source: draft-ietf-httpbis/latest/p5-range.xml @ 930

Last change on this file since 930 was 930, checked in by julian.reschke@…, 9 years ago

add IANA registry for range specifiers (see #85)

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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. Range units are defined in <xref target="range.units"/>.
528</t>
529<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"/>
530  <x:ref>Content-Range</x:ref> = "Content-Range" ":" <x:ref>OWS</x:ref> <x:ref>Content-Range-v</x:ref>
531  <x:ref>Content-Range-v</x:ref> = <x:ref>content-range-spec</x:ref>
532 
533  <x:ref>content-range-spec</x:ref>      = <x:ref>byte-content-range-spec</x:ref>
534                          / <x:ref>other-content-range-spec</x:ref>
535  <x:ref>byte-content-range-spec</x:ref> = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
536                            <x:ref>byte-range-resp-spec</x:ref> "/"
537                            ( <x:ref>instance-length</x:ref> / "*" )
538 
539  <x:ref>byte-range-resp-spec</x:ref>    = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
540                          / "*"
541                         
542  <x:ref>instance-length</x:ref>         = 1*<x:ref>DIGIT</x:ref>
543 
544  <x:ref>other-content-range-spec</x:ref> = <x:ref>other-range-unit</x:ref> <x:ref>SP</x:ref>
545                             <x:ref>other-range-resp-spec</x:ref>
546  <x:ref>other-range-resp-spec</x:ref>    = *<x:ref>CHAR</x:ref>
547</artwork></figure>
548<t>
549   The header &SHOULD; indicate the total length of the full representation,
550   unless this length is unknown or difficult to determine. The asterisk
551   "*" character means that the instance-length is unknown at the time
552   when the response was generated.
553</t>
554<t>
555   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
556   &MUST; only specify one range, and &MUST; contain
557   absolute byte positions for both the first and last byte of the
558   range.
559</t>
560<t>
561   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
562   value is less than its first-byte-pos value, or whose
563   instance-length value is less than or equal to its last-byte-pos
564   value, is invalid. The recipient of an invalid byte-content-range-spec
565   &MUST; ignore it and any content transferred along with it.
566</t>
567<t>
568   In the case of a byte range request:
569   A server sending a response with status code 416 (Requested range not
570   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
571   of "*". The instance-length specifies the current length of
572   the selected resource. A response with status code 206 (Partial
573   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
574</t>
575<t>
576   Examples of byte-content-range-spec values, assuming that the representation
577   contains a total of 1234 bytes:
578   <list style="symbols">
579      <t>
580        The first 500 bytes:
581<figure><artwork type="example" x:indent-with="   ">
582  bytes 0-499/1234
583</artwork></figure>
584      </t>   
585      <t>
586        The second 500 bytes:
587<figure><artwork type="example" x:indent-with="   ">
588  bytes 500-999/1234
589</artwork></figure>
590      </t>   
591      <t>
592        All except for the first 500 bytes:
593<figure><artwork type="example" x:indent-with="   ">
594  bytes 500-1233/1234
595</artwork></figure>
596      </t>   
597      <t>
598        The last 500 bytes:
599<figure><artwork type="example" x:indent-with="   ">
600  bytes 734-1233/1234
601</artwork></figure>
602      </t>   
603   </list>
604</t>
605<t>
606   When an HTTP message includes the content of a single range (for
607   example, a response to a request for a single range, or to a request
608   for a set of ranges that overlap without any holes), this content is
609   transmitted with a Content-Range header, and a Content-Length header
610   showing the number of bytes actually transferred. For example,
611</t>
612<figure><artwork type="example">
613  HTTP/1.1 206 Partial Content
614  Date: Wed, 15 Nov 1995 06:25:24 GMT
615  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
616  Content-Range: bytes 21010-47021/47022
617  Content-Length: 26012
618  Content-Type: image/gif
619</artwork></figure>
620<t>
621   When an HTTP message includes the content of multiple ranges (for
622   example, a response to a request for multiple non-overlapping
623   ranges), these are transmitted as a multipart message. The multipart
624   media type used for this purpose is "multipart/byteranges" as defined
625   in <xref target="internet.media.type.multipart.byteranges"/>.
626</t>
627<t>
628   A response to a request for a single range &MUST-NOT; be sent using the
629   multipart/byteranges media type.  A response to a request for
630   multiple ranges, whose result is a single range, &MAY; be sent as a
631   multipart/byteranges media type with one part. A client that cannot
632   decode a multipart/byteranges message &MUST-NOT; ask for multiple
633   ranges in a single request.
634</t>
635<t>
636   When a client requests multiple ranges in one request, the
637   server &SHOULD; return them in the order that they appeared in the
638   request.
