source: draft-ietf-httpbis/latest/p1-messaging.xml @ 1180

Last change on this file since 1180 was 1180, checked in by julian.reschke@…, 9 years ago

prepare publication of -13

  • Property svn:eol-style set to native
File size: 249.8 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "March">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY caching-overview       "<xref target='Part6' x:rel='#caching.overview' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY cache-incomplete       "<xref target='Part6' x:rel='#errors.or.incomplete.response.cache.behavior' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY payload                "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY media-types            "<xref target='Part3' x:rel='#media.types' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY content-codings        "<xref target='Part3' x:rel='#content.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY CONNECT                "<xref target='Part2' x:rel='#CONNECT' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY content.negotiation    "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY diff-mime              "<xref target='Part3' x:rel='#differences.between.http.and.mime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY representation         "<xref target='Part3' x:rel='#representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY header-cache-control   "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY header-expect          "<xref target='Part2' x:rel='#header.expect' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY header-mime-version    "<xref target='Part3' x:rel='#mime-version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY header-pragma          "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY header-warning         "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY idempotent-methods     "<xref target='Part2' x:rel='#idempotent.methods' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY status-codes           "<xref target='Part2' x:rel='#status.codes' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY status-100             "<xref target='Part2' x:rel='#status.100' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY status-1xx             "<xref target='Part2' x:rel='#status.1xx' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY status-3xx             "<xref target='Part2' x:rel='#status.3xx' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY status-414             "<xref target='Part2' x:rel='#status.414' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38]>
39<?rfc toc="yes" ?>
40<?rfc symrefs="yes" ?>
41<?rfc sortrefs="yes" ?>
42<?rfc compact="yes"?>
43<?rfc subcompact="no" ?>
44<?rfc linkmailto="no" ?>
45<?rfc editing="no" ?>
46<?rfc comments="yes"?>
47<?rfc inline="yes"?>
48<?rfc rfcedstyle="yes"?>
49<?rfc-ext allow-markup-in-artwork="yes" ?>
50<?rfc-ext include-references-in-index="yes" ?>
51<rfc obsoletes="2145,2616" updates="2817" category="std" x:maturity-level="draft"
52     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"
53     xmlns:x='http://purl.org/net/xml2rfc/ext'>
54<front>
55
56  <title abbrev="HTTP/1.1, Part 1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
57
58  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
59    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
60    <address>
61      <postal>
62        <street>345 Park Ave</street>
63        <city>San Jose</city>
64        <region>CA</region>
65        <code>95110</code>
66        <country>USA</country>
67      </postal>
68      <email>fielding@gbiv.com</email>
69      <uri>http://roy.gbiv.com/</uri>
70    </address>
71  </author>
72
73  <author initials="J." surname="Gettys" fullname="Jim Gettys">
74    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
75    <address>
76      <postal>
77        <street>21 Oak Knoll Road</street>
78        <city>Carlisle</city>
79        <region>MA</region>
80        <code>01741</code>
81        <country>USA</country>
82      </postal>
83      <email>jg@freedesktop.org</email>
84      <uri>http://gettys.wordpress.com/</uri>
85    </address>
86  </author>
87 
88  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
89    <organization abbrev="HP">Hewlett-Packard Company</organization>
90    <address>
91      <postal>
92        <street>HP Labs, Large Scale Systems Group</street>
93        <street>1501 Page Mill Road, MS 1177</street>
94        <city>Palo Alto</city>
95        <region>CA</region>
96        <code>94304</code>
97        <country>USA</country>
98      </postal>
99      <email>JeffMogul@acm.org</email>
100    </address>
101  </author>
102
103  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
104    <organization abbrev="Microsoft">Microsoft Corporation</organization>
105    <address>
106      <postal>
107        <street>1 Microsoft Way</street>
108        <city>Redmond</city>
109        <region>WA</region>
110        <code>98052</code>
111        <country>USA</country>
112      </postal>
113      <email>henrikn@microsoft.com</email>
114    </address>
115  </author>
116
117  <author initials="L." surname="Masinter" fullname="Larry Masinter">
118    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
119    <address>
120      <postal>
121        <street>345 Park Ave</street>
122        <city>San Jose</city>
123        <region>CA</region>
124        <code>95110</code>
125        <country>USA</country>
126      </postal>
127      <email>LMM@acm.org</email>
128      <uri>http://larry.masinter.net/</uri>
129    </address>
130  </author>
131 
132  <author initials="P." surname="Leach" fullname="Paul J. Leach">
133    <organization abbrev="Microsoft">Microsoft Corporation</organization>
134    <address>
135      <postal>
136        <street>1 Microsoft Way</street>
137        <city>Redmond</city>
138        <region>WA</region>
139        <code>98052</code>
140      </postal>
141      <email>paulle@microsoft.com</email>
142    </address>
143  </author>
144   
145  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
146    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
147    <address>
148      <postal>
149        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
150        <street>The Stata Center, Building 32</street>
151        <street>32 Vassar Street</street>
152        <city>Cambridge</city>
153        <region>MA</region>
154        <code>02139</code>
155        <country>USA</country>
156      </postal>
157      <email>timbl@w3.org</email>
158      <uri>http://www.w3.org/People/Berners-Lee/</uri>
159    </address>
160  </author>
161
162  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
163    <organization abbrev="W3C">World Wide Web Consortium</organization>
164    <address>
165      <postal>
166        <street>W3C / ERCIM</street>
167        <street>2004, rte des Lucioles</street>
168        <city>Sophia-Antipolis</city>
169        <region>AM</region>
170        <code>06902</code>
171        <country>France</country>
172      </postal>
173      <email>ylafon@w3.org</email>
174      <uri>http://www.raubacapeu.net/people/yves/</uri>
175    </address>
176  </author>
177
178  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
179    <organization abbrev="greenbytes">greenbytes GmbH</organization>
180    <address>
181      <postal>
182        <street>Hafenweg 16</street>
183        <city>Muenster</city><region>NW</region><code>48155</code>
184        <country>Germany</country>
185      </postal>
186      <phone>+49 251 2807760</phone>
187      <facsimile>+49 251 2807761</facsimile>
188      <email>julian.reschke@greenbytes.de</email>
189      <uri>http://greenbytes.de/tech/webdav/</uri>
190    </address>
191  </author>
192
193  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
194  <workgroup>HTTPbis Working Group</workgroup>
195
196<abstract>
197<t>
198   The Hypertext Transfer Protocol (HTTP) is an application-level
199   protocol for distributed, collaborative, hypertext information
200   systems. HTTP has been in use by the World Wide Web global information
201   initiative since 1990. This document is Part 1 of the seven-part specification
202   that defines the protocol referred to as "HTTP/1.1" and, taken together,
203   obsoletes RFC 2616.  Part 1 provides an overview of HTTP and
204   its associated terminology, defines the "http" and "https" Uniform
205   Resource Identifier (URI) schemes, defines the generic message syntax
206   and parsing requirements for HTTP message frames, and describes
207   general security concerns for implementations.
208</t>
209</abstract>
210
211<note title="Editorial Note (To be removed by RFC Editor)">
212  <t>
213    Discussion of this draft should take place on the HTTPBIS working group
214    mailing list (ietf-http-wg@w3.org). The current issues list is
215    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
216    and related documents (including fancy diffs) can be found at
217    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
218  </t>
219  <t>
220    The changes in this draft are summarized in <xref target="changes.since.13"/>.
221  </t>
222</note>
223</front>
224<middle>
225<section title="Introduction" anchor="introduction">
226<t>
227   The Hypertext Transfer Protocol (HTTP) is an application-level
228   request/response protocol that uses extensible semantics and MIME-like
229   message payloads for flexible interaction with network-based hypertext
230   information systems. HTTP relies upon the Uniform Resource Identifier (URI)
231   standard <xref target="RFC3986"/> to indicate the target resource and
232   relationships between resources.
233   Messages are passed in a format similar to that used by Internet mail
234   <xref target="RFC5322"/> and the Multipurpose Internet Mail Extensions
235   (MIME) <xref target="RFC2045"/> (see &diff-mime; for the differences
236   between HTTP and MIME messages).
237</t>
238<t>
239   HTTP is a generic interface protocol for information systems. It is
240   designed to hide the details of how a service is implemented by presenting
241   a uniform interface to clients that is independent of the types of
242   resources provided. Likewise, servers do not need to be aware of each
243   client's purpose: an HTTP request can be considered in isolation rather
244   than being associated with a specific type of client or a predetermined
245   sequence of application steps. The result is a protocol that can be used
246   effectively in many different contexts and for which implementations can
247   evolve independently over time.
248</t>
249<t>
250   HTTP is also designed for use as an intermediation protocol for translating
251   communication to and from non-HTTP information systems.
252   HTTP proxies and gateways can provide access to alternative information
253   services by translating their diverse protocols into a hypertext
254   format that can be viewed and manipulated by clients in the same way
255   as HTTP services.
256</t>
257<t>
258   One consequence of HTTP flexibility is that the protocol cannot be
259   defined in terms of what occurs behind the interface. Instead, we
260   are limited to defining the syntax of communication, the intent
261   of received communication, and the expected behavior of recipients.
262   If the communication is considered in isolation, then successful
263   actions ought to be reflected in corresponding changes to the
264   observable interface provided by servers. However, since multiple
265   clients might act in parallel and perhaps at cross-purposes, we
266   cannot require that such changes be observable beyond the scope
267   of a single response.
268</t>
269<t>
270   This document is Part 1 of the seven-part specification of HTTP,
271   defining the protocol referred to as "HTTP/1.1", obsoleting
272   <xref target="RFC2616"/> and <xref target="RFC2145"/>.
273   Part 1 describes the architectural elements that are used or
274   referred to in HTTP, defines the "http" and "https" URI schemes,
275   describes overall network operation and connection management,
276   and defines HTTP message framing and forwarding requirements.
277   Our goal is to define all of the mechanisms necessary for HTTP message
278   handling that are independent of message semantics, thereby defining the
279   complete set of requirements for message parsers and
280   message-forwarding intermediaries.
281</t>
282
283<section title="Requirements" anchor="intro.requirements">
284<t>
285   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
286   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
287   document are to be interpreted as described in <xref target="RFC2119"/>.
288</t>
289<t>
290   An implementation is not compliant if it fails to satisfy one or more
291   of the "MUST" or "REQUIRED" level requirements for the protocols it
292   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
293   level and all the "SHOULD" level requirements for its protocols is said
294   to be "unconditionally compliant"; one that satisfies all the "MUST"
295   level requirements but not all the "SHOULD" level requirements for its
296   protocols is said to be "conditionally compliant".
297</t>
298</section>
299
300<section title="Syntax Notation" anchor="notation">
301<iref primary="true" item="Grammar" subitem="ALPHA"/>
302<iref primary="true" item="Grammar" subitem="CR"/>
303<iref primary="true" item="Grammar" subitem="CRLF"/>
304<iref primary="true" item="Grammar" subitem="CTL"/>
305<iref primary="true" item="Grammar" subitem="DIGIT"/>
306<iref primary="true" item="Grammar" subitem="DQUOTE"/>
307<iref primary="true" item="Grammar" subitem="HEXDIG"/>
308<iref primary="true" item="Grammar" subitem="LF"/>
309<iref primary="true" item="Grammar" subitem="OCTET"/>
310<iref primary="true" item="Grammar" subitem="SP"/>
311<iref primary="true" item="Grammar" subitem="VCHAR"/>
312<iref primary="true" item="Grammar" subitem="WSP"/>
313<t>
314   This specification uses the Augmented Backus-Naur Form (ABNF) notation
315   of <xref target="RFC5234"/>.
316</t>
317<t anchor="core.rules">
318  <x:anchor-alias value="ALPHA"/>
319  <x:anchor-alias value="CTL"/>
320  <x:anchor-alias value="CR"/>
321  <x:anchor-alias value="CRLF"/>
322  <x:anchor-alias value="DIGIT"/>
323  <x:anchor-alias value="DQUOTE"/>
324  <x:anchor-alias value="HEXDIG"/>
325  <x:anchor-alias value="LF"/>
326  <x:anchor-alias value="OCTET"/>
327  <x:anchor-alias value="SP"/>
328  <x:anchor-alias value="VCHAR"/>
329  <x:anchor-alias value="WSP"/>
330   The following core rules are included by
331   reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
332   ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
333   DIGIT (decimal 0-9), DQUOTE (double quote),
334   HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
335   OCTET (any 8-bit sequence of data), SP (space),
336   VCHAR (any visible <xref target="USASCII"/> character),
337   and WSP (whitespace).
338</t>
339<t>
340   As a syntactic convention, ABNF rule names prefixed with "obs-" denote
341   "obsolete" grammar rules that appear for historical reasons.
342</t>
343
344<section title="ABNF Extension: #rule" anchor="notation.abnf">
345<t>
346  The #rule extension to the ABNF rules of <xref target="RFC5234"/> is used to
347  improve readability.
348</t>
349<t>
350  A construct "#" is defined, similar to "*", for defining comma-delimited
351  lists of elements. The full form is "&lt;n&gt;#&lt;m&gt;element" indicating
352  at least &lt;n&gt; and at most &lt;m&gt; elements, each separated by a single
353  comma (",") and optional whitespace (OWS,
354  <xref target="basic.rules"/>).   
355</t>
356<figure><preamble>
357  Thus,
358</preamble><artwork type="example">
359  1#element =&gt; element *( OWS "," OWS element )
360</artwork></figure>
361<figure><preamble>
362  and:
363</preamble><artwork type="example">
364  #element =&gt; [ 1#element ]
365</artwork></figure>
366<figure><preamble>
367  and for n &gt;= 1 and m &gt; 1:
368</preamble><artwork type="example">
369  &lt;n&gt;#&lt;m&gt;element =&gt; element &lt;n-1&gt;*&lt;m-1&gt;( OWS "," OWS element )
370</artwork></figure>
371<t>
372  For compatibility with legacy list rules, recipients &SHOULD; accept empty
373  list elements. In other words, consumers would follow the list productions:
374</t>
375<figure><artwork type="example">
376  #element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
377 
378  1#element =&gt; *( "," OWS ) element *( OWS "," [ OWS element ] )
379</artwork></figure>
380<t>
381  Note that empty elements do not contribute to the count of elements present,
382  though.
383</t>
384<t>
385  For example, given these ABNF productions:
386</t>
387<figure><artwork type="example">
388  example-list      = 1#example-list-elmt
389  example-list-elmt = token ; see <xref target="basic.rules"/> 
390</artwork></figure>
391<t>
392  Then these are valid values for example-list (not including the double
393  quotes, which are present for delimitation only):
394</t>
395<figure><artwork type="example">
396  "foo,bar"
397  " foo ,bar,"
398  "  foo , ,bar,charlie   "
399  "foo ,bar,   charlie "
400</artwork></figure>
401<t>
402  But these values would be invalid, as at least one non-empty element is
403  required:
404</t>
405<figure><artwork type="example">
406  ""
407  ","
408  ",   ,"
409</artwork></figure>
410<t>
411  <xref target="collected.abnf"/> shows the collected ABNF, with the list rules
412  expanded as explained above.
413</t>
414</section>
415
416<section title="Basic Rules" anchor="basic.rules">
417<t anchor="rule.CRLF">
418  <x:anchor-alias value="CRLF"/>
419   HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all
420   protocol elements other than the message-body
421   (see <xref target="tolerant.applications"/> for tolerant applications).
422</t>
423<t anchor="rule.LWS">
424   This specification uses three rules to denote the use of linear
425   whitespace: OWS (optional whitespace), RWS (required whitespace), and
426   BWS ("bad" whitespace).
427</t>
428<t>
429   The OWS rule is used where zero or more linear whitespace octets might
430   appear. OWS &SHOULD; either not be produced or be produced as a single
431   SP. Multiple OWS octets that occur within field-content &SHOULD;
432   be replaced with a single SP before interpreting the field value or
433   forwarding the message downstream.
434</t>
435<t>
436   RWS is used when at least one linear whitespace octet is required to
437   separate field tokens. RWS &SHOULD; be produced as a single SP.
438   Multiple RWS octets that occur within field-content &SHOULD; be
439   replaced with a single SP before interpreting the field value or
440   forwarding the message downstream.
441</t>
442<t>
443   BWS is used where the grammar allows optional whitespace for historical
444   reasons but senders &SHOULD-NOT; produce it in messages. HTTP/1.1
445   recipients &MUST; accept such bad optional whitespace and remove it before
446   interpreting the field value or forwarding the message downstream.
447</t>
448<t anchor="rule.whitespace">
449  <x:anchor-alias value="BWS"/>
450  <x:anchor-alias value="OWS"/>
451  <x:anchor-alias value="RWS"/>
452  <x:anchor-alias value="obs-fold"/>
453</t>
454<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="OWS"/><iref primary="true" item="Grammar" subitem="RWS"/><iref primary="true" item="Grammar" subitem="BWS"/>
455  <x:ref>OWS</x:ref>            = *( [ obs-fold ] <x:ref>WSP</x:ref> )
456                 ; "optional" whitespace
457  <x:ref>RWS</x:ref>            = 1*( [ obs-fold ] <x:ref>WSP</x:ref> )
458                 ; "required" whitespace
459  <x:ref>BWS</x:ref>            = <x:ref>OWS</x:ref>
460                 ; "bad" whitespace
461  <x:ref>obs-fold</x:ref>       = <x:ref>CRLF</x:ref>
462                 ; see <xref target="header.fields"/>
463</artwork></figure>
464<t anchor="rule.token.separators">
465  <x:anchor-alias value="tchar"/>
466  <x:anchor-alias value="token"/>
467  <x:anchor-alias value="special"/>
468  <x:anchor-alias value="word"/>
469   Many HTTP/1.1 header field values consist of words (token or quoted-string)
470   separated by whitespace or special characters. These special characters
471   &MUST; be in a quoted string to be used within a parameter value (as defined
472   in <xref target="transfer.codings"/>).
473</t>
474<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="word"/><iref primary="true" item="Grammar" subitem="token"/><iref primary="true" item="Grammar" subitem="tchar"/><iref primary="true" item="Grammar" subitem="special"/>
475  <x:ref>word</x:ref>           = <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref>
476
477  <x:ref>token</x:ref>          = 1*<x:ref>tchar</x:ref>
478<!--
479  IMPORTANT: when editing "tchar" make sure that "special" is updated accordingly!!!
480 -->
481  <x:ref>tchar</x:ref>          = "!" / "#" / "$" / "%" / "&amp;" / "'" / "*"
482                 / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
483                 / <x:ref>DIGIT</x:ref> / <x:ref>ALPHA</x:ref>
484                 ; any <x:ref>VCHAR</x:ref>, except <x:ref>special</x:ref>
485
486  <x:ref>special</x:ref>        = "(" / ")" / "&lt;" / ">" / "@" / ","
487                 / ";" / ":" / "\" / DQUOTE / "/" / "["
488                 / "]" / "?" / "=" / "{" / "}"
489</artwork></figure>
490<t anchor="rule.quoted-string">
491  <x:anchor-alias value="quoted-string"/>
492  <x:anchor-alias value="qdtext"/>
493  <x:anchor-alias value="obs-text"/>
494   A string of text is parsed as a single word if it is quoted using
495   double-quote marks.
496</t>
497<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="quoted-string"/><iref primary="true" item="Grammar" subitem="qdtext"/><iref primary="true" item="Grammar" subitem="obs-text"/>
498  <x:ref>quoted-string</x:ref>  = <x:ref>DQUOTE</x:ref> *( <x:ref>qdtext</x:ref> / <x:ref>quoted-pair</x:ref> ) <x:ref>DQUOTE</x:ref>
499  <x:ref>qdtext</x:ref>         = <x:ref>OWS</x:ref> / %x21 / %x23-5B / %x5D-7E / <x:ref>obs-text</x:ref>
500                 ; <x:ref>OWS</x:ref> / &lt;<x:ref>VCHAR</x:ref> except <x:ref>DQUOTE</x:ref> and "\"&gt; / <x:ref>obs-text</x:ref> 
501  <x:ref>obs-text</x:ref>       = %x80-FF
502</artwork></figure>
503<t anchor="rule.quoted-pair">
504  <x:anchor-alias value="quoted-pair"/>
505   The backslash octet ("\") can be used as a single-octet
506   quoting mechanism within quoted-string constructs:
507</t>
508<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="quoted-pair"/>
509  <x:ref>quoted-pair</x:ref>    = "\" ( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
510</artwork></figure>
511<t>
512   Senders &SHOULD-NOT; escape octets that do not require escaping
513   (i.e., other than DQUOTE and the backslash octet).
514</t>
515</section>
516
517</section>
518</section>
519
520<section title="HTTP-related architecture" anchor="architecture">
521<t>
522   HTTP was created for the World Wide Web architecture
523   and has evolved over time to support the scalability needs of a worldwide
524   hypertext system. Much of that architecture is reflected in the terminology
525   and syntax productions used to define HTTP.
526</t>
527
528<section title="Client/Server Messaging" anchor="operation">
529<iref primary="true" item="client"/>
530<iref primary="true" item="server"/>
531<iref primary="true" item="connection"/>
532<t>
533   HTTP is a stateless request/response protocol that operates by exchanging
534   messages across a reliable transport or session-layer connection. An HTTP
535   "client" is a program that establishes a connection to a server for the
536   purpose of sending one or more HTTP requests.  An HTTP "server" is a
537   program that accepts connections in order to service HTTP requests by
538   sending HTTP responses.
539</t>
540<iref primary="true" item="user agent"/>
541<iref primary="true" item="origin server"/>
542<iref primary="true" item="browser"/>
543<iref primary="true" item="spider"/>
544<t>
545   Note that the terms client and server refer only to the roles that
546   these programs perform for a particular connection.  The same program
547   might act as a client on some connections and a server on others.  We use
548   the term "user agent" to refer to the program that initiates a request,
549   such as a WWW browser, editor, or spider (web-traversing robot), and
550   the term "origin server" to refer to the program that can originate
551   authoritative responses to a request.  For general requirements, we use
552   the term "sender" to refer to whichever component sent a given message
553   and the term "recipient" to refer to any component that receives the
554   message.
555</t>
556<t>
557   Most HTTP communication consists of a retrieval request (GET) for
558   a representation of some resource identified by a URI.  In the
559   simplest case, this might be accomplished via a single bidirectional
560   connection (===) between the user agent (UA) and the origin server (O).
561</t>
562<figure><artwork type="drawing">
563         request   &gt;
564    UA ======================================= O
565                                &lt;   response
566</artwork></figure>
567<iref primary="true" item="message"/>
568<iref primary="true" item="request"/>
569<iref primary="true" item="response"/>
570<t>
571   A client sends an HTTP request to the server in the form of a request
572   message (<xref target="request"/>), beginning with a method, URI, and
573   protocol version, followed by MIME-like header fields containing
574   request modifiers, client information, and payload metadata, an empty
575   line to indicate the end of the header section, and finally the payload
576   body (if any).
577</t>
578<t>
579   A server responds to the client's request by sending an HTTP response
580   message (<xref target="response"/>), beginning with a status line that
581   includes the protocol version, a success or error code, and textual
582   reason phrase, followed by MIME-like header fields containing server
583   information, resource metadata, and payload metadata, an empty line to
584   indicate the end of the header section, and finally the payload body (if any).
585</t>
586<t>
587   The following example illustrates a typical message exchange for a
588   GET request on the URI "http://www.example.com/hello.txt":
589</t>
590<figure><preamble>
591client request:
592</preamble><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
593GET /hello.txt HTTP/1.1
594User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3
595Host: www.example.com
596Accept: */*
597
598</artwork></figure>
599<figure><preamble>
600server response:
601</preamble><artwork type="message/http; msgtype=&#34;response&#34;" x:indent-with="  ">
602HTTP/1.1 200 OK
603Date: Mon, 27 Jul 2009 12:28:53 GMT
604Server: Apache
605Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT
606ETag: "34aa387-d-1568eb00"
607Accept-Ranges: bytes
608Content-Length: <x:length-of target="exbody"/>
609Vary: Accept-Encoding
610Content-Type: text/plain
611
612<x:span anchor="exbody">Hello World!
613</x:span></artwork></figure>
614</section>
615
616<section title="Connections and Transport Independence" anchor="transport-independence">
617<t>
618   HTTP messaging is independent of the underlying transport or
619   session-layer connection protocol(s).  HTTP only presumes a reliable
620   transport with in-order delivery of requests and the corresponding
621   in-order delivery of responses.  The mapping of HTTP request and
622   response structures onto the data units of the underlying transport
623   protocol is outside the scope of this specification.
624</t>
625<t>
626   The specific connection protocols to be used for an interaction
627   are determined by client configuration and the target resource's URI.
628   For example, the "http" URI scheme
629   (<xref target="http.uri"/>) indicates a default connection of TCP
630   over IP, with a default TCP port of 80, but the client might be
631   configured to use a proxy via some other connection port or protocol
632   instead of using the defaults.
633</t>
634<t>
635   A connection might be used for multiple HTTP request/response exchanges,
636   as defined in <xref target="persistent.connections"/>.
637</t>
638</section>
639
640<section title="Intermediaries" anchor="intermediaries">
641<iref primary="true" item="intermediary"/>
642<t>
643   HTTP enables the use of intermediaries to satisfy requests through
644   a chain of connections.  There are three common forms of HTTP
645   intermediary: proxy, gateway, and tunnel.  In some cases,
646   a single intermediary might act as an origin server, proxy, gateway,
647   or tunnel, switching behavior based on the nature of each request.
648</t>
649<figure><artwork type="drawing">
650         &gt;             &gt;             &gt;             &gt;
651    UA =========== A =========== B =========== C =========== O
652               &lt;             &lt;             &lt;             &lt;
653</artwork></figure>
654<t>
655   The figure above shows three intermediaries (A, B, and C) between the
656   user agent and origin server. A request or response message that
657   travels the whole chain will pass through four separate connections.
658   Some HTTP communication options
659   might apply only to the connection with the nearest, non-tunnel
660   neighbor, only to the end-points of the chain, or to all connections
661   along the chain. Although the diagram is linear, each participant might
662   be engaged in multiple, simultaneous communications. For example, B
663   might be receiving requests from many clients other than A, and/or
664   forwarding requests to servers other than C, at the same time that it
665   is handling A's request.
666</t>
667<t>
668<iref primary="true" item="upstream"/><iref primary="true" item="downstream"/>
669<iref primary="true" item="inbound"/><iref primary="true" item="outbound"/>
670   We use the terms "upstream" and "downstream" to describe various
671   requirements in relation to the directional flow of a message:
672   all messages flow from upstream to downstream.
673   Likewise, we use the terms "inbound" and "outbound" to refer to
674   directions in relation to the request path: "inbound" means toward
675   the origin server and "outbound" means toward the user agent.
676</t>
677<t><iref primary="true" item="proxy"/>
678   A "proxy" is a message forwarding agent that is selected by the
679   client, usually via local configuration rules, to receive requests
680   for some type(s) of absolute URI and attempt to satisfy those
681   requests via translation through the HTTP interface.  Some translations
682   are minimal, such as for proxy requests for "http" URIs, whereas
683   other requests might require translation to and from entirely different
684   application-layer protocols. Proxies are often used to group an
685   organization's HTTP requests through a common intermediary for the
686   sake of security, annotation services, or shared caching.
687</t>
688<t>
689<iref primary="true" item="transforming proxy"/>
690<iref primary="true" item="non-transforming proxy"/>
691   An HTTP-to-HTTP proxy is called a "transforming proxy" if it is designed
692   or configured to modify request or response messages in a semantically
693   meaningful way (i.e., modifications, beyond those required by normal
694   HTTP processing, that change the message in a way that would be
695   significant to the original sender or potentially significant to
696   downstream recipients).  For example, a transforming proxy might be
697   acting as a shared annotation server (modifying responses to include
698   references to a local annotation database), a malware filter, a
699   format transcoder, or an intranet-to-Internet privacy filter.  Such
700   transformations are presumed to be desired by the client (or client
701   organization) that selected the proxy and are beyond the scope of
702   this specification.  However, when a proxy is not intended to transform
703   a given message, we use the term "non-transforming proxy" to target
704   requirements that preserve HTTP message semantics.
705</t>
706<t><iref primary="true" item="gateway"/><iref primary="true" item="reverse proxy"/>
707<iref primary="true" item="accelerator"/>
708   A "gateway" (a.k.a., "reverse proxy") is a receiving agent that acts
709   as a layer above some other server(s) and translates the received
710   requests to the underlying server's protocol.  Gateways are often
711   used to encapsulate legacy or untrusted information services, to
712   improve server performance through "accelerator" caching, and to
713   enable partitioning or load-balancing of HTTP services across
714   multiple machines.
715</t>
716<t>
717   A gateway behaves as an origin server on its outbound connection and
718   as a user agent on its inbound connection.
719   All HTTP requirements applicable to an origin server
720   also apply to the outbound communication of a gateway.
721   A gateway communicates with inbound servers using any protocol that
722   it desires, including private extensions to HTTP that are outside
723   the scope of this specification.  However, an HTTP-to-HTTP gateway
724   that wishes to interoperate with third-party HTTP servers &MUST;
725   comply with HTTP user agent requirements on the gateway's inbound
726   connection and &MUST; implement the Connection
727   (<xref target="header.connection"/>) and Via (<xref target="header.via"/>)
728   header fields for both connections.
729</t>
730<t><iref primary="true" item="tunnel"/>
731   A "tunnel" acts as a blind relay between two connections
732   without changing the messages. Once active, a tunnel is not
733   considered a party to the HTTP communication, though the tunnel might
734   have been initiated by an HTTP request. A tunnel ceases to exist when
735   both ends of the relayed connection are closed. Tunnels are used to
736   extend a virtual connection through an intermediary, such as when
737   transport-layer security is used to establish private communication
738   through a shared firewall proxy.
739</t>
740<t><iref primary="true" item="interception proxy"/><iref primary="true" item="transparent proxy"/>
741<iref primary="true" item="captive portal"/>
742   In addition, there may exist network intermediaries that are not
743   considered part of the HTTP communication but nevertheless act as
744   filters or redirecting agents (usually violating HTTP semantics,
745   causing security problems, and otherwise making a mess of things).
