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1<?xml version="1.0" encoding="UTF-8"?>
2<!--
3    This XML document is the output of clean-for-DTD.xslt; a tool that strips
4    extensions to RFC2629(bis) from documents for processing with xml2rfc.
5-->
6<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
7<?rfc toc="yes" ?>
8<?rfc symrefs="yes" ?>
9<?rfc sortrefs="yes" ?>
10<?rfc compact="yes"?>
11<?rfc subcompact="no" ?>
12<?rfc linkmailto="no" ?>
13<?rfc editing="no" ?>
14<?rfc comments="yes"?>
15<?rfc inline="yes"?>
16<!DOCTYPE rfc
17  PUBLIC "" "rfc2629.dtd">
18<rfc obsoletes="2616" category="std" ipr="full3978" docName="draft-ietf-httpbis-p5-range-02">
19<front>
20
21  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
22
23  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
24    <organization abbrev="Day Software">Day Software</organization>
25    <address>
26      <postal>
27        <street>23 Corporate Plaza DR, Suite 280</street>
28        <city>Newport Beach</city>
29        <region>CA</region>
30        <code>92660</code>
31        <country>USA</country>
32      </postal>
33      <phone>+1-949-706-5300</phone>
34      <facsimile>+1-949-706-5305</facsimile>
35      <email>fielding@gbiv.com</email>
36      <uri>http://roy.gbiv.com/</uri>
37    </address>
38  </author>
39
40  <author initials="J." surname="Gettys" fullname="Jim Gettys">
41    <organization>One Laptop per Child</organization>
42    <address>
43      <postal>
44        <street>21 Oak Knoll Road</street>
45        <city>Carlisle</city>
46        <region>MA</region>
47        <code>01741</code>
48        <country>USA</country>
49      </postal>
50      <email>jg@laptop.org</email>
51      <uri>http://www.laptop.org/</uri>
52    </address>
53  </author>
54 
55  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
56    <organization abbrev="HP">Hewlett-Packard Company</organization>
57    <address>
58      <postal>
59        <street>HP Labs, Large Scale Systems Group</street>
60        <street>1501 Page Mill Road, MS 1177</street>
61        <city>Palo Alto</city>
62        <region>CA</region>
63        <code>94304</code>
64        <country>USA</country>
65      </postal>
66      <email>JeffMogul@acm.org</email>
67    </address>
68  </author>
69
70  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
71    <organization abbrev="Microsoft">Microsoft Corporation</organization>
72    <address>
73      <postal>
74        <street>1 Microsoft Way</street>
75        <city>Redmond</city>
76        <region>WA</region>
77        <code>98052</code>
78        <country>USA</country>
79      </postal>
80      <email>henrikn@microsoft.com</email>
81    </address>
82  </author>
83
84  <author initials="L." surname="Masinter" fullname="Larry Masinter">
85    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
86    <address>
87      <postal>
88        <street>345 Park Ave</street>
89        <city>San Jose</city>
90        <region>CA</region>
91        <code>95110</code>
92        <country>USA</country>
93      </postal>
94      <email>LMM@acm.org</email>
95      <uri>http://larry.masinter.net/</uri>
96    </address>
97  </author>
98 
99  <author initials="P." surname="Leach" fullname="Paul J. Leach">
100    <organization abbrev="Microsoft">Microsoft Corporation</organization>
101    <address>
102      <postal>
103        <street>1 Microsoft Way</street>
104        <city>Redmond</city>
105        <region>WA</region>
106        <code>98052</code>
107      </postal>
108      <email>paulle@microsoft.com</email>
109    </address>
110  </author>
111   
112  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
113    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
114    <address>
115      <postal>
116        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
117        <street>The Stata Center, Building 32</street>
118        <street>32 Vassar Street</street>
119        <city>Cambridge</city>
120        <region>MA</region>
121        <code>02139</code>
122        <country>USA</country>
123      </postal>
124      <email>timbl@w3.org</email>
125      <uri>http://www.w3.org/People/Berners-Lee/</uri>
126    </address>
127  </author>
128
129  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
130    <organization abbrev="W3C">World Wide Web Consortium</organization>
131    <address>
132      <postal>
133        <street>W3C / ERCIM</street>
134        <street>2004, rte des Lucioles</street>
135        <city>Sophia-Antipolis</city>
136        <region>AM</region>
137        <code>06902</code>
138        <country>France</country>
139      </postal>
140      <email>ylafon@w3.org</email>
141      <uri>http://www.raubacapeu.net/people/yves/</uri>
142    </address>
143  </author>
144
145  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
146    <organization abbrev="greenbytes">greenbytes GmbH</organization>
147    <address>
148      <postal>
149        <street>Hafenweg 16</street>
150        <city>Muenster</city><region>NW</region><code>48155</code>
151        <country>Germany</country>
152      </postal>
153      <phone>+49 251 2807760</phone>   
154      <facsimile>+49 251 2807761</facsimile>   
155      <email>julian.reschke@greenbytes.de</email>       
156      <uri>http://greenbytes.de/tech/webdav/</uri>     
157    </address>
158  </author>
159
160  <date month="February" year="2008" day="24"/>
161
162<abstract>
163<t>
164   The Hypertext Transfer Protocol (HTTP) is an application-level
165   protocol for distributed, collaborative, hypermedia information
166   systems. HTTP has been in use by the World Wide Web global information
167   initiative since 1990. This document is Part 5 of the seven-part specification
168   that defines the protocol referred to as "HTTP/1.1" and, taken together,
169   obsoletes RFC 2616.  Part 5 defines range-specific requests and
170   the rules for constructing and combining responses to those requests.