639</t>
640<t>
641   If the server ignores a byte-range-spec because it is syntactically
642   invalid, the server &SHOULD; treat the request as if the invalid Range
643   header field did not exist. (Normally, this means return a 200
644   response containing the full representation).
645</t>
646<t>
647   If the server receives a request (other than one including an If-Range
648   request-header field) with an unsatisfiable Range request-header
649   field (that is, all of whose byte-range-spec values have a
650   first-byte-pos value greater than the current length of the selected
651   resource), it &SHOULD; return a response code of 416 (Requested range
652   not satisfiable) (<xref target="status.416"/>).
653</t>
654<x:note>
655  <t>
656    <x:h>Note:</x:h> Clients cannot depend on servers to send a 416 (Requested
657    range not satisfiable) response instead of a 200 (OK) response for
658    an unsatisfiable Range request-header, since not all servers
659    implement this request-header.
660  </t>
661</x:note>
662</section>
663
664<section title="If-Range" anchor="header.if-range">
665  <iref primary="true" item="If-Range header" x:for-anchor=""/>
666  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
667  <x:anchor-alias value="If-Range"/>
668  <x:anchor-alias value="If-Range-v"/>
669<t>
670   If a client has a partial copy of a representation in its cache, and wishes
671   to have an up-to-date copy of the entire representation in its cache, it
672   could use the Range request-header with a conditional GET (using
673   either or both of If-Unmodified-Since and If-Match.) However, if the
674   condition fails because the representation has been modified, the client
675   would then have to make a second request to obtain the entire current
676   representation.
677</t>
678<t>
679   The "If-Range" request-header field allows a client to "short-circuit" the second
680   request. Informally, its meaning is "if the representation is unchanged, send
681   me the part(s) that I am missing; otherwise, send me the entire new
682   representation".
683</t>
684<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/><iref primary="true" item="Grammar" subitem="If-Range-v"/>
685  <x:ref>If-Range</x:ref>   = "If-Range" ":" <x:ref>OWS</x:ref> <x:ref>If-Range-v</x:ref>
686  <x:ref>If-Range-v</x:ref> = <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref>
687</artwork></figure>
688<t>
689   If the client has no entity-tag for a representation, but does have a Last-Modified
690   date, it &MAY; use that date in an If-Range header. (The
691   server can distinguish between a valid HTTP-date and any form of
692   entity-tag by examining no more than two characters.) The If-Range
693   header &SHOULD; only be used together with a Range header, and &MUST; be
694   ignored if the request does not include a Range header, or if the
695   server does not support the sub-range operation.
696</t>
697<t>
698   If the entity-tag given in the If-Range header matches the current
699   cache validator for the representation, then the server &SHOULD; provide the
700   specified sub-range of the representation using a 206 (Partial Content)
701   response. If the cache validator does not match, then the server &SHOULD;
702   return the entire representation using a 200 (OK) response.
703</t>
704</section>
705
706<section title="Range" anchor="header.range">
707  <iref primary="true" item="Range header" x:for-anchor=""/>
708  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
709
710<section title="Byte Ranges" anchor="byte.ranges">
711<t>
712   Since all HTTP representations are transferred as sequences
713   of bytes, the concept of a byte range is meaningful for any HTTP
714   representation. (However, not all clients and servers need to support byte-range
715   operations.)
716</t>
717<t>
718   Byte range specifications in HTTP apply to the sequence of bytes in
719   the representation body (not necessarily the same as the message-body).
720</t>
721<t anchor="rule.ranges-specifier">
722  <x:anchor-alias value="byte-range-set"/>
723  <x:anchor-alias value="byte-range-spec"/>
724  <x:anchor-alias value="byte-ranges-specifier"/>
725  <x:anchor-alias value="first-byte-pos"/>
726  <x:anchor-alias value="last-byte-pos"/>
727  <x:anchor-alias value="ranges-specifier"/>
728  <x:anchor-alias value="suffix-byte-range-spec"/>
729  <x:anchor-alias value="suffix-length"/>
730
731   A byte range operation &MAY; specify a single range of bytes, or a set
732   of ranges within a single representation.
733</t>
734<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"/>
735  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
736  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
737  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [ <x:ref>last-byte-pos</x:ref> ]
738  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
739  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
740</artwork></figure>
741<t>
742   The first-byte-pos value in a byte-range-spec gives the byte-offset
743   of the first byte in a range. The last-byte-pos value gives the
744   byte-offset of the last byte in the range; that is, the byte
745   positions specified are inclusive. Byte offsets start at zero.
746</t>
747<t>
748   If the last-byte-pos value is present, it &MUST; be greater than or
749   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
750   is syntactically invalid. The recipient of a byte-range-set
751   that includes one or more syntactically invalid byte-range-spec
752   values &MUST; ignore the header field that includes that byte-range-set.