746   Such a network intermediary, often referred to as an "interception proxy"
747   <xref target="RFC3040"/>, "transparent proxy" <xref target="RFC1919"/>,
748   or "captive portal",
749   differs from an HTTP proxy because it has not been selected by the client.
750   Instead, the network intermediary redirects outgoing TCP port 80 packets
751   (and occasionally other common port traffic) to an internal HTTP server.
752   Interception proxies are commonly found on public network access points,
753   as a means of enforcing account subscription prior to allowing use of
754   non-local Internet services, and within corporate firewalls to enforce
755   network usage policies.
756   They are indistinguishable from a man-in-the-middle attack.
757</t>
758</section>
759
760<section title="Caches" anchor="caches">
761<iref primary="true" item="cache"/>
762<t>
763   A "cache" is a local store of previous response messages and the
764   subsystem that controls its message storage, retrieval, and deletion.
765   A cache stores cacheable responses in order to reduce the response
766   time and network bandwidth consumption on future, equivalent
767   requests. Any client or server &MAY; employ a cache, though a cache
768   cannot be used by a server while it is acting as a tunnel.
769</t>
770<t>
771   The effect of a cache is that the request/response chain is shortened
772   if one of the participants along the chain has a cached response
773   applicable to that request. The following illustrates the resulting
774   chain if B has a cached copy of an earlier response from O (via C)
775   for a request which has not been cached by UA or A.
776</t>
777<figure><artwork type="drawing">
778            &gt;             &gt;
779       UA =========== A =========== B - - - - - - C - - - - - - O
780                  &lt;             &lt;
781</artwork></figure>
782<t><iref primary="true" item="cacheable"/>
783   A response is "cacheable" if a cache is allowed to store a copy of
784   the response message for use in answering subsequent requests.
785   Even when a response is cacheable, there might be additional
786   constraints placed by the client or by the origin server on when
787   that cached response can be used for a particular request. HTTP
788   requirements for cache behavior and cacheable responses are
789   defined in &caching-overview;
790</t>
791<t>
792   There are a wide variety of architectures and configurations
793   of caches and proxies deployed across the World Wide Web and
794   inside large organizations. These systems include national hierarchies
795   of proxy caches to save transoceanic bandwidth, systems that
796   broadcast or multicast cache entries, organizations that distribute
797   subsets of cached data via optical media, and so on.
798</t>
799</section>
800
801<section title="Protocol Versioning" anchor="http.version">
802  <x:anchor-alias value="HTTP-Version"/>
803  <x:anchor-alias value="HTTP-Prot-Name"/>
804<t>
805   HTTP uses a "&lt;major&gt;.&lt;minor&gt;" numbering scheme to indicate
806   versions of the protocol. This specification defines version "1.1".
807   The protocol version as a whole indicates the sender's compliance
808   with the set of requirements laid out in that version's corresponding
809   specification of HTTP.
810</t>
811<t>
812   The version of an HTTP message is indicated by an HTTP-Version field
813   in the first line of the message. HTTP-Version is case-sensitive.
814</t>
815<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-Version"/><iref primary="true" item="Grammar" subitem="HTTP-Prot-Name"/>
816  <x:ref>HTTP-Version</x:ref>   = <x:ref>HTTP-Prot-Name</x:ref> "/" 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
817  <x:ref>HTTP-Prot-Name</x:ref> = <x:abnf-char-sequence>"HTTP"</x:abnf-char-sequence> ; "HTTP", case-sensitive
818</artwork></figure>
819<t>
820   The HTTP version number consists of two non-negative decimal integers
821   separated by a "." (period or decimal point).  The first
822   number ("major version") indicates the HTTP messaging syntax, whereas
823   the second number ("minor version") indicates the highest minor
824   version to which the sender is at least conditionally compliant and
825   able to understand for future communication.  The minor version
826   advertises the sender's communication capabilities even when the
827   sender is only using a backwards-compatible subset of the protocol,
828   thereby letting the recipient know that more advanced features can
829   be used in response (by servers) or in future requests (by clients).
830</t>
831<t>
832   When comparing HTTP versions, the numbers &MUST; be compared
833   numerically rather than lexically.  For example, HTTP/2.4 is a lower
834   version than HTTP/2.13, which in turn is lower than HTTP/12.3.
835   Leading zeros &MUST; be ignored by recipients and &MUST-NOT; be sent.
836</t>
837<t>
838   When an HTTP/1.1 message is sent to an HTTP/1.0 recipient
839   <xref target="RFC1945"/> or a recipient whose version is unknown,
840   the HTTP/1.1 message is constructed such that it can be interpreted
841   as a valid HTTP/1.0 message if all of the newer features are ignored.
842   This specification places recipient-version requirements on some
843   new features so that a compliant sender will only use compatible
844   features until it has determined, through configuration or the
845   receipt of a message, that the recipient supports HTTP/1.1.
846</t>
847<t>
848   The interpretation of an HTTP header field does not change
849   between minor versions of the same major version, though the default
850   behavior of a recipient in the absence of such a field can change.
851   Unless specified otherwise, header fields defined in HTTP/1.1 are
852   defined for all versions of HTTP/1.x.  In particular, the Host and
853   Connection header fields ought to be implemented by all HTTP/1.x
854   implementations whether or not they advertise compliance with HTTP/1.1.
855</t>
856<t>
857   New header fields can be defined such that, when they are
858   understood by a recipient, they might override or enhance the
859   interpretation of previously defined header fields.  When an
860   implementation receives an unrecognized header field, the recipient
861   &MUST; ignore that header field for local processing regardless of
862   the message's HTTP version.  An unrecognized header field received
863   by a proxy &MUST; be forwarded downstream unless the header field's
864   field-name is listed in the message's Connection header-field
865   (see <xref target="header.connection"/>).
866   These requirements allow HTTP's functionality to be enhanced without
867   requiring prior update of all compliant intermediaries.
868</t>
869<t>
870   Intermediaries that process HTTP messages (i.e., all intermediaries
871   other than those acting as a tunnel) &MUST; send their own HTTP-Version
872   in forwarded messages.  In other words, they &MUST-NOT; blindly
873   forward the first line of an HTTP message without ensuring that the
874   protocol version matches what the intermediary understands, and
875   is at least conditionally compliant to, for both the receiving and
876   sending of messages.  Forwarding an HTTP message without rewriting
877   the HTTP-Version might result in communication errors when downstream
878   recipients use the message sender's version to determine what features
879   are safe to use for later communication with that sender.
880</t>
881<t>
882   An HTTP client &SHOULD; send a request version equal to the highest
883   version for which the client is at least conditionally compliant and
884   whose major version is no higher than the highest version supported
885   by the server, if this is known.  An HTTP client &MUST-NOT; send a
886   version for which it is not at least conditionally compliant.
887</t>
888<t>
889   An HTTP client &MAY; send a lower request version if it is known that
890   the server incorrectly implements the HTTP specification, but only
891   after the client has attempted at least one normal request and determined
892   from the response status or header fields (e.g., Server) that the
893   server improperly handles higher request versions.
894</t>
895<t>
896   An HTTP server &SHOULD; send a response version equal to the highest
897   version for which the server is at least conditionally compliant and
898   whose major version is less than or equal to the one received in the
899   request.  An HTTP server &MUST-NOT; send a version for which it is not
900   at least conditionally compliant.  A server &MAY; send a 505 (HTTP
901   Version Not Supported) response if it cannot send a response using the
902   major version used in the client's request.
903</t>
904<t>
905   An HTTP server &MAY; send an HTTP/1.0 response to an HTTP/1.0 request
906   if it is known or suspected that the client incorrectly implements the
907   HTTP specification and is incapable of correctly processing later
908   version responses, such as when a client fails to parse the version
909   number correctly or when an intermediary is known to blindly forward
910   the HTTP-Version even when it doesn't comply with the given minor
911   version of the protocol. Such protocol downgrades &SHOULD-NOT; be
912   performed unless triggered by specific client attributes, such as when
913   one or more of the request header fields (e.g., User-Agent) uniquely
914   match the values sent by a client known to be in error.
915</t>
916<t>
917   The intention of HTTP's versioning design is that the major number
918   will only be incremented if an incompatible message syntax is
919   introduced, and that the minor number will only be incremented when
920   changes made to the protocol have the effect of adding to the message
921   semantics or implying additional capabilities of the sender.  However,
922   the minor version was not incremented for the changes introduced between
923   <xref target="RFC2068"/> and <xref target="RFC2616"/>, and this revision
924   is specifically avoiding any such changes to the protocol.
925</t>
926</section>
927
928<section title="Uniform Resource Identifiers" anchor="uri">
929<iref primary="true" item="resource"/>
930<t>
931   Uniform Resource Identifiers (URIs) <xref target="RFC3986"/> are used
932   throughout HTTP as the means for identifying resources. URI references
933   are used to target requests, indicate redirects, and define relationships.
934   HTTP does not limit what a resource might be; it merely defines an interface
935   that can be used to interact with a resource via HTTP. More information on
936   the scope of URIs and resources can be found in <xref target="RFC3986"/>.
937</t>
938  <x:anchor-alias value="URI-reference"/>
939  <x:anchor-alias value="absolute-URI"/>
940  <x:anchor-alias value="relative-part"/>
941  <x:anchor-alias value="authority"/>
942  <x:anchor-alias value="path-abempty"/>
943  <x:anchor-alias value="path-absolute"/>
944  <x:anchor-alias value="port"/>
945  <x:anchor-alias value="query"/>
946  <x:anchor-alias value="uri-host"/>
947  <x:anchor-alias value="partial-URI"/>
948<t>
949   This specification adopts the definitions of "URI-reference",
950   "absolute-URI", "relative-part", "port", "host",
951   "path-abempty", "path-absolute", "query", and "authority" from the
952   URI generic syntax <xref target="RFC3986"/>.
953   In addition, we define a partial-URI rule for protocol elements
954   that allow a relative URI but not a fragment.
955</t>
956<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="URI-reference"/><iref primary="true" item="Grammar" subitem="absolute-URI"/><iref primary="true" item="Grammar" subitem="authority"/><iref primary="true" item="Grammar" subitem="path-absolute"/><iref primary="true" item="Grammar" subitem="port"/><iref primary="true" item="Grammar" subitem="query"/><iref primary="true" item="Grammar" subitem="uri-host"/>
957  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in <xref target="RFC3986" x:fmt="," x:sec="4.1"/>&gt;
958  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in <xref target="RFC3986" x:fmt="," x:sec="4.3"/>&gt;
959  <x:ref>relative-part</x:ref> = &lt;relative-part, defined in <xref target="RFC3986" x:fmt="," x:sec="4.2"/>&gt;
960  <x:ref>authority</x:ref>     = &lt;authority, defined in <xref target="RFC3986" x:fmt="," x:sec="3.2"/>&gt;
961  <x:ref>path-abempty</x:ref>  = &lt;path-abempty, defined in <xref target="RFC3986" x:fmt="," x:sec="3.3"/>&gt;
962  <x:ref>path-absolute</x:ref> = &lt;path-absolute, defined in <xref target="RFC3986" x:fmt="," x:sec="3.3"/>&gt;
963  <x:ref>port</x:ref>          = &lt;port, defined in <xref target="RFC3986" x:fmt="," x:sec="3.2.3"/>&gt;
964  <x:ref>query</x:ref>         = &lt;query, defined in <xref target="RFC3986" x:fmt="," x:sec="3.4"/>&gt;
965  <x:ref>uri-host</x:ref>      = &lt;host, defined in <xref target="RFC3986" x:fmt="," x:sec="3.2.2"/>&gt;
966 
967  <x:ref>partial-URI</x:ref>   = relative-part [ "?" query ]
968</artwork></figure>
969<t>
970   Each protocol element in HTTP that allows a URI reference will indicate
971   in its ABNF production whether the element allows any form of reference
972   (URI-reference), only a URI in absolute form (absolute-URI), only the
973   path and optional query components, or some combination of the above.
974   Unless otherwise indicated, URI references are parsed relative to the
975   effective request URI, which defines the default base URI for references
976   in both the request and its corresponding response.
977</t>
978
979<section title="http URI scheme" anchor="http.uri">
980  <x:anchor-alias value="http-URI"/>
981  <iref item="http URI scheme" primary="true"/>
982  <iref item="URI scheme" subitem="http" primary="true"/>
983<t>
984   The "http" URI scheme is hereby defined for the purpose of minting
985   identifiers according to their association with the hierarchical
986   namespace governed by a potential HTTP origin server listening for
987   TCP connections on a given port.
988</t>
989<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="http-URI"/>
990  <x:ref>http-URI</x:ref> = "http:" "//" <x:ref>authority</x:ref> <x:ref>path-abempty</x:ref> [ "?" <x:ref>query</x:ref> ]
991</artwork></figure>
992<t>
993   The HTTP origin server is identified by the generic syntax's
994   <x:ref>authority</x:ref> component, which includes a host identifier
995   and optional TCP port (<xref target="RFC3986" x:fmt="," x:sec="3.2.2"/>).
996   The remainder of the URI, consisting of both the hierarchical path
997   component and optional query component, serves as an identifier for
998   a potential resource within that origin server's name space.
999</t>
1000<t>
1001   If the host identifier is provided as an IP literal or IPv4 address,
1002   then the origin server is any listener on the indicated TCP port at
1003   that IP address. If host is a registered name, then that name is
1004   considered an indirect identifier and the recipient might use a name
1005   resolution service, such as DNS, to find the address of a listener
1006   for that host.
1007   The host &MUST-NOT; be empty; if an "http" URI is received with an
1008   empty host, then it &MUST; be rejected as invalid.
1009   If the port subcomponent is empty or not given, then TCP port 80 is
1010   assumed (the default reserved port for WWW services).
1011</t>
1012<t>
1013   Regardless of the form of host identifier, access to that host is not
1014   implied by the mere presence of its name or address. The host might or might
1015   not exist and, even when it does exist, might or might not be running an
1016   HTTP server or listening to the indicated port. The "http" URI scheme
1017   makes use of the delegated nature of Internet names and addresses to
1018   establish a naming authority (whatever entity has the ability to place
1019   an HTTP server at that Internet name or address) and allows that
1020   authority to determine which names are valid and how they might be used.
1021</t>
1022<t>
1023   When an "http" URI is used within a context that calls for access to the
1024   indicated resource, a client &MAY; attempt access by resolving
1025   the host to an IP address, establishing a TCP connection to that address
1026   on the indicated port, and sending an HTTP request message to the server
1027   containing the URI's identifying data as described in <xref target="request"/>.
1028   If the server responds to that request with a non-interim HTTP response
1029   message, as described in <xref target="response"/>, then that response
1030   is considered an authoritative answer to the client's request.
1031</t>
1032<t>
1033   Although HTTP is independent of the transport protocol, the "http"
1034   scheme is specific to TCP-based services because the name delegation
1035   process depends on TCP for establishing authority.
1036   An HTTP service based on some other underlying connection protocol
1037   would presumably be identified using a different URI scheme, just as
1038   the "https" scheme (below) is used for servers that require an SSL/TLS
1039   transport layer on a connection. Other protocols might also be used to
1040   provide access to "http" identified resources &mdash; it is only the
1041   authoritative interface used for mapping the namespace that is
1042   specific to TCP.
1043</t>
1044<t>
1045   The URI generic syntax for authority also includes a deprecated
1046   userinfo subcomponent (<xref target="RFC3986" x:fmt="," x:sec="3.2.1"/>)
1047   for including user authentication information in the URI.  Some
1048   implementations make use of the userinfo component for internal
1049   configuration of authentication information, such as within command
1050   invocation options, configuration files, or bookmark lists, even
1051   though such usage might expose a user identifier or password.
1052   Senders &MUST-NOT; include a userinfo subcomponent (and its "@"
1053   delimiter) when transmitting an "http" URI in a message.  Recipients
1054   of HTTP messages that contain a URI reference &SHOULD; parse for the
1055   existence of userinfo and treat its presence as an error, likely
1056   indicating that the deprecated subcomponent is being used to obscure
1057   the authority for the sake of phishing attacks.
1058</t>
1059</section>
1060
1061<section title="https URI scheme" anchor="https.uri">
1062   <x:anchor-alias value="https-URI"/>
1063   <iref item="https URI scheme"/>
1064   <iref item="URI scheme" subitem="https"/>
1065<t>
1066   The "https" URI scheme is hereby defined for the purpose of minting
1067   identifiers according to their association with the hierarchical
1068   namespace governed by a potential HTTP origin server listening for
1069   SSL/TLS-secured connections on a given TCP port.
1070</t>
1071<t>
1072   All of the requirements listed above for the "http" scheme are also
1073   requirements for the "https" scheme, except that a default TCP port
1074   of 443 is assumed if the port subcomponent is empty or not given,
1075   and the TCP connection &MUST; be secured for privacy through the
1076   use of strong encryption prior to sending the first HTTP request.
1077</t>
1078<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="https-URI"/>
1079  <x:ref>https-URI</x:ref> = "https:" "//" <x:ref>authority</x:ref> <x:ref>path-abempty</x:ref> [ "?" <x:ref>query</x:ref> ]
1080</artwork></figure>
1081<t>
1082   Unlike the "http" scheme, responses to "https" identified requests
1083   are never "public" and thus &MUST-NOT; be reused for shared caching.
1084   They can, however, be reused in a private cache if the message is
1085   cacheable by default in HTTP or specifically indicated as such by
1086   the Cache-Control header field (&header-cache-control;).
1087</t>
1088<t>
1089   Resources made available via the "https" scheme have no shared
1090   identity with the "http" scheme even if their resource identifiers
1091   indicate the same authority (the same host listening to the same
1092   TCP port).  They are distinct name spaces and are considered to be
1093   distinct origin servers.  However, an extension to HTTP that is
1094   defined to apply to entire host domains, such as the Cookie protocol
1095   <xref target="draft-ietf-httpstate-cookie"/>, can allow information
1096   set by one service to impact communication with other services
1097   within a matching group of host domains.
1098</t>
1099<t>
1100   The process for authoritative access to an "https" identified
1101   resource is defined in <xref target="RFC2818"/>.
1102</t>
1103</section>
1104
1105<section title="http and https URI Normalization and Comparison" anchor="uri.comparison">
1106<t>
1107   Since the "http" and "https" schemes conform to the URI generic syntax,
1108   such URIs are normalized and compared according to the algorithm defined
1109   in <xref target="RFC3986" x:fmt="," x:sec="6"/>, using the defaults
1110   described above for each scheme.
1111</t>
1112<t>
1113   If the port is equal to the default port for a scheme, the normal
1114   form is to elide the port subcomponent. Likewise, an empty path
1115   component is equivalent to an absolute path of "/", so the normal
1116   form is to provide a path of "/" instead. The scheme and host
1117   are case-insensitive and normally provided in lowercase; all
1118   other components are compared in a case-sensitive manner.
1119   Characters other than those in the "reserved" set are equivalent
1120   to their percent-encoded octets (see <xref target="RFC3986"
1121   x:fmt="," x:sec="2.1"/>): the normal form is to not encode them.
1122</t>
1123<t>
1124   For example, the following three URIs are equivalent:
1125</t>
1126<figure><artwork type="example">
1127   http://example.com:80/~smith/home.html
1128   http://EXAMPLE.com/%7Esmith/home.html
1129   http://EXAMPLE.com:/%7esmith/home.html
1130</artwork></figure>
1131</section>
1132</section>
1133</section>
1134
1135<section title="Message Format" anchor="http.message">
1136<x:anchor-alias value="generic-message"/>
1137<x:anchor-alias value="message.types"/>
1138<x:anchor-alias value="HTTP-message"/>
1139<x:anchor-alias value="start-line"/>
1140<iref item="header section"/>
1141<iref item="headers"/>
1142<iref item="header field"/>
1143<t>
1144   All HTTP/1.1 messages consist of a start-line followed by a sequence of
1145   octets in a format similar to the Internet Message Format
1146   <xref target="RFC5322"/>: zero or more header fields (collectively
1147   referred to as the "headers" or the "header section"), an empty line
1148   indicating the end of the header section, and an optional message-body.
1149</t>
1150<t>
1151   An HTTP message can either be a request from client to server or a
1152   response from server to client.  Syntactically, the two types of message
1153   differ only in the start-line, which is either a Request-Line (for requests)
1154   or a Status-Line (for responses), and in the algorithm for determining
1155   the length of the message-body (<xref target="message.body"/>).
1156   In theory, a client could receive requests and a server could receive
1157   responses, distinguishing them by their different start-line formats,
1158   but in practice servers are implemented to only expect a request
1159   (a response is interpreted as an unknown or invalid request method)
1160   and clients are implemented to only expect a response.
1161</t>
1162<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-message"/>
1163  <x:ref>HTTP-message</x:ref>    = <x:ref>start-line</x:ref>
1164                    *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )
1165                    <x:ref>CRLF</x:ref>
1166                    [ <x:ref>message-body</x:ref> ]
1167  <x:ref>start-line</x:ref>      = <x:ref>Request-Line</x:ref> / <x:ref>Status-Line</x:ref>
1168</artwork></figure>
1169<t>
1170   Implementations &MUST-NOT; send whitespace between the start-line and
1171   the first header field. The presence of such whitespace in a request
1172   might be an attempt to trick a server into ignoring that field or
1173   processing the line after it as a new request, either of which might
1174   result in a security vulnerability if other implementations within
1175   the request chain interpret the same message differently.
1176   Likewise, the presence of such whitespace in a response might be
1177   ignored by some clients or cause others to cease parsing.
1178</t>
1179
1180<section title="Message Parsing Robustness" anchor="message.robustness">
1181<t>
1182   In the interest of robustness, servers &SHOULD; ignore at least one
1183   empty line received where a Request-Line is expected. In other words, if
1184   the server is reading the protocol stream at the beginning of a
1185   message and receives a CRLF first, it &SHOULD; ignore the CRLF.
1186</t>
1187<t>
1188   Some old HTTP/1.0 client implementations send an extra CRLF
1189   after a POST request as a lame workaround for some early server
1190   applications that failed to read message-body content that was
1191   not terminated by a line-ending. An HTTP/1.1 client &MUST-NOT;
1192   preface or follow a request with an extra CRLF.  If terminating
1193   the request message-body with a line-ending is desired, then the
1194   client &MUST; include the terminating CRLF octets as part of the
1195   message-body length.
1196</t>
1197<t>
1198   When a server listening only for HTTP request messages, or processing
1199   what appears from the start-line to be an HTTP request message,
1200   receives a sequence of octets that does not match the HTTP-message
1201   grammar aside from the robustness exceptions listed above, the
1202   server &MUST; respond with an HTTP/1.1 400 (Bad Request) response. 
1203</t>
1204<t>
1205   The normal procedure for parsing an HTTP message is to read the
1206   start-line into a structure, read each header field into a hash
1207   table by field name until the empty line, and then use the parsed
1208   data to determine if a message-body is expected.  If a message-body
1209   has been indicated, then it is read as a stream until an amount
1210   of octets equal to the message-body length is read or the connection
1211   is closed.  Care must be taken to parse an HTTP message as a sequence
1212   of octets in an encoding that is a superset of US-ASCII.  Attempting
1213   to parse HTTP as a stream of Unicode characters in a character encoding
1214   like UTF-16 might introduce security flaws due to the differing ways
1215   that such parsers interpret invalid characters.
1216</t>
1217<t>
1218   HTTP allows the set of defined header fields to be extended without
1219   changing the protocol version (see <xref target="header.field.registration"/>).
1220   Unrecognized header fields &MUST; be forwarded by a proxy unless the
1221   proxy is specifically configured to block or otherwise transform such
1222   fields.  Unrecognized header fields &SHOULD; be ignored by other recipients.
1223</t>
1224</section>
1225
1226<section title="Header Fields" anchor="header.fields">
1227  <x:anchor-alias value="header-field"/>
1228  <x:anchor-alias value="field-content"/>
1229  <x:anchor-alias value="field-name"/>
1230  <x:anchor-alias value="field-value"/>
1231  <x:anchor-alias value="OWS"/>
1232<t>
1233   Each HTTP header field consists of a case-insensitive field name
1234   followed by a colon (":"), optional whitespace, and the field value.
1235</t>
1236<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="header-field"/><iref primary="true" item="Grammar" subitem="field-name"/><iref primary="true" item="Grammar" subitem="field-value"/><iref primary="true" item="Grammar" subitem="field-content"/>
1237  <x:ref>header-field</x:ref>   = <x:ref>field-name</x:ref> ":" <x:ref>OWS</x:ref> [ <x:ref>field-value</x:ref> ] <x:ref>OWS</x:ref>
1238  <x:ref>field-name</x:ref>     = <x:ref>token</x:ref>
1239  <x:ref>field-value</x:ref>    = *( <x:ref>field-content</x:ref> / <x:ref>OWS</x:ref> )
1240  <x:ref>field-content</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
1241</artwork></figure>
1242<t>
1243   No whitespace is allowed between the header field name and colon. For
1244   security reasons, any request message received containing such whitespace
1245   &MUST; be rejected with a response code of 400 (Bad Request). A proxy
1246   &MUST; remove any such whitespace from a response message before
1247   forwarding the message downstream.
1248</t>
1249<t>
1250   A field value &MAY; be preceded by optional whitespace (OWS); a single SP is
1251   preferred. The field value does not include any leading or trailing white
1252   space: OWS occurring before the first non-whitespace octet of the
1253   field value or after the last non-whitespace octet of the field value
1254   is ignored and &SHOULD; be removed before further processing (as this does
1255   not change the meaning of the header field).
1256</t>
1257<t>
1258   The order in which header fields with differing field names are
1259   received is not significant. However, it is "good practice" to send
1260   header fields that contain control data first, such as Host on
1261   requests and Date on responses, so that implementations can decide
1262   when not to handle a message as early as possible.  A server &MUST;
1263   wait until the entire header section is received before interpreting
1264   a request message, since later header fields might include conditionals,
1265   authentication credentials, or deliberately misleading duplicate
1266   header fields that would impact request processing.
1267</t>
1268<t>
1269   Multiple header fields with the same field name &MUST-NOT; be
1270   sent in a message unless the entire field value for that
1271   header field is defined as a comma-separated list [i.e., #(values)].
1272   Multiple header fields with the same field name can be combined into
1273   one "field-name: field-value" pair, without changing the semantics of the
1274   message, by appending each subsequent field value to the combined
1275   field value in order, separated by a comma. The order in which
1276   header fields with the same field name are received is therefore
1277   significant to the interpretation of the combined field value;
1278   a proxy &MUST-NOT; change the order of these field values when
1279   forwarding a message.
1280</t>
1281<x:note>
1282  <t>
1283   <x:h>Note:</x:h> The "Set-Cookie" header field as implemented in
1284   practice can occur multiple times, but does not use the list syntax, and
1285   thus cannot be combined into a single line (<xref target="draft-ietf-httpstate-cookie"/>). (See Appendix A.2.3 of <xref target="Kri2001"/>
1286   for details.) Also note that the Set-Cookie2 header field specified in
1287   <xref target="RFC2965"/> does not share this problem.
1288  </t>
1289</x:note>
1290<t>
1291   Historically, HTTP header field values could be extended over multiple
1292   lines by preceding each extra line with at least one space or horizontal
1293   tab octet (line folding). This specification deprecates such line
1294   folding except within the message/http media type
1295   (<xref target="internet.media.type.message.http"/>).
1296   HTTP/1.1 senders &MUST-NOT; produce messages that include line folding
1297   (i.e., that contain any field-content that matches the obs-fold rule) unless
1298   the message is intended for packaging within the message/http media type.
1299   HTTP/1.1 recipients &SHOULD; accept line folding and replace any embedded
1300   obs-fold whitespace with a single SP prior to interpreting the field value
1301   or forwarding the message downstream.
1302</t>
1303<t>
1304   Historically, HTTP has allowed field content with text in the ISO-8859-1
1305   <xref target="ISO-8859-1"/> character encoding and supported other
1306   character sets only through use of <xref target="RFC2047"/> encoding.
1307   In practice, most HTTP header field values use only a subset of the
1308   US-ASCII character encoding <xref target="USASCII"/>. Newly defined
1309   header fields &SHOULD; limit their field values to US-ASCII octets.
1310   Recipients &SHOULD; treat other (obs-text) octets in field content as
1311   opaque data.
1312</t>
1313<t anchor="rule.comment">
1314  <x:anchor-alias value="comment"/>
1315  <x:anchor-alias value="ctext"/>
1316   Comments can be included in some HTTP header fields by surrounding
1317   the comment text with parentheses. Comments are only allowed in
1318   fields containing "comment" as part of their field value definition.
1319</t>
1320<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="comment"/><iref primary="true" item="Grammar" subitem="ctext"/>
1321  <x:ref>comment</x:ref>        = "(" *( <x:ref>ctext</x:ref> / <x:ref>quoted-cpair</x:ref> / <x:ref>comment</x:ref> ) ")"
1322  <x:ref>ctext</x:ref>          = <x:ref>OWS</x:ref> / %x21-27 / %x2A-5B / %x5D-7E / <x:ref>obs-text</x:ref>
1323                 ; <x:ref>OWS</x:ref> / &lt;<x:ref>VCHAR</x:ref> except "(", ")", and "\"&gt; / <x:ref>obs-text</x:ref>
1324</artwork></figure>
1325<t anchor="rule.quoted-cpair">
1326  <x:anchor-alias value="quoted-cpair"/>
1327   The backslash octet ("\") can be used as a single-octet
1328   quoting mechanism within comment constructs:
1329</t>
1330<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="quoted-cpair"/>
1331  <x:ref>quoted-cpair</x:ref>    = "\" ( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
1332</artwork></figure>
1333<t>
1334   Senders &SHOULD-NOT; escape octets that do not require escaping
1335   (i.e., other than the backslash octet "\" and the parentheses "(" and
1336   ")").
1337</t>
1338</section>
1339
1340<section title="Message Body" anchor="message.body">
1341  <x:anchor-alias value="message-body"/>
1342<t>
1343   The message-body (if any) of an HTTP message is used to carry the
1344   payload body associated with the request or response.
