source: draft-ietf-httpbis/latest/p5-range.xml @ 962

Last change on this file since 962 was 962, checked in by julian.reschke@…, 9 years ago

add a paragraph break into intro of content-range

  • Property svn:eol-style set to native
File size: 63.0 KB
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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "July">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY entity-tags                "<xref target='Part4' x:rel='#entity.tags' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY weak-and-strong-validators "<xref target='Part4' x:rel='#weak.and.strong.validators' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24]>
25<?rfc toc="yes" ?>
26<?rfc symrefs="yes" ?>
27<?rfc sortrefs="yes" ?>
28<?rfc compact="yes"?>
29<?rfc subcompact="no" ?>
30<?rfc linkmailto="no" ?>
31<?rfc editing="no" ?>
32<?rfc comments="yes"?>
33<?rfc inline="yes"?>
34<?rfc rfcedstyle="yes"?>
35<?rfc-ext allow-markup-in-artwork="yes" ?>
36<?rfc-ext include-references-in-index="yes" ?>
37<rfc obsoletes="2616" category="std" x:maturity-level="draft"
38     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p5-range-&ID-VERSION;"     xmlns:x='http://purl.org/net/xml2rfc/ext'>
39<front>
40
41  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
42
43  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
44    <organization abbrev="Day Software">Day Software</organization>
45    <address>
46      <postal>
47        <street>23 Corporate Plaza DR, Suite 280</street>
48        <city>Newport Beach</city>
49        <region>CA</region>
50        <code>92660</code>
51        <country>USA</country>
52      </postal>
53      <phone>+1-949-706-5300</phone>
54      <facsimile>+1-949-706-5305</facsimile>
55      <email>fielding@gbiv.com</email>
56      <uri>http://roy.gbiv.com/</uri>
57    </address>
58  </author>
59
60  <author initials="J." surname="Gettys" fullname="Jim Gettys">
61    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
62    <address>
63      <postal>
64        <street>21 Oak Knoll Road</street>
65        <city>Carlisle</city>
66        <region>MA</region>
67        <code>01741</code>
68        <country>USA</country>
69      </postal>
70      <email>jg@freedesktop.org</email>
71      <uri>http://gettys.wordpress.com/</uri>
72    </address>
73  </author>
74 
75  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
76    <organization abbrev="HP">Hewlett-Packard Company</organization>
77    <address>
78      <postal>
79        <street>HP Labs, Large Scale Systems Group</street>
80        <street>1501 Page Mill Road, MS 1177</street>
81        <city>Palo Alto</city>
82        <region>CA</region>
83        <code>94304</code>
84        <country>USA</country>
85      </postal>
86      <email>JeffMogul@acm.org</email>
87    </address>
88  </author>
89
90  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
91    <organization abbrev="Microsoft">Microsoft Corporation</organization>
92    <address>
93      <postal>
94        <street>1 Microsoft Way</street>
95        <city>Redmond</city>
96        <region>WA</region>
97        <code>98052</code>
98        <country>USA</country>
99      </postal>
100      <email>henrikn@microsoft.com</email>
101    </address>
102  </author>
103
104  <author initials="L." surname="Masinter" fullname="Larry Masinter">
105    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
106    <address>
107      <postal>
108        <street>345 Park Ave</street>
109        <city>San Jose</city>
110        <region>CA</region>
111        <code>95110</code>
112        <country>USA</country>
113      </postal>
114      <email>LMM@acm.org</email>
115      <uri>http://larry.masinter.net/</uri>
116    </address>
117  </author>
118 
119  <author initials="P." surname="Leach" fullname="Paul J. Leach">
120    <organization abbrev="Microsoft">Microsoft Corporation</organization>
121    <address>
122      <postal>
123        <street>1 Microsoft Way</street>
124        <city>Redmond</city>
125        <region>WA</region>
126        <code>98052</code>
127      </postal>
128      <email>paulle@microsoft.com</email>
129    </address>
130  </author>
131   
132  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
133    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
134    <address>
135      <postal>
136        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
137        <street>The Stata Center, Building 32</street>
138        <street>32 Vassar Street</street>
139        <city>Cambridge</city>
140        <region>MA</region>
141        <code>02139</code>
142        <country>USA</country>
143      </postal>
144      <email>timbl@w3.org</email>
145      <uri>http://www.w3.org/People/Berners-Lee/</uri>
146    </address>
147  </author>
148
149  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
150    <organization abbrev="W3C">World Wide Web Consortium</organization>
151    <address>
152      <postal>
153        <street>W3C / ERCIM</street>
154        <street>2004, rte des Lucioles</street>
155        <city>Sophia-Antipolis</city>
156        <region>AM</region>
157        <code>06902</code>
158        <country>France</country>
159      </postal>
160      <email>ylafon@w3.org</email>
161      <uri>http://www.raubacapeu.net/people/yves/</uri>
162    </address>
163  </author>
164
165  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
166    <organization abbrev="greenbytes">greenbytes GmbH</organization>
167    <address>
168      <postal>
169        <street>Hafenweg 16</street>
170        <city>Muenster</city><region>NW</region><code>48155</code>
171        <country>Germany</country>
172      </postal>
173      <phone>+49 251 2807760</phone>
174      <facsimile>+49 251 2807761</facsimile>
175      <email>julian.reschke@greenbytes.de</email>
176      <uri>http://greenbytes.de/tech/webdav/</uri>
177    </address>
178  </author>
179
180  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
181  <workgroup>HTTPbis Working Group</workgroup>
182
183<abstract>
184<t>
185   The Hypertext Transfer Protocol (HTTP) is an application-level
186   protocol for distributed, collaborative, hypermedia information
187   systems. HTTP has been in use by the World Wide Web global information
188   initiative since 1990. This document is Part 5 of the seven-part specification
189   that defines the protocol referred to as "HTTP/1.1" and, taken together,
190   obsoletes RFC 2616.  Part 5 defines range-specific requests and
191   the rules for constructing and combining responses to those requests.
192</t>
193</abstract>
194
195<note title="Editorial Note (To be removed by RFC Editor)">
196  <t>
197    Discussion of this draft should take place on the HTTPBIS working group
198    mailing list (ietf-http-wg@w3.org). The current issues list is
199    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
200    and related documents (including fancy diffs) can be found at
201    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
202  </t>
203  <t>
204    The changes in this draft are summarized in <xref target="changes.since.10"/>.
205  </t>
206</note>
207</front>
208<middle>
209<section title="Introduction" anchor="introduction">
210<t>
211   HTTP clients often encounter interrupted data transfers as a result
212   of cancelled requests or dropped connections.  When a cache has stored
213   a partial representation, it is desirable to request the remainder
214   of that representation in a subsequent request rather than transfer
215   the entire representation.
216   There are also a number of Web applications that benefit from being
217   able to request only a subset of a larger representation, such as a
218   single page of a very large document or only part of an image to be
219   rendered by a device with limited local storage.
220</t>
221<t>
222   This document defines HTTP/1.1 range requests,
223   partial responses, and the multipart/byteranges media type.
