source: draft-ietf-httpbis/latest/p3-payload.xml @ 858

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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 message-length           "<xref target='Part1' x:rel='#message.body.length' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY header-fields            "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='#internet.media.type.multipart.byteranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY full-date                "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42]>
43<?rfc toc="yes" ?>
44<?rfc symrefs="yes" ?>
45<?rfc sortrefs="yes" ?>
46<?rfc compact="yes"?>
47<?rfc subcompact="no" ?>
48<?rfc linkmailto="no" ?>
49<?rfc editing="no" ?>
50<?rfc comments="yes"?>
51<?rfc inline="yes"?>
52<?rfc rfcedstyle="yes"?>
53<?rfc-ext allow-markup-in-artwork="yes" ?>
54<?rfc-ext include-references-in-index="yes" ?>
55<rfc obsoletes="2616" category="std" x:maturity-level="draft"
56     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
57     xmlns:x='http://purl.org/net/xml2rfc/ext'>
58<front>
59
60  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
61
62  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
63    <organization abbrev="Day Software">Day Software</organization>
64    <address>
65      <postal>
66        <street>23 Corporate Plaza DR, Suite 280</street>
67        <city>Newport Beach</city>
68        <region>CA</region>
69        <code>92660</code>
70        <country>USA</country>
71      </postal>
72      <phone>+1-949-706-5300</phone>
73      <facsimile>+1-949-706-5305</facsimile>
74      <email>fielding@gbiv.com</email>
75      <uri>http://roy.gbiv.com/</uri>
76    </address>
77  </author>
78
79  <author initials="J." surname="Gettys" fullname="Jim Gettys">
80    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
81    <address>
82      <postal>
83        <street>21 Oak Knoll Road</street>
84        <city>Carlisle</city>
85        <region>MA</region>
86        <code>01741</code>
87        <country>USA</country>
88      </postal>
89      <email>jg@freedesktop.org</email>
90      <uri>http://gettys.wordpress.com/</uri>
91    </address>
92  </author>
93 
94  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
95    <organization abbrev="HP">Hewlett-Packard Company</organization>
96    <address>
97      <postal>
98        <street>HP Labs, Large Scale Systems Group</street>
99        <street>1501 Page Mill Road, MS 1177</street>
100        <city>Palo Alto</city>
101        <region>CA</region>
102        <code>94304</code>
103        <country>USA</country>
104      </postal>
105      <email>JeffMogul@acm.org</email>
106    </address>
107  </author>
108
109  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
110    <organization abbrev="Microsoft">Microsoft Corporation</organization>
111    <address>
112      <postal>
113        <street>1 Microsoft Way</street>
114        <city>Redmond</city>
115        <region>WA</region>
116        <code>98052</code>
117        <country>USA</country>
118      </postal>
119      <email>henrikn@microsoft.com</email>
120    </address>
121  </author>
122
123  <author initials="L." surname="Masinter" fullname="Larry Masinter">
124    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
125    <address>
126      <postal>
127        <street>345 Park Ave</street>
128        <city>San Jose</city>
129        <region>CA</region>
130        <code>95110</code>
131        <country>USA</country>
132      </postal>
133      <email>LMM@acm.org</email>
134      <uri>http://larry.masinter.net/</uri>
135    </address>
136  </author>
137 
138  <author initials="P." surname="Leach" fullname="Paul J. Leach">
139    <organization abbrev="Microsoft">Microsoft Corporation</organization>
140    <address>
141      <postal>
142        <street>1 Microsoft Way</street>
143        <city>Redmond</city>
144        <region>WA</region>
145        <code>98052</code>
146      </postal>
147      <email>paulle@microsoft.com</email>
148    </address>
149  </author>
150   
151  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
152    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
153    <address>
154      <postal>
155        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
156        <street>The Stata Center, Building 32</street>
157        <street>32 Vassar Street</street>
158        <city>Cambridge</city>
159        <region>MA</region>
160        <code>02139</code>
161        <country>USA</country>
162      </postal>
163      <email>timbl@w3.org</email>
164      <uri>http://www.w3.org/People/Berners-Lee/</uri>
165    </address>
166  </author>
167
168  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
169    <organization abbrev="W3C">World Wide Web Consortium</organization>
170    <address>
171      <postal>
172        <street>W3C / ERCIM</street>
173        <street>2004, rte des Lucioles</street>
174        <city>Sophia-Antipolis</city>
175        <region>AM</region>
176        <code>06902</code>
177        <country>France</country>
178      </postal>
179      <email>ylafon@w3.org</email>
180      <uri>http://www.raubacapeu.net/people/yves/</uri>
181    </address>
182  </author>
183
184  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
185    <organization abbrev="greenbytes">greenbytes GmbH</organization>
186    <address>
187      <postal>
188        <street>Hafenweg 16</street>
189        <city>Muenster</city><region>NW</region><code>48155</code>
190        <country>Germany</country>
191      </postal>
192      <phone>+49 251 2807760</phone>
193      <facsimile>+49 251 2807761</facsimile>
194      <email>julian.reschke@greenbytes.de</email>
195      <uri>http://greenbytes.de/tech/webdav/</uri>
196    </address>
197  </author>
198
199  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
200  <workgroup>HTTPbis Working Group</workgroup>
201
202<abstract>
203<t>
204   The Hypertext Transfer Protocol (HTTP) is an application-level
205   protocol for distributed, collaborative, hypermedia information
206   systems. HTTP has been in use by the World Wide Web global information
207   initiative since 1990. This document is Part 3 of the seven-part specification
208   that defines the protocol referred to as "HTTP/1.1" and, taken together,
209   obsoletes RFC 2616.  Part 3 defines HTTP message content,
210   metadata, and content negotiation.
211</t>
212</abstract>
213
214<note title="Editorial Note (To be removed by RFC Editor)">
215  <t>
216    Discussion of this draft should take place on the HTTPBIS working group
217    mailing list (ietf-http-wg@w3.org). The current issues list is
218    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
219    and related documents (including fancy diffs) can be found at
220    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
221  </t>
222  <t>
223    The changes in this draft are summarized in <xref target="changes.since.10"/>.
224  </t>
225</note>
226</front>
227<middle>
228<section title="Introduction" anchor="introduction">
229<t>
230   This document defines HTTP/1.1 message payloads (a.k.a., content), the
231   associated metadata header fields that define how the payload is intended
232   to be interpreted by a recipient, the request header fields that
233   may influence content selection, and the various selection algorithms
234   that are collectively referred to as HTTP content negotiation.
235</t>
236<t>
237   This document is currently disorganized in order to minimize the changes
238   between drafts and enable reviewers to see the smaller errata changes.
239   The next draft will reorganize the sections to better reflect the content.
240   In particular, the sections on entities will be renamed payload and moved
241   to the first half of the document, while the sections on content negotiation
242   and associated request header fields will be moved to the second half.  The
243   current mess reflects how widely dispersed these topics and associated
244   requirements had become in <xref target="RFC2616"/>.
245</t>
246
247<section title="Terminology" anchor="terminology">
248<t>
249   This specification uses a number of terms to refer to the roles
250   played by participants in, and objects of, the HTTP communication.
251</t>
252<t>
253  <iref item="content negotiation"/>
254  <x:dfn>content negotiation</x:dfn>
255  <list>
256    <t>
257      The mechanism for selecting the appropriate representation when
258      servicing a request. The representation in any response
259      can be negotiated (including error responses).
260    </t>
261  </list>
262</t>
263<t>
264  <iref item="payload"/>
265  <x:dfn>payload</x:dfn>
266  <list>
267    <t>
268      The information transferred within a given message is called the
269      payload, consisting  of optional payload metadata and an optional
270      payload body.  The payload in HTTP is always a partial or complete
271      representation of some resource, though which resource is represented
272      is dependent on the type of message (request or response), the
273      request method, and the response status code.
274    </t>
275  </list>
276</t>
277<t>
278  <iref item="representation"/>
279  <x:dfn>representation</x:dfn>
280  <list>
281    <t>
282      A representation is information in a format that can be readily
283      communicated from one party to another.  For our purposes, a
284      representation is binary data and its associated metadata.
285      A representation of a resource is information that reflects the
286      state of that resource, as observed at some point in the past
287      or to be desired at some point in the future.
288    </t>
289  </list>
290</t>
291</section>
292
293<section title="Requirements" anchor="intro.requirements">
294<t>
295   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
296   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
297   document are to be interpreted as described in <xref target="RFC2119"/>.
298</t>
299<t>
300   An implementation is not compliant if it fails to satisfy one or more
301   of the "MUST" or "REQUIRED" level requirements for the protocols it
302   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
303   level and all the "SHOULD" level requirements for its protocols is said
304   to be "unconditionally compliant"; one that satisfies all the "MUST"
305   level requirements but not all the "SHOULD" level requirements for its
306   protocols is said to be "conditionally compliant".
307</t>
308</section>
309
310<section title="Syntax Notation" anchor="notation">
311  <x:anchor-alias value="ALPHA"/>
312  <x:anchor-alias value="CR"/>
313  <x:anchor-alias value="DIGIT"/>
314  <x:anchor-alias value="LF"/>
315  <x:anchor-alias value="OCTET"/>
316  <x:anchor-alias value="VCHAR"/>
317  <x:anchor-alias value="WSP"/>
318<t>
319  This specification uses the ABNF syntax defined in &notation; (which
320  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
321  <xref target="collected.abnf"/> shows the collected ABNF, with the list
322  rule expanded.
323</t>
324<t>
325  The following core rules are included by
326  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
327  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
328  DIGIT (decimal 0-9), DQUOTE (double quote),
329  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
330  OCTET (any 8-bit sequence of data), SP (space),
331  VCHAR (any visible USASCII character),
332  and WSP (whitespace).
333</t>
334
335<section title="Core Rules" anchor="core.rules">
336  <x:anchor-alias value="quoted-string"/>
337  <x:anchor-alias value="token"/>
338  <x:anchor-alias value="word"/>
339  <x:anchor-alias value="OWS"/>
340<t>
341  The core rules below are defined in &basic-rules;:
342</t>
343<figure><artwork type="abnf2616">
344  <x:ref>quoted-string</x:ref>  = &lt;quoted-string, defined in &basic-rules;&gt;
345  <x:ref>token</x:ref>          = &lt;token, defined in &basic-rules;&gt;
346  <x:ref>word</x:ref>           = &lt;word, defined in &basic-rules;&gt;
347  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
348</artwork></figure>
349</section>
350
351<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
352  <x:anchor-alias value="absolute-URI"/>
353  <x:anchor-alias value="Allow"/>
354  <x:anchor-alias value="Content-Length"/>
355  <x:anchor-alias value="Content-Range"/>
356  <x:anchor-alias value="Expires"/>
357  <x:anchor-alias value="Last-Modified"/>
358  <x:anchor-alias value="header-field"/>
359  <x:anchor-alias value="partial-URI"/>
360  <x:anchor-alias value="qvalue"/>
361<t>
362  The ABNF rules below are defined in other parts:
363</t>
364<figure><!--Part1--><artwork type="abnf2616">
365  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
366  <x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in &header-content-length;&gt;
367  <x:ref>header-field</x:ref>   = &lt;header-field, defined in &header-fields;&gt;
368  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
369  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
370</artwork></figure>
371<figure><!--Part4--><artwork type="abnf2616">
372  <x:ref>Last-Modified</x:ref>  = &lt;Last-Modified, defined in &header-last-modified;&gt;
373</artwork></figure>
374<figure><!--Part5--><artwork type="abnf2616">
375  <x:ref>Content-Range</x:ref>  = &lt;Content-Range, defined in &header-content-range;&gt;
376</artwork></figure>
377<figure><!--Part6--><artwork type="abnf2616">
378  <x:ref>Expires</x:ref>        = &lt;Expires, defined in &header-expires;&gt;
379</artwork></figure>
380</section>
381
382</section>
383
384</section>
385
386<section title="Protocol Parameters" anchor="protocol.parameters">
387
388<section title="Character Sets" anchor="character.sets">
389<t>
390   HTTP uses the same definition of the term "character set" as that
391   described for MIME:
392</t>
393<t>
394   The term "character set" is used in this document to refer to a
395   method used with one or more tables to convert a sequence of octets
396   into a sequence of characters. Note that unconditional conversion in
397   the other direction is not required, in that not all characters may
398   be available in a given character set and a character set may provide
399   more than one sequence of octets to represent a particular character.
400   This definition is intended to allow various kinds of character
401   encoding, from simple single-table mappings such as US-ASCII to
402   complex table switching methods such as those that use ISO-2022's
403   techniques. However, the definition associated with a MIME character
404   set name &MUST; fully specify the mapping to be performed from octets
405   to characters. In particular, use of external profiling information
406   to determine the exact mapping is not permitted.
407</t>
408<x:note>
409  <t>
410    <x:h>Note:</x:h> This use of the term "character set" is more commonly
411    referred to as a "character encoding." However, since HTTP and
412    MIME share the same registry, it is important that the terminology
413    also be shared.
414  </t>
415</x:note>
416<t anchor="rule.charset">
417  <x:anchor-alias value="charset"/>
418   HTTP character sets are identified by case-insensitive tokens. The
419   complete set of tokens is defined by the IANA Character Set registry
420   (<eref target="http://www.iana.org/assignments/character-sets"/>).
421</t>
422<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
423  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
424</artwork></figure>
425<t>
426   Although HTTP allows an arbitrary token to be used as a charset
427   value, any token that has a predefined value within the IANA
428   Character Set registry &MUST; represent the character set defined
429   by that registry. Applications &SHOULD; limit their use of character
430   sets to those defined by the IANA registry.
431</t>
432<t>
433   HTTP uses charset in two contexts: within an Accept-Charset request
434   header (in which the charset value is an unquoted token) and as the
435   value of a parameter in a Content-Type header (within a request or
436   response), in which case the parameter value of the charset parameter
437   may be quoted.
