      <address><email>jgm+@cmu.edu</email></address>
2054    </author>
2055    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2056      <organization>Dover Beach Consulting, Inc.</organization>
2057      <address><email>mrose@dbc.mtview.ca.us</email></address>
2058    </author>
2059    <date month="October" year="1995"/>
2060  </front>
2061  <seriesInfo name="RFC" value="1864"/>
2062</reference>
2063
2064<reference anchor="RFC1950">
2065  <front>
2066    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2067    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2068      <organization>Aladdin Enterprises</organization>
2069      <address><email>ghost@aladdin.com</email></address>
2070    </author>
2071    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2072    <date month="May" year="1996"/>
2073  </front>
2074  <seriesInfo name="RFC" value="1950"/>
2075  <annotation>
2076    RFC 1950 is an Informational RFC, thus it might be less stable than
2077    this specification. On the other hand, this downward reference was
2078    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2079    therefore it is unlikely to cause problems in practice. See also
2080    <xref target="BCP97"/>.
2081  </annotation>
2082</reference>
2083
2084<reference anchor="RFC1951">
2085  <front>
2086    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2087    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2088      <organization>Aladdin Enterprises</organization>
2089      <address><email>ghost@aladdin.com</email></address>
2090    </author>
2091    <date month="May" year="1996"/>
2092  </front>
2093  <seriesInfo name="RFC" value="1951"/>
2094  <annotation>
2095    RFC 1951 is an Informational RFC, thus it might be less stable than
2096    this specification. On the other hand, this downward reference was
2097    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2098    therefore it is unlikely to cause problems in practice. See also
2099    <xref target="BCP97"/>.
2100  </annotation>
2101</reference>
2102
2103<reference anchor="RFC1952">
2104  <front>
2105    <title>GZIP file format specification version 4.3</title>
2106    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2107      <organization>Aladdin Enterprises</organization>
2108      <address><email>ghost@aladdin.com</email></address>
2109    </author>
2110    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2111      <address><email>gzip@prep.ai.mit.edu</email></address>
2112    </author>
2113    <author initials="M." surname="Adler" fullname="Mark Adler">
2114      <address><email>madler@alumni.caltech.edu</email></address>
2115    </author>
2116    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2117      <address><email>ghost@aladdin.com</email></address>
2118    </author>
2119    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2120      <address><email>randeg@alumni.rpi.edu</email></address>
2121    </author>
2122    <date month="May" year="1996"/>
2123  </front>
2124  <seriesInfo name="RFC" value="1952"/>
2125  <annotation>
2126    RFC 1952 is an Informational RFC, thus it might be less stable than
2127    this specification. On the other hand, this downward reference was
2128    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2129    therefore it is unlikely to cause problems in practice. See also
2130    <xref target="BCP97"/>.
2131  </annotation>
2132</reference>
2133
2134<reference anchor="RFC2045">
2135  <front>
2136    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2137    <author initials="N." surname="Freed" fullname="Ned Freed">
2138      <organization>Innosoft International, Inc.</organization>
2139      <address><email>ned@innosoft.com</email></address>
2140    </author>
2141    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2142      <organization>First Virtual Holdings</organization>
2143      <address><email>nsb@nsb.fv.com</email></address>
2144    </author>
2145    <date month="November" year="1996"/>
2146  </front>
2147  <seriesInfo name="RFC" value="2045"/>
2148</reference>
2149
2150<reference anchor="RFC2046">
2151  <front>
2152    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2153    <author initials="N." surname="Freed" fullname="Ned Freed">
2154      <organization>Innosoft International, Inc.</organization>
2155      <address><email>ned@innosoft.com</email></address>
2156    </author>
2157    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2158      <organization>First Virtual Holdings</organization>
2159      <address><email>nsb@nsb.fv.com</email></address>
2160    </author>
2161    <date month="November" year="1996"/>
2162  </front>
2163  <seriesInfo name="RFC" value="2046"/>
2164</reference>
2165
2166<reference anchor="RFC2119">
2167  <front>
2168    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2169    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2170      <organization>Harvard University</organization>
2171      <address><email>sob@harvard.edu</email></address>
2172    </author>
2173    <date month="March" year="1997"/>
2174  </front>
2175  <seriesInfo name="BCP" value="14"/>
2176  <seriesInfo name="RFC" value="2119"/>
2177</reference>
2178
2179<reference anchor='RFC4647'>
2180  <front>
2181    <title>Matching of Language Tags</title>
2182    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
2183      <organization>Yahoo! Inc.</organization>
2184      <address><email>addison@inter-locale.com</email></address>