171</t>
172</abstract>
173
174<note title="Editorial Note (To be removed by RFC Editor)">
175  <t>
176    Discussion of this draft should take place on the HTTPBIS working group
177    mailing list (ietf-http-wg@w3.org). The current issues list is
178    at <eref target="http://www.tools.ietf.org/wg/httpbis/trac/report/11"/>
179    and related documents (including fancy diffs) can be found at
180    <eref target="http://www.tools.ietf.org/wg/httpbis/"/>.
181  </t>
182  <t>
183    This draft incorporates those issue resolutions that were either
184    collected in the original RFC2616 errata list (<eref target="http://purl.org/NET/http-errata"/>),
185    or which were agreed upon on the mailing list between October 2006 and
186    November 2007 (as published in "draft-lafon-rfc2616bis-03").
187  </t>
188</note>
189</front>
190<middle>
191<section title="Introduction" anchor="introduction">
192<t>
193   HTTP clients often encounter interrupted data transfers as a result
194   of cancelled requests or dropped connections.  When a cache has stored
195   a partial representation, it is desirable to request the remainder
196   of that representation in a subsequent request rather than transfer
197   the entire representation.
198   There are also a number of Web applications that benefit from being
199   able to request only a subset of a larger representation, such as a
200   single page of a very large document or only part of an image to be
201   rendered by a device with limited local storage.
202</t>
203<t>
204   This document defines HTTP/1.1 range requests,
205   partial responses, and the multipart/byteranges media type.
206   The protocol for range requests is an OPTIONAL feature of HTTP,
207   designed so resources or recipients that do not implement this feature
208   can respond as if it is a normal GET request without impacting
209   interoperability.  Partial responses are indicated by a distinct status
210   code to not be mistaken for full responses by intermediate caches
211   that might not implement the feature.
212</t>
213<t>
214   Although the HTTP range request mechanism is designed to allow for
215   extensible range types, this specification only defines requests for
216   byte ranges.
217</t>
218
219<section title="Requirements" anchor="intro.requirements">
220<t>
221   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
222   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
223   document are to be interpreted as described in <xref target="RFC2119"/>.
224</t>
225<t>
226   An implementation is not compliant if it fails to satisfy one or more
227   of the MUST or REQUIRED level requirements for the protocols it
228   implements. An implementation that satisfies all the MUST or REQUIRED
229   level and all the SHOULD level requirements for its protocols is said
230   to be "unconditionally compliant"; one that satisfies all the MUST
231   level requirements but not all the SHOULD level requirements for its
232   protocols is said to be "conditionally compliant."
233</t>
234</section>
235</section>
236
237<section title="Notational Conventions and Generic Grammar" anchor="notation">
238<t>
239  This specification uses the ABNF syntax defined in Section 2.1 of <xref target="Part1"/> and
240  the core rules defined in Section 2.2 of <xref target="Part1"/>:
241  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
242  &lt;http://tools.ietf.org/wg/httpbis/trac/ticket/36&gt;.</cref>
243</t>
244<figure><artwork type="abnf2616"><![CDATA[
245  DIGIT      = <DIGIT, defined in [Part1], Section 2.2>
246  SP         = <SP, defined in [Part1], Section 2.2>
247]]></artwork></figure>
248<figure><artwork type="abnf2616"><![CDATA[
249  token      = <token, defined in [Part1], Section 2.2>
250]]></artwork></figure>
251<t anchor="abnf.dependencies">
252  The ABNF rules below are defined in other parts:
253</t>
254<figure><!--Part1--><artwork type="abnf2616"><![CDATA[
255  HTTP-date  = <HTTP-date, defined in [Part1], Section 3.3.1>
256]]></artwork></figure>
257<figure><!--Part4--><artwork type="abnf2616"><![CDATA[
258  entity-tag = <entity-tag, defined in [Part4], Section 3>
259]]></artwork></figure>
260</section>
261
262<section title="Range Units" anchor="range.units">
263<t>
264   HTTP/1.1 allows a client to request that only part (a range of) the
265   response entity be included within the response. HTTP/1.1 uses range
266   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
267   header fields. An entity can be broken down into subranges according
268   to various structural units.
269</t>
270<figure><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"/><artwork type="abnf2616"><![CDATA[
271  range-unit       = bytes-unit | other-range-unit
272  bytes-unit       = "bytes"
273  other-range-unit = token
274]]></artwork></figure>
275<t>
276   The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
277   implementations MAY ignore ranges specified using other units.
278</t>
279<t>
280   HTTP/1.1 has been designed to allow implementations of applications
281   that do not depend on knowledge of ranges.
282</t>
283</section>
284
285<section title="Status Code Definitions">
286<section title="206 Partial Content" anchor="status.206">
287  <iref primary="true" item="206 Partial Content (status code)"/>
288  <iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
289<t>
290   The server has fulfilled the partial GET request for the resource.
291   The request MUST have included a Range header field (<xref target="header.range"/>)
292   indicating the desired range, and MAY have included an If-Range
293   header field (<xref target="header.if-range"/>) to make the request conditional.
294</t>
295<t>
296   The response MUST include the following header fields:
297  <list style="symbols">
298    <t>
299        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
300        the range included with this response, or a multipart/byteranges
301        Content-Type including Content-Range fields for each part. If a
302        Content-Length header field is present in the response, its
303        value MUST match the actual number of OCTETs transmitted in the
304        message-body.