753</t>
754<t>
755   If the last-byte-pos value is absent, or if the value is greater than
756   or equal to the current length of the representation body, last-byte-pos is
757   taken to be equal to one less than the current length of the representation
758   in bytes.
759</t>
760<t>
761   By its choice of last-byte-pos, a client can limit the number of
762   bytes retrieved without knowing the size of the representation.
763</t>
764<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
765  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
766  <x:ref>suffix-length</x:ref> = 1*<x:ref>DIGIT</x:ref>
767</artwork></figure>
768<t>
769   A suffix-byte-range-spec is used to specify the suffix of the
770   representation body, of a length given by the suffix-length value. (That is,
771   this form specifies the last N bytes of a representation.) If the
772   representation is shorter than the specified suffix-length, the entire
773   representation is used.
774</t>
775<t>
776   If a syntactically valid byte-range-set includes at least one byte-range-spec
777   whose first-byte-pos is less than the current length of
778   the representation, or at least one suffix-byte-range-spec with a non-zero
779   suffix-length, then the byte-range-set is satisfiable.
780   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
781   is unsatisfiable, the server &SHOULD; return a response with a
782   416 (Requested range not satisfiable) status code. Otherwise, the server
783   &SHOULD; return a response with a 206 (Partial Content) status code
784   containing the satisfiable ranges of the representation.
785</t>
786<t>
787   Examples of byte-ranges-specifier values (assuming a representation of
788   length 10000):
789  <list style="symbols">
790     <t>The first 500 bytes (byte offsets 0-499, inclusive):
791<figure><artwork type="example" x:indent-with="   ">
792  bytes=0-499
793</artwork></figure>
794    </t>
795     <t>The second 500 bytes (byte offsets 500-999, inclusive):
796<figure><artwork type="example" x:indent-with="   ">
797  bytes=500-999
798</artwork></figure>
799    </t>
800     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
801<figure><artwork type="example" x:indent-with="   ">
802  bytes=-500
803</artwork></figure>
804    Or:
805<figure><artwork type="example" x:indent-with="   ">
806  bytes=9500-
807</artwork></figure>
808    </t>
809     <t>The first and last bytes only (bytes 0 and 9999):
810<figure><artwork type="example" x:indent-with="   ">
811  bytes=0-0,-1
812</artwork></figure>
813     </t>
814     <t>Several legal but not canonical specifications of the second 500
815        bytes (byte offsets 500-999, inclusive):
816<figure><artwork type="example" x:indent-with="   ">
817  bytes=500-600,601-999
818  bytes=500-700,601-999
819</artwork></figure>
820     </t>
821  </list>
822</t>
823</section>
824
825<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
826  <x:anchor-alias value="Range"/>
827  <x:anchor-alias value="Range-v"/>
828  <x:anchor-alias value="other-ranges-specifier"/>
829  <x:anchor-alias value="other-range-set"/>
830<t>
831   The "Range" request-header field defines the GET method (conditional or
832   not) to request one or more sub-ranges of the response representation body, instead
833   of the entire representation body.
834</t>
835<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/>
836  <x:ref>Range</x:ref>   = "Range" ":" <x:ref>OWS</x:ref> <x:ref>Range-v</x:ref>
837  <x:ref>Range-v</x:ref> = <x:ref>byte-ranges-specifier</x:ref>
838          / <x:ref>other-ranges-specifier</x:ref>
839  <x:ref>other-ranges-specifier</x:ref> = <x:ref>other-range-unit</x:ref> "=" <x:ref>other-range-set</x:ref>
840  <x:ref>other-range-set</x:ref> = 1*<x:ref>CHAR</x:ref>
841</artwork></figure>
842<t>
843   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
844   servers and intermediate caches ought to support byte ranges when
845   possible, since Range supports efficient recovery from partially
846   failed transfers, and supports efficient partial retrieval of large
847   representations.
848</t>
849<t>
850   If the server supports the Range header and the specified range or
851   ranges are appropriate for the representation:
852  <list style="symbols">
853     <t>The presence of a Range header in an unconditional GET modifies
854        what is returned if the GET is otherwise successful. In other
855        words, the response carries a status code of 206 (Partial
856        Content) instead of 200 (OK).</t>
857
858     <t>The presence of a Range header in a conditional GET (a request
859        using one or both of If-Modified-Since and If-None-Match, or
860        one or both of If-Unmodified-Since and If-Match) modifies what
861        is returned if the GET is otherwise successful and the
862        condition is true. It does not affect the 304 (Not Modified)
863        response returned if the conditional is false.</t>
864  </list>
865</t>
866<t>
867   In some cases, it might be more appropriate to use the If-Range
868   header (see <xref target="header.if-range"/>) in addition to the Range header.