2185    </author>
2186    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
2187      <organization>Google</organization>
2188      <address><email>mark.davis@macchiato.com</email></address>
2189    </author>
2190    <date year='2006' month='September' />
2191  </front>
2192  <seriesInfo name='BCP' value='47' />
2193  <seriesInfo name='RFC' value='4647' />
2194</reference>
2195
2196<reference anchor="RFC5234">
2197  <front>
2198    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2199    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2200      <organization>Brandenburg InternetWorking</organization>
2201      <address>
2202        <email>dcrocker@bbiw.net</email>
2203      </address> 
2204    </author>
2205    <author initials="P." surname="Overell" fullname="Paul Overell">
2206      <organization>THUS plc.</organization>
2207      <address>
2208        <email>paul.overell@thus.net</email>
2209      </address>
2210    </author>
2211    <date month="January" year="2008"/>
2212  </front>
2213  <seriesInfo name="STD" value="68"/>
2214  <seriesInfo name="RFC" value="5234"/>
2215</reference>
2216
2217<reference anchor='RFC5646'>
2218  <front>
2219    <title>Tags for Identifying Languages</title>
2220    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2221      <organization>Lab126</organization>
2222      <address><email>addison@inter-locale.com</email></address>
2223    </author>
2224    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2225      <organization>Google</organization>
2226      <address><email>mark.davis@google.com</email></address>
2227    </author>
2228    <date month='September' year='2009' />
2229  </front>
2230  <seriesInfo name='BCP' value='47' />
2231  <seriesInfo name='RFC' value='5646' />
2232</reference>
2233
2234</references>
2235
2236<references title="Informative References">
2237
2238<reference anchor="RFC1945">
2239  <front>
2240    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2241    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2242      <organization>MIT, Laboratory for Computer Science</organization>
2243      <address><email>timbl@w3.org</email></address>
2244    </author>
2245    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2246      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2247      <address><email>fielding@ics.uci.edu</email></address>
2248    </author>
2249    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2250      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2251      <address><email>frystyk@w3.org</email></address>
2252    </author>
2253    <date month="May" year="1996"/>
2254  </front>
2255  <seriesInfo name="RFC" value="1945"/>
2256</reference>
2257
2258<reference anchor="RFC2049">
2259  <front>
2260    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2261    <author initials="N." surname="Freed" fullname="Ned Freed">
2262      <organization>Innosoft International, Inc.</organization>
2263      <address><email>ned@innosoft.com</email></address>
2264    </author>
2265    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2266      <organization>First Virtual Holdings</organization>
2267      <address><email>nsb@nsb.fv.com</email></address>
2268    </author>
2269    <date month="November" year="1996"/>
2270  </front>
2271  <seriesInfo name="RFC" value="2049"/>
2272</reference>
2273
2274<reference anchor="RFC2068">
2275  <front>
2276    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2277    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2278      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2279      <address><email>fielding@ics.uci.edu</email></address>
2280    </author>
2281    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2282      <organization>MIT Laboratory for Computer Science</organization>
2283      <address><email>jg@w3.org</email></address>
2284    </author>
2285    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2286      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2287      <address><email>mogul@wrl.dec.com</email></address>
2288    </author>
2289    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2290      <organization>MIT Laboratory for Computer Science</organization>
2291      <address><email>frystyk@w3.org</email></address>
2292    </author>
2293    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2294      <organization>MIT Laboratory for Computer Science</organization>
2295      <address><email>timbl@w3.org</email></address>
2296    </author>
2297    <date month="January" year="1997"/>
2298  </front>
2299  <seriesInfo name="RFC" value="2068"/>
2300</reference>
2301
2302<reference anchor="RFC2076">
2303  <front>
2304    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2305    <author initials="J." surname="Palme" fullname="Jacob Palme">
2306      <organization>Stockholm University/KTH</organization>
2307      <address><email>jpalme@dsv.su.se</email></address>
2308    </author>
2309    <date month="February" year="1997"/>
2310  </front>
2311  <seriesInfo name="RFC" value="2076"/>
2312</reference>
2313
2314<reference anchor="RFC2183">
2315  <front>
2316    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2317    <author initials="R." surname="Troost" fullname="Rens Troost">
2318      <organization>New Century Systems</organization>
2319      <address><email>rens@century.com</email></address>
2320    </author>