305    </t>
306    <t>
307        Date
308    </t>
309    <t>
310        ETag and/or Content-Location, if the header would have been sent
311        in a 200 response to the same request
312    </t>
313    <t>
314        Expires, Cache-Control, and/or Vary, if the field-value might
315        differ from that sent in any previous response for the same
316        variant
317    </t>
318  </list>
319</t>
320<t>
321   If the 206 response is the result of an If-Range request, the response
322   SHOULD NOT include other entity-headers. Otherwise, the response
323   MUST include all of the entity-headers that would have been returned
324   with a 200 (OK) response to the same request.
325</t>
326<t>
327   A cache MUST NOT combine a 206 response with other previously cached
328   content if the ETag or Last-Modified headers do not match exactly,
329   see <xref target="combining.byte.ranges"/>.
330</t>
331<t>
332   A cache that does not support the Range and Content-Range headers
333   MUST NOT cache 206 (Partial Content) responses.
334</t>
335</section>
336
337<section title="416 Requested Range Not Satisfiable" anchor="status.416">
338  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
339  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
340<t>
341   A server SHOULD return a response with this status code if a request
342   included a Range request-header field (<xref target="header.range"/>), and none of
343   the range-specifier values in this field overlap the current extent
344   of the selected resource, and the request did not include an If-Range
345   request-header field. (For byte-ranges, this means that the first-byte-pos
346   of all of the byte-range-spec values were greater than the
347   current length of the selected resource.)
348</t>
349<t>
350   When this status code is returned for a byte-range request, the
351   response SHOULD include a Content-Range entity-header field
352   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
353   This response MUST NOT use the multipart/byteranges content-type.
354</t>
355</section>
356</section>
357
358<section title="Combining Byte Ranges" anchor="combining.byte.ranges">
359<t>
360   A response might transfer only a subrange of the bytes of an entity-body,
361   either because the request included one or more Range
362   specifications, or because a connection was broken prematurely. After
363   several such transfers, a cache might have received several ranges of
364   the same entity-body.
365</t>
366<t>
367   If a cache has a stored non-empty set of subranges for an entity, and
368   an incoming response transfers another subrange, the cache MAY
369   combine the new subrange with the existing set if both the following
370   conditions are met:
371  <list style="symbols">
372    <t>Both the incoming response and the cache entry have a cache
373        validator.</t>
374    <t>The two cache validators match using the strong comparison
375        function (see Section 5 of <xref target="Part4"/>).</t>
376  </list>
377</t>
378<t>
379   If either requirement is not met, the cache MUST use only the most
380   recent partial response (based on the Date values transmitted with
381   every response, and using the incoming response if these values are
382   equal or missing), and MUST discard the other partial information.
383</t>
384</section>
385
386<section title="Header Field Definitions" anchor="header.fields">
387<t>
388   This section defines the syntax and semantics of HTTP/1.1 header fields
389   related to range requests and partial responses.
390</t>
391<t>
392   For entity-header fields, both sender and recipient refer to either the
393   client or the server, depending on who sends and who receives the entity.
394</t>
395
396<section title="Accept-Ranges" anchor="header.accept-ranges">
397  <iref primary="true" item="Accept-Ranges header"/>
398  <iref primary="true" item="Headers" subitem="Accept-Ranges"/>
399<t>
400      The Accept-Ranges response-header field allows the server to
401      indicate its acceptance of range requests for a resource:
402</t>
403<figure><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/><artwork type="abnf2616"><![CDATA[
404  Accept-Ranges     = "Accept-Ranges" ":" acceptable-ranges
405  acceptable-ranges = 1#range-unit | "none"
406]]></artwork></figure>
407<t>
408      Origin servers that accept byte-range requests MAY send
409</t>
410<figure><artwork type="example"><![CDATA[
411       Accept-Ranges: bytes
412]]></artwork></figure>
413<t>
414      but are not required to do so. Clients MAY generate byte-range
415      requests without having received this header for the resource
416      involved. Range units are defined in <xref target="range.units"/>.
417</t>
418<t>
419      Servers that do not accept any kind of range request for a
420      resource MAY send
421</t>
422<figure><artwork type="example"><![CDATA[
423       Accept-Ranges: none
424]]></artwork></figure>
425<t>
426      to advise the client not to attempt a range request.
427</t>
428</section>
429
430<section title="Content-Range" anchor="header.content-range">
431  <iref primary="true" item="Content-Range header"/>
432  <iref primary="true" item="Headers" subitem="Content-Range"/>
433<t>
434   The Content-Range entity-header is sent with a partial entity-body to
435   specify where in the full entity-body the partial body should be
436   applied. Range units are defined in <xref target="range.units"/>.
437</t>
438<figure><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"/><artwork type="abnf2616"><![CDATA[
439  Content-Range = "Content-Range" ":" content-range-spec
440 
441  content-range-spec      = byte-content-range-spec
442  byte-content-range-spec = bytes-unit SP
443                            byte-range-resp-spec "/"
444                            ( instance-length | "*" )
445 
446  byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
447                                 | "*"
448  instance-length           = 1*DIGIT
449]]></artwork></figure>
450<t>
451   The header SHOULD indicate the total length of the full entity-body,
452   unless this length is unknown or difficult to determine. The asterisk
453   "*" character means that the instance-length is unknown at the time
454   when the response was generated.
455</t>
456<t>
457   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
458   MUST only specify one range, and MUST contain
459   absolute byte positions for both the first and last byte of the
460   range.