869</t>
870<t>
871   If a proxy that supports ranges receives a Range request, forwards
872   the request to an inbound server, and receives an entire representation in
873   reply, it &SHOULD; only return the requested range to its client. It
874   &SHOULD; store the entire received response in its cache if that is
875   consistent with its cache allocation policies.
876</t>
877</section>
878</section>
879</section>
880
881<section title="IANA Considerations" anchor="IANA.considerations">
882
883<section title="Status Code Registration" anchor="status.code.registration">
884<t>
885   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
886   should be updated with the registrations below:
887</t>
888<?BEGININC p5-range.iana-status-codes ?>
889<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
890<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
891   <ttcol>Value</ttcol>
892   <ttcol>Description</ttcol>
893   <ttcol>Reference</ttcol>
894   <c>206</c>
895   <c>Partial Content</c>
896   <c>
897      <xref target="status.206"/>
898   </c>
899   <c>416</c>
900   <c>Requested Range Not Satisfiable</c>
901   <c>
902      <xref target="status.416"/>
903   </c>
904</texttable>
905<!--(END)-->
906<?ENDINC p5-range.iana-status-codes ?>
907</section>
908
909<section title="Header Field Registration" anchor="header.field.registration">
910<t>
911   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
912   with the permanent registrations below (see <xref target="RFC3864"/>):
913</t>
914<?BEGININC p5-range.iana-headers ?>
915<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
916<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
917   <ttcol>Header Field Name</ttcol>
918   <ttcol>Protocol</ttcol>
919   <ttcol>Status</ttcol>
920   <ttcol>Reference</ttcol>
921
922   <c>Accept-Ranges</c>
923   <c>http</c>
924   <c>standard</c>
925   <c>
926      <xref target="header.accept-ranges"/>
927   </c>
928   <c>Content-Range</c>
929   <c>http</c>
930   <c>standard</c>
931   <c>
932      <xref target="header.content-range"/>
933   </c>
934   <c>If-Range</c>
935   <c>http</c>
936   <c>standard</c>
937   <c>
938      <xref target="header.if-range"/>
939   </c>
940   <c>Range</c>
941   <c>http</c>
942   <c>standard</c>
943   <c>
944      <xref target="header.range"/>
945   </c>
946</texttable>
947<!--(END)-->
948<?ENDINC p5-range.iana-headers ?>
949<t>
950   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
951</t>
952</section>
953
954<section title="Range Specifier Registration" anchor="range.specifier.registration">
955<t>
956  The registration procedure for HTTP Range Specifiers is defined by
957  <xref target="range.specifier.registry"/> of this document.
958</t>
959<t>
960   The HTTP Range Specifier Registry should be created at <eref target="http://www.iana.org/assignments/http-range-specifiers"/>
961   and be populated with the registrations below:
962</t>
963<texttable align="left" suppress-title="true" anchor="iana.range.specifiers.table">
964   <ttcol>Range Specifier Name</ttcol>
965   <ttcol>Description</ttcol>
966   <ttcol>Reference</ttcol>
967
968   <c>bytes</c>
969   <c>a range of octets</c>
970   <c>(this specification)</c>
971</texttable>
972<t>
973   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
974</t>
975</section>
976</section>
977
978<section title="Security Considerations" anchor="security.considerations">
979<t>
980   No additional security considerations have been identified beyond
981   those applicable to HTTP in general &messaging;.
982</t>
983</section>
984
985<section title="Acknowledgments" anchor="ack">
986<t>
987   Most of the specification of ranges is based on work originally done
988   by Ari Luotonen and John Franks, with additional input from Steve
989   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
990   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
991   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
992</t>
993</section>
994</middle>
995<back>
996
997<references title="Normative References">
998
999<reference anchor="Part1">
1000  <front>
1001    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1002    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1003      <organization abbrev="Day Software">Day Software</organization>
1004      <address><email>fielding@gbiv.com</email></address>
1005    </author>
1006    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1007      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1008      <address><email>jg@freedesktop.org</email></address>
1009    </author>
1010    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1011      <organization abbrev="HP">Hewlett-Packard Company</organization>
1012      <address><email>JeffMogul@acm.org</email></address>
1013    </author>
1014    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1015      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1016      <address><email>henrikn@microsoft.com</email></address>
1017    </author>
1018    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1019      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1020      <address><email>LMM@acm.org</email></address>
1021    </author>
1022    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1023      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1024      <address><email>paulle@microsoft.com</email></address>
1025    </author>
1026    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1027      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1028      <address><email>timbl@w3.org</email></address>
1029    </author>
1030    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1031      <organization abbrev="W3C">World Wide Web Consortium</organization>
1032      <address><email>ylafon@w3.org</email></address>
1033    </author>
1034    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1035      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1036      <address><email>julian.reschke@greenbytes.de</email></address>