438</t>
439<t>
440   Implementors should be aware of IETF character set requirements <xref target="RFC3629"/>
441   <xref target="RFC2277"/>.
442</t>
443
444<section title="Missing Charset" anchor="missing.charset">
445<t>
446   Some HTTP/1.0 software has interpreted a Content-Type header without
447   charset parameter incorrectly to mean "recipient should guess."
448   Senders wishing to defeat this behavior &MAY; include a charset
449   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and &SHOULD; do so when
450   it is known that it will not confuse the recipient.
451</t>
452<t>
453   Unfortunately, some older HTTP/1.0 clients did not deal properly with
454   an explicit charset parameter. HTTP/1.1 recipients &MUST; respect the
455   charset label provided by the sender; and those user agents that have
456   a provision to "guess" a charset &MUST; use the charset from the
457   content-type field if they support that charset, rather than the
458   recipient's preference, when initially displaying a document. See
459   <xref target="canonicalization.and.text.defaults"/>.
460</t>
461</section>
462</section>
463
464<section title="Content Codings" anchor="content.codings">
465  <x:anchor-alias value="content-coding"/>
466<t>
467   Content coding values indicate an encoding transformation that has
468   been or can be applied to an entity. Content codings are primarily
469   used to allow a document to be compressed or otherwise usefully
470   transformed without losing the identity of its underlying media type
471   and without loss of information. Frequently, the entity is stored in
472   coded form, transmitted directly, and only decoded by the recipient.
473</t>
474<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
475  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
476</artwork></figure>
477<t>
478   All content-coding values are case-insensitive. HTTP/1.1 uses
479   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
480   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
481   describes the content-coding, what is more important is that it
482   indicates what decoding mechanism will be required to remove the
483   encoding.
484</t>
485<t>
486   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
487  <list>
488    <t>
489      See &compress-coding;.
490    </t>
491  </list>
492</t>
493<t>
494   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
495  <list>
496    <t>
497      See &deflate-coding;.
498    </t>
499  </list>
500</t>
501<t>
502   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
503  <list>
504    <t>
505      See &gzip-coding;.
506    </t>
507  </list>
508</t>
509<t>
510   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
511  <list><t>
512        The default (identity) encoding; the use of no transformation
513        whatsoever. This content-coding is used only in the Accept-Encoding
514        header, and &SHOULD-NOT;  be used in the Content-Encoding
515        header.
516  </t></list>
517</t>
518
519<section title="Content Coding Registry" anchor="content.coding.registry">
520<t>
521   The HTTP Content Coding Registry defines the name space for the content
522   coding names.
523</t>
524<t>
525   Registrations &MUST; include the following fields:
526   <list style="symbols">
527     <t>Name</t>
528     <t>Description</t>
529     <t>Pointer to specification text</t>
530   </list>
531</t>
532<t>
533   Names of content codings &MUST-NOT; overlap with names of transfer codings
534   (&transfer-codings;), unless the encoding transformation is identical (as it
535   is the case for the compression codings defined in
536   &compression-codings;).
537</t>
538<t>
539   Values to be added to this name space require expert review and a specification
540   (see "Expert Review" and "Specification Required" in
541   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
542   conform to the purpose of content coding defined in this section.
543</t>
544<t>
545   The registry itself is maintained at
546   <eref target="http://www.iana.org/assignments/http-parameters"/>.
547</t>
548</section>
549
550</section>
551
552<section title="Media Types" anchor="media.types">
553  <x:anchor-alias value="media-type"/>
554  <x:anchor-alias value="type"/>
555  <x:anchor-alias value="subtype"/>
556<t>
557   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
558   and Accept (<xref target="header.accept"/>) header fields in order to provide
559   open and extensible data typing and type negotiation.
560</t>
561<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"/>
562  <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> )
563  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
564  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
565</artwork></figure>
566<t anchor="rule.parameter">
567  <x:anchor-alias value="attribute"/>
568  <x:anchor-alias value="parameter"/>
569  <x:anchor-alias value="value"/>
570   Parameters &MAY; follow the type/subtype in the form of attribute/value
571   pairs.
572</t>
573<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"/>
574  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
575  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
576  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
577</artwork></figure>
578<t>
579   The type, subtype, and parameter attribute names are case-insensitive.
580   Parameter values might or might not be case-sensitive, depending on the
581   semantics of the parameter name.  The presence or absence of a parameter might
582   be significant to the processing of a media-type, depending on its
583   definition within the media type registry.
584</t>
585<t>
586   A parameter value that matches the <x:ref>token</x:ref> production may be
587   transmitted as either a token or within a quoted-string. The quoted and
588   unquoted values are equivalent.
589</t>
590<t>
591   Note that some older HTTP applications do not recognize media type
592   parameters. When sending data to older HTTP applications,
593   implementations &SHOULD; only use media type parameters when they are
594   required by that type/subtype definition.
595</t>
596<t>
597   Media-type values are registered with the Internet Assigned Number
598   Authority (IANA). The media type registration process is
599   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
600   discouraged.
601</t>
602
603<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
604<t>
605   Internet media types are registered with a canonical form. An
606   entity-body transferred via HTTP messages &MUST; be represented in the
607   appropriate canonical form prior to its transmission except for
608   "text" types, as defined in the next paragraph.
609</t>
610<t>
611   When in canonical form, media subtypes of the "text" type use CRLF as
612   the text line break. HTTP relaxes this requirement and allows the
613   transport of text media with plain CR or LF alone representing a line
614   break when it is done consistently for an entire entity-body. HTTP
615   applications &MUST; accept CRLF, bare CR, and bare LF as being
616   representative of a line break in text media received via HTTP. In
617   addition, if the text is represented in a character set that does not
618   use octets 13 and 10 for CR and LF respectively, as is the case for
619   some multi-byte character sets, HTTP allows the use of whatever octet
620   sequences are defined by that character set to represent the
621   equivalent of CR and LF for line breaks. This flexibility regarding
622   line breaks applies only to text media in the entity-body; a bare CR
623   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
624   structures (such as header fields and multipart boundaries).
625</t>
626<t>
627   If an entity-body is encoded with a content-coding, the underlying
628   data &MUST; be in a form defined above prior to being encoded.
629</t>
630<t>
631   The "charset" parameter is used with some media types to define the
632   character set (<xref target="character.sets"/>) of the data. When no explicit charset
633   parameter is provided by the sender, media subtypes of the "text"
634   type are defined to have a default charset value of "ISO-8859-1" when
635   received via HTTP. Data in character sets other than "ISO-8859-1" or
636   its subsets &MUST; be labeled with an appropriate charset value. See
637   <xref target="missing.charset"/> for compatibility problems.
638</t>
639</section>
640
641<section title="Multipart Types" anchor="multipart.types">
642<t>
643   MIME provides for a number of "multipart" types -- encapsulations of
644   one or more entities within a single message-body. All multipart
645   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
646   and &MUST; include a boundary parameter as part of the media type
647   value. The message body is itself a protocol element and &MUST;
648   therefore use only CRLF to represent line breaks between body-parts.
649</t>
650<t>
651   In general, HTTP treats a multipart message-body no differently than
652   any other media type: strictly as payload.  HTTP does not use the
653   multipart boundary as an indicator of message-body length.
654   <!-- jre: re-insert removed text pointing to caching? -->
655   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
656   behavior as a MIME user agent would upon receipt of a multipart type.
657   The MIME header fields within each body-part of a multipart message-body
658   do not have any significance to HTTP beyond that defined by
659   their MIME semantics.
660</t>
661<t>
662   If an application receives an unrecognized multipart subtype, the
663   application &MUST; treat it as being equivalent to "multipart/mixed".
664</t>
665<x:note>
666  <t>
667    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
668    for carrying form data suitable for processing via the POST
669    request method, as described in <xref target="RFC2388"/>.
670  </t>
671</x:note>
672</section>
673</section>
674
675<section title="Language Tags" anchor="language.tags">
676  <x:anchor-alias value="language-tag"/>
677<t>
678   A language tag, as defined in <xref target="RFC5646"/>, identifies a
679   natural language spoken, written, or otherwise conveyed by human beings for
680   communication of information to other human beings. Computer languages are
681   explicitly excluded. HTTP uses language tags within the Accept-Language and
682   Content-Language fields.
683</t>
684<t>
685   In summary, a language tag is composed of one or more parts: A primary
686   language subtag followed by a possibly empty series of subtags:
687</t>
688<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
689  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
690</artwork></figure>
691<t>
692   White space is not allowed within the tag and all tags are case-insensitive.
693   The name space of language subtags is administered by the IANA (see
694   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
695</t>
696<figure>
697  <preamble>Example tags include:</preamble>
698<artwork type="example">
699  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
700</artwork>
701</figure>
702<t>
703   See <xref target="RFC5646"/> for further information.
704</t>
705</section>
706</section>
707
708<section title="Entity" anchor="entity">
709<t>
710   Request and Response messages &MAY; transfer an entity if not otherwise
711   restricted by the request method or response status code. An entity
712   consists of entity-header fields and an entity-body, although some
713   responses will only include the entity-headers.
714</t>
715<t>
716   In this section, both sender and recipient refer to either the client
717   or the server, depending on who sends and who receives the entity.
718</t>
719
720<section title="Entity Header Fields" anchor="entity.header.fields">
721  <x:anchor-alias value="entity-header"/>
722  <x:anchor-alias value="extension-header"/>
723<t>
724   Entity-header fields define metainformation about the entity-body or,
725   if no body is present, about the resource identified by the request.
726</t>
727<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="entity-header"/><iref primary="true" item="Grammar" subitem="extension-header"/>
728  <x:ref>entity-header</x:ref>  = <x:ref>Content-Encoding</x:ref>         ; <xref target="header.content-encoding"/>
729                 / <x:ref>Content-Language</x:ref>         ; <xref target="header.content-language"/>
730                 / <x:ref>Content-Length</x:ref>           ; &header-content-length;
731                 / <x:ref>Content-Location</x:ref>         ; <xref target="header.content-location"/>
732                 / <x:ref>Content-MD5</x:ref>              ; <xref target="header.content-md5"/>
733                 / <x:ref>Content-Range</x:ref>            ; &header-content-range;
734                 / <x:ref>Content-Type</x:ref>             ; <xref target="header.content-type"/>
735                 / <x:ref>Expires</x:ref>                  ; &header-expires;
736                 / <x:ref>Last-Modified</x:ref>            ; &header-last-modified;
737                 / <x:ref>extension-header</x:ref>
738 
739  <x:ref>extension-header</x:ref> = <x:ref>header-field</x:ref>
740</artwork></figure>
741<t>
742   The extension-header mechanism allows additional entity-header fields
743   to be defined without changing the protocol, but these fields cannot
744   be assumed to be recognizable by the recipient. Unrecognized header
745   fields &SHOULD; be ignored by the recipient and &MUST; be forwarded by
746   transparent proxies.
747</t>
748</section>
749
750<section title="Entity Body" anchor="entity.body">
751  <x:anchor-alias value="entity-body"/>
752<t>
753   The entity-body (if any) sent with an HTTP request or response is in
754   a format and encoding defined by the entity-header fields.
755</t>
756<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="entity-body"/>
757  <x:ref>entity-body</x:ref>    = *<x:ref>OCTET</x:ref>
758</artwork></figure>
759<t>
760   An entity-body is only present in a message when a message-body is
761   present, as described in &message-body;. The entity-body is obtained
762   from the message-body by decoding any Transfer-Encoding that might
763   have been applied to ensure safe and proper transfer of the message.
764</t>
765
766<section title="Type" anchor="type">
767<t>
768   When an entity-body is included with a message, the data type of that
769   body is determined via the header fields Content-Type and Content-Encoding.
770   These define a two-layer, ordered encoding model:
771</t>
772<figure><artwork type="example">
773  entity-body := Content-Encoding( Content-Type( data ) )
774</artwork></figure>
775<t>
776   Content-Type specifies the media type of the underlying data. Any HTTP/1.1
777   message containing an entity-body &SHOULD; include a Content-Type header
778   field defining the media type of that body, unless that information is
779   unknown.
780</t>
781<t>   
782   If the Content-Type header field is not present, it indicates that
783   the sender does not know the media type of the data; recipients &MAY;
784   either assume that it is "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
785   or examine the content to determine its type.
786</t>
787<t>
788   In practice, currently-deployed servers sometimes provide a Content-Type
789   header which does not correctly convey the intended interpretation of the
790   content sent, with the result that some clients will examine the response
791   body's content and override the specified type.
792</t>
793<t>
794   Client that do so risk drawing incorrect conclusions, which may expose
795   additional security risks (e.g., "privilege escalation"). Implementers are
796   encouraged to provide a means of disabling such "content sniffing" when it
797   is used.
798</t>
799<t>
800   Content-Encoding may be used to indicate any additional content
801   codings applied to the data, usually for the purpose of data
802   compression, that are a property of the requested resource.  There is
803   no default encoding.
804</t>
805</section>
806   
807</section>
808</section>
809
810<section title="Content Negotiation" anchor="content.negotiation">
811<t>
812   HTTP responses include a representation which contains information for
813   interpretation, whether by a human user or for further processing.
814   Often, the server has different ways of representing the
815   same information; for example, in different formats, languages,
816   or using different character encodings.
817</t>
818<t>
819   HTTP clients and their users might have different or variable
820   capabilities, characteristics or preferences which would influence
821   which representation, among those available from the server,
822   would be best for the server to deliver. For this reason, HTTP
823   provides mechanisms for "content negotiation" -- a process of
824   allowing selection of a representation of a given resource,
825   when more than one is available.