461</t>
462<t>
463   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
464   value is less than its first-byte-pos value, or whose
465   instance-length value is less than or equal to its last-byte-pos
466   value, is invalid. The recipient of an invalid byte-content-range-spec
467   MUST ignore it and any content transferred along with it.
468</t>
469<t>
470   A server sending a response with status code 416 (Requested range not
471   satisfiable) SHOULD include a Content-Range field with a byte-range-resp-spec
472   of "*". The instance-length specifies the current length of
473   the selected resource. A response with status code 206 (Partial
474   Content) MUST NOT include a Content-Range field with a byte-range-resp-spec of "*".
475</t>
476<t>
477   Examples of byte-content-range-spec values, assuming that the entity
478   contains a total of 1234 bytes:
479   <list style="symbols">
480      <t>
481        The first 500 bytes:
482<figure><artwork type="text/plain"><![CDATA[
483   bytes 0-499/1234
484]]></artwork></figure>
485      </t>   
486      <t>
487        The second 500 bytes:
488<figure><artwork type="text/plain"><![CDATA[
489   bytes 500-999/1234
490]]></artwork></figure>
491      </t>   
492      <t>
493        All except for the first 500 bytes:
494<figure><artwork type="text/plain"><![CDATA[
495   bytes 500-1233/1234
496]]></artwork></figure>
497      </t>   
498      <t>
499        The last 500 bytes:
500<figure><artwork type="text/plain"><![CDATA[
501   bytes 734-1233/1234
502]]></artwork></figure>
503      </t>   
504   </list>
505</t>
506<t>
507   When an HTTP message includes the content of a single range (for
508   example, a response to a request for a single range, or to a request
509   for a set of ranges that overlap without any holes), this content is
510   transmitted with a Content-Range header, and a Content-Length header
511   showing the number of bytes actually transferred. For example,
512</t>
513<figure><artwork type="example"><![CDATA[
514    HTTP/1.1 206 Partial Content
515    Date: Wed, 15 Nov 1995 06:25:24 GMT
516    Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
517    Content-Range: bytes 21010-47021/47022
518    Content-Length: 26012
519    Content-Type: image/gif
520]]></artwork></figure>
521<t>
522   When an HTTP message includes the content of multiple ranges (for
523   example, a response to a request for multiple non-overlapping
524   ranges), these are transmitted as a multipart message. The multipart
525   media type used for this purpose is "multipart/byteranges" as defined
526   in <xref target="internet.media.type.multipart.byteranges"/>. See <xref target="changes.from.rfc.2068"/> for a compatibility issue.
527</t>
528<t>
529   A response to a request for a single range MUST NOT be sent using the
530   multipart/byteranges media type.  A response to a request for
531   multiple ranges, whose result is a single range, MAY be sent as a
532   multipart/byteranges media type with one part. A client that cannot
533   decode a multipart/byteranges message MUST NOT ask for multiple
534   byte-ranges in a single request.
535</t>
536<t>
537   When a client requests multiple byte-ranges in one request, the
538   server SHOULD return them in the order that they appeared in the
539   request.
540</t>
541<t>
542   If the server ignores a byte-range-spec because it is syntactically
543   invalid, the server SHOULD treat the request as if the invalid Range
544   header field did not exist. (Normally, this means return a 200
545   response containing the full entity).
546</t>
547<t>
548   If the server receives a request (other than one including an If-Range
549   request-header field) with an unsatisfiable Range request-header
550   field (that is, all of whose byte-range-spec values have a
551   first-byte-pos value greater than the current length of the selected
552   resource), it SHOULD return a response code of 416 (Requested range
553   not satisfiable) (<xref target="status.416"/>).
554  <list><t>
555      Note: clients cannot depend on servers to send a 416 (Requested
556      range not satisfiable) response instead of a 200 (OK) response for
557      an unsatisfiable Range request-header, since not all servers
558      implement this request-header.
559  </t></list>
560</t>
561</section>
562
563<section title="If-Range" anchor="header.if-range">
564  <iref primary="true" item="If-Range header"/>
565  <iref primary="true" item="Headers" subitem="If-Range"/>
566<t>
567   If a client has a partial copy of an entity in its cache, and wishes
568   to have an up-to-date copy of the entire entity in its cache, it
569   could use the Range request-header with a conditional GET (using
570   either or both of If-Unmodified-Since and If-Match.) However, if the
571   condition fails because the entity has been modified, the client
572   would then have to make a second request to obtain the entire current
573   entity-body.
574</t>
575<t>
576   The If-Range header allows a client to "short-circuit" the second
577   request. Informally, its meaning is `if the entity is unchanged, send
578   me the part(s) that I am missing; otherwise, send me the entire new
579   entity'.
580</t>
581<figure><iref primary="true" item="Grammar" subitem="If-Range"/><artwork type="abnf2616"><![CDATA[
582  If-Range = "If-Range" ":" ( entity-tag | HTTP-date )
583]]></artwork></figure>
584<t>
585   If the client has no entity tag for an entity, but does have a Last-Modified
586   date, it MAY use that date in an If-Range header. (The
587   server can distinguish between a valid HTTP-date and any form of
588   entity-tag by examining no more than two characters.) The If-Range
589   header SHOULD only be used together with a Range header, and MUST be
590   ignored if the request does not include a Range header, or if the
591   server does not support the sub-range operation.
592</t>
593<t>
594   If the entity tag given in the If-Range header matches the current
595   entity tag for the entity, then the server SHOULD provide the
596   specified sub-range of the entity using a 206 (Partial Content)
597   response. If the entity tag does not match, then the server SHOULD
598   return the entire entity using a 200 (OK) response.