1037    </author>
1038    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1039  </front>
1040  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1041  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1042</reference>
1043
1044<reference anchor="Part4">
1045  <front>
1046    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1047    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1048      <organization abbrev="Day Software">Day Software</organization>
1049      <address><email>fielding@gbiv.com</email></address>
1050    </author>
1051    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1052      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1053      <address><email>jg@freedesktop.org</email></address>
1054    </author>
1055    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1056      <organization abbrev="HP">Hewlett-Packard Company</organization>
1057      <address><email>JeffMogul@acm.org</email></address>
1058    </author>
1059    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1060      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1061      <address><email>henrikn@microsoft.com</email></address>
1062    </author>
1063    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1064      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1065      <address><email>LMM@acm.org</email></address>
1066    </author>
1067    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1068      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1069      <address><email>paulle@microsoft.com</email></address>
1070    </author>
1071    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1072      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1073      <address><email>timbl@w3.org</email></address>
1074    </author>
1075    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1076      <organization abbrev="W3C">World Wide Web Consortium</organization>
1077      <address><email>ylafon@w3.org</email></address>
1078    </author>
1079    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1080      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1081      <address><email>julian.reschke@greenbytes.de</email></address>
1082    </author>
1083    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1084  </front>
1085  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1086  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1087</reference>
1088
1089<reference anchor="RFC2046">
1090  <front>
1091    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1092    <author initials="N." surname="Freed" fullname="Ned Freed">
1093      <organization>Innosoft International, Inc.</organization>
1094      <address><email>ned@innosoft.com</email></address>
1095    </author>
1096    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1097      <organization>First Virtual Holdings</organization>
1098      <address><email>nsb@nsb.fv.com</email></address>
1099    </author>
1100    <date month="November" year="1996"/>
1101  </front>
1102  <seriesInfo name="RFC" value="2046"/>
1103</reference>
1104
1105<reference anchor="RFC2119">
1106  <front>
1107    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1108    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1109      <organization>Harvard University</organization>
1110      <address><email>sob@harvard.edu</email></address>
1111    </author>
1112    <date month="March" year="1997"/>
1113  </front>
1114  <seriesInfo name="BCP" value="14"/>
1115  <seriesInfo name="RFC" value="2119"/>
1116</reference>
1117
1118<reference anchor="RFC5234">
1119  <front>
1120    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1121    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1122      <organization>Brandenburg InternetWorking</organization>
1123      <address>
1124        <email>dcrocker@bbiw.net</email>
1125      </address> 
1126    </author>
1127    <author initials="P." surname="Overell" fullname="Paul Overell">
1128      <organization>THUS plc.</organization>
1129      <address>
1130        <email>paul.overell@thus.net</email>
1131      </address>
1132    </author>
1133    <date month="January" year="2008"/>
1134  </front>
1135  <seriesInfo name="STD" value="68"/>
1136  <seriesInfo name="RFC" value="5234"/>
1137</reference>
1138
1139</references>
1140
1141<references title="Informative References">
1142
1143<reference anchor="RFC2616">
1144  <front>
1145    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1146    <author initials="R." surname="Fielding" fullname="R. Fielding">
1147      <organization>University of California, Irvine</organization>
1148      <address><email>fielding@ics.uci.edu</email></address>
1149    </author>
1150    <author initials="J." surname="Gettys" fullname="J. Gettys">
1151      <organization>W3C</organization>
1152      <address><email>jg@w3.org</email></address>
1153    </author>
1154    <author initials="J." surname="Mogul" fullname="J. Mogul">
1155      <organization>Compaq Computer Corporation</organization>
1156      <address><email>mogul@wrl.dec.com</email></address>
1157    </author>
1158    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1159      <organization>MIT Laboratory for Computer Science</organization>
1160      <address><email>frystyk@w3.org</email></address>
1161    </author>
1162    <author initials="L." surname="Masinter" fullname="L. Masinter">
1163      <organization>Xerox Corporation</organization>
1164      <address><email>masinter@parc.xerox.com</email></address>
1165    </author>
1166    <author initials="P." surname="Leach" fullname="P. Leach">
1167      <organization>Microsoft Corporation</organization>
1168      <address><email>paulle@microsoft.com</email></address>
1169    </author>
1170    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1171      <organization>W3C</organization>