224   The protocol for range requests is an &OPTIONAL; feature of HTTP,
225   designed so resources or recipients that do not implement this feature
226   can respond as if it is a normal GET request without impacting
227   interoperability.  Partial responses are indicated by a distinct status
228   code to not be mistaken for full responses by intermediate caches
229   that might not implement the feature.
230</t>
231<t>
232   Although the HTTP range request mechanism is designed to allow for
233   extensible range types, this specification only defines requests for
234   byte ranges.
235</t>
236
237<section title="Requirements" anchor="intro.requirements">
238<t>
239   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
240   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
241   document are to be interpreted as described in <xref target="RFC2119"/>.
242</t>
243<t>
244   An implementation is not compliant if it fails to satisfy one or more
245   of the "MUST" or "REQUIRED" level requirements for the protocols it
246   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
247   level and all the "SHOULD" level requirements for its protocols is said
248   to be "unconditionally compliant"; one that satisfies all the "MUST"
249   level requirements but not all the "SHOULD" level requirements for its
250   protocols is said to be "conditionally compliant".
251</t>
252</section>
253
254<section title="Syntax Notation" anchor="notation">
255  <x:anchor-alias value="ALPHA"/>
256  <x:anchor-alias value="CHAR"/>
257  <x:anchor-alias value="CR"/>
258  <x:anchor-alias value="DIGIT"/>
259  <x:anchor-alias value="LF"/>
260  <x:anchor-alias value="OCTET"/>
261  <x:anchor-alias value="SP"/>
262  <x:anchor-alias value="VCHAR"/>
263  <x:anchor-alias value="WSP"/>
264<t>
265  This specification uses the ABNF syntax defined in &notation; (which
266  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
267  <xref target="collected.abnf"/> shows the collected ABNF, with the list
268  rule expanded.
269</t>
270<t>
271  The following core rules are included by
272  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
273  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
274  DIGIT (decimal 0-9), DQUOTE (double quote),
275  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
276  OCTET (any 8-bit sequence of data), SP (space),
277  VCHAR (any visible USASCII character),
278  and WSP (whitespace).
279</t>
280
281<section title="Core Rules" anchor="core.rules">
282  <x:anchor-alias value="token"/>
283  <x:anchor-alias value="OWS"/>
284<t>
285  The core rules below are defined in &basic-rules;:
286</t>
287<figure><artwork type="abnf2616">
288  <x:ref>token</x:ref>      = &lt;token, defined in &basic-rules;&gt;
289  <x:ref>OWS</x:ref>        = &lt;OWS, defined in &basic-rules;&gt;
290</artwork></figure>
291</section>
292
293<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
294  <x:anchor-alias value="entity-tag"/>
295  <x:anchor-alias value="HTTP-date"/>
296<t>
297  The ABNF rules below are defined in other parts:
298</t>
299<figure><!--Part1--><artwork type="abnf2616">
300  <x:ref>HTTP-date</x:ref>  = &lt;HTTP-date, defined in &full-date;&gt;
301</artwork></figure>
302<figure><!--Part4--><artwork type="abnf2616">
303  <x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in &entity-tags;&gt;
304</artwork></figure>
305</section>
306
307</section>
308
309</section>
310
311
312<section title="Range Units" anchor="range.units">
313  <x:anchor-alias value="bytes-unit"/>
314  <x:anchor-alias value="other-range-unit"/>
315  <x:anchor-alias value="range-unit"/>
316<t>
317   HTTP/1.1 allows a client to request that only part (a range of) the
318   representation be included within the response. HTTP/1.1 uses range
319   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
320   header fields. A representation can be broken down into subranges according
321   to various structural units.
322</t>
323<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="range-unit"/><iref primary="true" item="Grammar" subitem="bytes-unit"/><iref primary="true" item="Grammar" subitem="other-range-unit"/>
324  <x:ref>range-unit</x:ref>       = <x:ref>bytes-unit</x:ref> / <x:ref>other-range-unit</x:ref>
325  <x:ref>bytes-unit</x:ref>       = "bytes"
326  <x:ref>other-range-unit</x:ref> = <x:ref>token</x:ref>
327</artwork></figure>
328<t>
329  HTTP/1.1 has been designed to allow implementations of applications
330  that do not depend on knowledge of ranges. The only range unit defined
331  by HTTP/1.1 is "bytes". Additional specifiers can be defined as described
332  in <xref target="range.specifier.registry"/>.
333</t>
334<t>
335  If a range unit is not understood in a request, a server &MUST; ignore
336  the whole Range header (<xref target="header.range" />).
337  If a range unit is not understood in a response, an intermediary
338  &SHOULD; pass the response to the client; a client &MUST; fail.
339</t>
340
341<section title="Range Specifier Registry" anchor="range.specifier.registry">
342<t>
343   The HTTP Ranger Specifier Registry defines the name space for the range
344   specifier names.
345</t>
346<t>
347   Registrations &MUST; include the following fields:
348   <list style="symbols">
349     <t>Name</t>
350     <t>Description</t>
351     <t>Pointer to specification text</t>
352   </list>
353</t>
354<t>
355  Values to be added to this name space are subject to IETF review
356  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
357</t>
358<t>
359   The registry itself is maintained at
360   <eref target="http://www.iana.org/assignments/http-range-specifiers"/>.
361</t>
362</section>
363
364</section>
365
366<section title="Status Code Definitions" anchor="status.code.definitions">
367<section title="206 Partial Content" anchor="status.206">
368  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
369  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
370<t>
371   The server has fulfilled the partial GET request for the resource.
372   The request &MUST; have included a Range header field (<xref target="header.range"/>)
373   indicating the desired range, and &MAY; have included an If-Range
374   header field (<xref target="header.if-range"/>) to make the request conditional.
375</t>
376<t>
377   The response &MUST; include the following header fields:
378  <list style="symbols">
379    <t>
380        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
381        the range included with this response, or a multipart/byteranges
382        Content-Type including Content-Range fields for each part. If a
383        Content-Length header field is present in the response, its
384        value &MUST; match the actual number of octets transmitted in the
385        message-body.
386    </t>
387    <t>
388        Date
389    </t>
390    <t>
391        Cache-Control, ETag, Expires, Content-Location, Last-Modified,
392        and/or Vary, if the header field would have been sent in a 200
393        response to the same request
394    </t>
395  </list>
396</t>
397<t>
398   If the 206 response is the result of an If-Range request, the response
399   &SHOULD-NOT; include other entity-headers. Otherwise, the response
400   &MUST; include all of the entity-headers that would have been returned
401   with a 200 (OK) response to the same request.
402</t>
403<t>
404   A cache &MUST-NOT; combine a 206 response with other previously cached
405   content if the ETag or Last-Modified headers do not match exactly,
406   see <xref target="combining.byte.ranges"/>.
407</t>
408<t>
409   A cache that does not support the Range and Content-Range headers
410   &MUST-NOT; cache 206 (Partial Content) responses. Furthermore,
411   if a response uses a range unit that is not understood by the cache,
412   then it &MUST-NOT; be cached either.
