source: draft-ietf-httpbis/latest/p5-range.xml @ 371

Last change on this file since 371 was 371, checked in by julian.reschke@…, 11 years ago

Cleanup. (related to #36)

  • Property svn:eol-style set to native
File size: 57.1 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "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="DIGIT"/>
255  <x:anchor-alias value="SP"/>
256  <x:anchor-alias value="token"/>
257  <x:anchor-alias value="OWS"/>
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  <x:ref>OWS</x:ref>        = &lt;OWS, defined in &basic-rules;&gt;
271</artwork></figure>
272<t anchor="abnf.dependencies">
273  <x:anchor-alias value="entity-tag"/>
274  <x:anchor-alias value="HTTP-date"/>
275  The ABNF rules below are defined in other parts:
276</t>
277<figure><!--Part1--><artwork type="abnf2616">
278  <x:ref>HTTP-date</x:ref>  = &lt;HTTP-date, defined in &full-date;&gt;
279</artwork></figure>
280<figure><!--Part4--><artwork type="abnf2616">
281  <x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in &entity-tags;&gt;
282</artwork></figure>
283</section>
284
285<section title="Range Units" anchor="range.units">
286  <x:anchor-alias value="bytes-unit"/>
287  <x:anchor-alias value="other-range-unit"/>
288  <x:anchor-alias value="range-unit"/>
289<t>
290   HTTP/1.1 allows a client to request that only part (a range of) the
291   response entity be included within the response. HTTP/1.1 uses range
292   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
293   header fields. An entity can be broken down into subranges according
294   to various structural units.
295</t>
296<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"/>
297  <x:ref>range-unit</x:ref>       = <x:ref>bytes-unit</x:ref> / <x:ref>other-range-unit</x:ref>
298  <x:ref>bytes-unit</x:ref>       = "bytes"
299  <x:ref>other-range-unit</x:ref> = <x:ref>token</x:ref>
300</artwork></figure>
301<t>
302   The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
303   implementations &MAY; ignore ranges specified using other units.
304</t>
305<t>
306   HTTP/1.1 has been designed to allow implementations of applications
307   that do not depend on knowledge of ranges.
308</t>
309</section>
310
311<section title="Status Code Definitions">
312<section title="206 Partial Content" anchor="status.206">
313  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
314  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
315<t>
316   The server has fulfilled the partial GET request for the resource.
317   The request &MUST; have included a Range header field (<xref target="header.range"/>)
318   indicating the desired range, and &MAY; have included an If-Range
319   header field (<xref target="header.if-range"/>) to make the request conditional.
320</t>
321<t>
322   The response &MUST; include the following header fields:
323  <list style="symbols">
324    <t>
325        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
326        the range included with this response, or a multipart/byteranges
327        Content-Type including Content-Range fields for each part. If a
328        Content-Length header field is present in the response, its
329        value &MUST; match the actual number of OCTETs transmitted in the
330        message-body.
331    </t>
332    <t>
333        Date
334    </t>
335    <t>
336        ETag and/or Content-Location, if the header would have been sent
337        in a 200 response to the same request
338    </t>
339    <t>
340        Expires, Cache-Control, and/or Vary, if the field-value might
341        differ from that sent in any previous response for the same
342        variant
343    </t>
344  </list>
345</t>
346<t>
347   If the 206 response is the result of an If-Range request, the response
348   &SHOULD-NOT; include other entity-headers. Otherwise, the response
349   &MUST; include all of the entity-headers that would have been returned
350   with a 200 (OK) response to the same request.
351</t>
352<t>
353   A cache &MUST-NOT; combine a 206 response with other previously cached
354   content if the ETag or Last-Modified headers do not match exactly,
355   see <xref target="combining.byte.ranges"/>.
356</t>
357<t>
358   A cache that does not support the Range and Content-Range headers
359   &MUST-NOT; cache 206 (Partial Content) responses.
360</t>
361</section>
362
363<section title="416 Requested Range Not Satisfiable" anchor="status.416">
364  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
365  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
366<t>
367   A server &SHOULD; return a response with this status code if a request
368   included a Range request-header field (<xref target="header.range"/>), and none of
369   the ranges-specifier values in this field overlap the current extent
370   of the selected resource, and the request did not include an If-Range
371   request-header field. (For byte-ranges, this means that the first-byte-pos
372   of all of the byte-range-spec values were greater than the
373   current length of the selected resource.)
374</t>
375<t>
376   When this status code is returned for a byte-range request, the
377   response &SHOULD; include a Content-Range entity-header field
378   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
379   This response &MUST-NOT; use the multipart/byteranges content-type.
380</t>
381</section>
382</section>
383
384<section title="Combining Byte Ranges" anchor="combining.byte.ranges">
385<t>
386   A response might transfer only a subrange of the bytes of an entity-body,
387   either because the request included one or more Range
388   specifications, or because a connection was broken prematurely. After
389   several such transfers, a cache might have received several ranges of
390   the same entity-body.
