source: draft-ietf-httpbis/latest-roy/p5-range.xml @ 383

Last change on this file since 383 was 358, checked in by ylafon@…, 12 years ago

expectation about support of range units by server/intermediaries/clients

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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 "November">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY entity-tags                "<xref target='Part4' x:rel='#entity.tags' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY weak-and-strong-validators "<xref target='Part4' x:rel='#weak.and.strong.validators' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23]>
24<?rfc toc="yes" ?>
25<?rfc symrefs="yes" ?>
26<?rfc sortrefs="yes" ?>
27<?rfc compact="yes"?>
28<?rfc subcompact="no" ?>
29<?rfc linkmailto="no" ?>
30<?rfc editing="no" ?>
31<?rfc comments="yes"?>
32<?rfc inline="yes"?>
33<?rfc-ext allow-markup-in-artwork="yes" ?>
34<?rfc-ext include-references-in-index="yes" ?>
35<rfc obsoletes="2616" category="std" x:maturity-level="draft"
36     ipr="full3978" docName="draft-ietf-httpbis-p5-range-&ID-VERSION;"
37     xmlns:x='http://purl.org/net/xml2rfc/ext'>
38<front>
39
40  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
41
42  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
43    <organization abbrev="Day Software">Day Software</organization>
44    <address>
45      <postal>
46        <street>23 Corporate Plaza DR, Suite 280</street>
47        <city>Newport Beach</city>
48        <region>CA</region>
49        <code>92660</code>
50        <country>USA</country>
51      </postal>
52      <phone>+1-949-706-5300</phone>
53      <facsimile>+1-949-706-5305</facsimile>
54      <email>fielding@gbiv.com</email>
55      <uri>http://roy.gbiv.com/</uri>
56    </address>
57  </author>
58
59  <author initials="J." surname="Gettys" fullname="Jim Gettys">
60    <organization>One Laptop per Child</organization>
61    <address>
62      <postal>
63        <street>21 Oak Knoll Road</street>
64        <city>Carlisle</city>
65        <region>MA</region>
66        <code>01741</code>
67        <country>USA</country>
68      </postal>
69      <email>jg@laptop.org</email>
70      <uri>http://www.laptop.org/</uri>
71    </address>
72  </author>
73 
74  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
75    <organization abbrev="HP">Hewlett-Packard Company</organization>
76    <address>
77      <postal>
78        <street>HP Labs, Large Scale Systems Group</street>
79        <street>1501 Page Mill Road, MS 1177</street>
80        <city>Palo Alto</city>
81        <region>CA</region>
82        <code>94304</code>
83        <country>USA</country>
84      </postal>
85      <email>JeffMogul@acm.org</email>
86    </address>
87  </author>
88
89  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
90    <organization abbrev="Microsoft">Microsoft Corporation</organization>
91    <address>
92      <postal>
93        <street>1 Microsoft Way</street>
94        <city>Redmond</city>
95        <region>WA</region>
96        <code>98052</code>
97        <country>USA</country>
98      </postal>
99      <email>henrikn@microsoft.com</email>
100    </address>
101  </author>
102
103  <author initials="L." surname="Masinter" fullname="Larry Masinter">
104    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
105    <address>
106      <postal>
107        <street>345 Park Ave</street>
108        <city>San Jose</city>
109        <region>CA</region>
110        <code>95110</code>
111        <country>USA</country>
112      </postal>
113      <email>LMM@acm.org</email>
114      <uri>http://larry.masinter.net/</uri>
115    </address>
116  </author>
117 
118  <author initials="P." surname="Leach" fullname="Paul J. Leach">
119    <organization abbrev="Microsoft">Microsoft Corporation</organization>
120    <address>
121      <postal>
122        <street>1 Microsoft Way</street>
123        <city>Redmond</city>
124        <region>WA</region>
125        <code>98052</code>
126      </postal>
127      <email>paulle@microsoft.com</email>
128    </address>
129  </author>
130   
131  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
132    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
133    <address>
134      <postal>
135        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
136        <street>The Stata Center, Building 32</street>
137        <street>32 Vassar Street</street>
138        <city>Cambridge</city>
139        <region>MA</region>
140        <code>02139</code>
141        <country>USA</country>
142      </postal>
143      <email>timbl@w3.org</email>
144      <uri>http://www.w3.org/People/Berners-Lee/</uri>
145    </address>
146  </author>
147
148  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
149    <organization abbrev="W3C">World Wide Web Consortium</organization>
150    <address>
151      <postal>
152        <street>W3C / ERCIM</street>
153        <street>2004, rte des Lucioles</street>
154        <city>Sophia-Antipolis</city>
155        <region>AM</region>
156        <code>06902</code>
157        <country>France</country>
158      </postal>
159      <email>ylafon@w3.org</email>
160      <uri>http://www.raubacapeu.net/people/yves/</uri>
161    </address>
162  </author>
163
164  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
165    <organization abbrev="greenbytes">greenbytes GmbH</organization>
166    <address>
167      <postal>
168        <street>Hafenweg 16</street>
169        <city>Muenster</city><region>NW</region><code>48155</code>
170        <country>Germany</country>
171      </postal>
172      <phone>+49 251 2807760</phone>   
173      <facsimile>+49 251 2807761</facsimile>   
174      <email>julian.reschke@greenbytes.de</email>       
175      <uri>http://greenbytes.de/tech/webdav/</uri>     
176    </address>
177  </author>
178
179  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
180
181<abstract>
182<t>
183   The Hypertext Transfer Protocol (HTTP) is an application-level
184   protocol for distributed, collaborative, hypermedia information
185   systems. HTTP has been in use by the World Wide Web global information
186   initiative since 1990. This document is Part 5 of the seven-part specification
187   that defines the protocol referred to as "HTTP/1.1" and, taken together,
188   obsoletes RFC 2616.  Part 5 defines range-specific requests and
189   the rules for constructing and combining responses to those requests.