413</t>
414</section>
415
416<section title="416 Requested Range Not Satisfiable" anchor="status.416">
417  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
418  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
419<t>
420   A server &SHOULD; return a response with this status code if a request
421   included a Range request-header field (<xref target="header.range"/>), and none of
422   the ranges-specifier values in this field overlap the current extent
423   of the selected resource, and the request did not include an If-Range
424   request-header field (<xref target="header.if-range"/>). (For byte-ranges,
425   this means that the first-byte-pos of all of the byte-range-spec values were
426   greater than the current length of the selected resource.)
427</t>
428<t>
429   When this status code is returned for a byte-range request, the
430   response &SHOULD; include a Content-Range entity-header field
431   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
432   This response &MUST-NOT; use the multipart/byteranges content-type.
433</t>
434</section>
435</section>
436
437<section title="Combining Ranges" anchor="combining.byte.ranges">
438<t>
439   A response might transfer only a subrange of a representation, either because
440   the request included one or more Range specifications, or because
441   a connection closed prematurely.
442   After several such transfers, a cache might have received several
443   ranges of the same representation.
444</t>
445<t>
446   If a cache has a stored non-empty set of subranges for a representation, and
447   an incoming response transfers another subrange, the cache &MAY;
448   combine the new subrange with the existing set if both the following
449   conditions are met:
450  <list style="symbols">
451    <t>Both the incoming response and the cache entry have a cache
452        validator.</t>
453    <t>The two cache validators match using the strong comparison
454        function (see &weak-and-strong-validators;).</t>
455  </list>
456</t>
457<t>
458   If either requirement is not met, the cache &MUST; use only the most
459   recent partial response (based on the Date values transmitted with
460   every response, and using the incoming response if these values are
461   equal or missing), and &MUST; discard the other partial information.
462</t>
463</section>
464
465<section title="Header Field Definitions" anchor="header.fields">
466<t>
467   This section defines the syntax and semantics of HTTP/1.1 header fields
468   related to range requests and partial responses.
469</t>
470<t>
471   For entity-header fields, both sender and recipient refer to either the
472   client or the server, depending on who sends and who receives the message.
473</t>
474
475<section title="Accept-Ranges" anchor="header.accept-ranges">
476  <iref primary="true" item="Accept-Ranges header" x:for-anchor=""/>
477  <iref primary="true" item="Headers" subitem="Accept-Ranges" x:for-anchor=""/>
478  <x:anchor-alias value="Accept-Ranges"/>
479  <x:anchor-alias value="Accept-Ranges-v"/>
480  <x:anchor-alias value="acceptable-ranges"/>
481<t>
482   The "Accept-Ranges" response-header field allows a resource to indicate
483   its acceptance of range requests.
484</t>
485<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="Accept-Ranges-v"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/>
486  <x:ref>Accept-Ranges</x:ref>     = "Accept-Ranges" ":" <x:ref>OWS</x:ref> <x:ref>Accept-Ranges-v</x:ref>
487  <x:ref>Accept-Ranges-v</x:ref>   = <x:ref>acceptable-ranges</x:ref>
488  <x:ref>acceptable-ranges</x:ref> = 1#<x:ref>range-unit</x:ref> / "none"
489</artwork></figure>
490<t>
491      Origin servers that accept byte-range requests &MAY; send
492</t>
493<figure><artwork type="example">
494  Accept-Ranges: bytes
495</artwork></figure>
496<t>
497      but are not required to do so. Clients &MAY; generate range
498      requests without having received this header for the resource
499      involved. Range units are defined in <xref target="range.units"/>.
500</t>
501<t>
502      Servers that do not accept any kind of range request for a
503      resource &MAY; send
504</t>
505<figure><artwork type="example">
506  Accept-Ranges: none
507</artwork></figure>
508<t>
509      to advise the client not to attempt a range request.
510</t>
511</section>
512
513<section title="Content-Range" anchor="header.content-range">
514  <iref primary="true" item="Content-Range header" x:for-anchor=""/>
515  <iref primary="true" item="Headers" subitem="Content-Range" x:for-anchor=""/>
516  <x:anchor-alias value="byte-content-range-spec"/>
517  <x:anchor-alias value="byte-range-resp-spec"/>
518  <x:anchor-alias value="Content-Range"/>
519  <x:anchor-alias value="Content-Range-v"/>
520  <x:anchor-alias value="content-range-spec"/>
521  <x:anchor-alias value="instance-length"/>
522  <x:anchor-alias value="other-content-range-spec"/>
523  <x:anchor-alias value="other-range-resp-spec"/>
524<t>
525   The "Content-Range" entity-header field is sent with a partial representation to
526   specify where in the full representation the partial body should be
527   applied.
528</t>
529<t>   
530   Range units are defined in <xref target="range.units"/>.
531</t>
532<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Range"/><iref primary="true" item="Grammar" subitem="Content-Range-v"/><iref primary="true" item="Grammar" subitem="content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-range-resp-spec"/><iref primary="true" item="Grammar" subitem="instance-length"/>
533  <x:ref>Content-Range</x:ref> = "Content-Range" ":" <x:ref>OWS</x:ref> <x:ref>Content-Range-v</x:ref>
534  <x:ref>Content-Range-v</x:ref> = <x:ref>content-range-spec</x:ref>
535 
536  <x:ref>content-range-spec</x:ref>      = <x:ref>byte-content-range-spec</x:ref>
537                          / <x:ref>other-content-range-spec</x:ref>
538  <x:ref>byte-content-range-spec</x:ref> = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
539                            <x:ref>byte-range-resp-spec</x:ref> "/"
540                            ( <x:ref>instance-length</x:ref> / "*" )
541 
542  <x:ref>byte-range-resp-spec</x:ref>    = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
543                          / "*"
544                         
545  <x:ref>instance-length</x:ref>         = 1*<x:ref>DIGIT</x:ref>
546 
547  <x:ref>other-content-range-spec</x:ref> = <x:ref>other-range-unit</x:ref> <x:ref>SP</x:ref>
548                             <x:ref>other-range-resp-spec</x:ref>
549  <x:ref>other-range-resp-spec</x:ref>    = *<x:ref>CHAR</x:ref>
550</artwork></figure>
551<t>
552   The header &SHOULD; indicate the total length of the full representation,
553   unless this length is unknown or difficult to determine. The asterisk
554   "*" character means that the instance-length is unknown at the time
555   when the response was generated.
556</t>
557<t>
558   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
559   &MUST; only specify one range, and &MUST; contain
560   absolute byte positions for both the first and last byte of the
561   range.
562</t>
563<t>
564   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
565   value is less than its first-byte-pos value, or whose
566   instance-length value is less than or equal to its last-byte-pos
567   value, is invalid. The recipient of an invalid byte-content-range-spec
568   &MUST; ignore it and any content transferred along with it.