391</t>
392<t>
393   If a cache has a stored non-empty set of subranges for an entity, and
394   an incoming response transfers another subrange, the cache &MAY;
395   combine the new subrange with the existing set if both the following
396   conditions are met:
397  <list style="symbols">
398    <t>Both the incoming response and the cache entry have a cache
399        validator.</t>
400    <t>The two cache validators match using the strong comparison
401        function (see &weak-and-strong-validators;).</t>
402  </list>
403</t>
404<t>
405   If either requirement is not met, the cache &MUST; use only the most
406   recent partial response (based on the Date values transmitted with
407   every response, and using the incoming response if these values are
408   equal or missing), and &MUST; discard the other partial information.
409</t>
410</section>
411
412<section title="Header Field Definitions" anchor="header.fields">
413<t>
414   This section defines the syntax and semantics of HTTP/1.1 header fields
415   related to range requests and partial responses.
416</t>
417<t>
418   For entity-header fields, both sender and recipient refer to either the
419   client or the server, depending on who sends and who receives the entity.
420</t>
421
422<section title="Accept-Ranges" anchor="header.accept-ranges">
423  <iref primary="true" item="Accept-Ranges header" x:for-anchor=""/>
424  <iref primary="true" item="Headers" subitem="Accept-Ranges" x:for-anchor=""/>
425  <x:anchor-alias value="Accept-Ranges"/>
426  <x:anchor-alias value="Accept-Ranges-v"/>
427  <x:anchor-alias value="acceptable-ranges"/>
428<t>
429      The response-header "Accept-Ranges" field allows the server to
430      indicate its acceptance of range requests for a resource:
431</t>
432<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"/>
433  <x:ref>Accept-Ranges</x:ref>     = "Accept-Ranges" ":" <x:ref>OWS</x:ref> <x:ref>Accept-Ranges-v</x:ref>
434  <x:ref>Accept-Ranges-v</x:ref>   = <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 byte-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-v"/>
467  <x:anchor-alias value="content-range-spec"/>
468  <x:anchor-alias value="instance-length"/>
469<t>
470   The entity-header "Content-Range" is sent with a partial entity-body to
471   specify where in the full entity-body the partial body should be
472   applied. Range units are defined in <xref target="range.units"/>.
473</t>
474<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"/>
475  <x:ref>Content-Range</x:ref> = "Content-Range" ":" <x:ref>OWS</x:ref> <x:ref>Content-Range-v</x:ref>
476  <x:ref>Content-Range-v</x:ref> = <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>byte-content-range-spec</x:ref> = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
480                            <x:ref>byte-range-resp-spec</x:ref> "/"
481                            ( <x:ref>instance-length</x:ref> / "*" )
482 
483  <x:ref>byte-range-resp-spec</x:ref>    = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
484                          / "*"
485                         
486  <x:ref>instance-length</x:ref>         = 1*<x:ref>DIGIT</x:ref>
487</artwork></figure>
488<t>
489   The header &SHOULD; indicate the total length of the full entity-body,
490   unless this length is unknown or difficult to determine. The asterisk
491   "*" character means that the instance-length is unknown at the time
492   when the response was generated.
493</t>
494<t>
495   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
496   &MUST; only specify one range, and &MUST; contain
497   absolute byte positions for both the first and last byte of the
498   range.
499</t>
500<t>
501   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
502   value is less than its first-byte-pos value, or whose
503   instance-length value is less than or equal to its last-byte-pos
504   value, is invalid. The recipient of an invalid byte-content-range-spec
505   &MUST; ignore it and any content transferred along with it.
506</t>
507<t>
508   A server sending a response with status code 416 (Requested range not
509   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
510   of "*". The instance-length specifies the current length of
511   the selected resource. A response with status code 206 (Partial
512   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
513</t>
514<t>
515   Examples of byte-content-range-spec values, assuming that the entity
516   contains a total of 1234 bytes:
517   <list style="symbols">
518      <t>
519        The first 500 bytes:
520<figure><artwork type="text/plain">
521   bytes 0-499/1234
522</artwork></figure>
523      </t>   
524      <t>
525        The second 500 bytes:
526<figure><artwork type="text/plain">
527   bytes 500-999/1234
528</artwork></figure>
529      </t>   
530      <t>
531        All except for the first 500 bytes:
532<figure><artwork type="text/plain">
533   bytes 500-1233/1234
534</artwork></figure>
535      </t>   
536      <t>
537        The last 500 bytes:
538<figure><artwork type="text/plain">
539   bytes 734-1233/1234
540</artwork></figure>
541      </t>   
542   </list>
543</t>
544<t>
545   When an HTTP message includes the content of a single range (for
546   example, a response to a request for a single range, or to a request
547   for a set of ranges that overlap without any holes), this content is
548   transmitted with a Content-Range header, and a Content-Length header
549   showing the number of bytes actually transferred. For example,
550</t>
551<figure><artwork type="example">
552  HTTP/1.1 206 Partial Content
553  Date: Wed, 15 Nov 1995 06:25:24 GMT
554  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
555  Content-Range: bytes 21010-47021/47022
556  Content-Length: 26012
557  Content-Type: image/gif
558</artwork></figure>
559<t>
560   When an HTTP message includes the content of multiple ranges (for
561   example, a response to a request for multiple non-overlapping
562   ranges), these are transmitted as a multipart message. The multipart
563   media type used for this purpose is "multipart/byteranges" as defined
564   in <xref target="internet.media.type.multipart.byteranges"/>. See <xref target="changes.from.rfc.2068"/> for a compatibility issue.