826</t>
827<t>
828   This specification defines two patterns of content negotiation;
829   "server-driven", where the server selects the representation based
830   upon the client's stated preferences, and "agent-driven" negotiation,
831   where the server provides a list of representations for the client to
832   choose from, based upon their metadata. In addition,  there are
833   other patterns: some applications use an "active content" pattern,
834   where the server returns active content which runs on the client
835   and, based on client available parameters, selects additional
836   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
837   has also been proposed.
838</t>
839<t>
840   These patterns are all widely used, and have trade-offs in applicability
841   and practicality. In particular, when the number of preferences or
842   capabilities to be expressed by a client are large (such as when many
843   different formats are supported by a user-agent), server-driven
844   negotiation becomes unwieldy, and may not be appropriate. Conversely,
845   when the number of representations to choose from is very large,
846   agent-driven negotiation may not be appropriate.
847</t>
848<t>
849   Note that in all cases, the supplier of representations has the
850   responsibility for determining which representations might be
851   considered to be the "same information".
852</t>
853
854<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
855<t>
856   If the selection of the best representation for a response is made by
857   an algorithm located at the server, it is called server-driven
858   negotiation. Selection is based on the available representations of
859   the response (the dimensions over which it can vary; e.g., language,
860   content-coding, etc.) and the contents of particular header fields in
861   the request message or on other information pertaining to the request
862   (such as the network address of the client).
863</t>
864<t>
865   Server-driven negotiation is advantageous when the algorithm for
866   selecting from among the available representations is difficult to
867   describe to the user agent, or when the server desires to send its
868   "best guess" to the client along with the first response (hoping to
869   avoid the round-trip delay of a subsequent request if the "best
870   guess" is good enough for the user). In order to improve the server's
871   guess, the user agent &MAY; include request header fields (Accept,
872   Accept-Language, Accept-Encoding, etc.) which describe its
873   preferences for such a response.
874</t>
875<t>
876   Server-driven negotiation has disadvantages:
877  <list style="numbers">
878    <t>
879         It is impossible for the server to accurately determine what
880         might be "best" for any given user, since that would require
881         complete knowledge of both the capabilities of the user agent
882         and the intended use for the response (e.g., does the user want
883         to view it on screen or print it on paper?).
884    </t>
885    <t>
886         Having the user agent describe its capabilities in every
887         request can be both very inefficient (given that only a small
888         percentage of responses have multiple representations) and a
889         potential violation of the user's privacy.
890    </t>
891    <t>
892         It complicates the implementation of an origin server and the
893         algorithms for generating responses to a request.
894    </t>
895    <t>
896         It may limit a public cache's ability to use the same response
897         for multiple user's requests.
898    </t>
899  </list>
900</t>
901<t>
902   HTTP/1.1 includes the following request-header fields for enabling
903   server-driven negotiation through description of user agent
904   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
905   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
906   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
907   However, an origin server is not limited to these dimensions and &MAY; vary
908   the response based on any aspect of the request, including information
909   outside the request-header fields or within extension header fields
910   not defined by this specification.
911</t>
912<x:note>
913  <t>
914    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
915    because new clients might not be recognized.
916  </t>
917</x:note>
918<t>
919   The Vary header field (&header-vary;) can be used to express the parameters the
920   server uses to select a representation that is subject to server-driven
921   negotiation.
922</t>
923</section>
924
925<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
926<t>
927   With agent-driven negotiation, selection of the best representation
928   for a response is performed by the user agent after receiving an
929   initial response from the origin server. Selection is based on a list
930   of the available representations of the response included within the
931   header fields or entity-body of the initial response, with each
932   representation identified by its own URI. Selection from among the
933   representations may be performed automatically (if the user agent is
934   capable of doing so) or manually by the user selecting from a
935   generated (possibly hypertext) menu.
936</t>
937<t>
938   Agent-driven negotiation is advantageous when the response would vary
939   over commonly-used dimensions (such as type, language, or encoding),
940   when the origin server is unable to determine a user agent's
941   capabilities from examining the request, and generally when public
942   caches are used to distribute server load and reduce network usage.
943</t>
944<t>
945   Agent-driven negotiation suffers from the disadvantage of needing a
946   second request to obtain the best alternate representation. This
947   second request is only efficient when caching is used. In addition,
948   this specification does not define any mechanism for supporting
949   automatic selection, though it also does not prevent any such
950   mechanism from being developed as an extension and used within
951   HTTP/1.1.
952</t>
953<t>
954   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
955   status codes for enabling agent-driven negotiation when the server is
956   unwilling or unable to provide a varying response using server-driven
957   negotiation.
958</t>
959</section>
960</section>
961
962<section title="Header Field Definitions" anchor="header.fields">
963<t>
964   This section defines the syntax and semantics of HTTP/1.1 header fields
965   related to the payload of messages.
966</t>
967<t>
968   For entity-header fields, both sender and recipient refer to either the
969   client or the server, depending on who sends and who receives the entity.
970</t>
971
972<section title="Accept" anchor="header.accept">
973  <iref primary="true" item="Accept header" x:for-anchor=""/>
974  <iref primary="true" item="Headers" subitem="Accept" x:for-anchor=""/>
975  <x:anchor-alias value="Accept"/>
976  <x:anchor-alias value="Accept-v"/>
977  <x:anchor-alias value="accept-ext"/>
978  <x:anchor-alias value="accept-params"/>
979  <x:anchor-alias value="media-range"/>
980<t>
981   The "Accept" request-header field can be used by user agents to specify
982   response media types that are acceptable. Accept headers can be used to
983   indicate that the request is specifically limited to a small set of desired
984   types, as in the case of a request for an in-line image.
985</t>
986<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"/>
987  <x:ref>Accept</x:ref>   = "Accept" ":" <x:ref>OWS</x:ref> <x:ref>Accept-v</x:ref>
988  <x:ref>Accept-v</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
989 
990  <x:ref>media-range</x:ref>    = ( "*/*"
991                   / ( <x:ref>type</x:ref> "/" "*" )
992                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
993                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
994  <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> )
995  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref>
996                   [ "=" <x:ref>word</x:ref> ]
997</artwork></figure>
998<t>
999   The asterisk "*" character is used to group media types into ranges,
1000   with "*/*" indicating all media types and "type/*" indicating all
1001   subtypes of that type. The media-range &MAY; include media type
1002   parameters that are applicable to that range.
1003</t>
1004<t>
1005   Each media-range &MAY; be followed by one or more accept-params,
1006   beginning with the "q" parameter for indicating a relative quality
1007   factor. The first "q" parameter (if any) separates the media-range
1008   parameter(s) from the accept-params. Quality factors allow the user
1009   or user agent to indicate the relative degree of preference for that
1010   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
1011   default value is q=1.
1012</t>
1013<x:note>
1014  <t>
1015    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
1016    parameters from Accept extension parameters is due to historical
1017    practice. Although this prevents any media type parameter named
1018    "q" from being used with a media range, such an event is believed
1019    to be unlikely given the lack of any "q" parameters in the IANA
1020    media type registry and the rare usage of any media type
1021    parameters in Accept. Future media types are discouraged from
1022    registering any parameter named "q".
1023  </t>
1024</x:note>
1025<t>
1026   The example
1027</t>
1028<figure><artwork type="example">
1029  Accept: audio/*; q=0.2, audio/basic
1030</artwork></figure>
1031<t>
1032   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
1033   type if it is the best available after an 80% mark-down in quality."
1034</t>
1035<t>
1036   If no Accept header field is present, then it is assumed that the
1037   client accepts all media types. If an Accept header field is present,
1038   and if the server cannot send a response which is acceptable
1039   according to the combined Accept field value, then the server &SHOULD;
1040   send a 406 (Not Acceptable) response.
1041</t>
1042<t>
1043   A more elaborate example is
1044</t>
1045<figure><artwork type="example">
1046  Accept: text/plain; q=0.5, text/html,
1047          text/x-dvi; q=0.8, text/x-c
1048</artwork></figure>
1049<t>
1050   Verbally, this would be interpreted as "text/html and text/x-c are
1051   the preferred media types, but if they do not exist, then send the
1052   text/x-dvi entity, and if that does not exist, send the text/plain
1053   entity."
1054</t>
1055<t>
1056   Media ranges can be overridden by more specific media ranges or
1057   specific media types. If more than one media range applies to a given
1058   type, the most specific reference has precedence. For example,
1059</t>
1060<figure><artwork type="example">
1061  Accept: text/*, text/html, text/html;level=1, */*
1062</artwork></figure>
1063<t>
1064   have the following precedence:
1065   <list style="numbers">
1066    <t>text/html;level=1</t>
1067    <t>text/html</t>
1068    <t>text/*</t>
1069    <t>*/*</t>
1070   </list>
1071</t>
1072<t>
1073   The media type quality factor associated with a given type is
1074   determined by finding the media range with the highest precedence
1075   which matches that type. For example,
1076</t>
1077<figure><artwork type="example">
1078  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1079          text/html;level=2;q=0.4, */*;q=0.5
1080</artwork></figure>
1081<t>
1082   would cause the following values to be associated:
1083</t>
1084<texttable align="left">
1085  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1086  <c>text/html;level=1</c>    <c>1</c>
1087  <c>text/html</c>            <c>0.7</c>
1088  <c>text/plain</c>           <c>0.3</c>
1089  <c>image/jpeg</c>           <c>0.5</c>
1090  <c>text/html;level=2</c>    <c>0.4</c>
1091  <c>text/html;level=3</c>    <c>0.7</c>
1092</texttable>
1093<t>
1094      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1095      values for certain media ranges. However, unless the user agent is
1096      a closed system which cannot interact with other rendering agents,
1097      this default set ought to be configurable by the user.
1098</t>
1099</section>
1100
1101<section title="Accept-Charset" anchor="header.accept-charset">
1102  <iref primary="true" item="Accept-Charset header" x:for-anchor=""/>
1103  <iref primary="true" item="Headers" subitem="Accept-Charset" x:for-anchor=""/>
1104  <x:anchor-alias value="Accept-Charset"/>
1105  <x:anchor-alias value="Accept-Charset-v"/>
1106<t>
1107   The "Accept-Charset" request-header field can be used by user agents to
1108   indicate what response character sets are acceptable. This field allows
1109   clients capable of understanding more comprehensive or special-purpose
1110   character sets to signal that capability to a server which is capable of
1111   representing documents in those character sets.
1112</t>
1113<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/>
1114  <x:ref>Accept-Charset</x:ref>   = "Accept-Charset" ":" <x:ref>OWS</x:ref>
1115          <x:ref>Accept-Charset-v</x:ref>
1116  <x:ref>Accept-Charset-v</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1117                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1118</artwork></figure>
1119<t>
1120   Character set values are described in <xref target="character.sets"/>. Each charset &MAY;
1121   be given an associated quality value which represents the user's
1122   preference for that charset. The default value is q=1. An example is
1123</t>
1124<figure><artwork type="example">
1125  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1126</artwork></figure>
1127<t>
1128   The special value "*", if present in the Accept-Charset field,
1129   matches every character set (including ISO-8859-1) which is not
1130   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1131   in an Accept-Charset field, then all character sets not explicitly
1132   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1133   a quality value of 1 if not explicitly mentioned.
1134</t>
1135<t>
1136   If no Accept-Charset header is present, the default is that any
1137   character set is acceptable. If an Accept-Charset header is present,
1138   and if the server cannot send a response which is acceptable
1139   according to the Accept-Charset header, then the server &SHOULD; send
1140   an error response with the 406 (Not Acceptable) status code, though
1141   the sending of an unacceptable response is also allowed.
1142</t>
1143</section>
1144
1145<section title="Accept-Encoding" anchor="header.accept-encoding">
1146  <iref primary="true" item="Accept-Encoding header" x:for-anchor=""/>
1147  <iref primary="true" item="Headers" subitem="Accept-Encoding" x:for-anchor=""/>
1148  <x:anchor-alias value="Accept-Encoding"/>
1149  <x:anchor-alias value="Accept-Encoding-v"/>
1150  <x:anchor-alias value="codings"/>
1151<t>
1152   The "Accept-Encoding" request-header field can be used by user agents to
1153   indicate what response content-codings (<xref target="content.codings"/>)
1154   are acceptable in the response.
1155</t>
1156<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"/>
1157  <x:ref>Accept-Encoding</x:ref>    = "Accept-Encoding" ":" <x:ref>OWS</x:ref>
1158                     <x:ref>Accept-Encoding-v</x:ref>
1159  <x:ref>Accept-Encoding-v</x:ref>  =
1160                     #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1161  <x:ref>codings</x:ref>            = ( <x:ref>content-coding</x:ref> / "*" )
1162</artwork></figure>
1163<t>
1164   Each codings value &MAY; be given an associated quality value which
1165   represents the preference for that encoding. The default value is q=1.
1166</t>
1167<t>
1168   Examples of its use are:
1169</t>
1170<figure><artwork type="example">
1171  Accept-Encoding: compress, gzip
1172  Accept-Encoding:
1173  Accept-Encoding: *
1174  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1175  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1176</artwork></figure>
1177<t>
1178   A server tests whether a content-coding is acceptable, according to
1179   an Accept-Encoding field, using these rules:
1180  <list style="numbers">
1181      <t>If the content-coding is one of the content-codings listed in
1182         the Accept-Encoding field, then it is acceptable, unless it is
1183         accompanied by a qvalue of 0. (As defined in &qvalue;, a
1184         qvalue of 0 means "not acceptable.")</t>
1185
1186      <t>The special "*" symbol in an Accept-Encoding field matches any
1187         available content-coding not explicitly listed in the header
1188         field.</t>
1189
1190      <t>If multiple content-codings are acceptable, then the acceptable
1191         content-coding with the highest non-zero qvalue is preferred.</t>
1192
1193      <t>The "identity" content-coding is always acceptable, unless
1194         specifically refused because the Accept-Encoding field includes
1195         "identity;q=0", or because the field includes "*;q=0" and does
1196         not explicitly include the "identity" content-coding. If the
1197         Accept-Encoding field-value is empty, then only the "identity"
1198         encoding is acceptable.</t>
1199  </list>
1200</t>
1201<t>
1202   If an Accept-Encoding field is present in a request, and if the
1203   server cannot send a response which is acceptable according to the
1204   Accept-Encoding header, then the server &SHOULD; send an error response
1205   with the 406 (Not Acceptable) status code.