190</t>
191</abstract>
192
193<note title="Editorial Note (To be removed by RFC Editor)">
194  <t>
195    Discussion of this draft should take place on the HTTPBIS working group
196    mailing list (ietf-http-wg@w3.org). The current issues list is
197    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
198    and related documents (including fancy diffs) can be found at
199    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
200  </t>
201  <t>
202    The changes in this draft are summarized in <xref target="changes.since.04"/>.
203  </t>
204</note>
205</front>
206<middle>
207<section title="Introduction" anchor="introduction">
208<t>
209   HTTP clients often encounter interrupted data transfers as a result
210   of cancelled requests or dropped connections.  When a cache has stored
211   a partial representation, it is desirable to request the remainder
212   of that representation in a subsequent request rather than transfer
213   the entire representation.
214   There are also a number of Web applications that benefit from being
215   able to request only a subset of a larger representation, such as a
216   single page of a very large document or only part of an image to be
217   rendered by a device with limited local storage.
218</t>
219<t>
220   This document defines HTTP/1.1 range requests,
221   partial responses, and the multipart/byteranges media type.
222   The protocol for range requests is an &OPTIONAL; feature of HTTP,
223   designed so resources or recipients that do not implement this feature
224   can respond as if it is a normal GET request without impacting
225   interoperability.  Partial responses are indicated by a distinct status
226   code to not be mistaken for full responses by intermediate caches
227   that might not implement the feature.
228</t>
229<t>
230   Although the HTTP range request mechanism is designed to allow for
231   extensible range types, this specification only defines requests for
232   byte ranges.
233</t>
234
235<section title="Requirements" anchor="intro.requirements">
236<t>
237   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
238   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
239   document are to be interpreted as described in <xref target="RFC2119"/>.
240</t>
241<t>
242   An implementation is not compliant if it fails to satisfy one or more
243   of the &MUST; or &REQUIRED; level requirements for the protocols it
244   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
245   level and all the &SHOULD; level requirements for its protocols is said
246   to be "unconditionally compliant"; one that satisfies all the &MUST;
247   level requirements but not all the &SHOULD; level requirements for its
248   protocols is said to be "conditionally compliant."
249</t>
250</section>
251</section>
252
253<section title="Notational Conventions and Generic Grammar" anchor="notation">
254  <x:anchor-alias value="CHAR"/>
255  <x:anchor-alias value="DIGIT"/>
256  <x:anchor-alias value="SP"/>
257  <x:anchor-alias value="token"/>
258<t>
259  This specification uses the ABNF syntax defined in &notation-abnf; and
260  the core rules defined in &basic-rules;:
261  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
262  <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>.</cref>
263</t>
264<figure><artwork type="abnf2616">
265  <x:ref>DIGIT</x:ref>      = &lt;DIGIT, defined in &basic-rules;&gt;
266  <x:ref>SP</x:ref>         = &lt;SP, defined in &basic-rules;&gt;
267</artwork></figure>
268<figure><artwork type="abnf2616">
269  <x:ref>token</x:ref>      = &lt;token, defined in &basic-rules;&gt;
270</artwork></figure>
271<t anchor="abnf.dependencies">
272  <x:anchor-alias value="entity-tag"/>
273  <x:anchor-alias value="HTTP-date"/>
274  The ABNF rules below are defined in other parts:
275</t>
276<figure><!--Part1--><artwork type="abnf2616">
277  <x:ref>HTTP-date</x:ref>  = &lt;HTTP-date, defined in &full-date;&gt;
278</artwork></figure>
279<figure><!--Part4--><artwork type="abnf2616">
280  <x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in &entity-tags;&gt;
281</artwork></figure>
282</section>
283
284<section title="Range Units" anchor="range.units">
285  <x:anchor-alias value="bytes-unit"/>
286  <x:anchor-alias value="other-range-unit"/>
287  <x:anchor-alias value="range-unit"/>
288<t>
289   HTTP/1.1 allows a client to request that only part (a range of) the
290   response entity be included within the response. HTTP/1.1 uses range
291   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
292   header fields. An entity can be broken down into subranges according
293   to various structural units.
294</t>
295<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"/>
296  <x:ref>range-unit</x:ref>       = <x:ref>bytes-unit</x:ref> / <x:ref>other-range-unit</x:ref>
297  <x:ref>bytes-unit</x:ref>       = "bytes"
298  <x:ref>other-range-unit</x:ref> = <x:ref>token</x:ref>
299</artwork></figure>
300<t>
301  HTTP/1.1 has been designed to allow implementations of applications
302  that do not depend on knowledge of ranges. The only range unit defined
303  by HTTP/1.1 is "bytes".
304</t>
305<t>
306  If a range unit is not understood in a request, a server &MUST; ignore
307  the whole Range header (<xref target="header.range" />).
308  If a range unit is not understood in a response, an intermediary
309  &SHOULD; pass the response to the client; a client &MUST; fail.
310</t>
311</section>
312
313<section title="Status Code Definitions">
314<section title="206 Partial Content" anchor="status.206">
315  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
316  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
317<t>
318   The server has fulfilled the partial GET request for the resource.
319   The request &MUST; have included a Range header field (<xref target="header.range"/>)
320   indicating the desired range, and &MAY; have included an If-Range
321   header field (<xref target="header.if-range"/>) to make the request conditional.
322</t>
323<t>
324   The response &MUST; include the following header fields:
325  <list style="symbols">
326    <t>
327        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
328        the range included with this response, or a multipart/byteranges
329        Content-Type including Content-Range fields for each part. If a
330        Content-Length header field is present in the response, its
331        value &MUST; match the actual number of OCTETs transmitted in the
332        message-body.
333    </t>
334    <t>
335        Date
336    </t>
337    <t>
338        ETag and/or Content-Location, if the header would have been sent
339        in a 200 response to the same request
340    </t>
341    <t>
342        Expires, Cache-Control, and/or Vary, if the field-value might
343        differ from that sent in any previous response for the same
344        variant
345    </t>
346  </list>
347</t>
348<t>
349   If the 206 response is the result of an If-Range request, the response
350   &SHOULD-NOT; include other entity-headers. Otherwise, the response
351   &MUST; include all of the entity-headers that would have been returned
352   with a 200 (OK) response to the same request.