565</t>
566<t>
567   A response to a request for a single range &MUST-NOT; be sent using the
568   multipart/byteranges media type.  A response to a request for
569   multiple ranges, whose result is a single range, &MAY; be sent as a
570   multipart/byteranges media type with one part. A client that cannot
571   decode a multipart/byteranges message &MUST-NOT; ask for multiple
572   byte-ranges in a single request.
573</t>
574<t>
575   When a client requests multiple byte-ranges in one request, the
576   server &SHOULD; return them in the order that they appeared in the
577   request.
578</t>
579<t>
580   If the server ignores a byte-range-spec because it is syntactically
581   invalid, the server &SHOULD; treat the request as if the invalid Range
582   header field did not exist. (Normally, this means return a 200
583   response containing the full entity).
584</t>
585<t>
586   If the server receives a request (other than one including an If-Range
587   request-header field) with an unsatisfiable Range request-header
588   field (that is, all of whose byte-range-spec values have a
589   first-byte-pos value greater than the current length of the selected
590   resource), it &SHOULD; return a response code of 416 (Requested range
591   not satisfiable) (<xref target="status.416"/>).
592  <list><t>
593      <x:h>Note:</x:h> clients cannot depend on servers to send a 416 (Requested
594      range not satisfiable) response instead of a 200 (OK) response for
595      an unsatisfiable Range request-header, since not all servers
596      implement this request-header.
597  </t></list>
598</t>
599</section>
600
601<section title="If-Range" anchor="header.if-range">
602  <iref primary="true" item="If-Range header" x:for-anchor=""/>
603  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
604  <x:anchor-alias value="If-Range"/>
605  <x:anchor-alias value="If-Range-v"/>
606<t>
607   If a client has a partial copy of an entity in its cache, and wishes
608   to have an up-to-date copy of the entire entity in its cache, it
609   could use the Range request-header with a conditional GET (using
610   either or both of If-Unmodified-Since and If-Match.) However, if the
611   condition fails because the entity has been modified, the client
612   would then have to make a second request to obtain the entire current
613   entity-body.
614</t>
615<t>
616   The request header "If-Range" allows a client to "short-circuit" the second
617   request. Informally, its meaning is `if the entity is unchanged, send
618   me the part(s) that I am missing; otherwise, send me the entire new
619   entity'.
620</t>
621<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/><iref primary="true" item="Grammar" subitem="If-Range-v"/>
622  <x:ref>If-Range</x:ref>   = "If-Range" ":" <x:ref>OWS</x:ref> <x:ref>If-Range-v</x:ref>
623  <x:ref>If-Range-v</x:ref> = <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref>
624</artwork></figure>
625<t>
626   If the client has no entity tag for an entity, but does have a Last-Modified
627   date, it &MAY; use that date in an If-Range header. (The
628   server can distinguish between a valid HTTP-date and any form of
629   entity-tag by examining no more than two characters.) The If-Range
630   header &SHOULD; only be used together with a Range header, and &MUST; be
631   ignored if the request does not include a Range header, or if the
632   server does not support the sub-range operation.
633</t>
634<t>
635   If the entity tag given in the If-Range header matches the current
636   entity tag for the entity, then the server &SHOULD; provide the
637   specified sub-range of the entity using a 206 (Partial Content)
638   response. If the entity tag does not match, then the server &SHOULD;
639   return the entire entity using a 200 (OK) response.
640</t>
641</section>
642
643<section title="Range" anchor="header.range">
644  <iref primary="true" item="Range header" x:for-anchor=""/>
645  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
646
647<section title="Byte Ranges" anchor="byte.ranges">
648<t>
649   Since all HTTP entities are represented in HTTP messages as sequences
650   of bytes, the concept of a byte range is meaningful for any HTTP
651   entity. (However, not all clients and servers need to support byte-range
652   operations.)
653</t>
654<t>
655   Byte range specifications in HTTP apply to the sequence of bytes in
656   the entity-body (not necessarily the same as the message-body).