1172      <address><email>timbl@w3.org</email></address>
1173    </author>
1174    <date month="June" year="1999"/>
1175  </front>
1176  <seriesInfo name="RFC" value="2616"/>
1177</reference>
1178
1179<reference anchor='RFC3864'>
1180  <front>
1181    <title>Registration Procedures for Message Header Fields</title>
1182    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1183      <organization>Nine by Nine</organization>
1184      <address><email>GK-IETF@ninebynine.org</email></address>
1185    </author>
1186    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1187      <organization>BEA Systems</organization>
1188      <address><email>mnot@pobox.com</email></address>
1189    </author>
1190    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1191      <organization>HP Labs</organization>
1192      <address><email>JeffMogul@acm.org</email></address>
1193    </author>
1194    <date year='2004' month='September' />
1195  </front>
1196  <seriesInfo name='BCP' value='90' />
1197  <seriesInfo name='RFC' value='3864' />
1198</reference>
1199
1200<reference anchor="RFC4288">
1201  <front>
1202    <title>Media Type Specifications and Registration Procedures</title>
1203    <author initials="N." surname="Freed" fullname="N. Freed">
1204      <organization>Sun Microsystems</organization>
1205      <address>
1206        <email>ned.freed@mrochek.com</email>
1207      </address>
1208    </author>
1209    <author initials="J." surname="Klensin" fullname="J. Klensin">
1210      <address>
1211        <email>klensin+ietf@jck.com</email>
1212      </address>
1213    </author>
1214    <date year="2005" month="December"/>
1215  </front>
1216  <seriesInfo name="BCP" value="13"/>
1217  <seriesInfo name="RFC" value="4288"/>
1218</reference>
1219
1220<reference anchor='RFC5226'>
1221  <front>
1222    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
1223    <author initials='T.' surname='Narten' fullname='T. Narten'>
1224      <organization>IBM</organization>
1225      <address><email>narten@us.ibm.com</email></address>
1226    </author>
1227    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
1228      <organization>Google</organization>
1229      <address><email>Harald@Alvestrand.no</email></address>
1230    </author>
1231    <date year='2008' month='May' />
1232  </front>
1233  <seriesInfo name='BCP' value='26' />
1234  <seriesInfo name='RFC' value='5226' />
1235</reference>
1236
1237</references>
1238
1239<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1240<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1241<iref item="multipart/byteranges Media Type" primary="true"/>
1242<t>
1243   When an HTTP 206 (Partial Content) response message includes the
1244   content of multiple ranges (a response to a request for multiple
1245   non-overlapping ranges), these are transmitted as a multipart
1246   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1247   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1248</t>
1249<x:note>
1250  <t>
1251    <x:h>Note:</x:h> Despite the name "multipart/byteranges" is not limited to the byte ranges only.
1252  </t>
1253</x:note>
1254<t>
1255   The multipart/byteranges media type includes one or more parts, each
1256   with its own Content-Type and Content-Range fields. The required
1257   boundary parameter specifies the boundary string used to separate
1258   each body-part.
1259</t>
1260<t>
1261  <list style="hanging" x:indent="12em">
1262    <t hangText="Type name:">
1263      multipart
1264    </t>
1265    <t hangText="Subtype name:">
1266      byteranges
1267    </t>
1268    <t hangText="Required parameters:">
1269      boundary
1270    </t>
1271    <t hangText="Optional parameters:">
1272      none
1273    </t>
1274    <t hangText="Encoding considerations:">
1275      only "7bit", "8bit", or "binary" are permitted
1276    </t>
1277    <t hangText="Security considerations:">
1278      none
1279    </t>
1280    <t hangText="Interoperability considerations:">
1281      none
1282    </t>
1283    <t hangText="Published specification:">
1284      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1285    </t>
1286    <t hangText="Applications that use this media type:">
1287    </t>
1288    <t hangText="Additional information:">
1289      <list style="hanging">
1290        <t hangText="Magic number(s):">none</t>
1291        <t hangText="File extension(s):">none</t>
1292        <t hangText="Macintosh file type code(s):">none</t>
1293      </list>
1294    </t>
1295    <t hangText="Person and email address to contact for further information:">
1296      See Authors Section.
1297    </t>
1298    <t hangText="Intended usage:">
1299      COMMON
1300    </t>
1301    <t hangText="Restrictions on usage:">
1302      none
1303    </t>
1304    <t hangText="Author/Change controller:">
1305      IESG
1306    </t>
1307  </list>
1308</t>
1309<figure><preamble>
1310   For example:
1311</preamble><artwork type="example">
1312  HTTP/1.1 206 Partial Content
1313  Date: Wed, 15 Nov 1995 06:25:24 GMT
1314  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1315  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1316 
1317  --THIS_STRING_SEPARATES
1318  Content-type: application/pdf
1319  Content-range: bytes 500-999/8000
1320 
1321  ...the first range...
1322  --THIS_STRING_SEPARATES
1323  Content-type: application/pdf
1324  Content-range: bytes 7000-7999/8000
1325 
1326  ...the second range
1327  --THIS_STRING_SEPARATES--
1328</artwork></figure>
1329<figure><preamble>
1330   Other example:
1331</preamble>
1332<artwork type="example">
1333  HTTP/1.1 206 Partial Content
1334  Date: Tue, 14 Nov 1995 06:25:24 GMT
1335  Last-Modified: Tue, 14 July 04:58:08 GMT
1336  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1337 
1338  --THIS_STRING_SEPARATES
1339  Content-type: video/example
1340  Content-range: exampleunit 1.2-4.3/25
1341 
1342  ...the first range...