569</t>
570<t>
571   In the case of a byte range request:
572   A server sending a response with status code 416 (Requested range not
573   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
574   of "*". The instance-length specifies the current length of
575   the selected resource. A response with status code 206 (Partial
576   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
577</t>
578<t>
579   Examples of byte-content-range-spec values, assuming that the representation
580   contains a total of 1234 bytes:
581   <list style="symbols">
582      <t>
583        The first 500 bytes:
584<figure><artwork type="example" x:indent-with="   ">
585  bytes 0-499/1234
586</artwork></figure>
587      </t>   
588      <t>
589        The second 500 bytes:
590<figure><artwork type="example" x:indent-with="   ">
591  bytes 500-999/1234
592</artwork></figure>
593      </t>   
594      <t>
595        All except for the first 500 bytes:
596<figure><artwork type="example" x:indent-with="   ">
597  bytes 500-1233/1234
598</artwork></figure>
599      </t>   
600      <t>
601        The last 500 bytes:
602<figure><artwork type="example" x:indent-with="   ">
603  bytes 734-1233/1234
604</artwork></figure>
605      </t>   
606   </list>
607</t>
608<t>
609   When an HTTP message includes the content of a single range (for
610   example, a response to a request for a single range, or to a request
611   for a set of ranges that overlap without any holes), this content is
612   transmitted with a Content-Range header, and a Content-Length header
613   showing the number of bytes actually transferred. For example,
614</t>
615<figure><artwork type="example">
616  HTTP/1.1 206 Partial Content
617  Date: Wed, 15 Nov 1995 06:25:24 GMT
618  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
619  Content-Range: bytes 21010-47021/47022
620  Content-Length: 26012
621  Content-Type: image/gif
622</artwork></figure>
623<t>
624   When an HTTP message includes the content of multiple ranges (for
625   example, a response to a request for multiple non-overlapping
626   ranges), these are transmitted as a multipart message. The multipart
627   media type used for this purpose is "multipart/byteranges" as defined
628   in <xref target="internet.media.type.multipart.byteranges"/>.
629</t>
630<t>
631   A response to a request for a single range &MUST-NOT; be sent using the
632   multipart/byteranges media type.  A response to a request for
633   multiple ranges, whose result is a single range, &MAY; be sent as a
634   multipart/byteranges media type with one part. A client that cannot
635   decode a multipart/byteranges message &MUST-NOT; ask for multiple
636   ranges in a single request.
637</t>
638<t>
639   When a client requests multiple ranges in one request, the
640   server &SHOULD; return them in the order that they appeared in the
641   request.
642</t>
643<t>
644   If the server ignores a byte-range-spec because it is syntactically
645   invalid, the server &SHOULD; treat the request as if the invalid Range
646   header field did not exist. (Normally, this means return a 200
647   response containing the full representation).
648</t>
649<t>
650   If the server receives a request (other than one including an If-Range
651   request-header field) with an unsatisfiable Range request-header
652   field (that is, all of whose byte-range-spec values have a
653   first-byte-pos value greater than the current length of the selected
654   resource), it &SHOULD; return a response code of 416 (Requested range
655   not satisfiable) (<xref target="status.416"/>).
656</t>
657<x:note>
658  <t>
659    <x:h>Note:</x:h> Clients cannot depend on servers to send a 416 (Requested
660    range not satisfiable) response instead of a 200 (OK) response for
661    an unsatisfiable Range request-header, since not all servers
662    implement this request-header.
663  </t>
664</x:note>
665</section>
666
667<section title="If-Range" anchor="header.if-range">
668  <iref primary="true" item="If-Range header" x:for-anchor=""/>
669  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
670  <x:anchor-alias value="If-Range"/>
671  <x:anchor-alias value="If-Range-v"/>
672<t>
673   If a client has a partial copy of a representation in its cache, and wishes
674   to have an up-to-date copy of the entire representation in its cache, it
675   could use the Range request-header with a conditional GET (using
676   either or both of If-Unmodified-Since and If-Match.) However, if the
677   condition fails because the representation has been modified, the client
678   would then have to make a second request to obtain the entire current
679   representation.
680</t>
681<t>
682   The "If-Range" request-header field allows a client to "short-circuit" the second
683   request. Informally, its meaning is "if the representation is unchanged, send
684   me the part(s) that I am missing; otherwise, send me the entire new
685   representation".
686</t>
687<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/><iref primary="true" item="Grammar" subitem="If-Range-v"/>
688  <x:ref>If-Range</x:ref>   = "If-Range" ":" <x:ref>OWS</x:ref> <x:ref>If-Range-v</x:ref>
689  <x:ref>If-Range-v</x:ref> = <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref>
690</artwork></figure>
691<t>
692   If the client has no entity-tag for a representation, but does have a Last-Modified
693   date, it &MAY; use that date in an If-Range header. (The
694   server can distinguish between a valid HTTP-date and any form of
695   entity-tag by examining no more than two characters.) The If-Range
696   header &SHOULD; only be used together with a Range header, and &MUST; be
697   ignored if the request does not include a Range header, or if the
698   server does not support the sub-range operation.
699</t>
700<t>
701   If the entity-tag given in the If-Range header matches the current
702   cache validator for the representation, then the server &SHOULD; provide the
703   specified sub-range of the representation using a 206 (Partial Content)
704   response. If the cache validator does not match, then the server &SHOULD;
705   return the entire representation using a 200 (OK) response.
706</t>
707</section>
708
709<section title="Range" anchor="header.range">
710  <iref primary="true" item="Range header" x:for-anchor=""/>
711  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
712
713<section title="Byte Ranges" anchor="byte.ranges">
714<t>
715   Since all HTTP representations are transferred as sequences
716   of bytes, the concept of a byte range is meaningful for any HTTP
717   representation. (However, not all clients and servers need to support byte-range
718   operations.)
719</t>
720<t>
721   Byte range specifications in HTTP apply to the sequence of bytes in
722   the representation body (not necessarily the same as the message-body).
723</t>
724<t anchor="rule.ranges-specifier">
725  <x:anchor-alias value="byte-range-set"/>
726  <x:anchor-alias value="byte-range-spec"/>
727  <x:anchor-alias value="byte-ranges-specifier"/>
728  <x:anchor-alias value="first-byte-pos"/>
729  <x:anchor-alias value="last-byte-pos"/>
730  <x:anchor-alias value="ranges-specifier"/>
731  <x:anchor-alias value="suffix-byte-range-spec"/>
732  <x:anchor-alias value="suffix-length"/>
733
734   A byte range operation &MAY; specify a single range of bytes, or a set
735   of ranges within a single representation.
736</t>
737<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="ranges-specifier"/><iref primary="true" item="Grammar" subitem="byte-ranges-specifier"/><iref primary="true" item="Grammar" subitem="byte-range-set"/><iref primary="true" item="Grammar" subitem="byte-range-spec"/><iref primary="true" item="Grammar" subitem="first-byte-pos"/><iref primary="true" item="Grammar" subitem="last-byte-pos"/>
738  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
739  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
740  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [ <x:ref>last-byte-pos</x:ref> ]
741  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
742  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
743</artwork></figure>
744<t>
745   The first-byte-pos value in a byte-range-spec gives the byte-offset
746   of the first byte in a range. The last-byte-pos value gives the
747   byte-offset of the last byte in the range; that is, the byte
748   positions specified are inclusive. Byte offsets start at zero.
749</t>
750<t>
751   If the last-byte-pos value is present, it &MUST; be greater than or
752   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
753   is syntactically invalid. The recipient of a byte-range-set
754   that includes one or more syntactically invalid byte-range-spec
755   values &MUST; ignore the header field that includes that byte-range-set.