657</t>
658<t anchor="rule.ranges-specifier">
659  <x:anchor-alias value="byte-range-set"/>
660  <x:anchor-alias value="byte-range-spec"/>
661  <x:anchor-alias value="byte-ranges-specifier"/>
662  <x:anchor-alias value="first-byte-pos"/>
663  <x:anchor-alias value="last-byte-pos"/>
664  <x:anchor-alias value="ranges-specifier"/>
665  <x:anchor-alias value="suffix-byte-range-spec"/>
666  <x:anchor-alias value="suffix-length"/>
667   A byte range operation &MAY; specify a single range of bytes, or a set
668   of ranges within a single entity.
669</t>
670<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"/>
671  <x:ref>ranges-specifier</x:ref> = <x:ref>byte-ranges-specifier</x:ref>
672  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
673  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
674  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [<x:ref>last-byte-pos</x:ref>]
675  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
676  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
677</artwork></figure>
678<t>
679   The first-byte-pos value in a byte-range-spec gives the byte-offset
680   of the first byte in a range. The last-byte-pos value gives the
681   byte-offset of the last byte in the range; that is, the byte
682   positions specified are inclusive. Byte offsets start at zero.
683</t>
684<t>
685   If the last-byte-pos value is present, it &MUST; be greater than or
686   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
687   is syntactically invalid. The recipient of a byte-range-set
688   that includes one or more syntactically invalid byte-range-spec
689   values &MUST; ignore the header field that includes that byte-range-set.
690</t>
691<t>
692   If the last-byte-pos value is absent, or if the value is greater than
693   or equal to the current length of the entity-body, last-byte-pos is
694   taken to be equal to one less than the current length of the entity-body
695   in bytes.
696</t>
697<t>
698   By its choice of last-byte-pos, a client can limit the number of
699   bytes retrieved without knowing the size of the entity.
700</t>
701<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
702  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
703  <x:ref>suffix-length</x:ref> = 1*<x:ref>DIGIT</x:ref>
704</artwork></figure>
705<t>
706   A suffix-byte-range-spec is used to specify the suffix of the
707   entity-body, of a length given by the suffix-length value. (That is,
708   this form specifies the last N bytes of an entity-body.) If the
709   entity is shorter than the specified suffix-length, the entire
710   entity-body is used.
711</t>
712<t>
713   If a syntactically valid byte-range-set includes at least one byte-range-spec
714   whose first-byte-pos is less than the current length of
715   the entity-body, or at least one suffix-byte-range-spec with a non-zero
716   suffix-length, then the byte-range-set is satisfiable.
717   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
718   is unsatisfiable, the server &SHOULD; return a response with a status
719   of 416 (Requested range not satisfiable). Otherwise, the server
720   &SHOULD; return a response with a status of 206 (Partial Content)
721   containing the satisfiable ranges of the entity-body.
722</t>
723<t>
724   Examples of byte-ranges-specifier values (assuming an entity-body of
725   length 10000):
726  <list style="symbols">
727     <t>The first 500 bytes (byte offsets 0-499, inclusive):  bytes=0-499</t>
728
729     <t>The second 500 bytes (byte offsets 500-999, inclusive):
730        bytes=500-999</t>
731
732     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
733        bytes=-500</t>
734
735     <t>Or bytes=9500-</t>
736
737     <t>The first and last bytes only (bytes 0 and 9999):  bytes=0-0,-1</t>
738
739     <t>Several legal but not canonical specifications of the second 500
740        bytes (byte offsets 500-999, inclusive):
741        <vspace/>
742         bytes=500-600,601-999<vspace/>
743         bytes=500-700,601-999</t>
744  </list>
745</t>
746</section>
747
748<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
749  <x:anchor-alias value="Range"/>
750  <x:anchor-alias value="Range-v"/>
751<t>
752   HTTP retrieval requests using conditional or unconditional GET
753   methods &MAY; request one or more sub-ranges of the entity, instead of
754   the entire entity, using the Range request header, which applies to
755   the entity returned as the result of the request:
756</t>
757<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/><iref primary="true" item="Grammar" subitem="Range-v"/>
758  <x:ref>Range</x:ref>   = "Range" ":" <x:ref>OWS</x:ref> <x:ref>Range-v</x:ref>
759  <x:ref>Range-v</x:ref> = <x:ref>ranges-specifier</x:ref>
760</artwork></figure>
761<t>
762   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
763   servers and intermediate caches ought to support byte ranges when
764   possible, since Range supports efficient recovery from partially
765   failed transfers, and supports efficient partial retrieval of large
766   entities.
767</t>
768<t>
769   If the server supports the Range header and the specified range or
770   ranges are appropriate for the entity:
771  <list style="symbols">
772     <t>The presence of a Range header in an unconditional GET modifies
773        what is returned if the GET is otherwise successful. In other
774        words, the response carries a status code of 206 (Partial
775        Content) instead of 200 (OK).</t>
776
777     <t>The presence of a Range header in a conditional GET (a request
778        using one or both of If-Modified-Since and If-None-Match, or
779        one or both of If-Unmodified-Since and If-Match) modifies what
780        is returned if the GET is otherwise successful and the
781        condition is true. It does not affect the 304 (Not Modified)
782        response returned if the conditional is false.</t>
783  </list>
784</t>
785<t>
786   In some cases, it might be more appropriate to use the If-Range
787   header (see <xref target="header.if-range"/>) in addition to the Range header.