1343  --THIS_STRING_SEPARATES
1344  Content-type: video/example
1345  Content-range: exampleunit 11.2-14.3/25
1346 
1347  ...the second range
1348  --THIS_STRING_SEPARATES--
1349</artwork>
1350</figure>
1351<t>
1352      Notes:
1353  <list style="numbers">
1354      <t>Additional CRLFs &MAY; precede the first boundary string in the body.</t>
1355
1356      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1357         quoted, some existing implementations handle a quoted boundary
1358         string incorrectly.</t>
1359
1360      <t>A number of browsers and servers were coded to an early draft
1361         of the byteranges specification to use a media type of
1362         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1363         compatible with the version documented in HTTP/1.1.</t>
1364  </list>
1365</t>
1366</section>
1367
1368<section title="Compatibility with Previous Versions" anchor="compatibility">
1369<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1370<t>
1371  Clarify that it is not ok to use a weak cache validator in a 206 response.
1372  (<xref target="status.206"/>)
1373</t>
1374<t>
1375  Clarify that multipart/byteranges can consist of a single part.
1376  (<xref target="internet.media.type.multipart.byteranges"/>)
1377</t>
1378
1379</section>
1380
1381</section>
1382
1383<?BEGININC p5-range.abnf-appendix ?>
1384<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
1385<figure>
1386<artwork type="abnf" name="p5-range.parsed-abnf">
1387<x:ref>Accept-Ranges</x:ref> = "Accept-Ranges:" OWS Accept-Ranges-v
1388<x:ref>Accept-Ranges-v</x:ref> = acceptable-ranges
1389
1390<x:ref>Content-Range</x:ref> = "Content-Range:" OWS Content-Range-v
1391<x:ref>Content-Range-v</x:ref> = content-range-spec
1392
1393<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
1394
1395<x:ref>If-Range</x:ref> = "If-Range:" OWS If-Range-v
1396<x:ref>If-Range-v</x:ref> = entity-tag / HTTP-date
1397
1398<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
1399
1400<x:ref>Range</x:ref> = "Range:" OWS Range-v
1401<x:ref>Range-v</x:ref> = byte-ranges-specifier / other-ranges-specifier
1402
1403<x:ref>acceptable-ranges</x:ref> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
1404 range-unit ] ) ) / "none"
1405
1406<x:ref>byte-content-range-spec</x:ref> = bytes-unit SP byte-range-resp-spec "/" (
1407 instance-length / "*" )
1408<x:ref>byte-range-resp-spec</x:ref> = ( first-byte-pos "-" last-byte-pos ) / "*"
1409<x:ref>byte-range-set</x:ref> = ( *( "," OWS ) byte-range-spec ) / (
1410 suffix-byte-range-spec *( OWS "," [ ( OWS byte-range-spec ) /
1411 suffix-byte-range-spec ] ) )
1412<x:ref>byte-range-spec</x:ref> = first-byte-pos "-" [ last-byte-pos ]
1413<x:ref>byte-ranges-specifier</x:ref> = bytes-unit "=" byte-range-set
1414<x:ref>bytes-unit</x:ref> = "bytes"
1415
1416<x:ref>content-range-spec</x:ref> = byte-content-range-spec /
1417 other-content-range-spec
1418
1419<x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in [Part4], Section 2&gt;
1420
1421<x:ref>first-byte-pos</x:ref> = 1*DIGIT
1422
1423<x:ref>instance-length</x:ref> = 1*DIGIT
1424
1425<x:ref>last-byte-pos</x:ref> = 1*DIGIT
1426
1427<x:ref>other-content-range-spec</x:ref> = other-range-unit SP other-range-resp-spec