1206</t>
1207<t>
1208   If no Accept-Encoding field is present in a request, the server &MAY;
1209   assume that the client will accept any content coding. In this case,
1210   if "identity" is one of the available content-codings, then the
1211   server &SHOULD; use the "identity" content-coding, unless it has
1212   additional information that a different content-coding is meaningful
1213   to the client.
1214</t>
1215<x:note>
1216  <t>
1217    <x:h>Note:</x:h> If the request does not include an Accept-Encoding field,
1218    and if the "identity" content-coding is unavailable, then
1219    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1220    "gzip" and "compress") are preferred; some older clients
1221    improperly display messages sent with other content-codings.  The
1222    server might also make this decision based on information about
1223    the particular user-agent or client.
1224  </t>
1225</x:note>
1226<x:note>
1227  <t>
1228    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1229    associated with content-codings. This means that qvalues will not
1230    work and are not permitted with x-gzip or x-compress.
1231  </t>
1232</x:note>
1233</section>
1234
1235<section title="Accept-Language" anchor="header.accept-language">
1236  <iref primary="true" item="Accept-Language header" x:for-anchor=""/>
1237  <iref primary="true" item="Headers" subitem="Accept-Language" x:for-anchor=""/>
1238  <x:anchor-alias value="Accept-Language"/>
1239  <x:anchor-alias value="Accept-Language-v"/>
1240  <x:anchor-alias value="language-range"/>
1241<t>
1242   The "Accept-Language" request-header field can be used by user agents to
1243   indicate the set of natural languages that are preferred in the response.
1244   Language tags are defined in <xref target="language.tags"/>.
1245</t>
1246<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"/>
1247  <x:ref>Accept-Language</x:ref>   = "Accept-Language" ":" <x:ref>OWS</x:ref>
1248                    <x:ref>Accept-Language-v</x:ref>
1249  <x:ref>Accept-Language-v</x:ref> =
1250                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1251  <x:ref>language-range</x:ref>    =
1252            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
1253</artwork></figure>
1254<t>
1255   Each language-range can be given an associated quality value which
1256   represents an estimate of the user's preference for the languages
1257   specified by that range. The quality value defaults to "q=1". For
1258   example,
1259</t>
1260<figure><artwork type="example">
1261  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1262</artwork></figure>
1263<t>
1264   would mean: "I prefer Danish, but will accept British English and
1265   other types of English."
1266   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
1267</t>
1268<t>
1269   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1270   several matching schemes. Implementations can offer the most appropriate
1271   matching scheme for their requirements.
1272</t>
1273<x:note>
1274  <t>
1275    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
1276    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1277    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
1278  </t>
1279</x:note>
1280<t>
1281   It might be contrary to the privacy expectations of the user to send
1282   an Accept-Language header with the complete linguistic preferences of
1283   the user in every request. For a discussion of this issue, see
1284   <xref target="privacy.issues.connected.to.accept.headers"/>.
1285</t>
1286<t>
1287   As intelligibility is highly dependent on the individual user, it is
1288   recommended that client applications make the choice of linguistic
1289   preference available to the user. If the choice is not made
1290   available, then the Accept-Language header field &MUST-NOT; be given in
1291   the request.
1292</t>
1293<x:note>
1294  <t>
1295    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1296    the user, we remind implementors of  the fact that users are not
1297    familiar with the details of language matching as described above,
1298    and should provide appropriate guidance. As an example, users
1299    might assume that on selecting "en-gb", they will be served any
1300    kind of English document if British English is not available. A
1301    user agent might suggest in such a case to add "en" to get the
1302    best matching behavior.
1303  </t>
1304</x:note>
1305</section>
1306
1307<section title="Content-Encoding" anchor="header.content-encoding">
1308  <iref primary="true" item="Content-Encoding header" x:for-anchor=""/>
1309  <iref primary="true" item="Headers" subitem="Content-Encoding" x:for-anchor=""/>
1310  <x:anchor-alias value="Content-Encoding"/>
1311  <x:anchor-alias value="Content-Encoding-v"/>
1312<t>
1313   The "Content-Encoding" entity-header field indicates what content-codings
1314   have been applied to the entity-body, and thus what decoding mechanisms
1315   must be applied in order to obtain the media-type referenced by the
1316   Content-Type header field. Content-Encoding is primarily used to allow a
1317   document to be compressed without losing the identity of its underlying
1318   media type.
1319</t>
1320<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/>
1321  <x:ref>Content-Encoding</x:ref>   = "Content-Encoding" ":" <x:ref>OWS</x:ref> <x:ref>Content-Encoding-v</x:ref>
1322  <x:ref>Content-Encoding-v</x:ref> = 1#<x:ref>content-coding</x:ref>
1323</artwork></figure>
1324<t>
1325   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1326</t>
1327<figure><artwork type="example">
1328  Content-Encoding: gzip
1329</artwork></figure>
1330<t>
1331   The content-coding is a characteristic of the entity identified by
1332   the Effective Request URI (&effective-request-uri;). Typically, the entity-body is stored with this
1333   encoding and is only decoded before rendering or analogous usage.
1334   However, a non-transparent proxy &MAY; modify the content-coding if the
1335   new coding is known to be acceptable to the recipient, unless the
1336   "no-transform" cache-control directive is present in the message.
1337</t>
1338<t>
1339   If the content-coding of an entity is not "identity", then the
1340   response &MUST; include a Content-Encoding entity-header (<xref target="header.content-encoding"/>)
1341   that lists the non-identity content-coding(s) used.
1342</t>
1343<t>
1344   If the content-coding of an entity in a request message is not
1345   acceptable to the origin server, the server &SHOULD; respond with a
1346   status code of 415 (Unsupported Media Type).
1347</t>
1348<t>
1349   If multiple encodings have been applied to an entity, the content
1350   codings &MUST; be listed in the order in which they were applied.
1351   Additional information about the encoding parameters &MAY; be provided
1352   by other entity-header fields not defined by this specification.
1353</t>
1354</section>
1355
1356<section title="Content-Language" anchor="header.content-language">
1357  <iref primary="true" item="Content-Language header" x:for-anchor=""/>
1358  <iref primary="true" item="Headers" subitem="Content-Language" x:for-anchor=""/>
1359  <x:anchor-alias value="Content-Language"/>
1360  <x:anchor-alias value="Content-Language-v"/>
1361<t>
1362   The "Content-Language" entity-header field describes the natural
1363   language(s) of the intended audience for the entity. Note that this might
1364   not be equivalent to all the languages used within the entity-body.
1365</t>
1366<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/>
1367  <x:ref>Content-Language</x:ref>   = "Content-Language" ":" <x:ref>OWS</x:ref> <x:ref>Content-Language-v</x:ref>
1368  <x:ref>Content-Language-v</x:ref> = 1#<x:ref>language-tag</x:ref>
1369</artwork></figure>
1370<t>
1371   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1372   Content-Language is to allow a user to identify and differentiate
1373   entities according to the user's own preferred language. Thus, if the
1374   body content is intended only for a Danish-literate audience, the
1375   appropriate field is
1376</t>
1377<figure><artwork type="example">
1378  Content-Language: da
1379</artwork></figure>
1380<t>
1381   If no Content-Language is specified, the default is that the content
1382   is intended for all language audiences. This might mean that the
1383   sender does not consider it to be specific to any natural language,
1384   or that the sender does not know for which language it is intended.
1385</t>
1386<t>
1387   Multiple languages &MAY; be listed for content that is intended for
1388   multiple audiences. For example, a rendition of the "Treaty of
1389   Waitangi," presented simultaneously in the original Maori and English
1390   versions, would call for
1391</t>
1392<figure><artwork type="example">
1393  Content-Language: mi, en
1394</artwork></figure>
1395<t>
1396   However, just because multiple languages are present within an entity
1397   does not mean that it is intended for multiple linguistic audiences.
1398   An example would be a beginner's language primer, such as "A First
1399   Lesson in Latin," which is clearly intended to be used by an
1400   English-literate audience. In this case, the Content-Language would
1401   properly only include "en".
1402</t>
1403<t>
1404   Content-Language &MAY; be applied to any media type -- it is not
1405   limited to textual documents.
1406</t>
1407</section>
1408
1409<section title="Content-Location" anchor="header.content-location">
1410  <iref primary="true" item="Content-Location header" x:for-anchor=""/>
1411  <iref primary="true" item="Headers" subitem="Content-Location" x:for-anchor=""/>
1412  <x:anchor-alias value="Content-Location"/>
1413  <x:anchor-alias value="Content-Location-v"/>
1414<t>
1415   The "Content-Location" header field supplies a URI that can be used
1416   as a specific identifier for the representation in this message.
1417   In other words, if one were to perform a GET on this URI at the time
1418   of this message's generation, then a 200 response would contain the
1419   same representation that is enclosed as payload in this message.
1420</t>
1421<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/>
1422  <x:ref>Content-Location</x:ref>   = "Content-Location" ":" <x:ref>OWS</x:ref>
1423                    <x:ref>Content-Location-v</x:ref>
1424  <x:ref>Content-Location-v</x:ref> =
1425                    <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
1426</artwork></figure>
1427<t>
1428   The Content-Location value is not a replacement for the Effective
1429   Request URI (&effective-request-uri;).  It is representation metadata.
1430   It has the same syntax and semantics as the header field of the same name
1431   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
1432   However, its appearance in an HTTP message has some special implications
1433   for HTTP recipients.
1434</t>
1435<t>
1436   If Content-Location is included in a response message and its value
1437   is the same as the Effective Request URI, then the response payload
1438   &SHOULD; be considered the current representation of that resource.
1439   For a GET or HEAD request, this is the same as the default semantics
1440   when no Content-Location is provided by the server.  For a state-changing
1441   method like PUT or POST, it implies that the server's response contains
1442   the new representation of that resource, thereby distinguishing it from
1443   representations that might only report about the action (e.g., "It worked!").
1444   This allows authoring applications to update their local copies without
1445   the need for a subsequent GET request.
1446</t>
1447<t>
1448   If Content-Location is included in a response message and its value
1449   differs from the Effective Request URI, then the origin server is
1450   informing recipients that this representation has its own, presumably
1451   more specific, identifier.  For a GET or HEAD request, this is an
1452   indication that the Effective Request URI identifies a resource that
1453   is subject to content negotiation and the representation selected for
1454   this response can also be found at the identified URI.  For other
1455   methods, such a Content-Location indicates that this representation
1456   contains a report on the action's status and the same report is
1457   available (for future access with GET) at the given URI.  For
1458   example, a purchase transaction made via the POST method may
1459   include a receipt document as the payload of the 200 response;
1460   the Content-Location value provides an identifier for retrieving
1461   a copy of that same receipt in the future.
1462</t>
1463<t>
1464   If Content-Location is included in a request message, then it &MAY;
1465   be interpreted by the origin server as an indication of where the
1466   user agent originally obtained the content of the enclosed
1467   representation (prior to any subsequent modification of the content
1468   by that user agent).  In other words, the user agent is providing
1469   the same representation metadata that it received with the original
1470   representation.  However, such interpretation &MUST-NOT; be used to
1471   alter the semantics of the method requested by the client.  For
1472   example, if a client makes a PUT request on a negotiated resource
1473   and the origin server accepts that PUT (without redirection), then the
1474   new set of values for that resource is expected to be consistent with
1475   the one representation supplied in that PUT; the Content-Location
1476   cannot be used as a form of reverse content selection that
1477   identifies only one of the negotiated representations to be updated.
1478   If the user agent had wanted the latter semantics, it would have applied
1479   the PUT directly to the Content-Location URI.
1480</t>
1481<t>
1482   A Content-Location field received in a request message is transitory
1483   information that &SHOULD-NOT; be saved with other representation
1484   metadata for use in later responses.  The Content-Location's value
1485   might be saved for use in other contexts, such as within source links
1486   or other metadata.
1487</t>
1488<t>
1489   A cache cannot assume that a representation with a Content-Location
1490   different from the URI used to retrieve it can be used to respond to
1491   later requests on that Content-Location URI.
1492</t>
1493<t>
1494   If the Content-Location value is a partial URI, it is
1495   interpreted relative to the Effective Request URI.
1496</t>
1497</section>
1498
1499<section title="Content-MD5" anchor="header.content-md5">
1500  <iref primary="true" item="Content-MD5 header" x:for-anchor=""/>
1501  <iref primary="true" item="Headers" subitem="Content-MD5" x:for-anchor=""/>
1502  <x:anchor-alias value="Content-MD5"/>
1503  <x:anchor-alias value="Content-MD5-v"/>
1504<t>
1505   The "Content-MD5" entity-header field, as defined in <xref target="RFC1864"/>, is
1506   an MD5 digest of the entity-body that provides an end-to-end message
1507   integrity check (MIC) of the entity-body. Note that a MIC is good for
1508   detecting accidental modification of the entity-body in transit, but is not
1509   proof against malicious attacks.
1510</t>
1511<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/>
1512  <x:ref>Content-MD5</x:ref>   = "Content-MD5" ":" <x:ref>OWS</x:ref> <x:ref>Content-MD5-v</x:ref>
1513  <x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per <xref target="RFC1864"/>&gt;
1514</artwork></figure>
1515<t>
1516   The Content-MD5 header field &MAY; be generated by an origin server or
1517   client to function as an integrity check of the entity-body. Only
1518   origin servers or clients &MAY; generate the Content-MD5 header field;
1519   proxies and gateways &MUST-NOT; generate it, as this would defeat its
1520   value as an end-to-end integrity check. Any recipient of the entity-body,
1521   including gateways and proxies, &MAY; check that the digest value
1522   in this header field matches that of the entity-body as received.