599</t>
600</section>
601
602<section title="Range" anchor="header.range">
603  <iref primary="true" item="Range header"/>
604  <iref primary="true" item="Headers" subitem="Range"/>
605
606<section title="Byte Ranges" anchor="byte.ranges">
607<t>
608   Since all HTTP entities are represented in HTTP messages as sequences
609   of bytes, the concept of a byte range is meaningful for any HTTP
610   entity. (However, not all clients and servers need to support byte-range
611   operations.)
612</t>
613<t>
614   Byte range specifications in HTTP apply to the sequence of bytes in
615   the entity-body (not necessarily the same as the message-body).
616</t>
617<t>
618   A byte range operation MAY specify a single range of bytes, or a set
619   of ranges within a single entity.
620</t>
621<figure><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"/><artwork type="abnf2616"><![CDATA[
622  ranges-specifier = byte-ranges-specifier
623  byte-ranges-specifier = bytes-unit "=" byte-range-set
624  byte-range-set  = 1#( byte-range-spec | suffix-byte-range-spec )
625  byte-range-spec = first-byte-pos "-" [last-byte-pos]
626  first-byte-pos  = 1*DIGIT
627  last-byte-pos   = 1*DIGIT
628]]></artwork></figure>
629<t>
630   The first-byte-pos value in a byte-range-spec gives the byte-offset
631   of the first byte in a range. The last-byte-pos value gives the
632   byte-offset of the last byte in the range; that is, the byte
633   positions specified are inclusive. Byte offsets start at zero.
634</t>
635<t>
636   If the last-byte-pos value is present, it MUST be greater than or
637   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
638   is syntactically invalid. The recipient of a byte-range-set
639   that includes one or more syntactically invalid byte-range-spec
640   values MUST ignore the header field that includes that byte-range-set.
641</t>
642<t>
643   If the last-byte-pos value is absent, or if the value is greater than
644   or equal to the current length of the entity-body, last-byte-pos is
645   taken to be equal to one less than the current length of the entity-body
646   in bytes.
647</t>
648<t>
649   By its choice of last-byte-pos, a client can limit the number of
650   bytes retrieved without knowing the size of the entity.
651</t>
652<figure><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/><artwork type="abnf2616"><![CDATA[
653  suffix-byte-range-spec = "-" suffix-length
654  suffix-length = 1*DIGIT
655]]></artwork></figure>
656<t>
657   A suffix-byte-range-spec is used to specify the suffix of the
658   entity-body, of a length given by the suffix-length value. (That is,
659   this form specifies the last N bytes of an entity-body.) If the
660   entity is shorter than the specified suffix-length, the entire
661   entity-body is used.
662</t>
663<t>
664   If a syntactically valid byte-range-set includes at least one byte-range-spec
665   whose first-byte-pos is less than the current length of
666   the entity-body, or at least one suffix-byte-range-spec with a non-zero
667   suffix-length, then the byte-range-set is satisfiable.
668   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
669   is unsatisfiable, the server SHOULD return a response with a status
670   of 416 (Requested range not satisfiable). Otherwise, the server
671   SHOULD return a response with a status of 206 (Partial Content)
672   containing the satisfiable ranges of the entity-body.
673</t>
674<t>
675   Examples of byte-ranges-specifier values (assuming an entity-body of
676   length 10000):
677  <list style="symbols">
678     <t>The first 500 bytes (byte offsets 0-499, inclusive):  bytes=0-499</t>
679
680     <t>The second 500 bytes (byte offsets 500-999, inclusive):
681        bytes=500-999</t>
682
683     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
684        bytes=-500</t>
685
686     <t>Or bytes=9500-</t>
687
688     <t>The first and last bytes only (bytes 0 and 9999):  bytes=0-0,-1</t>
689
690     <t>Several legal but not canonical specifications of the second 500
691        bytes (byte offsets 500-999, inclusive):
692        <vspace/>
693         bytes=500-600,601-999<vspace/>
694         bytes=500-700,601-999</t>
695  </list>
696</t>
697</section>
698
699<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
700<t>
701   HTTP retrieval requests using conditional or unconditional GET
702   methods MAY request one or more sub-ranges of the entity, instead of
703   the entire entity, using the Range request header, which applies to
704   the entity returned as the result of the request:
705</t>
706<figure><iref primary="true" item="Grammar" subitem="Range"/><artwork type="abnf2616"><![CDATA[
707  Range = "Range" ":" ranges-specifier
708]]></artwork></figure>
709<t>
710   A server MAY ignore the Range header. However, HTTP/1.1 origin
711   servers and intermediate caches ought to support byte ranges when
712   possible, since Range supports efficient recovery from partially
713   failed transfers, and supports efficient partial retrieval of large
714   entities.
715</t>
716<t>
717   If the server supports the Range header and the specified range or
718   ranges are appropriate for the entity:
719  <list style="symbols">
720     <t>The presence of a Range header in an unconditional GET modifies
721        what is returned if the GET is otherwise successful. In other
722        words, the response carries a status code of 206 (Partial
723        Content) instead of 200 (OK).</t>
724
725     <t>The presence of a Range header in a conditional GET (a request
726        using one or both of If-Modified-Since and If-None-Match, or
727        one or both of If-Unmodified-Since and If-Match) modifies what
728        is returned if the GET is otherwise successful and the
729        condition is true. It does not affect the 304 (Not Modified)
730        response returned if the conditional is false.</t>
731  </list>
732</t>
733<t>
734   In some cases, it might be more appropriate to use the If-Range
735   header (see <xref target="header.if-range"/>) in addition to the Range header.