1345</t>
1346<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="message-body"/>
1347  <x:ref>message-body</x:ref> = *OCTET
1348</artwork></figure>
1349<t>
1350   The message-body differs from the payload body only when a transfer-coding
1351   has been applied, as indicated by the Transfer-Encoding header field
1352   (<xref target="header.transfer-encoding"/>).  If more than one
1353   Transfer-Encoding header field is present in a message, the multiple
1354   field-values &MUST; be combined into one field-value, according to the
1355   algorithm defined in <xref target="header.fields"/>, before determining
1356   the message-body length.
1357</t>
1358<t>
1359   When one or more transfer-codings are applied to a payload in order to
1360   form the message-body, the Transfer-Encoding header field &MUST; contain
1361   the list of transfer-codings applied. Transfer-Encoding is a property of
1362   the message, not of the payload, and thus &MAY; be added or removed by
1363   any implementation along the request/response chain under the constraints
1364   found in <xref target="transfer.codings"/>.
1365</t>
1366<t>
1367   If a message is received that has multiple Content-Length header fields
1368   (<xref target="header.content-length"/>) with field-values consisting
1369   of the same decimal value, or a single Content-Length header field with
1370   a field value containing a list of identical decimal values (e.g.,
1371   "Content-Length: 42, 42"), indicating that duplicate Content-Length
1372   header fields have been generated or combined by an upstream message
1373   processor, then the recipient &MUST; replace the duplicated fields or
1374   field-values with a single valid Content-Length field containing that
1375   decimal value prior to determining the message-body length.
1376</t>
1377<t>
1378   The rules for when a message-body is allowed in a message differ for
1379   requests and responses.
1380</t>
1381<t>
1382   The presence of a message-body in a request is signaled by the
1383   inclusion of a Content-Length or Transfer-Encoding header field in
1384   the request's header fields, even if the request method does not
1385   define any use for a message-body.  This allows the request
1386   message framing algorithm to be independent of method semantics.
1387</t>
1388<t>
1389   For response messages, whether or not a message-body is included with
1390   a message is dependent on both the request method and the response
1391   status code (<xref target="status.code.and.reason.phrase"/>).
1392   Responses to the HEAD request method never include a message-body
1393   because the associated response header fields (e.g., Transfer-Encoding,
1394   Content-Length, etc.) only indicate what their values would have been
1395   if the request method had been GET.  All 1xx (Informational), 204 (No Content),
1396   and 304 (Not Modified) responses &MUST-NOT; include a message-body.
1397   All other responses do include a message-body, although the body
1398   &MAY; be of zero length.
1399</t>
1400<t>
1401   The length of the message-body is determined by one of the following
1402   (in order of precedence):
1403</t>
1404<t>
1405  <list style="numbers">
1406    <x:lt><t>
1407     Any response to a HEAD request and any response with a status
1408     code of 100-199, 204, or 304 is always terminated by the first
1409     empty line after the header fields, regardless of the header
1410     fields present in the message, and thus cannot contain a message-body.
1411    </t></x:lt>
1412    <x:lt><t>
1413     If a Transfer-Encoding header field is present
1414     and the "chunked" transfer-coding (<xref target="transfer.codings"/>)
1415     is the final encoding, the message-body length is determined by reading
1416     and decoding the chunked data until the transfer-coding indicates the
1417     data is complete.
1418    </t>
1419    <t>
1420     If a Transfer-Encoding header field is present in a response and the
1421     "chunked" transfer-coding is not the final encoding, the message-body
1422     length is determined by reading the connection until it is closed by
1423     the server.
1424     If a Transfer-Encoding header field is present in a request and the
1425     "chunked" transfer-coding is not the final encoding, the message-body
1426     length cannot be determined reliably; the server &MUST; respond with
1427     the 400 (Bad Request) status code and then close the connection.
1428    </t>
1429    <t>
1430     If a message is received with both a Transfer-Encoding header field
1431     and a Content-Length header field, the Transfer-Encoding overrides
1432     the Content-Length.
1433     Such a message might indicate an attempt to perform request or response
1434     smuggling (bypass of security-related checks on message routing or content)
1435     and thus ought to be handled as an error.  The provided Content-Length &MUST;
1436     be removed, prior to forwarding the message downstream, or replaced with
1437     the real message-body length after the transfer-coding is decoded.
1438    </t></x:lt>
1439    <x:lt><t>
1440     If a message is received without Transfer-Encoding and with either
1441     multiple Content-Length header fields having differing field-values or
1442     a single Content-Length header field having an invalid value, then the
1443     message framing is invalid and &MUST; be treated as an error to
1444     prevent request or response smuggling.
1445     If this is a request message, the server &MUST; respond with
1446     a 400 (Bad Request) status code and then close the connection.
1447     If this is a response message received by a proxy, the proxy
1448     &MUST; discard the received response, send a 502 (Bad Gateway)
1449     status code as its downstream response, and then close the connection.
1450     If this is a response message received by a user-agent, it &MUST; be
1451     treated as an error by discarding the message and closing the connection.
1452    </t></x:lt>
1453    <x:lt><t>
1454     If a valid Content-Length header field
1455     is present without Transfer-Encoding, its decimal value defines the
1456     message-body length in octets.  If the actual number of octets sent in
1457     the message is less than the indicated Content-Length, the recipient
1458     &MUST; consider the message to be incomplete and treat the connection
1459     as no longer usable.
1460     If the actual number of octets sent in the message is more than the indicated
1461     Content-Length, the recipient &MUST; only process the message-body up to the
1462     field value's number of octets; the remainder of the message &MUST; either
1463     be discarded or treated as the next message in a pipeline.  For the sake of
1464     robustness, a user-agent &MAY; attempt to detect and correct such an error
1465     in message framing if it is parsing the response to the last request on
1466     on a connection and the connection has been closed by the server.
1467    </t></x:lt>
1468    <x:lt><t>
1469     If this is a request message and none of the above are true, then the
1470     message-body length is zero (no message-body is present).
1471    </t></x:lt>
1472    <x:lt><t>
1473     Otherwise, this is a response message without a declared message-body
1474     length, so the message-body length is determined by the number of octets
1475     received prior to the server closing the connection.
1476    </t></x:lt>
1477  </list>
1478</t>
1479<t>
1480   Since there is no way to distinguish a successfully completed,
1481   close-delimited message from a partially-received message interrupted
1482   by network failure, implementations &SHOULD; use encoding or
1483   length-delimited messages whenever possible.  The close-delimiting
1484   feature exists primarily for backwards compatibility with HTTP/1.0.
1485</t>
1486<t>
1487   A server &MAY; reject a request that contains a message-body but
1488   not a Content-Length by responding with 411 (Length Required).
1489</t>
1490<t>
1491   Unless a transfer-coding other than "chunked" has been applied,
1492   a client that sends a request containing a message-body &SHOULD;
1493   use a valid Content-Length header field if the message-body length
1494   is known in advance, rather than the "chunked" encoding, since some
1495   existing services respond to "chunked" with a 411 (Length Required)
1496   status code even though they understand the chunked encoding.  This
1497   is typically because such services are implemented via a gateway that
1498   requires a content-length in advance of being called and the server
1499   is unable or unwilling to buffer the entire request before processing.
1500</t>
1501<t>
1502   A client that sends a request containing a message-body &MUST; include a
1503   valid Content-Length header field if it does not know the server will
1504   handle HTTP/1.1 (or later) requests; such knowledge can be in the form
1505   of specific user configuration or by remembering the version of a prior
1506   received response.
1507</t>
1508<t>
1509   Request messages that are prematurely terminated, possibly due to a
1510   cancelled connection or a server-imposed time-out exception, &MUST;
1511   result in closure of the connection; sending an HTTP/1.1 error response
1512   prior to closing the connection is &OPTIONAL;.
1513   Response messages that are prematurely terminated, usually by closure
1514   of the connection prior to receiving the expected number of octets or by
1515   failure to decode a transfer-encoded message-body, &MUST; be recorded
1516   as incomplete.  A user agent &MUST-NOT; render an incomplete response
1517   message-body as if it were complete (i.e., some indication must be given
1518   to the user that an error occurred).  Cache requirements for incomplete
1519   responses are defined in &cache-incomplete;.
1520</t>
1521<t>
1522   A server &MUST; read the entire request message-body or close
1523   the connection after sending its response, since otherwise the
1524   remaining data on a persistent connection would be misinterpreted
1525   as the next request.  Likewise,
1526   a client &MUST; read the entire response message-body if it intends
1527   to reuse the same connection for a subsequent request.  Pipelining
1528   multiple requests on a connection is described in <xref target="pipelining"/>.
1529</t>
1530</section>
1531
1532<section title="General Header Fields" anchor="general.header.fields">
1533  <x:anchor-alias value="general-header"/>
1534<t>
1535   There are a few header fields which have general applicability for
1536   both request and response messages, but which do not apply to the
1537   payload being transferred. These header fields apply only to the
1538   message being transmitted.
1539</t>
1540<texttable align="left">
1541  <ttcol>Header Field Name</ttcol>
1542  <ttcol>Defined in...</ttcol>
1543 
1544  <c>Connection</c> <c><xref target="header.connection"/></c>
1545  <c>Date</c> <c><xref target="header.date"/></c>
1546  <c>Trailer</c> <c><xref target="header.trailer"/></c>
1547  <c>Transfer-Encoding</c> <c><xref target="header.transfer-encoding"/></c>
1548  <c>Upgrade</c> <c><xref target="header.upgrade"/></c>
1549  <c>Via</c> <c><xref target="header.via"/></c>
1550</texttable>
1551</section>
1552</section>
1553
1554<section title="Request" anchor="request">
1555  <x:anchor-alias value="Request"/>
1556<t>
1557   A request message from a client to a server begins with a
1558   Request-Line, followed by zero or more header fields, an empty
1559   line signifying the end of the header block, and an optional
1560   message body.
1561</t>
1562<!--                 Host                      ; should be moved here eventually -->
1563<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Request"/>
1564  <x:ref>Request</x:ref>       = <x:ref>Request-Line</x:ref>              ; <xref target="request-line"/>
1565                  *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )    ; <xref target="header.fields"/>
1566                  <x:ref>CRLF</x:ref>
1567                  [ <x:ref>message-body</x:ref> ]          ; <xref target="message.body"/>
1568</artwork></figure>
1569
1570<section title="Request-Line" anchor="request-line">
1571  <x:anchor-alias value="Request-Line"/>
1572<t>
1573   The Request-Line begins with a method token, followed by a single
1574   space (SP), the request-target, another single space (SP), the
1575   protocol version, and ending with CRLF.
1576</t>
1577<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Request-Line"/>
1578  <x:ref>Request-Line</x:ref>   = <x:ref>Method</x:ref> <x:ref>SP</x:ref> <x:ref>request-target</x:ref> <x:ref>SP</x:ref> <x:ref>HTTP-Version</x:ref> <x:ref>CRLF</x:ref>
1579</artwork></figure>
1580
1581<section title="Method" anchor="method">
1582  <x:anchor-alias value="Method"/>
1583<t>
1584   The Method token indicates the request method to be performed on the
1585   target resource. The request method is case-sensitive.
1586</t>
1587<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
1588  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
1589</artwork></figure>
1590</section>
1591
1592<section title="request-target" anchor="request-target">
1593  <x:anchor-alias value="request-target"/>
1594<t>
1595   The request-target identifies the target resource upon which to apply
1596   the request.  In most cases, the user agent is provided a URI reference
1597   from which it determines an absolute URI for identifying the target
1598   resource.  When a request to the resource is initiated, all or part
1599   of that URI is used to construct the HTTP request-target.
1600</t>
1601<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-target"/>
1602  <x:ref>request-target</x:ref> = "*"
1603                 / <x:ref>absolute-URI</x:ref>
1604                 / ( <x:ref>path-absolute</x:ref> [ "?" <x:ref>query</x:ref> ] )
1605                 / <x:ref>authority</x:ref>
1606</artwork></figure>
1607<t>
1608   The four options for request-target are dependent on the nature of the
1609   request.
1610</t>   
1611<t><iref item="asterisk form (of request-target)"/>
1612   The asterisk "*" form of request-target, which &MUST-NOT; be used
1613   with any request method other than OPTIONS, means that the request
1614   applies to the server as a whole (the listening process) rather than
1615   to a specific named resource at that server.  For example,
1616</t>
1617<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1618OPTIONS * HTTP/1.1
1619</artwork></figure>
1620<t><iref item="absolute-URI form (of request-target)"/>
1621   The "absolute-URI" form is &REQUIRED; when the request is being made to a
1622   proxy. The proxy is requested to either forward the request or service it
1623   from a valid cache, and then return the response. Note that the proxy &MAY;
1624   forward the request on to another proxy or directly to the server
1625   specified by the absolute-URI. In order to avoid request loops, a
1626   proxy that forwards requests to other proxies &MUST; be able to
1627   recognize and exclude all of its own server names, including
1628   any aliases, local variations, and the numeric IP address. An example
1629   Request-Line would be:
1630</t>
1631<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1632GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
1633</artwork></figure>
1634<t>
1635   To allow for transition to absolute-URIs in all requests in future
1636   versions of HTTP, all HTTP/1.1 servers &MUST; accept the absolute-URI
1637   form in requests, even though HTTP/1.1 clients will only generate
1638   them in requests to proxies.
1639</t>
1640<t>
1641   If a proxy receives a host name that is not a fully qualified domain
1642   name, it &MAY; add its domain to the host name it received. If a proxy
1643   receives a fully qualified domain name, the proxy &MUST-NOT; change
1644   the host name.
1645</t>
1646<t><iref item="authority form (of request-target)"/>
1647   The "authority form" is only used by the CONNECT request method (&CONNECT;).
1648</t>
1649<t><iref item="origin form (of request-target)"/>
1650   The most common form of request-target is that used when making
1651   a request to an origin server ("origin form").
1652   In this case, the absolute path and query components of the URI
1653   &MUST; be transmitted as the request-target, and the authority component
1654   &MUST; be transmitted in a Host header field. For example, a client wishing
1655   to retrieve a representation of the resource, as identified above,
1656   directly from the origin server would open (or reuse) a TCP connection
1657   to port 80 of the host "www.example.org" and send the lines:
1658</t>
1659<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1660GET /pub/WWW/TheProject.html HTTP/1.1
1661Host: www.example.org
1662</artwork></figure>
1663<t>
1664   followed by the remainder of the Request. Note that the origin form
1665   of request-target always starts with an absolute path; if the target
1666   resource's URI path is empty, then an absolute path of "/" &MUST; be
1667   provided in the request-target.
1668</t>
1669<t>
1670   If a proxy receives an OPTIONS request with an absolute-URI form of
1671   request-target in which the URI has an empty path and no query component,
1672   then the last proxy on the request chain &MUST; use a request-target
1673   of "*" when it forwards the request to the indicated origin server.
1674</t>
1675<figure><preamble>   
1676   For example, the request
1677</preamble><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1678OPTIONS http://www.example.org:8001 HTTP/1.1
1679</artwork></figure>
1680<figure><preamble>   
1681  would be forwarded by the final proxy as
1682</preamble><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1683OPTIONS * HTTP/1.1
1684Host: www.example.org:8001
1685</artwork>
1686<postamble>
1687   after connecting to port 8001 of host "www.example.org".
1688</postamble>
1689</figure>
1690<t>
1691   The request-target is transmitted in the format specified in
1692   <xref target="http.uri"/>. If the request-target is percent-encoded
1693   (<xref target="RFC3986" x:fmt="," x:sec="2.1"/>), the origin server
1694   &MUST; decode the request-target in order to
1695   properly interpret the request. Servers &SHOULD; respond to invalid
1696   request-targets with an appropriate status code.
1697</t>
1698<t>
1699   A non-transforming proxy &MUST-NOT; rewrite the "path-absolute" part of the
1700   received request-target when forwarding it to the next inbound server,
1701   except as noted above to replace a null path-absolute with "/" or "*".
1702</t>
1703<x:note>
1704  <t>
1705    <x:h>Note:</x:h> The "no rewrite" rule prevents the proxy from changing the
1706    meaning of the request when the origin server is improperly using
1707    a non-reserved URI character for a reserved purpose.  Implementors
1708    need to be aware that some pre-HTTP/1.1 proxies have been known to
1709    rewrite the request-target.
1710  </t>
1711</x:note>
1712<t>
1713   HTTP does not place a pre-defined limit on the length of a request-target.
1714   A server &MUST; be prepared to receive URIs of unbounded length and
1715   respond with the 414 (URI Too Long) status code if the received
1716   request-target would be longer than the server wishes to handle
1717   (see &status-414;).
1718</t>
1719<t>
1720   Various ad-hoc limitations on request-target length are found in practice.
1721   It is &RECOMMENDED; that all HTTP senders and recipients support
1722   request-target lengths of 8000 or more octets.
1723</t>
1724<x:note>
1725  <t>
1726    <x:h>Note:</x:h> Fragments (<xref target="RFC3986" x:fmt="," x:sec="3.5"/>)
1727    are not part of the request-target and thus will not be transmitted
1728    in an HTTP request.
1729  </t>
1730</x:note>
1731</section>
1732</section>
1733
1734<section title="The Resource Identified by a Request" anchor="the.resource.identified.by.a.request">
1735<t>
1736   The exact resource identified by an Internet request is determined by
1737   examining both the request-target and the Host header field.
1738</t>
1739<t>
1740   An origin server that does not allow resources to differ by the
1741   requested host &MAY; ignore the Host header field value when
1742   determining the resource identified by an HTTP/1.1 request. (But see
1743   <xref target="changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses"/>
1744   for other requirements on Host support in HTTP/1.1.)
1745</t>
1746<t>
1747   An origin server that does differentiate resources based on the host
1748   requested (sometimes referred to as virtual hosts or vanity host
1749   names) &MUST; use the following rules for determining the requested
1750   resource on an HTTP/1.1 request:
1751  <list style="numbers">
1752    <t>If request-target is an absolute-URI, the host is part of the
1753     request-target. Any Host header field value in the request &MUST; be
1754     ignored.</t>
1755    <t>If the request-target is not an absolute-URI, and the request includes
1756     a Host header field, the host is determined by the Host header
1757     field value.</t>
1758    <t>If the host as determined by rule 1 or 2 is not a valid host on
1759     the server, the response &MUST; be a 400 (Bad Request) error message.</t>
1760  </list>
1761</t>
1762<t>
1763   Recipients of an HTTP/1.0 request that lacks a Host header field &MAY;
1764   attempt to use heuristics (e.g., examination of the URI path for
1765   something unique to a particular host) in order to determine what
1766   exact resource is being requested.
1767</t>
1768</section>
1769
1770<section title="Effective Request URI" anchor="effective.request.uri">
1771  <iref primary="true" item="effective request URI"/>
1772  <iref primary="true" item="target resource"/>
1773<t>
1774   HTTP requests often do not carry the absolute URI (<xref target="RFC3986" x:fmt="," x:sec="4.3"/>)
1775   for the target resource; instead, the URI needs to be inferred from the
1776   request-target, Host header field, and connection context. The result of
1777   this process is called the "effective request URI".  The "target resource"
1778   is the resource identified by the effective request URI.
1779</t>
1780<t>
1781   If the request-target is an absolute-URI, then the effective request URI is
1782   the request-target.
1783</t>
1784<t>
1785   If the request-target uses the path-absolute form or the asterisk form,
1786   and the Host header field is present, then the effective request URI is
1787   constructed by concatenating
1788</t>
1789<t>
1790  <list style="symbols">
1791    <t>
1792      the scheme name: "http" if the request was received over an insecure
1793      TCP connection, or "https" when received over a SSL/TLS-secured TCP
1794      connection,
1795    </t>
1796    <t>
1797      the octet sequence "://",
1798    </t>
1799    <t>
1800      the authority component, as specified in the Host header field
1801      (<xref target="header.host"/>), and
1802    </t>
1803    <t>
1804      the request-target obtained from the Request-Line, unless the
1805      request-target is just the asterisk "*".
1806    </t>
1807  </list>
1808</t>
1809<t>
1810   If the request-target uses the path-absolute form or the asterisk form,
1811   and the Host header field is not present, then the effective request URI is
1812   undefined.
1813</t>
1814<t>
1815   Otherwise, when request-target uses the authority form, the effective
1816   request URI is undefined.
1817</t>
1818<figure>
1819<preamble>
1820   Example 1: the effective request URI for the message
1821</preamble> 
1822<artwork type="example" x:indent-with="  ">
1823GET /pub/WWW/TheProject.html HTTP/1.1
1824Host: www.example.org:8080
1825</artwork>
1826<postamble>
1827  (received over an insecure TCP connection) is "http", plus "://", plus the
1828  authority component "www.example.org:8080", plus the request-target
1829  "/pub/WWW/TheProject.html", thus
1830  "http://www.example.org:8080/pub/WWW/TheProject.html".
1831</postamble>
1832</figure>
1833<figure>
1834<preamble>
1835   Example 2: the effective request URI for the message
1836</preamble> 
1837<artwork type="example" x:indent-with="  ">
1838GET * HTTP/1.1
1839Host: www.example.org
1840</artwork>
1841<postamble>
1842  (received over an SSL/TLS secured TCP connection) is "https", plus "://", plus the
1843  authority component "www.example.org", thus "https://www.example.org".
1844</postamble>
1845</figure>
1846<t>
1847   Effective request URIs are compared using the rules described in
1848   <xref target="uri.comparison"/>, except that empty path components &MUST-NOT;
1849   be treated as equivalent to an absolute path of "/".
1850</t> 
1851</section>
1852
1853</section>
1854
1855
1856<section title="Response" anchor="response">
1857  <x:anchor-alias value="Response"/>
1858<t>
1859   After receiving and interpreting a request message, a server responds
1860   with an HTTP response message.
1861</t>
1862<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Response"/>
1863  <x:ref>Response</x:ref>      = <x:ref>Status-Line</x:ref>               ; <xref target="status-line"/>
1864                  *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )    ; <xref target="header.fields"/>
1865                  <x:ref>CRLF</x:ref>
1866                  [ <x:ref>message-body</x:ref> ]          ; <xref target="message.body"/>
1867</artwork></figure>
1868
1869<section title="Status-Line" anchor="status-line">
1870  <x:anchor-alias value="Status-Line"/>
1871<t>
1872   The first line of a Response message is the Status-Line, consisting
1873   of the protocol version, a space (SP), the status code, another space,
1874   a possibly-empty textual phrase describing the status code, and
1875   ending with CRLF.
1876</t>
1877<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Line"/>
1878  <x:ref>Status-Line</x:ref> = <x:ref>HTTP-Version</x:ref> <x:ref>SP</x:ref> <x:ref>Status-Code</x:ref> <x:ref>SP</x:ref> <x:ref>Reason-Phrase</x:ref> <x:ref>CRLF</x:ref>
1879</artwork></figure>
1880
1881<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
1882  <x:anchor-alias value="Reason-Phrase"/>
1883  <x:anchor-alias value="Status-Code"/>
1884<t>
1885   The Status-Code element is a 3-digit integer result code of the
1886   attempt to understand and satisfy the request. These codes are fully
1887   defined in &status-codes;.  The Reason Phrase exists for the sole
1888   purpose of providing a textual description associated with the numeric
1889   status code, out of deference to earlier Internet application protocols
1890   that were more frequently used with interactive text clients.
1891   A client &SHOULD; ignore the content of the Reason Phrase.
1892</t>
1893<t>
1894   The first digit of the Status-Code defines the class of response. The
1895   last two digits do not have any categorization role. There are 5
1896   values for the first digit:
1897  <list style="symbols">
1898    <t>
1899      1xx: Informational - Request received, continuing process
1900    </t>
1901    <t>
1902      2xx: Success - The action was successfully received,
1903        understood, and accepted
1904    </t>
1905    <t>
1906      3xx: Redirection - Further action must be taken in order to
1907        complete the request
1908    </t>
1909    <t>
1910      4xx: Client Error - The request contains bad syntax or cannot
1911        be fulfilled
1912    </t>
1913    <t>
1914      5xx: Server Error - The server failed to fulfill an apparently
1915        valid request
1916    </t>
1917  </list>
1918</t>
1919<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
1920  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
1921  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
1922</artwork></figure>
1923</section>
1924</section>
1925
1926</section>
1927
1928
1929<section title="Protocol Parameters" anchor="protocol.parameters">
1930
1931<section title="Date/Time Formats: Full Date" anchor="date.time.formats.full.date">
1932  <x:anchor-alias value="HTTP-date"/>
1933<t>
1934   HTTP applications have historically allowed three different formats
1935   for date/time stamps. However, the preferred format is a fixed-length subset
1936   of that defined by <xref target="RFC1123"/>:
1937</t>
1938<figure><artwork type="example" x:indent-with="  ">
1939Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
1940</artwork></figure>
1941<t>
1942   The other formats are described here only for compatibility with obsolete
1943   implementations.
1944</t>
1945<figure><artwork type="example" x:indent-with="  ">
1946Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
1947Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
1948</artwork></figure>
1949<t>
1950   HTTP/1.1 clients and servers that parse a date value &MUST; accept
1951   all three formats (for compatibility with HTTP/1.0), though they &MUST;
1952   only generate the RFC 1123 format for representing HTTP-date values
1953   in header fields. See <xref target="tolerant.applications"/> for further information.
1954</t>
1955<t>
1956   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
1957   (GMT), without exception. For the purposes of HTTP, GMT is exactly
1958   equal to UTC (Coordinated Universal Time). This is indicated in the
1959   first two formats by the inclusion of "GMT" as the three-letter
1960   abbreviation for time zone, and &MUST; be assumed when reading the
1961   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
1962   additional whitespace beyond that specifically included as SP in the
1963   grammar.
1964</t>
1965<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
1966  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
1967</artwork></figure>
1968<t anchor="preferred.date.format">
1969  <x:anchor-alias value="rfc1123-date"/>
1970  <x:anchor-alias value="time-of-day"/>
1971  <x:anchor-alias value="hour"/>
1972  <x:anchor-alias value="minute"/>
1973  <x:anchor-alias value="second"/>
1974  <x:anchor-alias value="day-name"/>
1975  <x:anchor-alias value="day"/>
1976  <x:anchor-alias value="month"/>
1977  <x:anchor-alias value="year"/>
1978  <x:anchor-alias value="GMT"/>
1979  Preferred format:
1980</t>
1981<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc1123-date"/><iref primary="true" item="Grammar" subitem="date1"/><iref primary="true" item="Grammar" subitem="time-of-day"/><iref primary="true" item="Grammar" subitem="hour"/><iref primary="true" item="Grammar" subitem="minute"/><iref primary="true" item="Grammar" subitem="second"/><iref primary="true" item="Grammar" subitem="day-name"/><iref primary="true" item="Grammar" subitem="day-name-l"/><iref primary="true" item="Grammar" subitem="day"/><iref primary="true" item="Grammar" subitem="month"/><iref primary="true" item="Grammar" subitem="year"/><iref primary="true" item="Grammar" subitem="GMT"/>
1982  <x:ref>rfc1123-date</x:ref> = <x:ref>day-name</x:ref> "," <x:ref>SP</x:ref> date1 <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
1983  ; fixed length subset of the format defined in
1984  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
1985 
1986  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
1987               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
1988               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
1989               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
1990               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
1991               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
1992               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
1993               
1994  <x:ref>date1</x:ref>        = <x:ref>day</x:ref> <x:ref>SP</x:ref> <x:ref>month</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
1995               ; e.g., 02 Jun 1982
1996
1997  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
1998  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
1999               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2000               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2001               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2002               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2003               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2004               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2005               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2006               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2007               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2008               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2009               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2010  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2011
2012  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2013
2014  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2015                 ; 00:00:00 - 23:59:59
2016                 
2017  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2018  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2019  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2020</artwork></figure>
2021<t>
2022  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2023  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2024  same as those defined for the RFC 5322 constructs
2025  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2026</t>
2027<t anchor="obsolete.date.formats">
2028  <x:anchor-alias value="obs-date"/>
2029  <x:anchor-alias value="rfc850-date"/>
2030  <x:anchor-alias value="asctime-date"/>
2031  <x:anchor-alias value="date1"/>
2032  <x:anchor-alias value="date2"/>
2033  <x:anchor-alias value="date3"/>
2034  <x:anchor-alias value="rfc1123-date"/>
2035  <x:anchor-alias value="day-name-l"/>
2036  Obsolete formats:
2037</t>
2038<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2039  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2040</artwork></figure>
2041<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2042  <x:ref>rfc850-date</x:ref>  = <x:ref>day-name-l</x:ref> "," <x:ref>SP</x:ref> <x:ref>date2</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2043  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2044                 ; day-month-year (e.g., 02-Jun-82)
2045
2046  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2047         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2048         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2049         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2050         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2051         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2052         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2053</artwork></figure>
2054<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2055  <x:ref>asctime-date</x:ref> = <x:ref>day-name</x:ref> <x:ref>SP</x:ref> <x:ref>date3</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2056  <x:ref>date3</x:ref>        = <x:ref>month</x:ref> <x:ref>SP</x:ref> ( 2<x:ref>DIGIT</x:ref> / ( <x:ref>SP</x:ref> 1<x:ref>DIGIT</x:ref> ))
2057                 ; month day (e.g., Jun  2)
2058</artwork></figure>
2059<x:note>
2060  <t>
2061    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2062    accepting date values that might have been sent by non-HTTP
2063    applications, as is sometimes the case when retrieving or posting
2064    messages via proxies/gateways to SMTP or NNTP.
2065  </t>
2066</x:note>
2067<x:note>
2068  <t>
2069    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2070    to their usage within the protocol stream. Clients and servers are
2071    not required to use these formats for user presentation, request
2072    logging, etc.
2073  </t>
2074</x:note>
2075</section>
2076
2077<section title="Transfer Codings" anchor="transfer.codings">
2078  <x:anchor-alias value="transfer-coding"/>
2079  <x:anchor-alias value="transfer-extension"/>
2080<t>
2081   Transfer-coding values are used to indicate an encoding
2082   transformation that has been, can be, or might need to be applied to a
2083   payload body in order to ensure "safe transport" through the network.
2084   This differs from a content coding in that the transfer-coding is a
2085   property of the message rather than a property of the representation
2086   that is being transferred.