788</t>
789<t>
790   If a proxy that supports ranges receives a Range request, forwards
791   the request to an inbound server, and receives an entire entity in
792   reply, it &SHOULD; only return the requested range to its client. It
793   &SHOULD; store the entire received response in its cache if that is
794   consistent with its cache allocation policies.
795</t>
796</section>
797</section>
798</section>
799
800<section title="IANA Considerations" anchor="IANA.considerations">
801<section title="Message Header Registration" anchor="message.header.registration">
802<t>
803   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
804   with the permanent registrations below (see <xref target="RFC3864"/>):
805</t>
806<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
807<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
808   <ttcol>Header Field Name</ttcol>
809   <ttcol>Protocol</ttcol>
810   <ttcol>Status</ttcol>
811   <ttcol>Reference</ttcol>
812
813   <c>Accept-Ranges</c>
814   <c>http</c>
815   <c>standard</c>
816   <c>
817      <xref target="header.accept-ranges"/>
818   </c>
819   <c>Content-Range</c>
820   <c>http</c>
821   <c>standard</c>
822   <c>
823      <xref target="header.content-range"/>
824   </c>
825   <c>If-Range</c>
826   <c>http</c>
827   <c>standard</c>
828   <c>
829      <xref target="header.if-range"/>
830   </c>
831   <c>Range</c>
832   <c>http</c>
833   <c>standard</c>
834   <c>
835      <xref target="header.range"/>
836   </c>
837</texttable>
838<!--(END)-->
839<t>
840   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
841</t>
842</section>
843</section>
844
845<section title="Security Considerations" anchor="security.considerations">
846<t>
847   No additional security considerations have been identified beyond
848   those applicable to HTTP in general &messaging;.
849</t>
850</section>
851
852<section title="Acknowledgments" anchor="ack">
853<t>
854   Most of the specification of ranges is based on work originally done
855   by Ari Luotonen and John Franks, with additional input from Steve
856   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
857   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
858   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
859</t>
860</section>
861</middle>
862<back>
863
864<references title="Normative References">
865
866<reference anchor="Part1">
867  <front>
868    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
869    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
870      <organization abbrev="Day Software">Day Software</organization>
871      <address><email>fielding@gbiv.com</email></address>
872    </author>
873    <author initials="J." surname="Gettys" fullname="Jim Gettys">
874      <organization>One Laptop per Child</organization>
875      <address><email>jg@laptop.org</email></address>
876    </author>
877    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
878      <organization abbrev="HP">Hewlett-Packard Company</organization>
879      <address><email>JeffMogul@acm.org</email></address>
880    </author>
881    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
882      <organization abbrev="Microsoft">Microsoft Corporation</organization>
883      <address><email>henrikn@microsoft.com</email></address>
884    </author>
885    <author initials="L." surname="Masinter" fullname="Larry Masinter">
886      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
887      <address><email>LMM@acm.org</email></address>
888    </author>
889    <author initials="P." surname="Leach" fullname="Paul J. Leach">
890      <organization abbrev="Microsoft">Microsoft Corporation</organization>
891      <address><email>paulle@microsoft.com</email></address>
892    </author>
893    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
894      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
895      <address><email>timbl@w3.org</email></address>
896    </author>
897    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
898      <organization abbrev="W3C">World Wide Web Consortium</organization>
899      <address><email>ylafon@w3.org</email></address>
900    </author>
901    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
902      <organization abbrev="greenbytes">greenbytes GmbH</organization>
903      <address><email>julian.reschke@greenbytes.de</email></address>
904    </author>
905    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
906  </front>
907  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
908  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
909</reference>
910
911<reference anchor="Part3">
912  <front>
913    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
914    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
915      <organization abbrev="Day Software">Day Software</organization>
916      <address><email>fielding@gbiv.com</email></address>
917    </author>
918    <author initials="J." surname="Gettys" fullname="Jim Gettys">
919      <organization>One Laptop per Child</organization>
920      <address><email>jg@laptop.org</email></address>
921    </author>
922    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
923      <organization abbrev="HP">Hewlett-Packard Company</organization>
924      <address><email>JeffMogul@acm.org</email></address>
925    </author>
926    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
927      <organization abbrev="Microsoft">Microsoft Corporation</organization>
928      <address><email>henrikn@microsoft.com</email></address>
929    </author>
930    <author initials="L." surname="Masinter" fullname="Larry Masinter">
931      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
932      <address><email>LMM@acm.org</email></address>
933    </author>
934    <author initials="P." surname="Leach" fullname="Paul J. Leach">
935      <organization abbrev="Microsoft">Microsoft Corporation</organization>
936      <address><email>paulle@microsoft.com</email></address>
937    </author>
938    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
939      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
940      <address><email>timbl@w3.org</email></address>