353</t>
354<t>
355   A cache &MUST-NOT; combine a 206 response with other previously cached
356   content if the ETag or Last-Modified headers do not match exactly,
357   see <xref target="combining.byte.ranges"/>.
358</t>
359<t>
360   A cache that does not support the Range and Content-Range headers or
361   the range unit &MUST-NOT; cache 206 (Partial Content) responses.
362</t>
363</section>
364
365<section title="416 Requested Range Not Satisfiable" anchor="status.416">
366  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
367  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
368<t>
369   A server &SHOULD; return a response with this status code if a request
370   included a Range request-header field (<xref target="header.range"/>), and none of
371   the ranges-specifier values in this field overlap the current extent
372   of the selected resource, and the request did not include an If-Range
373   request-header field. (For byte-ranges, this means that the first-byte-pos
374   of all of the byte-range-spec values were greater than the
375   current length of the selected resource.)
376</t>
377<t>
378   When this status code is returned for a byte-range request, the
379   response &SHOULD; include a Content-Range entity-header field
380   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
381   This response &MUST-NOT; use the multipart/byteranges content-type.
382</t>
383</section>
384</section>
385
386<section title="Combining Ranges" anchor="combining.byte.ranges">
387<t>
388  A response might transfer only a subrange of an entity-body, either
389  the request included one or more Range specifications, or because
390  a connection was broken prematurely.
391  After several such transfers, a cache might have received several
392  ranges of the same entity-body.
393</t>
394<t>
395   If a cache has a stored non-empty set of subranges for an entity, and
396   an incoming response transfers another subrange, the cache &MAY;
397   combine the new subrange with the existing set if both the following
398   conditions are met:
399  <list style="symbols">
400    <t>Both the incoming response and the cache entry have a cache
401        validator.</t>
402    <t>The two cache validators match using the strong comparison
403        function (see &weak-and-strong-validators;).</t>
404  </list>
405</t>
406<t>
407   If either requirement is not met, the cache &MUST; use only the most
408   recent partial response (based on the Date values transmitted with
409   every response, and using the incoming response if these values are
410   equal or missing), and &MUST; discard the other partial information.
411</t>
412</section>
413
414<section title="Header Field Definitions" anchor="header.fields">
415<t>
416   This section defines the syntax and semantics of HTTP/1.1 header fields
417   related to range requests and partial responses.
418</t>
419<t>
420   For entity-header fields, both sender and recipient refer to either the
421   client or the server, depending on who sends and who receives the entity.
422</t>
423
424<section title="Accept-Ranges" anchor="header.accept-ranges">
425  <iref primary="true" item="Accept-Ranges header" x:for-anchor=""/>
426  <iref primary="true" item="Headers" subitem="Accept-Ranges" x:for-anchor=""/>
427  <x:anchor-alias value="Accept-Ranges"/>
428  <x:anchor-alias value="acceptable-ranges"/>
429<t>
430      The Accept-Ranges response-header field allows the server to
431      indicate its acceptance of range requests for a resource:
432</t>
433<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/>
434  <x:ref>Accept-Ranges</x:ref>     = "Accept-Ranges" ":" <x:ref>acceptable-ranges</x:ref>
435  <x:ref>acceptable-ranges</x:ref> = 1#<x:ref>range-unit</x:ref> / "none"
436</artwork></figure>
437<t>
438      Origin servers that accept byte-range requests &MAY; send
439</t>
440<figure><artwork type="example">
441       Accept-Ranges: bytes
442</artwork></figure>
443<t>
444  but are not required to do so. Clients &MAY; generate range
445  requests without having received this header for the resource
446  involved. Range units are defined in <xref target="range.units"/>.
447</t>
448<t>
449      Servers that do not accept any kind of range request for a
450      resource &MAY; send
451</t>
452<figure><artwork type="example">
453       Accept-Ranges: none
454</artwork></figure>
455<t>
456      to advise the client not to attempt a range request.
457</t>
458</section>
459
460<section title="Content-Range" anchor="header.content-range">
461  <iref primary="true" item="Content-Range header" x:for-anchor=""/>
462  <iref primary="true" item="Headers" subitem="Content-Range" x:for-anchor=""/>
463  <x:anchor-alias value="byte-content-range-spec"/>
464  <x:anchor-alias value="byte-range-resp-spec"/>
465  <x:anchor-alias value="Content-Range"/>
466  <x:anchor-alias value="content-range-spec"/>
467  <x:anchor-alias value="instance-length"/>
468  <x:anchor-alias value="other-content-range-spec"/>
469  <x:anchor-alias value="other-range-resp-spec"/>
470<t>
471   The Content-Range entity-header is sent with a partial entity-body to
472   specify where in the full entity-body the partial body should be
473   applied. Range units are defined in <xref target="range.units"/>.
474</t>
475<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Range"/><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"/>
476  <x:ref>Content-Range</x:ref> = "Content-Range" ":" <x:ref>content-range-spec</x:ref>
477 
478  <x:ref>content-range-spec</x:ref>       = <x:ref>byte-content-range-spec</x:ref>
479                             / <x:ref>other-content-range-spec</x:ref>
480  <x:ref>byte-content-range-spec</x:ref>  = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
481                             <x:ref>byte-range-resp-spec</x:ref> "/"
482                             ( <x:ref>instance-length</x:ref> / "*" )
483 
484  <x:ref>byte-range-resp-spec</x:ref>     = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
485                             / "*"
486                         
487  <x:ref>instance-length</x:ref>          = 1*<x:ref>DIGIT</x:ref>
488 
489  <x:ref>other-content-range-spec</x:ref> = <x:ref>other-range-unit</x:ref> <x:ref>SP</x:ref>
490                             <x:ref>other-range-resp-spec</x:ref>
491  <x:ref>other-range-resp-spec</x:ref>    = *<x:ref>CHAR</x:ref>
492</artwork></figure>
493<t>
494   The header &SHOULD; indicate the total length of the full entity-body,
495   unless this length is unknown or difficult to determine. The asterisk
496   "*" character means that the instance-length is unknown at the time
497   when the response was generated.