2321    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2322      <organization>QUALCOMM Incorporated</organization>
2323      <address><email>sdorner@qualcomm.com</email></address>
2324    </author>
2325    <author initials="K." surname="Moore" fullname="Keith Moore">
2326      <organization>Department of Computer Science</organization>
2327      <address><email>moore@cs.utk.edu</email></address>
2328    </author>
2329    <date month="August" year="1997"/>
2330  </front>
2331  <seriesInfo name="RFC" value="2183"/>
2332</reference>
2333
2334<reference anchor="RFC2277">
2335  <front>
2336    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2337    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2338      <organization>UNINETT</organization>
2339      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2340    </author>
2341    <date month="January" year="1998"/>
2342  </front>
2343  <seriesInfo name="BCP" value="18"/>
2344  <seriesInfo name="RFC" value="2277"/>
2345</reference>
2346
2347<reference anchor='RFC2295'>
2348  <front>
2349    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2350    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2351      <organization>Technische Universiteit Eindhoven</organization>
2352      <address>
2353        <email>koen@win.tue.nl</email>
2354      </address>
2355    </author>
2356    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2357      <organization>Hewlett-Packard Company</organization>
2358      <address>
2359        <email>mutz@hpl.hp.com</email>
2360      </address>
2361    </author>
2362    <date year='1998' month='March'/>
2363  </front>
2364  <seriesInfo name='RFC' value='2295'/>
2365</reference>
2366
2367<reference anchor="RFC2388">
2368  <front>
2369    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2370    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2371      <organization>Xerox Palo Alto Research Center</organization>
2372      <address><email>masinter@parc.xerox.com</email></address>
2373    </author>
2374    <date year="1998" month="August"/>
2375  </front>
2376  <seriesInfo name="RFC" value="2388"/>
2377</reference>
2378
2379<reference anchor="RFC2557">
2380  <front>
2381    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2382    <author initials="F." surname="Palme" fullname="Jacob Palme">
2383      <organization>Stockholm University and KTH</organization>
2384      <address><email>jpalme@dsv.su.se</email></address>
2385    </author>
2386    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2387      <organization>Microsoft Corporation</organization>
2388      <address><email>alexhop@microsoft.com</email></address>
2389    </author>
2390    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2391      <organization>Lotus Development Corporation</organization>
2392      <address><email>Shelness@lotus.com</email></address>
2393    </author>
2394    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2395      <address><email>stef@nma.com</email></address>
2396    </author>
2397    <date year="1999" month="March"/>
2398  </front>
2399  <seriesInfo name="RFC" value="2557"/>
2400</reference>
2401
2402<reference anchor="RFC2616">
2403  <front>
2404    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2405    <author initials="R." surname="Fielding" fullname="R. Fielding">
2406      <organization>University of California, Irvine</organization>
2407      <address><email>fielding@ics.uci.edu</email></address>
2408    </author>
2409    <author initials="J." surname="Gettys" fullname="J. Gettys">
2410      <organization>W3C</organization>
2411      <address><email>jg@w3.org</email></address>
2412    </author>
2413    <author initials="J." surname="Mogul" fullname="J. Mogul">
2414      <organization>Compaq Computer Corporation</organization>
2415      <address><email>mogul@wrl.dec.com</email></address>
2416    </author>
2417    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2418      <organization>MIT Laboratory for Computer Science</organization>
2419      <address><email>frystyk@w3.org</email></address>
2420    </author>
2421    <author initials="L." surname="Masinter" fullname="L. Masinter">
2422      <organization>Xerox Corporation</organization>
2423      <address><email>masinter@parc.xerox.com</email></address>
2424    </author>
2425    <author initials="P." surname="Leach" fullname="P. Leach">
2426      <organization>Microsoft Corporation</organization>
2427      <address><email>paulle@microsoft.com</email></address>
2428    </author>
2429    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2430      <organization>W3C</organization>
2431      <address><email>timbl@w3.org</email></address>
2432    </author>
2433    <date month="June" year="1999"/>
2434  </front>
2435  <seriesInfo name="RFC" value="2616"/>
2436</reference>
2437
2438<reference anchor="RFC3629">
2439  <front>
2440    <title>UTF-8, a transformation format of ISO 10646</title>
2441    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2442      <organization>Alis Technologies</organization>
2443      <address><email>fyergeau@alis.com</email></address>
2444    </author>
2445    <date month="November" year="2003"/>
2446  </front>
2447  <seriesInfo name="RFC" value="3629"/>
2448  <seriesInfo name="STD" value="63"/>
2449</reference>
2450
2451<reference anchor='RFC3864'>
2452  <front>
2453    <title>Registration Procedures for Message Header Fields</title>
2454    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2455      <organization>Nine by Nine</organization>