941    </author>
942    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
943      <organization abbrev="W3C">World Wide Web Consortium</organization>
944      <address><email>ylafon@w3.org</email></address>
945    </author>
946    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
947      <organization abbrev="greenbytes">greenbytes GmbH</organization>
948      <address><email>julian.reschke@greenbytes.de</email></address>
949    </author>
950    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
951  </front>
952  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
953  <x:source href="p3-payload.xml" basename="p3-payload"/>
954</reference>
955
956<reference anchor="Part4">
957  <front>
958    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
959    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
960      <organization abbrev="Day Software">Day Software</organization>
961      <address><email>fielding@gbiv.com</email></address>
962    </author>
963    <author initials="J." surname="Gettys" fullname="Jim Gettys">
964      <organization>One Laptop per Child</organization>
965      <address><email>jg@laptop.org</email></address>
966    </author>
967    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
968      <organization abbrev="HP">Hewlett-Packard Company</organization>
969      <address><email>JeffMogul@acm.org</email></address>
970    </author>
971    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
972      <organization abbrev="Microsoft">Microsoft Corporation</organization>
973      <address><email>henrikn@microsoft.com</email></address>
974    </author>
975    <author initials="L." surname="Masinter" fullname="Larry Masinter">
976      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
977      <address><email>LMM@acm.org</email></address>
978    </author>
979    <author initials="P." surname="Leach" fullname="Paul J. Leach">
980      <organization abbrev="Microsoft">Microsoft Corporation</organization>
981      <address><email>paulle@microsoft.com</email></address>
982    </author>
983    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
984      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
985      <address><email>timbl@w3.org</email></address>
986    </author>
987    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
988      <organization abbrev="W3C">World Wide Web Consortium</organization>
989      <address><email>ylafon@w3.org</email></address>
990    </author>
991    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
992      <organization abbrev="greenbytes">greenbytes GmbH</organization>
993      <address><email>julian.reschke@greenbytes.de</email></address>
994    </author>
995    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
996  </front>
997  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
998  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
999</reference>
1000
1001<reference anchor="Part6">
1002  <front>
1003    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1004    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1005      <organization abbrev="Day Software">Day Software</organization>
1006      <address><email>fielding@gbiv.com</email></address>
1007    </author>
1008    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1009      <organization>One Laptop per Child</organization>
1010      <address><email>jg@laptop.org</email></address>
1011    </author>
1012    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1013      <organization abbrev="HP">Hewlett-Packard Company</organization>
1014      <address><email>JeffMogul@acm.org</email></address>
1015    </author>
1016    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1017      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1018      <address><email>henrikn@microsoft.com</email></address>
1019    </author>
1020    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1021      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1022      <address><email>LMM@acm.org</email></address>
1023    </author>
1024    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1025      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1026      <address><email>paulle@microsoft.com</email></address>
1027    </author>
1028    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1029      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1030      <address><email>timbl@w3.org</email></address>
1031    </author>
1032    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1033      <organization abbrev="W3C">World Wide Web Consortium</organization>
1034      <address><email>ylafon@w3.org</email></address>
1035    </author>
1036    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1037      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1038      <address><email>julian.reschke@greenbytes.de</email></address>
1039    </author>
1040    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1041  </front>
1042  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1043  <x:source href="p6-cache.xml" basename="p6-cache"/>
1044</reference>
1045
1046<reference anchor="RFC2046">
1047  <front>
1048    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1049    <author initials="N." surname="Freed" fullname="Ned Freed">
1050      <organization>Innosoft International, Inc.</organization>
1051      <address><email>ned@innosoft.com</email></address>
1052    </author>
1053    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1054      <organization>First Virtual Holdings</organization>
1055      <address><email>nsb@nsb.fv.com</email></address>
1056    </author>
1057    <date month="November" year="1996"/>
1058  </front>
1059  <seriesInfo name="RFC" value="2046"/>
1060</reference>
1061
1062<reference anchor="RFC2119">
1063  <front>
1064    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1065    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1066      <organization>Harvard University</organization>
1067      <address><email>sob@harvard.edu</email></address>
1068    </author>
1069    <date month="March" year="1997"/>
1070  </front>
1071  <seriesInfo name="BCP" value="14"/>