498</t>
499<t>
500   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
501   &MUST; only specify one range, and &MUST; contain
502   absolute byte positions for both the first and last byte of the
503   range.
504</t>
505<t>
506   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
507   value is less than its first-byte-pos value, or whose
508   instance-length value is less than or equal to its last-byte-pos
509   value, is invalid. The recipient of an invalid byte-content-range-spec
510   &MUST; ignore it and any content transferred along with it.
511</t>
512<t>
513  In the case of a byte range request: A server sending a response with
514  status code 416 (Requested range not satisfiable) &SHOULD; include a
515  Content-Range field with a byte-range-resp-spec of "*".
516  The instance-length specifies the current length of the selected resource.
517  A response with status code 206 (Partial Content) &MUST-NOT; include a
518  Content-Range field with a byte-range-resp-spec of "*".
519</t>
520<t>
521   Examples of byte-content-range-spec values, assuming that the entity
522   contains a total of 1234 bytes:
523   <list style="symbols">
524      <t>
525        The first 500 bytes:
526<figure><artwork type="text/plain">
527   bytes 0-499/1234
528</artwork></figure>
529      </t>   
530      <t>
531        The second 500 bytes:
532<figure><artwork type="text/plain">
533   bytes 500-999/1234
534</artwork></figure>
535      </t>   
536      <t>
537        All except for the first 500 bytes:
538<figure><artwork type="text/plain">
539   bytes 500-1233/1234
540</artwork></figure>
541      </t>   
542      <t>
543        The last 500 bytes:
544<figure><artwork type="text/plain">
545   bytes 734-1233/1234
546</artwork></figure>
547      </t>   
548   </list>
549</t>
550<t>
551   When an HTTP message includes the content of a single range (for
552   example, a response to a request for a single range, or to a request
553   for a set of ranges that overlap without any holes), this content is
554   transmitted with a Content-Range header, and a Content-Length header
555   showing the number of bytes actually transferred. For example,
556</t>
557<figure><artwork type="example">
558    HTTP/1.1 206 Partial Content
559    Date: Wed, 15 Nov 1995 06:25:24 GMT
560    Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
561    Content-Range: bytes 21010-47021/47022
562    Content-Length: 26012
563    Content-Type: image/gif
564</artwork></figure>
565<t>
566   When an HTTP message includes the content of multiple ranges (for
567   example, a response to a request for multiple non-overlapping
568   ranges), these are transmitted as a multipart message. The multipart
569   media type used for this purpose is "multipart/byteranges" as defined
570   in <xref target="internet.media.type.multipart.byteranges"/>. See <xref target="changes.from.rfc.2068"/> for a compatibility issue.
571</t>
572<t>
573   A response to a request for a single range &MUST-NOT; be sent using the
574   multipart/byteranges media type.  A response to a request for
575   multiple ranges, whose result is a single range, &MAY; be sent as a
576   multipart/byteranges media type with one part. A client that cannot
577   decode a multipart/byteranges message &MUST-NOT; ask for multiple
578   ranges in a single request.
579</t>
580<t>
581   When a client requests multiple byte-ranges in one request, the
582   server &SHOULD; return them in the order that they appeared in the
583   request.
584</t>
585<t>
586   If the server ignores a byte-range-spec because it is syntactically
587   invalid, the server &SHOULD; treat the request as if the invalid Range
588   header field did not exist. (Normally, this means return a 200
589   response containing the full entity).
590</t>
591<t>
592   If the server receives a request (other than one including an If-Range
593   request-header field) with an unsatisfiable Range request-header
594   field (that is, all of whose byte-range-spec values have a
595   first-byte-pos value greater than the current length of the selected
596   resource), it &SHOULD; return a response code of 416 (Requested range
597   not satisfiable) (<xref target="status.416"/>).
598  <list><t>
599      <x:h>Note:</x:h> clients cannot depend on servers to send a 416 (Requested
600      range not satisfiable) response instead of a 200 (OK) response for
601      an unsatisfiable Range request-header, since not all servers
602      implement this request-header.
603  </t></list>
604</t>
605</section>
606
607<section title="If-Range" anchor="header.if-range">
608  <iref primary="true" item="If-Range header" x:for-anchor=""/>
609  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
610  <x:anchor-alias value="If-Range"/>
611<t>
612   If a client has a partial copy of an entity in its cache, and wishes
613   to have an up-to-date copy of the entire entity in its cache, it
614   could use the Range request-header with a conditional GET (using
615   either or both of If-Unmodified-Since and If-Match.) However, if the
616   condition fails because the entity has been modified, the client
617   would then have to make a second request to obtain the entire current
618   entity-body.
619</t>
620<t>
621   The If-Range header allows a client to "short-circuit" the second
622   request. Informally, its meaning is `if the entity is unchanged, send
623   me the part(s) that I am missing; otherwise, send me the entire new
624   entity'.
625</t>
626<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/>
627  <x:ref>If-Range</x:ref> = "If-Range" ":" ( <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref> )
628</artwork></figure>
629<t>
630   If the client has no entity tag for an entity, but does have a Last-Modified
631   date, it &MAY; use that date in an If-Range header. (The
632   server can distinguish between a valid HTTP-date and any form of
633   entity-tag by examining no more than two characters.) The If-Range
634   header &SHOULD; only be used together with a Range header, and &MUST; be
635   ignored if the request does not include a Range header, or if the
636   server does not support the sub-range operation.
637</t>
638<t>
639   If the entity tag given in the If-Range header matches the current
640   entity tag for the entity, then the server &SHOULD; provide the
641   specified sub-range of the entity using a 206 (Partial Content)
642   response. If the entity tag does not match, then the server &SHOULD;
643   return the entire entity using a 200 (OK) response.
644</t>
645</section>
646
647<section title="Range" anchor="header.range">
648  <iref primary="true" item="Range header" x:for-anchor=""/>
649  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
650
651<section title="Byte Ranges" anchor="byte.ranges">
652<t>
653   Since all HTTP entities are represented in HTTP messages as sequences
654   of bytes, the concept of a byte range is meaningful for any HTTP
655   entity. (However, not all clients and servers need to support byte-range
656   operations.)