2087</t>
2088<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="transfer-coding"/><iref primary="true" item="Grammar" subitem="transfer-extension"/>
2089  <x:ref>transfer-coding</x:ref>         = "chunked" ; <xref target="chunked.encoding"/>
2090                          / "compress" ; <xref target="compress.coding"/>
2091                          / "deflate" ; <xref target="deflate.coding"/>
2092                          / "gzip" ; <xref target="gzip.coding"/>
2093                          / <x:ref>transfer-extension</x:ref>
2094  <x:ref>transfer-extension</x:ref>      = <x:ref>token</x:ref> *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>transfer-parameter</x:ref> )
2095</artwork></figure>
2096<t anchor="rule.parameter">
2097  <x:anchor-alias value="attribute"/>
2098  <x:anchor-alias value="transfer-parameter"/>
2099  <x:anchor-alias value="value"/>
2100   Parameters are in the form of attribute/value pairs.
2101</t>
2102<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="transfer-parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/><iref primary="true" item="Grammar" subitem="date2"/><iref primary="true" item="Grammar" subitem="date3"/>
2103  <x:ref>transfer-parameter</x:ref>      = <x:ref>attribute</x:ref> <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>value</x:ref>
2104  <x:ref>attribute</x:ref>               = <x:ref>token</x:ref>
2105  <x:ref>value</x:ref>                   = <x:ref>word</x:ref>
2106</artwork></figure>
2107<t>
2108   All transfer-coding values are case-insensitive. HTTP/1.1 uses
2109   transfer-coding values in the TE header field (<xref target="header.te"/>) and in
2110   the Transfer-Encoding header field (<xref target="header.transfer-encoding"/>).
2111</t>
2112<t>
2113   Transfer-codings are analogous to the Content-Transfer-Encoding values of
2114   MIME, which were designed to enable safe transport of binary data over a
2115   7-bit transport service (<xref target="RFC2045" x:fmt="," x:sec="6"/>).
2116   However, safe transport
2117   has a different focus for an 8bit-clean transfer protocol. In HTTP,
2118   the only unsafe characteristic of message-bodies is the difficulty in
2119   determining the exact message body length (<xref target="message.body"/>),
2120   or the desire to encrypt data over a shared transport.
2121</t>
2122<t>
2123   A server that receives a request message with a transfer-coding it does
2124   not understand &SHOULD; respond with 501 (Not Implemented) and then
2125   close the connection. A server &MUST-NOT; send transfer-codings to an HTTP/1.0
2126   client.
2127</t>
2128
2129<section title="Chunked Transfer Coding" anchor="chunked.encoding">
2130  <iref item="chunked (Coding Format)"/>
2131  <iref item="Coding Format" subitem="chunked"/>
2132  <x:anchor-alias value="chunk"/>
2133  <x:anchor-alias value="Chunked-Body"/>
2134  <x:anchor-alias value="chunk-data"/>
2135  <x:anchor-alias value="chunk-ext"/>
2136  <x:anchor-alias value="chunk-ext-name"/>
2137  <x:anchor-alias value="chunk-ext-val"/>
2138  <x:anchor-alias value="chunk-size"/>
2139  <x:anchor-alias value="last-chunk"/>
2140  <x:anchor-alias value="trailer-part"/>
2141  <x:anchor-alias value="quoted-str-nf"/>
2142  <x:anchor-alias value="qdtext-nf"/>
2143<t>
2144   The chunked encoding modifies the body of a message in order to
2145   transfer it as a series of chunks, each with its own size indicator,
2146   followed by an &OPTIONAL; trailer containing header fields. This
2147   allows dynamically produced content to be transferred along with the
2148   information necessary for the recipient to verify that it has
2149   received the full message.
2150</t>
2151<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Chunked-Body"/><iref primary="true" item="Grammar" subitem="chunk"/><iref primary="true" item="Grammar" subitem="chunk-size"/><iref primary="true" item="Grammar" subitem="last-chunk"/><iref primary="true" item="Grammar" subitem="chunk-ext"/><iref primary="true" item="Grammar" subitem="chunk-ext-name"/><iref primary="true" item="Grammar" subitem="chunk-ext-val"/><iref primary="true" item="Grammar" subitem="chunk-data"/><iref primary="true" item="Grammar" subitem="trailer-part"/><iref primary="true" item="Grammar" subitem="quoted-str-nf"/><iref primary="true" item="Grammar" subitem="qdtext-nf"/>
2152  <x:ref>Chunked-Body</x:ref>   = *<x:ref>chunk</x:ref>
2153                   <x:ref>last-chunk</x:ref>
2154                   <x:ref>trailer-part</x:ref>
2155                   <x:ref>CRLF</x:ref>
2156 
2157  <x:ref>chunk</x:ref>          = <x:ref>chunk-size</x:ref> *WSP [ <x:ref>chunk-ext</x:ref> ] <x:ref>CRLF</x:ref>
2158                   <x:ref>chunk-data</x:ref> <x:ref>CRLF</x:ref>
2159  <x:ref>chunk-size</x:ref>     = 1*<x:ref>HEXDIG</x:ref>
2160  <x:ref>last-chunk</x:ref>     = 1*("0") *WSP [ <x:ref>chunk-ext</x:ref> ] <x:ref>CRLF</x:ref>
2161 
2162  <x:ref>chunk-ext</x:ref>      = *( ";" *WSP <x:ref>chunk-ext-name</x:ref>
2163                      [ "=" <x:ref>chunk-ext-val</x:ref> ] *WSP )
2164  <x:ref>chunk-ext-name</x:ref> = <x:ref>token</x:ref>
2165  <x:ref>chunk-ext-val</x:ref>  = <x:ref>token</x:ref> / <x:ref>quoted-str-nf</x:ref>
2166  <x:ref>chunk-data</x:ref>     = 1*<x:ref>OCTET</x:ref> ; a sequence of chunk-size octets
2167  <x:ref>trailer-part</x:ref>   = *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )
2168 
2169  <x:ref>quoted-str-nf</x:ref>  = <x:ref>DQUOTE</x:ref> *( <x:ref>qdtext-nf</x:ref> / <x:ref>quoted-pair</x:ref> ) <x:ref>DQUOTE</x:ref>
2170                 ; like <x:ref>quoted-string</x:ref>, but disallowing line folding
2171  <x:ref>qdtext-nf</x:ref>      = <x:ref>WSP</x:ref> / %x21 / %x23-5B / %x5D-7E / <x:ref>obs-text</x:ref>
2172                 ; <x:ref>WSP</x:ref> / &lt;<x:ref>VCHAR</x:ref> except <x:ref>DQUOTE</x:ref> and "\"&gt; / <x:ref>obs-text</x:ref> 
2173</artwork></figure>
2174<t>
2175   The chunk-size field is a string of hex digits indicating the size of
2176   the chunk-data in octets. The chunked encoding is ended by any chunk whose size is
2177   zero, followed by the trailer, which is terminated by an empty line.
2178</t>
2179<t>
2180   The trailer allows the sender to include additional HTTP header
2181   fields at the end of the message. The Trailer header field can be
2182   used to indicate which header fields are included in a trailer (see
2183   <xref target="header.trailer"/>).
2184</t>
2185<t>
2186   A server using chunked transfer-coding in a response &MUST-NOT; use the
2187   trailer for any header fields unless at least one of the following is
2188   true:
2189  <list style="numbers">
2190    <t>the request included a TE header field that indicates "trailers" is
2191     acceptable in the transfer-coding of the  response, as described in
2192     <xref target="header.te"/>; or,</t>
2193     
2194    <t>the trailer fields consist entirely of optional metadata, and the
2195    recipient could use the message (in a manner acceptable to the server where
2196    the field originated) without receiving it. In other words, the server that
2197    generated the header (often but not always the origin server) is willing to
2198    accept the possibility that the trailer fields might be silently discarded
2199    along the path to the client.</t>
2200  </list>
2201</t>
2202<t>
2203   This requirement prevents an interoperability failure when the
2204   message is being received by an HTTP/1.1 (or later) proxy and
2205   forwarded to an HTTP/1.0 recipient. It avoids a situation where
2206   compliance with the protocol would have necessitated a possibly
2207   infinite buffer on the proxy.
2208</t>
2209<t>
2210   A process for decoding the "chunked" transfer-coding
2211   can be represented in pseudo-code as:
2212</t>
2213<figure><artwork type="code">
2214  length := 0
2215  read chunk-size, chunk-ext (if any) and CRLF
2216  while (chunk-size &gt; 0) {
2217     read chunk-data and CRLF
2218     append chunk-data to decoded-body
2219     length := length + chunk-size
2220     read chunk-size and CRLF
2221  }
2222  read header-field
2223  while (header-field not empty) {
2224     append header-field to existing header fields
2225     read header-field
2226  }
2227  Content-Length := length
2228  Remove "chunked" from Transfer-Encoding
2229</artwork></figure>
2230<t>
2231   All HTTP/1.1 applications &MUST; be able to receive and decode the
2232   "chunked" transfer-coding and &MUST; ignore chunk-ext extensions
2233   they do not understand.
2234</t>
2235<t>
2236   Since "chunked" is the only transfer-coding required to be understood
2237   by HTTP/1.1 recipients, it plays a crucial role in delimiting messages
2238   on a persistent connection.  Whenever a transfer-coding is applied to
2239   a payload body in a request, the final transfer-coding applied &MUST;
2240   be "chunked".  If a transfer-coding is applied to a response payload
2241   body, then either the final transfer-coding applied &MUST; be "chunked"
2242   or the message &MUST; be terminated by closing the connection. When the
2243   "chunked" transfer-coding is used, it &MUST; be the last transfer-coding
2244   applied to form the message-body. The "chunked" transfer-coding &MUST-NOT;
2245   be applied more than once in a message-body.
2246</t>
2247</section>
2248
2249<section title="Compression Codings" anchor="compression.codings">
2250<t>
2251   The codings defined below can be used to compress the payload of a
2252   message.
2253</t>
2254<x:note><t>
2255   <x:h>Note:</x:h> Use of program names for the identification of encoding formats
2256   is not desirable and is discouraged for future encodings. Their
2257   use here is representative of historical practice, not good
2258   design.
2259</t></x:note>
2260<x:note><t>
2261   <x:h>Note:</x:h> For compatibility with previous implementations of HTTP,
2262   applications &SHOULD; consider "x-gzip" and "x-compress" to be
2263   equivalent to "gzip" and "compress" respectively.
2264</t></x:note>
2265
2266<section title="Compress Coding" anchor="compress.coding">
2267<iref item="compress (Coding Format)"/>
2268<iref item="Coding Format" subitem="compress"/>
2269<t>
2270   The "compress" format is produced by the common UNIX file compression
2271   program "compress". This format is an adaptive Lempel-Ziv-Welch
2272   coding (LZW).
2273</t>
2274</section>
2275
2276<section title="Deflate Coding" anchor="deflate.coding">
2277<iref item="deflate (Coding Format)"/>
2278<iref item="Coding Format" subitem="deflate"/>
2279<t>
2280   The "deflate" format is defined as the "deflate" compression mechanism
2281   (described in <xref target="RFC1951"/>) used inside the "zlib"
2282   data format (<xref target="RFC1950"/>).
2283</t>
2284<x:note>
2285  <t>
2286    <x:h>Note:</x:h> Some incorrect implementations send the "deflate"
2287    compressed data without the zlib wrapper.
2288   </t>
2289</x:note>
2290</section>
2291
2292<section title="Gzip Coding" anchor="gzip.coding">
2293<iref item="gzip (Coding Format)"/>
2294<iref item="Coding Format" subitem="gzip"/>
2295<t>
2296   The "gzip" format is produced by the file compression program
2297   "gzip" (GNU zip), as described in <xref target="RFC1952"/>. This format is a
2298   Lempel-Ziv coding (LZ77) with a 32 bit CRC.
2299</t>
2300</section>
2301
2302</section>
2303
2304<section title="Transfer Coding Registry" anchor="transfer.coding.registry">
2305<t>
2306   The HTTP Transfer Coding Registry defines the name space for the transfer
2307   coding names.
2308</t>
2309<t>
2310   Registrations &MUST; include the following fields:
2311   <list style="symbols">
2312     <t>Name</t>
2313     <t>Description</t>
2314     <t>Pointer to specification text</t>
2315   </list>
2316</t>
2317<t>
2318   Names of transfer codings &MUST-NOT; overlap with names of content codings
2319   (&content-codings;), unless the encoding transformation is identical (as it
2320   is the case for the compression codings defined in
2321   <xref target="compression.codings"/>).
2322</t>
2323<t>
2324   Values to be added to this name space require a specification
2325   (see "Specification Required" in <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
2326   conform to the purpose of transfer coding defined in this section.
2327</t>
2328<t>
2329   The registry itself is maintained at
2330   <eref target="http://www.iana.org/assignments/http-parameters"/>.
2331</t>
2332</section>
2333</section>
2334
2335<section title="Product Tokens" anchor="product.tokens">
2336  <x:anchor-alias value="product"/>
2337  <x:anchor-alias value="product-version"/>
2338<t>
2339   Product tokens are used to allow communicating applications to
2340   identify themselves by software name and version. Most fields using
2341   product tokens also allow sub-products which form a significant part
2342   of the application to be listed, separated by whitespace. By
2343   convention, the products are listed in order of their significance
2344   for identifying the application.
2345</t>
2346<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="product"/><iref primary="true" item="Grammar" subitem="product-version"/>
2347  <x:ref>product</x:ref>         = <x:ref>token</x:ref> ["/" <x:ref>product-version</x:ref>]
2348  <x:ref>product-version</x:ref> = <x:ref>token</x:ref>
2349</artwork></figure>
2350<t>
2351   Examples:
2352</t>
2353<figure><artwork type="example">
2354  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2355  Server: Apache/0.8.4
2356</artwork></figure>
2357<t>
2358   Product tokens &SHOULD; be short and to the point. They &MUST-NOT; be
2359   used for advertising or other non-essential information. Although any
2360   token octet &MAY; appear in a product-version, this token &SHOULD;
2361   only be used for a version identifier (i.e., successive versions of
2362   the same product &SHOULD; only differ in the product-version portion of
2363   the product value).
2364</t>
2365</section>
2366
2367<section title="Quality Values" anchor="quality.values">
2368  <x:anchor-alias value="qvalue"/>
2369<t>
2370   Both transfer codings (TE request header field, <xref target="header.te"/>)
2371   and content negotiation (&content.negotiation;) use short "floating point"
2372   numbers to indicate the relative importance ("weight") of various
2373   negotiable parameters.  A weight is normalized to a real number in
2374   the range 0 through 1, where 0 is the minimum and 1 the maximum
2375   value. If a parameter has a quality value of 0, then content with
2376   this parameter is "not acceptable" for the client. HTTP/1.1
2377   applications &MUST-NOT; generate more than three digits after the
2378   decimal point. User configuration of these values &SHOULD; also be
2379   limited in this fashion.
2380</t>
2381<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="qvalue"/>
2382  <x:ref>qvalue</x:ref>         = ( "0" [ "." 0*3<x:ref>DIGIT</x:ref> ] )
2383                 / ( "1" [ "." 0*3("0") ] )
2384</artwork></figure>
2385<x:note>
2386  <t>
2387     <x:h>Note:</x:h> "Quality values" is a misnomer, since these values merely represent
2388     relative degradation in desired quality.
2389  </t>
2390</x:note>
2391</section>
2392
2393</section>
2394
2395<section title="Connections" anchor="connections">
2396
2397<section title="Persistent Connections" anchor="persistent.connections">
2398
2399<section title="Purpose" anchor="persistent.purpose">
2400<t>
2401   Prior to persistent connections, a separate TCP connection was
2402   established for each request, increasing the load on HTTP servers
2403   and causing congestion on the Internet. The use of inline images and
2404   other associated data often requires a client to make multiple
2405   requests of the same server in a short amount of time. Analysis of
2406   these performance problems and results from a prototype
2407   implementation are available <xref target="Pad1995"/> <xref target="Spe"/>. Implementation experience and
2408   measurements of actual HTTP/1.1 implementations show good
2409   results <xref target="Nie1997"/>. Alternatives have also been explored, for example,
2410   T/TCP <xref target="Tou1998"/>.
2411</t>
2412<t>
2413   Persistent HTTP connections have a number of advantages:
2414  <list style="symbols">
2415      <t>
2416        By opening and closing fewer TCP connections, CPU time is saved
2417        in routers and hosts (clients, servers, proxies, gateways,
2418        tunnels, or caches), and memory used for TCP protocol control
2419        blocks can be saved in hosts.
2420      </t>
2421      <t>
2422        HTTP requests and responses can be pipelined on a connection.
2423        Pipelining allows a client to make multiple requests without
2424        waiting for each response, allowing a single TCP connection to
2425        be used much more efficiently, with much lower elapsed time.
2426      </t>
2427      <t>
2428        Network congestion is reduced by reducing the number of packets
2429        caused by TCP opens, and by allowing TCP sufficient time to
2430        determine the congestion state of the network.
2431      </t>
2432      <t>
2433        Latency on subsequent requests is reduced since there is no time
2434        spent in TCP's connection opening handshake.
2435      </t>
2436      <t>
2437        HTTP can evolve more gracefully, since errors can be reported
2438        without the penalty of closing the TCP connection. Clients using
2439        future versions of HTTP might optimistically try a new feature,
2440        but if communicating with an older server, retry with old
2441        semantics after an error is reported.
2442      </t>
2443    </list>
2444</t>
2445<t>
2446   HTTP implementations &SHOULD; implement persistent connections.
2447</t>
2448</section>
2449
2450<section title="Overall Operation" anchor="persistent.overall">
2451<t>
2452   A significant difference between HTTP/1.1 and earlier versions of
2453   HTTP is that persistent connections are the default behavior of any
2454   HTTP connection. That is, unless otherwise indicated, the client
2455   &SHOULD; assume that the server will maintain a persistent connection,
2456   even after error responses from the server.
2457</t>
2458<t>
2459   Persistent connections provide a mechanism by which a client and a
2460   server can signal the close of a TCP connection. This signaling takes
2461   place using the Connection header field (<xref target="header.connection"/>). Once a close
2462   has been signaled, the client &MUST-NOT; send any more requests on that
2463   connection.
2464</t>
2465
2466<section title="Negotiation" anchor="persistent.negotiation">
2467<t>
2468   An HTTP/1.1 server &MAY; assume that a HTTP/1.1 client intends to
2469   maintain a persistent connection unless a Connection header field including
2470   the connection-token "close" was sent in the request. If the server
2471   chooses to close the connection immediately after sending the
2472   response, it &SHOULD; send a Connection header field including the
2473   connection-token "close".
2474</t>
2475<t>
2476   An HTTP/1.1 client &MAY; expect a connection to remain open, but would
2477   decide to keep it open based on whether the response from a server
2478   contains a Connection header field with the connection-token close. In case
2479   the client does not want to maintain a connection for more than that
2480   request, it &SHOULD; send a Connection header field including the
2481   connection-token close.
2482</t>
2483<t>
2484   If either the client or the server sends the close token in the
2485   Connection header field, that request becomes the last one for the
2486   connection.
2487</t>
2488<t>
2489   Clients and servers &SHOULD-NOT;  assume that a persistent connection is
2490   maintained for HTTP versions less than 1.1 unless it is explicitly
2491   signaled. See <xref target="compatibility.with.http.1.0.persistent.connections"/> for more information on backward
2492   compatibility with HTTP/1.0 clients.
2493</t>
2494<t>
2495   In order to remain persistent, all messages on the connection &MUST;
2496   have a self-defined message length (i.e., one not defined by closure
2497   of the connection), as described in <xref target="message.body"/>.
2498</t>
2499</section>
2500
2501<section title="Pipelining" anchor="pipelining">
2502<t>
2503   A client that supports persistent connections &MAY; "pipeline" its
2504   requests (i.e., send multiple requests without waiting for each
2505   response). A server &MUST; send its responses to those requests in the
2506   same order that the requests were received.
2507</t>
2508<t>
2509   Clients which assume persistent connections and pipeline immediately
2510   after connection establishment &SHOULD; be prepared to retry their
2511   connection if the first pipelined attempt fails. If a client does
2512   such a retry, it &MUST-NOT; pipeline before it knows the connection is
2513   persistent. Clients &MUST; also be prepared to resend their requests if
2514   the server closes the connection before sending all of the
2515   corresponding responses.
2516</t>
2517<t>
2518   Clients &SHOULD-NOT; pipeline requests using non-idempotent request methods or
2519   non-idempotent sequences of request methods (see &idempotent-methods;). Otherwise, a
2520   premature termination of the transport connection could lead to
2521   indeterminate results. A client wishing to send a non-idempotent
2522   request &SHOULD; wait to send that request until it has received the
2523   response status line for the previous request.
2524</t>
2525</section>
2526</section>
2527
2528<section title="Proxy Servers" anchor="persistent.proxy">
2529<t>
2530   It is especially important that proxies correctly implement the
2531   properties of the Connection header field as specified in <xref target="header.connection"/>.
2532</t>
2533<t>
2534   The proxy server &MUST; signal persistent connections separately with
2535   its clients and the origin servers (or other proxy servers) that it
2536   connects to. Each persistent connection applies to only one transport
2537   link.
2538</t>
2539<t>
2540   A proxy server &MUST-NOT; establish a HTTP/1.1 persistent connection
2541   with an HTTP/1.0 client (but see <xref x:sec="19.7.1" x:fmt="of" target="RFC2068"/>
2542   for information and discussion of the problems with the Keep-Alive header field
2543   implemented by many HTTP/1.0 clients).
2544</t>
2545
2546<section title="End-to-end and Hop-by-hop Header Fields" anchor="end-to-end.and.hop-by-hop.header-fields">
2547<!--<t>
2548  <cref anchor="TODO-end-to-end" source="jre">
2549    Restored from <eref target="http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-05#section-7.1"/>.
2550    See also <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/60"/>.
2551  </cref>
2552</t>-->
2553<t>
2554   For the purpose of defining the behavior of caches and non-caching
2555   proxies, we divide HTTP header fields into two categories:
2556  <list style="symbols">
2557      <t>End-to-end header fields, which are  transmitted to the ultimate
2558        recipient of a request or response. End-to-end header fields in
2559        responses MUST be stored as part of a cache entry and &MUST; be
2560        transmitted in any response formed from a cache entry.</t>
2561
2562      <t>Hop-by-hop header fields, which are meaningful only for a single
2563        transport-level connection, and are not stored by caches or
2564        forwarded by proxies.</t>
2565  </list>
2566</t>
2567<t>
2568   The following HTTP/1.1 header fields are hop-by-hop header fields:
2569  <list style="symbols">
2570      <t>Connection</t>
2571      <t>Keep-Alive</t>
2572      <t>Proxy-Authenticate</t>
2573      <t>Proxy-Authorization</t>
2574      <t>TE</t>
2575      <t>Trailer</t>
2576      <t>Transfer-Encoding</t>
2577      <t>Upgrade</t>
2578  </list>
2579</t>
2580<t>
2581   All other header fields defined by HTTP/1.1 are end-to-end header fields.
2582</t>
2583<t>
2584   Other hop-by-hop header fields &MUST; be listed in a Connection header field
2585   (<xref target="header.connection"/>).
2586</t>
2587</section>
2588
2589<section title="Non-modifiable Header Fields" anchor="non-modifiable.header-fields">
2590<!--<t>
2591  <cref anchor="TODO-non-mod-headers" source="jre">
2592    Restored from <eref target="http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-05#section-7.2"/>.
2593    See also <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/60"/>.
2594  </cref>
2595</t>-->
2596<t>
2597   Some features of HTTP/1.1, such as Digest Authentication, depend on the
2598   value of certain end-to-end header fields. A non-transforming proxy &SHOULD-NOT;
2599   modify an end-to-end header field unless the definition of that header field requires
2600   or specifically allows that.
2601</t>
2602<t>
2603   A non-transforming proxy &MUST-NOT; modify any of the following fields in a
2604   request or response, and it &MUST-NOT; add any of these fields if not
2605   already present:
2606  <list style="symbols">
2607      <t>Content-Location</t>
2608      <t>Content-MD5</t>
2609      <t>ETag</t>
2610      <t>Last-Modified</t>
2611  </list>
2612</t>
2613<t>
2614   A non-transforming proxy &MUST-NOT; modify any of the following fields in a
2615   response:
2616  <list style="symbols">
2617    <t>Expires</t>
2618  </list>
2619</t>
2620<t>
2621   but it &MAY; add any of these fields if not already present. If an
2622   Expires header field is added, it &MUST; be given a field-value identical to
2623   that of the Date header field in that response.
2624</t>
2625<t>
2626   A proxy &MUST-NOT; modify or add any of the following fields in a
2627   message that contains the no-transform cache-control directive, or in
2628   any request:
2629  <list style="symbols">
2630    <t>Content-Encoding</t>
2631    <t>Content-Range</t>
2632    <t>Content-Type</t>
2633  </list>
2634</t>
2635<t>
2636   A transforming proxy &MAY; modify or add these fields to a message
2637   that does not include no-transform, but if it does so, it &MUST; add a
2638   Warning 214 (Transformation applied) if one does not already appear
2639   in the message (see &header-warning;).
2640</t>
2641<x:note>
2642  <t>
2643    <x:h>Warning:</x:h> Unnecessary modification of end-to-end header fields might
2644    cause authentication failures if stronger authentication
2645    mechanisms are introduced in later versions of HTTP. Such
2646    authentication mechanisms &MAY; rely on the values of header fields
2647    not listed here.
2648  </t>
2649</x:note>
2650<t>
2651   A non-transforming proxy &MUST; preserve the message payload (&payload;),
2652   though it &MAY; change the message-body through application or removal
2653   of a transfer-coding (<xref target="transfer.codings"/>).
2654</t>
2655</section>
2656
2657</section>
2658
2659<section title="Practical Considerations" anchor="persistent.practical">
2660<t>
2661   Servers will usually have some time-out value beyond which they will
2662   no longer maintain an inactive connection. Proxy servers might make
2663   this a higher value since it is likely that the client will be making
2664   more connections through the same server. The use of persistent
2665   connections places no requirements on the length (or existence) of
2666   this time-out for either the client or the server.
2667</t>
2668<t>
2669   When a client or server wishes to time-out it &SHOULD; issue a graceful
2670   close on the transport connection. Clients and servers &SHOULD; both
2671   constantly watch for the other side of the transport close, and
2672   respond to it as appropriate. If a client or server does not detect
2673   the other side's close promptly it could cause unnecessary resource
2674   drain on the network.
2675</t>
2676<t>
2677   A client, server, or proxy &MAY; close the transport connection at any
2678   time. For example, a client might have started to send a new request
2679   at the same time that the server has decided to close the "idle"
2680   connection. From the server's point of view, the connection is being
2681   closed while it was idle, but from the client's point of view, a
2682   request is in progress.
2683</t>
2684<t>
2685   This means that clients, servers, and proxies &MUST; be able to recover
2686   from asynchronous close events. Client software &SHOULD; reopen the
2687   transport connection and retransmit the aborted sequence of requests
2688   without user interaction so long as the request sequence is
2689   idempotent (see &idempotent-methods;). Non-idempotent request methods or sequences
2690   &MUST-NOT; be automatically retried, although user agents &MAY; offer a
2691   human operator the choice of retrying the request(s). Confirmation by
2692   user-agent software with semantic understanding of the application
2693   &MAY; substitute for user confirmation. The automatic retry &SHOULD-NOT; 
2694   be repeated if the second sequence of requests fails.
2695</t>
2696<t>
2697   Servers &SHOULD; always respond to at least one request per connection,
2698   if at all possible. Servers &SHOULD-NOT;  close a connection in the
2699   middle of transmitting a response, unless a network or client failure
2700   is suspected.
2701</t>
2702<t>
2703   Clients (including proxies) &SHOULD; limit the number of simultaneous
2704   connections that they maintain to a given server (including proxies).
2705</t>
2706<t>
2707   Previous revisions of HTTP gave a specific number of connections as a
2708   ceiling, but this was found to be impractical for many applications. As a
2709   result, this specification does not mandate a particular maximum number of
2710   connections, but instead encourages clients to be conservative when opening
2711   multiple connections.
2712</t>
2713<t>
2714   In particular, while using multiple connections avoids the "head-of-line
2715   blocking" problem (whereby a request that takes significant server-side
2716   processing and/or has a large payload can block subsequent requests on the
2717   same connection), each connection used consumes server resources (sometimes
2718   significantly), and furthermore using multiple connections can cause
2719   undesirable side effects in congested networks.
2720</t>
2721<t>
2722   Note that servers might reject traffic that they deem abusive, including an
2723   excessive number of connections from a client.
2724</t>
2725</section>
2726</section>
2727
2728<section title="Message Transmission Requirements" anchor="message.transmission.requirements">
2729
2730<section title="Persistent Connections and Flow Control" anchor="persistent.flow">
2731<t>
2732   HTTP/1.1 servers &SHOULD; maintain persistent connections and use TCP's
2733   flow control mechanisms to resolve temporary overloads, rather than
2734   terminating connections with the expectation that clients will retry.
2735   The latter technique can exacerbate network congestion.
2736</t>
2737</section>
2738
2739<section title="Monitoring Connections for Error Status Messages" anchor="persistent.monitor">
2740<t>
2741   An HTTP/1.1 (or later) client sending a message-body &SHOULD; monitor
2742   the network connection for an error status code while it is transmitting
2743   the request. If the client sees an error status code, it &SHOULD;
2744   immediately cease transmitting the body. If the body is being sent
2745   using a "chunked" encoding (<xref target="transfer.codings"/>), a zero length chunk and
2746   empty trailer &MAY; be used to prematurely mark the end of the message.
2747   If the body was preceded by a Content-Length header field, the client &MUST;
2748   close the connection.
2749</t>
2750</section>
2751
2752<section title="Use of the 100 (Continue) Status" anchor="use.of.the.100.status">
2753<t>
2754   The purpose of the 100 (Continue) status code (see &status-100;) is to
2755   allow a client that is sending a request message with a request body
2756   to determine if the origin server is willing to accept the request
2757   (based on the request header fields) before the client sends the request
2758   body. In some cases, it might either be inappropriate or highly
2759   inefficient for the client to send the body if the server will reject
2760   the message without looking at the body.