736</t>
737<t>
738   If a proxy that supports ranges receives a Range request, forwards
739   the request to an inbound server, and receives an entire entity in
740   reply, it SHOULD only return the requested range to its client. It
741   SHOULD store the entire received response in its cache if that is
742   consistent with its cache allocation policies.
743</t>
744</section>
745</section>
746</section>
747
748<section title="IANA Considerations" anchor="IANA.considerations">
749<t>
750   <cref>TBD.</cref>
751</t>
752</section>
753
754<section title="Security Considerations" anchor="security.considerations">
755<t>
756   No additional security considerations have been identified beyond
757   those applicable to HTTP in general <xref target="Part1"/>.
758</t>
759</section>
760
761<section title="Acknowledgments" anchor="ack">
762<t>
763   Most of the specification of ranges is based on work originally done
764   by Ari Luotonen and John Franks, with additional input from Steve
765   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
766   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
767   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
768</t>
769</section>
770</middle>
771<back>
772
773<references title="Normative References">
774
775<reference anchor="Part1">
776  <front>
777    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
778    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
779      <organization abbrev="Day Software">Day Software</organization>
780      <address><email>fielding@gbiv.com</email></address>
781    </author>
782    <author initials="J." surname="Gettys" fullname="Jim Gettys">
783      <organization>One Laptop per Child</organization>
784      <address><email>jg@laptop.org</email></address>
785    </author>
786    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
787      <organization abbrev="HP">Hewlett-Packard Company</organization>
788      <address><email>JeffMogul@acm.org</email></address>
789    </author>
790    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
791      <organization abbrev="Microsoft">Microsoft Corporation</organization>
792      <address><email>henrikn@microsoft.com</email></address>
793    </author>
794    <author initials="L." surname="Masinter" fullname="Larry Masinter">
795      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
796      <address><email>LMM@acm.org</email></address>
797    </author>
798    <author initials="P." surname="Leach" fullname="Paul J. Leach">
799      <organization abbrev="Microsoft">Microsoft Corporation</organization>
800      <address><email>paulle@microsoft.com</email></address>
801    </author>
802    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
803      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
804      <address><email>timbl@w3.org</email></address>
805    </author>
806    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
807      <organization abbrev="W3C">World Wide Web Consortium</organization>
808      <address><email>ylafon@w3.org</email></address>
809    </author>
810    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
811      <organization abbrev="greenbytes">greenbytes GmbH</organization>
812      <address><email>julian.reschke@greenbytes.de</email></address>
813    </author>
814    <date month="February" year="2008"/>
815  </front>
816  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-02"/>
817 
818</reference>
819
820<reference anchor="Part3">
821  <front>
822    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
823    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
824      <organization abbrev="Day Software">Day Software</organization>
825      <address><email>fielding@gbiv.com</email></address>
826    </author>
827    <author initials="J." surname="Gettys" fullname="Jim Gettys">
828      <organization>One Laptop per Child</organization>
829      <address><email>jg@laptop.org</email></address>
830    </author>
831    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
832      <organization abbrev="HP">Hewlett-Packard Company</organization>
833      <address><email>JeffMogul@acm.org</email></address>
834    </author>
835    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
836      <organization abbrev="Microsoft">Microsoft Corporation</organization>
837      <address><email>henrikn@microsoft.com</email></address>
838    </author>
839    <author initials="L." surname="Masinter" fullname="Larry Masinter">
840      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
841      <address><email>LMM@acm.org</email></address>
842    </author>
843    <author initials="P." surname="Leach" fullname="Paul J. Leach">
844      <organization abbrev="Microsoft">Microsoft Corporation</organization>
845      <address><email>paulle@microsoft.com</email></address>
846    </author>
847    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
848      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
849      <address><email>timbl@w3.org</email></address>
850    </author>
851    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
852      <organization abbrev="W3C">World Wide Web Consortium</organization>
853      <address><email>ylafon@w3.org</email></address>
854    </author>
855    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
856      <organization abbrev="greenbytes">greenbytes GmbH</organization>
857      <address><email>julian.reschke@greenbytes.de</email></address>
858    </author>
859    <date month="February" year="2008"/>
860  </front>
861  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-02"/>
862 
863</reference>
864
865<reference anchor="Part4">
866  <front>
867    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
868    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
869      <organization abbrev="Day Software">Day Software</organization>
870      <address><email>fielding@gbiv.com</email></address>
871    </author>
872    <author initials="J." surname="Gettys" fullname="Jim Gettys">
873      <organization>One Laptop per Child</organization>
874      <address><email>jg@laptop.org</email></address>
875    </author>
876    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
877      <organization abbrev="HP">Hewlett-Packard Company</organization>
878      <address><email>JeffMogul@acm.org</email></address>
879    </author>
880    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
881      <organization abbrev="Microsoft">Microsoft Corporation</organization>
882      <address><email>henrikn@microsoft.com</email></address>
883    </author>
884    <author initials="L." surname="Masinter" fullname="Larry Masinter">
885      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
886      <address><email>LMM@acm.org</email></address>
887    </author>
888    <author initials="P." surname="Leach" fullname="Paul J. Leach">
889      <organization abbrev="Microsoft">Microsoft Corporation</organization>
890      <address><email>paulle@microsoft.com</email></address>
891    </author>
892    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
893      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
894      <address><email>timbl@w3.org</email></address>