1523</t>
1524<t>
1525   The MD5 digest is computed based on the content of the entity-body,
1526   including any content-coding that has been applied, but not including
1527   any transfer-encoding applied to the message-body. If the message is
1528   received with a transfer-encoding, that encoding &MUST; be removed
1529   prior to checking the Content-MD5 value against the received entity.
1530</t>
1531<t>
1532   This has the result that the digest is computed on the octets of the
1533   entity-body exactly as, and in the order that, they would be sent if
1534   no transfer-encoding were being applied.
1535</t>
1536<t>
1537   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1538   composite media-types (e.g., multipart/* and message/rfc822), but
1539   this does not change how the digest is computed as defined in the
1540   preceding paragraph.
1541</t>
1542<t>
1543   There are several consequences of this. The entity-body for composite
1544   types &MAY; contain many body-parts, each with its own MIME and HTTP
1545   headers (including Content-MD5, Content-Transfer-Encoding, and
1546   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1547   or Content-Encoding header, it is assumed that the content
1548   of the body-part has had the encoding applied, and the body-part is
1549   included in the Content-MD5 digest as is -- i.e., after the
1550   application. The Transfer-Encoding header field is not allowed within
1551   body-parts.
1552</t>
1553<t>
1554   Conversion of all line breaks to CRLF &MUST-NOT; be done before
1555   computing or checking the digest: the line break convention used in
1556   the text actually transmitted &MUST; be left unaltered when computing
1557   the digest.
1558</t>
1559<x:note>
1560  <t>
1561    <x:h>Note:</x:h> While the definition of Content-MD5 is exactly the same for
1562    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1563    in which the application of Content-MD5 to HTTP entity-bodies
1564    differs from its application to MIME entity-bodies. One is that
1565    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1566    does use Transfer-Encoding and Content-Encoding. Another is that
1567    HTTP more frequently uses binary content types than MIME, so it is
1568    worth noting that, in such cases, the byte order used to compute
1569    the digest is the transmission byte order defined for the type.
1570    Lastly, HTTP allows transmission of text types with any of several
1571    line break conventions and not just the canonical form using CRLF.
1572  </t>
1573</x:note>
1574</section>
1575
1576<section title="Content-Type" anchor="header.content-type">
1577  <iref primary="true" item="Content-Type header" x:for-anchor=""/>
1578  <iref primary="true" item="Headers" subitem="Content-Type" x:for-anchor=""/>
1579  <x:anchor-alias value="Content-Type"/>
1580  <x:anchor-alias value="Content-Type-v"/>
1581<t>
1582   The "Content-Type" entity-header field indicates the media type of the
1583   entity-body. In the case of responses to the HEAD method, the media type is
1584   that which would have been sent had the request been a GET.
1585</t>
1586<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/>
1587  <x:ref>Content-Type</x:ref>   = "Content-Type" ":" <x:ref>OWS</x:ref> <x:ref>Content-Type-v</x:ref>
1588  <x:ref>Content-Type-v</x:ref> = <x:ref>media-type</x:ref>
1589</artwork></figure>
1590<t>
1591   Media types are defined in <xref target="media.types"/>. An example of the field is
1592</t>
1593<figure><artwork type="example">
1594  Content-Type: text/html; charset=ISO-8859-4
1595</artwork></figure>
1596<t>
1597   Further discussion of methods for identifying the media type of an
1598   entity is provided in <xref target="type"/>.
1599</t>
1600</section>
1601
1602</section>
1603
1604<section title="IANA Considerations" anchor="IANA.considerations">
1605<section title="Message Header Registration" anchor="message.header.registration">
1606<t>
1607   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
1608   with the permanent registrations below (see <xref target="RFC3864"/>):
1609</t>
1610<?BEGININC p3-payload.iana-headers ?>
1611<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1612<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1613   <ttcol>Header Field Name</ttcol>
1614   <ttcol>Protocol</ttcol>
1615   <ttcol>Status</ttcol>
1616   <ttcol>Reference</ttcol>
1617
1618   <c>Accept</c>
1619   <c>http</c>
1620   <c>standard</c>
1621   <c>
1622      <xref target="header.accept"/>
1623   </c>
1624   <c>Accept-Charset</c>
1625   <c>http</c>
1626   <c>standard</c>
1627   <c>
1628      <xref target="header.accept-charset"/>
1629   </c>
1630   <c>Accept-Encoding</c>
1631   <c>http</c>
1632   <c>standard</c>
1633   <c>
1634      <xref target="header.accept-encoding"/>
1635   </c>
1636   <c>Accept-Language</c>
1637   <c>http</c>
1638   <c>standard</c>
1639   <c>
1640      <xref target="header.accept-language"/>
1641   </c>
1642   <c>Content-Disposition</c>
1643   <c>http</c>
1644   <c/>
1645   <c>
1646      <xref target="content-disposition"/>
1647   </c>
1648   <c>Content-Encoding</c>
1649   <c>http</c>
1650   <c>standard</c>
1651   <c>
1652      <xref target="header.content-encoding"/>
1653   </c>
1654   <c>Content-Language</c>
1655   <c>http</c>
1656   <c>standard</c>
1657   <c>
1658      <xref target="header.content-language"/>
1659   </c>
1660   <c>Content-Location</c>
1661   <c>http</c>
1662   <c>standard</c>
1663   <c>
1664      <xref target="header.content-location"/>
1665   </c>
1666   <c>Content-MD5</c>
1667   <c>http</c>
1668   <c>standard</c>
1669   <c>
1670      <xref target="header.content-md5"/>
1671   </c>
1672   <c>Content-Type</c>
1673   <c>http</c>
1674   <c>standard</c>
1675   <c>
1676      <xref target="header.content-type"/>
1677   </c>
1678   <c>MIME-Version</c>
1679   <c>http</c>
1680   <c/>
1681   <c>
1682      <xref target="mime-version"/>
1683   </c>
1684</texttable>
1685<!--(END)-->
1686<?ENDINC p3-payload.iana-headers ?>
1687<t>
1688   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1689</t>
1690</section>
1691
1692<section title="Content Coding Registry" anchor="content.coding.registration">
1693<t>
1694   The registration procedure for HTTP Content Codings is now defined
1695   by <xref target="content.coding.registry"/> of this document.
1696</t>
1697<t>
1698   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1699   should be updated with the registration below:
1700</t>
1701<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1702   <ttcol>Name</ttcol>
1703   <ttcol>Description</ttcol>
1704   <ttcol>Reference</ttcol>
1705   <c>compress</c>
1706   <c>UNIX "compress" program method</c>
1707   <c>
1708      &compress-coding;
1709   </c>
1710   <c>deflate</c>
1711   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1712   the "zlib" data format (<xref target="RFC1950"/>)
1713   </c>
1714   <c>
1715      &deflate-coding;
1716   </c>
1717   <c>gzip</c>
1718   <c>Same as GNU zip <xref target="RFC1952"/></c>
1719   <c>
1720      &gzip-coding;
1721   </c>
1722   <c>identity</c>
1723   <c>No transformation</c>
1724   <c>
1725      <xref target="content.codings"/>
1726   </c>
1727</texttable>
1728</section>
1729
1730</section>
1731
1732<section title="Security Considerations" anchor="security.considerations">
1733<t>
1734   This section is meant to inform application developers, information
1735   providers, and users of the security limitations in HTTP/1.1 as
1736   described by this document. The discussion does not include
1737   definitive solutions to the problems revealed, though it does make
1738   some suggestions for reducing security risks.
1739</t>
1740
1741<section title="Privacy Issues Connected to Accept Headers" anchor="privacy.issues.connected.to.accept.headers">
1742<t>
1743   Accept request-headers can reveal information about the user to all
1744   servers which are accessed. The Accept-Language header in particular
1745   can reveal information the user would consider to be of a private
1746   nature, because the understanding of particular languages is often
1747   strongly correlated to the membership of a particular ethnic group.
1748   User agents which offer the option to configure the contents of an
1749   Accept-Language header to be sent in every request are strongly
1750   encouraged to let the configuration process include a message which
1751   makes the user aware of the loss of privacy involved.
1752</t>
1753<t>
1754   An approach that limits the loss of privacy would be for a user agent
1755   to omit the sending of Accept-Language headers by default, and to ask
1756   the user whether or not to start sending Accept-Language headers to a
1757   server if it detects, by looking for any Vary response-header fields
1758   generated by the server, that such sending could improve the quality
1759   of service.
1760</t>
1761<t>
1762   Elaborate user-customized accept header fields sent in every request,
1763   in particular if these include quality values, can be used by servers
1764   as relatively reliable and long-lived user identifiers. Such user
1765   identifiers would allow content providers to do click-trail tracking,
1766   and would allow collaborating content providers to match cross-server
1767   click-trails or form submissions of individual users. Note that for
1768   many users not behind a proxy, the network address of the host
1769   running the user agent will also serve as a long-lived user
1770   identifier. In environments where proxies are used to enhance
1771   privacy, user agents ought to be conservative in offering accept
1772   header configuration options to end users. As an extreme privacy
1773   measure, proxies could filter the accept headers in relayed requests.
1774   General purpose user agents which provide a high degree of header
1775   configurability &SHOULD; warn users about the loss of privacy which can
1776   be involved.
1777</t>
1778</section>
1779
1780<section title="Content-Disposition Issues" anchor="content-disposition.issues">
1781<t>
1782   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
1783   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1784   serious security considerations. Content-Disposition is not part of
1785   the HTTP standard, but since it is widely implemented, we are
1786   documenting its use and risks for implementors. See <xref target="RFC2183" x:fmt="of" x:sec="5"/>
1787   for details.
1788</t>
1789</section>
1790
1791</section>
1792
1793<section title="Acknowledgments" anchor="ack">
1794</section>
1795</middle>
1796<back>
1797
1798<references title="Normative References">
1799
1800<reference anchor="ISO-8859-1">
1801  <front>
1802    <title>
1803     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1804    </title>
1805    <author>
1806      <organization>International Organization for Standardization</organization>
1807    </author>
1808    <date year="1998"/>
1809  </front>
1810  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1811</reference>
1812
1813<reference anchor="Part1">
1814  <front>
1815    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1816    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1817      <organization abbrev="Day Software">Day Software</organization>
1818      <address><email>fielding@gbiv.com</email></address>
1819    </author>
1820    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1821      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1822      <address><email>jg@freedesktop.org</email></address>
1823    </author>
1824    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1825      <organization abbrev="HP">Hewlett-Packard Company</organization>
1826      <address><email>JeffMogul@acm.org</email></address>
1827    </author>
1828    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1829      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1830      <address><email>henrikn@microsoft.com</email></address>
1831    </author>
1832    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1833      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1834      <address><email>LMM@acm.org</email></address>
1835    </author>
1836    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1837      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1838      <address><email>paulle@microsoft.com</email></address>
1839    </author>
1840    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1841      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1842      <address><email>timbl@w3.org</email></address>
1843    </author>
1844    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1845      <organization abbrev="W3C">World Wide Web Consortium</organization>
1846      <address><email>ylafon@w3.org</email></address>
1847    </author>
1848    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1849      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1850      <address><email>julian.reschke@greenbytes.de</email></address>
1851    </author>
1852    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1853  </front>
1854  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1855  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1856</reference>
1857
1858<reference anchor="Part2">
1859  <front>
1860    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1861    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1862      <organization abbrev="Day Software">Day Software</organization>
1863      <address><email>fielding@gbiv.com</email></address>
1864    </author>
1865    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1866      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1867      <address><email>jg@freedesktop.org</email></address>
1868    </author>
1869    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1870      <organization abbrev="HP">Hewlett-Packard Company</organization>
1871      <address><email>JeffMogul@acm.org</email></address>
1872    </author>
1873    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1874      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1875      <address><email>henrikn@microsoft.com</email></address>
1876    </author>
1877    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1878      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1879      <address><email>LMM@acm.org</email></address>
1880    </author>
1881    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1882      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1883      <address><email>paulle@microsoft.com</email></address>
1884    </author>
1885    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1886      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1887      <address><email>timbl@w3.org</email></address>
1888    </author>
1889    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1890      <organization abbrev="W3C">World Wide Web Consortium</organization>
1891      <address><email>ylafon@w3.org</email></address>
1892    </author>
1893    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1894      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1895      <address><email>julian.reschke@greenbytes.de</email></address>
1896    </author>
1897    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1898  </front>
1899  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1900  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1901</reference>
1902
1903<reference anchor="Part4">
1904  <front>
1905    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1906    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1907      <organization abbrev="Day Software">Day Software</organization>
1908      <address><email>fielding@gbiv.com</email></address>
1909    </author>
1910    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1911      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1912      <address><email>jg@freedesktop.org</email></address>
1913    </author>
1914    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1915      <organization abbrev="HP">Hewlett-Packard Company</organization>
1916      <address><email>JeffMogul@acm.org</email></address>
1917    </author>
1918    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1919      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1920      <address><email>henrikn@microsoft.com</email></address>
1921    </author>
1922    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1923      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1924      <address><email>LMM@acm.org</email></address>
1925    </author>
1926    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1927      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1928      <address><email>paulle@microsoft.com</email></address>
1929    </author>
1930    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1931      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1932      <address><email>timbl@w3.org</email></address>
1933    </author>
1934    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1935      <organization abbrev="W3C">World Wide Web Consortium</organization>
1936      <address><email>ylafon@w3.org</email></address>
1937    </author>
1938    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1939      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1940      <address><email>julian.reschke@greenbytes.de</email></address>
1941    </author>
1942    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1943  </front>
1944  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1945  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1946</reference>
1947
1948<reference anchor="Part5">
1949  <front>
1950    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1951    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1952      <organization abbrev="Day Software">Day Software</organization>
1953      <address><email>fielding@gbiv.com</email></address>
1954    </author>
1955    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1956      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1957      <address><email>jg@freedesktop.org</email></address>
1958    </author>
1959    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1960      <organization abbrev="HP">Hewlett-Packard Company</organization>
1961      <address><email>JeffMogul@acm.org</email></address>
1962    </author>
1963    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1964      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1965      <address><email>henrikn@microsoft.com</email></address>
1966    </author>
1967    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1968      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1969      <address><email>LMM@acm.org</email></address>
1970    </author>
1971    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1972      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1973      <address><email>paulle@microsoft.com</email></address>
1974    </author>
1975    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1976      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1977      <address><email>timbl@w3.org</email></address>
1978    </author>
1979    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1980      <organization abbrev="W3C">World Wide Web Consortium</organization>
1981      <address><email>ylafon@w3.org</email></address>
1982    </author>
1983    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1984      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1985      <address><email>julian.reschke@greenbytes.de</email></address>
1986    </author>
1987    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1988  </front>
1989  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1990  <x:source href="p5-range.xml" basename="p5-range"/>
1991</reference>
1992
1993<reference anchor="Part6">
1994  <front>
1995    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1996    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1997      <organization abbrev="Day Software">Day Software</organization>
1998      <address><email>fielding@gbiv.com</email></address>
1999    </author>
2000    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2001      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2002      <address><email>jg@freedesktop.org</email></address>
2003    </author>
2004    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2005      <organization abbrev="HP">Hewlett-Packard Company</organization>
2006      <address><email>JeffMogul@acm.org</email></address>
2007    </author>
2008    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2009      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2010      <address><email>henrikn@microsoft.com</email></address>
2011    </author>
2012    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2013      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2014      <address><email>LMM@acm.org</email></address>
2015    </author>
2016    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2017      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2018      <address><email>paulle@microsoft.com</email></address>
2019    </author>
2020    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2021      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2022      <address><email>timbl@w3.org</email></address>
2023    </author>
2024    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2025      <organization abbrev="W3C">World Wide Web Consortium</organization>
2026      <address><email>ylafon@w3.org</email></address>
2027    </author>
2028    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2029      <address><email>mnot@mnot.net</email></address>
2030    </author>
2031    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2032      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2033      <address><email>julian.reschke@greenbytes.de</email></address>
2034    </author>
2035    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2036  </front>
2037  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2038  <x:source href="p6-cache.xml" basename="p6-cache"/>
2039</reference>
2040
2041<reference anchor="RFC1864">
2042  <front>
2043    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
2044    <author initials="J." surname="Myers" fullname="John G. Myers">
2045      <organization>Carnegie Mellon University</organization>
2046      <address><email>jgm+@cmu.edu</email></address>
2047    </author>
2048    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2049      <organization>Dover Beach Consulting, Inc.</organization>
2050      <address><email>mrose@dbc.mtview.ca.us</email></address>
2051    </author>
2052    <date month="October" year="1995"/>
2053  </front>
2054  <seriesInfo name="RFC" value="1864"/>
2055</reference>
2056
2057<reference anchor="RFC1950">
2058  <front>
2059    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2060    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2061      <organization>Aladdin Enterprises</organization>
2062      <address><email>ghost@aladdin.com</email></address>
2063    </author>
2064    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2065    <date month="May" year="1996"/>
2066  </front>
2067  <seriesInfo name="RFC" value="1950"/>
2068  <annotation>
2069    RFC 1950 is an Informational RFC, thus it may be less stable than
2070    this specification. On the other hand, this downward reference was
2071    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2072    therefore it is unlikely to cause problems in practice. See also
2073    <xref target="BCP97"/>.