2761</t>
2762<t>
2763   Requirements for HTTP/1.1 clients:
2764  <list style="symbols">
2765    <t>
2766        If a client will wait for a 100 (Continue) response before
2767        sending the request body, it &MUST; send an Expect header
2768        field (&header-expect;) with the "100-continue" expectation.
2769    </t>
2770    <t>
2771        A client &MUST-NOT; send an Expect header field (&header-expect;)
2772        with the "100-continue" expectation if it does not intend
2773        to send a request body.
2774    </t>
2775  </list>
2776</t>
2777<t>
2778   Because of the presence of older implementations, the protocol allows
2779   ambiguous situations in which a client might send "Expect: 100-continue"
2780   without receiving either a 417 (Expectation Failed)
2781   or a 100 (Continue) status code. Therefore, when a client sends this
2782   header field to an origin server (possibly via a proxy) from which it
2783   has never seen a 100 (Continue) status code, the client &SHOULD-NOT; 
2784   wait for an indefinite period before sending the request body.
2785</t>
2786<t>
2787   Requirements for HTTP/1.1 origin servers:
2788  <list style="symbols">
2789    <t> Upon receiving a request which includes an Expect header
2790        field with the "100-continue" expectation, an origin server &MUST;
2791        either respond with 100 (Continue) status code and continue to read
2792        from the input stream, or respond with a final status code. The
2793        origin server &MUST-NOT; wait for the request body before sending
2794        the 100 (Continue) response. If it responds with a final status
2795        code, it &MAY; close the transport connection or it &MAY; continue
2796        to read and discard the rest of the request.  It &MUST-NOT;
2797        perform the request method if it returns a final status code.
2798    </t>
2799    <t> An origin server &SHOULD-NOT;  send a 100 (Continue) response if
2800        the request message does not include an Expect header
2801        field with the "100-continue" expectation, and &MUST-NOT; send a
2802        100 (Continue) response if such a request comes from an HTTP/1.0
2803        (or earlier) client. There is an exception to this rule: for
2804        compatibility with <xref target="RFC2068"/>, a server &MAY; send a 100 (Continue)
2805        status code in response to an HTTP/1.1 PUT or POST request that does
2806        not include an Expect header field with the "100-continue"
2807        expectation. This exception, the purpose of which is
2808        to minimize any client processing delays associated with an
2809        undeclared wait for 100 (Continue) status code, applies only to
2810        HTTP/1.1 requests, and not to requests with any other HTTP-version
2811        value.
2812    </t>
2813    <t> An origin server &MAY; omit a 100 (Continue) response if it has
2814        already received some or all of the request body for the
2815        corresponding request.
2816    </t>
2817    <t> An origin server that sends a 100 (Continue) response &MUST;
2818    ultimately send a final status code, once the request body is
2819        received and processed, unless it terminates the transport
2820        connection prematurely.
2821    </t>
2822    <t> If an origin server receives a request that does not include an
2823        Expect header field with the "100-continue" expectation,
2824        the request includes a request body, and the server responds
2825        with a final status code before reading the entire request body
2826        from the transport connection, then the server &SHOULD-NOT;  close
2827        the transport connection until it has read the entire request,
2828        or until the client closes the connection. Otherwise, the client
2829        might not reliably receive the response message. However, this
2830        requirement is not be construed as preventing a server from
2831        defending itself against denial-of-service attacks, or from
2832        badly broken client implementations.
2833      </t>
2834    </list>
2835</t>
2836<t>
2837   Requirements for HTTP/1.1 proxies:
2838  <list style="symbols">
2839    <t> If a proxy receives a request that includes an Expect header
2840        field with the "100-continue" expectation, and the proxy
2841        either knows that the next-hop server complies with HTTP/1.1 or
2842        higher, or does not know the HTTP version of the next-hop
2843        server, it &MUST; forward the request, including the Expect header
2844        field.
2845    </t>
2846    <t> If the proxy knows that the version of the next-hop server is
2847        HTTP/1.0 or lower, it &MUST-NOT; forward the request, and it &MUST;
2848        respond with a 417 (Expectation Failed) status code.
2849    </t>
2850    <t> Proxies &SHOULD; maintain a cache recording the HTTP version
2851        numbers received from recently-referenced next-hop servers.
2852    </t>
2853    <t> A proxy &MUST-NOT; forward a 100 (Continue) response if the
2854        request message was received from an HTTP/1.0 (or earlier)
2855        client and did not include an Expect header field with
2856        the "100-continue" expectation. This requirement overrides the
2857        general rule for forwarding of 1xx responses (see &status-1xx;).
2858    </t>
2859  </list>
2860</t>
2861</section>
2862
2863<section title="Client Behavior if Server Prematurely Closes Connection" anchor="connection.premature">
2864<t>
2865   If an HTTP/1.1 client sends a request which includes a request body,
2866   but which does not include an Expect header field with the
2867   "100-continue" expectation, and if the client is not directly
2868   connected to an HTTP/1.1 origin server, and if the client sees the
2869   connection close before receiving a status line from the server, the
2870   client &SHOULD; retry the request.  If the client does retry this
2871   request, it &MAY; use the following "binary exponential backoff"
2872   algorithm to be assured of obtaining a reliable response:
2873  <list style="numbers">
2874    <t>
2875      Initiate a new connection to the server
2876    </t>
2877    <t>
2878      Transmit the request-line, header fields, and the CRLF that
2879      indicates the end of header fields.
2880    </t>
2881    <t>
2882      Initialize a variable R to the estimated round-trip time to the
2883         server (e.g., based on the time it took to establish the
2884         connection), or to a constant value of 5 seconds if the round-trip
2885         time is not available.
2886    </t>
2887    <t>
2888       Compute T = R * (2**N), where N is the number of previous
2889         retries of this request.
2890    </t>
2891    <t>
2892       Wait either for an error response from the server, or for T
2893         seconds (whichever comes first)
2894    </t>
2895    <t>
2896       If no error response is received, after T seconds transmit the
2897         body of the request.
2898    </t>
2899    <t>
2900       If client sees that the connection is closed prematurely,
2901         repeat from step 1 until the request is accepted, an error
2902         response is received, or the user becomes impatient and
2903         terminates the retry process.
2904    </t>
2905  </list>
2906</t>
2907<t>
2908   If at any point an error status code is received, the client
2909  <list style="symbols">
2910      <t>&SHOULD-NOT;  continue and</t>
2911
2912      <t>&SHOULD; close the connection if it has not completed sending the
2913        request message.</t>
2914    </list>
2915</t>
2916</section>
2917</section>
2918</section>
2919
2920
2921<section title="Miscellaneous notes that might disappear" anchor="misc">
2922<section title="Scheme aliases considered harmful" anchor="scheme.aliases">
2923<t>
2924   <cref anchor="TBD-aliases-harmful">describe why aliases like webcal are harmful.</cref>
2925</t>
2926</section>
2927
2928<section title="Use of HTTP for proxy communication" anchor="http.proxy">
2929<t>
2930   <cref anchor="TBD-proxy-other">Configured to use HTTP to proxy HTTP or other protocols.</cref>
2931</t>
2932</section>
2933
2934<section title="Interception of HTTP for access control" anchor="http.intercept">
2935<t>
2936   <cref anchor="TBD-intercept">Interception of HTTP traffic for initiating access control.</cref>
2937</t>
2938</section>
2939
2940<section title="Use of HTTP by other protocols" anchor="http.others">
2941<t>
2942   <cref anchor="TBD-profiles">Profiles of HTTP defined by other protocol.
2943   Extensions of HTTP like WebDAV.</cref>
2944</t>
2945
2946</section>
2947<section title="Use of HTTP by media type specification" anchor="http.media">
2948<t>
2949   <cref anchor="TBD-hypertext">Instructions on composing HTTP requests via hypertext formats.</cref>
2950</t>
2951</section>
2952</section>
2953
2954<section title="Header Field Definitions" anchor="header.field.definitions">
2955<t>
2956   This section defines the syntax and semantics of HTTP header fields
2957   related to message framing and transport protocols.
2958</t>
2959
2960<section title="Connection" anchor="header.connection">
2961  <iref primary="true" item="Connection header field" x:for-anchor=""/>
2962  <iref primary="true" item="Header Fields" subitem="Connection" x:for-anchor=""/>
2963  <x:anchor-alias value="Connection"/>
2964  <x:anchor-alias value="connection-token"/>
2965  <x:anchor-alias value="Connection-v"/>
2966<t>
2967   The "Connection" header field allows the sender to specify
2968   options that are desired only for that particular connection.
2969   Such connection options &MUST; be removed or replaced before the
2970   message can be forwarded downstream by a proxy or gateway.
2971   This mechanism also allows the sender to indicate which HTTP
2972   header fields used in the message are only intended for the
2973   immediate recipient ("hop-by-hop"), as opposed to all recipients
2974   on the chain ("end-to-end"), enabling the message to be
2975   self-descriptive and allowing future connection-specific extensions
2976   to be deployed in HTTP without fear that they will be blindly
2977   forwarded by previously deployed intermediaries.
2978</t>
2979<t>
2980   The Connection header field's value has the following grammar:
2981</t>
2982<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Connection"/><iref primary="true" item="Grammar" subitem="Connection-v"/><iref primary="true" item="Grammar" subitem="connection-token"/>
2983  <x:ref>Connection</x:ref>       = "Connection" ":" <x:ref>OWS</x:ref> <x:ref>Connection-v</x:ref>
2984  <x:ref>Connection-v</x:ref>     = 1#<x:ref>connection-token</x:ref>
2985  <x:ref>connection-token</x:ref> = <x:ref>token</x:ref>
2986</artwork></figure>
2987<t>
2988   A proxy or gateway &MUST; parse a received Connection
2989   header field before a message is forwarded and, for each
2990   connection-token in this field, remove any header field(s) from
2991   the message with the same name as the connection-token, and then
2992   remove the Connection header field itself or replace it with the
2993   sender's own connection options for the forwarded message.
2994</t>
2995<t>
2996   A sender &MUST-NOT; include field-names in the Connection header
2997   field-value for fields that are defined as expressing constraints
2998   for all recipients in the request or response chain, such as the
2999   Cache-Control header field (&header-cache-control;).
3000</t>
3001<t>
3002   The connection options do not have to correspond to a header field
3003   present in the message, since a connection-specific header field
3004   might not be needed if there are no parameters associated with that
3005   connection option.  Recipients that trigger certain connection
3006   behavior based on the presence of connection options &MUST; do so
3007   based on the presence of the connection-token rather than only the
3008   presence of the optional header field.  In other words, if the
3009   connection option is received as a header field but not indicated
3010   within the Connection field-value, then the recipient &MUST; ignore
3011   the connection-specific header field because it has likely been
3012   forwarded by an intermediary that is only partially compliant.
3013</t>
3014<t>
3015   When defining new connection options, specifications ought to
3016   carefully consider existing deployed header fields and ensure
3017   that the new connection-token does not share the same name as
3018   an unrelated header field that might already be deployed.
3019   Defining a new connection-token essentially reserves that potential
3020   field-name for carrying additional information related to the
3021   connection option, since it would be unwise for senders to use
3022   that field-name for anything else.
3023</t>
3024<t>
3025   HTTP/1.1 defines the "close" connection option for the sender to
3026   signal that the connection will be closed after completion of the
3027   response. For example,
3028</t>
3029<figure><artwork type="example">
3030  Connection: close
3031</artwork></figure>
3032<t>
3033   in either the request or the response header fields indicates that
3034   the connection &SHOULD-NOT;  be considered "persistent" (<xref target="persistent.connections"/>)
3035   after the current request/response is complete.
3036</t>
3037<t>
3038   An HTTP/1.1 client that does not support persistent connections &MUST;
3039   include the "close" connection option in every request message.
3040</t>
3041<t>
3042   An HTTP/1.1 server that does not support persistent connections &MUST;
3043   include the "close" connection option in every response message that
3044   does not have a 1xx (Informational) status code.
3045</t>
3046</section>
3047
3048<section title="Content-Length" anchor="header.content-length">
3049  <iref primary="true" item="Content-Length header field" x:for-anchor=""/>
3050  <iref primary="true" item="Header Fields" subitem="Content-Length" x:for-anchor=""/>
3051  <x:anchor-alias value="Content-Length"/>
3052  <x:anchor-alias value="Content-Length-v"/>
3053<t>
3054   The "Content-Length" header field indicates the size of the
3055   message-body, in decimal number of octets, for any message other than
3056   a response to a HEAD request or a response with a status code of 304.
3057   In the case of a response to a HEAD request, Content-Length indicates
3058   the size of the payload body (not including any potential transfer-coding)
3059   that would have been sent had the request been a GET.
3060   In the case of a 304 (Not Modified) response to a GET request,
3061   Content-Length indicates the size of the payload body (not including
3062   any potential transfer-coding) that would have been sent in a 200 (OK)
3063   response.
3064</t>
3065<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Length"/><iref primary="true" item="Grammar" subitem="Content-Length-v"/>
3066  <x:ref>Content-Length</x:ref>   = "Content-Length" ":" <x:ref>OWS</x:ref> 1*<x:ref>Content-Length-v</x:ref>
3067  <x:ref>Content-Length-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
3068</artwork></figure>
3069<t>
3070   An example is
3071</t>
3072<figure><artwork type="example">
3073  Content-Length: 3495
3074</artwork></figure>
3075<t>
3076   Implementations &SHOULD; use this field to indicate the message-body
3077   length when no transfer-coding is being applied and the
3078   payload's body length can be determined prior to being transferred.
3079   <xref target="message.body"/> describes how recipients determine the length
3080   of a message-body.
3081</t>
3082<t>
3083   Any Content-Length greater than or equal to zero is a valid value.
3084</t>
3085<t>
3086   Note that the use of this field in HTTP is significantly different from
3087   the corresponding definition in MIME, where it is an optional field
3088   used within the "message/external-body" content-type.
3089</t>
3090</section>
3091
3092<section title="Date" anchor="header.date">
3093  <iref primary="true" item="Date header field" x:for-anchor=""/>
3094  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
3095  <x:anchor-alias value="Date"/>
3096  <x:anchor-alias value="Date-v"/>
3097<t>
3098   The "Date" header field represents the date and time at which
3099   the message was originated, having the same semantics as the Origination
3100   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
3101   The field value is an HTTP-date, as described in <xref target="date.time.formats.full.date"/>;
3102   it &MUST; be sent in rfc1123-date format.
3103</t>
3104<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/><iref primary="true" item="Grammar" subitem="Date-v"/>
3105  <x:ref>Date</x:ref>   = "Date" ":" <x:ref>OWS</x:ref> <x:ref>Date-v</x:ref>
3106  <x:ref>Date-v</x:ref> = <x:ref>HTTP-date</x:ref>
3107</artwork></figure>
3108<t>
3109   An example is
3110</t>
3111<figure><artwork type="example">
3112  Date: Tue, 15 Nov 1994 08:12:31 GMT
3113</artwork></figure>
3114<t>
3115   Origin servers &MUST; include a Date header field in all responses,
3116   except in these cases:
3117  <list style="numbers">
3118      <t>If the response status code is 100 (Continue) or 101 (Switching
3119         Protocols), the response &MAY; include a Date header field, at
3120         the server's option.</t>
3121
3122      <t>If the response status code conveys a server error, e.g., 500
3123         (Internal Server Error) or 503 (Service Unavailable), and it is
3124         inconvenient or impossible to generate a valid Date.</t>
3125
3126      <t>If the server does not have a clock that can provide a
3127         reasonable approximation of the current time, its responses
3128         &MUST-NOT; include a Date header field. In this case, the rules
3129         in <xref target="clockless.origin.server.operation"/> &MUST; be followed.</t>
3130  </list>
3131</t>
3132<t>
3133   A received message that does not have a Date header field &MUST; be
3134   assigned one by the recipient if the message will be cached by that
3135   recipient.
3136</t>
3137<t>
3138   Clients can use the Date header field as well; in order to keep request
3139   messages small, they are advised not to include it when it doesn't convey
3140   any useful information (as it is usually the case for requests that do not
3141   contain a payload).
3142</t>
3143<t>
3144   The HTTP-date sent in a Date header field &SHOULD-NOT;  represent a date and
3145   time subsequent to the generation of the message. It &SHOULD; represent
3146   the best available approximation of the date and time of message
3147   generation, unless the implementation has no means of generating a
3148   reasonably accurate date and time. In theory, the date ought to
3149   represent the moment just before the payload is generated. In
3150   practice, the date can be generated at any time during the message
3151   origination without affecting its semantic value.
3152</t>
3153
3154<section title="Clockless Origin Server Operation" anchor="clockless.origin.server.operation">
3155<t>
3156   Some origin server implementations might not have a clock available.
3157   An origin server without a clock &MUST-NOT; assign Expires or Last-Modified
3158   values to a response, unless these values were associated
3159   with the resource by a system or user with a reliable clock. It &MAY;
3160   assign an Expires value that is known, at or before server
3161   configuration time, to be in the past (this allows "pre-expiration"
3162   of responses without storing separate Expires values for each
3163   resource).
3164</t>
3165</section>
3166</section>
3167
3168<section title="Host" anchor="header.host">
3169  <iref primary="true" item="Host header field" x:for-anchor=""/>
3170  <iref primary="true" item="Header Fields" subitem="Host" x:for-anchor=""/>
3171  <x:anchor-alias value="Host"/>
3172  <x:anchor-alias value="Host-v"/>
3173<t>
3174   The "Host" header field in a request provides the host and port
3175   information from the target resource's URI, enabling the origin
3176   server to distinguish between resources while servicing requests
3177   for multiple host names on a single IP address.  Since the Host
3178   field-value is critical information for handling a request, it
3179   &SHOULD; be sent as the first header field following the Request-Line.
3180</t>
3181<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Host"/><iref primary="true" item="Grammar" subitem="Host-v"/>
3182  <x:ref>Host</x:ref>   = "Host" ":" <x:ref>OWS</x:ref> <x:ref>Host-v</x:ref>
3183  <x:ref>Host-v</x:ref> = <x:ref>uri-host</x:ref> [ ":" <x:ref>port</x:ref> ] ; <xref target="http.uri"/>
3184</artwork></figure>
3185<t>
3186   A client &MUST; send a Host header field in all HTTP/1.1 request
3187   messages.  If the target resource's URI includes an authority
3188   component, then the Host field-value &MUST; be identical to that
3189   authority component after excluding any userinfo (<xref target="http.uri"/>).
3190   If the authority component is missing or undefined for the target
3191   resource's URI, then the Host header field &MUST; be sent with an
3192   empty field-value.
3193</t>
3194<t>
3195   For example, a GET request to the origin server for
3196   &lt;http://www.example.org/pub/WWW/&gt; would begin with:
3197</t>
3198<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
3199GET /pub/WWW/ HTTP/1.1
3200Host: www.example.org
3201</artwork></figure>
3202<t>
3203   The Host header field &MUST; be sent in an HTTP/1.1 request even
3204   if the request-target is in the form of an absolute-URI, since this
3205   allows the Host information to be forwarded through ancient HTTP/1.0
3206   proxies that might not have implemented Host.
3207</t>
3208<t>
3209   When an HTTP/1.1 proxy receives a request with a request-target in
3210   the form of an absolute-URI, the proxy &MUST; ignore the received
3211   Host header field (if any) and instead replace it with the host
3212   information of the request-target.  When a proxy forwards a request,
3213   it &MUST; generate the Host header field based on the received
3214   absolute-URI rather than the received Host.
3215</t>
3216<t>
3217   Since the Host header field acts as an application-level routing
3218   mechanism, it is a frequent target for malware seeking to poison
3219   a shared cache or redirect a request to an unintended server.
3220   An interception proxy is particularly vulnerable if it relies on
3221   the Host header field value for redirecting requests to internal
3222   servers, or for use as a cache key in a shared cache, without
3223   first verifying that the intercepted connection is targeting a
3224   valid IP address for that host.
3225</t>
3226<t>
3227   A server &MUST; respond with a 400 (Bad Request) status code to
3228   any HTTP/1.1 request message that lacks a Host header field and
3229   to any request message that contains more than one Host header field
3230   or a Host header field with an invalid field-value.
3231</t>
3232<t>
3233   See Sections <xref target="the.resource.identified.by.a.request" format="counter"/>
3234   and <xref target="changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" format="counter"/>
3235   for other requirements relating to Host.
3236</t>
3237</section>
3238
3239<section title="TE" anchor="header.te">
3240  <iref primary="true" item="TE header field" x:for-anchor=""/>
3241  <iref primary="true" item="Header Fields" subitem="TE" x:for-anchor=""/>
3242  <x:anchor-alias value="TE"/>
3243  <x:anchor-alias value="TE-v"/>
3244  <x:anchor-alias value="t-codings"/>
3245  <x:anchor-alias value="te-params"/>
3246  <x:anchor-alias value="te-ext"/>
3247<t>
3248   The "TE" header field indicates what extension transfer-codings
3249   it is willing to accept in the response, and whether or not it is
3250   willing to accept trailer fields in a chunked transfer-coding.
3251</t>
3252<t>
3253   Its value consists of the keyword "trailers" and/or a comma-separated
3254   list of extension transfer-coding names with optional accept
3255   parameters (as described in <xref target="transfer.codings"/>).
3256</t>
3257<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="TE"/><iref primary="true" item="Grammar" subitem="TE-v"/><iref primary="true" item="Grammar" subitem="t-codings"/><iref primary="true" item="Grammar" subitem="te-params"/><iref primary="true" item="Grammar" subitem="te-ext"/>
3258  <x:ref>TE</x:ref>        = "TE" ":" <x:ref>OWS</x:ref> <x:ref>TE-v</x:ref>
3259  <x:ref>TE-v</x:ref>      = #<x:ref>t-codings</x:ref>
3260  <x:ref>t-codings</x:ref> = "trailers" / ( <x:ref>transfer-extension</x:ref> [ <x:ref>te-params</x:ref> ] )
3261  <x:ref>te-params</x:ref> = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>te-ext</x:ref> )
3262  <x:ref>te-ext</x:ref>    = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
3263</artwork></figure>
3264<t>
3265   The presence of the keyword "trailers" indicates that the client is
3266   willing to accept trailer fields in a chunked transfer-coding, as
3267   defined in <xref target="chunked.encoding"/>. This keyword is reserved for use with
3268   transfer-coding values even though it does not itself represent a
3269   transfer-coding.
3270</t>
3271<t>
3272   Examples of its use are:
3273</t>
3274<figure><artwork type="example">
3275  TE: deflate
3276  TE:
3277  TE: trailers, deflate;q=0.5
3278</artwork></figure>
3279<t>
3280   The TE header field only applies to the immediate connection.
3281   Therefore, the keyword &MUST; be supplied within a Connection header
3282   field (<xref target="header.connection"/>) whenever TE is present in an HTTP/1.1 message.
3283</t>
3284<t>
3285   A server tests whether a transfer-coding is acceptable, according to
3286   a TE field, using these rules:
3287  <list style="numbers">
3288    <x:lt>
3289      <t>The "chunked" transfer-coding is always acceptable. If the
3290         keyword "trailers" is listed, the client indicates that it is
3291         willing to accept trailer fields in the chunked response on
3292         behalf of itself and any downstream clients. The implication is
3293         that, if given, the client is stating that either all
3294         downstream clients are willing to accept trailer fields in the
3295         forwarded response, or that it will attempt to buffer the
3296         response on behalf of downstream recipients.
3297      </t><t>
3298         <x:h>Note:</x:h> HTTP/1.1 does not define any means to limit the size of a
3299         chunked response such that a client can be assured of buffering
3300         the entire response.</t>
3301    </x:lt>
3302    <x:lt>
3303      <t>If the transfer-coding being tested is one of the transfer-codings
3304         listed in the TE field, then it is acceptable unless it
3305         is accompanied by a qvalue of 0. (As defined in <xref target="quality.values"/>, a
3306         qvalue of 0 means "not acceptable".)</t>
3307    </x:lt>
3308    <x:lt>
3309      <t>If multiple transfer-codings are acceptable, then the
3310         acceptable transfer-coding with the highest non-zero qvalue is
3311         preferred.  The "chunked" transfer-coding always has a qvalue
3312         of 1.</t>
3313    </x:lt>
3314  </list>
3315</t>
3316<t>
3317   If the TE field-value is empty or if no TE field is present, the only
3318   transfer-coding is "chunked". A message with no transfer-coding is
3319   always acceptable.
3320</t>
3321</section>
3322
3323<section title="Trailer" anchor="header.trailer">
3324  <iref primary="true" item="Trailer header field" x:for-anchor=""/>
3325  <iref primary="true" item="Header Fields" subitem="Trailer" x:for-anchor=""/>
3326  <x:anchor-alias value="Trailer"/>
3327  <x:anchor-alias value="Trailer-v"/>
3328<t>
3329   The "Trailer" header field indicates that the given set of
3330   header fields is present in the trailer of a message encoded with
3331   chunked transfer-coding.
3332</t>
3333<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Trailer"/><iref primary="true" item="Grammar" subitem="Trailer-v"/>
3334  <x:ref>Trailer</x:ref>   = "Trailer" ":" <x:ref>OWS</x:ref> <x:ref>Trailer-v</x:ref>
3335  <x:ref>Trailer-v</x:ref> = 1#<x:ref>field-name</x:ref>
3336</artwork></figure>
3337<t>
3338   An HTTP/1.1 message &SHOULD; include a Trailer header field in a
3339   message using chunked transfer-coding with a non-empty trailer. Doing
3340   so allows the recipient to know which header fields to expect in the
3341   trailer.
3342</t>
3343<t>
3344   If no Trailer header field is present, the trailer &SHOULD-NOT;  include
3345   any header fields. See <xref target="chunked.encoding"/> for restrictions on the use of
3346   trailer fields in a "chunked" transfer-coding.
3347</t>
3348<t>
3349   Message header fields listed in the Trailer header field &MUST-NOT;
3350   include the following header fields:
3351  <list style="symbols">
3352    <t>Transfer-Encoding</t>
3353    <t>Content-Length</t>
3354    <t>Trailer</t>
3355  </list>
3356</t>
3357</section>
3358
3359<section title="Transfer-Encoding" anchor="header.transfer-encoding">
3360  <iref primary="true" item="Transfer-Encoding header field" x:for-anchor=""/>
3361  <iref primary="true" item="Header Fields" subitem="Transfer-Encoding" x:for-anchor=""/>
3362  <x:anchor-alias value="Transfer-Encoding"/>
3363  <x:anchor-alias value="Transfer-Encoding-v"/>
3364<t>
3365   The "Transfer-Encoding" header field indicates what transfer-codings
3366   (if any) have been applied to the message body. It differs from
3367   Content-Encoding (&content-codings;) in that transfer-codings are a property
3368   of the message (and therefore are removed by intermediaries), whereas
3369   content-codings are not.
3370</t>
3371<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Transfer-Encoding"/><iref primary="true" item="Grammar" subitem="Transfer-Encoding-v"/>
3372  <x:ref>Transfer-Encoding</x:ref>   = "Transfer-Encoding" ":" <x:ref>OWS</x:ref>
3373                        <x:ref>Transfer-Encoding-v</x:ref>
3374  <x:ref>Transfer-Encoding-v</x:ref> = 1#<x:ref>transfer-coding</x:ref>
3375</artwork></figure>
3376<t>
3377   Transfer-codings are defined in <xref target="transfer.codings"/>. An example is:
3378</t>
3379<figure><artwork type="example">
3380  Transfer-Encoding: chunked
3381</artwork></figure>
3382<t>
3383   If multiple encodings have been applied to a representation, the transfer-codings
3384   &MUST; be listed in the order in which they were applied.
3385   Additional information about the encoding parameters &MAY; be provided
3386   by other header fields not defined by this specification.
3387</t>
3388<t>
3389   Many older HTTP/1.0 applications do not understand the Transfer-Encoding
3390   header field.
3391</t>
3392</section>
3393
3394<section title="Upgrade" anchor="header.upgrade">
3395  <iref primary="true" item="Upgrade header field" x:for-anchor=""/>
3396  <iref primary="true" item="Header Fields" subitem="Upgrade" x:for-anchor=""/>
3397  <x:anchor-alias value="Upgrade"/>
3398  <x:anchor-alias value="Upgrade-v"/>
3399<t>
3400   The "Upgrade" header field allows the client to specify what
3401   additional communication protocols it would like to use, if the server
3402   chooses to switch protocols. Servers can use it to indicate what protocols
3403   they are willing to switch to.
3404</t>
3405<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Upgrade"/><iref primary="true" item="Grammar" subitem="Upgrade-v"/>
3406  <x:ref>Upgrade</x:ref>   = "Upgrade" ":" <x:ref>OWS</x:ref> <x:ref>Upgrade-v</x:ref>
3407  <x:ref>Upgrade-v</x:ref> = 1#<x:ref>product</x:ref>
3408</artwork></figure>
3409<t>
3410   For example,
3411</t>
3412<figure><artwork type="example">
3413  Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
3414</artwork></figure>
3415<t>
3416   The Upgrade header field is intended to provide a simple mechanism
3417   for transition from HTTP/1.1 to some other, incompatible protocol. It
3418   does so by allowing the client to advertise its desire to use another
3419   protocol, such as a later version of HTTP with a higher major version
3420   number, even though the current request has been made using HTTP/1.1.
3421   This eases the difficult transition between incompatible protocols by
3422   allowing the client to initiate a request in the more commonly
3423   supported protocol while indicating to the server that it would like
3424   to use a "better" protocol if available (where "better" is determined
3425   by the server, possibly according to the nature of the request method
3426   or target resource).
3427</t>
3428<t>
3429   The Upgrade header field only applies to switching application-layer
3430   protocols upon the existing transport-layer connection. Upgrade
3431   cannot be used to insist on a protocol change; its acceptance and use
3432   by the server is optional. The capabilities and nature of the
3433   application-layer communication after the protocol change is entirely
3434   dependent upon the new protocol chosen, although the first action
3435   after changing the protocol &MUST; be a response to the initial HTTP
3436   request containing the Upgrade header field.