657</t>
658<t>
659   Byte range specifications in HTTP apply to the sequence of bytes in
660   the entity-body (not necessarily the same as the message-body).
661</t>
662<t anchor="rule.ranges-specifier">
663  <x:anchor-alias value="byte-range-set"/>
664  <x:anchor-alias value="byte-range-spec"/>
665  <x:anchor-alias value="byte-ranges-specifier"/>
666  <x:anchor-alias value="first-byte-pos"/>
667  <x:anchor-alias value="last-byte-pos"/>
668  <x:anchor-alias value="ranges-specifier"/>
669  <x:anchor-alias value="suffix-byte-range-spec"/>
670  <x:anchor-alias value="suffix-length"/>
671  <x:anchor-alias value="other-ranges-specifier"/>
672
673   A byte range operation &MAY; specify a single range of bytes, or a set
674   of ranges within a single entity.
675</t>
676<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"/>
677  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
678  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
679  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [<x:ref>last-byte-pos</x:ref>]
680  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
681  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
682</artwork></figure>
683<t>
684   The first-byte-pos value in a byte-range-spec gives the byte-offset
685   of the first byte in a range. The last-byte-pos value gives the
686   byte-offset of the last byte in the range; that is, the byte
687   positions specified are inclusive. Byte offsets start at zero.
688</t>
689<t>
690   If the last-byte-pos value is present, it &MUST; be greater than or
691   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
692   is syntactically invalid. The recipient of a byte-range-set
693   that includes one or more syntactically invalid byte-range-spec
694   values &MUST; ignore the header field that includes that byte-range-set.
695</t>
696<t>
697   If the last-byte-pos value is absent, or if the value is greater than
698   or equal to the current length of the entity-body, last-byte-pos is
699   taken to be equal to one less than the current length of the entity-body
700   in bytes.
701</t>
702<t>
703   By its choice of last-byte-pos, a client can limit the number of
704   bytes retrieved without knowing the size of the entity.
705</t>
706<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
707  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
708  <x:ref>suffix-length</x:ref>          = 1*<x:ref>DIGIT</x:ref>
709</artwork></figure>
710<t>
711   A suffix-byte-range-spec is used to specify the suffix of the
712   entity-body, of a length given by the suffix-length value. (That is,
713   this form specifies the last N bytes of an entity-body.) If the
714   entity is shorter than the specified suffix-length, the entire
715   entity-body is used.
716</t>
717<t>
718   If a syntactically valid byte-range-set includes at least one byte-range-spec
719   whose first-byte-pos is less than the current length of
720   the entity-body, or at least one suffix-byte-range-spec with a non-zero
721   suffix-length, then the byte-range-set is satisfiable.
722   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
723   is unsatisfiable, the server &SHOULD; return a response with a status
724   of 416 (Requested range not satisfiable). Otherwise, the server
725   &SHOULD; return a response with a status of 206 (Partial Content)
726   containing the satisfiable ranges of the entity-body.
727</t>
728<t>
729   Examples of byte-ranges-specifier values (assuming an entity-body of
730   length 10000):
731  <list style="symbols">
732     <t>The first 500 bytes (byte offsets 0-499, inclusive):  bytes=0-499</t>
733
734     <t>The second 500 bytes (byte offsets 500-999, inclusive):
735        bytes=500-999</t>
736
737     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
738        bytes=-500</t>
739
740     <t>Or bytes=9500-</t>
741
742     <t>The first and last bytes only (bytes 0 and 9999):  bytes=0-0,-1</t>
743
744     <t>Several legal but not canonical specifications of the second 500
745        bytes (byte offsets 500-999, inclusive):
746        <vspace/>
747         bytes=500-600,601-999<vspace/>
748         bytes=500-700,601-999</t>
749  </list>
750</t>
751</section>
752
753<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
754  <x:anchor-alias value="Range"/>
755<t>
756   HTTP retrieval requests using conditional or unconditional GET
757   methods &MAY; request one or more sub-ranges of the entity, instead of
758   the entire entity, using the Range request header, which applies to
759   the entity returned as the result of the request:
760</t>
761<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/>
762  <x:ref>Range</x:ref> = "Range" ":" <x:ref>ranges-specifier</x:ref>
763  <x:ref>ranges-specifier</x:ref>       = <x:ref>byte-ranges-specifier</x:ref>
764                           / <x:ref>other-ranges-specifier</x:ref>
765  <x:ref>other-ranges-specifier</x:ref> = 1*<x:ref>CHAR</x:ref>
766</artwork></figure>
767<t>
768   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
769   servers and intermediate caches ought to support byte ranges when
770   possible, since Range supports efficient recovery from partially
771   failed transfers, and supports efficient partial retrieval of large
772   entities.
773</t>
774<t>
775   If the server supports the Range header and the specified range or
776   ranges are appropriate for the entity:
777  <list style="symbols">
778     <t>The presence of a Range header in an unconditional GET modifies
779        what is returned if the GET is otherwise successful. In other
780        words, the response carries a status code of 206 (Partial
781        Content) instead of 200 (OK).</t>
782
783     <t>The presence of a Range header in a conditional GET (a request
784        using one or both of If-Modified-Since and If-None-Match, or
785        one or both of If-Unmodified-Since and If-Match) modifies what
786        is returned if the GET is otherwise successful and the
787        condition is true. It does not affect the 304 (Not Modified)
788        response returned if the conditional is false.</t>
789  </list>
790</t>
791<t>
792   In some cases, it might be more appropriate to use the If-Range
793   header (see <xref target="header.if-range"/>) in addition to the Range header.
794</t>
795<t>
796   If a proxy that supports ranges receives a Range request, forwards
797   the request to an inbound server, and receives an entire entity in
798   reply, it &SHOULD; only return the requested range to its client. It
799   &SHOULD; store the entire received response in its cache if that is
800   consistent with its cache allocation policies.