2074  </annotation>
2075</reference>
2076
2077<reference anchor="RFC1951">
2078  <front>
2079    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2080    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2081      <organization>Aladdin Enterprises</organization>
2082      <address><email>ghost@aladdin.com</email></address>
2083    </author>
2084    <date month="May" year="1996"/>
2085  </front>
2086  <seriesInfo name="RFC" value="1951"/>
2087  <annotation>
2088    RFC 1951 is an Informational RFC, thus it may be less stable than
2089    this specification. On the other hand, this downward reference was
2090    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2091    therefore it is unlikely to cause problems in practice. See also
2092    <xref target="BCP97"/>.
2093  </annotation>
2094</reference>
2095
2096<reference anchor="RFC1952">
2097  <front>
2098    <title>GZIP file format specification version 4.3</title>
2099    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2100      <organization>Aladdin Enterprises</organization>
2101      <address><email>ghost@aladdin.com</email></address>
2102    </author>
2103    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2104      <address><email>gzip@prep.ai.mit.edu</email></address>
2105    </author>
2106    <author initials="M." surname="Adler" fullname="Mark Adler">
2107      <address><email>madler@alumni.caltech.edu</email></address>
2108    </author>
2109    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2110      <address><email>ghost@aladdin.com</email></address>
2111    </author>
2112    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2113      <address><email>randeg@alumni.rpi.edu</email></address>
2114    </author>
2115    <date month="May" year="1996"/>
2116  </front>
2117  <seriesInfo name="RFC" value="1952"/>
2118  <annotation>
2119    RFC 1952 is an Informational RFC, thus it may be less stable than
2120    this specification. On the other hand, this downward reference was
2121    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2122    therefore it is unlikely to cause problems in practice. See also
2123    <xref target="BCP97"/>.
2124  </annotation>
2125</reference>
2126
2127<reference anchor="RFC2045">
2128  <front>
2129    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2130    <author initials="N." surname="Freed" fullname="Ned Freed">
2131      <organization>Innosoft International, Inc.</organization>
2132      <address><email>ned@innosoft.com</email></address>
2133    </author>
2134    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2135      <organization>First Virtual Holdings</organization>
2136      <address><email>nsb@nsb.fv.com</email></address>
2137    </author>
2138    <date month="November" year="1996"/>
2139  </front>
2140  <seriesInfo name="RFC" value="2045"/>
2141</reference>
2142
2143<reference anchor="RFC2046">
2144  <front>
2145    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2146    <author initials="N." surname="Freed" fullname="Ned Freed">
2147      <organization>Innosoft International, Inc.</organization>
2148      <address><email>ned@innosoft.com</email></address>
2149    </author>
2150    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2151      <organization>First Virtual Holdings</organization>
2152      <address><email>nsb@nsb.fv.com</email></address>
2153    </author>
2154    <date month="November" year="1996"/>
2155  </front>
2156  <seriesInfo name="RFC" value="2046"/>
2157</reference>
2158
2159<reference anchor="RFC2119">
2160  <front>
2161    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2162    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2163      <organization>Harvard University</organization>
2164      <address><email>sob@harvard.edu</email></address>
2165    </author>
2166    <date month="March" year="1997"/>
2167  </front>
2168  <seriesInfo name="BCP" value="14"/>
2169  <seriesInfo name="RFC" value="2119"/>
2170</reference>
2171
2172<reference anchor='RFC4647'>
2173  <front>
2174    <title>Matching of Language Tags</title>
2175    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
2176      <organization>Yahoo! Inc.</organization>
2177      <address><email>addison@inter-locale.com</email></address>
2178    </author>
2179    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
2180      <organization>Google</organization>
2181      <address><email>mark.davis@macchiato.com</email></address>
2182    </author>
2183    <date year='2006' month='September' />
2184  </front>
2185  <seriesInfo name='BCP' value='47' />
2186  <seriesInfo name='RFC' value='4647' />
2187</reference>
2188
2189<reference anchor="RFC5234">
2190  <front>
2191    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2192    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2193      <organization>Brandenburg InternetWorking</organization>
2194      <address>
2195        <email>dcrocker@bbiw.net</email>
2196      </address> 
2197    </author>
2198    <author initials="P." surname="Overell" fullname="Paul Overell">
2199      <organization>THUS plc.</organization>
2200      <address>
2201        <email>paul.overell@thus.net</email>
2202      </address>
2203    </author>
2204    <date month="January" year="2008"/>
2205  </front>
2206  <seriesInfo name="STD" value="68"/>
2207  <seriesInfo name="RFC" value="5234"/>
2208</reference>
2209
2210<reference anchor='RFC5646'>
2211  <front>
2212    <title>Tags for Identifying Languages</title>
2213    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2214      <organization>Lab126</organization>
2215      <address><email>addison@inter-locale.com</email></address>
2216    </author>
2217    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2218      <organization>Google</organization>
2219      <address><email>mark.davis@google.com</email></address>
2220    </author>
2221    <date month='September' year='2009' />
2222  </front>
2223  <seriesInfo name='BCP' value='47' />
2224  <seriesInfo name='RFC' value='5646' />
2225</reference>
2226
2227</references>
2228
2229<references title="Informative References">
2230
2231<reference anchor="RFC1945">
2232  <front>
2233    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2234    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2235      <organization>MIT, Laboratory for Computer Science</organization>
2236      <address><email>timbl@w3.org</email></address>
2237    </author>
2238    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2239      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2240      <address><email>fielding@ics.uci.edu</email></address>
2241    </author>
2242    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2243      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2244      <address><email>frystyk@w3.org</email></address>
2245    </author>
2246    <date month="May" year="1996"/>
2247  </front>
2248  <seriesInfo name="RFC" value="1945"/>
2249</reference>
2250
2251<reference anchor="RFC2049">
2252  <front>
2253    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2254    <author initials="N." surname="Freed" fullname="Ned Freed">
2255      <organization>Innosoft International, Inc.</organization>
2256      <address><email>ned@innosoft.com</email></address>
2257    </author>
2258    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2259      <organization>First Virtual Holdings</organization>
2260      <address><email>nsb@nsb.fv.com</email></address>
2261    </author>
2262    <date month="November" year="1996"/>
2263  </front>
2264  <seriesInfo name="RFC" value="2049"/>
2265</reference>
2266
2267<reference anchor="RFC2068">
2268  <front>
2269    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2270    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2271      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2272      <address><email>fielding@ics.uci.edu</email></address>
2273    </author>
2274    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2275      <organization>MIT Laboratory for Computer Science</organization>
2276      <address><email>jg@w3.org</email></address>
2277    </author>
2278    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2279      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2280      <address><email>mogul@wrl.dec.com</email></address>
2281    </author>
2282    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2283      <organization>MIT Laboratory for Computer Science</organization>
2284      <address><email>frystyk@w3.org</email></address>
2285    </author>
2286    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2287      <organization>MIT Laboratory for Computer Science</organization>
2288      <address><email>timbl@w3.org</email></address>
2289    </author>
2290    <date month="January" year="1997"/>
2291  </front>
2292  <seriesInfo name="RFC" value="2068"/>
2293</reference>
2294
2295<reference anchor="RFC2076">
2296  <front>
2297    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2298    <author initials="J." surname="Palme" fullname="Jacob Palme">
2299      <organization>Stockholm University/KTH</organization>
2300      <address><email>jpalme@dsv.su.se</email></address>
2301    </author>
2302    <date month="February" year="1997"/>
2303  </front>
2304  <seriesInfo name="RFC" value="2076"/>
2305</reference>
2306
2307<reference anchor="RFC2183">
2308  <front>
2309    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2310    <author initials="R." surname="Troost" fullname="Rens Troost">
2311      <organization>New Century Systems</organization>
2312      <address><email>rens@century.com</email></address>
2313    </author>
2314    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2315      <organization>QUALCOMM Incorporated</organization>
2316      <address><email>sdorner@qualcomm.com</email></address>
2317    </author>
2318    <author initials="K." surname="Moore" fullname="Keith Moore">
2319      <organization>Department of Computer Science</organization>
2320      <address><email>moore@cs.utk.edu</email></address>
2321    </author>
2322    <date month="August" year="1997"/>
2323  </front>
2324  <seriesInfo name="RFC" value="2183"/>
2325</reference>
2326
2327<reference anchor="RFC2277">
2328  <front>
2329    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2330    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2331      <organization>UNINETT</organization>
2332      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2333    </author>
2334    <date month="January" year="1998"/>
2335  </front>
2336  <seriesInfo name="BCP" value="18"/>
2337  <seriesInfo name="RFC" value="2277"/>
2338</reference>
2339
2340<reference anchor='RFC2295'>
2341  <front>
2342    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2343    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2344      <organization>Technische Universiteit Eindhoven</organization>
2345      <address>
2346        <email>koen@win.tue.nl</email>
2347      </address>
2348    </author>
2349    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2350      <organization>Hewlett-Packard Company</organization>
2351      <address>
2352        <email>mutz@hpl.hp.com</email>
2353      </address>
2354    </author>
2355    <date year='1998' month='March'/>
2356  </front>
2357  <seriesInfo name='RFC' value='2295'/>
2358</reference>
2359
2360<reference anchor="RFC2388">
2361  <front>
2362    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2363    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2364      <organization>Xerox Palo Alto Research Center</organization>
2365      <address><email>masinter@parc.xerox.com</email></address>
2366    </author>
2367    <date year="1998" month="August"/>
2368  </front>
2369  <seriesInfo name="RFC" value="2388"/>
2370</reference>
2371
2372<reference anchor="RFC2557">
2373  <front>
2374    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2375    <author initials="F." surname="Palme" fullname="Jacob Palme">
2376      <organization>Stockholm University and KTH</organization>
2377      <address><email>jpalme@dsv.su.se</email></address>
2378    </author>
2379    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2380      <organization>Microsoft Corporation</organization>
2381      <address><email>alexhop@microsoft.com</email></address>
2382    </author>
2383    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2384      <organization>Lotus Development Corporation</organization>
2385      <address><email>Shelness@lotus.com</email></address>
2386    </author>
2387    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2388      <address><email>stef@nma.com</email></address>
2389    </author>
2390    <date year="1999" month="March"/>
2391  </front>
2392  <seriesInfo name="RFC" value="2557"/>
2393</reference>
2394
2395<reference anchor="RFC2616">
2396  <front>
2397    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2398    <author initials="R." surname="Fielding" fullname="R. Fielding">
2399      <organization>University of California, Irvine</organization>
2400      <address><email>fielding@ics.uci.edu</email></address>
2401    </author>
2402    <author initials="J." surname="Gettys" fullname="J. Gettys">
2403      <organization>W3C</organization>
2404      <address><email>jg@w3.org</email></address>
2405    </author>
2406    <author initials="J." surname="Mogul" fullname="J. Mogul">
2407      <organization>Compaq Computer Corporation</organization>
2408      <address><email>mogul@wrl.dec.com</email></address>
2409    </author>
2410    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2411      <organization>MIT Laboratory for Computer Science</organization>
2412      <address><email>frystyk@w3.org</email></address>
2413    </author>
2414    <author initials="L." surname="Masinter" fullname="L. Masinter">
2415      <organization>Xerox Corporation</organization>
2416      <address><email>masinter@parc.xerox.com</email></address>
2417    </author>
2418    <author initials="P." surname="Leach" fullname="P. Leach">
2419      <organization>Microsoft Corporation</organization>
2420      <address><email>paulle@microsoft.com</email></address>
2421    </author>
2422    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2423      <organization>W3C</organization>
2424      <address><email>timbl@w3.org</email></address>
2425    </author>
2426    <date month="June" year="1999"/>
2427  </front>
2428  <seriesInfo name="RFC" value="2616"/>
2429</reference>
2430