756</t>
757<t>
758   If the last-byte-pos value is absent, or if the value is greater than
759   or equal to the current length of the representation body, last-byte-pos is
760   taken to be equal to one less than the current length of the representation
761   in bytes.
762</t>
763<t>
764   By its choice of last-byte-pos, a client can limit the number of
765   bytes retrieved without knowing the size of the representation.
766</t>
767<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
768  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
769  <x:ref>suffix-length</x:ref> = 1*<x:ref>DIGIT</x:ref>
770</artwork></figure>
771<t>
772   A suffix-byte-range-spec is used to specify the suffix of the
773   representation body, of a length given by the suffix-length value. (That is,
774   this form specifies the last N bytes of a representation.) If the
775   representation is shorter than the specified suffix-length, the entire
776   representation is used.
777</t>
778<t>
779   If a syntactically valid byte-range-set includes at least one byte-range-spec
780   whose first-byte-pos is less than the current length of
781   the representation, or at least one suffix-byte-range-spec with a non-zero
782   suffix-length, then the byte-range-set is satisfiable.
783   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
784   is unsatisfiable, the server &SHOULD; return a response with a
785   416 (Requested range not satisfiable) status code. Otherwise, the server
786   &SHOULD; return a response with a 206 (Partial Content) status code
787   containing the satisfiable ranges of the representation.
788</t>
789<t>
790   Examples of byte-ranges-specifier values (assuming a representation of
791   length 10000):
792  <list style="symbols">
793     <t>The first 500 bytes (byte offsets 0-499, inclusive):
794<figure><artwork type="example" x:indent-with="   ">
795  bytes=0-499
796</artwork></figure>
797    </t>
798     <t>The second 500 bytes (byte offsets 500-999, inclusive):
799<figure><artwork type="example" x:indent-with="   ">
800  bytes=500-999
801</artwork></figure>
802    </t>
803     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
804<figure><artwork type="example" x:indent-with="   ">
805  bytes=-500
806</artwork></figure>
807    Or:
808<figure><artwork type="example" x:indent-with="   ">
809  bytes=9500-
810</artwork></figure>
811    </t>
812     <t>The first and last bytes only (bytes 0 and 9999):
813<figure><artwork type="example" x:indent-with="   ">
814  bytes=0-0,-1
815</artwork></figure>
816     </t>
817     <t>Several legal but not canonical specifications of the second 500
818        bytes (byte offsets 500-999, inclusive):
819<figure><artwork type="example" x:indent-with="   ">
820  bytes=500-600,601-999
821  bytes=500-700,601-999
822</artwork></figure>
823     </t>
824  </list>
825</t>
826</section>
827
828<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
829  <x:anchor-alias value="Range"/>
830  <x:anchor-alias value="Range-v"/>
831  <x:anchor-alias value="other-ranges-specifier"/>
832  <x:anchor-alias value="other-range-set"/>
833<t>
834   The "Range" request-header field defines the GET method (conditional or
835   not) to request one or more sub-ranges of the response representation body, instead
836   of the entire representation body.
837</t>
838<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/>
839  <x:ref>Range</x:ref>   = "Range" ":" <x:ref>OWS</x:ref> <x:ref>Range-v</x:ref>
840  <x:ref>Range-v</x:ref> = <x:ref>byte-ranges-specifier</x:ref>
841          / <x:ref>other-ranges-specifier</x:ref>
842  <x:ref>other-ranges-specifier</x:ref> = <x:ref>other-range-unit</x:ref> "=" <x:ref>other-range-set</x:ref>
843  <x:ref>other-range-set</x:ref> = 1*<x:ref>CHAR</x:ref>
844</artwork></figure>
845<t>
846   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
847   servers and intermediate caches ought to support byte ranges when
848   possible, since Range supports efficient recovery from partially
849   failed transfers, and supports efficient partial retrieval of large
850   representations.
851</t>
852<t>
853   If the server supports the Range header and the specified range or
854   ranges are appropriate for the representation:
855  <list style="symbols">
856     <t>The presence of a Range header in an unconditional GET modifies
857        what is returned if the GET is otherwise successful. In other
858        words, the response carries a status code of 206 (Partial
859        Content) instead of 200 (OK).</t>
860
861     <t>The presence of a Range header in a conditional GET (a request
862        using one or both of If-Modified-Since and If-None-Match, or
863        one or both of If-Unmodified-Since and If-Match) modifies what
864        is returned if the GET is otherwise successful and the
865        condition is true. It does not affect the 304 (Not Modified)
866        response returned if the conditional is false.</t>
867  </list>
868</t>
869<t>
870   In some cases, it might be more appropriate to use the If-Range
871   header (see <xref target="header.if-range"/>) in addition to the Range header.
872</t>
873<t>
874   If a proxy that supports ranges receives a Range request, forwards
875   the request to an inbound server, and receives an entire representation in
876   reply, it &SHOULD; only return the requested range to its client. It
877   &SHOULD; store the entire received response in its cache if that is
878   consistent with its cache allocation policies.
879</t>
880</section>
881</section>
882</section>
883
884<section title="IANA Considerations" anchor="IANA.considerations">
885
886<section title="Status Code Registration" anchor="status.code.registration">
887<t>
888   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
889   should be updated with the registrations below:
890</t>
891<?BEGININC p5-range.iana-status-codes ?>
892<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
893<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
894   <ttcol>Value</ttcol>
895   <ttcol>Description</ttcol>
896   <ttcol>Reference</ttcol>
897   <c>206</c>
898   <c>Partial Content</c>
899   <c>
900      <xref target="status.206"/>
901   </c>
902   <c>416</c>
903   <c>Requested Range Not Satisfiable</c>
904   <c>
905      <xref target="status.416"/>
906   </c>
907</texttable>
908<!--(END)-->
909<?ENDINC p5-range.iana-status-codes ?>
910</section>
911
912<section title="Header Field Registration" anchor="header.field.registration">
913<t>
914   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
915   with the permanent registrations below (see <xref target="RFC3864"/>):
916</t>
917<?BEGININC p5-range.iana-headers ?>
918<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
919<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
920   <ttcol>Header Field Name</ttcol>
921   <ttcol>Protocol</ttcol>
922   <ttcol>Status</ttcol>
923   <ttcol>Reference</ttcol>
924
925   <c>Accept-Ranges</c>
926   <c>http</c>
927   <c>standard</c>
928   <c>
929      <xref target="header.accept-ranges"/>
930   </c>
931   <c>Content-Range</c>
932   <c>http</c>
933   <c>standard</c>
934   <c>
935      <xref target="header.content-range"/>
936   </c>
937   <c>If-Range</c>
938   <c>http</c>
939   <c>standard</c>
940   <c>
941      <xref target="header.if-range"/>
942   </c>
943   <c>Range</c>
944   <c>http</c>
945   <c>standard</c>
946   <c>
947      <xref target="header.range"/>
948   </c>
949</texttable>
950<!--(END)-->
951<?ENDINC p5-range.iana-headers ?>
952<t>
953   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
954</t>
955</section>
956
957<section title="Range Specifier Registration" anchor="range.specifier.registration">
958<t>
959  The registration procedure for HTTP Range Specifiers is defined by
960  <xref target="range.specifier.registry"/> of this document.