1428<x:ref>other-range-resp-spec</x:ref> = *CHAR
1429<x:ref>other-range-set</x:ref> = 1*CHAR
1430<x:ref>other-range-unit</x:ref> = token
1431<x:ref>other-ranges-specifier</x:ref> = other-range-unit "=" other-range-set
1432
1433<x:ref>range-unit</x:ref> = bytes-unit / other-range-unit
1434
1435<x:ref>suffix-byte-range-spec</x:ref> = "-" suffix-length
1436<x:ref>suffix-length</x:ref> = 1*DIGIT
1437
1438<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
1439</artwork>
1440</figure>
1441<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
1442; Accept-Ranges defined but not used
1443; Content-Range defined but not used
1444; If-Range defined but not used
1445; Range defined but not used
1446</artwork></figure></section>
1447<?ENDINC p5-range.abnf-appendix ?>
1448
1449
1450<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1451
1452<section title="Since RFC2616">
1453<t>
1454  Extracted relevant partitions from <xref target="RFC2616"/>.
1455</t>
1456</section>
1457
1458<section title="Since draft-ietf-httpbis-p5-range-00">
1459<t>
1460  Closed issues:
1461  <list style="symbols"> 
1462    <t>
1463      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1464      "Cache validators in 206 responses"
1465      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1466    </t>
1467    <t>
1468      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1469      "Normative and Informative references"
1470    </t>
1471    <t>
1472      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1473      "Normative up-to-date references"
1474    </t>
1475  </list>
1476</t>
1477</section>
1478
1479<section title="Since draft-ietf-httpbis-p5-range-01">
1480<t>
1481  Closed issues:
1482  <list style="symbols"> 
1483    <t>
1484      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1485      "Updating to RFC4288"
1486    </t>
1487  </list>
1488</t>
1489<t>
1490  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1491  <list style="symbols"> 
1492    <t>
1493      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1494    </t>
1495  </list>
1496</t>
1497</section>
1498
1499<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1500<t>
1501  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1502  <list style="symbols"> 
1503    <t>
1504      Reference RFC 3984, and update header registrations for headers defined
1505      in this document.
1506    </t>
1507  </list>
1508</t>
1509</section>
1510
1511<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1512<t>
1513</t>
1514</section>
1515
1516<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1517<t>
1518  Closed issues:
1519  <list style="symbols"> 
1520    <t>
1521      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1522      "multipart/byteranges minimum number of parts"
1523    </t>
1524  </list>
1525</t>
1526<t>
1527  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1528  <list style="symbols"> 
1529    <t>
1530      Use "/" instead of "|" for alternatives.
1531    </t>
1532    <t>
1533      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
1534      whitespace ("OWS") and required whitespace ("RWS").
1535    </t>
1536    <t>
1537      Rewrite ABNFs to spell out whitespace rules, factor out
1538      header value format definitions.
1539    </t>
1540  </list>
1541</t>
1542</section>
1543
1544<section title="Since draft-ietf-httpbis-p5-range-05" anchor="changes.since.05">
1545<t>
1546  Closed issues:
1547  <list style="symbols"> 
1548    <t>
1549      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/142"/>:
1550      "State base for *-byte-pos and suffix-length"
1551    </t>
1552  </list>
1553</t>
1554<t>
1555  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1556  <list style="symbols"> 
1557    <t>
1558      Remove bias in favor of byte ranges; allow custom ranges in ABNF.
1559    </t>
1560  </list>
1561</t>
1562<t>
1563  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1564  <list style="symbols"> 
1565    <t>
1566      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
1567    </t>
1568  </list>
1569</t>
1570</section>
1571
1572<section title="Since draft-ietf-httpbis-p5-range-06" anchor="changes.since.06">
1573<t>
1574  Closed issues:
1575  <list style="symbols"> 
1576    <t>
1577      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/161"/>:
1578      "base for numeric protocol elements"
1579    </t>
1580  </list>
1581</t>
1582</section>
1583
1584<section title="Since draft-ietf-httpbis-p5-range-07" anchor="changes.since.07">
1585<t>
1586  Closed issues:
1587  <list style="symbols">
1588    <t>
1589      Fixed discrepancy in the If-Range definition about allowed validators.
1590    </t>
1591    <t>
1592      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/150" />: "multipart/byteranges for custom range units"
1593    </t>
1594    <t>
1595      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/151" />: "range unit missing from other-ranges-specifier in Range header"
1596    </t>
1597    <t>
1598      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
1599      "move IANA registrations for optional status codes"
1600    </t>
1601  </list>
1602</t>
1603</section>
1604
1605<section title="Since draft-ietf-httpbis-p5-range-08" anchor="changes.since.08">
1606<t>
1607  No significant changes.
1608</t>
1609</section>
1610
1611<section title="Since draft-ietf-httpbis-p5-range-09" anchor="changes.since.09">
1612<t>
1613 No significant changes.
1614</t>
1615</section>
1616
1617<section title="Since draft-ietf-httpbis-p5-range-10" anchor="changes.since.10">
1618<t>
1619  Closed issues:
1620  <list style="symbols"> 
1621    <t>
1622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
1623      "Clarify 'Requested Variant'"
1624    </t>
1625    <t>
1626      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
1627      "Clarify entity / representation / variant terminology"
1628    </t>
1629    <t>
1630      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
1631      "Clarify entity / representation / variant terminology"
1632    </t>
1633    <t>
1634      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
1635      "consider removing the 'changes from 2068' sections"
1636    </t>
1637  </list>
1638</t>
1639<t>
1640  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1641  <list style="symbols"> 
1642    <t>
1643      Add IANA registry.
1644    </t>
1645  </list>
1646</t>
1647</section>
1648
1649</section>
1650
1651</back>
1652</rfc>
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