2431<reference anchor="RFC3629">
2432  <front>
2433    <title>UTF-8, a transformation format of ISO 10646</title>
2434    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2435      <organization>Alis Technologies</organization>
2436      <address><email>fyergeau@alis.com</email></address>
2437    </author>
2438    <date month="November" year="2003"/>
2439  </front>
2440  <seriesInfo name="RFC" value="3629"/>
2441  <seriesInfo name="STD" value="63"/>
2442</reference>
2443
2444<reference anchor='RFC3864'>
2445  <front>
2446    <title>Registration Procedures for Message Header Fields</title>
2447    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2448      <organization>Nine by Nine</organization>
2449      <address><email>GK-IETF@ninebynine.org</email></address>
2450    </author>
2451    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2452      <organization>BEA Systems</organization>
2453      <address><email>mnot@pobox.com</email></address>
2454    </author>
2455    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2456      <organization>HP Labs</organization>
2457      <address><email>JeffMogul@acm.org</email></address>
2458    </author>
2459    <date year='2004' month='September' />
2460  </front>
2461  <seriesInfo name='BCP' value='90' />
2462  <seriesInfo name='RFC' value='3864' />
2463</reference>
2464
2465<reference anchor="RFC4288">
2466  <front>
2467    <title>Media Type Specifications and Registration Procedures</title>
2468    <author initials="N." surname="Freed" fullname="N. Freed">
2469      <organization>Sun Microsystems</organization>
2470      <address>
2471        <email>ned.freed@mrochek.com</email>
2472      </address>
2473    </author>
2474    <author initials="J." surname="Klensin" fullname="J. Klensin">
2475      <address>
2476        <email>klensin+ietf@jck.com</email>
2477      </address>
2478    </author>
2479    <date year="2005" month="December"/>
2480  </front>
2481  <seriesInfo name="BCP" value="13"/>
2482  <seriesInfo name="RFC" value="4288"/>
2483</reference>
2484
2485<reference anchor='RFC5226'>
2486  <front>
2487    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2488    <author initials='T.' surname='Narten' fullname='T. Narten'>
2489      <organization>IBM</organization>
2490      <address><email>narten@us.ibm.com</email></address>
2491    </author>
2492    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2493      <organization>Google</organization>
2494      <address><email>Harald@Alvestrand.no</email></address>
2495    </author>
2496    <date year='2008' month='May' />
2497  </front>
2498  <seriesInfo name='BCP' value='26' />
2499  <seriesInfo name='RFC' value='5226' />
2500</reference>
2501
2502<reference anchor="RFC5322">
2503  <front>
2504    <title>Internet Message Format</title>
2505    <author initials="P." surname="Resnick" fullname="P. Resnick">
2506      <organization>Qualcomm Incorporated</organization>
2507    </author>
2508    <date year="2008" month="October"/>
2509  </front> 
2510  <seriesInfo name="RFC" value="5322"/>
2511</reference>
2512
2513<reference anchor='BCP97'>
2514  <front>
2515    <title>Handling Normative References to Standards-Track Documents</title>
2516    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2517      <address>
2518        <email>klensin+ietf@jck.com</email>
2519      </address>
2520    </author>
2521    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2522      <organization>MIT</organization>
2523      <address>
2524        <email>hartmans-ietf@mit.edu</email>
2525      </address>
2526    </author>
2527    <date year='2007' month='June' />
2528  </front>
2529  <seriesInfo name='BCP' value='97' />
2530  <seriesInfo name='RFC' value='4897' />
2531</reference>
2532
2533
2534</references>
2535
2536<section title="Differences Between HTTP Entities and RFC 2045 Entities" anchor="differences.between.http.entities.and.rfc.2045.entities">
2537<t>
2538   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
2539   allow entities to be transmitted in an open variety of
2540   representations and with extensible mechanisms. However, RFC 2045
2541   discusses mail, and HTTP has a few features that are different from
2542   those described in RFC 2045. These differences were carefully chosen
2543   to optimize performance over binary connections, to allow greater
2544   freedom in the use of new media types, to make date comparisons
2545   easier, and to acknowledge the practice of some early HTTP servers
2546   and clients.
2547</t>
2548<t>
2549   This appendix describes specific areas where HTTP differs from RFC
2550   2045. Proxies and gateways to strict MIME environments &SHOULD; be
2551   aware of these differences and provide the appropriate conversions
2552   where necessary. Proxies and gateways from MIME environments to HTTP
2553   also need to be aware of the differences because some conversions
2554   might be required.
2555</t>
2556
2557<section title="MIME-Version" anchor="mime-version">
2558  <iref primary="true" item="MIME-Version header" x:for-anchor=""/>
2559  <iref primary="true" item="Headers" subitem="MIME-Version" x:for-anchor=""/>
2560  <x:anchor-alias value="MIME-Version"/>
2561  <x:anchor-alias value="MIME-Version-v"/>
2562<t>
2563   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2564   include a single MIME-Version general-header field to indicate what
2565   version of the MIME protocol was used to construct the message. Use
2566   of the MIME-Version header field indicates that the message is in
2567   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2568   Proxies/gateways are responsible for ensuring full compliance (where
2569   possible) when exporting HTTP messages to strict MIME environments.
2570</t>
2571<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/>
2572  <x:ref>MIME-Version</x:ref>   = "MIME-Version" ":" <x:ref>OWS</x:ref> <x:ref>MIME-Version-v</x:ref>
2573  <x:ref>MIME-Version-v</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2574</artwork></figure>
2575<t>
2576   MIME version "1.0" is the default for use in HTTP/1.1. However,
2577   HTTP/1.1 message parsing and semantics are defined by this document
2578   and not the MIME specification.
2579</t>
2580</section>
2581
2582<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2583<t>
2584   <xref target="RFC2045"/> requires that an Internet mail entity be converted to
2585   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
2586   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2587   allowed for subtypes of the "text" media type when transmitted over
2588   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2589   line breaks as CRLF and forbids the use of CR or LF outside of line
2590   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2591   line break within text content when a message is transmitted over
2592   HTTP.
2593</t>
2594<t>
2595   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2596   environment &SHOULD; translate all line breaks within the text media
2597   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2598   canonical form of CRLF. Note, however, that this might be complicated
2599   by the presence of a Content-Encoding and by the fact that HTTP
2600   allows the use of some character sets which do not use octets 13 and
2601   10 to represent CR and LF, as is the case for some multi-byte
2602   character sets.
2603</t>
2604<t>
2605   Implementors should note that conversion will break any cryptographic
2606   checksums applied to the original content unless the original content
2607   is already in canonical form. Therefore, the canonical form is
2608   recommended for any content that uses such checksums in HTTP.
2609</t>
2610</section>
2611
2612
2613<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2614<t>
2615   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2616   simplify the process of date comparison. Proxies and gateways from
2617   other protocols &SHOULD; ensure that any Date header field present in a
2618   message conforms to one of the HTTP/1.1 formats and rewrite the date
2619   if necessary.
2620</t>
2621</section>
2622
2623<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2624<t>
2625   RFC 2045 does not include any concept equivalent to HTTP/1.1's
2626   Content-Encoding header field. Since this acts as a modifier on the
2627   media type, proxies and gateways from HTTP to MIME-compliant
2628   protocols &MUST; either change the value of the Content-Type header
2629   field or decode the entity-body before forwarding the message. (Some
2630   experimental applications of Content-Type for Internet mail have used
2631   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2632   a function equivalent to Content-Encoding. However, this parameter is
2633   not part of RFC 2045).
2634</t>
2635</section>
2636
2637<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2638<t>
2639   HTTP does not use the Content-Transfer-Encoding field of RFC
2640   2045. Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
2641   remove any Content-Transfer-Encoding
2642   prior to delivering the response message to an HTTP client.
2643</t>
2644<t>
2645   Proxies and gateways from HTTP to MIME-compliant protocols are
2646   responsible for ensuring that the message is in the correct format
2647   and encoding for safe transport on that protocol, where "safe
2648   transport" is defined by the limitations of the protocol being used.
2649   Such a proxy or gateway &SHOULD; label the data with an appropriate
2650   Content-Transfer-Encoding if doing so will improve the likelihood of
2651   safe transport over the destination protocol.
2652</t>
2653</section>
2654
2655<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2656<t>
2657   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
2658   Proxies/gateways &MUST; remove any transfer-coding prior to
2659   forwarding a message via a MIME-compliant protocol.
2660</t>
2661</section>
2662
2663<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2664<t>
2665   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2666   need to be aware of MIME line length limitations. Since HTTP does not
2667   have this limitation, HTTP does not fold long lines. MHTML messages
2668   being transported by HTTP follow all conventions of MHTML, including
2669   line length limitations and folding, canonicalization, etc., since
2670   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2671   does not interpret the content or any MIME header lines that might be
2672   contained therein.
2673</t>
2674</section>
2675</section>
2676
2677<section title="Additional Features" anchor="additional.features">
2678<t>
2679   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2680   existing HTTP implementations, but not consistently and correctly
2681   across most HTTP/1.1 applications. Implementors are advised to be
2682   aware of these features, but cannot rely upon their presence in, or
2683   interoperability with, other HTTP/1.1 applications. Some of these
2684   describe proposed experimental features, and some describe features
2685   that experimental deployment found lacking that are now addressed in
2686   the base HTTP/1.1 specification.
2687</t>
2688<t>
2689   A number of other headers, such as Content-Disposition and Title,
2690   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2691</t>
2692
2693<section title="Content-Disposition" anchor="content-disposition">
2694<iref item="Headers" subitem="Content-Disposition" primary="true" x:for-anchor=""/>
2695<iref item="Content-Disposition header" primary="true" x:for-anchor=""/>
2696  <x:anchor-alias value="content-disposition"/>
2697  <x:anchor-alias value="content-disposition-v"/>
2698  <x:anchor-alias value="disposition-type"/>
2699  <x:anchor-alias value="disposition-parm"/>
2700  <x:anchor-alias value="disp-extension-parm"/>
2701  <x:anchor-alias value="disp-extension-token"/>
2702  <x:anchor-alias value="filename-parm"/>
2703<t>
2704   The "Content-Disposition" response-header field has been proposed as a
2705   means for the origin server to suggest a default filename if the user
2706   requests that the content is saved to a file. This usage is derived
2707   from the definition of Content-Disposition in <xref target="RFC2183"/>.
2708</t>
2709<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"/>
2710  <x:ref>content-disposition</x:ref> = "Content-Disposition" ":" <x:ref>OWS</x:ref>
2711                        <x:ref>content-disposition-v</x:ref>
2712  <x:ref>content-disposition-v</x:ref> = <x:ref>disposition-type</x:ref>
2713                          *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>disposition-parm</x:ref> )
2714  <x:ref>disposition-type</x:ref> = "attachment" / <x:ref>disp-extension-token</x:ref>
2715  <x:ref>disposition-parm</x:ref> = <x:ref>filename-parm</x:ref> / <x:ref>disp-extension-parm</x:ref>
2716  <x:ref>filename-parm</x:ref> = "filename" "=" <x:ref>quoted-string</x:ref>
2717  <x:ref>disp-extension-token</x:ref> = <x:ref>token</x:ref>
2718  <x:ref>disp-extension-parm</x:ref> = <x:ref>token</x:ref> "=" <x:ref>word</x:ref>
2719</artwork></figure>
2720<t>
2721   An example is
2722</t>
2723<figure><artwork type="example">
2724  Content-Disposition: attachment; filename="fname.ext"
2725</artwork></figure>
2726<t>
2727   The receiving user agent &SHOULD-NOT;  respect any directory path
2728   information present in the filename-parm parameter, which is the only
2729   parameter believed to apply to HTTP implementations at this time. The
2730   filename &SHOULD; be treated as a terminal component only.
2731</t>
2732<t>
2733   If this header is used in a response with the application/octet-stream
2734   content-type, the implied suggestion is that the user agent
2735   should not display the response, but directly enter a "save response
2736   as..." dialog.
2737</t>
2738<t>
2739   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
2740</t>
2741</section>
2742</section>
2743
2744<section title="Compatibility with Previous Versions" anchor="compatibility">
2745<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2746<t>
2747   Transfer-coding and message lengths all interact in ways that
2748   required fixing exactly when chunked encoding is used (to allow for
2749   transfer encoding that may not be self delimiting); it was important
2750   to straighten out exactly how message lengths are computed.