2456      <address><email>GK-IETF@ninebynine.org</email></address>
2457    </author>
2458    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2459      <organization>BEA Systems</organization>
2460      <address><email>mnot@pobox.com</email></address>
2461    </author>
2462    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2463      <organization>HP Labs</organization>
2464      <address><email>JeffMogul@acm.org</email></address>
2465    </author>
2466    <date year='2004' month='September' />
2467  </front>
2468  <seriesInfo name='BCP' value='90' />
2469  <seriesInfo name='RFC' value='3864' />
2470</reference>
2471
2472<reference anchor="RFC4288">
2473  <front>
2474    <title>Media Type Specifications and Registration Procedures</title>
2475    <author initials="N." surname="Freed" fullname="N. Freed">
2476      <organization>Sun Microsystems</organization>
2477      <address>
2478        <email>ned.freed@mrochek.com</email>
2479      </address>
2480    </author>
2481    <author initials="J." surname="Klensin" fullname="J. Klensin">
2482      <address>
2483        <email>klensin+ietf@jck.com</email>
2484      </address>
2485    </author>
2486    <date year="2005" month="December"/>
2487  </front>
2488  <seriesInfo name="BCP" value="13"/>
2489  <seriesInfo name="RFC" value="4288"/>
2490</reference>
2491
2492<reference anchor='RFC5226'>
2493  <front>
2494    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2495    <author initials='T.' surname='Narten' fullname='T. Narten'>
2496      <organization>IBM</organization>
2497      <address><email>narten@us.ibm.com</email></address>
2498    </author>
2499    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2500      <organization>Google</organization>
2501      <address><email>Harald@Alvestrand.no</email></address>
2502    </author>
2503    <date year='2008' month='May' />
2504  </front>
2505  <seriesInfo name='BCP' value='26' />
2506  <seriesInfo name='RFC' value='5226' />
2507</reference>
2508
2509<reference anchor="RFC5322">
2510  <front>
2511    <title>Internet Message Format</title>
2512    <author initials="P." surname="Resnick" fullname="P. Resnick">
2513      <organization>Qualcomm Incorporated</organization>
2514    </author>
2515    <date year="2008" month="October"/>
2516  </front> 
2517  <seriesInfo name="RFC" value="5322"/>
2518</reference>
2519
2520<reference anchor='BCP97'>
2521  <front>
2522    <title>Handling Normative References to Standards-Track Documents</title>
2523    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2524      <address>
2525        <email>klensin+ietf@jck.com</email>
2526      </address>
2527    </author>
2528    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2529      <organization>MIT</organization>
2530      <address>
2531        <email>hartmans-ietf@mit.edu</email>
2532      </address>
2533    </author>
2534    <date year='2007' month='June' />
2535  </front>
2536  <seriesInfo name='BCP' value='97' />
2537  <seriesInfo name='RFC' value='4897' />
2538</reference>
2539
2540
2541</references>
2542
2543<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2544<t>
2545   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
2546   allow a message-body to be transmitted in an open variety of
2547   representations and with extensible mechanisms. However, RFC 2045
2548   discusses mail, and HTTP has a few features that are different from
2549   those described in MIME. These differences were carefully chosen
2550   to optimize performance over binary connections, to allow greater
2551   freedom in the use of new media types, to make date comparisons
2552   easier, and to acknowledge the practice of some early HTTP servers
2553   and clients.
2554</t>
2555<t>
2556   This appendix describes specific areas where HTTP differs from MIME.
2557   Proxies and gateways to strict MIME environments &SHOULD; be
2558   aware of these differences and provide the appropriate conversions
2559   where necessary. Proxies and gateways from MIME environments to HTTP
2560   also need to be aware of the differences because some conversions
2561   might be required.
2562</t>
2563
2564<section title="MIME-Version" anchor="mime-version">
2565  <iref primary="true" item="MIME-Version header" x:for-anchor=""/>
2566  <iref primary="true" item="Headers" subitem="MIME-Version" x:for-anchor=""/>
2567  <x:anchor-alias value="MIME-Version"/>
2568  <x:anchor-alias value="MIME-Version-v"/>
2569<t>
2570   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2571   include a single MIME-Version general-header field to indicate what
2572   version of the MIME protocol was used to construct the message. Use
2573   of the MIME-Version header field indicates that the message is in
2574   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2575   Proxies/gateways are responsible for ensuring full compliance (where
2576   possible) when exporting HTTP messages to strict MIME environments.
2577</t>
2578<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/>
2579  <x:ref>MIME-Version</x:ref>   = "MIME-Version" ":" <x:ref>OWS</x:ref> <x:ref>MIME-Version-v</x:ref>
2580  <x:ref>MIME-Version-v</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2581</artwork></figure>
2582<t>
2583   MIME version "1.0" is the default for use in HTTP/1.1. However,
2584   HTTP/1.1 message parsing and semantics are defined by this document
2585   and not the MIME specification.