801</t>
802</section>
803</section>
804</section>
805
806<section title="IANA Considerations" anchor="IANA.considerations">
807<section title="Message Header Registration" anchor="message.header.registration">
808<t>
809   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
810   with the permanent registrations below (see <xref target="RFC3864"/>):
811</t>
812<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
813<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
814   <ttcol>Header Field Name</ttcol>
815   <ttcol>Protocol</ttcol>
816   <ttcol>Status</ttcol>
817   <ttcol>Reference</ttcol>
818
819   <c>Accept-Ranges</c>
820   <c>http</c>
821   <c>standard</c>
822   <c>
823      <xref target="header.accept-ranges"/>
824   </c>
825   <c>Content-Range</c>
826   <c>http</c>
827   <c>standard</c>
828   <c>
829      <xref target="header.content-range"/>
830   </c>
831   <c>If-Range</c>
832   <c>http</c>
833   <c>standard</c>
834   <c>
835      <xref target="header.if-range"/>
836   </c>
837   <c>Range</c>
838   <c>http</c>
839   <c>standard</c>
840   <c>
841      <xref target="header.range"/>
842   </c>
843</texttable>
844<!--(END)-->
845<t>
846   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
847</t>
848</section>
849</section>
850
851<section title="Security Considerations" anchor="security.considerations">
852<t>
853   No additional security considerations have been identified beyond
854   those applicable to HTTP in general &messaging;.
855</t>
856</section>
857
858<section title="Acknowledgments" anchor="ack">
859<t>
860   Most of the specification of ranges is based on work originally done
861   by Ari Luotonen and John Franks, with additional input from Steve
862   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
863   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
864   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
865</t>
866</section>
867</middle>
868<back>
869
870<references title="Normative References">
871
872<reference anchor="Part1">
873  <front>
874    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
875    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
876      <organization abbrev="Day Software">Day Software</organization>
877      <address><email>fielding@gbiv.com</email></address>
878    </author>
879    <author initials="J." surname="Gettys" fullname="Jim Gettys">
880      <organization>One Laptop per Child</organization>
881      <address><email>jg@laptop.org</email></address>
882    </author>
883    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
884      <organization abbrev="HP">Hewlett-Packard Company</organization>
885      <address><email>JeffMogul@acm.org</email></address>
886    </author>
887    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
888      <organization abbrev="Microsoft">Microsoft Corporation</organization>
889      <address><email>henrikn@microsoft.com</email></address>
890    </author>
891    <author initials="L." surname="Masinter" fullname="Larry Masinter">
892      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
893      <address><email>LMM@acm.org</email></address>
894    </author>
895    <author initials="P." surname="Leach" fullname="Paul J. Leach">
896      <organization abbrev="Microsoft">Microsoft Corporation</organization>
897      <address><email>paulle@microsoft.com</email></address>
898    </author>
899    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
900      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
901      <address><email>timbl@w3.org</email></address>
902    </author>
903    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
904      <organization abbrev="W3C">World Wide Web Consortium</organization>
905      <address><email>ylafon@w3.org</email></address>
906    </author>
907    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
908      <organization abbrev="greenbytes">greenbytes GmbH</organization>
909      <address><email>julian.reschke@greenbytes.de</email></address>
910    </author>
911    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
912  </front>
913  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
914  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
915</reference>
916
917<reference anchor="Part3">
918  <front>
919    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
920    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
921      <organization abbrev="Day Software">Day Software</organization>
922      <address><email>fielding@gbiv.com</email></address>
923    </author>
924    <author initials="J." surname="Gettys" fullname="Jim Gettys">
925      <organization>One Laptop per Child</organization>
926      <address><email>jg@laptop.org</email></address>
927    </author>
928    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
929      <organization abbrev="HP">Hewlett-Packard Company</organization>
930      <address><email>JeffMogul@acm.org</email></address>
931    </author>
932    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
933      <organization abbrev="Microsoft">Microsoft Corporation</organization>
934      <address><email>henrikn@microsoft.com</email></address>
935    </author>
936    <author initials="L." surname="Masinter" fullname="Larry Masinter">
937      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
938      <address><email>LMM@acm.org</email></address>
939    </author>
940    <author initials="P." surname="Leach" fullname="Paul J. Leach">
941      <organization abbrev="Microsoft">Microsoft Corporation</organization>
942      <address><email>paulle@microsoft.com</email></address>
943    </author>
944    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
945      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
946      <address><email>timbl@w3.org</email></address>
947    </author>
948    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
949      <organization abbrev="W3C">World Wide Web Consortium</organization>
950      <address><email>ylafon@w3.org</email></address>
951    </author>
952    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
953      <organization abbrev="greenbytes">greenbytes GmbH</organization>
954      <address><email>julian.reschke@greenbytes.de</email></address>
955    </author>
956    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
957  </front>
958  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
959  <x:source href="p3-payload.xml" basename="p3-payload"/>
960</reference>
961
962<reference anchor="Part4">
963  <front>
964    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
965    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
966      <organization abbrev="Day Software">Day Software</organization>
967      <address><email>fielding@gbiv.com</email></address>
968    </author>
969    <author initials="J." surname="Gettys" fullname="Jim Gettys">
970      <organization>One Laptop per Child</organization>
971      <address><email>jg@laptop.org</email></address>
972    </author>
973    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
974      <organization abbrev="HP">Hewlett-Packard Company</organization>
975      <address><email>JeffMogul@acm.org</email></address>
976    </author>
977    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
978      <organization abbrev="Microsoft">Microsoft Corporation</organization>
979      <address><email>henrikn@microsoft.com</email></address>
980    </author>
981    <author initials="L." surname="Masinter" fullname="Larry Masinter">
982      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
983      <address><email>LMM@acm.org</email></address>
984    </author>
985    <author initials="P." surname="Leach" fullname="Paul J. Leach">
986      <organization abbrev="Microsoft">Microsoft Corporation</organization>
987      <address><email>paulle@microsoft.com</email></address>
988    </author>
989    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
990      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
991      <address><email>timbl@w3.org</email></address>
992    </author>