961</t>
962<t>
963   The HTTP Range Specifier Registry should be created at <eref target="http://www.iana.org/assignments/http-range-specifiers"/>
964   and be populated with the registrations below:
965</t>
966<texttable align="left" suppress-title="true" anchor="iana.range.specifiers.table">
967   <ttcol>Range Specifier Name</ttcol>
968   <ttcol>Description</ttcol>
969   <ttcol>Reference</ttcol>
970
971   <c>bytes</c>
972   <c>a range of octets</c>
973   <c>(this specification)</c>
974</texttable>
975<t>
976   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
977</t>
978</section>
979</section>
980
981<section title="Security Considerations" anchor="security.considerations">
982<t>
983   No additional security considerations have been identified beyond
984   those applicable to HTTP in general &messaging;.
985</t>
986</section>
987
988<section title="Acknowledgments" anchor="ack">
989<t>
990   Most of the specification of ranges is based on work originally done
991   by Ari Luotonen and John Franks, with additional input from Steve
992   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
993   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
994   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
995</t>
996</section>
997</middle>
998<back>
999
1000<references title="Normative References">
1001
1002<reference anchor="Part1">
1003  <front>
1004    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1005    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1006      <organization abbrev="Day Software">Day Software</organization>
1007      <address><email>fielding@gbiv.com</email></address>
1008    </author>
1009    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1010      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1011      <address><email>jg@freedesktop.org</email></address>
1012    </author>
1013    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1014      <organization abbrev="HP">Hewlett-Packard Company</organization>
1015      <address><email>JeffMogul@acm.org</email></address>
1016    </author>
1017    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1018      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1019      <address><email>henrikn@microsoft.com</email></address>
1020    </author>
1021    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1022      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1023      <address><email>LMM@acm.org</email></address>
1024    </author>
1025    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1026      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1027      <address><email>paulle@microsoft.com</email></address>
1028    </author>
1029    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1030      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1031      <address><email>timbl@w3.org</email></address>
1032    </author>
1033    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1034      <organization abbrev="W3C">World Wide Web Consortium</organization>
1035      <address><email>ylafon@w3.org</email></address>
1036    </author>
1037    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1038      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1039      <address><email>julian.reschke@greenbytes.de</email></address>
1040    </author>
1041    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1042  </front>
1043  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1044  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1045</reference>
1046
1047<reference anchor="Part4">
1048  <front>
1049    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1050    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1051      <organization abbrev="Day Software">Day Software</organization>
1052      <address><email>fielding@gbiv.com</email></address>
1053    </author>
1054    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1055      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1056      <address><email>jg@freedesktop.org</email></address>
1057    </author>
1058    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1059      <organization abbrev="HP">Hewlett-Packard Company</organization>
1060      <address><email>JeffMogul@acm.org</email></address>
1061    </author>
1062    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1063      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1064      <address><email>henrikn@microsoft.com</email></address>
1065    </author>
1066    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1067      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1068      <address><email>LMM@acm.org</email></address>
1069    </author>
1070    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1071      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1072      <address><email>paulle@microsoft.com</email></address>
1073    </author>
1074    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1075      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1076      <address><email>timbl@w3.org</email></address>
1077    </author>
1078    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1079      <organization abbrev="W3C">World Wide Web Consortium</organization>
1080      <address><email>ylafon@w3.org</email></address>
1081    </author>
1082    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1083      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1084      <address><email>julian.reschke@greenbytes.de</email></address>
1085    </author>
1086    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1087  </front>
1088  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1089  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1090</reference>
1091
1092<reference anchor="RFC2046">
1093  <front>
1094    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1095    <author initials="N." surname="Freed" fullname="Ned Freed">
1096      <organization>Innosoft International, Inc.</organization>
1097      <address><email>ned@innosoft.com</email></address>
1098    </author>
1099    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1100      <organization>First Virtual Holdings</organization>
1101      <address><email>nsb@nsb.fv.com</email></address>
1102    </author>
1103    <date month="November" year="1996"/>
1104  </front>
1105  <seriesInfo name="RFC" value="2046"/>
1106</reference>
1107
1108<reference anchor="RFC2119">
1109  <front>
1110    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1111    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1112      <organization>Harvard University</organization>
1113      <address><email>sob@harvard.edu</email></address>
1114    </author>
1115    <date month="March" year="1997"/>
1116  </front>
1117  <seriesInfo name="BCP" value="14"/>
1118  <seriesInfo name="RFC" value="2119"/>
1119</reference>
1120
1121<reference anchor="RFC5234">
1122  <front>
1123    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1124    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1125      <organization>Brandenburg InternetWorking</organization>
1126      <address>
1127        <email>dcrocker@bbiw.net</email>
1128      </address> 
1129    </author>
1130    <author initials="P." surname="Overell" fullname="Paul Overell">
1131      <organization>THUS plc.</organization>
1132      <address>
1133        <email>paul.overell@thus.net</email>
1134      </address>
1135    </author>
1136    <date month="January" year="2008"/>
1137  </front>
1138  <seriesInfo name="STD" value="68"/>
1139  <seriesInfo name="RFC" value="5234"/>
1140</reference>
1141
1142</references>
1143
1144<references title="Informative References">
1145
1146<reference anchor="RFC2616">
1147  <front>
1148    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1149    <author initials="R." surname="Fielding" fullname="R. Fielding">
1150      <organization>University of California, Irvine</organization>
1151      <address><email>fielding@ics.uci.edu</email></address>
1152    </author>
1153    <author initials="J." surname="Gettys" fullname="J. Gettys">