895    </author>
896    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
897      <organization abbrev="W3C">World Wide Web Consortium</organization>
898      <address><email>ylafon@w3.org</email></address>
899    </author>
900    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
901      <organization abbrev="greenbytes">greenbytes GmbH</organization>
902      <address><email>julian.reschke@greenbytes.de</email></address>
903    </author>
904    <date month="February" year="2008"/>
905  </front>
906  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-02"/>
907 
908</reference>
909
910<reference anchor="Part6">
911  <front>
912    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
913    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
914      <organization abbrev="Day Software">Day Software</organization>
915      <address><email>fielding@gbiv.com</email></address>
916    </author>
917    <author initials="J." surname="Gettys" fullname="Jim Gettys">
918      <organization>One Laptop per Child</organization>
919      <address><email>jg@laptop.org</email></address>
920    </author>
921    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
922      <organization abbrev="HP">Hewlett-Packard Company</organization>
923      <address><email>JeffMogul@acm.org</email></address>
924    </author>
925    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
926      <organization abbrev="Microsoft">Microsoft Corporation</organization>
927      <address><email>henrikn@microsoft.com</email></address>
928    </author>
929    <author initials="L." surname="Masinter" fullname="Larry Masinter">
930      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
931      <address><email>LMM@acm.org</email></address>
932    </author>
933    <author initials="P." surname="Leach" fullname="Paul J. Leach">
934      <organization abbrev="Microsoft">Microsoft Corporation</organization>
935      <address><email>paulle@microsoft.com</email></address>
936    </author>
937    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
938      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
939      <address><email>timbl@w3.org</email></address>
940    </author>
941    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
942      <organization abbrev="W3C">World Wide Web Consortium</organization>
943      <address><email>ylafon@w3.org</email></address>
944    </author>
945    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
946      <organization abbrev="greenbytes">greenbytes GmbH</organization>
947      <address><email>julian.reschke@greenbytes.de</email></address>
948    </author>
949    <date month="February" year="2008"/>
950  </front>
951  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-02"/>
952 
953</reference>
954
955<reference anchor="RFC2046">
956  <front>
957    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
958    <author initials="N." surname="Freed" fullname="Ned Freed">
959      <organization>Innosoft International, Inc.</organization>
960      <address><email>ned@innosoft.com</email></address>
961    </author>
962    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
963      <organization>First Virtual Holdings</organization>
964      <address><email>nsb@nsb.fv.com</email></address>
965    </author>
966    <date month="November" year="1996"/>
967  </front>
968  <seriesInfo name="RFC" value="2046"/>
969</reference>
970
971<reference anchor="RFC2119">
972  <front>
973    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
974    <author initials="S." surname="Bradner" fullname="Scott Bradner">
975      <organization>Harvard University</organization>
976      <address><email>sob@harvard.edu</email></address>
977    </author>
978    <date month="March" year="1997"/>
979  </front>
980  <seriesInfo name="BCP" value="14"/>
981  <seriesInfo name="RFC" value="2119"/>
982</reference>
983
984</references>
985
986<references title="Informative References">
987
988<reference anchor="RFC2616">
989  <front>
990    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
991    <author initials="R." surname="Fielding" fullname="R. Fielding">
992      <organization>University of California, Irvine</organization>
993      <address><email>fielding@ics.uci.edu</email></address>
994    </author>
995    <author initials="J." surname="Gettys" fullname="J. Gettys">
996      <organization>W3C</organization>
997      <address><email>jg@w3.org</email></address>
998    </author>
999    <author initials="J." surname="Mogul" fullname="J. Mogul">
1000      <organization>Compaq Computer Corporation</organization>
1001      <address><email>mogul@wrl.dec.com</email></address>
1002    </author>
1003    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1004      <organization>MIT Laboratory for Computer Science</organization>
1005      <address><email>frystyk@w3.org</email></address>
1006    </author>
1007    <author initials="L." surname="Masinter" fullname="L. Masinter">
1008      <organization>Xerox Corporation</organization>
1009      <address><email>masinter@parc.xerox.com</email></address>
1010    </author>
1011    <author initials="P." surname="Leach" fullname="P. Leach">
1012      <organization>Microsoft Corporation</organization>
1013      <address><email>paulle@microsoft.com</email></address>
1014    </author>
1015    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1016      <organization>W3C</organization>
1017      <address><email>timbl@w3.org</email></address>
1018    </author>
1019    <date month="June" year="1999"/>
1020  </front>
1021  <seriesInfo name="RFC" value="2616"/>
1022</reference>
1023
1024<reference anchor="RFC4288">
1025  <front>
1026    <title>Media Type Specifications and Registration Procedures</title>
1027    <author initials="N." surname="Freed" fullname="N. Freed">
1028      <organization>Sun Microsystems</organization>
1029      <address>
1030        <email>ned.freed@mrochek.com</email>
1031      </address>
1032    </author>
1033    <author initials="J." surname="Klensin" fullname="J. Klensin">
1034      <organization/>
1035      <address>
1036        <email>klensin+ietf@jck.com</email>
1037      </address>
1038    </author>
1039    <date year="2005" month="December"/>
1040  </front>
1041  <seriesInfo name="BCP" value="13"/>
1042  <seriesInfo name="RFC" value="4288"/>
1043</reference>
1044
1045</references>
1046
1047<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1048<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1049<iref item="multipart/byteranges Media Type" primary="true"/>
1050<t>
1051   When an HTTP 206 (Partial Content) response message includes the
1052   content of multiple ranges (a response to a request for multiple
1053   non-overlapping ranges), these are transmitted as a multipart
1054   message-body <xref target="RFC2046"/>. The media type for this purpose is called
1055   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1056</t><t>
1057   The multipart/byteranges media type includes two or more parts, each
1058   with its own Content-Type and Content-Range fields. The required
1059   boundary parameter specifies the boundary string used to separate
1060   each body-part.