993    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
994      <organization abbrev="W3C">World Wide Web Consortium</organization>
995      <address><email>ylafon@w3.org</email></address>
996    </author>
997    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
998      <organization abbrev="greenbytes">greenbytes GmbH</organization>
999      <address><email>julian.reschke@greenbytes.de</email></address>
1000    </author>
1001    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1002  </front>
1003  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1004  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1005</reference>
1006
1007<reference anchor="Part6">
1008  <front>
1009    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1010    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1011      <organization abbrev="Day Software">Day Software</organization>
1012      <address><email>fielding@gbiv.com</email></address>
1013    </author>
1014    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1015      <organization>One Laptop per Child</organization>
1016      <address><email>jg@laptop.org</email></address>
1017    </author>
1018    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1019      <organization abbrev="HP">Hewlett-Packard Company</organization>
1020      <address><email>JeffMogul@acm.org</email></address>
1021    </author>
1022    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1023      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1024      <address><email>henrikn@microsoft.com</email></address>
1025    </author>
1026    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1027      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1028      <address><email>LMM@acm.org</email></address>
1029    </author>
1030    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1031      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1032      <address><email>paulle@microsoft.com</email></address>
1033    </author>
1034    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1035      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1036      <address><email>timbl@w3.org</email></address>
1037    </author>
1038    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1039      <organization abbrev="W3C">World Wide Web Consortium</organization>
1040      <address><email>ylafon@w3.org</email></address>
1041    </author>
1042    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1043      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1044      <address><email>julian.reschke@greenbytes.de</email></address>
1045    </author>
1046    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1047  </front>
1048  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1049  <x:source href="p6-cache.xml" basename="p6-cache"/>
1050</reference>
1051
1052<reference anchor="RFC2046">
1053  <front>
1054    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1055    <author initials="N." surname="Freed" fullname="Ned Freed">
1056      <organization>Innosoft International, Inc.</organization>
1057      <address><email>ned@innosoft.com</email></address>
1058    </author>
1059    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1060      <organization>First Virtual Holdings</organization>
1061      <address><email>nsb@nsb.fv.com</email></address>
1062    </author>
1063    <date month="November" year="1996"/>
1064  </front>
1065  <seriesInfo name="RFC" value="2046"/>
1066</reference>
1067
1068<reference anchor="RFC2119">
1069  <front>
1070    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1071    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1072      <organization>Harvard University</organization>
1073      <address><email>sob@harvard.edu</email></address>
1074    </author>
1075    <date month="March" year="1997"/>
1076  </front>
1077  <seriesInfo name="BCP" value="14"/>
1078  <seriesInfo name="RFC" value="2119"/>
1079</reference>
1080
1081</references>
1082
1083<references title="Informative References">
1084
1085<reference anchor="RFC2616">
1086  <front>
1087    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1088    <author initials="R." surname="Fielding" fullname="R. Fielding">
1089      <organization>University of California, Irvine</organization>
1090      <address><email>fielding@ics.uci.edu</email></address>
1091    </author>
1092    <author initials="J." surname="Gettys" fullname="J. Gettys">
1093      <organization>W3C</organization>
1094      <address><email>jg@w3.org</email></address>
1095    </author>
1096    <author initials="J." surname="Mogul" fullname="J. Mogul">
1097      <organization>Compaq Computer Corporation</organization>
1098      <address><email>mogul@wrl.dec.com</email></address>
1099    </author>
1100    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1101      <organization>MIT Laboratory for Computer Science</organization>
1102      <address><email>frystyk@w3.org</email></address>
1103    </author>
1104    <author initials="L." surname="Masinter" fullname="L. Masinter">
1105      <organization>Xerox Corporation</organization>
1106      <address><email>masinter@parc.xerox.com</email></address>
1107    </author>
1108    <author initials="P." surname="Leach" fullname="P. Leach">
1109      <organization>Microsoft Corporation</organization>
1110      <address><email>paulle@microsoft.com</email></address>
1111    </author>
1112    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1113      <organization>W3C</organization>
1114      <address><email>timbl@w3.org</email></address>
1115    </author>
1116    <date month="June" year="1999"/>
1117  </front>
1118  <seriesInfo name="RFC" value="2616"/>
1119</reference>
1120
1121<reference anchor='RFC3864'>
1122  <front>
1123    <title>Registration Procedures for Message Header Fields</title>
1124    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1125      <organization>Nine by Nine</organization>
1126      <address><email>GK-IETF@ninebynine.org</email></address>
1127    </author>
1128    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1129      <organization>BEA Systems</organization>
1130      <address><email>mnot@pobox.com</email></address>
1131    </author>
1132    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1133      <organization>HP Labs</organization>
1134      <address><email>JeffMogul@acm.org</email></address>
1135    </author>
1136    <date year='2004' month='September' />
1137  </front>
1138  <seriesInfo name='BCP' value='90' />
1139  <seriesInfo name='RFC' value='3864' />
1140</reference>
1141
1142<reference anchor="RFC4288">
1143  <front>
1144    <title>Media Type Specifications and Registration Procedures</title>
1145    <author initials="N." surname="Freed" fullname="N. Freed">
1146      <organization>Sun Microsystems</organization>
1147      <address>
1148        <email>ned.freed@mrochek.com</email>
1149      </address>
1150    </author>
1151    <author initials="J." surname="Klensin" fullname="J. Klensin">
1152      <organization/>
1153      <address>
1154        <email>klensin+ietf@jck.com</email>
1155      </address>
1156    </author>
1157    <date year="2005" month="December"/>
1158  </front>
1159  <seriesInfo name="BCP" value="13"/>
1160  <seriesInfo name="RFC" value="4288"/>
1161</reference>
1162
1163</references>
1164
1165<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1166<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1167<iref item="multipart/byteranges Media Type" primary="true"/>
1168<t>
1169   When an HTTP 206 (Partial Content) response message includes the
1170   content of multiple ranges (a response to a request for multiple
1171   non-overlapping ranges), these are transmitted as a multipart
1172   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1173   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1174</t><t>
1175   The multipart/byteranges media type includes one or more parts, each
1176   with its own Content-Type and Content-Range fields. The required
1177   boundary parameter specifies the boundary string used to separate
1178   each body-part.