3437</t>
3438<t>
3439   The Upgrade header field only applies to the immediate connection.
3440   Therefore, the upgrade keyword &MUST; be supplied within a Connection
3441   header field (<xref target="header.connection"/>) whenever Upgrade is present in an
3442   HTTP/1.1 message.
3443</t>
3444<t>
3445   The Upgrade header field cannot be used to indicate a switch to a
3446   protocol on a different connection. For that purpose, it is more
3447   appropriate to use a 3xx redirection response (&status-3xx;).
3448</t>
3449<t>
3450   Servers &MUST; include the "Upgrade" header field in 101 (Switching
3451   Protocols) responses to indicate which protocol(s) are being switched to,
3452   and &MUST; include it in 426 (Upgrade Required) responses to indicate
3453   acceptable protocols to upgrade to. Servers &MAY; include it in any other
3454   response to indicate that they are willing to upgrade to one of the
3455   specified protocols.
3456</t>
3457<t>
3458   This specification only defines the protocol name "HTTP" for use by
3459   the family of Hypertext Transfer Protocols, as defined by the HTTP
3460   version rules of <xref target="http.version"/> and future updates to this
3461   specification. Additional tokens can be registered with IANA using the
3462   registration procedure defined below. 
3463</t>
3464
3465<section title="Upgrade Token Registry" anchor="upgrade.token.registry">
3466<t>
3467   The HTTP Upgrade Token Registry defines the name space for product
3468   tokens used to identify protocols in the Upgrade header field.
3469   Each registered token is associated with contact information and
3470   an optional set of specifications that details how the connection
3471   will be processed after it has been upgraded.
3472</t>
3473<t>
3474   Registrations are allowed on a First Come First Served basis as
3475   described in <xref target="RFC5226" x:sec="4.1" x:fmt="of"/>. The
3476   specifications need not be IETF documents or be subject to IESG review.
3477   Registrations are subject to the following rules:
3478  <list style="numbers">
3479    <t>A token, once registered, stays registered forever.</t>
3480    <t>The registration &MUST; name a responsible party for the
3481       registration.</t>
3482    <t>The registration &MUST; name a point of contact.</t>
3483    <t>The registration &MAY; name a set of specifications associated with that
3484       token. Such specifications need not be publicly available.</t>
3485    <t>The responsible party &MAY; change the registration at any time.
3486       The IANA will keep a record of all such changes, and make them
3487       available upon request.</t>
3488    <t>The responsible party for the first registration of a "product"
3489       token &MUST; approve later registrations of a "version" token
3490       together with that "product" token before they can be registered.</t>
3491    <t>If absolutely required, the IESG &MAY; reassign the responsibility
3492       for a token. This will normally only be used in the case when a
3493       responsible party cannot be contacted.</t>
3494  </list>
3495</t>
3496</section>
3497
3498
3499</section>
3500
3501<section title="Via" anchor="header.via">
3502  <iref primary="true" item="Via header field" x:for-anchor=""/>
3503  <iref primary="true" item="Header Fields" subitem="Via" x:for-anchor=""/>
3504  <x:anchor-alias value="protocol-name"/>
3505  <x:anchor-alias value="protocol-version"/>
3506  <x:anchor-alias value="pseudonym"/>
3507  <x:anchor-alias value="received-by"/>
3508  <x:anchor-alias value="received-protocol"/>
3509  <x:anchor-alias value="Via"/>
3510  <x:anchor-alias value="Via-v"/>
3511<t>
3512   The "Via" header field &MUST; be sent by a proxy or gateway to
3513   indicate the intermediate protocols and recipients between the user
3514   agent and the server on requests, and between the origin server and
3515   the client on responses. It is analogous to the "Received" field
3516   used by email systems (<xref target="RFC5322" x:fmt="of" x:sec="3.6.7"/>)
3517   and is intended to be used for tracking message forwards,
3518   avoiding request loops, and identifying the protocol capabilities of
3519   all senders along the request/response chain.
3520</t>
3521<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Via"/><iref primary="true" item="Grammar" subitem="Via-v"/><iref primary="true" item="Grammar" subitem="received-protocol"/><iref primary="true" item="Grammar" subitem="protocol-name"/><iref primary="true" item="Grammar" subitem="protocol-version"/><iref primary="true" item="Grammar" subitem="received-by"/><iref primary="true" item="Grammar" subitem="pseudonym"/>
3522  <x:ref>Via</x:ref>               = "Via" ":" <x:ref>OWS</x:ref> <x:ref>Via-v</x:ref>
3523  <x:ref>Via-v</x:ref>             = 1#( <x:ref>received-protocol</x:ref> <x:ref>RWS</x:ref> <x:ref>received-by</x:ref>
3524                          [ <x:ref>RWS</x:ref> <x:ref>comment</x:ref> ] )
3525  <x:ref>received-protocol</x:ref> = [ <x:ref>protocol-name</x:ref> "/" ] <x:ref>protocol-version</x:ref>
3526  <x:ref>protocol-name</x:ref>     = <x:ref>token</x:ref>
3527  <x:ref>protocol-version</x:ref>  = <x:ref>token</x:ref>
3528  <x:ref>received-by</x:ref>       = ( <x:ref>uri-host</x:ref> [ ":" <x:ref>port</x:ref> ] ) / <x:ref>pseudonym</x:ref>
3529  <x:ref>pseudonym</x:ref>         = <x:ref>token</x:ref>
3530</artwork></figure>
3531<t>
3532   The received-protocol indicates the protocol version of the message
3533   received by the server or client along each segment of the
3534   request/response chain. The received-protocol version is appended to
3535   the Via field value when the message is forwarded so that information
3536   about the protocol capabilities of upstream applications remains
3537   visible to all recipients.
3538</t>
3539<t>
3540   The protocol-name is excluded if and only if it would be "HTTP". The
3541   received-by field is normally the host and optional port number of a
3542   recipient server or client that subsequently forwarded the message.
3543   However, if the real host is considered to be sensitive information,
3544   it &MAY; be replaced by a pseudonym. If the port is not given, it &MAY;
3545   be assumed to be the default port of the received-protocol.
3546</t>
3547<t>
3548   Multiple Via field values represent each proxy or gateway that has
3549   forwarded the message. Each recipient &MUST; append its information
3550   such that the end result is ordered according to the sequence of
3551   forwarding applications.
3552</t>
3553<t>
3554   Comments &MAY; be used in the Via header field to identify the software
3555   of each recipient, analogous to the User-Agent and Server header fields.
3556   However, all comments in the Via field are optional and &MAY; be removed
3557   by any recipient prior to forwarding the message.
3558</t>
3559<t>
3560   For example, a request message could be sent from an HTTP/1.0 user
3561   agent to an internal proxy code-named "fred", which uses HTTP/1.1 to
3562   forward the request to a public proxy at p.example.net, which completes
3563   the request by forwarding it to the origin server at www.example.com.
3564   The request received by www.example.com would then have the following
3565   Via header field:
3566</t>
3567<figure><artwork type="example">
3568  Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
3569</artwork></figure>
3570<t>
3571   A proxy or gateway used as a portal through a network firewall
3572   &SHOULD-NOT; forward the names and ports of hosts within the firewall
3573   region unless it is explicitly enabled to do so. If not enabled, the
3574   received-by host of any host behind the firewall &SHOULD; be replaced
3575   by an appropriate pseudonym for that host.
3576</t>
3577<t>
3578   For organizations that have strong privacy requirements for hiding
3579   internal structures, a proxy or gateway &MAY; combine an ordered
3580   subsequence of Via header field entries with identical received-protocol
3581   values into a single such entry. For example,
3582</t>
3583<figure><artwork type="example">
3584  Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
3585</artwork></figure>
3586<t>
3587  could be collapsed to
3588</t>
3589<figure><artwork type="example">
3590  Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
3591</artwork></figure>
3592<t>
3593   Senders &SHOULD-NOT; combine multiple entries unless they are all
3594   under the same organizational control and the hosts have already been
3595   replaced by pseudonyms. Senders &MUST-NOT; combine entries which
3596   have different received-protocol values.
3597</t>
3598</section>
3599
3600</section>
3601
3602<section title="IANA Considerations" anchor="IANA.considerations">
3603
3604<section title="Header Field Registration" anchor="header.field.registration">
3605<t>
3606   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3607   with the permanent registrations below (see <xref target="RFC3864"/>):
3608</t>
3609<?BEGININC p1-messaging.iana-headers ?>
3610<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3611<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3612   <ttcol>Header Field Name</ttcol>
3613   <ttcol>Protocol</ttcol>
3614   <ttcol>Status</ttcol>
3615   <ttcol>Reference</ttcol>
3616
3617   <c>Connection</c>
3618   <c>http</c>
3619   <c>standard</c>
3620   <c>
3621      <xref target="header.connection"/>
3622   </c>
3623   <c>Content-Length</c>
3624   <c>http</c>
3625   <c>standard</c>
3626   <c>
3627      <xref target="header.content-length"/>
3628   </c>
3629   <c>Date</c>
3630   <c>http</c>
3631   <c>standard</c>
3632   <c>
3633      <xref target="header.date"/>
3634   </c>
3635   <c>Host</c>
3636   <c>http</c>
3637   <c>standard</c>
3638   <c>
3639      <xref target="header.host"/>
3640   </c>
3641   <c>TE</c>
3642   <c>http</c>
3643   <c>standard</c>
3644   <c>
3645      <xref target="header.te"/>
3646   </c>
3647   <c>Trailer</c>
3648   <c>http</c>
3649   <c>standard</c>
3650   <c>
3651      <xref target="header.trailer"/>
3652   </c>
3653   <c>Transfer-Encoding</c>
3654   <c>http</c>
3655   <c>standard</c>
3656   <c>
3657      <xref target="header.transfer-encoding"/>
3658   </c>
3659   <c>Upgrade</c>
3660   <c>http</c>
3661   <c>standard</c>
3662   <c>
3663      <xref target="header.upgrade"/>
3664   </c>
3665   <c>Via</c>
3666   <c>http</c>
3667   <c>standard</c>
3668   <c>
3669      <xref target="header.via"/>
3670   </c>
3671</texttable>
3672<!--(END)-->
3673<?ENDINC p1-messaging.iana-headers ?>
3674<t>
3675   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3676</t>
3677</section>
3678
3679<section title="URI Scheme Registration" anchor="uri.scheme.registration">
3680<t>
3681   The entries for the "http" and "https" URI Schemes in the registry located at
3682   <eref target="http://www.iana.org/assignments/uri-schemes.html"/>
3683   shall be updated to point to Sections <xref target="http.uri" format="counter"/>
3684   and <xref target="https.uri" format="counter"/> of this document
3685   (see <xref target="RFC4395"/>).
3686</t>
3687</section>
3688
3689<section title="Internet Media Type Registrations" anchor="internet.media.type.http">
3690<t>
3691   This document serves as the specification for the Internet media types
3692   "message/http" and "application/http". The following is to be registered with
3693   IANA (see <xref target="RFC4288"/>).
3694</t>
3695<section title="Internet Media Type message/http" anchor="internet.media.type.message.http">
3696<iref item="Media Type" subitem="message/http" primary="true"/>
3697<iref item="message/http Media Type" primary="true"/>
3698<t>
3699   The message/http type can be used to enclose a single HTTP request or
3700   response message, provided that it obeys the MIME restrictions for all
3701   "message" types regarding line length and encodings.
3702</t>
3703<t>
3704  <list style="hanging" x:indent="12em">
3705    <t hangText="Type name:">
3706      message
3707    </t>
3708    <t hangText="Subtype name:">
3709      http
3710    </t>
3711    <t hangText="Required parameters:">
3712      none
3713    </t>
3714    <t hangText="Optional parameters:">
3715      version, msgtype
3716      <list style="hanging">
3717        <t hangText="version:">
3718          The HTTP-Version number of the enclosed message
3719          (e.g., "1.1"). If not present, the version can be
3720          determined from the first line of the body.
3721        </t>
3722        <t hangText="msgtype:">
3723          The message type &mdash; "request" or "response". If not
3724          present, the type can be determined from the first
3725          line of the body.
3726        </t>
3727      </list>
3728    </t>
3729    <t hangText="Encoding considerations:">
3730      only "7bit", "8bit", or "binary" are permitted
3731    </t>
3732    <t hangText="Security considerations:">
3733      none
3734    </t>
3735    <t hangText="Interoperability considerations:">
3736      none
3737    </t>
3738    <t hangText="Published specification:">
3739      This specification (see <xref target="internet.media.type.message.http"/>).
3740    </t>
3741    <t hangText="Applications that use this media type:">
3742    </t>
3743    <t hangText="Additional information:">
3744      <list style="hanging">
3745        <t hangText="Magic number(s):">none</t>
3746        <t hangText="File extension(s):">none</t>
3747        <t hangText="Macintosh file type code(s):">none</t>
3748      </list>
3749    </t>
3750    <t hangText="Person and email address to contact for further information:">
3751      See Authors Section.
3752    </t>
3753    <t hangText="Intended usage:">
3754      COMMON
3755    </t>
3756    <t hangText="Restrictions on usage:">
3757      none
3758    </t>
3759    <t hangText="Author/Change controller:">
3760      IESG
3761    </t>
3762  </list>
3763</t>
3764</section>
3765<section title="Internet Media Type application/http" anchor="internet.media.type.application.http">
3766<iref item="Media Type" subitem="application/http" primary="true"/>
3767<iref item="application/http Media Type" primary="true"/>
3768<t>
3769   The application/http type can be used to enclose a pipeline of one or more
3770   HTTP request or response messages (not intermixed).
3771</t>
3772<t>
3773  <list style="hanging" x:indent="12em">
3774    <t hangText="Type name:">
3775      application
3776    </t>
3777    <t hangText="Subtype name:">
3778      http
3779    </t>
3780    <t hangText="Required parameters:">
3781      none
3782    </t>
3783    <t hangText="Optional parameters:">
3784      version, msgtype
3785      <list style="hanging">
3786        <t hangText="version:">
3787          The HTTP-Version number of the enclosed messages
3788          (e.g., "1.1"). If not present, the version can be
3789          determined from the first line of the body.
3790        </t>
3791        <t hangText="msgtype:">
3792          The message type &mdash; "request" or "response". If not
3793          present, the type can be determined from the first
3794          line of the body.
3795        </t>
3796      </list>
3797    </t>
3798    <t hangText="Encoding considerations:">
3799      HTTP messages enclosed by this type
3800      are in "binary" format; use of an appropriate
3801      Content-Transfer-Encoding is required when
3802      transmitted via E-mail.
3803    </t>
3804    <t hangText="Security considerations:">
3805      none
3806    </t>
3807    <t hangText="Interoperability considerations:">
3808      none
3809    </t>
3810    <t hangText="Published specification:">
3811      This specification (see <xref target="internet.media.type.application.http"/>).
3812    </t>
3813    <t hangText="Applications that use this media type:">
3814    </t>
3815    <t hangText="Additional information:">
3816      <list style="hanging">
3817        <t hangText="Magic number(s):">none</t>
3818        <t hangText="File extension(s):">none</t>
3819        <t hangText="Macintosh file type code(s):">none</t>
3820      </list>
3821    </t>
3822    <t hangText="Person and email address to contact for further information:">
3823      See Authors Section.
3824    </t>
3825    <t hangText="Intended usage:">
3826      COMMON
3827    </t>
3828    <t hangText="Restrictions on usage:">
3829      none
3830    </t>
3831    <t hangText="Author/Change controller:">
3832      IESG
3833    </t>
3834  </list>
3835</t>
3836</section>
3837</section>
3838
3839<section title="Transfer Coding Registry" anchor="transfer.coding.registration">
3840<t>
3841   The registration procedure for HTTP Transfer Codings is now defined by
3842   <xref target="transfer.coding.registry"/> of this document.
3843</t>
3844<t>
3845   The HTTP Transfer Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
3846   shall be updated with the registrations below:
3847</t>
3848<texttable align="left" suppress-title="true" anchor="iana.transfer.coding.registration.table">
3849   <ttcol>Name</ttcol>
3850   <ttcol>Description</ttcol>
3851   <ttcol>Reference</ttcol>
3852   <c>chunked</c>
3853   <c>Transfer in a series of chunks</c>
3854   <c>
3855      <xref target="chunked.encoding"/>
3856   </c>
3857   <c>compress</c>
3858   <c>UNIX "compress" program method</c>
3859   <c>
3860      <xref target="compress.coding"/>
3861   </c>
3862   <c>deflate</c>
3863   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
3864   the "zlib" data format (<xref target="RFC1950"/>)
3865   </c>
3866   <c>
3867      <xref target="deflate.coding"/>
3868   </c>
3869   <c>gzip</c>
3870   <c>Same as GNU zip <xref target="RFC1952"/></c>
3871   <c>
3872      <xref target="gzip.coding"/>
3873   </c>
3874</texttable>
3875</section>
3876
3877<section title="Upgrade Token Registration" anchor="upgrade.token.registration">
3878<t>
3879   The registration procedure for HTTP Upgrade Tokens &mdash; previously defined
3880   in <xref target="RFC2817" x:fmt="of" x:sec="7.2"/> &mdash; is now defined
3881   by <xref target="upgrade.token.registry"/> of this document.
3882</t>
3883<t>
3884   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-upgrade-tokens/"/>
3885   shall be updated with the registration below:
3886</t>
3887<texttable align="left" suppress-title="true">
3888   <ttcol>Value</ttcol>
3889   <ttcol>Description</ttcol>
3890   <ttcol>Reference</ttcol>
3891
3892   <c>HTTP</c>
3893   <c>Hypertext Transfer Protocol</c> 
3894   <c><xref target="http.version"/> of this specification</c>
3895<!-- IANA should add this without our instructions; emailed on June 05, 2009
3896   <c>TLS/1.0</c>
3897   <c>Transport Layer Security</c>
3898   <c><xref target="RFC2817"/></c> -->
3899
3900</texttable>
3901</section>
3902
3903</section>
3904
3905<section title="Security Considerations" anchor="security.considerations">
3906<t>
3907   This section is meant to inform application developers, information
3908   providers, and users of the security limitations in HTTP/1.1 as
3909   described by this document. The discussion does not include
3910   definitive solutions to the problems revealed, though it does make
3911   some suggestions for reducing security risks.
3912</t>
3913
3914<section title="Personal Information" anchor="personal.information">
3915<t>
3916   HTTP clients are often privy to large amounts of personal information
3917   (e.g., the user's name, location, mail address, passwords, encryption
3918   keys, etc.), and &SHOULD; be very careful to prevent unintentional
3919   leakage of this information.
3920   We very strongly recommend that a convenient interface be provided
3921   for the user to control dissemination of such information, and that
3922   designers and implementors be particularly careful in this area.
3923   History shows that errors in this area often create serious security
3924   and/or privacy problems and generate highly adverse publicity for the
3925   implementor's company.
3926</t>
3927</section>
3928
3929<section title="Abuse of Server Log Information" anchor="abuse.of.server.log.information">
3930<t>
3931   A server is in the position to save personal data about a user's
3932   requests which might identify their reading patterns or subjects of
3933   interest. This information is clearly confidential in nature and its
3934   handling can be constrained by law in certain countries. People using
3935   HTTP to provide data are responsible for ensuring that
3936   such material is not distributed without the permission of any
3937   individuals that are identifiable by the published results.
3938</t>
3939</section>
3940
3941<section title="Attacks Based On File and Path Names" anchor="attack.pathname">
3942<t>
3943   Implementations of HTTP origin servers &SHOULD; be careful to restrict
3944   the documents returned by HTTP requests to be only those that were
3945   intended by the server administrators. If an HTTP server translates
3946   HTTP URIs directly into file system calls, the server &MUST; take
3947   special care not to serve files that were not intended to be
3948   delivered to HTTP clients. For example, UNIX, Microsoft Windows, and
3949   other operating systems use ".." as a path component to indicate a
3950   directory level above the current one. On such a system, an HTTP
3951   server &MUST; disallow any such construct in the request-target if it
3952   would otherwise allow access to a resource outside those intended to
3953   be accessible via the HTTP server. Similarly, files intended for
3954   reference only internally to the server (such as access control
3955   files, configuration files, and script code) &MUST; be protected from
3956   inappropriate retrieval, since they might contain sensitive
3957   information. Experience has shown that minor bugs in such HTTP server
3958   implementations have turned into security risks.
3959</t>
3960</section>
3961
3962<section title="DNS Spoofing" anchor="dns.spoofing">
3963<t>
3964   Clients using HTTP rely heavily on the Domain Name Service, and are
3965   thus generally prone to security attacks based on the deliberate
3966   mis-association of IP addresses and DNS names. Clients need to be
3967   cautious in assuming the continuing validity of an IP number/DNS name
3968   association.
3969</t>
3970<t>
3971   In particular, HTTP clients &SHOULD; rely on their name resolver for
3972   confirmation of an IP number/DNS name association, rather than
3973   caching the result of previous host name lookups. Many platforms
3974   already can cache host name lookups locally when appropriate, and
3975   they &SHOULD; be configured to do so. It is proper for these lookups to
3976   be cached, however, only when the TTL (Time To Live) information
3977   reported by the name server makes it likely that the cached
3978   information will remain useful.
3979</t>
3980<t>
3981   If HTTP clients cache the results of host name lookups in order to
3982   achieve a performance improvement, they &MUST; observe the TTL
3983   information reported by DNS.
3984</t>
3985<t>
3986   If HTTP clients do not observe this rule, they could be spoofed when
3987   a previously-accessed server's IP address changes. As network
3988   renumbering is expected to become increasingly common <xref target="RFC1900"/>, the
3989   possibility of this form of attack will grow. Observing this
3990   requirement thus reduces this potential security vulnerability.
3991</t>
3992<t>
3993   This requirement also improves the load-balancing behavior of clients
3994   for replicated servers using the same DNS name and reduces the
3995   likelihood of a user's experiencing failure in accessing sites which
3996   use that strategy.
3997</t>
3998</section>
3999
4000<section title="Proxies and Caching" anchor="attack.proxies">
4001<t>
4002   By their very nature, HTTP proxies are men-in-the-middle, and
4003   represent an opportunity for man-in-the-middle attacks. Compromise of
4004   the systems on which the proxies run can result in serious security
4005   and privacy problems. Proxies have access to security-related
4006   information, personal information about individual users and
4007   organizations, and proprietary information belonging to users and
4008   content providers. A compromised proxy, or a proxy implemented or
4009   configured without regard to security and privacy considerations,
4010   might be used in the commission of a wide range of potential attacks.
4011</t>
4012<t>
4013   Proxy operators need to protect the systems on which proxies run as
4014   they would protect any system that contains or transports sensitive
4015   information. In particular, log information gathered at proxies often
4016   contains highly sensitive personal information, and/or information
4017   about organizations. Log information needs to be carefully guarded, and
4018   appropriate guidelines for use need to be developed and followed.
4019   (<xref target="abuse.of.server.log.information"/>).
4020</t>
4021<t>
4022   Proxy implementors need to consider the privacy and security
4023   implications of their design and coding decisions, and of the
4024   configuration options they provide to proxy operators (especially the
4025   default configuration).
4026</t>
4027<t>
4028   Users of a proxy need to be aware that proxies are no trustworthier than
4029   the people who run them; HTTP itself cannot solve this problem.
4030</t>
4031<t>
4032   The judicious use of cryptography, when appropriate, might suffice to
4033   protect against a broad range of security and privacy attacks. Such
4034   cryptography is beyond the scope of the HTTP/1.1 specification.
4035</t>
4036</section>
4037
4038<section title="Denial of Service Attacks on Proxies" anchor="attack.DoS">
4039<t>
4040   They exist. They are hard to defend against. Research continues.
4041   Beware.
4042</t>
4043</section>
4044</section>
4045
4046<section title="Acknowledgments" anchor="ack">
4047<t>
4048   HTTP has evolved considerably over the years. It has
4049   benefited from a large and active developer community &mdash; the many
4050   people who have participated on the www-talk mailing list &mdash; and it is
4051   that community which has been most responsible for the success of
4052   HTTP and of the World-Wide Web in general. Marc Andreessen, Robert
4053   Cailliau, Daniel W. Connolly, Bob Denny, John Franks, Jean-Francois
4054   Groff, Phillip M. Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob
4055   McCool, Lou Montulli, Dave Raggett, Tony Sanders, and Marc
4056   VanHeyningen deserve special recognition for their efforts in
4057   defining early aspects of the protocol.
4058</t>
4059<t>
4060   This document has benefited greatly from the comments of all those
4061   participating in the HTTP-WG. In addition to those already mentioned,
4062   the following individuals have contributed to this specification:
4063</t>
4064<t>
4065   Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf,
4066   Paul Burchard, Maurizio Codogno, Josh Cohen, Mike Cowlishaw, Roman Czyborra,
4067   Michael A. Dolan, Daniel DuBois, David J. Fiander, Alan Freier, Marc Hedlund, Greg Herlihy,
4068   Koen Holtman, Alex Hopmann, Bob Jernigan, Shel Kaphan, Rohit Khare,
4069   John Klensin, Martijn Koster, Alexei Kosut, David M. Kristol,
4070   Daniel LaLiberte, Ben Laurie, Paul J. Leach, Albert Lunde,
4071   John C. Mallery, Jean-Philippe Martin-Flatin, Mitra, David Morris,
4072   Gavin Nicol, Ross Patterson, Bill Perry, Jeffrey Perry, Scott Powers, Owen Rees,
4073   Luigi Rizzo, David Robinson, Marc Salomon, Rich Salz,
4074   Allan M. Schiffman, Jim Seidman, Chuck Shotton, Eric W. Sink,
4075   Simon E. Spero, Richard N. Taylor, Robert S. Thau,
4076   Bill (BearHeart) Weinman, Francois Yergeau, Mary Ellen Zurko.
4077</t>
4078<t>
4079   Thanks to the "cave men" of Palo Alto. You know who you are.
4080</t>
4081<t>
4082   Jim Gettys (the editor of <xref target="RFC2616"/>) wishes particularly
4083   to thank Roy Fielding, the editor of <xref target="RFC2068"/>, along
4084   with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen
4085   Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott Lawrence, and
4086   Larry Masinter for their help. And thanks go particularly to Jeff
4087   Mogul and Scott Lawrence for performing the "MUST/MAY/SHOULD" audit.
4088</t>
4089<t>
4090   The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik
4091   Frystyk implemented RFC 2068 early, and we wish to thank them for the
4092   discovery of many of the problems that this document attempts to
4093   rectify.
4094</t>
4095<t>
4096   This specification makes heavy use of the augmented BNF and generic
4097   constructs defined by David H. Crocker for <xref target="RFC5234"/>. Similarly, it
4098   reuses many of the definitions provided by Nathaniel Borenstein and
4099   Ned Freed for MIME <xref target="RFC2045"/>. We hope that their inclusion in this
4100   specification will help reduce past confusion over the relationship
4101   between HTTP and Internet mail message formats.