1061</t>
1062<t>
1063  <list style="hanging">
1064    <t hangText="Type name:">
1065      multipart
1066    </t>
1067    <t hangText="Subtype name:">
1068      byteranges
1069    </t>
1070    <t hangText="Required parameters:">
1071      boundary
1072    </t>
1073    <t hangText="Optional parameters:">
1074      none
1075    </t>
1076    <t hangText="Encoding considerations:">
1077      only "7bit", "8bit", or "binary" are permitted
1078    </t>
1079    <t hangText="Security considerations:">
1080      none
1081    </t>
1082    <t hangText="Interoperability considerations:">
1083      none
1084    </t>
1085    <t hangText="Published specification:">
1086      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1087    </t>
1088    <t hangText="Applications that use this media type:">
1089    </t>
1090    <t hangText="Additional information:">
1091      <list style="hanging">
1092        <t hangText="Magic number(s):">none</t>
1093        <t hangText="File extension(s):">none</t>
1094        <t hangText="Macintosh file type code(s):">none</t>
1095      </list>
1096    </t>
1097    <t hangText="Person and email address to contact for further information:">
1098      See Authors Section.
1099    </t>
1100                <t hangText="Intended usage:">
1101                  COMMON
1102    </t>
1103                <t hangText="Restrictions on usage:">
1104                  none
1105    </t>
1106    <t hangText="Author/Change controller:">
1107      IESG
1108    </t>
1109  </list>
1110</t>
1111<figure><preamble>
1112   For example:
1113</preamble><artwork type="example"><![CDATA[
1114   HTTP/1.1 206 Partial Content
1115   Date: Wed, 15 Nov 1995 06:25:24 GMT
1116   Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1117   Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1118
1119   --THIS_STRING_SEPARATES
1120   Content-type: application/pdf
1121   Content-range: bytes 500-999/8000
1122
1123   ...the first range...
1124   --THIS_STRING_SEPARATES
1125   Content-type: application/pdf
1126   Content-range: bytes 7000-7999/8000
1127
1128   ...the second range
1129   --THIS_STRING_SEPARATES--
1130]]></artwork></figure>
1131<t>
1132      Notes:
1133  <list style="numbers">
1134      <t>Additional CRLFs may precede the first boundary string in the
1135         entity.</t>
1136
1137      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1138         quoted, some existing implementations handle a quoted boundary
1139         string incorrectly.</t>
1140
1141      <t>A number of browsers and servers were coded to an early draft
1142         of the byteranges specification to use a media type of
1143         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1144         compatible with the version documented in HTTP/1.1.</t>
1145  </list>
1146</t>
1147</section>
1148
1149<section title="Compatibility with Previous Versions" anchor="compatibility">
1150<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
1151<t>
1152   Transfer-coding and message lengths all interact in ways that
1153   required fixing exactly when chunked encoding is used (to allow for
1154   transfer encoding that may not be self delimiting); it was important
1155   to straighten out exactly how message lengths are computed.
1156   (<xref target="header.content-range"/>,
1157   see also <xref target="Part1"/>, <xref target="Part3"/> and <xref target="Part6"/>)
1158</t>
1159<t>
1160   There are situations where a server (especially a proxy) does not
1161   know the full length of a response but is capable of serving a
1162   byterange request. We therefore need a mechanism to allow byteranges
1163   with a content-range not indicating the full length of the message.
1164   (<xref target="header.content-range"/>)
1165</t>
1166<t>
1167   Range request responses would become very verbose if all meta-data
1168   were always returned; by allowing the server to only send needed
1169   headers in a 206 response, this problem can be avoided.
1170   (Section <xref target="status.206" format="counter"/>
1171   and <xref target="header.if-range" format="counter"/>)
1172</t>
1173<t>
1174   Fix problem with unsatisfiable range requests; there are two cases:
1175   syntactic problems, and range doesn't exist in the document. The 416
1176   status code was needed to resolve this ambiguity needed to indicate
1177   an error for a byte range request that falls outside of the actual
1178   contents of a document. (Section <xref target="status.416" format="counter"/>, <xref target="header.content-range" format="counter"/>)
1179</t>
1180</section>
1181
1182<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1183<t>
1184  Clarify that it is not ok to use a weak cache validator in a 206 response.
1185  (<xref target="status.206"/>)
1186</t>
1187</section>
1188
1189</section>
1190
1191<section title="Change Log (to be removed by RFC Editor before publication)">
1192
1193<section title="Since RFC2616">
1194<t>
1195  Extracted relevant partitions from <xref target="RFC2616"/>.
1196</t>
1197</section>
1198
1199<section title="Since draft-ietf-httpbis-p5-range-00">
1200<t>
1201  Closed issues:
1202  <list style="symbols"> 
1203    <t>
1204      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1205      "Cache validators in 206 responses"
1206      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1207    </t>
1208    <t>
1209      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1210      "Normative and Informative references"
1211    </t>
1212    <t>
1213      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1214      "Normative up-to-date references"
1215    </t>
1216  </list>
1217</t>
1218</section>
1219
1220<section title="Since draft-ietf-httpbis-p5-range-01">
1221<t>
1222  Closed issues:
1223  <list style="symbols"> 
1224    <t>
1225      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1226      "Updating to RFC4288"
1227    </t>
1228  </list>
1229</t>
1230<t>
1231  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1232  <list style="symbols"> 
1233    <t>
1234      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1235    </t>
1236  </list>
1237</t>
1238</section>
1239
1240</section>
1241
1242</back>
1243</rfc>
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