2586</t>
2587</section>
2588
2589<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2590<t>
2591   MIME requires that an Internet mail body-part be converted to
2592   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
2593   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2594   allowed for subtypes of the "text" media type when transmitted over
2595   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2596   line breaks as CRLF and forbids the use of CR or LF outside of line
2597   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2598   line break within text content when a message is transmitted over
2599   HTTP.
2600</t>
2601<t>
2602   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2603   environment &SHOULD; translate all line breaks within the text media
2604   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2605   canonical form of CRLF. Note, however, that this might be complicated
2606   by the presence of a Content-Encoding and by the fact that HTTP
2607   allows the use of some character sets which do not use octets 13 and
2608   10 to represent CR and LF, as is the case for some multi-byte
2609   character sets.
2610</t>
2611<t>
2612   Implementors should note that conversion will break any cryptographic
2613   checksums applied to the original content unless the original content
2614   is already in canonical form. Therefore, the canonical form is
2615   recommended for any content that uses such checksums in HTTP.
2616</t>
2617</section>
2618
2619
2620<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2621<t>
2622   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2623   simplify the process of date comparison. Proxies and gateways from
2624   other protocols &SHOULD; ensure that any Date header field present in a
2625   message conforms to one of the HTTP/1.1 formats and rewrite the date
2626   if necessary.
2627</t>
2628</section>
2629
2630<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2631<t>
2632   MIME does not include any concept equivalent to HTTP/1.1's
2633   Content-Encoding header field. Since this acts as a modifier on the
2634   media type, proxies and gateways from HTTP to MIME-compliant
2635   protocols &MUST; either change the value of the Content-Type header
2636   field or decode the representation before forwarding the message. (Some
2637   experimental applications of Content-Type for Internet mail have used
2638   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2639   a function equivalent to Content-Encoding. However, this parameter is
2640   not part of the MIME standards).
2641</t>
2642</section>
2643
2644<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2645<t>
2646   HTTP does not use the Content-Transfer-Encoding field of MIME.
2647   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
2648   remove any Content-Transfer-Encoding
2649   prior to delivering the response message to an HTTP client.
2650</t>
2651<t>
2652   Proxies and gateways from HTTP to MIME-compliant protocols are
2653   responsible for ensuring that the message is in the correct format
2654   and encoding for safe transport on that protocol, where "safe
2655   transport" is defined by the limitations of the protocol being used.
2656   Such a proxy or gateway &SHOULD; label the data with an appropriate
2657   Content-Transfer-Encoding if doing so will improve the likelihood of
2658   safe transport over the destination protocol.
2659</t>
2660</section>
2661
2662<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2663<t>
2664   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
2665   Proxies/gateways &MUST; remove any transfer-coding prior to
2666   forwarding a message via a MIME-compliant protocol.
2667</t>
2668</section>
2669
2670<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2671<t>
2672   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2673   need to be aware of MIME line length limitations. Since HTTP does not
2674   have this limitation, HTTP does not fold long lines. MHTML messages
2675   being transported by HTTP follow all conventions of MHTML, including
2676   line length limitations and folding, canonicalization, etc., since
2677   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2678   does not interpret the content or any MIME header lines that might be
2679   contained therein.
2680</t>
2681</section>
2682</section>
2683
2684<section title="Additional Features" anchor="additional.features">
2685<t>
2686   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2687   existing HTTP implementations, but not consistently and correctly
2688   across most HTTP/1.1 applications. Implementors are advised to be
2689   aware of these features, but cannot rely upon their presence in, or
2690   interoperability with, other HTTP/1.1 applications. Some of these
2691   describe proposed experimental features, and some describe features
2692   that experimental deployment found lacking that are now addressed in
2693   the base HTTP/1.1 specification.
2694</t>
2695<t>
2696   A number of other headers, such as Content-Disposition and Title,
2697   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2698</t>
2699
2700<section title="Content-Disposition" anchor="content-disposition">
2701<iref item="Headers" subitem="Content-Disposition" primary="true" x:for-anchor=""/>
2702<iref item="Content-Disposition header" primary="true" x:for-anchor=""/>
2703  <x:anchor-alias value="content-disposition"/>
2704  <x:anchor-alias value="content-disposition-v"/>
2705  <x:anchor-alias value="disposition-type"/>
2706  <x:anchor-alias value="disposition-parm"/>
2707  <x:anchor-alias value="disp-extension-parm"/>
2708  <x:anchor-alias value="disp-extension-token"/>
2709  <x:anchor-alias value="filename-parm"/>
2710<t>
2711   The "Content-Disposition" response-header field has been proposed as a
2712   means for the origin server to suggest a default filename if the user
2713   requests that the content is saved to a file. This usage is derived
2714   from the definition of Content-Disposition in <xref target="RFC2183"/>.