4102</t>
4103<!--
4104
4105Acknowledgements TODO list
4106
4107- Jeff Hodges ("effective request URI")
4108
4109-->
4110</section>
4111
4112</middle>
4113<back>
4114
4115<references title="Normative References">
4116
4117<reference anchor="ISO-8859-1">
4118  <front>
4119    <title>
4120     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
4121    </title>
4122    <author>
4123      <organization>International Organization for Standardization</organization>
4124    </author>
4125    <date year="1998"/>
4126  </front>
4127  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
4128</reference>
4129
4130<reference anchor="Part2">
4131  <front>
4132    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
4133    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
4134      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4135      <address><email>fielding@gbiv.com</email></address>
4136    </author>
4137    <author initials="J." surname="Gettys" fullname="Jim Gettys">
4138      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
4139      <address><email>jg@freedesktop.org</email></address>
4140    </author>
4141    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
4142      <organization abbrev="HP">Hewlett-Packard Company</organization>
4143      <address><email>JeffMogul@acm.org</email></address>
4144    </author>
4145    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
4146      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4147      <address><email>henrikn@microsoft.com</email></address>
4148    </author>
4149    <author initials="L." surname="Masinter" fullname="Larry Masinter">
4150      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4151      <address><email>LMM@acm.org</email></address>
4152    </author>
4153    <author initials="P." surname="Leach" fullname="Paul J. Leach">
4154      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4155      <address><email>paulle@microsoft.com</email></address>
4156    </author>
4157    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
4158      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
4159      <address><email>timbl@w3.org</email></address>
4160    </author>
4161    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
4162      <organization abbrev="W3C">World Wide Web Consortium</organization>
4163      <address><email>ylafon@w3.org</email></address>
4164    </author>
4165    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
4166      <organization abbrev="greenbytes">greenbytes GmbH</organization>
4167      <address><email>julian.reschke@greenbytes.de</email></address>
4168    </author>
4169    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
4170  </front>
4171  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
4172  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
4173</reference>
4174
4175<reference anchor="Part3">
4176  <front>
4177    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
4178    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
4179      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4180      <address><email>fielding@gbiv.com</email></address>
4181    </author>
4182    <author initials="J." surname="Gettys" fullname="Jim Gettys">
4183      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
4184      <address><email>jg@freedesktop.org</email></address>
4185    </author>
4186    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
4187      <organization abbrev="HP">Hewlett-Packard Company</organization>
4188      <address><email>JeffMogul@acm.org</email></address>
4189    </author>
4190    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
4191      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4192      <address><email>henrikn@microsoft.com</email></address>
4193    </author>
4194    <author initials="L." surname="Masinter" fullname="Larry Masinter">
4195      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4196      <address><email>LMM@acm.org</email></address>
4197    </author>
4198    <author initials="P." surname="Leach" fullname="Paul J. Leach">
4199      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4200      <address><email>paulle@microsoft.com</email></address>
4201    </author>
4202    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
4203      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
4204      <address><email>timbl@w3.org</email></address>
4205    </author>
4206    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
4207      <organization abbrev="W3C">World Wide Web Consortium</organization>
4208      <address><email>ylafon@w3.org</email></address>
4209    </author>
4210    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
4211      <organization abbrev="greenbytes">greenbytes GmbH</organization>
4212      <address><email>julian.reschke@greenbytes.de</email></address>
4213    </author>
4214    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
4215  </front>
4216  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
4217  <x:source href="p3-payload.xml" basename="p3-payload"/>
4218</reference>
4219
4220<reference anchor="Part6">
4221  <front>
4222    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
4223    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
4224      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4225      <address><email>fielding@gbiv.com</email></address>
4226    </author>
4227    <author initials="J." surname="Gettys" fullname="Jim Gettys">
4228      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
4229      <address><email>jg@freedesktop.org</email></address>
4230    </author>
4231    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
4232      <organization abbrev="HP">Hewlett-Packard Company</organization>
4233      <address><email>JeffMogul@acm.org</email></address>
4234    </author>
4235    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
4236      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4237      <address><email>henrikn@microsoft.com</email></address>
4238    </author>
4239    <author initials="L." surname="Masinter" fullname="Larry Masinter">
4240      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
4241      <address><email>LMM@acm.org</email></address>
4242    </author>
4243    <author initials="P." surname="Leach" fullname="Paul J. Leach">
4244      <organization abbrev="Microsoft">Microsoft Corporation</organization>
4245      <address><email>paulle@microsoft.com</email></address>
4246    </author>
4247    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
4248      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
4249      <address><email>timbl@w3.org</email></address>
4250    </author>
4251    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
4252      <organization abbrev="W3C">World Wide Web Consortium</organization>
4253      <address><email>ylafon@w3.org</email></address>
4254    </author>
4255    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
4256      <address><email>mnot@mnot.net</email></address>
4257    </author>
4258    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
4259      <organization abbrev="greenbytes">greenbytes GmbH</organization>
4260      <address><email>julian.reschke@greenbytes.de</email></address>
4261    </author>
4262    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
4263  </front>
4264  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
4265  <x:source href="p6-cache.xml" basename="p6-cache"/>
4266</reference>
4267
4268<reference anchor="RFC5234">
4269  <front>
4270    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
4271    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
4272      <organization>Brandenburg InternetWorking</organization>
4273      <address>
4274        <email>dcrocker@bbiw.net</email>
4275      </address> 
4276    </author>
4277    <author initials="P." surname="Overell" fullname="Paul Overell">
4278      <organization>THUS plc.</organization>
4279      <address>
4280        <email>paul.overell@thus.net</email>
4281      </address>
4282    </author>
4283    <date month="January" year="2008"/>
4284  </front>
4285  <seriesInfo name="STD" value="68"/>
4286  <seriesInfo name="RFC" value="5234"/>
4287</reference>
4288
4289<reference anchor="RFC2119">
4290  <front>
4291    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
4292    <author initials="S." surname="Bradner" fullname="Scott Bradner">
4293      <organization>Harvard University</organization>
4294      <address><email>sob@harvard.edu</email></address>
4295    </author>
4296    <date month="March" year="1997"/>
4297  </front>
4298  <seriesInfo name="BCP" value="14"/>
4299  <seriesInfo name="RFC" value="2119"/>
4300</reference>
4301
4302<reference anchor="RFC3986">
4303 <front>
4304  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
4305  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
4306    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
4307    <address>
4308       <email>timbl@w3.org</email>
4309       <uri>http://www.w3.org/People/Berners-Lee/</uri>
4310    </address>
4311  </author>
4312  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
4313    <organization abbrev="Day Software">Day Software</organization>
4314    <address>
4315      <email>fielding@gbiv.com</email>
4316      <uri>http://roy.gbiv.com/</uri>
4317    </address>
4318  </author>
4319  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
4320    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
4321    <address>
4322      <email>LMM@acm.org</email>
4323      <uri>http://larry.masinter.net/</uri>
4324    </address>
4325  </author>
4326  <date month='January' year='2005'></date>
4327 </front>
4328 <seriesInfo name="STD" value="66"/>
4329 <seriesInfo name="RFC" value="3986"/>
4330</reference>
4331
4332<reference anchor="USASCII">
4333  <front>
4334    <title>Coded Character Set -- 7-bit American Standard Code for Information Interchange</title>
4335    <author>
4336      <organization>American National Standards Institute</organization>
4337    </author>
4338    <date year="1986"/>
4339  </front>
4340  <seriesInfo name="ANSI" value="X3.4"/>
4341</reference>
4342
4343<reference anchor="RFC1950">
4344  <front>
4345    <title>ZLIB Compressed Data Format Specification version 3.3</title>
4346    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
4347      <organization>Aladdin Enterprises</organization>
4348      <address><email>ghost@aladdin.com</email></address>
4349    </author>
4350    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
4351    <date month="May" year="1996"/>
4352  </front>
4353  <seriesInfo name="RFC" value="1950"/>
4354  <annotation>
4355    RFC 1950 is an Informational RFC, thus it might be less stable than
4356    this specification. On the other hand, this downward reference was
4357    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
4358    therefore it is unlikely to cause problems in practice. See also
4359    <xref target="BCP97"/>.
4360  </annotation>
4361</reference>
4362
4363<reference anchor="RFC1951">
4364  <front>
4365    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
4366    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
4367      <organization>Aladdin Enterprises</organization>
4368      <address><email>ghost@aladdin.com</email></address>
4369    </author>
4370    <date month="May" year="1996"/>
4371  </front>
4372  <seriesInfo name="RFC" value="1951"/>
4373  <annotation>
4374    RFC 1951 is an Informational RFC, thus it might be less stable than
4375    this specification. On the other hand, this downward reference was
4376    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
4377    therefore it is unlikely to cause problems in practice. See also
4378    <xref target="BCP97"/>.
4379  </annotation>
4380</reference>
4381
4382<reference anchor="RFC1952">
4383  <front>
4384    <title>GZIP file format specification version 4.3</title>
4385    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
4386      <organization>Aladdin Enterprises</organization>
4387      <address><email>ghost@aladdin.com</email></address>
4388    </author>
4389    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
4390      <address><email>gzip@prep.ai.mit.edu</email></address>
4391    </author>
4392    <author initials="M." surname="Adler" fullname="Mark Adler">
4393      <address><email>madler@alumni.caltech.edu</email></address>
4394    </author>
4395    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
4396      <address><email>ghost@aladdin.com</email></address>
4397    </author>
4398    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
4399      <address><email>randeg@alumni.rpi.edu</email></address>
4400    </author>
4401    <date month="May" year="1996"/>
4402  </front>
4403  <seriesInfo name="RFC" value="1952"/>
4404  <annotation>
4405    RFC 1952 is an Informational RFC, thus it might be less stable than
4406    this specification. On the other hand, this downward reference was
4407    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
4408    therefore it is unlikely to cause problems in practice. See also
4409    <xref target="BCP97"/>.
4410  </annotation>
4411</reference>
4412
4413</references>
4414
4415<references title="Informative References">
4416
4417<reference anchor="Nie1997" target="http://doi.acm.org/10.1145/263105.263157">
4418  <front>
4419    <title>Network Performance Effects of HTTP/1.1, CSS1, and PNG</title>
4420    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen"/>
4421    <author initials="J." surname="Gettys" fullname="J. Gettys"/>
4422    <author initials="E." surname="Prud'hommeaux" fullname="E. Prud'hommeaux"/>
4423    <author initials="H." surname="Lie" fullname="H. Lie"/>
4424    <author initials="C." surname="Lilley" fullname="C. Lilley"/>
4425    <date year="1997" month="September"/>
4426  </front>
4427  <seriesInfo name="ACM" value="Proceedings of the ACM SIGCOMM '97 conference on Applications, technologies, architectures, and protocols for computer communication SIGCOMM '97"/>
4428</reference>
4429
4430<reference anchor="Pad1995" target="http://portal.acm.org/citation.cfm?id=219094">
4431  <front>
4432    <title>Improving HTTP Latency</title>
4433    <author initials="V.N." surname="Padmanabhan" fullname="Venkata N. Padmanabhan"/>
4434    <author initials="J.C." surname="Mogul" fullname="Jeffrey C. Mogul"/>
4435    <date year="1995" month="December"/>
4436  </front>
4437  <seriesInfo name="Computer Networks and ISDN Systems" value="v. 28, pp. 25-35"/>
4438</reference>
4439
4440<reference anchor="RFC1123">
4441  <front>
4442    <title>Requirements for Internet Hosts - Application and Support</title>
4443    <author initials="R." surname="Braden" fullname="Robert Braden">
4444      <organization>University of Southern California (USC), Information Sciences Institute</organization>
4445      <address><email>Braden@ISI.EDU</email></address>
4446    </author>
4447    <date month="October" year="1989"/>
4448  </front>
4449  <seriesInfo name="STD" value="3"/>
4450  <seriesInfo name="RFC" value="1123"/>
4451</reference>
4452
4453<reference anchor="RFC1900">
4454  <front>
4455    <title>Renumbering Needs Work</title>
4456    <author initials="B." surname="Carpenter" fullname="Brian E. Carpenter">
4457      <organization>CERN, Computing and Networks Division</organization>
4458      <address><email>brian@dxcoms.cern.ch</email></address>
4459    </author>
4460    <author initials="Y." surname="Rekhter" fullname="Yakov Rekhter">
4461      <organization>cisco Systems</organization>
4462      <address><email>yakov@cisco.com</email></address>
4463    </author>
4464    <date month="February" year="1996"/>
4465  </front>
4466  <seriesInfo name="RFC" value="1900"/>
4467</reference>
4468
4469<reference anchor='RFC1919'>
4470  <front>
4471    <title>Classical versus Transparent IP Proxies</title>
4472    <author initials='M.' surname='Chatel' fullname='Marc Chatel'>
4473      <address><email>mchatel@pax.eunet.ch</email></address>
4474    </author>
4475    <date year='1996' month='March' />
4476  </front>
4477  <seriesInfo name='RFC' value='1919' />
4478</reference>
4479
4480<reference anchor="RFC1945">
4481  <front>
4482    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
4483    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
4484      <organization>MIT, Laboratory for Computer Science</organization>
4485      <address><email>timbl@w3.org</email></address>
4486    </author>
4487    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
4488      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
4489      <address><email>fielding@ics.uci.edu</email></address>
4490    </author>
4491    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
4492      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
4493      <address><email>frystyk@w3.org</email></address>
4494    </author>
4495    <date month="May" year="1996"/>
4496  </front>
4497  <seriesInfo name="RFC" value="1945"/>
4498</reference>
4499
4500<reference anchor="RFC2045">
4501  <front>
4502    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
4503    <author initials="N." surname="Freed" fullname="Ned Freed">
4504      <organization>Innosoft International, Inc.</organization>
4505      <address><email>ned@innosoft.com</email></address>
4506    </author>
4507    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
4508      <organization>First Virtual Holdings</organization>
4509      <address><email>nsb@nsb.fv.com</email></address>
4510    </author>
4511    <date month="November" year="1996"/>
4512  </front>
4513  <seriesInfo name="RFC" value="2045"/>
4514</reference>
4515
4516<reference anchor="RFC2047">
4517  <front>
4518    <title abbrev="Message Header Extensions">MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text</title>
4519    <author initials="K." surname="Moore" fullname="Keith Moore">
4520      <organization>University of Tennessee</organization>
4521      <address><email>moore@cs.utk.edu</email></address>
4522    </author>
4523    <date month="November" year="1996"/>
4524  </front>
4525  <seriesInfo name="RFC" value="2047"/>
4526</reference>
4527
4528<reference anchor="RFC2068">
4529  <front>
4530    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
4531    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
4532      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
4533      <address><email>fielding@ics.uci.edu</email></address>
4534    </author>
4535    <author initials="J." surname="Gettys" fullname="Jim Gettys">
4536      <organization>MIT Laboratory for Computer Science</organization>
4537      <address><email>jg@w3.org</email></address>
4538    </author>
4539    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
4540      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
4541      <address><email>mogul@wrl.dec.com</email></address>
4542    </author>
4543    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
4544      <organization>MIT Laboratory for Computer Science</organization>
4545      <address><email>frystyk@w3.org</email></address>
4546    </author>
4547    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
4548      <organization>MIT Laboratory for Computer Science</organization>
4549      <address><email>timbl@w3.org</email></address>
4550    </author>
4551    <date month="January" year="1997"/>
4552  </front>
4553  <seriesInfo name="RFC" value="2068"/>
4554</reference>
4555
4556<reference anchor="RFC2145">
4557  <front>
4558    <title abbrev="HTTP Version Numbers">Use and Interpretation of HTTP Version Numbers</title>
4559    <author initials="J.C." surname="Mogul" fullname="Jeffrey C. Mogul">
4560      <organization>Western Research Laboratory</organization>
4561      <address><email>mogul@wrl.dec.com</email></address>
4562    </author>
4563    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
4564      <organization>Department of Information and Computer Science</organization>
4565      <address><email>fielding@ics.uci.edu</email></address>
4566    </author>
4567    <author initials="J." surname="Gettys" fullname="Jim Gettys">
4568      <organization>MIT Laboratory for Computer Science</organization>
4569      <address><email>jg@w3.org</email></address>
4570    </author>
4571    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
4572      <organization>W3 Consortium</organization>
4573      <address><email>frystyk@w3.org</email></address>
4574    </author>
4575    <date month="May" year="1997"/>
4576  </front>
4577  <seriesInfo name="RFC" value="2145"/>
4578</reference>
4579
4580<reference anchor="RFC2616">
4581  <front>
4582    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
4583    <author initials="R." surname="Fielding" fullname="R. Fielding">
4584      <organization>University of California, Irvine</organization>
4585      <address><email>fielding@ics.uci.edu</email></address>
4586    </author>
4587    <author initials="J." surname="Gettys" fullname="J. Gettys">
4588      <organization>W3C</organization>
4589      <address><email>jg@w3.org</email></address>
4590    </author>
4591    <author initials="J." surname="Mogul" fullname="J. Mogul">
4592      <organization>Compaq Computer Corporation</organization>
4593      <address><email>mogul@wrl.dec.com</email></address>
4594    </author>
4595    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
4596      <organization>MIT Laboratory for Computer Science</organization>
4597      <address><email>frystyk@w3.org</email></address>
4598    </author>
4599    <author initials="L." surname="Masinter" fullname="L. Masinter">
4600      <organization>Xerox Corporation</organization>
4601      <address><email>masinter@parc.xerox.com</email></address>
4602    </author>
4603    <author initials="P." surname="Leach" fullname="P. Leach">
4604      <organization>Microsoft Corporation</organization>
4605      <address><email>paulle@microsoft.com</email></address>
4606    </author>
4607    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
4608      <organization>W3C</organization>
4609      <address><email>timbl@w3.org</email></address>
4610    </author>
4611    <date month="June" year="1999"/>
4612  </front>
4613  <seriesInfo name="RFC" value="2616"/>
4614</reference>
4615
4616<reference anchor='RFC2817'>
4617  <front>
4618    <title>Upgrading to TLS Within HTTP/1.1</title>
4619    <author initials='R.' surname='Khare' fullname='R. Khare'>
4620      <organization>4K Associates / UC Irvine</organization>
4621      <address><email>rohit@4K-associates.com</email></address>
4622    </author>
4623    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
4624      <organization>Agranat Systems, Inc.</organization>
4625      <address><email>lawrence@agranat.com</email></address>
4626    </author>
4627    <date year='2000' month='May' />
4628  </front>
4629  <seriesInfo name='RFC' value='2817' />
4630</reference>
4631
4632<reference anchor='RFC2818'>
4633  <front>
4634    <title>HTTP Over TLS</title>
4635    <author initials='E.' surname='Rescorla' fullname='Eric Rescorla'>
4636      <organization>RTFM, Inc.</organization>
4637      <address><email>ekr@rtfm.com</email></address>
4638    </author>
4639    <date year='2000' month='May' />
4640  </front>
4641  <seriesInfo name='RFC' value='2818' />
4642</reference>
4643
4644<reference anchor='RFC2965'>
4645  <front>
4646    <title>HTTP State Management Mechanism</title>
4647    <author initials='D. M.' surname='Kristol' fullname='David M. Kristol'>
4648      <organization>Bell Laboratories, Lucent Technologies</organization>
4649      <address><email>dmk@bell-labs.com</email></address>
4650    </author>
4651    <author initials='L.' surname='Montulli' fullname='Lou Montulli'>
4652      <organization>Epinions.com, Inc.</organization>
4653      <address><email>lou@montulli.org</email></address>
4654    </author>
4655    <date year='2000' month='October' />
4656  </front>
4657  <seriesInfo name='RFC' value='2965' />
4658</reference>
4659
4660<reference anchor='RFC3040'>
4661  <front>
4662    <title>Internet Web Replication and Caching Taxonomy</title>
4663    <author initials='I.' surname='Cooper' fullname='I. Cooper'>
4664      <organization>Equinix, Inc.</organization>
4665    </author>
4666    <author initials='I.' surname='Melve' fullname='I. Melve'>
4667      <organization>UNINETT</organization>
4668    </author>
4669    <author initials='G.' surname='Tomlinson' fullname='G. Tomlinson'>
4670      <organization>CacheFlow Inc.</organization>
4671    </author>
4672    <date year='2001' month='January' />
4673  </front>
4674  <seriesInfo name='RFC' value='3040' />
4675</reference>
4676
4677<reference anchor='RFC3864'>
4678  <front>
4679    <title>Registration Procedures for Message Header Fields</title>
4680    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
4681      <organization>Nine by Nine</organization>
4682      <address><email>GK-IETF@ninebynine.org</email></address>
4683    </author>
4684    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
4685      <organization>BEA Systems</organization>
4686      <address><email>mnot@pobox.com</email></address>
4687    </author>
4688    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
4689      <organization>HP Labs</organization>
4690      <address><email>JeffMogul@acm.org</email></address>
4691    </author>
4692    <date year='2004' month='September' />
4693  </front>
4694  <seriesInfo name='BCP' value='90' />
4695  <seriesInfo name='RFC' value='3864' />
4696</reference>
4697
4698<reference anchor="RFC4288">
4699  <front>
4700    <title>Media Type Specifications and Registration Procedures</title>
4701    <author initials="N." surname="Freed" fullname="N. Freed">
4702      <organization>Sun Microsystems</organization>
4703      <address>
4704        <email>ned.freed@mrochek.com</email>
4705      </address>
4706    </author>
4707    <author initials="J." surname="Klensin" fullname="J. Klensin">
4708      <address>
4709        <email>klensin+ietf@jck.com</email>
4710      </address>
4711    </author>
4712    <date year="2005" month="December"/>
4713  </front>
4714  <seriesInfo name="BCP" value="13"/>
4715  <seriesInfo name="RFC" value="4288"/>
4716</reference>
4717
4718<reference anchor='RFC4395'>
4719  <front>
4720    <title>Guidelines and Registration Procedures for New URI Schemes</title>
4721    <author initials='T.' surname='Hansen' fullname='T. Hansen'>
4722      <organization>AT&amp;T Laboratories</organization>
4723      <address>
4724        <email>tony+urireg@maillennium.att.com</email>
4725      </address>
4726    </author>
4727    <author initials='T.' surname='Hardie' fullname='T. Hardie'>
4728      <organization>Qualcomm, Inc.</organization>
4729      <address>
4730        <email>hardie@qualcomm.com</email>
4731      </address>
4732    </author>
4733    <author initials='L.' surname='Masinter' fullname='L. Masinter'>
4734      <organization>Adobe Systems</organization>
4735      <address>
4736        <email>LMM@acm.org</email>
4737      </address>
4738    </author>
4739    <date year='2006' month='February' />
4740  </front>
4741  <seriesInfo name='BCP' value='115' />
4742  <seriesInfo name='RFC' value='4395' />
4743</reference>
4744
4745<reference anchor='RFC5226'>
4746  <front>
4747    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
4748    <author initials='T.' surname='Narten' fullname='T. Narten'>
4749      <organization>IBM</organization>
4750      <address><email>narten@us.ibm.com</email></address>
4751    </author>
4752    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
4753      <organization>Google</organization>
4754      <address><email>Harald@Alvestrand.no</email></address>
4755    </author>
4756    <date year='2008' month='May' />
4757  </front>
4758  <seriesInfo name='BCP' value='26' />
4759  <seriesInfo name='RFC' value='5226' />
4760</reference>
4761
4762<reference anchor="RFC5322">
4763  <front>
4764    <title>Internet Message Format</title>
4765    <author initials="P." surname="Resnick" fullname="P. Resnick">
4766      <organization>Qualcomm Incorporated</organization>
4767    </author>
4768    <date year="2008" month="October"/>
4769  </front> 
4770  <seriesInfo name="RFC" value="5322"/>
4771</reference>
4772
4773<reference anchor='draft-ietf-httpstate-cookie'>
4774  <front>
4775    <title>HTTP State Management Mechanism</title>
4776    <author initials="A." surname="Barth" fullname="Adam Barth">
4777      <organization abbrev="U.C. Berkeley">
4778        University of California, Berkeley
4779      </organization>
4780      <address><email>abarth@eecs.berkeley.edu</email></address>
4781    </author>
4782    <date year='2011' month='March' />
4783  </front>
4784  <seriesInfo name="Internet-Draft" value="draft-ietf-httpstate-cookie-23"/>
4785</reference>
4786
4787<reference anchor='BCP97'>
4788  <front>
4789    <title>Handling Normative References to Standards-Track Documents</title>
4790    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
4791      <address>
4792        <email>klensin+ietf@jck.com</email>
4793      </address>
4794    </author>
4795    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
4796      <organization>MIT</organization>
4797      <address>
4798        <email>hartmans-ietf@mit.edu</email>
4799      </address>
4800    </author>
4801    <date year='2007' month='June' />
4802  </front>
4803  <seriesInfo name='BCP' value='97' />
4804  <seriesInfo name='RFC' value='4897' />
4805</reference>
4806
4807<reference anchor="Kri2001" target="http://arxiv.org/abs/cs.SE/0105018">
4808  <front>
4809    <title>HTTP Cookies: Standards, Privacy, and Politics</title>
4810    <author initials="D." surname="Kristol" fullname="David M. Kristol"/>
4811    <date year="2001" month="November"/>
4812  </front>
4813  <seriesInfo name="ACM Transactions on Internet Technology" value="Vol. 1, #2"/>
4814</reference>
4815
4816<reference anchor="Spe" target="http://sunsite.unc.edu/mdma-release/http-prob.html">
4817  <front>
4818    <title>Analysis of HTTP Performance Problems</title>
4819    <author initials="S." surname="Spero" fullname="Simon E. Spero"/>
4820    <date/>
4821  </front>
4822</reference>
4823
4824<reference anchor="Tou1998" target="http://www.isi.edu/touch/pubs/http-perf96/">
4825  <front>
4826  <title>Analysis of HTTP Performance</title>
4827  <author initials="J." surname="Touch" fullname="Joe Touch">
4828    <organization>USC/Information Sciences Institute</organization>
4829    <address><email>touch@isi.edu</email></address>
4830  </author>
4831  <author initials="J." surname="Heidemann" fullname="John Heidemann">
4832    <organization>USC/Information Sciences Institute</organization>
4833    <address><email>johnh@isi.edu</email></address>
4834  </author>
4835  <author initials="K." surname="Obraczka" fullname="Katia Obraczka">
4836    <organization>USC/Information Sciences Institute</organization>
4837    <address><email>katia@isi.edu</email></address>
4838  </author>
4839  <date year="1998" month="Aug"/>
4840  </front>
4841  <seriesInfo name="ISI Research Report" value="ISI/RR-98-463"/>
4842  <annotation>(original report dated Aug. 1996)</annotation>
4843</reference>
4844
4845</references>
4846
4847
4848<section title="Tolerant Applications" anchor="tolerant.applications">
4849<t>
4850   Although this document specifies the requirements for the generation
4851   of HTTP/1.1 messages, not all applications will be correct in their
4852   implementation. We therefore recommend that operational applications
4853   be tolerant of deviations whenever those deviations can be
4854   interpreted unambiguously.
4855</t>
4856<t>
4857   The line terminator for header fields is the sequence CRLF.
4858   However, we recommend that applications, when parsing such headers fields,
4859   recognize a single LF as a line terminator and ignore the leading CR.
4860</t>
4861<t>
4862   The character encoding of a representation &SHOULD; be labeled as the lowest
4863   common denominator of the character codes used within that representation, with
4864   the exception that not labeling the representation is preferred over labeling
4865   the representation with the labels US-ASCII or ISO-8859-1. See &payload;.
4866</t>
4867<t>
4868   Additional rules for requirements on parsing and encoding of dates
4869   and other potential problems with date encodings include:
4870</t>
4871<t>
4872  <list style="symbols">
4873     <t>HTTP/1.1 clients and caches &SHOULD; assume that an RFC-850 date
4874        which appears to be more than 50 years in the future is in fact
4875        in the past (this helps solve the "year 2000" problem).</t>
4876
4877     <t>Although all date formats are specified to be case-sensitive,
4878        recipients &SHOULD; match day, week and timezone names
4879        case-insensitively.</t>
4880             
4881     <t>An HTTP/1.1 implementation &MAY; internally represent a parsed
4882        Expires date as earlier than the proper value, but &MUST-NOT;
4883        internally represent a parsed Expires date as later than the
4884        proper value.</t>
4885
4886     <t>All expiration-related calculations &MUST; be done in GMT. The
4887        local time zone &MUST-NOT; influence the calculation or comparison
4888        of an age or expiration time.</t>
4889
4890     <t>If an HTTP header field incorrectly carries a date value with a time
4891        zone other than GMT, it &MUST; be converted into GMT using the
4892        most conservative possible conversion.</t>
4893  </list>
4894</t>
4895</section>
4896
4897<section title="HTTP Version History" anchor="compatibility">
4898<t>
4899   HTTP has been in use by the World-Wide Web global information initiative
4900   since 1990. The first version of HTTP, later referred to as HTTP/0.9,
4901   was a simple protocol for hypertext data transfer across the Internet
4902   with only a single request method (GET) and no metadata.
4903   HTTP/1.0, as defined by <xref target="RFC1945"/>, added a range of request
4904   methods and MIME-like messaging that could include metadata about the data
4905   transferred and modifiers on the request/response semantics. However,
4906   HTTP/1.0 did not sufficiently take into consideration the effects of
4907   hierarchical proxies, caching, the need for persistent connections, or
4908   name-based virtual hosts. The proliferation of incompletely-implemented
4909   applications calling themselves "HTTP/1.0" further necessitated a
4910   protocol version change in order for two communicating applications
4911   to determine each other's true capabilities.
4912</t>
4913<t>
4914   HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
4915   requirements that enable reliable implementations, adding only
4916   those new features that will either be safely ignored by an HTTP/1.0
4917   recipient or only sent when communicating with a party advertising
4918   compliance with HTTP/1.1.
4919</t>
4920<t>
4921   It is beyond the scope of a protocol specification to mandate
4922   compliance with previous versions. HTTP/1.1 was deliberately
4923   designed, however, to make supporting previous versions easy.
4924   We would expect a general-purpose HTTP/1.1 server to understand
4925   any valid request in the format of HTTP/1.0 and respond appropriately
4926   with an HTTP/1.1 message that only uses features understood (or
4927   safely ignored) by HTTP/1.0 clients.  Likewise, would expect
4928   an HTTP/1.1 client to understand any valid HTTP/1.0 response.
4929</t>
4930<t>
4931   Since HTTP/0.9 did not support header fields in a request,
4932   there is no mechanism for it to support name-based virtual
4933   hosts (selection of resource by inspection of the Host header
4934   field).  Any server that implements name-based virtual hosts
4935   ought to disable support for HTTP/0.9.  Most requests that
4936   appear to be HTTP/0.9 are, in fact, badly constructed HTTP/1.x
4937   requests wherein a buggy client failed to properly encode
4938   linear whitespace found in a URI reference and placed in
4939   the request-target.
4940</t>
4941
4942<section title="Changes from HTTP/1.0" anchor="changes.from.1.0">
4943<t>
4944   This section summarizes major differences between versions HTTP/1.0
4945   and HTTP/1.1.
4946</t>
4947
4948<section title="Multi-homed Web Servers" anchor="changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses">
4949<t>
4950   The requirements that clients and servers support the Host header
4951   field (<xref target="header.host"/>), report an error if it is
4952   missing from an HTTP/1.1 request, and accept absolute URIs (<xref target="request-target"/>)
4953   are among the most important changes defined by HTTP/1.1.
4954</t>
4955<t>
4956   Older HTTP/1.0 clients assumed a one-to-one relationship of IP
4957   addresses and servers; there was no other established mechanism for
4958   distinguishing the intended server of a request than the IP address
4959   to which that request was directed. The Host header field was
4960   introduced during the development of HTTP/1.1 and, though it was
4961   quickly implemented by most HTTP/1.0 browsers, additional requirements
4962   were placed on all HTTP/1.1 requests in order to ensure complete
4963   adoption.  At the time of this writing, most HTTP-based services
4964   are dependent upon the Host header field for targeting requests.
4965</t>
4966</section>
4967
4968<section title="Keep-Alive Connections" anchor="compatibility.with.http.1.0.persistent.connections">
4969<t>
4970   For most implementations of HTTP/1.0, each connection is established
4971   by the client prior to the request and closed by the server after
4972   sending the response. However, some implementations implement the
4973   Keep-Alive version of persistent connections described in
4974   <xref x:sec="19.7.1" x:fmt="of" target="RFC2068"/>.
4975</t>
4976<t>
4977   Some clients and servers might wish to be compatible with some
4978   previous implementations of persistent connections in HTTP/1.0
4979   clients and servers. Persistent connections in HTTP/1.0 are
4980   explicitly negotiated as they are not the default behavior. HTTP/1.0
4981   experimental implementations of persistent connections are faulty,
4982   and the new facilities in HTTP/1.1 are designed to rectify these
4983   problems. The problem was that some existing HTTP/1.0 clients might
4984   send Keep-Alive to a proxy server that doesn't understand
4985   Connection, which would then erroneously forward it to the next
4986   inbound server, which would establish the Keep-Alive connection and
4987   result in a hung HTTP/1.0 proxy waiting for the close on the
4988   response. The result is that HTTP/1.0 clients must be prevented from
4989   using Keep-Alive when talking to proxies.
4990</t>
4991<t>
4992   However, talking to proxies is the most important use of persistent
4993   connections, so that prohibition is clearly unacceptable. Therefore,
4994   we need some other mechanism for indicating a persistent connection
4995   is desired, which is safe to use even when talking to an old proxy
4996   that ignores Connection. Persistent connections are the default for
4997   HTTP/1.1 messages; we introduce a new keyword (Connection: close) for
4998   declaring non-persistence. See <xref target="header.connection"/>.