2751</t>
2752<t>
2753   Charset wildcarding is introduced to avoid explosion of character set
2754   names in accept headers. (<xref target="header.accept-charset"/>)
2755</t>
2756<t>
2757   Content-Base was deleted from the specification: it was not
2758   implemented widely, and there is no simple, safe way to introduce it
2759   without a robust extension mechanism. In addition, it is used in a
2760   similar, but not identical fashion in MHTML <xref target="RFC2557"/>.
2761</t>
2762<t>
2763   A content-coding of "identity" was introduced, to solve problems
2764   discovered in caching. (<xref target="content.codings"/>)
2765</t>
2766<t>
2767   The Alternates<iref item="Alternates header" primary="true"/><iref item="Headers" subitem="Alternate" primary="true"/>, Content-Version<iref item="Content-Version header" primary="true"/><iref item="Headers" subitem="Content-Version" primary="true"/>, Derived-From<iref item="Derived-From header" primary="true"/><iref item="Headers" subitem="Derived-From" primary="true"/>, Link<iref item="Link header" primary="true"/><iref item="Headers" subitem="Link" primary="true"/>, URI<iref item="URI header" primary="true"/><iref item="Headers" subitem="URI" primary="true"/>, Public<iref item="Public header" primary="true"/><iref item="Headers" subitem="Public" primary="true"/> and
2768   Content-Base<iref item="Content-Base header" primary="true"/><iref item="Headers" subitem="Content-Base" primary="true"/> header fields were defined in previous versions of this
2769   specification, but not commonly implemented. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.2"/>.
2770</t>
2771</section>
2772
2773<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2774<t>
2775  Clarify contexts that charset is used in.
2776  (<xref target="character.sets"/>)
2777</t>
2778<t>
2779  Remove base URI setting semantics for Content-Location due to poor
2780  implementation support, which was caused by too many broken servers emitting
2781  bogus Content-Location headers, and also the potentially undesirable effect
2782  of potentially breaking relative links in content-negotiated resources.
2783  (<xref target="header.content-location"/>)
2784</t>
2785<t>
2786  Remove reference to non-existant identity transfer-coding value tokens.
2787  (<xref target="no.content-transfer-encoding"/>)
2788</t>
2789</section>
2790
2791</section>
2792
2793<?BEGININC p3-payload.abnf-appendix ?>
2794<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
2795<figure>
2796<artwork type="abnf" name="p3-payload.parsed-abnf">
2797<x:ref>Accept</x:ref> = "Accept:" OWS Accept-v
2798<x:ref>Accept-Charset</x:ref> = "Accept-Charset:" OWS Accept-Charset-v
2799<x:ref>Accept-Charset-v</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2800 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2801 qvalue ] ] )
2802<x:ref>Accept-Encoding</x:ref> = "Accept-Encoding:" OWS Accept-Encoding-v
2803<x:ref>Accept-Encoding-v</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2804 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2805<x:ref>Accept-Language</x:ref> = "Accept-Language:" OWS Accept-Language-v
2806<x:ref>Accept-Language-v</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
2807 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2808 ] )
2809<x:ref>Accept-v</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2810 OWS media-range [ accept-params ] ] ) ]
2811
2812<x:ref>Content-Encoding</x:ref> = "Content-Encoding:" OWS Content-Encoding-v
2813<x:ref>Content-Encoding-v</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
2814 content-coding ] )
2815<x:ref>Content-Language</x:ref> = "Content-Language:" OWS Content-Language-v
2816<x:ref>Content-Language-v</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
2817 language-tag ] )
2818<x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in [Part1], Section 9.2&gt;
2819<x:ref>Content-Location</x:ref> = "Content-Location:" OWS Content-Location-v
2820<x:ref>Content-Location-v</x:ref> = absolute-URI / partial-URI
2821<x:ref>Content-MD5</x:ref> = "Content-MD5:" OWS Content-MD5-v
2822<x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per [RFC1864]&gt;
2823<x:ref>Content-Range</x:ref> = &lt;Content-Range, defined in [Part5], Section 5.2&gt;
2824<x:ref>Content-Type</x:ref> = "Content-Type:" OWS Content-Type-v
2825<x:ref>Content-Type-v</x:ref> = media-type
2826
2827<x:ref>Expires</x:ref> = &lt;Expires, defined in [Part6], Section 3.3&gt;
2828
2829<x:ref>Last-Modified</x:ref> = &lt;Last-Modified, defined in [Part4], Section 6.6&gt;
2830
2831<x:ref>MIME-Version</x:ref> = "MIME-Version:" OWS MIME-Version-v
2832<x:ref>MIME-Version-v</x:ref> = 1*DIGIT "." 1*DIGIT
2833
2834<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
2835
2836<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
2837<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
2838<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2839<x:ref>attribute</x:ref> = token
2840
2841<x:ref>charset</x:ref> = token
2842<x:ref>codings</x:ref> = ( content-coding / "*" )
2843<x:ref>content-coding</x:ref> = token
2844<x:ref>content-disposition</x:ref> = "Content-Disposition:" OWS
2845 content-disposition-v
2846<x:ref>content-disposition-v</x:ref> = disposition-type *( OWS ";" OWS
2847 disposition-parm )
2848
2849<x:ref>disp-extension-parm</x:ref> = token "=" word
2850<x:ref>disp-extension-token</x:ref> = token
2851<x:ref>disposition-parm</x:ref> = filename-parm / disp-extension-parm
2852<x:ref>disposition-type</x:ref> = "attachment" / disp-extension-token
2853
2854<x:ref>entity-body</x:ref> = *OCTET
2855<x:ref>entity-header</x:ref> = Content-Encoding / Content-Language / Content-Length
2856 / Content-Location / Content-MD5 / Content-Range / Content-Type /
2857 Expires / Last-Modified / extension-header
2858<x:ref>extension-header</x:ref> = header-field
2859
2860<x:ref>filename-parm</x:ref> = "filename=" quoted-string
2861
2862<x:ref>header-field</x:ref> = &lt;header-field, defined in [Part1], Section 3.2&gt;
2863
2864<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
2865<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2866
2867<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2868 ";" OWS parameter )
2869<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2870
2871<x:ref>parameter</x:ref> = attribute "=" value
2872<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
2873
2874<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
2875<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2876
2877<x:ref>subtype</x:ref> = token
2878
2879<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
2880<x:ref>type</x:ref> = token
2881
2882<x:ref>value</x:ref> = word
2883
2884<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 1.2.2&gt;
2885</artwork>
2886</figure>
2887<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2888; Accept defined but not used
2889; Accept-Charset defined but not used
2890; Accept-Encoding defined but not used
2891; Accept-Language defined but not used
2892; MIME-Version defined but not used
2893; content-disposition defined but not used
2894; entity-body defined but not used
2895; entity-header defined but not used
2896</artwork></figure></section>
2897<?ENDINC p3-payload.abnf-appendix ?>
2898
2899<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2900
2901<section title="Since RFC2616">
2902<t>
2903  Extracted relevant partitions from <xref target="RFC2616"/>.
2904</t>
2905</section>
2906
2907<section title="Since draft-ietf-httpbis-p3-payload-00">
2908<t>
2909  Closed issues:
2910  <list style="symbols"> 
2911    <t>
2912      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2913      "Media Type Registrations"
2914      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2915    </t>
2916    <t>
2917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2918      "Clarification regarding quoting of charset values"
2919      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2920    </t>
2921    <t>
2922      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2923      "Remove 'identity' token references"
2924      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2925    </t>
2926    <t>
2927      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2928      "Accept-Encoding BNF"
2929    </t>
2930    <t>
2931      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2932      "Normative and Informative references"
2933    </t>
2934    <t>
2935      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2936      "RFC1700 references"
2937    </t>
2938    <t>
2939      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2940      "Updating to RFC4288"
2941    </t>
2942    <t>
2943      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2944      "Informative references"
2945    </t>
2946    <t>
2947      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2948      "ISO-8859-1 Reference"
2949    </t>
2950    <t>
2951      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2952      "Encoding References Normative"
2953    </t>
2954    <t>
2955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2956      "Normative up-to-date references"
2957    </t>
2958  </list>
2959</t>
2960</section>
2961
2962<section title="Since draft-ietf-httpbis-p3-payload-01">
2963<t>
2964  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2965  <list style="symbols"> 
2966    <t>
2967      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2968    </t>
2969  </list>
2970</t>
2971</section>
2972
2973<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2974<t>
2975  Closed issues:
2976  <list style="symbols"> 
2977    <t>
2978      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2979      "Quoting Charsets"
2980    </t>
2981    <t>
2982      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2983      "Classification for Allow header"
2984    </t>
2985    <t>
2986      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2987      "missing default for qvalue in description of Accept-Encoding"
2988    </t>
2989  </list>
2990</t>
2991<t>
2992  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2993  <list style="symbols"> 
2994    <t>
2995      Reference RFC 3984, and update header registrations for headers defined
2996      in this document.
2997    </t>
2998  </list>
2999</t>
3000</section>
3001
3002<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
3003<t>
3004  Closed issues:
3005  <list style="symbols"> 
3006    <t>
3007      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
3008      "Quoting Charsets"
3009    </t>
3010    <t>
3011      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
3012      "language tag matching (Accept-Language) vs RFC4647"
3013    </t>
3014    <t>
3015      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
3016      "RFC 1806 has been replaced by RFC2183"
3017    </t>
3018  </list>
3019</t>
3020<t>
3021  Other changes:
3022  <list style="symbols"> 
3023    <t>
3024      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
3025      "Encoding References Normative" -- rephrase the annotation and reference
3026      <xref target="BCP97"/>.
3027    </t>
3028  </list>
3029</t>
3030 </section>
3031
3032<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
3033<t>
3034  Closed issues:
3035  <list style="symbols"> 
3036    <t>
3037      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3038      "RFC 2822 is updated by RFC 5322"
3039    </t>
3040  </list>
3041</t>
3042<t>
3043  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3044  <list style="symbols"> 
3045    <t>
3046      Use "/" instead of "|" for alternatives.
3047    </t>
3048    <t>
3049      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3050      whitespace ("OWS") and required whitespace ("RWS").
3051    </t>
3052    <t>
3053      Rewrite ABNFs to spell out whitespace rules, factor out
3054      header value format definitions.
3055    </t>
3056  </list>
3057</t>
3058</section>
3059
3060<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
3061<t>
3062  Closed issues:
3063  <list style="symbols"> 
3064    <t>
3065      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
3066      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3067    </t>
3068  </list>
3069</t>
3070<t>
3071  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3072  <list style="symbols"> 
3073    <t>
3074      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3075    </t>
3076  </list>
3077</t>
3078<t>
3079  Other changes:
3080  <list style="symbols"> 
3081    <t>
3082      Move definition of quality values into Part 1.
3083    </t>
3084  </list>
3085</t>
3086</section>
3087
3088<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
3089<t>
3090  Closed issues:
3091  <list style="symbols"> 
3092    <t>
3093      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3094      "Content-Location isn't special"
3095    </t>
3096    <t>
3097      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3098      "Content Sniffing"
3099    </t>
3100  </list>
3101</t>
3102</section>
3103
3104<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
3105<t>
3106  Closed issues:
3107  <list style="symbols"> 
3108    <t>
3109      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
3110      "Updated reference for language tags"
3111    </t>
3112    <t>
3113      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3114      "Clarify rules for determining what entities a response carries"
3115    </t>
3116    <t>
3117      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
3118      "Content-Location base-setting problems"
3119    </t>
3120    <t>
3121      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3122      "Content Sniffing"
3123    </t>
3124    <t>
3125      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
3126      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3127    </t>
3128    <t>
3129      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
3130      "move definitions of gzip/deflate/compress to part 1"
3131    </t>
3132  </list>
3133</t>
3134<t>
3135  Partly resolved issues:
3136  <list style="symbols"> 
3137    <t>
3138      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
3139      "update IANA requirements wrt Transfer-Coding values" (add the
3140      IANA Considerations subsection)
3141    </t>
3142    <t>
3143      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
3144      "update IANA requirements wrt Content-Coding values" (add the
3145      IANA Considerations subsection)
3146    </t>
3147  </list>
3148</t>
3149</section>
3150
3151<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
3152<t>
3153  Closed issues:
3154  <list style="symbols"> 
3155    <t>
3156      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
3157      "Content Negotiation for media types"
3158    </t>
3159    <t>
3160      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
3161      "Accept-Language: which RFC4647 filtering?"
3162    </t>
3163  </list>
3164</t>
3165</section>
3166
3167<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
3168<t>
3169  Closed issues:
3170  <list style="symbols"> 
3171    <t>
3172      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
3173      "IANA registry for content/transfer encodings"
3174    </t>
3175    <t>
3176      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3177      "Content Sniffing"
3178    </t>
3179    <t>
3180      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
3181      "use of term "word" when talking about header structure"
3182    </t>
3183  </list>
3184</t>
3185<t>
3186  Partly resolved issues:
3187  <list style="symbols"> 
3188    <t>
3189      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3190      "Term for the requested resource's URI"
3191    </t>
3192  </list>
3193</t>
3194</section>
3195
3196<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
3197<t>
3198  Closed issues:
3199  <list style="symbols"> 
3200    <t>
3201      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3202      "Clarify 'Requested Variant'"
3203    </t>
3204    <t>
3205      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3206      "Content-Location isn't special"
3207    </t>
3208    <t>
3209      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
3210      "Delimiting messages with multipart/byteranges"
3211    </t>
3212    <t>
3213      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3214      "Clarify entity / representation / variant terminology"
3215    </t>
3216    <t>
3217      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
3218      "confusing req. language for Content-Location"
3219    </t>
3220    <t>
3221      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
3222      "Content-Location on 304 responses"
3223    </t>
3224  </list>
3225</t>
3226</section>
3227
3228</section>
3229
3230</back>
3231</rfc>
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