1072  <seriesInfo name="RFC" value="2119"/>
1073</reference>
1074
1075</references>
1076
1077<references title="Informative References">
1078
1079<reference anchor="RFC2616">
1080  <front>
1081    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1082    <author initials="R." surname="Fielding" fullname="R. Fielding">
1083      <organization>University of California, Irvine</organization>
1084      <address><email>fielding@ics.uci.edu</email></address>
1085    </author>
1086    <author initials="J." surname="Gettys" fullname="J. Gettys">
1087      <organization>W3C</organization>
1088      <address><email>jg@w3.org</email></address>
1089    </author>
1090    <author initials="J." surname="Mogul" fullname="J. Mogul">
1091      <organization>Compaq Computer Corporation</organization>
1092      <address><email>mogul@wrl.dec.com</email></address>
1093    </author>
1094    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1095      <organization>MIT Laboratory for Computer Science</organization>
1096      <address><email>frystyk@w3.org</email></address>
1097    </author>
1098    <author initials="L." surname="Masinter" fullname="L. Masinter">
1099      <organization>Xerox Corporation</organization>
1100      <address><email>masinter@parc.xerox.com</email></address>
1101    </author>
1102    <author initials="P." surname="Leach" fullname="P. Leach">
1103      <organization>Microsoft Corporation</organization>
1104      <address><email>paulle@microsoft.com</email></address>
1105    </author>
1106    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1107      <organization>W3C</organization>
1108      <address><email>timbl@w3.org</email></address>
1109    </author>
1110    <date month="June" year="1999"/>
1111  </front>
1112  <seriesInfo name="RFC" value="2616"/>
1113</reference>
1114
1115<reference anchor='RFC3864'>
1116  <front>
1117    <title>Registration Procedures for Message Header Fields</title>
1118    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1119      <organization>Nine by Nine</organization>
1120      <address><email>GK-IETF@ninebynine.org</email></address>
1121    </author>
1122    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1123      <organization>BEA Systems</organization>
1124      <address><email>mnot@pobox.com</email></address>
1125    </author>
1126    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1127      <organization>HP Labs</organization>
1128      <address><email>JeffMogul@acm.org</email></address>
1129    </author>
1130    <date year='2004' month='September' />
1131  </front>
1132  <seriesInfo name='BCP' value='90' />
1133  <seriesInfo name='RFC' value='3864' />
1134</reference>
1135
1136<reference anchor="RFC4288">
1137  <front>
1138    <title>Media Type Specifications and Registration Procedures</title>
1139    <author initials="N." surname="Freed" fullname="N. Freed">
1140      <organization>Sun Microsystems</organization>
1141      <address>
1142        <email>ned.freed@mrochek.com</email>
1143      </address>
1144    </author>
1145    <author initials="J." surname="Klensin" fullname="J. Klensin">
1146      <organization/>
1147      <address>
1148        <email>klensin+ietf@jck.com</email>
1149      </address>
1150    </author>
1151    <date year="2005" month="December"/>
1152  </front>
1153  <seriesInfo name="BCP" value="13"/>
1154  <seriesInfo name="RFC" value="4288"/>
1155</reference>
1156
1157</references>
1158
1159<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1160<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1161<iref item="multipart/byteranges Media Type" primary="true"/>
1162<t>
1163   When an HTTP 206 (Partial Content) response message includes the
1164   content of multiple ranges (a response to a request for multiple
1165   non-overlapping ranges), these are transmitted as a multipart
1166   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1167   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1168</t><t>
1169   The multipart/byteranges media type includes one or more parts, each
1170   with its own Content-Type and Content-Range fields. The required
1171   boundary parameter specifies the boundary string used to separate
1172   each body-part.
1173</t>
1174<t>
1175  <list style="hanging" x:indent="12em">
1176    <t hangText="Type name:">
1177      multipart
1178    </t>
1179    <t hangText="Subtype name:">
1180      byteranges
1181    </t>
1182    <t hangText="Required parameters:">
1183      boundary
1184    </t>
1185    <t hangText="Optional parameters:">
1186      none
1187    </t>
1188    <t hangText="Encoding considerations:">
1189      only "7bit", "8bit", or "binary" are permitted
1190    </t>
1191    <t hangText="Security considerations:">
1192      none
1193    </t>
1194    <t hangText="Interoperability considerations:">
1195      none
1196    </t>
1197    <t hangText="Published specification:">
1198      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1199    </t>
1200    <t hangText="Applications that use this media type:">
1201    </t>
1202    <t hangText="Additional information:">
1203      <list style="hanging">
1204        <t hangText="Magic number(s):">none</t>
1205        <t hangText="File extension(s):">none</t>
1206        <t hangText="Macintosh file type code(s):">none</t>
1207      </list>
1208    </t>
1209    <t hangText="Person and email address to contact for further information:">
1210      See Authors Section.
1211    </t>
1212                <t hangText="Intended usage:">
1213                  COMMON
1214    </t>
1215                <t hangText="Restrictions on usage:">
1216                  none
1217    </t>
1218    <t hangText="Author/Change controller:">
1219      IESG
1220    </t>
1221  </list>
1222</t>
1223<figure><preamble>
1224   For example:
1225</preamble><artwork type="example">
1226   HTTP/1.1 206 Partial Content
1227   Date: Wed, 15 Nov 1995 06:25:24 GMT
1228   Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1229   Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1230
1231   --THIS_STRING_SEPARATES
1232   Content-type: application/pdf
1233   Content-range: bytes 500-999/8000
1234
1235   ...the first range...