2715</t>
2716<figure><artwork type="abnf2616"><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"/>
2717  <x:ref>content-disposition</x:ref> = "Content-Disposition" ":" <x:ref>OWS</x:ref>
2718                        <x:ref>content-disposition-v</x:ref>
2719  <x:ref>content-disposition-v</x:ref> = <x:ref>disposition-type</x:ref>
2720                          *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>disposition-parm</x:ref> )
2721  <x:ref>disposition-type</x:ref> = "attachment" / <x:ref>disp-extension-token</x:ref>
2722  <x:ref>disposition-parm</x:ref> = <x:ref>filename-parm</x:ref> / <x:ref>disp-extension-parm</x:ref>
2723  <x:ref>filename-parm</x:ref> = "filename" "=" <x:ref>quoted-string</x:ref>
2724  <x:ref>disp-extension-token</x:ref> = <x:ref>token</x:ref>
2725  <x:ref>disp-extension-parm</x:ref> = <x:ref>token</x:ref> "=" <x:ref>word</x:ref>
2726</artwork></figure>
2727<t>
2728   An example is
2729</t>
2730<figure><artwork type="example">
2731  Content-Disposition: attachment; filename="fname.ext"
2732</artwork></figure>
2733<t>
2734   The receiving user agent &SHOULD-NOT;  respect any directory path
2735   information present in the filename-parm parameter, which is the only
2736   parameter believed to apply to HTTP implementations at this time. The
2737   filename &SHOULD; be treated as a terminal component only.
2738</t>
2739<t>
2740   If this header is used in a response with the application/octet-stream
2741   content-type, the implied suggestion is that the user agent
2742   should not display the response, but directly enter a "save response
2743   as..." dialog.
2744</t>
2745<t>
2746   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
2747</t>
2748</section>
2749</section>
2750
2751<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2752<t>
2753  Clarify contexts that charset is used in.
2754  (<xref target="character.sets"/>)
2755</t>
2756<t>
2757  Remove base URI setting semantics for Content-Location due to poor
2758  implementation support, which was caused by too many broken servers emitting
2759  bogus Content-Location headers, and also the potentially undesirable effect
2760  of potentially breaking relative links in content-negotiated resources.
2761  (<xref target="header.content-location"/>)
2762</t>
2763<t>
2764  Remove reference to non-existant identity transfer-coding value tokens.
2765  (<xref target="no.content-transfer-encoding"/>)
2766</t>
2767</section>
2768
2769<?BEGININC p3-payload.abnf-appendix ?>
2770<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
2771<figure>
2772<artwork type="abnf" name="p3-payload.parsed-abnf">
2773<x:ref>Accept</x:ref> = "Accept:" OWS Accept-v
2774<x:ref>Accept-Charset</x:ref> = "Accept-Charset:" OWS Accept-Charset-v
2775<x:ref>Accept-Charset-v</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2776 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2777 qvalue ] ] )
2778<x:ref>Accept-Encoding</x:ref> = "Accept-Encoding:" OWS Accept-Encoding-v
2779<x:ref>Accept-Encoding-v</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2780 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2781<x:ref>Accept-Language</x:ref> = "Accept-Language:" OWS Accept-Language-v
2782<x:ref>Accept-Language-v</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
2783 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2784 ] )
2785<x:ref>Accept-v</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2786 OWS media-range [ accept-params ] ] ) ]
2787
2788<x:ref>Content-Encoding</x:ref> = "Content-Encoding:" OWS Content-Encoding-v
2789<x:ref>Content-Encoding-v</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
2790 content-coding ] )
2791<x:ref>Content-Language</x:ref> = "Content-Language:" OWS Content-Language-v
2792<x:ref>Content-Language-v</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
2793 language-tag ] )
2794<x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in [Part1], Section 9.2&gt;
2795<x:ref>Content-Location</x:ref> = "Content-Location:" OWS Content-Location-v
2796<x:ref>Content-Location-v</x:ref> = absolute-URI / partial-URI
2797<x:ref>Content-MD5</x:ref> = "Content-MD5:" OWS Content-MD5-v
2798<x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per [RFC1864]&gt;
2799<x:ref>Content-Range</x:ref> = &lt;Content-Range, defined in [Part5], Section 5.2&gt;
2800<x:ref>Content-Type</x:ref> = "Content-Type:" OWS Content-Type-v
2801<x:ref>Content-Type-v</x:ref> = media-type
2802
2803<x:ref>Expires</x:ref> = &lt;Expires, defined in [Part6], Section 3.3&gt;
2804
2805<x:ref>Last-Modified</x:ref> = &lt;Last-Modified, defined in [Part4], Section 6.6&gt;
2806
2807<x:ref>MIME-Version</x:ref> = "MIME-Version:" OWS MIME-Version-v
2808<x:ref>MIME-Version-v</x:ref> = 1*DIGIT "." 1*DIGIT
2809
2810<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
2811
2812<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
2813<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
2814<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2815<x:ref>attribute</x:ref> = token
2816
2817<x:ref>charset</x:ref> = token
2818<x:ref>codings</x:ref> = ( content-coding / "*" )
2819<x:ref>content-coding</x:ref> = token
2820<x:ref>content-disposition</x:ref> = "Content-Disposition:" OWS
2821 content-disposition-v
2822<x:ref>content-disposition-v</x:ref> = disposition-type *( OWS ";" OWS
2823 disposition-parm )
2824
2825<x:ref>disp-extension-parm</x:ref> = token "=" word