4999</t>
5000</section>
5001</section>
5002
5003<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
5004<t>
5005  Empty list elements in list productions have been deprecated.
5006  (<xref target="notation.abnf"/>)
5007</t>
5008<t>
5009  Rules about implicit linear whitespace between certain grammar productions
5010  have been removed; now it's only allowed when specifically pointed out
5011  in the ABNF. The NUL octet is no longer allowed in comment and quoted-string
5012  text. The quoted-pair rule no longer allows escaping control characters other than HTAB.
5013  Non-ASCII content in header fields and reason phrase has been obsoleted and
5014  made opaque (the TEXT rule was removed)
5015  (<xref target="basic.rules"/>)
5016</t>
5017<t>
5018  Clarify that HTTP-Version is case sensitive.
5019  (<xref target="http.version"/>)
5020</t>
5021<t>
5022  Require that invalid whitespace around field-names be rejected.
5023  (<xref target="header.fields"/>)
5024</t>
5025<t>
5026  Require recipients to handle bogus Content-Length header fields as errors.
5027  (<xref target="message.body"/>)
5028</t>
5029<t>
5030  Remove reference to non-existent identity transfer-coding value tokens.
5031  (Sections <xref format="counter" target="message.body"/> and
5032  <xref format="counter" target="transfer.codings"/>)
5033</t>
5034<t>
5035  Update use of abs_path production from RFC 1808 to the path-absolute + query
5036  components of RFC 3986. State that the asterisk form is allowed for the OPTIONS
5037  request method only.
5038  (<xref target="request-target"/>)
5039</t>
5040<t>
5041  Clarification that the chunk length does not include the count of the octets
5042  in the chunk header and trailer. Furthermore disallowed line folding
5043  in chunk extensions.
5044  (<xref target="chunked.encoding"/>)
5045</t>
5046<t>
5047  Remove hard limit of two connections per server.
5048  (<xref target="persistent.practical"/>)
5049</t>
5050<t>
5051  Clarify exactly when close connection options must be sent.
5052  (<xref target="header.connection"/>)
5053</t>
5054<t>
5055  Define the semantics of the "Upgrade" header field in responses other than
5056  101 (this was incorporated from <xref target="RFC2817"/>).
5057  (<xref target="header.upgrade"/>)
5058</t>
5059</section>
5060</section>
5061
5062<?BEGININC p1-messaging.abnf-appendix ?>
5063<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
5064<figure>
5065<artwork type="abnf" name="p1-messaging.parsed-abnf">
5066<x:ref>BWS</x:ref> = OWS
5067
5068<x:ref>Chunked-Body</x:ref> = *chunk last-chunk trailer-part CRLF
5069<x:ref>Connection</x:ref> = "Connection:" OWS Connection-v
5070<x:ref>Connection-v</x:ref> = *( "," OWS ) connection-token *( OWS "," [ OWS
5071 connection-token ] )
5072<x:ref>Content-Length</x:ref> = "Content-Length:" OWS 1*Content-Length-v
5073<x:ref>Content-Length-v</x:ref> = 1*DIGIT
5074
5075<x:ref>Date</x:ref> = "Date:" OWS Date-v
5076<x:ref>Date-v</x:ref> = HTTP-date
5077
5078<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
5079
5080<x:ref>HTTP-Prot-Name</x:ref> = %x48.54.54.50 ; HTTP
5081<x:ref>HTTP-Version</x:ref> = HTTP-Prot-Name "/" 1*DIGIT "." 1*DIGIT
5082<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
5083<x:ref>HTTP-message</x:ref> = start-line *( header-field CRLF ) CRLF [ message-body
5084 ]
5085<x:ref>Host</x:ref> = "Host:" OWS Host-v
5086<x:ref>Host-v</x:ref> = uri-host [ ":" port ]
5087
5088<x:ref>Method</x:ref> = token
5089
5090<x:ref>OWS</x:ref> = *( [ obs-fold ] WSP )
5091
5092<x:ref>RWS</x:ref> = 1*( [ obs-fold ] WSP )
5093<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
5094<x:ref>Request</x:ref> = Request-Line *( header-field CRLF ) CRLF [ message-body ]
5095<x:ref>Request-Line</x:ref> = Method SP request-target SP HTTP-Version CRLF
5096<x:ref>Response</x:ref> = Status-Line *( header-field CRLF ) CRLF [ message-body ]
5097
5098<x:ref>Status-Code</x:ref> = 3DIGIT
5099<x:ref>Status-Line</x:ref> = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
5100
5101<x:ref>TE</x:ref> = "TE:" OWS TE-v
5102<x:ref>TE-v</x:ref> = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
5103<x:ref>Trailer</x:ref> = "Trailer:" OWS Trailer-v
5104<x:ref>Trailer-v</x:ref> = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
5105<x:ref>Transfer-Encoding</x:ref> = "Transfer-Encoding:" OWS Transfer-Encoding-v
5106<x:ref>Transfer-Encoding-v</x:ref> = *( "," OWS ) transfer-coding *( OWS "," [ OWS
5107 transfer-coding ] )
5108
5109<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [RFC3986], Section 4.1&gt;
5110<x:ref>Upgrade</x:ref> = "Upgrade:" OWS Upgrade-v
5111<x:ref>Upgrade-v</x:ref> = *( "," OWS ) product *( OWS "," [ OWS product ] )
5112
5113<x:ref>Via</x:ref> = "Via:" OWS Via-v
5114<x:ref>Via-v</x:ref> = *( "," OWS ) received-protocol RWS received-by [ RWS comment
5115 ] *( OWS "," [ OWS received-protocol RWS received-by [ RWS comment ]
5116 ] )
5117
5118<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [RFC3986], Section 4.3&gt;
5119<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
5120<x:ref>attribute</x:ref> = token
5121<x:ref>authority</x:ref> = &lt;authority, defined in [RFC3986], Section 3.2&gt;
5122
5123<x:ref>chunk</x:ref> = chunk-size *WSP [ chunk-ext ] CRLF chunk-data CRLF
5124<x:ref>chunk-data</x:ref> = 1*OCTET
5125<x:ref>chunk-ext</x:ref> = *( ";" *WSP chunk-ext-name [ "=" chunk-ext-val ] *WSP )
5126<x:ref>chunk-ext-name</x:ref> = token
5127<x:ref>chunk-ext-val</x:ref> = token / quoted-str-nf
5128<x:ref>chunk-size</x:ref> = 1*HEXDIG
5129<x:ref>comment</x:ref> = "(" *( ctext / quoted-cpair / comment ) ")"
5130<x:ref>connection-token</x:ref> = token
5131<x:ref>ctext</x:ref> = OWS / %x21-27 ; '!'-'''
5132 / %x2A-5B ; '*'-'['
5133 / %x5D-7E ; ']'-'~'
5134 / obs-text
5135
5136<x:ref>date1</x:ref> = day SP month SP year
5137<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
5138<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
5139<x:ref>day</x:ref> = 2DIGIT
5140<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
5141 / %x54.75.65 ; Tue
5142 / %x57.65.64 ; Wed
5143 / %x54.68.75 ; Thu
5144 / %x46.72.69 ; Fri
5145 / %x53.61.74 ; Sat
5146 / %x53.75.6E ; Sun
5147<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
5148 / %x54.75.65.73.64.61.79 ; Tuesday
5149 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
5150 / %x54.68.75.72.73.64.61.79 ; Thursday
5151 / %x46.72.69.64.61.79 ; Friday
5152 / %x53.61.74.75.72.64.61.79 ; Saturday
5153 / %x53.75.6E.64.61.79 ; Sunday
5154
5155<x:ref>field-content</x:ref> = *( WSP / VCHAR / obs-text )
5156<x:ref>field-name</x:ref> = token
5157<x:ref>field-value</x:ref> = *( field-content / OWS )
5158
5159<x:ref>header-field</x:ref> = field-name ":" OWS [ field-value ] OWS
5160<x:ref>hour</x:ref> = 2DIGIT
5161<x:ref>http-URI</x:ref> = "http://" authority path-abempty [ "?" query ]
5162<x:ref>https-URI</x:ref> = "https://" authority path-abempty [ "?" query ]
5163
5164<x:ref>last-chunk</x:ref> = 1*"0" *WSP [ chunk-ext ] CRLF
5165
5166<x:ref>message-body</x:ref> = *OCTET
5167<x:ref>minute</x:ref> = 2DIGIT
5168<x:ref>month</x:ref> = %x4A.61.6E ; Jan
5169 / %x46.65.62 ; Feb
5170 / %x4D.61.72 ; Mar
5171 / %x41.70.72 ; Apr
5172 / %x4D.61.79 ; May
5173 / %x4A.75.6E ; Jun
5174 / %x4A.75.6C ; Jul
5175 / %x41.75.67 ; Aug
5176 / %x53.65.70 ; Sep
5177 / %x4F.63.74 ; Oct
5178 / %x4E.6F.76 ; Nov
5179 / %x44.65.63 ; Dec
5180
5181<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
5182<x:ref>obs-fold</x:ref> = CRLF
5183<x:ref>obs-text</x:ref> = %x80-FF
5184
5185<x:ref>partial-URI</x:ref> = relative-part [ "?" query ]
5186<x:ref>path-abempty</x:ref> = &lt;path-abempty, defined in [RFC3986], Section 3.3&gt;
5187<x:ref>path-absolute</x:ref> = &lt;path-absolute, defined in [RFC3986], Section 3.3&gt;
5188<x:ref>port</x:ref> = &lt;port, defined in [RFC3986], Section 3.2.3&gt;
5189<x:ref>product</x:ref> = token [ "/" product-version ]
5190<x:ref>product-version</x:ref> = token
5191<x:ref>protocol-name</x:ref> = token
5192<x:ref>protocol-version</x:ref> = token
5193<x:ref>pseudonym</x:ref> = token
5194
5195<x:ref>qdtext</x:ref> = OWS / "!" / %x23-5B ; '#'-'['
5196 / %x5D-7E ; ']'-'~'
5197 / obs-text
5198<x:ref>qdtext-nf</x:ref> = WSP / "!" / %x23-5B ; '#'-'['
5199 / %x5D-7E ; ']'-'~'
5200 / obs-text
5201<x:ref>query</x:ref> = &lt;query, defined in [RFC3986], Section 3.4&gt;
5202<x:ref>quoted-cpair</x:ref> = "\" ( WSP / VCHAR / obs-text )
5203<x:ref>quoted-pair</x:ref> = "\" ( WSP / VCHAR / obs-text )
5204<x:ref>quoted-str-nf</x:ref> = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
5205<x:ref>quoted-string</x:ref> = DQUOTE *( qdtext / quoted-pair ) DQUOTE
5206<x:ref>qvalue</x:ref> = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
5207
5208<x:ref>received-by</x:ref> = ( uri-host [ ":" port ] ) / pseudonym
5209<x:ref>received-protocol</x:ref> = [ protocol-name "/" ] protocol-version
5210<x:ref>relative-part</x:ref> = &lt;relative-part, defined in [RFC3986], Section 4.2&gt;
5211<x:ref>request-target</x:ref> = "*" / absolute-URI / ( path-absolute [ "?" query ] )
5212 / authority
5213<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
5214<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
5215
5216<x:ref>second</x:ref> = 2DIGIT
5217<x:ref>special</x:ref> = "(" / ")" / "&lt;" / "&gt;" / "@" / "," / ";" / ":" / "\" /
5218 DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}"
5219<x:ref>start-line</x:ref> = Request-Line / Status-Line
5220
5221<x:ref>t-codings</x:ref> = "trailers" / ( transfer-extension [ te-params ] )
5222<x:ref>tchar</x:ref> = "!" / "#" / "$" / "%" / "&amp;" / "'" / "*" / "+" / "-" / "." /
5223 "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
5224<x:ref>te-ext</x:ref> = OWS ";" OWS token [ "=" word ]
5225<x:ref>te-params</x:ref> = OWS ";" OWS "q=" qvalue *te-ext
5226<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
5227<x:ref>token</x:ref> = 1*tchar
5228<x:ref>trailer-part</x:ref> = *( header-field CRLF )
5229<x:ref>transfer-coding</x:ref> = "chunked" / "compress" / "deflate" / "gzip" /
5230 transfer-extension
5231<x:ref>transfer-extension</x:ref> = token *( OWS ";" OWS transfer-parameter )
5232<x:ref>transfer-parameter</x:ref> = attribute BWS "=" BWS value
5233
5234<x:ref>uri-host</x:ref> = &lt;host, defined in [RFC3986], Section 3.2.2&gt;
5235
5236<x:ref>value</x:ref> = word
5237
5238<x:ref>word</x:ref> = token / quoted-string
5239
5240<x:ref>year</x:ref> = 4DIGIT
5241</artwork>
5242</figure>
5243<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
5244; Chunked-Body defined but not used
5245; Connection defined but not used
5246; Content-Length defined but not used
5247; Date defined but not used
5248; HTTP-message defined but not used
5249; Host defined but not used
5250; Request defined but not used
5251; Response defined but not used
5252; TE defined but not used
5253; Trailer defined but not used
5254; Transfer-Encoding defined but not used
5255; URI-reference defined but not used
5256; Upgrade defined but not used
5257; Via defined but not used
5258; http-URI defined but not used
5259; https-URI defined but not used
5260; partial-URI defined but not used
5261; special defined but not used
5262</artwork></figure></section>
5263<?ENDINC p1-messaging.abnf-appendix ?>
5264
5265<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
5266
5267<section title="Since RFC 2616">
5268<t>
5269  Extracted relevant partitions from <xref target="RFC2616"/>.
5270</t>
5271</section>
5272
5273<section title="Since draft-ietf-httpbis-p1-messaging-00">
5274<t>
5275  Closed issues:
5276  <list style="symbols"> 
5277    <t>
5278      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/1"/>:
5279      "HTTP Version should be case sensitive"
5280      (<eref target="http://purl.org/NET/http-errata#verscase"/>)
5281    </t>
5282    <t>
5283      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/2"/>:
5284      "'unsafe' characters"
5285      (<eref target="http://purl.org/NET/http-errata#unsafe-uri"/>)
5286    </t>
5287    <t>
5288      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/3"/>:
5289      "Chunk Size Definition"
5290      (<eref target="http://purl.org/NET/http-errata#chunk-size"/>)
5291    </t>
5292    <t>
5293      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/4"/>:
5294      "Message Length"
5295      (<eref target="http://purl.org/NET/http-errata#msg-len-chars"/>)
5296    </t>
5297    <t>
5298      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
5299      "Media Type Registrations"
5300      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
5301    </t>
5302    <t>
5303      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/11"/>:
5304      "URI includes query"
5305      (<eref target="http://purl.org/NET/http-errata#uriquery"/>)
5306    </t>
5307    <t>
5308      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/15"/>:
5309      "No close on 1xx responses"
5310      (<eref target="http://purl.org/NET/http-errata#noclose1xx"/>)
5311    </t>
5312    <t>
5313      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
5314      "Remove 'identity' token references"
5315      (<eref target="http://purl.org/NET/http-errata#identity"/>)
5316    </t>
5317    <t>
5318      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/26"/>:
5319      "Import query BNF"
5320    </t>
5321    <t>
5322      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/31"/>:
5323      "qdtext BNF"
5324    </t>
5325    <t>
5326      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
5327      "Normative and Informative references"
5328    </t>
5329    <t>
5330      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
5331      "RFC2606 Compliance"
5332    </t>
5333    <t>
5334      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/45"/>:
5335      "RFC977 reference"
5336    </t>
5337    <t>
5338      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
5339      "RFC1700 references"
5340    </t>
5341    <t>
5342      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/47"/>:
5343      "inconsistency in date format explanation"
5344    </t>
5345    <t>
5346      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/48"/>:
5347      "Date reference typo"
5348    </t>
5349    <t>
5350      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
5351      "Informative references"
5352    </t>
5353    <t>
5354      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
5355      "ISO-8859-1 Reference"
5356    </t>
5357    <t>
5358      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
5359      "Normative up-to-date references"
5360    </t>
5361  </list>
5362</t>
5363<t>
5364  Other changes:
5365  <list style="symbols"> 
5366    <t>
5367      Update media type registrations to use RFC4288 template.
5368    </t>
5369    <t>
5370      Use names of RFC4234 core rules DQUOTE and WSP,
5371      fix broken ABNF for chunk-data
5372      (work in progress on <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>)
5373    </t>
5374  </list>
5375</t>
5376</section>
5377
5378<section title="Since draft-ietf-httpbis-p1-messaging-01">
5379<t>
5380  Closed issues:
5381  <list style="symbols"> 
5382    <t>
5383      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/19"/>:
5384      "Bodies on GET (and other) requests"
5385    </t>
5386    <t>
5387      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
5388      "Updating to RFC4288"
5389    </t>
5390    <t>
5391      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/57"/>:
5392      "Status Code and Reason Phrase"
5393    </t>
5394    <t>
5395      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/82"/>:
5396      "rel_path not used"
5397    </t>
5398  </list>
5399</t>
5400<t>
5401  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
5402  <list style="symbols"> 
5403    <t>
5404      Get rid of duplicate BNF rule names ("host" -> "uri-host", "trailer" ->
5405      "trailer-part").
5406    </t>
5407    <t>
5408      Avoid underscore character in rule names ("http_URL" ->
5409      "http-URL", "abs_path" -> "path-absolute").
5410    </t>
5411    <t>
5412      Add rules for terms imported from URI spec ("absoluteURI", "authority",
5413      "path-absolute", "port", "query", "relativeURI", "host) &mdash; these will
5414      have to be updated when switching over to RFC3986.
5415    </t>
5416    <t>
5417      Synchronize core rules with RFC5234.
5418    </t>
5419    <t>
5420      Get rid of prose rules that span multiple lines.
5421    </t>
5422    <t>
5423      Get rid of unused rules LOALPHA and UPALPHA.
5424    </t>
5425    <t>
5426      Move "Product Tokens" section (back) into Part 1, as "token" is used
5427      in the definition of the Upgrade header field.
5428    </t>
5429    <t>
5430      Add explicit references to BNF syntax and rules imported from other parts of the specification.
5431    </t>
5432    <t>
5433      Rewrite prose rule "token" in terms of "tchar", rewrite prose rule "TEXT".
5434    </t>
5435  </list>
5436</t>
5437</section>
5438
5439<section title="Since draft-ietf-httpbis-p1-messaging-02" anchor="changes.since.02">
5440<t>
5441  Closed issues:
5442  <list style="symbols"> 
5443    <t>
5444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/51"/>:
5445      "HTTP-date vs. rfc1123-date"
5446    </t>
5447    <t>
5448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/64"/>:
5449      "WS in quoted-pair"
5450    </t>
5451  </list>
5452</t>
5453<t>
5454  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
5455  <list style="symbols"> 
5456    <t>
5457      Reference RFC 3984, and update header field registrations for headers defined
5458      in this document.
5459    </t>
5460  </list>
5461</t>
5462<t>
5463  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
5464  <list style="symbols"> 
5465    <t>
5466      Replace string literals when the string really is case-sensitive (HTTP-Version).
5467    </t>
5468  </list>
5469</t>
5470</section>
5471
5472<section title="Since draft-ietf-httpbis-p1-messaging-03" anchor="changes.since.03">
5473<t>
5474  Closed issues:
5475  <list style="symbols"> 
5476    <t>
5477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/28"/>:
5478      "Connection closing"
5479    </t>
5480    <t>
5481      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/97"/>:
5482      "Move registrations and registry information to IANA Considerations"
5483    </t>
5484    <t>
5485      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/120"/>:
5486      "need new URL for PAD1995 reference"
5487    </t>
5488    <t>
5489      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/127"/>:
5490      "IANA Considerations: update HTTP URI scheme registration"
5491    </t>
5492    <t>
5493      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/128"/>:
5494      "Cite HTTPS URI scheme definition"
5495    </t>
5496    <t>
5497      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/129"/>:
5498      "List-type headers vs Set-Cookie"
5499    </t>
5500  </list>
5501</t>
5502<t>
5503  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
5504  <list style="symbols"> 
5505    <t>
5506      Replace string literals when the string really is case-sensitive (HTTP-Date).
5507    </t>
5508    <t>
5509      Replace HEX by HEXDIG for future consistence with RFC 5234's core rules.
5510    </t>
5511  </list>
5512</t>
5513</section>
5514
5515<section title="Since draft-ietf-httpbis-p1-messaging-04" anchor="changes.since.04">
5516<t>
5517  Closed issues:
5518  <list style="symbols"> 
5519    <t>
5520      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/34"/>:
5521      "Out-of-date reference for URIs"
5522    </t>
5523    <t>
5524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
5525      "RFC 2822 is updated by RFC 5322"
5526    </t>
5527  </list>
5528</t>
5529<t>
5530  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
5531  <list style="symbols"> 
5532    <t>
5533      Use "/" instead of "|" for alternatives.
5534    </t>
5535    <t>
5536      Get rid of RFC822 dependency; use RFC5234 plus extensions instead.
5537    </t>
5538    <t>
5539      Only reference RFC 5234's core rules.
5540    </t>
5541    <t>
5542      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
5543      whitespace ("OWS") and required whitespace ("RWS").
5544    </t>
5545    <t>
5546      Rewrite ABNFs to spell out whitespace rules, factor out
5547      header field value format definitions.
5548    </t>
5549  </list>
5550</t>
5551</section>
5552
5553<section title="Since draft-ietf-httpbis-p1-messaging-05" anchor="changes.since.05">
5554<t>
5555  Closed issues:
5556  <list style="symbols"> 
5557    <t>
5558      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/30"/>:
5559      "Header LWS"
5560    </t>
5561    <t>
5562      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/52"/>:
5563      "Sort 1.3 Terminology"
5564    </t>
5565    <t>
5566      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/63"/>:
5567      "RFC2047 encoded words"
5568    </t>
5569    <t>
5570      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/74"/>:
5571      "Character Encodings in TEXT"
5572    </t>
5573    <t>
5574      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/77"/>:
5575      "Line Folding"
5576    </t>
5577    <t>
5578      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/83"/>:
5579      "OPTIONS * and proxies"
5580    </t>
5581    <t>
5582      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
5583      "Reason-Phrase BNF"
5584    </t>
5585    <t>
5586      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/111"/>:
5587      "Use of TEXT"
5588    </t>
5589    <t>
5590      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
5591      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
5592    </t>
5593    <t>
5594      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/134"/>:
5595      "RFC822 reference left in discussion of date formats"
5596    </t>
5597  </list>
5598</t>
5599<t>
5600  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
5601  <list style="symbols"> 
5602    <t>
5603      Rewrite definition of list rules, deprecate empty list elements.
5604    </t>
5605    <t>
5606      Add appendix containing collected and expanded ABNF.
5607    </t>
5608  </list>
5609</t>
5610<t>
5611  Other changes:
5612  <list style="symbols"> 
5613    <t>
5614      Rewrite introduction; add mostly new Architecture Section.
5615    </t>
5616    <t>
5617      Move definition of quality values from Part 3 into Part 1;
5618      make TE request header field grammar independent of accept-params (defined in Part 3).
5619    </t>
5620  </list>
5621</t>
5622</section>
5623
5624<section title="Since draft-ietf-httpbis-p1-messaging-06" anchor="changes.since.06">
5625<t>
5626  Closed issues:
5627  <list style="symbols"> 
5628    <t>
5629      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/161"/>:
5630      "base for numeric protocol elements"
5631    </t>
5632    <t>
5633      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/162"/>:
5634      "comment ABNF"
5635    </t>
5636  </list>
5637</t>
5638<t>
5639  Partly resolved issues:
5640  <list style="symbols"> 
5641    <t>
5642      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
5643      "205 Bodies" (took out language that implied that there might be
5644      methods for which a request body MUST NOT be included)
5645    </t>
5646    <t>
5647      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/163"/>:
5648      "editorial improvements around HTTP-date"
5649    </t>
5650  </list>
5651</t>
5652</section>
5653
5654<section title="Since draft-ietf-httpbis-p1-messaging-07" anchor="changes.since.07">
5655<t>
5656  Closed issues:
5657  <list style="symbols"> 
5658    <t>
5659      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/93"/>:
5660      "Repeating single-value headers"
5661    </t>
5662    <t>
5663      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/131"/>:
5664      "increase connection limit"
5665    </t>
5666    <t>
5667      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/157"/>:
5668      "IP addresses in URLs"
5669    </t>
5670    <t>
5671      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/172"/>:
5672      "take over HTTP Upgrade Token Registry"
5673    </t>
5674    <t>
5675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/173"/>:
5676      "CR and LF in chunk extension values"
5677    </t>
5678    <t>
5679      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/184"/>:
5680      "HTTP/0.9 support"
5681    </t>
5682    <t>
5683      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
5684      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
5685    </t>
5686    <t>
5687      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
5688      "move definitions of gzip/deflate/compress to part 1"
5689    </t>
5690    <t>
5691      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/194"/>:
5692      "disallow control characters in quoted-pair"
5693    </t>
5694  </list>
5695</t>
5696<t>
5697  Partly resolved issues:
5698  <list style="symbols"> 
5699    <t>
5700      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
5701      "update IANA requirements wrt Transfer-Coding values" (add the
5702      IANA Considerations subsection)
5703    </t>
5704  </list>
5705</t>
5706</section>
5707
5708<section title="Since draft-ietf-httpbis-p1-messaging-08" anchor="changes.since.08">
5709<t>
5710  Closed issues:
5711  <list style="symbols"> 
5712    <t>
5713      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/201"/>:
5714      "header parsing, treatment of leading and trailing OWS"
5715    </t>
5716  </list>
5717</t>
5718<t>
5719  Partly resolved issues:
5720  <list style="symbols"> 
5721    <t>
5722      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/60"/>:
5723      "Placement of 13.5.1 and 13.5.2"
5724    </t>
5725    <t>
5726      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
5727      "use of term "word" when talking about header structure"
5728    </t>
5729  </list>
5730</t>
5731</section>
5732
5733<section title="Since draft-ietf-httpbis-p1-messaging-09" anchor="changes.since.09">
5734<t>
5735  Closed issues:
5736  <list style="symbols"> 
5737    <t>
5738      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/73"/>:
5739      "Clarification of the term 'deflate'"
5740    </t>
5741    <t>
5742      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/83"/>:
5743      "OPTIONS * and proxies"
5744    </t>
5745    <t>
5746      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
5747      "MIME-Version not listed in P1, general header fields"
5748    </t>
5749    <t>
5750      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
5751      "IANA registry for content/transfer encodings"
5752    </t>
5753    <t>
5754      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/165"/>:
5755      "Case-sensitivity of HTTP-date"
5756    </t>
5757    <t>
5758      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
5759      "use of term "word" when talking about header structure"
5760    </t>
5761  </list>
5762</t>
5763<t>
5764  Partly resolved issues:
5765  <list style="symbols"> 
5766    <t>
5767      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
5768      "Term for the requested resource's URI"
5769    </t>
5770  </list>
5771</t>
5772</section>
5773
5774<section title="Since draft-ietf-httpbis-p1-messaging-10" anchor="changes.since.10">
5775<t>
5776  Closed issues:
5777  <list style="symbols">
5778    <t>
5779      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/28"/>:
5780      "Connection Closing"
5781    </t>
5782    <t>
5783      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
5784      "Delimiting messages with multipart/byteranges"
5785    </t>
5786    <t>
5787      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/95"/>:
5788      "Handling multiple Content-Length headers"
5789    </t>
5790    <t>
5791      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
5792      "Clarify entity / representation / variant terminology"
5793    </t>
5794    <t>
5795      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
5796      "consider removing the 'changes from 2068' sections"
5797    </t>
5798  </list>
5799</t>
5800<t>
5801  Partly resolved issues:
5802  <list style="symbols"> 
5803    <t>
5804      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/159"/>:
5805      "HTTP(s) URI scheme definitions"
5806    </t>
5807  </list>
5808</t>
5809</section>
5810
5811<section title="Since draft-ietf-httpbis-p1-messaging-11" anchor="changes.since.11">
5812<t>
5813  Closed issues:
5814  <list style="symbols">
5815    <t>
5816      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/193"/>:
5817      "Trailer requirements"
5818    </t>
5819    <t>
5820      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/204"/>:
5821      "Text about clock requirement for caches belongs in p6"
5822    </t>
5823    <t>
5824      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/221"/>:
5825      "effective request URI: handling of missing host in HTTP/1.0"
5826    </t>
5827    <t>
5828      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/248"/>:
5829      "confusing Date requirements for clients"
5830    </t>
5831  </list>
5832</t>
5833<t>
5834  Partly resolved issues:
5835  <list style="symbols"> 
5836    <t>
5837      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/95"/>:
5838      "Handling multiple Content-Length headers"
5839    </t>
5840  </list>
5841</t>
5842</section>
5843
5844<section title="Since draft-ietf-httpbis-p1-messaging-12" anchor="changes.since.12">
5845<t>
5846  Closed issues:
5847  <list style="symbols">
5848    <t>
5849      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/75"/>:
5850      "RFC2145 Normative"
5851    </t>
5852    <t>
5853      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/159"/>:
5854      "HTTP(s) URI scheme definitions" (tune the requirements on userinfo)
5855    </t>
5856    <t>
5857      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/210"/>:
5858      "define 'transparent' proxy"
5859    </t>
5860    <t>
5861      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
5862      "Header Classification"
5863    </t>
5864    <t>
5865      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/233"/>:
5866      "Is * usable as a request-uri for new methods?"
5867    </t>
5868    <t>
5869      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
5870      "Migrate Upgrade details from RFC2817"
5871    </t>
5872    <t>
5873      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
5874      "untangle ABNFs for header fields"
5875    </t>
5876    <t>
5877      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/279"/>:
5878      "update RFC 2109 reference"
5879    </t>
5880  </list>
5881</t>
5882</section>
5883
5884<section title="Since draft-ietf-httpbis-p1-messaging-13" anchor="changes.since.13">
5885<t>
5886  None yet.
5887</t>
5888</section>
5889
5890</section>
5891
5892</back>
5893</rfc>
Note: See TracBrowser for help on using the repository browser.