1236   --THIS_STRING_SEPARATES
1237   Content-type: application/pdf
1238   Content-range: bytes 7000-7999/8000
1239
1240   ...the second range
1241   --THIS_STRING_SEPARATES--
1242</artwork></figure>
1243<t>
1244      Notes:
1245  <list style="numbers">
1246      <t>Additional CRLFs may precede the first boundary string in the
1247         entity.</t>
1248
1249      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1250         quoted, some existing implementations handle a quoted boundary
1251         string incorrectly.</t>
1252
1253      <t>A number of browsers and servers were coded to an early draft
1254         of the byteranges specification to use a media type of
1255         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1256         compatible with the version documented in HTTP/1.1.</t>
1257  </list>
1258</t>
1259</section>
1260
1261<section title="Compatibility with Previous Versions" anchor="compatibility">
1262<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
1263<t>
1264   Transfer-coding and message lengths all interact in ways that
1265   required fixing exactly when chunked encoding is used (to allow for
1266   transfer encoding that may not be self delimiting); it was important
1267   to straighten out exactly how message lengths are computed.
1268   (<xref target="header.content-range"/>,
1269   see also <xref target="Part1"/>, <xref target="Part3"/> and <xref target="Part6"/>)
1270</t>
1271<t>
1272   There are situations where a server (especially a proxy) does not
1273   know the full length of a response but is capable of serving a
1274   byterange request. We therefore need a mechanism to allow byteranges
1275   with a content-range not indicating the full length of the message.
1276   (<xref target="header.content-range"/>)
1277</t>
1278<t>
1279   Range request responses would become very verbose if all meta-data
1280   were always returned; by allowing the server to only send needed
1281   headers in a 206 response, this problem can be avoided.
1282   (Section <xref target="status.206" format="counter"/>
1283   and <xref target="header.if-range" format="counter"/>)
1284</t>
1285<t>
1286   Fix problem with unsatisfiable range requests; there are two cases:
1287   syntactic problems, and range doesn't exist in the document. The 416
1288   status code was needed to resolve this ambiguity needed to indicate
1289   an error for a byte range request that falls outside of the actual
1290   contents of a document. (Section <xref target="status.416" format="counter"/>, <xref target="header.content-range" format="counter"/>)
1291</t>
1292</section>
1293
1294<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1295<t>
1296  Clarify that it is not ok to use a weak cache validator in a 206 response.
1297  (<xref target="status.206"/>)
1298</t>
1299<t>
1300  Clarify that multipart/byteranges can consist of a single part.
1301  (<xref target="internet.media.type.multipart.byteranges"/>)
1302</t>
1303
1304</section>
1305
1306</section>
1307
1308<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1309
1310<section title="Since RFC2616">
1311<t>
1312  Extracted relevant partitions from <xref target="RFC2616"/>.
1313</t>
1314</section>
1315
1316<section title="Since draft-ietf-httpbis-p5-range-00">
1317<t>
1318  Closed issues:
1319  <list style="symbols"> 
1320    <t>
1321      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1322      "Cache validators in 206 responses"
1323      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1324    </t>
1325    <t>
1326      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1327      "Normative and Informative references"
1328    </t>
1329    <t>
1330      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1331      "Normative up-to-date references"
1332    </t>
1333  </list>
1334</t>
1335</section>
1336
1337<section title="Since draft-ietf-httpbis-p5-range-01">
1338<t>
1339  Closed issues:
1340  <list style="symbols"> 
1341    <t>
1342      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1343      "Updating to RFC4288"
1344    </t>
1345  </list>
1346</t>
1347<t>
1348  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1349  <list style="symbols"> 
1350    <t>
1351      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1352    </t>
1353  </list>
1354</t>
1355</section>
1356
1357<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1358<t>
1359  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1360  <list style="symbols"> 
1361    <t>
1362      Reference RFC 3984, and update header registrations for headers defined
1363      in this document.
1364    </t>
1365  </list>
1366</t>
1367</section>
1368
1369<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1370<t>
1371</t>
1372</section>
1373
1374<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1375<t>
1376  Closed issues:
1377  <list style="symbols"> 
1378    <t>
1379      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1380      "multipart/byteranges minimum number of parts"
1381    </t>
1382  </list>
1383</t>
1384<t>
1385  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1386  <list style="symbols"> 
1387    <t>
1388      Use "/" instead of "|" for alternatives.
1389    </t>
1390    <t>
1391      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
1392      whitespace ("OWS") and required whitespace ("RWS").
1393    </t>
1394    <t>
1395      Rewrite ABNFs to spell out whitespace rules, factor out
1396      header value format definitions.
1397    </t>
1398  </list>
1399</t>
1400</section>
1401
1402</section>
1403
1404</back>
1405</rfc>
Note: See TracBrowser for help on using the repository browser.