2826<x:ref>disp-extension-token</x:ref> = token
2827<x:ref>disposition-parm</x:ref> = filename-parm / disp-extension-parm
2828<x:ref>disposition-type</x:ref> = "attachment" / disp-extension-token
2829
2830<x:ref>filename-parm</x:ref> = "filename=" quoted-string
2831
2832<x:ref>header-field</x:ref> = &lt;header-field, defined in [Part1], Section 3.2&gt;
2833
2834<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
2835<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2836
2837<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2838 ";" OWS parameter )
2839<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2840
2841<x:ref>parameter</x:ref> = attribute "=" value
2842<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
2843
2844<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
2845<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2846
2847<x:ref>subtype</x:ref> = token
2848
2849<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
2850<x:ref>type</x:ref> = token
2851
2852<x:ref>value</x:ref> = word
2853
2854<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 1.2.2&gt;
2855</artwork>
2856</figure>
2857<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2858; Accept defined but not used
2859; Accept-Charset defined but not used
2860; Accept-Encoding defined but not used
2861; Accept-Language defined but not used
2862; MIME-Version defined but not used
2863; content-disposition defined but not used
2864</artwork></figure></section>
2865<?ENDINC p3-payload.abnf-appendix ?>
2866
2867<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2868
2869<section title="Since RFC2616">
2870<t>
2871  Extracted relevant partitions from <xref target="RFC2616"/>.
2872</t>
2873</section>
2874
2875<section title="Since draft-ietf-httpbis-p3-payload-00">
2876<t>
2877  Closed issues:
2878  <list style="symbols"> 
2879    <t>
2880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2881      "Media Type Registrations"
2882      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2883    </t>
2884    <t>
2885      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2886      "Clarification regarding quoting of charset values"
2887      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2888    </t>
2889    <t>
2890      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2891      "Remove 'identity' token references"
2892      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2893    </t>
2894    <t>
2895      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2896      "Accept-Encoding BNF"
2897    </t>
2898    <t>
2899      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2900      "Normative and Informative references"
2901    </t>
2902    <t>
2903      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2904      "RFC1700 references"
2905    </t>
2906    <t>
2907      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2908      "Updating to RFC4288"
2909    </t>
2910    <t>
2911      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2912      "Informative references"
2913    </t>
2914    <t>
2915      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2916      "ISO-8859-1 Reference"
2917    </t>
2918    <t>
2919      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2920      "Encoding References Normative"
2921    </t>
2922    <t>
2923      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2924      "Normative up-to-date references"
2925    </t>
2926  </list>
2927</t>
2928</section>
2929
2930<section title="Since draft-ietf-httpbis-p3-payload-01">
2931<t>
2932  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2933  <list style="symbols"> 
2934    <t>
2935      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2936    </t>
2937  </list>
2938</t>
2939</section>
2940
2941<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2942<t>
2943  Closed issues:
2944  <list style="symbols"> 
2945    <t>
2946      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2947      "Quoting Charsets"
2948    </t>
2949    <t>
2950      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2951      "Classification for Allow header"
2952    </t>
2953    <t>
2954      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2955      "missing default for qvalue in description of Accept-Encoding"
2956    </t>
2957  </list>
2958</t>
2959<t>
2960  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2961  <list style="symbols"> 
2962    <t>
2963      Reference RFC 3984, and update header registrations for headers defined
2964      in this document.
2965    </t>
2966  </list>
2967</t>
2968</section>
2969
2970<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2971<t>
2972  Closed issues:
2973  <list style="symbols"> 
2974    <t>
2975      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2976      "Quoting Charsets"
2977    </t>
2978    <t>
2979      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2980      "language tag matching (Accept-Language) vs RFC4647"
2981    </t>
2982    <t>
2983      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2984      "RFC 1806 has been replaced by RFC2183"
2985    </t>
2986  </list>
2987</t>
2988<t>
2989  Other changes:
2990  <list style="symbols"> 
2991    <t>
2992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2993      "Encoding References Normative" -- rephrase the annotation and reference
2994      <xref target="BCP97"/>.