1154      <organization>W3C</organization>
1155      <address><email>jg@w3.org</email></address>
1156    </author>
1157    <author initials="J." surname="Mogul" fullname="J. Mogul">
1158      <organization>Compaq Computer Corporation</organization>
1159      <address><email>mogul@wrl.dec.com</email></address>
1160    </author>
1161    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1162      <organization>MIT Laboratory for Computer Science</organization>
1163      <address><email>frystyk@w3.org</email></address>
1164    </author>
1165    <author initials="L." surname="Masinter" fullname="L. Masinter">
1166      <organization>Xerox Corporation</organization>
1167      <address><email>masinter@parc.xerox.com</email></address>
1168    </author>
1169    <author initials="P." surname="Leach" fullname="P. Leach">
1170      <organization>Microsoft Corporation</organization>
1171      <address><email>paulle@microsoft.com</email></address>
1172    </author>
1173    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1174      <organization>W3C</organization>
1175      <address><email>timbl@w3.org</email></address>
1176    </author>
1177    <date month="June" year="1999"/>
1178  </front>
1179  <seriesInfo name="RFC" value="2616"/>
1180</reference>
1181
1182<reference anchor='RFC3864'>
1183  <front>
1184    <title>Registration Procedures for Message Header Fields</title>
1185    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1186      <organization>Nine by Nine</organization>
1187      <address><email>GK-IETF@ninebynine.org</email></address>
1188    </author>
1189    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1190      <organization>BEA Systems</organization>
1191      <address><email>mnot@pobox.com</email></address>
1192    </author>
1193    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1194      <organization>HP Labs</organization>
1195      <address><email>JeffMogul@acm.org</email></address>
1196    </author>
1197    <date year='2004' month='September' />
1198  </front>
1199  <seriesInfo name='BCP' value='90' />
1200  <seriesInfo name='RFC' value='3864' />
1201</reference>
1202
1203<reference anchor="RFC4288">
1204  <front>
1205    <title>Media Type Specifications and Registration Procedures</title>
1206    <author initials="N." surname="Freed" fullname="N. Freed">
1207      <organization>Sun Microsystems</organization>
1208      <address>
1209        <email>ned.freed@mrochek.com</email>
1210      </address>
1211    </author>
1212    <author initials="J." surname="Klensin" fullname="J. Klensin">
1213      <address>
1214        <email>klensin+ietf@jck.com</email>
1215      </address>
1216    </author>
1217    <date year="2005" month="December"/>
1218  </front>
1219  <seriesInfo name="BCP" value="13"/>
1220  <seriesInfo name="RFC" value="4288"/>
1221</reference>
1222
1223<reference anchor='RFC5226'>
1224  <front>
1225    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
1226    <author initials='T.' surname='Narten' fullname='T. Narten'>
1227      <organization>IBM</organization>
1228      <address><email>narten@us.ibm.com</email></address>
1229    </author>
1230    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
1231      <organization>Google</organization>
1232      <address><email>Harald@Alvestrand.no</email></address>
1233    </author>
1234    <date year='2008' month='May' />
1235  </front>
1236  <seriesInfo name='BCP' value='26' />
1237  <seriesInfo name='RFC' value='5226' />
1238</reference>
1239
1240</references>
1241
1242<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1243<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1244<iref item="multipart/byteranges Media Type" primary="true"/>
1245<t>
1246   When an HTTP 206 (Partial Content) response message includes the
1247   content of multiple ranges (a response to a request for multiple
1248   non-overlapping ranges), these are transmitted as a multipart
1249   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1250   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1251</t>
1252<x:note>
1253  <t>
1254    <x:h>Note:</x:h> Despite the name "multipart/byteranges" is not limited to the byte ranges only.
1255  </t>
1256</x:note>
1257<t>
1258   The multipart/byteranges media type includes one or more parts, each
1259   with its own Content-Type and Content-Range fields. The required
1260   boundary parameter specifies the boundary string used to separate
1261   each body-part.
1262</t>
1263<t>
1264  <list style="hanging" x:indent="12em">
1265    <t hangText="Type name:">
1266      multipart
1267    </t>
1268    <t hangText="Subtype name:">
1269      byteranges
1270    </t>
1271    <t hangText="Required parameters:">
1272      boundary
1273    </t>
1274    <t hangText="Optional parameters:">
1275      none
1276    </t>
1277    <t hangText="Encoding considerations:">
1278      only "7bit", "8bit", or "binary" are permitted
1279    </t>
1280    <t hangText="Security considerations:">
1281      none
1282    </t>
1283    <t hangText="Interoperability considerations:">
1284      none
1285    </t>
1286    <t hangText="Published specification:">
1287      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1288    </t>
1289    <t hangText="Applications that use this media type:">
1290    </t>
1291    <t hangText="Additional information:">
1292      <list style="hanging">
1293        <t hangText="Magic number(s):">none</t>
1294        <t hangText="File extension(s):">none</t>
1295        <t hangText="Macintosh file type code(s):">none</t>
1296      </list>
1297    </t>
1298    <t hangText="Person and email address to contact for further information:">
1299      See Authors Section.
1300    </t>
1301    <t hangText="Intended usage:">
1302      COMMON
1303    </t>
1304    <t hangText="Restrictions on usage:">
1305      none
1306    </t>
1307    <t hangText="Author/Change controller:">
1308      IESG
1309    </t>
1310  </list>
1311</t>
1312<figure><preamble>
1313   For example:
1314</preamble><artwork type="example">
1315  HTTP/1.1 206 Partial Content
1316  Date: Wed, 15 Nov 1995 06:25:24 GMT
1317  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1318  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1319 
1320  --THIS_STRING_SEPARATES
1321  Content-type: application/pdf
1322  Content-range: bytes 500-999/8000
1323 
1324  ...the first range...
1325  --THIS_STRING_SEPARATES
1326  Content-type: application/pdf
1327  Content-range: bytes 7000-7999/8000
1328 
1329  ...the second range
1330  --THIS_STRING_SEPARATES--
1331</artwork></figure>
1332<figure><preamble>
1333   Other example:
1334</preamble>
1335<artwork type="example">
1336  HTTP/1.1 206 Partial Content
1337  Date: Tue, 14 Nov 1995 06:25:24 GMT
1338  Last-Modified: Tue, 14 July 04:58:08 GMT
1339  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1340 
1341  --THIS_STRING_SEPARATES
1342  Content-type: video/example
1343  Content-range: exampleunit 1.2-4.3/25
1344 
1345  ...the first range...
1346  --THIS_STRING_SEPARATES
1347  Content-type: video/example
1348  Content-range: exampleunit 11.2-14.3/25
1349 
1350  ...the second range
1351  --THIS_STRING_SEPARATES--
1352</artwork>
1353</figure>
1354<t>
1355      Notes:
1356  <list style="numbers">
1357      <t>Additional CRLFs &MAY; precede the first boundary string in the body.</t>
1358
1359      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1360         quoted, some existing implementations handle a quoted boundary
1361         string incorrectly.</t>
1362
1363      <t>A number of browsers and servers were coded to an early draft
1364         of the byteranges specification to use a media type of
1365         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1366         compatible with the version documented in HTTP/1.1.</t>
1367  </list>
1368</t>
1369</section>
1370
1371<section title="Compatibility with Previous Versions" anchor="compatibility">
1372<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1373<t>
1374  Clarify that it is not ok to use a weak cache validator in a 206 response.
1375  (<xref target="status.206"/>)