1179</t>
1180<t>
1181  <list style="hanging" x:indent="12em">
1182    <t hangText="Type name:">
1183      multipart
1184    </t>
1185    <t hangText="Subtype name:">
1186      byteranges
1187    </t>
1188    <t hangText="Required parameters:">
1189      boundary
1190    </t>
1191    <t hangText="Optional parameters:">
1192      none
1193    </t>
1194    <t hangText="Encoding considerations:">
1195      only "7bit", "8bit", or "binary" are permitted
1196    </t>
1197    <t hangText="Security considerations:">
1198      none
1199    </t>
1200    <t hangText="Interoperability considerations:">
1201      none
1202    </t>
1203    <t hangText="Published specification:">
1204      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1205    </t>
1206    <t hangText="Applications that use this media type:">
1207    </t>
1208    <t hangText="Additional information:">
1209      <list style="hanging">
1210        <t hangText="Magic number(s):">none</t>
1211        <t hangText="File extension(s):">none</t>
1212        <t hangText="Macintosh file type code(s):">none</t>
1213      </list>
1214    </t>
1215    <t hangText="Person and email address to contact for further information:">
1216      See Authors Section.
1217    </t>
1218                <t hangText="Intended usage:">
1219                  COMMON
1220    </t>
1221                <t hangText="Restrictions on usage:">
1222                  none
1223    </t>
1224    <t hangText="Author/Change controller:">
1225      IESG
1226    </t>
1227  </list>
1228</t>
1229<figure><preamble>
1230   For example:
1231</preamble><artwork type="example">
1232   HTTP/1.1 206 Partial Content
1233   Date: Wed, 15 Nov 1995 06:25:24 GMT
1234   Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1235   Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1236
1237   --THIS_STRING_SEPARATES
1238   Content-type: application/pdf
1239   Content-range: bytes 500-999/8000
1240
1241   ...the first range...
1242   --THIS_STRING_SEPARATES
1243   Content-type: application/pdf
1244   Content-range: bytes 7000-7999/8000
1245
1246   ...the second range
1247   --THIS_STRING_SEPARATES--
1248</artwork></figure>
1249<t>
1250      Notes:
1251  <list style="numbers">
1252      <t>Additional CRLFs may precede the first boundary string in the
1253         entity.</t>
1254
1255      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1256         quoted, some existing implementations handle a quoted boundary
1257         string incorrectly.</t>
1258
1259      <t>A number of browsers and servers were coded to an early draft
1260         of the byteranges specification to use a media type of
1261         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1262         compatible with the version documented in HTTP/1.1.</t>
1263  </list>
1264</t>
1265</section>
1266
1267<section title="Compatibility with Previous Versions" anchor="compatibility">
1268<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
1269<t>
1270   Transfer-coding and message lengths all interact in ways that
1271   required fixing exactly when chunked encoding is used (to allow for
1272   transfer encoding that may not be self delimiting); it was important
1273   to straighten out exactly how message lengths are computed.
1274   (<xref target="header.content-range"/>,
1275   see also <xref target="Part1"/>, <xref target="Part3"/> and <xref target="Part6"/>)
1276</t>
1277<t>
1278   There are situations where a server (especially a proxy) does not
1279   know the full length of a response but is capable of serving a
1280   byterange request. We therefore need a mechanism to allow byteranges
1281   with a content-range not indicating the full length of the message.
1282   (<xref target="header.content-range"/>)
1283</t>
1284<t>
1285   Range request responses would become very verbose if all meta-data
1286   were always returned; by allowing the server to only send needed
1287   headers in a 206 response, this problem can be avoided.
1288   (Section <xref target="status.206" format="counter"/>
1289   and <xref target="header.if-range" format="counter"/>)
1290</t>
1291<t>
1292   Fix problem with unsatisfiable range requests; there are two cases:
1293   syntactic problems, and range doesn't exist in the document. The 416
1294   status code was needed to resolve this ambiguity needed to indicate
1295   an error for a byte range request that falls outside of the actual
1296   contents of a document. (Section <xref target="status.416" format="counter"/>, <xref target="header.content-range" format="counter"/>)
1297</t>
1298</section>
1299
1300<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1301<t>
1302  Clarify that it is not ok to use a weak cache validator in a 206 response.
1303  (<xref target="status.206"/>)
1304</t>
1305<t>
1306  Clarify that multipart/byteranges can consist of a single part.
1307  (<xref target="internet.media.type.multipart.byteranges"/>)
1308</t>
1309
1310</section>
1311
1312</section>
1313
1314<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1315
1316<section title="Since RFC2616">
1317<t>
1318  Extracted relevant partitions from <xref target="RFC2616"/>.
1319</t>
1320</section>
1321
1322<section title="Since draft-ietf-httpbis-p5-range-00">
1323<t>
1324  Closed issues:
1325  <list style="symbols">
1326    <t>
1327      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1328      "Cache validators in 206 responses"
1329      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1330    </t>
1331    <t>
1332      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1333      "Normative and Informative references"
1334    </t>
1335    <t>
1336      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1337      "Normative up-to-date references"
1338    </t>
1339  </list>
1340</t>
1341</section>
1342
1343<section title="Since draft-ietf-httpbis-p5-range-01">
1344<t>
1345  Closed issues:
1346  <list style="symbols">
1347    <t>
1348      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1349      "Updating to RFC4288"
1350    </t>
1351  </list>
1352</t>
1353<t>
1354  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1355  <list style="symbols">
1356    <t>
1357      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1358    </t>
1359  </list>
1360</t>
1361</section>
1362
1363<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1364<t>
1365  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1366  <list style="symbols">
1367    <t>
1368      Reference RFC 3984, and update header registrations for headers defined
1369      in this document.
1370    </t>
1371  </list>
1372</t>
1373</section>
1374
1375<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1376<t>
1377</t>
1378</section>
1379
1380<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1381<t>
1382  Closed issues:
1383  <list style="symbols">
1384    <t>
1385      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1386      "multipart/byteranges minimum number of parts"
1387    </t>
1388  </list>
1389</t>
1390<t>
1391  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1392  <list style="symbols">
1393    <t>
1394      Use "/" instead of "|" for alternatives.
1395    </t>
1396  </list>
1397</t>
1398</section>
1399
1400</section>
1401
1402</back>
1403</rfc>
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