2995    </t>
2996  </list>
2997</t>
2998 </section>
2999
3000<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
3001<t>
3002  Closed issues:
3003  <list style="symbols"> 
3004    <t>
3005      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3006      "RFC 2822 is updated by RFC 5322"
3007    </t>
3008  </list>
3009</t>
3010<t>
3011  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3012  <list style="symbols"> 
3013    <t>
3014      Use "/" instead of "|" for alternatives.
3015    </t>
3016    <t>
3017      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3018      whitespace ("OWS") and required whitespace ("RWS").
3019    </t>
3020    <t>
3021      Rewrite ABNFs to spell out whitespace rules, factor out
3022      header value format definitions.
3023    </t>
3024  </list>
3025</t>
3026</section>
3027
3028<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
3029<t>
3030  Closed issues:
3031  <list style="symbols"> 
3032    <t>
3033      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
3034      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3035    </t>
3036  </list>
3037</t>
3038<t>
3039  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3040  <list style="symbols"> 
3041    <t>
3042      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3043    </t>
3044  </list>
3045</t>
3046<t>
3047  Other changes:
3048  <list style="symbols"> 
3049    <t>
3050      Move definition of quality values into Part 1.
3051    </t>
3052  </list>
3053</t>
3054</section>
3055
3056<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
3057<t>
3058  Closed issues:
3059  <list style="symbols"> 
3060    <t>
3061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3062      "Content-Location isn't special"
3063    </t>
3064    <t>
3065      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3066      "Content Sniffing"
3067    </t>
3068  </list>
3069</t>
3070</section>
3071
3072<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
3073<t>
3074  Closed issues:
3075  <list style="symbols"> 
3076    <t>
3077      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
3078      "Updated reference for language tags"
3079    </t>
3080    <t>
3081      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3082      "Clarify rules for determining what entities a response carries"
3083    </t>
3084    <t>
3085      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
3086      "Content-Location base-setting problems"
3087    </t>
3088    <t>
3089      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3090      "Content Sniffing"
3091    </t>
3092    <t>
3093      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
3094      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3095    </t>
3096    <t>
3097      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
3098      "move definitions of gzip/deflate/compress to part 1"
3099    </t>
3100  </list>
3101</t>
3102<t>
3103  Partly resolved issues:
3104  <list style="symbols"> 
3105    <t>
3106      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
3107      "update IANA requirements wrt Transfer-Coding values" (add the
3108      IANA Considerations subsection)
3109    </t>
3110    <t>
3111      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
3112      "update IANA requirements wrt Content-Coding values" (add the
3113      IANA Considerations subsection)
3114    </t>
3115  </list>
3116</t>
3117</section>
3118
3119<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
3120<t>
3121  Closed issues:
3122  <list style="symbols"> 
3123    <t>
3124      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
3125      "Content Negotiation for media types"
3126    </t>
3127    <t>
3128      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
3129      "Accept-Language: which RFC4647 filtering?"
3130    </t>
3131  </list>
3132</t>
3133</section>
3134
3135<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
3136<t>
3137  Closed issues:
3138  <list style="symbols"> 
3139    <t>
3140      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
3141      "MIME-Version not listed in P1, general header fields"
3142    </t>
3143    <t>
3144      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
3145      "IANA registry for content/transfer encodings"
3146    </t>
3147    <t>
3148      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3149      "Content Sniffing"
3150    </t>
3151    <t>
3152      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
3153      "use of term "word" when talking about header structure"
3154    </t>
3155  </list>
3156</t>
3157<t>
3158  Partly resolved issues:
3159  <list style="symbols"> 
3160    <t>
3161      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3162      "Term for the requested resource's URI"
3163    </t>
3164  </list>
3165</t>
3166</section>
3167
3168<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
3169<t>
3170  Closed issues:
3171  <list style="symbols"> 
3172    <t>
3173      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3174      "Clarify 'Requested Variant'"
3175    </t>
3176    <t>
3177      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3178      "Content-Location isn't special"
3179    </t>
3180    <t>
3181      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
3182      "Delimiting messages with multipart/byteranges"
3183    </t>
3184    <t>
3185      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3186      "Clarify entity / representation / variant terminology"
3187    </t>
3188    <t>
3189      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
3190      "confusing req. language for Content-Location"
3191    </t>
3192    <t>
3193      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
3194      "Content-Location on 304 responses"
3195    </t>
3196    <t>
3197      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
3198      "'requested resource' in content-encoding definition"
3199    </t>
3200    <t>
3201      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3202      "consider removing the 'changes from 2068' sections"
3203    </t>
3204  </list>
3205</t>
3206<t>
3207  Partly resolved issues:
3208  <list style="symbols"> 
3209    <t>
3210      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3211      "Content-MD5 and partial responses"
3212    </t>
3213  </list>
3214</t>
3215</section>
3216
3217</section>
3218
3219</back>
3220</rfc>
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