1376</t>
1377<t>
1378  Clarify that multipart/byteranges can consist of a single part.
1379  (<xref target="internet.media.type.multipart.byteranges"/>)
1380</t>
1381
1382</section>
1383
1384</section>
1385
1386<?BEGININC p5-range.abnf-appendix ?>
1387<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
1388<figure>
1389<artwork type="abnf" name="p5-range.parsed-abnf">
1390<x:ref>Accept-Ranges</x:ref> = "Accept-Ranges:" OWS Accept-Ranges-v
1391<x:ref>Accept-Ranges-v</x:ref> = acceptable-ranges
1392
1393<x:ref>Content-Range</x:ref> = "Content-Range:" OWS Content-Range-v
1394<x:ref>Content-Range-v</x:ref> = content-range-spec
1395
1396<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
1397
1398<x:ref>If-Range</x:ref> = "If-Range:" OWS If-Range-v
1399<x:ref>If-Range-v</x:ref> = entity-tag / HTTP-date
1400
1401<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
1402
1403<x:ref>Range</x:ref> = "Range:" OWS Range-v
1404<x:ref>Range-v</x:ref> = byte-ranges-specifier / other-ranges-specifier
1405
1406<x:ref>acceptable-ranges</x:ref> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
1407 range-unit ] ) ) / "none"
1408
1409<x:ref>byte-content-range-spec</x:ref> = bytes-unit SP byte-range-resp-spec "/" (
1410 instance-length / "*" )
1411<x:ref>byte-range-resp-spec</x:ref> = ( first-byte-pos "-" last-byte-pos ) / "*"
1412<x:ref>byte-range-set</x:ref> = ( *( "," OWS ) byte-range-spec ) / (
1413 suffix-byte-range-spec *( OWS "," [ ( OWS byte-range-spec ) /
1414 suffix-byte-range-spec ] ) )
1415<x:ref>byte-range-spec</x:ref> = first-byte-pos "-" [ last-byte-pos ]
1416<x:ref>byte-ranges-specifier</x:ref> = bytes-unit "=" byte-range-set
1417<x:ref>bytes-unit</x:ref> = "bytes"
1418
1419<x:ref>content-range-spec</x:ref> = byte-content-range-spec /
1420 other-content-range-spec
1421
1422<x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in [Part4], Section 2&gt;
1423
1424<x:ref>first-byte-pos</x:ref> = 1*DIGIT
1425
1426<x:ref>instance-length</x:ref> = 1*DIGIT
1427
1428<x:ref>last-byte-pos</x:ref> = 1*DIGIT
1429
1430<x:ref>other-content-range-spec</x:ref> = other-range-unit SP other-range-resp-spec
1431<x:ref>other-range-resp-spec</x:ref> = *CHAR
1432<x:ref>other-range-set</x:ref> = 1*CHAR
1433<x:ref>other-range-unit</x:ref> = token
1434<x:ref>other-ranges-specifier</x:ref> = other-range-unit "=" other-range-set
1435
1436<x:ref>range-unit</x:ref> = bytes-unit / other-range-unit
1437
1438<x:ref>suffix-byte-range-spec</x:ref> = "-" suffix-length
1439<x:ref>suffix-length</x:ref> = 1*DIGIT
1440
1441<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
1442</artwork>
1443</figure>
1444<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
1445; Accept-Ranges defined but not used
1446; Content-Range defined but not used
1447; If-Range defined but not used
1448; Range defined but not used
1449</artwork></figure></section>
1450<?ENDINC p5-range.abnf-appendix ?>
1451
1452
1453<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1454
1455<section title="Since RFC2616">
1456<t>
1457  Extracted relevant partitions from <xref target="RFC2616"/>.
1458</t>
1459</section>
1460
1461<section title="Since draft-ietf-httpbis-p5-range-00">
1462<t>
1463  Closed issues:
1464  <list style="symbols"> 
1465    <t>
1466      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1467      "Cache validators in 206 responses"
1468      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1469    </t>
1470    <t>
1471      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1472      "Normative and Informative references"
1473    </t>
1474    <t>
1475      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1476      "Normative up-to-date references"
1477    </t>
1478  </list>
1479</t>
1480</section>
1481
1482<section title="Since draft-ietf-httpbis-p5-range-01">
1483<t>
1484  Closed issues:
1485  <list style="symbols"> 
1486    <t>
1487      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1488      "Updating to RFC4288"
1489    </t>
1490  </list>
1491</t>
1492<t>
1493  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1494  <list style="symbols"> 
1495    <t>
1496      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1497    </t>
1498  </list>
1499</t>
1500</section>
1501
1502<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1503<t>
1504  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1505  <list style="symbols"> 
1506    <t>
1507      Reference RFC 3984, and update header registrations for headers defined
1508      in this document.
1509    </t>
1510  </list>
1511</t>
1512</section>
1513
1514<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1515<t>
1516</t>
1517</section>
1518
1519<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1520<t>
1521  Closed issues:
1522  <list style="symbols"> 
1523    <t>
1524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1525      "multipart/byteranges minimum number of parts"
1526    </t>
1527  </list>
1528</t>
1529<t>
1530  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1531  <list style="symbols"> 
1532    <t>
1533      Use "/" instead of "|" for alternatives.
1534    </t>
1535    <t>
1536      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
1537      whitespace ("OWS") and required whitespace ("RWS").
1538    </t>
1539    <t>
1540      Rewrite ABNFs to spell out whitespace rules, factor out
1541      header value format definitions.
1542    </t>
1543  </list>
1544</t>
1545</section>
1546
1547<section title="Since draft-ietf-httpbis-p5-range-05" anchor="changes.since.05">
1548<t>
1549  Closed issues:
1550  <list style="symbols"> 
1551    <t>
1552      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/142"/>:
1553      "State base for *-byte-pos and suffix-length"
1554    </t>
1555  </list>
1556</t>
1557<t>
1558  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1559  <list style="symbols"> 
1560    <t>
1561      Remove bias in favor of byte ranges; allow custom ranges in ABNF.
1562    </t>
1563  </list>
1564</t>
1565<t>
1566  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1567  <list style="symbols"> 
1568    <t>
1569      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
1570    </t>
1571  </list>
1572</t>
1573</section>
1574
1575<section title="Since draft-ietf-httpbis-p5-range-06" anchor="changes.since.06">
1576<t>
1577  Closed issues:
1578  <list style="symbols"> 
1579    <t>
1580      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/161"/>:
1581      "base for numeric protocol elements"
1582    </t>
1583  </list>
1584</t>
1585</section>
1586
1587<section title="Since draft-ietf-httpbis-p5-range-07" anchor="changes.since.07">
1588<t>
1589  Closed issues:
1590  <list style="symbols">
1591    <t>
1592      Fixed discrepancy in the If-Range definition about allowed validators.
1593    </t>
1594    <t>
1595      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/150" />: "multipart/byteranges for custom range units"
1596    </t>
1597    <t>
1598      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/151" />: "range unit missing from other-ranges-specifier in Range header"
1599    </t>
1600    <t>
1601      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
1602      "move IANA registrations for optional status codes"
1603    </t>
1604  </list>
1605</t>
1606</section>
1607
1608<section title="Since draft-ietf-httpbis-p5-range-08" anchor="changes.since.08">
1609<t>
1610  No significant changes.
1611</t>
1612</section>
1613
1614<section title="Since draft-ietf-httpbis-p5-range-09" anchor="changes.since.09">
1615<t>
1616 No significant changes.
1617</t>
1618</section>
1619
1620<section title="Since draft-ietf-httpbis-p5-range-10" anchor="changes.since.10">
1621<t>
1622  Closed issues:
1623  <list style="symbols"> 
1624    <t>
1625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
1626      "Clarify 'Requested Variant'"
1627    </t>
1628    <t>
1629      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
1630      "Clarify entity / representation / variant terminology"
1631    </t>
1632    <t>
1633      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
1634      "Clarify entity / representation / variant terminology"
1635    </t>
1636    <t>
1637      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
1638      "consider removing the 'changes from 2068' sections"
1639    </t>
1640  </list>
1641</t>
1642<t>
1643  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1644  <list style="symbols"> 
1645    <t>
1646      Add IANA registry.
1647    </t>
1648  </list>
1649</t>
1650</section>
1651
1652</section>
1653
1654</back>
1655</rfc>
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